Wafer-Level Arc Detection Using RF Transient Sensor
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Solution Overview
Problem
Existing 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 plasma reactor system with an RF voltage sensor and differential amplifier, coupled with an arc detection comparator circuit, is implemented to accurately sense voltage changes at the electrostatic chuck, allowing for reliable wafer-level arc detection and automatic shutdown of the reactor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If RF power is applied to the wafer support pedestal and inductive coil, then plasma processing is enabled, but RF noise is generated that masks wafer-level arcing signals
Solution Approach 1:
A differential amplifier is introduced as an intermediary device between the voltage sensor and the detection system. The amplifier compares the voltage at the electrostatic chuck electrode with a reference voltage, amplifying only the differential signal that represents true arcing events while rejecting common-mode RF noise from the plasma processing system.
Solution Approach 2:
The system changes the detection parameter from monitoring absolute voltage levels to monitoring voltage differentials or transients. By detecting changes in voltage rather than absolute values, the system can distinguish true arcing events from the background RF noise environment, as arcing produces characteristic transient voltage spikes that differ from steady-state RF operation.
2Reliability
If voltage or current monitoring is used for arc detection, then arcing events can be detected, but process-induced transients create false alarms that reduce detection reliability
Solution Approach 1:
The system incorporates a comparator that provides feedback-based discrimination. The comparator circuit compares the detected voltage transient against predetermined thresholds and provides feedback control to distinguish true arcing events from process-induced transients. The system can learn or adapt to normal process transient patterns and only trigger shutdowns when genuine arcing signatures are detected.
3Reliability
If monitoring is performed at the sputter target, then target arcing can be detected, but wafer-level arcing remains undetected
Solution Approach 1:
The monitoring system is segmented into multiple independent detection points: one at the sputter target and another at the electrostatic chuck electrode. Each segment monitors its local environment independently, allowing the system to detect and distinguish between target-level arcing events and wafer-level arcing events, providing comprehensive protection throughout the plasma processing chamber.
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 system effectively distinguishes between arcing events and process-induced transients, enabling timely shutdown and reducing consumable wear, thereby preventing damage to wafers and extending the life of reactor components.
Implementation Method 1
A sensor is provided and includes a differential amplifier having a first input coupled to one of (a) the contact rod or (b) the at least one chucking electrode, the differential amplifier having a second input coupled to a voltage reference
Implementation Method 2
An arc detection comparator circuit having a comparison threshold and an input coupled to an output of the differential amplifier
Implementation Method 3
The reactor also comprises an RF bias generator having an RF control input and an RF output coupled to the at least one chucking electrode
Data Source
AI summary
Wafer level arc detection is provided in a plasma reactor using an RF transient sensor sensing voltage at an electrostatic chucking electrode, the RF sensor being coupled to a threshold comparator, and a system controller responsive to the threshold comparator.