Plasma Reactor Gas Injector Array for Etch Uniformity
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Solution Overview
Problem
The mask etch process for ultra large scale integrated (ULSI) circuits faces challenges in achieving uniform etch rate distribution across the mask surface, leading to non-uniform critical dimensions and etch depth, which is exacerbated by RF electrical non-uniformities in the plasma reactor's support pedestal and sensitivity to consumable component variations.
Innovation Solution
The introduction of a plasma reactor design with enhanced RF uniformity features, including a continuous titanium ring, nickel plating for improved conductivity, and an RF gasket between the cathode and facilities plate, along with backside optical sensing for real-time etch rate monitoring and feedback-controlled gas distribution, allows for continuous uniformity adjustments during the etch process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional plasma reactor with simple cathode support is used, then the device complexity is low, but the etch rate uniformity across the mask surface deteriorates due to RF electrical non-uniformities
Solution Approach 1:
The cathode support structure implements local quality by using a continuous titanium ring with nickel plating at specific locations where RF electrical contact is needed, rather than uniform material distribution. The nickel plating is applied selectively to the facilities plate and cathode perimeter surfaces to enhance RF conductivity only where required, while the rest of the structure maintains its original properties. This localized enhancement resolves the contradiction by improving etch rate uniformity through targeted RF electrical property modification without unnecessarily increasing overall device complexity.
Solution Approach 2:
The cathode support structure uses composite materials by combining titanium (for structural integrity and RF conductivity) with nickel plating (for enhanced RF conductivity). The facilities plate and cathode are constructed as composite structures with different materials in specific configurations: a titanium cathode with aluminum facilities plate, or aluminum cathode with titanium facilities plate. This composite approach resolves the contradiction by leveraging the complementary properties of different materials to achieve both structural requirements and uniform RF electrical characteristics for improved etch uniformity.
2Manufacturing precision
If periodic etch depth measurement and process interruption is implemented, then the etch depth control precision is improved, but the productivity deteriorates due to repeated mask removal and re-introduction
Solution Approach 1:
The system replaces mechanical measurement methods (physical mask removal, photoresist stripping, and manual depth measurement) with optical sensing technology. Optical sensors positioned in the reactor chamber detect etch depth through non-contact optical measurements during the etch process, eliminating the need to mechanically remove and handle the mask repeatedly. This substitution resolves the contradiction by maintaining precise etch depth control while preserving productivity, as the mask remains in the chamber throughout the process.
Solution Approach 2:
The system implements feedback control by continuously monitoring etch depth through optical sensors and using this information to control the etch process in real-time. The optical measurement system provides feedback signals that allow the etch process to be terminated automatically when the target depth is reached, eliminating the need for periodic manual interruptions. This feedback mechanism resolves the contradiction by achieving precise etch depth control through continuous monitoring while maintaining high productivity through uninterrupted processing.
3Manufacturing precision
If simple gas distribution is used, then the device complexity is low, but the etch rate uniformity deteriorates
Solution Approach 1:
The gas distribution system implements segmentation by dividing the gas flow control into multiple independently controllable zones or channels. Instead of a single uniform gas distribution system, the reactor uses segmented gas flow paths that can be individually adjusted to compensate for local variations in etch rate. This segmentation resolves the contradiction by enabling precise control of gas distribution to achieve uniform etch rates across the mask surface while keeping each individual gas channel relatively simple in design.
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 approach significantly reduces non-uniformity in etch rate distribution, enabling precise control of etch depth and line width, improving productivity and reducing contamination risks while maintaining stringent tolerance requirements.
Implementation Method 1
backside optical sensing for real-time etch rate monitoring
Implementation Method 2
RF plasma source power applicator
Implementation Method 3
RF source power generator coupled to the applicator
Data Source
AI summary
A plasma reactor has an array of plural gas injectors arranged around a circular side wall that are individually controlled.