Turbine Cap Deflects Particles in Turbo-Molecular Pump Bolt Cavities
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Solution Overview
Problem
Conventional turbo-molecular pumps require increased maintenance due to excessive residual process particulate accumulation in the bolt cavity, leading to contamination of semiconductor wafers, especially with reduced process geometries.
Innovation Solution
A turbine cap assembly with a cap member, plate member, and o-ring system that allows adjustable positioning to secure and seal the cap assembly to the turbine, preventing particle settlement and contamination, featuring a conically shaped upper surface to deflect particles toward the turbine fins for effective evacuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional turbine design with an open bolt cavity is used, then the structure is simple and easy to manufacture, but particles accumulate in the bolt cavity and are emitted back into the chamber causing contamination
Solution Approach 1:
The turbine is segmented into two parts: the original turbine body with the bolt cavity, and a separate cap member that covers the cavity. This segmentation allows the turbine to maintain its simple original structure while adding a protective cap to prevent particle accumulation and emission, thus improving reliability without significantly complicating the base design
Solution Approach 2:
The harmful feature (open bolt cavity allowing particle accumulation) is extracted and isolated by introducing a cap member. The cap member is a separate component that can be removed and reinstalled, allowing the harmful particle accumulation issue to be contained without permanently altering the original turbine structure
2Reliability
If the bolt cavity is sealed to prevent particle accumulation, then contamination is reduced, but maintenance and cleaning become more difficult
Solution Approach 1:
The cap member is designed with dynamic characteristics - it can be installed to seal the bolt cavity during operation, and removed when maintenance or cleaning is needed. The cap member's ability to transition between sealed and open states allows the system to switch between contamination prevention mode and maintenance mode, resolving the contradiction between sealing and accessibility
3Reliability
If a cap member is added to cover the bolt cavity, then particle emission is prevented, but the device complexity increases
Solution Approach 1:
The cap member is designed as a simple, inexpensive component that can be easily manufactured and replaced if needed. By using a simple cap structure rather than a complex integrated solution, the overall device complexity increase is minimized while still achieving the particle emission prevention goal
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 solution reduces maintenance intervals and contamination by preventing particle accumulation in the bolt cavity and enhancing particle deflection and evacuation, compatible with existing pumps without reconfiguration.
Implementation Method 1
a first position in which the o-ring is compressed by the cap member and the plate member
Implementation Method 2
featuring a conically shaped upper surface to deflect particles toward the turbine fins for effective evacuation
Data Source
AI summary
A turbine assembly mounted to a pump rotor via mounting bolts. The turbine includes fins extending therefrom for pumping gasses and suspended particles from a semiconductor processing chamber. The tops of the bolts are recessed from the top surface of the turbine in a bolt cavity having an open end. A cap member is mounted over and seals the open end of the bolt cavity via a center bolt. The cap member has a shaped upper surface (conical, parabolic, squared, rounded) for deflecting particles away from the center of the turbine and toward the turbine's fins. The cap member's upper surface can include particle deflecting features such as fins, channels or asymmetric shapes to enhance particle deflection as the cap member rotates. The cap member can include a compressible o-ring for a friction fit mounting to the turbine.