JPH1150241A - Sputtering target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a target which has a joining strength between a sputtering target material and a backing plate, high heat resistance and lessens abnormal discharge at the time of sputtering by joining the sputtering target material and the backing plate by friction pressure welding, thereby constituting the target. SOLUTION: The friction pressure welding is usually executed in the stage of a columnar blank (t) for the target prior to plastic working and a columnar blank (b) for the backing plate with approximately the same outside diameter as the outside diameter thereof. Both blanks (t), (b) are first fixed to the front ends of the chuck and spindle of a fixing base of an automatic friction pressure welding machine. The plane at the front end of the blank (b) is mated flush with the plane at the front end of the blank (t) and both are pressure welded, then, in this state, the blank (b) is rotated at a high speed by rotating the spindle. As a result, the contact surfaces of both blanks (t), (b) are rubbed against each other, by which heat is generated until finally fused layers are formed at the contact surfaces. The rotation is stopped in this state and the blanks are allowed to cool naturally, by which the fused layers are made into secure joint parts. The joined body of the blank (t) and the blank (b) is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering target, and more particularly to a sputtering target (hereinafter simply abbreviated as a target material) having a high bonding strength with a backing plate and a high heat resistance. The present invention relates to a sputtering target with less abnormal discharge at the time of the above.

[0002]

2. Description of the Related Art Sputtering involves irradiating the surface of a target material with ion particles such as argon in a high vacuum, and depositing atoms or clusters of several atoms from the surface of the target material. This is a processing method for forming a thin film by depositing it on a substrate, and is widely used in the field of semiconductor thin film circuit formation and the like.

[0003] The target material is usually adjusted to a standard of a sputtering apparatus after bonding a backing plate to the back surface by a method of soldering or diffusion bonding.
Used after cutting the surface. In this specification, the combined target material and backing plate are simply referred to as a target.

The solder used for the above soldering is basically made of an alloy of tin and lead, and has a melting point of about 20%.
It is about 0 ° C. Soldering is performed by forming a molten coating of solder on the respective surfaces of the target material and the backing plate to be joined, and cooling while keeping both surfaces in close contact. The bonding strength by such a method is usually
It is on the order of 4 to 6 Kgf / mm ² .

When the target material and the backing plate are joined by soldering, the temperature of the target material easily rises above the melting point under sputtering under severe conditions because the melting point of the solder is low. In such a case, the solder melts and the target material and the backing plate are separated, leading to a serious accident.

[0006] On the other hand, the bonding surface of the target material or the backing plate usually has an oxide film which causes a reduction in the bonding strength of soldering. Therefore, in general soldering, a flux is used together to avoid the influence of the oxide film on the surface. However, the flux usually contains chlorine and cannot be used for soldering the target material as in the present invention. Therefore, in the joining method by soldering, the adhesive strength tends to vary due to the oxide film.

[0007] The target obtained by bonding by soldering as described above tends to cause abnormal discharge when subjected to sputtering. As a result, particles and the like, which are coarse particles, are generated, and the film characteristics of the sputtered thin film are impaired. It is.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a high bonding strength between a target material and a backing plate, high heat resistance, and abnormalities in sputtering. An object is to provide a target with less discharge.

[0009]

That is, the gist of the present invention is to provide a sputtering target formed by joining a sputtering target material and a backing plate.
A sputtering target characterized in that a sputtering target material and a backing plate are joined by friction welding.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The target of the present invention is characterized in that the target material and the backing plate are joined by a friction welding method.

The above-mentioned target material is usually formed by subjecting a material for the target material to plastic working such as pressing or rolling and heat treatment to reduce the grain size of the internal structure and cutting out the material to a predetermined size. As the material for the above target material, aluminum, aluminum alloy, titanium,
Examples include copper, nickel, cobalt, tantalum, platinum and the like. Among them, aluminum alloy has excellent electric conductivity,
Since the price is relatively inexpensive, it is widely used as a target material for various uses.

The above-mentioned backing plate is joined to the back surface of the target material, and the back surface is passed with cooling water or set in a water-cooled jacket. Then, the target material is cooled through the cooling of the backing plate. As the material for the backing plate, a material having excellent thermal conductivity is usually used, and examples thereof include copper or a copper-based alloy, aluminum or an aluminum-based alloy, titanium, and stainless steel.

[0013] The above friction welding method is a method in which, while applying pressure to both surfaces to be joined, they generate heat by rubbing each other to form a molten layer on the joining surface, then stop the friction and cool as it is to join. Is the way. As the friction welding method, for example, a method using an automatic friction welding machine can be mentioned.

Hereinafter, a method of manufacturing the target of the present invention will be described by taking a friction welding method using an automatic friction welding machine as an example.

The friction welding is usually performed at the stage of a cylindrical target material before plastic working and a cylindrical backing plate material having substantially the same outer diameter as the target material. The diameters of the two materials before the plastic working are appropriately determined in consideration of an increase in the thickness (outer diameter) due to the plastic working in the subsequent process.
It is 0 mm or more, preferably 50 to 300 mm. In addition, their length is usually 100 to 400 mm, though it depends on the size of the above-mentioned automatic friction welding machine.

First, the target material and the backing plate material before the plastic working described above are fixed to the chuck and the tip of the spindle of the fixing table of the automatic friction welding machine, respectively. Then, the spindle is rotated to rotate the backing plate material at a high speed in a state in which the front surface of the backing plate material is pressed against the front surface of the target material. Pressure in the above pressure welding,
Both the rotation speed and the rotation time are appropriately determined to the extent that the interface portion is heated and melted depending on the material of both materials, but are usually about 1 to 10 kgf / mm ² , respectively,
000 rpm, 1 to 30 seconds.

As described above, the contact surfaces of the target material and the backing plate material before the plastic working generate heat due to mutual friction, and finally a molten layer is formed on the contact surfaces. Then, the rotation is stopped as it is in the state where the molten layer is formed, and by natural cooling, the molten layer solidifies to a strong joint, and the material for the target material and the material for the backing plate before plastic working are formed. A conjugate is obtained. The above friction welding method can be applied even if the material of the target material and the material of the backing plate are different, and the operation time is extremely short. In addition, since the above-described joining is performed by fusing the materials, the joining strength is higher and the heat resistance of the joining is remarkably higher than in the case of soldering.

At the time of the above-mentioned joining, the oxide film formed on both joining surfaces of the target material material and the backing plate material before the plastic working is scraped off at the time of friction rotation and extruded to the peripheral edge of the joining surface. Even if both surfaces for joining are not pretreated, they do not hinder joining. The extruded metal or oxide film can be removed by cutting after cooling.

The joined body joined as described above has a necessary target material portion in consideration of the thickness of the target material layer and the backing plate layer of the target and a dimensional change due to plastic working in a later step. Cut and remove the excess part, leaving the length of the backing plate material part. Then, by a known method such as pressing or rolling, a predetermined processing rate (thickness reduction rate by rolling or pressing)
After subjecting the joined body to plastic working so as to obtain, heat treatment is performed. And, further, the target is cut out to the standard size of the sputtering apparatus, and the front and back surfaces are cut,
Served for use.

[0020]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention.

Example 1 A cylinder having a diameter of 150 mm and a length of 250 mm was cut out from a billet of an aluminum alloy material containing 0.5% by weight of copper manufactured by a continuous casting method, and used as a target material.

Separately, a billet made of an aluminum alloy material containing 1% by weight of silicon and 0.5% by weight of copper was prepared from a billet of 150 mm in diameter and 25 mm in length in the same manner as the target material.
A 0 mm cylinder was cut out and used as a backing plate material. The above-described target material was fixed to a chuck of an automatic friction welding machine ("FW170U type automatic friction welding machine" manufactured by Shimizu Metal Co., Ltd.). The aluminum alloy backing plate material was fixed to a work gripping adapter attached to the tip of a spindle of an automatic friction welding machine.

Then, the spindle support table is moved to press the backing plate material against the target material so as to have a contact stress of 2.5 kg / mm ² .
While maintaining the pressure, the spindle was rotated at a rotation speed of 700 rpm. When the above rotation is continued for 10 seconds, the two pressure contact interfaces between the target material and the backing plate generate heat due to friction, a molten layer is formed at the interface, and the target material and the backing plate material are integrated by the molten layer at the interface. Had become. Then, at that time, the rotation was stopped and the mixture was naturally cooled to obtain a joined body. Such a joining operation was completed in about 10 minutes.

After cooling, the peripheral side surface of the joined body was cut to remove the surface oxide film and the extruded portion extruded on the peripheral side surface of the joined portion. The joint was inspected for defects. As a result, the defect echo was 10% or less, and the bonding state was good.

Approximately 140 mm from both ends of the above joined body
After being cut and removed one by one, the remaining portion was compressed (plastically processed) by a press so as to have a processing rate of 85%, and then heat-treated for recrystallization. Both end surfaces of the obtained joined body were cut into planes to reduce the thickness of the target material portion to 6 mm and the thickness of the backing plate portion to 9 mm, and then cut out a target having a diameter of 250 mm. In addition, about 4.
Six 5 mm round tensile test pieces were cut out, and the bonding strength was measured. As a result, the average was 14 kgf / mm ² .

Sputtering equipment (M manufactured by Nippon Vacuum Engineering Co., Ltd.)
LX3000), the target was set in a water-cooled jacket, and sputtering was performed. A silicon wafer having an outer diameter of 6 inches was set as a substrate to be sputtered. The sputtering operation is performed for 75 seconds,
As a result, an aluminum alloy thin film having a thickness of about 1 μm was formed on the silicon wafer.

Then, the number of abnormal discharges occurring during the above sputtering was measured. Measurement of the number of abnormal discharges
First, the above-mentioned sputtering is performed on 96 wafers as pre-sputtering, and subsequently, sputtering is performed on 12 wafers.
The monitoring was performed by monitoring the fluctuation of the discharge voltage during the subsequent 12 sputterings. Abnormal discharge is 1
The case where there was a change of 0% or more was counted. As a result, the number of abnormal discharges during sputtering of 12 wafers was 16 in total.

Comparative Example 1 A target was prepared in the same manner as in Example 1 except that the method of joining the target material and the material for the backing plate and performing plastic working were performed, and the bonding strength and the number of abnormal discharges were measured. .

As a material for the target material and a material for the backing plate before the plastic working, a 50 mm-thick piece was cut out from an aluminum alloy billet having the same composition as that used in Example 1 and both materials were pressed by 15 mm each.
mm (a processing rate of 85%), and then a heat treatment for recrystallization was performed to obtain a target material and a backing plate, which were joined by soldering to produce a target.

In the above-mentioned joining by soldering, the target material and the backing plate are placed on a hot plate for two minutes.
After heating to 30 ° C., tin / lead having a melting point of 183 ° C. = 62/3 on the respective surfaces of the target material and the backing plate.
After placing solder having a eutectic composition of No. 8 and heating and melting to uniformly coat each surface, the two solder coated surfaces are brought into contact with each other,
The cooling was performed under a load. Such a series of joining operations required about 60 minutes.

After cooling, both surfaces of the solder and the joined body extruded on the peripheral side of the joining surface of the obtained joined body are cut to reduce the thickness of the target material portion to 6 mm and the thickness of the backing plate portion to 9 mm. After that, a target having a diameter of 250 mm was cut out. Furthermore, about 4.5 mm from the remaining part
Example 1 Six test pieces for a tensile test of a circle were cut out.
As a result of measuring the joining strength by the same method as in the above, the average was 5 kg.
f / mm ² . The number of abnormal discharges was measured for the cut target in the same manner as in Example 1. As a result, the number of abnormal discharges during the sputtering of 12 wafers reached a total of 44 times.

As described above, the target described in Example 1 in which the target material and the backing plate were joined by friction welding was shorter in joining operation time and the joining strength than the target in Comparative Example 1 joined by soldering. It was confirmed that the occurrence of abnormal discharge was small when subjected to sputtering. Furthermore, since the target of Example 1 does not use solder having a low melting point for bonding, the target has high heat resistance.

[0033]

According to the present invention described above, since the target is joined to the target material and the backing plate by friction welding, the joining operation can be performed in a short time, and the joining strength is large and the joining operation is large. A target having high strength and high heat resistance and having less abnormal discharge during sputtering can be provided, and the industrial value of the present invention is great.

Claims (1)

[Claims] 1. A sputtering target formed by joining a sputtering target material and a backing plate, wherein the sputtering target material and the backing plate are joined by friction welding.