Multi-Location Arc Sensing with Adaptive Thresholds
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Solution Overview
Problem
Current plasma reactors face challenges in detecting arcing at the wafer level due to RF noise and large dynamic range of transients, making it difficult to prevent damage to semiconductor workpieces and maintain reactor chamber cleanliness.
Innovation Solution
A method is implemented to monitor voltage or current transients at multiple power applicators and the wafer support surface, determining arc detection thresholds above noise levels, and comparing transients to these thresholds to issue an arc flag, which is used to identify the location of arcing events and control power generators, thereby preventing further processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If arc detection is performed at the sputter target using voltage or current transients from the high voltage D.C. power supply, then arcing events at or near the sputter target can be reliably detected, but wafer level arcing cannot be reliably detected due to RF noise from the wafer support pedestal and inductive coil
Solution Approach 1:
The arc detection system is segmented into multiple independent monitoring locations: the sputter target at the ceiling and the wafer support pedestal at the wafer level. Each location has its own voltage or current transient monitoring circuitry, allowing independent detection of arcing events at each location without interference from RF noise at other locations.
Solution Approach 2:
The patent introduces an intermediary approach by monitoring voltage or current transients at the power supply inputs to each consumable component rather than directly at the components themselves. This intermediary measurement point allows detection of arcing events while being isolated from the RF noise environment generated by the plasma process.
2Reliability
If monitoring is performed at multiple locations with adaptive thresholds, then both sputter target and wafer level arcing can be detected, but the system complexity increases due to multiple power applicators and power generators
Solution Approach 1:
The monitoring system uses a universal approach by applying the same voltage or current transient monitoring methodology to all power applicators and power generators in the system. Each consumable component (sputter target, wafer support pedestal, inductive coil) is monitored using identical principles, allowing the system to scale to multiple locations without proportionally increasing complexity.
Solution Approach 2:
The system dynamically adjusts the arc detection threshold for each power applicator and power generator based on the specific RF noise environment and operational conditions at each location. This adaptive thresholding allows the system to maintain high reliability across multiple locations while using a standardized monitoring framework.
3Measurement precision
If arc detection threshold is set above noise level, then false positives from RF generator transitions are reduced, but detection sensitivity may be reduced for weak arcing events
Solution Approach 1:
The system changes the threshold parameter dynamically based on the operational context, including the type of power applicator, the current process step, and the measured noise level. By adjusting the threshold parameter adaptively rather than using a fixed value, the system maintains high detection accuracy while preserving sensitivity to weak arcing events.
Solution Approach 2:
The system uses feedback from continuous monitoring of the plasma process conditions and noise levels to dynamically adjust the arc detection threshold. This feedback mechanism allows the threshold to be optimized in real-time, ensuring that weak arcing events are detected while false positives from RF generator transitions are minimized.
Data Source
AI summary
A method of responding to voltage or current transients during processing of a wafer in a plasma reactor at each of plural RF power applicators and at the wafer support surface. For each process step and for each of the power applicators and the wafer support surface, the method includes determining an arc detection threshold lying above a noise level. The method further includes comparing each transient with the threshold determined for the corresponding power applicator or wafer support surface, and issuing an arc detect flag if the transient exceeds the threshold.