Doped Epitaxial NIR Sensor Structure for Dark Current Suppression
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Solution Overview
Problem
Image sensor integrated chips (ICs) that detect near-infrared radiation face performance limitations due to defects at the interface between silicon and germanium-based materials, leading to dark current leakage and reduced quantum efficiency.
Innovation Solution
A doped epitaxial layer is disposed along the interface between a silicon base substrate and a germanium-based epitaxial material to passivate defects, reducing thermal generation of free charge carriers and thereby improving the performance of near-infrared sensing by forming a doped epitaxial layer using a deposition process that minimizes implantation damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a silicon base substrate with germanium-based epitaxial material is used for NIR detection, then the quantum efficiency of near-infrared detection is improved, but defects at the interface cause dark current leakage and reduced performance
Solution Approach 1:
An intermediate layer comprising alternating first and second epitaxial layers is introduced between the silicon base substrate and the germanium-based epitaxial material. This intermediate layer acts as a buffer to reduce lattice mismatch and passivate defects at the interface, thereby reducing dark current leakage while maintaining high quantum efficiency for near-infrared detection.
Solution Approach 2:
The intermediate layer is constructed as a composite structure with alternating epitaxial layers of different materials (e.g., silicon germanium with different germanium concentrations). This composite approach allows optimization of both mechanical strain management and electrical properties, achieving reduced dark current while preserving NIR detection performance.
2Measurement precision
If additional illumination is added to improve 3D sensing performance, then the sensing capability is enhanced, but power consumption increases and battery life is reduced
Solution Approach 1:
The image sensor is designed to utilize ambient near-infrared radiation naturally present in the environment for 3D sensing operations. By improving the quantum efficiency of NIR detection through the intermediate layer structure, the sensor can achieve accurate depth mapping and 3D reconstruction without requiring active illumination, thereby eliminating additional power consumption while maintaining sensing capability.
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 solution reduces dark current by up to 70% and enhances the quantum efficiency of near-infrared detection, allowing for improved performance in 3D sensing applications without the need for additional illumination, thus extending battery life and reducing power consumption.
Implementation Method 1
passivate defects, reducing thermal generation of free charge carriers
Implementation Method 2
forming a doped epitaxial layer using a deposition process that minimizes implantation damage
Data Source
AI summary
The present disclosure relates an integrated chip structure. The integrated chip structure includes a base substrate having one or more interior surfaces defining a recess within an upper surface of the base substrate. An epitaxial material is disposed within the recess. A first doped photodiode region is disposed within the epitaxial material and has a first doping type. A second doped photodiode region is disposed within the epitaxial material and has a second doping type. The second doped photodiode region laterally surrounds the first doped photodiode region. A doped epitaxial layer is disposed horizontally and vertically between the base substrate and the epitaxial material. The doped epitaxial layer has the second doping type.