CMP Torque Monitoring with Multi-Frequency Pressure Segmentation
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Solution Overview
Problem
Conventional motor torque monitoring in chemical mechanical polishing lacks spatial resolution, making it difficult to determine the polishing endpoint accurately due to variations in material removal rates across the substrate.
Innovation Solution
Applying pressures with different frequencies to distinct regions of the substrate using a multi-chamber carrier head, combined with in-situ motor torque monitoring, allows for spatial resolution of friction distribution and precise determination of the polishing endpoint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional motor torque monitoring is used during CMP, then the polishing process can be monitored in-situ, but the measurement lacks spatial resolution and cannot accurately determine the polishing endpoint
Solution Approach 1:
The carrier head is divided into multiple independently controllable chambers that apply pressure to different regions of the substrate. Each chamber can apply pressure with a distinct frequency, allowing the motor torque signal to be segmented and analyzed by frequency to determine friction characteristics of specific substrate regions, thereby recovering spatial resolution.
Solution Approach 2:
Different regions of the substrate receive differentiated pressure applications with unique frequencies. This allows local friction characteristics of each substrate region to be independently measured and analyzed, enabling spatially resolved endpoint detection rather than a single averaged measurement.
2Manufacturing precision
If pressure is applied uniformly across the substrate, then the polishing process is simple to control, but spatial variations in material removal rate cannot be detected
Solution Approach 1:
The pressure application system transitions from static uniform pressure to dynamic region-specific pressure modulation. Each chamber can independently vary pressure with different frequencies, allowing the system to adapt to spatial variations in material removal rate and achieve more uniform polishing across the substrate.
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
Enhances polishing uniformity, reduces dishing and residue, and enables reliable halting of the process at the correct endpoint by analyzing the spatial distribution of friction changes.
Implementation Method 1
monitoring the substrate with an in-situ motor torque monitoring system to generate a sequence of measured values
Implementation Method 2
applying a first pressure in a first cyclic waveform having a first frequency to a first region of the substrate, applying a second pressure in a second cyclic waveform having a different second frequency to a different second region of the substrate
Data Source
AI summary
A method of polishing includes holding a substrate with a carrier head against a polishing surface of a polishing pad, generating relative motion between the substrate and polishing pad, applying a first pressure in a first cyclic waveform having a first frequency to a first region of the substrate, applying a second pressure in a second cyclic waveform having a different second frequency to a different second region of the substrate, during polishing of the substrate, monitoring the substrate with an in-situ motor torque monitoring system to generate a sequence of measured values, and determining a relative contribution to the sequence of measured values from the first region and second region based on distinguishing the first frequency from the second frequency.