BSI Imaging Structure With Crystal-Plane Light Shielding
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Solution Overview
Problem
In backside illumination type solid-state imaging devices, there is a possibility of noise generation due to light entering the charge-holding section without being absorbed in the photoelectric conversion section.
Innovation Solution
The implementation of a light-shielding section with a horizontal light-shielding part formed by crystalline anisotropic etching on an Si substrate, which includes three Si backbonds or less in a horizontal direction and three Si backbonds in a vertical direction, positioned between the photoelectric conversion section and the charge-holding section to prevent light from reaching the charge-holding section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light-shielding section is added to prevent light from reaching the charge-holding section, then noise generation is suppressed, but device complexity increases
Solution Approach 1:
The light-shielding section is formed by nesting multiple crystal planes ({111} and {110>) within the semiconductor substrate itself, creating a compact hierarchical structure that shields the charge-holding section without adding external components
Solution Approach 2:
The light-shielding section acts as an intermediary structure formed within the substrate, using crystalline etching to create intermediate planes that block light paths between the photoelectric conversion section and charge-holding section
2Manufacturing precision
If crystalline anisotropic etching is used to form the light-shielding section, then manufacturing precision is improved, but ease of manufacture decreases
Solution Approach 1:
The etching process utilizes changes in crystallographic parameters by selectively exposing different crystal planes ({111} and {110>) to the etching solution, causing differential etching rates that automatically form the light-shielding structure with high precision
Solution Approach 2:
The mechanical precision requirement is replaced by utilizing the inherent crystalline structure of the semiconductor substrate, where the crystal planes themselves define the light-shielding geometry through chemical etching rather than mechanical machining
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 effectively suppresses noise generation and enhances imaging capability by ensuring that light is either absorbed or reflected back to the photoelectric conversion section, thereby improving the imaging performance.
Implementation Method 1
a photoelectric conversion section generating charges corresponding to an amount of light reception by means of photoelectric conversion
Implementation Method 2
the horizontal light-shielding part is formed, for example, by performing crystalline anisotropic etching on an Si substrate using an etching solution. For example, in a case of etching using an alkaline solution, the etching progresses from a reaction between an Si dangling bond and an OH ion as a starting point
Data Source
AI summary
An imaging device having a superior light-shielding property for a charge-holding section is provided. The imaging device includes: an Si {111} substrate extending along a horizontal plane; a photoelectric conversion section provided in the Si {111} substrate and generating charges corresponding to a light reception amount by photoelectric conversion; a charge-holding section provided in the Si {111} substrate and holding charges transferred from the photoelectric conversion section; and a light-shielding section including a horizontal light-shielding part positioned between the photoelectric conversion section and the charge-holding section in a thickness direction and extending along the horizontal plane and a vertical light-shielding part orthogonal thereto. The horizontal light-shielding section includes a first plane along a first crystal plane of the Si {111} substrate of a plane index {111} orthogonal to the thickness direction, and a second plane along a second crystal plane of the Si {111} substrate inclined to the thickness direction.