Specific Process Knowledge/Lithography/Pretreatment: Difference between revisions
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'''Dehydration:''' | '''Dehydration:''' | ||
A dehydration bake immediately before spin coating removes the moisture adsorbed to the surface, and greatly improves the adhesion of resist on most surfaces. For thin hydrophilic layers, a few minutes on a hotplate at or above 100°C may suffice. For thicker layers or bulk oxide samples, a dehydration bake at 250°C over night is recommended. | A dehydration bake immediately before spin coating removes the moisture adsorbed to the surface, and greatly improves the adhesion of resist on most surfaces. For thin hydrophilic layers, a few minutes on a hotplate at or above 100°C may suffice. For thicker layers or bulk oxide samples, a dehydration bake at 250°C over night is recommended. | ||
'''BHF dip:''' | '''BHF dip:''' | ||
Stripping the native oxide using BHF only works if the native oxide of the substrate is etched by BHF, and if resist has good adhesion to the substrate material itself, which basically narrows it down to silicon. | Stripping the native oxide using BHF only works if the native oxide of the substrate is etched by BHF, and if resist has good adhesion to the substrate material itself, which basically narrows it down to silicon. | ||
'''HMDS:''' | '''HMDS:''' | ||
In the HMDS priming process, the -OH groups on the surface of the substrate are replaced with Si(CH<sub>3</sub>)<sub>3</sub>, thus changing the surface from hydrophilic to (more) hydrophobic. Substrates with surfaces of silicon or it's oxides or nitrides all work very well with HMDS pretreatment. Other semiconductors, insulators, or metals that form -OH groups on the surface may be suitable as well. | In the HMDS priming process, the -OH groups on the surface of the substrate are replaced with Si(CH<sub>3</sub>)<sub>3</sub>, thus changing the surface from hydrophilic to (more) hydrophobic. Substrates with surfaces of silicon or it's oxides or nitrides all work very well with HMDS pretreatment. Other semiconductors, insulators, or metals that form -OH groups on the surface may be suitable as well. | ||
'''Dip/spin-on adhesion promoter:''' | '''Dip/spin-on adhesion promoter:''' | ||
Adhesion promoters for dip or spin-on application are commercially available. Most are solvent based with some, usually proprietary, additives. They work by first cleaning the substrate surface, and subsequently priming the surface with the additives as the solvent evaporates. | Adhesion promoters for dip or spin-on application are commercially available. Most are solvent based with some, usually proprietary, additives. They work by first cleaning the substrate surface, and subsequently priming the surface with the additives as the solvent evaporates. | ||