Electrostatic Chuck Power Supply Trapezoidal Waveform
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Solution Overview
Problem
Existing electrostatic chuck power supplies face challenges in providing AC power without peak-to-peak voltage concerns and detecting substrate presence, especially with thin dielectrics, which can lead to voltage breakdown and require additional in-vacuum components and sensors, affecting semiconductor processing quality.
Innovation Solution
A power supply system that includes a signal generating circuit, amplifying circuit, transformer, and voltage divider to produce trapezoidal waveforms with minimal dead-time, and a ripple detection circuit to detect substrate presence, allowing for AC power delivery to AC chucks and substrate detection without peak-to-peak voltage issues, and optional rectification for DC chucks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If AC voltage is used to drive the electrostatic chuck, then the chuck can be de-chucked by reversing polarity, but the peak-to-peak voltage required approaches the breakdown voltage of thin dielectrics
Solution Approach 1:
The patent employs periodic square wave voltage signals to drive the electrostatic chuck, enabling controlled chucking and de-chucking cycles. The square wave alternates between positive and negative voltage levels, creating periodic electrostatic forces that clamp the substrate during the positive half-cycle and release it during the negative half-cycle, thus achieving de-chuck capability through periodic polarity reversal.
Solution Approach 2:
The patent changes the voltage waveform from traditional sinusoidal AC to square wave, and dynamically adjusts the voltage amplitude based on substrate presence detection. By monitoring the impedance change when substrate is loaded, the system adapts the voltage parameters to maintain safe operating levels below dielectric breakdown while still achieving effective clamping forces.
2Difficulty of detecting and measuring
If traditional frequency-to-voltage techniques are used to detect substrate presence, then substrate detection is possible, but additional in-vacuum components and sensors are required which are potential sources of particles
Solution Approach 1:
The patent makes the voltage divider circuit serve dual functions: it acts as a voltage scaling component for the amplifying circuit and simultaneously serves as the detection circuit for substrate presence. By monitoring the impedance change in the voltage divider network when substrate is loaded, the system detects substrate presence without requiring separate sensors or additional in-vacuum components, thus reducing particle contamination risk.
Solution Approach 2:
The patent combines the voltage division function and substrate detection function into a single circuit network. The same resistive divider that scales down the high voltage for safe handling also provides the detection signal by measuring impedance changes, merging two previously separate functions into one integrated circuit to eliminate additional components.
3Force
If the dielectric layer is made thinner to increase clamping force, then higher clamping force is achieved, but the voltage breakdown risk increases
Solution Approach 1:
The patent changes the voltage waveform characteristics from sinusoidal to square wave, which allows for more efficient utilization of the voltage amplitude. The square wave maintains high voltage levels for longer duration during each cycle, achieving the required clamping force with lower peak voltages compared to sinusoidal waves, thus reducing breakdown risk in thin dielectrics while maintaining high clamping force.
Solution Approach 2:
The patent implements feedback control by monitoring the impedance change in the voltage divider circuit to detect substrate presence. When substrate is detected, the system adjusts the voltage amplitude to optimal levels, preventing excessive voltage application that could cause breakdown in thin dielectrics while maintaining sufficient clamping force for effective substrate holding.
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
The solution enables reliable AC power delivery to electrostatic chucks with reduced peak-voltage stress, detects substrate presence without additional in-vacuum sensors, and maintains high clamping forces, enhancing semiconductor processing quality and reducing particle contamination.
Implementation Method 1
The transformer has a primary winding and a secondary winding. The primary winding is electrically connected to the amplifying circuit, and the secondary winding is configured to be electrically connected to the electrostatic chuck. The secondary winding produces a signal for the electrostatic chuck.
Implementation Method 2
The chucks typically comprise a dielectric ceramic layer, or similar dielectric material, with the poles comprising a conductive material just below the clamping surface. High voltages are applied to a single pole, or pole-to-pole, relying on field changes in the dielectric layer effecting opposite field changes in the substrate, resulting in electrostatic forces to hold the substrate to the chuck.
Implementation Method 3
The chucks typically comprise a dielectric ceramic layer, or similar dielectric material, with the poles comprising a conductive material just below the clamping surface.
Data Source
AI summary
A power supply is provided for an electrostatic chuck. A signal generating circuit of the power supply is configured to generate a square wave signal. An amplifying circuit is electrically connected to the square wave circuit and configured to amplify the square wave signal. A transformer has a primary and a secondary winding. The primary winding is electrically connected to the amplifying circuit and the secondary winding is configured to be electrically connected to the electrostatic chuck. The secondary winding produces a signal for the electrostatic chuck. A voltage divider circuit is electrically connected to the secondary winding and to the amplifying circuit. The voltage divider circuit is configured to reduce the voltage of the signal for the electrostatic chuck and feed back the reduced voltage signal to the amplifying circuit. The signal from the secondary winding is a trapezoidal waveform with approximately flat tops and minimal dead-time between phase reversals.