Eddy Current Endpoint Monitoring With Doping Compensation
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in determining the endpoint accurately due to variations in material removal rates caused by factors like slurry composition, polishing pad condition, and substrate conductivity, leading to non-uniformity within and between wafers.
Innovation Solution
An in-situ electromagnetic induction monitoring system compensates for the conductivity of doped semiconductor wafers by using a neural network to adjust the measured trace, subtracting a modified reference trace from a measured trace to generate an adjusted trace, which improves accuracy in determining the polishing endpoint and thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If in-situ electromagnetic induction monitoring is used to detect polishing endpoint, then real-time monitoring capability is improved, but measurement precision deteriorates due to substrate doping interference
Solution Approach 1:
The patent extracts and removes the substrate doping contribution from the measured eddy current signal by subtracting a reference trace obtained from a doped substrate. This separation isolates the conductive layer thickness information from the substrate interference, restoring measurement precision while maintaining real-time monitoring capability
Solution Approach 2:
The patent introduces a reference trace as an intermediary element that represents the substrate's conductivity contribution. By comparing the measured trace against this reference intermediary, the system can identify and eliminate substrate interference from the signal, improving accuracy without sacrificing real-time detection
2Device complexity
If conventional polishing monitoring based on polishing time is used, then process simplicity is maintained, but manufacturing precision deteriorates due to material removal rate variations
Solution Approach 1:
The patent implements real-time feedback monitoring during polishing by continuously measuring eddy current signals and comparing them against reference traces. This feedback mechanism allows dynamic adjustment and precise endpoint detection, ensuring manufacturing precision while maintaining relatively simple process integration
Solution Approach 2:
The patent replaces time-based mechanical monitoring with electromagnetic induction-based electrical monitoring. This substitution enables direct measurement of conductive layer thickness through electrical signals rather than relying on mechanical polishing time correlations, significantly improving manufacturing precision
3Adaptability or versatility
If eddy current monitoring is applied to doped semiconductor wafers, then monitoring capability is extended to real substrates, but measurement precision deteriorates due to substrate conductivity contribution
Solution Approach 1:
The patent extracts the substrate doping contribution from the total eddy current signal by using a reference trace obtained from a doped substrate without conductive layers. Subtracting this reference removes the substrate interference, allowing precise measurement of conductive layer thickness on real doped semiconductor wafers
Solution Approach 2:
The patent performs preliminary measurement on a doped substrate to generate a reference trace before measuring the actual substrate. This preliminary action characterizes the substrate's conductivity contribution, enabling subsequent accurate measurements on real substrates by removing this known interference
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 method mitigates inaccuracies in eddy current signals due to substrate doping, especially at the edge, enhancing the reliability of endpoint detection and reducing within-wafer non-uniformity during CMP processes.
Implementation Method 1
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.
Data Source
AI summary
A method of compensating for a contribution of conductivity of the semiconductor wafer to a measured trace by an in-situ electromagnetic induction monitoring system includes storing or generating a modified reference trace. The modified reference trace represents measurements of a bare doped reference semiconductor wafer by an in-situ electromagnetic induction monitoring system as modified by a neutral network. The substrate is monitored with an in-situ electromagnetic induction monitoring system to generate a measured trace that depends on a thickness of the conductive layer, and at least a portion of the measured trace is applied to a neural network to generate a modified measured trace. An adjusted trace is generated, including subtracting the modified reference trace from the modified measured trace.