JPH04285159A - Sputtering device - Google Patents

Abstract

PURPOSE:To prevent a crack of a target during sputtering and to enhance the throughput of a sputtering device by expandably holding the target placed on a target electrode parallel to the sputtering face thereof. CONSTITUTION:A film having the target substance as the constitutional substance is formed on the surface of a base plate by sputtering a target 2 placed on a target electrode. In the target electrode of the sputtering device, the target 2 is fixed to a backing plate (unshown in figure) by the constitutional member 4a of a target pressing fitting. Moreover, the target 2 is held in a stopping state by interposing the gaps 70 with the metal 4a. Thereby the target 2 is made expandable in parallel for the sputtering face and a crack is not caused for temp. rise at a time of sputtering. Furthermore, temp. rise of the target 2 is preferably prevented by providing a sealing material between the backing plate and the target 2, and closely holding a thermal conductive medium such as liquid metal and gas or passing a cooling agent.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a sputtering apparatus,
In particular, the present invention relates to a sputtering apparatus suitable for forming a thick insulating film.

0002

2. Description of the Related Art Sputtering equipment is in increasing demand in various fields as a film forming equipment for various materials. For example, it is used to form an insulating film as a protective film for thin-film magnetic heads, etc., and at this time, a relatively thick film of several tens of microns is applied. When forming such a thick film, the film forming time can be as long as ten or more hours, so there is a strong desire to improve throughput, which indicates the number of wafers processed per unit time. In order to improve throughput, it is necessary to increase the film formation rate or increase the number of substrates processed by increasing the target size. Of course, it would be even better if both were increased.

[0003] Since the film formation rate is proportional to the power input to the target, in order to increase the film formation rate, this input power is increased. In addition, in order to increase the number of substrates processed, for example, in the past, eight φ3" substrates were processed at the same time using a φ15" target size, but by changing the target size to φ21" and simultaneously processing eight φ3" substrates. We are taking measures such as increasing the number of sheets processed from 8 to 16.

[0004] Generally, the insulating film used as a protective film is often a metal oxide such as Al2O3 or SiO2, and therefore the target is often a sintered body of these. Additionally, the target is cooled to prevent temperature rise during sputtering. on the other hand,
Sintered bodies are relatively fragile, so when using a sintered body as a target, the target is fixed to a metal plate called a backing plate using metal bonding, and during sputtering,
Cooling the backing plate indirectly cools the target.

FIG. 5 shows a state in which a target is fixed to a backing plate. FIG. 5 is a sectional view showing a state in which a target is fixed to a backing plate. As shown in the figure, the target 2 is surrounded by a discharge prevention ring 61 and fixed to the backing plate 3 via a metal 62. Further, the discharge prevention ring 61 is fixed to the backing plate 3 with a plurality of bolts 31.

The reason for providing the discharge prevention ring 61 will be explained. The target 2 is fixed to the backing plate 3 with a metal 62 such as In. The metal 62 is solid at room temperature, and the backing plate 3 and target 2 are heated when they are bonded together. Further, the thickness of the metal 62 is approximately 1/100 mm. During bonding, it is impossible to completely eliminate the protrusion of the metal 62 from the periphery of the target. For this purpose, a discharge prevention ring 61 is used to prevent the metal 62 from protruding, thereby preventing abnormal discharge at the metal 62 portion during sputter discharge.

In the case of the above structure, target 2
is completely fixed to the backing plate 3 via the metal 62. During sputter discharge, there is a heat input of about several w/cm 2 from the target surface. For this reason,
The target 2 is cooled by water-cooling the surface of the backing plate 3 opposite to the metal 62. However, due to the difference in thermal conductivity between the target 2 and the backing plate 3 and their respective thicknesses, the target 2
A considerable temperature difference occurs between the surface of the backing plate 3 and the backing plate 3. Furthermore, the heated target 2 tends to expand due to heating. However, in the conventional structure shown in FIG. 5, the target 2 is completely fixed to the backing plate 3 via the metal 62, and therefore cannot be stretched, resulting in thermal stress. As the amount of heat input to the target 2 increases, the thermal stress also increases, the target 2 cannot withstand this thermal stress, and as a result, cracks occur in the target. This becomes especially noticeable as the target becomes larger. As described above, the configuration shown in the figure has a problem in that the target cracks due to thermal stress during the bonding process or during sputtering.

[0008] In order to solve the above problem, Japanese Patent Laid-Open No. 1-1
Publication No. 77368, Japanese Unexamined Patent Publication No. 170268/1983,
There is also a technique described in Japanese Unexamined Patent Publication No. 61-279672. These techniques attempt to cool the target directly. Japanese Unexamined Patent Publication No. 1-177368 discloses that a gas introduction hole is formed in the cathode of a sputtering device to introduce a cooling gas between an electrostatic chuck electrode and a target electrostatically chucked thereto. , describes a technique that allows a target to be detachably attached to a cathode. Furthermore, in Japanese Patent Application Laid-Open No. 59-170268, a target and a backing plate are screwed together, and a reduced pressure gas is flowed through a small gap in the structure, so that the heat of the target is absorbed through the gas into the cooling water of the backing plate. Techniques are described that facilitate target cooling and replacement. Also, JP-A-61-279
No. 672 discloses a technique in which a cooling fluid is brought into direct contact with the surface of the target opposite to the sputtering surface to cool the target.
A technique is described that enables the application of a high voltage to increase the speed of sputtering.

[0009]

[Problem to be solved by the invention] In the above conventional technology,
During sputtering, the target is directly cooled, but the temperature rise of the target cannot be suppressed to zero. On the other hand, the target is completely restrained to the backing plate by screws, bonding material, or electrostatic force. Therefore, in order to further improve throughput, it is necessary to increase the power per unit area to the target more than before, further increase the film formation rate, or increase the number of substrates processed than before by increasing the target size. In some cases, the target heats up even more and expands. In this case, in the above-mentioned conventional technology, the entire surface of one side of the target or the outer periphery of one side is fixed to a backing plate that is cooled and hardly expands, so thermal stress is generated, resulting in cracks in the target. The problem is that there are cases.

Furthermore, when bonding the target and the backing plate using a bonding material, the target becomes larger and the thickness of the bonding material tends to vary. If there are variations in the thickness of the bonding material and there are parts where the bonding material is not attached, the cooling efficiency will be poor in those parts, resulting in uneven temperature distribution inside the target. There is a problem in that stress is generated and target cracking occurs.

An object of the present invention is to provide a sputtering apparatus equipped with a target electrode that can prevent target cracking during sputtering and improve throughput.

0012

[Means for Solving the Problems] The above object can be achieved by a sputtering apparatus equipped with a target electrode, in which the target electrode can hold the target so as to be expandable parallel to the sputtering surface of the target. Further, it is even better if the backing plate has a space that seals the heat transfer medium. Liquid metal, gas, or the like can be used as this heat conductive medium.

[0013]

[Operation] During sputtering, the temperature of the sputtering surface of the target increases due to the impact of ions and the like. In order to prevent this temperature increase, the target is cooled directly or indirectly. However, as the power input to the target increases or the target becomes larger, the target cannot be cooled sufficiently. On the other hand, the target is fixed to a backing plate or the like. Therefore, thermal stress occurs in the target due to thermal expansion of the target, resulting in
Cracks may occur on the target.

In the sputtering apparatus according to the present invention, the target is held so as to be movable in the horizontal direction with respect to the sputtering surface of the target, so that even when the target is heated, it can expand freely without being restricted in any way. No thermal stress occurs. This movable amount is the gap between the outer periphery of the target and the target holding means, or the play hole of the bolt fixing the target holding means. This movable amount is proportional to the thermal expansion of the target.
Make sure you have enough.

Further, according to the present invention, the target electrode can hold the target by interposing a sealed thermally conductive medium made of a fluid between the target and the backing plate, so a metal bonding process is not necessary. It is. As a result, the step of raising the temperature of the target in the metal bonding step can be omitted, thereby eliminating target cracking that conventionally occurred in this step.

Furthermore, the hermetically sealed heat transfer medium made of a fluid such as Ga-In that is sandwiched between the backing plate and the target is liquid at room temperature, so it cannot be partially heated as in conventional metal bonding. It spreads evenly between the target and the backing plate without any distortion. Therefore, due to the heat load during sputtering,
The target is not partially heated, and cracking of the target due to non-uniform temperature distribution inside the target, which is caused by a partial imbalance in cooling efficiency during sputtering, can be prevented.

[0017] The above effects are not limited to the case where liquid metal is used as the heat conduction medium interposed between the target and the backing plate, and gas may be used as the heat conduction medium.

[0018]

[Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a sectional view showing a schematic structure of a sputtering apparatus according to the present invention. Inside the vacuum chamber 1, a target electrode holder 5 which holds a target 2, a backing plate 3, etc. and serves as a cathode when performing sputter discharge, and a substrate 9 on which a film is to be formed and a substrate holder 23 are held and which performs sputter discharge. A substrate electrode 8, which will serve as an anode during the process, is provided via an insulator 6 or an insulator 11, respectively. Earth shields 7 and 10 are provided around the target electrode holder 5 and the substrate electrode 8, respectively, for stable sputter discharge.
They are provided in the vacuum container 1 at regular intervals.

A high frequency is applied to the target electrode holder 5 from a high frequency power source 18 through a high frequency matching circuit 16. Similarly, a high frequency is applied to the substrate electrode 8 from a high frequency power supply 19 through a high frequency matching circuit 17. The cooling water inlet 12 and cooling water outlet 13 of the target electrode holder 5, and the cooling water inlet 14 and cooling water outlet 15 of the substrate electrode 8 are each connected to a cooling water supply device (not shown), and each Cooling water flows to cool the target 2 and the substrate 9.

The vacuum container 1 is connected to an exhaust device 21 via a gate valve 20, and the inside of the vacuum container 1 can be maintained at a high vacuum. Further, from the gas inlet 24, Ar
A sputtering gas such as can be introduced into the vacuum container 1.

[0021] A shutter plate 22 provided inside the vacuum container 1
can be moved horizontally by a drive system (not shown). Depending on the process conditions, the shutter plate 2
By moving the shutter plate 2, electric discharge can be caused between the substrate holder 23 or the target 2 and the shutter plate 22. The target 2 is held by target holding means such as a target holding fitting 4 and a backing plate 3, and the target holding fitting 4 and the backing plate 3 are usually called a target electrode. Next, an example of a detailed structure of a target electrode of a sputtering apparatus according to the present invention will be shown with reference to FIG. FIG. 1 is a cross-sectional view of the target electrode.

As shown in FIG. 1, the backing plate 3
is provided with a recess for filling with a thermally conductive medium such as liquid metal 33. In the recess, for example, Ga-In
The target 2 and the backing plate 3 are closely connected to each other in a state where the metal 33 which is liquid at room temperature is filled without any gaps. The target holding fitting 4 is fixed at a plurality of locations in the circumferential direction by bolts 31. In addition, in order to prevent the liquid metal 33 from leaking, the structure is sealed with an O-ring 32. In addition, even if the target 2 expands due to heat input to the surface of the target 2 during sputter discharge, in order to prevent the expansion from being restrained by the target holding fitting 4, the outer periphery of the target 2 and the target holding fitting 4 are provided.
A gap 70 of about 1 to 2 mm is provided between the inner surface and the inner surface.

Next, a specific example of the target holding fitting 4 will be shown using FIGS. 6 and 7. FIG. 6 is a sectional view showing only the target holding fitting 4 and the target 2, and FIG. 7 is a plan view thereof. In reality, the target holding fixture 4 is provided with a plurality of bolt holes, but these holes are omitted in FIGS. 6 and 7. As shown in FIG. 6, the cross section of the target holding fitting 4 has a stepped portion, and the target 2
It has a shape that is supported by the stepped portion. This target holding fixture 4 is not manufactured in one piece, but consists of four structural members 4a, as shown in FIG. The reason why it is divided into four parts is due to the thermal expansion of the target holding fitting 4.
This is to apply stress to the target and to allow only a portion to be replaced. Note that this target holding metal fitting 4 may be divided into two parts, or may be manufactured by dividing it into more parts.

Next, a case in which the above sputtering apparatus operates will be explained. During sputtering, the temperature of the sputtering surface of the target 2 increases due to the impact of ions, etc., and the target 2 is partially or entirely heated due to the heat. Heat generated in the target 2 is conducted to the backing plate 3 by a heat transfer medium such as liquid metal 33. Since this backing plate 3 is cooled, the target 2
will be cooled. However, if the power input to the target 2 increases or if the target 2 becomes larger, the amount of heat generated in the target increases, and the target 2 cannot be cooled sufficiently. As a result, heat is accumulated in the target 2 and the target 2 expands. In the above configuration, even if thermal expansion occurs in the target 2, the gap 70 is provided and the target 2 will not be restrained, so no thermal stress will be generated in the target 2, and as a result, cracks will occur in the target. It never occurs.

Furthermore, as described above, if the target 2 is held in the target holding fixture 4, the conventional metal bonding process is not necessary, so cracking of the target that occurs during heating in this process is also prevented. can do.

Next, another example of the detailed structure of the target electrode will be shown using FIG. FIG. 2 shows the liquid metal 33 of FIG.
Instead, it is a cross-sectional view showing the structure of a target electrode in which a gas 41 such as He is confined.

Gas 41 is introduced through the gas inlet 42 and sealed by the closing flange 43. In the example shown in FIG. 2, the target can be cooled using gas 41 as a heat transfer medium.

Next, another example of the detailed structure of the target electrode will be shown using FIG. FIG. 3 is a sectional view showing a state in which the target electrode and the target electrode holder 5 are combined. When using a gas, as in the case of the liquid metal described above, it is confined between the target 2 and the backing plate 3, and the heat from the surface of the target 2 is transferred to the gas.
In addition to the method of cooling the target 2 by water-cooling the back surface of the backing plate 3, a direct cooling method using gas is also possible. This method uses the backing plate 3
A gas pipe is provided in the target 2, and gas is flowed while maintaining the gas pressure at about 10 Torr, and the target 2 is directly cooled by this gas.

As shown in FIG. 3, the backing plate 3
is fixed to the target electrode holder 5 by bolts 55. During sputter discharge, the gas inlet 51 and gas outlet 52 are connected to a gas supply device (not shown), and the internal pressure is always maintained at about 10 Torr.
Cool target 2. The gas flows through the O-rings 53 and 5.
4, it has a unique structure. According to this example, unlike the other examples, the step of sandwiching the liquid metal can be omitted, making assembly even easier.

[0030] Also, in gas cooling, normally 0.1w
It has a cooling effect of about /cm2·°C, and the temperature rise of the target can be suppressed to about several tens of degrees with respect to the amount of heat input to the target w/cm2 during sputtering. In the case of water cooling, even greater cooling efficiency can be expected. Naturally, even in the case of the gas cooling structure, as in the case of the liquid metal described above, the target is not restrained by the backing plate, and cracking of the target due to thermal load during sputtering can be prevented.

[0031]

[Effects of the Invention] According to the present invention, the target can be held without being completely fixed and the target can be efficiently cooled, thereby eliminating thermal stress caused by expansion of the target during sputter discharge. , target cracking during sputter discharge can be prevented. Therefore, even if the target becomes larger, cracking of the target can be prevented, which contributes to stabilizing productivity. Further, even if a power several times higher than the conventional power density is applied to the target, thermal stress is not generated in the target, so it is possible to increase the film formation rate and improve productivity. Furthermore, since the conventional metal bonding process can be omitted, cracking of the target during the temperature raising process during metal bonding can be prevented.

[Brief explanation of the drawing]

[FIG. 1] A cross-sectional view of a target electrode of a sputtering apparatus according to the present invention.

[Figure 2] Cross-sectional view showing a target electrode containing a gas such as He

[Fig. 3] Cross-sectional view showing a combined state of a target electrode and a target electrode holder

FIG. 4 is a sectional view of a sputtering apparatus according to the present invention.

[Figure 5] Cross-sectional view showing the target fixed to the backing plate

[Figure 6] Cross-sectional view showing only the target holding bracket and target

[Fig. 7] A plan view of the target presser and target shown in Fig. 6.

[Explanation of symbols]

2...Target, 3...Backing plate, 4...Target holding fitting, 4a... Constituent members of target holding fitting,
32...O ring, 33...liquid metal, 41...gas, 70...
gap

Claims (10)

[Claims] 1. A sputtering apparatus equipped with a target electrode, wherein the target electrode is capable of holding the target so as to be expandable parallel to the sputtering surface of the target. 2. The target electrode includes a backing plate that holds the target, and target holding means that presses the target, and the target holding means includes:
2. The sputtering apparatus according to claim 1, wherein the sputtering apparatus is a locking member that holds the target. 3. The target electrode is characterized in that a backing plate and a target are fixed via a sealing material, and a heat conductive medium made of a fluid is hermetically held between the backing plate and the target. Claim 2
The sputtering apparatus described. 4. The sputtering apparatus according to claim 3, wherein the heat conductive medium is a liquid metal. 5. The sputtering apparatus according to claim 3, wherein the heat conductive medium is a gas. 6. The sputtering apparatus according to claim 1, wherein the backing plate is provided with a recessed portion through which a coolant directly contacts the target. 7. A target electrode for a sputtering apparatus comprising a backing plate and target holding means for holding a target, wherein the backing plate has a heat conductive medium made of a fluid between the backing plate and the target. A target electrode characterized in that it has a recessed part for airtight holding and fixes a target to a backing plate via a sealing material. 8. The target electrode according to claim 7, wherein the target holding means is a locking member capable of holding the target, and is also capable of holding the target so as to be expandable parallel to the sputtering surface of the target. . 9. The target holding means according to claim 7 or 8, wherein the target holding means is constructed by arranging constituent members constituting the target holding means at a plurality of locations along the outer periphery of the target. target electrode. 10. The target electrode according to claim 8, wherein said target holding means is constructed such that opposing portions of adjacent structural members have tooth portions that engage with each other.