Ion Source Electromagnet for Plasma Density Control
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Solution Overview
Problem
Conventional ion sources exhibit non-uniform ion beam profiles due to convex plasma density distributions, which affect process uniformity and cannot be adequately compensated by grid transparency adjustments, leading to variations in etch rates and profiles across substrates.
Innovation Solution
The use of an electromagnet with tubular pole pieces inside a re-entrant vessel to generate a magnetic field that modifies the plasma density distribution, allowing for real-time adjustments to achieve tailored ion beam profiles by comparing actual and desired density distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ion sources with convex plasma density distributions are used, then ion beam generation is achieved, but process uniformity deteriorates due to non-uniform ion current density distribution
Solution Approach 1:
The patent applies local quality by varying the transparency of different regions of the ion optics grids. Specifically, the center region of the grids has different transparency compared to the peripheral regions, allowing selective modulation of ion current density in different spatial zones. This compensates for the convex plasma density distribution by reducing ion transmission in the center where density is highest, thereby achieving more uniform ion current density across the substrate surface.
2Manufacturing precision
If grid transparency is varied to compensate for plasma density non-uniformities, then ion current density uniformity improves, but adaptability to different operating conditions deteriorates
Solution Approach 1:
The patent implements dynamics by making the ion optics grids adjustable in transparency. Rather than using fixed transparency patterns, the grids can be dynamically reconfigured to have different transparency values in central and peripheral regions. This allows the system to adapt to various operating conditions such as different RF powers, beam voltages, and gas types by adjusting the grid transparency to achieve optimal ion current density uniformity for each specific condition.
3Device complexity
If fixed ion optics transparency is used, then device complexity is reduced, but ability to compensate for source and ion optics variations deteriorates
Solution Approach 1:
The patent resolves this contradiction by introducing adjustable transparency mechanisms in the ion optics grids while maintaining a relatively simple overall structure. The grids incorporate regions with variable transparency that can be dynamically adjusted, allowing compensation for variations in source characteristics and ion optics performance without requiring complete redesign of the entire system. This provides a balance between structural simplicity and functional adaptability.
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 approach enables improved uniformity and control over ion beam etch rates and profiles, reducing waste and increasing yields by dynamically adjusting the magnetic field to match desired etch characteristics.
Implementation Method 1
The electromagnet is adapted to induce a magnetic field for changing a shape of the plasma inside the plasma discharge vessel
Implementation Method 2
The antenna of the ion source, when carrying an oscillating high frequency current, induces a time-varying magnetic field inside the discharge vessel. In accordance with Faraday's law, the time-varying magnetic field induces a solenoidal high frequency electric field, which accelerates the electrons
Data Source
AI summary
Methods of operating an electromagnet of an ion source for generating an ion beam with a controllable ion current density distribution. The methods may include generating plasma in a discharge space of the ion source, generating and shaping a magnetic field in the discharge space by applying a current to an electromagnet that is effective to define a plasma density distribution, extracting an ion beam from the plasma, measuring a distribution profile for the ion beam density, and comparing the actual distribution profile with a desired distribution profile for the ion beam density. Based upon the comparison, the current applied to the electromagnet may be adjusted either manually or automatically to modify the magnetic field in the discharge space and, thereby, alter the plasma density distribution.