Photodiode Array Through-Hole Design for Aperture Ratio
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Solution Overview
Problem
The existing photodiode arrays face challenges in improving aperture ratio and reliability due to the requirement for sufficient distance between P+-type semiconductor regions, leading to reduced electrical characteristics and potential stress issues.
Innovation Solution
A photodiode array design featuring a first semiconductor region of one conductivity type, a second semiconductor region with higher impurity concentration surrounding the first, and a third semiconductor region of the opposite conductivity type forming a light detection region, with a through-hole passing through both to reduce distance between photodiodes and alleviate stress, while preventing shorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sufficient distance is provided between adjacent P+-type semiconductor regions for through-hole formation, then through-hole fabrication is enabled, but aperture ratio is reduced
Solution Approach 1:
The patent applies nesting by placing the through-hole inside the light detection region formed by the P+-type semiconductor region and n-type semiconductor substrate. The light detection region is configured to surround the through-hole, allowing the through-hole to be nested within the functional detection area rather than requiring separate spacing between regions.
Solution Approach 2:
The patent transitions from a two-dimensional layout where through-holes require lateral spacing between semiconductor regions to a three-dimensional configuration where the light detection region vertically surrounds the through-hole. This dimensional change allows the through-hole to pass through the center of the light detection region, eliminating the need for lateral distance while maintaining fabrication feasibility.
2Ease of operation
If through-holes are provided in semiconductor substrate, then electrode connection is enabled, but surface leakage current increases
Solution Approach 1:
The patent introduces an insulating film as an intermediary substance coating the inner wall of the through-hole. This insulating film acts as a mediator between the conductive electrode and the semiconductor substrate, preventing direct contact that would cause leakage current while still allowing electrical connection through the through-hole structure.
Solution Approach 2:
The patent extracts the harmful interaction between the electrode and semiconductor substrate by removing the direct conductive path along the through-hole wall. The insulating film is applied to the inner wall to extract or eliminate the leakage pathway, separating the electrode from direct contact with the semiconductor surface.
3Ease of operation
If through-holes are provided in semiconductor substrate, then electrode connection is enabled, but stress concentration occurs
Solution Approach 1:
The patent applies beforehand cushioning by filling the through-hole with an insulating film before inserting the electrode. This insulating film acts as a cushioning layer that distributes and reduces stress concentration on the semiconductor substrate, preventing crack propagation and strengthening the overall structure while maintaining electrode connectivity.
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 configuration enhances the aperture ratio, reduces surface leakage current, and improves the strength and reliability of the photodiode array by minimizing stress and preventing shorting between semiconductor regions.
Implementation Method 1
The second semiconductor region through which the through-hole passes has an impurity concentration higher than the impurity concentration of the first semiconductor region. Therefore, a surface leakage current generated in the inner wall of the through-hole and directed toward the light detection region can be reduced by the second semiconductor region.
Implementation Method 2
a third semiconductor region of a second conductivity type, provided with respect to the first semiconductor region on the one surface side so as to surround the second semiconductor region separately from the second semiconductor region, and constituting a light detection region together with the first semiconductor region
Data Source
AI summary
A photodiode array includes a plurality of photodiodes formed in a semiconductor substrate. Each of the photodiodes includes a first semiconductor region of a first conductivity type, a second semiconductor region of the first conductivity type, provided with respect to the first semiconductor region on one surface side of the semiconductor substrate, and having an impurity concentration higher than an impurity concentration of the first semiconductor region, a third semiconductor region of a second conductivity type, provided with respect to the first semiconductor region on the one surface side so as to surround the second semiconductor region separately from the second semiconductor region, and constituting a light detection region together with the first semiconductor region, and a through-electrode provided within a through-hole passing through the first semiconductor region and the second semiconductor region, and electrically connected to the third semiconductor region.