JPH0718432A - Cathode for sputtering and its production - Google Patents

Abstract

PURPOSE:To produce a cathode for sputtering ensuring a high rate of film formation by making it possible to apply high sputtering power to the ceramic cathode for sputtering without destructing the cathode. CONSTITUTION:A metallic material 2 having >=0.1mm thickness is tightly bonded to the entire bottom and/or side of a ceramic target plate 1. A metallic material having >=0.1mm thickness is tightly bonded to the entire bottom and/or side of a ceramic target plate retaining compressive stress. A metallic material having >=0.1mm thickness and a higher coefft. of thermal expansion than a ceramic target plate is tightly bonded to the target plate in an atmosphere at a temp. above room temp. A metallic compd. as powdery stock is tightly bonded by hot pressing to the top of a metallic section having >=0.1mm thickness. Thereby, the rate of film formation is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode for sputtering used for forming a metal compound film on a substrate, which is suitable for forming the film at high speed.

[0002]

2. Description of the Related Art Conventionally, when a metal compound film such as a metal oxide film is formed by a sputtering method, the following two methods are widely used. One of them is to use a cathode in which a metal target for forming a target compound film is bonded to a backing plate with a bonding material of a low melting point metal such as indium, and during sputtering film formation while cooling the backing plate. Is a so-called reactive sputtering method in which a reactive gas such as oxygen is mixed with a sputtering gas such as Ar to form a film. The other is to target a mass of ceramics of a target compound film material, This is a method in which a cathode adhered to a backing plate with a low-melting metal bonding material is used, and while the backing plate is cooled, sputtering film formation is performed with a sputtering gas of an inert gas.

[0003]

In the case of the former metal target, a simple direct current method can be used as a sputtering method, and it has an advantage that film formation can be carried out at a relatively high speed, but the composition of the film obtained with respect to the composition of the target. There are drawbacks such as a large deviation and a stable and homogeneous alloy target cannot be produced when the composition includes an active metal material. On the other hand, in the latter sputtering method targeting a mass of ceramics, it may be necessary to add a slight amount of reaction gas.
Although there is almost no compositional deviation and it does not hinder the production of a target having a desired composition, in general, this type of target has a high electric resistance, it is necessary to use a high frequency sputtering method, and the film formation rate is slower than the former. It is a drawback.

The sputtering power applied to the cathode and the film formation rate are generally in a proportional relationship. Therefore, in order to increase the film formation rate, the applied power should be increased as much as possible. The surface of the target is heated by the plasma impact as the power is increased, but in the former case, the target is a metal material, so the heat conduction is good, and if the cooling of the backing plate is sufficient, the bonding material will not melt, Further, since the target has good rigidity and brittleness, even if there is a slight temperature difference between the upper surface and the lower surface of the target, the target is not destroyed, and thus high power can be applied. On the other hand, in the latter case, the mass of ceramics used as the target is worse than in the former case, and if too much power is applied, a large temperature difference easily occurs between the upper and lower surfaces of the target, and the amount of thermal expansion between the upper and lower surfaces is increased. However, since the target material has low rigidity and high brittleness, the target is cracked and broken. Further, in this case, there is a disadvantage that the target tends to extend in the radial direction of the target due to the temperature rise and cracks tend to occur. Further, the bonding material exudes from the cracked portion and the bonding material is mixed into the film, so that the film characteristics may be deteriorated. Therefore, when using ceramics as a target,
Since high power could not be applied, a high film formation rate could not be obtained.

A first object of the present invention is to provide a sputtering cathode which is capable of applying a high sputtering power to a sputtering cathode using ceramics as a target material without destroying the sputtering cathode and thereby obtaining a high film forming rate. A second object of the present invention is to provide a method of manufacturing a sputtering cathode suitable for this.

[0006]

According to the present invention, a ceramic target plate having a thickness of 0.
By firmly adhering a metal material having a thickness of 1 mm or more, or by firmly adhering a metal material having a thickness of 0.1 mm or more to the entire bottom surface and / or side surface of a ceramic target having a compressive stress, To achieve the purpose of. The second purpose is to firmly fix a metal material having a thermal expansion coefficient larger than that of the ceramic target plate and having a thickness of 0.1 mm or more to the entire bottom surface and / or side surface of the ceramic target plate in an atmosphere at a temperature higher than room temperature. By adhering or by using metal compound raw material powder with a thickness of 0.1 m
It is achieved by firmly adhering to a metal mold material of m or more by a hot pressing method.

[0007]

When the sputtering is carried out using a cathode having a metal material firmly adhered to the entire bottom surface and / or side surface of the ceramic target plate, the composition of the target itself is adjusted. The fact that there is no deviation and that a metal oxide film of the desired composition can be formed on the substrate is the same as in the conventional case, but the sputtering power is increased to increase the film formation rate, and the target plate is heated to a high temperature accordingly. However, the target plate is firmly adhered to the metal material, and the metal material is cooled by a backing plate or the like to have a smaller thermal expansion amount than the target plate, and as a result, the target plate has a compressive stress. Therefore, even if the temperature of the target plate rises, damage such as cracks hardly occurs. That is, although the ceramics target plate according to the inventors' knowledge shows very strong strength against compressive stress, it is weak against tensile stress and easily cracks. Since the target plate has a compressive stress as its temperature rises, it is less likely to be damaged by heat, and the sputtering power can be increased to increase the film formation rate.

When the ceramic target plate has a compressive stress in advance, even if the target plate is heated to a high temperature during sputtering, the generation of tensile stress due to thermal expansion is reduced, and the target is prevented from being damaged by heat. .

The ceramic target plate and a metal material having a coefficient of thermal expansion greater than 0.1 mm and a thickness of 0.1 mm or more are placed in an atmosphere at a temperature higher than room temperature, and the metal material is placed on the bottom surface and / or side surface of the ceramic target plate. When the target is firmly adhered to the target material, the metal material is bonded in a state where the thermal expansion amount is larger than that of the target plate, and when the temperature is lowered thereafter, the metal material contracts more than the target material, and the target material is It becomes a state where compressive stress is accumulated,
In addition, even when the metal compound raw material powder is adhered to a metal mold material having a thickness of 0.1 mm or more by the hot pressing method, the metal material shrinks more than the target material and a compressive stress is applied to the target material. You can make a strong bond with.

[0010]

[Examples] As a result of intensive studies by the inventors, it was found that the plate-shaped ceramic target is very strong against compressive stress but weak against tensile stress and easily cracks. Based on this, as shown in FIGS. 1 and 2, when an attempt was made to firmly bond the metal material 2 having a thickness of 0.1 mm or more to the entire bottom surface of the ceramic target plate 1, the tensile force applied to the target plate 1 was reduced. The stress, that is, the force of the target plate 1 extending outward in the radial direction, is countered by the strength of the metal material 2 adhered to the bottom surface thereof, and the target plate 1 stores compressive stress and even if a high sputtering power is applied. The result is that the target is very hard to break. Similar results were obtained even when the metal material 2 was firmly adhered to the side surface of the ceramic target plate 1 as shown in FIGS. 3 and 4.

When a conventional bonding material made of a low melting point metal such as indium or tin alloy is used to bond the target plate 1 and the metal material 2 to each other, these metals are relatively soft. Cannot withstand the tensile stress of, and the target and the metal material are separated and the required effect cannot be obtained. Therefore, when the target is molded as described later, it is necessary to cause the target and the metal material to react metallurgically to firmly bond them, or to bond them firmly with a bonding material that is not easily plastically deformed. When the metal material is bonded to the backing plate, even if a conventional soft bonding material having a low melting point is used, since the metal material has a structure that resists tensile stress, the target plate is less likely to crack. Bonded target plate 1
The metal material 2 is usually adhered to the backing plate 3 as shown in FIG. 5 and configured as a cathode. However, if the metal material has a thickness of 5 mm or more, the metal material is directly used for the backing plate. Can be used instead. The metal material is required to have a strength capable of withstanding the expansion force of the target plate, and 0.1 mm or more is required to satisfy this strength.

In the development from the above results, when a metal material having a coefficient of thermal expansion higher than that of the target plate is used as the metal material, the result that the target plate is more difficult to crack is obtained. When the ceramic target plate 1 and the metal material 2 are strongly bonded to each other, generally, a bonding material or a metal sheet is interposed between the target plate 1 and the metal material 2 and both of them are heated at a temperature of 100 ° C. or more higher than room temperature. Bonding is performed, or as in Examples described later, the two are pressed at a temperature of several hundreds of degrees Celsius, and their interfaces react metallurgically to directly bond. In such a bonding method, both the target material 1 and the metal material 2 are in an atmosphere at a temperature higher than room temperature, so that both are thermally expanded, and the coefficient of thermal expansion of the metal material 2 is higher than that of the ceramic target plate 1. If it is large, the metal material 2 is bonded in a state in which the amount of thermal expansion is large. After that, when the temperature of both is decreased, the ratio of shrinkage of the metal material 2 is larger, so that compressive stress is stored inside the ceramic target plate 1. To be done. Therefore, when sputtering is performed with high power using the cathode made of the ceramic target plate 1 and the metal material 2, even if the target plate 1 is heated and tries to expand, compressive stress is accumulated inside the target plate 1. Even at high temperatures, it does not turn into tensile stress, becomes very strong against cracking, and enables high-speed film formation.

Specific examples of the present invention will be described below. (Example 1) A stainless steel plate having a thickness of 0.1 mm was formed on the entire bottom surface of a disc-shaped ceramic target plate 1 as shown in FIG. 1 having an outer diameter of 4 inches and a thickness of 6 mm obtained by firing SrTiO ₃ powder. The material 2 is firmly bonded using an AgSn-based alloy, and the metal material 2 is further backed by a copper backing plate 3
Bonded using indium. This is used as a cathode in a vacuum chamber of a batch type sputtering apparatus, the vacuum chamber is evacuated to 1 × 10 ⁻⁴ Pa or less, and then an RF magnetron system is introduced while introducing 0.1 Pa of Ar and 0.01 Pa of O ₂ gas. To form a film on a Si substrate. FIG. 6 shows the relationship with the film formation rate when the power of the cathode is gradually increased. In this case, at 1280 W or less, there is no change in the surface of the target plate 1 and 20 nm /
Although a film forming rate of min was obtained, it was confirmed that when 1600 W was applied, the surface of the target plate 1 was cracked and the edge portion was slightly chipped. For comparison with this, a ceramic target plate having an outer diameter of 4 inches and a thickness of 6 mm obtained by firing SrTiO ₃ powder is directly bonded to a copper backing plate by using indium, and is used as a cathode to form a vacuum chamber of the above apparatus. And sputtering was performed under the same conditions as in the above example. When the power input to this cathode is increased,
The target plate cracked at 400 W, and indium ooze out from a part of the crack. The film forming rate at this time was about 5 mn / min.

(Embodiment 2) A stainless ring-shaped metal material 2 as shown in FIG. 1 is attached to the side surface of a ceramic target plate 1 having the same material and dimensions as those of Embodiment 1, and indium is attached to a backing plate. Used and bonded. Using this as a cathode, sputtering was performed in the same apparatus as in Example 1 under the same conditions. The thickness of the metal material is 1
mm. The relationship between the increase in the power input to the cathode and the film formation rate was almost the same as in FIG. 6, but the power when the target plate cracked increased to 2100W.

(Embodiment 3) FIG. 7 and FIG. 8 as the metal material 2.
The thickness of the flange on the outer periphery of the target as shown in 3m
m, the thickness of the bottom is 5 mm, the diameter is 4 inches, and the depth is 6 mm. A dish-shaped metal material is prepared, and ordinary indium is used for the metal target plate 1 having the same material and size as those of the first embodiment. Bonded. This was directly attached to the same apparatus as in Example 1 as a cathode without using a backing plate, and sputtering was performed under the same conditions as in Example 1 while increasing the input power. The relationship between the increase in the power input to the cathode and the film formation rate was almost the same as in FIG. 6, but the power when the target plate cracked increased to 2500 W.

[0016] (Example _{4) Ba 0. 5 Sr 0} . 5 · TiO 3 powder outer diameter 4 inches were sintered, providing a plurality of disc-shaped target plate thickness 6 mm, the respective Thickness of 10mm
The Cu, Ti, and Mo metal materials were bonded together. The bond is
A Ti sheet having a thickness of 0.3 mm was sandwiched between the target plate and the metal material and heated to about 900 ° C. while applying force to both. Then, as in Example 1, the metal material was bonded to a backing plate, and sputtering was performed using this as a cathode. The sputtering power was gradually increased, and the power when the target plate was cracked and the film forming rate at that time were as shown in Table 1. (Example _{5) Ba 0. 5 Sr 0} . 5 · when TiO ₃ of the powder is sintered, 7, and preparing a metal material Ti of the shape shown in FIG. 8, the powder to the recess Then, the powder was sintered by a hot pressing method while applying force from above, and this was directly used as the cathode. The sputtering power applied to the cathode and the film formation rate are shown in FIG. When 3500 W was applied, a very high film formation rate of 57 nm / min was obtained, but fine cracks were found on the surface of the target plate. After that, when the applied power is continuously increased, the film forming rate is 75 nm / min at 4000 W and 8 nm at 4500 W.
7 nm / min, the cracks gradually became larger, and the discharge was not stable at 5000 W, and the film formation rate was 60 n.
It fell to m / min and the target was shattered.

In the case of Comparative Example 1 described above, when sputtering with a high applied power is performed on a ceramic target plate made of SiTiO ₃ , the surface of the target plate becomes high in temperature and tends to thermally expand. Since the target plate and the backing plate are bonded with soft indium, the target plate can freely stretch. Since the ceramic target is brittle against tensile stress, cracking occurs, and in some cases low-melting-point indium exudes from the cracked part and reaches the surface of the target plate, so indium is mixed into the film and causes deterioration of film characteristics. . On the other hand, in Example 1, since the ceramic target plate is firmly adhered to the stainless metal material, even if the target plate tries to expand due to thermal expansion, the expansion amount of the cooled metal material is smaller than that. Since it is small, a compressive stress is generated inside the target plate and it becomes difficult to crack even if a large power is applied, and as a result, a high film formation rate can be obtained. Similarly, in Example 2, the expansion of the ceramic target plate is suppressed by the metal material of the outer peripheral ring, and in Example 3, the metal material surrounding the bottom surface and the side surfaces suppresses the expansion of the target material. Is less likely to crack, and a high film formation rate can be obtained. Further, in Example 4, since the materials of the metal materials are various and the respective thermal expansion coefficients are different, the compressive stress accumulated inside the ceramic target plate is large and small, but in all cases, the room temperature state Since it already has compressive stress, even if the applied power is increased and the temperature of the target plate rises and thermal expansion is attempted, tensile stress does not occur and cracks and cracks are less likely to occur. In addition, in Example 5, the structure is such that the bottom surface and side surfaces of the ceramic target plate are subjected to compression, and furthermore, the target plate and the metal material of Ti react at the interface and are firmly adhered, so that it is extremely It has a structure that is hard to break. T used as a metal material for this
Since i is also an element constituting the target plate, there is no possibility that impurities will be mixed even if the target plate is cracked, and if the cracks are to some extent, there is an advantage that film formation can be continued.

In the above examples, SrTiO ₃ and (Ba, Sr) Ti were used as the material of the ceramic target plate.
O ₃ was used, but instead of (Pb, Zr) Ti
_{O 3, MgO, TiO 2,} LiNbO 3, Ta 2 O 5 or the like oxide target plate, Si ₃ N _4, may be used a nitride target plate such as AlN. Further, as the metal material, W, Ta, Nb, alloys thereof, or the like may be used in addition to those described in the above embodiments.

[0019]

As described above, according to the present invention, in a sputtering cathode in which a ceramic target plate is used, the entire bottom surface and / or side surface of the target plate is made of a metal material having a thickness of 0.1 mm or more. By adhering to the target, it is possible to suppress the thermal expansion of the target plate when the sputter power is increased and to prevent tensile stress from being generated in it, so that a large sputter power can be stably applied, and as a result, a high sputtering power can be obtained. There is an effect that the film speed can be obtained, and also by making the target plate retain a compressive stress, it is possible to prevent the generation of tensile stress due to its thermal expansion, and the same effect can be obtained. Furthermore, the metal material has a coefficient of thermal expansion larger than that of the ceramic target plate and has a thickness of 0.
1 mm or more and firmly bond it to the target plate in an atmosphere at a temperature higher than room temperature, or firmly bond metal compound raw material powder onto a metal mold material with a thickness of 0.1 mm or more by hot pressing. By doing so, it is possible to easily manufacture a cathode in which the target plate has a compressive stress.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention.

2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a perspective view of another embodiment of the present invention.

FIG. 4 is a sectional view taken along line 4-4 of FIG.

5 is a perspective view showing a state where the ceramics target plate to which the metal material of the embodiment of FIG. 1 is attached is attached to a backing plate.

6 is a diagram showing the relationship between the sputtering power of the cathode and the film formation rate in the embodiment of FIG.

FIG. 7 is a perspective view of a modification of the metal material.

8 is a sectional view taken along line 8-8 of FIG.

9 is a diagram showing the relationship between the sputtering power of the cathode and the film formation rate of an example using the metal material shown in FIG.

[Explanation of symbols]

 1 Ceramics target plate 2 Metal material 3 Backing plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michio Ishikawa 523 Yokota, Yamatake-cho, Sanmu-gun, Chiba Japan Vacuum Technology Co., Ltd. Chiba Institute for Supermaterials (72) Inventor Hisami Nakamura 523 Yokota, Yamatake-cho, Sanmu-gun, Japan Vacuum Technology Co., Ltd. Chiba Institute for Materials Research

Claims (5)

[Claims] 1. A bottom surface of a ceramic target plate and / or
Alternatively, a cathode for sputtering is characterized in that a metal material having a thickness of 0.1 mm or more is firmly adhered to the entire side surface. 2. A thickness of 0.1 m on the entire bottom surface and / or side surface of the ceramic target plate having compressive stress.
A sputtering cathode characterized in that a metal material of m or more is firmly bonded. 3. The sputtering cathode according to claim 1, wherein the metal material is bonded to a backing plate that is cooled during sputtering. 4. The bottom surface of the ceramic target plate and / or
Alternatively, a method for producing a sputtering cathode, characterized in that a metal material having a thermal expansion coefficient larger than that of the ceramic target plate and having a thickness of 0.1 mm or more is firmly adhered to the entire side surface in an atmosphere at a temperature higher than room temperature. 5. A method for manufacturing a cathode for sputtering, characterized in that a metal compound raw material powder is firmly adhered to a metal mold material having a thickness of 0.1 mm or more by a hot pressing method.