MULTI-FOCUS METHOD OF ENHANCED THREE-DIMENSIONAL EXPOSURE OF RESIST
First Claim
1. A method of forming a three-dimensional latent image with good depth and shape control in a thick resist layer applied over a workpiece surface, the method including:
- using in the thick resist layer a positive resist;
selecting multiple focal planes at which to focus exposing energy, wherein at least one of the focal planes is in a lower half of the thick resist layer, the lower half being the half that is further from a surface to which exposing energy is applied;
converting a relief map that represents a three-dimensional surface into point-by-point and layer-by-layer exposure doses calculated to exceed an exposure threshold of the positive resist at a plurality of controlled depths within the resist layer, taking into account a numerical aperture value to be used during patterning, producing an exposure map; and
patterning the resist layer using the multiple focal planes to form a three-dimensional latent image using a pattern generator that varies effective exposure doses on a point-by-point basis using the exposure map.
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Accused Products
Abstract
The field of this disclosure is making three-dimensional topographic structures by means of graduated exposure in a photosensitive material, such as a photoresist, photosensitive polymide, or similar. Such patterns may be written either to be used directly as optical, mechanical, fluidic, etc. components, e.g. diffusors, non-reflecting surfaces, Fresnel lenses and Fresnel prisms, computer-generated holograms, lenslet arrays, etc, or to be used as masters for the fabrication of such components by replication. Replication can be done by molding, pressing, embossing, electroplating, etching, as known in the art. This disclosure includes descriptions of using passive absorbing components in thin resist, using high gamma thick resists with high resolution pattern generators, using multiple focal planes including at least one focal plane in the bottom half of the resist, and iterative simulation of patterning and adjustment of an exposure map.
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Citations
17 Claims
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1. A method of forming a three-dimensional latent image with good depth and shape control in a thick resist layer applied over a workpiece surface, the method including:
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using in the thick resist layer a positive resist; selecting multiple focal planes at which to focus exposing energy, wherein at least one of the focal planes is in a lower half of the thick resist layer, the lower half being the half that is further from a surface to which exposing energy is applied; converting a relief map that represents a three-dimensional surface into point-by-point and layer-by-layer exposure doses calculated to exceed an exposure threshold of the positive resist at a plurality of controlled depths within the resist layer, taking into account a numerical aperture value to be used during patterning, producing an exposure map; and patterning the resist layer using the multiple focal planes to form a three-dimensional latent image using a pattern generator that varies effective exposure doses on a point-by-point basis using the exposure map. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification