Electrostatic Chuck Conductive Path for Charge Dissipation
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Solution Overview
Problem
Electrostatic chucks face issues with charge accumulation leading to workpiece sticking, damage, and processing interruptions due to inadequate grounding, which limits throughput and causes non-uniformities in plasma doping ion implanters.
Innovation Solution
An electrostatic chuck with a conductive path covering the workpiece-contacting surface, featuring a surface resistivity range of 10^8 to 10^12 ohms per square, utilizing diamond-like carbon coatings and a conductive grounding layer to effectively dissipate excessive charge without damaging the workpiece.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spring loaded grounding pins are used to dissipate charge, then charge accumulation is reduced, but the number of contact points is limited and sharp edges can damage the workpiece
Solution Approach 1:
The grounding function is segmented from discrete pin contacts to a continuous conductive path that covers the entire workpiece-contacting surface, allowing charge dissipation across multiple distributed points rather than limited pin contacts
Solution Approach 2:
A conductive coating layer acts as an intermediary between the workpiece and the grounding system, providing a smooth contact surface that prevents workpiece damage while effectively conducting charge away
2Reliability
If higher conductivity is used in the main field area, then charge dissipation improves, but clamping force may be reduced due to charge leakage
Solution Approach 1:
Different conductivity levels are applied to different regions: the gas seal ring area has high conductivity for effective charge dissipation, while the main field area has controlled conductivity to maintain clamping force while allowing sufficient charge dissipation
Solution Approach 2:
The surface resistivity in the main field area is optimized to a specific range (10^8 to 10^12 ohms per square) that balances charge dissipation needs with clamping force requirements
3Productivity
If throughput is increased in plasma doping ion implanter, then productivity improves, but excessive charge accumulation occurs leading to non-uniformities and arcing
Solution Approach 1:
The conductive path is pre-established on the electrostatic chuck surface before workpiece processing, enabling continuous charge dissipation during high-speed processing without waiting for charge accumulation problems to develop
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 solution effectively neutralizes surface charge, reducing wafer sticking and handling issues while maintaining clamping force, preventing damage and ensuring uniform processing.
Implementation Method 1
a conductive path covering at least a portion of a workpiece-contacting surface of a gas seal ring of the electrostatic chuck, the conductive path comprising at least a portion of an electrical path to ground
Implementation Method 2
Electrostatic charge may accumulate on the workpiece and also on the platen surface supporting the workpiece
Data Source
AI summary
In accordance with an embodiment of the invention, there is provided an electrostatic chuck comprising a conductive path covering at least a portion of a workpiece-contacting surface of a gas seal ring of the electrostatic chuck, the conductive path comprising at least a portion of an electrical path to ground; and a main field area of a workpiece-contacting surface of the electrostatic chuck comprising a surface resistivity in the range of from about 108 to about 1012 ohms per square.