Image Sensor Recess Patterns and Transfer Gates for Color Separation
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Solution Overview
Problem
Conventional image sensors face challenges in simultaneously improving color separation and quantum efficiency characteristics, with color filter arrays leading to low quantum efficiency and alternative structures complicating manufacturing and color separation.
Innovation Solution
An image sensor design featuring first and second impurity regions with recess patterns and transfer gates, where the depth of the recess patterns and impurity regions are controlled to optimize light absorption and separation, eliminating the need for a color filter array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a color filter array is used in the image sensor, then color separation characteristics are improved, but quantum efficiency deteriorates due to light absorption by the filters
Solution Approach 1:
The invention extracts and removes the color filter array from the optical path, eliminating the component that blocks light. Instead of using filters to separate colors, the patent uses the natural wavelength-dependent absorption characteristics of the semiconductor substrate and strategically positioned impurity regions to achieve color separation without sacrificing quantum efficiency.
Solution Approach 2:
The invention replaces the mechanical/optical filtering system (color filter array) with an electrical/semiconductor-based solution. By using impurity regions with different depths and doping concentrations, the system achieves color separation through electrical characteristics and light absorption physics rather than physical filters, thereby improving quantum efficiency while maintaining color separation capability.
2Loss of energy
If the optical sensor uses a complicated structure with multiple stacked photodiodes to improve quantum efficiency, then color separation becomes difficult due to overlapping light absorption depths
Solution Approach 1:
The invention applies local quality by creating impurity regions with different doping concentrations and depths at specific locations within the semiconductor substrate. Each impurity region is locally optimized to detect specific wavelength ranges: shallow regions for blue light, intermediate regions for green light, and deep regions for red light. This spatial differentiation of impurity region characteristics enables color separation without requiring multiple stacked photodiodes.
Solution Approach 2:
The invention transitions from a vertical stacking approach (multiple photodiodes stacked in depth) to a lateral differentiation approach (impurity regions distributed across the substrate at different depths and positions). By utilizing both vertical depth and lateral positioning as differentiating dimensions, the system achieves color separation while maintaining good quantum efficiency, avoiding the overlapping absorption problem of stacked structures.
3Ease of manufacture
If conventional fabrication processes are used, then manufacturing is simpler, but the ability to precisely control impurity region depths and transfer gate structures is insufficient
Solution Approach 1:
The invention employs preliminary action by forming isolation layers and defining active regions before creating the impurity regions. The isolation layers are pre-formed to establish boundaries, and etching patterns are prepared in advance to guide the formation of impurity regions at precise depths. This sequential preparation ensures that subsequent doping and gate formation processes can achieve the required precision without requiring complete process redesign.
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 design enhances both quantum efficiency and color separation characteristics by controlling light absorption depths and transfer gate structures, improving photoelectron transfer efficiency.
Implementation Method 1
blue B, green G, and red R colors of light in order are detected by progressively deeper regions of the N-type impurity region 13 in the optical sensor 15
Implementation Method 2
Each of the blue pixel active region 20B, the green pixel active region 20G, and the red pixel active region 20R includes an optical sensor 15, which is formed by a junction of a P-type impurity region 14 and an N-type impurity region 13, and a transfer gate 16
Data Source
AI summary
An image sensor includes first impurity regions formed in a substrate, second impurity regions formed in the first impurity regions, wherein the second impurity regions has a junction with the first impurity regions, recess patterns formed over the first impurity regions in contact with the second impurity regions, and transfer gates filling the recess patterns.