Curved Silicon Detector Fabrication via Gray Tone Lithography
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Solution Overview
Problem
Current optical imaging systems with flat focal plane detectors face challenges such as optical aberrations, weight, and limited spectral range due to the need for multiple lenses to correct for spherical aberrations, which restricts field of view and leads to non-uniform illumination.
Innovation Solution
A method using gray tone lithography in combination with plasma etching to shape silicon into a curved surface, allowing for the fabrication of focal plane arrays that match the contour of optical devices like telescopes, thereby reducing aberrations and improving field of view without mechanical bending, which is prone to breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flat focal plane detectors are used, then manufacturing is simpler, but optical aberrations increase and field of view is limited
Solution Approach 1:
The patent applies curvature to the focal plane detector surface to match the curved focal surface of optical systems. This resolves the contradiction by accepting the increased manufacturing complexity of curved surfaces in exchange for dramatically reduced optical aberrations and improved field of view, eliminating the need for multiple corrective lenses.
2Manufacturing precision
If multiple lenses are added to correct spherical aberrations, then image quality improves, but system weight and complexity increase
Solution Approach 1:
The patent extracts the aberration correction function from the optical path by placing the curvature directly on the detector surface rather than using separate corrective lenses. This eliminates multiple optical elements while maintaining image quality, thereby reducing system weight and complexity.
3Shape
If mechanical bending is used to create curved detectors, then the desired curvature is achieved, but device reliability decreases due to breakage risk
Solution Approach 1:
The patent performs preliminary action by creating the curved shape during the semiconductor fabrication process itself, before the detector is fully assembled and operational. This prevents the need for post-fabrication mechanical bending that could cause breakage, thereby maintaining high reliability while achieving the required curvature.
4Adaptability or versatility
If curved focal plane arrays are implemented, then field of view and spectral range improve, but manufacturing complexity increases
Solution Approach 1:
The patent replaces mechanical post-fabrication bending with a semiconductor fabrication-based shaping process. This substitution integrates curvature creation into the standard manufacturing flow, reducing overall system complexity despite the added precision requirements in the fabrication process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the production of curved silicon detectors with good charge collection and energy resolution, reducing the need for complex optics and improving the spectral range and field of view while maintaining low production costs.
Implementation Method 1
Gray-Tone Lithography Using Optical Diffusers
Implementation Method 2
a plasma etching operation to etch the silicon to a desired shape
Data Source
AI summary
Gray tone lithography is used to form curved silicon topographies for semiconductor based solid-state imaging devices. The imagers are curved to a specific curvature and shaped directly for the specific application; such as curved focal planes. The curvature of the backside is independent from the front surface, which allows thinning of the detector using standard semiconductor processing.