photolithography
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| photolithography [2023/05/16 13:14] – dublin | photolithography [2024/03/19 14:27] (current) – dublin | ||
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| (2) Set spinner to 4000 RPM (ramp rate = 1000 R/s). | (2) Set spinner to 4000 RPM (ramp rate = 1000 R/s). | ||
| - | (3) Cleanly pipette P20 and drop onto chip; wait about 30 s. for solution to spread. Spin for 45 s. | + | (3) Cleanly pipette P20 and drop onto chip; wait about 30 s. for solution to spread. Spin for 45 s. NOTE: According to the manufacturer, |
| (4) Cleanly pipette LOR onto center of chip. Immediately spin for 45 s. | (4) Cleanly pipette LOR onto center of chip. Immediately spin for 45 s. | ||
| Line 28: | Line 28: | ||
| (8) Edge bead removal: The edges of the chip will have built-up photoresist that is many times thicker than the rest of the chip. Edge bead removal is particularly important for fine features on small substrates, as edge beads prevent the chip from fully contacting the mask. | (8) Edge bead removal: The edges of the chip will have built-up photoresist that is many times thicker than the rest of the chip. Edge bead removal is particularly important for fine features on small substrates, as edge beads prevent the chip from fully contacting the mask. | ||
| - | Try carefully scraping | + | Try putting a tiny amount of Remover PG on the tip of a swab and wiping it on a betawipe, then swab your edges at a 45 deg. angle to remove edge beads. |
| (II) Exposure | (II) Exposure | ||
| Line 39: | Line 39: | ||
| Note: warning light will blink for about 1 minute. If it blinks longer the bulb needs to be replaced. | Note: warning light will blink for about 1 minute. If it blinks longer the bulb needs to be replaced. | ||
| - | (3) Carefully insert mask, with purple side facing sample. Add chip and align properly. Exposure time is 10-12 s. ~~Update Dublin 2022 ECE 418 aligner is no longer in use. The other aligner has less than half the light power, around 6 mW/cm^2, requiring over twice the exposure time (ECE418: 3-4 s. New aligner, 10-12 s.) | + | (3) Carefully insert mask, with purple side facing sample. Add chip and align properly. Exposure time is 10-12 s. |
| - | If using LOR, expose for 10 seconds | + | |
| + | ~~Update Dublin 2022: ECE 418 aligner is no longer in use. The other aligner has less than half the light power, around 6 mW/cm^2, requiring over twice the exposure time (ECE418: 3-4 s. New aligner, 10-12 s.) | ||
| (4) After all exposures, remove mask. Turn off bulb but leave N2 on until system is cool (30 minutes). If necessary, clean mask with acetone/ | (4) After all exposures, remove mask. Turn off bulb but leave N2 on until system is cool (30 minutes). If necessary, clean mask with acetone/ | ||
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| May 2023: | May 2023: | ||
| - | Development time for LOR: I found that using this recipe, but with 12 second exposure at 6 mJ/cm^2 and 100 seconds development gave a ~0.3 um undercut. - Dublin | + | Development time for LOR: Baking LOR at 180C, 12 second exposure at 6 mJ/cm^2, and 100 seconds development gave a ~0.3 um undercut. - Dublin |
| ===SU-8 Photoresist=== | ===SU-8 Photoresist=== | ||
| - | * SU-8 is a polymer like negative photoresist. | + | * SU-8 is a polymer-like negative photoresist. |
| * We use SU-8 in liquid gated GFETs as a passivation layer to protect metal leads from the gate electrolyte. | * We use SU-8 in liquid gated GFETs as a passivation layer to protect metal leads from the gate electrolyte. | ||
| * Read the SU-8 process guide for SU-8 2002 [[https:// | * Read the SU-8 process guide for SU-8 2002 [[https:// | ||
photolithography.1684268084.txt.gz · Last modified: 2023/05/16 13:14 by dublin