Showerhead Faceplate Aperture Layout for Hollow Cathode Suppression
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Solution Overview
Problem
Conventional showerheads in semiconductor fabrication systems face challenges in preventing hollow cathode discharge (HCD) formation, which leads to process non-uniformity and electrical arcing, especially at higher pressures and RF powers, due to limitations in drilling small diameter holes and the resulting high cost and low yield in manufacturing.
Innovation Solution
The design incorporates a faceplate with small apertures of shallow depth on the plasma-side and larger openings through the plenum-side, where the apertures have a hollow cathode discharge suppression dimension to prevent HCD formation, and the openings are arranged in various patterns such as lattice arrays and Vogel patterns to ensure efficient process gas flow and uniform distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If small diameter holes are drilled through the entire faceplate thickness to prevent HCD, then HCD suppression is achieved, but manufacturing cost increases and yield decreases
Solution Approach 1:
The flow path is divided into two segments: a first portion through a first opening in the plenum-side faceplate and a second portion through a second opening in the plasma-side faceplate. This segmentation allows each opening to be optimized independently - the plenum-side opening can be larger for easier manufacturing while the plasma-side opening provides HCD suppression, resolving the contradiction between manufacturing ease and HCD prevention.
Solution Approach 2:
Different opening sizes are used at different locations of the faceplate. The plenum-side openings have larger dimensions for manufacturing ease, while the plasma-side openings have smaller dimensions for HCD suppression. This local differentiation allows each region to optimize for its specific function, resolving the contradiction between ease of manufacture and reliability.
2Reliability
If small diameter holes are drilled through the entire faceplate thickness, then HCD suppression is achieved, but manufacturing complexity increases
Solution Approach 1:
The single through-hole is segmented into two separate openings at different faceplates. The plenum-side opening can be manufactured with standard drilling equipment, while the plasma-side opening is manufactured separately. This segmentation reduces manufacturing complexity by avoiding the need to drill precise small holes through the entire thick faceplate assembly.
Solution Approach 2:
Instead of varying hole diameter in one dimension (which would require complex drilling), the solution varies the opening size in the depth dimension by using two separate faceplates. The plenum-side faceplate has larger openings for ease of manufacture, while the plasma-side faceplate has smaller openings for HCD suppression, resolving the contradiction without increasing manufacturing complexity.
3Ease of manufacture
If larger openings are used in the faceplate, then manufacturing is easier and yield is higher, but HCD suppression is reduced
Solution Approach 1:
The faceplate system uses different opening sizes at different locations: larger plenum-side openings for manufacturing ease and smaller plasma-side openings for HCD suppression. This local quality differentiation allows each opening to be optimized for its specific functional requirement, resolving the contradiction between ease of manufacture and HCD suppression capability.
Solution Approach 2:
The flow path is segmented into two portions through two separate openings in different faceplates. This allows the plenum-side opening to be larger (easier to manufacture) while the plasma-side opening is smaller (better HCD suppression), with both working together to achieve the desired performance without compromising manufacturing ease.
Data Source
AI summary
A faceplate of a showerhead has a bottom side that faces a plasma generation region and a top side that faces a plenum into which a process gas is supplied during operation of a substrate processing system. The faceplate includes apertures formed through the bottom side and openings formed through the top side. Each of the apertures is formed to extend through a portion of an overall thickness of the faceplate to intersect with at least one of the openings to form a corresponding flow path for process gas through the faceplate. Each of the apertures has a cross-section that has a hollow cathode discharge suppression dimension in at least one direction. Each of the openings has a cross-section that has a smallest cross-sectional dimension that is greater than the hollow cathode discharge suppression dimension.