JPH05234893A - Sputtering method - Google Patents

Abstract

PURPOSE:To provide a sputtering method in which a film having high step coverage can be realized at a high speed and uniformity of a surface of a film growth of a wafer for advancing an increase in its diameter can be improved. CONSTITUTION:A plurality of targets 18 are arranged to constitute a sputter gun assembly 31. The targets 18 respectively have recesses 33 at sides opposed to a wafer 12, and locally generate plasmas in the recesses 33. Sputter particles from the targets 18 sputtered by the plasmas are controlled in flying directions by the walls of the recesses 33, flown in a relatively low pressure processing space 60, and deposited on the wafer 12. A driving shaft 14a is coupled to a placing base 14 for placing the wafer 12, and driven by a Z-axis driver 22, an X table 24 and a Y table 26 to movably scan the wafer 12 with respect to the targets 18 in perpendicular three axial directions.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a sputtering method for depositing a thin film on, for example, a semiconductor wafer or a magnetic disk.

[0002]

2. Description of the Related Art As a conventional magnetron sputtering electrode target, one having a flat plate type or an inverted conical sputtering surface having a gentle gradient, which is provided facing a substrate (wafer), is used. ing. The target diameter is 1.4 to 1.
The diameter of the wafer is about 8 times larger than that of the wafer.

Further, as the degree of integration of ICs increases, the diameter of via holes or contact holes decreases to, for example, 0.5 microns, while the thickness of each layer does not change so much, so that the aspect ratio of via holes or contact holes is large. Is becoming.

[0004]

In order to process a wafer having such a high density, when a conventional flat plate-shaped target is used, a problem as shown in FIG. 10 arises.

That is, in the sputtering apparatus using the flat target 80, the flying directions of the sputtered particles ejected from the surface of the target have a distribution that substantially follows the cosine law. That is, as the flight direction component,
It has components in various directions as indicated by the circle 82.

ULSI having a high degree of integration higher than 4M-DRAM
When a via hole or contact hole 70 having a diameter of 0.5 micron and a depth of 1 micron, that is, an aspect ratio of 2, is sputtered, not only the sputtered particles from the vertical direction are present in the via hole or contact hole 70, Sputtered particles are incident from all angles. Therefore, the deposition of sputtered particles on the shoulder portion of the contact hole 70 increases, and the entrance of the contact hole 70 is blocked, so that the conductive film 72 having a sufficient thickness cannot be formed on the inner surface of the contact hole. According to experiments by the present inventors, only a film of about 0.1 μm is formed in the contact hole 70, and the step coverage (coverage of step, in other words, deposition rate) is 10% or less. ing. That is, in the ULSI, particularly in the conventional flat plate type sputter gun for contact holes or via holes having a diameter of 0.5 μm or less, the step coverage (step coverage) and the amount deposited on the bottom of the hole are reduced to several% or less. There is.

Further, since the plasma generation is not stable unless the sputtering gas pressure is higher than 1 mTorr,
The pressure in the entire processing space must be increased to a stable pressure, and the collision between sputtered particles and sputtered gas particles becomes a non-negligible amount, which causes increase in scattering of sputtered particles.

Under such a condition of the sputtering gas pressure that the scattering of sputtered particles cannot be ignored, a conventional technique for providing an incident beam or a honeycomb filter between the target and the wafer to regulate the incident angle of the sputtered particles is known. Since the sputter particles that pass through the girder or the filter are significantly reduced, the productivity is significantly reduced. Moreover, such a method has a drawback that the amount of deposition on the side wall of the hole is reduced.

Further, in recent years, the size of a semiconductor wafer is 6
From 12 inches to 8 inches, and 12 inches in the future, the trend is toward larger diameters. As the diameter of the semiconductor wafer increases, in the plane of the semiconductor wafer with the increased diameter,
It is more difficult to ensure the uniformity of step coverage.

Therefore, an object of the present invention is to provide a sputtering method capable of achieving high step coverage deposition at a high speed and improving the uniformity of the deposition rate within the surface of a film formation target member. To provide.

[0011]

In the sputtering method according to the present invention, a film forming member is arranged at a position facing a sputter gun assembly having a plurality of targets, and each target faces the film forming member. A plasma generating gas is supplied to each concave portion formed on the surface side, and plasma is locally generated in each hollow portion surrounded by each concave portion, the target is sputtered by this plasma, and the flight direction is caused by the wall of the concave portion. It is characterized in that the sputtered particles, which are regulated in the above-mentioned manner, are caused to fly to the film formation target member that is moved and scanned relative to the respective targets to deposit the sputtered particles on the film formation target member.

[0012]

In the method of the present invention, when the plasma generating gas is supplied to the recesses of the plurality of targets, the plasma is locally generated in the recesses of the target due to the action of the electrode of the sputter gun assembly. The flight direction of the sputtered particles from the target sputtered by this plasma is regulated by the walls of the recesses of the target itself, and becomes highly-directed sputtered particles toward the film formation target member, and the hole bottom wall of the film formation target member And deposit on the sidewalls. At this time, if the target and the member to be film-formed are fixed, by being always positioned between the plurality of targets, there will be an area on the member to be film-formed in which sputtered particles are less likely to be vertically incident. By relatively moving and scanning both of them, the in-plane uniformity of the deposition amount and the deposition shape is improved.

Further, since a plurality of targets are used, the diameter of each target can be made smaller than the diameter of the member to be film-formed, which is becoming larger, and various sizes of the film can be formed without increasing the target diameter. The sputtering process of the member can be adapted by optimizing the number and arrangement of the targets.

Furthermore, it is not necessary to increase the gas pressure in the entire other processing space by locally generating plasma in the target recess, and in a space where sputtered particles fly,
The pressure can be maintained at a low pressure that can reduce the chance of sputtered particles colliding with the gas, and the sputtering efficiency is improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment to which the sputtering method according to the present invention is applied will be specifically described below with reference to the drawings.

FIG. 1 shows an embodiment of the structure of a sputtering apparatus for carrying out the method of the present invention. Vacuum chamber 10
Can be evacuated by the vacuum pump 11. A wafer 12, which is an example of a member to be film-formed, is mounted on a mounting table 14 provided in the vacuum chamber 10 and having a heating function, and the mounting table 14 is connected and fixed to a drive shaft 14a. Above the wafer 12 via the shutter 16,
A sputter gun assembly 31 configured using a plurality of targets 18 is located. The arrangement configuration of the target 18 in the sputter gun assembly 31 will be described later.

The drive shaft 14a is connected to the mounting table drive unit 20. The mounting table drive unit 20 includes, for example, a Z drive mechanism 22,
It is composed of an X table 24 and a Y table 26. The Z drive mechanism 22 enables an up-and-down function, for example, a rotational force of a motor to be converted into a linear drive force by a ball screw structure or the like, and allows the mounting table 14 connected to the drive shaft 14a to move up and down. The X table 24 is a table movable in the X direction together with the Z drive mechanism 22, and the Y table 26 is a table movable in the Y direction together with the Z drive mechanism 22 and the X table 24, and is mounted on the drive shaft 14a. Table 1
4 can also move in the X and Y directions. The Z drive mechanism 22, the X table 24, and the Y table 26
Operate independently of each other, so that the mounting table 14 connected to the drive shaft 14a can move independently in the X, Y, and Z directions. Further, since the mounting table drive unit 20 is provided outside the vacuum chamber 10, it is possible to prevent the heat and dust generated from the drive mechanism from adversely affecting the vacuum state in the vacuum chamber 10.

The bottom of the mounting table 14 and the vacuum chamber 10
Bellows 28 are provided between the bottom portions of the. The bellows 28 expands and contracts when moving in the Z direction, and tilts and deforms with respect to the vertical axis when moving in the X and Y directions. As a result, even when the mounting table 14 is moved in the X, Y, and Z directions by the mounting table driving unit 20, the vacuum state in the vacuum chamber can be kept airtight with respect to the outside atmosphere.

Next, the structure of the sputter gun 30, which constitutes the sputter gun assembly 31, will be described with reference to FIG.

The sputter gun 30 comprises a target 18, an anode 40, a target clamp assembly 46, a target cooling block 42, an insulating material 52, a magnetic forming means such as an electromagnet 36, and a yoke 38.

The target 18 is made of a film forming material such as aluminum, copper, titanium, titanium nitride or the like, and has a bottomed recess 33 having an opening on the surface facing the wafer. In the embodiment, the cross-sectional shape of the recess 33 is an inverse taper shape in which the diameter increases toward the opening end.
A gas supply hole 34 for supplying plasma gas is opened at the center of the bottom of the recess 33.

An electromagnet 36 is arranged on the back surface of the target 18, and the target 18, the electromagnet 36 and the anode 40 are arranged.
A yoke 38 constitutes a magnetic closed circuit between the electromagnet 36 and the electromagnet 36. As a result, the magnetic lines of force 2 are formed between the target 18 and the anode 40 provided on the opening surface side. The anode 40 has an opening equal to or larger than the opening of the target 18.

The target 18 is fitted and held in a space provided in a target cooling block 42 having a cooling fluid space 44, and its open end side is fixed by a target clamp assembly 46. The anode 40 has pins 5 in the notches 48 provided in the yoke 38 and the anode 40.
0 is inserted and fixed, and the target clamp assembly 46
Is fixed by inserting a pin 50 into the notch portion 48 provided in the target clamp assembly 46 and the target cooling block 42. The target 18 and the anode 40 are electrically insulated by an insulating material 52.

A coolant is supplied to the cooling fluid space 44 of the target cooling block 42 through a cooling water supply / drain pipe 54 to cool the target 18. Also,
The target 18 has a DC power supply 56 of −300 to −80.
A voltage of 0V is applied and the anode 40 is grounded.

Next, the operation of the sputter gun 30 will be described.

When a plasma generating gas such as argon is supplied to the hollow portion 32 of the target 18 having this structure from the gas inlet 58 through the gas supply hole 34, plasma is locally generated in the hollow portion 32. By increasing the conductance from the small gas supply hole 34 of the target 18 to the hollow portion 32, a pressure gradient of the introduced gas is formed, and plasma is stably generated even if the processing space 60 has a low pressure. For example, the pressure in the plasma region 3 is set to a pressure at which plasma can be stably generated, for example, on the order of 1 mm Torr, and in the processing space 60 where the sputtered particles 1 move, the sputtered particles 1
Pressure that can reduce the chances of collision with gas, eg 0.1
It can be mm Torr.

The electrons 4 in the plasma region 3 are confined in the hollow portion 32 by the magnetic lines of force 2, and the ions in the plasma, for example, argon ions, collide with the wall of the target 18 and knock out the sputtered particles 1. The sputtered particles 1 are knocked out from the opening of the target 18 toward the wafer 12, and the sputtered particles 1 hitting the wall of the recess 33 of the target 18 are deposited on the target 18 again, but are sputtered again by the argon ion and The sputtered particles 1 are emitted along the opening direction of 18, and the flow direction of the sputtered particles 1 is controlled. As a result, it can be seen that the flight direction component of the sputtered particles 1 has the distribution of the ellipse 6 shown in FIG. 1, and the sputtered particles 1 have directivity. Moreover,
The flow of the sputtered particles 1 is less likely to collide with gas in the low-pressure processing space 60. In this way, sputtered particles 1
The sputtering efficiency does not decrease even though the directivity is increased. The target 18 is gradually consumed due to the generation of the sputtered particles 1, and the sputtered portion 5 becomes larger as shown by the broken line. However, only the size of the concave portion 33 is changed, and even if the target 18 is consumed, the same operation is performed. Can be secured.

The target 18 is made slightly smaller than the size of the space so that it can be easily fitted into the space of the target cooling block 42. That is, the target 1 is placed between the outer peripheral surface of the target and the inner peripheral surface of the cooling device.
8 can be easily attached and detached, and has a clearance such that the target 18 is brought into close contact with the inner peripheral surface of the target cooling block 42 by thermal expansion of the target 18. Therefore, when the exhausted target 18 is replaced, since the target 18 becomes cold and shrinks, there is a gap between the target 18 and the target cooling block 42.
The target 18 can be removed from the target cooling block 42 and a new target 18 can be attached very easily. When this target electrode is operated, the target 18 and the target cooling block 42 expand due to heat and both are securely fixed, and the heat of the target 18 is transmitted to the target cooling block 42. Therefore, a cooling means is provided for the target 18 itself. Instead, the target 18 can be cooled. Therefore, the target 18 can be configured simply by providing the gas supply hole 34, and the cooling water supply / drainage means for the target cooling block 42 need not be attached / detached once it is fixed. The water supply and drainage means can be simple.

For example, when the target 18 is used to sputter the contact hole 70 having a diameter of 0.5 μm and a depth of 1 μm, the amount of sputtered particles from the oblique direction is small, and therefore the shoulder portion of the contact hole cannot be projected and the contact is made. The sputtered particles reach the inside of the hole sufficiently. Therefore, when a 1-micron film was formed on the wafer surface, a 0.8-micron film was formed in the contact hole, that is, a deposition rate of 80% or more could be obtained at high speed.

Next, an example of a sputter gun assembly 31 constructed by incorporating a plurality of sputter guns 30 having the above-mentioned construction will be described with reference to FIG.

The sputter gun assembly 31 is constructed by arranging the targets 18 of, for example, seven sputter guns 30 as shown in FIG. 3, for example. In FIG. 3, seven targets 18 are arranged at the center A of the sputter gun assembly 31 and at each vertex of a hexagon having the center A as the center of gravity. According to this arrangement, the targets 18 can be arranged in the closest arrangement. Therefore, the space occupied by the sputter gun assembly 31 can be minimized by using the sputter gun 30 having a constant space, which is advantageous in terms of space efficiency. However, it is needless to say that the arrangement of the targets 18 can be appropriately changed depending on various conditions such as the size of the wafer 12 and the size of the opening of the sputter gun 30, without being restricted by this arrangement.

Next, the operation when the wafer 12 is scanned with respect to the sputter gun assembly 31 will be described with reference to FIGS.
Will be explained.

As described above, the sputter gun 30 having the target 18 in which the recess 33 is formed has a strong directivity in the flight direction of the sputtered particles 1. Therefore target 1
For holes that exist at positions facing the range of 8 caliber,
Many sputtered particles 1 flying in a substantially vertical direction can be used for film formation. However, if the wafer 12 is fixed, 2
There is a hole that always exists in a position facing the intermediate position of one of the targets 18, and the sputtered particles from the substantially vertical direction toward the hole are small. This is clear from FIG. A large amount of sputtered particles fly from the vertical direction to the holes 70 at points A and B existing immediately below the two targets 18, but such sputtered particles do not flow to the hole 70 at point D, which is an intermediate position. Few. Therefore, the deposition shape varies depending on the hole position.

Therefore, as shown in FIG. 4, the wafer 12 can be scanned in the X or Y direction parallel to the main surface of the wafer 12. For example, if scanning is performed in the X direction, the holes 70 located at D in FIG.
It is possible to face the target 18 for substantially the same time as the point hole 70, and under the same conditions on the wafer 12 surface,
It becomes possible to deposit sputtered particles 1. In particular, in this embodiment, since the directivity is given to the flight direction of the sputtered particles 1 from each target 18, it is not necessary to scan the wafer with respect to the target that hits out the sputtered particles obliquely as in the conventional case. For the first time, it was possible to improve both of the properties that were possible, namely the step coverage and the in-plane uniformity. Therefore, it is possible to form a uniform and high-quality film on the surface of the wafer 12. The scanning range in this case is, for example, the point A in FIG.
It is appropriate to set the distance to the point D, which is the middle point between AB, that is, L ₁ or more. The number of scans is
If it takes, for example, 1 minute to form the film, it is appropriate to reciprocate 3 to 5 times during that time. If the number of times is 6 times or more, it is suitable for ensuring the uniformity of the film, but the mechanical load of the mounting table drive portion is large, and if it is less than 3 times, it is not sufficient to ensure the uniformity of the film. Because.

FIG. 5 schematically shows experimental data on film formation in the case where the sputter gun assembly 31 is scanned in the X direction and sputtered. In this experiment, titanium is used as the material of the film. Also, UL of 4M-DRAM or more
A contact hole 70 having a diameter of 0.5 μ and an aspect ratio of 2, which is actually used in SI, is subjected to a sputtering process, and a wafer having a diameter of 6 inches is used.

As shown in the experimental data, the step coverage is 8 at the contact hole 70 located at the center A of the wafer, the edge B of the wafer, and the middle D between them.
In addition to 0% or more, we succeeded in keeping the degree of uniformity within ± 10%.

Next, the case where the wafer 12 is scanned in the Y direction in FIG. 4 will be described. In this case, it is appropriate that the scanning range is set to a distance from C shown in FIG. 3 to E, which is the center of gravity of the triangle formed by the center positions ABC of the three targets 18, that is, L ₂ or more. .. Other operations are the same as in the case of scanning in the X direction.

Next, referring to FIG. 4, the wafer 12 is moved in the Z direction.
The case of scanning will be described. In this case, when the sputter gun structure 31 is brought closer to the wafer 12, the angle of view with respect to the target 18 seen from the contact hole increases, and more sputter particles are deposited on the shoulder portion of the contact hole. On the contrary, when the sputter gun assembly 31 is moved away, the angle of view is reduced and more sputter particles are deposited in the contact hole. Therefore, the shape of the film can be controlled by scanning in the Z direction.

In this case, the range of scanning in the Z direction, that is, the range of variation of the distance L ₃ in FIG. 1 is, for example, 100 mm to 250 mm. Within this range, the volume of the vacuum chamber 10 is not changed and Z is changed. It is possible to scan in the direction.

The scanning in the X, Y and Z directions is
As mentioned above, each can be scanned independently,
If necessary, only one of these directions may be used, and by combining these scanning directions, it becomes possible to form a film with higher uniformity.

Next, a modification of scan driving will be described.

FIG. 6 shows an embodiment in which a rotary scan with the center of the wafer 12 as the rotation axis is added to the scans in the X, Y, and Z directions. By adding this rotation scan, it is possible to improve the uniformity of film formation on the circumference connecting the centers of the targets 18. The rotation scan is one of the scans in the X, Y, and Z axis directions.
In addition to the above-described combination, only the rotation scan may be performed independently.

FIG. 7 shows an embodiment in which the scanning of the eccentric rotary motion with the eccentric axis offset from the center of the wafer 12 as the central axis is added to the scanning in the Y, Y and Z directions.

In the above-mentioned scanning by the rotary motion,
In order to improve the uniformity of film formation in the radial direction, it is necessary to make the distances from the centers of the peripheral targets different from each other. In such a case, there is a limitation that the arrangement of the targets 18 in the sputter gun assembly has a close-packed structure, and the apparatus structure becomes complicated. However, in the embodiment in which the scanning of the eccentric motion is added, the uniformity of the film formation in the radial direction as well as the circumferential direction is achieved without complicating the device structure while keeping the arrangement of the targets 18 in a close-packed structure. It is possible to improve. Needless to say, only this eccentric rotation scan may be performed independently.

FIG. 8 shows an embodiment in which a revolution scan having the center axis of the sputter gun assembly 31 as the revolution axis and a revolution scan having the center axis of the wafer 12 as the rotation axis are combined. According to this embodiment, it is possible to improve the uniformity of film formation on a wider two-dimensional plane on the wafer 12.

When the rotational drive shown in FIGS. 6 to 8 is performed, a magnetic seal, an O-ring or other airtight seal that allows rotation may be adopted as the airtight seal.

The sputtering method according to the present invention is not limited to the above-mentioned embodiments, and various modified embodiments are possible without departing from the gist of the present invention.

For example, in the sputtering method scanning method according to the present invention, a combination of the X, Y, Z directions, circular motion, eccentric motion, and revolving motion may be applied, for example, as a combination different from the above-mentioned embodiment. It is possible. Alternatively, the wafer 12 may be fixed and the sputter gun assembly 31 may be moved.

Further, for example, the shape of the target 18 is shown in FIG.
It is also possible to deform as in (a), (b) and (c). FIG. 9A is an example in which the shape of the concave portion 33 is a cylinder and a funnel-shaped bottom portion connected to the cylinder, and the gas supply hole 34 is opened at the center of the bottom portion. FIG. 9B shows the recess 33.
Is a conical shape and a hemispherical bottom portion continuing to the cone shape, and the gas supply hole 34 is formed at the center of the bottom portion in the same manner as the above example.
Is open. FIG. 9C shows an example in which the shape of the recess 33 is a truncated cone or a quadrangular pyramid, and the gas supply hole 34 is opened at the center of the bottom of the recess as in the above example. Further, although the above embodiment relates to a sputtering method for a semiconductor wafer, the present invention is not limited to this. For example, the substrate to be processed is an LCD substrate,
It is also applicable to magnetic disks and magnetic tapes.

[0050]

As described above, according to the present invention, plasma is locally generated in the recesses formed in a plurality of targets, and the flight direction of sputtered particles is regulated by the presence of the recesses, and the directivity is high. By causing sputtered particles to fly in a space maintained at a relatively low pressure, it is possible to realize film formation with high step coverage at high speed. Further, by performing the relative movement scanning of the target and the film formation target member together, it is possible to increase the in-plane uniformity of the deposition amount and the deposition shape of the film formation target member whose diameter is increasing.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an embodiment of a sputtering apparatus for carrying out the method of the present invention.

FIG. 2 is a schematic cross-sectional view of one sputter gun that constitutes a sputter gun assembly used in the apparatus of the embodiment shown in FIG.

FIG. 3 is a schematic explanatory view showing an arrangement example of a plurality of targets.

FIG. 4 is a schematic perspective view for explaining movement scanning of a wafer in a direction of three orthogonal axes with respect to a plurality of targets.

FIG. 5 is a schematic explanatory view for explaining a coating operation on a contact hole using the sputter gun assembly of the apparatus of the embodiment.

FIG. 6 is a schematic perspective view for explaining movement scanning of a wafer in a direction of three orthogonal axes and a rotation direction with respect to a plurality of targets.

FIG. 7 is a schematic perspective view for explaining movement scanning of a wafer with respect to a plurality of targets in directions of three orthogonal axes of a wafer and a rotation direction around an eccentric axis.

FIG. 8 is a schematic perspective view for explaining movement scanning of a plurality of targets by rotation around a central axis of a wafer and revolution around an eccentric axis.

FIG. 9 is a schematic cross-sectional view for explaining a modified example of the concave shape of the target.

FIG. 10 is a schematic explanatory view for explaining a coating operation on a contact hole using a conventional flat target.

[Explanation of symbols]

 12 film forming member (wafer) 18 target 20 mounting table drive unit 22 Z-axis drive unit 24 X table 26 Y table 28 bellows 30 sputter gun 31 sputter gun assembly 32 hollow portion 33 recessed portion 34 gas supply port

Claims (4)

[Claims] 1. A film forming member is arranged at a position facing a sputtering gun assembly having a plurality of targets, and a plasma generating gas is supplied to each recess formed on the surface side of each target facing the film forming member. The plasma is locally generated in each hollow portion surrounded by each recess, the target is sputtered by this plasma, and the sputtered particles whose flight direction is restricted by the wall of the recess are supplied to each target. A sputtering method, wherein sputtered particles are deposited on the film forming member by causing the film forming member that is relatively moved and scanned relative to the film forming member to fly. 2. The sputtering method according to claim 1, wherein the relative movement direction of the film formation target member with respect to each target includes a direction parallel to the surface of the film formation target member. 3. The sputtering method according to claim 1, wherein a relative movement direction of the film formation target member with respect to each target includes a direction perpendicular to a surface of the film formation target member. 4. The moving direction of the film forming member relative to each of the targets according to claim 1, including a rotation direction around an axis perpendicular to a surface of the film forming member. And a sputtering method.