JPS61201773A - Sputtering method and its device - Google Patents

Abstract

PURPOSE:To improve utilization efficiency of target by changing polarity as well as the intensity of magnetic field by a low-frequency current in releasing components from a target by use of plasma so as to carry out plasma control to the target. CONSTITUTION:The target is composed of a couple of side faces 1a, 1b and the base 1c, a cathode 2 is disposed at the rear of the both side targets 1a, 1b and further, at the rear of the above, an electromagnet yoke 5 is disposed. On generating a magnetic field in this state between the both sides of the electromagnet yoke 5, plasma P is produced in a space formed by the side targets 1a, 1b and the base target 1c. At this time, a low-frequency current is used as exciting current of the electromagnet yoke 5 and, e.g., by periodically changing the intensity and waveform of the current, the position, density, shifting range, etc., of the plasma P are controlled. In this way, the local consumption of target is effectively prevented, so that a uniform thin film can be formed on a substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to sputtering technology, and more particularly to a sputtering method and apparatus that can efficiently use a target in so-called magnetron sputtering.

(Prior Art and Problems) In general, sputtering is a process in which plasma ions generated by glow discharge or arc discharge collide with a flat target surface, and atoms or molecules ejected from the target by this impact are deposited on the substrate surface to form a thin film. It forms the

There are many types of sputtering technology, but the so-called magnetron type sputtering is relatively low temperature,
Moreover, thin films can be formed at high speed.

It is often used especially when producing ferromagnetic thin films.

This magnetron method, for example, as shown in Figure 8,
In order to increase the sputtering speed, a permanent magnet 3 is provided on the back side of the cathode 2 that supports the six-disk-shaped target 1, and a magnetic field is applied near the target surface to increase the density distribution of the plasma P.

Although this method has been widely put into practical use, the target is unevenly consumed because the magnetic field on the target surface is not uniform (FIG. 9). This tendency is particularly noticeable when the target is a ferromagnetic material, and the magnetic field concentrates on the worn part, further accelerating the wear and tear, and eventually a hole penetrates the target in a short period of time, making it unusable. be. This phenomenon significantly reduces the efficiency of using expensive targets and causes problems such as making continuous operation impossible.

On the other hand, as a method that makes it easier to apply a uniform magnetic field near the target, as shown in FIG. A so-called facing sputtering method in which a magnetic field is generated between targets 1 has been proposed. However, in this case, two substrates (anodes) are provided.

However, although this method can relatively reduce the local concentration of the magnetic field and improve target utilization efficiency, it does not take up much space in the substrate arrangement or vacuum chamber because it uses two independent cathodes 1, 1. There are difficult problems such as the size of the space, and the workability is not good.

(Objective of the Invention) The present invention has been made to solve the above-mentioned problems of magnetron type sputtering, and uses a simple configuration to significantly reduce the local concentration of the magnetic field and improve target utilization efficiency. An object of the present invention is to provide a sputtering method and apparatus that can be significantly improved.

(Structure of the Invention) In order to achieve the above object, the present inventor paid attention to the fact that the conventional magnetron system maintains the symmetry of plasma, and studied the symmetry.

That is, in the normal magnetron method, the target is arranged so that plasma is generated symmetrically with respect to the movement of secondary electrons in the plasma formed near the target surface. therefore.

For example, as shown in FIG. 11, the secondary electrons e- flow out from the surface of the target 1 while maintaining the symmetrical interaction between the magnetic fields (Lorentz force). As a result, the current carried by the secondary electrons e- flows symmetrically into the target 1 from all directions (thick arrows in the figure), the Lorentz force also becomes symmetrical, and no force is exerted on the plasma.

This also applies to the facing sputtering method shown in FIG. 10 (FIG. 12).

Therefore, in the conventional magnetron method, the target was consumed under the non-uniformity of the magnetic field without the plasma being biased in one direction.

In contrast, in the present invention, the target is configured to intentionally destroy the symmetry of the plasma that causes local consumption of the target, and the target is controlled using a low-frequency current to utilize the Lorentz force generated thereby. By changing the strength, polarity, etc. of the magnetic field using electromagnets, the position, density, moving distance, etc. of the plasma near the target surface are controlled, and the aim is to prevent local wear and tear of the target.

The present invention will be explained in detail below.

First, the configuration of the sputtering electrode in the present invention is made asymmetric by intentionally breaking the symmetry by giving the target and the cathode a specific arrangement relationship as described above.

For this purpose, for example, as shown in FIG.
The target 1 is composed of a pair of side targets 1a, 1b and a bottom target 1c, and one cathode 2 is disposed on the back surfaces of these targets. Further, an electromagnetic yoke 5 is arranged further behind the targets 1a and 1b on both sides. Note that 6 is an excitation winding, and the substrate is not shown.

In the case of the sputtering electrode having this configuration, when a magnetic field is generated between the electromagnetic yokes 5, plasma P is formed in the space created by the side targets 1a, b and the bottom target 1c. In this case, simply generating a magnetic field between the electromagnet yokes under excitation conditions with constant characteristics will not cause the target
Because la, 1b, and 1c intentionally break the symmetry,
As shown in Figure 2, most of the secondary electrons flow out from the upper opening, and therefore the current (indicated by the thick white arrow in the figure) flows in from only one direction, and there is a gap between the secondary electrons and the magnetic field. F=
A Lorentz force called IXB is generated. This results in the plasma P being biased towards one direction of the target.

Therefore, in the present invention, in order to further control the direction and strength of this Lorentz force, that is, to control the plasma P, an electromagnet controlled using a low frequency current is used. That is, the direction in which the plasma is biased (the direction of the Lorentz force) becomes the opposite direction when the direction of the magnetic field B is reversed. In other words, 2
This means that the two asymmetric Lorentz forces can be controlled in various ways by the excitation current of an external electromagnet.

For example, by using a low-frequency excitation current and periodically changing its strength and waveform, it is possible to control the position, density, moving distance, etc. of the plasma P, thereby effectively reducing local consumption of the target. This makes it possible to prevent Note that the low frequency current used in the present invention is preferably at most about 10 c/s, and if it exceeds this, the stability of the plasma tends to deteriorate.

Under this principle, the configuration of the target, in conjunction with the magnetic field generated by the electromagnet, is possible as shown in FIGS. 3 and 4 (the cathode and the bottom target are not shown). In the case shown in FIG. 3, the electromagnetic yoke 5 is placed behind the entire surface of the pair of targets 1a and 1b, and the plasma P is moved up and down by repeatedly reversing the polarity of the excitation current of the excitation winding 6. I can do it. In the case shown in FIG. 4, the electromagnet yoke 5 is connected to a pair of targets 1.
Plasma P is separated into upper and lower portions by arranging it behind both ends of the electrodes a and 1b, but it is possible to repeat the process of concentrating the plasma P in the center as the polarity of the excitation current is reversed. Of course, in either case, the moving distance, density, etc. can be adjusted by changing the strength of the excitation current.

Note that various configurations of the target are possible; 1. Usually, a pair of side targets la.

1b and a bottom target 1c. As a result, the number of sputtered particles can be increased, and the flight direction of each particle is restricted by the opening, giving directionality toward the substrate, so the amount of film produced per unit time can be significantly improved. Enables highly productive sputtering.

Furthermore, if the areas of the side targets la and lb are larger than the area of the bottom target 1c, particles sputtered from the side surfaces will accumulate on the bottom surface, causing the bottom target 1
c is not consumed at all. That is, with appropriate design, the bottom target 1c is not necessary and the cathode surface may be bare. Of course, in this case, omitting the bottom target 1G will have an adverse effect on the movement of the plasma P, etc. There isn't.

Furthermore, even when the material of the target is a ferromagnetic material such as pure iron (Fe), the present invention can be effectively applied, and it is possible to prevent uneven consumption of the target as in the prior art, and prevent local consumption. It is possible to avoid situations such as non-use due to hole penetration etc.

(Example) As shown in FIG. 5, a pair of Fa targets la and lb having dimensions of 150 x 60 x 5 (t) mm were placed facing each other and separated from each other, and their back surfaces were supported by the cathode 2 as shown. This cathode 2
An electromagnetic yoke 5 is arranged behind both sides of the
connected. Note that 9 is a DC power source, which is connected to the cathode 2 and the substrate 10, respectively, and the cathode 2 is cooled by cooling water W. Of course, the entire sputtering electrode is housed in a thin film forming chamber (not shown), which is equipped with a vacuum pump.

A gas introduction pipe such as Ar is connected.

Using the above device, an excitation current of ±7 A (magnetic field ±150 gauss) was set in an Ar atmosphere of 3×10″″3 Torr.

Discharge was performed for 1 minute while changing the excitation frequency in the range of 0 (DC excitation) to 5 c/s. The discharge current is 4A (600
V, D, C,).

As a result, a film deposition rate of 1500 persons/min was obtained, and the 6th
The film thickness distribution and the target consumption situation are shown in FIG. In each figure, the upper figure shows the film thickness distribution on the substrate after 1 minute of discharge.

The lower figure shows targets (la, lb) after long-term sputtering.
) shows the condition of the worn parts (shaded areas).

Figure 6 shows the results of a comparative example in which the excitation frequency is Oc8, that is, DC excitation, and the excitation current conditions are not changed. You can see that things are changing.

On the other hand, FIG. 7 shows the results of an example of the present invention in which the excitation frequency was varied from 2 to 5 c/s, and the consumption of the target was fairly uniform and no clear dependence on frequency was observed. Good results were obtained with very uniform film thickness distribution.

(Effects of the Invention) As detailed above, according to the present invention, the symmetry of plasma, which has been an essential condition in magnetron sputtering, is intentionally broken.

Since the resulting Lorentz force is used to control the plasma position, density, moving distance, etc., local consumption of the target can be prevented, the target can be used efficiently, and a thin film can be uniformly formed on the substrate. . Furthermore, since the configuration is simple, workability is also good.

It can be driven stably. The present invention is suitable for forming a ferromagnetic thin film, which has been considered difficult in the past.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, FIG. 3, and FIG. 4 are diagrams each showing a configuration example of a sputtering electrode in the present invention. FIG. 2 is an explanatory diagram showing the Lorentz force used in the present invention. FIG. 5 is a diagram showing a sputtering apparatus according to an embodiment of the present invention, FIGS. 6 and 7 are diagrams showing target consumption and film thickness distribution, FIG. 6 is a comparative example, and FIG. 7 is a diagram showing the present invention. 8 and 10 to 12 are diagrams illustrating the principle of conventional magnetron sputtering, and FIG. 9 is a diagram illustrating local consumption of the target caused by the conventional method. 1... Target, la, 1b... Side target, 1c... Bottom target, 2... Cathode, 3
...Permanent magnet, 5...Electromagnetic yoke,
6... Excitation winding, 7... Power amplifier. 8... Oscillator, 9... DC power supply, 10
...Substrate, P... plasma. Patent Applicant Showa Denko K.K. Patent Attorney Takashi Nakamura Figure 1 Figure 2 Figure 3 P Figure 4 Figure 5wA Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11! Figure 112

Claims (1)

[Claims] 1. In sputtering, in which a magnetic field is generated near the target surface to increase plasma density and component atoms or molecules are emitted from the target radiation surface toward the substrate, a low-frequency current is used to control the strength and intensity of the magnetic field. A sputtering method characterized by controlling plasma directed to a target by/or changing polarity. 2. In a sputtering device that generates a magnetic field near the target surface to increase plasma density and emit component atoms or molecules from the target emission surface toward the substrate, a magnetic field generator is provided near the target and an electromagnet that generates the magnetic field. A sputtering apparatus characterized in that a low frequency current supply means for periodically changing the strength and/or polarity of the magnetic field is provided.