Substrate Pedestal RF Mesh Layout for Uniform Wafer Heating
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Solution Overview
Problem
Semiconductor processing apparatuses face challenges with non-uniform temperature distribution across wafers due to increased RF power, leading to localized heating and thermal stress at the braze joint between the conductive mesh and electrode, which can cause substrate pedestal breakage.
Innovation Solution
The use of a substrate pedestal with an RF mesh connected to a single RF rod or multiple RF rods, which are thermally conductive and designed to distribute RF current spatially, reducing localized heating and thermal stress through braided or insulated configurations, and employing mesh adapter pieces to manage thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If increased RF power is applied to achieve higher deposition rates, then plasma radial density is increased, but large Joule heat is generated at the braze joint causing localized heating and non-uniform temperature distribution
Solution Approach 1:
The conductive electrode is segmented into multiple conductive segments (first conductive segment, second conductive segment, etc.) that are spatially distributed across the substrate pedestal. This segmentation distributes the RF current across multiple connection points to the mesh, preventing concentration of Joule heat at a single braze joint and thereby reducing localized heating while maintaining high RF power for high deposition rates.
2Productivity
If increased RF power is applied to achieve higher deposition rates, then plasma radial density is increased, but thermal stress at the interface increases causing substrate pedestal breakage
Solution Approach 1:
The conductive electrode is divided into multiple conductive segments that are spatially distributed, which distributes thermal stress across multiple interfaces rather than concentrating it at a single braze joint. This segmentation reduces the thermal stress burden on each individual interface, preventing substrate pedestal breakage even when high RF power is applied for high deposition rates.
Solution Approach 2:
Different conductive segments are positioned at different locations on the substrate pedestal, creating non-uniform spatial distribution of thermal and mechanical loads. This local quality variation allows each segment to handle stress independently, preventing catastrophic failure and improving overall reliability of the substrate pedestal under high power conditions.
3Device complexity
If a single braze joint connects the mesh and electrode, then the structure is simple, but localized heating and thermal stress concentrate at the interface
Solution Approach 1:
The single braze joint is replaced with multiple braze joints connecting the mesh to distributed conductive segments. Although this increases structural complexity, it distributes the RF current and thermal load across multiple connection points, eliminating localized heating and improving temperature uniformity across the substrate pedestal.
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 achieves more uniform temperature distribution across the wafer and reduces the occurrence of substrate pedestal breakage by minimizing thermal stress at the interface, ensuring consistent processing results.
Implementation Method 1
each conductive rod having a first end and a second end, and a sensor. The first end of each conductive rod is electrically coupled to the mesh
Implementation Method 2
due to an increased RF current induced by the increased RF power, large Joule heat is generated at a braze joint between the conductive mesh and the conductive electrode
Implementation Method 3
a difference in thermal expansion coefficients of the conductive mesh and the conductive electrode generates thermal stress at an interface
Data Source
AI summary
A substrate pedestal includes a thermally conductive substrate support including a mesh, a thermally conductive shaft including a plurality of conductive rods therein, each conductive rod having a first end and a second end, and a sensor. The first end of each conductive rod is electrically coupled to the mesh, and the sensor is disposed between the first and second ends of each conductive rod and configured to detect current flow through each conductive rod.