System and method for analog replication of microdevices having a desired surface contour

Abstract

A master wafer is replicated by creating a mold by plating a nickel electroform on a surface of a silicon wafer. Thereafter, a child wafer is prepared with a layer of photoresist or similar material that is compatible with plasma-etching techniques. Thereafter, the mold shape is transferred to the photoresist through compression molding, thereafter the child wafer is etched.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates generally to a replication technique for use in reproducing surface contours in devices, such as microdevices. Specifically, the present invention is directed to a method of making a master wafer whereby the master wafer is replicated and used to produce hi-fidelity copies. [0003] 2. Description of Related Art [0004] Conventional gray scale etching processes enable the creation of various shapes and curves, both symmetric and asymmetric, thereby lending itself well for the use in fabrication of micro-optical systems. Traditional binary optics, such as RIE (Reactive Ion Etching) and DRIE (Deep Reactive Ion Etching) utilizes step etches which are used to approximate a smooth curve. However, gray scale etching processes can actually create smooth curves such as smooth ramps, lens, torroids, turbo machines, gears, and other complex shapes. [0005] The utilization of gray scale optics in the formati...

AI Technical Summary

Benefits of technology

This approach significantly reduces the need for parameter adjustments and ensures high-fidelity replication of micro-optical structures, improving yield and consistency in manufacturing by producing wafers with precise surface characteristics.

Problems solved by technology

However, gray scale etching processes can actually create smooth curves such as smooth ramps, lens, torroids, turbo machines, gears, and other complex shapes.

However, differential ion milling has the disadvantage of not being able to readily perform the deep etching necessary to form the structures necessary for micro-lenses or turbine rotors.

Standard gray scale techniques, such as that of Gal, allow the etching of shallow (<100 μm) structures, but have the disadvantage of needing thick layers of photoresist, wherein approximately 20 μm layer of photoresist is required to produce a 100 μm structure, for example.

However, there are at least two main sources of errors that plague the surface profile of structures, in photosensitive materials, resulting from a gray scale or analog lithography process.

The first source of error arises from general roughness in the surface of the photosensitive material.

This error may be caused by the slight variations in the dose of the writing tool, usually an electron beam (e-beam) or laser.

In the case of the half tone process, the chosen pixel shape scheme may cause this error.

The second source error is the stitching error, i.e., it is geometric and is induced by slight variations in the positioning and size of the writing tool.

Stitching error is due to slight inaccuracies of the stage and field of the writing tool.

The stage of the writing tool refers to the horizontal sweep, wherein slight variation in the positioning of the horizontal line results in stitching error.

The field refers to the width of the writing line, wherein variation in the width of the writing line also results in stitching error.

The stitching error is of low frequency period and manifests itself in the slight vertical lines in the surface

Unfortunately, the patterning process also drifts and the associated parameters must be adjusted to compensate for this drift.

The combination of etching and patterning process variants unfortunately translates into extremely low yield.

For this reason, for customers requiring high-volume, the issues of cost, consistency, and quality become significant.

Images