CMP Endpoint Detection Using Regional Eddy Current Sensing
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Solution Overview
Problem
Existing chemical mechanical polishing (CMP) processes struggle to accurately determine the endpoint, leading to issues such as overpolishing or underpolishing, which can cause increased circuit resistance or electrical shorts due to variations in material removal rates and initial layer thickness.
Innovation Solution
A method and apparatus using an in-situ monitoring system with eddy current sensors to detect differences in substrate measurements across multiple regions, applying independently controllable pressures, and a controller to adjust polishing based on tolerance thresholds to ensure precise endpoint detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional CMP endpoint detection methods are used, then the polishing process can be completed, but the detection precision of the endpoint is insufficient leading to overpolishing or underpolishing
Solution Approach 1:
The substrate surface is divided into multiple regions (first region and second region) for separate measurement. The monitoring system independently detects thickness or material presence in each region, allowing comparison of differential removal rates across different areas of the substrate during polishing.
Solution Approach 2:
Different regions of the substrate are measured independently to capture local variations in polishing behavior. The system applies local quality control by comparing measurements from specific regions rather than treating the entire substrate uniformly, enabling detection of regional endpoint variations.
2Reliability
If overpolishing is performed to ensure complete removal of blanket conductive layer, then field region polishing is assured, but circuit resistance increases
Solution Approach 1:
The monitoring system provides real-time feedback during polishing by continuously measuring substrate regions and comparing the measurements. When the differential measurement indicates that the blanket layer is completely removed in both regions, the system signals endpoint achievement, allowing immediate termination of polishing to prevent overpolishing and associated circuit resistance increases.
Solution Approach 2:
The system performs preliminary detection of the blanket layer presence and removal status in different regions before completing the polishing process. By monitoring the differential removal rate and detecting when both regions show consistent measurements indicating complete blanket layer removal, the system prepares for endpoint termination before actual overpolishing occurs.
3Manufacturing precision
If underpolishing occurs to preserve conductive layer thickness, then circuit resistance is minimized, but electrical shorts occur due to remaining blanket portion
Solution Approach 1:
The monitoring system provides continuous feedback on the removal status of the blanket conductive layer in multiple regions. By comparing measurements from different regions and detecting when the differential removal rate indicates complete blanket layer removal, the system ensures that polishing continues sufficiently to remove all blanket portions and prevent electrical shorts, while stopping before excessive material removal occurs.
Solution Approach 2:
The system performs preliminary detection to identify when the blanket layer is completely removed from all regions before terminating the polishing process. This preliminary action ensures that no remaining blanket portions cause electrical shorts, while the controlled monitoring prevents excessive polishing that would increase circuit resistance.
4Adaptability or versatility
If variations in initial layer thickness, slurry composition, pad condition, and polishing parameters occur, then polishing process flexibility is maintained, but material removal rate consistency deteriorates
Solution Approach 1:
The monitoring system dynamically adapts to variations in polishing conditions by continuously measuring substrate regions during the polishing process. Rather than relying on fixed predetermined polishing parameters, the system adjusts its endpoint detection based on real-time measurements of material removal rates, accommodating variations in initial layer thickness, slurry composition, pad condition, and other polishing parameters.
Solution Approach 2:
The system changes its measurement and detection parameters based on observed polishing behavior. By monitoring the differential removal rate between regions and adjusting its endpoint criteria accordingly, the system maintains consistent results despite variations in polishing parameters such as slurry composition, pad condition, and initial layer thickness.
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 the accuracy of CMP by reducing the likelihood of residual material on the substrate surface, thereby improving process yield and reducing the risk of electrical shorts or increased circuit resistance.
Implementation Method 1
A method and apparatus using an in-situ monitoring system with eddy current sensors to detect differences in substrate measurements across multiple regions
Data Source
AI summary
An apparatus for processing a substrate, the apparatus comprising a polishing assembly and a controller. The polishing assembly is configured to (a) polish a surface of the substrate. The controller is configured to (b) detect a first substrate measurement corresponding to a first region of the substrate, (c) detect a second substrate measurement corresponding to a second region of the substrate; (d) determine a difference between the first substrate measurement at the first region and the second substrate measurement at the second region; stop the polishing of the surface of the substrate in response to a determination that the difference between the first substrate measurement and the second substrate measurement is within a tolerance threshold; and repeat (a)-(d) in response to a determination that the difference between the first substrate measurement and the second substrate measurement is outside of the tolerance threshold.