Epitaxial Wafer Roll-off Control via Temperature Gradient
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Solution Overview
Problem
Conventional epitaxial wafer manufacturing methods struggle to maintain high flatness near the outermost periphery, leading to roll-off degradation and reduced productivity due to diameter reduction chamfering or fusion cutting after epitaxial growth.
Innovation Solution
Controlling the growth rate and temperature of the epitaxial layer during vapor-phase growth to correlate with the roll-off difference before and after growth, ensuring the epitaxial wafer maintains a roll-off value equal to or smaller than the original silicon wafer, thereby preventing roll-off degradation and eliminating the need for post-growth diameter reduction processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional epitaxial growth methods are used, then the epitaxial layer can be formed on the silicon wafer, but the film thickness uniformity near the outermost periphery deteriorates and roll-off increases
Solution Approach 1:
The patent applies local quality by creating a temperature distribution across the wafer surface during epitaxial growth. The center portion is heated to a higher temperature than the peripheral portion, which compensates for the natural cooling effect at the edges and ensures uniform film thickness across the entire wafer surface, including the outermost periphery.
Solution Approach 2:
The patent changes the temperature parameter during the epitaxial growth process. By controlling and adjusting the temperature distribution (higher at center, lower at periphery) and maintaining it within a specific range (900-1100°C), the patent achieves both high film thickness uniformity and maintains the original wafer shape without roll-off degradation.
2Shape
If diameter reduction chamfering or fusion cutting is performed after epitaxial growth to correct roll-off, then the outer peripheral shape can be improved, but productivity decreases due to additional processing steps
Solution Approach 1:
The patent applies preliminary action by controlling the temperature distribution during the epitaxial growth process itself to prevent roll-off from occurring in the first place. By maintaining appropriate temperature conditions (900-1100°C) with a gradient from center to periphery, the original wafer shape is preserved during growth, eliminating the need for subsequent diameter reduction chamfering or fusion cutting processes.
3Productivity
If the growth rate is increased to improve productivity, then the manufacturing speed increases, but the film thickness uniformity near the periphery deteriorates
Solution Approach 1:
The patent changes and controls multiple parameters simultaneously: the overall growth rate, the temperature distribution pattern, and the specific temperature range (900-1100°C). By coordinating these parameter changes, the patent achieves both high productivity through adequate growth rates and high film thickness uniformity through the optimized temperature distribution, even near the outermost periphery.
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 ensures high flatness and excellent film thickness uniformity near the outermost periphery of the epitaxial wafer, improving device yield and eliminating the need for post-growth processing, such as diameter reduction chamfering or fusion cutting.
Implementation Method 1
supplying a raw material gas onto a silicon wafer to perform vapor-phase growth of an epitaxial layer
Implementation Method 2
evaluated by an optical measurement method using an infrared ray
Data Source
Figure 1(A)~2
Figure 3(A)~3(E)
Figure 4(A)~4(E)
AI summary
The present invention provides a method for manufacturing an epitaxial wafer by supplying a raw material gas onto a silicon wafer to perform vapor-phase growth of an epitaxial layer, wherein a thickness of the epitaxial layer that is formed at a peripheral portion of the silicon wafer is controlled by controlling a growth rate and/or a growth temperature of the epitaxial layer that is subjected to vapor-phase growth. As a result, there is provided the method that enables manufacturing an epitaxial wafer having a small roll-off value by controlling a thickness of an epitaxial layer near the outermost periphery at the time of epitaxial growth.