Trench Ge Optical Sensor Doping for Lower Dark Current
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Solution Overview
Problem
Existing semiconductor manufacturing processes for optical image sensors face challenges with high dark current due to poor quality interfaces between semiconductor layers, particularly in germanium (Ge)-based sensors, which degrades device performance and reliability.
Innovation Solution
The introduction of dopant species such as P-type materials (e.g., boron, aluminum) or Group VIIA materials (e.g., fluorine, chlorine) at the Ge-Si interface through ion implantation or diffusion to passivate the interface, optimizing the Ge-Si interface and reducing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If semiconductor layers are stacked to form optical image sensors, then device functionality is achieved, but interface quality deteriorates leading to high dark current
Solution Approach 1:
An intermediary layer comprising alternating Ge-rich and Si-rich semiconductor layers is introduced between the Ge photodetector layer and the Si substrate. This intermediate structure acts as a buffer to improve interface quality, reduce defects, and minimize dark current while maintaining the functionality of the optical image sensor.
2Productivity
If device dimensions are scaled down, then production efficiency improves and costs decrease, but manufacturing process complexity increases
Solution Approach 1:
The semiconductor structure is segmented into multiple thin alternating layers of Ge-rich and Si-rich materials. This segmentation approach allows for better control of each individual layer during manufacturing, reducing the complexity associated with scaling down while maintaining production efficiency.
3Measurement precision
If Ge layer is used for optical detection, then optical sensitivity improves, but electron leakage increases due to poor interface quality
Solution Approach 1:
The alternating Ge-rich and Si-rich intermediate layers serve as a mediator that passivates the interface between Ge and Si, reducing electron leakage and dark current while preserving the high optical sensitivity of the Ge photodetector layer.
Solution Approach 2:
The composition of the intermediate layers is optimized by controlling the Ge/Si ratio in alternating layers, with Ge-rich layers providing optical detection capability and Si-rich layers reducing electron leakage. This parameter optimization balances optical sensitivity with leakage reduction.
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 and dark current in Ge-based sensors, improving optical performance and reliability by blocking electrons from entering the Ge layer, resulting in a reduction of about 10% leakage current.
Implementation Method 1
The introduction of dopant species such as P-type materials (e.g., boron, aluminum) or Group VIIA materials (e.g., fluorine, chlorine) at the Ge-Si interface through ion implantation or diffusion to passivate the interface
Implementation Method 2
The introduction of dopant species such as P-type materials (e.g., boron, aluminum) or Group VIIA materials (e.g., fluorine, chlorine) at the Ge-Si interface through ion implantation or diffusion to passivate the interface
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.