Wafer Hold Detection via Transfer Pad Voltage Measurement
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Solution Overview
Problem
In vacuum processing apparatuses, it is difficult to reliably check whether a wafer is sufficiently held by an electrostatic chuck during loading and unheld during unloading, which can lead to issues like arcing, tape burning, and wafer damage.
Innovation Solution
A method involving a vacuum processing apparatus with an electrostatic chuck, a transfer pad, and voltage measuring means, where the transfer pad connects the wafer to the electrostatic chuck, and power is supplied or stopped to determine the hold/unhold condition by measuring voltage across a resistor, indicating sufficient holding or release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electrostatic chuck is used to hold the wafer in a vacuum chamber, then the wafer can be reliably held during plasma etching, but it becomes difficult to check whether the wafer is sufficiently held or unheld
Solution Approach 1:
A transfer pad is introduced as an intermediary component between the wafer and the electrostatic chuck. The transfer pad includes a conductive layer that enables electrical connection, allowing voltage measurement to detect the hold condition. This mediator solves the detection difficulty while maintaining the reliable electrostatic holding capability.
Solution Approach 2:
The patent replaces direct mechanical contact detection methods with electrical field-based detection. By measuring voltage between the transfer pad and electrostatic chuck through the wafer, the system can non-contactly determine hold status, avoiding the limitations of mechanical detection in vacuum environments.
2Device complexity
If the wafer is not sufficiently held by the electrostatic chuck, then the setup is simpler, but arcing or tape burning may occur during plasma etching
Solution Approach 1:
The patent implements a feedback mechanism where the voltage measurement result is used to control the plasma etching process. The control unit determines whether to start plasma etching based on whether the measured voltage indicates sufficient holding, preventing arcing and tape burning by ensuring proper hold conditions before processing begins.
Solution Approach 2:
The voltage measurement and hold condition verification are performed before initiating plasma etching. This preliminary check ensures that the wafer is properly held before the high-energy plasma process begins, preventing harmful effects like arcing and tape burning without adding complexity to the holding mechanism itself.
3Speed
If the transfer pad is raised before the electrostatic holding is sufficiently canceled, then the unloading process is faster, but the wafer may be pulled in opposite directions causing damage
Solution Approach 1:
The patent uses voltage measurement feedback to determine when to raise the transfer pad during unloading. The control unit monitors the voltage between the transfer pad and electrostatic chuck, and only raises the pad when the voltage indicates that electrostatic holding has been sufficiently canceled, preventing wafer damage from conflicting forces.
Solution Approach 2:
The system prepares for potential wafer damage by implementing a safety check mechanism before the critical action of raising the transfer pad. The voltage-based verification acts as a cushioning measure, ensuring conditions are safe before proceeding with the unloading action that could otherwise cause wafer damage.
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 easy determination of wafer hold/unhold conditions, preventing damage and ensuring safe operation by confirming adequate electrostatic holding or release, thus preventing arcing and wafer damage.
Implementation Method 1
A voltage is applied between the holding surface and the wafer to produce an electrostatic force therebetween, thereby electrostatically holding the wafer on the holding surface
Implementation Method 2
voltage measuring means having a resistor inserted in the first wiring or the second wiring and a voltmeter for measuring a voltage across the resistor
Data Source
AI summary
Disclosed herein is a hold checking method for checking whether or not a wafer is held by an electrostatic chuck in loading the wafer to the electrostatic chuck by operating a transfer unit holding the wafer. The hold checking method includes a connecting step of bringing the wafer held by a transfer pad into contact with the electrostatic chuck to thereby connect the transfer pad through the wafer to the electrostatic chuck, and a hold determining step of supplying electric power from a DC power source through first wiring to the electrostatic chuck after performing the connecting step, and next determining that the wafer is held by the electrostatic chuck when the voltage across a resistor inserted in the first wiring has reached a predetermined voltage value.