JP2014091851A - Gallium nitride target and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a gallium nitride target in which a joint portion is not peeled off even if sputtering is performed at high temperature.SOLUTION: A method of producing a gallium nitride target includes steps of subjecting a gallium nitride molding as a target material to UV cleaning, and then forming a tungsten thin film from 1000 nm to 2500 nm on the molding.

Description

  The present invention relates to a gallium nitride target used when manufacturing a gallium nitride thin film by a sputtering method. Specifically, the present invention relates to a gallium nitride target in which a joint portion with a metal member is not peeled even when sputtering is performed at a high temperature.

  Gallium nitride is attracting attention as a light emitting layer for blue light emitting diodes (LEDs) and a raw material for blue laser diodes (LDs). In the future, it is also attracting attention as a material for applications such as power devices.

  As a method for producing a gallium nitride thin film, a sputtering method can be mentioned. However, since gallium nitride is difficult to sinter, the density is improved only to about 50% by ordinary firing, so that it is not suitable for use as a target. As a method for improving the density of gallium nitride, a molded body in which a gallium nitride sintered body is impregnated with metal gallium has been proposed (see, for example, Patent Document 1), but gallium has a low melting point of about 30 ° C. When the substrate is heated and sputtered, the target material is also heated, gallium is deposited from the target material, and reacts with Ni, Cu, and In-based solder, which is a barrier layer at the joint with the metal member, and the bonding force is weakened. There is a problem that the bonding between the target material and the metal member is peeled off.

  In addition, there is a Ba-based alloy sputtering target in which a metal barrier layer is formed as a target with improved bonding failure with a metal member (see, for example, Patent Document 2). Since the wettability of the barrier layer is insufficient with this method, the barrier layer and the metal member cannot be brazed directly with solder, and it is necessary to form a wettability improving layer of Ni or Cu on the barrier layer. There was a problem that the process was complicated and the cost was high. Furthermore, since gallium diffuses in a liquid state, a barrier layer that is easier to diffuse than Ba-based and has higher adhesion is required.

JP 2012-144805 A JP 2009-35762 A

  An object of the present invention is to provide a sputtering target of gallium nitride in which a bonded portion that does not react with gallium is formed on a gallium nitride molded article so that the bonded portion does not peel off even when sputtering is performed at a high temperature. .

  In a gallium nitride target, it is common to form a thin film of Ni or Cu on the target material to improve wettability, and braze the metal member as a bonding layer with an In-based solder having a low melting point. However, when the substrate is heated and the gallium nitride target is sputtered, gallium may be deposited on the target surface. Since gallium has the property of eroding many metals, when a thin film of Ni or Cu is formed, a part of the thin film reacts with gallium, and further gallium reacts with In-based solder, resulting in a decrease in adhesion at the joint. However, the bond between the target material and the metal member may be peeled off.

  Therefore, the present inventors have found that by forming a tungsten thin film on the joint surface between the gallium nitride molded product and the metal member, the thin film does not react with gallium and gallium does not precipitate on the surface of the thin film, thereby completing the present invention. It came.

  That is, the present invention is a method for producing a gallium nitride target, characterized by forming a tungsten thin film having a thickness of 1000 nm to 2500 nm on the molding after the gallium nitride molding as a target material is UV-cleaned.

  Hereinafter, the present invention will be described in detail.

  The molded product refers to a molded body including those obtained by solidifying powder by various methods such as molding and baking. In the present invention, the gallium nitride molded product includes a sintered body containing gallium nitride as a main component, a molded body obtained by impregnating a gallium nitride sintered body with metal gallium, and the like. In a molded body in which metal gallium is impregnated into a gallium nitride sintered body, since the metal gallium is present in the voids of the gallium nitride sintered body, a situation in which gallium is likely to precipitate from the target material during sputtering is particularly likely. The present invention can be suitably used.

  In the present invention, the adhesion of the tungsten thin film is very important. If the adhesion of the tungsten thin film is poor, not only is it easy to peel off, but also the tungsten thin film is likely to oxidize and the wettability is liable to be lowered, the solder of the bonding layer cannot be applied sufficiently, and the joint portion with the metal member may be peeled off There is. Therefore, in order to improve the adhesion of the tungsten thin film, the surface of the gallium nitride molded product is irradiated with ultraviolet rays (UV) having a short wavelength of 100 nm to 280 nm for 3 minutes or more, preferably 5 minutes or more, and then the tungsten thin film is formed.

  The thickness of the tungsten thin film formed on the gallium nitride molded product is desirably 1000 nm or more and less than 2500 nm. If it is thinner than 1000 nm, gallium deposition cannot be completely prevented. If the tungsten thin film is thicker than 2500 nm, the thin film may be peeled off due to the stress of the film.

  In the present invention, the tungsten thin film formed on the gallium nitride molded article is preferably formed by sputtering, and more preferably formed by RF sputtering. DC sputtering can be formed at a higher speed. However, if the film forming speed is too high, the adhesion of the tungsten thin film may be reduced and the film may be cracked. It is preferable to form a film at 85 Å / min or less.

  In the present invention, the erosion of the tungsten thin film by gallium can be determined by, for example, heating the molded article on which the thin film is formed at a high temperature of about 200 ° C. and observing whether gallium is precipitated. At 200 ° C., gallium becomes a silvery liquid and can be easily distinguished.

  According to the present invention, by forming a tungsten thin film on a gallium nitride molded product, the gallium in the molded product does not precipitate at the joint with the metal member even when sputtering is performed at a high temperature, and the tungsten thin film does not peel off. It is possible to produce a target.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

In the example of the present invention, a gallium nitride molded product in which gallium nitride and metal gallium were mixed (size 76.2 mmφ × 3.5 mmt, density 5.2 g / cm ³ ) was used. See Patent Document 1 for a detailed manufacturing method.

(UV cleaning of molded product)
UV cleaning was performed for 5 minutes using an optical surface treatment apparatus (ultraviolet wavelength 184.9 nm, 253.7 nm) on the surface of the molded body on which the thin film was to be formed.

(Formation of thin film layer)
The UV-cleaned molded body was set in a sputtering apparatus within 10 minutes, evacuated, and a metal target was sputtered under the following film forming conditions to form a thin film.
Discharge method: RF sputtering, DC sputtering Film forming pressure: 0.5 Pa
Additive gas: Argon discharge power: 100W
(Evaluation of thin film layer)
The molded body on which the thin film layer was formed was heated in a vacuum oven at 200 ° C. for 3 hours. Evaluation was made based on whether gallium was deposited on the thin film layer after heating.

(Joining with metal parts)
The In solder material that was heated and melted was applied to the surface of the molded body on which the thin film was formed and the Cu backing plate, and the molded body and the backing plate were joined together to cure the solder material. The produced target was heated in a vacuum oven at 200 ° C. for 3 hours, and it was evaluated whether the formed body and the metal member were peeled off after heating.

Example 1
A tungsten thin film having a thickness of 1000 nm was formed on the green body by UV sputtering on a UV-cleaned gallium nitride molded body at a deposition rate of 50 Å / min.

  When the molded body on which the thin film layer was formed was heated at 200 ° C., no precipitation of gallium on the surface was observed.

  When the formed body on which the thin film layer was formed and the Cu backing plate were bonded with In solder and heated at 200 ° C., the bonded portion with the metal member was not peeled off.

(Example 2)
A tungsten thin film having a thickness of 2000 nm was formed on the molded body of the UV-cleaned gallium nitride formed by RF sputtering with tungsten at a deposition rate of 60 Å / min.

  When the molded body on which the thin film layer was formed was heated at 200 ° C., no precipitation of gallium on the surface was observed.

  When the formed body on which the thin film layer was formed and the Cu backing plate were bonded with In solder and heated at 200 ° C., the bonded portion with the metal member was not peeled off.

(Example 3)
A tungsten thin film having a thickness of 2500 nm was formed on the molded body of the UV-cleaned gallium nitride molded body by RF sputtering at a deposition rate of 70 Å / min.

  When the molded body on which the thin film layer was formed was heated at 200 ° C., no precipitation of gallium on the surface was observed.

  When the formed body on which the thin film layer was formed and the Cu backing plate were bonded with In solder and heated at 200 ° C., the bonded portion with the metal member was not peeled off.

(Example 4)
A tungsten thin film with a thickness of 1500 nm was formed on the molded body of the UV-cleaned gallium nitride molded body with RF sputtering at a deposition rate of 50 Å / min.

  When the molded body on which the thin film layer was formed was heated at 200 ° C., no precipitation of gallium on the surface was observed.

  When the formed body on which the thin film layer was formed and the Cu backing plate were bonded with In solder and heated at 200 ° C., the bonded portion with the metal member was not peeled off.

(Comparative Example 1)
A 1000 nm copper thin film was formed on the molded body of the UV-cleaned gallium nitride formed on the molded body by RF sputtering with Cu at a deposition rate of 120 Å / min.

  When the molded body on which the thin film layer was formed was heated at 200 ° C., precipitation of gallium was observed on the surface of the molded body.

  When the molded body on which the thin film layer was formed and the Cu backing plate were joined with In solder and heated at 200 ° C., the metal member and the molded body were peeled off.

(Comparative Example 2)
A tungsten thin film having a thickness of 500 nm was formed on the compacted gallium nitride molded body subjected to UV cleaning with RF sputtering at a deposition rate of 50 Å / min.

  When the molded body on which the thin film layer was formed was heated at 200 ° C., gallium was deposited on the surface of the molded body.

  When the molded body on which the thin film layer was formed and the Cu backing plate were joined with In solder and heated at 200 ° C., the metal member and the molded body were peeled off.

(Comparative Example 3)
A tungsten thin film having a thickness of 3000 nm was formed on the compacted gallium nitride molded body subjected to UV cleaning by DC sputtering with a deposition rate of 90 Å / min.

  When the molded body on which the thin film layer was formed was heated at 200 ° C., gallium was deposited on the surface of the molded body.

  When the molded body on which the thin film layer was formed and the Cu backing plate were joined with In solder and heated at 200 ° C., the metal member and the molded body were peeled off.

(Comparative Example 4)
A tungsten thin film having a thickness of 1000 nm was formed on the molded body of gallium nitride that had not been UV-cleaned by RF sputtering at a deposition rate of 50 Å / min.

  When the molded body on which the thin film layer was formed was heated at 200 ° C., gallium was deposited on the surface of the molded body.

  When the molded body on which the thin film layer was formed and the Cu backing plate were joined with In solder and heated at 200 ° C., the metal member and the molded body were peeled off.

Claims (1)

  A method for producing a gallium nitride target, comprising: cleaning a gallium nitride molded article as a target material with UV; and forming a tungsten thin film of 1000 nm to 2500 nm on the molded article.