Capacitance Sensing Circuit for Electrostatic Chuck Positioning
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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, and DC power supplies lack the ability to sense load capacitance effectively, leading to issues in proper workpiece positioning and clamping.
Innovation Solution
A capacitance measurement apparatus and method using a DC power source and a time-varying signal source in series, combined with a current monitor and capacitance module, to determine capacitance by measuring current and adjusting signal frequency or amplitude to maintain a constant current or voltage level, and incorporating autoranging and temperature compensation to account for environmental factors.
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 combined with a time-varying signal source. This substitution eliminates the need for bulky amplifiers while maintaining capacitance sensing capability through a different technical approach using series circuit configuration and current measurement.
Solution Approach 2:
The patent changes the operating parameters by using a DC power supply with superimposed time-varying signals instead of traditional AC amplifiers. This parameter change allows capacitance sensing to be performed with a compact DC power supply configuration, reducing device size while maintaining measurement precision.
2Weight of moving object
If DC power supplies are used for high current delivery, then device size is reduced, but capacitance sensing capability is lost
Solution Approach 1:
The patent merges the functions of DC power supply and capacitance sensing by combining a DC power supply with a time-varying signal source in series. This integration allows the DC power supply to deliver high current while simultaneously enabling capacitance sensing through the superimposed time-varying signals and current measurement.
Solution Approach 2:
The patent makes the DC power supply multi-functional by enabling it to both deliver high current and perform capacitance sensing. The time-varying signal source and current monitor are integrated into the DC power supply system, allowing a single device to serve multiple functions without requiring separate amplifiers.
3Ease of operation
If traditional capacitance monitoring is used, then workpiece positioning can be detected, but accuracy is reduced due to non-linearities and calibration drift
Solution Approach 1:
The patent implements feedback through current monitoring in the series circuit. By measuring the current through the load and using this feedback signal, the system can accurately determine capacitance changes related to workpiece positioning while compensating for non-linearities and calibration drift through the established current-capacitance relationship.
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 high-resolution capacitance measurement, improving workpiece positioning and clamping accuracy by minimizing non-linearities and calibration drift, while accommodating changes in environmental conditions.
Implementation Method 1
determine the capacitance based upon the measured current
Implementation Method 2
monitoring a capacitance of a combination of the workpiece and the electrostatic chuck
Implementation Method 3
Electrostatic chucks use electrostatic force to hold the workpiece in place
Data Source
AI summary
Systems, methods, and apparatuses for measuring capacitance of a load. An apparatus includes a ground connector, an output connector configured to couple to the load, and a time-varying signal source configured to inject a time-varying voltage signal onto a conduction path between the ground connector and the output connector. A DC power source or amplifier is configured to apply a DC offset to the time-varying voltage signal, and a current monitor is configured to measure time-varying current in the conduction path. A capacitance module is configured to determine the capacitance based upon at least one of the time-varying current, and accuracy of this measurement is improved by arranging an AC shunt across the DC power source or amplifier.