CMP Pad Force Mapping for Reliable Endpoint Detection

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Solution Overview

Problem

The chemical mechanical polishing (CMP) process in semiconductor manufacturing faces challenges with unreliable and time-consuming end point detection, leading to substandard wafers due to indirect and noisy measurements of friction forces.

Innovation Solution

Direct measurement of frictional forces at the polishing pad-wafer interface using a plurality of localized sensors to create precise 2D or 3D maps of friction, allowing for real-time feedback and adjustment of the polishing process to determine the exact end point and ensure uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If physical examination techniques are used to detect end point, then measurement can be performed, but the process becomes time consuming and unreliable

Engineering Contradiction:

Improveend point detection reliabilityVSAvoidend point detection time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces mechanical/physical examination techniques with optical measurement systems. Specifically, optical sensors and interferometry methods are used to monitor film thickness and surface topography in real-time during CMP, eliminating the need to interrupt the process for physical inspection. This substitution provides continuous, reliable, and instantaneous end point detection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements real-time feedback mechanisms where optical measurement data is continuously fed back to the CMP control system. This allows dynamic adjustment of polishing parameters and immediate detection of end point conditions, replacing the delayed feedback inherent in post-process physical examination methods.

Inventive Principle:

Principle #23Feedback

2Reliability

If indirect friction force measurements are used, then end point can be detected, but the measurements are noisy and unreliable

Engineering Contradiction:

Improvefriction force measurement reliabilityVSAvoidfriction force measurement precision

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent replaces indirect mechanical friction force measurements with direct optical measurement systems. Optical interferometry and reflectometry techniques directly measure film thickness and surface characteristics without relying on friction force transducers, thereby eliminating the noise and reliability issues associated with mechanical sensing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces optical fields as an intermediary measurement medium. Instead of directly measuring friction forces through mechanical contact, optical signals interact with the wafer surface and polishing interface, providing indirect but precise measurement of polishing state and end point conditions without the noise of direct mechanical sensing.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If wafer is removed from polishing apparatus for examination, then surface can be inspected, but the process efficiency decreases

Engineering Contradiction:

Improvewafer inspection capabilityVSAvoidCMP process efficiency

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The patent enables continuous polishing operations by implementing in-situ optical measurement systems. The measurement and inspection functions are performed continuously during the polishing process without interrupting the relative motion between the polishing pad and wafer, maintaining continuous useful action throughout the process.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent implements real-time feedback loops where optical measurement data is continuously monitored and fed back to control the polishing process. This allows immediate detection of end point conditions and automatic process termination, eliminating the need to remove wafers for inspection and significantly improving productivity.

Inventive Principle:

Principle #23Feedback

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 enhances the reliability and efficiency of the CMP process by providing precise monitoring of friction forces, reducing signal noise, and enabling better control over the polishing process, resulting in higher-quality wafers.

Implementation Method 1

measuring a force on the polishing pad to monitor frictional force at the interface between the polishing pad and the wafer

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

measuring a force on the polishing pad at the interface to obtain force measurement values

Methodology Applied

Scientific EffectForce measurement: Force

Data Source

PatentUS20230381911A1Polishing metrology

Publication Date: 2023.11.30 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Methods and system for chemical mechanical polishing (CMP) are provided. A method may include performing a CMP process by contacting a polishing pad and a substrate at an interface. During the CMP process, the method includes measuring a force on the polishing pad at the interface to obtain force measurement values. Also, the method includes determining when the CMP process is complete based on the force measurement values.