DE2355531A1 - PROCESS FOR THE PRODUCTION OF LAYERS OF PURE METALS, METALLOIDS OR ALLOYS FROM A VAPORED FLUORIDE OF THE SAME - Google Patents

Description

PAT E lsi TA N Wm hT

HÄiSJS ULHiGH MäV

D S ΜΒΝΟΗέΜ 2, ÖtTÖSTRÄSSE la

TELESRAMME: UiAYPATENT MUNICH! 235553 I.

. TELEPHONE CÖS1O 593682.

P 470/1 ^ 35 Munich * am --7 «HoV, 1973

B "6t DM / i

Ciommissäriät ä 1 * Energie Ätömigüe in Paris / France

Process for the production of layers of pure metallic metalloids or alloys made of a vaporous pluoride of the same.

The invention relates to a method for producing layers

Metals, metalloids or alloys from a vaporous Fitiörid

Eö bökäimti fietaläheicht is to be made from metal fluorides, indeift ffiän this fluoride in the oil state with both & right back and certain temperature * decomposed on a metal-coated base * whereby the layer of material itself consists of metal or is made of a fused substance.

diisem ancestors §cheidet at Otserfläöhe a ^ s ftetalls Wed Welshes in ierühruttg'.ait the damping of its ilüörids ^ ₁ ^ Ά Diö Wertig it diessüs metal means) is _t hei Einei * femperätiig the M§täll this Pltiaä? ids according of the following from ί

- .Sf η 'φ '

Cöarapf) Cädiöribii ^ tl CHetäll) (adsöi «biert)

Each time a molecule of the gaseous HF _n hits the metal surface, the impact causes the metallatora to be deposited and two fluorine atoms to be chemically adsorbed. The incorporation of the metal atom into the surface lattice of the absorbing metal takes place very quickly. The two adsorbed fluorine atoms are mobile under the experimental conditions and desorb from the surface of the metal, which is thus permanently free again, with desorption being recognized as one of the main factors which determine the kinetics of the deposition.

If a fluoride MP _n comes into contact in the vapor state at the appropriate temperature with a substrate that provides volatile fluoride »the fluorides formed volatilize and only leave the pure metal«

When a fluoride MF "in vapor state at the appropriate temperature comes into contact with a metal that is not volatile Fluoride forms, and when the pure metal formed is soluble in the underlying metal, alloys are formed. This happens, for example, when there are two metals platinum and copper.

If a vaporous fluoride MF _n comes into contact with a substrate at the appropriate temperature, which does not supply any volatile fluorides »and the substrate and the metal produced are immiscible», the fluoride in contact with the substrate can be decomposed and this can then be removed and the pure metal to win. .

409819 / Ö944

The coating ^ thus obtained are of good quality, erfordernjedoch a ¹ extremely careful and difficult production of benutzten- fluoride, which can be decomposed thermally directly ·. Certain fluorides are so hygroscopic that their previous preparation would not be suitable outside the "Kanan" used for vapor phase deposition, since their handling is practically impossible because of their "great instability with respect to the traces of water vapor that are always present in the atmosphere during handling . ■

Another known process in which a fluoride is replaced by hydrogen is reduced, also provides good quality coatings, but has significant disadvantages. In particular Cases, especially when the geometric shape of the substrate to be coated prevents easy renewal of the reagents, The hydrogen overburden can change the hydrogen / gaseous fluoride ratio to such an extent that it deteriorates the metal deposition or even an interruption of the vapor phase deposition entry.

The presence of hydrogen causes the formation of fluorine waters toff gas, which has to be discharged as well as stored, what are known to be dangerous operations. Too high a concentration of hydrogen fluoride gas near the substrate can lead to a reversal of the desired reaction, i.e. Return the deposited metal to the fluoride.

The separation of metals by reducing the fluoride is therefore different in all of them. Cases where the geometrical shape of the objects to be coated is complicated or where there are deposits in the curve.

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heavily branched workpieces or, for example, longer inside narrow pipes are to be created.

It has now been found that the mentioned disadvantages of the known method can be avoided by a process (Sub-fluoride) based on thermal decomposition of a lower fluoride of a metal or metalloid that in place by Umsetztaag the corresponding Pluorids of Metal of higher valence is obtained on the corresponding metal or metalloid. Here, "lower fluoride" means a fluoride in which the metal or metalloid has a lower valence level.

The invention therefore relates to a method of the type mentioned at the beginning Type, which is characterized in that at least one fluoride of a metal or metalloid of a higher level of proficiency in Vapor form is brought into a chamber that has at least one to metallizing base and a source for the metal or metalloid to be deposited contains, the source is heated so that the higher valence fluoride in contact with the source in converts at least one lower fluoride, which evaporates, condenses on the substrate and there into fluorine and the metal or Metalloid, which is the desired deposit, converts.

It is known that the fluorides of higher proficiency are fluorinating agents and cannot be thermally decomposed until the metal is deposited. Just a reduction of these fluorides by Hydrogen enables complete chemical decomposition. On the other hand, the lower fluorides are generally not fluorinating agents and can be thermally on a hot surface

409819/0944

are decomposed, deliver in the dioect clas metal au, - -

According to the invention, the formation of the lower fluorides (sub-fluorides) and their thermal decomposition take place at the same time. A lower fluoride of the general formula MF _m is formed from a higher fluoride of the general formula MF _n and the metal (or metalloid) M according to the following reaction scheme:

m. MF _n * (n ~ m) M »» «——— f η gas metal gas

where η and m mean the valence of the element M and n is greater than m "

Examples of higher fluorides kQmien provide a thermal decomposable lower fluoride were dit. the following compounds named (without limitation): W ₆ , MOFg ₉ ReF ₆ , PtF ₆ , TaF ₅ , NbF ^ ₅ BF ₅ TiF ₄ , CF ₄ , SiF ₄

To obtain the useful lower fluoride, the higher fluoride is allowed to react with the appropriate metal or metalloid heated to a suitable temperature. It should be noted that the source serving as a metal or metalloid in the Hähe of can be brought to be coated workpiece easily, thereby forming the lower fluoride in _e Oer vicinity of the surface to be coated.

The metal deposition takes place according to the following general scheme s

MF _m -LL ^, MF _m , ^ "^ M +" - ■ mF _ «^ ,. M 4 · ■" JÜ P ₂ ^ gas adsorbed adsorbed adsorbed metal desorbed

beer (solid)

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When a gas molecule of the lower fluoride MF _Ja hits the substrate to be coated, heated to a suitable temperature, the MF molecule is sufficiently activated by the impact that it is chemically adsorbed by the substrate. In chemical adsorption, dissociation takes place, and the adsorbed lower fluoride decomposes into metal M and fluorine atoms. The metal produced is incorporated into the crystal lattice of the surface and the fluorine is desorbed, allowing other molecules of the lower fluoride to enter and the deposition to continue from the steaming phase. The deposition of tungsten from the vapor phase may be mentioned as an example of the implementation of the method according to the invention. The hexafluoride WFg reacts with the metal tungsten W according to the equation s

5 WF ₆ + V? > 6 ₅

Gas metal '. gas

and the tungsten tafluoride formed thermally decomposes according to the following scheme:

V7 + 5F-S ,. W ₊ I

Gas adsorbed adsorbed adsorbed Metal desorbed

The formation of the lower fluoride and its decomposition take place » at the same time, when the substrate to be coated and the metal serving as the source of the lower fluoride on different » carefully selected temperatures -be- heated. By choosing these temperatures you can't just get the process at all run advantageously, but also on the kinetics of the deposition from the vapor phase and on the properties of the obtained Act on metal layers *

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It should be noted that, in the special case of tungsten, excellent coatings are obtained ₉ if the source is heated to a temperature of about 400 ^° C. and the substrate is heated to a somewhat lower temperature. Similar coatings are obtained when the known reduction process is used, but at least one has to be heated to a temperature. of about 700 ° C, and in addition, this known method has the disadvantages mentioned at the beginning.

The metal of the source and the metal of the intruding into the reaction zone gaseous pluorids may be the same or different-· If the two metals are the same _t run according to the following reactions from;

tf P ₆ + v? - "f TS P ₅ '-7- W * 5 P -. ■' ■ 'Ta F _K + Ta' - * -? TaF" -— £ Ta ψ 3 P Ti F, '+. Ti -> Ti P - ■ "> Ti t 3P

If different metals are _s running reactions as shown in the following from: -

¥ F, - * Cu -— = - ~ f WP _e + GuP - «=» - 4 Cu + UP,

It should be noted * that this set in at the beginning of the reaction Tungsten »HexafIxiorid is regenerated at the end of this reaction and So behaves like a catalyst · One can therefore initiate the of the gas in the reaction area and carry out the reaction at constant pressure.

More generally, the above reaction can be written as follows:

WF ₆ + M> WP ₅ ^: + 'MF

or ' .

2 WP ₆ * M-

A09819 / 0944

The formed metal fluoride fliF or MP _{2 then} decomposes on the workpiece heated to the appropriate temperature and releases the metal which is deposited

MF --- - ^ MP -—> M + ρ _ -> M. + ' F. gas adsorbed adsor adsor secluded desorbed beer beer metal

M + 2F ~~ *> M.

Gas, adsor-adsor-adsor ~ separated desorbed beer beer beer beer metal

That by the thermal decomposition of the fluoride MF or Any released fluorine combines again with WF * in order to Fluoride WFg, i.e. the gaseous catalytic converter, to be returned em.

Numerous metal deposits can be obtained in this way. As an example, copper coatings based on CuF ₂ and CuF and nickel coatings based on NiF ₂ and NiF may be mentioned. The following metals are also transported and deposited from the vapor phase using this process: bis-iron, cobalt, zinc, silver, gold, cadmium and aluminum, just to mention the most commonly used. -

The reaction has the advantage that it also removes metals the vapor phase, such as nickel, copper, aluminum j zinc, cadmium, zirconium, whose fluorides are not sufficiently volatile and cannot be used in other technical vapor deposition processes.

The process conditions and results of several examples are

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-9-. ■ -_. given in Table I below t

TABLE I.

Type of to ~ type of tempering input "

guided source nature of gas pressure

Gas source (Torr)

Or «

fwsgi ϊΜΛ ^ 3ί ι ust

Ta Gu

1100

1000

1200

900

2J10

Temperature deposition of the speed to be layered in the substrate Micron / hour (OG)

700 40 700 40 700 16 750 20th

The method according to the invention offers numerous other advantages. Layers of metals can be obtained whose fluorides are very little volatile and therefore only with difficulty or not at all in the usual methods of metal deposition from the vapor phase , especially the reducing processes, can be used *

In the gas phase since no hydrogen is present _f no hydrofluoric acid, which might adversely affect the formation of good quality deposits forming.

The process of adsorption of molecules lower fluorides and desorption TOn Pluoratpmen formed automatically adjusts so _s are ~ keep it that layers of good quality, the deposition rate, even one wemx operates at temperatures>. which, for example, were considered to be too low in a reduction process "Man-dated metal layers deposit on substrates which would not be able to withstand higher temperatures" The deposits obtained according to the process according to the invention are compact, uniform, adhesive and epi-tactical. if the properties of the

£ 098 19/0944.

Substrate and the deposited scliiclit allow this.

A very interesting technology of vapor deposition can be developed, since the fluoride used for this purpose, MF or MP _{2, can be produced} in the vicinity of the surface to be coated, regardless of its geometric shape. It suffices to arrange the source metal in the vicinity of the substrate. This results in a particularly significant advantage for the production of coatings in the interior of various workpieces, such as pipes, valves, connections and vessels. The shape of the workpiece to be coated has no effect on the excellent penetration effect which is obtained in the process according to the invention.

For the process to be carried out properly, the source metal must be heated sufficiently that the useful fluoride MF or MF ₂ evaporates and is transported to the substrate to be coated. The metal source can be a wire or rod heated by Joule heat. A rod that is indirectly heated by a non-consumable heating element can also serve as a source. The shape of the rod can be chosen accordingly for each case. This rod can either be coated with sintered metal or form a container which contains pieces of the metal to be deposited from the vapor phase.

In certain, for the application of the method according to the invention Suitable devices can heat the workpiece to be coated directly by the metal source of the metal M, whereby In this case, a thermal insulation surrounding the workpiece is used will. .

409819/09 44 '

The process according to the invention can be carried out in apparatus, the shape of which is the form, type and number of those with a metal coating objects to be provided is adapted. The following are two examples of metal coating of pipes with reference to the attached drawings: They show:

Fig. II

A section of a device for metal coating the inner wall of a 'pipe j'.
Fig. 2:

A section through a device for simultaneous indoor and outdoor External coating of a pipe with metal.

Fig.1 shows a tube 1 made of any metal alloy that is to be coated with metal on the inside. This tube will go into a heat insulating sleeve 2 brought to heat loss due to radiation to prevent as much as possible «A rod 3 made of metal or metalloid is held in the tube by plugs 4 and 5 at its ends. A feed line 6 for fluoride with a higher level leads through the plug 4 Valence level. For the operation of this device, the rod 3 heated to a certain temperature before passing through the supply line 6 the fluoride is introduced, which is in contact with the rod 3 a lower fluoride, which is deposited on the inner wall of the Pipe 1 separates.

In Fig. 2, corresponding parts are given the same reference numerals as provided in FIG. The tube 1 is inside a chamber 7 held by supports not shown. The metal coating of the Tube 1 takes place inside as described above, but allows the device shown by the additional rods 3 * and 3 ", which how the rod 3 are sources of metal or metalloid, and the

■ 40 98 19/09 44

Fluoride supply lines? · And 5 "also the metal coating of the pipe outer wall. It should be noted that the inner wall of the chamber 7 from a material that will not accept a metal coating.

In addition to the advantage that the inventive method without the presence run off of hydrogen and hydrogen fluoride, can also the fluorine formed by dissociation of the lower fluoride can be removed by recombination and the metal of the source. Me reaction interface and more precisely the composition of the gas phase therefore remain constant over the entire duration of the deposition from the gas phase, regardless of the shape of the workpiece to be coated.

As a result of the nature of the crystal growth, which is caused by the adsorption of the molecules of the lower fluoride and the desorption of the formed Fluorine atoms, which automatically regulate the deposition rate, is the layer deposited from the vapor phase always of good quality, which is retained even after the separation takes place at temperatures which would be far too low for reduction processes. From this it follows that after the invention according to the method can coat materials that would be changed or irreversibly converted at higher temperatures. In this context, the deposition on metals should be mentioned, which show allotropic transformations at high temperature and in which the quality of the coating-substrate interface is passed through of the allotropic transformation point would worsen during cooling.

It should be mentioned that the deposits obtained when using the method according to the invention are simultaneously adhesive, compact,

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'' - '■' ■ - '■' .23.55531 dense, pure and .gleichmäßig grow epitaxially · sind.und, that is that their growing crystal lattice atom to atom in accordance with the crystal lattice of the surface yielding if desired single crystals obtained with certain alignment can.

These depositions can take place on a large number of substrates, especially since the process according to the invention permits the production of excellent layers at much lower temperatures than those required in known processes. ·.

Excellent VJoIframschichten made of tungsten hexafluoride VJPg can be obtained on the following documents, for example: tungsten, molybdenum -, - copper ,. Nickel , Monel metal (a Ni-Cu alloy),; ^. ■. 'a Ni-Cr-Pe- or Ni-Co-Gr-. _; Alloy; C Vlnconel ^'r -? E.WzV), iron, Qraphit ,. Silicon, aluminum.

Alloys can also be deposited from the vapor phase. Two metals can be deposited together by utilizing the chemical properties of the metal source and the gaseous plupride of higher valency. For example, <··.; -.- excellent results were obtained with the joint deposition of molybdenum.?> Tungsten starting from a metal source. made of tungsten and molybdenum> -hexafluoride as process gas. . -. _: . ...-. ■ '

The process according to the invention can be used quite generally, especially for the production of electronic components, especially for the production of emitters for electronic Itowrandlers: from Wolf jpam _; and anticathodes of X-ray tubes, and especially for aerospace applications, during manufacture

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of titanium heat loops. The following areas of application should also be mentioned:

The internal coating of small diameter pipes; The manufacture of metal pipes by depositing the metal inside or on the outer wall of support tubes, which are mechanically or can be removed chemically; The manufacture of reflective or semi-reflective metal layers of a refractory metal, especially tungsten, tantalum, molybdenum on highly refractory substrates such as ruby, Corundum intended for use at high temperatures;

The deposition of layers of high temperature resistant metals different types of glasses, which according to the invention can be done at low temperature j

The deposition of different metals on opposite to hydrogen sensitive substrates j

The manufacture of catalysts by the deposition of metals with a large specific surface.

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Claims (12)

Claims ^) Process - for the production of layers of pure metals, Metalloids or alloys of a vaporous fluoride thereof, characterized in that at least one fluoride one Metal or metalloids in a higher valence level in vapor form is introduced into a chamber, which is at least one with metal, Metalloid or alloy coating substrate to be coated and contains a source for the metal or metalloid to be deposited, and the source is heated so that the fluoride of higher valence in contact with it is converted into at least one fluoride inferior Converts valence, which evaporates, condenses on the substrate and converts there into fluorine and the metal or metalloid, which forms the desired deposit. 2. The method according to claim 1, characterized in that the Metal of the metal fluoride supplied in the vapor state and the Metal of the source are equal " 3 · The method according to claim 1, characterized in that the Metal of the metal fluoride supplied in vapor form and the metal are different from the source 4. The method according to claim 2, characterized in that the pluride supplied in vapor form is molybdenum kexafluoride and the source is molybdenum. - '. ' 5. The method according to claim 3, characterized in that the fluoride supplied in vapor form is molybdenum hexafluoride and the source Are tungsten. ■ '._-. "409819/0944 6. The method according to claim 3 *, characterized in that the fluoride supplied in vapor form tungsten hexafluoride and the source one of the metals nickel, copper, aluminum, zinc, cadmium, zirconium are « 7. The method according to claim 1 »characterized in that the The fluoride of the metal or metalloid with a higher valency is one of the following fluorides: WF ₆ , MoF ₆ , ReF ₆ , PtF ₆ , TaF ₅ , NbF ₅ , BF ₅ ^ TiF ₄ , CF ₄ , SiF ₄ 9. The method according to any one of claims 1-7, characterized in that that the substrate is made of tungsten, molybdenum, copper, nickel, nickel-copper, nickel-chromium-iron or · nickel-cobalt-chromium. Alloy, iron, graphite, silicon, aluminum. 9. The method according to any one of claims 1-8, characterized in that that the metal or metalloid donating source is heated to a temperature above the temperature of the substrate vird. "·". "" ". 10. PROCEDURES "according to one of claims 1 - 9 characterized in that the source is made of tungsten and * door heated to a temperature of about 400 ⁰ C vird. 11. A method according to one of claims 1 »- 10 _s characterized in that the source consists of a through Joule effect heated ßraht or rod. 12. The method according to claim 11, characterized in that the Rod with a by sintering or vapor deposition 409819/0944 ti covered is »" * ^; ' 13 * A process according to claim 11, characterized in that: # 'DAtF the rod in the form of a vessel, has "eiithäft ^·." Which pieces of the vapor · äitfftiÄeldenden Metals - ■ 14 * method according to one of the imprüchiöi * - 13 »characterized in that the substrate is the inner wall of a ^; Mb ^ e's'"is and the source is solid the supply line for the fluoride inside a Söhres ^ ängeördhiet are * * -: ^; /: - .- i $ i procedure i ^ eh a ^ m ider ^^ prÜöh% ^ i daiäurbh draws, däö the Subäträif diö ÄuÖe ^ and ^ ines l ^ toes 'is the oueiien and supply lines for the fluoride in the area dis ißöaiis ri-h eiHeilEäffimöri' ^ ldhe das äbzüäähüideiide iiltali Blank page