Polishing Head with Segmented Pressure Zones for Wafer Flatness
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Solution Overview
Problem
Conventional polishing heads using the rubber-chuck method struggle to maintain stable flatness and uniform polishing stock removal due to variations in workpiece thickness and template shape, and are unable to readily adjust polishing profiles for non-flat workpieces.
Innovation Solution
A polishing head with an annular rigid ring, a rubber film bonded with uniform tension, a mid plate forming a space with the rigid ring and rubber film, and an annular template, divided by an annular wall to create multiple sealed spaces, allowing separate pressure control to ensure uniform polishing pressure across the workpiece, regardless of thickness variations and template rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional polishing head with a single sealed space is used, then the structure is simple, but stable flatness cannot be obtained due to thickness variations of the workpiece and template
Solution Approach 1:
The single sealed space is divided into multiple sealed spaces (first, second, and third sealed spaces) by annular partitions. Each sealed space can be independently pressurized to compensate for thickness variations at different radial positions of the workpiece, thereby achieving stable flatness while managing structural complexity through modular segmentation.
Solution Approach 2:
Different regions of the rubber film are pressurized to different pressures based on local thickness variations. The first sealed space applies higher pressure to the central region, the second sealed space addresses intermediate regions, and the third sealed space handles outer regions, creating localized pressure distribution that compensates for non-uniform workpiece and template thickness.
2Adaptability or versatility
If uniform pressure is applied across the entire workpiece, then the structure is simple, but polishing profile cannot be adjusted for non-flat workpieces
Solution Approach 1:
The pressure control system is segmented into multiple independent pressure sources, each controlling a specific sealed space. This allows different pressure profiles to be applied to different radial zones of the workpiece, enabling adjustment of polishing profiles for non-flat workpieces while maintaining manageable device complexity through modular pressure control.
Solution Approach 2:
The pressure in each sealed space can be dynamically adjusted independently during the polishing process. This dynamic pressure control allows the system to adapt to different workpiece geometries and achieve desired polishing profiles by varying pressure distribution across different sealed spaces based on real-time requirements.
3Force
If the rubber film is inflated with uniform pressure, then the workpiece is held firmly, but pressure variations occur due to thickness variations of workpiece and template
Solution Approach 1:
The single pressure chamber is segmented into multiple sealed spaces with independent pressure control. This segmentation allows the holding force to be maintained firmly across the entire workpiece while compensating for pressure variations caused by thickness differences in different regions, achieving both strong holding and pressure uniformity.
Solution Approach 2:
The pressure parameter is changed and optimized for each sealed space based on the local thickness characteristics of the workpiece and template. By adjusting pressure parameters independently in each sealed space, the system maintains firm holding force while achieving uniform pressure distribution across the entire workpiece surface.
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 configuration ensures consistent flatness and polishing stock removal uniformity, enabling adjustment of polishing profiles to achieve a flat shape even for non-flat workpieces, particularly effective for large silicon wafers, by controlling pressure in multiple sealed spaces to maintain uniform pressure distribution.
Implementation Method 1
a pressurized fluid such as air is poured into a back face of the elastic film, and the elastic film is inflated by a uniform pressure so as to press the workpiece toward the polishing pad
Implementation Method 2
a workpiece holding portion is made of an elastic film, a pressurized fluid such as air is poured into a back face of the elastic film
Data Source
AI summary
A polishing head for holding a workpiece when a surface of the workpiece is polished and a polishing apparatus provided with the polishing head, and more particularly a polishing head for holding the workpiece on a rubber film and a polishing apparatus provided with the polishing head. The polishing head and the polishing apparatus provided with the polishing head that can adjust the polishing profile on the basis of the shape of the workpiece before polishing and can stably obtain good flatness.