Shower Plate Aperture Distribution for Plasma Uniformity
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Solution Overview
Problem
Conventional plasma CVD apparatuses face challenges in forming thin films with desired properties due to non-uniform plasma distribution caused by irregularly shaped reaction chambers, leading to inconsistent film thickness and properties.
Innovation Solution
A specially designed shower plate with varying aperture sizes and densities is used to adjust gas flow resistance and plasma distribution, compensating for irregularities in the reaction chamber, allowing for increased in-plane uniformity of film deposition by reducing gas flow in specific areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional shower plate with uniform aperture distribution is used, then the structure is simple and easy to manufacture, but the film thickness uniformity deteriorates due to plasma diffusion at irregular chamber portions
Solution Approach 1:
The shower plate is designed with non-uniform aperture distribution where different regions have different aperture densities. Specifically, regions corresponding to irregular portions of the reaction chamber have lower aperture densities to compensate for plasma diffusion, while other regions maintain higher densities. This local variation in aperture quality enables precise control of gas flow and plasma distribution across different areas, achieving uniform film thickness despite chamber irregularities.
Solution Approach 2:
The aperture distribution pattern on the shower plate is intentionally made asymmetric and non-uniform to match the asymmetric irregularities of the reaction chamber. Instead of a symmetric honeycomb pattern, the apertures are strategically positioned with varying densities in different regions, creating an asymmetric structure that compensates for the asymmetric plasma diffusion caused by chamber irregularities.
2Duration of action of moving object
If the gas flow rate is reduced to prolong residence time and increase film thickness, then the film deposition efficiency improves, but the plasma uniformity deteriorates due to chamber irregularities
Solution Approach 1:
The shower plate implements local quality control by varying aperture density across different regions. In regions where plasma diffusion occurs due to chamber irregularities, the aperture density is reduced to maintain appropriate gas flow and plasma uniformity. This localized adjustment ensures that gas residence time is optimized in each region independently, achieving both prolonged residence time and uniform film thickness simultaneously.
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
The solution enhances the in-plane uniformity of film thickness and properties by prolonging gas residence time over selected areas, improving the controllability and reproducibility of film deposition.
Implementation Method 1
the size of the apertures within a selected position or positions of the shower plate is made smaller than that of other apertures, thereby increasing gas flow resistance or decreasing conductance of gas flow locally
Implementation Method 2
a plasma enhanced deposition apparatus, which is able to form a thin film having uniform properties
Data Source
AI summary
A shower plate is adapted to be attached to the showerhead and includes a front surface adapted to face the susceptor; and a rear surface opposite to the front surface. The shower plate has multiple apertures each extending from the rear surface to the front surface for passing gas therethrough in this direction, and the shower plate has at least one quadrant section defined by radii, wherein the one quadrant section has an opening ratio of a total volume of openings of all the apertures distributed in the section to a total volume of the one quadrant section, which opening ratio is substantially smaller than an opening ratio of another quadrant section of the shower plate.