Ion Source Magnetic Field Sources for Uniform Beam
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Solution Overview
Problem
Ion implanters face challenges in achieving uniform ion density profiles, especially when using ion sources with extraction apertures greater than 100 mm, which affects the uniformity of the ion beam implanted across larger substrates like 450 mm wafers, due to non-uniformity issues and space-charge loading during beam transport.
Innovation Solution
The use of a pair of magnetic field sources with cores and coils, aligned parallel to the longitudinal axis of the ionization chamber, and independently controlled coil segments to produce a uniform magnetic field, ensuring a consistent ion density profile along the beam's longitudinal axis, is employed to address the non-uniformity issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional ion sources with large extraction apertures (>100 mm) are used to produce extended ribbon beams for large substrates, then the beam length and coverage area are improved, but the ion density uniformity deteriorates
Solution Approach 1:
The ion source is divided into multiple independently controllable cathode segments along the longitudinal axis. Each cathode segment can be controlled to emit different ion currents, allowing the ion density profile to be adjusted and equalized across the entire extraction aperture. This segmentation enables uniform ion density distribution while maintaining large beam length for extended substrate coverage.
2Manufacturing precision
If multiple cathodes are used to improve ion density uniformity, then the ion density profile control is improved, but the device complexity increases
Solution Approach 1:
The cathode is segmented into multiple independently controllable sections along the longitudinal axis, with each section having its own emission control. This allows localized adjustment of ion density without requiring separate complete cathode assemblies, reducing complexity compared to using multiple full cathodes.
Solution Approach 2:
Different regions of the cathode are given different emission characteristics to compensate for non-uniform ion density. By controlling each segment's emission independently, the ion density can be equalized across the extraction aperture without adding complex overall system architecture.
3Manufacturing precision
If corrector optics are added to the beam line to adjust ion density profile, then the beam uniformity can be improved, but the device complexity and space-charge loading increase
Solution Approach 1:
The ion density profile is equalized at the source before beam extraction and transport. By controlling cathode segment emissions to produce uniform ion density at the aperture, the beam exits with uniform density, eliminating the need for downstream corrector optics to adjust the profile during transport.
Solution Approach 2:
The function of profile correction is extracted from the beam transport system and moved to the ion source itself. Instead of using corrector optics in the beam line, the source is designed to produce the correct profile directly, simplifying the overall system by removing unnecessary correction components.
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 configuration enables the generation of a uniform ion beam with a ribbon extent suitable for 300-mm or 450-mm substrates, maintaining beam dimensions during transport and ensuring high dose rates by reducing space charge blowup, thus improving the uniformity of ion implantation across the substrate.
Implementation Method 1
a magnetic field source assembly adapted to produce a magnetic field within the ion source structure
Implementation Method 2
an electromagnetic coil assembly (604a-b) generally wound around the core (602a-b)
Implementation Method 3
The magnetic field is adapted to confine the electron beam generated by each of the electron guns
Data Source
AI summary
An ion source is provided that includes an ionization chamber and two magnetic field sources. The ionization chamber has a longitudinal axis extending therethrough and includes two opposing chamber walls, each chamber wall being parallel to the longitudinal axis. The two magnetic field sources each comprises (i) a core and (ii) a coil wound substantially around the core. Each magnetic field source is aligned with and adjacent to an external surface of respective one of the opposing chamber walls and oriented substantially parallel to the longitudinal axis. The cores of the magnetic field sources are physically separated and electrically isolated from each other.