Post-exposure heat treatment to reduce surface roughness of PMMA surfaces formed by radiation lithography
AssigneeBoard of Supervisors of Louisiana State University and Agricultural and Mechanical College
InventorsKun Lian, Zhong-Geng Ling
Life of this patent
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Abstract
A method to decrease the surface roughness of exposed PMMA surfaces has been discovered. PMMA surface roughness was decreased by a post-exposure heat treatment of less than 70° C. The optimum post-exposure heat treatment to produce a PMMA microstructures with a smooth surface was found to be about 60° C. for about 30 min. The structural features of post-exposure heat-treated PMMA patterns were not statistically different from otherwise identical features of untreated PMMA patterns. This method produces a smoother PMMA structure that may then optionally be glued on a substrate or that may be assembled with other PMMA structures into a three-dimensional or multilayer microstructure.
Claims21
A method for producing a microstructure in a poly(methyl methacrylate) resist attached to a substrate during radiation exposure, comprising the steps of:
- (a) exposing the resist to radiation in a pattern corresponding to the microstructure, wherein the irradiation suffices to form a latent image in the resist;
- and
- (b) heating the resist with the latent image to a temperature between about 40° C. and about 65° C.;
- and
- (c) developing the latent image to produce a poly(methyl methacrylate) microstructure;
- wherein:
- (d) the duration of said heating step is sufficient to reduce the surface roughness of the produced microstructure substantially below the surface roughness of a microstructure that would be produced by an otherwise identical method that omits said heating step.
A method for producing a microstructure in a poly(methyl methacrylate) resist freestanding during radiation exposure, comprising the steps of:
- (a) exposing the resist to radiation in a pattern corresponding to the microstructure, wherein the irradiation suffices to form a latent image in the resist;
- and
- (b) heating the resist with the latent image to a temperature between about 40° C. and about 65° C.;
- (c) attaching the resist to a substrate;
- and
- (d) developing the latent image to produce a poly(methyl methacrylate) microstructure;
- wherein:
- (e) the duration of said heating step is sufficient to reduce the surface roughness of the produced microstructure substantially below the surface roughness of a microstructure that would be produced by an otherwise identical method that omits said heating step.
A poly(methyl methacrylate) microstructure comprising at least one feature having a characteristic dimension less than about 10 μm in at least one direction, wherein said microstructure has a root mean square bottom surface roughness less than about 0.1 μm.
Dependencies are inferred from the claim text.