Dual Spherical Bearing Coupling Mechanism for Polishing Head Stability
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Solution Overview
Problem
In semiconductor manufacturing, the increasing complexity of multilayer interconnects leads to reduced step coverage and planarization, causing issues with surface irregularities that affect optical lithography and polishing performance, resulting in suboptimal polishing and dressing of polishing pads due to vibrations and flutter in the dressing apparatus.
Innovation Solution
A coupling mechanism with upper and lower spherical bearings and a damping member is used to tiltably couple rotating bodies like the polishing head and dresser to a drive shaft, allowing for precise control of the rotational center position and pressing load to prevent vibrations and flutter, enabling effective planarization and dressing within a smaller load range than the body's gravity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a single spherical bearing is used to couple the rotating body to the drive shaft, then the structure is simple, but the rotating body cannot adequately follow surface undulation and experiences vibrations
Solution Approach 1:
The single spherical bearing is divided into two separate spherical bearings (first and second spherical bearings) arranged at different positions along the rotation axis. This segmentation allows each bearing to independently accommodate surface undulations at different locations, improving the rotating body's ability to follow surface irregularities while reducing vibrations and flutter.
2Manufacturing precision
If the pressing load is increased to improve polishing/dressing effectiveness, then the polishing performance improves, but vibrations and flutter occur in the rotating body
Solution Approach 1:
The dual spherical bearing configuration acts as a counterbalancing mechanism that distributes and stabilizes the pressing load. By providing two points of contact rather than one, the system counteracts the destabilizing effects of high pressing loads, preventing vibrations and flutter while maintaining effective polishing and dressing pressure on the workpiece.
3Area of moving object
If the rotating body diameter is increased to process larger wafers, then the processing capability improves, but the rotating body becomes more prone to flutter and vibration
Solution Approach 1:
The solution transitions from a single-point contact (zero-dimensional) to a distributed two-point contact system (one-dimensional arrangement along the rotation axis). This dimensional change allows the larger rotating body to maintain stability by distributing contact forces across two spherical bearings positioned at different axial locations, preventing flutter and vibration even as the rotating body diameter increases to accommodate larger wafers.
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 solution allows for precise control of the polishing and dressing processes, preventing vibrations and ensuring uniform polishing surfaces, thereby improving the planarization and polishing efficiency in semiconductor manufacturing.
Implementation Method 1
a coupling mechanism that couples the rotating body to a drive shaft through a spherical bearing, is used. Since the coupling mechanism allows the rotating body to be tiltably coupled to the drive shaft, the rotating body can follow the undulation of the polishing surface.
Implementation Method 2
A coupling mechanism with upper and lower spherical bearings and a damping member is used to tiltably couple rotating bodies like the polishing head and dresser to a drive shaft
Implementation Method 3
When the dresser is pressed against the polishing pad, a relatively large moment due to a frictional force is exerted on the spherical bearing. As a result, the dresser may flutter or vibrate.
Data Source
AI summary
A coupling mechanism which enables a rotating body to follow an undulation of a polishing surface without generating flutter or vibration of the rotating body, and can finely control a load on the rotating body on a polishing surface in a load range which is smaller than the gravity of rotating body is disclosed. The coupling mechanism includes an upper spherical bearing and a lower spherical bearing disposed between a drive shaft and the rotating body. The upper spherical bearing has a first concave contact surface and a second convex contact surface which are in contact with each other, and the lower spherical bearing has a third concave contact surface and a fourth convex contact surface which are in contact with each other. The first concave contact surface and the second convex contact surface are located above the third concave contact surface and the fourth convex contact surface. The first concave contact surface, the second convex contact surface, the third concave contact surface, the fourth convex contact surface are arranged concentrically.