Solid State Image Sensor Pixel Overlap for Autofocus Alignment
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Solution Overview
Problem
In semiconductor devices with large chip sizes, divided exposure techniques lead to size variations and misregistration issues due to different masks used in exposure steps, resulting in image abnormalities and autofocus detection errors in solid state image sensors.
Innovation Solution
A semiconductor device design where the first and second exposure regions overlap in a third region, with photodiodes from each region positioned closer to the side of the adjacent region, allowing for improved alignment and reduced output differences between photodiodes, thereby minimizing image abnormalities and enhancing autofocus performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If divided exposure treatment is performed using different masks for large chip size, then the chip area can be increased, but size variation and misregistration occur leading to image abnormalities
Solution Approach 1:
An overlapping region is introduced as an intermediary zone between the first exposure region and second exposure region. This overlapping region contains pixels with photodiodes formed by both masks, serving as a transition zone that mediates the alignment between the two exposure regions and reduces visible boundary abnormalities
Solution Approach 2:
Different regions of the chip are assigned different exposure characteristics: the first exposure region uses a first mask, the second exposure region uses a second mask, and the overlapping region combines both. This local differentiation allows each region to be optimized independently while the overlapping region ensures smooth transitions
2Manufacturing precision
If photodiodes are positioned asymmetrically in the overlapping region, then alignment and output consistency improve, but device structure becomes more complex
Solution Approach 1:
The photodiode arrangement is optimized locally for each pixel type: pixels in the first exposure region have photodiodes formed by the first mask, pixels in the second exposure region have photodiodes formed by the second mask, and pixels in the overlapping region have asymmetrically arranged photodiodes from both masks. This local optimization improves output consistency while managing complexity through regional differentiation
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 image quality by reducing visible abnormalities at the boundary between exposure regions and accelerates autofocus detection, leading to enhanced performance and precision in image-plane phase-detection autofocusing systems.
Implementation Method 1
a pixel having a light receiving portion including two photodiodes PD2 and PD3
Data Source
AI summary
In a solid state image sensor which has two photodiodes juxtaposed in a predetermined direction in each pixel and is formed by carrying out divided exposure, that is, exposure treatment of an entire chip by a plurality of times of exposure, image quality is improved and autofocusing speed is increased. Provided is a solid state image sensor having a first exposure region having a first region and a second exposure region having a second region. They overlap with each other in a third region between the first and second regions. In a pixel formed in the third region, a photodiode formed through a mask for first exposure region is placed at a position closer to the side of the second region than another photodiode formed through a mask for second exposure region is.