Ion Source Wall Protrusion for Uniform Ribbon Beam Extraction
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Solution Overview
Problem
Ribbon ion beams extracted from indirectly heated cathode (IHC) ion sources often exhibit non-uniformity along their width, leading to uneven ion concentrations in semiconductor fabrication, which complicates and costs the beam line system.
Innovation Solution
Incorporating a protrusion on one of the ion source's interior walls, which acts as a sink for free electrons and ions, reducing plasma density and enhancing beam current uniformity, with adjustable protrusion elements allowing for customizable shapes and positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional components such as quadrupole lenses are used to compensate for non-uniformity, then beam uniformity is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies local quality by introducing a protrusion at a specific location on the ion source wall to create a localized loss area. This protrusion selectively affects plasma density in specific regions, thereby modifying beam current distribution locally to achieve uniformity without requiring complex beam line components. The protrusion's position and shape are optimized to address non-uniformity at the source rather than compensating downstream.
2Productivity
If the ion source extracts a ribbon ion beam with large width, then productivity is improved, but beam current uniformity deteriorates
Solution Approach 1:
The protrusion creates localized loss areas that selectively reduce plasma density in regions where beam current is excessive. This allows the ion source to maintain a wide extraction aperture for high productivity while achieving uniform beam current distribution through localized plasma density modification near the protrusion.
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 achieves improved uniformity of the ribbon ion beam by modifying the beam current distribution, reducing plasma density near the protrusion, and simplifying the beam line system by minimizing the need for additional complexity and components.
Implementation Method 1
a plasma generator to generate a plasma within the chamber
Implementation Method 2
The protrusion creates a loss area that serves as a sink for free electrons and ions
Implementation Method 3
As current is passed through the filament, the filament emits thermionic electrons
Implementation Method 4
An ion source capable of extracting a ribbon ion beam with improved uniformity
Data Source
AI summary
An ion source capable of extracting a ribbon ion beam with improved uniformity is disclosed. One of the walls of the ion source has a protrusion on its interior surface facing the chamber. The protrusion creates a loss area that serves as a sink for free electrons and ions. This causes a reduction in plasma density near the protrusion, and may improve the uniformity of the ribbon ion beam that is extracted from the ion source by modifying the beam current near the protrusion. The shape of the protrusion may be modified to achieve the desired uniformity. The protrusion may also be utilized with a cylindrical ion source. In certain embodiments, the protrusion is created by a plurality of mechanically adjustable protrusion elements.