JPH04325669A - Material for vacuum deposition - Google Patents

Abstract

PURPOSE:To obtain a material for vacuum deposition of a Ta2O5 deposit stably working by subjecting a specified ratio of powder mixture of Ta2O5 and metallic Ta to compacting and sintering. CONSTITUTION:Powdery Ta2O5 and powdery metallic Ta by 4 to 55wt.% to the above Ta2O5 are mixed. This mixed powder is compacted into a desired shape and is thereafter heated, e.g. to 1500 deg.C in vacuum and is sintered to manufacture the material for vacuum deposition for forming a Ta2O5 thin deposit by a vacuum vapor deposition method. At the time of forming a Ta2O5 thin deposit by executing heating, melting and evaporating by the irradiation of electron beams or the like in vacuum, the material for Ta2O5 deposition is melted in a short time, and the Ta2O5 thin deposit can stably be formed without the generation of a phenomenon such as sudden boiling.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deposition material used in forming a ditantalum pentoxide film by vacuum deposition.

0002

2. Description of the Related Art Vacuum deposition is a process in which a material for deposition is completely melted and deposited in a vacuum chamber using an electron gun or resistance heating, thereby forming a deposited film on the surface of an object. The ditantalum pentoxide vapor deposited film formed using ditantalum pentoxide as a deposition material has a high refractive index and high hardness, so it has traditionally been used as a high refractive material for multilayer films such as filters and dichroic mirrors. .

[0003] Typical ditantalum pentoxide vapor deposition materials include pellets and targets formed by press-molding ditantalum pentoxide powder into sintered bodies.

0004

[Problems to be Solved by the Invention] The above-mentioned deposition pellets decompose during melting and release significant oxygen, so it takes time for the chamber to reach a vacuum level that allows deposition, and the heating time is long. generates a large amount of radiant heat, and when vapor deposition is performed on a plastic surface that is sensitive to heat, it may have an adverse effect such as deformation on the substrate. In addition, evaporation does not occur unless the vapor deposition material completely melts, and if it is partially melted, the material that melts and flows from that part is rapidly cooled in a cooled container, similar to a bumping phenomenon. There are problems such as causing a situation.

The present invention was made in view of the above circumstances, and its purpose is to reduce the amount of oxygen generated during melting, thereby shortening the melting time, and furthermore, to reduce the occurrence of a phenomenon similar to bumping. An object of the present invention is to provide a material for vapor deposition that can be easily evaporated without causing any evaporation.

[0006]

[Means for Solving the Problems] The object of the present invention is to mix ditantalum pentoxide and tantalum metal in a predetermined ratio, and heat-treat the mixture in an inert atmosphere at a high temperature at least high enough to sinter the mixture. This is achieved by using vapor deposition materials that can be made into various shapes such as pellets. That is, the present invention uses ditantalum pentoxide and the ditantalum pentoxide.
This relates to a material for vapor deposition formed by sintering 55% by weight of tantalum metal.

The present invention will be explained in detail below.

[0008] The ditantalum pentoxide and tantalum metal used in the present invention are not particularly limited, and any of them can be used, but it is preferably in the form of powder with an appropriate particle size so that it can be easily sintered. The average particle diameter of these particles is preferably about 0.5 to 1 μm for ditantalum pentoxide, and about 10 to 50 μm for tantalum metal.

In the present invention, the ditantalum pentoxide and tantalum metal are sintered, but it is desirable to mix the two in advance before sintering. Examples of the mixing method include a method using a ball mill.

The blending ratio of ditantalum pentoxide and tantalum metal is 4 to 55% by weight based on ditantalum pentoxide. In this case, if the amount of tantalum metal is 4% by weight or less, it will not be very effective in preventing the release of oxygen during heating and melting. If it is more than 55% by weight, the bumping phenomenon of the tantalum metal itself becomes more intense, and the light transmittance of the deposited film deteriorates due to the influence of the tantalum metal, resulting in increased light absorption, which is not preferable.

In the present invention, the mixture in the above ratio is sintered to obtain the vapor deposition material according to the present invention.

Sintering is carried out in an inert state. For this reason, it is preferable to heat in vacuum or in an inert gas such as N2 or Ar. Although the heating temperature varies depending on the blending ratio of tantalum metal, it is preferably 1450 to 1600°C. The heating time is about 2 to 6 hours. Examples of the apparatus for performing the above-mentioned sintering include a vacuum electric furnace and the like.

[0013] The shape of the material for vapor deposition according to the present invention is as follows:
It can be made into pellets, granules, or other shapes.

Conventional ditantalum pentoxide has a melting temperature of 2100° C. and an evaporation temperature of 2500° C. when an electron gun is used during vapor deposition. The temperature at which the material begins to melt is 2,300°C and the temperature at which it evaporates is 2,500°C, and the difference between the melting and evaporating temperatures is small. Therefore, evaporation can occur immediately after melting begins, reducing the influence of radiant heat on the substrate during vapor deposition. In addition, since the difference between the melting temperature and the evaporation temperature is small, the viscosity is high and it is possible to prevent the material from flowing out.

[0015]

[Examples] The present invention will be explained in more detail with reference to Examples below. Example 1 Dtantalum pentoxide (average particle size 0.7 μm) and tantalum metal (average particle size 45 μm) were mixed at a weight ratio of 87:13, press-molded, and then sintered at 1500°C for about 4 hours in a vacuum. A pellet for deposition was obtained. Next, the pellets are set in an electron beam evaporation hearth placed in a vacuum chamber, and the inside of the apparatus is evacuated to 1 x 10-5 Torr, and then melted with an electron beam to determine the optical film thickness. Vapor deposition was performed so that nd=375 nm. Figure 1 shows the change in total pressure in the vacuum chamber over time during pellet dissolution.
Further, the partial pressure of oxygen is shown in FIG. Compared to the total pressure change (FIG. 3) and oxygen partial pressure (FIG. 4) during evaporation of ditantalum pentoxide alone, which were measured as a comparative example, the pellets of the present invention clearly contained less decomposed gas. Normally, when ditantalum pentoxide is used as a material for vapor deposition, the vapor deposition is carried out under an oxygen atmosphere of 1.times.10@-4 Torr in order to prevent light absorption in the resulting vapor deposited film. The material for vapor deposition according to this example was similarly evaporated at 300 m
Optical film thickness nd = 125 nm on a glass substrate kept at ℃
As a result of vapor deposition, the refractive index was 2.10,
There was no difference from the case where ordinary tantalum pentoxide was deposited. In this case, since the amount of oxygen generated from the material was small, the melting time was 10% shorter than that of the conventional material. Furthermore, since the material melted as shown in Figure 5, it did not flow out and a phenomenon similar to bumping did not occur.

The vapor deposition material of this example is a mixed sintered body of tantalum metal and ditantalum pentoxide, but the reaction between the two has hardly progressed. However, depending on the sintering conditions, tantalum oxides with slightly different oxygen contents may be produced, but this does not affect the pellets for deposition of the present invention in any way. Example 2 Ditantalum pentoxide (average particle size 0.7 μm) and tantalum metal (average particle size 45 μm) were mixed at a weight ratio of 95:5,
4 at 1500°C in a vacuum atmosphere as in Example 1.
When a pellet for vapor deposition was created by heating for a certain period of time and a similar vapor deposition was performed, gas was released during vapor deposition, but about 50% of the gas released in the case of a single vapor deposition pellet of ditantalum pentoxide was generated.
%, it was much less. Example 3 Dtantalum pentoxide (average particle size: 0.7 μm) and tantalum metal (average particle size: 45 μm) were mixed at a weight ratio of 50:50 to prepare vapor-deposited pellets. Sintering was done by heating at 1500° C. for 4 hours in a vacuum atmosphere. When vapor deposition was carried out in the same manner as in Example 1, the vapor deposition was successful in the same manner as in Example 1, but a phenomenon such as slight bumping was observed due to the influence of the metal tantalum.

[0017]

Effects of the Invention As explained above, according to the vapor deposition material of the present invention, the amount of oxygen released is reduced, and the vapor deposition becomes easier, so the vapor deposition time is shortened, and the thermal influence on the substrate is reduced. This makes it possible to prevent phenomena such as bumping.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the change over time in the total pressure inside the chamber when dissolution is performed using the product of the present invention.

FIG. 2 is a mass spectrum showing the change in partial pressure in the chamber over time when dissolution is performed using the product of the present invention.

FIG. 3 is a graph showing the change over time in the total pressure inside the chamber when melting was performed using a comparative product.

FIG. 4 is a mass spectrum showing the change in partial pressure in the chamber over time when dissolution was performed using a comparative product.

[Figure 5] Comparative product (Ta2O5) and inventive product (T
FIG. 2 is a schematic diagram showing a vapor deposition residue of a2 O5 +Ta).

Claims (1)

[Claims] 1. A vapor deposition material obtained by sintering ditantalum pentoxide and tantalum metal in a proportion of 4 to 55% by weight based on the ditantalum pentoxide.