DeVito Declaration – Ex. 1005 -- ‘773 US1
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`DOCKET NO: 0110198.00194US1
`’773 PATENT – CLAIMS 1-20, 34-39
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`
`IN THE UNITED STATES PATENT AND TRADEMARK OFFICE
`
`PATENT:
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`6,896,773
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`INVENTOR: ROMAN CHISTYAKOV
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`
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`FILED:
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`NOVEMBER 14, 2002
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`ISSUED: MAY 24, 2005
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`HIGH DEPOSITION SPUTTERING RATE
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`TITLE:
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`Mail Stop PATENT BOARD
`Patent Trial and Appeal Board
`U.S. Patent & Trademark Office
`P.O. Box 1450
`Alexandria, VA 22313-1450
`
`
`DECLARATION OF RICHARD DEVITO, REGARDING
`U.S. PATENT NO. 6,896,773
`
`I, Richard DeVito, declare as follows:
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`
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`1. My name is Richard DeVito.
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`2.
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`I received my B.S. in Physics from Suffolk University, cum laude in
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`1982. I received my M.S. in Experimental Solid State Physics from Syracuse
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`University in 1986.
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`1
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`TSMC et al. v. Zond, Inc.
`GILLETTE-1005
`Page 1 of 108
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`DOCKET NO: 0110198.00194US1
`’773 PATENT – CLAIMS 1-20, 34-39
`
`
`IN THE UNITED STATES PATENT AND TRADEMARK OFFICE
`
`PATENT:
`
`6,896,773
`
`INVENTOR: ROMAN CHISTYAKOV
`
`
`
`FILED:
`
`NOVEMBER 14, 2002
`
`ISSUED: MAY 24, 2005
`
`HIGH DEPOSITION SPUTTERING RATE
`
`TITLE:
`
`Mail Stop PATENT BOARD
`Patent Trial and Appeal Board
`U.S. Patent & Trademark Office
`P.O. Box 1450
`Alexandria, VA 22313-1450
`
`
`DECLARATION OF RICHARD DEVITO, REGARDING
`U.S. PATENT NO. 6,896,773
`
`I, Richard DeVito, declare as follows:
`
`
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`1. My name is Richard DeVito.
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`2.
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`I received my B.S. in Physics from Suffolk University, cum laude in
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`1982. I received my M.S. in Experimental Solid State Physics from Syracuse
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`University in 1986.
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`1
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`TSMC et al. v. Zond, Inc.
`GILLETTE-1005
`Page 1 of 108
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`DeVito Declaration – Ex. 1005 -- ‘773 US1
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`3.
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`I am the Founder and President of VAECO Inc. I have been the
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`Director at the “Kostas” Facility for Microfabrication and Nanotechnology at
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`Northeastern University, since October 2005.
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`4.
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`Between 1987 and 1994, I was a Physical Scientist and then Senior
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`Physical Scientist at Litton-Itek Optical Systems. I was a Senior Process Engineer
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`from 1994-1995, and then a Project / Process Engineer from 1995 -1997 at The
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`Gillette Co. Between 1997 and 2000, I was a Sr. Project Engineer at
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`Corning/OCA/NetOptics. Between 2000 and 2001, I was a Director of thin film
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`processing at Opnetics Corp. Between 2001 and 2002, I was a Director of thin
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`film processing at Unaxis Corp. Between August 2002 and October 2003, I was a
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`Process Manager at Nexx Systems. Between October 2003 and March 2004, I was
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`a consultant at Fluens Corp. I am also a co-founder of Fluens Corp. Between
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`March 2004 and October 2005, I was a Principal Process Development Fab
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`Engineer at Aegis Semiconductor.
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`5.
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`Thus, for over fifteen years, I have been focused on using plasmas to
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`deposit thin films, and I have worked with a wide range of different equipment for
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`working with many different materials.
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`6.
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`I make this declaration in my personal capacity and not on behalf of
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`Northeastern University.
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`DeVito Declaration – Ex. 1005 -- ‘773 US1
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`7.
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`8.
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`A copy of my latest curriculum vitae (CV) is attached as Appendix A.
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`I have been retained by the Gillette Company (“Gillette” or
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`“Petitioner”) as an expert in the field of plasma technology and sputtering to
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`provide my opinions regarding U.S. Patent No. 6,896,773 (the “‘773 patent”) (Ex.
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`1001).
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`9.
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`I am being compensated at my normal consulting rate of $250/hour
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`for my time. My compensation is not dependent on and in no way affects the
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`substance of my statements in this Declaration.
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`10.
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`I have no financial interest in the Petitioner. I similarly have no
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`financial interest in the ’773 patent, and have had no contact with the named
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`inventor of the ’773 patent.
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`11.
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`I have reviewed the specification, claims, and file history of the ‘773
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`patent.
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`12.
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`I have also reviewed the publications cited in this declaration,
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`including:
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` D.V. Mozgrin, et al, High-Current Low-Pressure Quasi-Stationary
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`Discharge in a Magnetic Field: Experimental Research, Plasma Physics
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`Reports, Vol. 21, No. 5, 1995 (“Mozgrin” (Ex. 1002)).
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` U.S. Pat. No. 6,413,382 (“Wang” (Ex. 1003)).
`3
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`GILLETTE-1005 / Page 3 of 108
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`DeVito Declaration – Ex. 1005 -- ‘773 US1
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` Certified Translation of Encyclopedia of Low-Temperature Plasma
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`Physics, Introductory Vol. III, Section VI, Fortov, V.E., Ed.,
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`Nauka/Interperiodica, Moscow (2000); pp. 117-126 (“Fortov” (Ex.
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`1004)).
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` A. A. Kudryavtsev, et al, Ionization relaxation in a plasma produced by a
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`pulsed inert-gas discharge, Sov. Phys. Tech. Phys. 28(1), January 1983
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`(“Kudryavtsev” (Ex. 1006)).
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` U.S. Patent No. 6,306,265 (“Fu” (Ex. 1007)).
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` U.S. Patent No. 6,190,512 (“Lantsman” (Ex. 1008)).
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` U.S. Patent No. 5,958,155 (“Kawamata” (Ex. 1009)).
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` U.S. Patent No. 6,398,929 (“Chiang” (Ex. 1011)).
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` Gas Discharge Physics, by Raizer, Table of Contents, pp. 1-35, Springer
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`1997 (“Raizer” (Ex. 1012)).
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` Certified Translation of D.V. Mozgrin, High-Current Low-Pressure
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`Quasi-Stationary Discharge in a Magnetic Field: Experimental Research,
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`Thesis at Moscow Engineering Physics Institute, 1994 (“Mozgrin Thesis”
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`(Ex. 1015)).
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`4
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`13.
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`I believe that the disclosure of each of these publications, read in the
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`light of a person of ordinary skill in the field, provides sufficient information for
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`someone in the field to make and use the plasma generation systems and perform
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`the processes that are described in the above publications.
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`I.
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`RELEVANT LAW
`14.
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`I am not an attorney. For the purposes of this declaration, I have been
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`informed about certain aspects of the law that are relevant to my opinions. My
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`understanding of the law is as follows:
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`15.
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`I have been informed and understand that a patent claim is anticipated
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`(not novel) and therefore invalid if a prior art document discloses all the limitations
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`of the claim, explicitly or inherently.
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`16.
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`I have been informed and understand that if a patent claim is novel, it
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`can be invalid if it is considered to have been obvious to a person of ordinary skill
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`in the art at the time the application was filed. This means that, even if all of the
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`requirements of a claim are not found in a single prior art reference, the claim is
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`not patentable if the differences between the subject matter in the prior art and the
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`subject matter in the claim would have been obvious to a person of ordinary skill in
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`the art at the time the application was filed.
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`17.
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`I have been informed and understand that a determination of whether
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`a claim would have been obvious should be based upon several factors, including,
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`among others:
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` the level of ordinary skill in the art at the time the application was filed;
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` the scope and content of the prior art;
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` what differences, if any, existed between the claimed invention and the
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`prior art.
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`18.
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`I have been informed and understand that the teachings of two or
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`more references may be combined in the same way as disclosed in the claims, if
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`such a combination would have been obvious to one having ordinary skill in the
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`art. In determining whether a combination or modification based on either a single
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`reference or multiple references would have been obvious, it is appropriate to
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`consider, among other factors:
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` whether the teachings of the prior art references disclose known concepts
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`combined in familiar ways, and when combined, would yield predictable
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`results;
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` whether a person of ordinary skill in the art could implement a
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`predictable variation, and would see the benefit of doing so;
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`DeVito Declaration – Ex. 1005 -- ‘773 US1
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` whether the claimed elements represent one of a limited number of
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`known design choices, and would have a reasonable expectation of
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`success by those skilled in the art;
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` whether a person of ordinary skill would have recognized a reason to
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`combine known elements in the manner described in the claim;
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` whether there is some teaching or suggestion in the prior art to make the
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`modification or combination of elements claimed in the patent; and
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` whether the innovation applies a known technique that had been used to
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`improve a similar device or method in a similar way.
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`19.
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`I understand that one of ordinary skill in the art has ordinary
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`creativity, and is not an automaton.
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`20.
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`I understand that in considering obviousness, it is important not to
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`determine obviousness using the benefit of hindsight derived from the patent being
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`considered.
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`21.
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`I have considered certain issues from the perspective of a person of
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`ordinary skill in the art at the time the ‘773 patent application was filed. In my
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`opinion, a person of ordinary skill in the art for the ‘773 patent would have found
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`the ‘773 invalid.
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`II. BACKGROUND DESCRIPTION OF TECHNOLOGY
`Overview of Sputtering
`22. Sputtering is a technique for depositing a thin film of a material onto a
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`surface called a substrate. This technology is widely used in thin film deposition
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`processes, including semiconductor wafer processing and razor blade
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`manufacturing.
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`23. Sputtering is performed in a plasma chamber under low pressure, e.g.,
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`between 1-100 mTorr, and typically with an inert feed gas, such as argon. The
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`material to be deposited is typically provided in the form of a solid disk, or a plate,
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`and is referred to as a target. A plasma of ground state argon atoms, excited argon
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`atoms, positive argon ions, and electrons is created by applying an electric field to
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`electrodes near the feed gas. The target develops a negative potential, Vb, related
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`to the applied field. Positive argon ions in the plasma are attracted to the target and
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`are accelerated at a potential Vb. These ions strike the target and cause target
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`atoms to be dislodged through momentum exchange. These atoms can themselves
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`become ionized. The dislodged target atoms are then deposited on the substrate,
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`often by providing a bias signal on the substrate to attract the ionized argon atoms
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`to bombard and densify the growing film or similarly any ionized sputtered atoms.
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`A magnet system or “magnetron” is often used to control the location of the
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`plasma relative to the target by trapping electrons close to the target.
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`24. High voltages or currents can be useful in the sputtering process to
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`increase the plasma density, but the use of higher power makes it more likely that
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`arcing will occur in the plasma. Arcing is an uncontrolled collapse of the plasma
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`to a localized region. It is generally considered undesirable during the sputtering
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`process because it can cause larger portions of the target to be deposited on the
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`substrate, potentially causing defects.
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`25. Further detail about plasma sputtering, including sputtering with high
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`power pulses for providing an electric field is provided below.
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`Plasma Sputtering
`26. Sputtering is a vacuum and plasma-based method for physically
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`removing a layer of material atoms. When the top or surface layer of material is
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`removed and cleaned away, it is referred to as “etching.” While etching can be
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`performed using magnetron sputtering systems, some etching systems do not need
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`or require a magnetron. However, the atoms that are removed can be used to
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`deposit thin films on a substrate in a process known as physical vapor deposition
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`(PVD). My discussion here is mostly about film deposition, but much of the
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`discussion would apply to an etching process as well.
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`27. The process properties of PVD allow it to produce very thin coatings,
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`e.g., on the order of angstroms, of a “target” material on a substrate, such as a
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`silicon wafer in microelectronics, a razor blade, a ball bearing, or a mirror. The
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`process can be used to deposit metals (copper, titanium, etc.); compound material
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`such as titanium tungsten (TiW); oxide and nitride materials such as TiN (titanium
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`nitride) and Al2O3 (aluminum oxide); and other materials like MgF2 (magnesium
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`fluoride). The process of compound sputtering with reactive gases is referred to as
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`reactive magnetron sputtering.
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`28. To obtain thin films of high purity material and free of defects,
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`sputtering is usually carried out in a vacuum environment. An anode (usually
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`grounded), a cathode that is typically mounted with the target material, and a
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`substrate holder are placed in a chamber. In some cases the substrate holder is tied
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`to the anode ground, but it can be floating or at a separate potential as well as being
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`heated or cooled.
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`29. The chamber is evacuated to some low pressure and back filled with
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`gas, such as argon. Other gases such as Ne or Xe can be used for non-reactive
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`sputtering. For sputter deposition, high purity argon is the gas of choice for
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`sustaining the plasma environment due to its cost, abundance, and mass.
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`30.
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`In the vacuum chamber, a sufficient voltage is applied between the
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`anode and the cathode to strike a plasma. The plasma breakdown or “glow” is
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`achieved according to the Paschen effect, which states that for any given product
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`of pressure and distance (P x d) in a plasma system, there is generally a voltage at
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`which breakdown will occur in which any free electrons created will collide with
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`other atoms, thereby creating other electrons to further collide with atoms.
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`31. Electrons are accelerated because of the force exerted on them by the
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`electric field (F=qE), where F is force, q is charge and E is the electric field. As
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`the electrons move, they acquire an energy εi. Some will acquire enough energy to
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`ionize an argon atom if the energy εi is greater than the ionization potential, Vi (for
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`Argon, Vi=15.7 eV). If the electrons collide with argon atoms, some of these
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`electrons will cause the argon atoms to ionize through election impact, that is:
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`e- + Ar e- + Ar+ + e-
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`32.
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`In this scenario, depicted in FIG. 1 below, an additional electron and a
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`positively-charged ion are created. These extra electrons can cause further
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`ionization through impact. The argon ions created will reach the cathode, which
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`usually holds the target material to be sputtered, e.g., in the form of a circular plate.
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`The ions than impact the target are accelerated at the potential of the cathode. The
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`target emits “secondary electrons” through inelastic collisions that also contribute
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`to the ionization process. When the electrons reach the anode, a current flows, and
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`the breakdown occurs. These cascading effects can cause the plasma to be self-
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`sustaining.
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`33.
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`In some cases, the electrons can collide with neutral argon atoms and
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`cause them to go to a higher excited state, where they are referred to as excited
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`atoms. These excited atoms can be ionized through collisions as well. The plasma
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`now has neutral ground state argon atoms, excited argon atoms (neutral charge but
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`at a higher energy state), electrons with a negative charge, and positively charged
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`argon ions.
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`34. Diode sputtering is a form of sputtering where a constant voltage is
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`applied across the anode and cathode. It can take place at what would be
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`considered a high pressure of 100 mTorr or so because the high mobility of
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`electrons in the plasma requires this high pressure to ensure that enough collisions
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`occur to sustain the plasma before the electrons are lost to ground. FIG. 1 depicts a
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`diode sputtering apparatus, having a cathode spaced a distance “d” from an anode
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`and a voltage source Vo.
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`cathode
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`Eo=Vo/d
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`4.50d
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`+
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`‐(‐)
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`e
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`e
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`Impact ionization
`by free elctron
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`anode
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`(+)
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`Vo
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`(‐)
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`(+)
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`ioR
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`FIG. 1: An anode/cathode structure with an applied DC voltage to
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`demonstrate the Paschen effect for plasma ignition
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`35. The plasma is quasi-neutral, that is, the number of ions is
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`approximately equal to the number of electrons, implying from Gauss’ law that the
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`plasma has no electric field. Any local disturbance of the quasi neutrality caused
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`within the plasma is shielded from the rest of the plasma. This is known as Debye
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`shielding. This constant shifting of the plasma to maintain quasi-neutrality is set
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`by the plasma frequency ωp =9x103 ne
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`1/2, where ne is density of electrons. This
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`dependence on electron density is caused by the restoring forces of the plasma,
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`which are determined by higher mobility electrons and not ions. The plasma
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`frequency for ne=1010 ion/cm3 is on the order of 109 Hz which means that the time
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`for the plasma can reconfigure itself in nanoseconds with each disturbance.
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`constant, since E=(cid:1487)V , hence all voltage is dropped across the cathode in a distance
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`36. This relationship also implies that the potential though the plasma is
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`called the “sheath.” Because electrons have higher mobility (high speed due to
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`low mass) than ions, any object placed in a plasma will charge up negatively with
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`respect to the plasma.
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`Vp Plasma Potential
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`Vf Floating Potential
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`0 Volts / gnd
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`DC
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`+
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`+
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`+
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`+
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`E=e(Vp+Vc)= 625 eV
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`Cathode -600 V
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`Cathode DS
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`Anode DS
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`Wall/ Anode gnd
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`FIG. 2 Potential Diagram of a DC discharge
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`37.
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`In these plasmas and in a magnetron plasma (described below), about
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`0.1 %-1% of the gas is ionized. The number of plasma ions np is much less than the
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`number of neutral gas atoms in the chamber, represented by n=p/kbTg , where n is
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`the number of gas atoms, p is pressure, kb is Boltzman’s constant, and Tg is the
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`temperature of the gas.
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`38. Sputtering of the target material occurs when ions accelerated to the
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`cathode/target by the electric field strike the cathode and cause a physical transfer
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`of momentum to the target material. The ions impact the target surface at about
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`the energy of the cathode, which would be the power supply voltage (ignoring a
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`small voltage gained from the plasma potential, depicted in FIG. 2). For each ion
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`at a specific energy that strikes the target, there is a “yield” of target atoms that are
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`sputtered (dislodged) from the target. This yield Y is expressed in atoms/ion
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`below.
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`atoms sputtered
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`ions bombing
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`atom target
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` of mass :M
` of mass ion bombing :m
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` of ion bombingenergy kinetic :E
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`metal target
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` Bonding ofenergy :U
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` angle /incident
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` strikingon depends :
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`Y
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`Mm
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`
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`Mm
`UE
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`Mm
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`mM
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`2
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`39. Since sputtering is a momentum transfer process, the relative mass of
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`the target atoms (e.g., metal) and sputtering atom (e.g., argon) matters. The yield
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`numbers are usually provided by tables. Yield curves for an element typically
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`show that optimum voltage from most target mass and ion mass combinations is
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`between 500-1000 volts. After that, the yield can drop off because the ions can
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`become implanted in the target rather than colliding and bouncing off. In any case,
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`the momentum of the impacting ions mass causes atoms to be dislodged
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`(sputtered) from the surface of the cathode/target. This ejection from the target
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`overall is referred to as “erosion” of the target.
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`40. The erosion rate (ER) in angstroms/min of the target is a function of
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`the yield according to the equation
` (AMWjY
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`***2.62
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`41. Here j is the target current density ( I/A), I is the power supply current
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`Eqn. 1
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`ER
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`
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`/
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`.)min
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`A is the discharge area on the target, MW is the molecular weight of target, ρ is
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`density of target and Y is the sputter yield. From this ER, the deposition rate on
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`the substrate can be approximated.
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`42. The ejected target atoms are emitted in a cosine distribution from the
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`target surface and some are deposited on the substrate. The number of target atoms
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`that reach the substrate is determined mainly by the mean free path and distance to
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`the substrate. The mean free path is the distance the atoms travel before they
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`encounter another particle. A simplified expression of the mean free path (MFP) is
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`presented below.
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`Eqn. 2
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`
`
` MFP(cid:4666)cm(cid:4667)(cid:3404) (cid:2868).(cid:2868)(cid:2868)(cid:2873)
`(cid:2900)(cid:4666)(cid:2930)(cid:2925)(cid:2928)(cid:2928)(cid:4667)
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`43. At 100 mtorr, the MFP is only 0.05 cm. Many atoms can be scattered
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`by interacting with the existing gas atoms if the pressure is too high, and thus the
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`atoms might never reach the substrate and end up elsewhere in the chamber. The
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`energy of the target atoms that reach the substrate is also decreased by about half
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`for every collision with the gas atoms. With many collisions, the atoms can lose
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`energy acquired through the sputtering process, thus rendering films of poor
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`quality. This is referred to as thermalization of the atoms.
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`44. Under the right plasma conditions, the ejected atoms can become
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`ionized themselves, in which case they can be drawn to the substrate by a bias
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`voltage applied to the substrate.
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`45. A benefit of sputtering (e.g., compared to a thermal evaporation
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`process) is that the incoming atoms to the substrate have energies that are
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`substantially higher, and thus provide better adhesion on a substrate surface.
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`Sputtering can lead to dense and adherent films because the atoms on the surface
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`have high mobility and the ability to “hop” around on the surface to find a stable
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`bonding site, as well as be densified by the bombarding energies of the other
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`atoms. Given the above discussion, diode sputtering suffers from several
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`drawbacks, including the high speed electrons being quickly lost to chamber
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`ground or the anode resulting higher operating pressure. This effect can
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`necessitate closer substrate distances as well as non-optimal discharge voltages.
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`Magnetron Sputtering
`46. To overcome the above-mentioned drawbacks of diode sputtering, it
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`was well known that a magnetic field could be set up behind the target. In this
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`example when a discharge is created, the free electrons are trapped by the magnetic
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`field lines. Also, the secondary electrons created by ion impact at the target, which
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`move very fast and are normally lost to the discharge very quickly, can now be
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`trapped by the magnetic field as they are accelerated by the electric field from the
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`target. In FIG. 3, a direct current “DC” supply is shown, but a radio frequency
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`“RF” or pulsed supply could also be used.
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`FIG. 3 Simplified model for the detail of a magnetron sputter cathode and
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`associated plasma interactions.
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`47. The electrons are now trapped around the magnetic field lines because
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`of the Lorentz force described in the equation below, where F is the Lorentz force,
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`q is charge, v is velocity and B is magnetic field.
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`Eqn. 3
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`DeVito Declaration – Ex. 1005 -- ‘773 US1
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`F(cid:3404)qv x B
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`48. One designs the magnetic field to hold the electrons and hence the
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`plasma close to the target surface to improve ion bombardment and hence
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`sputtering rate. Depending on where the electrons are generated, as the electrons
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`escape from the surface and are accelerated, they gain energy from the electric
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`field. The electrons are then trapped in the magnetic field and travel back and
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`forth as depicted in FIG. 3. If they encounter other neutrals on the way, the
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`neutrals will be ionized if the energetics are correct. Then, as the electrons
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`decelerate to the surface again, they are pushed back into the magnetic field to
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`being in the oscillation again, since they have lost the energy to fully decelerate
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`back to the target.
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`49. The interaction of the electric “E” and magnetic “B” field creates the
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`ExB effect of the electrons as there is another right angle force exerted on the
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`electrons resulting in a “Hall current.”
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`E Field
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`Line of B
`flux
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`N
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`S
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`N
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`Magnetic
`Yoke plate
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`FIG. 4: Sweet spot of plasma bombardment
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`50.
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` As a result there is an intense trapping of electrons where the E field
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`is perpendicular to the B field, and hence a strong plasma density and high ion
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`bombardment locally. This “sweet spot” is depicted in FIG. 4. The direction of
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`the EXB path of electron is in a circular path about this sweet spot in FIG. 4.
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`51.
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` Since the magnetic and electric fields are not perpendicular
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`everywhere, this process can cause an erosion profile known as a “race track,” as
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`shown in FIG. 5,whose location and width are determined by the magnetic field
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`designs as well as operating parameters such as power and also pressure.
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`Magnetron designers generally try to design a flat B-field profiled over the target
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`surface to enhance uniform erosion of the target and hence the uniformity of the
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`deposited film.
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`Non erosion
`zones
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`FIG. 5: Target erosion profile and re-deposition zones: source of particulates
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`52. Many suppliers and equipment manufacturers to the microelectronics
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`industry use a circular magnetron with rotating magnet packs that are a fraction of
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`the target size for single wafer coating tools. These packs rotate in a cyclical path
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`behind the target surface to create a uniform, high target utilization. In addition to
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`longer target life through higher utilization, this process eliminates the re-
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`deposition zone reducing this as an arc contribution. These designs also tend to
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`produce films with better uniformity.
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`Biased Sputtering
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`53. Another benefit of sputtering is that the argon ions that can also be
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`used to bombard the substrate during film growth. This bombardment of the
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`substrate concurrent with the growing film helps to make the film denser, and
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`contributes to stress changes as shown in classic papers by Thornton and Hoffman.
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`Thornton, J. and Hoffman, D.W. Stress related effects in thin films, Thin Sold
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`Films, 171, 1989, 5-31 (Ex. 1017). In these papers, the authors show that reducing
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`the process pressure can increase the mean free path of all energetic particles
`
`(neutrals and ions) to help bombard the substrate and improve the film quality.
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`54. To tune the bombardment energies independent of pressure, it was
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`well-known that one could also negatively bias a substrate with DC, pulsed DC, or
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`RF voltage. The ions would accelerate across the sheath at an energy
`
`approximately equal to the applied bias. The argon ion flux is limited to the
`
`available ions that migrate to the biased substrate. Since, as described above, one
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`purposefully confines most of those ions to the target, that flux can be limited.
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`This issue can be addressed by unbalancing the magnetron by ensuring that rather
`
`than have closed B-field lines as in FIG. 4, the field lines are allowed to extend to
`
`the substrate. Some electrons will follow these field lines and cause ionization
`
`away from the target allowing a high impingent flux of ions available for
`
`bombardment. This was demonstrated in N. Savvides and B. Window,
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`Unbalanced magnetron ion‐assisted deposition and property modification of thin
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`films, J. Vac. Sci. Technol. A 4 , 504, 1986 (1018).
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`Arcing
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`55.
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`In the course of normal sputtering of a metal target, asperities
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`(roughness) within the target surface, or particles that flake off on the surface, can
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`cause local heating sufficient to create thermionic emission. This can result in a
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`high point of conductivity in the plasma that can cause the plasma to collapse to
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`this single point characterized by a high power density on a small spot. And, this
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`intense power concentration causes localized melting and eruption of particles
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`from the target to the substrate which can be detrimental to product yield. This
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`process is referred to as “arcing” or “electrical breakdown condition.” The arcing
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`can also be caused by the charging of insulating impurities on the surface. That
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`essentially creates a capacitor with one plate being the target and the other plate
`
`being the plasma. The parasitic capacitance of this dielectric may not be able to
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`withstand the full voltages of the process and break down at some point causing
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`localized plasma disruption and particle formation. For many reasons, these events
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`are problematic for microelectronics and other processes. However, arcing can be
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`addressed through a power supply design.
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`FIG. 6: Power supply voltage waveforms during arcing event according to
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`Advanced Energy
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`56. FIG. 6 from Advanced Energy White Paper (a power supply
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`manufacturer) (Grove TC. Arcing problems encountered during sputter deposition
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`of aluminum, White Papers, ed: Advanced Energy, 2000 (Ex. 1019)), displays a
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`typical response of a power supply to a unipolar arc events. The sputter process is
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`operating at 20 amps and 400 volts, and then suddenly there is a rapid climb in
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`current and a corresponding decrease in voltage, all occurring at the single point in
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`the plasma. Most power supplies can monitor the slopes of these lines and beyond
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`a certain threshold (set by the user in advanced designs) the power supply briefly
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`opens up a switch to shunt the power to a dummy load to give the process time to
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`dissipate any charging or heating at the surface and the supply is then switched
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`back into the process. These passive techniques are good, but being proactive is
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`better as described below.
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`57. For proactive arc prevention, asymmetric bipolar pulsing can be used.
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`The supply is maintained at its normal voltage and current, for example 400 volts
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`and 20 amps. Sputtering occurs during the normal negative cycle in FIG. 7. Also if
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`there is an insulating asperity, it will also charge up to the cathode voltage at some
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`point reducing the magnitude of the sputter voltage to zero. Periodically, the
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`voltage is switched positively to dissipate any charge layers. Electrons are now
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`swept to the surface to neutralize positive charge buildup. Then on switching back
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`the voltage, the layers are re-sputtered by argon before charging positive again.
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`This is shown by the T1-T2 part of the pulse and the FIG. 7.
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`FIG. 7 Asymmetric bipolar pulsed sputtering according to Sellers in
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`Asymmetric bipolar pulsed DC: the enabling technology for reactive PVD.
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`Sellers, J. Surface & Coatings Technology vol. 98 issue 1-3 January, 1998.
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`p. 1245-1250 (Ex. 1020).
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`
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`58. A side benefit of pulsed sputtering is the higher sputtering efficiency
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`of the target, that is, more uniform erosion of the target. This improvement, in
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`turn, produces a more uniform film. The higher utilization is a benefit that arises
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`with pulsing because the instantaneous power is higher than the average power
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`during the pulse.
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`59. These effects can also be attained by increasing cathode power in a
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`static manner, but at high power densities the cathode/target and magnet typically
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`cannot sustain the long term higher power density for long times and will be
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`damaged. The benefit of this pulsing the target with high power have been
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`combined with new power supply technology to deliver very high power densities
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`in short time span. This process is known as high impulse pulsed magnetron
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`sputtering, or HiPIMS. HiPIMS can give all the above benefits of ionized neutrals,
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`sufficient ionized argon for biasing and high target utilization. The prior art to
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`Wang, Mozgrin, and Kouznetsov are all examples of HiPIMS systems.
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`60. The prior art to Wang, Mozgrin, and Kouznetsov are also examples
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`describing how creating a weakly-ionized plasma, also referred to as pre-
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`ionizatio
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