Semiconductor device using magnetic domain wall movement

Abstract

A semiconductor device to which magnetic domain wall movement is applied is provided. The semiconductor device includes a magnetic substance film in which magnetic domain walls are moved, and the magnetic substance film has a damping constant of 0.015 to 0.1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:

FIG. 1 is a magnetization-time (M-T) graph showing a magnetization characteristic of magnetic substance samples having a fixed damping constant according to the variation in magnetic field;

FIGS. 2A through 2C are M-T graphs showing magnetization characteristics of magnetic substance samples according to the variation in damping constant and magnetic field;

FIG. 3 is a cross-sectional view illustrating a semiconductor device that uses magnetic domain wall movement according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

A semiconductor device that uses magnetic domain wall movement according to an exemplary embodiment of the present invention will now be described more fully with reference to the accompanying drawings.

First, a theoretical principle of the present invention will be described.

In order to investigate the movement phenomenon of magnetic domain walls within a magnetic field, the following experiments were conducted. Through the experiments, the causes of interference with the movement of the magnetic domain walls and a method of improving the speed of movement of the magnetic domain walls were found.

First, the movement phenomenon of magnetic domain walls in five magnetic substance samples having an identical damping constant and each having two magnetic domains in different directions from each other was examined by applying magnetic fields that were different from each other. The results are shown in FIG. 1. At this time, each of the magnetic substance samples is a bar type and includes magnetic domains magnetized in opposite directions from each other along a longitudinal direction, and the damping constant of the samples was 0.01. The magnetic fields were applied to the samples in one of the longitudinal directions of the bar with a magnitude of 5, 10, 15, 20, and 40 oersted (Oe).

Referring to FIG. 1, as the magnitude of the magnetic field increases from 5 Oe to 15 Oe, the speed of converging to a magnetic moment value per unit volume (magnetization value: M) of −1.0 tends to increase. This denotes that magnetization rapidly progresses due to the increase in the speed of movement of the magnetic domain walls as the magnitude of the magnetic field increases. However, when the magnitude of the magnetic field increases to 20 Oe or more, the magnetization curve oscillates largely and the time taken to converge to the magnetization value M of −1.0 takes approximately 20 ns. When the magnitude of the magnetic field increases to 40 Oe, the time taken to converge to the magnetization M of −1.0 is much longer than 20 ns. The reason why the time taken to converge to the magnetization value M of −1.0 is slow when the magnitude of the magnetic field is over 20 Oe is because the magnetic domain walls oscillate. That is, when the magnitude of the magnetic field increases to a value greater than a specific value, the movement speed of the magnetic domain walls is slow due to the oscillation effect of the magnetic domain walls.

In order to identify the cause of the slow movement of the magnetic domain walls, a plurality of magnetic substance samples having different damping constants were examined by applying magnetic fields. The results are shown in FIGS. 2A through 2C. The basic shapes of the magnetic substance samples and the direction of the magnetic fields are identical to the magnetic substance samples described with reference to FIG. 1, and the damping constant of each magnetic substance sample and the condition of applying the magnetic fields are indicated in each graph.

Referring to FIG. 2A, when a magnetic field of 15 Oe is applied to the magnetic substance samples, it is found that a sample having a damping constant (α) of 0.015 shows a slightly higher magnetization speed than a sample having a damping constant of 0.01. The sample having a damping constant of 0.015 also shows a less minute oscillation of a magnetization curve than the sample having a damping constant of 0.01 at region A where the magnetic moment value M approaches −0.1.

Referring to FIG. 2B, when a magnetic field of 20 Oe is applied to the magnetic substance samples, the magnetization speed of a sample having a damping constant of 0.01 is 20 ns, but the magnetization speed of a sample having a damping constant of 0.015 is 7 to 8 ns. That is, it is determined that as the damping constant increases from 0.01 to 0.015, the oscillation of the magnetization curve is greatly reduced and the speed of movement of the magnetic domain walls greatly increases.

Referring to FIG. 2C, when a magnetic field of 40 Oe is applied to the magnetic substance samples, as the damping constant increases from 0.01 through 0.015 to 0.02, the magnetization speed gradually increases, but the oscillation of the magnetization curve is maintained almost the same. However, in the case of a sample having a damping constant of 0.03, although a magnetic field of 40 Oe is applied, it is seen that the oscillation of the magnetization curve barely occurs and the magnetization speed increases to a similar level to the magnetization curve in FIG. 2A. In this case, the oscillation of the magnetic domain walls barely occurs.

From the experimental results of FIG. 1 and FIGS. 2A through 2C, it is determined that the movement of the magnetic domain walls is interfered with the oscillation effect of the magnetic domain walls, and the oscillation effect of the magnetic domain walls can be removed by increasing the damping constant of a magnetic substance.

Here, the damping constant is a constant relating to the degree of distribution of energy applied to the magnetic substance, and it is indicated as a in the Landau-Lifshitz-Gilbert equation (Equation 1) given below.

$\begin{array}{cc}\frac{M}{t}=-\gamma \left(M\times H_{\mathrm{eff}}\right)+\frac{\alpha }{M_s}\left(M\times \frac{M}{t}\right)& \left[\mathrm{Equation}1\right]\end{array}$

In Equation 1, M indicates magnetization, which is a magnetic moment per unit volume, γ indicates a gyromagnetic ratio, H_eff indicates an effective magnetic field applied to the samples, and M_s indicates saturation magnetization.

The increase in the damping constant α in equation 1, as proved in the above experiments, causes a reduction in the magnetic resonance of magnetic domain walls by dissipating energy from a magnetic field applied to the sample. That is, as the damping constant α increases, the oscillation of the magnetic domain walls reduces, thereby increasing the magnetization speed.

Therefore, in an exemplary embodiment of the present invention, the oscillation of the magnetic domain walls is reduced by using a magnetic substance film having a damping constant of at least 0.015, and more specifically, in a range from 0.015 to 0.1 for a semiconductor device that uses the magnetic domain wall movement. In this way, the magnetic domain walls can stably move at a high speed. Accordingly, an exemplary embodiment of the present invention can provide a semiconductor device that can greatly increase an operating speed using magnetic domain wall movement. A semiconductor device that uses the magnetic domain wall movement can be a data storing device like a HDD, a memory device like a RAM, or a logic device.

Exemplary embodiments of the present invention provide three methods of increasing the damping constant of a magnetic substance film as follows.

First, a damping constant of a magnetic substance film can be increased to 0.015 or more by using an alloy in which a non-magnetic substance is included in the magnetic substance. The magnetic substance can be one selected from Ni—Fe, Co, Co—Ni, Co—Fe, and Co—Fe—Ni, and the non-magnetic substance can be one selected from Os, Nb, Ru, Rh, Ta, Pt, Zr, Ti, Pd, B, Zn, and Ag. The contents of the non-magnetic substance can be 0.5 to 10 atom %.

As the amount of osmium added to Ni₈₀Fe₂₀ (Py), which is a magnetic substance, increases, a damping constant α of the magnetic substance increases.

Second, a damping constant of a magnetic substance can be increased to 0.015 or more by including a non-magnetic substance film on at least one of an upper surface and a lower surface of a magnetic substance film. At this time, the non-magnetic substance film included on the lower surface of the magnetic substance film can be named as a non-magnetic seed layer, and the non-magnetic substance film included on the upper surface of the magnetic substance film can be named as a non-magnetic capping layer. The non-magnetic seed layer or the non-magnetic capping layer can be formed to a thickness of 30 to 300 Å using a substance selected from Cu, Os, Ru, Rh, Ta, Pt, Zr, Ti, Pd, B, Zn, and Ag.

In an N—Py—N structure in which both a non-magnetic seed layer and a non-magnetic capping layer are included on a magnetic substance film formed of Py, as the thickness of a non-magnetic substance film (the non-magnetic seed layer or the non-magnetic capping layer) increases, a damping constant α of the magnetic substance film increases. Here, N is a non-magnetic substance film formed of Pt, Pd, Ta, or Cu. That is, the non-magnetic substance films included on the upper and lower surfaces of the magnetic substance film causes an increase in the damping constant α.

Third, the speed of movement of magnetic domain walls can be increased in order to meet an aspect of the present invention by using a magnetic substance film intrinsically having a damping constant of at least 0.015, for example, Co, CoFe, CoNi, or CoFeNi. In this case, an improvement in the operation speed of a semiconductor device due to the improved speed of movement of the magnetic domain walls can be obtained without including a non-magnetic substance in the magnetic substance film or additionally including the non-magnetic substance films on the upper and lower surfaces of the magnetic substance film. However, a damping constant α that is further increased can be obtained and can maximize the effect of an exemplary embodiment the present invention by additionally using the first and second methods.

FIG. 3 is a cross-sectional view illustrating a semiconductor device that uses magnetic domain wall movement according to an exemplary embodiment of the present invention. Reference numerals 10, 20, and 30 respectively indicate a non-magnetic seed layer, a magnetic substance film, and a non-magnetic capping layer. Here, the magnetic substance film 20 has a damping constant of 0.015 to 0.1, and can include a non-magnetic substance such as Os, Nb, Ru, Rh, Ta, Pt, Zr, Ti, Pd, B, Zn, or Ag. The non-magnetic seed layer 10 and the non-magnetic capping layer 30 are optional constituent elements.

As described above, according to exemplary embodiments of the present invention, the speed of movement of magnetic domain walls can be greatly increased using a magnetic substance, which has a damping constant of at least 0.015, as a magnetic substance film of a semiconductor device that uses a principle of magnetic domain wall movement.

Accordingly, the present invention facilitates a rapid and stable movement of magnetic domain walls in a semiconductor device to which magnetic domain wall movement can be applied, for example, a data storing device such as a HDD, a memory device such as a non-volatile RAM, or a logic device, thereby greatly increasing operation speed of the semiconductor device.

While this invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

The magnetic substance film having a high damping constant, which is proposed in the present invention, can be applied to various semiconductor devices including a data storing device such as a HDD, a memory device such as an RAM, or a logic device, and in some cases, the kind of the magnetic substance films and a constituent element added to the magnetic substance film can differ from those described herein. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims.

Claims

1. A semiconductor device that comprises a magnetic substance film in which magnetic domain walls are moved, wherein the magnetic substance film has a damping constant of at least 0.015.

2. The semiconductor device of claim 1, wherein the magnetic substance film is an alloy in which a non-magnetic substance is included in a magnetic substance.

3. The semiconductor device of claim 2, wherein the non-magnetic substance is at least one selected from Os, Nb, Ru, Rh, Ta, Pt, Zr, Ti, Pd, B, Zn, and Ag.

4. The semiconductor device of claim 2, wherein the magnetic substance film comprises 0.5 to 10 atom % of the non-magnetic substance.

5. The semiconductor device of claim 1, wherein the magnetic substance film is an alloy comprising a non-magnetic substance and at least one magnetic substance selected from Ni—Fe, Co, Co—Ni, Co—Fe, and Co—Fe—Ni.

6. The semiconductor device of claim 5, wherein the Ni—Fe is Ni80Fe20.

7. The semiconductor device of claim 5, wherein the non-magnetic substance is at least one selected from Os, Nb, Ru, Rh, Ta, Pt, Zr, Ti, Pd, B, Zn, and Ag.

8. The semiconductor device of claim 5, wherein the magnetic substance film comprises 0.5 to 10 atom % of the non-magnetic substance.

9. The semiconductor device of claim 1, wherein the magnetic substance film is one selected from Co, CoFe, CoNi, and CoFeNi.

10. The semiconductor device of claim 1, further comprising a non-magnetic seed layer on a lower surface of the magnetic substance film.

11. The semiconductor device of claim 10, wherein the non-magnetic seed layer is formed of one selected from Cu, Os, Ru, Rh, Ta, Pt, Zr, Ti, Pd, B, Zn, and Ag.

12. The semiconductor device of claim 10, wherein the non-magnetic seed layer has a thickness of 30 to 300 Å.

13. The semiconductor device of claim 1, further comprising a non-magnetic capping layer on an upper surface of the magnetic substance film.

14. The semiconductor device of claim 13, wherein the non-magnetic capping layer is formed of one selected from Cu, Os, Ru, Rh, Ta, Pt, Zr, Ti, Pd, B, Zn, and Ag.

15. The semiconductor device of claim 13, wherein the non-magnetic capping layer has a thickness of 30 to 300 Å.

16. The semiconductor device of claim 1, wherein the magnetic substance film has a damping constant of not more than 0.1.