Ion Implanter Platen Deposit Detection via Capacitance Monitoring
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Solution Overview
Problem
The accumulation of deposits on the clamping surface of ion implanter platens, particularly during hot ion implant processes, leads to reduced clamping force, risk of wafer drop, and increased maintenance interruptions due to unpredictable and difficult-to-monitor deposit buildup.
Innovation Solution
An ion implanter system with a platen having electrodes and a controller that monitors an AC signal to detect excessive deposits on the clamping surface by comparing the signal amplitude with predetermined thresholds, initiating a sputter clean process when necessary to prevent wafer damage and optimize processing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sputter clean process is used to remove deposits, then clamping surface cleanliness is improved, but processing throughput deteriorates due to frequent interruptions
Solution Approach 1:
The system performs preliminary monitoring of deposit accumulation on the clamping surface using capacitance sensing during wafer processing. By detecting deposits before they reach critical levels, the system schedules sputter cleaning operations proactively rather than reactively, optimizing the balance between maintaining cleanliness and minimizing interruptions to throughput
Solution Approach 2:
The system continuously monitors the clamping surface condition through capacitance measurements and provides feedback to the control system. This feedback loop enables dynamic adjustment of cleaning frequency based on actual deposit accumulation rates, allowing the system to maintain reliability while minimizing unnecessary cleaning interruptions that would reduce productivity
2Reliability
If sputter clean process is performed frequently, then risk of wafer drop is reduced, but processing time is lost due to cleaning interruptions
Solution Approach 1:
The capacitance monitoring system detects deposit accumulation trends during normal processing and predicts when cleaning will be necessary. This allows the system to perform cleaning at optimal intervals before wafer clamping security is compromised, rather than using excessive cleaning frequency that would waste time
Solution Approach 2:
The system dynamically adjusts the cleaning threshold and frequency based on processing conditions, deposit accumulation rates, and wafer handling patterns. By optimizing these parameters, the system maintains adequate wafer clamping security while minimizing the total time lost to cleaning operations
3Device complexity
If deposit accumulation is not monitored, then system complexity is reduced, but ability to detect excessive deposits deteriorates
Solution Approach 1:
The system replaces complex mechanical or optical inspection methods with electrical capacitance sensing to detect deposit accumulation. This substitution maintains high deposit detection capability while significantly reducing system complexity, as capacitance sensors can be integrated into the existing platen structure without adding mechanical moving parts or complex optical paths
Solution Approach 2:
The system uses capacitance as an intermediary parameter to indirectly measure deposit thickness and distribution on the clamping surface. This indirect measurement approach provides effective deposit detection capability while avoiding the complexity of direct physical measurement systems
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 monitors and manages deposit accumulation, reducing the risk of wafer breakage and maintaining throughput by automatically triggering cleaning when deposits exceed thresholds, ensuring consistent clamping performance and minimizing downtime.
Implementation Method 1
Most platens are electrostatic chucks that utilize electrostatic forces to clamp the wafer to a clamping surface of the platen
Implementation Method 2
The controller is configured to receive the sensed signal from the clamping power supply when no wafer is clamped to the clamping surface. The controller is further configured to monitor the sensed signal and determine if the sensed signal is representative of deposits on the clamping surface
Implementation Method 3
A sputter clean process where low energy ions are directed to the clamping surface of a platen may be used to effectively clean the clamping surface
Data Source
AI summary
An ion implanter includes a platen having a clamping surface configured to support a wafer for treatment with ions, the platen also having at least one pair of electrodes under the clamping surface, a clamping power supply configured to provide an AC signal to the at least one pair of electrodes and a sensed signal representative of the AC signal, and a controller. The controller is configured to receive the sensed signal from the clamping power supply when no wafer is clamped to the clamping surface. The controller is further configured to monitor the sensed signal and determine if the sensed signal is representative of deposits on the clamping surface exceeding a predetermined deposit threshold.