JPH01319668A - Method for coating nitride ceramics with metal - Google Patents

Abstract

PURPOSE:To form a metal coat on the surface of nitride ceramics with satisfactory adhesion by sputtering a metal with adsorbed Cs vapor as a target in plasma to generate negative metal ion beams and by irradiating the ceramics with the beams. CONSTITUTION:A target 1 obtd. by adsorbing Cs on the surface of a metal is exposed to plasma of a positively charged rare gas and negative potential is impressed on the plasma. The Cs adsorbed on the target 1 provides electrons to sputtered metal particles to convert the particles into negative ions. A potential difference is produced between an outer vessel 8 and an electrode 20 to extract negative metal ion beams and nitride ceramics is irradiated with the beams. A uniform metal coat having high bonding strength can be formed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method of coating nitride ceramics with metal.Nitride ceramics coated with metal are used as heat sinks used for heat dissipation in semiconductor lasers, microwave devices, etc. It is also used as a highly thermally conductive substrate for hybrid ICs.

[Prior Art] As electronic circuits become more integrated and semiconductor lasers and microwave elements become more sophisticated, it has become important to efficiently radiate heat generated from component parts. A I N,,3
Nitride ceramics such as 13N4 and BN have high thermal conductivity (and good electrical insulation) and are expected to be excellent heat dissipation materials. In particular, AβN is a highly thermally conductive substrate for hybrid river C. In addition, cubic boron nitride (C-BN) is attracting attention as a heat sink material for semiconductor lasers and microwave devices.
In order to form an electric circuit, the high thermal conductive substrate of IC is coated with metal on the surface of the substrate, and the heat sink material is also used to bond the element and the heat sink, or to use the heat sink as an electrode. For this reason, it is necessary to coat the surface of the heat sink with metal.

Generally, nitride ceramics such as AQN, SI3N4, and BN are not easy to coat with metal.
On the other hand, for example, (-BN metal coating method, ■Method of forming Ni film by spackling method [Journal of Physics T: Applied Physics (J, Phys, D: 8pp1.Phys, ),
Volume 9 (1976), page 225 - hereinafter referred to as Reference ■]
and ■ forming a transition metal film of Groups 4a and 5a of the periodic table and Ga, and (, at the interface with -BN, these borides,
Method for forming nitrides and boron nitrides (JP-A-61-1)
17856). Also, as a metal coating method for aluminum nitride, a method of forming a thick film circuit on a substrate by screen printing technology using a paste composition containing molybdenum and/or tungsten powder, niobium powder, and nickel and/or cobalt powder. is known (Japanese Unexamined Patent Publication No. 63-79778).

However, in the method (2), the adhesion of the film formed by sputtering to (-BN) is insufficient and it easily peels off. The transition metals in Groups 5a and 6a of the periodic table have poor conductivity and increase the thermal resistance between the heat sink and the metallized layer, and the compounds formed at the interface with C-BN are all inert in the air. Because it is stable and easily oxidized, there are problems with long-term stability and reliability during soldering.
The disadvantage of this method is that the pattern accuracy is poor.

An object of the present invention is to provide a method for forming a chemically stable metal coating with sufficient adhesive strength on the surface of nitride ceramics such as AffN, Si, N4, BN, etc. with high precision. .

[Means for Solving the Problems] The present inventors conducted various studies based on the idea of coating nitride ceramics with metal using an ion source used in semiconductor manufacturing processes. As a result, we were able to shorten the processing time to a practically usable level and succeeded in obtaining a metal coating with high adhesive strength.

That is, the present invention provides a method for coating nitride ceramics with a metal, in which a metal whose surface has adsorbed cesium vapor is used as a target laser 1-, the target is exposed to a plasma of a positively charged rare gas, and the A method for coating nitride ceramics with metal, characterized in that a negative ion beam of the metal is generated by applying a negative potential to a target and sputtering, and the nitride ceramic is irradiated with the negative ion beam.

This invention will be explained in detail below with reference to FIGS. 1 and 2. The Targera I-1 used in this invention has cesium vapor adsorbed on the surface of the same metal as the metal to be coated. The target laser 1- is exposed to a positively charged rare gas plasma, and a negative potential is applied to the plasma.

Plasma can be formed by arc discharge. The noble gas is argon, neon or xenon. In order to effectively confine the plasma, it is preferable to attach the magnet 7 to the outside of the outer container 8 (the container containing the target, rare gas, etc.).

Since the cesium adsorbed on the target has a low work function, it gives electrons to the sputtered particles, and the particles are converted into negative ions. A negative metal ion beam can be extracted by applying a potential difference between the outer container 8 and the extraction electrode 20, but it is preferable to attach a magnet 9 in the middle in order to simultaneously perform an I-ramp on the extracted electrons. In addition, in order to effectively pull out negative metal ions generated on the surface of the target 71 from the opening 5 of the outer container, the target 1
It is preferable that the surface is processed into a concave shape.

The negative metal ion beam is accelerated to 5KV to 50KV and
Nitride ceramics such as IN, Si3N4, BN are irradiated to form a metallization. From a negative metal ion source,
Since O- ion beams resulting from residual 02 in the vacuum atmosphere and other impurity ion beams are included, if this contaminates the metal coating layer and causes a problem, the outer container 8 and the nitride irradiated with the negative ion beam may A mass spectrometer may be installed between the ceramics to extract only the necessary negative metal ion beam.

By doing this, the ion beam intensity can be increased by more than two orders of magnitude compared to a normal ion source, from several mA to several tens of mA.
Because it is possible to extract the negative metal ion beam of A,
Surface modification of materials can be carried out at a sufficient level for practical use.

The metal coating process may be performed by irradiating only a negative metal ion beam, but the same or different metals may be vapor-deposited simultaneously or alternately with the ion implantation. The metal coating layer formed by the method of the present invention has extremely high adhesive strength because a bonding layer in which metal atoms and atoms constituting the nitride ceramic are mixed is formed at the interface with the nitride ceramic.

Usually, it is efficient to form a first layer including a bonding layer by the method of the present invention, and then form a second layer to a predetermined thickness by performing general sputtering, EB vapor deposition, etc.

The type of metal to be coated is limited to (nickel, silver,
Platinum, gold, etc. are used.

According to the method of the present invention, since negative ion beams J are irradiated onto nitride ceramics, the charge amplifier is Due to its small size, ion beam irradiation is stable and uniform metal coating can be obtained.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Three types of nitride ceramics were used as described below.

Manufacturing of nitride ceramic substrate ■ When the substrate is boron nitride - A plate of pyrolytic boron nitride is diffused and impregnated with Mg5BN3 as a synthesis catalyst,
A high-temperature, high-pressure treatment was performed at 158,000 atmospheres for 30 minutes to form a sintered body of C-BN, which had a diameter of 7 and a thickness of 0.
It was processed into a 5 mm disk.

■ When the substrate is aluminum nitride - average grain size 1, 5
95 parts by weight of aluminum nitride powder of pm and an average particle size of 0.
5 parts by weight of 8 μm indium oxide powder was mixed and Hontfuss sintered in a nitrogen atmosphere at a pressure of 400 kg/afl and a temperature of 1900'C for 30 minutes to produce AI! , N
A Y203 sintered body was obtained. This was processed into a disk with a diameter of 7 mm and a thickness of 5 mm.

■ When the substrate is silicon nitride - 97 parts by weight of S I 3N 4 powder with an average particle size of 1 μm and an alpha phase content of 94% and 3 parts by weight of magnesium oxide powder with an average particle size of 0.7 μm were mixed, and the mixture was heated at a pressure of 300 kg/ cffl, hot press sintered at a temperature of 1800°C for 60 minutes in a nitrogen atmosphere to form Si3N
A 4-Mg◯ sintered body was obtained. This has a diameter of 7 mm and a thickness of 5
It was processed into a disk of mm.

Examples 1 to 5 A nitride ceramic base 16 was fixed to a sample boulder 17. Targeter 1, which was obtained by processing the same metal as the first coating layer shown in the table into a concave shape, was fixed to Target Y I Boulder-14. A bomb containing cesium was connected to the cesium inlet 4. After evacuating the inside of the outer container 8,
Cesium vapor was introduced and adsorbed onto the surface of Targera 1-1. Additionally, xenon was introduced from the rare gas inlet 6.

The hot cathode 3 is 1. , aB6 was used. An arc voltage of 60 μ was applied between the hot cathode 3 and the outer container to generate arc discharge.

A negative potential of 950 cm was applied to the target with respect to the outer container 8, an accelerating voltage shown in the table was applied between the outer container and the extraction electrode 20, and a metal negative ion beam was extracted using an ion beam current not shown in the table. Dose it 10 for substrate 16 at room temperature
The first coating layer was formed by irradiating metal negative ions under the conditions of 1 ounce/cf for the time shown in the table.
The vapor deposition device 23 was not operated.

Next, the substrate was removed from the sample boulder 17, transferred to a spackling chamber, and coated with the same metal as the coating metal of the second coating layer shown in the table using the known spackling method (method described in the above-mentioned document ①). Targera [-, thickness 100
0 people formed the second coating layer.

All of the metal coatings formed were homogeneous without swelling or uneven thickness. A scratch test I. with a diamond needle was performed on 5 of the 10 substrates of the coating layer. In addition, for the remaining five pieces, the temperature was 200°C in the atmosphere.
The same scratch test was performed after 0 hours of heating. For the scratch test, hold a diamond needle between your fingers and rub the disk several times to remove scratches.The scratches are observed using a scanning electron microscope. The disc was examined to see if there was any peeling. The results are shown in the table.

Comparative Example 1.2 As shown in the table, the metal coating of the first coating layer was performed by the spankling method (method according to the above-mentioned document ①) without metal ion irradiation, and then the second coating layer was further coated by the same spackle method. Metal coating of the coating layer was performed. Examples 1-5
When a scratch test was conducted in the same manner as above, as shown in the table, there were discs with peeling due to scratch test 1 to 1 both before and after heating.

Example 6 The same boron nitride substrate 10 as the substrate used in Examples 1 to 5
Negative ion irradiation of gold and gold vapor deposition by EB vapor deposition were performed simultaneously using the same. Negative ion irradiation of gold targets gold with an acceleration voltage of 50 KV and an ion beam current of 5 mA.
, and an ion beam intensity of 0.25 rn A/ct. The cesium vapor treatment and other ion irradiation conditions for Targera I. were the same as in Examples 1-5. In the EB evaporation method, gold in an EB evaporator 23 is irradiated with an electron beam from an electron gun 22 to evaporate the gold, and the gold is deposited on the substrate 16 .

In this way, gold negative ion irradiation and gold deposition by EB evaporation were performed simultaneously for 11 minutes, and further EB evaporation was performed for 10 minutes to form a gold coating layer with a thickness of 1,000 layers. The coating layer was homogeneous, with no swelling or uneven thickness.

When the scratch test 1- was carried out in the same manner as in Examples 1 to 5, there was no peeling due to the scratch test I- both before and after heating.

[Effects of the Invention] According to the metal coating method of the present invention, a homogeneous metal coating with high adhesive strength can be formed on the surface of nitride ceramics.

[Brief explanation of the drawing]

FIG. 2 is a cross-sectional view of the device used in the embodiment of the present invention.
FIG. 1 is a sectional view of the main part. Code 1... Target, 2... Quartz glass, 3...
...Hot cathode, 4.Cesium inlet, 5.
・Opening, 6. Rare gas inlet, 7. Magnet, 8. Outer container, 9. Magnet.
10...External power supply, 11...External power supply, ]2
...Arc power source, 13...Output power source, 14...Target holder, 15...Insulator, 16.
...Base, 17...Sample boulder-118...Einzel lens, 19...Magnet, 20...
Extraction electrode, 21...Exhaust port, 22...Electron gun, 23...EB evaporator. Patent applicant Denki Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] (1) In a method of coating nitride ceramics with metal, a metal with cesium vapor adsorbed on the surface of the metal is used as a target, and the target is exposed to plasma of a positively charged rare gas, and the target is placed at a negative potential. A method for coating a nitride ceramic with a metal, characterized in that a negative ion beam of the metal is generated by applying and sputtering, and the nitride ceramic is irradiated with the negative ion beam.