LPCVD Coating of Complex 3D Structures Using Vertical Boat Positioning
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Solution Overview
Problem
Current thin-film coating systems are inadequate for coating complex 3D structures, as they are designed for standard planar objects and do not accommodate the unique shapes and configurations of complex 3D structures like silicon germanium (SiGe) components of radioisotope thermoelectric generators (RTGs).
Innovation Solution
A method and system using a modified chemical vapor deposition (CVD) process where a boat with a horizontal platform is configured to support complex 3D structures within a low-pressure CVD furnace, employing a mount to secure the structures and utilizing witness wafers to analyze coating uniformity and stress, allowing for the deposition of silicon nitride coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If standard thin-film coating systems are used, then coating of planar objects is achieved, but complex 3D structures cannot be coated
Solution Approach 1:
The patent applies dimensionality change by rotating the wafer boat 90 degrees so that wafers are positioned vertically rather than horizontally. This allows the coating system designed for planar objects to accommodate and coat complex 3D structures effectively, as the vertical positioning enables proper gas flow and coating deposition on non-planar surfaces.
2Adaptability or versatility
If wafers are placed vertically in boat slots, then 3D structures can be supported, but wafer movement and instability occur
Solution Approach 1:
The patent applies preliminary action by pre-configuring the wafer boat with vertical wafer positioning and securing mechanisms before the coating process begins. The boat is specifically designed and prepared to hold wafers in a vertical orientation, preventing movement and ensuring stability during the coating process, rather than attempting to adapt horizontal positioning during operation.
3Manufacturing precision
If complex 3D structures are coated using modified CVD process, then coating uniformity is achieved, but process deviation from standard procedure increases
Solution Approach 1:
The patent applies parameter changes by modifying the physical orientation parameter of the wafer boat (rotating 90 degrees to vertical position) and adjusting process parameters such as gas flow rates and deposition conditions to accommodate 3D structures. These controlled parameter changes enable uniform coating thickness on complex geometries while maintaining a systematic approach to process modification.
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 approach enables the successful coating of complex 3D structures with uniform silicon nitride films, achieving tensile stress in the range of 50 MPa-150 MPa and maintaining thickness uniformity across surfaces, effectively replicating or improving upon legacy coating processes for RTG components.
Implementation Method 1
performing a coating of the 3D structures supported on the platform wafer in the CVD furnace
Data Source
AI summary
A boat used in a chemical vapor deposition (CVD) furnace is configured to hold one or more complex three-dimensional (3D) structures when performing a coating. A platform wafer is placed horizontally in the boat to support the complex 3D structures and a mount is positioned to secure the complex 3D structures on the platform wafer during the CVD process. One or more “witness” wafers may also be placed in the boat for analyzing the thin-film coating. The platform wafer may be positioned between or bracketed by the vertical wafers. Parts with coatings manufactured using LPCVD are further disclosed.