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Calibration wafers

Danchip has three calibration wafers for the KLA-Tencor Surfscan. The calibration wafers are 6" silicon wafer with a number of polystyrene latex spheres (PLS) uniformily spread over the surface.

Certified mean diameter and number PLS's:

Calibration wafer 1:

PLS mean diameter: 0.204 µm +/- 0.008 µm
Number of PLS's: 7234 +/- 10%

Calibration wafer 1:

PLS mean diameter: 1.112 µm +/- 0.018 µm
Number of PLS's: 7700 +/- 10%

Calibration wafer 1:

PLS mean diameter: 4.000 µm +/- 0.043 µm
Number of PLS's: 7587 +/- 10%

Repeatability check

Acceptance criterion:

10 scans are done on each of the three PLS calibration wafers. The wafers are loaded/unloaded to the cassette every time. The the repeatbility of +/- 1σ has to be less than 1%.

Results

Calibration wafer 1:

Measured average PLS diameter: 0.2063 µm Repeatability: 0,24%

Average number of PLS's: 7065 Repeatability: 0.11%

Calibration wafer 2:

Measured average PLS diameter: 1.100 µm Repeatability: 0%

Average number of PLS's: 7427 Repeatability: 0.20%

Calibration wafer 3:

Measured average PLS diameter: 3.970 µm Repeatability: 0,24%

Average number of PLS's: 7101 Repeatability: 0.10%

Uniformity check

Acceptance criterion:

Measure the average PSL diameter by boxing an area in five different locations on a PLS wafer. The measurement has to be within 3%.

Results

Calibration wafer 2:

Non-uniformity: 1,36%

Calibration wafer 3:

Non-uniformity: 0.38%

Handling test

Acceptance criterion:

Run a cassette of 25 wafers. The machine should be able to error-free handle the cassette 40 times, i.e. it should be able to handle 1000 wafers withot faling.

Results

6" cassette":

A cassette of 25 wafers was handled 40 times over night, i.e. the acceptance criterion was meet.

4" and 8" cassette:

A cassette of 25 wafers was handled two times. The scanning was then stopped to save time as we do not expect handling of more cassettes to caused problem.-s