Electric lamp and discharge devices – With positive or negative ion acceleration
Reexamination Certificate
2000-07-11
2003-01-07
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With positive or negative ion acceleration
C313S363100, C313S362100, C315S231000
Reexamination Certificate
active
06504294
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method and apparatus for the deposition of thin, hard, wear-resistant diamond-like carbon and silicon-doped diamond-like carbon coatings using gridless Hall-Current ion sources, and the use of the process to produce protective coatings for data storage and other applications.
BACKGROUND OF THE INVENTION
There are numerous examples in the prior art of the application of gridded ion sources to the direct deposition of diamond-like carbon coatings (DLC) from hydrocarbon gases, mixtures of hydrocarbon gases and mixtures of inert gases with hydrocarbon gases within the ion source. Two recent articles help to illustrate state-of-the-art application of gridded ion sources to the deposition of DLC coatings. M. Weiler et al., Applied Physics Letters, Vol. 64, pages 2792-2799 (1994), and Sattle et al., Journal of Applied Physics, Vol. 82, pages 4566-4575 (1997) describe application of a gridded ion source to the direct deposition of DLC using acetylene gas. Their work shows that DLC coatings with high sp
3
fraction and with hardness greater than 10 GPa can be deposited at moderate deposition rates up to about 10 Å per second provided that (1) a high degree of ionization of the feed gas is obtained, (2) a high C/H ratio of ion species is formed and (3) the mean energy of the beam provides about 100 eV per C atom deposited from the ion beam. As such, gridded ion sources typically operate with ion energies near 100 to 250 eV in order to form hard (i.e. >10 GPa) DLC coatings.
It is also known that one may produce DLC coatings which incorporate other dopant elements, e.g. silicon. Such coatings are commonly referred to as silicon-doped DLC or Si-DLC. For example, Brown et al., pending patent application U.S. Ser. No. 08/707,188 filed Sep. 3, 1996, disclose a Si-DLC coating for magnetic transducers and magnetic recording media which is deposited by from silicon-containing and carbon-containing precursor gases by a direct ion beam deposition method. These Si-DLC coatings are characterized by the following features: Nanoindentation hardness in the range of about 12 GPa to 19 GPa, compressive stress in the range of about 0.4 GPa to 1.8 GPa, Raman spectral G-peak position in the range of about 1463 cm
−1
to about 1530 cm
−1
, a silicon concentration in the range of about 1 atomic % to about 30 atomic % and hydrogen concentration of about 25 atomic % to about 47 atomic %. In their examples, a gridded ion source is disclosed as the apparatus to deposit Si-DLC coatings.
However, it is well known that gridded ion sources are limited in DLC and Si-DLC deposition applications by the function of the electrostatic grid optics which are necessary to form near mono-energetic ion beams. In production, such grids limit the beam current density and, thereby, the deposition rates. Also the grids become coated substantially with deposits which eventually disrupt production, limit maintenance cycles, and cause extensive maintenance problems when removing such deposits from the grid optics. Gridded ion sources operate at low vacuum pressures, typically below 5×10
−4
Torr, and typically have ion beam DLC deposition rates of less than 10 Å/sec for most all variety of gaseous hydrocarbon chemistries.
In order to overcome the limitations with gridded ion sources, prior art attempts have been made to use gridless Hall-Current ion sources for the deposition of DLC coatings. In these DC or pulsed-DC devices, ions are accelerated from a region of ion production through an electric field, E, established within the bulk of the discharge near the anode of the apparatus. The electric field is brought about by a static magnetic field, B, imposed on the discharge in the vicinity of an anode wherein the electron drift motion from cathode to anode is impeded by the magnetic field. Electrons emitted from the cathode ionize feed gases as they drift toward the anode through the magnetic field via collisional and anomalous diffusion. The restricted mobility of electrons across the magnetic field lines forms a space-charge near the anode and an electric field that is substantially orthogonal to the imposed magnetic field. Ions generated within the anode discharge region are accelerated away from the anode. Since the anode discharge and ion acceleration regions do not exclude electrons, ion beam current densities are not restricted by space-charge limitations that are inherent in electrostatic acceleration optics. A fraction of the electrons emitted from the cathode and those released within the discharge from ionization also serve to electrically neutralize the ion beam as it propagates away from the anode's ion acceleration region. At pressures above 10
−4
Torr, ionization away from the anode discharge region and charge-exchange processes within the ion beam can form a diffusive background discharge making the output characteristics of the source appear as both an electrically neutralized ion beam and a quasi-neutral diffusive plasma. Unlike the near mono-energetic ion energy distribution of a gridded ion source, this gridless ion source has a broad energy spectrum and is capable of very high ion current densities. The combined output of both a self-neutralized ion beam and diffusive plasma is sometimes referred to as a “plasma beam”.
Another characteristic feature of this type of ion source is an E×B drift current motion of electrons in the anode discharge region. Electrons, which spiral about the lines of the magnetic field, experience an E×B or Hall-effect force and collectively drift in a direction perpendicular to both magnetic and electric fields. This is referred to as a Hall-effect drift current. In order to avoid Hall potentials which may form along this electron drift path, these ion sources have anode discharge regions or channels that allow Hall-effect current to drift along a continuous and closed path. The prior art refers to these types of ion sources by many names: “Magneto-plasma-dynamic Arc Thrusters”, “Hall Accelerators”, “Closed-Drift Thrusters”, and “Hall-Current Ion Sources”. For the purpose of this disclosure, these devices are referred to, in general, as “Hall-Current ion sources”. Yet another version of this technology is the “End-Hall” ion source described by Kaufman et al, U.S. Pat. No. 4,862,032, issued Aug. 29, 1989.
The following references illustrate the prior art with regard to the application of Hall-Current ion sources to the deposition of DLC coatings.
Okada et al., Japanese Journal of Applied Physics, Vol. 31, pages 1845-1854 (1992), describe a high energy Hall-Current ion source used for ion implantation and deposition of hard, abrasion resistant DLC coatings.
Fedoseev, et al. Diamond and Related Materials, Vol. 4, pages 314-317 (1995), describe a Hall-Current ion source used in deposition of relatively transparent DLC coatings.
Baldwin, et al., U.S. Pat. No. 5,616,179, issued Apr. 1, 1997, describe a process for the deposition of diamond-like, electrically conductive, and electron-emissive carbon-based films and coatings using the End-Hall ion source of the Kaufman et al. '032 patent.
Knapp et al., U.S. Pat. No. 5,508,368, issued Apr. 16, 1996 and Petrmichl et al., U.S. Pat. No. 5,618,619, issued Apr. 8, 1997 describe a process in which an End-Hall ion source or Hall-Current ion source is used to deposit highly transparent coatings comprised of C, Si, O and H, with Nanoindentation hardness of about 2 to 5 GPa, and having abrasion resistance comparable to glass.
It is desirable to deposit DLC and Si-DLC coatings in a production setting on a wide variety of substrates for many applications by direct ion beam deposition with a gridless Hall-Current ion source. More specifically, it is desirable to deposit DLC and Si-DLC coatings from a gridless Hall-Current ion source wherein such coatings have Nanoindentation hardness values greater than 10 GPa and wherein the deposition rates of such coatings are greater that 10 Å per second in a production setting. As an example, it is
Brown David Ward
Mahoney Leonard Joseph
Petrmichl Rudolph Hugo
Kilpatrick & Stockton LLP
Morgan Chemical Products, Inc.
Patel Vip
Russell Dean W.
Williams Joseph
LandOfFree
Method and apparatus for deposition of diamond-like carbon... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for deposition of diamond-like carbon..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for deposition of diamond-like carbon... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3005491