Non-Uniform Ion Extraction Grid for Flat Beam Distribution
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Solution Overview
Problem
Existing broad beam ion sources introduce non-uniformities in ion beam current and angular divergence, which cannot be corrected by wafer rotation, especially when the ion beam impacts the wafer at a non-zero angle, leading to non-uniform ion flux distribution across the substrate.
Innovation Solution
An electrode assembly with a gridded structure is designed to compensate for plasma non-uniformities by varying the hole radius across the electrodes based on a mirror function that complements the ion flux profile, ensuring a uniform ion beam current density across the substrate, even for angled ion beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform grid assembly is used for ion extraction, then the device structure is simple and easy to manufacture, but the ion flux distribution across the substrate becomes non-uniform
Solution Approach 1:
The patent applies local quality by varying the hole radius in different regions of the extraction grid. Specifically, holes closer to the center have different radii than holes at the periphery, creating a non-uniform grid pattern that compensates for the natural non-uniformity of ion flux distribution. This local variation in hole size ensures that the ion flux becomes uniform across the entire substrate surface, resolving the contradiction between simple manufacturing and precise flux control.
2Adaptability or versatility
If the ion beam is directed at a non-zero angle for processing, then the processing coverage is improved, but the ion flux non-uniformity increases across the substrate
Solution Approach 1:
The patent employs parameter changes by systematically varying the hole radii in the extraction grid according to a specific mathematical relationship. The hole radius is adjusted as a function of position and processing angle, allowing the system to maintain uniform ion flux distribution even when operating at non-zero beam angles. This parameter optimization enables both angle flexibility and flux uniformity to coexist.
3Productivity
If a large beam diameter is used to cover the whole wafer, then the processing throughput is improved, but the beam current non-uniformity increases
Solution Approach 1:
The patent applies local quality by implementing position-dependent hole radii across the extraction grid. Holes in different radial positions have specifically tailored sizes that compensate for the inherent non-uniformity in broad beam extraction. This local optimization across the entire grid area enables full wafer coverage while maintaining uniform beam current distribution, thus achieving both high throughput and precise current control.
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 a uniform ion beam current density across the substrate, reducing non-uniformity to less than 2% over a 300 mm region, and significantly improves uniformity by 70% compared to standard grid configurations, maintaining consistent beam current and angle across various angles of incidence.
Implementation Method 1
broad beam ion sources having gridded ion extraction optics
Implementation Method 2
electrode assembly, comprising at least two electrodes, where the at least two electrodes are defined by a grid pattern that includes a plurality of holes
Data Source
AI summary
A method may include receiving a beam profile function, derived from a beam density of an ion beam along a substrate plane, and generating a mirror function, based upon the beam profile function, wherein a sum of the mirror function and beam profile function generates a flat beam distribution. The method may include receiving a grid pattern for an electrode of an electrode assembly, the grid pattern comprising an array of hole locations, and calculating a normalized beam current as a function hole location for the array of hole locations. The method may further include generating an adjusted set of radii as a function of hole location for the array of hole locations based upon the mirror function and the normalized beam current, and generating an electrode assembly having an array of holes, based upon the grid pattern and the adjusted set of radii.