DE1621289B2 - METHOD OF PREPOSITING NIOB, VANADINE, TANTALUM, ZIRCONIUM OR TITANIUM - Google Patents

Description

The invention relates to a method for depositing niobium, vanadium, tantalum, or zirconium Titanium on a heated substrate by passing a gas mixture of a gaseous halogen compound over it of the refractory metal and hydrogen over the substrate.

In view of the low vapor pressure, high-melting or low-melting crystals can be used very difficult to precipitate in a vacuum. There is already a method of knocking this down Known refractory metals on a substrate, in which the refractory metal is converted into a halogen compound transferred with a relatively high vapor pressure and then evaporated and reduced, thermally decomposed or subjected to another reaction and thereby the refractory metal from the vapor phase is chemically deposited.

Halides of refractory metals can be reduced with hydrogen according to the following equation will

MX _n + -H ₂
2

M + mHX

wherein M is a metal such as Nb, Ta, V, Ti or Zr, and X is a halogen such as Cl, Br, F, J, and η is an integer.

When niobium pentachloride is reduced with hydrogen, a metallic niobium film can be formed from the Vapor phase on a substrate such as an electrical insulator or a metal according to the following Equation to be put down:

NbCl ₅ + - H ₂
2

Nb + 5 HCl

It is also known that a refractory metal can be obtained by thermal decomposition of a halogen compound can knock down.

For depositing a refractory metal onto a substrate by reacting the corresponding Halogen compound with hydrogen or by thermal decomposition of this compound must you heat the substrate to a certain temperature. To achieve satisfactory results

ίο you had to use a heating temperature ^{of at least 700 0 C with the known methods.} When tantalum was deposited by heating a gaseous mixture of tantalum halide and hydrogen, as described in US Pat. No. 2,604,395 (cf. in particular column 2, lines 43 to 46), the metal was deposited at temperatures above about 500 up to about 600 ^° C. However, this metal is deposited in powder form, and the deposition of a metal film has been difficult. The high temperature of the gas mixture is necessary because the reduction with hydrogen and the thermal decomposition are not complete at lower temperatures, so that the deposited film consists of a mixture of the refractory metal and its lower halides. Due to its colored, soft and hygroscopic nature, this film has completely different properties than a pure metal film.

According to the known method, a good quality metal film can be heated to over 700.degree knock down heated substrate; However, this assumes that the substrate by heating during The deposit is not destroyed or undesirably with the deposited metal reacted. For this reason, the number of substrates that can be used for this purpose is limited.

According to the known method for depositing niobium, for example, a gas mixture of gaseous niobium pentachloride (NbCl ₅ ) and hydrogen (H ₂ ) is introduced into a quartz reaction tube through a gas inlet. A substrate is placed on a heating pad on a rod-shaped support, and the latter is heated to an optimum temperature above 700 ° C., depending on the substrate used, by high-frequency induction heating. A metallic niobium film is deposited on the surface of the substrate according to the following equation:

5

NbCl ₅ + - H ₂ - »■ Nb + 5 HCl
2

The gas mixture is then discharged from the tube through an outlet conduit.

In this process, however, no complete reduction occurs when the temperature of the substrate is below 700 ^° C., and a precipitate of a highly hygroscopic and unstable mixture of niobium and its low chlorides, such as, for. B. niobium tetrachloride (NbCl ₄ ), triniobium octachloride (Nb ₃ Cl ₈ ) and the like, on the substrate, the properties of which are completely different from those of a pure niobium film.

The invention now provides a method for depositing pure niobium, vanadium and tantalum or zirconium on a substrate, the specialty of which is that the gas mixture is passed through a

meshed or porous preheater arranged in a reaction system conducts. However, the substrate is heated in this process to over 350 ⁰ C, below 700 ⁰ C.

According to the invention, a pure film of niobium, vanadium, tantalum or zirconium can be added for the first time precipitate at a lower temperature. The deposition according to the invention is carried out in that the Gas mixture through a mesh-shaped or porous preheater arranged in a reaction system is directed.

The preheater is heated to temperatures between 600 and 1300 ° C, but higher than the substrate. As a substrate for ceramic materials, quartz, metal or semiconductor are suitable, and the substrate is heated to 350 to 700 ⁰ C. The preheating device is expediently arranged at a distance of between 0.3 and 2.0 cm from the substrate.

The invention will now be further explained with reference to the following description and the drawings.

F i g. 1 denotes a schematic cross section through a known device for chemical Knock down;

F i g. 2 denotes a schematic cross section of a device preferred according to the invention for Precipitation of a refractory metal.

According to the known, in the device according to FIG. 1, for example, niobium is deposited on a substrate by introducing a gas mixture of gaseous niobium pentachloride (NbCl ₅ ) and hydrogen (H ₃ ) through a gas inlet 2 into the quartz tube 1. A substrate 5 is placed on the heating pad 4 carried by a rod 6, and this heating pad 4 is heated to an optimum temperature above 700 ° C. by a high frequency induction heater 3. A metallic niobium film is deposited on the surface of the substrate 5 according to the following equation:

NbCl ₅ + - H, -> Nb + 5HCl
2

The gas mixture is then discharged from the pipe 1 through outlet line 7.

In this process, however, the reduction reaction is not complete if the temperature of the substrate5 is below 700 ^° C .; therefore, one often obtains a highly hygroscopic one made from an unstable mixture of niobium and its lower chlorides, e.g. B. niobium tetrachloride (NbCl ₄ ), triniobium octachloride (Nb ₃ Cl ₈ ) and the like. Existing precipitate on the substrate 5, the properties of which are completely different from those of a pure metallic niobium film.

The in F i g. The device according to the invention shown in FIG. 2 is that in FIG. 1 shown known device very similar. However, it differs from the known device that a mesh-shaped or porous preheating device 8, for. B. 0.3 to 2.0 cm away from the substrate 15, between the substrate 15 and a gas inlet line 12 is located. The substrate 15 is housed in a quartz tube 11 on one located on a rod 16 and heated by a high frequency induction heating 13 heating pad 14. A high frequency induction 9 is attached to the quartz tube 11 relative to the mesh-shaped porous heater, thereby heating the preheater at 600-1300 ⁰ C. can be.

In the method according to the invention, the substrate 15 is on the heating pad 14, in contrast to the known method according to FIG. 1, heated to a temperature below 700 ° C.

In the device according to FIG. 2 is that introduced into the quartz tube 11 through the gas inlet line 12 Gas mixture from a gaseous halogen compound

ίο a refractory metal and hydrogen not blown directly onto the substrate 15, but rather through the preheating device heated to 600 to 1300 ° C 8 headed; as a result, the gas mixture is preheated before it passes over the surface of the substrate 15 to achieve the desired hydrogen reduction and then passed through gas outlet line 17 is carried out.

The preheating device 8 according to the invention differs considerably in terms of structure, Position and effect of the known heating devices, including the space around and the inflow to the substrate 15. The preheating effect according to the invention is achieved by using the preheating device 8 is arranged directly in front of the substrate 15 in the inflowing gas stream.

The deposition method according to the invention with preheating of the gas mixture by the preheating device 8 described above is superior to the known vacuum deposition methods in which a gas mixture of lower temperature than the temperature of the substrate is passed directly over the substrate; This is due to the fact that not only is the surface temperature of the substrate prevented from falling, but also activation of the reactants and acceleration of the hydrogen reduction occur, whereby the deposition of a refractory metal on the substrate is facilitated.
The inventive method also has the

4 "Advantage that as a result of a partial reduction in Halogen compound forms a hydrogen halide on the surface of the preheater, which is a has a cleaning effect on the surface of the substrate, causing the refractory material better to knock down.

According to the process according to the invention, a small or possibly larger amount of metal is deposited on the preheater, which is heated to a high temperature. The main amount is not deposited on the pre-heater, and a certain amount of metal is deposited on the downstream substrate, which is heated to a relatively low temperature from 350 to 700 ⁰ C.

The inventive method also has the advantage that the halogen compound of the refractory metal in the preheating device first is converted into lower halides, which are then converted to metal upon reaching the substrate surface can be reduced, which is deposited in the form of a pure metal film.

The preheater 8 has a mesh-shaped or porous structure through which the gas to the Substrate is passed; this has the additional advantage that there is a Metal film of uniform thickness forms, as the preheater similar to a variety of Nozzles works.

5 6

The invention achieves the best results if the temperature of the substrate is below 700 ° C

at the temperature of the preheater 8, the deposited film obtained is

adjusts to 900 to 1200 ° C and the Vorheizvorrich- without using the preheater 8, from one

device 8 at a distance of 0.3 to 1.2 cm from the mixture of metallic niobium, niobium tetrachloride,

Substrate 15 is arranged. The preheater 8 can 5 trinioboctachloride and other low chlorides, from a metal such as molybdenum or tantalum, or from

a non-metal such as carbon. Instead of example 2
of the above-described high-frequency induction heating

systems can be used as a heating system for the preheater. A mixture of gaseous vanadium tetrachloride tion also an electric heating system or an infrared io and hydrogen in the molar ratio 1: 100 was in the heating system can be applied. Instead of the in FIG. 2 device according to FIG. 2 through the gas inlet pipe illustrated vertically arranged device 12 with a flow rate of 2 liters per practically the same effect can be initiated with a minute. In this device the achieve horizontally arranged device. Preheater 8 with the outside of the quartz defiance the fact that the tube 11 according to the invention would have an inner diameter of 50 mm Metallic niobium obtained in a method with sensitive high-frequency induction heating device 9 a substrate temperature below 700 ° C precipitated heated to 1200 ° C. The gas mixture became the pre-will, the metal film is completely free of the heating device 8 on the one with the heating device 13 closed, unreduced lower halogen substrate 15 heated to 350 to 700 ° C.; included Den, is chemically extremely stable, has a good 20 struck a metallic vanadium film on the metallic luster, and the bond strength of the film substrate 15 down.

on the substrate is by no means inferior to a vanadium can be used as a solid film on many substrates, such as

Metal film that is deposited on ceramic materials, quartz, metals and other materials heated to over 700 ° C,

Substrate has been precipitated. such as B. semiconductors are applied. The best

The use of a preheater that gives 25 results when the preheater is

represents a special feature of the invention is not device 8 in the flow direction 0.5 to 1.2 cm before

only in the case of a substrate 15 heated to 350 to 700 ° C,
possible, but also in those cases where

a temperature range between 700 and 1000 ° C. B e i s ρ i e 1 3

is turned. In the latter case, the pre-30

heating device both for cleaning the substrate tantalum pentachloride (TaCl ₅ ) can be used in a similar manner, surface as well as for depositing the pure as described in Examples 1 and 2, with water-metal film. substance to form a metallic tantalum film

The invention has been reduced on the basis of the foregoing. To achieve a good metallide chemical deposition of niobium through 35 see tantalum film on the substrate 15 became a mole hydrogen explains reduction of a niobium halide; ratio of tantalum pentachloride to hydrogen of however, by using the preheater, 1: 100 and a flow rate of the gas can be made metal films of other refractory mixtures of 1.5 liters per minute were also used. the Metals such as zirconium, titanium, vanadium and tantalum, the temperature of the preheater 8 was 900 ° C similarly at a lower temperature than 40 and the temperature of the substrate 15 350 to 700 ° C; the known method by hydrogen reduction the preheater 8 was at a distance of precipitate a corresponding metal halide. 0.5 to 1.1 cm in front of the substrate 15.

The invention is now based on the following Bei- Tantalum can also be used as a solid film on many substrates

games further explained. th, such as ceramics, quartz, metals, and

45 other substances, such as B. Semiconductors, dejected

Example 1 will be.

As can be seen from the previous examples,

Gaseous niobium pentachloride and hydrogen is the arrangement of a preheater, in

were seen in a molar ratio of 1: 100 with each other in the direction of flow, immediately before the

mixes and in the device according to FIG. 2 by the 50 substrate so effective that one at the chemical

Gas inlet conduit 12 at a flow rate precipitating a refractory metal such as

initiated by 1 liter per minute. The preheating titanium, zirconium, niobium, vanadium or tantalum, among

Device 8 was made by a high frequency induction using the appropriate metal halide

tion device 9, which can achieve a pure metal film outside of the quartz, although the

tube 11 with an inner diameter of 50 mm 55 temperature of the substrate is below 700 ° C,

located, heated to 900 ° C. The gas mixture was The precipitation method according to the invention,

by the preheating device 8 on the on the front in which a precipitation of a refractory

heating device 14 located and possible with the heating pre- metal at a considerably lower temperature

direction 13 to 350 to 700 ° C heated substrate passed; is borrowed than with the known methods in which

a metallic niobium film formed on the 60 substrate temperatures above 700 ° C are required,

Substrate 15 down. represents a significant advance in technology.

The niobium can be deposited on a number of substrates, such as can also be used in the ceramic process according to the invention Fabrics, quartz, metal and other ren use many materials as substrates as the Substances such as B. semiconductors, deposited as a pure and compact metal film on such substances Film will be knocked down. The best results 65 can be obtained at temperatures above 600 ° C is achieved when the Vorheizvorrichtpng 8, decompose in gas or where chemical reactions at the Direction of flow seen, 0.5 to 1.2 cm in front of the interface between the deposited metal substrate 15 is attached. film and the substrate at these temperatures

step. Impurities in the metal film obtained are completely negligible. The film owns an extremely compact structure and is able to firmly metallize the surface of a substrate, since the Metal even in small pores on the substrate surface

can be knocked down. In the method according to the invention one can easily get a shiny Obtain surface by depositing the metal on an extremely smoothly ground substrate surface.

1 sheet of drawings

209 534/345

Claims (4)

Patent claims: 1. Process for depositing niobium, vanadium, tantalum, zirconium or titanium on a heated substrate by passing a gas mixture of a gaseous halogen compound over it of the refractory metal and hydrogen over the substrate, characterized in that that the gas mixture through a arranged in a reaction system mesh or porous preheater is passed. 2. The method according to claim 1, characterized in that the preheating device is heated to temperatures between 600 and 1300 ⁰ C ₅ but higher than the substrate. 3. The method of claim 1 or 2, characterized in that used as the substrate ceramics, quartz, metal or semiconductor and the substrate is heated to 350 to 700 ⁰ C. 4. The method according to claim 1, 2 or 3, characterized in that the preheating device in a distance between 0.3 and 2.0 cm from the substrate.