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 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
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 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


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


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%

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:

Sensofar A13 result

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