Electrostatic Chuck Distance Measurement for Neutralization

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Solution Overview

Problem

Existing methods for neutralizing an electrostatic chuck in plasma processing apparatuses fail to accurately detect the charge amount, leading to potential misalignment or cracking of target objects during detachment.

Innovation Solution

A method involving the calculation of the distance between the target object's back surface and the electrostatic chuck's base portion using a spectroscope and light interference patterns to determine the attraction force and subsequently neutralize the chuck.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a voltage having the opposite polarity is applied to neutralize the electrostatic chuck, then the neutralization process can be performed, but the charge amount cannot be correctly detected leading to incomplete neutralization

Engineering Contradiction:

Improveneutralization effectivenessVSAvoidcharge amount detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent replaces direct electrical measurement of charge amount with an optical measurement system. A spectroscope measures the wavelength spectrum of reflected light, and the distance between the workpiece back surface and electrostatic chuck base portion is calculated from interference patterns. This optical-mechanical substitution enables precise indirect detection of the attraction force without requiring direct charge measurement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an intermediary measurement approach by using the distance between the workpiece and electrostatic chuck as a mediator to infer the charge amount. Instead of measuring charge directly, the system measures the gap distance through light interference, which correlates with the attraction force, thereby indirectly determining the charge state for accurate neutralization control.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the electrostatic chuck surface is not neutralized, then the processing can be continuous, but the target object may be misaligned or cracked upon detachment

Engineering Contradiction:

Improveprocessing continuityVSAvoidtarget object damage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback control system where the spectroscope continuously or periodically measures the distance between the workpiece back surface and electrostatic chuck base portion. The measured distance provides feedback about the attraction force state, allowing the system to determine when neutralization is complete and when it is safe to detach the workpiece, preventing damage while maintaining processing efficiency.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent performs preliminary measurement of the workpiece-back surface-to-chuck-base-distance before detachment using the spectroscope. This preliminary action allows the system to assess the neutralization state in advance and only proceed with detachment when the measured distance indicates sufficient neutralization, thereby preventing misalignment or cracking.

Inventive Principle:

Principle #10Preliminary action

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 precise neutralization of the electrostatic chuck, preventing misalignment or cracking of target objects by accurately determining the attraction force and adjusting the voltage accordingly.

Implementation Method 1

A method for calculating a distance between a back surface of a target object to be processed and a base portion of an electrostatic chuck... acquiring a first wavelength spectrum, with respect to intensity, of reflected light of light emitted from a light source and irradiated on the back surface of the target object and the base portion of the electrostatic chuck

Methodology Applied

Scientific EffectLight interference: Interference

Implementation Method 2

The target object is attracted to and held on the electrostatic chuck by a coulomb force generated by the voltage

Methodology Applied

Scientific EffectCoulomb force: Coulomb's Law

Implementation Method 3

the back surface of the target object is elastically deformed and a distance between the back surface of the target object and the base portion of the electrostatic chuck is varied depending on an attraction force of the electrostatic chuck

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS9812996B2Method for calculating distance, method for neutralizing electrostatic chuck, and processing apparatus

Publication Date: 2017.11.07 TOKYO ELECTRON LTD

AI summary

There are provided a method for obtaining a distance between a base portion of an electrostatic chuck and a back surface of a target object and a method for neutralizing the electrostatic chuck based on the obtained distance. The electrostatic chuck has an upper surface including the base portion and a plurality of convex portions projecting from the base portion. The target object is mounted on apexes of the convex portions of the electrostatic chuck such that the back surface is in contact with the apexes. By processing a first wavelength spectrum output from a spectroscope based on reflected light of light emitted from a light source, a distance between the back surface of the target object and the base portion of the electrostatic chuck is calculated. Based on the calculated distance, a voltage is applied to the electrostatic chuck to neutralize the electrostatic chuck.