JPH0776418B2 - Sputtering method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Use) The present invention is a population in which a plurality of thin films of two or three or more kinds, which are composed of two or more kinds of plural kinds of atoms, are finely laminated. The present invention relates to a sputtering method for producing a multi-component thin film such as an artificial lattice film or a composition modulation film having a periodical structure.

(Prior Art) As a method of forming a multi-component thin film by sputtering using a plurality of targets, conventionally, a shutter is provided between two or more types of targets and a substrate, and the components constituting each target are layered by opening and closing the shutter. Alternatively, a method for forming a thin film with a constant ratio composition and a method for forming a layered or constant ratio composition thin film of individual components of a plurality of targets by rotating the substrate and continuously changing the positions of the plurality of targets have been proposed. . Further, in recent years, a method has been proposed in which the power applied to a plurality of targets in the same region is independently controlled, and a plasma flow from the targets is simultaneously and continuously irradiated to obtain a multi-component thin film (JP-A-59-123768). There is.

(Problems to be Solved by the Invention) In the conventionally proposed shutter opening / closing method, an operating mechanism for opening / closing the shutter is required in the sputtering apparatus, which complicates the apparatus and forms a thin film from the target on the shutter section. The components are deposited and fall, which contaminates the thin film itself or causes abnormal sputtering, which hinders the uniformity of the thin film. Further, the substrate rotation method has a problem that a blank time during which the thin film is not formed occurs during the movement (rotation) and film contamination such as oxidation occurs. In a method of forming a multi-component thin film in which the power applied to multiple targets is independently controlled and at the same time the substrate is irradiated with a plasma stream without interruption, a thin film having a uniform compositional composition or a compositional composition continuously changing in the film thickness direction Can only create.

(Means for Solving Problems) The problems of the above-mentioned conventional technology are solved, and the apparatus does not particularly complicate the inside of the sputtering chamber, and has a composition modulation period of 200 Å or less in the film thickness direction using the target. As a result of investigations for producing an artificial lattice film or a composition modulation film, the present invention has been reached. That is, the present invention is applied to a target in a sputtering method for producing an artificial lattice film or a composition modulation film, which is composed of a plurality of kinds of atoms of two or more kinds and has a composition modulation period of 200 Å or less in the film thickness direction. The sputtering method is characterized by periodically modulating a voltage or a current.

The thin film to be produced in the present invention is a thin film having an artificial periodic structure in which a plurality of atoms of two or more kinds are stacked in layers as a fine film having a thickness of several Å to several hundred Å. The fine film having a thickness of several Å to several hundred Å may be composed of a single atom, or may be composed of a plurality of atoms such as an oxide or an amorphous alloy. Is composed of at least different fine layers, and the stacking order thereof is not particularly limited, but one fine layer is A, another fine layer is B, and another fine layer is C ... , ABABABABAB ..., ACBACBACB ...
., ABABCABABC ... can be exemplified. This is also illustrated in FIG. 3, and the present invention is a comparatively simple method in which an artificial lattice film or a composition modulation film in which the above-described fine films are repeatedly laminated in a constant cycle in multiple layers is formed by sputtering. It is a method that can be produced in a variety of controlled states that are controlled accurately and accurately by a device at high speed.

The composition modulation period in the present invention means ABAB · shown in FIG.
.. "AB" -repeating unit
When ABCABABC ... means the repeating unit of “ABABC”. The present invention is a method for producing an artificial lattice film or a composition modulation film having a composition modulation period of 200 Å or less, and the composition modulation period is preferably 150 Å or less, more preferably 100
Å This method is effectively applied to the production of artificial lattice films or composition-modulated films below. The number of repetitions is not particularly limited, but is 10 or more, preferably 20 or more.

In the production of such a multi-layered thin film of fine films, it is difficult to produce it by a mechanical control method such as a conventional shutter opening / closing method, a substrate rotation method, and the like. It must be controlled.

In the present invention, when a plurality of targets are used, the control application of voltage or current to each target is preferably frequency modulation or waveform modulation, more preferably frequency synchronous modulation or waveform synchronous modulation.
Specific examples of these controls include square wave synchronous modulation, sine wave synchronous modulation, triangular wave synchronous modulation, and the cycle of these cycle synchronous modulation is 200 seconds or less, preferably 50 seconds or less, more preferably 30 seconds. It is less than a second. The synchronous modulation means that the control voltage applied to the plurality of targets is controlled by the correlation between the targets of the plurality of targets in relation to each other. Controllably or in a wave shape.

As a specific example, one example of these frequency synchronous modulation or waveform synchronous modulation is shown in FIG. In FIG. 2, A and B
Shows the control of the applied current by the square wave synchronous modulation using two targets, the solid line shows the applied current to the target A, the broken line shows the applied current to the target B. For A, 0.03A current is first applied for 7.5 seconds. Then, apply a current of 0.8A for 7.5 seconds. For B, only a current of 0.03A is applied for the first 15 seconds, and when the voltage applied to A drops to 0.03A.
It shows that a current of 0.8A is applied to B in 7.5 seconds, and thereafter, the application to A and the application to B are performed appropriately times.
The values of 0.03A and 0.8A indicate that the mating is repeated. The sputtering method of the present invention is applicable to any conventionally known sputtering method, and specific examples thereof include a magnetron sputtering method, a bipolar sputtering method, a multipolar sputtering method, a DC electrode sputtering method, and a high frequency electrode. Examples thereof include a sputtering method, a physical sputtering method, and a reactive sputtering method involving reaction. In the present invention, it is possible to use a single target in reactive sputtering, but it is preferable to use a physical sputtering method and to use two (two) or more targets to periodically modulate each target. It can be applied to a method of controlling and applying a voltage or a current.

Examples of the target used in the sputtering method of the present invention include various targets, an inorganic target, preferably a metal or metal-based alloy target, particularly preferably magnetic as a multi-layered thin film, Fe , Co, Ni, transition metals such as Pr, Nd, G
It is composed of one of rare earth elements such as d, Ce, Dy, Tb and Sm, or an alloy of two or more thereof.

Examples will be shown below, but the present invention is not limited thereto.

(Example) [Example-1] As a target A using an apparatus as shown in FIG.
Using Co as the target B and Cu as the target B, atmosphere Ar gas pressure 10
Millitor, Ar gas flow rate 10SCC / M, minimum distance 170mm between target A and target B, vertical distance 133mm between substrate and target. Square wave synchronous modulation control shown in Fig.2, 0.03A minimum for A and 0.8A maximum. In the same manner, each of the currents was applied to the target B for 7.5 seconds so that the minimum current and the maximum current of each of them became different from each other. The total application time is 25.6 minutes. The multilayer film formed on the substrate is a film as shown in the schematic diagram in Fig. 3, where Co is a fine film layer with a thickness of 15Å and Cu is
The film was alternately laminated with a film thickness of 33.75Å, and the total film thickness was 5000A. Small-angle X-ray diffraction confirmed a compositional modulation period consisting of one layer of Co and one layer of Cu.

Furthermore, from X-ray diffraction, the further crystal structure of Co shows that it is stable at room temperature.
It was confirmed that it was not the hcp but the high temperature stable phase fcc. It is considered that the Co phase is fcc because it was epitaxially grown with the Cu phase.

[Examples-2 and 3, Comparative Example-1] Similar to Example 1, Tb was used as the target A and Fe was used as the target B. The results are shown in Table-1.
In Example-2, Example-3, and Comparative Example-1, the ratio of Tb in all thin films was set to 20 atom%. Comparative Example-1 used an alloy single target of TbFe.

It was confirmed that in both Example-2 and Example-3 according to the present invention, the Te fine thin film and the Fe fine thin film were uniformly laminated. Compared with Comparative Example-1, both have large coercive force Hc, large uniaxial magnetic anisotropy Ku, high density recording, and excellent characteristics as a magnetic film with high stability of perpendicular magnetization. It was

(Effect of the invention) When a multi-element thin film composed of a plurality of atoms is formed by a sputtering method, an artificial lattice film having a composition modulation period in the film thickness direction, a composition modulation film is formed to impart a new function or increase conventional functions, For the purpose of expansion, it is extremely advantageous to periodically modulate the voltage or current with respect to the individual targets of the target of the present invention, which is economically simple in device, and has a uniform quality artificial lattice film or composition. A modulation film is obtained.

[Brief description of drawings]

FIG. 1 is a diagram of an example of an apparatus used in the present invention, and FIG. 2 shows an example of periodic modulation of a current applied to each target among a plurality of targets. Three
FIG. 3 is a schematic view of a film obtained by the present invention.

Claims (3)

[Claims] 1. A sputtering method for producing an artificial lattice film or composition modulation film, which comprises two or more kinds of atoms of a plurality of kinds and has a composition modulation period of 200 Å or less in the film thickness direction, is applied to a target. A sputtering method characterized by periodically modulating voltage or current. 2. The sputtering method according to claim 1, wherein the target is a plurality of two or three or more targets. 3. The sputtering method according to claim 1, wherein the period for periodically modulating the voltage or current applied to the target is 200 seconds or less.