Cyclical Epitaxial Deposition and Etch for Defect Control
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Solution Overview
Problem
Current semiconductor processing methods for selective epitaxial deposition often result in poor quality epitaxial growth with pronounced crystallographic defects, particularly in source/drain recesses, and fail to efficiently achieve strained epitaxial material for enhanced electrical properties.
Innovation Solution
A cyclical epitaxial deposition and etch process is employed, where pulses of silicon-containing source vapor are alternated with continuous etchant flow to selectively deposit high-quality epitaxial material on semiconductor surfaces, maintaining isothermal and isobaric conditions to ensure high throughput and minimize defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If selective deposition is performed using conventional CVD methods, then epitaxial growth can be achieved on selected surfaces, but the quality of the epitaxial material is poor with pronounced crystallographic defects
Solution Approach 1:
The conventional single-step selective deposition process is segmented into multiple sequential steps: initial deposition step followed by removal step, then additional deposition steps. This segmentation allows the process to achieve both selectivity and high quality epitaxial growth by separating the nucleation/growth phases from the defect removal phase.
Solution Approach 2:
The initial deposition step performs a preliminary action by depositing material that will subsequently be removed. This preliminary deposition enables the formation of a foundation layer that facilitates high-quality epitaxial growth in subsequent steps, while the removed portion eliminates crystallographic defects from corners and sidewalls.
2Productivity
If conventional selective deposition processes are used, then epitaxial growth can be achieved, but the process is inefficient and lacks high throughput
Solution Approach 1:
The methodology maintains continuity of useful action by performing multiple deposition steps without interrupting the overall process flow. The sequential steps of deposition and removal are designed to continue building quality epitaxial material throughout the process, maximizing throughput while ensuring high material quality through the bottom-up growth approach.
3Reliability
If strain is introduced to enhance electrical properties, then electron and hole mobility can be improved, but the process complexity increases
Solution Approach 1:
The methodology implements strain by changing material composition parameters during the epitaxial growth process. By adjusting the silicon germanium alloy composition and incorporating carbon-doped silicon in specific layers, the process achieves desired strain levels to enhance electron and hole mobility without requiring complex additional processing steps.
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 method achieves high-quality, selectively grown epitaxial layers with controlled strain, improving the electrical properties of semiconductor devices by reducing defects and enhancing growth uniformity across recesses and surfaces.
Implementation Method 1
One of the most widely used methods is chemical vapor deposition (CVD), in which atoms or molecules contained in a vapor deposit on a surface to form a film. CVD allows for the growth of films on device surface areas, including epitaxial films comprised of a crystalline silicon-containing material.
Implementation Method 2
An etchant is added to the deposition process which has a greater effect upon the poorly nucleating film as compared to the rapidly nucleating film, therefore allowing growth on only specified surface areas.
Data Source
AI summary
Methods for selectively depositing high quality epitaxial material include introducing pulses of a silicon-source containing vapor while maintaining a continuous etchant flow. Epitaxial material is deposited on areas of a substrate, such as source and drain recesses. Between pulses, the etchant flow continues such that lower quality epitaxial material may be removed, as well as any non-epitaxial material that may have been deposited. The pulse of silicon-source containing vapor may be repeated until a desired thickness of epitaxial material is selectively achieved in semiconductor windows, such as recessed source/drain regions.