CMOS Image Sensor Filter Stack for Color Mixing Suppression
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Solution Overview
Problem
Conventional solid-state imaging apparatuses experience color mixing and deterioration of signal-to-noise ratio due to the similar transmittance of visible light and infrared light pixels, leading to increased processing complexity and difficulty in maintaining consistent infrared light transmission across different angles.
Innovation Solution
A solid-state imaging apparatus with a configuration that includes a plurality of pixels, each having a first optical filter layer and a second optical filter layer, where either the first or second layer is an infrared cut filter, and the other is a color filter, separated by a wall, to suppress color mixing and maintain consistent infrared light transmission independent of the incident angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an infrared cut filter is formed by a multilayer interference film obtained by alternately laminating substances having high and low refractive indexes, then the transmission distribution of infrared light can be controlled, but the number of steps increases and the process difficulty level increases
Solution Approach 1:
The optical filter is divided into two separate layers: a first optical filter layer (infrared cut filter) and a second optical filter layer (color filter). This segmentation allows each layer to have a simpler structure with fewer manufacturing steps while achieving the desired transmission distribution control through the combination of layers.
Solution Approach 2:
The patent uses a composite structure combining an infrared cut filter layer and a color filter layer. Each layer can be formed by different materials and processes optimized for their specific function, avoiding the complexity of a single multilayer interference film while achieving comparable or superior transmission control.
2Manufacturing precision
If an infrared cut filter is formed by a multilayer interference film, then transmission distribution can be adjusted, but the transmission distribution depends on the incident angle
Solution Approach 1:
The first optical filter layer (infrared cut filter) is designed with specific local optical properties that make its transmission distribution independent of incident angle. By optimizing the material and structure of this specific layer, the patent achieves angle-independent infrared light blocking while the second layer handles color filtering.
3Device complexity
If all pixels have substantially the same transmittance in the infrared light region, then the structure is simple, but color mixing occurs and signal-to-noise ratio deteriorates
Solution Approach 1:
Different optical filter configurations are applied to different pixel types: visible light pixels receive both an infrared cut filter layer and a color filter layer to block infrared light and filter colors, while infrared light pixels receive only the color filter layer (or different filter configuration) to allow infrared light transmission. This local differentiation prevents color mixing and improves signal-to-noise ratio.
Solution Approach 2:
The pixel array is segmented into different types of pixels (visible light pixels and infrared light pixels) with different optical filter configurations. This segmentation allows each pixel type to have optimized transmission characteristics for its intended function, preventing cross-contamination between visible and infrared light detection.
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 color mixing and maintains consistent infrared light transmission, reducing the complexity of the manufacturing process and improving signal-to-noise ratio by using a combination of infrared cut filters and color filters in a specific layer configuration.
Implementation Method 1
Either the first optical filter layer or the second optical filter layer in at least one of the pixels is formed by an infrared cut filter
Implementation Method 2
the other is formed by a color filter
Data Source
AI summary
The present technology relates to a solid-state imaging apparatus capable of suppressing occurrence of color mixing, a method for manufacturing the solid-state imaging apparatus, and an electronic device. The solid-state imaging apparatus includes a plurality of pixels arranged in a pixel region. Each of the pixels has: a first optical filter layer disposed on a photoelectric conversion unit; a second optical filter layer disposed on the first optical filter layer; and a separation wall separating at least a part of the first optical filter layer for each of the pixels. Either the first optical filter layer or the second optical filter layer in at least one of the pixels is formed by an infrared cut filter, while the other is formed by a color filter. The present technology can be applied to a CMOS image sensor including a visible light pixel.