Grooved Backing Plate for Plasma Chamber Standing Wave Compensation
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Solution Overview
Problem
Higher RF frequencies in plasma processing chambers lead to non-uniform plasma intensity due to standing wave effects, particularly when the reactor size approaches or exceeds the free space wavelength of the RF electromagnetic wave, causing issues with film uniformity on large substrates.
Innovation Solution
The implementation of grooved surfaces on the backing plate within the plasma processing chamber, which adjust the RF return path length by varying the groove profiles, helps to compensate for standing wave effects and maintain uniform plasma density across larger substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher RF frequencies (27.12 MHz or 40.68 MHz) are used to increase deposition rates and productivity, then productivity is improved, but plasma processing uniformity deteriorates due to standing wave effects in large area reactors
Solution Approach 1:
The backing plate incorporates grooves with non-uniform cross-sectional areas along the RF return path. The groove cross-sectional area varies to create different local impedances along the RF return path, which compensates for standing wave effects and achieves uniform plasma distribution across the large area substrate while maintaining high frequency operation
Solution Approach 2:
The invention changes the physical parameter of the RF return path by introducing grooves with varying cross-sectional areas. This modifies the electrical characteristics of the return path to compensate for standing wave effects at higher frequencies, enabling both high productivity and uniform plasma processing
2Area of stationary object
If the reactor size is increased to process larger substrates, then substrate area is improved, but plasma intensity uniformity deteriorates due to standing wave spatial oscillation
Solution Approach 1:
The grooves are strategically positioned and dimensioned to create local impedance variations along the RF return path that are specific to different regions of the large area reactor. This local customization of the return path characteristics compensates for the standing wave patterns that arise in large volume reactors
Solution Approach 2:
The invention addresses the two-dimensional uniformity problem across the substrate by introducing a third dimensional feature - grooves with varying cross-sectional areas through the backing plate thickness. This additional degree of freedom enables precise control of RF current distribution to achieve uniform plasma across large substrate areas
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 grooved surfaces effectively mitigate standing wave effects, ensuring more uniform plasma distribution and film properties across larger substrates, enhancing the productivity and quality of thin film deposition processes.
Implementation Method 1
the RF wave is distributed according to the beginning of a 'standing wave' spatial oscillation within the reactor
Implementation Method 2
the free space wavelength of the RF electromagnetic wave driving the plasma
Data Source
AI summary
Implementations described herein generally relate to components and methods used in plasma processing, and more specifically relate to grooved surfaces for controlling RF return path lengths in plasma processing chambers and methods for forming the same. In one implementation, a backing plate for a plasma processing chamber is provided. The backing plate comprises a rectangular body. The rectangular body has a front surface, a back surface opposing the front surface, a first axis perpendicular to a center of the rectangular body and a plurality of grooves formed in the front surface. At least one groove of the plurality of grooves has a first length across the groove in a first location and a second length across the groove in a second location.