DE2535569A1 - Metal evapn. vessel of conductive ceramic with coating - based on refractory carbide, tungsten, tantalum or molybdenum for good wetting - Google Patents

Abstract

A vessel of electrically conductive ceramic material (I) for the evapn. of metal has coating based on TiC, ZrC, HfC, VC, NbC, TaC, Cr3C2, Mo2C, WC, W Ta and/or Mo on the surface in contact with the molten metal. The vessel pref. is a boat or crucible. (I) pref. consists of 20-95 wt.% electrically conductive corrosion-proof material (II) and the rest an electrically insulating corrosion-proof material (III) and has a specific resistance of 40-6000 uohm. cm. The vessel is wetted well by the molten metal and leads to high evapn. rates.

Description

Metal Evaporation Container The invention relates to an improved one Container for vacuum evaporation of metal. The container consists of a conductive one Ceramic material. In particular, the invention relates to a container for vaporizing of metal which is excellently wettable by the molten metal and leads to a high rate of evaporation.

So far, metal containers have been used as containers for vaporizing metal which are made of a metal with a high melting point such as tungsten (W), tantalum (Ta), molybdenum (Mo) or the like. These containers (e.g. boats) are excellently wettable by the molten metal.

However, they are easily corroded and therefore difficult to obtain To use the shuttle repeatedly. Containers for vacuum evaporation of metal, which are made of an electrically conductive ceramic material (TiB2, ZrB2 or the like) show good corrosion resistance and conductivity. These containers are therefore superior to the metallic container because they are used repeatedly can. However, they have the disadvantage that they are less affected by the molten metal can be wetted well.

The molten metal is mainly through conduction heated from the surface of the container and evaporated in a vacuum. But if now a container is not wetted by the molten metal, the container surface becomes in the essentially not wetted by the molten metal and the heat conduction is very bad. Accordingly, a very slow increase is observed in this case the temperature of the molten metal and because of the low heat conduction the achievable evaporation rate or evaporation rate is not great enough.

It is therefore an object of the present invention to provide a container for To create evaporation of metal, which is distinguished by the molten metal is wettable and leads to high evaporation rates.

According to the invention, this object is achieved by a container for evaporation detached from metal, which has a base made of an electrically conductive ceramic material comprises which on the surface in contact with the molten metal is coated with one or more of the following materials: titanium carbide, Zirconium carbide, hafnium carbide, vanadium carbide, niobium carbide, tantalum carbide, chromium carbide, Molybdenum carbide, tungsten carbide and tungsten metal, tantalum metal and molybdenum metal.

The containers for vaporizing metal are preferably to boats or crucibles or other containers conventionally used for manufacture can be used by vacuum evaporation layers.

Electrically conductive ceramic materials within the meaning of the present Invention are preferably materials, which 20 to 95 Ges.% Of an electrical contain conductive corrosion-resistant refractory material, such as TiB2, ZrB2 or like that. The rest of the major component can be electrical insulating corrosion-resistant connection act like BN, A1N or the like a specific resistance of 40 to 6.ooojucL-cm.

As carbides for coating the electrically conductive ceramic material in particular titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, niobium carbide, Tantalum carbide, chromium carbide, molybdenum carbide or tungsten carbide or mixtures thereof in question. These carbides are by the molten metals, e.g. by molten ones Aluminum, by fused nichrome or the like, which are commonly used become, excellently wettable, and they have a relative at high temperatures low vapor pressure.

The metals tungsten, tantalum and molybdenum have a high melting point and they can be used as materials for containers for making vacuum vapor deposition layers be used.

These metal are by the molten metals, e.g. by molten ones Aluminum, nichrome or the like which are commonly used are excellent wettable and they show a relatively low vapor pressure at high temperatures.

The specific carbide and metal can be mixed with other ceramic materials or other metals. However, it is required to have more than 30 Total 0.6 to be provided. When the content of the specific carbide or metal below 30 wt., The wettability by the molten metal is poor.

The surface of the container made of electrically conductive ceramic material can preferably by one of the following methods with the specific carbide or the specific metal to be coated: (1) coating-drying method; (2) coating (spraying) from the melt; (3) Evaporation coating method or similar.

In the coating-drying method, a suspension becomes a Powder of the specific carbide or metal in a vaporizable -Medium such as water, toluene, hexane or the like for coating the surface of the container is used and the coating is then dried and sintered.

In a coating-drying method, a mixture of the powder is used the specific carbide or metal with an aqueous dispersion of an alumina sol, a silicon oxide sol or aluminum nitrate for coating the surface of the container is used, and the layer formed is then dried and sintered. In both cases, the temperature is for the flat-ended coating to dry preferably in the range from 60 to 200 ° C. The temperature for sintering is preferably in the range from 200 to 1,000 ° C. The thickness of the coating is preferably in the range from 30 to 300 In the melt-coating method, it is preferred to apply or spray a molten carbide in a conventional manner or to spray or apply a molten metal (200 to 300 meshes / 2.5 cm).

In the evaporation coating method, a gas mixture is composed from methane gas and a metal chloride, which corresponds to the specific carbide, introduced into a reaction vessel from lo 4 to lo Torr, whereby the specific Carbide in solid form on the one made of an electrically conductive ceramic material Container, which is heated to 800 to 1.6000C, separates. When applying of a metal by the evaporation coating method becomes a gas of a chloride, eg of tungsten chloride (WCl6) in a hydrogen gas stream at a temperature above 7000C, with the specific metal, such as tungsten, on the surface of the Container is deposited in solid form and forms a coating there.

In the following, the invention is explained in more detail with the aid of exemplary embodiments explained. These examples will be Boats for vacuum evaporation coating manufactured. In the following, these are briefly referred to as shuttles.

Example 1 A boat consisting of an electrically conductive Ceramic material whose main component is TiB2 (manufactured by Thought Kagaku Kogyo K.K.) has the shape of a stick with a width of 6 mm, one Thickness of 4 mm and a length of 100 mm with a recess which is a wide of 4 mm has a length of 40 mm and a depth of 2 mm in the middle.

On the inner surface of the recess of the boat is a Brush a suspension of 20 parts by volume of finely powdered TiC, ZrC, HfC, VC, NbC, TaC, Cr3C2, Mo2C or WC (325 meshes / 2.5 cm) in 80 parts by volume Water carried on so that a layer is formed. The layer is in one Tumble dried at 12o0C. After the drying stage, which lasts 30 minutes, you give o, 2 g nichrome wire (80% Ni; 20% Cr) with a diameter of 1 mm into the recess and then the boat is placed in a vacuum vapor deposition apparatus and the evaporation coating test is carried out. During evaporation there is a voltage of 8 volts between the ends of the boat during 6 rend 4o Seconds. A pressure of 3 x 10 6 Torr is chosen. After this use the boat is removed and the wetting state of the recess of the boat (Wetting with the nichrome) is being investigated. For comparison, this test is used with repeated on a boat which was not coated. The results are compiled in table 1.

Table 1 Example test carbide wetting by nichrome no.

1 TiC excellent 2 ZrC 3 HfC 4 VC good (a small part on the edge the recess is not wetted) 5 NbC good 6 TaC excellent 7 Cr3C2 II 8 MoC good 9 toilets excellent ver 1o no stratification Only the middle area is evenly stratified the recess is wetted. Bumping is observed during evaporation. Example 2 10 parts by weight of alumina sol (lo alumina, manufactured by Nissan Chemical Co., Ltd-.) Are added to 100 parts by weight of a mixture of 50 parts by weight of TiC and 50 wt. °, S Al 2 O 3 and the mixture is molded in a mold and at 1.ooo ° C sintered under a nitrogen gas atmosphere for 30 minutes. The sintered The product is ground and sieved, whereby particles with 150 to 250 mesh / 2.5 cm) can be obtained. The deepening of the boat according to Example 1 is made with these Particles coated (plasma melt injection).

In each case, 0.3 g of aluminum, 0.2 g of antimony or 0.4 g of nickel are used in The well is placed and the boat is placed in a vacuum vapor deposition apparatus given to carry out the evaporation test under the conditions of Example 1. To the For comparison, the same test is repeated with an uncoated boat. The results of the wetting of the boat by the respective metal and the The times until the end of the evaporation are given in Table 2.

Table 2 Test metal coating wetting duration up to No. for the processing by terminating the evaporation metal evaporation (sec.) Example 11 Al coating marked 12 12 Sb II II 45 13 Ni "" II 62 Ver 14 Al none unwetted, 220 equal spherical state, slow evaporation 15 Sb none two edges 322 of the recess are not coated 1I 16 Ni none unwetted, -spherical state, rather slow evaporation. Example 3 The boat is coated by the method of Example 1, but using a suspension of 20 parts by volume a fine powder of W, Mo or Ta (325 mesh / 2.5 cm passage) is used in 80 parts by volume of acetone. This suspension is used instead of the carbide suspension. 0.3 g of aluminum wire with a diameter of 1.2 mm are placed in the well and the boat is placed in an apparatus for vacuum vapor deposition to conduct the evaporation coating test.

The evaporation takes place by applying a voltage of 8 volts the ends of the shuttle at 2 x lo-6 Torr. After about 10 seconds, measured by At the beginning of the application, the aluminum wire begins to melt. After finished Melting, the boat is removed and the wetting state of the recess the shuttle is examined. For comparison, the same test is used without a coating of the shuttle carried out. The results are shown in Table 3.

Table 3 Test coating metal wetting by No. aluminum Example 17 W good 18 Mo excellent 19 Ta 2c W 50; Ta 50% 21 million 40%; Al203 60% good comparative The recess is example 22 none not wetted by aluminum Example 4 The recess of the boat according to Example 3 is coated with molybdenum. Molybdenum metal powder (loo up to 200 meshes / 2.5 cm) used. The coating is done by argon plasma melt injection. Respectively 0.3 g aluminum, 0.2 g antimony or 0.4 g nickel are added to the well and the boat is placed in a vacuum vapor deposition apparatus perform the evaporation test. A Voltage -6 of 8 volts applied. The pressure is 2 x 1c -6 Torr. For comparison the same test is repeated without coating the boat. The results the investigation of the wetting condition of the boat (wetting by the metal) and the respective times to complete the evaporation are in the table 4 compiled.

Table 4 Test of metal loading by duration to number for the layering the metal to end the vaporization evaporation (sec.) Example 23 Al loading good 30 layering "24 Sb" "55 25 25 Ni" "II 65 comp. 26 Al none not wetted, 220 example spherical state, slow evaporation 27 Sb "two edges of 322 Wells are not wetted 28 Ni "not wetted, spherical state, quite slow Evaporation Example 5 Following the procedure of Example 1 is coated the boat, but using the following coating agents become: 40 total% ZrC and 60 total% W; 70 wt% TiC and 30 wt% Mo; 20 wt% TaC and 80 wt% Ta.

0.2 g of nichrome wire are placed in the respective well and the respective boat is placed in an apparatus for vacuum vapor deposition set to carry out the evaporation test according to Example 1. The results are compiled in Table 5.

Table 5 Test coating wetting by no. Composition the metal example 29 40 ZrC - óo W excellent 30 70 TiC - 30 Mo excellent 31 20 TaC - 80 Ta good From these comparative examples and examples it is clear that the container according to the invention for metal evaporation is shown to be wetted by the molten metal, allowing heat conduction or heat transfer from the container to the molten metal is very good. The rate of evaporation is accordingly high. Thus, the containers according to the invention are conventional Considerably superior to containers.

Claims (4)

Claims 1y container for the evaporation of metal from an electrically conductive Ceramic material, characterized in that those with the molten metal in Contacting surface of the container is coated with a layer, which contains as main component one or more of the following materials: titanium carbide, Zirconium carbide, hafnium carbide, vanadium carbide, niobium carbide, tantalum carbide, chromium carbide, Molybdenum carbide, tungsten carbide, tungsten metal-tantalum metal, and molybdenum metal. 2. Container according to claim 1, characterized in that it has the shape a boat with a recess. 3. Container according to claim 1, characterized in that it has the shape of a crucible. 4. Container according to one of claims 1 to 3, characterized in that that the electrically conductive ceramic material 20 to 95 Gew.i 'of an electrically comprises conductive corrosion-resistant material, the remainder of an electrically insulating corrosion-resistant material and that the electrically conductive Ceramic material has a specific resistance of 40 to 6,000 t Q-cm.