Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Patent
1987-11-06
1990-05-01
Berman, Jack I.
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
250398, 3133601, H01J 37304, H01J 37317
Patent
active
049221060
DESCRIPTION:
BRIEF SUMMARY
This invention relates in general to a method and apparatus for ion beam scanning, and more particularly concerns novel apparatus and techniques for ion beam fast parallel scanning. The present invention, in one application, facilitates ion implantation processing of relatively large semiconductor wafers with high dose accuracy with a relatively compact machine.
One prior ion implanter uses two magnetic deflectors to produce a parallel scanning beam in one dimension. See, for example, U.S. Pat. No. 4,276,477. A disadvantage of this approach is that scan rates are low, typically of the order of only one Hertz. Furthermore, this prior art machine scans after acceleration of the ion beam, thereby requiring relatively large deflector fields. There is a problem in uniformly spreading the beam with such an ion beam implanter, that is in providing a spatially uniform dosage over a semiconductor wafer or other target object.
The prior art also includes medium current ion implanters that use two-dimensional scanning of an ion beam with electrostatic deflectors. However, such systems do not produce a parallel scanning beam, produce scanning after acceleration, and produce a beam whose intensity is subject to uncontrolled fluctuation.
Further, it is known in the manufacture of integrated circuits, with ion beam implantation of a semiconductor wafer, that accurate and precise ion dosage of the semiconductor are important for proper ic performance. Faulty ion implantation typically is not detected until too late to correct. It thereby renders the wafer, or at least parts of it, worthless even after costly processing.
Accordingly, it is an object of this invention to provide an improved ion implantation apparatus and method.
Another object of the invention is to provide an ion beam implanting method and apparatus for attaining relatively precise and accurate ion dosage with relatively large semiconductor wafers, with further relatively high throughput. Further objects are that the implanting method and apparatus be suited for providing a relatively wide beam scan, and that the components of the apparatus have relatively low energy consumption and be relatively compact.
A further object of the invention is to provide improvements for a method and apparatus for producing a scanning ion beam. Specific improvements are desired in beam scanning and deflection, in beam acceleration, in equipment configuration and compactness, in energy consumption, and in beam control.
Other objects of the invention will in part be obvious, and will in part appear hereinafter.
SUMMARY OF THE INVENTION
According to one feature of the invention, an ion beam with an initially stationary, i.e., time invariant, spatial profile performs a fast one-dimensional oscillatory motion in such a way that (i) ion trajectories remain parallel to one another at all phases of the oscillation; (ii) the amplitude of the oscillation is easily controlled; and (iii) the waveform of the oscillation is easily controlled.
An ion beam scanning apparatus and method according to one feature of the invention has a magnetic, ion beam-deflector in which two sector-shaped pole pieces are both truncated. The pair of truncated pole pieces are so located that the axis along which the ion beam enters the beam scanner, and hence prior to scanning deflection, passes between the point in space where each pole piece would come to a point if it were not truncated, and the near side of the scanning beam in the gap between the two pole pieces.
More particularly, apparatus for producing a scanning ion beam according to this feature of the invention typically has a source of an ion beam directed along an initial selected axis, and has scanning means for deflecting the ion beam from that axis to form a substantially planar scanning beam. A magnetic deflector, for deflecting the scanning ion beam to have parallel or otherwise selectively oriented beam paths, includes a sector magnet which has at least two pole pieces. The pole pieces are located in register with one another and spaced a
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Berrian Donald W.
Kaim Robert E.
Vanderpot John W.
Berman Jack I.
Varian Associates Inc.
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