Ge Optical Sensor Interface Passivation for Lower Dark Current
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Solution Overview
Problem
Existing semiconductor manufacturing processes for optical image sensors face challenges in reducing dark current due to poor interface quality between semiconductor layers, particularly in germanium (Ge)-based sensors, which affects device performance and reliability.
Innovation Solution
The implementation of a method to passivate the Ge-Si interface by doping with P-type or Group VIIA materials through ion implantation or diffusion, optimizing the interface to prevent electron leakage and reduce dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If semiconductor layers are scaled down to improve production efficiency and lower costs, then productivity increases, but manufacturing precision deteriorates due to increased process complexity
Solution Approach 1:
A passivation layer is introduced as an intermediary between the Ge layer and Si substrate. This passivation layer acts as a mediator that improves interface quality by reducing interface states and preventing electron leakage, thereby resolving the degradation in manufacturing precision caused by scaling down semiconductor layers
Solution Approach 2:
The patent modifies the interface properties by changing the doping concentration and material composition of the passivation layer. By adjusting these parameters, the interface quality is improved to compensate for the effects of scaling, maintaining manufacturing precision while benefiting from increased productivity
2Ease of manufacture
If conventional manufacturing processes are used, then ease of manufacture is maintained, but reliability deteriorates due to significant dark current from poor interface quality
Solution Approach 1:
The passivation layer serves as an intermediary that improves reliability by eliminating interface defects responsible for dark current. This layer can be integrated into existing manufacturing processes using standard techniques such as thermal oxidation or chemical vapor deposition, maintaining ease of manufacture while significantly improving device reliability
Solution Approach 2:
The patent employs composite material structures combining Ge, Si, and passivation layer materials. This composite approach allows the device to benefit from the high carrier mobility of Ge while the passivation layer compensates for interface quality issues, thereby improving reliability without complicating the manufacturing process
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 significantly mitigates leakage current in Ge-based sensors, improving device performance by reducing dark current by about 10% and enhancing the overall reliability of optical image sensors.
Implementation Method 1
doping with P-type or Group VIIA materials through ion implantation or diffusion
Implementation Method 2
doping with P-type or Group VIIA materials through ion implantation or diffusion
Data Source
AI summary
A method and structure providing an optical sensor having an optimized Ge—Si interface includes providing a substrate having a pixel region and a logic region. In some embodiments, the method further includes forming a trench within the pixel region. In various examples, and after forming the trench, the method further includes forming a doped semiconductor layer along sidewalls and along a bottom surface of the trench. In some embodiments, the method further includes forming a germanium layer within the trench and over the doped semiconductor layer. In some examples, and after forming the germanium layer, the method further includes forming an optical sensor within the germanium layer.