Passive Capacitance Sensing for Electrostatic Chuck Position Detection
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Solution Overview
Problem
Existing electrostatic chuck systems face challenges in accurately monitoring capacitance due to the use of bulky and lossy high-power amplifiers, which are inefficient in sensing load capacitance, particularly during workpiece positioning and clamping processes.
Innovation Solution
Implementing a capacitance monitoring system that utilizes a DC power supply with integrated switching components to introduce a noise voltage, coupled with current and voltage monitoring, to determine capacitance through the equation C=Idt/dv, enabling precise detection of workpiece position relative to the electrostatic chuck.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-power amplifiers are used for capacitance sensing, then sensing capability is improved, but device size increases and energy loss increases
Solution Approach 1:
The patent replaces traditional high-power amplifiers with a DC power supply that has integrated switching components. This substitution eliminates the need for bulky external amplifiers while maintaining capacitance sensing capability through the noise voltage generated by the switching components.
Solution Approach 2:
The DC power supply is designed to perform multiple functions: it provides DC voltage for electrostatic chuck operation and simultaneously generates noise voltage for capacitance sensing through its integrated switching components. This multi-functionality eliminates the need for separate sensing amplifiers.
2Measurement precision
If high-power amplifiers are used for capacitance sensing, then sensing capability is improved, but energy efficiency deteriorates
Solution Approach 1:
The DC power supply performs dual functions: providing operating voltage and generating sensing signals. The switching components generate noise voltage as a byproduct of normal operation, which is then used for capacitance sensing. This eliminates energy-wasting separate sensing amplifiers.
Solution Approach 2:
The DC power supply uses its own switching components to generate the noise voltage needed for capacitance sensing. The system serves itself by utilizing the inherent switching noise rather than requiring external sensing equipment, thereby improving energy efficiency.
3Device complexity
If DC power supply with integrated switching is used, then device complexity is reduced, but capacitance sensing capability is improved
Solution Approach 1:
The patent replaces complex external amplifiers with a simplified DC power supply structure that has integrated switching components. The switching components inherently generate noise voltage that can be used for capacitance sensing, reducing overall system complexity while maintaining sensing capability.
Solution Approach 2:
The switching components act as an intermediary that converts DC power supply operation into usable noise voltage for capacitance sensing. This intermediary mechanism allows the simple DC power supply structure to achieve accurate capacitance sensing without requiring complex additional circuitry.
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 and efficient monitoring of capacitance for proper workpiece positioning and clamping, utilizing a compact and efficient DC power supply with integrated noise voltage injection, enhancing process control in electrostatic chucking systems.
Implementation Method 1
a DC power supply with integrated switching components to introduce a noise voltage
Implementation Method 2
An electrostatic chuck has electrodes that are energized with a clamping voltage, which electrostatically clamps the workpiece to the surface of the electrostatic chuck
Implementation Method 3
determine capacitance through the equation C=Idt/dv, enabling precise detection of workpiece position
Data Source
AI summary
Devices and methods for measuring capacitance of a load. A device may include a ground connector configured to couple to ground and an output connector configured to couple to the load. The device may include a direct current (DC) supply arranged in a conduction path between the ground connector and the output connector wherein the DC supply is configured to apply a DC voltage and noise voltage onto the conduction path. The device may include a voltage monitor configured to monitor the noise voltage applied by the DC supply and the device may include a current monitor configured to measure current in the conduction path that results from the noise voltage. The device may include a capacitance module coupled to the current monitor and voltage monitor, the capacitance module configured to determine the capacitance based upon the monitored current and noise voltage.