Electrostatic Chuck Charge Control for Consistent Clamping

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Solution Overview

Problem

Conventional electrostatic clamps in semiconductor manufacturing require interruptive mechanical testing to maintain clamping forces, which are not adequately accounted for in real-time, leading to potential variations in clamping pressure due to factors like age, surface coatings, and contamination.

Innovation Solution

A system and method that uses a power supply and data acquisition system to measure current and integrate charge values, allowing a controller to selectively vary clamping voltage and frequency to maintain a consistent clamping force by continuously monitoring and adjusting the electrostatic clamping pressure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional mechanical testing methods (workpiece lifting tests or pop-off tests) are used to assess clamping capability, then clamping force measurement is achieved, but production time is lost due to interruptive testing and specialized equipment requirements

Engineering Contradiction:

Improveclamping force measurementVSAvoidproduction time

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces mechanical testing systems (load cells, physical workpiece lifting) with an electrical measurement system. The controller measures electrical parameters (voltage, current, power) of the electrostatic clamp during normal operation to assess clamping capability, eliminating the need for mechanical testing equipment and interruptive physical tests.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The electrostatic clamp performs self-assessment by utilizing its own operational electrical parameters. The controller monitors voltage, current, and power consumption during normal clamping operations to determine clamping force, allowing the system to assess its own performance without external testing equipment or production interruptions.

Inventive Principle:

Principle #25Self-service

2Device complexity

If clamping parameters remain fixed between tests, then system simplicity is maintained, but clamping pressure varies due to electrostatic clamp deterioration from age, surface coatings, and contamination

Engineering Contradiction:

Improveparameter control systemVSAvoidclamping pressure consistency

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The controller continuously monitors electrical parameters (power, voltage, current) during clamping operations and uses this feedback to assess the actual clamping force. This real-time feedback mechanism detects deterioration from age, surface coatings, and contamination, allowing the system to maintain reliable clamping pressure despite changing conditions.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system transitions from static fixed parameters to dynamic adjustable parameters. The controller can modify voltage and current settings in real-time based on measured electrical parameters and assessed clamping capability, adapting to deterioration and maintaining consistent clamping pressure throughout the electrostatic clamp's service life.

Inventive Principle:

Principle #15Dynamics

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 approach enables real-time assessment and maintenance of clamping capability without interruptive testing, ensuring consistent clamping forces and preventing quick deterioration of electrostatic clamp performance.

Implementation Method 1

an electrostatic clamp configured to selectively electrostatically clamp a workpiece to a clamping surface associated therewith via one or more electrodes

Methodology Applied

Scientific EffectElectrostatic attraction: Electrostatics

Implementation Method 2

A data acquisition system is further operably coupled to the power supply and configured to measure a current associated with the one or more electrodes... The controller is further configured to integrate the measured current over time, therein defining a determined charge value

Methodology Applied

Scientific EffectElectrostatic charge deposition: Electrostatic Deposition

Implementation Method 3

The controller is further configured to selectively vary one or more of the clamping voltage and clamping frequency based on the determined charge value, thereby maintaining a desired clamping force

Methodology Applied

Scientific EffectElectrostatic force control: Electrostatics

Data Source

PatentUS10692749B2Method to provide consistent electrostatic clamping through real time control of electrostatic charge deposition in an electrostatic chuck

Publication Date: 2020.06.23 AXCELIS TECHNOLOGIES INC

AI summary

An electrostatic clamp monitoring system has an electrostatic clamp configured to selectively electrostatically clamp a workpiece to a clamping surface associated therewith via one or more electrodes. A power supply is electrically coupled to the electrostatic clamp and configured to selectively supply a clamping voltage at a clamping frequency to the electrostatic clamp. A data acquisition system measures a current supplied to the one or more electrodes, and a controller integrates the measured current over time, therein determining a charge value associated a clamping force between the workpiece and electrostatic clamp. The controller is further configured to selectively vary one or more of the clamping voltage and clamping frequency based on the determined charge value, thereby maintaining a desired clamping force between the workpiece and electrostatic clamp.