Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
1998-12-18
2001-03-20
Berman, Jack (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S492200, C250S492300, C250S42300F, C250S281000, C250S282000, C315S111210, C315S111610
Reexamination Certificate
active
06204510
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains generally to apparatus which will accelerate ions of a plasma in a predetermined direction. More specifically, the present invention pertains to apparatus which generate plasmas for use in altering the surface of a substrate by deposition or etching. The present invention is particularly, but not exclusively, useful as an apparatus which will accelerate ions in a plasma to a common translational velocity.
BACKGROUND OF THE INVENTION
It is well known that plasmas can be generated and used for altering substrate surfaces through either deposition or etching processes. In etching processes, the depth of the etching into the substrate surface can be an important consideration. On the other hand, in deposition processes, the resultant build-up on a substrate surface can be an important consideration. For instance, the operational applications of many of the high-performance chips and wafers require that the etching or deposition depths be uniformly controlled. It happens, however, that some substrate surfaces will be more resistive to an etching action than will others, and that some substrate surfaces can be more easily worked with during a deposition than others. Accordingly, the differences between substrate materials, and the eventual operational requirements of the etched substrate, must be accounted for. Stated differently, it is desirable to have as much control over the rate and effect of a plasma etching or deposition process as is possible.
One method for controlling ion bombardment of a substrate surface is to control the velocity at which ions impact against the substrate surface. Control of this velocity can be accomplished by controlling the acceleration of the ions. Practical aspects, however, require that the apparatus used to accomplish acceleration control be physically robust and technically precise.
In light of the above, it is an object of the present invention to provide an apparatus and method for altering a substrate surface which is capable of taking all ions in a plasma to a common translational velocity regardless of their initial boundary conditions. It is another object of the present invention to provide an apparatus and method for altering a substrate surface which is capable of controlling, establishing, and maintaining the common translational velocity of ions in a plasma. Yet another object of the present invention is to provide an apparatus and method for altering a substrate surface which is relatively, technically uncomplicated, and which has minimal components for generating crossed electric and magnetic fields inside a vacuum vessel chamber. Still another object of the present invention is to provide an apparatus and method for altering a substrate surface which is simple to manufacture, easy to use, and comparatively cost effective.
SUMMARY OF THE PREFERRED EMBODIMENTS
An apparatus and method for altering a substrate surface includes a housing which is formed with an enclosed chamber and which has a first end and a second end. Further, the chamber defines a longitudinal axis which extends from the first end to the second end. The substrate that is to be altered by the apparatus can then be positioned in the chamber and the surface of the substrate exposed to the interior of the chamber.
The apparatus of the present invention also includes at least one pair, but preferably multiple pairs, of elongated co-planar juxtaposed conductors which are mounted in the chamber and which are aligned substantially parallel to the longitudinal axis of the chamber. In their operation, each of these conductors carries a current, and together, they establish a magnetic field (B) in the chamber. A consequence of this configuration is that the magnetic field is oriented substantially perpendicular to the longitudinal axis of the chamber.
In addition to the conductors, the apparatus of the present invention includes two sets of casings which are separated from each other by a dielectric material. One set of these casings, the first set, is near the first end of the chamber while the second set is nearer the second end of the chamber. Each casing, however, in both the first set and the second set will respectively surround one of the conductors.
For the operation of the casings of the first set, opposite polarity, time alternating voltages are applied to adjacent casings in the set to induce an electron flow in the magnetic field. As is well known, these opposite polarity, time alternating voltages will generate a plasma. As is also well known in the pertinent art, the plurality of ions in the resulting plasma are useful for altering the substrate surface.
For the second set of casings, each casing in the second set, like the casings of the first set, surround a respective conductor. As indicated above, each of the casings in this second set is electrically insulated from a respective casing of the first set by a dielectric insulator. This insulation allows a dc voltage to be placed on the casings of the second set which will establish an electric field (E) in the chamber. Importantly, this electric field is crossed with the magnetic field (E×B) to establish crossed electric and magnetic fields. The crossed electric and magnetic fields will then accelerate ions in the plasma in a direction that is substantially parallel to the longitudinal axis of the chamber. Specifically, the ions in the crossed electric magnetic fields are accelerated from the first end of the chamber toward the second end of the chamber to impact against the substrate surface.
An additional aspect of the present invention is that the ratio of the electric field to the magnetic field (E/B) is preferably established so as to be constant or uniform throughout the chamber. This can be effectively accomplished by applying the electrostatic potentials to the ring casings in a manner that ensures the potential is constant on a magnetic flux surface. The object of the uniform ratio E/B in the chamber is to accelerate ions to a common translational velocity prior to their impact with the substrate surface.
During operation of the apparatus of the present invention, the substrate surface can be rotated in the chamber about the longitudinal axis of the chamber. Such rotation may be desirable due to the configuration and orientation of the magnetic lines in the magnetic field B. Specifically, as noted above, the magnetic field lines will lie in a plane that is substantially perpendicular to the longitudinal axis of the chamber. Further, these magnetic field lines will either encircle one of the conductors or they will be enclosed, contiguous and somewhat oblong around all of the conductors. A consequence of this geometry can be that there is an increased ion density in one direction as opposed to another direction, particularly for only two conductors. In order to compensate for this it may be determined to rotate the substrate. If done, such a rotation will tend to neutralize any variation in ion density that may develop due to the configuration of magnetic field lines relative to the direction of ion acceleration in the chamber. Also, employing multiple conductors will result in a radial profile of ion density that is nearly flat in the center, thus ensuring uniform ion flux.
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patent: 5225740 (1993-07-01), Ohkawa
patent: 5350454 (1994-09-01), Ohkawa
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patent: 5616919 (1997-04-01), Broadbent et al.
patent: 5681434 (1997-10-01), Eastlund
patent: 5868909 (1999-02-01), Eastlund
Ohkawa, T., et al., Plasma Confinement in a Toroidal Quadrupole, Physics of Fluids, 12, p. 1926 (1969).
Ohkawa T., et al., Plasma Confinement in D.C. Octopole, Phys Rev. Letters 24, p. 95 (1970).
Archimedes Technology Group, Inc.
Berman Jack
Nydegger & Associates
Wells Nikita
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