Electrostatic Lens End Plates for Ion Beam Uniformity
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Solution Overview
Problem
Ion implantation tools face beam aberrations due to the mutual repulsion of positively charged ions, leading to beam divergence and distortion, which existing solutions have not adequately addressed, especially in high current and low energy applications.
Innovation Solution
An electrostatic lens assembly with a terminal electrode, suppression electrode, and ground electrode, where end plates are shaped to match the electrostatic equipotentials, ensuring a uniform electric field and maintaining beam focus across the width of the ion beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If voltage potentials are applied to electrodes to decelerate ions, then ion energy control is improved, but beam aberrations and distortion increase
Solution Approach 1:
The patent applies equipotentiality by shaping electrode end plates to match the electrostatic equipotential lines of the adjacent electrode. This creates a smooth transition of electric field lines at the beam edges, eliminating the abrupt field changes that cause beam aberrations. The end plates are configured to have the same electrostatic potential as the adjacent electrode, ensuring continuous equipotential surfaces that prevent beam distortion while maintaining effective ion deceleration.
2Manufacturing precision
If electrode width is increased to reduce beam aberrations, then beam uniformity improves, but mechanical structure constraints are violated
Solution Approach 1:
The patent resolves the contradiction by transitioning from a two-dimensional electrode width problem to a three-dimensional solution. Instead of increasing electrode width in the horizontal dimension, the invention extends electrodes in the vertical dimension by adding end plates that match equipotential lines. This dimensional transformation allows the electric field to be shaped properly at the beam edges without requiring wider electrodes, thus maintaining mechanical structure compatibility while achieving beam uniformity.
3Manufacturing precision
If electrodes are bent or angled at edges to focus beam, then beam focus improves, but electrode geometry complexity increases
Solution Approach 1:
The patent applies curvature by shaping the end plates of the electrodes to follow the curved equipotential lines of the electrostatic field. Rather than bending or angling the main electrode bodies, the invention uses curved end plate geometries that match the natural equipotential contours. This approach achieves beam focusing by creating smooth, continuous electric field lines at the edges while keeping the main electrode structures simple and easy to manufacture.
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 effectively minimizes beam aberrations, maintaining beam uniformity and focus, even at the edges of the electrodes, thereby improving the precision and accuracy of ion implantation in semiconductor manufacturing.
Implementation Method 1
An electrostatic lens assembly includes a terminal electrode configured to receive an ion beam between a top and bottom portion. A ground electrode is configured to exit the ion beam from the electrostatic lens assembly between a top and bottom portions.
Implementation Method 2
The suppression electrode has an associated electrostatic equipotential. Shaping the electrode end plate in this way assures that the electric field and the consequent ion focusing is uniform across the width of the beam.
Implementation Method 3
beam 'blow-up' which is due to the effect of the space charge. This effect is caused by the mutual repulsion of the positively charged ions in the beam causing the beam to diverge and grow in cross section.
Data Source
AI summary
An ion implantation system includes an electrostatic lens. The electrostatic lens includes a terminal electrode, a ground electrode and a suppression electrode disposed therebetween. An ion beam enters the electrostatic lens through the terminal electrode and exits through the ground electrode. The electrodes have associated electrostatic equipotentials. An end plate is disposed between a top and bottom portion of the suppression electrode and/or the top and bottom portion of the ground electrode. The respective end plate has a shape which corresponds to the electrostatic equipotential associated with the particular electrode in order to maintain uniformity of the beam as it passes through the electrostatic lens.