Passive Capacitance Sensing for Electrostatic Chuck Clamping
Find Innovative SolutionsGenerate Solutions
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 hinder precise positioning and clamping of workpieces during processing, especially with the advent of higher power amplifiers.
Innovation Solution
A capacitance monitoring apparatus and method utilizing a DC supply to apply DC voltage and noise voltage, combined with a voltage and current monitor, to determine capacitance based on monitored current and noise voltage, enabling precise capacitance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AC voltage generators are used to monitor capacitance, then capacitance sensing capability is provided, but the system becomes bulky and lossy
Solution Approach 1:
The patent changes the fundamental parameter from AC voltage to DC voltage for capacitance measurement. The DC power supply applies a DC voltage to the load, and capacitance is determined by monitoring the transient current response and noise voltage characteristics. This parameter change eliminates the need for bulky AC voltage generators while maintaining capacitance sensing capability.
Solution Approach 2:
The patent substitutes the mechanical/electrical AC voltage generation system with a DC power supply system. Instead of using AC voltage generators to sense capacitance, the system uses a DC supply with current and voltage monitoring capabilities to determine capacitance through electrical characteristic analysis, resulting in a more compact and efficient system.
2Device complexity
If DC power supplies are used to deliver high current, then high current capability is achieved in small form factor, but the ability to sense load capacitance is lost
Solution Approach 1:
The patent incorporates feedback mechanisms by monitoring the current and voltage characteristics of the DC power supply. The system continuously measures the current response and noise voltage when DC voltage is applied to the load, and uses this feedback information to calculate and determine the load capacitance, thus maintaining sensing capability while using a compact DC supply.
Solution Approach 2:
The DC power supply is designed to perform multiple functions: it delivers high current to the load and simultaneously senses the load capacitance through monitoring its own electrical characteristics. This multi-functionality eliminates the need for separate AC voltage generators dedicated to capacitance sensing, achieving both high current delivery and capacitance measurement in a single compact device.
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 detection of workpiece position and clamping status by monitoring capacitance, facilitating proper positioning and clamping in electrostatic chuck systems, even with high-power amplifiers.
Implementation Method 1
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
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.