JPH01292699A - Bloch line memory element - Google Patents

Abstract

PURPOSE:To form a very fine pattern by irradiating a high coercive force film selectively with a convergent corpuscular beam capable of beam deflection, and forming different magnetized structure periodically. CONSTITUTION:A groove 3 is formed on a magnetic garnet film 1, and a minor loop as the storage area of a BL (Bloch line) pair is formed by a stripe magnetic domain 2 surrounding the groove 3. The BL pair 4 existing in the magnetic wall of a magnetic domain end part becomes the information unit of this memory. The BL pair 4 performs transfer lying along the magnetic wall by the vibration of a bias magnetic field. Next, after the groove 3 is filled up with polyimide resin and is leveled, it is covered with Co-Pt 5. Afterward, after the Co-Pt is cut into a magnetic film pattern, it is set in a vacuum chamber, and is stabilized by heat, and is irradiated with the convergent ion beam 7 of Ga<+> ion as running along the pattern in a very small period. Thus, the very fine pattern with little residual distortion and little deterioration of a magnetic characteristic can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a Bloch line memory device, and particularly to a structure and manufacturing method of a Bloch line transfer path suitable for realizing high density recording information.

[Prior art] In the conventional Bloch line memory,
As described in No. 84, "Bloch line" (hereinafter referred to as BL
) was proposed. Optical interferometry has been proposed as a method for obtaining periodic patterns.
It is stated that it is relatively easy to form a grating structure or a dot structure with a period of about 1 μm. The materials used include
A permalloy thin film, which is a typical soft magnetic material, has been disclosed, and the permalloy is magnetized by the leakage magnetic field of a BL pair to fix bits. Subsequently, IE, Transaction on Magnetics, and MNG22. (198
6) pages 784 to 789 (IEEE, Tran
s, Magnetics, MAG 22 (1986) p.
p784-789).

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into account the method of forming a magnetic film fine pattern of an arbitrary shape and the magnetization structure formed according to the method, and is not suitable for practical Bloch line memory including curved transfer paths. This was a problem in manufacturing the device.

With conventional photolithography, it is impossible to form a pattern of 0.5 μm or less, which is necessary for high-density BL memory of 64 Mb/alt or more. Furthermore, the optical interference method described in the known example allows the formation of fine resist patterns in the form of straight lines or dot patterns. However, practical level B
L memories also have problems such as the need for curved transfer paths, and even if it is possible to form a resist pattern, it is more difficult to actually form a high coercive force film pattern. Furthermore, in lithography using a conventional electron beam lithography system, after forming a resist pattern as described above, problems of side etching and film deterioration due to the introduction of a strained layer occur at the stage of forming a magnetic film pattern by etching, milling, etc. Inevitable. This is fatal in forming a magnetic film pattern of 0.5 μm or less.

The purpose of the present invention is to provide a method for forming ultra-fine patterns at the 0.1 μm level in order to solve the above problems, and to form a periodic potential along an arbitrarily shaped BL transfer path using a new concept of magnetization structure. It consists in building a Bloch line memory.

[Means to solve the problem]

The above object is achieved by selectively irradiating a high coercive force film, which is a bit fixing film, with a focused particle beam capable of beam deflection to form periodically different magnetization structures.

〔Example〕

In the present invention, after a magnetic film is deposited to form a rough pattern, the temperature of the entire element is raised to such an extent that the BL medium and strain relaxation agent (polyimide resin, etc.) do not change in quality. In this state, the magnetic film is irradiated with a focused high current density particle beam (electron beam or ion beam). The magnetic film in the irradiated portion does not necessarily need to be scattered to form a separation pattern. It is only necessary to form a periodic in-plane magnetic potential so that the BL pair is fixed. Therefore, even if the magnetic film itself is a continuous film,
Periodically make it magnetic and non-magnetic. ■Vertical, in-plane,
A periodic potential can be created by methods such as (1) changing in-plane anisotropy, and (2) arranging magnetization reversal patterns. The BL pair is stably fixed by these periodic potentials and the bit position is secured, so that no malfunction occurs.

〔Example〕

Example 1 A first embodiment of the present invention will be described with reference to FIG.

A groove 3 is formed in the magnetic garnet 1, and the striped magnetic domains 2 surrounding the groove form a minor loop as a storage area for BL pairs. The BL pair 4 existing on the domain wall at the end of the magnetic domain becomes the information unit of this memory. This BL pair performs transfer along the domain wall by vibration of the bias magnetic field. In this example, after the groove 3 is backfilled with polyimide resin (not shown) and flattened, a high coercive force film of Go-Pt (residual magnetic flux density 5 KG, coercive force 3 KG) 5 is deposited to a thickness of 300 mm using a sputtering method. It was covered. After that, a magnetic film pattern of several tens of microns wide by several hundred microns was cut out along the magnetic domain using axial photolithography, and then placed in a vacuum chamber that could be irradiated with a focused ion beam.
The membrane temperature was stabilized at 350°C. Then acceleration voltage 50K
A focused ion beam (FIB) 7 of Ga+ ions focused to a diameter of 0.08 μm at eV is 0.0 μm along the pattern.
Irradiation was performed at a period of 2 μm as shown in the figure.

As a result, the ion irradiation section 6 became non-magnetic due to the irradiation damage and temperature rise of Ga+ ions. Magnetization of non-irradiated area 8
is originally in-plane magnetization, but it is not necessarily magnetized uniformly in the direction along the striped domain from the beginning as shown in the figure. Normally, after the desired beam irradiation is completed, the remaining processes (formation of the control conductor, detection magnetic film pattern, and coercive film) are completed, and the device is magnetized in a certain direction when the device fabrication is completed. . As a result of the above, it is possible to form a magnetic potential with an in-plane magnetic field amplitude of 100e at a bit period of 0.2 μm, and a B of bit density IGb/cJ class.
It has become clear that it is compatible with L memory.

Example 2 A second example will be explained with reference to FIG. Among the transfer paths in the BL memory, there are curved transfer paths (2, 2, 3) as shown in the figure.
3) is also required, so a bit fixed pattern that can be twisted is required. Here, a high coercivity perpendicular magnetization film Co-Cr 9 proposed for perpendicular magnetic recording was deposited on top of the striped magnetic domains. After that, the device wafer is placed in a vacuum chamber that can be irradiated with a focused electron beam, and
It was kept at ℃. The focused electron beam 10 in magnetic field radiation mode is a high-energy beam with a current density of 1000 A/d and focused to 0.1 μmφ. This beam was periodically irradiated almost orthogonally to the curved transfer path as shown in the figure to form the magnetized structure shown in the figure. That is, the magnetization 11 of the non-irradiated area 9
The easy axis was perpendicular to the film surface, but the humidity in the area irradiated with beam 10 temporarily rose to 600°C, and Cr in the film began to thermally diffuse, destroying the vertical anisotropy. An in-plane magnetized film 12 whose magnetization is oriented in random directions is now formed. After completing the device fabrication, as a result of magnetization in the direction perpendicular to the film surface, the magnetization 11 in the non-irradiated area is uniformly magnetized (in the perpendicular direction)
However, the magnetization of the irradiation section 12 was not oriented perpendicularly. As a result of the above, approximately 0.3 μm period (~4oOM
A magnetic potential of b/d) was formed.

Example 3 A third example will be described using FIG. 3. The figure schematically shows a part of a cross section of a BL memory element. In this method, after the bit fixing perpendicular magnetization film 15 is deposited and rough patterning is completed, polyimide resin 1 is applied between the layers.
4 to form the control conductor 16 and the like to complete the wafer process. Thereafter, a periodic magnetic potential for bit fixation is realized using a method similar to magneto-optical recording.

That is, after saturated upward in advance, the bias magnetic field 17 is applied downward. Thereafter, the focused laser 18 is scanned to heat a desired portion. When the Co-Cr film 15 approaches the Curie temperature to 500° C., magnetization reversal occurs in the direction of the bias magnetic field. Since this method uses a laser beam, it was impossible to form a 0.1 μm pattern, but due to the temperature rise in the high energy density part at the center of the laser,
．． A periodic potential of 2 μm and 0.5 μm could be formed. As a result, an elemental technology for producing a BL memory with a recording density of 256 Mb/cd was obtained.

Example 4 A fourth embodiment will be described using FIG. 4.

In this embodiment, a fine pattern is formed using an electron beam 7. A focused beam is used in which the diameter of the beam 7 is 0.1 μm and the current density is increased to 5,000A/ffl. The above current density can be achieved by a method in which the acceleration voltage is set to 10 KeV and then decelerated to 1 eV before the beam reaches the film 8. Further, before patterning, the polyimide resin was not used, and planarization was performed using 5iOz19.

In this example, the sample temperature is raised to 700℃ before beam irradiation, and a total of 4 halide ions CQ"' and F- are added to the sample part.
Pa was introduced. The electron gun section (not shown) maintains a pressure of 10-'Pa by differential pumping. Under the above conditions, the high coercive force film G o-N i (4πM r = 5 K
As a result of beam irradiation on G, Hc = 3 K G ) 8, the irradiated portion was instantly dissolved and a bit pattern (period: 0.3 μm) shown in - could be formed. According to this embodiment, since the sample is kept at a high temperature and etching is performed while taking chemical reactions into consideration, it is possible to form a fine pattern with little residual strain and little change in magnetic properties.

〔Effect of the invention〕

According to the present invention, since a fine magnetized structure can be formed without contacting the film sample, there is an effect that the possibility of defects being introduced is reduced. Furthermore, since magnetization to a desired size occurs after the element process on the wafer is completed, it has the advantage of not being affected by heat or distortion accompanying the element process.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the Bloch line pair portion of the first embodiment of the present invention, Fig. 2 is a plan view of the Bloch line curved part of the second embodiment, and Fig. 3 is the main part of the Bloch line memory of the third embodiment. The cross-sectional view and FIG. 4 are schematic diagrams of the pair of Bloch lines in Example 4. 1...Magnetic garnet film, 2...Stripe magnetic domain,
3... Groove, 4... Bloch line pair, 5... In-plane magnetized film. 6... Ion irradiation section, 7... Ga+ ion beam,
8... In-plane magnetization, 9... Perpendicular magnetization film, 10... Electron beam, 11... Perpendicular magnetization, 12... In-plane random magnetization, 13... Non-magnetic garnet 1-substrate, 14...
・Polyimide resin, 15... Perpendicular magnetization film, 16...
Control conductor, 17... Bias magnetic field, 18...
-Laser beam, 19...SiO2, layer.

Claims (1)

[Claims] 1. A pair of domain walls formed around striped magnetic domains existing in a magnetic film having an axis of easy magnetization in a direction perpendicular to the film surface, including means for writing, reading and storing information. In a magnetic memory element that uses vertical Bloch lines (VBL) as a memory unit, the upper part of the striped magnetic domain is almost covered with a high coercive force magnetic film, and if necessary, the entire element is heated, and a focused particle beam is (electron beam, ion beam)
Alternatively, a Bloch line memory element characterized in that the magnetic property of the magnetic film changes with a minute period by irradiating at least a part of the magnetic film with a focused laser beam. 2. The Bloch line according to claim 1, wherein the high coercive force film is a perpendicular magnetization film, and the beam irradiation part has a structure in which perpendicular anisotropy is reduced or destroyed due to temperature increase due to beam collision or radiation damage. memory element. 3. The Bloch line memory element according to claim 1, wherein the high coercive force film is an in-plane magnetized film, and the in-plane anisotropic axis of the irradiated part is different from that of the non-irradiated part by beam irradiation. 4. The Bloch line memory element according to claim 1, wherein the high coercive force film has a structure partially made non-magnetic by beam irradiation. 5. The Bloch line memory element according to claim 1, wherein the high coercive force film is an amorphous film, and the beam irradiation portion has a polycrystalline structure. 6. After magnetizing the entire high coercive force film in one direction in advance,
Claim 1: The film has a structure in which, if necessary, beam irradiation is performed while applying a bias magnetic field in the opposite direction to the magnetization within a range that does not exceed the coercive force, and the film temperature is partially increased to reverse the magnetization of that part. The Bloch line memory device described in Section 1. 7. A claim characterized in that the beam is deflected by computer control, and a periodic potential is formed along the domain wall not only in the straight portions of the striped magnetic domains but also in the curved portions as necessary. The Bloch line memory device according to item 1. 8. The Bloch line memory element according to claim 1, wherein a gas containing at least halide ions is introduced into the chamber during the beam irradiation. 9. The high coercive force film is made of CoCr, CoPt, CoNi
2. The Bloch line memory element according to claim 1, wherein the Bloch line memory element is an alloy magnet material containing at least one of NiFeB, SmCo, Sr ferrite, Ba ferrite, and AlNiCo.