Inductively Coupled Plasma Ion Source Using Multiple RF Antennas
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Solution Overview
Problem
Existing ion implantation technologies face limitations in producing wide ion beams due to physical constraints on RF antenna length and dielectric window size, which affect plasma uniformity and density, making it difficult to extend ion beam width beyond a certain limit.
Innovation Solution
A wide ion beam source is developed using multiple RF windows and antennas with independent RF sources operating at slightly different frequencies, allowing for the creation of spatially-overlapping plasmas and extending ion beam width without continuous phase monitoring and adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a single long RF antenna is used to produce wide ion beams, then the ion beam width can be increased, but standing wave effects limit the antenna length to 1/4 of the RF electromagnetic wavelength
Solution Approach 1:
The patent divides a single long antenna into multiple shorter antenna segments (e.g., four 1.2-meter segments instead of one 5-meter antenna). Each segment is fed by an independent RF source, allowing the system to achieve the effective length of a long antenna while avoiding standing wave limitations of individual segments. This segmentation enables wide ion beam production without the 1/4 wavelength constraint on each antenna element.
2Area of stationary object
If larger dielectric windows are used to accommodate wider plasma chambers, then the plasma chamber size can be increased, but window thickness must be increased which deteriorates RF power coupling
Solution Approach 1:
The patent divides a single large dielectric window into multiple smaller window segments (e.g., four 30cm x 30cm windows instead of one 1.2m x 1.2m window). Each smaller window maintains adequate RF power coupling characteristics while collectively providing the necessary opening area for a wide plasma chamber. This segmentation allows the plasma chamber to be widened without requiring excessively thick individual windows that would degrade RF coupling.
3Device complexity
If multiple RF sources operate at the same frequency, then the system is simpler to control, but phase variations cause ion beam current fluctuations
Solution Approach 1:
The patent deliberately changes the operating frequency parameter of each RF source to be slightly different from the others (e.g., 13.56 MHz, 13.57 MHz, 13.55 MHz, 13.58 MHz). This frequency differentiation eliminates the need for continuous phase synchronization while preventing the constructive and destructive interference that causes current fluctuations. The small frequency offsets ensure that the plasma remains stable and uniform across all antenna segments without requiring complex phase monitoring and adjustment systems.
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 solution enables the production of very wide ion beams with improved plasma uniformity and density, reducing current variations and achieving uniform ion distribution across large areas.
Implementation Method 1
inductively coupled plasma (ICP) sources have proven to be a suitable solution for producing wide ribbon ion beams
Implementation Method 2
dielectric windows, which allow RF power transmission therethrough and provide vacuum sealing of plasma chambers
Implementation Method 3
a plurality of RF sources, each RF source coupled to a respective RF antenna of the plurality of RF antennas, wherein a difference in frequency of a first RF signal produced by a first RF source coupled to a first RF antenna from that of a second RF signal produced by a second RF source coupled to an RF antenna adjacent to the first RF antenna is greater than 10 kHz
Data Source
AI summary
A wide ion beam source includes a plurality of RF windows arranged in a predetermined relationship, a single plasma chamber disposed on a first side of the plurality of RF windows, a plurality of RF antennas, each RF antenna of the plurality of RF antennas disposed on a second side of a respective RF window of the plurality of RF windows, the second side being opposite the first side, and a plurality of RF sources, each RF source coupled to a respective RF antenna of the plurality of RF antennas, wherein a difference in frequency of a first RF signal produced by a first RF source coupled to a first RF antenna from that of a second RF signal produced by a second RF source coupled to an RF antenna adjacent to the first RF antenna is greater than 10 kHz.