Specific Process Knowledge/Lithography/4562
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AZ 4562 is a positive UV photoresist for thick coatings (5µm and above).
Priming
Spin coating
The thickest coating using a normal spin cycle is probably 10-15µm. However, reducing the spin-off time to a few seconds at 2000rpm has successfully been used to increase the coating thickness beyond 20µm on a Gamma coater. The substrate is rested for 1min before softbake in order to reduce the edge bead height.
Exposure
In order to avoid heating during exposure, leading to the formation of bubbles, it is recommended to use multiple exposure, limiting the exposure time for each cycle to 10-15s, and using a 10-15s pause between cycles.
Development
The recommended development speed for AZ 4562 is 2µm/min. A 6.2µm resist film thus requires 3min development, usually as three 60s puddles of TMAH (AZ 726 MIF). 10µm AZ 4562 has successfully been developed using 4x60s development