Ion Implanter Repeller Assembly for Gas Leakage and Plasma Isolation
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Solution Overview
Problem
Existing repeller assemblies in ion implanters suffer from reduced operating times and increased maintenance due to plasma coating and gas leakage, leading to short circuits and mechanical instability within the arc chamber.
Innovation Solution
A repeller assembly design featuring a knob-shaped body with a narrowing repeller shaft, a tubular insert, and self-aligning insulators, which minimizes gas leakage and extends the tortuous plasma path, allowing for easier installation and replacement, and reducing the frequency of maintenance shutdowns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a repeller assembly is mounted in an arc chamber with conventional design, then the ion implanter can operate, but plasma coating occurs on electrically isolated parts leading to short circuits and reduced operating time
Solution Approach 1:
The patent extends the tortuous path from a simple gap into a multi-dimensional complex path using the insulator structure with recesses and protrusions. The plasma path is forced to navigate through three-dimensional space, increasing the effective path length and delaying coating formation on electrically isolated parts.
Solution Approach 2:
The insulator structure acts as an intermediary element between the repeller shaft and the arc chamber wall. It provides both electrical isolation and creates a tortuous plasma path, mediating between the need for electrical isolation and the need to prevent plasma coating on isolated parts.
2Ease of operation
If gaps are provided between repeller assembly parts and arc chamber wall, then assembly installation is facilitated, but gas leakage increases reducing arc chamber vacuum quality
Solution Approach 1:
The insulator structure provides different gap characteristics at different locations: larger gaps where needed for assembly installation and smaller gaps where critical for preventing gas leakage. The recesses and protrusions create localized gap variations that balance installation ease with vacuum quality.
3Device complexity
If repeller shaft is made cantilevered for mounting, then structure is simplified, but mechanical stability decreases allowing contact with arc chamber walls
Solution Approach 1:
The repeller assembly uses composite construction with the repeller shaft made of one material and the insulator made of electrically insulating material (such as ceramic). This composite structure provides both mechanical support and electrical isolation, maintaining stability while preventing contact with charged chamber walls.
4Ease of manufacture
If conventional repeller assembly design is used, then manufacturing is straightforward, but maintenance frequency increases due to plasma coating and gas loss
Solution Approach 1:
The repeller assembly is segmented into distinct components: repeller shaft, insulator with recesses and protrusions, and arc chamber. This segmentation allows each part to be manufactured separately using conventional processes while the assembled structure provides the tortuous path functionality that reduces maintenance frequency.
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 design enhances the operational efficiency and longevity of the ion implanter by reducing gas leakage, delaying plasma layer buildup, and simplifying part replacement, thereby lowering operating costs and improving service life.
Implementation Method 1
the cathode assembly is heated, for example, by a filament, and its purpose is to emit electrons by thermionic emission during operation
Implementation Method 2
an arc chamber to generate a plasma containing a variety of ion species to be implanted in the surface of the semiconductor wafer
Data Source
AI summary
A repeller assembly mounts in an arc chamber of an ion implanter. The repeller assembly contains a repeller, a tubular insert, first and second insulators, a contact member, and a lock member. The repeller has a knob-shaped body placed on an inner side of the arc chamber opposite to a cathode assembly. A repeller shaft is arranged extending through an opening of a wall of the arc chamber to an outer side. The repeller shaft has a step narrowing down the repeller shaft. The tubular insert is mounted concentrically to the repeller shaft. The first insulator has a collar shape and is attached to the tubular insert so that an inner shoulder of the first insulator is pressed against an outer side of the wall of the arc chamber. The second insulator is cap-nut shaped and is attached to the first insulator with an outer flange thereof.