JPH07316802A - Mosaic target and its production - Google Patents

Abstract

PURPOSE:To relieve shearing stress produced by the difference in thermal expansion in a solid phase joined mosaic target and to prevent the deformation of the materials and peeling at the joined interfaces during solid phase joining or in a subsequent working process. CONSTITUTION:When a mosaic target is composed of plural pieces 1, 2 of different materials, opposite key grooves 4 are cut in the joining faces 3 of adjacent pieces of the different materials, a key 5 is fixed in each through hole formed by the opposite key grooves and the pieces are subjected to solid phase joining along the joining faces 3 to produce the objective mosaic target. Since solid phase joining is carried out while restraining the expansion of each piece having a high coefft. of thermal expansion with the keys, shearing stress produced by the difference in thermal expansion is relieved and peeling at the joined interfaces is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-phase-bonded mosaic target composed of a plurality of pieces of different materials and a method for manufacturing the same, and in particular, it is necessary to dispose adjacent heterogeneous heterogeneous targets in order to prevent separation at the bonding interface. A key groove formed opposite to each other at one or more positions on respective joining surfaces of the pieces of material, and a key fitted into a through hole formed by the opposed key groove. The present invention relates to a mosaic target and a method for manufacturing the same.

[0002]

2. Description of the Related Art A target is usually a disk-shaped plate which serves as a sputtering source for forming electrodes, gates, wirings, elements, insulating films, protective films, etc. of various semiconductor devices on a substrate by sputtering. . When the accelerated particles collide with the target surface, the atoms constituting the target are released into space by the exchange of momentum and are deposited on the facing substrate. As a sputtering target, A
l and Al alloy targets, refractory metals and alloys (W,
Mo, Ti, Ta, Zr, Nb etc. and their alloys such as W-Ti) targets, metal suicides (MoSi _x ,
Targets such as WSi _x , NiSi _x, etc. have been typically used.

Generally, as a method for producing an alloy or compound target having two or more components, an alloy or compound target is prepared by a melting method or a powder metallurgy method, but there are problems such as density, composition and oxygen concentration. When a good quality target cannot be obtained by such a method, a mosaic method is often adopted. The mosaic method is a process in which a single component or its alloy or compound is processed into an appropriate shape when the target has two or more components, and these are appropriately combined to form a disc or square plate as a whole. However, the target composition is set as the whole target. The targets thus combined and arranged are called mosaic targets. In this mosaic target, a bulk or plate material of a single component or its alloy or compound processed into an appropriate shape, which forms a constituent unit and is arranged in a butt relationship, is called a piece.
For example, in a Ta-Mo mosaic target, Ta pieces and Mo pieces are arranged alternately in stripes or in a radial pattern. Examples of the mosaic target include Ta-W and Ta-T in addition to the Ta-Mo target described above.
Examples of the target include a target made of an alloy of a refractory metal such as i and W-Ti, and a silicide target. In the metal silicide target, metal pieces and silicon pieces are arranged alternately in stripes or in a radial pattern.

In the conventional mosaic target, each piece is abutted and bonded to the backing plate as it is by using a brazing material such as In, or is directly burned on the backing plate. However, according to this method, a gap of several μm to several hundreds μm is generated on the abutting surfaces, abnormal discharge occurs in this portion, or the spattering speed is locally increased to cause a particle generation source, or a brazing material or When the backing plate material was sputtered together, the sputtered film was contaminated and the film characteristics were deteriorated.

The "particles" refer to particles dispersed in the apparatus during the formation of a thin film by sputtering, which are clustered and deposited on the substrate. The clustered particles have a diameter of several μm. When it is deposited on the substrate, for example, L
In the case of SI, problems such as short-circuiting of wiring or conversely disconnection occur, which causes an increase in defective rate. These particles are due to the particles emitted from the target.

In order to prevent the raw material or the backing plate material from being directly sputtered, a method of step-processing or obliquely cutting the abutting surfaces of the pieces has been adopted.
The piece of material A and the piece of material B were bonded to the backing plate so that the backing plate and the butted portion were concealed from the sputter surface by abutting the stepped surface or the abutted surface. However, even with this method, abnormal discharge and generation of particles cannot be avoided.

The present inventor has previously found that such a problem can be solved by solid-phase joining between adjacent pieces of a mosaic target by HIP, hot pressing, explosive welding, etc., and is composed of a plurality of pieces. We succeeded in developing a mosaic target characterized in that the abutted portions of the pieces were solid-phase joined (Japanese Patent Application No. 5-196712). What is explosion?
It is a method of joining by utilizing the instantaneous high pressure of the explosion of explosives.

[0008]

When this diffusion bonding mosaic target is used, spattering can be carried out under stable conditions without abnormal discharge or generation of particles, and the sputtered film produced is a brazing material or a backing. There was no contamination by the plate material and it showed high quality film characteristics. However, with the recent increase in the size of the target, in the method of solid-phase joining the joints of each piece in a plane-like manner,
When the coefficient of thermal expansion of each piece is significantly different, shear stress is generated at the joint interface due to the difference in thermal expansion, and the material deforms or peels off at the joint interface to reduce the shear strength of the joint interface. It became a problem again. In the case of a sputtering target, after solid-phase joining of pieces, mechanical processing such as cutting, cutting, and polishing into a desired shape is performed. In any process, if the bonding strength is insufficient, the bonding interface is likely to peel during processing,
Product yield is poor.

The object of the present invention is to reduce the shear stress caused by the difference in thermal expansion in the solid phase bonding mosaic target and prevent the deformation of the material and the peeling at the bonding interface during the solid phase bonding or the subsequent processing steps. Is to establish.

[0010]

DISCLOSURE OF THE INVENTION The present inventor has found that it is very effective to provide a key and a key groove on the joint surface in order to reduce the shear stress caused by the difference in thermal expansion at the joint interface. I arrived. The shear stress caused by the difference in thermal expansion is relaxed by restraining the expansion of the piece having a large coefficient of thermal expansion by the key fitted into the through hole formed by the opposed key groove while solid-phase joining, and at the joining interface. Can be prevented. Thus, the present invention provides (1) a mosaic target composed of a plurality of pieces of different materials, which are formed at one or two or more positions on the respective bonding surfaces of adjacent pieces of different materials facing each other. And a key fitted into a through hole formed by the opposing key groove, and solid-phase bonded to each other along the bonding surface. It is preferable that the key to be fitted is one of the adjacent materials of different kinds of materials constituting the mosaic target. It is preferable that all bonding surfaces including the interface between the key and the through hole are solid-phase bonded. The present invention also provides (2) a method of manufacturing a mosaic target composed of a plurality of pieces of different materials, wherein the keyways are opposed to each other at one or more positions on the joint surface of each piece of the different materials. Provided is a method for manufacturing a mosaic target, which is characterized in that the key is fitted into a through hole formed by the facing key groove and the keys are solid-phase bonded to each other along the bonding surface.

[0011]

[Function] In solid-state bonding, solid materials are placed in contact with each other,
It is a method of joining solids by diffusion of atoms at the contact interface or by interatomic force by applying appropriate pressure at appropriate temperature. By solid-phase joining the abutting parts of each piece of the mosaic target, the gaps in the abutting parts can be eliminated, and abnormal discharge due to the gap and contamination of the sputtered film due to simultaneous sputtering of the brazing material or backing plate material can be avoided. . By providing a key groove and a key on the joint surface to relieve the shear stress caused by the difference in thermal expansion at the joint interface, solid-phase joining is performed by restraining the expansion of the piece with a large coefficient of thermal expansion, and It relieves the shear stress that occurs and prevents peeling at the joint interface.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a refractory metal alloy (W, Mo, Ti, Ta, Zr, Nb, etc.) target, metal silicide (MoSi _x , WSi _x , NiS).
i _x, etc.) targets, intermetallic compound targets, etc. In particular, the present invention is adopted when a high-quality target cannot be produced due to problems such as density, composition, and oxygen concentration depending on the melting method or powder metallurgy method, or when melting is difficult, and especially thermal expansion between different materials. This is useful when the difference between the coefficients is large. Preferred examples thereof are Ta-Mo, Ta-W, Ta-T.
i, an alloy mosaic target of a refractory metal such as W-Ti.

As described above, the solid phase joining is to join the solid materials together by a diffusion action, an atomic force, etc. by placing the solid materials in contact with each other and applying an appropriate pressure at an appropriate temperature. By applying the solid phase bonding method to the mosaic target, the mosaic target can be integrated by eliminating the gaps between the pieces without substantially sacrificing the density, composition and other characteristics of each target piece. Pieces composed of blocks or plate materials of a single component or an alloy or compound thereof are arranged in abutted state in combination so as to constitute a desired mosaic target. Solid phase bonding can be achieved by methods such as HIP, hot pressing, and bombardment. Bonding at the piece interface can be brought about by applying an appropriate pressure at a temperature suitable for the target material or holding it for a certain period of time without load.
The bonding temperature and pressure depend on the materials and the bonding method used. For example, in the case of solid-state bonding by HIP or hot pressing of a target in which Ta pieces and Mo pieces are combined, 700 to 2000 ° C., preferably 1000 to 15 ° C.
Solid state bonding is possible in a temperature range of 00 and a load range of 1000 to 1500 atm. The target-bonding material thus solid-phase-bonded is sliced in the length direction to a predetermined target thickness and machined to have a predetermined target diameter.

FIG. 4 shows an example of arrangement of target pieces and an example of application of pressure. Here, (a) is a state in which block-shaped pieces 1 of material A and pieces 2 of material B are alternately arranged in a radial pattern, and they are solid-phase bonded by, for example, HIP to form a right columnar target bonding material. Indicates. (B)
Indicates a target bonding material in which flat pieces A of material A and pieces 2 of material B are alternately stacked and solid-phase bonded by, for example, hot pressing. The solid-phase bonded target bonding material is machined into a target having a predetermined diameter and thickness. However, in the method of solid-phase joining the joints of each piece in the same plane, when the thermal expansion coefficient of each piece is significantly different, shear stress is generated at the joint interface due to the difference in thermal expansion, and the shear strength of the joint interface is increased. As a result, the material may be deformed or peeling may occur at the bonding interface. This is especially likely to occur with large size targets.

Therefore, according to the present invention, as shown in FIG. 1, when a flat piece 1 of material A and a flat piece 2 of material B are alternately superposed and solid-phase bonded to each other, adjacent pieces 1 and The key groove 4 is formed on each of the joint surfaces 3 of the two so as to face each other, and the key 5 is fitted into the through hole formed by the key grooves 4 facing each other. After fitting the key half part in the key groove of the first material and then fitting the key half part projecting into the key groove in the next material, the pieces 1 and 2 may be arranged in a necessary number of layers. Alternatively, the key may be inserted into the formed through hole after stacking a required number of pieces. In this way, solid-phase joining is provided along the joining surface 3 with the key fitted in the key groove. For example, when the material of the piece 1 is Ta having a large thermal expansion and the material of the piece 2 is Mo having a small thermal expansion, the expansion of Ta having a large thermal expansion is restricted by the key and the small thermal expansion Mo into which the key penetrates,
The shear stress generated at the bonding interface is contained between the keys without being propagated to both ends. The paper surface of FIG. 1 constitutes the target sputtering surface. The dimension in the direction perpendicular to the paper surface of FIG. 1 is the target thickness direction. When the dimension of the solid-phase joined body in the target thickness direction is large, it is sliced into an appropriate target thickness.

In FIG. 1, one key groove is formed near both ends, but the invention is not limited to this. More keyways and keys may be provided at appropriate intervals, including in the center. It is preferable that all of the key groove and the key have the same shape, and that the positions of the key groove and the key are aligned in the overlapping direction (vertical direction in FIG. 1). As the material of the key, either material A or material B is used. In FIG. 1, all keys aligned in the overlapping direction on the one end side are made of the same material A, and all keys aligned in the overlapping direction on the other side are made of the same material B. This makes it possible to make the binding action the same on each bonding surface while maintaining the composition ratio of the entire target. However, every other key that is aligned in the overlapping direction on the one end side is made of material A
It is also possible to use the material B for every other key aligned in the overlapping direction on the other side.

As shown in FIGS. 2 (A), 2 (B) and 2 (C), the key has a cylindrical shape with a circular cross section, a square shape with a cross section,
It can be a prism such as a rectangle, a rhombus, or a hexagon. The keyway has a cross-sectional shape such as a semi-circle, a half-angle, a triangle, etc. to receive the half of the key. The size of the key is such that the key is located within 0.1 mm from the inner peripheral surface of the through hole formed by the key groove. A simple shape of the keyway and key is sufficient to save the raw material processing ratio. The presence of a slight gap is useful for absorbing the thermal expansion of high thermal expansion materials, while too large a gap does not result in a solid phase bond between the key and the keyway.

The depth of the key groove (that is, the size of the key) is appropriately determined depending on the material and the piece thickness. If the depth of the key groove is small, the shear stress relaxation effect is small, while if it is too large, the amount of material processed increases. The depth of the keyway can be in the range of approximately 5-30% of the piece thickness.

A similar restraining action can be obtained by forming a concavo-convex taper step along the joint interface of the pieces to be joined, instead of providing a key groove, but when the concavo-convex taper step is provided, a complicated shape is required. Since processing to
It is more advantageous to form the key and the key groove in terms of the raw material processing ratio.

(Examples and Comparative Examples) Ta pieces and Mo pieces having dimensions as shown in FIG. 3 were prepared (only two pieces are shown). The Ta piece and the Mo piece have the same dimensions. The keyway was semi-circular and a cylindrical key was used. In FIG. 3, the dimensions of each display are as follows: L = 500 mm, L ₁ = 50 mm, D = 30 mm, d =
3 mm. The length of these pieces in the direction perpendicular to the paper surface (length in the thickness direction of the product) was 100 mm. In FIG. 3, the key near the right end is made of Ta and the key near the left end is made of Mo. These pieces were alternately stacked and solid-phase bonded by HIP using a HIP capsule at 1400 ° C. and a pressure of 1000 atm. The solid phase bonded product was machined into a 4-inch target. After solid-phase bonding, the bonded part is SEM
It was confirmed by observation that there were no gaps. No material deformation occurred and no delamination between the pieces occurred during machining. When the key and the key groove were not provided, peeling of the material occurred.

A target on which a piece having a key and a key groove was solid-phase bonded was bonded to a Cu backing plate using an In brazing material. This was actually sputtered, the state of abnormal discharge during sputtering was observed, and the characteristics of the sputtered film produced were evaluated. As a result of sputtering this target assembly under the following sputtering conditions, abnormal discharge was zero in 10 minutes. From the sputtered film, Cu that constitutes the backing plate and In that constitutes the brazing material.
None was detected. (Sputtering conditions): Atmosphere: Ar Pressure: 0.5 Pa Power density: 5 W / cm ² Substrate: Corning 7059 glass Substrate temperature: Room temperature

[0022]

[Effects of the Invention] In the solid phase bonding mosaic target,
We have succeeded in remarkably increasing the yield of target manufacturing through the establishment of the technology to alleviate the shear stress caused by the difference in thermal expansion and prevent the material from deforming and peeling at the bonding interface during solid phase bonding or in the subsequent processing steps.

[Brief description of drawings]

1 is a top view of an exemplary mosaic target consisting of a piece of material A and a piece of material B having keys and keyways according to the present invention. FIG.

2 (A), (B) and (C) illustrate key configurations. FIG.

FIG. 3 Ta using the cylindrical key used in the examples
It is a top view which shows the dimension shape of a piece and Mo mosaic piece.

FIG. 4 shows an example of arrangement of target pieces and an example of application of pressure. In FIG. 4A, two kinds of block-shaped pieces are alternately arranged in a radial pattern, and solid-phase bonding is carried out by HIP to form a right columnar target bonding material. The produced state is shown, and (b) shows a state in which two types of flat plate-like pieces are alternately stacked and a target joining material is produced by solid-state joining by hot pressing.

[Explanation of symbols]

 1 piece of material A 2 piece of material B 3 joining surface 4 keyway 5 key

Continued Front Page (72) Inventor Issei Takahashi, 187 Usba, Hwagawa-cho, Kitaibaraki-shi, Ibaraki 4 Japan Energy Isohara Factory

Claims (4)

[Claims] 1. In a mosaic target composed of a plurality of pieces of different materials, a key groove formed at one or more positions on each joining surface of adjacent pieces of different materials facing each other. A mosaic target, comprising a key fitted into a through hole formed by the opposed key grooves, and being solid-phase bonded to each other along the bonding surface. 2. The mosaic target according to claim 1, wherein the key to be fitted is one of adjacent materials of different kinds of materials constituting the mosaic target. 3. The mosaic target according to claim 1, wherein all the bonding surfaces including the interface between the key and the through hole are solid-phase bonded. 4. A method of manufacturing a mosaic target composed of a plurality of pieces of different materials, wherein key grooves are formed so as to face each other at one or more positions on a bonding surface of each piece of the different materials. A method of manufacturing a mosaic target, characterized in that a key is fitted in a through hole formed by the opposed key grooves, and the keys are solid-phase bonded to each other along a bonding surface.