Pixel Separation Structure for Area-Efficient Solid-State Imaging
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Solution Overview
Problem
Existing solid-state imaging elements face challenges in maintaining area efficiency due to the presence of deep element separation sections that reduce the effective pixel size for optical and electrical separation between pixels.
Innovation Solution
The implementation of a semiconductor substrate with first and second element separation sections having different configurations, including a p+++ region with high impurity concentration, which defines the active region of the pixel transistor, preventing the area efficiency from being compromised by deep element separation sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a deep element separation section is provided for optical and electrical separation between pixels, then separation effectiveness is improved, but area efficiency deteriorates
Solution Approach 1:
The element separation section is divided into two distinct parts: a first element separation section with a first semiconductor region and a second element separation section with a second semiconductor region having different impurity concentrations. This segmentation allows each part to perform specific functions - the first section provides basic separation while the second section with different impurity concentration enhances optical and electrical separation effectiveness, thereby achieving reliable pixel separation without requiring a single deep separation structure that would reduce area efficiency.
Solution Approach 2:
Different semiconductor regions are used in different locations of the element separation section. The first semiconductor region in the first element separation section has one impurity concentration, while the second semiconductor region in the second element separation section has a different impurity concentration. This local quality variation optimizes the separation characteristics in different areas, enabling effective optical and electrical separation between pixels while maintaining compact dimensions for high area efficiency.
2Area of stationary object
If the pixel size is reduced to improve area efficiency, then area efficiency is improved, but optical and electrical separation between pixels deteriorates
Solution Approach 1:
The impurity concentration parameter is changed between the first and second semiconductor regions. The first semiconductor region has a first impurity concentration while the second semiconductor region has a second impurity concentration that is different from the first. This parameter change enables the second element separation section to provide enhanced optical and electrical separation characteristics, allowing compact pixel sizes for high area efficiency while maintaining effective separation between pixels.
Data Source
AI summary
A solid-state imaging element of an embodiment of the present disclosure includes: a semiconductor substrate including a photoelectric conversion section for each pixel; a pixel transistor provided on one surface of the semiconductor substrate; and an element separation section provided in the semiconductor substrate and including a first element separation section and a second element separation section that have mutually different configurations, the element separation section defining an active region of the pixel transistor, in which the second element separation section has, on a side surface, a first semiconductor region and a second semiconductor region that have mutually different impurity concentrations in a depth direction of the second element separation section.