Grooved Wafer Vacuum Chuck Cleaning
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Solution Overview
Problem
Current methods for cleaning photolithography tools require opening the system, which is undesirable due to potential hardware issues and risk of further contamination, and cannot use upside-down wafers with continuous vacuum clamping due to the perfect vacuum seal preventing wafer release.
Innovation Solution
A method and device where a wafer is cycled polished-side down through the lithography tool with grooves extending to the peripheral edge, breaking the vacuum seal and allowing release, using conventional robotics for loading and unloading, and attracting contaminating particles from the vacuum chuck.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If USD wafers are used on continuously vacuum clamping chucks to clean the tool, then particle scavenging is effective, but the vacuum seal prevents wafer release for loading and unloading
Solution Approach 1:
The wafer back surface is segmented into two regions: a central highly polished region for particle attraction and a peripheral region with lower polish or micro-roughness features. This segmentation allows the central region to maintain strong particle scavenging capability while the peripheral region provides controlled vacuum release points, enabling wafer detachment without compromising cleaning effectiveness.
Solution Approach 2:
Different regions of the wafer back surface are given different surface qualities - the central area has high polish for optimal particle attraction, while the peripheral area has reduced polish or intentional micro-roughness. This local quality differentiation allows the wafer to simultaneously achieve effective particle scavenging on the polished surface and controlled vacuum release at the edges for easy loading and unloading.
2Ease of manufacture
If the system is opened to mechanically clean the chuck, then particle contamination can be physically removed, but hardware issues and further contamination risk increase
Solution Approach 1:
The cleaning system is self-service in that it uses the wafer itself as the cleaning tool. The wafer's highly polished back surface automatically attracts and removes particles from the chuck during normal operation, eliminating the need for external mechanical cleaning interventions and the associated risks of opening the system.
Solution Approach 2:
The wafer back surface acts as an intermediary between the chuck and the particle contamination. Instead of directly contacting and mechanically removing particles (which requires opening the system), the polished wafer surface serves as a mediator that passively attracts particles through electrostatic or adhesion forces, enabling cleaning without system opening.
3Manufacturing precision
If the vacuum seal is made perfect for continuous clamping, then wafer positioning stability is improved, but wafer release for cleaning becomes impossible
Solution Approach 1:
The wafer back surface is segmented into a central highly polished region for stable vacuum clamping during exposure and a peripheral region with controlled vacuum release. This segmentation maintains strong overall vacuum adhesion for positioning stability while providing localized release points that enable wafer detachment when needed for loading and unloading operations.
Solution Approach 2:
Different regions of the wafer-back interface have different vacuum adhesion properties. The central polished region provides strong adhesion for stable positioning during lithography, while the peripheral region with reduced polish or micro-roughness features provides controlled release capability, allowing the system to adapt between stable clamping and easy release states.
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
Enables cleaning of photolithography tools without opening the system, maintaining a pristine vacuum chuck and preventing deformation, thus avoiding downtime and mechanical disruptions while allowing for effective particle scavenging.
Implementation Method 1
the confronting surfaces are so smooth that a virtually perfect vacuum seal is formed between the wafer and the chuck or vacuum ring
Implementation Method 2
Upside-down (USD) wafers with highly-polished surfaces are known to attract particles that may be contained on a chuck
Data Source
AI summary
A system for cleaning semiconductor lithography tools provides for cycling a polished-side down semiconductor wafer through the lithography tool using conventional automated robotics for loading and unloading the wafer from a vacuum chuck of the lithography tool. The vacuum chuck may provide a continuous clamping vacuum feature and may include a vacuum ring that surround the periphery of the vacuum chuck. The chuck and vacuum ring may advantageously be formed of a high accuracy ceramic or plastic such as ZeroDur ceramic. The polished side of the semiconductor wafer includes grooves in a polished surface and which extend inwardly from a peripheral edge of the wafer, the grooves provide gaps between the wafer and chuck allowing the wafer to be released by a slow loss of vacuum-pressure through the gaps. The pristine clean polished surface of the wafer getters contaminating particles from the chuck.