JPH0427105A - Magnetic body and its manufacturing method - Google Patents

Abstract

PURPOSE:To enable a soft magnetic iron nitride thin film for improving corrosion resistance and wear resistance to be formed on a substrate by making a surface layer of an iron nitride layer which consists of a substrate and the iron nitride layer which is formed on it to be a one-layer nitride layer. CONSTITUTION:A nitrogen molecule or an argon molecule within a vacuum bath is ionized by collision with thermions which are emitted from a filament 6. Partially ionized iron passes through a grid 8 and ionization is further accelerated. An iron which is ionized to a positive ion is accelerated toward a substrate 11 due to operation of electric field which faces from the grid 8 toward an opposing electrode 12 and faces a substrate with high energy. An intricate thin film of iron nitride is formed on a substrate 11. After a thin iron nitride film is formed, introduction gas is introduced into a vacuum bath, is ionized, is allowed to collide with the substrate, thus forming a layer where nitrification is further advanced on a surface of the iron nitride.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to an iron nitride magnetic material and a method for manufacturing the same.

[Prior art]

Conventionally, various methods have been proposed for forming an iron-based magnetic film on a substrate for forming a thin film, and the methods thereof are also extremely diverse.

Pure iron has the highest saturation magnetization value of any single substance, and research and development are being carried out on thinning iron films with the aim of increasing the density of magnetic recording. Corrosion resistance, as pure iron has problems with corrosion resistance and abrasion resistance.

It is used in the form of iron nitride to improve wear resistance.

Conventionally, the method of forming an iron nitride thin film is to generate a high-frequency electromagnetic field between an evaporation source and an object to be evaporated, to ionize the evaporated material in an active or inert gas, and perform vacuum evaporation. The so-called ion brating method (Special Publication No. 52-2
9971) etc. However, with these techniques, it has been difficult to control crystallinity and stress with good reproducibility and form a thin film with good soft magnetic properties.

〔the purpose〕

The present invention relates to a soft magnetic iron nitride thin film formed on a substrate with improved corrosion resistance and wear resistance, and a method for manufacturing the same.

〔composition〕

The present invention relates to a magnetic material comprising a substrate and an iron nitride layer formed thereon, characterized in that the surface layer of the iron nitride layer is a layer that is further nitrided.

Another aspect of the present invention is to apply an electric field directed from a grid toward the substrate to a magnetic body consisting of a substrate and an iron nitride layer formed thereon.
A claim characterized in that the iron nitride layer is placed in a vacuum chamber in which the electric field is in the opposite direction to the evaporation source, and nitrogen and/or ammonia gas is introduced into the vacuum chamber to further nitridize the surface of the iron nitride layer. The present invention relates to a method of manufacturing the magnetic material according to item 1.

In the present invention, the effect can be further enhanced by repeatedly laminating a composite layer consisting of a single nitrided iron nitride layer. In addition, the thickness of the iron nitride layer (N single-layer nitrided layer) is 0.005 to 0.05 μm.
is preferred.

In the present invention, it is preferable that the same device be used for forming the iron nitride layer on the substrate and for further nitriding the iron nitride layer.

The manufacturing method of the present invention satisfies the requirements defined as the manufacturing method of the present invention by using the thin film deposition apparatus described in Japanese Patent Application Laid-Open No. 59-89763, which was invented by Ota, one of the inventors of the present invention. I can do it.

This device includes a vacuum chamber into which an active gas, an inert gas, or a mixture thereof is introduced, an evaporation source for evaporating an evaporable substance within the vacuum chamber, and a substrate disposed within the vacuum chamber. a counter electrode held to face the evaporation source; a grid disposed between the evaporation source and the counter electrode and capable of passing the evaporated substance; It has a filament for generating thermionic electrons placed on the side and a means for setting this grid at a positive potential with respect to the potential of the filament, and generates plasma by ionizing the gas introduced into the vacuum chamber. This is a thin film deposition apparatus characterized by the following features:

What are the preferred conditions for using the apparatus when forming an iron nitride layer on a substrate?

■The introduced gas is nitrogen gas, ■The pressure range of the introduced gas is 10-3 to 101 Pa,
(2) The film formation rate is 0.1 to 100 people/S, (2) The voltage applied to the grid is 300 or less, and (2) The current density flowing per unit area of the grid is 1 to 100 OA/S.

Further, the preferable conditions for using the apparatus for plasma nitriding the surface of the iron nitride layer, which is a feature of the present invention, are as follows: (1) the pressure range of the introduced gas is 10-2 to 101 Pa, and (2) the grid applied voltage is less than 500■.

Further, in the above method, the introduced gas can be diluted with an inert gas such as argon.

The preferred thin film forming apparatus used in the present invention is based on the invention by Ota, one of the inventors, and its configuration and principle include a vacuum chamber, a counter electrode, a grid, a filament for generating thermionic electrons, and an evaporation source. An active gas, an inert gas, or a mixture thereof is introduced into the vacuum chamber.

A counter electrode is disposed within the vacuum chamber and holds the substrate, with the substrate facing the evaporation source.

A grid, through which the evaporated substance can pass, is disposed between the evaporation source and the counter electrode and is at a positive potential with respect to the potential of the filament and the counter electrode.

Therefore, there is an electric field in the vacuum chamber directed from the grid to the substrate,
An electric field is formed in the opposite direction from the grid toward the evaporation source.

A filament for generating thermionic electrons is arranged on the evaporation source side with respect to the grid in the vacuum chamber, and the thermionic electrons generated by the filament are used to ionize a part of the evaporated substance.

A portion of the evaporated material from the evaporation source is ionized into positive ions by electrons from the filament. The partially ionized vaporized substance passes through the grid, is further ionized into positive ions by the ionized gas, and is accelerated toward the substrate by the action of the electric field.

Note that the electrons from the filament are emitted from the filament with kinetic energy corresponding to the filament temperature, so they are not immediately attracted to the positive potential grid, but pass through it, are pulled back by the Coulomb force of the grid, and further, The vibrational motion is repeated around the grid, and the electrons are absorbed by the grid, so they do not reach the substrate, and the substrate is not subjected to electron bombardment, so there is no heating caused by it, and the temperature of the substrate decreases. Increase can be prevented. Therefore, even materials without heat resistance such as plastics can be used as the substrate.

The embodiments shown in the figures will be described below.

In the figure, the base plate 1 and the Pelger 2 are integrated via a backing 15 to form a vacuum chamber. The base plate 1 includes electrodes 3.5, 7., which also serve as supports.
9, but the penetrating portions of these support electrodes 3 and the like are of course airtight, and furthermore, these support electrodes 3, 5, 7.9 and the base plate 1 are electrically insulated. . Further, a hole IA formed in the center of the base plate 1 is connected to a vacuum exhaust system (not shown).

A pair of support electrodes 3 support a resistance heating type evaporation source 4 made of metal such as tungsten or molybdenum in a boat shape.

Moreover, it may be replaced with a boat shape and may be a coil shape.

Note that instead of such an evaporation source, an evaporation source used in a conventional vacuum evaporation method, such as an electron beam evaporation source, can be used as appropriate. Furthermore, a plurality of evaporation sources may be installed.

A filament 6 made of tungsten or the like for generating thermoelectrons is supported between the pair of electrodes 5 that also serve as supports.

The shape of the filament 6 is determined by arranging a plurality of filaments in parallel or forming a mesh so as to cover the spread of particles of the evaporated substance evaporated from the evaporation source. The support electrode 7 includes
A grid 8 is supported. The grid has a shape that allows the evaporated substance to pass through, and in this example, it has a mesh shape. A counter electrode IO is supported on the support 9, and a substrate 11 is held below it by an appropriate method.

If this state is viewed from the side of the evaporation source 4, the counter electrode 10 is placed behind the substrate 11.

Now, the support electrodes 3, 5, and 7.9 are conductors and also serve as electrodes, and the ends protruding outside the vacuum chamber are connected to various power sources as shown in the figure. ing.

First, a pair of support electrodes 3 are connected via an evaporation power source 12. Further, in the illustrated example, the support electrode 7 is connected to the positive terminal of the DC voltage power source 14, and the support electrode 9 is grounded.

Actually, these electrical connections include various switches, and the operation of these switches realizes the film forming process, but these switches are not shown in the figure.

Hereinafter, the formation of an iron nitride thin film using this example of the apparatus will be explained using an example.

The substrate 11 is set as shown in the figure, and the evaporation source 4 holds pure iron as the evaporation substance. Here, for example, it is assumed that the evaporation source is a resistance heating type evaporation source.

The inside of the vacuum chamber is set to a pressure of 10-4 to 10-'Pa in advance, and if necessary, nitrogen gas alone, ammonia gas alone, or an inert gas such as argon is added to the pressure of 10-4 to 10-'Pa. It is introduced at a pressure of 10-'P'a. Here, it is assumed that the introduced gas is, for example, nitrogen alone. When using an EB gun as an evaporation source, it is desirable to connect a differential exhaust device to the EB gun in areas where the gas pressure is high to reduce the gas pressure in areas where high voltage is applied.

In this state, the power supply is activated and a positive potential is applied to the grid 8, the counter electrode 10 is grounded, and the filament 6
A current is passed through. Here, for example, the grid has a mesh shape and a potential of +100V is applied, and the filament is a tungsten wire and a power of 400W is applied.

The filament 6 is heated by resistance heating and emits thermoelectrons. Nitrogen molecules or argon molecules in the vacuum chamber are
It is ionized by collision with thermionic electrons emitted from the filament 6.

The evaporated iron particles spread out and fly toward the substrate, but some of them, and.

The introduced gas is ionized by collision with thermionic electrons emitted from the filament 6.

In this way, the partially ionized iron passes through the grid 8, but at this time, it is further ionized due to the collision between the thermionic electrons vibrating up and down in the vicinity of the grid and the ionized introduced gas. promoted.

The portion of the evaporated material that has passed through the grid 8 that has not yet been ionized is further ionized between the grid and the substrate.
Due to the collision with the ionized introduced gas, it is ionized into positive ions and the ionization rate is increased.

In this way, the iron ionized into positive ions is transferred to the substrate 1 by the action of the electric field from the grid 8 toward the counter electrode 12.
It is accelerated toward 1 and heads toward the substrate with high energy. A thin film of iron nitride is formed on the substrate 11, and a dense thin film is formed by the action of the ions. In this case, in a region where the grid voltage is 500 V or less, a thin film with extremely little damage to crystallinity is formed.

Actual film formation is carried out by matching the introduced gas pressure, the density of iron particles incident on the substrate, and the density of ions. The conditions for forming a good thin film are ■Introduced gas pressure range: 10-3 ~
10'Pa, ■Deposition rate 0.1-100 people/S, ■Current density flowing in unit area of grid 1-1000A
It is 7m.

After forming the iron nitride thin film, nitrogen or ammonia, a mixture of these gases, or a mixture of these gases diluted with an inert gas is introduced into the vacuum chamber, and this is ionized by the action of thermionic electrons mentioned above. By causing the iron nitride to collide with the substrate, a more highly nitrided layer can be formed on the aforementioned iron nitride surface. Note that neutral excited species excited by thermal electrons from the filament also contribute to this nitriding (this process can be called plasma nitriding).

Since the grid voltage in this nitriding is 500 V or less, no serious damage is caused to the surface of the iron nitride film. Although the composition and depth of the nitrided layer depend on the plasma nitriding conditions, a good nitrided layer is formed when the pressure of the introduced gas is in the range of 10-2 to 101 Pa.

Most of the thermoelectrons are eventually absorbed by the grid 8, and some of the thermoelectrons pass through the grid 8, but are decelerated by the action of the electric field between the grid 8 and the substrate 11. Therefore, even if it reaches the substrate 11, it will not heat the substrate 11.

〔effect〕

The method of the present invention allows the iron nitride to be extremely thin (film thickness 0.005 to 0.05 mm) without seriously damaging the crystallinity of the iron nitride.
05 μm) A nitride layer with a higher degree of nitridation can be formed on the surface of the iron nitride thin film, making it possible to refine and densify the crystal grains, and form a thin film with good soft magnetic properties, corrosion resistance, and abrasion resistance. At the same time, eddy current loss can be reduced. Therefore, the magnetic material according to the present invention is a durable magnetic material that generates little noise.

[Brief explanation of the drawing]

FIG. 1 depicts a thin film deposition apparatus preferably used in the method of the present invention. 1... Base plate IA... Hole 2... Pelger 3... Electrode that also serves as support 4... Evaporation source
5... Electrode serving as support 6... Filament
7... Electrode that also serves as support 8... Grid
9... Electrode serving as support 10... Counter electrode 11... Substrate 12... Evaporation power source 13... Filament power source 14... DC voltage power source 15... Backing diagram

Claims (2)

[Claims] 1. 1. A magnetic material comprising a substrate and an iron nitride layer formed thereon, characterized in that a surface layer of the iron nitride layer is a further nitrided layer. 2. A magnetic material consisting of a substrate and an iron nitride layer formed on it is placed in a vacuum chamber in which the electric field from the grid to the substrate and the electric field from the grid to the evaporation source are in opposite directions. 2. The method of manufacturing a magnetic material according to claim 1, further comprising introducing gas into a vacuum chamber to further nitridize the surface of the iron nitride layer.