Automatic Reference Spectra Generation for CMP Endpoint Detection

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Chemical mechanical polishing (CMP) processes face challenges in achieving consistent material removal rates due to variations in substrate thickness, slurry composition, polishing pad conditions, and load, making it difficult to determine the polishing endpoint and achieve a desired profile.

Innovation Solution

A computer-implemented method generates reference spectra by measuring spectra during polishing and associating them with index values, allowing for the determination of a target index value and adjustment of polishing parameters to achieve uniform thickness across zones, using in-situ monitoring systems like spectrographic, motor torque, eddy current, or friction monitoring.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If preset algorithms are used to determine polishing endpoint, then the process is simple to operate, but the manufacturing precision deteriorates due to variations in substrate thickness, slurry composition, polishing pad conditions, and load

Engineering Contradiction:

Improvesimplicity of endpoint determinationVSAvoidpolishing endpoint accuracy

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent implements real-time optical monitoring during polishing to detect changes in substrate reflectivity. The system continuously measures optical properties and compares them against reference spectra to determine when the polishing endpoint has been reached, providing feedback control that adapts to variations in substrate thickness, slurry composition, pad conditions, and load.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces mechanical/time-based endpoint determination with optical measurement. Instead of relying on preset time algorithms or mechanical sensors, the system uses optical monitoring to detect material removal by measuring changes in light reflectivity from the substrate surface, enabling more precise and adaptive endpoint detection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If constant pressure is applied during polishing, then the operation is simple, but the manufacturing precision deteriorates due to variations in material removal rate across substrate and from substrate to substrate

Engineering Contradiction:

Improvesimplicity of pressure controlVSAvoidprofile consistency

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent enables dynamic adjustment of polishing pressure based on real-time optical feedback. The system monitors optical properties during polishing and can modulate the applied pressure to compensate for variations in material removal rate, achieving consistent profiles across different zones and substrates while maintaining operational simplicity through automated control.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the control parameter from fixed time or constant pressure to dynamic optical property monitoring. By measuring optical reflectivity changes during polishing, the system can adapt pressure parameters in real-time to maintain optimal material removal rates and achieve consistent profiles despite variations in substrate initial thickness, slurry composition, pad conditions, and load.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If manual creation of reference spectra is performed, then the device complexity is low, but the productivity deteriorates due to time-consuming setup procedures

Engineering Contradiction:

Improvereference spectra creation processVSAvoidtime to begin polishing new substrates

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent implements automated reference spectra generation where the system automatically measures optical properties during polishing and creates reference spectra without manual intervention. The automated process eliminates time-consuming manual setup procedures, significantly improving productivity while the complexity is managed through integrated software algorithms that automatically process and store reference data.

Inventive Principle:

Principle #25Self-service

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 automates the creation of reference spectra and target index values, reducing the time to begin polishing new substrates and eliminating the need for preset algorithms, enabling more precise control of polishing rates to achieve consistent thickness across multiple zones.

Implementation Method 1

measuring a sequence of spectra from the substrate during polishing with an in-situ monitoring system

Methodology Applied

Scientific EffectSpectroscopy: Absorption Spectroscopy

Data Source

PatentUS9579767B2Automatic generation of reference spectra for optical monitoring of substrates

Publication Date: 2017.02.28 APPLIED MATERIALS INC

AI summary

A computer-implemented method of generating reference spectra includes polishing a first substrate in a polishing apparatus having a rotatable platen, measuring a sequence of spectra from the substrate during polishing with an in-situ monitoring system, associating each spectrum in the sequence of spectra with a index value equal to a number of platen rotations at which the each spectrum was measured, and storing the sequence of spectra as reference spectra.