Before apply photoresist I follow 6-step simple cleaning
1. Acetone 10min
2. Methanol 10min
3. IPA 10min
4. DI water rinse
5. N2 blow dry
6. Bake in 150 degree oven for 15min
The substrate is InAs, GaSb and InAsSb. I was thought Acetone can dissolve organic compounds but evaporated fast and leave many residual. Methanol will absorb the residual from Acetone and leave less residual. Then IPA will give even less residual and DI water can wash the acetone. finally, high temperature bake in oven will dehydrate the wafer surface.
Recently, I want to apply HMDS to enhance the adhesion. But I also found that a document mentioned that DI water is not necessary and may damage the cleaning effect.[1] So, I tried to clean without DI water and N2 blow dry. Then observe the wafer surface under a DIC microscope. It shows that there are many small residuals on the surface. But after DI water rinse, the surface is perfect clean.
Thus, I have three questions.
1. Does the DI water rinse may cause side effect?
2. Is it possible to N2 blow dry after cleaning with IPA without residual? could there exist some trick that I don’t know?
3. Because HMDS need a dehydrate surface, is the DI rinse specifically forbidden for cleaning procedure before applying HMDS?
[1] Microchemical - substrate preparatio https://www.microchemicals.com/technical_information/substrate_cleaning_adhesion_photoresist.pdf
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