WO2000036193A1

WO2000036193A1 - Diamond structure and method of manufacture thereof

Info

Publication number: WO2000036193A1
Application number: PCT/JP1999/007057
Authority: WO
Inventors: Mitsuharu Okada; Michifumi Tanga
Original assignee: Toyo Kohan Co., Ltd.
Priority date: 1998-12-16
Filing date: 1999-12-16
Publication date: 2000-06-22
Also published as: AU1686800A

Abstract

A method is provided for efficiently producing diamond structures having upper and lower sides exhibiting improved insulation. According to this method, a diamond substrate is covered with a metalized layer alone or together with an adhesive layer, covered further with a BN protective coating, and cut into pieces by a laser beam. They are then oxidized in an oxygen atmosphere, for example, using an ECR plasma technique to remove the conductive, modified layer formed on the cuts, and immersed in water to remove the BN protective coating.

Description

Description Method of manufacturing diamond structure and diamond structure manufactured by using the method

The present invention relates to a method for producing a diamond structure and a diamond structure produced by using the method. More specifically, when a diamond substrate with a metallized layer formed on the surface is cut using a laser, a protective film is provided to protect the metallized layer and to have conductivity generated on the cut surface. The present invention relates to a method for manufacturing a diamond structure by removing an altered layer and a protective film, and a diamond structure such as a heat sink or a thermistor manufactured using the method. Background art

(i In recent years, materials with excellent thermal conductivity, such as semiconductor high-frequency devices, semiconductor laser diodes, and light-emitting diodes, that efficiently release the heat generated when operating devices to the outside, have been required. Attempts have been made to use diamonds that have a significantly higher thermal conductivity compared to natural or synthetic single-crystal diamonds or synthetic polycrystalline v-crystal diamonds. Is used.

Heat transfer materials made of these diamonds have conventionally been manufactured as follows. That is,

1) After grinding the diamond so that the upper and lower surfaces are parallel, cut it to a predetermined size using a diamond saw. The cut diamonds are arranged flat without gaps, and lf a metallized layer is formed on the upper and lower surfaces.

2) Cut the diamond into the specified size as described above and finish After metallization, a metallized layer is formed on the entire surface, leaving two upper and lower surfaces, and the other side is diamond-polished to remove the metallized layer.

3) After grinding so that the upper and lower surfaces of the diamond are parallel, metallized layers are formed on the upper and lower surfaces, and then cut to a predetermined size using a diamond saw, and finished to the final shape.

These methods 1) to 3) have the following disadvantages. In other words, the methods 1) and 2) cut the diamond into individual heat sink sizes and rearrange them to form a metallized layer, or form a metallized layer on the entire surface of each divided body. Then, only the side surface is polished and removed, requiring a complicated process such as polishing, resulting in extremely poor productivity. The method 3) is also poor in productivity because the cutting speed of diamond is slow and it takes a long time to cut.

As a method of manufacturing a diamond heat sink that overcomes such a drawback, a method described in Japanese Patent Application Laid-Open No. H10-226569 is disclosed. In this manufacturing method, after cutting a polycrystalline diamond having a metal film formed on the upper and lower surfaces in a vertical direction, the cut | ff section is subjected to plasma treatment to remove a conductive layer formed on the cut surface, and It is said that a diamond heat sink with secured insulation can be obtained.

However, when this method is used, the cutting is performed so that the plasma does not penetrate to the upper and lower surfaces of the diamond when the diamond is cut and the plasma processing is performed, so that the metal film is not exposed to the plasma and damaged. An extra process of rearranging the cut diamond heat sink is required, for example, by overlapping the cut diamond heat sink V with a soft resin such as Teflon resin to mask the surface other than the cut surface. Also, as is clear from the figure of Japanese Patent Application Laid-Open No. H10-226569, at least one of the cut surfaces is processed in contact with the table and is not exposed to plasma. The work of rearranging the cut diamond heat sink must be performed at least twice.>) Poor production efficiency.

The present invention provides a method for efficiently producing a diamond structure having excellent insulating properties on the upper and lower surfaces. It is an object of the present invention to provide a method for producing a diamond structure that can be used, and a diamond structure produced by using the method. Disclosure of the invention

The method for producing a diamond structure according to claim 1, wherein a metallized layer or a metallized layer and an adhesive layer are formed on a diamond substrate, and then a protective film is formed thereon, and then the diamond substrate is formed by using a laser. It is characterized in that it is cut vertically and then oxidized in an oxygen atmosphere to remove the conductive alteration layer formed on the cut surface, and then the protective film is removed.

The manufacturing method according to claim 2 is characterized in that the protective film is formed in an argon gas containing hydrogen or oxygen by using RF sputtering with BN as a target. The manufacturing method according to claim 3, wherein the oxidation treatment is an oxygen plasma treatment for generating plasma in an oxygen atmosphere.

The manufacturing method according to claim 4 is characterized in that the oxygen plasma treatment uses an electron cyclotron resonance method as a means for generating plasma.

The manufacturing method according to claim 5, wherein the oxygen plasma treatment uses a microphone mouth wave as a means for generating plasma.

The production method according to claim 6, wherein the oxidation treatment is an ozone treatment for generating nascent oxygen in an oxygen atmosphere.

^ The manufacturing method according to claim 7, wherein in the ozone treatment, the conductive deteriorated layer is irradiated with ultraviolet rays.

9. The manufacturing method according to claim 8, wherein the oxidation treatment is a reactive ion etching treatment.

The manufacturing method according to claim 9 is characterized in that the protective film remaining after the oxidation treatment is immersed in water;

The diamond structure according to claim 10, wherein the method for manufacturing a diamond structure is It is characterized in that it is manufactured by using.

In the diamond structure according to claim 11, the diamond structure is preferably a heat sink.

In the diamond structure according to claim 12, it is desirable that the diamond structure be f at the thermistor.

BEST MODE FOR CARRYING OUT THE INVENTION

In the method for producing a diamond structure of the present invention, a metallized layer or a metallized layer and an adhesive layer are formed on a diamond substrate, and then a protective film is formed on the metallized layer and the adhesive layer.

10 After the formation, the diamond substrate is cut vertically using a laser, and then oxidized in an oxygen atmosphere to remove the conductive alteration layer formed on the cut surface, and then the protective film is removed. Become. By providing this protective layer, it is possible to prevent abrasion when the diamond substrate is cut by a laser and damage to the metallized layer and the adhesive layer due to the subsequent oxidation treatment in an oxygen atmosphere. This protective layer is made of water

It can be easily removed simply by dipping in the solvent of ^.

Hereinafter, the present invention will be described in detail mainly by taking the case where the diamond structure is a heat sink as an example.

First, the diamond material used in the present invention will be described. In the present invention, diamond is cut and divided using a laser such as a YAG laser, a gas laser, an excimer laser, or the like, so that any of synthetic diamond, high-pressure synthetic diamond, and natural diamond may be used as the diamond material. Further, both single crystal diamond and polycrystalline diamond can be applied. However, in the present invention, from the viewpoints of productivity and yield, it is preferable to use diamond produced by a gas phase synthesis method such as a microwave plasma CVD method.

When forming these diamonds into heat sinks, Polish the upper and lower surfaces. Next, after performing hydrogen plasma cleaning or oxygen plasma cleaning, a metallized layer is formed using a DC magnetron sputtering method, an RF magnetron sputtering method, or a vacuum evaporation method. The metallized layer reacts chemically with the diamond to improve adhesion, has heat resistance, and must be capable of brazing (W, Ti, Mo, Ni, Cr) , Pt, Pd, Au, Ag, or Cu, or an alloy film or a composite film composed of two or more of these elements, preferably a Ti—Pt—Au alloy film. Is more preferred.

The metallization layer described above may itself be brazed to devices such as semiconductor laser chips, but some devices may break down when heated to high temperatures. Further, in order to enable brazing of the sensor IC and the like at a low temperature, it is preferable to provide an adhesive layer that can be brazed at a relatively low temperature on the metallized layer. Such an adhesive layer includes, for example, an Au—Sn alloy layer formed using a magnetron sputtering method or a vacuum evaporation method. Or it may be a so-called solder layer. This solder layer can be formed by using either a wet plating method or a vacuum deposition method. The solder preferably has an alloy composition with a Pb / Sn in the range of 1/9 to 6Z4.

As described above, after forming a metallized layer or a metallized layer and an adhesive layer on the diamond surface, a protective film is formed thereon. Protective coating YAG laser _t The gas laser, heated as it is cut by a laser such as an excimer laser, and electronic oxygen plasma treatment and the use of cyclotron resonance and a microwave, such as ozone treatment using oxygen nascent It must be made of a material that has sufficient heat resistance and oxidation resistance to withstand oxidation treatment, and that can be easily peeled without deteriorating the metallized layer and the adhesive layer after laser cutting and oxidation treatment. No. The material that satisfies these requirements l, carbon, carbides, oxides, and the like nitrides, among Z N_〇, T a ₂ 〇 _{5, S i O 2, I} TO ( indium - tin oxide ), BN, carbon Is preferred. These protective films are formed on the above metallized layer or adhesive layer by an RF magnetron pass method in an argon atmosphere. Among them, the protective film made of BN is particularly preferable because it can be removed in a relatively short time only by immersion in water. This easily removable BN protective film can be formed by the RF magnetron sputtering method in an argon atmosphere containing hydrogen or oxygen. The protective film need not be formed on both sides of the metallized layer or the diamond substrate on which the metallized layer and the adhesive layer are formed, but may be formed only on one side. That is, after a protective film is formed on one side, it is placed on a gantry so that the opposite side is in contact with the gantry, and cut into a predetermined size using a laser. Then cut individual

The I C diamond substrate is subjected to the following oxidation treatment, which will be described later, while remaining on the gantry.

Therefore, there is no need to rearrange the individual diamond substrates that have been cut. Thus, after forming a metallized layer, or a metallized layer and a bonding layer on the diamond surface, and then forming a protective film on the metallized layer and the bonding layer, a laser beam such as a YAG laser, a gas laser, or an excimer laser is used. Cut to dimensions. This leh

^ The diamond thermally transforms into a conductive material made of carbon when cut by the laser, and forms a conductive film on the cut surface.

The conductive film formed on the cut surface is treated with the following electron cyclotron resonance (ECR) method, oxygen plasma treatment using microwaves, or ozone treatment. Is removed by oxidation treatment.

C First, the oxygen plasma treatment will be described.

A sample cut to a predetermined size by a laser as described above is placed in an oxygen atmosphere at a constant flow rate, and an oxygen plasma is generated by applying an ECR or microwave having an output of 100 to 800 W. The conductive film is oxidized by this oxygen plasma, gasified and removed. Metallized layer or metallized layer and adhesive layer on diamond surface

Since ^ is formed, the upper limit of the output of the ECR or Mic mouth wave is set to 800 W or less in order to prevent the heating and melting of these layers. Oxidation treatment takes more than 15 minutes _¾ i

A processing time of 20 to 80 minutes is preferable from the viewpoint of stable removal and saturation of the processing effect. By such processing, ¹ 0 1 ³ Ω or more insulation resistance value at the cut surface after treatment is obtained.

Next, the ozone treatment will be described.

I In ozone treatment, a sample cut to a predetermined size by a laser is placed in an ozone generator that generates a certain amount of ozone in a constant flow of oxygen atmosphere, and the conductive film is oxidized by the nascent oxygen generated by ozone. And gasified and removed. At this time, by irradiating with ultraviolet rays, it is possible to remove the particles more efficiently. In either case, the sample must be heated to 200 ° C or higher. The higher the temperature, the faster it is possible to oxidize and remove the conductive film. When an adhesive layer is formed, the heating temperature of the sample must be lower than the melting point of the adhesive layer in order not to melt the low-melting adhesive layer. Even with this ozone treatment, an insulation resistance value of 10 ³ Ω or more can be obtained on the cut surface after the treatment.

Next, the reactive ion etching (hereinafter referred to as R IE) process will be described. Place the sample cut to a predetermined size with a laser in an oxygen atmosphere at a constant flow rate,

A microwave having an output power of 100 to 800 W is applied to generate oxygen plasma. The oxygen plasma oxidizes the conductive film, gasifies and removes it. The upper limit of the microwave output is preferably 800 W or less, which is such that the metallized layer on the diamond surface, or the metallized layer and the adhesive layer are not melted by heating. The oxidation time is preferably 20 to 80 minutes from the viewpoint of stable removal and saturation of the treatment effect. By ^{performing the} RI treatment in this manner, an insulation resistance value of 10 ′ ^{: ίΩ} or more can be obtained on the cut surface after the treatment.

After cutting and dividing as described above to remove the conductive film by oxidation, the metallized layer of the diamond substrate or the protective film formed on the metallized layer and the adhesive layer is removed. It is preferable that the protective film is BN because it can be removed in a short time only by immersion in water. Example

Hereinafter, the present invention will be described more specifically with reference to examples.

First, the case of making a diamond heat sink will be described.

(Example 1)

ly [creating diamonds]

A 0.35 mm thick, 25 mm long and 25 mm wide diamond was fabricated using microwave CVD. The upper and lower surfaces of the diamond were polished to obtain a substrate having a thickness of 0.25 mm. The diamond substrate thus obtained had a specific resistance of 10 ¹³ Ω · cm and a thermal conductivity of 13 W / cm · K.

10 [Formation of metallized layer]

After the diamond substrate was cleaned with hydrogen plasma in this way, each layer was formed on the upper and lower surfaces in this order by Ti, Pt :, and Au by using a DC magnetenetron sputtering method. The thickness of each layer was set to Ti: 100 nm, Pt: 100 nm, and Au: 500 ηm.

[Formation of adhesive layer]

An adhesive layer was formed further above the diamond substrate on which the metallized layer was formed. That is, an Au—Sn alloy layer (AuZSn = 80 wt% Z20 wt%) was formed to a thickness of 2.8 xm on one side of the diamond substrate on which the metallized layer was formed by using a DC magnetron method.

0 [Formation of protective film]

The diamond substrate on which the metallized layer and the adhesive layer were formed was placed in an atmosphere having a flow rate of argon 2 OSCC i and hydrogen 0.08 SCCM, and RF sputtering was performed at an output of 250 W for 60 minutes using BN as a target. A BN protective film having a thickness of 1.0 was formed.

^ [Cut and split]

Next, the diamond having the metallized layer, the adhesive layer, and the protective film is provided. The Mondo substrate was cut and divided into a square lattice of 0.65 mm pitch under the following conditions using an Nd-YAG laser.

Average output: 10W

Q switch frequency: 5 kHz

^ Processing speed: 15mmZs e c

Number of scans: 20

[Removal of conductive film]

Next, the conductive film formed on the cut surface of the cut and divided sample by the laser was removed under the following conditions using an ozone treatment method of irradiating ultraviolet rays during treatment.

iP oxygen flow rate: 2 1 Zm i n

Substrate temperature: 2501:

Time: 40 minutes

Ultraviolet light source: Low pressure mercury lamp (wavelength: 184.9 nm)

[Removal of protective film]

After removing the conductive film as described above, the sample was immersed in water for 10 minutes to remove the protective film. In this way, it has a thickness of 0.25mm, a height of 0.65mm, and a width of 0.65mm. resistance diamond heat sink was obtained a 1 0 ^'3 Ω · cm. Next, a case of creating a diamond sample will be described.

> _c (Example 2)

[Create diamond]

Using a microwave CVD method, an AND diamond (thickness: 0.3 mm, length: 5 mm, width: 5 mm) consisting of carbon only was prepared and its upper and lower surfaces were polished. The specific resistance of this diamond was ^10Ι4 Ω · cm. Next, a boron-doped diamond layer (volume resistivity: 6 Ω · cm) doped with boron was formed on one surface thereof by using a microwave CVD method, and this surface was polished to obtain a substrate. [Formation of selective metallization layer]

A resist was applied to the polished boron-doped diamond layer of the diamond substrate by a conventional method. Next, after exposing and developing a predetermined pattern and removing the resist only at the portion where the metallized layer is to be provided, each layer is formed in the order of T ii, P, and Au using a DC magnetron sputtering method to form a metallized layer. . Next, the remaining resist layer was removed together with the metallized layer formed thereon to obtain a selective metallized layer having a metallized layer formed only on a predetermined pattern.

[Selective formation of silicon dioxide film]

A resist was applied to the surface of the diamond substrate on which the selective metallization layer was formed, on which the metallization layer was formed, by a conventional method. Next, a predetermined pattern was exposed and developed to remove the resist only at the portion where the silicon dioxide film was to be provided, and then a silicon dioxide film was formed using an RF magnetron pass-through method. Next, the remaining resist layer was removed together with the silicon dioxide film formed thereon to obtain a thermistor substrate having a silicon dioxide film formed only on a predetermined pattern.

| ^ [Formation of protective film]

The diamond substrate on which the metallized layer and the adhesive layer were formed was placed in an atmosphere having a flow rate of argon 20 SCCM and oxygen 0.08 SCCM, and RF sputtering was performed at an output of 250 W for 60 minutes using BN overnight. A BN protective film with a thickness of 1.0 / m was formed.

> 0 [cutting split]

Next, the diamond substrate provided with the metallized layer, the adhesive layer, and the protective film was cut and divided using an Nd-YAG laser under the following conditions.

Average output: 10W

Q switch frequency: 5 kHz

Caroe speed: 15 mm / sec

Number of scans: 20 [Removal of conductive film]

Next, the conductive film formed on the cut surface of the cut and divided sample by the laser was removed using a microwave oxygen plasma method under the following conditions.

Oxygen flow rate: 5 S C C M

Output: 300 W

Time: 45 minutes

[Removal of protective film]

After removing the conductive film as described above, the sample was immersed in water for 10 minutes to remove the protective film. It was then annealed by heating in vacuum at 400 for 5 minutes. As shown in (D), a diamond thermistor was obtained in which a metallized layer and a silicon dioxide film were formed on a diamond substrate consisting of two layers, an AND diamond and a boron dove diamond. insulation resistance of the cut plane was 1 0 1 ⁴ Ω · cm.

| Industrial applicability

In the method for producing a diamond structure of the present invention, a metallized layer or a metallized layer and an adhesive layer are formed on a diamond substrate, and then a protective film made of BN is formed thereon, and then the diamond substrate is formed using a laser. Is cut in the vertical direction, and then subjected to an oxidation treatment such as an ECR plasma method, a microwave plasma method, and an ozone treatment accompanied by violet yC external irradiation in an oxygen atmosphere to remove a conductive alteration layer generated on the cut surface. Thereafter, the BN protective film is removed. By providing this BN protective layer, abrasion when cutting the diamond substrate by laser and subsequent damage of the metallized layer and the adhesive layer due to oxidation treatment in an oxygen atmosphere are prevented. The BN protective layer can be easily removed simply by dipping in a solvent such as water.

^ ij- is possible, and a diamond structure excellent in insulation can be efficiently manufactured by using the method for manufacturing a diamond structure of the present invention. The diamond structure manufactured by using the manufacturing method of the present invention can be applied to heat sinks, thermistors, and the like.

Claims

The scope of the claims

1. A metallized layer or a metallized layer and an adhesive layer are formed on a diamond substrate, and then a protective film is formed thereon.

^ The diamond substrate is cut in the vertical direction, and then oxidized in an oxygen atmosphere to remove the conductive alteration layer formed on the cut surface, and thereafter, the protective film is removed. Method.

2. The diamond according to claim 1, wherein the protective film is formed by using rf sputtering with BN as a target in argon containing hydrogen or oxygen.

Method for producing I C monde constructs.

3. The method for producing a diamond structure according to claim 1, wherein the oxidation treatment is an oxygen plasma treatment for generating plasma in an oxygen atmosphere.

4. The method according to claim 3, wherein the oxygen plasma treatment uses an electron cyclotron resonance method as a means for generating plasma.

Itj- Manufacturing method.

5. The method for producing a diamond structure according to claim 3, wherein the oxygen plasma treatment uses a microwave as a means for generating plasma.

6. The method for producing a diamond structure according to claim 1, wherein the oxidation treatment is an ozone treatment for generating nascent oxygen in an oxygen atmosphere.

_(? 7. In the ozone treatment, and FEATURE: applying ultraviolet light to the conductive degraded layer, producing a diamond construction according to claim 6.

8. The method for producing a diamond structure according to claim 1, wherein the oxidation treatment is a reactive ion etching treatment.

9. The method for producing a diamond structure according to claim 1, wherein the protective film remaining after the oxidation treatment is immersed in water and removed.

10. The method for producing a diamond structure according to any one of 1 to 9 above, A diamond structure produced.

11. The diamond structure according to claim 10, wherein the diamond structure is a heat sink.

12. The diamond structure according to claim 10, wherein the diamond structure is a thermistor.