Wafer Carrier Pocket With Orientation Notch for Epitaxial Growth
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Solution Overview
Problem
Existing semiconductor wafer carriers do not adequately accommodate Group III-nitride-based wafers during high-temperature epitaxial growth, leading to issues such as non-uniform temperature distribution, mechanical stress, and defects like slip lines and cracks due to mismatched shapes and thermal expansion.
Innovation Solution
A wafer carrier with a pocket designed to conform to the wafer's shape, featuring a notch to provide stress relief and prevent rotation, along with an optional removable orientation marker to ensure precise alignment and uniform temperature distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional circular pocket is used to hold the wafer, then the wafer can be accommodated, but the wafer rotates during epitaxial growth causing non-uniform temperature distribution and defects
Solution Approach 1:
The patent introduces a flat face feature on the circular perimeter of the pocket, creating an asymmetric geometry that prevents rotational movement of the wafer. This asymmetric design allows the wafer to be held in a fixed orientation during epitaxial growth, eliminating the rotation problem while maintaining proper wafer accommodation.
2Ease of operation
If the pocket tightly fits the wafer to prevent rotation, then orientation is controlled, but thermal expansion mismatch causes mechanical stress and defects
Solution Approach 1:
The patent applies different geometric properties to different parts of the pocket: the overall circular shape provides close fitting for orientation control, while the flat face creates a localized region with increased gap. This local modification allows thermal expansion space in critical areas while maintaining orientation control through the flat-face constraint.
Solution Approach 2:
The flat face feature is pre-designed into the pocket geometry to anticipate and accommodate thermal expansion during the epitaxial growth process. This preliminary design feature prevents mechanical stress by providing expansion space before thermal issues arise during processing.
3Reliability
If the wafer is held securely in the pocket, then position is fixed, but wafer removal becomes difficult after processing
Solution Approach 1:
The pocket design allows dynamic adaptation: during processing, the flat face constrains the wafer for stable positioning, but during removal, the increased gap at the flat face enables easy extraction. The same geometric feature serves different functional needs at different operational stages.
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 solution enhances the quality of epitaxial layers by reducing defects, improving yield, and facilitating easy wafer removal, thereby producing high-quality semiconductor structures like GaN-based HEMT devices.
Implementation Method 1
leading to issues such as non-uniform temperature distribution, mechanical stress, and defects like slip lines and cracks due to mismatched shapes and thermal expansion
Implementation Method 2
epitaxially depositing a semiconductor layer on the wafer while rotating the wafer carrier in the predetermined direction of rotation
Data Source
AI summary
A wafer carrier includes a pocket sized and shaped to accommodate a wafer, the pocket having a base and a substantially circular perimeter, and a removable orientation marker, the removable orientation marker comprising an outer surface and an inner surface, the outer surface having an arcuate form sized and shaped to mate with the substantially circular perimeter of the pocket, and the inner surface comprising a flat face, wherein the removable orientation marker further comprises a notch at a first end of the flat face.