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1 -------------------------------------------------- 1 --------------------------------------------------
2 Jun 7 2011 2 Jun 7 2011
3 3
4 Cleaned 2-inch SSP wafer (doping unknown, surplus) with presaturated Texwipe (70% IPA / 30% DI 4 Cleaned 2-inch SSP wafer (doping unknown, surplus) with presaturated Texwipe (70% IPA / 30% DI
5 water), air dried. Spin coated with ~0.25 ml of Emulsitone Tantalumfilm. 5 water), air dried. Spin coated with ~0.25 ml of Emulsitone Tantalumfilm.
6 6
7 Adhesion was good but numerous pinholes were observed due to surface contamination. Edges of wafer 7 Adhesion was good but numerous pinholes were observed due to surface contamination. Edges of wafer
8 were not completely covered, not enough Tantalumfilm was used for a good coating. 8 were not completely covered, not enough Tantalumfilm was used for a good coating.
9 9
10 Baked wafer in air for 1 hour at 200C. Film evenness appeared to have slightly improved but pinholes 10 Baked wafer in air for 1 hour at 200C. Film evenness appeared to have slightly improved but pinholes
11 were still present. 11 were still present.
12 12
13 Cleaved wafer perpendicular to flat, broke smaller piece parallel to flat and created 7 dies ~2mm 13 Cleaved wafer perpendicular to flat, broke smaller piece parallel to flat and created 7 dies ~2mm
14 square from resulting piece. Placed in gel box #5, positions A1-A7. 14 square from resulting piece. Placed in gel box #5, positions A1-A7.
15 15
16 Initial inspection at 10x/30x. 16 Initial inspection at 10x/30x.
17 A1: Very uneven coating, some large holes, but a few good areas. Yellow plus some purple rings. 17 A1: Very uneven coating, some large holes, but a few good areas. Yellow plus some purple rings.
18 A2: Lots of midsized pinholes. Pink to orange. 18 A2: Lots of midsized pinholes. Pink to orange.
19 A3: Pretty even, lots of medium-small pinholes. Yellow. 19 A3: Pretty even, lots of medium-small pinholes. Yellow.
20 A4: A few large holes, some small ones. Deep purple. 20 A4: A few large holes, some small ones. Deep purple.
21 A5: One large hole, a few small ones. Even coating. Yellow. 21 A5: One large hole, a few small ones. Even coating. Yellow.
22 A6: Very even, a few medium-small holes. Yellow. 22 A6: Very even, a few medium-small holes. Yellow.
23 A7: Extremely uneven (edge of wafer). Larger pinholes. Purple. 23 A7: Extremely uneven (edge of wafer). Larger pinholes. Purple.
24 24
25 Coating appears relatively thick - 150-200nm. 25 Coating appears relatively thick - 150-200nm.
26 26
27 Etched die A2 in 3% HF for 5 minutes at room temperature. No detectable thinning of film. 27 Etched die A2 in 3% HF for 5 minutes at room temperature. No detectable thinning of film.
28 28
29 Etched die A2 in 3% HF for 5 minutes at 50C (water bath). Most of the film was removed, some traces 29 Etched die A2 in 3% HF for 5 minutes at 50C (water bath). Most of the film was removed, some traces
30 left in thicker areas. After another 5 minutes all but the thickest spots are gone. More heat is 30 left in thicker areas. After another 5 minutes all but the thickest spots are gone. More heat is
31 probably advisable for future etches. 31 probably advisable for future etches.
32 32
33 Prepared developer - 550mg NaOH in 50ml distilled water. 33 Prepared developer - 550mg NaOH in 50ml distilled water.
34 34
35 Spin coated die A6 in Shipley SP24 photoresist. Exposed 15um half-pitch test pattern for 12 minutes 35 Spin coated die A6 in Shipley SP24 photoresist. Exposed 15um half-pitch test pattern for 12 minutes
36 using 40x objective and microscope halogen lamp. Developed, looks pretty sharp. 36 using 40x objective and microscope halogen lamp. Developed, looks pretty sharp.
37 37
38 Etched hardmask on A6 in 3% HF for 5 minutes in 65C water bath. Poor photoresist adhesion observed, 38 Etched hardmask on A6 in 3% HF for 5 minutes in 65C water bath. Poor photoresist adhesion observed,
39 hardmask not entirely etched. Baked wafer on hot plate for 5 minutes in hopes of improving adhesion 39 hardmask not entirely etched. Baked wafer on hot plate for 5 minutes in hopes of improving adhesion
40 of remaining resist. Many of the stress patterns disappeared, indicating successful increase in 40 of remaining resist. Many of the stress patterns disappeared, indicating successful increase in
41 adhesion. (Photoresist was later found floating in Rinse 1 bath indicating thermal shock from 41 adhesion. (Photoresist was later found floating in Rinse 1 bath indicating thermal shock from
42 heated HF to cold rinse as a possible source of adhesion problems.) 42 heated HF to cold rinse as a possible source of adhesion problems.)
43 43
44 Returned A6 to HF for 3 minutes. Hardmask is not quite gone in surrounding areas, needs a little 44 Returned A6 to HF for 3 minutes. Hardmask is not quite gone in surrounding areas, needs a little
45 more time. Etched hardmask for another 3 minutes. 45 more time. Etched hardmask for another 3 minutes.
46 46
47 Hardmask still not fully penetrated, but PR is flaking off still. Aborted processing and returned 47 Hardmask still not fully penetrated, but PR is flaking off still. Aborted processing and returned
48 A6 to gel box for future analysis. 48 A6 to gel box for future analysis.
49 49
50 -------------------------------------------------- 50 --------------------------------------------------
51 51
52 June 8: 52 June 8:
53 53
54 Cleaved several more dies out of Ta2O5-coated wafer. Placed in gel box #5, positions A8 - C2. 54 Cleaved several more dies out of Ta2O5-coated wafer. Placed in gel box #5, positions A8 - C2.
55 Cell B2 was skipped due to poor adhesion. 55 Cell B2 was skipped due to poor adhesion.
56 56
57 Prepared 30% KOH / 15% IPA / 55% distilled water etchant: 57 Prepared 30% KOH / 15% IPA / 55% distilled water etchant:
58 7.5 ml 99% IPA dissolved in 27.5ml distilled water, followed by 15 g KOH under low heat. Spattering 58 7.5 ml 99% IPA dissolved in 27.5ml distilled water, followed by 15 g KOH under low heat. Spattering
59 from stirrer was observed, beaker was removed from heat and spatter removed from hot plate surface. 59 from stirrer was observed, beaker was removed from heat and spatter removed from hot plate surface.
60 60
61 After cooling, beaker was gently reheated to 65C while stirring slowly. 61 After cooling, beaker was gently reheated to 65C while stirring slowly.
62 62
63 Etched die B7 for 5 minutes at 65C (expected etch depth 2.5um). Returned to heat at 80C for another 63 Etched die B7 for 5 minutes at 65C (expected etch depth 2.5um). Returned to heat at 80C for another
64 5 mins to ensure a deep etch (expected depth 6.25um, total 8.75 um). No agitation during etch. 64 5 mins to ensure a deep etch (expected depth 6.25um, total 8.75 um). No agitation during etch.
65 65
66 Very nice etching observed, snapped a few pictures. Placed water bath on hot plate to preheat before 66 Very nice etching observed, snapped a few pictures. Placed water bath on hot plate to preheat before
67 etching. 67 etching.
68 68
69 Stripped hardmask with 3% HF in 70C water bath for 15 minutes. Some traces of hardmask left in thick 69 Stripped hardmask with 3% HF in 70C water bath for 15 minutes. Some traces of hardmask left in thick
70 spots but almost entirely removed. 70 spots but almost entirely removed.
71 71
72 Processing on B7 completed, ready for SEM imaging. Returned to gel tray. 72 Processing on B7 completed, ready for SEM imaging. Returned to gel tray.
73 73
74 Removed B3-B6 from gel tray (all are similar condition; yellow with a few pinholes) and spin coated 74 Removed B3-B6 from gel tray (all are similar condition; yellow with a few pinholes) and spin coated
75 with SP24 resist for ~30 sec. Soft baked at 85C for 30 seconds. Most dies stuck to carrier wafer 75 with SP24 resist for ~30 sec. Soft baked at 85C for 30 seconds. Most dies stuck to carrier wafer
76 and were scratched during removal. 76 and were scratched during removal.
77 77
78 Exposed first die for 30 sec using new 1W UV LED. Developed, severely underexposed. Placed in gel 78 Exposed first die for 30 sec using new 1W UV LED. Developed, severely underexposed. Placed in gel
79 tray at B3. 79 tray at B3.
80 80
81 Exposed second die for 60 sec. Developed, also underexposed. Placed in gel tray at B4. 81 Exposed second die for 60 sec. Developed, also underexposed. Placed in gel tray at B4.
82 82
83 Exposed third die for 5 mins. Developed, most fine features obliterated. Looks overexposed. Placed 83 Exposed third die for 5 mins. Developed, most fine features obliterated. Looks overexposed. Placed
84 in gel tray at B5. Might try etching later since the FOV ring is intact. 84 in gel tray at B5. Might try etching later since the FOV ring is intact.
85 85
86 Exposed fourth die for 2 mins. Looks slightly out of focus; UV method definitely needs some tweaks. 86 Exposed fourth die for 2 mins. Looks slightly out of focus; UV method definitely needs some tweaks.
87 87
88 Hard baked B6 at 110C for 60 sec. Wet etched in 3% HF in 75C water bath for 15 minutes. Serious 88 Hard baked B6 at 110C for 60 sec. Wet etched in 3% HF in 75C water bath for 15 minutes. Serious
89 bubbling of photoresist observed but it stayed mostly intact. 89 bubbling of photoresist observed but it stayed mostly intact.
90 90
91 Stripped photoresist in acetone. Die now appears almost blank, looks like hardmask is gone. Returned 91 Stripped photoresist in acetone. Die now appears almost blank, looks like hardmask is gone. Returned
92 B6 to die tray and stopped work for the night. 92 B6 to die tray and stopped work for the night.
93 93
94 -------------------------------------------------- 94 --------------------------------------------------
95 95
96 June 9: 96 June 9:
97 97
98 Placed die A3 (fairly even gold color) in petri dish containing colloidal silica and rubbed against 98 Placed die A3 (fairly even gold color) in petri dish containing colloidal silica and rubbed against
99 bottom of dish for 1 minute. Film was slightly abraded but far from removed. Some pinholes grew 99 bottom of dish for 1 minute. Film was slightly abraded but far from removed. Some pinholes grew
100 in size. Returned to die tray. 100 in size. Returned to die tray.
101 101
102 Cleaved a small piece of <100> SSP Si from a 2-inch wafer. Cleaned in acetone and IPA, baked on 102 Cleaved a small piece of <100> SSP Si from a 2-inch wafer. Cleaned in acetone and IPA, baked on
103 hot plate at 80C for 2 min. 103 hot plate at 80C for 2 min.
104 104
105 Prepared a solution of 2 drops Tantalumfilm in 5 drops denatured alcohol; spin coated one drop onto 105 Prepared a solution of 2 drops Tantalumfilm in 5 drops denatured alcohol; spin coated one drop onto
106 test wafer at maximum speed. Coating had pinholes due to surface contamination. 106 test wafer at maximum speed. Coating had pinholes due to surface contamination.
107 107
108 Stripped coating by rubbing with denatured alcohol and a Texwipe. Some traces remained around edges 108 Stripped coating by rubbing with denatured alcohol and a Texwipe. Some traces remained around edges
109 but center was clear. Cleaned wafer in acetone and IPA; baked on hot plate at 110C for 2 min. 109 but center was clear. Cleaned wafer in acetone and IPA; baked on hot plate at 110C for 2 min.
110 110
111 Spin coated using 2:5 dilution of Tantalumfilm in denatured alcohol. A deep blue-violet film 111 Spin coated using 2:5 dilution of Tantalumfilm in denatured alcohol. A deep blue-violet film
112 resulted, changing to brown as the solvent evaporated. Estimated film thickness 65nm. 112 resulted, changing to brown as the solvent evaporated. Estimated film thickness 65nm.
113 113
114 Baked in air for 1 hour at 200C. No significant color change. Placed in 2-inch cassette for future 114 Baked in air for 1 hour at 200C. No significant color change. Placed in 2-inch cassette for future
115 processing. 115 processing.
116 116
117 Diced wafer and placed in die tray at C5 - E5. Initial visual inspection of film quality: some 117 Diced wafer and placed in die tray at C5 - E5. Initial visual inspection of film quality: some
118 pinholes but overall quite good. 118 pinholes but overall quite good.
119 119
120 -------------------------------------------------- 120 --------------------------------------------------
121 121
122 June 11: 122 June 11:
123 123
124 Etched die D3 in 3% HF for 5 mins at 35C (bath had not been allowed to heat adequately). No etching 124 Etched die D3 in 3% HF for 5 mins at 35C (bath had not been allowed to heat adequately). No etching
125 observed. Waited for bath to heat to 55C and etched for 5 minutes. Light brown areas of coating were 125 observed. Waited for bath to heat to 55C and etched for 5 minutes. Light brown areas of coating were
126 completely removed; thicker areas remained in part. Returned to die tray. 126 completely removed; thicker areas remained in part. Returned to die tray.
127 127
128 Spin coated die C8 in SP24 photoresist; soft baked on hot plate for 30 sec at 100C. 128 Spin coated die C8 in SP24 photoresist; soft baked on hot plate for 30 sec at 100C.
129 129
130 Exposed companion cube test mask for 15 minutes using halogen-exposure process and 40x objective. 130 Exposed companion cube test mask for 15 minutes using halogen-exposure process and 40x objective.
131 Did not develop properly for reasons unknown. Stripped resist in acetone and re-coated. Soft baked 131 Did not develop properly for reasons unknown. Stripped resist in acetone and re-coated. Soft baked
132 for 15 sec. 132 for 15 sec.
133 133
134 Exposed 10um pitch ruler as contact mask for 5 mins using 1W UV LED. Developed and hard baked for 134 Exposed 10um pitch ruler as contact mask for 5 mins using 1W UV LED. Developed and hard baked for
135 90 sec on 110C hot plate. 135 90 sec on 110C hot plate.
136 136
137 Etched in 3% HF for 5 mins at ~80C. Photoresist still severely damaged. Stripped in acetone, all 137 Etched in 3% HF for 5 mins at ~80C. Photoresist still severely damaged. Stripped in acetone, all
138 features obliterated. Returned C8 to die tray. 138 features obliterated. Returned C8 to die tray.
139 139
140 Spin coated C9 in photoresist, soft baked for 30 sec. 140 Spin coated C9 in photoresist, soft baked for 30 sec.
141 141
142 Exposed 400um pitch ruler as contact mask for 5 mins using 1W UV LED. Developed, etched for 2 mins 142 Exposed 400um pitch ruler as contact mask for 5 mins using 1W UV LED. Developed, etched for 2 mins
143 in 3% HF at ~80C. No excessive PR damage observed. Stripped PR in acetone. Unsure if hardmask was 143 in 3% HF at ~80C. No excessive PR damage observed. Stripped PR in acetone. Unsure if hardmask was
144 completely etched or not, coating is very thin and hard to observe. 144 completely etched or not, coating is very thin and hard to observe.
145 145
146 Wet etched in KOH for 2 mins at ~60C. Looks like hardmask was not completely penetrated. Returned 146 Wet etched in KOH for 2 mins at ~60C. Looks like hardmask was not completely penetrated. Returned
147 C9 to die tray. 147 C9 to die tray.
148 148
149 -------------------------------------------------- 149 --------------------------------------------------
150 150
151 June 13: 151 June 13:
152 152
153 Spin coated die C10 in SP24 resist (slow speed for thick coating), soft baked 90 sec at 80C. Exposed 153 Spin coated die C10 in SP24 resist (slow speed for thick coating), soft baked 90 sec at 80C. Exposed
154 15 minutes using halogen microscope lamp and developed. 154 15 minutes using halogen microscope lamp and developed.
155 155
156 Hard baked 5 mins at 125C. Slight bubbling was observed. Allowed to cool, baked another 3 mins at 156 Hard baked 5 mins at 125C. Slight bubbling was observed. Allowed to cool, baked another 3 mins at
157 130C. No additional bubbling observed, looks like resist is adequately outgassed. 157 130C. No additional bubbling observed, looks like resist is adequately outgassed.
158 158
159 Wet etched 2 mins in dilute HF in 85C water bath. Some etching observed but some PR degradation. 159 Wet etched 2 mins in dilute HF in 85C water bath. Some etching observed but some PR degradation.
160 Much improved over previous etches, more baking might help more. 160 Much improved over previous etches, more baking might help more.
161 161
162 Returned to HF for 4 minutes. Can't tell if hardmask is etched through. 162 Returned to HF for 4 minutes. Can't tell if hardmask is etched through.
163 163
164 Stripped resist in acetone, pattern was almost obliterated. Returned C10 to die tray. 164 Stripped resist in acetone, pattern was almost obliterated. Returned C10 to die tray.
165 165
166 Spin coated D2 in SP24 resist at low speed, soft baked 60 sec at 130C with silicon spacer. 166 Spin coated D2 in SP24 resist at low speed, soft baked 60 sec at 130C with silicon spacer.
167 167
168 Exposed cross pattern for 5 minutes using UV LED. Developed but did not hard bake, returned to die 168 Exposed cross pattern for 5 minutes using UV LED. Developed but did not hard bake, returned to die
169 tray for future processing. 169 tray for future processing.
170 170
171 -------------------------------------------------- 171 --------------------------------------------------
172 172
173 June 16: 173 June 16:
174 174
175 Spin coated five dies (D6-7-8-9, E4) in SP24 resist. Preparation: acetone rinse, IPA rinse, 175 Spin coated five dies (D6-7-8-9, E4) in SP24 resist. Preparation: acetone rinse, IPA rinse,
176 dehydration bake for 3 min on 140 C hot plate. Used low speed for thick film. 176 dehydration bake for 3 min on 140 C hot plate. Used low speed for thick film.
177 177
178 Soft baked all dies for 60 sec on 120 C hot plate, moved to hot carrier wafer for 2 min, let cool. 178 Soft baked all dies for 60 sec on 120 C hot plate, moved to hot carrier wafer for 2 min, let cool.
179 179
180 Exposed all dies for 8 mins using UV LED and contact mask, developed. 180 Exposed all dies for 8 mins using UV LED and contact mask, developed.
181 181
182 No hard bake. 182 No hard bake.
183 183
184 Prepared five etch tubes: 184 Prepared five etch tubes:
185 A - distilled water 185 A - distilled water
186 B - 3% HF 186 B - 3% HF
187 C - HCl solution diluted to same pH as HF 187 C - HCl solution diluted to same pH as HF
188 D - 3% HF buffered to near-neutral pH with NaOH 188 D - 3% HF buffered to near-neutral pH with NaOH
189 E - 3% HF 189 E - 3% HF
190 190
191 Heated all tubes but E in 61C water bath, etched 5 mins. 191 Heated all tubes but E in 61C water bath, etched 5 mins.
192 192
193 Suctioned etchants, rinsed, imaged. 193 Suctioned etchants, rinsed, imaged.
194 194
195 A - no visible damage. Returned to die tray, D6. 195 A - no visible damage. Returned to die tray, D6.
196 B - lots of small bubbles, one big chunk cracked off. Returned to die tray, D7. 196 B - lots of small bubbles, one big chunk cracked off. Returned to die tray, D7.
197 C - No visible damage. Returned to die tray, D8. 197 C - No visible damage. Returned to die tray, D8.
198 D - completely obliterated, no trace of resist. Returned to die tray, D9. 198 D - completely obliterated, no trace of resist. Returned to die tray, D9.
199 E - lots of big chunks broken off. Returned to die tray, E4. 199 E - lots of big chunks broken off. Returned to die tray, E4.
200 200
201 -------------------------------------------------- 201 --------------------------------------------------
202 202
203 June 17: 203 June 17:
204 204
205 Scribed several more dies out of blank <100> wafer, placed in die tray (E7:F3). 205 Scribed several more dies out of blank <100> wafer, placed in die tray (E7:F3).
206 206
207 Spin coated E7 in SP24 resist, soft baked 60 sec, exposed companion cube 15 mins under microscope 207 Spin coated E7 in SP24 resist, soft baked 60 sec, exposed companion cube 15 mins under microscope
208 at 10x objective, developed. No hard bake. 208 at 10x objective, developed. No hard bake.
209 209
210 Spin coated E7 and E8 in 2:5 dilution of Tantalumfilm in denatured alcohol. 210 Spin coated E7 and E8 in 2:5 dilution of Tantalumfilm in denatured alcohol.
211 211
212 Tested un-baked Tantalumfilm on E8 for acetone resistance, no degradation observed. 212 Tested un-baked Tantalumfilm on E8 for acetone resistance, no degradation observed.
213 213
214 Inspected E7 under microscope, good lift-off profile visible. 214 Inspected E7 under microscope, good lift-off profile visible.
215 215
216 Lifted off E7 in acetone with gentle rubbing of a cleanroom swab. Sonication would be preferable 216 Lifted off E7 in acetone with gentle rubbing of a cleanroom swab. Sonication would be preferable
217 but no ultrasonic cleaner was available and this was just a test. 217 but no ultrasonic cleaner was available and this was just a test.
218 218
219 Results were very good, took several images. Baked E7 at 200C for 1 hour, returned to die tray. 219 Results were very good, took several images. Baked E7 at 200C for 1 hour, returned to die tray.
220 220
221 -------------------------------------------------- 221 --------------------------------------------------
222 222
223 June 18: 223 June 18:
224 224
225 Etched E7 in 30% KOH / 15% IPA for 5 mins at 85C. 225 Etched E7 in 30% KOH / 15% IPA for 5 mins at 85C.
226 226
227 Visually inspected under microscope, some black contamination (not sure what). Etch isn't that deep, 227 Visually inspected under microscope, some black contamination (not sure what). Etch isn't that deep,
228 stuck it back in the KOH for another 5 mins. 228 stuck it back in the KOH for another 5 mins.
229 229
230 Stripped hardmask in 3% HF for 5 mins in water bath. Contamination still present, not identified. 230 Stripped hardmask in 3% HF for 5 mins in water bath. Contamination still present, not identified.
231 231
232 Returned E7 to die tray. 232 Returned E7 to die tray.
233 233
234 -------------------------------------------------- 234 --------------------------------------------------
235 235
236 June 19: 236 June 19:
237 237
238 Spin coated E9 and E10 in SP24 resist, soft baked 60 sec at 80C. 238 Spin coated E9 and E10 in SP24 resist, soft baked 60 sec at 80C.
239 239
240 Preparation: 90 sec dehydration bake at 80C, acetone rinse, blow dry. 240 Preparation: 90 sec dehydration bake at 80C, acetone rinse, blow dry.
241 241
242 Exposed darkfield companion cube mask on E9 through camera tube with Mag-Lite for 15 minutes using 242 Exposed darkfield companion cube mask on E9 through camera tube with Mag-Lite for 15 minutes using
243 10x objective, developed. Some areas underexposed due to uneven illumination, imperfect focus, but 243 10x objective, developed. Some areas underexposed due to uneven illumination, imperfect focus, but
244 most features resolved. 244 most features resolved.
245 245
246 Spin coated E9 with one drop of undiluted Tantalumfilm. Some damage to resist observed, possibly 246 Spin coated E9 with one drop of undiluted Tantalumfilm. Some damage to resist observed, possibly
247 from solvent? 247 from solvent?
248 248
249 Lifted off, severe damage to film visible. Need thicker layer next time. 249 Lifted off, severe damage to film visible. Need thicker layer next time.
250 250
251 Returned E9 to die tray. 251 Returned E9 to die tray.
252 252
253 Exposed darkfield companion cube mask on E10 thorough camera tube with Mag-Lite for 15 minutes using 253 Exposed darkfield companion cube mask on E10 thorough camera tube with Mag-Lite for 15 minutes using
254 10x objective, developed. 254 10x objective, developed.
255 255
256 Spin coated E10 with one drop of undiluted Tantalumfilm at maximum speed. Coverage in low-lying 256 Spin coated E10 with one drop of undiluted Tantalumfilm at maximum speed. Coverage in low-lying
257 areas was poor. 257 areas was poor.
258 258
259 Wondering if contamination on die after developing is responsible. Placed one drop of IPA onto die, 259 Wondering if contamination on die after developing is responsible. Placed one drop of IPA onto die,
260 blew dry. 260 blew dry.
261 261
262 Spin coated with another drop of Tantalumfilm, using lower speed. Poorer lift-off profile observed. 262 Spin coated with another drop of Tantalumfilm, using lower speed. Poorer lift-off profile observed.
263 263
264 Lifted off in acetone. Decent results - film looks undamaaged, but some residue around desired areas. 264 Lifted off in acetone. Decent results - film looks undamaaged, but some residue around desired areas.
265 265
266 Baked E10 in air at 200C for 1 hour. Some cracking observed. 266 Baked E10 in air at 200C for 1 hour. Some cracking observed.
267 267
268 Etched in 30% KOH at 95C for 5 mins. Hardmask appears to have broken off - thermal shock? Some 268 Etched in 30% KOH at 95C for 5 mins. Hardmask appears to have broken off - thermal shock? Some
269 traces of patterns still visible. Need to try less aggressive etch. 269 traces of patterns still visible. Need to try less aggressive etch.
270 270
271 -------------------------------------------------- 271 --------------------------------------------------
272 272
273 June 20: 273 June 20:
274 274
275 Spin coated F1 with SP24 resist. Preparation: acetone rinse, blow dry. 275 Spin coated F1 with SP24 resist. Preparation: acetone rinse, blow dry.
276 276
277 Soft baked at 70 C for 90 sec. 277 Soft baked at 70 C for 90 sec.
278 278
279 Exposed darkfield companion cube mask at 10 objective through photo port for 15 minutes. 279 Exposed darkfield companion cube mask at 10 objective through photo port for 15 minutes.
280 280
281 Die slipped out of tweezers during developing and was slightly overdeveloped. 281 Die slipped out of tweezers during developing and was slightly overdeveloped.
282 282
283 Spin coated with one drop of Tantalumfilm at moderate speed. 283 Spin coated with one drop of Tantalumfilm at moderate speed.
284 284
285 Tantalumfilm was allowed to soak too long, photoresist degraded. Aborted processing, returning to 285 Tantalumfilm was allowed to soak too long, photoresist degraded. Aborted processing, returning to
286 die tray. Forgot to take pictures before coating. 286 die tray. Forgot to take pictures before coating.
287 287
288 -------------------------------------------------- 288 --------------------------------------------------
289 289
290 June 22: 290 June 22:
291 291
292 Prepared several short pieces of 406 micron tungsten wire and 5 mL of 20% KOH solution. 292 Prepared several short pieces of 406 micron tungsten wire and 5 mL of 20% KOH solution.
293 293
294 Electropolished one piece of wire for 5 minutes at 140 mA (2VDC) until wire broke. Looks very sharp, 294 Electropolished one piece of wire for 5 minutes at 140 mA (2VDC) until wire broke. Looks very sharp,
295 almost definitely submicron tip. 295 almost definitely submicron tip.
296 296
297 Repeated for another probe. Duller (a micron or so?), possibly not immersed deep enough. 297 Repeated for another probe. Duller (a micron or so?), possibly not immersed deep enough.
298 298
299 -------------------------------------------------- 299 --------------------------------------------------
300 300
301 June 23: 301 June 23:
302 302
303 Prepared solution of 4 ml distilled water : 500mg KOH. 303 Prepared solution of 4 ml distilled water : 500mg KOH.
304 304
305 Etched three probes at 3VDC. Nice tips but not super sharp, 2um ish. 305 Etched three probes at 3VDC. Nice tips but not super sharp, 2um ish.
306 306
307 Going to try building a more repeatable power supply in the future. 307 Going to try building a more repeatable power supply in the future.
308 308
309 -------------------------------------------------- 309 --------------------------------------------------
310 310
311 June 25: 311 June 25:
312 312
313 Prepared several more specimens from <100> Si (doping unknown), placed in die tray at F4:G3. 313 Prepared several more specimens from <100> Si (doping unknown), placed in die tray at F4:G3.
314 314
315 Spin coated dies F2:G3 with SP24 resist, soft baked 60 sec at 80C. 315 Spin coated dies F2:G3 with SP24 resist, soft baked 60 sec at 80C.
316 316
317 Three dies had severe edge rings, stripped and returned to die tray (F2:F4). Remaining dies looked 317 Three dies had severe edge rings, stripped and returned to die tray (F2:F4). Remaining dies looked
318 good, placed in gel tray in light-tight bag (F5:G3) for future work. No time to run any litho 318 good, placed in gel tray in light-tight bag (F5:G3) for future work. No time to run any litho
319 experiments tonight. 319 experiments tonight.
320 320
321 -------------------------------------------------- 321 --------------------------------------------------
322 322
323 June 27: 323 June 27:
324 324
325 Tried making probe tips again. Etched 120 sec at 3V, followed by 1.0V until snapping. 325 Tried making probe tips again. Etched 120 sec at 3V, followed by 1.0V until snapping.
326 326
327 First try was decent but no record. 327 First try was decent but no record.
328 328
329 Second attempt looks to be 1.05 um diameter / ~500nm radius. 329 Second attempt looks to be 1.05 um diameter / ~500nm radius.
330 330
331 Exposed die F6 for 15 mins using darkfield companion cube at 100x. Developed, hard baked 120 sec at 331 Exposed die F6 for 15 mins using darkfield companion cube at 100x. Developed, hard baked 120 sec at
332 140C. As expected, some underexposed areas due to flashlight exposure but otherwise fine. 332 140C. As expected, some underexposed areas due to flashlight exposure but otherwise fine.
333 333
334 Spin coated one drop of 30% Tantalumfilm in denatured alcohol at high speed. Coating was patchy 334 Spin coated one drop of 30% Tantalumfilm in denatured alcohol at high speed. Coating was patchy
335 as expected, brown. 335 as expected, brown.
336 336
337 Applied a second coat, one layer at high speed, without baking. Coating was uneven but a bit 337 Applied a second coat, one layer at high speed, without baking. Coating was uneven but a bit
338 thicker, blue. 338 thicker, blue.
339 339
340 Applied a third coat, one layer at high speed, without baking. Blue to yellow. 340 Applied a third coat, one layer at high speed, without baking. Blue to yellow.
341 341
342 Lifted off resist in acetone, looks very good. Preheated oven to 200C while processing F9, 342 Lifted off resist in acetone, looks very good. Preheated oven to 200C while processing F9,
343 stuck F6 in die tray in the meantime. 343 stuck F6 in die tray in the meantime.
344 344
345 Processed F9 in same manner as F6, stopped before hard bake, returned to die tray. 345 Processed F9 in same manner as F6, stopped before hard bake, returned to die tray.
346 346
347 Processed G2 in same manner as F6, stopped before hardmask deposition. Hot plate heated to 160C 347 Processed G2 in same manner as F6, stopped before hardmask deposition. Hot plate heated to 160C
348 since then. Returned to die tray. 348 since then. Returned to die tray.
349 349
350 Baked F6 in air at 200C for 60 mins. Looks good, some roughness but no visible cracking. 350 Baked F6 in air at 200C for 60 mins. Looks good, some roughness but no visible cracking.
351 351
352 Possible test dies to do later: 352 Possible test dies to do later:
353 TODO: after etch? 353 TODO: after etch?
354 TODO: before hardmask bake 354 TODO: before hardmask bake
355 TODO: before lift-off 355 TODO: before lift-off
356 TODO: before hard bake 356 TODO: before hard bake
357 357
358 Samples to SEM image (in order of priority): 358 Samples to SEM image (in order of priority):
359 Left hand probe tip, F6, G2, F9, E10, C9, C6, E5. 359 Left hand probe tip, F6, G2, F9, E10, C9, C6, E5.
360 360
361 -------------------------------------------------- 361 --------------------------------------------------
362 362
363 June 28: 363 June 28:
364 364
365 Brought tray 5 up to campus, temporarily storing today's runs in tray 6 until done with SEM work 365 Brought tray 5 up to campus, temporarily storing today's runs in tray 6 until done with SEM work
366 on Thurs. 366 on Thurs.
367 367
368 Processed G3 in same manner as F6. Hardmask still has strange black particles in it, some chipping 368 Processed G3 in same manner as F6. Hardmask still has strange black particles in it, some chipping
369 on edges. Baked for 1 hour at 200C. 369 on edges. Baked for 1 hour at 200C.
370 370
371 Processed F7 in same manner as F6 but used one drop of full-strength Tantalumfilm. Totally black 371 Processed F7 in same manner as F6 but used one drop of full-strength Tantalumfilm. Totally black
372 surface, still no idea what it is. Baked one hour at 200C. 372 surface, still no idea what it is. Baked one hour at 200C.
373 373
374 Etched G3 for two 1 min periods in 30% KOH (no IPA) at 60C. Looks good so far but needs more time. 374 Etched G3 for two 1 min periods in 30% KOH (no IPA) at 60C. Looks good so far but needs more time.
375 375
376 Etched G3 another 2 mins nonstop. Hardmask appears to have degraded. 376 Etched G3 another 2 mins nonstop. Hardmask appears to have degraded.
377 377
378 Removed F7 from oven, inspected. No signs of thermal cracking. 378 Removed F7 from oven, inspected. No signs of thermal cracking.
379 379
380 Etched F7 for 1 min in 30% KOH at ~80C. Hardmask started to degrade after first etch step, 380 Etched F7 for 1 min in 30% KOH at ~80C. Hardmask started to degrade after first etch step,
381 thermal shock? Stopped KOH etching, stripped hardmask in 3% HF in 60C water bath for 90 sec. 381 thermal shock? Stopped KOH etching, stripped hardmask in 3% HF in 60C water bath for 90 sec.
382 382
383 Not stripped completly, left in bath for another 5 mins. Strange crystals visible. pH strip 383 Not stripped completly, left in bath for another 5 mins. Strange crystals visible. pH strip
384 shows slight alkalinity (pH ~9) in rinse water, this may be the problem. Changed rinse water. 384 shows slight alkalinity (pH ~9) in rinse water, this may be the problem. Changed rinse water.
385 385
386 Replaced acid in etch tube, stripped for 10 mins. Still not removed. 386 Replaced acid in etch tube, stripped for 10 mins. Still not removed.
387 387
388 Going to repeat experiment tomorrow with separate rinse for acid and base steps. 388 Going to repeat experiment tomorrow with separate rinse for acid and base steps.
389 389
390 -------------------------------------------------- 390 --------------------------------------------------
391 391
392 Jul 5 and 11: 392 Jul 5 and 11:
393 393
394 Imaged several samples (F6, F7, G2, G3) and one probe tip under JEOL JSM-840 scanning electron microscope after sputtering in 394 Imaged several samples (F6, F7, G2, G3) and one probe tip under JEOL JSM-840 scanning electron microscope after sputtering in
395 ~100A of Pt. Probe tip was bumpy but sharp, final point was roughly cylindrical and 200nm in diameter. 395 ~100A of Pt. Probe tip was bumpy but sharp, final point was roughly cylindrical and 200nm in diameter.
396 396
397 Performed EDS analysis of contaminant on F6. 397 Performed EDS analysis of contaminant on F6.
398 398
399 Results were inconclusive - one particle of brass and one of organic dust were located, but the majority of contaminated 399 Results were inconclusive - one particle of brass and one of organic dust were located, but the majority of contaminated
400 surface showed nothing but silicon, tantalum chloride, and tantalum oxide. 400 surface showed nothing but silicon, tantalum chloride, and tantalum oxide.
401 401
402 -------------------------------------------------- 402 --------------------------------------------------
403 403
404 Jul 14: 404 Jul 14:
405 405
406 Inspected wafer test dies were taken from under light microscopy. Clearly visible particulate contamination. Current hypothesis 406 Inspected wafer test dies were taken from under light microscopy. Clearly visible particulate contamination. Current hypothesis
407 is that careless handling of wafer during scribing allowed silicon dust to stick to surface. 407 is that careless handling of wafer during scribing allowed silicon dust to stick to surface.
408 408
409 Created new Glade library lithography_tests/default_600dpi for test patterns optimized for 600DPI printing. 409 Created new Glade library lithography_tests/default_600dpi for test patterns optimized for 600DPI printing.
410 410
411 Lambda is 42.333um on the mask or 1.058 um on the dies at 40x reduction. Initial design rules: 411 Lambda is 42.333um on the mask or 1.058 um on the dies at 40x reduction. Initial design rules:
412 * Minimum axially aligned trench = 5 lambda / 5.290 um 412 * Minimum axially aligned trench = 5 lambda / 5.290 um
413 * Minimum axially aligned space = 5 lambda / 5.290 um 413 * Minimum axially aligned space = 5 lambda / 5.290 um
414 * Minimum axially aligned feature = 5 lambda / 5.290 um 414 * Minimum axially aligned feature = 5 lambda / 5.290 um
415 * Reticle size = 500 lambda / 529 um disk 415 * Reticle size = 500 lambda / 529 um disk
416 416
417 Created test pattern: 20x20 dots, 5 lambda across, 5 lambda spacing. Printed positive and negative versions of mask. 417 Created test pattern: 20x20 dots, 5 lambda across, 5 lambda spacing. Printed positive and negative versions of mask.
418 418
419 Cleaned two dies by rubbing with cleanroom swab saturated in 70% IPA, then dripping IPA onto 419 Cleaned two dies by rubbing with cleanroom swab saturated in 70% IPA, then dripping IPA onto
420 die and blowing dry. Particle counts decreased significantly, nearly eliminated. 420 die and blowing dry. Particle counts decreased significantly, nearly eliminated.
421 421
422 Ran both dies through slightly modified RCA clean: 422 Ran both dies through slightly modified RCA clean:
423 * Distilled water soak 423 * Distilled water soak
424 * SC1 (6 ml 3% H2O2 + 1 ml household ammonia @ 85C) for 10 mins 424 * SC1 (6 ml 3% H2O2 + 1 ml household ammonia @ 85C) for 10 mins
425 * Distilled water soak for 1 min 425 * Distilled water soak for 1 min
426 * 3% HF for 15 sec 426 * 3% HF for 15 sec
427 * Distilled water soak for 1 min 427 * Distilled water soak for 1 min
428 * SC2 (6 ml 3% H2O2 + 1 ml conc HCl) for 10 min 428 * SC2 (6 ml 3% H2O2 + 1 ml conc HCl) for 10 min
429 * Distilled water soak for 1 min 429 * Distilled water soak for 1 min
430 * Blow dry with R-134A 430 * Blow dry with R-134A
431 431
432 Spin coated both dies in SP24 resist, soft baked 1 min at 55C. 432 Spin coated both dies in SP24 resist, soft baked 1 min at 55C.
433 433
434 Exposed 20um dots pattern on first die for 15 mins using maglite. 434 Exposed 20um dots pattern on first die for 15 mins using maglite.
435 435
436 Developed, all small features obliterated (developer too strong?) 436 Developed, all small features obliterated (developer too strong?)
437 437
438 Spin coated with one drop of full strength Tantalumfilm, lifted off in acetone using swab. Some 438 Spin coated with one drop of full strength Tantalumfilm, lifted off in acetone using swab. Some
439 residue dried onto die, not sure if this will be enough to contaminate results. 439 residue dried onto die, not sure if this will be enough to contaminate results.
440 440
441 Exposed second 20um holes pattern on second die for 15 mins using maglite, developed. Looks slightly 441 Exposed second 20um holes pattern on second die for 15 mins using maglite, developed. Looks slightly
442 underexposed but many holes resolved. 442 underexposed but many holes resolved.
443 443
444 Spin coated with one drop of dilute Tantalumfilm, lifted off in beaker of acetone to avoid surface 444 Spin coated with one drop of dilute Tantalumfilm, lifted off in beaker of acetone to avoid surface
445 contaminants drying. Results look pretty good. 445 contaminants drying. Results look pretty good.
446 446
447 Baked both dies in air at 200C for 1 hour. Slight cracking observed. 447 Baked both dies in air at 200C for 1 hour. Slight cracking observed.
448 448
449 Etched first die in 30% KOH at 85C for 2 min. Hardmask broke off. 449 Etched first die in 30% KOH at 85C for 2 min. Hardmask broke off.
450 450
451 Returned to die tray, G4. 451 Returned to die tray, G4.
452 452
453 Etched second die in 30% KOH at 85C for 30 sec. Not much etching observed, tossed in another 30 sec. 453 Etched second die in 30% KOH at 85C for 30 sec. Not much etching observed, tossed in another 30 sec.
454 Repeated once more. 454 Repeated once more.
455 455
456 Stripped in 3% HF at 85C for 1 min. Hardmask not removed, stripped another 10 mins. 456 Stripped in 3% HF at 85C for 1 min. Hardmask not removed, stripped another 10 mins.
457 457
458 Not completely stripped (but visibly thinned), out of time for tonight. Returned to die tray, G5. 458 Not completely stripped (but visibly thinned), out of time for tonight. Returned to die tray, G5.
459 459
460 -------------------------------------------------- 460 --------------------------------------------------
461 461
462 Jul 19: 462 Jul 19:
463 463
464 Prepared substrates for evaporation tests on Thursday: scribe, wipe with acetone-soaked swab, 464 Prepared substrates for evaporation tests on Thursday: scribe, wipe with acetone-soaked swab,
465 acetone rinse, IPA rinse, blow dry with R-134a. 465 acetone rinse, IPA rinse, blow dry with R-134a.
466 466
467 6A3-6A4: <100> Si, SSP 467 6A3-6A4: <100> Si, SSP
468 6A5-6B7: glass microscope coverslip 468 6A5-6B7: glass microscope coverslip
469 469
470 Prepared 50% dilution of SP24 resist in acetone. 470 Prepared 50% dilution of SP24 resist in acetone.
471 471
472 Exposed an older die with 20um dark-points mask, developed. Spin coated with 1 drop of dilute 472 Exposed an older die with 20um dark-points mask, developed. Spin coated with 1 drop of dilute
473 Tantalumfilm, lifted off in acetone. Pattern severely degraded, looks like it had dust under the 473 Tantalumfilm, lifted off in acetone. Pattern severely degraded, looks like it had dust under the
474 mask. Returned to die tray, G6. 474 mask. Returned to die tray, G6.
475 475
476 Spin coated G7 and G8 (<100> Si) with diluted resist. Soft baked for 90 sec. 476 Spin coated G7 and G8 (<100> Si) with diluted resist. Soft baked for 90 sec.
477 Exposed comb drive test mask through 10x objective on G7 for 10 mins, developed. Beautiful results, 477 Exposed comb drive test mask through 10x objective on G7 for 10 mins, developed. Beautiful results,
478 except for the usual artifacts caused by use of a maglite instead of a uniform light source. 478 except for the usual artifacts caused by use of a maglite instead of a uniform light source.
479 479
480 Spin coated in one drop of full strength Tantalumfilm, dried, repeated. Lifted off in acetone. 480 Spin coated in one drop of full strength Tantalumfilm, dried, repeated. Lifted off in acetone.
481 Way too much Tantalumfilm, coating didnt lift off fully. Returned to die tray, G7. 481 Way too much Tantalumfilm, coating didnt lift off fully. Returned to die tray, G7.
482 482
483 Exposed comb drive test mask through 40x objective on G8 for 10 mins, developed. Focuser drifted 483 Exposed comb drive test mask through 40x objective on G8 for 10 mins, developed. Focuser drifted
484 during exposure, blurred beyond usability. Returned to die tray. 484 during exposure, blurred beyond usability. Returned to die tray.
485 485
486 -------------------------------------------------- 486 --------------------------------------------------
487 487
488 Jul 20: 488 Jul 20:
489 489
490 Cleaved several tantalum oxide-coated dies out of original test wafer. Cleaned one die in acetone, 490 Cleaved several tantalum oxide-coated dies out of original test wafer. Cleaned one die in acetone,
491 spin coated in 50% diluted SP24 photoresist. Soft baked 90 sec at 75C. 491 spin coated in 50% diluted SP24 photoresist. Soft baked 90 sec at 75C.
492 492
493 Exposed darkfield companion cube mask at 10x for 10 minutes, developed. 493 Exposed darkfield companion cube mask at 10x for 10 minutes, developed.
494 494
495 Made centrifuge tube of BOE solution - 3% HF + household ammonia titrated to neutral pH. 495 Made centrifuge tube of BOE solution - 3% HF + household ammonia titrated to neutral pH.
496 496
497 Etched die in BOE in 80C water bath for 60 sec. No visible etching. 497 Etched die in BOE in 80C water bath for 60 sec. No visible etching.
498 498
499 Returned to BOE bath for 3 mins. Some degradation of mask visible after rinse. 499 Returned to BOE bath for 3 mins. Some degradation of mask visible after rinse.
500 500
501 Annealed at 90C for 90 sec. 501 Annealed at 90C for 90 sec.
502 502
503 Returned to BOE bath for 5 mins. Resist severely degraded, no significant attack of hardmask. 503 Returned to BOE bath for 5 mins. Resist severely degraded, no significant attack of hardmask.
504 504
505 Returned to die tray, 5G9. 505 Returned to die tray, 5G9.
506 506
507 Spin coated second die in 50% SP24, soft baked 90 sec. 507 Spin coated second die in 50% SP24, soft baked 90 sec.
508 508
509 Exposed darkfield companion cube mask at 10x for 10 minutes. Developed, spin coated in full strength 509 Exposed darkfield companion cube mask at 10x for 10 minutes. Developed, spin coated in full strength
510 Tantalumfilm. Rough dark-colored pattern again, looks like photoresist is definitely the contaminant. 510 Tantalumfilm. Rough dark-colored pattern again, looks like photoresist is definitely the contaminant.
511 Will test a deliberate mixture of the two tomorrow. Returned to die tray, 5G10. 511 Will test a deliberate mixture of the two tomorrow. Returned to die tray, 5G10.
512 512
513 -------------------------------------------------- 513 --------------------------------------------------
514 514
515 Jul 21: 515 Jul 21:
516 516
517 Coated several samples with evaporated copper (exact thickness unknown, around 200nm is current 517 Coated several samples with evaporated copper (exact thickness unknown, around 200nm is current
518 estimate): 518 estimate):
519 * Quarter of 2" <100> SSP wafer, bare 519 * Quarter of 2" <100> SSP wafer, bare
520 * Quarter of 2" <100> SSP wafer with tantalum oxide thin film 520 * Quarter of 2" <100> SSP wafer with tantalum oxide thin film
521 * Two <100> SSP dies, bare 521 * Two <100> SSP dies, bare
522 * 13 glass substrates (from microscope cover slip) 522 * 13 glass substrates (from microscope cover slip)
523 523
524 Inspected glass sample under light microscope. Some slight defects, unsure of cause so far. 524 Inspected glass sample under light microscope. Some slight defects, unsure of cause so far.
525 525
526 Performed "Scotch tape test" on glass sample to test adhesion. Near-complete delamination observed. 526 Performed "Scotch tape test" on glass sample to test adhesion. Near-complete delamination observed.
527 527
528 Etched glass sample in 3% HF in 70C water bath for 5 mins. Film did not degrade, but delaminated. 528 Etched glass sample in 3% HF in 70C water bath for 5 mins. Film did not degrade, but delaminated.
529 529
530 Spin coated silicon sample in 50% SP24, soft baked 90 sec at 90C. Exposed comb drive wet etch 530 Spin coated silicon sample in 50% SP24, soft baked 90 sec at 90C. Exposed comb drive wet etch
531 mask at 10x for 10 mins, developed. 531 mask at 10x for 10 mins, developed.
532 532
533 Etched 1 min in SC2 at 80C. Photoresist degraded (overetch?). Stripped in acetone, pattern 533 Etched 1 min in SC2 at 80C. Photoresist degraded (overetch?). Stripped in acetone, pattern
534 obliterated. Returned to die tray, 5H1. 534 obliterated. Returned to die tray, 5H1.
535 535
536 Spin coated silicon sample in 50% SP24, soft baked 90 sec at 90C. Exposed comb drive wet etch 536 Spin coated silicon sample in 50% SP24, soft baked 90 sec at 90C. Exposed comb drive wet etch
537 mask at 10x for 12 mins, developed. 537 mask at 10x for 12 mins, developed.
538 538
539 Wet etched in SC2 at room temperature for 60 sec. Not fully etched, put in for another 60. 539 Wet etched in SC2 at room temperature for 60 sec. Not fully etched, put in for another 60.
540 540
541 Etch appears to have penetrated sideways into Cu film, not sure of reason for this. 541 Etch appears to have penetrated sideways into Cu film, not sure of reason for this.
542 542
543 Returned to die tray, 5H2. 543 Returned to die tray, 5H2.
544 544
545 -------------------------------------------------- 545 --------------------------------------------------
546 546
547 Jul 22: 547 Jul 22:
548 548
549 Etched Cu-coated glass sample in SC2 until film was removed. Less than 5 seconds to near-complete 549 Etched Cu-coated glass sample in SC2 until film was removed. Less than 5 seconds to near-complete
550 removal (some traces visible). 550 removal (some traces visible).
551 551
552 Scribed Ta2O5 + Cu thin film coated wafer to release several dies, cleaned with acetone rinse + blow 552 Scribed Ta2O5 + Cu thin film coated wafer to release several dies, cleaned with acetone rinse + blow
553 dry. Placed in die tray, 6C1 - 6C7. 553 dry. Placed in die tray, 6C1 - 6C7.
554 554
555 Spin coated one sample in 50% SP24 resist, soft baked 90 sec at 70 C. 555 Spin coated one sample in 50% SP24 resist, soft baked 90 sec at 70 C.
556 556
557 Exposed darkfield companion cube mask at 10x for 10 mins, developed. 557 Exposed darkfield companion cube mask at 10x for 10 mins, developed.
558 558
559 Wet etched 5 sec in SC2, copper completely removed from exposed areas. 559 Wet etched 5 sec in SC2, copper completely removed from exposed areas.
560 560
561 Placed in heated 3% HF, leaving PR intact (mechanical barrier to help hold Cu in place). Etched 561 Placed in heated 3% HF, leaving PR intact (mechanical barrier to help hold Cu in place). Etched
562 5 mins. Copper separated from oxide layer during rinse, oxide not fully penetrated. 562 5 mins. Copper separated from oxide layer during rinse, oxide not fully penetrated.
563 563
564 Returned die to HF for 5 more mins. Mask is gone so isotropic etch will widen features, but it may 564 Returned die to HF for 5 more mins. Mask is gone so isotropic etch will widen features, but it may
565 be good enough for a PoC. 565 be good enough for a PoC.
566 566
567 Too long, all features obliterated. Going to repeat this experiment using 8 min initial etch. 567 Too long, all features obliterated. Going to repeat this experiment using 8 min initial etch.
568 Returned to die tray, 5H3. 568 Returned to die tray, 5H3.
569 569
570 Spin coated one sample in 50% SP24, soft baked 90 sec. 570 Spin coated one sample in 50% SP24, soft baked 90 sec.
571 571
572 Exposed darkfield companion cube mask at 10x for 10 mins, developed. 572 Exposed darkfield companion cube mask at 10x for 10 mins, developed.
573 573
574 Wet etched 5 sec in SC2, copper completely removed from exposed areas. 574 Wet etched 5 sec in SC2, copper completely removed from exposed areas.
575 575
576 Placed in heated 3% HF, etched 8 mins. Mask degraded but seems to have survived long enough to have 576 Placed in heated 3% HF, etched 8 mins. Mask degraded but seems to have survived long enough to have
577 a significant effect. If oxide layer is thinner this process should be very successful. 577 a significant effect. If oxide layer is thinner this process should be very successful.
578 578
579 Stripped remaining photoresist and copper in acetone followed by SC2. 579 Stripped remaining photoresist and copper in acetone followed by SC2.
580 580
581 Inspected sample under optical microscope. Hardmask is definitely degraded from undercut of Cu, but 581 Inspected sample under optical microscope. Hardmask is definitely degraded from undercut of Cu, but
582 there may be enough left for a shallow etch. 582 there may be enough left for a shallow etch.
583 583
584 Wet etched 2 mins in 30% KOH, rinsed in water. 584 Wet etched 2 mins in 30% KOH, rinsed in water.
585 585
586 Dark precipitate visible on surface of etched areas, not sure what it is. Attempted to remove with 586 Dark precipitate visible on surface of etched areas, not sure what it is. Attempted to remove with
587 SC2 at room temp for a few sec, no results. Attempted to remove by swabbing with IPA, no success. 587 SC2 at room temp for a few sec, no results. Attempted to remove by swabbing with IPA, no success.
588 Attempted to remove with 60C SC2 for 10 mins, no luck. 588 Attempted to remove with 60C SC2 for 10 mins, no luck.
589 589
590 Stripped hardmask in heated 3% HF for 5 mins. 590 Stripped hardmask in heated 3% HF for 5 mins.
591 591
592 Returned to die tray, 5H4. 592 Returned to die tray, 5H4.
593 593
594 -------------------------------------------------- 594 --------------------------------------------------
595 595
596 Jul 24: 596 Jul 24:
597 597
598 Spin coated Cu-coated glass substrate in 50% SP24, soft baked. 598 Spin coated Cu-coated glass substrate in 50% SP24, soft baked.
599 599
600 Exposed negative twin-spiral mask at 10x for 10 mins, developed. Etched in SC2. 600 Exposed negative twin-spiral mask at 10x for 10 mins, developed. Etched in SC2.
601 601
602 Discovered after rinse that the wrong sample had been used - it was actually Ta2O5 + Cu coated Si. 602 Discovered after rinse that the wrong sample had been used - it was actually Ta2O5 + Cu coated Si.
603 Going to cross section this die to measure typical layer thicknesses. 603 Going to cross section this die to measure typical layer thicknesses.
604 604
605 Returned to die tray, 5H5. 605 Returned to die tray, 5H5.
606 606
607 Spin coated Cu-coated glass substrate in 50% SP24, soft baked. 607 Spin coated Cu-coated glass substrate in 50% SP24, soft baked.
608 608
609 Exposed Nyan Cat mask at 40x for 10 mins, developed. 609 Exposed Nyan Cat mask at 40x for 10 mins, developed.
610 610
611 Exposed Nyan Cat mask on same die at 10x for 10 mins, developed. 611 Exposed Nyan Cat mask on same die at 10x for 10 mins, developed.
612 612
613 Etched in SC2. Overetched, possibly due to double exposure weakening resist. Returned to die tray, 5H6. 613 Etched in SC2. Overetched, possibly due to double exposure weakening resist. Returned to die tray, 5H6.
614 614
615 -------------------------------------------------- 615 --------------------------------------------------
616 616
617 Jul 30: 617 Jul 30:
618 618
619 Etched Cu-coated glass substrate in 30% KOH for 10 mins, increasing heat from 50C to 80C. Copper did 619 Etched Cu-coated glass substrate in 30% KOH for 10 mins, increasing heat from 50C to 80C. Copper did
620 not visibly degrade but delaminated from substrate. Looks like an adhesion layer of some sort will 620 not visibly degrade but delaminated from substrate. Looks like an adhesion layer of some sort will
621 be necessary for future experiments. 621 be necessary for future experiments.
622 622
623 Created dilute SC2 solution: 8 ml 3% H2O2 and 0.5 ml conc. HCl, tested with Cu-coated Si sample. Too 623 Created dilute SC2 solution: 8 ml 3% H2O2 and 0.5 ml conc. HCl, tested with Cu-coated Si sample. Too
624 strong. 624 strong.
625 625
626 Diluted solution further - 1 ml of SC2 solution to 4 ml distilled water. Complete etch of film in 626 Diluted solution further - 1 ml of SC2 solution to 4 ml distilled water. Complete etch of film in
627 around 8 sec. 627 around 8 sec.
628 628
629 -------------------------------------------------- 629 --------------------------------------------------
630 630
631 Aug 06: 631 Aug 06:
632 632
633 Spin coated Cu-coated Si substrate in 50% SP24, soft baked. 633 Spin coated Cu-coated Si substrate in 50% SP24, soft baked.
634 634
635 Exposed Nyan Cat mask for 10 mins with 10x objective, developed, hard baked. 635 Exposed Nyan Cat mask for 10 mins with 10x objective, developed, hard baked.
636 636
637 Created slow Cu etch based on SC2: 0.1 ml conc. HCl, 0.5 ml 3% H2O2, 5 ml distilled water. Projected etch rate: 350-400nm/min 637 Created slow Cu etch based on SC2: 0.1 ml conc. HCl, 0.5 ml 3% H2O2, 5 ml distilled water. Projected etch rate: 350-400nm/min
638 assuming linear variation with concentration. 638 assuming linear variation with concentration.
639 639
640 Etched die for 15 sec, stripped in acetone. Layer not fully penetrated. 640 Etched die for 15 sec, stripped in acetone. Layer not fully penetrated.
641 641
642 Re-coated same die, exposed, developed, baked. 642 Re-coated same die, exposed, developed, baked.
643 643
644 Etched die for 30 sec, stripped in acetone. Very good results. Returned to die tray, H7. 644 Etched die for 30 sec, stripped in acetone. Very good results. Returned to die tray, H7.
645 645
646 -------------------------------------------------- 646 --------------------------------------------------
647 647
648 Aug 11: 648 Aug 11:
649 649
650 Spin coated cu-coated Si substrate in 50% SP24, soft baked. 650 Spin coated cu-coated Si substrate in 50% SP24, soft baked.
651 651
652 Exposed ruler mask for 10 mins with 10x objective using fiber-optic illuminator and tissue-paper diffuser. Image was too dim, 652 Exposed ruler mask for 10 mins with 10x objective using fiber-optic illuminator and tissue-paper diffuser. Image was too dim,
653 not adequately exposed. Repeated using maglite, developed. 653 not adequately exposed. Repeated using maglite, developed.
654 654
655 Wet etched in dilute SC2. 655 Wet etched in dilute SC2.
656 656
657 Etched die for 8 mins in 80C 3% HF. As with previous samples, delamination of Cu and PR layers (as a unit) was observed 657 Etched die for 8 mins in 80C 3% HF. As with previous samples, delamination of Cu and PR layers (as a unit) was observed
658 upon placing sample in rinse water. HF was observed to have penetrated sample through etched holes in Cu. Cr adhesion layer is 658 upon placing sample in rinse water. HF was observed to have penetrated sample through etched holes in Cu. Cr adhesion layer is
659 definitely going to be necessary but process appears sound otherwise. 659 definitely going to be necessary but process appears sound otherwise.
660 660
661 Returned to die tray, H8. 661 Returned to die tray, H8.
662 662
663 -------------------------------------------------- 663 --------------------------------------------------
664 664
665 Aug 15: 665 Aug 15:
666 666
667 Prepared coating solution: 0.2 ml Tantalumfilm in 1.8 ml denatured alcohol. 667 Prepared coating solution: 0.2 ml Tantalumfilm in 1.8 ml denatured alcohol.
668 668
669 Placed 2-inch 2SP <110> wafer on spin coater, swabbed with acetone, spin dried. 669 Placed 2-inch 2SP <110> wafer on spin coater, swabbed with acetone, spin dried.
670 670
671 First attempt at spin coating Tantalumfilm failed: coating beaded up for reasons unknown. Stripped in denatured alcohol 671 First attempt at spin coating Tantalumfilm failed: coating beaded up for reasons unknown. Stripped in denatured alcohol
672 followed by HF dip to remove native oxide and start clean. 672 followed by HF dip to remove native oxide and start clean.
673 673
674 Baked in air at 200C for 10 mins to promote growth of new oxide layer. 674 Baked in air at 200C for 10 mins to promote growth of new oxide layer.
675 675
676 Repeated process except without acetone rinse. Same result. 676 Repeated process except without acetone rinse. Same result.
677 677
678 Stripped, soaked wafer in 3% H2O2 (room temp 15 mins, low heat on hot plate 10 mins). 678 Stripped, soaked wafer in 3% H2O2 (room temp 15 mins, low heat on hot plate 10 mins).
679 679
680 Beginning to suspect that my denatured alcohol is unsuitable for diluting Tantalumfilm. One of the additives destroys 680 Beginning to suspect that my denatured alcohol is unsuitable for diluting Tantalumfilm. One of the additives destroys
681 the proper surface tension. 681 the proper surface tension.
682 682
683 Re-coated using pure Tantalumfilm. Some pinholes (probably due to residue from previous experiments). 683 Re-coated using pure Tantalumfilm. Some pinholes (probably due to residue from previous experiments).
684 684
685 Baked in air for 1 hour at 200C. 685 Baked in air for 1 hour at 200C.
686 686
687 Coated other side of wafer with pure Tantalumfilm. Poor coverage for reasons unknown. This can be the back side 687 Coated other side of wafer with pure Tantalumfilm. Poor coverage for reasons unknown. This can be the back side
688 as some defects there are tolerable. 688 as some defects there are tolerable.
689 689
690 Baked in air 1 hour at 200C. 690 Baked in air 1 hour at 200C.
691 691
692 -------------------------------------------------- 692 --------------------------------------------------
693 693
694 Aug 16: 694 Aug 16:
695 695
696 Evaporated ~10nm Cr + ~1000nm Cu over two 2-inch <110> wafers - both sides of 2SP wafer prepared yesterday and polished 696 Evaporated ~10nm Cr + ~1000nm Cu over two 2-inch <110> wafers - both sides of 2SP wafer prepared yesterday and polished
697 side of a blank 1SP wafer. 697 side of a blank 1SP wafer.
698 698
699 -------------------------------------------------- 699 --------------------------------------------------
700 700
701 Sep 13: 701 Sep 13:
702 702
703 Cleaved several dies out of a <110> wafer (SSP, 10nm Cr, 1000nm Cu) and spin coated with SP24 resist. Air dried, no soft bake. 703 Cleaved several dies out of a <110> wafer (SSP, 10nm Cr, 1000nm Cu) and spin coated with SP24 resist. Air dried, no soft bake.
704 704
705 Exposed five dies with varying parameters using fiber optic illuminator at maximum brightness and min-space parallel-lines mask. 705 Exposed five dies with varying parameters using fiber optic illuminator at maximum brightness and min-space parallel-lines mask.
706 706
707 I3: 10 mins, 10x objective. Severely overexposed. 707 I3: 10 mins, 10x objective. Severely overexposed.
708 I4: 5 mins, 10x objective. Very good. 708 I4: 5 mins, 10x objective. Very good.
709 I5: 5 mins, 40x objective. Overdeveloped. 709 I5: 5 mins, 40x objective. Overdeveloped.
710 I6: 5 mins, 40x objective. Blurred. 710 I6: 5 mins, 40x objective. Blurred.
711 I7: 5 min, 10x objective. Very good. 711 I7: 5 min, 10x objective. Very good.
712 712
713 Etched I4 and I7 in full strength SC2, no discernable overetch. 713 Etched I4 and I7 in full strength SC2, no discernable overetch.
714 714
715 Planning to X-section one and top-down image the other on JSM-840 SEM in the near future. Ideally, a cross-section sample prep 715 Planning to X-section one and top-down image the other on JSM-840 SEM in the near future. Ideally, a cross-section sample prep
716 method can be found which does not attack photoresist so edge profiles can be observed. 716 method can be found which does not attack photoresist so edge profiles can be observed.
717 717
718 -------------------------------------------------- 718 --------------------------------------------------
719 719
720 Sep 15: 720 Sep 15:
721 721
722 Performed two tests of double patterning (dies I8 and I9) at 10x reduction with 2:30 time per exposure. Half-exposed areas were 722 Performed two tests of double patterning (dies I8 and I9) at 10x reduction with 2:30 time per exposure. Half-exposed areas were
723 removed so only fully unexposed areas were left, rather than full and half. 723 removed so only fully unexposed areas were left, rather than full and half.
724 724
725 Wet etched I4 and I9 in SC2 until copper was removed, plus an extra ~15 seconds to remove Cr. 725 Wet etched I4 and I9 in SC2 until copper was removed, plus an extra ~15 seconds to remove Cr.
726 726
727 Wet etched both in KOH for 10-15 mins at ~80C in water bath. No etching of Si observed - Cr incompletely removed? 727 Wet etched both in KOH for 10-15 mins at ~80C in water bath. No etching of Si observed - Cr incompletely removed?
728 728
729 -------------------------------------------------- 729 --------------------------------------------------
730 730
731 Sep 16: 731 Sep 16:
732 732
733 Attempted to polish a piece of copper-clad FR4 and <111> Si (unpolished solar wafer fragment) using Ted Pella diamond paste. 733 Attempted to polish a piece of copper-clad FR4 and <111> Si (unpolished solar wafer fragment) using Ted Pella diamond paste.
734 Polishing definitely worked however deep gouges were observed in the sample. Suspected cause is large abrasive particles not 734 Polishing definitely worked however deep gouges were observed in the sample. Suspected cause is large abrasive particles not
735 being completely removed before going to smaller sizes. 735 being completely removed before going to smaller sizes.
736 736
737 -------------------------------------------------- 737 --------------------------------------------------
738 738
739 Sep 18: 739 Sep 18:
740 740
741 Performed a test of double patterning (die 5I10) at 10x reduction. One minute per exposure. Severe line edge roughness, 741 Performed a test of double patterning (die 5I10) at 10x reduction. One minute per exposure. Severe line edge roughness,
742 looks slightly underexposed. Wet etched in SC2 until copper was removed, returned to die tray. 742 looks slightly underexposed. Wet etched in SC2 until copper was removed, returned to die tray.
743 743
744 Most likely last test before SEM session. Dies to image: 744 Most likely last test before SEM session. Dies to image:
745 * I3 or I8: (cross section, need to SC2 before prep) empty disk with some traces of lines 745 * I3 or I8: (cross section, need to SC2 before prep) empty disk with some traces of lines
746 * I4: 20um lines in Cu:Cr over <110> Si, no resist, partial KOH etch not penetrating Si 746 * I4: 20um lines in Cu:Cr over <110> Si, no resist, partial KOH etch not penetrating Si
747 * I7: 20um lines in Cu:Cr over <110> Si, with resist. 747 * I7: 20um lines in Cu:Cr over <110> Si, with resist.
748 * I10: 20um lines in Cu:Cr over <110> Si, with resist, very rough sidewalls 748 * I10: 20um lines in Cu:Cr over <110> Si, with resist, very rough sidewalls
749 749
750 -------------------------------------------------- 750 --------------------------------------------------
751 751
752 Sep 26: 752 Sep 26:
753 753
754 Began tests to determine how to remove Cr adhesion layer from trenches. 754 Began tests to determine how to remove Cr adhesion layer from trenches.
755 755
756 Prepared several dies, <110> with Cu:Cr. Wet etched in SC2 for 5 mins at around 70C, rinsed. No visible surface film, 756 Prepared several dies, <110> with Cu:Cr. Wet etched in SC2 for 5 mins at around 70C, rinsed. No visible surface film,
757 copper was removed after only a few seconds. Subsequent KOH etch failed to attack the surface - Cr must still be there. 757 copper was removed after only a few seconds. Subsequent KOH etch failed to attack the surface - Cr must still be there.
758 758
759 Created new etch bath from 2 ml of conc. HCl. Placed die in at room temp, no attack of copper observed (as expected). 759 Created new etch bath from 2 ml of conc. HCl. Placed die in at room temp, no attack of copper observed (as expected).
760 760
761 Added a couple of drops of 3% H2O2 and stirred. Copper film dissolved rapidly. Left die in etch for several minutes 761 Added a couple of drops of 3% H2O2 and stirred. Copper film dissolved rapidly. Left die in etch for several minutes
762 to allow Cr to etch; then rinsed and etched in KOH. Die etched as expected - this looks like a good etch. Next step 762 to allow Cr to etch; then rinsed and etched in KOH. Die etched as expected - this looks like a good etch. Next step
763 is to test if photoresist can mask it. 763 is to test if photoresist can mask it.
764 764
765 Spin coated several <110> + Cu:Cr dies in 50% SP24. 765 Spin coated several <110> + Cu:Cr dies in 50% SP24.
766 766
767 Exposed 50um line test pattern (4x) for 5 mins. Stepped sideways on die, exposed 20um lines (10x) for 5 mins. 767 Exposed 50um line test pattern (4x) for 5 mins. Stepped sideways on die, exposed 20um lines (10x) for 5 mins.
768 768
769 Etched in low-peroxide HCl:H2O2 for 60 sec. Copper was severely undercut. 769 Etched in low-peroxide HCl:H2O2 for 60 sec. Copper was severely undercut.
770 770
771 Etched in 30% KOH for 5 mins. Looks pretty good, seems that undercut Cu did not translate to damaged Cr. 771 Etched in 30% KOH for 5 mins. Looks pretty good, seems that undercut Cu did not translate to damaged Cr.
772 772
773 Stripped in SC2. Looks good except for some litho defects. Returned to die tray, J2. 773 Stripped in SC2. Looks good except for some litho defects. Returned to die tray, J2.
774 774
775 Exposed 20um lines for 4 mins at 10x, developed. Etched in low-peroxide HCl:H2O2 for 60 sec. 775 Exposed 20um lines for 4 mins at 10x, developed. Etched in low-peroxide HCl:H2O2 for 60 sec.
776 776
777 Etched in 30% KOH for 30 mins:. Done at 00:00 777 Etched in 30% KOH for 30 mins. Cr was etched through in some spots (perhaps HCl etch was too long?) but overall a very
778 good first die.
779
780 Copper was attacked (though some traces were present in sporadic locations). This goes against data reported
781 in several other sources indicating that KOH did not significantly attack copper - no explanation for this deviation yet.
782 Possibly contamination in KOH or impure copper? Both were technical grade (drain cleaner and scrap AC power cord) and
783 the KOH solution had been used several times before on different chips.
784
785 Stripped last remaining Cu residue in SC2 (no attempt made to remove Cr hardmask residue) and photographed. Returned
786 to die tray, J3.
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