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Rheology Control of Films Deposited by Spin Coating Techniques

IP.com Disclosure Number: IPCOM000080163D
Original Publication Date: 1973-Nov-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Esch, RP: AUTHOR [+2]

Abstract

New semiconductor technologies utilizing projection printing and high-density small-scale structures require close control of photoresist film variables, particularly planarity. Nonplanar photoresist surfaces will cause redistribution of actinic rays by defracting the incident light. The ultimate resolution and uniformity of exposure are affected by the redistribution.

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Rheology Control of Films Deposited by Spin Coating Techniques

New semiconductor technologies utilizing projection printing and high- density small-scale structures require close control of photoresist film variables, particularly planarity. Nonplanar photoresist surfaces will cause redistribution of actinic rays by defracting the incident light. The ultimate resolution and uniformity of exposure are affected by the redistribution.

Controlling the rate of resist evaporation during spinning results in uniform thickness for a resulting film. Short range variations of 300 angstroms to 700 angstroms for 5,000 angstroms thick films of positive photoresist are eliminated by this technique.

Restricting the ambient volume reduces the rate of resist solvent evaporation during spinning and overcomes the redistribution effect. A relatively small ambient volume surrounding the spinning photoresist, provides a larger partial pressure of the solvents spun off as excess photoresist. The film dries slower under these conditions, and must be spun longer to dry. The increased solvent partial pressure prevents air drying of the film surface. Previously the dry film surface forced the underlying liquid to channel radially during spinning, thereby resulting in the observed film thickness variations.

Increased solvent partial pressure may also be obtained by directing vapors over the spinner in a large volume system. Thickness variations of 1500 to 2000 angstroms on films of 15,000 an...