Backside Imaging Sensor Light Shielding 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
The implementation of a light-shielding section with a horizontal light-shielding part formed by crystalline anisotropic etching on an Si substrate, including three Si backbonds or less in a horizontal direction and three Si backbonds in a vertical direction, to prevent light from reaching the charge-holding section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If light-shielding sections are added to prevent light from entering the charge-holding section, then noise generation is suppressed, but device complexity increases
Solution Approach 1:
The light-shielding section is divided into two distinct parts: a horizontal light-shielding part and a vertical light-shielding part. This segmentation allows each part to address light leakage from different directions, effectively suppressing noise while maintaining a manageable structural complexity through modular design.
Solution Approach 2:
The invention transitions from conventional single-direction light shielding to two-dimensional light shielding by adding both horizontal and vertical components. This dimensional expansion creates comprehensive light blocking coverage without requiring excessive material or overly complex single-structure designs.
2Manufacturing precision
If crystalline anisotropic etching is used to form the horizontal light-shielding part, then manufacturing precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The invention changes the etching parameters by utilizing crystalline anisotropic etching on Si {111} substrates, which exploits the crystallographic orientation to achieve precise, self-limiting etch depths. This parameter change enables high manufacturing precision through the natural stopping planes of the crystal structure, though it requires specialized substrate preparation.
Solution Approach 2:
The invention replaces conventional mechanical or isotropic etching methods with chemically-driven crystalline anisotropic etching. This substitution leverages the chemical interaction between the etchant and crystal lattice to achieve precise shaping without complex mechanical tooling, improving precision while simplifying the etching process itself.
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 superior light-shielding properties, thereby improving the imaging performance of the solid-state imaging device.
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.