JPH033363B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing thin films by sputtering.

Amorphous magnetic thin films containing rare earth metals and ferrous metals as main components are attracting attention as materials for magnetic bubble memories and thermomagnetic recording. However, a problem in putting it into practical use is that it is extremely difficult to produce a film with uniform magnetic properties over a large area.

Taking an amorphous gadolinium-cobalt (GdCo) magnetic thin film as an example, when a GdCo thin film is formed on a glass substrate from a uniform GdCo alloy by sputtering, the amount of Co is higher at the periphery than at the center.
A property appears in which the composition ratio of Gd to Gd becomes apparently large. That is, the magnetic properties are different between the center and the periphery. Examples will be described below.

GdCo alloy target with a diameter of 60 mm, distance between target and substrate 40 mm, Ar gas pressure 8.0 × 10 ^-2 Torr,
When a thin film is formed on a glass substrate using the usual sputtering method at a voltage of 1000 V, the hysteresis loop of the thin film is drawn using the Kerr effect with a laser beam.

FIG. 1 shows an outline of the measurement method.
Here, 1 is a glass substrate, 2 is a GdCo thin film, and a cross section perpendicular to the substrate surface is shown. Further, the thickness of the thin film 2 has been increased. The thin film 2 has magnetization perpendicular to the thin film surface, and the upward arrow indicates the magnetization direction of Co, and the downward arrow indicates the magnetization direction of Gd. Of course, this arrow is originally microscopic, but it is enlarged for explanation purposes. Laser light 4 generated by laser light generator 3 becomes linearly polarized light by polarizer 5, and light 7 reflected by half mirror 6 enters the surface of thin film 2 perpendicularly and is reflected by the surface of thin film 2. The plane of polarization of the light is rotated by the Kerr effect, and then passes through the half mirror 6, passes through the analyzer 8, and enters the detector 9, where the rotation angle θ due to the Kerr effect is measured. Since only the magnetization of Co contributes to the Kerr effect, if the rotation angle due to the Kerr effect is known, the strength and direction of the magnetization due to Co in the thin film can be determined. Note that the external magnetic field H is applied in a direction perpendicular to the substrate.

Figure 2 shows a sample manufactured by the conventional method as described above.
The hysteresis loop due to the Kerr effect of the GdCo thin film is calculated when the distance l from the center of the thin film is 0, 5, 10,
The drawings are based on the measurement results for 15 and 20 mm, and the horizontal axis shows the magnetic field strength H, and the vertical axis shows the Kerr rotation angle θ. In the figure, the curve for l = 0 mm is upward to the right, whereas the curve for l = 5 mm or more is upward to the left.
At a position between mm and magnetization due to Gd,
This shows that the magnetization due to Co cancels each other out, that is, the magnitude of the magnetization due to Gd and the magnetization due to Co are reversed on both sides of that position.

As shown in Figure 2, the shape of the hysteresis loop is
A report (RJ
Kobliska, R. Ruf and J. Cuomo: AIP Conf.
Pnoc. No. 24 (1974) 570), but the inventor
We believe that the main reason is that the actual amount of oxygen increases closer to the periphery than the center of the thin film. In other words, Gd atoms bond with oxygen more easily than Co atoms, and Gd atoms bonded with oxygen (oxidized) have specific magnetism, so the part where Gd bonded with oxygen magnetically changes the composition of Co. This means that the influence of Co becomes stronger in the periphery. The causes of oxygen entering the thin film include oxygen remaining in the discharge vessel, and oxygen adsorbed on parts within the discharge vessel being released as the temperature of the vessel rises due to discharge. It seems that.

From the above, it is considered that making the amount of oxygen in the thin film uniform is the optimal means for making the magnetization characteristics of the thin film uniform. Conventionally, for example, methods for producing thin films with uniform thickness have been considered, such as rotating the substrate around a rotation axis perpendicular to the substrate surface and moving the central axis, or using a large-area target. However, both devices are large and expensive.

In view of the above-mentioned points, an object of the present invention is to provide a thin film manufacturing method that improves the uniformity of magnetic properties by making the amount of oxygen in the thin film uniform.

Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 4 shows an example of the configuration of a thin film manufacturing apparatus for carrying out the thin film manufacturing method by sputtering of the present invention. In the figure, 11 is a cylindrical stainless steel vacuum container, 12 is a cathode, and 13 is a substrate holder. The vacuum container 11 is airtightly connected to the cathode 12 via a ring-shaped insulator 14. Vacuum container 11
is airtightly connected to the substrate holder 13 via a ring-shaped insulator 15. The target 16 is fixed to the cathode, and the glass substrate 17 is fixed to the substrate fixing fittings 18,1.
8', it is fixed to the substrate holder 13 via the conductive terminal film 19 or directly. 21 is an anode-cathode voltage power supply, which applies a DC high voltage with a high frequency superimposed between the stainless steel container 11 as an anode and the cathode 12; The container 11 serving as an anode is grounded, and a bias voltage is applied to the substrate holder 13 by a bias power supply 22 with respect to the anode voltage. Note that arrows 20 and 20' indicate the flow of cooling water for the cathode 12 and substrate holder 13, respectively.

The target 16 is a flat plate with a diameter of 60 mm and is made of a GdCo alloy. The distance between target 16 and substrate 17 is 40
mm, Ar gas pressure is 8.0×10 ^-2 Torr, anode-cathode voltage is 1.0 kV, anode current is 100 mA, and bias voltage is -100 V. As the conductive terminal film 19, a film is used in which aluminum is previously deposited on a portion of the glass substrate 17 by vapor deposition before setting it in the above-mentioned sputtering apparatus.

The GdCo thin film produced on the surface of the glass substrate 17 using the above-mentioned sputtering apparatus was measured using the Kerr effect, and the obtained hysteresis characteristics are shown in FIG. Here l is the distance from the center. This fifth
The characteristics shown in the figure correspond to the characteristics shown in the second figure for the GdCo thin film produced by the conventional method.As can be seen by comparing the two, the GdCo thin film produced by the method of the present invention has square characteristics over the entire surface, Magnetic uniformity is also considerably improved.

Figure 6 shows the results of measuring the amount of oxygen in the GdCo thin film. Comparison with FIG. 3 reveals that the manufacturing method of the present invention improves the uniformity of oxygen content.

As described above, it has become clear that the thin film manufacturing method according to the present invention is superior, and the reasons for this are as follows. That is, at the stage when the GdCo thin film begins to be formed on the glass substrate, the potential of the very thin film becomes the potential of the substrate holder 13 via the aluminum conductive terminal film 19 deposited on the substrate surface in advance. Against the anode electrode -
This is because a bias voltage of 100V is uniformly applied. In addition, the reason why the distribution of oxygen amount becomes uniform by applying a negative bias voltage to the GdCo thin film is that some of the Ar ions 23' (4th
It is conceivable that the negative bias voltage causes the GdCo film to collide with the growing GdCo film, selectively sputtering oxygen or Gd oxides during the collision.

Conventionally, a method of applying a negative bias voltage to the substrate has been used to increase the magnetic anisotropy perpendicular to the thin film surface, but in this case the substrate is a conductive material such as Si, and this method is difficult to apply. It has not been possible to obtain uniform magnetic properties for insulating substrates such as glass substrates, which are the object of the present invention.

The conductive terminal film 19 shown in FIG. 4 described as an embodiment of the present invention may be modified to form a tapered conductive terminal film 79 by vapor deposition or fixation on a glass substrate 77, as shown in FIG. Alternatively, as shown in FIGS. 8A and 8B, the tips of the board fasteners 88 and 88' of the board 87 may be formed into thin conductive terminal films.

Next, the present invention will be explained using the "compensation temperature" used in ferrimagnetic materials such as GdCo films. In the GdCo amorphous magnetic thin film, the compensation temperature refers to the temperature at which the magnetization due to Gd and the magnetization due to Co cancel each other out, and the magnetization appears to be zero. 9th
The figure is a curve diagram showing the relationship between temperature T and magnetization M for a GdCo thin film when Gd is not bonded to oxygen (Co is difficult to bond to oxygen). Curve 91 is
For Co, curve 92 is for Gd. In the figure, Tc indicates the Curie temperature. At temperature T1, the positive direction magnetization of Co and the negative direction magnetization of Gd are equal, so characteristic curve 9
1.92, T1 is the compensation temperature. When Gd combines with oxygen, its magnetization decreases by that amount, so when a part of Gd combines with oxygen,
The curve for Gd looks like a broken curve 92'.
Therefore, curve 91 and curve 92' as described above
In the GdCo thin film, the compensation temperature is T2 in Figure 9.

In a GdCo magnetic thin film formed on a glass substrate by the conventional sputtering method, the composition ratio of Co to Gd is higher in the peripheral area than in the central area, and the amount of oxygen is measured as shown in Figure 3. There are more cases in the periphery than in the center. In other words, in the conventional GdCo magnetic thin film, the compensation temperature is lower at the periphery than at the center. In addition, in Figure 2, the curve at the l = 0 mm position is upward to the right, and the curve at the l = 5 mm position is upward to the left. This means that the compensation temperature at the l = 0 mm position is room temperature (temperature at the time of the test). It shows that the compensation temperature at the higher position, l=5 mm, is lower than room temperature. In the GdCo magnetic thin film produced on a glass substrate by the sputtering method of the present invention, no significant change in compensation temperature is observed depending on the distance from the center.

As is clear from the above description, according to the thin film manufacturing method of the present invention, the amount of oxygen in the thin film can be easily made uniform, and the magnetic properties can be made almost uniform over a large area.

The present invention is applicable not only to GdCo magnetic thin films, but also to amorphous magnetic thin films mainly composed of other rare earth or ferrous metals, such as GdFe, TbFe, GdCoMo, GdCoCu,
It can also be applied to the production of GdTbFe, etc. Furthermore, the present invention is applicable not only to amorphous magnetic thin films but also to amorphous silicon films, for example, when producing thin films that are not insulators by sputtering, in which the amount of oxygen contained affects their properties.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing an apparatus for measuring the hysteresis characteristics of a magnetic thin film due to the Kerr effect, Figure 2 is a characteristic curve diagram showing the hysteresis characteristics due to the Kerr effect of a GdCo thin film manufactured by the conventional method, and Figure 3 is a diagram showing the hysteresis characteristics of a GdCo thin film manufactured by the conventional method. A characteristic curve diagram showing the amount of oxygen in the GdCo thin film produced by the method, FIG. 4 is a configuration diagram showing an example of a sputtering apparatus using the thin film production method of the present invention, and FIG. 5 is a diagram showing the amount of oxygen in the GdCo thin film produced by the method of the present invention. A characteristic curve diagram showing the hysteresis characteristics due to the Kerr effect of a GdCo thin film.
A characteristic curve diagram showing the amount of oxygen in the thin film; FIG. 7 is a cross-sectional view showing a conductive terminal film with a tapered thickness;
FIGS. 8A and 8B are cross-sectional views showing substrate fixing fittings that also serve as conductive terminal films, and FIG. 9 is an explanatory diagram of the compensation temperature of the GdCo thin film. 1, 17, 77, 87...Glass substrate, 2...
GdCo thin film, 4... Laser light, 5... Polarizer, 6... Half mirror, 8... Analyzer,
11...Stainless steel vacuum container (anode), 12...
Cathode, 13...Substrate holder, 14, 15...Insulator, 16...Target, 18, 18'...Substrate fastener, 19...Conductive terminal film, 20, 20'
... Cooling water flow, 21 ... Anode-cathode voltage power supply, 22
...Bias voltage power supply, 23, 23'... Ar ion, 24... Spatter evaporated material, 79... Conductive terminal film, 88, 88'... Substrate fixing fitting.

Claims (1)

[Scope of Claims] 1. A method for depositing and growing a magnetic alloy thin film on an insulating substrate by sputtering a target containing an element to constitute the thin film with inert gas ions, in which a conductive film is deposited on the insulating substrate. A negative voltage is always applied to the magnetic alloy thin film with respect to the anode through the conductive terminal during the sputtering, and some of the ions of the inert gas are used to 1. A method for producing a thin film, which comprises sputtering oxygen taken into a magnetic alloy thin film during growth to make the oxygen concentration in the magnetic alloy thin film uniform. 2. In the method for manufacturing a thin film according to claim 1, the value of the negative bias voltage is approximately one-tenth of the voltage between anode and cathode, and a conductive terminal film is provided on at least one location on the surface of the insulating substrate. A method for manufacturing a thin film, characterized in that the conductive terminal film is deposited in advance and the bias voltage is applied to the conductive terminal film. 3. The thin film manufacturing method according to claim 2, wherein the conductive terminal film is tapered. 4. In the thin film manufacturing method according to claim 1, the value of the negative bias voltage is set to approximately one-tenth of the voltage value between anode and cathode, and a substrate fastening fitting fixes the insulating substrate to the substrate holder. A method for producing a thin film, characterized in that the tip of at least one of the tips is made thin so that it comes into contact with the surface on which the conductive thin film is formed, and the bias voltage is applied via the substrate stopper. 5. The thin film manufacturing method according to claim 1, wherein the magnetic alloy is a rare earth-transition metal magnetic alloy.