Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
1999-02-19
2001-03-27
Nguyen, Kiet T. (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S397000
Reexamination Certificate
active
06207964
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to high-energy ion implantation systems and more particularly to a continuously variable aperture for use in such systems.
BACKGROUND OF THE INVENTION
Ion implantation has become the technology preferred by industry to dope semiconductors with impurities in the large-scale manufacture of integrated circuits. High-energy ion implanters are used for deep implants into a substrate. Such deep implants are required to create, for example, retrograde wells. Eaton GSD/HE and GSD/VHE ion implanters are examples of such high-energy implanters. These implanters can provide ion beams at energy levels up to 5 MeV (million electron volts). U.S. Pat. No. 4,667,111, assigned to the assignee of the present invention, Eaton Corporation, and describing such a high-energy ion implanter, is incorporated by reference herein as if fully set forth.
Typically, implants are performed on semiconductor substrates in prescribed series of processes or recipes. Each series may include several recipes, each of which requires a particular level of ion beam current. Current methods of adjusting the ion beam current for different recipes involves an initial tuning of the ion beam source for a particular level of beam current, and then re-tuning the source for any subsequent different level of beam current. Such a method, however, can be time consuming and is most detrimental when beam recipes involving a common species (e.g., boron or phosphorous) are connected in a series chain. The time saved by running recipes in series is offset by the time required to re-tune the source between recipes.
It is known to utilize a variably sized aperture in an ion implanter beamline to allow one or more than one isotope of a desired ion to pass through the aperture and be implanted into a substrate. Such an aperture is shown in U.S. Pat. No. 5,130,552, wherein the aperture size is predetermined for each ion implant process and adjusted accordingly. It is not known, however, to provide such an aperture in a high-energy implantation system. Nor is it known to provide a control circuit for such an aperture using ion beam current feedback to permit dynamic adjustment thereof.
It is an object of the present invention, then, to provide an improved adjustable aperture for use in the beamline of an ion implantation system. It is a further object of the invention to provide such an adjustable aperture for use in a high-energy ion implantation system. It is yet a further object to provide a method of controlling such an adjustable aperture, wherein ion beam current is used as a feedback signal to the control system.
SUMMARY OF THE INVENTION
A variable aperture assembly is provided for controlling the amount of ion beam current passing therethrough in an ion implantation system. The aperture assembly comprises an aperture defined by opposing first and second aperture plates through which an ion beam passes; control arms connected, respectively, to the first and second aperture plates; and an aperture drive mechanism for simultaneously imparting movement to the control arms in opposite directions to adjust a gap between the aperture plates to thereby control the amount of current passing through the aperture. Each of the opposite directions in which the control arms move is generally perpendicular to an axis along which the ion beam passes. A control system is also provided for automatically adjusting the aperture gap based on inputs representing actual ion beam current passing through the implanter beamline, desired ion beam current, and aperture position. The control system includes control logic for receiving the inputs and outputting control signals to the aperture drive mechanism to adjust the aperture gap.
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DeLuca Donald E.
Dionne Gerald L.
Loomis Paul A.
Lu Jun
McIntyre Edward K.
Axcelis Technologies Inc.
Kastelic John A.
Nguyen Kiet T.
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