Characterization is essential to monitoring the fabrication process and, if necessary, changing the process to obtain better results. All final devices need to go through extensive testing to ensure that the device works as designed and to determine the yield of the process.
| 1. The inspection microscope is one of the most useful tools in the characterization lab. In particular it is used to monitor the patterning steps such as photolithography to make sure that patterns are true to the mask used. The computer-interfaced color CCD camera allows students to capture images and save them to disk for documentation and comparison purposes. |  |
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2. The Filmetrics F20 Thin-Film Measurement System can be used to measure film thickness by reflectometry. Most of the time it is used to measure the thickness of oxide layers grown by wet or dry thermal oxidation. |
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3. The Cascade Microtech 4-point probe station is used to measure the sheet resistance of a wafer to assay the doping level within the wafer. The 4-point probe configuration is used instead of a 2-point measurement in order to reduce the effects of contact resistance on the measured values. |
| 4. To make electrical contact to the fine features on the lithographically defined devices, an Alessi probe station is used to position and contact the probe needles. |  |
| 5. Finished devices are electrically tested, typically by measuring their current-voltage (I-V) and capacitance-voltage (C-V) curves. Computer interfaced source-measure units (SMUs) and LCR meters (L = inductance, C = capacitance and R = resistance) are used to collect IV and CV curves, repespectively | .  |