JPH02209478A - Sputtering target - Google Patents

Abstract

PURPOSE:To provide a target in which sputter grains sputtered diagonally toward the inside are secured and proper film formation is enabled by means of the above grains even it the erosion of target proceeds by forming a recessed part at least in the vicinity of the inside boundary of an erosion area in the sputter surface. CONSTITUTION:A recessed part 40 is previously formed at least in the vicinity of the inside boundary of an erosion area E in the sputter surface of a target 2, by which the formation of wall on the boundary can be prevented even if sputtering proceeds and as a result, sputter grains sputtered diagonally toward the central region can be always secured over a period from the beginning to the end of its period of service. Accordingly, even in the case when the prescribed film formation is applied to the inner wall of a hole, proper film formation can be performed by means of the above sputter grains with the above diagonal-direction components.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a sputtering target.

(Prior art) In general, a sputtering device is a gas-tight container into which ionizing sputtering gas is introduced, and ions in the plasma collide with a target such as aluminum material at a negative voltage to perform sputtering. A thin film is formed on the surface of a sample such as a semiconductor wafer. Here, taking DRAM as an example of a semiconductor chip, mass production of 1M-DRAM is beginning, and it is planned to shift to mass production of 4M-DRAM in the near future. As described above, with the increase in the density of semiconductor chips, it is necessary to respond to fine processing of semiconductor wafers.

Under these circumstances, when performing aluminum wiring on a semiconductor wafer using a sputtering device, for example, the diameter of the hole 100 to be filled with aluminum is on the order of submicrons, as shown in Figure 4. There is.

(Problems to be Solved by the Invention) In order to form an aluminum film in the hole 100 as described above, an appropriate film cannot be formed only with sputtered particles vertically emitted from a target placed opposite to the wafer. This is because if a film were formed using sputtered particles only in the vertical direction, it would not be possible to form a film on the inner wall of the hole 100 as shown in FIG.

Of course, the sputtered particles do not fly only in the vertical direction, but also diffuse and are emitted in diagonal directions, so the extreme case shown in Figure 7 cannot occur, but as the target becomes immersed in oil, the sea urchins A phenomenon was confirmed in which the number of sputtered particles diagonally directed toward the middle 6 side of /'% decreased, and the film thickness formed on the inner wall of the hole 100 became insufficient.

Therefore, an object of the present invention is to provide a sputtering target that can always secure sputtered particles diagonally toward the center of the object to be processed even if the target is eroded, and can perform appropriate film deposition. Our goal is to provide the following.

[Configuration of the Invention (Means for Solving the Problems) According to the present invention, a sputtering target is constructed by forming a concave portion on the sputtering surface at least near the inner boundary of the erosion area.

(Function) Plasma rings are difficult to form in the central region of the sputtering target due to the necessity of holding the sputtering target or cooling it.
Erosion areas are often secured outside this area. At this time, as the erosion of the target progresses, the uneroded portion becomes a wall at the inner boundary of the erosion area, and sputtered particles flying diagonally inward are obstructed by this wall and cannot reach the object to be processed.

Therefore, in the present invention, by forming a concave portion in advance near the inner boundary of this erosion area, it is possible to prevent a wall from being formed at the boundary even if sputtering progresses, and to prevent the formation of a wall at the boundary from the initial use to the end of its life. Until then, the sputtered particles continue to be directed diagonally toward the central region. As a result, it is possible to ensure an appropriate film thickness on the inner wall of the hole, etc.

(Example) Hereinafter, an example of the method of the present invention will be specifically described with reference to the drawings.

FIG. 1 shows a plate magretron type sputtering apparatus as an example of a sputtering apparatus, in which a semiconductor wafer 1 and a target 2 are placed facing each other in a vacuum vessel (not shown). The semiconductor wafer 1 is supported by a sample stage 4 that includes a wafer heating mechanism 3.

The target 2 placed above the wafer 1 is
It is held by a holding member 5. This target 2
The base material is selected depending on the material to be formed on the wafer 1, such as aluminum.

Silicon, tungsten, titanium, molybdenum.

It is made of chromium, cobalt, nickel, etc., or an alloy made of these materials, and in some cases, a material with poor thermal conductivity such as sintered metal is also used. A negative DC voltage is applied to this target 2, which constitutes a cathode electrode.

Further above the holding member 5, a base 6 is provided to support the holding member 5 and to rotatably support a magnet 10, which will be described later. A hollow cylindrical portion 6a is formed in the center of the base 6, and its lowermost end is in contact with the holding member 5. A bearing 7 is arranged around the cylindrical portion 6a, and a rotary disk 8 is rotatably supported by the bearing 7.

The magnet 10 is fixed to an eccentric position of the rotating disk 8. On the other hand, a magnet rotation motor 1 is fixed to the upper surface of the base 6, and a first gear 12 is fixed to the output shaft of this motor 1. Further, a second gear 13 is fixed concentrically with the rotating disk 8, and the first and second gears 12 and 13 mesh with each other. As a result, the magnet rotation motor 1
By driving the magnet 10, this rotational output is transmitted to the rotating disk 8 via the first gear 12 and the second gear 13, and the magnet 10 can be rotationally driven.

The holding member 5 holds the target 2 in a coolable manner, and for this purpose, a plurality of cooling jackets 15 are arranged inside the holding member 5. By circulating a cooling medium, for example, cooling water, in this cooling jacket 15, the holding member 5 is cooled, and heat exchange between this holding member 5 and the target 2 suppresses the temperature rise of the target 2 when plasma is generated. It is supposed to be suppressed.

An anode electrode 17 is provided around the target 2 with an insulator 16 interposed therebetween, and a shutter 18 is further provided to block the gap between the wafer 1 and the target 2 as necessary. The shutter 18 can be driven by a shutter drive mechanism 1.9.

As shown in FIG. 3, the target 2 is formed into a stepped approximately disc shape having a hole 2a for a gas introduction pipe 20, which will be described later, and includes a large diameter portion 21 having a sputtering surface, and a large diameter portion 21 having a sputtering surface. A small diameter portion 22 formed protrudingly at the center of the back side of 21
It is composed of. Incidentally, the peripheral portion 2 of the large diameter portion 21
The diameter of 1a is 11, and the diameter of the peripheral edge 22a of the small diameter portion 22 is 12. On the other hand, the holding member 5 for holding the target 2 has a stepped hole shape, with a large diameter hole 24 corresponding to the large diameter portion 21 of the target 2 and a small diameter hole 25 corresponding to the small diameter portion 22. It has In addition, the diameter of the inner peripheral surface 24a of the large diameter hole 24! , small diameter hole 25
The diameter of the inner peripheral surface 25a is 14. The size of the target 2 and the holding member 5 is 11~ at room temperature! The relationship between 4 is as follows.

J, <f! ,, I! 2<14 Here, the diametrical gap between the large diameter portion 21 and the large diameter hole 24 and the diametrical gap between the small diameter portion 22 and the small diameter hole 22 are set as follows.

That is, since the target 2 thermally expands due to temperature rise during plasma generation, the thermal expansion length of the large diameter portion 21 in the diametrical direction is greater than the length of the large diameter portion 21. The gap is approximately the same as the gap in the diametrical direction of the large diameter hole 24.

Similarly, the length of thermal expansion of the small diameter portion 22 due to thermal expansion of the target 2 is the length of the small diameter portion 22. The gap is approximately the same as the gap in the diameter direction of the small diameter hole 25.

Therefore, due to thermal expansion of the target 2, the large diameter portion 21
The peripheral edge portion 21a of the large diameter hole 24. and the peripheral edge portion 22a of the small diameter portion 22 expand, respectively. The inner circumferential surfaces 24 a + 25 a of the small diameter holes 25 are in close contact with substantially the same degree of sealing. Note that under the same temperature, the expansion lengths of the large diameter portion 21 and the small diameter portion 22 are different, so that the peripheral edges 21a, 22a and the inner peripheral surfaces 24a, 25a of the hole portions opposite thereto The gap distance between them is different. In this way, the peripheral edge 21a of each stage of the target 2
, 22a and the opposing inner peripheral surface 24a of the holding member 5,
25 a to ensure close contact with target 2.
This enables efficient cooling.

Further, the target 2 and the holding member 5 are clamped on the back side of the central part of the target.

That is, the peripheral portion 22 of the small diameter portion 22 of the target 2
A is formed with locking pins 23, 23 that project outward in the diametrical direction at opposing positions. On the other hand, the bottom surface 24b of the large diameter hole 24 of the holding member 5 communicates with the opposing position of the small diameter hole 25, and the locking pin 23.
Insertion slit 26, 26 with a predetermined depth into which 23 can be inserted.
Further, the insertion slit 26.26 has a locking groove 27.27 formed of a horizontal groove that communicates with the lower end side and extends in the same rotational direction. As a result, the locking pin 23° 23 is inserted into the insertion slit 26 so that the small diameter portion 22 of the target 2 is connected to the small diameter hole 25 of the holding member 5.
．． 26, and then by rotating the target 2 by a predetermined angle in a rotationally permissible direction, the locking pins 23.23 are inserted into the locking grooves 27.23 of the holding member 5. It can be placed at the end of 27.

By using such a lamp, the central region of the target 2, which is prone to rise or warp, is mechanically clamped, thereby ensuring close contact between the back surface of the target 2 and the holding member 5, and increasing cooling efficiency. There is. Furthermore, the clamp allows one-touch replacement, and since the clamp member is not exposed on the surface of the target 2, the entire surface of the target can be effectively used as an erosion area.

The hole 2 of the target 2 also passes through the center of the cylindrical portion 6a of the base 6 and further through the center of the holding member 5.
It has a gas introduction pipe 20 facing the sputtering surface through a. This gas introduction pipe 20 is for introducing a pressure correction sputtering gas of the same type as the main sputtering gas between the wafer 1 and the target 2 .

Next, to explain the shape of the target 2 as a characteristic configuration of the apparatus of this embodiment, a tapered surface 42 in the shape of, for example, a triangular pyramid is formed from near the inner boundary of the erosion area of the sputtering surface of the target 2 toward the center. The concave portion 40 is formed. The angle of the tapered surface 42 is appropriately selected depending on the surface condition of the material to be sputtered.

Next, the effect will be explained.

In order to perform sputtering with this sputtering apparatus, the degree of vacuum in a vacuum chamber (not shown) in which the wafer 1 and target 2 are placed is set to, for example, 10-1 to 10-'Torr while supporting each of the wafer 1 and target 2. Roughly pull. next,
The degree of vacuum in the vacuum container is 10-5 to 10-8 Torr.
A high vacuum is applied to the table, and then a main sputtering gas such as Ar gas is introduced into this J empty container, and the inside of the vacuum container is
Set to 10-3 Torr. Here, target 2
When a negative voltage is applied to the target 2, plasma is formed on the sputtering surface side of the target 2. Furthermore, by rotating the magnet 10 on the back surface side of the target 2, a plasma ring 30 is created in which the plasma is confined by a magnetic field. can be formed. This plasma ring 3
The formation of zero improves the ionization rate, and sputtering is performed in a predetermined erosion area on the sputtering surface of the target 2.

Here, in this embodiment, at the time of the above-mentioned sock and ivy, a pressure-correcting soot gas is introduced into the central region between the wafer 11 and the target 2 through the gas introduction pipe 20.

The reason for this is as follows. That is, the sputtered particles that are scattered and reach the wafer 1 tend to concentrate in the central region of the wafer X1 due to the scattering components on both the left and right sides, and the concentrated sorrel and ivy particles cause the sputtered particles to reach the wafer 1. The sputtering gas in the central region between the targets 2 is blown away, the soot and ivy gas in that region becomes diluted, and the pressure decreases. Furthermore, the decrease in pressure in the central region promotes the phenomenon that sputtered particles in the regions on both ends of the central region are further concentrated in the central region, resulting in deterioration of the uniformity of the film thickness formed on the wafer 11. At this time, if the pressure in the center area is 3 to 5 mTorr, the pressure on both sides is 7 mTorr.
It is expected to be around Torr.

Therefore, wafer 1. A sputtering gas for pressure correction is introduced into the central region where the pressure between the targets 2 is relatively low, and the wafer 1. The pressure gradient between targets 2 is eliminated. In this way, wafer 1. By reducing the pressure gradient between the targets 2, the flying direction of the sputtered particles is controlled to prevent the sputtered particles from concentrating on the central region of the wafer 1, and the uniformity of the film thickness formed on the wafer 1 is improved. It becomes possible to improve.

Here, when aluminum wiring is formed in the holes 100 on the submicron order by such a sputtering method, as shown in FIG. , it became possible to achieve a film thickness that was almost symmetrical.

In particular, in high-speed sputtering equipment with a distance between wafer 1 and target 2 of several tens of degrees, the formation of the pressure gradient described above is significant, so if the Kamikita method is applied to such equipment, good results can be obtained. can.

Next, considering the film formed on the inner wall of the hole 100, this film is formed by sputtered particles flying in an oblique direction.

If the erosion of the sputtering surface of the target 2 progresses, the target 2 will be consumed in the erosion area E as shown in FIG.

This erosion area E approximately corresponds to the formation position of the plasma ring 30 shown in FIG. 1, and therefore the central region of the target 2 does not become the erosion area E. At this time, as shown in FIG.
If the area near the inner boundary of the erosion area E in No. 2 is flat, when the sputtered particles near this boundary try to head diagonally inward, this flight will be blocked by the uneroded boundary wall 104. become.

That is, at the initial stage of use of the target 102, sputtered particles are allowed to fly in an oblique direction, but as the erosion progresses, these sputtered particles are prevented from flying, and eventually the film is not deposited on the inner wall of the hole]00. This will cause problems.

In this embodiment, the concave portion 40 is provided in advance inward from the vicinity of the boundary of the erosion area of the target 2 so that the wall 104 as described above does not impede the flight of sputtered particles. As a result, as shown in FIG. 5, sputtered particles can fly diagonally inward even near the boundary, and as shown in FIG. It becomes possible to carry out attachment. Particularly, by forming the concave portion 40 with a tapered surface 42, it is possible to effectively utilize the target material while sputtering the surface of the concave portion 40 without forming a wall.

Further, since the central region of the target is not normally sputtered, the unconsumed portion of the central region is wasted when the target is replaced due to its lifespan. However, according to this embodiment, the concave portion 4o is formed in advance. At the end of its life, it can be made almost flush with the consumable part in the erosion area, making it possible to effectively utilize the target 2 and reduce costs by reducing material costs.

Note that the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention.

For example, the shape of the concave portion 40 formed on the sputtering surface of the target 2 is not limited to a tapered surface, and may be of various shapes such as a curved surface that does not form a wall that prevents sputter from flying.

In addition, if the concave portion 40 is formed continuously to the center, the material in the portion that is not originally sputtered can be removed from the beginning, which is preferable since the target 2 can be used effectively. Considering only the securing of sputtered particles toward the erosion area, the four portions 40 may be configured as, for example, ring-shaped grooves near the inner boundary of the erosion area.

[Effects of the Invention] As explained above, according to the present invention, even if the target is immersed in oil, it is possible to always secure sputtered particles diagonally inward from the vicinity of the inner boundary of the erosion area of the sputtering surface, and to fill holes. Even when a film of a predetermined thickness is to be applied to the inner wall, the sputtered particles having the diagonal component can be used to properly apply the film.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of a sputtering apparatus to which a sputtering target according to the present invention is attached, and FIG. 2 shows a state of film thickness when aluminum wiring is formed in a hole using the embodiment apparatus of FIG. 1. A schematic explanatory diagram for explaining, FIG. 3 is a target. The attachment of the holding member is shown in a schematic perspective view for explaining the structure.
FIG. 4 is a schematic explanatory diagram of a hole in which aluminum is wired by a sputtering device, FIG. 5 is a schematic explanatory diagram for explaining the movement of sputtered particles diagonally inward, and FIG.
A schematic explanatory diagram for explaining the operation of preventing sputtered particles from flying diagonally inward when the entire surface of the target is flat. Figure 7 is for explaining film deposition on holes by only vertical components. FIG. DESCRIPTION OF SYMBOLS 1... Sample, 2... Target, 40... Concave part, 42... Tapered surface.

Claims (1)

[Claims] (1) A sputtering target characterized in that a concave portion is formed on the sputtering surface at least near the inner boundary of the erosion area.