Raised-Periphery Susceptor for Flat (110) Epitaxial Wafers
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Solution Overview
Problem
Existing susceptors for epitaxial growth struggle to produce highly flat (110) epitaxial wafers due to differences in crystal orientation, leading to uneven growth speeds and negative shifts in flatness indices like Front ZDD, especially when used with (100) wafers.
Innovation Solution
A susceptor design with a pocket and outer periphery featuring a raised portion adjacent to the pocket, where the wafer surface is positioned above the flat portion, and optionally with a depressed portion, to manage growth speeds and maintain flatness, specifically for (110) wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a susceptor designed for (100) wafers is used for (110) wafers, then the basic epitaxial growth function is maintained, but the flatness indices (ESFOR MAX and Front ZDD) deteriorate due to different crystal orientation growth characteristics
Solution Approach 1:
The susceptor outer periphery is divided into different regions with distinct functions: a flat portion and a raised portion. The raised portion is specifically positioned to correspond to the high growth speed region on the (110) wafer surface, providing localized control over the epitaxial growth process to achieve uniform flatness across the wafer.
2Ease of operation
If the side wall is raised to contain the wafer, then wafer positioning is improved, but process gas supply to the outer periphery is inhibited, causing epi-film thickness to decrease and Front ZDD to shift negatively
Solution Approach 1:
The outer periphery is segmented into a flat portion and a raised portion with different heights. The raised portion is strategically positioned to provide mechanical support and positioning without completely blocking gas flow, while the flat portion allows adequate process gas supply to maintain epi-film thickness and positive Front ZDD values.
Solution Approach 2:
The susceptor outer periphery features an asymmetric structure with a raised portion that is not uniformly distributed but specifically positioned to match the anisotropic growth characteristics of (110) wafers, creating non-uniform height distribution to optimize both positioning and gas flow.
3Reliability
If the pocket depth is increased to fully contain the wafer, then wafer stability is improved, but the height relationship between wafer and susceptor surface changes, affecting gas flow distribution and growth uniformity
Solution Approach 1:
The pocket depth is optimized to a specific parameter range where the wafer upper face position relative to the flat portion upper face is controlled within 0.05-0.35mm. This parameter optimization ensures both wafer stability during processing and appropriate gas flow distribution for uniform epitaxial growth across the wafer surface.
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 susceptor enables the production of highly flat (110) epitaxial wafers by controlling growth speed and reducing negative shifts in flatness indices, achieving improved ESFOR MAX and positive shifts in Front ZDD.
Implementation Method 1
performing vapor-phase growth
Implementation Method 2
susceptor for epitaxial growth on a wafer having a main surface of a (110) plane
Data Source
AI summary
The present invention is a susceptor for epitaxial growth on a wafer having a main surface of a (110) plane, the susceptor for epitaxial growth including: a pocket for mounting a wafer; and an outer periphery surrounding the pocket, wherein the outer periphery is provided with a flat portion and a raised portion that is a portion adjacent to the pocket and that has a portion projected from an upper face of the flat portion, and the pocket is designed such that, when the wafer is mounted on the pocket, a height of an upper face of the wafer is positioned above a height of the upper face of the flat portion. This provides a susceptor for epitaxial growth that can produce a highly flat (110) epitaxial wafer by using a wafer (a substrate) having a main surface of (110).