JPH049864B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sputtering film forming method and apparatus for forming a thin film material by sputtering.

Sputtering technology ionizes (plasma-like) low-pressure atmospheric gas by causing glow discharge.
A voltage applied between the cathode electrodes causes the plasma-like ions to be accelerated and impinge upon a plate of target material placed at the anode and cathode.

This is a technique in which the 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, the ions generated by the claw discharge are confined in a space at a high density and transported effectively onto the target material plate, which improves the deposition rate and reduces damage to the substrate caused by electrons. It is becoming important.

For this purpose, it is effective to confine the ions to a spatial region on the target material plate 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 thin film integrated circuits and semiconductor devices in the production process. It came to be widely used.

FIG. 1 is a conceptual cross-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 ring-shaped magnetic pole 2 magnetically coupled to the back surface of a target material flat plate (hereinafter referred to as target) 1 by a yoke 6, and a cylindrical magnet 3 in the center of the ring-shaped magnetic pole 2 are arranged to constitute a magnetic circuit. There is. These magnetic poles 2 and 3 create a distribution of magnetic flux lines in the space on the surface side of the target 1 (lower side in Figure 1), in other words, the torus is cut in half along a plane perpendicular to the height direction. , a tunnel-like magnetic field distribution 11 whose half-cut plane is parallel to the surface of the target 1 is generated. This tunnel-like magnetic field distribution 11 confines the plasma-like ions in a high concentration therein (not shown). These plasma ions were further generated by a high voltage applied to the anode 10 and the cathode 7 placed on the back surface of the target. Accelerated by an electric field substantially perpendicular to the surface of the target 1, the atoms or particles collide with the surface of the target 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 progresses as time passes in the sputtering process. Since the progress is limited to the eroded 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, resulting in a substantially downwardly convex quadratic curve distribution or upwardly convex quadratic curve distribution.

Therefore, if a large film thickness is desired or a long sputtering process is desired, it is impossible to do so, and this has been considered a limitation of conventional sputtering targets. after that,
In order to eliminate this drawback, it has been proposed to change the magnetic field distribution 11 so that the erosion region 12 is generated over a wide area on the surface of the target 1.

In this conventional planar magnetron sputtering device, the greatest target erosion occurs in the region aligned with and underlying the above point or region where the magnetic field lines are parallel to the target plate, thus Generating an auxiliary variable magnetic field in a direction perpendicular to the source with respect to the magnetic field generating means, and changing the auxiliary variable magnetic field to continuously move the position where the resultant magnetic field lines are parallel to the source. It is something.

In this way, in the conventional device, the glow discharge moves according to changes in the magnetic field distribution in the hollow space, but the glow discharge or a part of the glow discharge that occurs near the center of the target flat plate is located at a position relative to the anode. Electrons, which are part of the charged particles that form the discharge current, may also flow into the sample substrate side in large numbers. If such an electron beam flows into the sample substrate, it may cause permanent damage to semiconductor elements already formed on the sample substrate, resulting in a defective product.

It is an object of the present invention to eliminate the above-mentioned conventional drawbacks, to perform uniform film formation, and to significantly reduce the amount of negatively charged particles flowing into the sample substrate on which the film is to be formed. An object of the present invention is to provide a film forming method using sputtering that reduces damage to a sample, and an apparatus therefor.

That is, the present invention has a plurality of magnetic poles, in view of the fact that when magnetic lines of force are generated from one source of magnetic lines of force, they do not interlink as a matter of their nature, and that an attractive force or force called maxwell stress acts on the lines of magnetic force with each other. Excitation means (electromagnet) that constitutes one magnetic field line source and controls the magnetic field lines generated in some of the magnetic poles to move the position of the magnetic field line distribution emitted to the remaining magnetic poles, that is, the position of the plasma region. Using a planar magnetron electrode equipped with a magnetron, a current with a predetermined period is passed through the excitation means, and a potential close to ground is applied to the anode provided around and at the center of the electrode, thereby applying a potential to the substrate to be film-formed. While reducing the inflow of charged particles, the annular plasma generation region is moved at least once at a predetermined period, and the film thickness obtained in each annular plasma generation region is synthesized to obtain the above-mentioned film formation symmetry. The method is characterized in that a film is formed on a substrate.

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, 21 is a target disc-shaped flat plate made of sputtering material, Al-2%Si (purity 99.999%).
Materials and shapes with a diameter of 8"ψ and a plate thickness of 20 mmt were used. Reference numeral 22 is the first pole tip, which is made of a soft magnetic material (high permeability magnetic material). Reference numeral 23 is the second pole tip, which is a permanent magnet. It is made of a magnet. 24 is the third magnetic pole tip according to the present invention, and it is made of a soft magnetic material. 24a
is an excitation coil according to the present invention, which is located in the intermediate space between the first magnetic pole tip 22 and the third magnetic pole tip 24.
A toroidal coil wound 300 times, 25 a medium for cooling the target disc-shaped flat plate 21, here an inlet/outlet pipe of water, and 26 a magnetically connected entire first, second and third magnetic pole tip. 27 is a cathode, 28 is an insulating layer plate, and 32 is an eroded region. Reference numerals 29 and 30 denote a first anode and a second anode to which a voltage close to ground is applied, and they are provided around the target material flat plate 21 and in the center of the target material flat plate 21 so as to be electrically insulated from the target material flat plate 21. ing. The second anode 30 is cooled by a conduit having a coaxial structure that penetrates the sputter electrode structure shown in FIG. It is pulled out from the back of the structure.

3 and 4 are both explanatory views of the operation of the sputter electrode structure of the planar magnetron type sputtering apparatus shown in FIG. 2, and show the magnetic flux distribution on the target material flat plate 21. Figures 3 and 4
In the figure, 301 and 401 respectively indicate the height (mm) above the target material flat plate 21, and 302,
402 indicates the radial distance (mm) from the center of the target material disk.

Both FIG. 3 and FIG. 4 show the excitation coil 24a.
, the polarity of the magnetic pole at the second magnetic pole tip 22 is
A control current is passed in a direction opposite to the polarity of the flat plate of the target material caused by the permanent magnet.

FIG. 3 shows the case where this control excitation current is set to 0A and is not flowing. FIG. 4 shows the magnetic flux distribution when the control excitation current is 7A.

As is well known, in a planar magnetron sputter electrode, a plasma region is formed around the point where the magnetic field lines on the target material flat plate are parallel to the target material flat plate. The target material plate 32 closest to the target material is eroded.

As shown in FIGS. 3 and 4, in the sputter electrode according to the present invention, by changing the current flowing through the excitation coil, it is possible to move the point where the lines of magnetic force are parallel to the target material flat plate. It can be seen that the eroded region 32 can also be moved.

By the way, the permanent magnet 23 generates a magnetic field of 200 to 300 Gauss (0.02 Wb/m ² ) or more as shown in FIGS. The strength was determined at the point where the lines of magnetic force on the target flat plate became parallel to the target flat plate.

The sputtering process will be briefly explained below to show how it is incorporated into the sputtering process.

First, although the target structure according to the present invention is not shown in the drawings, it is equipped with a well-known vacuum evacuation system, a shutter, an Ar gas introduction system, two gate valves, and a transport means capable of continuously transporting wafers. Attach to one wall of a vacuum chamber with First, there is a distance above the space where the magnetic flux lines of the target disc-like flat plate 21 are formed (the arrangement is upside down in Fig. 3), stationary and facing the surface of the target disc-like flat plate 21.
A substrate to be film-formed is placed and held at a position of 70 mm parallel to its surface using well-known holding means. Next, this vacuum chamber is evacuated to about 1 to 3 x 10 ^-7 Torr, and after evacuation, Ar gas is introduced from the Ar gas introduction system, and the Ar gas pressure is set to 2 to 20 mTorr.

Next, the second anode 30 of the target structure 21
Apply 0 to +50V and -400V to the cathode 27,
When the first anode 29 and the vacuum chamber (not shown) are connected to ground, the Ar gas causes a glow discharge.
At this time, the excitation current flowing through the excitation coil 24a is set to 0.
When the magnetic force is changed by approximately 7A, the point where the magnetic field lines shown in Figures 3 and 4 become parallel to the target plate shifts, and as expected, Ar atoms are ionized and the confined plasma region is expanded. , we were able to visually and experimentally confirm that it moved.

FIG. 5 discloses the greatest technique made possible by this embodiment, which is the control of the film thickness distribution to form an arbitrary film thickness distribution with respect to the center of the substrate from the film thickness distribution obtained by sputtering. It is the acquisition of sexuality.

FIG. 5 shows some of the experimental results, and shows changes in the film thickness distribution within the substrate with respect to the radial distance from the center of the substrate when the control current applied to the excitation coil 24a is changed. It is something that
Solid line 501 (□ mark) is a downward convex film thickness distribution, solid line 5
04 (○ mark) is almost uniform film thickness distribution, solid line 505
(○ mark) indicates an upwardly convex film thickness distribution.

Based on the above experimental results, the current waveform of the current flowing through the excitation coil 24a was set such that one cycle is 12 seconds, the excitation current is 7A for 4 seconds of one cycle, and the excitation current is 0A for the remaining 8 seconds.

Next, the substrate to be film-formed is transported so as to directly face the first main plane of the target flat plate, the shutter for the target structure (not shown) is opened, and the cathode voltage is adjusted.
At 350V and cathode current of 15A, target material Al−
A 2% Si film was formed on the substrate for 2 minutes.

Incidentally, the distance between the substrate to be film-formed and the first main surface of the target flat plate at this time was 70 mm.

After the scheduled deposition time has elapsed, close the shutter and
The gate valve was opened and the substrate (Si wafer) on which the Al-2% Si film was deposited was taken out. The above is the result of an experiment that was virtually repeatable by repeating the same process.
I checked it for over 100 hours.

Figure 6 shows some of the experimental results60
1 shows the conventional film thickness distribution within the wafer, and 602 shows the change over time in the film thickness distribution within the wafer using the target structure according to the present invention. The effects of the present invention are obvious. Moreover, the Al-2%Si film thus formed showed good electrical properties as a film for semiconductor wiring.

The inventors' research results have revealed that such good intra-wafer film thickness distribution and electrical characteristics are extremely dependent on the shape of the erosion region on the wafer-facing surface of the target disk-like flat plate. The erosion area 32 in FIG. 1 is extremely narrow due to local erosion, and as time passes, the center of the local erosion area of the erosion area 32 is preferentially eroded, and finally the target disc-shaped plate is formed. 21, and the target disk-shaped flat plate 21 becomes unusable.

On the other hand, the erosion region 32 in FIG. 2 is created by selecting the current waveform that passes through the excitation coil 24a and periodically moving the plasma region, thereby maintaining uniform and good film deposition distribution characteristics over a long period of time. It was possible to form an eroded region relatively uniformly over a wide area of the material flat plate.

This has the effect of guaranteeing a long life of the expensive target material flat plate 21 and greatly reducing dead time mainly due to replacement of the target material flat plate, which is a major hindrance in the production process.

FIG. 7 shows the effect of the anode according to the present invention. In the sputter electrode of the present invention, when the current flowing through the excitation coil is increased, the plasma region can be contracted to the center on the target plane. However, in this case, a portion of the discharge current may flow into the substrate and damage the semiconductor elements on the substrate.

A curve 701 in FIG. 7 represents the defect rate of elements on one substrate when the anode according to the present invention is not provided. If the radius of the plasma ring is less than 50 mm, the defect rate increases. The defect rate of elements on one substrate when the anode according to the present invention is installed is shown by a curve 702 in the figure, and the effect of the anode according to the present invention is clear.

FIG. 8 is a sectional view of another embodiment of the target structure of the planar magnetron sputtering apparatus according to the present invention. In FIG. 8, the difference from the configuration in FIG. 2 is that the second magnetic pole tip 3
The first point is that a permanent magnet is not used, but a second multi-wound excitation coil 31a is provided on a soft magnetic material. 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 that the second magnetic pole tip 31 and the magnetic flux due to the third magnetic pole tip 24 can both be controlled. The process leading to the generation of other plasma regions is the same.

FIG. 9 shows a schematic configuration of a power source for excitation of the electrode structure shown in FIGS. 2 and 8. FIG. The main configuration of the excitation power supply section includes two current supply circuits for controlling the inner electromagnetic coil 31a and the outer electromagnetic coil 24a completely separately. The current applied to the excitation power source and the inner and outer magnet coils 31a and 24a can be applied completely arbitrarily, that is, a constant current that does not change over time, or a current waveform such as a rectangular waveform or a triangular waveform with a constant period. It uses a microprocessor 41 and a memory 42 so that it can be set to a keyboard 43 or a suitable external storage device 40.
(e.g. magnetic tape, magnetic disk), the output of the microprocessor 41 is applied to digital-to-analog signal converters 44a, 44b (D-A converter), and this is further applied to a current amplifier 45a. , 45b, of which:
It is amplified to a predetermined strength sufficient to excite the outer electromagnetic coils 24 and 25.

The excitation power supply unit shown in FIG. 9 has the following as a controlled object:
Since the inner and outer electromagnetic coils 31a and 24a are handled, the power supply has constant current characteristics, and the output current detectors 46a and 46b detect the output current, that is, the current value of each electromagnet, and convert this into a D/A converter. Current amplifiers 45a and 45 are used to compare and correct the predetermined current values output by the
It has a means of returning information to b. That is, it is configured such that a constant current or a constant rectangular wave current is applied to the electromagnetic coils 24 and 25.

As is well known, a high-voltage power supply for supplying the discharge force for sputtering, that is, a sputtering power supply, has an output voltage of about 0 to 800V and an output current of about 0 to 15A. there was. Furthermore, as is well known, this high-voltage power supply has constant current output characteristics in order to control the power input to the glow discharge.

With the above configuration, it is possible to magnetically saturate the magnetic material and use excess magnetic flux lines with easy controllability (the second pole tip 11
However, with permanent magnets, this effect is limited to those with thin plate thickness, so this effect appears to be impractical for practical use.) Therefore, although conventional sputtering film deposition of magnetic material was only possible with a facing target type sputtering apparatus, the present invention has made it practically possible with a planar magnetron type sputtering apparatus.

Furthermore, what has been stated above applies to the first magnetic pole tip and the second magnetic pole tip.
Regarding the special case of the magnetic pole tip and the third magnetic pole tip, each magnetic pole tip can be realized by any combination of a magnetic field control means consisting of a permanent magnet, a soft magnetic material (high permeability magnetic material), and an excitation coil. It is clear that all magnetic field control techniques are included in the technical idea of the present invention.

As described above, according to the present invention, the service life of the target disc-like flat plate can be extended, an arbitrary deposited film thickness distribution can be obtained, and the inflow of charged particles into the sample can be significantly reduced. This has the effect of reducing damage.

[Brief explanation of drawings]

Figure 1 is a cross-sectional structural diagram showing the electrode structure of a conventional planar magnetron type sputtering device.
FIG. 2 is a cross-sectional structural diagram showing one embodiment of the electrode structure of a planar magnetron type sputtering apparatus according to the present invention, and FIGS. Figure 5 is a diagram showing the thickness distribution of the film formed by the sputter electrode structure shown in Figure 2, and Figure 6 is a diagram showing the thickness distribution of the film formed by the sputter electrode structure shown in Figure 2.
FIG. 7 is an example showing the effect of installing the second anode according to the present invention. FIG. FIG. 9 is a sectional structural view showing another embodiment of the electrode structure of the sputtering apparatus according to the present invention, and FIG. 9 is a diagram showing a power source for excitation of the electrode structure of FIGS. 2 and 8. 21...Target disc-shaped flat plate, 24...Third
magnetic pole tip, 24a...first excitation coil, 26...
... Yoke, 27 ... Cathode, 29 ... First anode,
30...Second anode, 31...Central magnetic pole tip.

Claims (1)

[Claims] 1. has at least three magnetic poles, and at least two
At least one of the magnetic field generating means uses a planar magnetron electrode equipped with an electromagnet, and a current is passed through the electromagnet, and an anode provided at the periphery and center of the electrode is connected to the electrode. While applying a potential close to ground to reduce the inflow of charged particles to the substrate to be film-formed, annular plasma generation regions are generated in at least two locations, one on the inside and one on the outside, and in each annular plasma generation region. A method for forming a film by sputtering, characterized in that the obtained film thicknesses are synthesized and a film is formed on the substrate to be formed. 2 have at least three magnetic poles, and at least two
At least one of the magnetic field generating means is provided with a planar magnetron electrode equipped with an electromagnet, and a control means for flowing a current through the electromagnet is provided, and the periphery and center of the electrode are grounded. A sputtering film forming apparatus characterized by having an anode provided with a potential close to .