Stacked Visible-Infrared Sensor Layout for Pixel Crosstalk Isolation
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Solution Overview
Problem
Existing visible and infrared image sensors face challenges in improving aspects such as optical and electrical crosstalk between detection pixels, dark current, and modulation transfer function, particularly in manufacturing methods that integrate both types of sensors effectively.
Innovation Solution
A visible and infrared image sensor design featuring a first active layer for visible radiation detection and a second active layer for infrared detection, with isolation trenches forming islands or mesas in the infrared layer, a non-metallic interface layer, and a control integrated circuit, along with conductive vias for electrical connection, to minimize crosstalk and enhance detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If visible and infrared detection pixels are superimposed in a stacked configuration, then simultaneous detection of visible and infrared images is achieved, but optical and electrical crosstalk between detection pixels increases
Solution Approach 1:
The patent divides the sensor into separate stacked layers for visible and infrared detection, with each layer containing isolated detection pixels. Isolation trenches are introduced between adjacent infrared detection pixels to segment the continuous semiconductor layer, preventing both optical and electrical crosstalk while maintaining the stacked configuration that enables simultaneous detection of both spectral ranges.
Solution Approach 2:
The patent introduces an isolation layer filled with reflective material (such as aluminum or silver) between adjacent infrared detection pixels. This intermediary layer serves as both an optical reflector to prevent light crosstalk and an electrical isolator to prevent signal crosstalk, effectively addressing the crosstalk problem while preserving the superimposed sensor structure.
2Measurement precision
If isolation structures are introduced to reduce crosstalk, then modulation transfer function improves, but manufacturing complexity increases
Solution Approach 1:
The patent combines multiple functions into the isolation layer: it serves as both an optical reflector and an electrical isolator. By using a single layer with reflective material that provides both optical and electrical isolation properties, the design achieves improved modulation transfer function without proportionally increasing manufacturing complexity, as one structure accomplishes what would otherwise require multiple separate components.
Solution Approach 2:
The isolation layer is designed to perform multiple functions simultaneously: optical reflection to prevent light crosstalk, electrical isolation to prevent signal crosstalk, and structural support for the stacked configuration. This multi-functionality reduces the overall complexity compared to implementing separate structures for each function.
3Reliability
If the infrared active layer thickness is increased to improve infrared absorption, then quantum efficiency increases, but optical crosstalk from visible layer increases
Solution Approach 1:
The patent extracts or removes visible light wavelengths before they can reach the infrared detection layer by using a visible light blocking layer or wavelength-selective filters. This allows the infrared active layer to be made thicker for improved quantum efficiency without suffering from increased optical crosstalk, as the visible light is selectively removed while infrared radiation passes through to be detected.
Solution Approach 2:
The patent applies wavelength-selective properties at different locations and layers: the visible layer and its blocking structures are optimized for visible wavelengths, while the infrared layer is optimized for infrared wavelengths. This local quality approach allows each layer to have the thickness and properties needed for its specific wavelength range, with the infrared layer being sufficiently thick for high quantum efficiency while visible light is blocked by the intermediate layers.
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 reduces optical and electrical crosstalk, improves modulation transfer function, and increases absorption of infrared radiation, achieving high quantum efficiency and effective simultaneous detection of visible and infrared images.
Implementation Method 1
a first active layer for detecting visible radiation
Implementation Method 2
a second active layer for detecting infrared radiation
Implementation Method 3
isolation trenches extending vertically through at least part of the thickness of the second active layer
Data Source
AI summary
A visible and infrared image sensor, including: a first active layer for detecting visible radiation, in which a plurality of visible detection pixels are defined; and superimposed on the first active layer, a second active layer for detecting infrared radiation, in which a plurality of infrared detection pixels are defined, the sensor further including, on the side of the face of the second active layer opposite the first active layer, a control integrated circuit superimposed on the first and second active layers, wherein the sensor includes isolation trenches extending vertically through at least part of the thickness of the second active layer, and laterally delimiting in the second active layer islands or mesas forming the infrared detection pixels.