Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2000-09-01
2003-02-25
Anderson, Bruce (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S398000
Reexamination Certificate
active
06525326
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to inhibiting particle transport in an ion beam and, more particularly to a system and method for providing an electrostatic system and method for inhibiting transport of microscopic particles within an ion beam.
BACKGROUND
In the manufacture of semiconductor devices, an ion implanter is employed to dope a semiconductor wafer or glass substrate with impurities. In particular, ion beam implanters are used to treat silicon wafers with an ion beam, in order to produce n or p type extrinsic materials doping or to form passivation layers during fabrication of an integrated circuit. When used for doping semiconductors, an ion beam implanter injects a selected ion species to produce a desired extrinsic material. Implanting ions generated from source materials such as antimony, arsenic or phosphorus results in “n type” extrinsic material wafers, whereas if “p type” extrinsic material wafers are desired, ions generated with source materials such as boron, gallium or indium may be implanted.
Typical ion beam implanters include an ion source for generating positively charged ions from ionizable source materials. The generated ions are formed into a beam and directed along a predetermined beam path to an implantation station. The ion beam implanter may include beam forming and shaping structures extending between the ion source and the implantation station. The beam forming and shaping structures maintain the ion beam and bound an elongated interior cavity or passageway through which the beam passes en route to the implantation station. When operating an implanter, this passageway is evacuated to reduce the probability of ions being deflected from the predetermined beam path as a result of collisions with air molecules.
The mass of an ion relative to the charge thereon (e.g., charge-to-mass ratio) affects the degree to which it is accelerated both axially and transversely by an electrostatic or magnetic field. Therefore, the beam which reaches a desired area of a semiconductor wafer or other target can be made extremely pure since ions of undesirable molecular weight are deflected to positions away from the beam and implantation of other than desired materials can be avoided. The process of selectively separating ions of desired and undesired charge-to-mass ratios is known as mass analysis. Mass analyzers typically employ a mass analysis magnet creating a dipole magnetic field to deflect various ions in an ion beam via magnetic deflection in an arcuate passageway, which effectively separates ions of different charge-to-mass ratios.
The ion beam is focused and directed at a desired surface region of the substrate. Typically, the energetic ions of the ion beam are accelerated to a predetermined energy level to penetrate into the bulk of a workpiece. The ions are embedded into the crystalline lattice of the material to form a region of desired conductivity, with the beam energy determining the depth of implantation. Examples of ion implantation systems include those available from Axcelis Technologies of Beverly, Mass.
Operation of an ion implanter or other ion beam equipment (e.g., linear accelerators) may result in the production of contaminant particles. The contaminant particles, for example, may be less than about 1 &mgr;m in size. The momentum of the ions in the beam that strike the particles, in turn, cause the particles to be transported with the beam, although typically at a speed much less than the ions. Consequently, particles entrained in an ion beam may be transported with the beam toward the wafer (or other substrate), resulting in undesired contamination at the wafer.
As semiconductor devices are manufactured at reduced sizes with greater precision, higher accuracy and efficiency are required of apparatuses for manufacturing such semiconductor devices. Accordingly, it is desirable to reduce the level of contaminant particles in an ion beam so as to mitigate wafer contamination.
SUMMARY
The present invention relates to a system and method for inhibiting the transport of a particle entrained in an ion beam. As a particle moves with an ion beam through an electric field, the particle becomes increasingly charged with a polarity matching the polarity of the ion beam. An electric field having an opposite polarity, which may be oriented at about 90° relative to the beam, urges the charged particle out of the ion beam, which particle may be urged into a particle containment system operatively associated with the electric field generator. The containment system is configured to inhibit reentry of a particle back into the ion beam after being urged from the beam. The containment system also may provide a mechanism to discharge the charged particle to a neutral potential and/or to reduce the kinetic energy of the particle so that it does not reenter the beam. As a result, particles may be removed or diverted from an ion beam in accordance with the present invention, thereby mitigating contamination of a workpiece.
Another aspect of the present invention provides a system for inhibiting transport of particles with an ion beam. The system includes first and second electrodes for generating an electric field therebetween generally transverse to a path of travel for the ion beam. A particle located in the ion beam within a region of the electric field is charged to a polarity according to the ion beam, so that the electric field may urge the charged particle out of the ion beam.
Yet another aspect of the present invention provides an ion implantation system. The system includes an ion source for emitting ions to treat a substrate located at an implantation station. An analyzing magnet system diverts ions of an appropriate mass to an implantation trajectory. The ion implantation system also includes a particle removal system for inhibiting transport of particles with the diverted ions from the analyzing magnet system. The particle removal system includes a pair of electrodes for generating an electric field therebetween generally transverse to a direction of travel for the diverted ions. A particle entrained in an ion beam formed of the diverted ions within a region of the electric field is charged by interactions with the diverted ions, so that the electric field may urge the charged particle out of the ion beam. A substrate is supported at the implantation station for treatment with ions from the particle removal system. As a result, particle contamination at the substrate is mitigated.
Another aspect of the present invention provides a system for inhibiting transport of particles with an ion beam. The system includes means for generating an electric field generally transverse to a path of the ion beam. A particle entrained in the ion beam and within the electric field is charged to a polarity matching the ion beam, so that the electric field may urge the charged particle out of the ion beam.
Still another aspect of the present invention provides a method for inhibiting transport of particles with an ion beam. The method includes generating an electric field generally transverse to a path of the ion beam and charging particles located in the ion beam and in a region of the electric field with a polarity matching the ion beam. At least some of the charged particles are then urged out of the ion beam.
To the accomplishment of the foregoing and related ends, certain illustrative aspects of the invention are described herein in connection with the following description and the annexed drawings. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed and the present invention is intended to include all such aspects and their equivalents. Other advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.
REFERENCES:
patent: 4683922 (1987-08-01), Harrison et al.
patent: 4800396 (1989-01-01), Hertz
patent: 4999492 (1991-03-01), Nakagawa
patent: 5049739 (19
Benveniste Victor M.
Burgess Jeffrey A.
Harrington Eric R.
Ye John Z.
Anderson Bruce
Axcelis Technologies Inc.
Eschweiler & Associates LLC
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