Triple-Angle Susceptor Ledge for Uniform Epitaxial Deposition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional susceptor designs in epitaxial deposition processes suffer from ledge flatness variations, leading to non-uniform deposition rates and increased epitaxial delta edge roll-off (DERO), which negatively impact wafer flatness and edge roll-off profiles.
Innovation Solution
A susceptor design featuring a ledge with three surfaces oriented at different acute angles (α, θ, and β) that extend circumferentially, minimizing the impact of ledge flatness variations by controlling the flow of silicon source gas and reducing back surface deposition, thereby enhancing wafer flatness and DERO uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional susceptor design with a single-angle sloped ledge is used, then the wafer can be supported during epitaxial deposition, but ledge flatness variations cause non-uniform deposition rates and increased DERO
Solution Approach 1:
The ledge is segmented into three distinct surfaces with different angles (first surface at angle α, second surface at angle θ, third surface at angle β), where each surface serves a specific function in controlling gas flow and minimizing back surface deposition. This segmentation allows the ledge to compensate for flatness variations by having different angular characteristics in different circumferential regions.
Solution Approach 2:
Different portions of the ledge have different angular properties tailored to their specific functions: the first surface (angle α) provides initial support and controls gas flow at the outer periphery, the second surface (angle θ) provides intermediate support with a different flow characteristic, and the third surface (angle β) provides final support near the recess floor. This local differentiation of angular properties optimizes deposition uniformity across the wafer surface.
2Manufacturing precision
If the ledge supports the back surface near the peripheral edge, then the polished back surface is protected from damage, but silicon source gas leaks between the wafer and ledge causing excessive growth on the back surface
Solution Approach 1:
The angle parameters (α, θ, β) of the three ledge surfaces are specifically optimized to control the gap between the wafer and ledge. By changing these angular parameters, the design minimizes the leakage of silicon source gas while maintaining adequate support for the back surface, thereby reducing back surface deposition without compromising flatness protection.
3Device complexity
If a single-angle sloped ledge is used, then the susceptor structure remains simple, but DERO variations occur due to ledge flatness variations
Solution Approach 1:
The three-angle ledge design introduces dynamic adaptability to compensate for ledge flatness variations. By having three different angles (α > θ > β), the ledge can accommodate variations in flatness across different circumferential positions, allowing the gas flow and deposition profile to self-adjust and maintain uniform DERO despite manufacturing tolerances in ledge flatness.
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
The triple-angle ledge design effectively minimizes the impact of ledge flatness variations, resulting in improved wafer flatness and reduced DERO variations, enhancing the uniformity and quality of epitaxial layer growth on semiconductor wafers.
Implementation Method 1
introducing a vaporous silicon source gas to the front surface of the wafer to deposit and grow an epitaxial layer of silicon on the front surface
Data Source
AI summary
A susceptor for supporting a semiconductor wafer in a heated chamber includes a body that has a front surface, a rear surface, and a central plane between the front and rear surfaces. The susceptor also includes a recess that extends into the body from the front surface to a recess floor and a ledge that circumscribes the recess floor in the recess. The ledge includes a first surface oriented at a first angle relative to a horizontal plane parallel to the central plane, a second surface that extends radially inward from the first surface, the second surface optionally oriented at a second acute angle relative to the horizontal plane, and a third surface that extends between the second surface and the recess floor, the third surface oriented at a third acute angle relative to the horizontal plane. Each of the first, second, and third surfaces extends circumferentially along the ledge.