Multi-Chamber Bladder for CMP Wafer Temperature Control
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Solution Overview
Problem
Chemical mechanical polishing of semiconductor wafers faces challenges in maintaining uniform temperature and pressure across the wafer surface due to varying linear velocity and friction, leading to temperature gradients and potential warping, which affects planarization quality.
Innovation Solution
A multi-chamber bladder system within the polishing apparatus allows independent control of temperature and pressure across different regions of the wafer by mixing hotter and colder liquids at varying ratios and using eddy current measurements to maintain uniform temperature, with a liquid supply system providing temperature control fluids to each chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-chamber bladder is used for pressure control during polishing, then the structure is simple, but temperature uniformity across the wafer deteriorates due to varying friction and linear velocity
Solution Approach 1:
The bladder is divided into multiple independent chambers, each capable of independent pressure and temperature control. This segmentation allows different regions of the wafer to be controlled independently, compensating for temperature variations caused by different linear velocities and friction levels across the wafer surface.
Solution Approach 2:
Each chamber can be supplied with cooling liquid at different temperatures and flow rates tailored to the specific thermal conditions of its corresponding wafer region. This local quality approach ensures that areas with higher friction and temperature receive more aggressive cooling, while cooler areas receive less cooling, maintaining overall temperature uniformity.
2Ease of operation
If uniform pressure is applied across the entire wafer, then the pressure control is simple, but polishing uniformity deteriorates due to varying linear velocity across different radial positions
Solution Approach 1:
The bladder structure is segmented into multiple chambers that can independently adjust pressure. This allows the system to apply non-uniform pressure distributions across the wafer surface, compensating for the varying linear velocity effects that cause non-uniform polishing rates at different radial positions.
Solution Approach 2:
The pressure control system is made dynamic by allowing independent pressure adjustment in each chamber. This dynamic capability enables real-time compensation for velocity variations across the wafer, optimizing polishing uniformity while maintaining operational simplicity through automated control.
3Device complexity
If cooling liquid is supplied uniformly across the entire bladder, then the liquid supply system is simple, but temperature gradients across the wafer persist due to varying friction and linear velocity
Solution Approach 1:
The liquid supply system is segmented to provide independent cooling liquid supply to each bladder chamber. This allows different temperatures, flow rates, and cooling intensities to be applied to different wafer regions, effectively eliminating temperature gradients caused by varying friction and linear velocity across the wafer surface.
Solution Approach 2:
Each chamber receives cooling liquid with properties (temperature, flow rate) optimized for its specific thermal conditions. Regions with higher friction and temperature receive more aggressive cooling, while cooler regions receive less cooling, maintaining temperature uniformity across the wafer without requiring complex overall system redesign.
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 ensures high uniformity and reduces process variations by maintaining the wafer at a consistent temperature, minimizing warping and enhancing the quality of planarization during chemical mechanical polishing.
Implementation Method 1
providing a temperature control liquid to the bladder to at least one of cool or heat and maintain the substrate at substantially the same temperature
Implementation Method 2
measuring an eddy current in the substrate, determining a temperature of the substrate at a plurality of locations on the substrate
Data Source
AI summary
A chemical mechanical polishing apparatus includes a liquid filled bladder that exerts force on the back of the substrate being polished. The bladder can be a multi-chamber bladder having chambers filled with different ratios of hot and cold water. Eddy current detection during the polishing can be used to control the polishing process parameters.