Rare Earth Fluoride Coated Dummy Wafer for Plasma Etching
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Solution Overview
Problem
Dummy wafers used in semiconductor fabrication processes lack sufficient resistance to highly corrosive cleaning and etching gases, leading to instability and reduced service life, especially when exposed to halogen-based gases and plasmas.
Innovation Solution
A dummy wafer with a rare earth fluoride coating, specifically lanthanoid fluoride, yttrium fluoride, or scandium fluoride, applied as an outermost layer on a substrate, such as silicon, providing enhanced corrosion resistance and stability in halogen-based gas or plasma atmospheres.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon wafers or quartz wafers are used as dummy wafers, then they are readily available and easy to manufacture, but they have insufficient resistance to highly corrosive cleaning gases and etching gases, leading to thickness reduction and dusting
Solution Approach 1:
The dummy wafer employs a composite structure consisting of a silicon substrate combined with a silicon oxide coating layer. This composite material approach allows the wafer to benefit from both the mechanical properties of silicon and the corrosion resistance of silicon oxide, effectively resisting highly corrosive cleaning gases and etching gases while maintaining ease of manufacture through standard semiconductor fabrication processes.
2Reliability
If alumina or yttria-alumina compound ceramics are used as dummy wafers, then they have high corrosion resistance, but they are expensive and have low productivity due to long sintering and heating/cooling times
Solution Approach 1:
The invention uses a composite structure of silicon substrate with silicon oxide coating, which can be manufactured using standard semiconductor fabrication processes. This approach achieves high corrosion resistance comparable to ceramic materials while maintaining fast production cycles and high productivity, avoiding the expensive and time-consuming sintering processes required for alumina or yttria-alumina compound ceramics.
3Productivity
If cleaning gases of higher corrosive nature are used to reduce cleaning time, then productivity is improved, but the dummy wafer experiences faster degradation and reduced service life
Solution Approach 1:
The silicon oxide coating layer undergoes parameter changes in terms of its chemical composition and surface properties when exposed to fluorine-based gases. The coating transforms to form a more corrosion-resistant surface layer, adapting to the aggressive cleaning environment. This parameter change allows the dummy wafer to withstand higher corrosive cleaning gases, enabling faster cleaning cycles while maintaining service life.
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 coated wafers exhibit high corrosion resistance and prolonged service life, with minimal thickness reduction during plasma etching or cleaning operations, making them suitable for extended use in semiconductor fabrication processes.
Implementation Method 1
the rare earth fluoride coating, specifically sprayed as an outermost layer on a substrate... exhibits high corrosion resistance in a halogen-based gas or halogen-based plasma atmosphere
Data Source
AI summary
A wafer has a rare earth fluoride coating disposed, typically sprayed on a substrate as an outermost layer, the rare earth fluoride being selected from lanthanoid fluorides, yttrium fluoride, and scandium fluoride. It is useful as a dummy wafer in a plasma etching or deposition system.