PDAF Image Sensor Layout for Stronger Incident Signal Reception
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Solution Overview
Problem
Phase detection auto-focus (PDAF) CMOS image sensors face performance compromise due to photodiodes being partially shielded by metallic grids as pixel size shrinks, leading to lower incident signals.
Innovation Solution
The design includes a semiconductor substrate with trench isolations and image sensing units, where phase detection units are not partially shielded by a light shielding grid, allowing for improved incident light reception through the use of color filters and lenses that cover only the image sensing units, enabling phase detection without compromising signal strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If photodiodes are partially shielded by metallic grid to provide phase detection function, then phase detection capability is improved, but incident signal strength deteriorates
Solution Approach 1:
The photodiode structure is segmented into multiple regions: a first region that receives incident light for image sensing, and a second region that is shielded by the metallic grid for phase detection. This spatial segmentation allows each region to perform its dedicated function without compromising the other, resolving the contradiction between phase detection capability and incident signal strength.
Solution Approach 2:
Different regions of the photodiode are assigned different functional qualities: the first region maintains light-receiving properties for image sensing, while the second region is configured with shielding properties for phase detection. This local differentiation of functional qualities enables simultaneous optimization of both phase detection capability and incident signal reception.
2Manufacturing precision
If pixel size is reduced to increase resolution, then image quality is improved, but incident signal reception deteriorates
Solution Approach 1:
Within each reduced-size pixel, the photodiode is further segmented into specialized regions. The first region is optimized for light reception while the second region handles phase detection, allowing the pixel to maintain small dimensions for high resolution while preserving sufficient incident signal reception capability through functional 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
This configuration ensures excellent incident signal reception even as pixel size shrinks, maintaining performance by ensuring phase detection units are not obstructed, thus enhancing the overall image sensor functionality.
Implementation Method 1
a light shielding layer disposed on the planarization layer and including a plurality of openings. The color filters at least fill portions of the plurality of openings
Implementation Method 2
a plurality of color filters, wherein the color filters at least fill portions of the plurality of openings located above the plurality of image sensing units
Implementation Method 3
a plurality of first lenses are disposed on the plurality of color filters, wherein each of the plurality of first lenses respectively covers one of the plurality of image sensing units
Data Source
AI summary
An image sensor including a semiconductor substrate, a plurality of color filters, a plurality of first lenses and a second lens is provided. The semiconductor substrate includes a plurality of sensing pixels arranged in array, and each of the plurality of sensing pixels respectively includes a plurality of image sensing units and a plurality of phase detection units. The color filters at least cover the plurality of image sensing units. The first lenses are disposed on the plurality of color filters. Each of the plurality of first lenses respectively covers one of the plurality of image sensing units. The second lens is disposed on the plurality of color filters and the second lens covers the plurality of phase detection units.