JP2976694B2 - Method and apparatus for manufacturing artificial lattice film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an artificial lattice film and an apparatus for producing the same.

[0002]

2. Description of the Related Art The formation of an artificial lattice / multilayer film in which several substances are alternately stacked on a substrate such as glass or silicon while controlling the film thickness on the order of an atomic layer involves (1) turns. A substrate rotating sputtering method in which a substrate fixed to a table alternately moves on a sputter source with the rotation of the turntable; and (2) a shutter for opening and closing a molecular beam flow on a vapor deposition source and control of film thickness. This is performed by a multi-source evaporation method in which a film thickness gauge for performing the above-mentioned steps is provided, and evaporation is performed on a substrate at a predetermined position. In these methods of forming an artificial lattice / multilayer film, the substrate temperature is always kept at a constant temperature. The Co / Cu artificial lattice made of cobalt (Co) and copper (Cu) has a small magnetic field at which the magnetoresistance is saturated and a large magnetoresistance ratio (Journal of
Magnetics and Magnetic Materials, Vol. 94, L1 page, 1991), and applications to magnetic sensors and magnetic heads are conceivable. In particular, when used as a magnetic sensor, it is desirable that the amount of change in the magnetic resistance changes linearly with respect to the magnetic field and that there is no hysteresis. However, when the Co / Cu artificial lattice is formed on the substrate maintained at the above-mentioned constant temperature, the magnetic field dependence of the magnetic resistance is not linear, and the hysteresis is large.
The present invention has been made to solve such a conventional problem. In an artificial lattice made of two kinds of metals such as a Co / Cu artificial lattice, the magnetic field dependence of the magnetic resistance is linear, and there is no hysteresis. An object of the present invention is to provide a method of manufacturing an artificial lattice film and an apparatus for manufacturing the same.

[0003]

Means for Solving the Problems The present inventors have proposed Co / C
After examining the growth conditions of the u artificial lattice, it was found that an artificial lattice / multilayer film having an extremely flat interface structure was obtained by repeating the process of performing low-temperature growth and high-temperature heat treatment on all layers for one layer. It has been found that the Co / Cu artificial lattice that can be formed and thus produced has a magnetoresistance that changes linearly with the magnetic field and has no hysteresis.

That is, the present invention relates to a method of manufacturing an artificial lattice in which two kinds of metals are alternately stacked and has an artificial periodic structure in the stacking direction. This is a method for manufacturing an artificial lattice film, characterized by alternately repeating a step of performing and a step of performing a heat treatment after growing a second metal at a low temperature, and stacking two types of metals. The apparatus for producing an artificial lattice film used in the method includes a mechanism for generating a molecular beam flow necessary for growing two kinds of metal films, and a film thickness control for laminating two kinds of metals at a predetermined film thickness. Mechanism, a substrate holding mechanism maintained at a growth temperature of the metal film, a substrate heating mechanism for applying a temperature higher than the growth temperature of the metal film to the substrate, and applying a temperature lower than the growth temperature of the metal film to the substrate. A substrate cooling mechanism; and a transport mechanism for mutually moving the substrate between the substrate holding mechanism, the substrate heating mechanism, and the substrate cooling mechanism.

[0005]

In order to form a thin film having a flat surface,
After forming the metal film at a low temperature of about room temperature, it is effective to perform heat treatment by increasing the substrate temperature. When the substrate temperature is high, the metal to be deposited tends to agglomerate, resulting in an uneven surface.On the other hand, when the substrate temperature is low, the crystal grain size is small. Although a flat surface is obtained, when heat treatment is performed on the surface, recrystallization proceeds, and a very flat surface is obtained. When this method is applied to the formation of an artificial lattice film and the artificial lattice is manufactured by raising and lowering the substrate temperature for each layer, an artificial lattice film having an extremely flat interface structure is produced as compared to the case where the artificial lattice is manufactured on a substrate at a constant temperature. Is obtained. For example, C prepared by this method
The o / Cu artificial lattice film is suitable for a magnetoresistive element such as a magnetic sensor because the magnetoresistance changes linearly with respect to a magnetic field and has no hysteresis.

However, when forming an artificial lattice film, it is necessary to stack several tens of cycles with a film thickness of the order of an atomic layer, and in the conventional substrate rotation sputtering method and multi-source evaporation method, the substrate temperature is raised and lowered for each layer. This requires a very long time to form a thin film, which is not practical. Therefore, a mechanism for generating a molecular flow necessary for growing two kinds of metal films, a film thickness control mechanism for laminating two kinds of metals with a predetermined film thickness, and a substrate maintained at a growth temperature of the metal film. In addition to the holding mechanism, a substrate heating mechanism that applies a temperature higher than the growth temperature of the metal film to the substrate to heat-treat the substrate, and a metal film to the substrate to rapidly cool the substrate temperature to the growth temperature of the metal film A substrate cooling mechanism that gives a temperature lower than the growth temperature of the substrate, and a transport mechanism that allows the substrate placed on the substrate holding mechanism to move between the substrate holding mechanism, the substrate heating mechanism, and the substrate cooling mechanism during metal film formation. With the manufacturing apparatus provided with the conventional apparatus, the time required for raising and lowering the substrate temperature in the conventional apparatus can be eliminated, and the production of the artificial lattice film having a flat interface structure can be performed in a short time.

[0007]

Embodiments of the present invention will be described below. 1 and 2 are configuration diagrams of an example of an apparatus for producing an artificial lattice film according to the present invention. In FIG. 1, a vacuum chamber (evaporation chamber)
Among them, an electron beam evaporation source 2 or a molecular beam cell (resistance heating evaporation source) 3 is provided as a mechanism for generating a molecular beam flow necessary for growing two types of metal films. As a control mechanism for laminating with the film thickness set, there are a film thickness meter 4 using a quartz oscillator and a shutter 14 for opening and closing the vaporized molecular beam flow, and a substrate holding mechanism kept at the growth temperature of the metal film. A substrate heating stage (substrate heating mechanism) 8 heated by a heater to heat-treat the substrate through a gate valve 6 into a vacuum chamber (substrate heating / cooling chamber) 7; There is a substrate cooling stage (substrate cooling mechanism) 9 cooled with liquid nitrogen in order to rapidly cool the substrate to the growth temperature of the metal film. And it is adapted to be movable in the substrate heating stage 8 and the substrate cooling stage 9. The vacuum chambers 1 and 7 are evacuated by a cryopump and a turbo molecular pump (not shown).

In FIG. 2, two magnetron sputtering guns 12a, 12 are provided in a vacuum chamber 1 as a mechanism for generating a molecular beam flow necessary for growing two types of metal films.
b (partitioned by a partition plate 13a to prevent mutual interference between plasmas), and a quartz oscillator is used as a control mechanism for laminating two kinds of metals with a predetermined film thickness. There is a film thickness meter 4 and a shutter 14 for opening and closing the sputter plasma, and a sputter stage 15 as a substrate holding mechanism kept at the growth temperature of the metal film.
A substrate heating stage (substrate heating mechanism) 8 heated by a heater for heat-treating the substrate and a liquid for rapidly cooling the substrate temperature to the growth temperature of the metal film in the same vacuum chamber 1 with the partition plate 13b interposed therebetween. There is a substrate cooling stage (substrate cooling mechanism) 9 cooled by nitrogen, and a substrate holder 10 on which a substrate is placed can be moved to a sputtering stage 15, a substrate heating stage 8 and a substrate cooling stage 9 by a linear introduction device 11. Has become. The vacuum chamber 1 is evacuated by a cryopump (not shown).

Next, the electron beam evaporation source 2 shown in FIG.
Is evaporated from the molecular beam cell 3 to form silicon (S
An example in which a Co / Cu artificial lattice is formed on the (111) substrate in i) will be described. The substrate temperature during the deposition of Co and Cu was set to room temperature, and Si (11
1) An example of vapor deposition on a substrate at a vapor deposition rate of 1 Å / sec will be described. The fabricated artificial lattice contains 20 Co
Angstroms and Cu have a cycle of 15 Angstroms and are stacked for 50 cycles ([Co
It referred to as (20 Å) / Cu (15 Å)] _50. ). The degree of vacuum of the deposition chamber 1 is 3 ×
10 ^-9 Toor, the degree of vacuum in the substrate heating / cooling chamber is
It was 8 × 10 ⁻¹⁰ Torr. Co and C used
The purity of the u ingot is 4N and 5N, respectively. First, Co is vapor-deposited on the substrate on the vapor deposition stage 5 at 20 angstrom under the above conditions. Next, the substrate is heated to the substrate heating stage 8.
And heat-treated at 200 ° C. for 10 minutes. Thereafter, the substrate is moved to the substrate cooling stage 9 to rapidly cool the substrate. Since the substrate cooling stage 9 is cooled by liquid nitrogen, the substrate is cooled to room temperature or less in a few minutes. Thereafter, the substrate is transported to the vapor deposition stage 5 again, and Cu is reduced to 1 under the above conditions.
Deposit 5 angstrom. Next, the substrate is subjected to a heat treatment at 200 ° C. for 5 minutes on the substrate heating stage 8, and then rapidly cooled on the substrate cooling stage 9. Hereinafter, by repeating the above-described series of steps for 50 cycles, a Co / Cu artificial lattice (A) as designed was obtained.

For comparison, as a first comparative example, Si
A Co / Cu artificial lattice (B) having the same design structure as above was produced on (111) at a constant substrate temperature of 100 ° C. Further, as a second comparative example, a sample (C) obtained by fabricating a Co / Cu artificial lattice having the same design structure on Si (111) at a constant substrate temperature of room temperature and then performing a heat treatment at 200 ° C. for 20 minutes was used. Produced. The surface irregularities of the above three samples were measured by a scanning tunneling microscope, and -5 kOe to -5 kOe were measured by a DC four-terminal method.
Measure the magnetoresistance in the magnetic range up to kilo-Oersted,
The shape of the magnetoresistance curve and the presence or absence of hysteresis were examined. The magnetic field and the electric current were measured in an arrangement perpendicular to each other in the plane of the artificial lattice film. The measurement temperature is room temperature. Table 1 shows the results.

[0011]

[Table 1] ─────────────────────────────────── Sample surface condition Magnetoresistance curve Hysteresis (shape) ─ ────────────────────────────────── (A) Flat Decrease linearly No (B) Large irregularities Curve Yes (C) Large unevenness Yes

The shape of the magnetoresistance curve and the presence / absence of hysteresis are as shown in FIG. 3 for the sample (A) and FIG. 4 for the samples (B) and (C). In the figure, the arrows indicate the sweep direction of the magnetic field. The magnetoresistance change rate (%) is given by (resistance change / resistance under no magnetic field) × 100.

Next, the magnetron sputtering gun 12 shown in FIG.
a and 12b are provided with Co and Cu targets,
An example in which a Co / Cu artificial lattice is formed on a glass substrate will be described. An example in which the substrate temperature during Co and Cu sputtering is set to room temperature and the glass substrate on the sputtering stage 15 is sputtered at a deposition rate of 2 Å / sec will be described. The manufactured artificial lattice is formed by stacking 30 cycles of Co with 30 angstrom and 20 angstrom of Cu with one cycle ([Co (3
0 Å) / Cu (20 Angstroms)] referred to as _30. ). The sputtering gas was argon and the sputtering pressure was 5 mTorr. The purity of the used Co and Cu targets is 3N and 4N, respectively. First, 30 Å of Co is sputtered on the substrate on the sputtering stage 15 under the above conditions. Next, the substrate is moved to the substrate heating stage 8 and heat-treated at 200 ° C. for 10 minutes. Thereafter, the substrate is moved to the substrate cooling stage 9 to rapidly cool the substrate. Since the substrate cooling stage 9 is cooled by liquid nitrogen, the substrate is cooled to room temperature or less in a few minutes. Thereafter, the substrate is transported to the sputtering stage 15 again, and Cu is vapor-deposited at 20 angstrom under the above conditions.
After the substrate is subjected to a heat treatment at 200 ° C. for 5 minutes on the substrate heating stage 8, the substrate is rapidly cooled in the substrate cooling stage 9. Hereinafter, the above-described series of steps were repeated for 30 cycles to obtain a Co / Cu artificial lattice (D) as designed.

For comparison, as a third comparative example, a Co / Cu artificial lattice (E) having the same design structure as above was produced on glass at a constant substrate temperature of 100 ° C. As a fourth comparative example, a Co / Cu artificial lattice having the same design structure was formed on glass at a constant substrate temperature of room temperature, and then 200 ° C.
A sample (F) subjected to a heat treatment for 20 minutes was produced.
The surface irregularities of the three samples were measured by a scanning tunneling microscope, and the magnetoresistance up to a magnetic field of 5 kOe was measured by a DC four-terminal method to examine the shape of the magnetoresistance curve and the presence or absence of hysteresis. The directions in which the magnetic field and the current are applied are the same as those in Table 1. The measurement temperature is room temperature. Table 2 shows the results.

[0015]

[Table 2] ─────────────────────────────────── Sample surface condition Magnetoresistance curve Hysteresis (shape) ─ ────────────────────────────────── (D) Flat Linearly reduced No (E) Large unevenness Curved (F) Large unevenness Yes

Here, the shape of the magnetoresistive curve and the presence or absence of hysteresis are as shown in FIG. 5 for the sample (D) and FIG. 6 for the samples (E) and (F). In the figure, the arrows indicate the sweep direction of the magnetic field. The definition of the magnetoresistance ratio (%) is the same as in Table 1.
In the above-described embodiment, the artificial lattice made of cobalt and copper has been described. However, an artificial lattice film having a flat interface structure can be produced even with an artificial lattice made of another metal element or alloy.

[0017]

As described above, according to the present invention, it is possible to rapidly produce an artificial lattice film having a flat interface structure, and as a result, the magnetoresistance becomes linear with respect to the magnetic field. An artificial lattice film that changes and has no hysteresis is obtained. Therefore, a device such as a high-performance magnetic sensor can be manufactured.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an example of an apparatus for producing an artificial lattice film of the present invention.

FIG. 2 is a configuration diagram of an example of an apparatus for manufacturing an artificial lattice film of the present invention.

[3] having a flat interface structure manufactured according to this invention [Co (20 Å) / Cu (15 Å) is a graph showing a magnetoresistance curve of ₅₀ artificial lattice.

FIG. 4 shows a C having the same design structure as FIG. 3 manufactured by a conventional method.
It is a figure showing the magnetoresistance curve of o / Cu artificial lattice.

[5] having a flat interface structure manufactured according to this invention [Co (30 Å) / Cu (20 Å) is a graph showing a magnetoresistance curve of ₃₀ artificial lattice.

FIG. 6 shows a C having the same design structure as that of FIG. 5 manufactured by a conventional method.
It is a figure showing the magnetoresistance curve of o / Cu artificial lattice.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Electron beam evaporation source 3 Molecular beam cell 4 Quartz crystal film thickness meter 5 Evaporation stage 6 Gate valve 7 Vacuum chamber 8 Substrate heating stage 9 Substrate cooling stage 10 Substrate holder 11 Linear introduction machine 12a, 12b Magnetron sputter gun 13a , 13b Partition plate 14 Shutter 15 Sputter stage

Claims (2)

(57) [Claims] 1. A method of manufacturing an artificial lattice in which two kinds of metals are alternately stacked and having an artificial periodic structure in a stacking direction, a step of performing a heat treatment after growing the first metal at a low temperature. And a step of performing a heat treatment after growing the second metal at a low temperature, and alternately repeating the steps of stacking two kinds of metals. 2. A mechanism for generating a molecular beam flow required for growing two kinds of metal films, a film thickness control mechanism for laminating two kinds of metals with a predetermined film thickness, and maintaining a growth temperature of the metal films. A substrate holding mechanism for applying a temperature higher than the growth temperature of the metal film to the substrate; and a substrate cooling mechanism for applying a temperature lower than the growth temperature of the metal film to the substrate. An apparatus for manufacturing an artificial lattice film, comprising: a transport mechanism for mutually moving a substrate between a mechanism, the substrate heating mechanism, and the substrate cooling mechanism.