Turbomolecular Pump Assembly for Uniform Plasma Etching
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Solution Overview
Problem
Current semiconductor manufacturing processes face challenges in achieving uniform etching across substrates with high aspect ratios and varying feature densities due to non-symmetrical processing chamber designs, leading to inhomogeneities in plasma flow and etching results.
Innovation Solution
A symmetrical processing chamber design is implemented, featuring a turbomolecular pump with a central passage and spiral grooves on the stem or core to counter backstreaming gases, along with a movable stage and pump screen for precise gas management, ensuring uniform plasma distribution and independent pressure regions within the chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional non-symmetrical processing chamber design is used, then the device complexity is reduced, but the etching uniformity and plasma flow homogeneity deteriorate
Solution Approach 1:
The patent applies asymmetry in reverse - it deliberately introduces a non-symmetrical element (the offset pump and stage assembly) into an otherwise symmetrical chamber design. The pump and stage are positioned offset from the chamber center, creating an asymmetric configuration that maintains overall chamber symmetry for plasma uniformity while enabling functional asymmetry for gas management. This resolves the contradiction by showing that controlled asymmetry in specific components can achieve both manufacturing precision and functional efficiency.
Solution Approach 2:
The chamber is segmented into distinct functional regions: an upper processing region with the stage and chuck for substrate handling, and a lower pump region with the turbomolecular pump for vacuum maintenance. This segmentation allows each region to be optimized independently - the upper region for plasma uniformity and the lower region for efficient gas removal - thereby achieving etching uniformity without excessive overall complexity.
2Reliability
If a pump without spiral grooves is used, then the device complexity is reduced, but the ability to counter backstreaming gas deteriorates
Solution Approach 1:
The patent employs spiral grooves on the pump stem and/or core surface, utilizing curved geometries to create a pumping action that counters gas backstreaming. The spiral configuration transforms linear gas flow into rotational motion, effectively preventing gas from flowing back into the processing chamber. This curved surface design provides reliable gas control while adding minimal complexity to the pump structure.
Solution Approach 2:
The spiral grooves create a pneumatic pumping mechanism within the pump assembly. As gas molecules enter the gap between the stem and core, the spiral grooves guide them in a rotational path, creating a pressure gradient that pushes gas toward the exhaust port and prevents backstreaming into the chamber. This pneumatic mechanism provides reliable gas control through fluid dynamics principles.
3Manufacturing precision
If the stem passes through the core without spiral grooves, then the manufacturing precision is reduced, but the device complexity is reduced
Solution Approach 1:
The spiral grooves are applied locally to specific surfaces - either the stem surface, the core inner surface, or both - rather than requiring complex modifications to the entire pump assembly. This localized application of spiral grooves creates the necessary pumping action to maintain plasma flow homogeneity while minimizing the overall structural complexity and manufacturing difficulty.
4Manufacturing precision
If a movable stage with pump screen is used, then the gas management precision is improved, but the device complexity increases
Solution Approach 1:
The stage is designed to be movable between different positions - typically between a loading position near the chamber wall and a processing position centered under the gas port. This dynamic positioning capability allows precise control over gas distribution and plasma uniformity during etching, while the pump screen provides additional gas management control. The movability adds functional precision without requiring the entire chamber to be complex.
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 design enhances etching uniformity and control, reducing backstreaming and inhomogeneities, thereby improving the precision and consistency of semiconductor fabrication processes.
Implementation Method 1
one or more spiral grooves are formed in the stem opposing an inner surface of the core, each spiral groove having dimensions to provide pumping action to counter back streaming of the gas from an exhaust of the pump to the processing chamber in an intermediate and viscous flow regime inside a gap between the stem and the core
Data Source
AI summary
A processing chamber and method of etching a semi-conductor substrate are presented. The processing chamber is symmetric, with the centerlines of a chuck and stem of a stage to retain a semi-conductor substrate aligned with a centerline of a passage in a core of a pump used to evacuate the processing chamber and with a center-line of a gas port through which gas is introduced to the processing chamber. The stem extends through the passage and a spiral groove is formed in the passage in only one of the stem or an inner surface of the core to provide pumping action to counter back streaming of the gas from an exhaust of the pump in an intermediate and viscous flow regime inside a gap between the stem and the core.