JP2003027225A - Sputtering target and sputtering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a thin film uniformly at a high speed to a substrate of a large area. SOLUTION: A plurality of slopes 2a of a width(w) and a height(h) (>=1 to <=10 mm) are concentrically and continuously formed on the surface of a disk-shaped sputtering target in such a manner that the cross sections are formed like saw teeth alternately from the center. The slopes 2a are so formed that the angle θ3 of the slopes, i.e., the angle θ4 formed by the slope 2a and the slope 2a adjacent thereto is a dull angle. A boundary surface 31 of a plasma 30 and an ion sheath 21 is made smoother than the saw-like surface shape of the sputtering target formed with the slopes 2a and made nearly plane. Incident ions 20 which are incident positive ions on the sputtering target 2 are made incident at an incident angle θ1 diagonally with the slopes 2a which are the sputtering surfaces.

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 a sputtering apparatus used for forming a thin film in the production of various devices such as semiconductors and optical parts.

[0002]

2. Description of the Related Art The sputtering method is a technique in which a sputtering target is physically hit with accelerated ions, and a thin film is formed on the surface of a substrate by sputtered particles ejected from the sputtering target. The sputtering method is widely used as a method for forming a thin film of an insulator, a semiconductor, a conductor, etc. because of the following advantages. That is, the sputtering method is capable of forming (1) a thin film of a wide range of materials without limitation of a film forming material, (2) obtaining a large-area homogeneous and uniform thin film relatively easily, (3) magnetron plasma The use of such magnetized plasma has the advantage that high-speed film formation is relatively easy.

Conventionally, a sputtering target having a disk shape, a rectangular shape or the like has been used. These sputtering targets usually have a flat sputtering surface, and when the sputtering target and the substrate are faced with a parallel plate to form a film, there is a difference depending on the size ratio of the sputtering target and the substrate, but it is usually on the substrate. The film thickness distribution becomes thinner from the center to the periphery.

FIG. 7 is a schematic view showing an example of a sputtering process using a conventional flat plate sputtering target.

Flat plate-shaped sputtering target 10
The incident ions 120 which are positive ions are generated from the plasma 130 generated on the front surface of the sputtering target 102.
While passing through the upper ion sheath 121, the sputtering target 102 is accelerated by a self-bias voltage which is a potential difference between the sputtering target 102 and the plasma 130 and is incident on the sputtering target 102. The accelerated positive ions are vertically incident on the sputtering target 102.

The sputtered particles 122 hit by the positive ions from the sputtering target 102 ideally have a discharge angle distribution 123 according to the cosine law and are emitted from the sputtering target 102. Here, the emission angle distribution 123 according to the cosine law means that the sputtered particles 122 on the surface of the sputtering target 102.
Indicates that the sputtered particles 122 are emitted in an amount proportional to the cosine value of the angle of the direction in which the sputtered particles are emitted with respect to the normal line of the surface of the starting point. In the case of a flat sputtering target, sputtered particles according to the cosine law 12
Assuming an emission angle distribution 123 of 2, the thickness of the thin film formed on the substrate can be predicted to decrease considerably from the front of the sputtering target 102 toward the periphery.

In recent years, when a film having a uniform film thickness is formed on a large-area substrate, a method of using a mask for correcting the film thickness distribution or sputtering as disclosed in Japanese Patent Publication No. 7-15144. A method has been proposed in which the sputtering surface of the target has a shape other than a flat surface.

FIG. 8 shows a schematic diagram of a part of a cross section of a sputtering target disclosed in Japanese Patent Publication No. 7-15144. According to claim 1 of Japanese Examined Patent Publication No. 7-15144, "a straight line connecting an arbitrary point on the substrate facing the surface to be sputtered of the sputtering target material and the center of the sputtering target material is An incident surface formed with respect to the sputtering surface, an angle formed by a straight line connecting each point on the intersection line formed with respect to the sputtering surface and an arbitrary point on the substrate, and a normal line of each point on the intersection line. The sum of the cosine values of is approximately equal to any point on the substrate. "
According to Japanese Patent Laid-Open No. 15144, it is indispensable to eject from the sputtering target 202 with an emission angle distribution 223 according to the cosine law from the sputtering surface. This means that incident ions 2 which are positive ions with respect to the surface to be sputtered of the sputtering target 202.
It means that 20 incidents are made vertically,
As shown in FIG. 8, it is essential that the height h ₁ of the step or slope of the sputtering surface is larger than the thickness t ₁ of the ion sheath 221 formed on the surface of the sputtering target.

That is, the plasma 230 and the ion sheath 2
The boundary surface 231 with the plasma target 21 is always formed in a shape along the surface shape of the sputtering target 202.
Positive ions that have entered the ion sheath 221 from 30 are accelerated by the sheath electric field in the ion sheath 221, and enter the sputtering surface almost vertically, and the impact causes the sputtered particles 2
22 is emitted from the sputtering target 202 with an emission angle distribution 223 according to the cosine law from the sputtering surface. In this case,
As described in Japanese Patent No. 4 publication, when the sputtering target 202 shown in FIG. 8 is used, as compared with the flat plate-shaped sputtering target 102 shown in FIG. 7, more sputtered particles 222 fly to the peripheral portion of the substrate. Therefore, the uniformity of the film thickness distribution can be improved.

[0010]

However, in the method using the mask for correcting the film thickness distribution, defects such as pinholes are generated in the film formed for peeling off the film adhered on the mask. Since the mask shields the sputtered particles, there may be a problem that the film forming speed is reduced.

Further, in the method of forming the sputtering surface of the sputtering target into a shape other than a flat surface as disclosed in Japanese Patent Publication No. 7-15144, the sputtered particles ejected from the sputtering target are compared with the flat sputtering target. However, since the ratio of sputtered particles that are ejected in a direction other than the substrate is high, the problem may occur that the film formation rate is reduced.

Therefore, in order to overcome such problems, the present invention has developed a sputtering apparatus and a sputtering process having a sputtering target different from the conventional one, and is capable of uniformly and rapidly forming a large-area substrate. An object is to provide a film-forming sputtering target and a sputtering apparatus.

[0013]

In order to achieve the above object, the sputtering target of the present invention is a sputtering target used for forming a deposited film, which generates sputtered particles by causing ions to enter the surface to perform sputtering. , Height above the surface is 1 mm or more 1
It is characterized in that a plurality of inclined surfaces of 0 mm or less are formed.

In the sputtering target of the present invention constructed as described above, the surface to be sputtered has a height of 1 mm.
It is formed of a plurality of inclined surfaces of 10 mm or more and 10 mm or less. Therefore, the ions can be obliquely incident on the surface of the sputtering target, and the sputtering rate can be increased. Further, since the ions can be obliquely incident on the inclined surface of the sputtering target of the present invention, the emission angle distribution of the sputtered particles in another sputtering target in which the ions are vertically incident on the inclined surface is It is possible to obtain an inclined surface having an angle smaller than the angle of the inclined surface of another sputtering target, and thus it is possible to suppress reattachment of sputtered particles to the sputtering target.

Further, the sputtering target of the present invention may have an obtuse angle between adjacent inclined surfaces.

The sputtering target of the present invention may be circular and each inclined surface is formed in a concentric circle shape, or may be rectangular and each inclined surface may be linear. It may be formed side by side.

The sputtering apparatus of the present invention comprises a vacuum container capable of maintaining a substantially vacuum state inside, an exhaust means for exhausting the inside of the vacuum container, a gas supply means for supplying a gas for generating plasma, A power supply means for supplying power to a sputtering target arranged in a vacuum container, and a plasma is generated in the vicinity of the surface of the sputtering target to sputter the sputtering target to place the sputtering target on the substrate. In the sputtering apparatus for performing film formation, the sputtering target of the present invention can be arranged in the vacuum container as the sputtering target.

The sputtering apparatus of the present invention as described above can form a film on a substrate using the sputtering target of the present invention. That is, the sputtering rate is improved by allowing ions to be obliquely incident on a plurality of inclined surfaces having a height of 1 mm or more and 10 mm or less of the sputtering target. Further, since the emission angle distribution of sputtered particles in another sputtering target in which ions are vertically incident on the inclined surface can be obtained with the inclined surface having an angle smaller than the angle of the inclined surface of the another sputtering target. It is possible to suppress the reattachment of sputtered particles to the sputtering target.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional perspective view of an essential part of a disk-shaped sputtering target according to this embodiment.

The sputtering target 2 shown in FIG.
On the surface of a disk-shaped sputtering target has a width w,
A plurality of inclined surfaces 2a having a height h are continuously formed concentrically from the center so that their cross sections are sawtooth. By forming the inclined surface 2a in the concentric shape in this manner, it is possible to easily achieve the symmetry and the film thickness uniformity of the thin film formed and the stability of the processing accuracy of the inclined surface 2a.

FIG. 2 is a perspective view of a rectangular sputtering target according to this embodiment.

The sputtering target 2'shown in FIG.
On the surface of a rectangular sputtering target has a width w ′,
A plurality of inclined surfaces 2a ′ having a height h ′ are formed continuously in parallel and linearly so that their cross sections are sawtooth alternately. Also in the sputtering target 2 ', since the inclined surface 2a' is linear, the symmetry of the thin film to be formed and the ease of achieving the film thickness uniformity and the stability of the processing accuracy of the inclined surface 2a 'are secured. Has been done.

The material of each sputtering target 2, 2'is appropriately selected according to the thin film to be formed.

FIG. 3 is a schematic sectional view of an embodiment of the sputtering apparatus of the present invention, which can use the sputtering target of FIG. 1 or 2.

Since the sputtering by the sputtering apparatus of this embodiment can be applied to the circular sputtering target 2 as shown in FIG. 1 or the rectangular sputtering target 2'as shown in FIG. Hereinafter, the case where the circular sputtering target 2 is used will be described as an example.

The sputtering apparatus includes a vacuum container 1 capable of maintaining a substantially internal vacuum state, an exhaust system 5 connected to the vacuum container 1 and comprising a vacuum pump for exhausting the vacuum container 1, and the like.
A gas cylinder 6 for supplying a reactive gas, which is connected to the vacuum container 1 via a gas flow rate control valve 7 that controls the supply amount of the reactive gas for generating plasma.

In the vacuum chamber 1, a sputtering target 2 to be sputtered is arranged so as to be in contact with the cathode electrode 10. In the vacuum container 1, a substrate 3 on which a thin film is formed is held by a substrate holder 4 so as to face the sputtering target 2.
A high frequency power supply 11 is connected to the cathode electrode 10 via a matching circuit 12, and sputtering power is applied from the high frequency power supply 11 to the cathode electrode 10. The cathode electrode 10 is insulated by an insulating member 9 with respect to the earth shield 8 for preventing discharge other than the front surface of the sputtering target 2.

Next, a state in which the circular sputtering target 2 of FIG. 1 is being sputtered by the sputtering apparatus shown in FIG. 3 is a schematic partially enlarged sectional view of the sputtering target 2 shown in FIG. It demonstrates using.

In FIG. 4, the height h of the inclined surface 2a formed on the sputtering target 2 is smaller than the thickness t of the ion sheath 21 formed on the surface of the sputtering target. When the height h of the inclined surface 2a is smaller than the thickness t of the ion sheath 21 as described above, the boundary surface 31 between the plasma 30 and the ion sheath 21 has a sawtooth shape of the sputtering target 2 on which the inclined surface 2a is formed. Compared with the surface shape of, it becomes smoother and becomes closer to a plane. Therefore, the incident ions 20 that are positive ions that are incident on the sputtering target 2 are not inclined to the inclined surface 2a that is the sputtering surface.
The incident angle is θ _{1 with} respect to the normal line 24 that is set up, that is, the light is obliquely incident on the inclined surface 2 a. The incident angle dependence of the sputter rate depends on the incident angle θ ₁ which is the angle from the normal line 24 of the sputter surface as the incident angle θ ₁ is large, as described in “Thin film forming technology by sputtering method” p13 published by the Management Development Center. The rate is high. That is, in the case of sputtering using the conventional flat sputtering target shown in FIG. 7, the incident angle θ ₁ of incident ions is almost 0 (substantially parallel to the normal to the sputtering surface), and the sputtering rate is the lowest. You are in the process. On the other hand, in the case of the present embodiment, the incident angle can be made oblique by providing the inclined surface 2a as the sputtering surface, and a high sputtering rate can be obtained. As a result, it becomes possible to significantly improve the film formation rate as compared with the conventional film formation by sputtering in which the incident angle θ ₁ of incident ions on the sputtering surface is almost zero.

Further, in the conventional case, the emission angle distribution of sputtered particles is close to the cosine law as shown in FIGS. 7 and 8, and many sputtered particles fly in the direction directly facing the sputtering target. In the case of the present embodiment, positive ions are obliquely incident on the sputtering surface as shown in FIG. 4, so that the incident angle θ ₁ of the positive ions and the emission angle distribution of the sputtered particles 22 with reference to the normal line of the sputtering surface. The angle θ ₂ with the apex of 23 is a position of line symmetry. This makes it possible to reduce the angle θ ₃ of the inclined surface 2a for obtaining the same emission angle distribution 23 of sputtered particles as compared with FIG. Can be made smaller, which can contribute to the improvement of the film formation rate.

Normally, for example, in the case of high frequency sputtering, the thickness of the ion sheath is described as a cathode descending portion in "Technology development center issued thin film forming technology by sputtering method" p71, but the thickness is several centimeters. ing. Therefore, the effect is sufficiently exhibited when the height of the inclined surface portion of the sputtering target 2 of the present embodiment is 10 mm or less even if a margin is taken into consideration. On the other hand, when the height h of the inclined surface 2a of the sputtering target 2 is 1 mm or less, sputtering is performed for a long time, and when the erosion of the sputtering target 2 progresses, the shape of the inclined surface 2a is likely to change,
The change over time in the sputtering rate and the emission angle of sputtered particles becomes large, making stable film formation difficult. From the above, the heights h and h ′ of the inclined surfaces 2a and 2a ′ of the sputtering target of the present embodiment are 1 as described above.
It is preferable that it is not less than 10 mm and not more than 10 mm.

Further, in order to minimize reattachment of sputtered particles ejected from the sputtering target to the sputtering target, the angle θ ₃ of the inclined surface 2a is made small, that is, the inclined surface 2 adjacent to the inclined surface 2a.
The angle θ ₄ with a is preferably an obtuse angle.

As described above, according to the sputtering target 2 of the present embodiment having a plurality of inclined surfaces 2a formed on the surface thereof, (1) the incident ions 20 can be incident on the sputtering surface in an oblique direction. The rate has improved,
(2) Even if the slope of the sputter surface is smaller than the conventional one, the same emission angle distribution of the sputtered particles as the conventional one can be obtained, so that the reattachment of the sputtered particles to the sputtering target can be suppressed, and the sputtered particles reaching the substrate Can be significantly increased, so that the film formation rate can be significantly improved.

[0035]

EXAMPLES Examples of the present invention will be described below. (First Example) In this example, sputtering film formation was carried out by the sputtering apparatus shown in FIG. 3 using the disk-shaped sputtering target 2 shown in FIG.

The sputtering target 2 has a diameter of φ.
An Al disc having a diameter of about 150 mm (6 inch diameter), and a sloped surface 2 having a width w of 10 mm and a height h of 3 mm continuously concentrically on the surface so that the cross section is alternately sawtooth from the center.
a is formed.

The diameter of the substrate 3 on which the thin film is formed is φ14.
It is 0 mm.

For comparison with this embodiment, as a first comparative example, sputtering film formation by a sputtering target whose diameter is about 150 mm (6 inch diameter), which is the same as that of the sputtering target 2, but whose surface shape is flat. Was carried out.

As a second comparative example, the diameter is about 150 mm (6 inch diameter), which is the same as the sputtering target 2, but the width w of the inclined surface 2a is 40 mm and the height h is h.
The sputtering film formation was performed using a sputtering target having a diameter of 20 mm and changing only the dimensions of the inclined surface 2a.

The obtained results are shown in FIG. FIG. 5 is a graph in which the film forming rate in the radial direction of the substrate 3 is standardized by the maximum value of the film forming rate of the first comparative example.

In the flat plate sputtering target of the first comparative example, the film thickness distribution was ± 20%, but in the second comparative example, the film thickness distribution was ± 8%, and in the present invention, the film thickness distribution was ± 6%.
You can see that it has improved.

Further, in comparison with the center position of the substrate, the film forming speed is reduced by 18% in the second comparative example as compared with the first comparative example, whereas it is improved by 22% in the present invention. I understood. (Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings in comparison with a conventional one.

In this example, the sputtering apparatus shown in FIG. 3 was used to carry out sputtering film formation using the rectangular sputtering target 2'shown in FIG.

The sputtering target 2'is 150
A square surface 2a 'having a width w'of 10 mm and a height h'of 3 mm is formed continuously from the center in parallel so as to have a sawtooth cross section alternately from the center. .

The substrate 3 on which the thin film is formed is a 140 mm square substrate.

For comparison with this example, as a third comparative example, sputtering film formation was carried out using a sputtering target whose dimensions are the same 150 mm square as the sputtering target 2 ', but whose surface shape is flat. .

The obtained results are shown in FIG. FIG. 6 is a graph in which the film forming rate of the distance from the center of the substrate 3 in the direction orthogonal to the inclined surface 2a ′ of the sputtering target 2 ′ is standardized by the maximum value of the film forming rate of the third comparative example. .

In the flat plate sputtering target of the third comparative example, the film thickness distribution was ± 18%, but in the present invention, it can be seen that the film thickness distribution is improved to ± 5%.

Further, it was found that the film forming speed was improved by 20% in the present invention as compared with the third comparative example when compared at the substrate center position.

The embodiments of the present invention have been described above.
The present invention is not limited to the above-mentioned examples, and can adopt embodiments corresponding to various sputtering target materials and sizes and shapes of substrates.

[0051]

As described above, according to the present invention,
The surface of the sputtering target has a height of 1 mm or more 10
Since it is formed by a plurality of inclined surfaces of mm or less, ions can be made incident on the surface in an oblique direction, and the sputtering rate can be increased. Thereby, the film formation rate can be increased.

Further, according to the present invention, since the ions can be obliquely incident on each inclined surface, it is possible to suppress reattachment of sputtered particles to the sputtering target. Thereby, a thin film having a uniform film thickness distribution can be formed on the substrate.

[Brief description of drawings]

FIG. 1 is a cross-sectional perspective view of a main part of a sputtering target according to an embodiment of the present invention.

FIG. 2 is a perspective view of a sputtering target according to another embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of an embodiment of the sputtering apparatus of the present invention.

FIG. 4 is a schematic partially enlarged cross-sectional view of a sputtering target of the present invention for explaining a situation in which sputtering is performed.

FIG. 5 is a graph showing a film thickness distribution in the first embodiment of the present invention.

FIG. 6 is a graph showing a film thickness distribution in the second embodiment of the present invention.

FIG. 7 is a schematic view of an example of a sputtering process using a conventional flat plate sputtering target.

FIG. 8 is a schematic partial cross-sectional view of an example of a conventional sputtering target.

[Explanation of symbols]

1 vacuum container 2 Sputtering target 2a inclined surface 3 substrates 4 substrate holder 5 exhaust system 6 gas cylinders 7 Gas flow control valve 8 earth shield 9 Insulation member 10 Cathode electrode 11 High frequency power supply 12 Matching circuit 20 incident ions 21 Ion sheath 22 Sputtered particles 23 Emission angle distribution 24 normal 30 plasma 31 boundary

Claims (5)

[Claims] 1. A sputtering target, which is used for forming a deposited film and generates sputtering particles by sputtering a surface by ion bombardment, has a plurality of inclined surfaces having a height of 1 mm or more and 10 mm or less formed on the surface. The sputtering target is characterized in that 2. The sputtering target according to claim 1, wherein an angle between the inclined surfaces adjacent to each other is an obtuse angle. 3. The sputtering target according to claim 1, wherein the sputtering target is circular and each of the inclined surfaces is formed in a concentric shape. 4. The sputtering target according to claim 1, wherein the sputtering target has a rectangular shape, and the inclined surfaces are linearly arranged. 5. A vacuum container capable of maintaining a substantially vacuum state inside, an exhaust means for exhausting the inside of the vacuum container, a gas supply means for supplying a gas for generating plasma, and a gas supply means arranged in the vacuum container. And a power supply means for supplying power to the sputtering target, and plasma is generated in the vicinity of the surface of the sputtering target to sputter the sputtering target to form a film on a substrate arranged opposite to the sputtering target. In a sputtering device, the sputtering target according to any one of claims 1 to 4 can be arranged in the vacuum container as the sputtering target.