Ion Beam Tuning via Upstream Focusing Element
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Solution Overview
Problem
Conventional beam line ion implanters suffer from unacceptably high local beam angle spread, which adversely impacts channeling and dose uniformity, especially at higher ion beam energies, due to the ion beam expanding before reaching the scanner, leading to reduced effectiveness in applications like semiconductor wafer treatment.
Innovation Solution
Incorporating a focusing element with a focusing field positioned upstream of the scanner to focus the ion beam to a focal point at the scan origin, minimizing the local beam angle spread by ensuring the ion beam is concentrated and parallel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the ion beam is allowed to expand before reaching the scanner (conventional design), then the beam can be formed through the mass analyzer, but the local beam angle spread becomes unacceptably high (0.06°)
Solution Approach 1:
The patent applies preliminary action by positioning a focusing element upstream of the scanner to focus the ion beam to a focal point at the scan origin before the beam enters the scanner. This pre-focusing action prevents the beam from expanding prematurely, thereby minimizing the local beam angle spread to 0.01° while maintaining the necessary beam line configuration for mass analysis and scanning operations.
2Length of moving object
If the ion beam energy is increased for deeper implantation, then the implantation depth increases, but the channeling effect is adversely reduced due to higher sensitivity to angle variations
Solution Approach 1:
The patent applies parameter changes by precisely controlling the beam angle parameter through the focusing element. By focusing the beam to a focal point at the scan origin, the system maintains a minimal local beam angle spread (0.01°) even at high ion beam energies (3 MeV). This allows deeper implantation while preserving the channeling effect, as the crystalline lattice orientation can effectively guide the ions despite the higher energy.
3Measurement precision
If the focal point is positioned at the mass resolving aperture (conventional design), then the beam can be focused for mass analysis, but the beam expands by the time it reaches the scan origin
Solution Approach 1:
The patent introduces an intermediary focusing element positioned between the mass analyzer and the scanner. This intermediary component creates a focal point at the scan origin, serving as a mediator that allows the beam to be properly focused for mass analysis while preventing excessive expansion before scanning. The focusing element acts as an intermediate stage that reconciles the conflicting requirements of mass resolution and beam parallelism.
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 significantly reduces the local beam angle spread from 0.06° to 0.01°, improving channeling and dose uniformity, as demonstrated by a 3 MeV boron ion beam experiment, and enhances the parallelism of the ion beam, resulting in improved implantation depth and uniformity on semiconductor wafers.
Implementation Method 1
a focusing element having a focusing field positioned upstream of the scanner configured to focus the ion beam to a focal point at the scan origin
Implementation Method 2
The scanner may be an electrostatic scanner or a magnetic scanner
Implementation Method 3
The scanner may be an electrostatic scanner or a magnetic scanner
Implementation Method 4
An angle corrector downstream of the scanner accepts the scanned ion beam with diverging trajectories and deflects the same in an effort to produce more parallel trajectories
Data Source
AI summary
A beam line ion implanter includes an ion source configured to generate an ion beam, a scanner configured to scan the ion beam to produce a scanned ion beam having trajectories which diverge from a scan origin, and a focusing element having a focusing field positioned upstream of the scanner configured to focus the ion beam to a focal point at the scan origin. A method of ion beam tuning includes generating an ion beam, focusing the ion beam to a focal point positioned at a scan origin, and scanning the ion beam to produce a scanned ion beam having trajectories which diverge from the scan origin.