USH1792H - Selection of crystal orientation in diamond film chemical vapor deposition - Google Patents
Selection of crystal orientation in diamond film chemical vapor deposition Download PDFInfo
- Publication number
- USH1792H USH1792H US08/919,095 US91909597A USH1792H US H1792 H USH1792 H US H1792H US 91909597 A US91909597 A US 91909597A US H1792 H USH1792 H US H1792H
- Authority
- US
- United States
- Prior art keywords
- diamond
- substrate
- crystallites
- pressure
- orientation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 229910003460 diamond Inorganic materials 0.000 title claims abstract description 103
- 239000010432 diamond Substances 0.000 title claims abstract description 103
- 239000013078 crystal Substances 0.000 title claims abstract description 26
- 238000005229 chemical vapour deposition Methods 0.000 title claims description 30
- 239000000758 substrate Substances 0.000 claims abstract description 58
- 238000000151 deposition Methods 0.000 claims abstract description 44
- 239000007789 gas Substances 0.000 claims abstract description 42
- 150000004767 nitrides Chemical class 0.000 claims abstract description 27
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 22
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 19
- 239000001257 hydrogen Substances 0.000 claims abstract description 19
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 17
- 239000000203 mixture Substances 0.000 claims abstract description 12
- -1 carbon Chemical compound 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims description 22
- 239000008246 gaseous mixture Substances 0.000 claims description 16
- 239000000463 material Substances 0.000 claims description 13
- 150000001875 compounds Chemical class 0.000 claims description 3
- 238000007740 vapor deposition Methods 0.000 claims description 2
- 230000003213 activating effect Effects 0.000 claims 1
- 239000011229 interlayer Substances 0.000 abstract description 27
- 230000008021 deposition Effects 0.000 description 37
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 24
- 239000010410 layer Substances 0.000 description 22
- 230000003287 optical effect Effects 0.000 description 15
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 11
- 239000001301 oxygen Substances 0.000 description 11
- 229910052760 oxygen Inorganic materials 0.000 description 11
- 238000000576 coating method Methods 0.000 description 9
- 238000010899 nucleation Methods 0.000 description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 9
- 238000004544 sputter deposition Methods 0.000 description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 125000004429 atom Chemical group 0.000 description 6
- 230000001788 irregular Effects 0.000 description 6
- 229910052581 Si3N4 Inorganic materials 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 5
- 229910002804 graphite Inorganic materials 0.000 description 5
- 239000010439 graphite Substances 0.000 description 5
- 235000012239 silicon dioxide Nutrition 0.000 description 5
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 238000005299 abrasion Methods 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 150000002431 hydrogen Chemical class 0.000 description 4
- 230000006698 induction Effects 0.000 description 4
- 230000006911 nucleation Effects 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 4
- DRDVZXDWVBGGMH-UHFFFAOYSA-N zinc;sulfide Chemical compound [S-2].[Zn+2] DRDVZXDWVBGGMH-UHFFFAOYSA-N 0.000 description 4
- 239000005083 Zinc sulfide Substances 0.000 description 3
- 230000004913 activation Effects 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 238000005498 polishing Methods 0.000 description 3
- 230000001681 protective effect Effects 0.000 description 3
- 238000005086 pumping Methods 0.000 description 3
- 230000005855 radiation Effects 0.000 description 3
- 229910052984 zinc sulfide Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000012935 Averaging Methods 0.000 description 2
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 230000003628 erosive effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 238000001771 vacuum deposition Methods 0.000 description 2
- 229910052582 BN Inorganic materials 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- CFJRGWXELQQLSA-UHFFFAOYSA-N azanylidyneniobium Chemical compound [Nb]#N CFJRGWXELQQLSA-UHFFFAOYSA-N 0.000 description 1
- SKKMWRVAJNPLFY-UHFFFAOYSA-N azanylidynevanadium Chemical compound [V]#N SKKMWRVAJNPLFY-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910021387 carbon allotrope Inorganic materials 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 229910052735 hafnium Inorganic materials 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- DOTMOQHOJINYBL-UHFFFAOYSA-N molecular nitrogen;molecular oxygen Chemical compound N#N.O=O DOTMOQHOJINYBL-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000011253 protective coating Substances 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- MZLGASXMSKOWSE-UHFFFAOYSA-N tantalum nitride Chemical compound [Ta]#N MZLGASXMSKOWSE-UHFFFAOYSA-N 0.000 description 1
- 239000013077 target material Substances 0.000 description 1
- 235000012431 wafers Nutrition 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- ZVWKZXLXHLZXLS-UHFFFAOYSA-N zirconium nitride Chemical compound [Zr]#N ZVWKZXLXHLZXLS-UHFFFAOYSA-N 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
- C23C16/26—Deposition of carbon only
- C23C16/27—Diamond only
- C23C16/274—Diamond only using microwave discharges
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/02—Pretreatment of the material to be coated
- C23C16/0272—Deposition of sub-layers, e.g. to promote the adhesion of the main coating
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
- C23C16/26—Deposition of carbon only
- C23C16/27—Diamond only
- C23C16/279—Diamond only control of diamond crystallography
Definitions
- the present invention pertains to coating processes using vapor deposition of coatings including diamond.
- the carbon allotrope diamond has many potential uses. Diamond has extreme hardness, resistance to thermal and mechanical shock, and transparency to a wide range of electromagnetic wavelengths from ultraviolet through visible and infrared radiation to microwaves. Diamond would thus be an unexcelled coating for transmitting, reflecting, and absorbing optical and microwave elements subjected to weather, particulate erosion, and high energy radiation. Diamond also has high thermal conductivity and high electrical resistivity when pure. Diamond would thus make integrated circuits and other electrical and electronic devices incorporating a diamond film unexcelled for operation at high temperature, for convenience of cooling, and where transparency, environmental resistance, and radiation resistance are desirable.
- CVD chemical vapor deposition
- a film of polycrystalline diamond from an activated gaseous mixture which includes a gas containing carbon is well-known and would appear to make these potential uses practical.
- diamond films deposited heretofore by CVD on a non-diamond substrate do not adhere thereto sufficiently for practical purposes unless the substrate is first abraded, as with diamond grit, or seeded with diamond particles, as by such abrasion leaving diamond particles.
- the substrate is irregular and the crystallites forming the deposited film are irregular in size and spacing, very defected, and without preferred crystal orientation.
- the substrate and diamond film of the prior art are thus too irregular for use as an optical coating although continuous and smooth polycrystalline films are well-suited as optical coatings.
- prior art CVD diamond may be usable as a relatively massive heat sink, prior art CVD diamond is too irregular for use in an electronic device for doping as an active element of a transistor or the like or for use as an electrical insulating or thermal conducting layer within an integrated circuit.
- the irregularities of prior art CVD diamond films may be disadvantageous for mechanical protection even where optical and electrical properties are irrelevant.
- a very thick diamond layer may be rapidly deposited using a plasma torch or jet in which the carbon containing gas, which may be a portion of a flame, is activated by discharging the gas through an electric arc.
- the resulting diamond layer is so irregular and the crystallites so imperfectly joined that the layer has, despite its thickness, relatively poor resistance to weathering.
- the deposition, in a chamber containing gas at a pressure less than atmospheric, of a film or layer of a material onto a substrate is, of course, well-known.
- Such vacuum deposition may be carried out by sputtering where ions of a gas, typically argon heated by microwave energy, eject atoms to be deposited from a target of the material so that the freed atoms travel to an adjacent substrate and are deposited thereon. Movement of such freed atoms to the substrate may be motivated by a suitable electric potential between the target and substrate.
- An oxide or nitride of the target material may be deposited by including, respectively, oxygen or nitrogen in the gas in the chamber. Suitable materials, structures, temperatures, and pressures for sputtering deposition of oxides and nitrides of a variety of elements on a variety of substrate materials are readily available for selection by one skilled in the art of vacuum deposition.
- atoms to be deposited on a substrate are provided as atoms in molecules of a gas present in the chamber and activated while in contact with the substrate.
- the gas is activated by heating the gas by microwave energy, a hot filament, electric discharge, or combustion so that the gas releases free radicals containing the atoms to be deposited on the substrate.
- no electric potential relative to the substrate is provided, and the substrate is maintained at a suitable temperature by electrical resistance or induction heating.
- a gas containing the carbon which forms the diamond is provided as small proportion of a gaseous mixture in the chamber, the balance of the gas being predominantly hydrogen.
- a gaseous mixture may be activated by microwave energy at a frequency which excites the hydrogen molecule.
- the carbon containing gas is usually methane which is readily obtained in a pure state and is present in the mixture at a proportion less that 5% and, typically, 0.5% to 2%.
- the necessary carbon-containing free radicals may be obtained from vapors of other hydrocarbons, alcohols, or the like.
- Diamond may be deposited by CVD over a wide range of conditions.
- the vacuum chamber may be maintained at a pressure of 0.1 to 100 Torr by pumping while providing new gaseous mixture.
- the substrate is maintained at 550° to 1100° C. In general higher pressures increase the rate of diamond deposition as do higher substrate temperatures up to 900° or 1000° C.
- variations in substrate temperature, in gas activation method and temperature, in the proportion of carbon providing gas, and in the method of substrate abrasion provide some control over the crystal size and the irregularity of the deposited diamond.
- the deposited polycrystalline diamond is, as before stated, irregular and without a preferred crystal orientation.
- the film is deposited as a layer of polycrystalline diamond on a refractory nitride interlayer from a gaseous mixture of hydrogen and a gas, such as methane, containing carbon, the substrate and the interlayer being heated and the gaseous mixture being activated by microwave energy.
- the crystal orientation of the deposited diamond is selected by controlling the pressure of the mixture and other deposition conditions, a relatively lower pressure and corresponding microwave power resulting in the ⁇ 100> orientation being preferred and a relatively higher pressure and corresponding power resulting in the ⁇ 111> orientation being preferred.
- Another object is to provide such a high quality diamond film wherein the crystal orientation may be selected for high resistance to environmental effects.
- Another object is to provide such a high quality diamond film wherein the crystal orientation may be selected for relative ease in polishing.
- a representative vacuum chamber used in the practice of the present invention admits microwave energy at 2.45 GHz for resonance with hydrogen molecules to form a plasma ball of activated gas above a graphite stage mounting a substrate bearing a nitride interlayer on which diamond is deposited from the activated gas.
- such a chamber has walls constructed of stainless steel and connected to a system ground.
- One wall has a slot for admission of the microwave energy through a waveguide from a microwave source and power controller which provides a selected level of microwave energy to the waveguide. Since reflected microwave energy from the chamber may be minimized by adjustment. of suitable tuning stubs, this level is substantially that provided to the chamber.
- a quartz window isolates the chamber interior physically from the microwave supplying elements, but passes microwave energy to form the plasma ball.
- the substrate may be heated by induction heating to a selected temperature, and the interlayer surface contacted by the plasma ball and undergoing diamond deposition is viewable through a window by an optical pyrometer for determining the exact temperature of such surface.
- a thermocouple engages the stage and is connected to an induction heater power source and controller for maintaining the stage at a selected temperature.
- a DC power supply is connected so as to provide a selected DC bias voltage in a range of about positive 20 volts to about negative 80 volts between the vacuum chamber wall and the stage so that this bias voltage is substantially that between the substrate and the chamber wall.
- the chamber has a ring manifold for distributing feed gas to the chamber interior.
- the chamber is associated with an ionization gage for precise measurement of the vacuum within the chamber; an exhaust system for maintaining a selected chamber pressure by pumping while feed gas is being provided to the chamber; and a gas supply system connected between the ring manifold and bottles which contain the gases hydrogen, methane, and oxygen used in representative CVD of diamond involving the present invention.
- the gas supply system is adapted to provide the chamber with a selected flow of any gas or of any predetermined mixture of gases from the bottles by valves and flow meters through which each bottle is connected to the ring manifold.
- a gas flow controller receives signals from meters and provides signals to the valves so as to maintain the selected gas flow from each bottle.
- the exhaust system has a vacuum pump for continuously withdrawn a flow of gas from the vacuum chamber and has an exhaust valve for selectively throttling this flow.
- a precision manometer measures the vacuum in the chamber, and is connected to an exhaust valve controller is adpated to actuate the exhaust valve in accordance with signals from the precision manometer so as to maintain a selected such vacuum which may be monitored by the ionization gage.
- the selected gas or gas mixture enters the chamber at a selected flow rate and participates in the plasma ball while gases resulting from the ball and any other gases are continuously withdrawn by the exhaust system at a rate determined by the exhaust valve. A selected pressure is thus maintained in the chamber for CVD deposition or a related operation.
- the present invention is effective when this pressure is below about 100 torr and, typically, in a range of about 20 to about 50 torr.
- this pressure is below about 100 torr and, typically, in a range of about 20 to about 50 torr.
- relatively higher microwave powers providing faster rates of diamond deposition are possible and, preferably, are used with the relatively higher pressures in the range.
- the nitride interlayer is deposited on a substrate of any suitable material, and the diamond film is deposited directly on the interlayer surface opposite the substrate.
- the interlayer may be deposited directly on the substrate or may be deposited on an adhesion layer which is directly deposited on the substrate.
- the invention involves the discovery by the applicants that on such an interlayer and without either mechanical treatment, such as abrasion with diamond grit, or seeding with diamond particles, a continuous, adhering, polycrystalline diamond film is depositable on a substrate by CVD from an activated gaseous mixture including hydrogen and a gas providing the carbon for formation of diamond crystallites making up the film. Since such treatment or seeding are not required with the present invention, the smoothness, crystallite regularity, and continuity of the deposited film are not adversely affected by physical irregularities introduced in prior art CVD diamond deposition requiring such treatment and seeding. As a result, a diamond film deposited by CVD in accordance with the present invention may be suited for protective coatings or other uses in optical elements. However, it is believed apparent to one skilled in the art that diamond deposition on such an interlayer may be facilitated by mechanical treatment or seeding so that the resulting diamond film may also be useful where optical quality is not required as in mechanical protection without optical transmission or reflection.
- thermodynamic conditions for CVD deposition of diamond instead of graphite, where the diamond is deposited at a useful rate and with useful purity, require that the surface on which such deposition occurs be at 600° to about 1100° C. since lower temperatures result in substantially no deposition and higher temperatures result in the deposition of graphite only. It is apparent that a nitride used to form the interlayer must be refractory so as to resist these deposition temperatures.
- the present invention has been effectively practiced with silicon nitride; and it is believed that other refractory nitrides, for example but not limited to, aluminum nitride, boron nitride, hafnium nitride, zirconium nitride, tantalum nitride, niobium nitride, vanadium nitride, and titanium nitride, may be equally effective for the practice of the present invention.
- other refractory nitrides for example but not limited to, aluminum nitride, boron nitride, hafnium nitride, zirconium nitride, tantalum nitride, niobium nitride, vanadium nitride, and titanium nitride, may be equally effective for the practice of the present invention.
- the refractory nitride be sufficiently thick and regular to allow substantial and regular diamond nucleation. If the nitride interlayer is too thin, it may be so damaged by the highly erosive activated hydrogen of the plasma ball that diamond nucleation does not occur. A nitride interlayer thickness of at least 500 angstrom units has been found satisfactory to resist this activated hydrogen and to allow the interlayer surface to be effectively cleaned by exposure to a plasma ball of substantially pure hydrogen prior to introducing methane to commence diamond deposition.
- the subject invention is, typically, carried out using a refractory nitride interlayer about 2500 angstrom units in thickness; however, it is believed by the applicants that an adhering layer of refractory nitride material of any practical thickness or bulk nitride material which is suitably structured, regular, and free from interstices so as to allow widespread diamond nucleation may be coated with a diamond film in accordance with the subject invention to provide a preferred ⁇ 111> or ⁇ 100> orientation of crystallites forming the film.
- a suitable refractory nitride interlayer may be deposited b sputtering; and such an interlayer has been formed of silicon nitride or aluminum nitride deposited by the well-known RF diode sputtering process on a substrate of silicon or silicon carbide.
- An adhesion layer of silicon dioxide may be formed directly on the substrate in the same RF diode process before deposition of the nitride. The adhesion layer need only have a thickness of about 50 to 100 angstrom units.
- thermodynamic conditions for CVD deposition of diamond are the same for the subject invention as in the above discussed prior art deposition of diamond by CVD from a gaseous mixture of hydrogen and a gas, such as methane, containing carbon which forms the diamond, it is believed that, as in the prior art, the present invention may be also be practiced using carbon sources other than methane and may be practiced with any suitable apparatus, amount of microwave power for activation, or other source of activation energy.
- the above-described use of oxygen in the gaseous mixture when methane is initially introduced may result in such oxidation of the nitride interlayer that no diamond film is deposited thereon.
- the gaseous mixture may be provided without oxygen at the beginning of diamond deposition so that the nitride interlayer is not oxidized, and then, after a sufficient thickness of diamond has been deposited to protect the nitride, introducing oxygen into the mixture to promote faster growth and purity of the diamond subsequently deposited.
- the subject invention in its broadest aspect involves the deposition of diamond by CVD on any nitride material sufficiently refractory to withstand the temperature at which deposition occurs and sufficiently uniform for widespread nucleation of diamond crystallites and that deposition may be facilitated by mechanical treatment or seeding of the interlayer before diamond deposition where the resulting diamond film need not be optically perfect.
- the present invention is effective in the production of a layered structure--such as an optical element having a polycrystalline diamond film deposited directly on a refractory nitride interlayer which is deposited on a substrate such as zinc sulfide--it will be apparent to one skilled in the art that the invention is not limited to an optical element.
- the diamond layer may itself have subsequently deposited thereon an additional layer or coating; that a substrate may itself be deposited on a base substrate; and that, after deposition of the diamond layer, any or all of the interlayers and substrate may be removed, as by etching, leaving the diamond layer and any unremoved interlayer.
- the present invention is an improvement in a method for CVD deposition of diamond crystallites directly on a surface to form a continuous, adhering, polycrystalline film of the crystallites where the surface is a refractory nitride material and the crystallites are deposited from an activated gaseous mixture including hydrogen and a gaseous compound, such as methane, providing the carbon from which the crystallites are formed.
- the improvement is characterized by controlling the pressure of such gaseous mixture during such deposition so as to select the preferred crystal orientation, ⁇ 100> or ⁇ 111>, of the crystallites.
- the present invention involves maintaining the pressure of such gaseous mixture at least than about 30 torr so that the ⁇ 100> orientation is preferred or maintaining the pressure of such gaseous mixture at more than about 30 torr so that the ⁇ 111> orientation is preferred.
- a crystal orientation in the ⁇ 100> or ⁇ 111> direction is "preferred” if more than 50% of the deposited crystallites have that orientation as determined by scanning electron microscopy, Normarski micrographs, or any other suitable method.
- the proportion of the crystallites having the orientation selected in accordance with the present invention may be substantially higher than 50%.
- silicon was provided as 99.999% purity targets for sputtering and a single crystal wafers for substrates;
- silicon dioxide adhesion layers were deposited by RF diode sputtering from a silicon target in an argon and oxygen mixture to a thickness in the range of 50-100 angstrom units;
- silicon nitride was deposited by RF diode sputtering from a silicon target in an argon and nitrogen oxygen mixture to a thickness of 2500 angstrom units;
- deposition of diamond by CVD in accordance with the subject invention was carried out in a 1.5 kw microwave reactor system including a vacuum chamber, microwave generator, and induction substrate heating.
- This system a high pressure microwave system of well-known construction made by Applied Science and Technology Inc. of Cambridge, Mass., corresponds to that described above and in the above-referenced U.S. Pat. No. 5,169,676.
- An electrical bias was provided for the substrate by a conventional DC power supply.
- the vacuum pumping system was capable of providing a vacuum of 10 -4 torr and the vacuum was monitored and controlled by a capacitance manometer. The manometer was calibrated by a an ionization gauge.
- Hydrogen, methane, and oxygen were provided to the reactor system by a computer controlled and mass flow monitored system.
- the substrate temperature was monitored and controlled by a thermocouple received in a graphite stage mounting.
- the substrate, and the exact substrate temperature was determined by an optical pyrometer viewing the substrate through a window of the chamber.
- the substrate bias was the direct current voltage of the substrate relative to the chamber wall.
- the deposited diamond was examined for film uniformity, crystallite size, and crystal orientation by a scanning electron microscope.
- a substrate coated by RF diode sputtering with a silicon dioxide adhesion layer and then with a silicon nitride layer was utilized.
- the substrate was brought to 850° C. and the chamber vacuum pumped for 20 minutes.
- Hydrogen flow was then started, the chamber pressure set to 25 torr, and microwave power turned on to initiate the plasma ball.
- the hydrogen flow was then set to 186.3 sccm, the chamber pressure was set to 45 torr, the 3 microwave input power adjusted to 900 watts which corresponds to the 45 torr pressure, and the microwave tuning stubs adjusted to minimize reflected microwave power.
- the silicon nitride layer was then etched for 5 minutes in the hydrogen plasma.
- the substrate bias was turned on and set to a positive 20 volts.
- Methane flow as then started and set to 4.2 sccm and the deposition continued for 2 hours.
- Oxygen flow was then started and set to 0.85 sccm, and the deposition continued for 8 additional
- the deposited diamond was examined and found to be deposited in a continuous film about 5 micrometers in thickness so that the film growth rate was about 0.5 micrometers per hour.
- the film was formed of crystallites averaging 0.5 to 1.0 micron in diameter.
- the crystsallites were preferentially ordered in the ⁇ 111> plane.
- Example II was carried out substantially as in Example I except as follows: First, the chamber pressure was set to 20 torr when hydrogen flow was initiated, and this 20 torr pressure was maintained during diamond film deposition. Second, after initiating the plasma ball, the microwave power was adjusted to 600 watts, and this 600 watt power, which corresponds to the 20 torr pressure, was maintained during diamond film deposition.
- the deposited diamond was examined after the total deposition time of 10 hours and found to be deposited in a continuous film about 2.5 micrometers in thickness.
- the film growth rate was thus about 0.25 micrometers per hour, a slower growth rate than in Example I and corresponding to the lower pressure of 20 torr.
- the film was formed of crystallites averaging 0.5 to 1.0 micron in diameter. The crystallites were preferentially ordered in the ⁇ 100> plane.
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Abstract
In depositing an adhering, continuous, polycrystalline diamond film on a substrate by forming a refractory nitride interlayer on the substrate and depositing diamond on the interlayer in a vacuum chamber containing a microwave activated mixture of hydrogen and a gas including carbon, the crystal orientation of the deposited diamond, <111> or <100>, is selected by controlling the pressure in the chamber. Preferably, relatively higher microwave power is utilized at higher pressures.
Description
This application is a substitute for U.S. patent application Ser. No. 07/702,207 which was filed May 16, 1991 and which is now abandoned, on Aug. 13, 1995.
This application is a substitute for U.S. patent application Ser. No. 07/702,207 which was filed May 16, 1991 and which is now abandoned, on Aug. 13, 1995.
1. Field of the Invention
The present invention pertains to coating processes using vapor deposition of coatings including diamond.
2. Description of the Prior Art
The carbon allotrope diamond has many potential uses. Diamond has extreme hardness, resistance to thermal and mechanical shock, and transparency to a wide range of electromagnetic wavelengths from ultraviolet through visible and infrared radiation to microwaves. Diamond would thus be an unexcelled coating for transmitting, reflecting, and absorbing optical and microwave elements subjected to weather, particulate erosion, and high energy radiation. Diamond also has high thermal conductivity and high electrical resistivity when pure. Diamond would thus make integrated circuits and other electrical and electronic devices incorporating a diamond film unexcelled for operation at high temperature, for convenience of cooling, and where transparency, environmental resistance, and radiation resistance are desirable.
The chemical vapor deposition (CVD) of a film of polycrystalline diamond from an activated gaseous mixture which includes a gas containing carbon is well-known and would appear to make these potential uses practical. However, diamond films deposited heretofore by CVD on a non-diamond substrate do not adhere thereto sufficiently for practical purposes unless the substrate is first abraded, as with diamond grit, or seeded with diamond particles, as by such abrasion leaving diamond particles. As a result of the abrasion and/or seed particles, the substrate is irregular and the crystallites forming the deposited film are irregular in size and spacing, very defected, and without preferred crystal orientation. The substrate and diamond film of the prior art are thus too irregular for use as an optical coating although continuous and smooth polycrystalline films are well-suited as optical coatings.
Although prior art CVD diamond may be usable as a relatively massive heat sink, prior art CVD diamond is too irregular for use in an electronic device for doping as an active element of a transistor or the like or for use as an electrical insulating or thermal conducting layer within an integrated circuit.
The irregularities of prior art CVD diamond films may be disadvantageous for mechanical protection even where optical and electrical properties are irrelevant. For example, a very thick diamond layer may be rapidly deposited using a plasma torch or jet in which the carbon containing gas, which may be a portion of a flame, is activated by discharging the gas through an electric arc. However, the resulting diamond layer is so irregular and the crystallites so imperfectly joined that the layer has, despite its thickness, relatively poor resistance to weathering.
The deposition, in a chamber containing gas at a pressure less than atmospheric, of a film or layer of a material onto a substrate is, of course, well-known. Such vacuum deposition may be carried out by sputtering where ions of a gas, typically argon heated by microwave energy, eject atoms to be deposited from a target of the material so that the freed atoms travel to an adjacent substrate and are deposited thereon. Movement of such freed atoms to the substrate may be motivated by a suitable electric potential between the target and substrate. An oxide or nitride of the target material may be deposited by including, respectively, oxygen or nitrogen in the gas in the chamber. Suitable materials, structures, temperatures, and pressures for sputtering deposition of oxides and nitrides of a variety of elements on a variety of substrate materials are readily available for selection by one skilled in the art of vacuum deposition.
In chemical vapor deposition, atoms to be deposited on a substrate are provided as atoms in molecules of a gas present in the chamber and activated while in contact with the substrate. Typically, the gas is activated by heating the gas by microwave energy, a hot filament, electric discharge, or combustion so that the gas releases free radicals containing the atoms to be deposited on the substrate. Typically in CVD, no electric potential relative to the substrate is provided, and the substrate is maintained at a suitable temperature by electrical resistance or induction heating.
In deposition of diamond by CVD, a gas containing the carbon which forms the diamond is provided as small proportion of a gaseous mixture in the chamber, the balance of the gas being predominantly hydrogen. Such a mixture may be activated by microwave energy at a frequency which excites the hydrogen molecule. The carbon containing gas is usually methane which is readily obtained in a pure state and is present in the mixture at a proportion less that 5% and, typically, 0.5% to 2%. However, the necessary carbon-containing free radicals may be obtained from vapors of other hydrocarbons, alcohols, or the like. It is known in diamond CVD to add a small amount of oxygen to the mixture of hydrogen and carbon containing gas, the proportion of oxygen being substantially less than that of methane. The oxygen serves to increase the rate and quality of diamond deposition by oxidizing graphite which, depending on the deposition conditions, may be deposited along with the diamond.
Diamond may be deposited by CVD over a wide range of conditions. The vacuum chamber may be maintained at a pressure of 0.1 to 100 Torr by pumping while providing new gaseous mixture. The substrate is maintained at 550° to 1100° C. In general higher pressures increase the rate of diamond deposition as do higher substrate temperatures up to 900° or 1000° C. In prior art diamond CVD, variations in substrate temperature, in gas activation method and temperature, in the proportion of carbon providing gas, and in the method of substrate abrasion provide some control over the crystal size and the irregularity of the deposited diamond. However, in all prior art diamond CVD the deposited polycrystalline diamond is, as before stated, irregular and without a preferred crystal orientation.
The extreme hardness of diamond, while highly desirable in protective optical coatings and the like, is disadvantageous in that polishing of such a coating, as required for optical and other applications, is difficult. It is known that the <111> crystal orientation of diamond, which corresponds to a triangular face of a diamond crystal is somewhat less hard than the <100> crystal orientation corresponding to a square face of a diamond crystal. It would therefore, be highly desirable to selectively deposit diamond film with a preferred orientation so that the <111> orientation, which is sufficiently hard for most protective purposes, may be preferentially deposited for ease in polishing or the like or the <100> orientation may be preferentially deposited where extreme hardness is desired. However, heretofore there has been no way of providing diamond of a selected crystal orientation since crystallites of diamond deposited by prior art CVD methods are, like crystals of natural diamond and other synthetic diamond, a mixture of these orientations.
In a method of forming an adhering, continuous diamond film of optical or semiconductor quality on a substrate, the film is deposited as a layer of polycrystalline diamond on a refractory nitride interlayer from a gaseous mixture of hydrogen and a gas, such as methane, containing carbon, the substrate and the interlayer being heated and the gaseous mixture being activated by microwave energy. In such a method the crystal orientation of the deposited diamond is selected by controlling the pressure of the mixture and other deposition conditions, a relatively lower pressure and corresponding microwave power resulting in the <100> orientation being preferred and a relatively higher pressure and corresponding power resulting in the <111> orientation being preferred.
It is an object of the present invention to provide a polycrystalline diamond film which is of sufficiently high quality for optical and semiconductor uses and which, selectively, has a preferred <100> or <111> crystal orientation.
Another object is to provide such a high quality diamond film wherein the crystal orientation may be selected for high resistance to environmental effects.
Another object is to provide such a high quality diamond film wherein the crystal orientation may be selected for relative ease in polishing.
Apparatus, materials, and operating conditions which are an environment for the present invention are not a part of the invention but are now briefly described. Such apparatus, materials, and conditions are well-known, and a representative such environment is more fully described in U.S. Pat. No. 5,169,676 which issued Dec. 8, 1992 to the present inventors, which is commonly owned, and which is hereby incorporated by reference.
A representative vacuum chamber used in the practice of the present invention admits microwave energy at 2.45 GHz for resonance with hydrogen molecules to form a plasma ball of activated gas above a graphite stage mounting a substrate bearing a nitride interlayer on which diamond is deposited from the activated gas.
Typically, such a chamber has walls constructed of stainless steel and connected to a system ground. One wall has a slot for admission of the microwave energy through a waveguide from a microwave source and power controller which provides a selected level of microwave energy to the waveguide. Since reflected microwave energy from the chamber may be minimized by adjustment. of suitable tuning stubs, this level is substantially that provided to the chamber. A quartz window isolates the chamber interior physically from the microwave supplying elements, but passes microwave energy to form the plasma ball.
The substrate may be heated by induction heating to a selected temperature, and the interlayer surface contacted by the plasma ball and undergoing diamond deposition is viewable through a window by an optical pyrometer for determining the exact temperature of such surface. A thermocouple engages the stage and is connected to an induction heater power source and controller for maintaining the stage at a selected temperature.
A DC power supply is connected so as to provide a selected DC bias voltage in a range of about positive 20 volts to about negative 80 volts between the vacuum chamber wall and the stage so that this bias voltage is substantially that between the substrate and the chamber wall.
The chamber has a ring manifold for distributing feed gas to the chamber interior. The chamber is associated with an ionization gage for precise measurement of the vacuum within the chamber; an exhaust system for maintaining a selected chamber pressure by pumping while feed gas is being provided to the chamber; and a gas supply system connected between the ring manifold and bottles which contain the gases hydrogen, methane, and oxygen used in representative CVD of diamond involving the present invention. The gas supply system is adapted to provide the chamber with a selected flow of any gas or of any predetermined mixture of gases from the bottles by valves and flow meters through which each bottle is connected to the ring manifold. A gas flow controller receives signals from meters and provides signals to the valves so as to maintain the selected gas flow from each bottle.
The exhaust system has a vacuum pump for continuously withdrawn a flow of gas from the vacuum chamber and has an exhaust valve for selectively throttling this flow. A precision manometer measures the vacuum in the chamber, and is connected to an exhaust valve controller is adpated to actuate the exhaust valve in accordance with signals from the precision manometer so as to maintain a selected such vacuum which may be monitored by the ionization gage. When the chamber is in operation, the selected gas or gas mixture enters the chamber at a selected flow rate and participates in the plasma ball while gases resulting from the ball and any other gases are continuously withdrawn by the exhaust system at a rate determined by the exhaust valve. A selected pressure is thus maintained in the chamber for CVD deposition or a related operation.
The present invention is effective when this pressure is below about 100 torr and, typically, in a range of about 20 to about 50 torr. As is well-known in the art of chemical vapor deposition of diamond from a microwave activated gaseous mixture including hydrogen and a gas containing methane, relatively higher microwave powers providing faster rates of diamond deposition are possible and, preferably, are used with the relatively higher pressures in the range.
The nitride interlayer is deposited on a substrate of any suitable material, and the diamond film is deposited directly on the interlayer surface opposite the substrate. The interlayer may be deposited directly on the substrate or may be deposited on an adhesion layer which is directly deposited on the substrate.
The invention involves the discovery by the applicants that on such an interlayer and without either mechanical treatment, such as abrasion with diamond grit, or seeding with diamond particles, a continuous, adhering, polycrystalline diamond film is depositable on a substrate by CVD from an activated gaseous mixture including hydrogen and a gas providing the carbon for formation of diamond crystallites making up the film. Since such treatment or seeding are not required with the present invention, the smoothness, crystallite regularity, and continuity of the deposited film are not adversely affected by physical irregularities introduced in prior art CVD diamond deposition requiring such treatment and seeding. As a result, a diamond film deposited by CVD in accordance with the present invention may be suited for protective coatings or other uses in optical elements. However, it is believed apparent to one skilled in the art that diamond deposition on such an interlayer may be facilitated by mechanical treatment or seeding so that the resulting diamond film may also be useful where optical quality is not required as in mechanical protection without optical transmission or reflection.
The thermodynamic conditions for CVD deposition of diamond instead of graphite, where the diamond is deposited at a useful rate and with useful purity, require that the surface on which such deposition occurs be at 600° to about 1100° C. since lower temperatures result in substantially no deposition and higher temperatures result in the deposition of graphite only. It is apparent that a nitride used to form the interlayer must be refractory so as to resist these deposition temperatures. The present invention has been effectively practiced with silicon nitride; and it is believed that other refractory nitrides, for example but not limited to, aluminum nitride, boron nitride, hafnium nitride, zirconium nitride, tantalum nitride, niobium nitride, vanadium nitride, and titanium nitride, may be equally effective for the practice of the present invention.
It is also necessary that the refractory nitride be sufficiently thick and regular to allow substantial and regular diamond nucleation. If the nitride interlayer is too thin, it may be so damaged by the highly erosive activated hydrogen of the plasma ball that diamond nucleation does not occur. A nitride interlayer thickness of at least 500 angstrom units has been found satisfactory to resist this activated hydrogen and to allow the interlayer surface to be effectively cleaned by exposure to a plasma ball of substantially pure hydrogen prior to introducing methane to commence diamond deposition. The subject invention is, typically, carried out using a refractory nitride interlayer about 2500 angstrom units in thickness; however, it is believed by the applicants that an adhering layer of refractory nitride material of any practical thickness or bulk nitride material which is suitably structured, regular, and free from interstices so as to allow widespread diamond nucleation may be coated with a diamond film in accordance with the subject invention to provide a preferred <111> or <100> orientation of crystallites forming the film.
A suitable refractory nitride interlayer may be deposited b sputtering; and such an interlayer has been formed of silicon nitride or aluminum nitride deposited by the well-known RF diode sputtering process on a substrate of silicon or silicon carbide. An adhesion layer of silicon dioxide may be formed directly on the substrate in the same RF diode process before deposition of the nitride. The adhesion layer need only have a thickness of about 50 to 100 angstrom units.
Since the thermodynamic conditions for CVD deposition of diamond are the same for the subject invention as in the above discussed prior art deposition of diamond by CVD from a gaseous mixture of hydrogen and a gas, such as methane, containing carbon which forms the diamond, it is believed that, as in the prior art, the present invention may be also be practiced using carbon sources other than methane and may be practiced with any suitable apparatus, amount of microwave power for activation, or other source of activation energy.
It has been found that the above-described use of oxygen in the gaseous mixture when methane is initially introduced may result in such oxidation of the nitride interlayer that no diamond film is deposited thereon. However, the gaseous mixture may be provided without oxygen at the beginning of diamond deposition so that the nitride interlayer is not oxidized, and then, after a sufficient thickness of diamond has been deposited to protect the nitride, introducing oxygen into the mixture to promote faster growth and purity of the diamond subsequently deposited.
It has been found advantageous while depositing a diamond film such as that of the present invention to provide a bias voltage between the substrate and the vacuum chamber walls. Under typical conditions for effective diamond film deposition giving the substrate a bias of about 20 volts positive in relation to the wall has been found to promote more rapid growth of smaller and more regular crystallites.
It is apparent that the principles of the subject invention may be employed for deposition of a protective or other diamond coating on zinc sulfide, which sublimes at about 800° C., by sputtering a nitride interlayer on a substrate of zinc sulfides under well-known conditions which avoid damage to the zinc sulfide substrate, and then and in accordance with the present invention, depositing a diamond layer on the interlayer using temperature in the range of about 600° to about 800° C. which will not result in damage to the zinc sulfide substrate.
Therefore, it is believed apparent that the subject invention in its broadest aspect involves the deposition of diamond by CVD on any nitride material sufficiently refractory to withstand the temperature at which deposition occurs and sufficiently uniform for widespread nucleation of diamond crystallites and that deposition may be facilitated by mechanical treatment or seeding of the interlayer before diamond deposition where the resulting diamond film need not be optically perfect.
Although the present invention is effective in the production of a layered structure--such as an optical element having a polycrystalline diamond film deposited directly on a refractory nitride interlayer which is deposited on a substrate such as zinc sulfide--it will be apparent to one skilled in the art that the invention is not limited to an optical element. It will also be apparent that in an article of manufacture having a diamond layer deposited in accordance with a method embodying the present invention, the diamond layer may itself have subsequently deposited thereon an additional layer or coating; that a substrate may itself be deposited on a base substrate; and that, after deposition of the diamond layer, any or all of the interlayers and substrate may be removed, as by etching, leaving the diamond layer and any unremoved interlayer.
Specifically, the present invention is an improvement in a method for CVD deposition of diamond crystallites directly on a surface to form a continuous, adhering, polycrystalline film of the crystallites where the surface is a refractory nitride material and the crystallites are deposited from an activated gaseous mixture including hydrogen and a gaseous compound, such as methane, providing the carbon from which the crystallites are formed. The improvement is characterized by controlling the pressure of such gaseous mixture during such deposition so as to select the preferred crystal orientation, <100> or <111>, of the crystallites.
More specifically and when the crystallites are deposited as set forth in the immediately preceding paragraph, the present invention involves maintaining the pressure of such gaseous mixture at least than about 30 torr so that the <100> orientation is preferred or maintaining the pressure of such gaseous mixture at more than about 30 torr so that the <111> orientation is preferred.
For the purposes pf the present invention, a crystal orientation in the <100> or <111> direction is "preferred" if more than 50% of the deposited crystallites have that orientation as determined by scanning electron microscopy, Normarski micrographs, or any other suitable method. However, the proportion of the crystallites having the orientation selected in accordance with the present invention may be substantially higher than 50%.
The following examples and prior to chemical vapor deposition (CVD) of diamond in accordance with the subject invention, substrates and interlayers were provided by well-known techniques as follows:
silicon was provided as 99.999% purity targets for sputtering and a single crystal wafers for substrates;
silicon dioxide adhesion layers were deposited by RF diode sputtering from a silicon target in an argon and oxygen mixture to a thickness in the range of 50-100 angstrom units; and
silicon nitride was deposited by RF diode sputtering from a silicon target in an argon and nitrogen oxygen mixture to a thickness of 2500 angstrom units;
In the following examples, deposition of diamond by CVD in accordance with the subject invention was carried out in a 1.5 kw microwave reactor system including a vacuum chamber, microwave generator, and induction substrate heating. This system, a high pressure microwave system of well-known construction made by Applied Science and Technology Inc. of Cambridge, Mass., corresponds to that described above and in the above-referenced U.S. Pat. No. 5,169,676. An electrical bias was provided for the substrate by a conventional DC power supply. The vacuum pumping system was capable of providing a vacuum of 10-4 torr and the vacuum was monitored and controlled by a capacitance manometer. The manometer was calibrated by a an ionization gauge. Hydrogen, methane, and oxygen were provided to the reactor system by a computer controlled and mass flow monitored system. The substrate temperature was monitored and controlled by a thermocouple received in a graphite stage mounting. The substrate, and the exact substrate temperature was determined by an optical pyrometer viewing the substrate through a window of the chamber.
The substrate bias was the direct current voltage of the substrate relative to the chamber wall.
Neither the substrate, the silicon dioxide adhesion layer, nor the nitride layer were abraded with diamond or other grit or seeded with diamond.
The deposited diamond was examined for film uniformity, crystallite size, and crystal orientation by a scanning electron microscope.
A substrate coated by RF diode sputtering with a silicon dioxide adhesion layer and then with a silicon nitride layer was utilized. The substrate was brought to 850° C. and the chamber vacuum pumped for 20 minutes. Hydrogen flow was then started, the chamber pressure set to 25 torr, and microwave power turned on to initiate the plasma ball. The hydrogen flow was then set to 186.3 sccm, the chamber pressure was set to 45 torr, the 3 microwave input power adjusted to 900 watts which corresponds to the 45 torr pressure, and the microwave tuning stubs adjusted to minimize reflected microwave power. For cleaning, the silicon nitride layer was then etched for 5 minutes in the hydrogen plasma. The substrate bias was turned on and set to a positive 20 volts. Methane flow as then started and set to 4.2 sccm and the deposition continued for 2 hours. Oxygen flow was then started and set to 0.85 sccm, and the deposition continued for 8 additional hours.
The deposited diamond was examined and found to be deposited in a continuous film about 5 micrometers in thickness so that the film growth rate was about 0.5 micrometers per hour. The film was formed of crystallites averaging 0.5 to 1.0 micron in diameter. The crystsallites were preferentially ordered in the <111> plane.
Example II was carried out substantially as in Example I except as follows: First, the chamber pressure was set to 20 torr when hydrogen flow was initiated, and this 20 torr pressure was maintained during diamond film deposition. Second, after initiating the plasma ball, the microwave power was adjusted to 600 watts, and this 600 watt power, which corresponds to the 20 torr pressure, was maintained during diamond film deposition.
The deposited diamond was examined after the total deposition time of 10 hours and found to be deposited in a continuous film about 2.5 micrometers in thickness. The film growth rate was thus about 0.25 micrometers per hour, a slower growth rate than in Example I and corresponding to the lower pressure of 20 torr. The film was formed of crystallites averaging 0.5 to 1.0 micron in diameter. The crystallites were preferentially ordered in the <100> plane.
When these examples and the foregoing description are considered, it is evident that many modifications and variations are possible in light of the teachings therein. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced other than as specifically set forth above.
Claims (10)
1. A method for forming diamond crystallites, the method comprising:
providing a refractory nitride material having a surface;
depositing said diamond directly on said surface by chemical vapor deposition from an activated gaseous mixture including hydrogen and a gas containing carbon; and
controlling the pressure of said gaseous mixture during said vapor deposition so that said crystallites have preferred crystal orientation.
2. The method of claim 1 wherein said pressure is less than about 30 torr so that said orientation is the <100> crystal orientation.
3. The method of claim 1 wherein said pressure is greater than about 30 torr so that said orientation is the <111> crystal orientation.
4. The method of claim 1 wherein said nitride has a thickness of at least 500 angstrom units and wherein the method further comprises activating said mixture by microwave energy while maintaining said surface at a temperature in the range of about 600 to about 1100 degrees centigrade and maintaining said pressure below about 100 torr.
5. The method of claim 4 wherein said pressure is less than 30 torr so that said orientation is the <100> crystal orientation.
6. The method of claim 4 wherein said pressure is greater than 30 torr so that said orientation is the <111> crystal orientation.
7. In a method for depositing a film of diamond crystallites on a substrate from an activated gas providing carbon from which said crystallites are formed, an improvement for depositing said crystallites with a predetermined crystal orientation wherein the improvement comprises selecting the pressure of said gas so as to determine said crystal orientation.
8. The method of claim 7 wherein said crystallites are deposited on a refractory nitride material.
9. The improvement of claim 8:
wherein in said method, said gas consists of hydrogen and a compound including said carbon, and said substrate is maintained at a temperature in a range of 600 degrees to 1100 degrees centigrade; and
wherein said improvement further comprises selecting said pressure below about 30 torr so as to preferentially deposit said crystallites having the <100> orientation.
10. The improvement of claim 8:
wherein in said method, said gas consists of hydrogen and a compound including said carbon, and said substrate is maintained at a temperature in a range of 600 degrees to 1100 degrees centigrade; and
wherein said improvement further comprises selecting said pressure above about 30 torr so as to preferentially deposit said crystallites having the <111> orientation.
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US08/919,095 USH1792H (en) | 1997-07-14 | 1997-07-14 | Selection of crystal orientation in diamond film chemical vapor deposition |
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US08/919,095 USH1792H (en) | 1997-07-14 | 1997-07-14 | Selection of crystal orientation in diamond film chemical vapor deposition |
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Cited By (4)
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US20040058529A1 (en) * | 1999-04-20 | 2004-03-25 | Knut Beekman | Method of depositing a layer |
US8197701B2 (en) * | 2007-07-13 | 2012-06-12 | Advanced Diamond Technologies, Inc. | Diamond film deposition and probes |
WO2013011032A1 (en) * | 2011-07-21 | 2013-01-24 | The Swatch Group Research And Development Ltd | Micromechanical functional assembly |
US10066443B2 (en) | 2014-12-22 | 2018-09-04 | Haliburton Energy Services, Inc. | Chemically strengthened bond between thermally stable polycrystalline hard materials and braze material |
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US4985227A (en) * | 1987-04-22 | 1991-01-15 | Indemitsu Petrochemical Co., Ltd. | Method for synthesis or diamond |
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Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040058529A1 (en) * | 1999-04-20 | 2004-03-25 | Knut Beekman | Method of depositing a layer |
US6831010B2 (en) * | 1999-04-20 | 2004-12-14 | Trikon Technologies Limited | Method and depositing a layer |
US6905962B2 (en) | 1999-04-20 | 2005-06-14 | Trikon Technologies Limited | Method of depositing a layer |
US8197701B2 (en) * | 2007-07-13 | 2012-06-12 | Advanced Diamond Technologies, Inc. | Diamond film deposition and probes |
WO2013011032A1 (en) * | 2011-07-21 | 2013-01-24 | The Swatch Group Research And Development Ltd | Micromechanical functional assembly |
US9958830B2 (en) | 2011-07-21 | 2018-05-01 | The Swatch Group Research And Development Ltd | Functional micromechanical assembly |
US10066443B2 (en) | 2014-12-22 | 2018-09-04 | Haliburton Energy Services, Inc. | Chemically strengthened bond between thermally stable polycrystalline hard materials and braze material |
US10724305B2 (en) | 2014-12-22 | 2020-07-28 | Halliburton Energy Services, Inc. | Chemically strengthened bond between thermally stable polycrystalline hard materials and braze material |
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