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 the acceptance criteria

'	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:

A1	A2	A3

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
Threshold: 0.0%
Light source
- Levels: 2
  - 900 -> 60 (might need to be set a little different)
  - Gain: default

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:

A5

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:

Sensofar A5 result

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:

Sensofar A6 result no. 1	Sensofar A6 result no. 2

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:

Sensofar A7 result

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:

Sensofar A8 result

Results of acceptance test no. 9

Sample: Patterned silicon substrate.

Measurement: Narrow trench depth

Acceptance criteria: 20±2µm, see the SEM images here:

SEM profile image of structure

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
Speed factor: 1x
Threshold: 0.0%
Light source:
- Levels: 2
- 176 -> 30 (might need to be set a little different)
Gain: default

Result

Sensofar A9 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%

Result 5% ~0.3Å repeatability.