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%

It was done using interferometric measurements:

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

See the results here:

Sensofar A5 result