Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1999-03-03
2001-03-06
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S298260, C204S298110, C204S298190, C204S298160, C204S298080, C204S298120
Reexamination Certificate
active
06197165
ABSTRACT:
SUMMARY OF THE INVENTION
One objective of the present invention is to provide an IPVD method and an IPVD apparatus in which the placement of the coil or other coupling element does not adversely affect the geometry of the chamber of the processing apparatus. Another objective of the present invention is to provide an IPVD method and an IPVD apparatus in which the placement of the coil or other coupling element does not adversely affect the uniformity of the deposited film on the substrate. A still further objective of the present invention is to provide a more efficient and effective method and apparatus for the performance of IPVD.
According to the principles of the present invention, an IPVD apparatus is provided with a ring-shaped source of coating material having a central opening at its center with a central source of coating material that matches the material of the ring-shaped source situated in the opening, preferably at the center. The sources produce a vapor formed of atoms and minute particles of the coating material in a processing space within a vacuum chamber. An annular coupling element is provided at the central opening of the ring-shaped source surrounding the central source. The coupling element operates to reactively couple RF energy into the chamber to produce a high density, reactively coupled plasma in the processing space. The high density plasma ionizes coating material passing through the processing space. The ions of coating material drift toward a substrate, which is supported in the chamber at the opposite end of the processing space from the source, in paths influenced by electrostatic or electromagnetic fields that are present in the processing space. Ions that arrive within a certain distance of the substrate, for example, in the order of a centimeter from the substrate, encounter a sheath field and are accelerated toward the substrate by the potential between the plasma and the substrate. As a result, a high percentage of the coating material arrives on the substrate at angles normal to the substrate, thereby more effectively lining the bottoms and sides of, or filling, small and high aspect ratio features on the surface of the substrate.
In accordance with certain objectives of the invention, an IPVD apparatus and method are preferably provided with two independently powered metal sputtering targets, a coil and a Faraday shield, concentrically arranged. One target is a central circular plate. The Faraday shield is annular and surrounds the plate. The second target is also annular and surrounds the Faraday shield. The coil is situated behind the shield and couples RF energy through the shield into the processing space. The Faraday shield and coil are optimized to work in cooperation with the two concentric targets to deliver coating material to the substrate at high deposition rates and with uniformity that can be optimized through adjustment of the relative powers to the targets.
In a preferred embodiment of the invention, a coating material source, preferably including a ring-shaped sputtering target, is provided with an annular dielectric window placed in its central opening. Behind the window, outside the vacuum of the chamber, is located a ring-shaped plasma source which includes a coupling element. The element is connected to the output of an RF energy source. The coupling element is preferably a coil configured to inductively couple energy supplied from the energy source through the window at the opening at the center of the ring-shaped material source and into the region of the chamber between the coating material source and the substrate on a substrate support at the opposite end of the chamber from the coating material source.
In accordance with the preferred embodiment, the coating material source includes a central source, preferably, a circular sputtering target, situated in the center of the annular window to provide coating material that originates from the center of the source. The central source cooperates with the ring-shaped source to provide a uniform flux of material onto the substrate and particularly, supplements the coating of the sides of features on the substrate that face radially inward toward a central axis of the chamber on which the substrate and source are centered.
Preferably, the apparatus of the present invention includes an annular sputtering target and a central sputtering target between which is the annular dielectric window that seals an opening in the wall of the chamber. Behind the window is a coil or other coupling element. In certain preferred embodiments, the annular and central targets are flat or nearly flat and lie in a common plane. A magnetron magnet assembly is preferably positioned behind the targets to produce a plasma confining magnetic field over the targets. the magnet assembly preferably includes an annular magnetic tunnel over the ring-shaped target. The targets are simultaneously energized with a negative voltage, which are preferably produced by a DC or pulsed DC power supply. High energy sputtering plasma is generated, which is generally confined to the surfaces of the targets, to sputter material from the targets. Separate DC power supplies for each of the targets allow the relative sputtering rates of the targets to be separately controlled.
The coupling element is preferably a coil positioned behind and close to the back, outside surface of the dielectric window at the central opening of an annular sputtering target. RF energy of, for example, 13.56 MHZ, is applied to the coil to excite a high density inductively coupled plasma in the chamber between the targets and the substrate. The main sputtering plasma, which is trapped under a field of the magnetron magnets at the surfaces of the targets, sputters coating material from the targets and into the region of the processing space occupied by the dense secondary plasma, where a substantial portion of the material is stripped of electrons to form positive ions of the coating material. A negative bias voltage applied to a wafer on the substrate holder attracts the positive ions of sputtering material from the region of the secondary plasma and toward and onto the surface of the substrate. The angles of incidence of the material arriving on the substrate are nearly perpendicular to the substrate and enter holes and trenches on the substrate surface to coat the bottoms of these holes and trenches. The central target provides increased material to the radially inward facing sides of the features, enhancing the uniformity of the film. The relative powers applied to the targets are separately adjusted to achieve uniform coverage on the substrate. These powers are readjusted over the life of the target to maintain uniformity as the target erodes or as other parameters change.
According to the apparatus of the invention, the processing chamber is dimensioned to provide optimum spacing between the coating material source and the substrate to provide both optimal ionization of sputtered species as well as optimal uniformity of deposition on the wafers.
The present invention provides greater freedom of design choice in configuring the processing chamber to optimize the IPVD process and does so while overcoming the difficulties set forth in the background above, providing a uniform film on substrates having sub-micron sized high aspect ratio features thereon. In particular, the present invention achieves higher deposition rates, better flat field uniformity and more uniform step coverage on recessed features than systems of the prior art. These benefits allow the source to be conveniently used for flat field depositions as well as for step coverage and fill depositions.
These and other objectives and advantages of the present invention will be more readily apparent from the following detailed description of the drawings.
REFERENCES:
patent: 4415427 (1983-11-01), Hidler et al.
patent: 4721553 (1988-01-01), Saito et al.
patent: 4844775 (1989-07-01), Keeble
patent: 4911814 (1990-03-01), Matsuoka et al.
patent: 4948458 (1990-08-01), Ogle
patent: 49
Drewery John S.
Licata Thomas J.
Chacko-Davis Deborah
Nguyen Nam
Tokyo Electron Limited
Wood Herron & Evans L.L.P.
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