CN1297953C - Method for preparing dual-vertical spin valve and its structure - Google Patents

Abstract

A method and structure for preparing double vertical spin valves, a metal multilayer film structure prepared by means of plasma sputtering, magnetron sputtering or molecular beam epitaxy using glass or single crystal silicon substrates , and then by means of photolithography, electron beam printing, and ion etching, two electrodes are made on the top and bottom layers of the metal multilayer film, so that when the spin valve is working, the flow direction of the signal current is perpendicular to Metallic multilayer film surface. The advantage of the present invention is that the two characteristics of the current vertical film plane and the magnetic anisotropy easy axis perpendicular film plane are perfectly combined to greatly improve the magnetoresistance effect of the spin valve; effectively improve the magnetic uniformity of the spin valve , so that this spin valve material can still maintain a single magnetic domain structure when it is processed to the nanometer scale.

Description

A dual vertical spin valve

technical field

The invention belongs to the technical field of magnetic storage, and in particular provides a method for preparing a double vertical spin valve and its structure. The spin valve is used as a read head of a computer hard disk, or in devices such as magnetic random access memories, sensors, and the like.

technical background

The current era is the information age, and the information exchange of various industries puts forward higher and higher requirements for the storage density and stability of information. In the past ten years, information storage technology, especially magnetic recording technology, has developed rapidly. In particular, the magnetic head made of giant magnetoresistance spin valve thin film material has greatly improved the areal recording density of hard disks. At present, the longitudinal magnetic recording density in the laboratory has reached 150Gb/in ² , and it is marching towards the next goal of 1Tb/in ² . At present, the read head mainly adopts a giant magnetoresistance (GMR) spin-valve thin-film device (ie, CIP-SPV) with a current parallel to the plane configuration. As the theoretical research shows, if the CIP-SPV head is continued to be used, the storage density of the computer hard disk can only reach 200-250Gb/in ² at most, and it will become saturated. Therefore, the current perpendicular to the planar giant magnetoresistance spin valve (CPP-SPV) becomes the most potential next-generation read head material. Compared with CIP-SPV, the key advantage of CPP-SPV is that as the storage density increases, the size of the storage element is greatly reduced, and the GMR output signal of CIP-SPV will also decrease accordingly, while CPP-SPV is exactly On the contrary, the GMR output signal increases instead, and the readout sensitivity is further improved. Nevertheless, the easy axis direction of the magnetic anisotropy of the CPP-SPV thin film materials with the usual structure is parallel to the film surface. When components are made into sub-micron or even smaller sizes, a series of problems will be brought about: magnetization curling occurs at the edge of the film, which leads to vortex magnetization of the film and the appearance of eddy current magnetic domain structures. If it is used as a device, it will lead to the loss of stored information, thus limiting the further development of high information storage technology.

Contents of the invention

The object of the present invention is to provide a method and structure for preparing double vertical spin valves, that is, a spin valve film material with current perpendicular to the plane configuration and magnetic anisotropy easy axis perpendicular to the film surface and its preparation method.

The double vertical spin valve in the present invention is a kind of metal multilayer film structure prepared by means of plasma sputtering, magnetron sputtering or molecular beam epitaxy using glass or single crystal silicon substrate, and then through photographic Lithography, electron beam printing, and ion etching are used to make two electrodes on the top and bottom layers of the metal multilayer film, so that when the spin valve is working, the flow direction of the signal current is perpendicular to the metal multilayer film. film surface.

The double vertical spin valve in the present invention is a metal multilayer film structure, and the specific structure is as follows:

The bottom layer of the double vertical spin valve is metal platinum with a thickness of 1 to 20 nanometers, which is called the bottom electrode layer.

The second layer from bottom to top is a cobalt/platinum composite structure, which is composed of 2 to 20 layers of metal cobalt and metal platinum alternately overlapped (the bottom layer is metal cobalt, the top layer is metal platinum), and the thickness of the metal cobalt layer 0.1-0.4 nanometers, and the thickness of the metal platinum layer is 1-3 nanometers. called the bottom composite layer.

The third layer from bottom to top is metallic cobalt, with a thickness of 0.1 to 1 nanometer. The third layer combined with the second layer is called the free layer. Because their magnetic moments are free to rotate under an applied magnetic field.

The fourth layer from the bottom to the top is metal copper with a thickness of 1 to 10 nanometers, called the isolation layer. The isolation layer can also be replaced by metal platinum or aluminum oxide with a thickness of 1-4 nanometers.

The fifth layer from bottom to top is metallic cobalt, with a thickness of 0.1 to 2 nanometers.

The sixth layer from the bottom is another platinum/cobalt composite structure, known as the top composite layer. It is composed of 2-20 layers of metal platinum and metal cobalt alternately overlapping (the bottom layer is metal platinum, and the top layer is metal cobalt), wherein the thickness of metal platinum is 1-3 nanometers, and the thickness of metal cobalt is 0.1-0.4 nanometers. The magnetic moments of the composite structure (ie, the sixth layer) and the fifth layer are both pinned by the antiferromagnetic layer, so they are called pinned layers.

The seventh layer from bottom to top is an antiferromagnetic iron-manganese alloy or other manganese alloy layer with a thickness of 5-40 nanometers.

The eighth layer from bottom to top is metal platinum of 1 to 10 nanometers, which is the top electrode layer.

The invention has the advantages of skillfully combining the two characteristics of current vertical film plane and magnetic anisotropy easy axis vertical film plane perfectly. The magnetoresistance effect of the spin valve is greatly improved by passing the current perpendicular to the plane of the film; since the pinned layer and the free layer of the spin valve adopt a composite structure of extremely thin metal platinum and metal cobalt alternately overlapping, the pin The easy axes of the magnetic anisotropy of the pinned layer and the free layer are both perpendicular to the film surface, which effectively improves the magnetic uniformity of the spin valve, so that the spin valve material can still maintain a single magnetic domain structure when it is processed to the nanoscale .

Detailed ways

Example 1: Two kinds of spin valve materials were prepared by using a magnetron sputtering apparatus: one of them is a common spin valve structure, and its multilayer film is metal tantalum (6nm)/nickel-iron alloy (7nm) from the bottom to the top. /metal copper (2.6nm)/nickel-iron alloy (4nm)/iron-manganese alloy (15nm)/metal tantalum (6nm) (the data in brackets is the thickness of the film, nm means nanometer), which is characterized by the current parallel to the plane configuration, And the magnetic anisotropy easy axis is parallel to the film surface; the other is the double vertical spin valve structure of the present invention, which is platinum metal (6nm)/[cobalt metal (0.4nm)/platinum metal (2nm)]5/cobalt metal (0.8nm)/metallic copper (3nm)/Co(0.8nm)[Pt(2nm)/Co(0.4nm)]5/FeMn(15nm)/Pt(2nm) (the subscript number is the number of repeated layers of the composite structure ), which is characterized by the current perpendicular to the plane configuration and the easy axis of magnetic anisotropy perpendicular to the film plane. The detailed preparation process of the above two spin valves is as follows: the background vacuum degree of the sputtering chamber is 2×10 ^-5 Pa, the pressure of argon (99.99%) is 0.5 Pa during sputtering; the substrate is cooled by circulating water, and the structural A magnetic field of 250Oe is added parallel to the direction of the substrate to induce a parallel easy magnetization direction; for structure two, a magnetic field of 50Oe is added perpendicular to the direction of the substrate to induce a vertical easy magnetization direction. The sputtered two kinds of metal multilayer films were processed into 300nm×300nm components by means of electron beam printing and ion etching. The test results show that the room temperature magnetoresistance effect of the double vertical spin valve device is about 30% higher than that of the ordinary spin valve. In addition, the eddy current magnetic domain structure appears around the ordinary spin valve device, while the vertical spin valve presents a single magnetic domain structure.

Example 2: Ten kinds of double vertical spin valve devices with structures were experimentally prepared, and the structures are shown in the following table:

The present invention uses plasma sputtering, magnetron sputtering and molecular beam epitaxy to prepare a total of 30 double vertical spin valve devices with the above ten structures, and the size of the devices is 300 nanometers × 300 nanometers . Through testing, it is found that the magnetoresistance effects of all the above-mentioned spin valves at room temperature are more than 30% higher than those of the spin valves with conventional structures. Magnetic force microscopy tests revealed that these dual vertical spin-valve devices all exhibit good single magnetic domain characteristics.

Claims (2)

1. A double vertical spin valve, characterized in that: the structure is: a. The bottom layer of the double vertical spin valve is platinum metal with a thickness of 1 to 20 nanometers, which is called the bottom electrode layer; b. The second layer from bottom to top is a cobalt/platinum composite structure, which is composed of 2 to 20 layers of metal cobalt and metal platinum alternately overlapped. The bottom layer is metal cobalt, and the top layer is metal platinum. Among them, the metal cobalt layer The thickness is 0.1-0.4 nanometers, and the thickness of the metal platinum layer is 1-3 nanometers, which is called the bottom composite layer; c. The third layer from the bottom to the top is metal cobalt, with a thickness of 0.1 to 1 nanometer; d. The fourth layer from the bottom to the top is metal copper, with a thickness of 1 to 10 nanometers, called the isolation layer; e. The fifth layer from bottom to top is metal cobalt, with a thickness of 0.1-2 nanometers; f. The sixth layer from the bottom to the top is another platinum/cobalt composite structure, called the top composite layer; it is composed of 2 to 20 layers of metal platinum and metal cobalt alternately overlapped, the bottom layer is metal platinum, and the top layer is Metal cobalt, wherein the thickness of metal platinum is 1-3 nanometers, and the thickness of metal cobalt is 0.1-0.4 nanometers; g. The seventh layer from bottom to top is an antiferromagnetic iron-manganese alloy or manganese alloy layer, with a thickness of 5-40 nanometers; h. The eighth layer from bottom to top is metal platinum of 1-10 nanometers, which is the top electrode layer. 2. The double vertical spin valve according to claim 1, characterized in that the isolation layer is metal platinum or aluminum oxide with a thickness of 1-4 nanometers.