BSI Image Sensor Light-Shielding Structure for Charge-Holding Noise
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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
An imaging device with a light-shielding section including a horizontal light-shielding part and a vertical light-shielding part, where the horizontal light-shielding part is formed by crystalline anisotropic etching on an Si substrate using an alkaline solution, providing superior light-shielding properties to prevent noise generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional light-shielding structure is used in backside illumination type solid-state imaging devices, then the device can be manufactured with standard processes, but light may enter the charge-holding section without being absorbed in the photoelectric conversion section, causing noise generation
Solution Approach 1:
The light-shielding section is divided into two distinct parts: a horizontal light-shielding part that extends in the horizontal direction and a vertical light-shielding part that extends in the vertical direction. This segmentation allows each part to specifically block light from different directions, preventing light from reaching the charge-holding section and eliminating noise while maintaining manufacturing reliability.
Solution Approach 2:
The light-shielding structure transitions from a conventional single-plane configuration to a three-dimensional configuration with both horizontal and vertical components. By adding the vertical light-shielding part that extends in the depth direction, the structure effectively blocks light paths that would otherwise reach the charge-holding section, improving light-shielding reliability without compromising manufacturability.
2Manufacturing precision
If crystalline anisotropic etching is used to form the horizontal light-shielding part, then high dimensional accuracy and superior light-shielding properties are achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The invention utilizes crystalline anisotropic etching, which changes the etching rate based on crystal orientation parameters. By controlling the etching process to exploit the anisotropic properties of crystalline materials, the horizontal light-shielding part achieves precise dimensional accuracy and superior light-shielding properties. The process complexity is managed by leveraging well-established semiconductor etching techniques rather than introducing entirely new manufacturing methods.
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 solution effectively suppresses noise generation and enhances imaging capability by accurately forming a light-shielding layer with high dimensional accuracy, improving charge transfer properties and preventing dark current influences.
Implementation Method 1
the horizontal light-shielding part is formed by performing crystalline anisotropic etching on an Si substrate using an etching solution
Implementation Method 2
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
Implementation Method 3
a photoelectric conversion section generating charges corresponding to an amount of light reception by means of photoelectric conversion
Data Source
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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.