JPS63266061A - Producing of multielemental sputtering thin film and sputtering device - Google Patents

Abstract

PURPOSE:To form a thin alloy film and a multilayered thin film and also to enable change of both the composition ratio and kind of the film by changing sputtering acceleration voltage while synchronizing it with the rotation of a rotary target arranged with the plural kind of targets being a simple substance in the circumference. CONSTITUTION:A rotary target (cathode) is constituted by arranging targets 13, 14 being simple substance consisting of a different kind of element equally and alternately in the circumference of a target rotor 11. A thin alloy film and a multilayered thin film are formed on a base plate 16 fitted to an anode 15 by rotating this rotary target at high or slow speed with a motor 12 for driving the rotor and performing sputtering. At this time, a control circuit 18 is connected with the motor 12, the target rotor 11 and the anode 15 and sputtering acceleration voltage is changed by synchronizing it with the rotation of the rotary target. Thereby the thin alloy film and the multilayered thin film can be formed while using the targets being simple substance without replacing the targets and also the change of both the composition ratio and kind of the film is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a multi-element sputtered thin film and a sputtering apparatus.

[Prior art and problems to be solved by the invention] Recently, in magneto-optical disks, magnetic tapes, etc., thin films containing two or more elements, such as alloy thin films and multilayer films, that is, multi-element thin films, have been formed. Sputtering is an effective method along with vapor deposition and the like in forming these thin films, and is widely used. The sputtering device for forming a multi-element thin film includes a composite target 1 alloy target and a rotary target exchange device.

Rotating targets were used.

A composite target is a target in which materials made of different elements are mixed and arranged on the target holder surface to form a composite, and a desired composition ratio can be obtained by changing the exposed area ratio of each material to the sputtering chamber. Further, an alloy target is a target made by using an alloy formed by melting different kinds of elemental materials in a desired composition ratio in the form of an ingot or powder. However, although these targets can form alloy thin films, they cannot form multi-N thin films, and if the composition ratio or film type (change of compositional elements) is changed, the entire target must be replaced. The problem was that it didn't. Furthermore, since these targets require accurate mixing and melting of a plurality of elemental materials, there is also the problem that the target itself is difficult to manufacture and the manufacturing cost is high.

Furthermore, when these targets are used, composition deviations tend to occur due to differences in the sputtering characteristics of each compositional element, and if a composition deviation occurs, it is necessary to prepare and replace these targets again in order to repair this deviation. The problem was that it didn't.

In addition, as a rotary target exchange device, for example, Japanese Patent Application Laid-open No. 6
There is a method described in Japanese Patent No. 0-262969, in which a plurality of targets made of single materials of different elements are arranged on the circumferential surface of a target rotor, which is a cathode, and these targets are sequentially and selectively placed in a sputtering chamber. sputtering. It is true that this device has the advantage that the target manufacturing cost is low because it uses a single target, but although it can form multilayer thin films, it cannot form alloy thin films, and even though it can change the film type, it cannot change the composition ratio. This cannot be changed, and if a thin alloy film is formed or the type of film is changed, the entire target must be replaced, which poses the problem of increasing the cost of the target.

Furthermore, as a rotating target, there is one sold by Oua Tsuki Co., Ltd., for example, which has targets 2 and 3 made of single materials of different elements on the circumferential surface of a rotating cathode 1, as shown in FIG. An alloy thin film is formed by arranging a plurality of rotating cathodes and performing sputtering while rotating the cathode many times at high speed, and a multilayer GI film is formed by performing sputtering while rotating at low speed by a predetermined number of targets. It is. Although this target has the advantages of low target manufacturing cost and the ability to form alloy thin films and multilayer thin films, it is not possible to change the composition ratio or film type. If a change were to be made, there was a problem in that the entire target 7) would have to be converted.

Furthermore, target replacement requires equipment that can perform target replacement without changing the atmosphere inside the sputtering chamber, but since the size of the sputtering equipment and target replacement equipment is finite, there is a limit to the number of targets that can be stored. Even if a large target exchange device was installed in order to eliminate this problem even to some extent, when forming a film with a small number of constituent elements or film types, space would be extremely wasted and cost performance would be low.

In view of the above problems, the present invention makes it possible to form alloy thin films and multilayer thin films without replacing the target while using a single target, and it is also possible to change the composition ratio and film type, and it is also possible to repair compositional deviations. It is an object of the present invention to provide a method for producing a multi-element sputtered thin film and a sputtering apparatus that have extremely high cost performance.

[Means and effects for solving the problems] The method for producing a multi-element sputtered thin film according to the present invention makes it possible to change the rotational speed of a rotating target in which a plurality of types of single targets are arranged around the rotational speed of the rotating target. The feature is that the sputtering acceleration voltage is varied in synchronization with the rotation of the target. Further, the sputtering apparatus used in this method includes a rotating target including a plurality of types of single targets arranged around the rotating target, a target driving device for driving the rotating target, and a sputtering accelerating voltage applied between the rotating target and the substrate. The target driving device includes an accelerating voltage applying device, and a control circuit controlling the target driving device and the accelerating voltage applying device separately or synchronously.

And by these methods and devices, rotation
An alloy thin film can be formed by sputtering +77g while rotating the rotating target at low speed for a predetermined number of targets, and a multilayer thin film can be formed by sputtering while rotating the rotating target by a predetermined number of targets at a low speed. The composition ratio can be changed by changing the waveform of the sputtering accelerating voltage that is synchronized with the rotation of the target, and the film type can also be changed by changing the range in which the accelerating voltage becomes zero in the waveform change.

The accelerating voltage referred to here is a voltage that creates an electric field that imparts kinetic energy to ionized inert or active gas molecules or atoms in the sputtering chamber, and the molecules are accelerated by the electric field.

Atoms (hereinafter referred to as colliding particles) collide with the target to sputter target constituent molecules and atoms (hereinafter referred to as sputtered particles), so the magnitude of the accelerating voltage, which determines the magnitude of the kinetic energy of the colliding particles, depends on the generation of sputtered particles. It is related to the size of numbers.

Further, the accelerating voltage that fluctuates in synchronization with the rotation of the rotating target is an accelerating voltage that is not constant but changes in an orderly manner during one rotation of the rotating target. Here, "constant" means that the voltage is in a state where even small voltage fluctuations have no effect on the film forming conditions, and "changed in an orderly manner" means that the voltage changes within one revolution. It means that the waveform starts and ends, and that the timing does not shift or the waveform changes randomly. Furthermore, the waveform of the accelerating voltage that fluctuates in synchronization with the rotation of the rotating target does not necessarily have to be periodic for each rotation, but may consist of a group of multiple voltage waveforms selected from a prepared group of voltage waveforms. , the coughing means may be periodic (hereinafter referred to as hyperperiodic).

〔Example〕

Hereinafter, the present invention will be described in detail based on the illustrated embodiments.

FIG. 1 shows the structure of a first embodiment of a sputtering apparatus according to the present invention, and 11 is a target rotor rotated by a rotor drive motor 12, which also serves as a cathode. 13 and 14 are target rotors 11
four individual targets each made of different types of elements arranged equally and alternately on the circumferential surface of the target rotor 11, which together with the target rotor 11 constitute a rotating target;
For ease of explanation, two types of single targets 13.1
It is assumed that the sputtering efficiency of No. 4 is the same. 15 is an anode, and 16 is a substrate fixed to the anode 15. Reference numeral 17 denotes a slit with a fixed slit interval arranged close to the target rotor 11 between the target rotor 11 and the substrate 16, and the slit interval is the width (circumferential length) of the single target 13°14. is set narrower than 18 is a motor 12. target rotor 11,
A control circuit connected to the anode 15 and the motor 1
The target rotor 11 has a rotational speed of 2 and a cathode.
The sputtering acceleration voltage between the anode 15 and the anode 15 is controlled.

FIG. 2 is a block diagram of the control circuit 18, and 19 is a motor control power supply that outputs a drive voltage corresponding to the control content to the rotor drive motor 12, and basically controls the rotation of the motor 12 at a low speed. It is designed to be variably controlled from low to high speed.

20 is a digital waveform storage device that stores the waveform input from the digital waveform input device 21 and can be read out by command; 22 is a rotation detector directly connected to the rotation axis of the target rotor 11; 23 is a rotation This is a timing control device that outputs a synchronization signal and a sweep speed signal to the waveform storage device 20 based on the signal from the detection 122. Assuming that the waveform for one period of the sweep speed signal is composed of 100 digital signals, the time interval for converting each signal from digital to analog and outputting it is 1 period.
This is a signal that divides the time by 00 and outputs this time so that the above waveform can be output during one cycle. 24 is an output waveform selection device, and when using a combination of several types of waveforms (in the case of hyperperiod), for example, the waveform storage device 20
For example, when waveform patterns A, B, and C are repeatedly generated in the order of ACB, the readout signals are selected in the order of 1-3-2. This is a device that outputs data repeatedly. That is, at the same time as the sputtering start signal is input, a readout signal with a numerical value of 1 is output to the waveform storage device 20.
0 outputs the waveform pattern A corresponding to the numerical value 1, and when it ends, the waveform pattern end signal is sent to the waveform selection device 24.
When the end signal is input to the waveform selection bag M, 24 outputs a readout signal of numeric value 3 to the waveform storage device 20, and the waveform storage device 20 outputs a waveform pattern C corresponding to the numeric value 3. This action is repeated as shown below. 25 is a waveform shaper that converts the stepped digital waveform signal outputted from the waveform storage device 20 into a smooth signal and outputs it as a reference voltage signal; 26 is a sputtering acceleration voltage according to the reference voltage signal from the waveform shaper 25; This is an accelerating voltage power supply that applies this to the target rotor 11.

Next, the effect will be explained.

First, as mentioned above, the sputtering efficiency of the targets 13 and 14 is the same, and the slit interval of the slit 17 is also constant, so the number of each sputtered particle is determined by the exposed area ratio of each target 13 and 14 in the slit I7 at that time. It is proportional to the product with the accelerating voltage.

If the control circuit 18 sets the waveform of the sputtering acceleration voltage as shown in FIG. 3, for example, the number of each spuck particle becomes as shown in FIG. 4. It should be noted that the solid line indicates the effect due to the target 13, and the broken line indicates the effect due to the target 14.

In this example, since the number of sputtered particles shows periodic changes four times during one rotation, we will consider film formation using sputter particles at 174 rotations. The particles sputtered from the targets 13 and 14 are deposited in a layer on the substrate 16, and become a homogeneous film with a uniform composition due to atomic diffusion, that is, an alloy thin film.

However, each layer can be homogenized by diffusion of atoms at most 1
Therefore, when forming an alloy thin film, each layer is thin, that is, the rotation of the target rotor 11 is controlled by the motor control voltage. It is necessary to increase the speed by s19. On the other hand, if the rotation speed of the target rotor 11 is made low,
A multilayer film is formed as each layer becomes thicker.

Next, the composition ratio when homogenized as described above is the ratio of the integral value in one cycle of the number of sputtered particles of each target 13 and 14 in FIG. To express this in a formula, let the ratio of the slit interval to the sum of the widths of the targets 13 and 14 be γ, and let the ratio of the accelerating voltages a and b in FIG. Let the composition ratio with CajCl be P, +p,
= 1゜C^+C1-1, if γ≦1, C
A” (1-γ) pH→-1 ・-・・・・・−・−
(1), as shown in FIG. 5(A).

If r>1, the result will be as shown in FIG. 5(B). Also, if the dependence of C^ on γ is P, -0, then
The result will be as shown in FIG.

Here, the basis of formula (1) indicating the composition ratio will be explained in detail with reference to FIG. In FIG. 7, the solid line shows the change in the number of sputtered particles ejected from the target A, and the broken line shows the change in the number of sputtered particles ejected from the target B. The diagram below the horizontal axis in FIG. 7 shows the change in the center of targets A and B from being located at the center of the slit to moving in the direction of the arrow until they are in the same phase again. This is repeated periodically thereafter. Therefore,
The area of the solid line is the total number of particles coming out of target A in one cycle, and the area of the broken line is the total number of particles coming out of target B, so the area ratio of these is the composition ratio.

The area of the solid line is 1 ayb γ □ ・ a −−−・ −1 □ − □, and the area of the dashed line is , and the sum of both is −(a + b ). Therefore, each area is divided by this sum. If the value or composition ratio is respectively Cm + Cm, then the base metal power is a+b=P and a/P.

Let b/P be P, , Pb respectively, then P, , P, is P, +
It satisfies P, -1 and comes to represent the power distribution ratio.

If CA and CI are rewritten using only P of P- and Pb, γ = P, (1-γ) 10- = (1--)-P, (1-γ).

As is clear from the above, the composition ratio C^:C8 is the acceleration voltage ratio P, although it depends on the magnitude of γ.

By changing :P, it becomes possible to control (repair composition deviation, etc.) and change without converting the target.

In addition, to increase the control range, it is desirable that γ<0.5, and to narrow the control range, it is desirable that r>1. Note that the target is not limited to two types. Needless to say.

FIG. 8 shows a rotary target according to the second embodiment, in which three types of single targets 27, 28, and 29 are alternately arranged on the circumferential surface of the target rotor 11.

A description will be given of changing the film type using this rotating target.

First, when an accelerating voltage with a waveform pattern as shown in FIG. 9(A) is applied to the rotating target, the single target 2
When 7 and 28 meet the opening of the slit 17, the accelerating voltage has predetermined values a and b, and when the single target 29 coincides with the opening of the slit 17, the accelerating voltage becomes zero, so the single target A thin film consisting of the elements constituting elements 27 and 28 is formed. Next, when an accelerating voltage with a waveform pattern as shown in FIG. When the single target 28 meets the opening of the slit 17, the accelerating voltage has the predetermined values c and d, and when the single target 28 meets the opening of the slit 17, the accelerating voltage becomes zero. A thin film is formed. Thus, the film type can be changed by switching the waveform pattern of the accelerating voltage from FIG. 9(A) to FIG. 9(B) or vice versa.

Next, an experimental example will be shown.

] (劃) - Two metals, CO and Fe, were fixed alternately around the rotor as targets, as shown in Figure 1.

Each target was composed of two metal plates, and the rotor had a hexagonal stop. Sputtering tests were conducted on a quartz substrate using such rotating targets. As for the acceleration voltage, the voltage ratio a:b shown in FIG. 3 was set to 2:1. The holding time of each voltage value is one-eighth of the rotor rotation period. The rotation speed of the target rotor is Q, 3 rpm to 50
It was set between 0 rpm. Also, the slit interval ratio γ is r
-0,1.

When the rotor rotation Q is 3 rpm, a multilayer film of approximately 80 layers for the Co film and 40 layers for the Fe layer is obtained.If the zero rotation speed is set to 15 rpm, no periodic multilayer structure is observed and a homogeneous layer is obtained. According to the results of 0 analysis of the Co-Fe alloy thin film, C
o: Fe-65,5: Even when the 0 rotation speed was soorpm, no further change was observed in the film, which was the composition ratio of 34.5.

)LLLL When the accelerating voltage ratio a:b was set to 2:1.1 in Experimental Example 1, the composition ratio Co:Fe was 65 in the analysis results.
: I was able to change it to 35.

ii! uL The three main metals Tb, Fe, and Go were fixed alternately around the rotor as targets as shown in FIG. The acceleration voltage is a voltage ratio a:b of 2:1 as shown in Fig. 9 (A) and (B).
．． c:d was set to 4:1.

Further, the slit interval ratio was set to r -0.5, and the rotation speed of the rotor was set to 2Q rpm. As a result, Tb:Fe=62
:38. Two types of yl films with Tb:Co=69:31 could be formed.

〔Effect of the invention〕

As described above, the method and sputtering apparatus for producing a multi-element sputtered thin film according to the present invention can form alloy Y4 films and multilayer films without replacing the target while using a competitive target, and can also change the composition ratio and film type. It is also possible to repair compositional deviations, and has extremely high cost performance.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a first embodiment of a sputtering apparatus according to the present invention, FIG. 2 is a block diagram of a control circuit of the first embodiment, and FIG. 3 is a diagram showing a sputtering system applied to the first embodiment. FIG. 4 is a diagram showing the change in the number of sputtered particles when the accelerating voltage shown in FIG. 3 is applied in the first embodiment, and FIG. 5 is a diagram showing the accelerating voltage ratio in the first embodiment. 6 is a diagram showing the dependence of the composition ratio on the slit spacing ratio in the first embodiment. FIG. A diagram showing changes in the number of sputtered particles,
FIG. 8 is a diagram showing the configuration of the rotating target of the second embodiment,
FIG. 9 is a waveform pattern diagram of the sputtering acceleration voltage applied to the second embodiment, and FIG. 10 is a perspective view of a conventional rotating target. 11...Target rotor, 12...Rotor R
Dynamic motor, 13, 14, 27.28.29...Single target, 15...Anode, 16...Substrate, 17...Slit, 18...Control circuit, 1
9... Motor control power supply, 20... Waveform storage device, 21... Waveform input device, 22... 9 rotation detector, 23... Timing control device, 24... - Waveform selection device, 25... Waveform shaper, 26... Accelerating voltage power supply. Figure 4 Off Figure 18

Claims (2)

[Claims] (1) A multi-element thin film that is capable of changing the rotational speed of a rotating target consisting of multiple types of single targets arranged around it and varying the sputtering acceleration voltage in synchronization with the rotation of the rotating target. Production method. (2) A rotating target including a plurality of types of single targets arranged around the rotating target, a target driving device for driving the rotating target, and an accelerating voltage applying device for applying a sputtering accelerating voltage between the rotating target and the substrate. ,
A sputtering apparatus comprising a control circuit that controls the target driving device and the accelerating voltage applying device individually or synchronously.