Epitaxial Cap Layer Sequence for Semiconductor Auto-Doping Reduction
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Solution Overview
Problem
Existing semiconductor processing techniques face challenges in reducing auto-doping, which occurs when dopants from a doped region diffuse and are redeposited into subsequently grown semiconductor material, leading to unintended and undesirable electrical characteristics.
Innovation Solution
A method involving the formation of a doped layer in a semiconductor substrate, followed by epitaxial growth of a cap layer on the implanted region and subsequent epitaxial growth of another layer on both the cap layer and the substrate, with a purge step to remove dopants from the processing environment, thereby reducing auto-doping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dopant implantation is performed to create a doped layer, then the desired doping concentration and electrical characteristics are achieved, but auto-doping occurs during subsequent epitaxial growth leading to unintended dopant incorporation
Solution Approach 1:
A cap layer is grown preliminarily on the doped layer before growing the main epitaxial layer. This cap layer acts as a barrier to prevent dopant diffusion during the subsequent epitaxial growth process, thereby eliminating auto-doping while maintaining precise doping concentration control in the final device structure
Solution Approach 2:
The cap layer serves as an intermediary barrier between the doped layer and the epitaxial layer. It physically separates these two regions during processing, preventing direct interaction and dopant diffusion from the doped layer into the epitaxial layer, thus solving the auto-doping problem
2Object-generated harmful factors
If a cap layer is grown on the doped layer to prevent auto-doping, then dopant diffusion is reduced, but additional processing steps and time are required
Solution Approach 1:
The cap layer growth and the main epitaxial layer growth are combined into a single continuous epitaxial growth process without intermediate chamber purging or processing steps. The transition from cap layer to main epitaxial layer is achieved by simply changing precursor gas flow rates, thereby reducing processing time while still preventing auto-doping
Solution Approach 2:
The epitaxial growth process continues uninterrupted with the cap layer and main epitaxial layer grown in sequence within the same chamber environment. This continuous growth process eliminates idle time between steps and maintains efficient utilization of the epitaxial growth system throughout the entire 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 effectively minimizes auto-doping by forming a cap layer before the epitaxial layer, reducing the incorporation of unintended dopants and enhancing the activation of intended dopants, resulting in improved electrical characteristics of semiconductor devices.
Implementation Method 1
A cap layer is epitaxially grown on the doped layer
Implementation Method 2
Epitaxially growing the cap layer includes flowing a precursor gas in a chamber
Implementation Method 3
auto-doping, which occurs when dopants from a doped region diffuse and are redeposited
Implementation Method 4
Epitaxially growing the epitaxial layer includes flowing the precursor gas in the chamber
Data Source
AI summary
The present disclosure generally relates to reducing auto-doping in a semiconductor structure. In an example, semiconductor device structure includes a semiconductor substrate, a first epitaxial layer, and a second epitaxial layer. The semiconductor substrate has a first region and a second region. The first region includes a doped layer doped with a first dopant in the semiconductor substrate. The first epitaxial layer is on the doped layer in the first region. The second epitaxial layer is on the first epitaxial layer in the first region and on the semiconductor substrate in the second region.