Tripolar ESC Electrodes for In-Situ Gap and Tilt Measurement
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Solution Overview
Problem
In semiconductor processing, maintaining precise control over the pedestal-to-showerhead gap and tilt is challenging, especially at high temperatures, as existing measurement systems are indirect and require actual substrates, leading to waste and performance issues due to deposition on optical sensors and line-of-sight limitations.
Innovation Solution
A tripolar electrode arrangement in electrostatic chucks (ESCs) is used to measure and adjust the gap and tilt between the ESC and showerhead, employing a sensing circuit to sense substrate states and an additional inner electrode for relative tilt measurement, enabling in-situ direct measurement at high temperatures without using actual substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If indirect measurement systems using optical sensors are employed, then gap and tilt can be measured, but deposition on optical sensors degrades measurement precision and requires substrate waste for calibration
Solution Approach 1:
The patent replaces optical measurement systems with electrical impedance sensing through electrodes. The measurement system uses impedance changes between electrodes and the showerhead to detect gap and tilt, eliminating optical sensors that suffer from deposition contamination. This substitution of measurement modality (optical to electrical) resolves the contradiction by avoiding substrate waste while maintaining measurement capability.
Solution Approach 2:
The patent introduces electrodes as an intermediary element between the pedestal and showerhead for measurement purposes. These electrodes sense impedance changes caused by variations in gap and tilt, providing indirect electrical measurement without requiring direct line-of-sight optical paths that are blocked by deposition. The intermediary electrodes enable continuous measurement without substrate consumption.
2Measurement precision
If line-of-sight optical measurement is used, then gap and tilt can be measured, but deposition blocks the optical path and degrades measurement precision
Solution Approach 1:
The patent replaces line-of-sight optical measurement with electrical impedance sensing. The measurement system uses impedance changes between electrodes and the showerhead to detect gap and tilt, eliminating the need for optical paths that are blocked by deposition. This substitution of measurement modality (optical to electrical) resolves the contradiction by making measurement immune to deposition effects.
Solution Approach 2:
The patent introduces electrodes as an intermediary element that senses gap and tilt through electrical impedance rather than optical line-of-sight. The electrodes are positioned to sense impedance changes caused by variations in spacing and orientation, providing measurement capability that is not blocked by deposition on the showerhead or pedestal surfaces.
3Measurement precision
If tripolar electrode arrangement with additional inner electrode is used, then tilt measurement capability is improved, but device complexity increases
Solution Approach 1:
The patent makes the electrode arrangement multi-functional by designing it to perform both substrate clamping and gap/tilt measurement functions. The same tripolar electrode structure used for electrostatic clamping also serves as the sensing element for measurement, eliminating the need for separate measurement devices. This multi-functionality resolves the contradiction by achieving enhanced measurement capability without proportionally increasing device complexity.
Solution Approach 2:
The patent merges the clamping function and measurement function into a single integrated electrode system. The tripolar electrodes that provide electrostatic clamping force also serve as sensing elements whose impedance changes indicate gap and tilt conditions. This merging of functions allows the system to achieve precise tilt measurement capability while avoiding the complexity of adding separate measurement hardware.
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
This solution allows for precise and direct measurement and adjustment of the gap and tilt, improving process performance by avoiding substrate waste and maintaining uniformity, even in high-temperature processes.
Implementation Method 1
The controller is configured to measure a pedestal-to-showerhead gap and at least one of a magnitude and a direction of a relative tilt between the pedestal and the showerhead by sensing impedances between the at least three electrodes and the showerhead
Implementation Method 2
The pedestal is arranged below a showerhead in a processing chamber and includes at least three electrodes to clamp a substrate to the pedestal during processing
Data Source
AI summary
A system comprises a pedestal and a controller. The pedestal is arranged below a showerhead in a processing chamber and includes at least three electrodes to clamp a substrate to the pedestal during processing. The controller is configured to measure a pedestal-to-showerhead gap and at least one of a magnitude and a direction of a relative tilt between the pedestal and the showerhead by sensing impedances between the at least three electrodes and the showerhead.