Electrostatic Platen Current Monitoring for Cleaning Endpoint Control
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Solution Overview
Problem
Existing electrostatic platens in semiconductor processing tools suffer from deposits that interfere with proper clamping and cause particle contamination, leading to inefficient cleaning processes that either prolong tool downtime or reduce throughput.
Innovation Solution
A system and method to monitor current changes on the platen when no workpiece is present, using clamping voltage to detect when cleaning is needed and determine the endpoint of the cleaning process, allowing for precise control of the cleaning process without venting the chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cleaning is initiated after processing a certain number of workpieces, then deposits are removed from the platen, but cleaning may start too soon reducing throughput
Solution Approach 1:
The system continuously monitors current drawn by the platen during operation and uses this feedback to determine when cleaning is actually needed. The controller compares real-time current measurements against threshold values to trigger cleaning only when deposit accumulation reaches levels that interfere with proper clamping, preventing premature cleaning and maximizing throughput while maintaining reliability.
Solution Approach 2:
The patent replaces mechanical or time-based cleaning triggers with an electrical monitoring system that measures current characteristics. By substituting the mechanical assessment of platen cleanliness with electrical current measurement, the system achieves precise, real-time detection of deposit accumulation without requiring physical inspection or fixed scheduling.
2Reliability
If cleaning process is prolonged to ensure complete removal of deposits, then platen is thoroughly cleaned, but tool downtime increases
Solution Approach 1:
During the cleaning process, the system continuously monitors current changes to detect when deposits have been sufficiently removed. The feedback signal from current measurement allows the controller to terminate cleaning at the precise moment when the platen surface is restored to its original electrical characteristics, ensuring complete cleaning without unnecessary prolongation and minimizing tool downtime.
Solution Approach 2:
The platen's own electrical properties serve as the indicator of its cleanliness state. By measuring current drawn during normal operation, the system uses the platen's inherent electrical characteristics to self-diagnose when cleaning is needed and when cleaning is complete, eliminating the need for external inspection methods or extended cleaning cycles.
3Productivity
If cleaning is delayed to maintain throughput, then productivity is maximized, but deposits may cause particle contamination
Solution Approach 1:
The continuous current monitoring provides real-time feedback on platen condition, enabling the system to detect deposit accumulation at the exact point where it begins to create contamination risks. The controller responds to current threshold exceedances by initiating cleaning immediately, preventing the progression to particle detachment and contamination while maintaining maximum possible throughput by avoiding unnecessary early cleaning.
Solution Approach 2:
The system replaces physical inspection methods with electrical current measurement to detect the onset of contamination conditions. By monitoring changes in current characteristics, the system can identify when deposits have reached critical levels that may lead to particle generation, enabling preventive cleaning action before actual contamination occurs.
4Productivity
If current platen monitoring is implemented, then cleaning timing is optimized, but system complexity increases
Solution Approach 1:
The system uses the existing electrode power supply that is already required for platen operation during workpiece processing. This power supply serves dual functions: providing clamping voltage during normal operation and monitoring platen cleanliness through current measurement. By making the monitoring system multi-functional with an existing component, the patent avoids adding separate dedicated monitoring hardware, thereby minimizing system complexity while achieving optimized cleaning timing.
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 accurate determination of when to initiate and terminate the cleaning process, improving throughput by preventing premature or incomplete cleaning, and reducing the risk of particle contamination.
Implementation Method 1
an electrostatic platen, which provides an electrostatic force so as to clamp the workpiece in place. This electrostatic force is generated by electrodes disposed in the platen
Implementation Method 2
the deposited material may be conductive, allowing charges to move easily on the clamping surface of the platen. By monitoring the current in this manner, it is possible to terminate the cleaning process when a sufficient amount of deposited material has been removed
Implementation Method 3
a cleaning process may be initiated after processing a certain number of workpieces. This may start the cleaning process too soon and hence lower the throughput of the tool
Implementation Method 4
a cleaning process for the clamping surface of an electrostatic platen of a beamline ion implanter may include directing an argon ion beam at the clamping surface positioned at a defined larger tile angle relative to the ion beam to intentionally create a glancing blow of the ion beam that sputter cleans the clamping surface
Data Source
AI summary
A system and method to control the cleaning of an electrostatic platen is disclosed. A clamping voltage is applied to the electrostatic platen when a workpiece is not disposed on the top surface of the platen. Over time, the deposition of material on the clamping surface causes changes in the current that is supplied to the platen when the clamping voltage is applied. By monitoring the current in this manner, it is possible to terminate the cleaning process when a sufficient amount of deposited material has been removed. Additionally, by monitoring the current, it is also possible to determine when a cleaning process is warranted.