Ion beam implantation using conical magnetic scanning

Details Ion beam implantation using conical magnetic scanning Ion beam implantation using conical magnetic scanning

1998-12-23

2001-03-27

Berman, Jack (Department: 2881)

Radiant energy

Irradiation of objects or material

Irradiation of semiconductor devices

C250S42300F, C250S3960ML, C250S281000, C313S361100

Reexamination Certificate

active

06207963

ABSTRACT:

FIELD OF THE INVENTION
The present invention concerns a workpiece treatment system that uses positively charged ions for treating a workpiece. Such a system includes an ion source and structure for moving ions from the source to an implant station where target workpieces are situated for ion beam treatment.
BACKGROUND ART
One commercially available ion implantation system uses an ion source spaced from an implantation chamber where one or more workpieces are treated by ions from the source. An exit opening in an ion generation chamber allows ions to exit the source so they can be shaped, analyzed, and accelerated to form an ion beam. The ion beam is directed along an evacuated beam path to the ion implantation chamber where the ion beam strikes one or more workpieces, typically generally circular wafers. The energy of the ion beam is sufficient to cause ions which strike the wafers to penetrate those wafers in the implantation chamber. In a typical application of such a system the wafers are silicon wafers and the ions are used to “dope” the wafers to create a semiconductor material. Selective implantation with the use of masks and passivation layers allows an integrated circuit to be fabricated.
In a so-called medium current implanter, wafers are treated one at a time by placing them at an implant station and scanning an ion beam across a wafer surface along a controlled path. The scanning motion is applied by a scanning electrode that sets up an electrostatic field for deflecting the ions in the ion beam along controlled paths.
U.S. Pat. No. 5,373,164 to Benveniste, which issued from the United States Patent and Trademark Office on Dec. 13, 1994 concerns such a medium current implanter. An ion implanation system disclosed in the '164 patent includes structure to create a dipole field through which the ion beam passes. The strength and direction of the dipole field is controlled to adjust an angle of impact between the workpiece, typically a silicon wafer and the ion beam. A side-to-side scanning motion is used to provide controlled doping of an entire silicon wafer.
The technique disclosed in the '164 patent will not work for controlled deflection of the ion beam used to treat multiple wafers used with a high current implanter. Such an implanter is disclosed in U.S. Pat. No. 5,554,857 which is assigned to Eaton Corporation and which is incorporated herein by reference. Electric scanning such as the scanning disclosed in the '164 patent is not suitable since the electric field used to produce the side to side scanning tends to de-stabilize the background neutralization that allows high current beam transport.
DISCLOSURE OF THE INVENTION
An ion implanter constructed in accordance with the present invention includes an ion source that emits ions which traverse an ion beam travel path to an implantation chamber mounted in spaced relation to the ion source. A magnet that is positioned along the ion beam path between the ion source and the implantation chamber deflects ions through a controlled scan angle away from an entrance trajectory as the ion beam enters the magnet. While the amount of this deflection is generally fixed, the direction of deflection is controlled to cause the ion beam to sweep through an arcuate path. This controlled scanning can be used, for example, to scan the ion beam over an implant surface of a workpiece that is supported within the ion implantation chamber.
An exemplary magnet includes a coil support constructed from a ferromagnetic material that extends along a portion of the beam path. One or more coils carried by the coil support create a deflecting magnetic field that intercepts the ion beam in a deflection region bounded by the coil support. To achieve controlled deflection of the ion beam a controller electrically coupled to the one or more current carrying coils energizes the current carrying coils to create a magnetic field that scans the beam along the controlled scan angle. A result of this controlled deflection is to cause the ions in the beam to strike the workpieces at a time varying location on a wafer support.
These and other objects, advantages and features of the invention are described in greater detail in conjunction with the accompanying drawings.


REFERENCES:
patent: 4804852 (1989-02-01), Rose
patent: 5373164 (1994-12-01), Benveniste
patent: 5554853 (1996-09-01), Rose
patent: 5554857 (1996-09-01), Benveniste

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