Silicon Substrate Protrusions for Ultraviolet Range Sensor Sensitivity
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Solution Overview
Problem
Existing range sensors have limited spectral response in the ultraviolet wavelength band, which affects their performance in detecting ultraviolet light.
Innovation Solution
A range sensor design featuring a silicon substrate with protrusions on the second principal surface, where the (111) plane is exposed, and an anti-reflection film, enhancing light absorption and reducing dark current, thereby improving spectral response in the ultraviolet wavelength band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional flat silicon substrate surface is used, then the manufacturing process is simple, but the spectral response in ultraviolet wavelength band is poor
Solution Approach 1:
The invention applies curvature by forming protrusions with inclined surfaces on the silicon substrate instead of using a flat surface. The inclined surfaces of the protrusions cause incident ultraviolet light to be reflected at angles that increase the optical path length within the substrate, thereby enhancing absorption and spectral response in the ultraviolet wavelength band.
Solution Approach 2:
The invention changes the physical parameters of the substrate surface by creating protrusions with specific geometric parameters (height, inclination angle, spacing). These parameter changes modify the optical characteristics of the substrate, improving ultraviolet light absorption while maintaining compatibility with standard manufacturing processes.
2Reliability
If the silicon substrate surface is made irregular to enhance light absorption, then spectral response improves, but manufacturing precision requirements increase
Solution Approach 1:
The continuous silicon substrate surface is segmented into multiple discrete protrusions. Each protrusion can be independently formed using standard photolithography and etching techniques, allowing for controlled variation in dimensions while maintaining overall pattern fidelity. This segmentation approach reduces the cumulative precision requirements compared to forming a continuous irregular surface.
Solution Approach 2:
By optimizing the parameters of the protrusions (such as height, base width, and spacing), the invention achieves effective light absorption enhancement within the capabilities of standard manufacturing tolerances. The parameter optimization ensures that even with normal manufacturing variations, the optical performance remains above acceptable thresholds.
3Measurement precision
If protrusions are added to the silicon substrate, then ultraviolet detection sensitivity increases, but device complexity and fabrication steps increase
Solution Approach 1:
The invention applies the protrusion structure only in specific local regions where ultraviolet detection is required, rather than modifying the entire substrate uniformly. This localized application of structural modification enhances ultraviolet sensitivity in critical areas while minimizing the overall impact on device complexity and fabrication process.
Solution Approach 2:
The invention optimizes the parameters of existing fabrication steps (such as etch depth, photolithography exposure conditions, and deposition thickness) to form protrusions without requiring entirely new process equipment or methods. By adjusting parameters within existing process windows, the invention achieves enhanced ultraviolet detection sensitivity while adding minimal complexity to the fabrication workflow.
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
The design significantly enhances spectral response in both ultraviolet and near-infrared wavelength bands, improving photodetection sensitivity and accuracy in distance measurement.
Implementation Method 1
the slope is inclined with respect to the thickness direction of the silicon substrate. Therefore, for example, light reflected on the slope side of one protrusion is directed to the slope side of a protrusion adjacent to the one protrusion, and is incident on the silicon substrate from the slope of the adjacent protrusion
Implementation Method 2
Since the height of the protrusion is equal to or more than 200 nm, a surface area of the slope is large. Therefore, a large amount of light incident on the slope is taken into the silicon substrate
Implementation Method 3
The silicon substrate is provided with a charge generation region configured to generate a charge in response to incident light
Data Source
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AI summary
A range sensor includes a silicon substrate and a transfer electrode. The silicon substrate includes a first principal surface and a second principal surface opposing each other. The silicon substrate is provided with a charge generation region configured to generate a charge in response to incident light and a charge collection region configured to collect charges from the charge generation region, on the first principal surface side. The transfer electrode is disposed between the charge generation region and the charge collection region on the first principal surface. The transfer electrode causes the charge to flow from the charge generation region into the charge collection region in response to an inputted signal. A region of the second principal surface corresponding at least to the charge generation region is formed with a plurality of protrusions. The plurality of protrusions includes a slope inclined with respect to a thickness direction of the silicon substrate. A (111) plane of the silicon substrate is exposed as the slope at the protrusion. A height of the protrusion is 200 nm or more.