Backside Imaging Pixel Lens Layout to Reduce Color Mixture
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Solution Overview
Problem
The challenge in solid-state imaging devices is preventing the degradation of color mixture in rear surface irradiation type pixel structures where on-chip lenses larger than pixels are formed for every other pixel, as existing technologies face difficulties in maintaining sensitivity and reducing color mixture.
Innovation Solution
A solid-state imaging device with a matrix pattern of pixels, where on-chip lenses are larger than pixels and arranged for every other pixel, featuring color filters with a cross-sectional shape matching the on-chip lenses in width at the upper side and being shorter at the lower side near the photoelectric conversion portion, along with light-shielding structures to prevent light leakage and optimize sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If on-chip lenses larger than pixels are formed for every other pixel in rear surface irradiation type, then sensitivity is improved, but color mixture degradation occurs
Solution Approach 1:
The color filter is designed with different widths at different heights: the upper width (near the on-chip lens) matches the lens width while the lower width (near the photodiode) is reduced. This local variation in geometry prevents color mixture at the pixel boundaries while maintaining the large lens size needed for sensitivity improvement in rear surface irradiation type pixels.
2Area of moving object
If on-chip lenses are downsized to suit finer pixels, then pixel density increases, but manufacturing of lenses with desired curvature becomes difficult
Solution Approach 1:
Instead of downsizing all on-chip lenses uniformly, the invention applies large on-chip lenses selectively to every other pixel. This partial application allows maintaining manufacturable lens sizes with proper curvature while still achieving increased effective pixel density through the alternating pattern of large and small lens regions.
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 prevents color mixture and maintains sensitivity by ensuring that light is efficiently directed to the photodiodes, reducing vignetting and enhancing the dynamic range of the imaging device.
Implementation Method 1
Each of the pixels has a photoelectric conversion portion configured to photoelectrically convert light incident from a rear surface side of a semiconductor substrate
Implementation Method 2
The plurality of on-chip lenses are arranged for every other pixel. The on-chip lenses are larger in size than the pixels
Implementation Method 3
Each of color filters at the pixels where the on-chip lenses are present has a cross-sectional shape whose upper side close to the on-chip lens is the same in width as the on-chip lens and whose lower side close to the photoelectric conversion portion is shorter than the upper side
Data Source
AI summary
Disclosed is a solid-state imaging device including a plurality of pixels and a plurality of on-chip lenses. The plurality of pixels are arranged in a matrix pattern. Each of the pixels has a photoelectric conversion portion configured to photoelectrically convert light incident from a rear surface side of a semiconductor substrate. The plurality of on-chip lenses are arranged for every other pixel. The on-chip lenses are larger in size than the pixels. Each of color filters at the pixels where the on-chip lenses are present has a cross-sectional shape whose upper side close to the on-chip lens is the same in width as the on-chip lens and whose lower side close to the photoelectric conversion portion is shorter than the upper side.