Capacitive Shear Sensor for Polishing Endpoint Detection

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Solution Overview

Problem

Existing chemical mechanical polishing (CMP) technologies face challenges in determining the polishing endpoint accurately, particularly when the layers being polished have similar optical or conductive properties, leading to variations in material removal rates and time required to reach the endpoint.

Innovation Solution

The implementation of an in-situ friction monitoring system using capacitive sensors integrated into the polishing pad, which measures the frictional force between the substrate and the polishing pad, allowing for real-time monitoring and determination of the polishing endpoint.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If optical or eddy current sensors are used to detect polishing endpoint, then real-time monitoring is achieved, but detection is ineffective when layers have similar optical or conductive properties

Engineering Contradiction:

Improvepolishing endpoint detection accuracyVSAvoidsensor effectiveness across different layer combinations

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent replaces optical and eddy current sensors with a friction-based mechanical sensor. The sensor measures frictional force between the polishing pad and substrate, which changes when the polishing endpoint is reached. This mechanical measurement approach works regardless of the optical or conductive properties of the layers being polished, solving the limitation of previous sensor types.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If polishing endpoint is determined by polishing time, then process control is simplified, but variations in material removal rate cause inaccurate endpoint detection

Engineering Contradiction:

Improveendpoint determination simplicityVSAvoidendpoint detection accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the friction sensor continuously monitors polishing progress and provides real-time information about material removal. The system adjusts the polishing process based on friction measurements, allowing accurate endpoint detection that accounts for variations in material removal rate while maintaining automated process control.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If friction sensor is integrated into polishing pad, then in-situ monitoring is achieved, but device complexity increases

Engineering Contradiction:

Improvefriction measurement accuracyVSAvoidpolishing system structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the friction sensor with the polishing pad structure, integrating the measurement function into the existing polishing tool. The sensor is positioned within the polishing pad to directly contact the substrate during polishing, combining the polishing and measurement functions into a single integrated system rather than separate components.

Inventive Principle:

Principle #5Merging (Combining)

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 enables more accurate detection of the polishing endpoint, even when the layers have similar optical or conductive properties, by precisely measuring frictional changes, thus improving process control and reducing variations in material removal rates.

Implementation Method 1

The friction sensor includes a pad portion having a substrate contacting portion with an upper surface to contact the lower surface of the substrate, and a pair of capacitive sensors positioned below and on opposing sides of the substrate contacting portion

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

The in-situ friction monitoring system may be configured to determine a sequence of differences over time between a first signal from a first of the pair of capacitive sensors and a second signal from a second of the pair of capacitive sensors

Methodology Applied

Scientific EffectShear stress: Shear Stress

Data Source

PatentUS12233505B2Polishing system with capacitive shear sensor

Publication Date: 2025.02.25 APPLIED MATERIALS INC

AI summary

A polishing pad includes a sensor assembly surrounded by a lower portion of the polishing pad, and an upper portion including a pad portion disposed on the assembly and at least a portion of a polishing layer disposed on the lower portion. The sensor assembly includes a lower body having a first pair of electrodes formed thereon, a polymer body having a second pair of electrodes formed thereon and aligned with the first pair of electrodes, and a pair of gaps between the first pair of electrodes and the second pair of electrodes.