Phase-Detection Pixel Layout With Shared On-Chip Lens
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Solution Overview
Problem
Conventional phase-difference detection pixels in solid-state image pickup devices suffer from reduced sensitivity to incident light, inaccurate phase-difference detection, and limited angle range sensitivity due to metal light-shielding films, which become more pronounced with miniaturization and the use of lenses with variable Chief Ray Angles (CRA).
Innovation Solution
A solid-state image pickup device design where phase-difference detection pixels share a common on-chip lens with normal pixels, utilizing inter-pixel light-shielding structures and dummy light-condensing elements to enhance sensitivity and accuracy, allowing for wider angle detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a metal light-shielding film is used in phase-difference detection pixels, then optical color mixing between adjacent pixels is reduced, but sensitivity to incident light decreases and diffraction effects increase
Solution Approach 1:
The patent removes the metal light-shielding film from the phase-difference detection pixel structure. Instead of using a metal film with an opening, the invention uses a through-hole structure that extends from the upper surface to the lower surface of the semiconductor substrate, eliminating the metal film's light-shielding function while maintaining optical separation between pixels through the hole's geometric configuration.
Solution Approach 2:
The patent introduces a refractive index distribution control mechanism as an intermediary element. By controlling the refractive index distribution in the semiconductor substrate around the through-hole, the patent achieves both optical color mixing prevention and reduced diffraction effects without requiring a metal light-shielding film, thereby maintaining sensitivity to incident light.
2Object-generated harmful factors
If a metal light-shielding film is used in phase-difference detection pixels, then optical color mixing is reduced, but accuracy of phase-difference detection deteriorates due to diffraction
Solution Approach 1:
The patent removes the metal light-shielding film that causes diffraction effects. The through-hole structure without metal film eliminates the source of diffraction while maintaining the optical separation function, thereby improving phase-difference detection accuracy.
Solution Approach 2:
The patent changes the optical parameters by controlling the refractive index distribution in the semiconductor substrate. This parameter change allows the system to achieve both optical color mixing prevention and reduced diffraction effects, thereby improving measurement precision without sacrificing the harmful factor control.
3Object-generated harmful factors
If a metal light-shielding film is used in phase-difference detection pixels, then optical color mixing is reduced, but the angle range for sensitivity response becomes narrow
Solution Approach 1:
The patent removes the metal light-shielding film that limits the angle range. The through-hole structure without metal film allows light to enter from a wider range of angles while maintaining optical color mixing prevention through the hole's geometric configuration and refractive index control.
Solution Approach 2:
The patent changes the optical parameters by controlling the refractive index distribution to enable wider angle acceptance. This parameter change allows the system to expand the angle range for sensitivity response while maintaining optical color mixing prevention, thereby improving adaptability.
4Productivity
If pixels are miniaturized to increase the number of pixels, then resolution is improved, but diffraction effects and electromagnetic wave behaviors become more remarkable
Solution Approach 1:
The patent removes the metal light-shielding film that is the primary source of diffraction effects. By using a through-hole structure without metal film, the invention eliminates the diffraction source while maintaining pixel miniaturization, thereby allowing higher pixel density without significant diffraction problems.
Solution Approach 2:
The patent changes the optical parameters by controlling the refractive index distribution in the miniaturized pixel structure. This parameter change allows the system to suppress diffraction effects even as pixels are miniaturized, thereby enabling higher pixel density without significant degradation from diffraction.
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 design improves sensitivity and accuracy of phase-difference detection, enabling effective image-surface phase difference AF functions in various lighting conditions and with lenses having variable CRA, while minimizing optical color mixing and diffraction effects.
Implementation Method 1
an on-chip lens for condensing incident light to a photoelectric converter
Implementation Method 2
a photoelectric converter that generates a pixel signal
Data Source
AI summary
The present disclosure relates to a solid-state image pickup device and an electronic apparatus by which a phase-difference detection pixel that avoids defects such as lowering of sensitivity to incident light and lowering of phase-difference detection accuracy can be realized. A solid-state image pickup device as a first aspect of the present disclosure is a solid-state image pickup device in which a normal pixel that generates a pixel signal of an image and a phase-difference detection pixel that generates a pixel signal used in calculation of a phase-difference signal for controlling an image-surface phase difference AF function are arranged in a mixed manner, in which, in the phase-difference detection pixel, a shared on-chip lens for condensing incident light to a photoelectric converter that generates a pixel signal used in calculation of the phase-difference signal is formed for every plurality of adjacent phase-difference detection pixels. The present disclosure is applicable to a backside illumination CMOS image sensor and an electronic apparatus equipped with the same.