Filterless Image Sensor Using Depth-Differentiated Photodiodes
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Solution Overview
Problem
Conventional CMOS image sensors require color filters to distinguish between red, green, and blue wavelengths, which are difficult to manufacture and lead to light blockage, increasing chip size and manufacturing defects.
Innovation Solution
Designing an image sensor with a semiconductor substrate that includes a light receiving device and an electron collecting device, where the electron collecting device is isolated from light and electrons generated by the light receiving device are guided to it, allowing color detection without color filters by measuring the ratio of optical currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If color filters are used to distinguish wavelengths, then color detection capability is improved, but manufacturing difficulty increases and chip size increases
Solution Approach 1:
The patent removes color filters from the optical path entirely. Instead of using polymer-based color filter arrays that block most light, the invention extracts only the necessary light-receiving function and implements it through depth-differentiated photodiodes in the semiconductor substrate, eliminating the harmful filtering components.
Solution Approach 2:
The patent replaces the mechanical/optical filtering system (color filter arrays) with an electrical/electronic differentiation system. By creating photodiodes at different depths that respond differently to various wavelengths, the system substitutes physical light filtering with electronic signal differentiation based on photoelectric effects at varying penetration depths.
2Measurement precision
If color filters are used to distinguish wavelengths, then color detection capability is improved, but chip size increases
Solution Approach 1:
The patent transitions from a two-dimensional color filter array layout to a three-dimensional structure by varying photodiode depths within the semiconductor substrate. This vertical dimensionality allows multiple color detection functions to be stacked at different depths, eliminating the need for lateral expansion of color filter arrays and reducing overall chip area.
3Measurement precision
If color filters are used to distinguish wavelengths, then color detection capability is improved, but light blockage increases
Solution Approach 1:
The patent converts the previously harmful light blockage by color filters into a beneficial depth-dependent penetration effect. Different wavelengths naturally penetrate to different depths in the semiconductor substrate, and this physical phenomenon is harnessed to create wavelength-selective detection without requiring absorptive filters that waste light energy.
4Measurement precision
If polymer-based material is used for color filter array, then color filtering function is achieved, but manufacturing defects increase
Solution Approach 1:
The patent replaces fragile, difficult-to-handle polymer-based color filter materials with robust, permanent semiconductor photodiode structures that are integral to the chip. This substitution eliminates the need for separate filter material handling and bonding processes, significantly reducing manufacturing defects and improving yield.
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 approach eliminates the need for color filters, improving chip performance, reducing size, and minimizing manufacturing costs while accurately detecting colors.
Implementation Method 1
A light receiving device which may be configured to be formed within the semiconductor substrate to receive light
Implementation Method 2
An electron collecting device which may be configured to be formed within the semiconductor substrate to permit part of the electrons generated by the light in the light receiving device to move thereto
Data Source
AI summary
An image sensor for a semiconductor light-sensitive device including a semiconductor substrate and a light receiving device configured to receive light and generate a signal from the light. The image sensor may include an electron collecting device formed in the semiconductor substrate to receive at least a portion of the electrons generated by the light in the light receiving device. The image sensor may include a first type device isolation film configured to isolate the light receiving device from the electron collecting device. The image sensor may include a shielding film formed over the semiconductor substrate and configured to shield the first electron collecting device from the light.