CVD Upper Window Curvature for Uniform Gas Flow
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Solution Overview
Problem
Conventional chemical vapor deposition (CVD) systems face challenges in achieving uniform gas flow distribution across the substrate surface, leading to non-uniform epitaxy thickness profiles and longer process times.
Innovation Solution
The use of an upper window with a convex first face and a radially outer surface with a different radius of curvature than the radially inner surface, creating an air gap that directs gas flow uniformly across the substrate, thereby improving gas flow distribution and reducing epitaxial dips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional upper window with a curved surface is used, then the gas flow is directed towards the center of the substrate, but this produces turbulent gas flow resulting in dips or depressions in the epitaxy deposited on the substrate
Solution Approach 1:
The upper window incorporates a curved surface with a specific radius of curvature (R1) that is optimized to control gas flow patterns. The curvature is designed to direct gas flow uniformly across the substrate surface while avoiding turbulence that causes dips in epitaxy thickness. This applies the curvature principle by using a mathematically defined spherical surface geometry to achieve uniform flow distribution.
Solution Approach 2:
The invention changes the geometric parameters of the upper window, specifically the radius of curvature (R1) and the gap distance (G1) between the window and substrate. By optimizing these parameters, the system achieves uniform gas flow distribution across the substrate surface, eliminating the turbulent flow and associated dips that occur with conventional curved windows.
2Manufacturing precision
If the growth rate is decreased to minimize the depth of dips in epitaxy thickness profile, then the dips are reduced, but the process times become longer with only moderate changes in dip depth
Solution Approach 1:
The invention changes the geometric parameters of the upper window (radius of curvature R1 and gap distance G1) to fundamentally alter the gas flow pattern. This parameter change eliminates the root cause of dips by achieving uniform flow distribution, allowing high growth rates to be maintained without the need to slow down the process to reduce dip depth.
Solution Approach 2:
The invention creates an optimized geometric model (specific curvature and gap dimensions) that replicates ideal gas flow conditions. By copying this optimized geometry into the upper window design, the system achieves uniform epitaxy deposition at high growth rates, avoiding the need to reduce growth rate as a compensatory measure.
3Manufacturing precision
If a conventional upper window is used, then the structure is simple, but it does not direct a uniform gas flow distribution across the substrate surface
Solution Approach 1:
The upper window uses a precisely defined spherical curvature (radius R1) to achieve uniform gas flow distribution. While this introduces geometric complexity compared to a flat or simple curved window, the curvature is mathematically specified and can be manufactured using standard precision techniques, balancing the need for uniform flow with practical device complexity.
Solution Approach 2:
The invention optimizes specific geometric parameters (radius of curvature R1 and gap distance G1) to achieve uniform gas flow. While these parameter specifications increase design complexity, they enable the system to achieve the desired uniformity in gas flow distribution and epitaxy thickness that cannot be obtained with simpler conventional window designs.
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 configuration enhances the uniformity of gas flow distribution, reduces epitaxial dips, and allows for increased growth rates while maintaining uniformity in layer thickness, thereby improving processing efficiency and wafer quality.
Implementation Method 1
The upper window is positioned within the processing chamber to direct the gas from the gas inlet, through the air gap, and to the gas outlet
Implementation Method 2
an epitaxial layer is deposited on the single crystal substrate by introducing raw material gas and carrier gas into the reaction chamber
Data Source
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AI summary
A system for depositing a layer on a substrate includes a processing chamber defining a gas inlet for introducing gas into the processing chamber and a gas outlet to allow the gas to exit the processing chamber. A substrate support is positioned within the processing chamber and is configured to receive a substrate. A transparent upper window includes a convex first face spaced from the substrate support to define an air gap therebetween. The upper window is positioned within the processing chamber to direct the gas from the gas inlet, through the air gap, and to the gas outlet. The first face includes a radially outer surface and a radially inner surface circumscribed within the outer surface. The outer surface has a first radius of curvature and the inner surface has a second radius of curvature that is different from the first radius of curvature.