Showerhead Plenum Pillars for PECVD Thermal Stress Reduction
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Solution Overview
Problem
Showerheads in PECVD and ALD systems face issues with progressive deformation due to high thermomechanical stresses caused by temperature gradients, leading to process failures and reduced lifespan, especially under high RF power and faceplate temperature conditions.
Innovation Solution
The introduction of a high-solidity plenum design with a dense array of vertical pillars that enhances heat conduction in the vertical direction, reducing radial temperature gradients and distributing deformational loads across many pillars, combined with a conical backplate for improved heat conduction to a heat sink.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high RF power and faceplate temperature are used to increase deposition rates, then productivity is improved, but thermomechanical stresses increase causing progressive deformation and reducing reliability
Solution Approach 1:
The plenum is segmented into multiple vertical sections by dividing it into an upper plenum and a lower plenum separated by a mid-section. This segmentation allows for better heat distribution and stress management across different zones of the showerhead, reducing progressive deformation while maintaining high deposition rates
Solution Approach 2:
Different sections of the showerhead are given different structural properties to handle local thermal and mechanical conditions. The mid-section has specific thickness and material properties optimized for heat dissipation, while the upper and lower plenums have configurations optimized for gas distribution and heat conduction respectively, allowing each region to address its specific thermal and mechanical challenges
2Manufacturing precision
If high faceplate temperature is used to enable higher heat flux and improve film properties, then manufacturing precision is improved, but temperature gradients increase causing thermomechanical stresses that reduce stability
Solution Approach 1:
The showerhead design incorporates pre-calculated and pre-engineered heat conduction pathways through the plenum structure and mid-section that actively manage temperature distribution before excessive thermal gradients can develop. This preliminary thermal management prevents the formation of dangerous stress concentrations that would lead to deformation
Solution Approach 2:
The invention changes the physical parameters of the plenum structure, including the mid-section thickness, plenum volume, and gas flow characteristics, to optimize heat conduction and reduce temperature gradients. These parameter changes allow the system to maintain high faceplate temperatures for quality film deposition while preventing excessive thermal gradients that would compromise structural stability
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 design reduces thermomechanical stresses, lowers the rate of progressive deformation, and allows for higher faceplate heat flux, resulting in longer showerhead lifespan, higher deposition rates, and improved film properties.
Implementation Method 1
a dense array of vertical pillars that enhances heat conduction in the vertical direction, reducing radial temperature gradients
Implementation Method 2
combined with a conical backplate for improved heat conduction to a heat sink
Data Source
AI summary
Multiple single plenum and dual plenum showerhead designs are disclosed. In the designs, pillars are disposed in each plenum to increase solidity of the plenums to provide improved axial heat conduction through the showerheads. The heat conduction is further improved by providing solid and substantially conical backplates.