Specific Process Knowledge/Characterization/Profiler/Optical Profiler (Sensofar) acceptance test

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Results from the Optical Profiler (Sensofar) acceptance test

The acceptance test was performed in January 2012 by ST Instruments and Sensofar together with Pernille V. Larsen@ DTU nanolab and Berit G. Herstrøm @ DTU nanolab.

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 Trench depth with aspect ratio 1:10 on a 10 µm wide trench	Depth 100±2 µm
2	Patterned flat sample of silicon.	Sample material: Patterned silicon substrate Trench depth with aspect ratio 1:11 on a 8 µm wide trench	Depth 91±2 µm
3	Patterned flat sample of silicon	Sample material: Patterned silicon substrate Trench depth with aspect ratio 1:13 on a 6.4 µm wide trench	Depth 85±2 µm
4	Patterned flat sample of glass	3D profile of pattern etched down in a quartz sample. Pattern size 20 µm x 20 µm, depth 500 nm	Depth within ±1% from a standard profiler measurement and repeatability (3 successive measurements) within 0.1%
5	Flat sample of silicon with thick patterned oxide	Step height of patterned thick (10 µm) oxide on top of a silicon wafer. 7 µm deep pattern, trench width 6 µm	Step height must be within ±3% of a SEM profile measurement.
6	Flat sample of silicon with thick layer of patterned polymer	Sample material: SU8 on silicon. Pillar heights of 69 µm with 25 µm between pillar edges	Height 69±2 µm
7	Free standing structure	Measure bow due to stress of a membrane. Membrane material: Si(2 µm)/SiO2(~1 µm)/Au(50 nm) Membrane size: honey comb structure approximately 150 µm in diameter Bow < 500 nm	Membrane bow repeatability of 5 successive measurement within 2%
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 2.5 µm wide trench in silicon with a depth of 20 µm	Depth 20±2 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 Measure thickness of AZ-resist on pillars of 50 µm in diameter	Within ±1% from a standard profiler measurement.
13	Roughness repeatability	Sample material: Si wafer with poly-silicon layer 3 successive measurements of the roughness	Repeatability within 0.2%

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

Results

Test no. 1 was done in two ways:

1. With confocal objective EPI 100x-N: See the results here
2. 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

Settings 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 (<- choose 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 source: increased gain and contrast

Results of acceptance test no. 4

Sample material: Patterned flat sample of glass

Measurement: Depth of pattern

Standard profiler measurement:335 nm

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%

Average 4 images (to reduce noise)

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]	Repeated 20170925 with cover off	Repeated 20180816 after repair
1	337.5	347.9	341.1
2	336.5	333.9	340.4
3	334.7	341.5	337.2
4	335.5	343.2	330.8
5	339.2	347.7	339.0
6	337.2	345.4	340.0
7	334.2	341.8	338.8
8	335.5	337.9	339.8
9	341.1	342.1	334.6
10	344.4	335.9	336.4
Average depth	337.58	341.73	337.82
Repeatability	3.0% (the bad repeatability was accepted due to the high noise level in the room)	4.1%	3.0%

Results of acceptance test no. 5

Sample: Flat sample of silicon with thick patterned oxide (APOX).

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 successful:

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%

Note: Because the surface roughness of the sample was very low and the noise/vibration level too high we could not obtain the specified repeatability.

Result

• The surface roughness (Ra) was 0.5nm
• The repeatability over 10 measurements was 34%
• The maximum deviation in roughness was 0.2nm

Se the number in the file below:

Sensofar A13 result