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This document describes the standard procedure for measuring film thickness from PVD systems, as used for tool qualifications, etc., using the standard witnessspecimenchip and contact profilometry:The standard witness specimen chip is a Si chip, 10 mm × 10 mm, with patterned LOR 5B / AZ 1512 bilayer; in the above image, pink areas correspond to windows in the resist (i.e., where deposited material will remain after lift-off). The bottom row of patterned regions consists of gratings which are suitable for film thickness measurement with the Alpha-Step IQ profilometer. |
Deposition
- Mount a nanoFAB witness specimen in the deposition chamber. If it is necessary to clip the specimen to a platen, position the clip in the top-right quarter (large region of resist which will be lifted off).
- Perform the deposition as normal. A nominal film thickness of ~200 nm is recommended to ensure the film is thick enough to obtain a good measurement (sufficient signal to noise ratio).
Lift-off
- Perform lift-off by sonicating the specimen in a small beaker of Remover PG, using the Branson 200 ultrasonic cleaner. A single 5-minute cycle should be sufficient to remove the bulk of the metal; a second 5-minute cycle may be necessary to clear the large region in the top-right corner.
- Rinse the specimen with IPA, then DI water, then dry with N2 gun.
- Typical specimen appearance after lift-of:
Contact profilometry
- Load the specimen in the Alpha-Step IQ in the cleanroom. Position the stylus to measure across the 50 µm gratings, shown outlined in red in the above image.
- Use the following scan parameters:
- Scan Length: 300 µm, 1 Time
- Scan Speed: 10 µm/s
- Sampling Rate: 1000 Hz
- Sensor Range: 20 µm / 1.19 pm
- Analysis: Step Height Analysis
- Contact Speed: 3
- Scan Direction: →
- Perform a scan.
- Perform levelling with 2 zones:
- Right-click the levelled plot and choose Automatic Method:
- The film thickness will be displayed in the HeightMean field of the analysis results.