Electrostatic Chuck Residual Charge Measurement and Removal
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Solution Overview
Problem
Residual charge accumulation on electro-static chucks during plasma processing leads to attractive forces that can damage wafers, and existing methods fail to accurately measure and remove this charge, making it difficult to disengage wafers safely.
Innovation Solution
A method involving the vibration of wafers using support pins to induce current in an attracting electrode, allowing for the calculation of residual charge and application of a reverse voltage to safely disengage the wafer, utilizing a plasma processing apparatus with a control unit to manage the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma processing is repeated multiple times, then productivity increases, but residual charge accumulates on the electro-static chuck surface causing wafer damage
Solution Approach 1:
The system performs preliminary measurement of residual charge on the electro-static chuck surface before wafer disengagement. By measuring the induced current when the wafer is vibrated, the system calculates the residual charge amount in advance, allowing for preventive voltage application to remove the charge before it can cause wafer damage during subsequent processing cycles
Solution Approach 2:
The system implements a feedback mechanism where the measured induced current from wafer vibration is used to calculate residual charge, which then determines the voltage to be applied for charge removal. This closed-loop control ensures that the electro-static chuck is continuously maintained in a safe state for wafer handling, enabling repeated processing cycles without accumulating dangerous charge levels
2Device complexity
If residual charge is not measured, then device complexity is reduced, but accurate charge removal becomes impossible leading to wafer damage
Solution Approach 1:
The electro-static chuck system measures its own residual charge through the induced current generated during wafer vibration. The attracting electrode that already exists in the electro-static chuck structure serves dual purposes: both for electrostatic adhesion and for charge measurement, eliminating the need for separate measurement sensors and reducing overall system complexity
Solution Approach 2:
The system uses mechanical vibration of the wafer (through pin movement) to generate measurable induced current on the electro-static chuck surface. This vibration-based measurement approach converts the invisible residual charge into a detectable electrical signal, enabling accurate charge quantification without complex measurement equipment
3Reliability
If voltage is applied to remove residual charge, then wafer safety is improved, but device complexity increases due to additional control requirements
Solution Approach 1:
The system changes the voltage parameter on the attracting electrode based on the measured residual charge. By calculating the required voltage from the induced current measurement and applying it to the existing electrode structure, the system achieves adaptive charge removal without adding complex control hardware, using only parameter adjustment of the existing electrostatic system
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 estimation and removal of residual charge, preventing wafer damage by calculating the necessary voltage for safe disengagement, thus ensuring reliable plasma processing operations.
Implementation Method 1
a plasma processing apparatus for processing a wafer with gas-based plasma generated through application of high-frequency electric power while the wafer, which is placed on a stage in a processing container, is electrostatically adhered by an electro-static chuck
Implementation Method 2
calculating a residual charge amount of the wafer from an induced current flowing through an attracting electrode upon the vibrating of the wafer
Data Source
AI summary
A measurement method includes vibrating a wafer through up-and-down movement of one or more pins supporting the wafer after performing processing with gas-based plasma generated through application of high-frequency electric power while the wafer, which is placed on a stage in a processing container, is electrostatically adhered by an electro-static chuck, calculating a residual charge amount of the wafer from an induced current flowing through an attracting electrode upon the vibrating of the wafer, and calculating a voltage to be applied to the attracting electrode in response to the calculated residual charge amount of the wafer.