CMOS Pixel Light Guide Wall Layout for Sensitivity and Color Mixing
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Solution Overview
Problem
Conventional imaging elements suffer from insufficient sensitivity due to the light blocking film interrupting light guiding by the low refractive index film, as the thick light blocking film absorbs incident light intended for photoelectric conversion.
Innovation Solution
An imaging element with a light guide wall formed around the color filter, having a refractive index different from the color filter, guides incident light from the color filter to the photoelectric conversion unit, enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thick light blocking film is arranged at the bottom of the first wall to prevent color mixing, then color mixing is reduced, but the sensitivity is insufficient because the light blocking film absorbs incident light intended for photoelectric conversion
Solution Approach 1:
The invention extracts the light blocking function from the bottom of the first wall and relocates it to the second wall. The first wall's low refractive index film is extended downward without a light blocking film at its bottom, allowing light to pass through to the photoelectric conversion unit. The light blocking function is instead implemented in the second wall, which is positioned away from the photoelectric conversion unit, thus preventing color mixing without absorbing useful incident light.
Solution Approach 2:
The invention changes the spatial arrangement by introducing a second wall that extends in the vertical direction from the bottom surface of the first wall. This creates a multi-dimensional light blocking structure where the second wall intercepts obliquely incident light before it can reach adjacent pixels, preventing color mixing without interfering with vertically incident light that reaches the photoelectric conversion unit.
2Reliability
If a low refractive index film is used in the first wall to guide incident light to the photoelectric conversion unit, then sensitivity is improved, but color mixing occurs when obliquely incident light from adjacent pixels passes through the color filter
Solution Approach 1:
The invention segments the light blocking function into two separate walls: the first wall guides light using its low refractive index film without absorbing light, and the second wall provides light blocking at its bottom surface. This segmentation allows each wall to perform its specific function optimally - the first wall improves sensitivity through light guidance, while the second wall prevents color mixing through light blocking.
Solution Approach 2:
The second wall acts as an intermediary light blocking element positioned between the first wall and the adjacent pixels. It intercepts obliquely incident light that has passed through the first wall's low refractive index film, preventing this light from reaching adjacent pixels and causing color mixing, while allowing vertically incident light to pass through to the photoelectric conversion unit.
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 light guide wall effectively directs obliquely incident light to the photoelectric conversion unit, improving sensitivity and reducing color mixing, thus enhancing image quality.
Implementation Method 1
the light guide wall having an end portion disposed in a recess surrounding the pixel formed in the interlayer film at the boundary of the pixels to guide the incident light
Implementation Method 2
a photoelectric conversion unit arranged in a semiconductor substrate to perform photoelectric conversion on incident light
Data Source
AI summary
Provided is an imaging element that includes a plurality of pixels. The plurality of pixels includes a semiconductor substrate having a front side and a back side, a plurality of wiring layers on the front side of the semiconductor substrate, an interlayer film at the back side of the semiconductor substrate, where the interlayer film has a recess at a boundary of the plurality of pixels, a first color filter and a second color filter that are on a light incident side of the interlayer film in a cross-sectional view, a film at least on the recess, and a region between the first color filter and the second color filter. The film is between the region and the recess.