Plasma Etching Apparatus Chamber Geometry for Uniformity
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Solution Overview
Problem
Conventional plasma etching processes in semiconductor manufacturing face challenges in achieving uniform etch rates and efficient gas utilization, particularly in deep feature etching, due to the large diameter of the process chamber relative to the wafer, leading to non-uniform plasma distribution and high etch rates near the center with lower rates at the periphery.
Innovation Solution
A plasma etching apparatus with a second chamber having a cross-sectional area matching the wafer diameter and positioned close to the substrate, allowing plasma to flow directly onto the wafer, reducing gas loss and enhancing etch uniformity and rate, while a baffle can be used to increase etchant retention time around the wafer periphery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the process chamber diameter is made considerably larger than the wafer diameter to achieve uniform plasma distribution, then plasma uniformity is improved, but gas utilization efficiency deteriorates due to gas bypassing the wafer
Solution Approach 1:
The patent changes the geometric parameter of the process chamber by reducing its internal diameter to be substantially equal to the wafer diameter. This parameter change eliminates the gas bypass path while maintaining plasma uniformity, as evidenced by the etch rate uniformity across the wafer surface described in the patent.
Solution Approach 2:
The patent inverts the conventional design approach by making the chamber diameter equal to the wafer diameter rather than larger. This inversion forces the plasma-generating gas flow to pass over the wafer surface rather than bypassing it, thereby improving gas utilization efficiency while maintaining etch uniformity.
2Productivity
If high etch rates are used to reduce process time and increase productivity, then productivity is improved, but etch uniformity deteriorates
Solution Approach 1:
The patent changes the chamber geometry parameter (diameter ratio) to enable high etch rates while maintaining uniformity. The reduced chamber diameter creates a configuration where gas flow is optimized to provide both high etch rate and uniform plasma distribution across the wafer surface.
3Loss of energy
If the chamber diameter is reduced to match the wafer diameter to improve gas utilization, then gas utilization efficiency is improved, but plasma uniformity may deteriorate
Solution Approach 1:
The patent optimizes the chamber diameter parameter to be substantially equal to the wafer diameter. This specific parameter value achieves the dual benefit of preventing gas bypass (improving gas utilization) and maintaining plasma uniformity across the wafer surface, as described in the patent results.
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 configuration improves etch uniformity and rate, reducing gas wastage and optimizing etch performance across the wafer, as demonstrated by increased etch rates and reduced variability in etch depth, even for deep features like MEMS structures and through silicon vias.
Implementation Method 1
a plasma generation device for generating a plasma in the plasma generation region
Implementation Method 2
wherein the second chamber has an interface with the third chamber so that the plasma, or one or more etchant species associated with the plasma, can flow from the second chamber to plasma etch the substrate
Implementation Method 3
to plasma etch the substrate
Data Source
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AI summary
According to the invention there is a plasma etching apparatus for plasma etching a substrate, the apparatus including: a first chamber having a plasma generation region, the plasma generation region having a cross-sectional area and shape; a plasma generation device for generating a plasma in the plasma generation region; a second chamber into which the plasma generated in the plasma generation chamber can flow, wherein the second chamber defines an interior having a cross-sectional area and shape, and the cross-sectional area of the interior is greater than the cross-sectional area of the plasma generation region; a third chamber having a substrate support for supporting a substrate of the type having an upper surface to be plasma etched, wherein the third chamber has an interface with the second chamber so that the plasma, or one or more etchant species associated with the plasma, can flow from the second chamber to etch the substrate; in which: the inner cross-sectional area and shape of the second chamber interior substantially corresponds to the upper surface of the substrate; and the substrate support is disposed so that, in use, the substrate is substantially in register with the interior of the second chamber, and the upper surface of the substrate is positioned at a distance of 80mm or less from the interface.