JPH10195648A - Magnetron sputter device and backing plate for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetron sputter device in which electron confinement is secured even on the sputter face of a large diameter target. SOLUTION: This device is provided with a backing plate 14 for retaining a planar target 20 on one side, a magnetron assembly 40 which is arranged on the other side of the backing plate 14 so as to form a line of magnetic force near and along the sputter face P of the target 20, and a magnetic substance 21 installed inside the backing plate 14. In this structure, the magnetic substance 21 is magnetized with magnetic induction caused by the line of magnetic force, so that it can easily penetrate through the magnetic substance 21. Consequently, the line of magnetic force easily appears along the sputter face P to form a strong magnetic field on it, thus enhancing electron confinement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron sputtering apparatus, and more particularly, to a magnetron sputtering apparatus adapted to increase the size of an object to be processed.

[0002]

2. Description of the Related Art In recent years, in semiconductor devices in which elements are highly integrated, such as VLSIs, the tendency toward miniaturization and multilayering has been progressing. In such semiconductor devices,
The technology of electrode wiring for connecting each element is also moving toward miniaturization and multilayering. Conventionally, electrode wirings made of aluminum, titanium, or silicide or salicide thereof have been known. Further, the formation of the electrode wiring is performed by a magnetron sputtering method which is one of the sputtering methods.

[0003] The magnetron sputtering method is performed using a magnetron sputtering apparatus. In a magnetron sputtering apparatus, a flat target having one surface serving as a sputtering surface is held on a lower surface of a backing plate which forms a part of the vacuum chamber in an upper portion of the vacuum chamber.
A magnetron assembly is provided above the backing plate to form predetermined magnetic lines of force near the sputtering surface of the target along the sputtering surface. The backing plate is cooled by cooling water in order to prevent the sputtering surface of the target from becoming high during film formation.

[0004] According to this method, a magnetic field is formed near the sputtered surface of the target.
For this reason, the frequency of collision of electrons with a rare gas such as argon introduced into the vacuum chamber increases, and the plasma density near the sputtering surface can be increased.

[0005]

By the way, the next generation 1
In a gigabit-level semiconductor device, the diameter of a semiconductor wafer as a substrate to be processed tends to be increased from the viewpoint of improving productivity and the like. In accordance with such a tendency, the diameter of the target of the magnetron sputtering apparatus is also increased, and therefore, the size of the backing plate holding the target is also required. At this time, if the size of the backing plate is simply increased, the rigidity of the backing plate is reduced, and the backing plate may be deformed by the reduced pressure difference between the inside and outside of the vacuum chamber and the weight of the cooling water. For this reason, the rigidity is ensured by increasing the thickness of the backing plate. However, since the backing plate is generally made of a non-magnetic material such as aluminum or stainless steel, the number of lines of magnetic force passing through the backing plate decreases due to the increase in the thickness of the backing plate, and the backing plate is formed on the target surface. Magnetic field may decrease. Therefore, the confinement of electrons in the vicinity of the sputtering surface is reduced, and as a result, the density of plasma that can be formed in the vicinity of the sputtering surface may be reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetron sputtering apparatus in which electrons can be confined even on the sputtering surface of a large-diameter target.

[0007]

SUMMARY OF THE INVENTION A magnetron sputtering apparatus according to the present invention has been made in order to solve the above-mentioned problems, and has a backing plate for holding a flat target on one side and a near-sputtering surface of the target. In order to form lines of magnetic force along the sputter surface, the magnetic head includes a magnetic field forming means disposed on the other surface of the backing plate and a magnetic body provided inside the backing plate. According to this configuration, the magnetic body is magnetized by causing magnetic induction by the magnetic field lines, so that the magnetic field lines can easily penetrate the magnetic body. For this reason, the lines of magnetic force easily appear along the sputter surface, and a strong magnetic field is formed on the sputter surface, so that the confinement of electrons is improved.

In order to increase the number of lines of magnetic force appearing on the sputter surface, the magnetic material may be characterized in that the magnetic permeability in a direction perpendicular to the sputter surface is higher than the magnetic permeability in other directions. In practice, such a magnetic body is preferably made of an electromagnetic steel sheet having an easy axis of magnetization in a direction perpendicular to the sputtering surface.

Further, in order to prevent the magnetic field lines from the magnetic field forming means from generating eddy currents formed in the plane of the magnetic material perpendicular to the magnetic field lines and to reduce the number of net magnetic field lines appearing on the sputtered surface, The body may be made of a magnetic material strip wound around the center axis (A) of the target, or may be made of a plurality of magnetic materials each extending in a direction perpendicular to the sputtering surface and overlapping each other. Or a linear body made of a plurality of magnetic materials, each of which extends in a direction perpendicular to the sputtering surface and is bundled.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

FIG. 1 shows a flat plate magnetron sputtering apparatus to which the present invention is applied.
That. ) 10 is shown schematically.

In the flat plate magnetron device 10, there is a circular opening at the top of the electrically grounded vacuum chamber main body 11. The opening is closed by a backing plate 14 via an annular conductive adapter 12 and an insulator 13.

The backing plate 14 is shown in FIGS.
As shown in FIG. 5, the non-magnetic material such as aluminum or stainless steel is formed in a circular flat plate shape corresponding to the circular opening of the vacuum chamber body 14. The upper peripheral edge of the backing plate 14 is provided with a flange 16 having bolt holes 15 arranged at equal intervals in the circumferential direction.
The backing plate 14 is securely screwed to the upper surface. For this reason, the opening of the vacuum chamber main body 11 is closed, and the vacuum chamber 17 is configured. In addition, from the viewpoint of easy attachment and detachment of the backing plate 14, the backing plate 1 is located below the backing plate 14.
4 The outer peripheral surface is inclined inward. On the lower surface of the backing plate 14, a target 20 whose lower surface is a sputtering surface P is held via an adhesive (not shown). In the flat-plate magnetron device 10, a plasma having a relatively high density is basically formed on the sputtering surface P. Therefore, cooling water is supplied to a cooling chamber (not shown) provided above the backing plate 14 so as to prevent the temperature of the target 20 from rising due to such plasma, and the heat generated on the sputtering surface P is backed up. It is removed via the plate 14.

Although not shown, the vacuum chamber 17
Is connected to a vacuum pump for evacuating the vacuum chamber 17. Also, a supply source of a process gas such as an argon gas supply source, or a nitrogen gas supply source or an ammonia supply source for performing a reactive sputtering process such as titanium nitride is provided in addition to the argon gas supply source.
7 is connected. Further, in order to realize sputtering on the target 20, a cathode of a DC power supply is connected to the target 20 via an electric lead and a switch,
The anode is grounded.

A flat pedestal 30 serving as a support means is provided inside the vacuum chamber 17 to support an object to be processed such as a semiconductor wafer W. A drive shaft 31 having an elevating mechanism (not shown) is connected to the lower surface of the pedestal 30 in a state protected by a bellows 32, thereby enabling the pedestal 30 to be raised or lowered.

An annular pedestal cover 33 is arranged around the pedestal 30 to not only support the semiconductor wafer W from the back side but also prevent a target atom, which will be described later, from reaching the upper surface of the pedestal 30. ing. An annular clamp ring 34 is arranged around the pedestal cover 30. The pedestal cover 34 is raised by the lifting mechanism together with the pedestal 30, and as shown in FIG.
Is fixed at a predetermined height, the clamp ring 34 engages with the outer peripheral portion of the upper surface of the semiconductor wafer W.

A cylindrical shield 35 is provided in the vacuum chamber 17 to protect the inner wall surface of the vacuum chamber 17. That is, the shield 35 is screwed to the lower surface of the adapter 12 at the upper edge, and is folded upward at the lower edge. And pedestal 30
When the shield 35 is lowered, the shield 35 supports the clamp ring 34 to protect the inner wall surface of the vacuum chamber 17.

In the flat plate magnetron apparatus 10, a magnetron assembly 40 as a magnetic field forming means is provided above the backing plate 14 constituting the vacuum chamber 17, so that an annular line of magnetic force is formed on the sputtering surface P of the target 20. I have. The magnetron assembly 40 will be described with reference to FIG. 1. On a circular base plate 41, a plurality of U-shaped magnets 42 that form a downward annular magnetic field are fixed in a predetermined arrangement. The ends of each U-shaped magnet 42 face downward. The back surface of the U-shaped magnet 42 is fixed to the base plate 41 by a suitable fixing means, for example, a screw (not shown) or the like, in contact with the base plate 41. Further, a rotation drive unit 43 is connected to the magnetron assembly 40. Therefore, the rotation of the U-shaped magnet 42 on the backing plate 14 corrects the bias of the magnetic field that can be formed on the sputtering surface P via the backing plate 14.

In the present embodiment, the disk-shaped magnetic material 21 is formed so that the magnetic field lines from the magnetron assembly 40 easily appear on the sputtering surface P and the magnetic field on the sputtering surface P is increased.
Are provided in the backing plate 14 coaxially with the backing plate 14. It is preferable that the magnetic body 21 has a higher magnetic permeability in a direction perpendicular to the sputtering surface P than a magnetic permeability in other directions so as to easily increase the magnetic field on the sputtering surface P. From the practical point of view, such a magnetically permeable material is desirably formed of an electromagnetic steel sheet widely used as an iron core material of a transformer or the like. However, the magnetic material 21 may be formed of a ferromagnetic material such as iron, cobalt, and nickel, or a ferrimagnetic material.

The shape of the magnetic body 21 is such that eddy currents generated in a plane perpendicular to the magnetic body 21 are generated by the magnetic lines of force from the magnetron assembly 40, and the number of net magnetic lines of force appearing on the sputtering surface P is reduced. It is preferable to suppress such a situation. Specifically, it is desirable that the magnetic body 21 has a shape shown in FIGS. That is, the magnetic body 21
The target 20 is made of a band 22 made of the magnetic material wound around the center axis (A) of the target 20,
Each of the plurality of plate members 23 made of the above magnetic material extends in the direction perpendicular to the sputtering surface P and is overlapped with each other, or each extends in the direction perpendicular to the sputtering surface and bind tape 24. It is desirable that it be made up of a plurality of linear bodies 25 made of the above magnetic material that are bundled. It should be understood that those skilled in the art will not lose the features of the present invention even if a rod is used instead of the linear member 25 described above.

In order to manufacture the backing plate 21 having the above-described magnetically permeable material 21 inside, although not shown, the constituent members of the backing plate 21 are cast or forged so that the magnetic material is provided in the backing plate 21. It is cut and processed into a predetermined shape by the above method. Further, the magnetic body 21 having predetermined characteristics is processed into a predetermined shape. Then, after such a magnetic body 21 and the constituent members are joined by welding or the like and given a predetermined finish, the one shown in FIG. 2 is completed.

As described above, when the U-shaped magnet 42 is disposed above the backing plate 14 in which the magnetic body 21 is provided, a simulation of the state of the lines of magnetic force is shown in FIG. Indicated by dotted lines. In this simulation, the magnetic body 21 has a higher magnetic permeability than the nonmagnetic backing plate 14 in a direction perpendicular to the sputtering surface P preferentially. The effect of the eddy current is ignored. According to the result of FIG. 6, it is understood that the magnetic field lines are formed through the magnetic body 21. This is due to the property that the lines of magnetic force are easily magnetized by magnetic induction, that is, easily pass through the places with high magnetic permeability. Further, since the distance between the magnet 42 and the magnetically permeable body 21 is substantially reduced, most of the magnetic lines of force from the magnet 42 tend to appear on the upper surface of the magnetically permeable body 21. Therefore, most of the annular lines of magnetic force of the U-shaped magnet 42 pass through the magnetic body 21 in a direction perpendicular to the sputtering surface P at a position directly below each magnetic pole tip. As a result, annular lines of magnetic force having a strong magnetic field are efficiently formed on the sputtering surface P, so that the confinement of electrons required for magnetron sputtering is sufficiently enhanced.

The presence of the magnetic substance 21 is
This is extremely effective when the backing plate 14 is increased in size due to the increase in the diameter of. The backing plate 14 having a large size may be deformed due to the pressure difference between the inside and outside of the vacuum chamber and the weight of the cooling water.
To prevent such deformation, the backing plate 14 is thickened to ensure its rigidity. However, simply increasing the thickness of the backing plate 14 as shown in the simulation results in FIG.
The number of lines of magnetic force passing through FIG. 7 shows dotted lines of magnetic force lines having the same strength based on the result of a simulation performed in the same manner as in FIG. 6 except that the backing plate 18 in which the magnetic body 21 is not provided is used. In this case, since the backing plate 18 is made of a non-magnetic material, it is not magnetized, and the lines of magnetic force passing through the backing plate 18 are reduced. Therefore, the intensity of the magnetic field formed on the sputtering surface P is weakened. The target 20
It will be obvious to those skilled in the art that the same can be said for the backing plate 18 even when the thickness of the backing plate 18 is increased.

As described above, when the diameter of the target 20 is increased, the thickness of the backing plates 14 and 18 is increased because the rigidity of the backing plates 14 and 18 must be ensured. Are also common.
However, in terms of reducing the effective thickness of the backing plate 14 and forming a strong magnetic field on the sputtering surface P,
The backing plate 14 of FIG. 6 is different from the backing plate 18 of FIG. Thereby, in the present embodiment, even if the backing plate 14 is apparently thick,
The strength of the magnetic field on the sputtering surface P required for the electron confinement is sufficiently secured. In addition, the effective reduction in the thickness of the backing plate 14 can be predicted by substantially considering only the magnet 42, that is, ignoring the effect of the backing plate 14, and the magnetic field on the sputtering surface P. Therefore, the design of the target 20 or the arrangement / selection of the magnet 42 according to the film forming conditions by magnetron sputtering can be easily performed.

In this embodiment, when a magnetic field is formed on the sputtering surface P of the target 20 made of a ferromagnetic material such as nickel or cobalt, the magnet 42 having a large magnetization is used.
This is effective even when the magnetization of the target 20 is saturated. As shown by the two-dot chain line in FIG. 6, in the magnet 42 having a relatively large magnetization,
The lines of magnetic force extend downward and outward with respect to the pole tips. However, in the present embodiment, the direction of the magnetic force lines can be controlled by the magnetic material 21 so that most of the magnetic force lines pass through the magnetic material 21. Therefore, as shown in FIG. 2 or FIG. 7, the outer peripheral surface of the magnetic body 21 is inclined downward and
The magnetic field lines are prevented from appearing beyond the outer peripheral surface of No. 1.
As a result, no magnetic field is formed on the outer peripheral surface of the backing plate 14, and so-called abnormal discharge that occurs on the target 20 other than on the sputtering surface P hardly occurs.

In contrast to the case of FIG. 6 in which the direction of the lines of magnetic force is controlled by the magnetic substance 21, the lines of magnetic force are not substantially controlled in the backing plate 18 of FIG. For this reason, as indicated by a two-dot chain line in FIG. 7, leakage of lines of magnetic force may occur on the outer peripheral surface of the backing plate 18, and abnormal discharge may occur significantly on the outer peripheral surface of the backing plate 18.

In order to form a target material on a semiconductor wafer W to be processed by using the flat plate magnetron apparatus 10 configured as described above, the semiconductor wafer W is supported on the upper surface of the pedestal cover 33. Next, although not shown, the inside of the vacuum chamber is evacuated by a vacuum pump to reduce the pressure to a desired degree of vacuum. In this state, the rotation assembly 43 rotates the magnet assembly 40. In this case, eddy current hardly occurs in the magnetic body 21. In the magnetic body 21, most of the lines of magnetic force of the magnet 42 extend in a direction perpendicular to the direction along the sputter surface P, and are formed uniformly and annularly on the sputter surface P. Thereby, the magnetic field is strong on the sputtering surface P.

Thereafter, argon gas is supplied into the vacuum chamber 17 from an argon gas supply source. In this state, a voltage is applied to the target, and glow discharge is performed using argon gas. At this time, most of the electrons generated by the glow discharge spirally move on the sputtering surface P where the strong magnetic field is formed, and are sufficiently confined. As a result, a high-density argon plasma is generated on the sputtering surface P,
Due to the impact of argon ions therein, the target 20
Is sputtered, and more sputter atoms are emitted uniformly than before. Then, the released sputter atoms are uniformly and rapidly formed on the semiconductor wafer W.

As described above, in this embodiment, the sputtering surface P
Because of the excellent electron confinement property above, even if the process gas is at a relatively low pressure, argon plasma sufficient for film formation can be formed. Reducing the pressure of a process gas such as argon also suppresses collisions between argon ions and target atoms. Therefore, when the present apparatus is applied to a semiconductor wafer W having holes or the like, a film with high step coverage is formed. Even when the distance between the target 20 and the pedestal 30 is long, the chamber 17
Since the inside is low pressure and the mean free path is lengthened, such a film forming process is sufficiently performed.

Further, in the present embodiment, a magnetic field required for magnetron sputtering can be formed on the sputtering surface P even when the magnet 42 having a relatively small magnetization is used. For this reason, the formation of a magnetic field can be suppressed at the peripheral portion of the target 20 where the sputtered particles hardly contribute to the film formation and become particles. Therefore, the target 20 is not substantially sputtered at the peripheral portion of the target 20, and there is no possibility that particles are generated.

The magnetron sputtering apparatus according to the present invention is not limited to the above-mentioned flat plate magnetron sputtering apparatus 10. For example, facing target type sputtering (Fa
A cigTarget Sputtering (FTS) device may be used. Further, in the magnetron sputtering apparatus of the present invention, the method of forming a magnetic field and the method of applying a voltage are not limited to the above embodiment. For example, a high frequency power supply may be used instead of the DC power supply for the method of applying the voltage.

[0032]

According to the magnetron sputtering apparatus of the present invention, the magnetic material has a predetermined shape and is provided inside the backing plate. For this reason, even if the backing plate is enlarged due to the increase in the diameter of the target and its thickness is increased, most of the lines of magnetic force from the magnetic field forming means pass through the backing plate and appear on the sputtered surface. Therefore, the strength of the magnetic field on the sputter surface is sufficiently ensured that electrons can be confined when the size of the target is not increased. Therefore, high-density plasma can be formed, the target is easily sputtered, and the speed at which sputtered atoms are formed on an object to be processed such as a semiconductor wafer is increased.

Further, depending on the shape of the magnetic material, the direction of the magnetic field can be controlled at the peripheral portion of the target which does not contribute to the film formation. For this reason, sputter atoms are not emitted in such a place, generation of particles is suppressed, and the yield of semiconductor devices is improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a magnetron sputtering apparatus of the present invention.

FIG. 2 is a perspective view of the backing plate of FIG. 1;

FIG. 3 is a perspective view of the first embodiment of the magnetic body.

FIG. 4 is a perspective view of a second embodiment of the magnetic body.

FIG. 5 is a perspective view of a third embodiment of a magnetic body.

FIG. 6 is a diagram simulating a magnetic field formed on a sputtering surface when a magnetic material is provided inside a backing plate.

FIG. 7 is a diagram simulating a magnetic field formed on a sputtering surface when a magnetic material is not provided inside a backing plate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Magnetron sputtering apparatus, 11 ... Vacuum chamber main body, 14 ... Backing plate, 17 ... Vacuum chamber, 18 ... Backing plate, 20 ... Target, 2
DESCRIPTION OF SYMBOLS 1 ... Magnetic body, 22 ... Strip, 23 ... Plate, 25 ... Linear, 30 ... Pedestal, 40 ... Magnetron assembly, 42 ... Magnet, 43 ... Rotation drive unit, P ... Sputter surface, W ... Semiconductor wafer .

Claims (12)

[Claims] A backing plate for holding a flat target on one side; and a backing plate disposed on the other side of the backing plate for forming lines of magnetic force near the sputtered surface of the target along the sputtered surface. Magnetic field forming means, a magnetic body provided inside the backing plate,
A magnetron sputtering apparatus comprising: 2. The magnetron sputtering apparatus according to claim 1, wherein the magnetic material has a higher magnetic permeability in a direction perpendicular to the sputtering surface than in another direction. 3. The magnetron sputtering apparatus according to claim 1, wherein the magnetic body is made of an electromagnetic steel sheet having an easy axis of magnetization in a direction perpendicular to the sputtering surface. 4. The magnetic body according to claim 1, wherein the magnetic body is formed of a band made of a magnetic material and wound around a central axis (A) of the target. Item 3. The magnetron sputtering apparatus according to item 1. 5. The magnetic body according to claim 1, wherein each of the magnetic bodies is formed of a plurality of plate members made of a magnetic material and extending in a direction perpendicular to the sputtering surface and stacked on each other. The magnetron sputtering apparatus according to any one of the above. 6. The magnetic body according to claim 1, wherein each of the magnetic bodies is composed of a plurality of linear members made of a magnetic material and extending in a direction perpendicular to the sputtering surface.
The magnetron sputtering apparatus according to any one of claims 1 to 3. 7. A backing plate for a sputtering apparatus for holding a flat target, wherein a magnetic material is provided inside the backing plate. 8. The backing plate according to claim 7, wherein the magnetic material has a higher magnetic permeability in a direction perpendicular to the sputtering surface than in another direction. 9. The backing plate according to claim 7, wherein the magnetic body is made of an electromagnetic steel sheet having an easy axis of magnetization in a direction perpendicular to the sputtering surface. 10. The magnetic material according to claim 7, wherein the magnetic material is a band made of a magnetic material wound around a center axis (A) of the target. A backing plate according to the item. 11. The magnetic body according to claim 7, wherein the magnetic body is composed of a plurality of plate members made of a magnetic material, each of which extends in a direction perpendicular to the sputtering surface and is superimposed on each other. The backing plate according to any one of the above. 12. The magnetic body according to claim 7, wherein the magnetic body comprises a plurality of linear bodies made of a magnetic material, each of which extends in a direction perpendicular to the sputtering surface and is bundled. A backing plate according to any one of the preceding claims.