Substrate Rotation Speed Sensing for Uniform Epitaxial Deposition
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Solution Overview
Problem
Existing methods for measuring and controlling the rotation speed of substrates in hot-wall epitaxial deposition reactors are complex, hinder maintenance operations, and do not ensure precise uniformity in film deposition.
Innovation Solution
A method and assembly that utilize a lifting element with gas outlets and grooves/ridges to rotate the substrate support system, coupled with a pressure sensor to measure and control the rotation speed, allowing for precise measurement and control of the substrate's angular speed outside the reaction chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical actuating means are used to rotate the substrate support system, then the rotation speed can be precisely controlled, but the system complexity and maintenance difficulty increase due to interconnected mechanical parts
Solution Approach 1:
The patent replaces the mechanical actuating means with a gas flow-based rotation system. Gas outlets directed at the substrate support system create gas pressure that drives rotation, eliminating complex mechanical transmission components while maintaining precise rotation speed control through gas flow regulation.
Solution Approach 2:
The invention uses gas flow (pneumatics) to rotate the substrate support system. Gas outlets positioned to direct flow at the support system create rotational motion through gas pressure, replacing mechanical actuation with a pneumatic drive mechanism that simplifies the overall system.
2Measurement precision
If a shaft and structural elements are added to measure rotation speed, then measurement precision improves, but maintenance operations are hindered and reactor downtime increases
Solution Approach 1:
The patent extracts the measurement function from physical structural elements inside the reaction chamber and places it outside. A pressure sensor measures gas pressure variations in the gas conduit caused by rotating substrate support system, converting a complex internal measurement problem into a simple external pressure measurement that does not interfere with maintenance.
Solution Approach 2:
The invention introduces gas pressure as an intermediary medium to transmit rotation information. The rotating substrate support system modulates gas flow, creating pressure variations that carry rotation speed information to an external sensor, allowing indirect measurement without physical measurement components inside the chamber.
3Device complexity
If gas flow is used to rotate the substrate support system, then mechanical complexity is reduced, but rotation speed precision is insufficient because gas flow rate does not univocally correlate with rotation speed
Solution Approach 1:
The patent implements a feedback mechanism where a pressure sensor continuously monitors gas pressure variations caused by the rotating substrate support system. This pressure information is fed back to a control system that adjusts gas flow rate to maintain precise rotation speed, creating a closed-loop control system that overcomes the lack of direct correlation between gas flow rate and rotation speed.
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 solution enables accurate and precise control of substrate rotation speed, ensuring uniform epitaxial deposition while reducing the complexity of mechanical parts and minimizing reactor downtime for maintenance.
Implementation Method 1
The lifting element is adapted to receive a gas flow from a plurality of gas outlets provided on its bottom surface. The gas flow causes the lifting element to rotate around a rotation axis
Data Source
Figure 1
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AI summary
The present invention discloses a method for measuring and controlling the angular speed of a substrate in an epitaxial reactor for semiconductor film deposition. The present invention further discloses an assembly suitable to execute said method, as well as a reaction chamber and a reactor comprising said assembly. In particular, though not exclusively, the above assembly, reaction chamber, and method may be used in a hot-wall, crossflow reactor for the epitaxial deposition of silicon, silicon carbide or gallium nitride.