Specific Process Knowledge/Characterization/Profiler/Optical Profiler (Sensofar) acceptance test
Results from the Optical Profiler (Sensofar) acceptance test
The acceptance test was performed in January 2012 by STInstruments and Sensofar together with Pernille V. Larsen @ Danchip and Berit G. Herstrøm @ Danchip.
This Table shows an overview of the acceptance tests
| ' | Title | Sample description / measurement | Acceptance criteria |
| 1 | Patterned flat sample of silicon | Sample material: Patterned silicon substrate. | Depth 100±2 µm |
| Trench depth with aspect ratio 1:10 on a 10 µm wide trench | |||
| 2 | Patterned flat sample of silicon. | Sample material: Patterned silicon substrate. | Depth 91±2 µm |
| Trench depth with aspect ratio 1:11 on a 8 µm wide trench | |||
| 3 | Patterned flat sample of silicon | Sample material: Patterned silicon substrate | Depth 85±2 µm |
| Trench depth with aspect ratio 1:13 on a 6.4 µm wide trench | |||
| 4 | Patterned flat sample of glass | 3D profile of pattern etched down in a quartz sample. | Depth within ±1% from a standard profiler measurement and repeatability (3 successive measurements) within 0.1% |
| Pattern size 20 µm x 20 µm, depth 500 nm | |||
| 5 | Flat sample of silicon with thick patterned oxide | Step height of patterned thick (10 µm) oxide on top of a silicon wafer. | Step height must be within ±3% of a SEM profile measurement. |
| 7 µm deep pattern, trench width 6 µm | |||
| 6 | Flat sample of silicon with thick layer of patterned polymer | Sample material: SU8 on silicon. | Height 69±2 µm |
| Pillar heights of 69 µm with 25 µm between pillar edges | |||
| 7 | Free standing structure | Measure bow due to stress of a membrane. | Membrane bow repeatability of 5 successive measurement within 2% |
| Membrane material: Si(2 µm)/SiO2(~1 µm)/Au(50 nm). | |||
| Membrane size: honey comb structure approximately 150 µm in diameter. | |||
| Bow < 500 nm | |||
| 8 | Stitching of large area | Stitching 4 mm x 4 mm on same sample as in 7. The area consists of many closed packed honey comb formed membranes. | Membrane bow must the same as on 7 within 2% |
| 9 | Narrow trenches and holes | Sample material: Patterned silicon substrate. | Depth 20±2 µm |
| 2.5 µm wide trench in silicon with a depth of 20 µm | |||
| 10 | Film thickness measurement of transparent thin film | Transparent thin film thickness of 28 nm SiO2 on Si | SiO2 thickness 28±1 nm |
| 11 | Measurements of multiple stacks | 120 nm nitride on 110 nm oxide on a silicon substrate | Within ±2% on each layer from an ellipsometer measurement. |
| 12 | Film thickness measurements of transparent films on small structure | Sample material: Si with 1.5 µm patterned AZ-resist | Within ±1% from a standard profiler measurement. |
| Measure thickness of AZ-resist on pillars of 50 µm in diameter | |||
| 13 | Roughness repeatability | Sample material: Si wafer with poly-silicon layer. | Repeatability within 0.2% |
| 3 successive measurements of the roughness |
Results of acceptance test no. 1, 2 and 3
Sample material: Patterned silicon substrate
Measurement: Trench depth with aspect ratio 1:10, 1:11 and 1:13 on a 10µm, 8mm and 6.4µm wide trenches respectively
Acceptance criteria:Depth 100±2 µm, 91±2µm and 85±2µm. The SEM profile images of the three trenches are shown here:
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Results
Test no. 1 was done in two ways:
- With confocal objective EPI 100x-N: See the results here
- With Interferometric objective 50X DI: See the results here
Test no. 2 was done using: confocal objective EPI 100x-N: See the results here
Test no. 3 was done using: confocal objective EPI 100x-N: See the results here
Setting for methode no. 1 for test no. 1,2 and 3: confocal
Recipe: Trench
- Operation mode: trench
- + Raw smoothing confocal
- + fine shift
- Objective: EPI 100X-N
- Z scan
- Dual - bottom up
- top: 8µm
- Gap: 91µm (the trench depth)
- Bottom: 8µm
- Speed factor: 1x
- + Linear stage
- Dual - bottom up
- Threshold: 0.0%
- Light source
- Levels: 2
- 900 -> 60 (might need to be set a little different)
- Gain: default
- Levels: 2
Setting for methode no. 2 for test no. 1: interferometric
We do not have a recipe for that but we used:
- Objective: Interferometric 50x DI
- Z scan: VSI
- Light souce: increased gain and contrast
Results of acceptance test no. 4
Sample material: Patterned fused silica.
Measurement: Depth of pattern
Standard profiler measurement:335nm
Acceptance criteria:Depth within ±1% from a standard profiler measurement (331.65nm-338.35nm) and repeatability (3 successive measurements) within 0.1%
System settings:
Objective: DI 50x-N
VSI z scan: 10µm
Treshold: 1%
Results
It was repeated 10 Time.
The first measurement is shown here
This table show the depth value for the 10 measurements
| ' | Measured depth [nm] |
| 1 | 337.5 |
| 2 | 336.5 |
| 3 | 334.7 |
| 4 | 335.5 |
| 5 | 339.2 |
| 6 | 337.2 |
| 7 | 334.2 |
| 8 | 335.5 |
| 9 | 341.1 |
| 10 | 344.4 |
| Average depth | 336.58 |
| Repeatability | 3% (the bad repeatability was accepted due to the high noise level in the room) |
Results of acceptance test no. 5
Sample: Flat sample of silicon with thick patterned oxide.
Measurement: Step height of patterned thick (10 µm) oxide on top of a silicon wafer.The pattern is aprox. 7µm thick
Acceptance criteria: Step height must be within ±3% of a SEM profile measurement. See the SEM profile here:
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Settings:
- Recipe: Acceptance nr. 5 SMR
- Mode: default
- Objective: 50x-DI
- VSI Z scan 18.0µm
- Threshold 2%
- Note: Scan only in the APOX (not in the Si) or else the system will get confused.
See the result here:
Results of acceptance test no. 6
Sample: Flat sample of silicon with thick layer of patterned SU8.
Measure: step height.
Acceptance criteria: Height 69±2 µm
Settings:
- Recipe: Acceptance nr. 6 SMR
- Mode: application Acceptance 6
- Raw smoothing confocal
- Coarse shift single samle
- Reject multiple reflections
- Objective: Confocal EPI 20x-N
- Z scan range: 104µm
- Threshold: 2.0%
See the result here:
Results of acceptance test no. 7
Sample: Free standing structure. Membrane material: Si(2 µm)/SiO2(~1 µm)/Au(50 nm). Membrane size: honey comb structure approximately 150 µm in diameter
Measure: Measure bow due to stress of a membrane.
Acceptance criteria: Membrane bow repeatability of 5 successive measurement within 2%
The sample was not as we suspected. There was almost no bow. The membrane looked broken and it did not really make any sense to measure the bow.
Settings: Two different setting were tried out, the second was the most succesful:
Setting no. 1:
- Objective: DI 50x-N
- PSI
- Threshold 2%
Setting no. 2:
- Objective: DI 50x-N
- Z scan: VSI 10µm
- Threshold: 1.0%
Result
The measurement we did are shown here:
Results of acceptance test no. 8
Measurement: Stitching 4 mm x 4 mm on same sample as in 7.
Sample: The area consists of many closed packed honey comb formed membranes
Acceptance criteria: Membrane bow must the same as on 7 within 2%
Settings:
- Extended topography
- Objective: DI 20x-N
- Z scan: VSI: 40µm
- Threshold: 1.0%
Result:
We made a stitched image of the hole membrane and repeated it two times. It looked much the same but as for test 7 it was hard to do any measurements on it. See the images and profiles in the result file:
Results of acceptance test no. 9
Sample: Patterned silicon substrate.
Measurement: Narrow trench depth
Acceptance criteria: 20±2µm, see the SEM images here:
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Setting
Recipe: Narrow trench
- Operation mode: narrow trench
- Coarse shift single sampling
- Objective: EPI 100X-N
- Z scan:
- Dual - bottom up
- top: 4µm
- Gap: 20µm (the trench depth)
- Bottom: 4µm
- Dual - bottom up
- Speed factor: 1x
- Threshold: 0.0%
- Light source:
- Levels: 2
- 176 -> 30 (might need to be set a little different)
- Gain: default
Result
Results of acceptance test no. 10
Sample: Transparent thin film thickness of 28 nm SiO2 on Si
Measurement:Film thickness measurement of transparent thin film
Acceptance criteria:SiO2 thickness 28±1 nm
Settings
- Objective: EPI 20x-N
- Model: SiO2 thermal
Result
The result was 28.7nm
Results of acceptance test no. 11
Sample:120 nm nitride on 110 nm oxide on a silicon substrate
Measurement:Measurements of multiple stacks
Acceptance criteria: Within ±2% on each layer from an ellipsometer measurement (SiO2: 112nm, Si3N4: 139nm)
Settings Model layers use:
- SiO2_(therm)
- Si3N4
Result
- SiO2: 113.1nm
- Si3N4: 136.9nm
Results of acceptance test no. 12
Sample: Si with 1.4 µm patterned AZ-resist on 50µm pillars
Measurement:Film thickness measurements of transparent films on small structure
Acceptance criteria:Within ±1% from a standard profiler measurement.
Settings
Used Models -> Others -> Cauchy
Options -> Roughness -> change amplitude fitting
Result
Within limits
Results of acceptance test no. 13
Sample: Si wafer with poly-silicon layer
Measurement: Roughness repeatability, 3 successive measurements of the roughness
Acceptance criteria: Repeatability within 0.2%
Note: Because the surface roughness of the sample was very low and the noise/vibration level too high we could not obtain the specified repeatibility.
Result
- The surface roughness (Ra) was 0.5nm
- The repeatebility over 10 measurements was 34%
- The maximum deviation in roughness was 0.2nm
Se the number in the file below: