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Coating Solvent For Polysulfone

IP.com Disclosure Number: IPCOM000048795D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Baise, AI: AUTHOR

Abstract

Polysulfone is a polymer used as a lift-off layer for various applications in the semiconductor art as multilevel metallization and for top surface metallization, etc. This polymer is generally used as a solution in a 50/50 mixture of diglyme and N-methylpyrrolidone (NMP) solvents, and it is applied to substrates by spin coating to give films up to approximately 3 Mum in thickness.

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Coating Solvent For Polysulfone

Polysulfone is a polymer used as a lift-off layer for various applications in the semiconductor art as multilevel metallization and for top surface metallization, etc. This polymer is generally used as a solution in a 50/50 mixture of diglyme and N-methylpyrrolidone (NMP) solvents, and it is applied to substrates by spin coating to give films up to approximately 3 Mum in thickness.

One problem encountered in using this polymer is the inability to spin-coat films under conditions of high relative humidity (approximately 45 percent RH and higher). Both NMP and diglyme (but especially NMP) will absorb water, and this absorption at high relative humidities can cause the polymer to precipitate out of solution, giving rise to a milky-white film.

One solution to this problem is the use of an alternative solvent system, viz acetophenone. Experiments carried out have shown that this solvent absorbs five times less water than NMP under comparable conditions. This difference in moisture absorption allows the use acetophenone without any accompanying precipitation of polymer.

The following test method was used to demonstrate the effectiveness of acetophenone:
Polysulfone solutions were spin-coated onto silicon wafers at 2000 rpm for 30 seconds. The wafers were not heated but were placed immediately in a chamber at 25 degree C and 85 percent RH. The time required to produce a milky-white cloudiness was then measured. The following table summariz...