Polishing Head Decoupled Membrane Position Control
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Solution Overview
Problem
Existing chemical mechanical polishing systems face issues with wafer-to-wafer non-uniformity due to wear of the retaining ring, leading to inconsistent downforce on the substrate, which affects polishing quality and uniformity.
Innovation Solution
A carrier head design with a membrane assembly and flexible seals that allow independent control of pressure in multiple chambers, using sensors to measure distance changes and adjust chamber pressures to maintain consistent downforce despite retaining ring wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a retaining ring is used to hold the substrate during polishing, then the substrate can be securely mounted, but the retaining ring wears over time causing inconsistent downforce and wafer-to-wafer non-uniformity
Solution Approach 1:
The system dynamically changes the pressure parameter in the upper chamber to compensate for retaining ring wear. As the retaining ring wears and distance decreases, the controller reduces upper chamber pressure to maintain consistent total downforce, thereby maintaining polishing uniformity despite component wear
Solution Approach 2:
The system uses a sensor to continuously monitor the distance between the lower carrier body and membrane assembly, providing feedback to the controller. The controller adjusts upper chamber pressure based on this feedback to maintain consistent downforce, creating a closed-loop control system that compensates for retaining ring wear
2Manufacturing precision
If chamber pressure is increased to maintain downforce, then consistent loading is achieved, but the membrane and retaining ring wear faster
Solution Approach 1:
The system transitions from a static pressure system to a dynamic one where upper chamber pressure is continuously adjusted based on actual distance measurements. This dynamic adaptation allows the system to maintain consistent downforce while minimizing unnecessary pressure that would accelerate wear
Solution Approach 2:
The system changes the pressure parameter dynamically based on wear conditions. Instead of maintaining high constant pressure, the system adjusts pressure to match actual spacing, reducing wear while maintaining polishing quality
3Device complexity
If the distance between the lower carrier body and membrane assembly changes due to wear, then the system structure remains simple, but the downforce becomes inconsistent
Solution Approach 1:
A sensor provides feedback on the distance between the lower carrier body and membrane assembly, enabling the controller to detect wear-related changes and adjust pressure accordingly, maintaining loading consistency without complex mechanical adjustments
Solution Approach 2:
The system replaces complex mechanical adjustment mechanisms with a sensor-based feedback system that uses pressure control to compensate for dimensional changes, simplifying the overall structure while maintaining precision
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 system ensures consistent loading on the substrate across multiple polishing operations, reducing wafer-to-wafer non-uniformity and extending the lifespan of the retaining ring and membrane by compensating for wear-related changes in downforce.
Implementation Method 1
a flexible membrane secured to the membrane support to defining a plurality of pressurizable lower chambers, with the flexible membrane having a lower surface that provides a substrate mounting surface
Implementation Method 2
The flexure connects the membrane support to the housing, and the flexure extends through the pressurizable upper chamber
Implementation Method 3
A flexible seal forms a pressurizable upper chamber between the housing and the membrane support
Data Source
AI summary
Chemical mechanical polishing system and method include a substrate is loaded into a carrier head having a housing having an upper carrier body and a lower carrier body, and a membrane assembly beneath the lower carrier body. A space between the lower carrier body and the membrane assembly defines a pressurizable chamber, a distance from a sensor in the lower carrier body to the membrane assembly is measured, and pressure in the pressurizable chamber is controlled based on the measured distances to maintain a consistent total downforce on the membrane assembly as the distance between the sensor and the membrane assembly changes.