In-situ Vibration Monitoring for CMP Endpoint Detection

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Solution Overview

Problem

Chemical mechanical polishing (CMP) processes face challenges in determining the polishing endpoint due to variations in slurry distribution, polishing pad condition, and load on the substrate, leading to inconsistencies in material removal rates and time required to achieve desired flatness or thickness.

Innovation Solution

An in-situ vibration monitoring system is integrated into the CMP apparatus, featuring a vibration sensor supported by a flexible membrane that couples with the underside of the polishing pad, allowing for reliable detection of changes in vibration patterns indicative of the polishing endpoint, and a controller to halt the process when an underlying layer is exposed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional monitoring methods (torque monitoring, acoustic monitoring) are used, then the polishing endpoint can be monitored, but the signal strength is weak and detection reliability is insufficient

Engineering Contradiction:

Improveendpoint detection reliabilityVSAvoidsignal attenuation

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

A flexible membrane is introduced as an intermediary between the polishing pad and the vibration sensor. The membrane couples the vibration sensor to the underside of the polishing pad, allowing vibration signals to be transmitted from the pad to the sensor with reduced attenuation, thereby improving detection reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces traditional acoustic monitoring methods with direct mechanical vibration sensing. By physically coupling the vibration sensor to the polishing pad through the flexible membrane, the system directly measures mechanical vibrations rather than relying on acoustic signals, resulting in stronger signals and improved endpoint detection

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If polishing time is used to determine endpoint, then the process is simple to control, but variations in material removal rate cause inconsistent endpoint timing

Engineering Contradiction:

Improvepolishing process efficiencyVSAvoidendpoint consistency

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The vibration sensor provides real-time feedback on the polishing process by detecting changes in vibration patterns. When the underlying layer is exposed, the vibration characteristics change, providing immediate feedback that allows for precise endpoint detection and consistent results across different polishing runs

Inventive Principle:

Principle #23Feedback

3Measurement precision

If the vibration sensor is positioned to couple with the polishing pad, then vibration detection accuracy improves, but the device complexity increases

Engineering Contradiction:

Improvevibration detection accuracyVSAvoidsensor integration complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

A flexible membrane is used to couple the vibration sensor to the polishing pad. This thin film structure allows the sensor to be positioned in contact with the pad while maintaining flexibility and adaptability, achieving good vibration signal transmission without requiring complex rigid mounting structures

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The vibration sensor is positioned to detect vibrations from the underside of the polishing pad rather than from the top surface. This dimensional change in sensor placement allows for effective vibration monitoring while simplifying the overall sensor integration architecture

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 enhances the reliability of detecting the polishing endpoint and improves wafer-to-wafer uniformity by providing a stronger signal and reducing signal attenuation, allowing for more precise control of the CMP process.

Implementation Method 1

an in-situ vibration monitoring system to generate a signal. The in-situ vibration monitoring system includes a vibration sensor supported by the flexible membrane and positioned to couple to an underside of the polishing pad

Methodology Applied

Scientific EffectVibration: Vibration

Implementation Method 2

A volume below the flexible membrane may be pressurizable. The flexible membrane may provide an inflatable balloon. A pump may pressurize the volume and urge the vibration sensor into contact with the polishing pad

Methodology Applied

Scientific EffectPressurisation: Pressurisation

Implementation Method 3

The polishing pad may have a pad portion coupled to a remainder of the polishing pad by a material that is softer than the pad portion. The material may completely laterally surround the pad portion

Methodology Applied

Scientific EffectDamping: Damping

Data Source

PatentUS11701749B2Monitoring of vibrations during chemical mechanical polishing

Publication Date: 2023.07.18 APPLIED MATERIALS INC

AI summary

A chemical mechanical polishing apparatus includes a platen to support a polishing pad, the platen having a recess, a flexible membrane in the recess, and an in-situ vibration monitoring system to generate a signal. The in-situ acoustic monitoring system includes a vibration sensor supported by the flexible membrane and positioned to couple to an underside of the polishing pad.