Metal treatment – Barrier layer stock material – p-n type
Patent
1989-02-24
1994-12-20
Hearn, Brian E.
Metal treatment
Barrier layer stock material, p-n type
437225, 437228, 437233, H01L 2100, H01L 2102, H01L 2900, H01L 21469
Patent
active
053743180
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the production of thin, chemically bonded diamond or diamondlike films. More particularly, it relates to such films produced by ion beam deposition.
2. Description of Related Art
Deposition of diamondlike carbon films has been the subject of intense research for about thirty years. This research has accelerated markedly during the past few years. The basic interest in diamondlike carbon films stems from the unique set of physical properties of diamond: it is the hardest material known; it is an excellent electrical insulator yet is the best thermal conductor known; it has high dielectric strength, and is highly transparent in the ultraviolet, visible and infrared regions of the spectrum; it is chemically inert and therefore resistant to oxidation and corrosion; and, it is biologically compatible with body tissues.
Attempts to fabricate true diamond films have resulted in carbon films having properties which vary over a range of many orders of magnitude. For example, the electrical resistivity of such films has been reported to vary between 10.sup.-2 and 10.sup.12 ohm-cm. The unique characteristics of some of these films and the possibility of "tailoring" a combination of desired properties for a specific purpose result in many advantages of such films for a variety of applications. Proposed applications include: optical coatings (in particular for hazardous environments and outer space); protective thin film coatings for magnetic recording media (e.g., computer disks); heat sinks and high thermal conductivity coatings for semiconductor applications; solid state devices; moisture barriers; low friction coatings for tribological applications; protective coatings compatible with body tissues for medical applications; etc.
The literature on diamondlike films includes several hundred publications, most of them appearing after 1980.
The study of diamondlike carbon films is complicated by the ambiguous and inconsistent nomenclature which has been used in research on these films. These films are referred to as "diamondlike films", "hard carbonaceous films", "hard carbon", "a-C:H", and "i-C". In the past, different names have been used to describe materials which are very similar while at other times the same name was applied to very different materials. This confusion is also related to the sometimes overlooked fact that the field of carbon films covers several pure phases of carbon as well as hydrocarbon compounds. The two best known crystalline phases of carbon are graphite, the stable hexagonal form, and diamond, the metastable cubic form. Diamond is stable at very high temperatures and pressures. In the past two decades three additional metastable carbon phases have been discovered: Lonsdalite (also known as hexagonal diamond); Chaoite (a hexagonal high pressure carbon phase); and, two other cubic, high pressure phases of carbon. Present data on the properties of the carbon phases refers to either cubic diamond or graphite. Very little information is available on the properties of the other phases.
For the purposes of this disclosure, the term "diamond" will be used to refer to a pure carbon material wherein the carbon atoms have sp.sup.3 hybridization. The term "diamondlike" refers to any carbon deposit having a mixture of sp.sup.2 and sp.sup.3 hybridized bonds. The fraction of carbon atoms in a particular hybridization state may vary over a wide range. The process of the present invention may be used to deposit diamondlike (as opposed to diamond) films by employing a C.sup.+ ion beam of very low kinetic energy (less than about 20 eV). Alternatively, the substrate temperature may be adjusted to favor the formation of a diamondlike film. In general, elevated substrate temperatures favor the production of diamondlike rather than diamond films. The particular temperature chosen will depend on the substrate to be coated. For example, at a substrate temperature of 350.degree. C. a low energy, mass-selected C.sup.+ ion beam will not fo
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Kasi Srinandan R.
Rabalais John W.
Everhart B.
Hearn Brian E.
University of Houston
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