CMP Endpoint Detection via Substrate Conductivity Compensation

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Solution Overview

Problem

Chemical mechanical polishing (CMP) processes face challenges in determining the endpoint of planarization, leading to non-uniformity due to variations in slurry composition, polishing pad conditions, and substrate load, causing inaccuracies in material removal rate and time needed to reach the desired flatness or thickness.

Innovation Solution

An in-situ electromagnetic induction monitoring system is used to generate signal values based on the thickness of the conductive layer, with adjustments made to account for the conductivity of the semiconductor wafer, allowing for accurate determination of the polishing endpoint and compensation for doping effects, thereby improving control parameter reliability and reducing within-wafer non-uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Difficulty of detecting and measuring

If in-situ electromagnetic induction monitoring is used to detect polishing endpoint, then measurement capability is improved, but measurement precision deteriorates due to substrate conductivity interference

Engineering Contradiction:

Improvepolishing endpoint detection capabilityVSAvoidthickness measurement accuracy

Core Design Contradiction:

Difficulty of detecting and measuringVSMeasurement precision

Solution Approach 1:

The patent extracts and separates the substrate conductivity contribution from the total electromagnetic signal. By measuring the substrate signal independently (when conductive layer is absent or by using reference measurements) and subtracting it from the composite signal, the system isolates the conductive layer thickness information, thereby eliminating the interference effect and improving measurement precision

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the interpretation parameter of the electromagnetic signal by introducing substrate conductivity as a compensating parameter. The system adjusts the signal interpretation by accounting for substrate doping levels and conductivity variations, transforming the raw signal into accurate thickness measurements through parameter compensation and calibration

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If polishing time is used as the sole control parameter, then ease of operation is improved, but manufacturing precision deteriorates due to variations in material removal rate

Engineering Contradiction:

Improvepolishing process control simplicityVSAvoidplanarization uniformity

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent implements real-time feedback control by continuously monitoring conductive layer thickness during polishing using electromagnetic induction. The system feeds back thickness information to the control system, which automatically adjusts polishing parameters or terminates the process at the optimal endpoint, replacing simple time-based control with intelligent feedback-based control to achieve precise planarization

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces the mechanical/time-based polishing control system with an electromagnetic sensing and electronic control system. Instead of relying on mechanical timers and manual intervention, the system uses electromagnetic induction for real-time thickness measurement and electronic control for automated endpoint detection and parameter adjustment

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The solution enables more accurate detection of the polishing endpoint and adjustment of control parameters, reducing the risk of under-polish and within-wafer non-uniformity by mitigating inaccuracies caused by the semiconductor substrate's conductivity, leading to improved reliability and consistency in CMP processes.

Implementation Method 1

monitoring the substrate with an in-situ electromagnetic induction monitoring system as the conductive layer is polished to generate a sequence of signal values that depend on a thickness of the conductive layer

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

One monitoring technique is to induce an eddy current in the conductive layer and detect the change in the eddy current as the conductive layer is removed

Methodology Applied

Scientific EffectEddy current: Eddy Currents

Data Source

PatentUS11780045B2Compensation for substrate doping for in-situ electromagnetic inductive monitoring

Publication Date: 2023.10.10 APPLIED MATERIALS INC

AI summary

A method of chemical mechanical polishing includes bringing a substrate having a conductive layer disposed over a semiconductor wafer into contact with a polishing pad, generating relative motion between the substrate and the polishing pad, monitoring the substrate with an in-situ electromagnetic induction monitoring system as the conductive layer is polished to generate a sequence of signal values that depend on a thickness of the conductive layer, determining a sequence of thickness values for the conductive layer based on the sequence of signal values, and at least partially compensating for a contribution of conductivity of the semiconductor wafer to the signal values.