JPS5922788B2 - Planar magnetron sputtering device and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a planar-magnetron type sputtering apparatus and method thereof, which aims to extend the life of a target flat plate used in a thin film material sputtering apparatus and to control the distribution of deposited film thickness on a sample surface. It is related to.

In sputtering technology, low-pressure atmospheric gas is ionized (plasma-like) by causing a glow discharge, and the plasma-like ions are accelerated by a voltage applied between negative and positive electrodes and strike a flat plate of target material placed on the cathode. be made to collide.

This is a technique in which constituent atoms or particles of the target material ejected by the collided ions are deposited on a substrate provided near the anode to form a thin film of the target material.

In this case, it is important to confine the ions generated by the glow discharge in a space with a high density and carry them effectively onto the target material plate in order to improve the deposition rate and reduce damage to the substrate caused by electrons. It is becoming.

For this purpose, it is effective to confine the ions to a spatial region on the flat surface of the target material and increase the density.

The magnetic field configuration has also been studied. In particular, planar magnetron sputtering equipment has come to have a deposition rate comparable to that of conventional resistance heating vacuum evaporation equipment, and has recently been used as a thin film forming equipment for semiconductor devices such as thin film integrated circuits in the production process. It came to be widely used.

FIG. 1 is a conceptual sectional view showing the structure of a planar-magnetron type sputtering apparatus in the vicinity of a flat plate of target material according to the well-known prior art. A yoke 6 is attached to the back surface of the target material flat plate (hereinafter referred to as target flat plate) 1.
A ring-shaped magnetic pole 2 magnetically coupled to the ring-shaped magnetic pole 2 and a cylindrical magnet 3 at the center of the ring-shaped magnetic pole 2 are arranged to form a magnetic circuit. These magnetic poles 2 and 3 create a distribution of magnetic lines of force in the space on the surface side of the target 1 (lower side in Fig. 1), in other words, the torus is cut in half on a plane perpendicular to the height direction. , a semicircular annular magnetic field distribution whose half-cut plane is parallel to the surface of the target flat plate 1, commonly known as a tunnel-shaped magnetic field distribution 11, is generated. This tunnel-like magnetic field distribution 11 confines the plasma-like ions in a high concentration therein (not shown). This plasma-like ion is
Further, it is accelerated by an electric field almost perpendicular to the surface of the target flat plate 1 generated by a high voltage applied between the anode 10 and the cathode 7 installed on the back surface of the target flat plate 1.
The atoms or particles collide with the surface of the target flat plate 1, and as a result, the atoms or particles are sequentially ejected from the surface of the target 1, forming an eroded region 12. As estimated from the above explanation, the degree of erosion in this eroded region 12 increases as time passes during the sputtering process, but this erosion usually occurs in the target flat plate structure shown in FIG. Since the progress is limited to a specific area, it is said that only the volume of the eroded area can be effectively used.

Therefore, even if the desired uniform film thickness distribution is initially obtained, the formation of such erosion regions changes the direction and amount of the atoms of the target material that are ejected. The thickness distribution of the thin film to be deposited on the surface of the sample substrate is not uniform, and spontaneously becomes a substantially downward convex quadratic curve distribution or an upward convex quadratic curve distribution.

This makes it impossible to obtain a large film thickness or to perform a long sputtering process, and this has been considered a limitation of the conventional sputtering process.

Later, in order to eliminate this drawback, it was proposed to change the magnetic field distribution 11 so that the erosion region 12 is generated over a wide area on the surface soil of the target flat plate 1 (JP-A-51-8
6083, JP-A-53-7586). The theoretical background or technical idea of this technology can be found on page 2, lower right column, line 19 to page 3, upper left column, second line of JP-A-51-86083. It is said that ``the greatest target erosion occurs in the area aligned with and underlying the above point or area where the magnetic field lines are parallel to the target plate'', and thus Showa 51-860
No. 83, as stated in the first claim of the patent, generates an auxiliary variable magnetic field in the direction perpendicular to the source for the first magnetic field means, The device is equipped with a second magnet means for changing the auxiliary variable magnetic field and continuously moving the position where the resultant magnetic field lines are parallel to the source, as shown in FIG. 4 of the drawings as a specific technique. An embodiment in which the electromagnets shown in Fig. 1 are arranged in isolation is disclosed. On the other hand, in Japanese Patent Application Laid-Open No. 53-7586, the technique is simply to mechanically move the magnet means itself. However, the inventors reconsidered the technical ideas in the above-mentioned known examples in light of the experimental facts of the inventors, and found that the effects are even more effective than the technical means shown in the above-mentioned known examples. In addition, we were able to realize a new technology that allows almost arbitrary control of the thickness and distribution of the deposited thin film. The object of the present invention is to provide a target structure for a planar-magnetron sputtering apparatus that eliminates the drawbacks of the prior art described above and that makes it possible to extend the life of the target flat plate, that is, to make the sputtering process continuous, time-consuming, and automated. It's about offering your body. Another object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to prolong the life of the target flat plate, and at the same time, to provide a planar magnetron type sputtering apparatus that enables control of the thickness of the deposited thin film and its film thickness distribution. Provides a target structure.

Still other objects of the present invention are to eliminate the above-mentioned drawbacks of the prior art, to extend the life of the target plate, to increase the thickness of the deposited thin film, and to
The present invention also provides a magnetic flux control method for controlling a plasma region standing on a target flat surface in a hollow space during a sputtering process in order to control the film thickness distribution.

The key point of the present invention is that when magnetic flux lines are generated from one magnetic flux source, the magnetic fluxes do not interlink with each other due to their nature, and an attractive force or a force called Maxwell stress acts on each other. In consideration of the above, one magnetic flux source with three magnetic pole faces is configured, and the amount of magnetic flux generated on some of the magnetic pole faces is controlled to control the amount of magnetic flux generated on the remaining magnetic pole faces and its distribution. This is a target structure of a planar magnetron type sputtering device in which the standing position, that is, the area where the plasma stands, is moved.

Furthermore, the second point is that three magnetic pole bodies constitute one magnetic flux line source, and a DC or periodically changing alternating current is applied to the excitation means provided on some of the magnetic pole bodies during the sputtering process. A planer that forms and controls magnetic flux that extends the life of a target flat plate, controls film thickness, and controls film thickness distribution by moving the plasma region into a static flat region or by moving the plasma region over time. - A method for controlling the magnetic flux of a target structure in a magnetron sputtering device. Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a sectional structural view of one embodiment of a target structure of a planar magnetron type sputtering apparatus according to the present invention. In Fig. 2, reference numeral 1 denotes a target disc-shaped flat plate made of material to be sputtered, which is Al-2%Si (purity 99.9
99%) diameter 8''φ and plate thickness 20m7!L. Reference numeral 2 represents the second magnetic pole body, which is made of a soft magnetic material (high permeability magnetic material).

3 is a first magnetic pole body, which is made of a permanent magnet.

The second magnetic pole body 2 and the first magnetic pole body 3 constitute main magnetic flux generating means. 4 is a third magnetic pole body according to the present invention, which is made of a soft magnetic material.

Reference numeral 4a denotes an excitation coil according to the present invention, which constitutes a magnetic flux distribution control means with a multi-wound toroidal coil installed in an intermediate space between the second magnetic pole body 2 and the third magnetic pole body 4. .

Reference numeral 5 denotes a medium for cooling the target flat plate 1, in this case a water inlet/outlet pipe, and 6 a yoke as a first magnetic flux passing means for magnetically coupling the first, second, and third magnetic pole bodies as a whole. 6a is a yoke portion as a second magnetic flux passing means made of a soft magnetic material according to the present invention; 7 is a cathode; 8 is an insulating layer plate; 9 is a shield; 10 is an anode; 12 is an eroded area.

FIG. 3 is an explanatory diagram of the operation of the target structure of the planar magnetron type sputtering apparatus shown in FIG.
This is a case where an N pole is generated in the downward direction of the first magnetic pole body 3, and an S pole is generated in the downward direction of the third magnetic pole body 4, which is a magnetic flux distribution control means.

In such a structure, the magnetic flux emitted to the first magnetic pole body (permanent magnet) 3 passes through the yoke 6, and a part of the magnetic flux is transmitted to the second magnetic pole body 2,
The remaining flux is focused from each south pole of the third magnetic pole body 4 to the north pole of the second magnetic pole body 3, drawing a well-known magnetic flux line diagram.
That is, this magnetic flux forms a distribution shown by representative magnetic flux lines 11a and 11b, but this entire magnetic flux is distributed by a magnetic flux control current (not shown) passed through an excitation coil 4a attached to the third magnetic pole body 4. The magnetic flux distribution, that is, the shape of the magnetic flux line distribution is controlled. Therefore, in view of controlling the shape of the magnetic flux line distribution, a wide flat magnetic field region can be provided at a height above the target flat plate 1. Although such a magnetic field region can be estimated by well-known calculations of magnetic circuits, it can also be easily and directly obtained experimentally. The sputtering process will be briefly explained below to show how it is incorporated into the sputtering process.

First, although not shown, the target structure according to the present invention is equipped with a well-known vacuum evacuation system, a Z-type exhaust system, an Ar gas introduction system, two gate valves, and a transport means capable of continuously transporting wafers. Attach to one wall of the vacuum chamber.

Next, the upper side of the space where the magnetic flux lines 11a and 11b of the target flat plate 1 are formed (the arrangement with the top and bottom reversed in Fig. 3)
A Si wafer (42φ) is installed and held parallel to the surface of the target flat plate 1 at a distance of 60 U by well-known holding means. Next, this vacuum chamber is evacuated to about 1 to 3.times.10@-7 TOrr, and after exhausting, Ar gas is introduced from the Ar gas introduction system, and the Ar gas pressure is set to 2 to 10 mTorr. Next, a control current is applied to the excitation coil 4a of the target structure according to the present invention, and the magnitude and direction of the current are adjusted so as to obtain a magnetic field strength of 200 to 300 Gauss and a predetermined spatial magnetic flux distribution. Next, when a DC voltage of 400 to 700 V is applied between the anode 10 and the cathode 7 of the target structure 1, the Ar gas causes a glow discharge, and Ar atoms or particles are generated in the region represented by the magnetic flux lines 11a and 11b. An ionized and confined plasma region is generated. In the target structure according to the present invention, the Ar atoms or particles are ionized depending on the direction and magnitude of the control current, and the contraction or expansion of the confined plasma region can be visually and experimentally adjusted. can. Next, the shutter for the target structure (not shown) is closed, and after pre-sputtering is performed for about 30 minutes, the shutter is opened and the target material A is deposited onto the Si wafer at a sputtering rate of about 5000λ/-.
A thin film of 12% Si was deposited to a thickness of about 1 μm.

After the scheduled deposition time, close the shutter and deposit Al-2%
The gate valve was opened and the Si wafer on which the Si film was deposited was taken out. The same process was repeated and the results of the virtually repeatable experiment were checked over a period of over 150 hours. FIG. 8 shows some of the experimental results, with reference numeral 13 showing the film thickness distribution within a conventional wafer, and reference numeral 14 showing the film thickness distribution within a wafer using the target structure according to the present invention.

The effects of the present invention are obvious. Furthermore, the Al-2%Si film thus formed showed good electrical properties as a film for semiconductor wiring. It has been clarified by the research results of the inventors that such favorable intra-wafer film thickness distribution and electrical characteristics are extremely dependent on the shape of the eroded region on the surface of the target flat plate 1 facing the wafer.

The erosion area 12 according to the prior art in FIG. 1 is extremely narrow due to local erosion, and as time passes, the erosion area 12 becomes even more localized, and the center of the erosion area is preferentially eroded. Eventually, the thickness of the target flat plate 1 is reached, and the target flat plate 1 becomes unusable. On the other hand, the erosion area 12 in FIG. 2 is eroded relatively uniformly over a wide area by forming the magnetic flux line distribution by the excitation coil into a flat shape that spreads from the center to the periphery of the target flat plate 1. We were able to form an area. Although the above is a case where a static flat magnetic field distribution is used, an embodiment of another technique included in the technical idea of the present invention is as shown in FIG.

FIG. 4 shows a configuration in which the magnetic pole of the third magnetic pole body 4 is changed to the north pole by an excitation coil 4a for each magnetic pole body arrangement shown in FIG.

Other symbols in FIG. 4 have the same meanings as shown in FIG. Typical magnetic flux lines 11a and 11b in FIG. 4 are generated from the magnetic pole tip of the first magnetic pole body 2, and have a magnetic field distribution such that the second magnetic pole body 3 and the third magnetic pole body 4 have magnetic flux suction ends. Form. As a result, the magnetic flux is divided into two parts, is attracted from the two N poles, and returns to the first magnetic pole body 2 from the yoke 6 (a part of which includes the yoke portion 6a, which is a component of the present invention).

Therefore, the third magnetic pole body 4 is controlled by changing the control current flowing through the exciting coil 4a from a positive direction current to a negative direction current with a constant amplitude value and period, so that the magnetic flux distribution changes over time from the Maxwell stress relationship. That is, the plasma region was repeatedly contracted, expanded, or moved many times within the deposition time by the given control current, and a temporally uniform erosion region was formed.

This guarantees the long life of the expensive target plate 1 and has the great effect of reducing the dead time mainly due to replacement of the target plate 1, which is a major bottleneck in the process.

FIG. 5 is a sectional view of another embodiment of the target structure of the planar magnetron sputtering apparatus according to the present invention.

The difference in the configuration in FIG. 5 from that in FIG. 2 is that the first magnetic pole body 3 is made of a soft magnetic material instead of using a permanent magnet, and a second multi-wound excitation coil 3a is provided therein. This is the point. The other symbols have exactly the same meanings as those in FIGS. 2 to 5. The technical idea of the present invention includes the configuration of this embodiment, and the difference in operation in this embodiment from that of FIG. 2 is the difference in the configuration described above. and the magnetic flux caused by the third magnetic pole body 4 can both be controlled simultaneously.

The process leading to the generation of other plasma regions is the same. 9th
The figure discloses the greatest technology made possible by this example, and it is not limited to simply making the film thickness distribution obtained in the sputtering process uniform, but it can also be used to The ability to control the film thickness distribution, which forms the film thickness distribution, has been achieved.

Figure 9 shows some of the experimental results,
Wafer center when the magnetic flux control current flowing through the second excitation coil 3a (inner current in Fig. 9) is kept constant and the magnetic flux control current flowing through the first excitation coil 4a (outer current in Fig. 9) is varied. This figure shows the change in the inner membrane thickness distribution with respect to the radial distance from the wafer. A solid line 15 (mark) indicates a downwardly convex film thickness distribution, a solid line 16 (△ mark) indicates a substantially uniform film thickness distribution, and a solid line 17 (○ mark) indicates an upwardly convex film thickness distribution. Similar results were obtained by appropriately combining two other magnetic flux control current values. Conventionally, when the target flat plate 1 is made of a magnetic material, the magnetic flux lines 11a and 11b are absorbed by the target flat plate 1, making it difficult to form a magnetic field distribution that maintains the plasma region. It has been practically impossible to sputter a magnetic material using a target flat plate 1 of any practical thickness.

However, with the configuration of this embodiment, the magnetic material is magnetically saturated, and the excessive magnetic flux lines 11a,
11b can be used with easy control (
In the case where the second magnetic pole body 3 is a permanent magnet, the plate thickness is limited to a thin one, so an effect that seems to be impractical for practical use is produced. Therefore, although sputtered film deposition of magnetic materials was previously not possible with a facing target sputtering device, the present invention has made it practical to deposit a sputtered film with a planar magnetron sputtering device. . The above description relates to special cases regarding the first magnetic pole body, second magnetic pole body, and third magnetic pole body. It is clear that all magnetic field control techniques realized by any combination of magnetic flux distribution control means (high permeability magnetic material) and excitation coil are included in the technical idea of the present invention.

Furthermore, it is clear that the above-mentioned electromagnet-like magnetic pole body may be used as the magnetic flux distribution control means, and the magnetic flux control current flowing therein may be one of the Fourier expansion functions. As mentioned above, according to the target structure of the conventional planar magnetron sputtering apparatus, erosion on the surface of the target flat plate occurs in an extremely narrow local area, so the life of the target flat plate is short and the shape of the eroded area is short. However, according to the target structure of the planar-magnetron type sputtering apparatus and its magnetic flux control method according to the present invention, the above-mentioned This eliminates all the shortcomings of the conventional technology and makes it possible not only to extend the life of the target flat plate but also to ensure an arbitrary shape distribution of the deposited film thickness. The contribution of the technology of the present invention is extremely large.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural view showing a target structure of a conventional planar-magnetron sputtering apparatus, FIG. 2 is a cross-sectional structural view showing an embodiment of a target structure of a planar-magnetron sputtering apparatus according to the present invention, and FIG. Figure 4 is a cross-sectional structural diagram for explaining its operation.
FIG. 5 is a cross-sectional structural diagram showing another embodiment of the target structure of the same device of the present invention, FIGS. 6 and 7 are cross-sectional structural diagrams for explaining the operation, and FIG. 8 is a planar structural diagram of the present invention. - a target structure of a magnetron sputtering device;
Figure 9 shows the first and second profiles of the film thickness distribution within the wafer with respect to the distance from the wafer center in the second embodiment. FIG. 2 is an actually measured distribution diagram showing the control current (outer and inner) dependence of . 1: Target flat plate, 3a: Second excitation coil (inner coil), 4: Third magnetic pole body, 4a: First excitation coil (
outer coil), 6: yoke, 6a: yoke part, 11a,
11b: representative magnetic flux lines, 12: erosion region, 13: wafer inner film thickness distribution curve according to the prior art, 14: wafer inner film thickness distribution curve according to the technology of the present invention, 15, 16, 17: outer current value 1.

Claims (1)

[Claims] 1. In a planar magnetron type sputtering apparatus, a first magnetic pole body provided at the center of the target, an annular second magnetic pole body provided around the first magnetic pole body, and a second magnetic pole body provided around the first magnetic pole body provided at the center of the target. a ring-shaped third magnetic pole body, the tips of these magnetic pole bodies are close to or in contact with the target plate, and the rear ends of these magnetic pole bodies are magnetically connected to a plate-shaped body formed of a magnetic material, Main magnetic flux generating means for generating an annular tunnel-shaped main magnetic flux is provided at the tips of the first and second magnetic pole bodies, and between the second magnetic pole body and the third magnetic pole body, A planar magnetron type sputtering apparatus characterized in that an annular first electromagnetic coil for changing the diameter of a plasma ring formed at the tip is installed to constitute an integrated magnetic flux source. 2. Claim 1, characterized in that the main magnetic flux generating means is constructed by disposing a second annular electromagnetic coil between the first magnetic pole body and the second magnetic pole body. Planar magnetron type sputtering equipment. 3 In a planar magnetron sputtering method, a first magnetic pole body provided at the center of the target, an annular second magnetic pole body provided around it, and an annular third magnetic pole provided around it. The tips of these magnetic pole bodies are close to or in contact with the target plate, and the rear ends of these magnetic pole bodies are magnetically connected to a plate-shaped body formed of a magnetic material, and the main magnetic flux generating means generates a magnetic flux. This generates an annular tunnel-shaped main magnetic flux that confines a plasma ring at the tips of the first and second magnetic pole bodies, and generates a main magnetic flux in the form of an annular tunnel installed between the second and third magnetic pole bodies. A planar magnetron sputtering method characterized in that the diameter of a plasma ring that is synthesized and formed at the tips of these magnetic pole bodies is changed by controlling the value of current flowing through a first electromagnetic coil. 4. The planar magnetron sputtering method according to claim 3, wherein the current value passed through the first electromagnetic coil has periodicity.