CMP Polishing Head Zone Pressure Control
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in determining the completion of planarization, leading to variations in material removal rates and non-uniformity across semiconductor substrates due to factors like slurry distribution, polishing pad conditions, and load variations, which result in inconsistent dishing and erosion.
Innovation Solution
Implementing an in-situ monitoring system to detect clearance times across different substrate zones, adjusting polishing pressures based on calculated ratios to achieve uniform clearance times, and using independently adjustable pressure chambers to control polishing pressures across concentric zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If polishing pressure is increased to improve material removal rate, then productivity increases, but dishing and erosion non-uniformity worsens
Solution Approach 1:
The polishing head is divided into multiple independently controllable pressure zones (e.g., inner, middle, outer zones) that can be adjusted separately. This segmentation allows different regions of the substrate to receive optimized pressure levels, enabling high material removal rates in certain zones while maintaining uniformity across the entire substrate surface.
Solution Approach 2:
Different pressure levels are applied to different zones of the substrate based on their specific polishing requirements. The system applies local quality control by tailoring the polishing pressure to each zone's needs, thereby achieving both high productivity and uniform manufacturing precision across the entire substrate.
2Manufacturing precision
If polishing time is extended to achieve desired flatness, then manufacturing precision improves, but loss of time increases
Solution Approach 1:
An in-situ monitoring system continuously measures substrate topography during polishing and provides real-time feedback to the control system. This feedback mechanism allows the system to detect when the desired flatness is achieved and automatically adjust or terminate the polishing process, thereby achieving high manufacturing precision while minimizing polishing time.
Solution Approach 2:
The system performs preliminary measurements and calculations to determine the optimal polishing parameters and expected duration before actual polishing begins. By pre-planning the polishing process based on initial substrate conditions, the system can achieve desired flatness more quickly without excessive time loss.
3Manufacturing precision
If in-situ monitoring is implemented to detect clearance time, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The system replaces complex mechanical measurement systems with optical or electromagnetic sensing methods for in-situ monitoring. This substitution reduces mechanical complexity while maintaining or improving measurement accuracy for detecting clearance time and substrate topography during polishing.
Solution Approach 2:
The monitoring system is integrated directly into the polishing apparatus, allowing the system to self-monitor and self-adjust without requiring external complex measurement equipment. The polishing head incorporates sensors that automatically detect clearance conditions and provide feedback for real-time pressure adjustment, simplifying the overall system architecture.
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 enhances uniformity in dishing and erosion across the substrate, reduces within-wafer non-uniformity, and allows for consistent process control between different materials, improving the accuracy and efficiency of the polishing process.
Implementation Method 1
Optical monitoring can usually detect clearance of the overlying layer
Data Source
AI summary
A method of controlling polishing includes storing a desired ratio representing a ratio for a clearance time of a first zone of a substrate to a clearance time of a second zone of the substrate. During polishing of a first substrate, an overlying layer is monitored, a sequence of measurements is generated, and the measurements are sorted a first group associated with the first zone of the substrate and a second group associated with the second zone on the substrate. A first time and a second time at which the overlying layer is cleared is determined based on the measurements from the first group and the second group, respectively. At least one adjusted polishing pressure is calculated for the first zone based on a first pressure applied in the first zone during polishing the first substrate, the first time, the second time, and the desired ratio.