JPH04345987A - Magnetic thin film memory and its recording/reproducing method - Google Patents

Abstract

PURPOSE:To obtain a magnetic thin film memory which can secure a satisfactorily large reading signal even though the size of a memory element is reduced. CONSTITUTION:A current line 2 is connected to one of both ends of each magnetic thin film memory element 1, and the other end of the element 1 is grounded GND. Then a voltage line 3 is connected to the element 1 with the GND side used in common to the line 2. Thus a large reading signal is obtained with use of the abnormal Hall voltage, and a simple constitution is secured since the GND side is used in common by both lines 2 and 3. Then the degree of integration is improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic thin film memory using a magnetic thin film memory element and a recording and reproducing method thereof.

0002

[Prior Art] Figure 10 shows a schematic diagram of the assembly of a conventional magnetic thin film memory element (published in 1977).
Maruzen Co., Ltd. Magnetic Engineering Course 5 Magnetic Thin Film Engineering p
254). First, an example of the manufacturing method will be shown. A mask with rectangular holes (not shown) is placed in close contact with the smooth glass substrate 101, and Fe, Fe,
The Ni alloy is evaporated to form a vacuum deposited film with a thickness of about 2000 Å. In this way, a large number of magnetic thin films 102, which will become memory elements, are manufactured all at once in a matrix shape. The drive lines for driving the memory elements are made by photo-etching copper wires on both sides of a thin epoxy resin plate or polyester sheet so that they are perpendicular to each other. The lines on both sides of the sheet are word lines W1 to W3 and digit lines D1 to D3, respectively, and the sheet is assembled by pressing the magnetic thin films 102 so that their intersections overlap with each other. Note that in the following explanation, when there is no need to specify, W and D are simply used without the suffix.

Next, the principle of operation will be described. The lines arranged parallel to the easy axis of magnetization in the figure are word lines (word lines).
ne) W, and the lines perpendicular to it are digit lines.
line)D. The detection line for reading the memory state also serves as the digit line. Therefore, D will hereinafter be referred to as a digit line and a detection line. The thick upward arrow indicates the magnetization within the film corresponding to the memory state. It is assumed that an upward thick line arrow stores information of "0" and a downward thick line arrow stores information of "1". In addition, the magnetic thin film 102 is
Let Hd and Hw be the magnetic fields acting on the . When word current Iw, which is a unipolar pulse, is applied to selected word line W1,
A magnetic field Hw acts on all memory elements under that line,
Magnetization is directed toward the hard axis, which is perpendicular to the easy axis. At this time, pulse voltages of different polarities are induced in each digit line/detection line D depending on whether the magnetization rotates from the "1" state or from the "0" state, and this becomes the readout voltage. . During recording, the direction of magnetization is determined by passing a digit current Id so as to overlap with the falling edge of the pulse of the word current Iw, and superimposing a magnetic field Hd with a polarity corresponding to the information signal in a state where the magnetization is directed toward the difficult axis. , “1” or “
Information can be recorded in the state of 0''.Word current Iw
is a current value that generates a magnetic field Hw sufficient to rotate the magnetization of the magnetic thin film from the easy axis to the hard axis, and the digit current Id is a magnetic field H that is approximately 1/2 of the coercive force Hc of the magnetic thin film 102.
This is the current value that generates d.

0004

[Problems to be Solved by the Invention] In the conventional technology, an extremely small electromagnetic induction voltage generated by the rotation of magnetization is used as a reading method, so that the S
The N ratio was small, making reading difficult. Furthermore, since the electromagnetic induction voltage is proportional to the magnitude of the magnetic moment, it is necessary to make the size of the magnetic thin film 102 sufficiently large.
For this reason, there have been problems such as the impossibility of increasing the amount of storage per unit area.

The present invention was made to solve the above-mentioned problems, and provides a magnetic thin film memory that can obtain a sufficiently large readout signal even when the size of the memory element becomes small, and a recording device using the same. , the purpose is to provide a reproduction method.

[0006]

[Means for Solving the Problems] A magnetic thin film memory element according to the present invention utilizes the abnormal Hall effect of a thin film magnetic material and uses an abnormal Hall voltage as a read signal. An abnormal Hall voltage (normal Hall voltage is generated by an external magnetic field, but an abnormal Hall voltage is generated by a material,
A reproducing current line that outputs a signal (especially caused by magnetization inside a ferromagnetic material or ferrimagnetic material) and a reproducing voltage line that uses the other end of this current line as a common source to derive an abnormal Hall voltage. It is equipped with the following. Then, at least one of the current line and the voltage line for reproduction is used as a recording line, and the magnetic thin film memories are stacked vertically, and the voltage for reproduction of the magnetic thin film memory elements stacked at the same position is used. The lines are connected in common. Furthermore, a resistor is inserted between the magnetic thin film memory element and the reproduction voltage line, and a capacitor is provided for storing the output abnormal Hall voltage.

[0007] Furthermore, in the recording method of a magnetic thin film memory element of the present invention, at least one of a current line and a voltage line for reproduction is used as a recording line, and a current is applied during recording to record in a magnetic thin film memory element. Corresponding recording lines are provided for recording information "0" and "1", respectively, and "0" and "1" are recorded using the same direction of current flowing through each recording line.

Furthermore, in the method for reproducing a magnetic thin film memory element of the present invention, a pulse current is applied to a current line for reproduction, and the abnormal Hall voltage excited in the voltage line is read out as a reproduction signal.

[0009]

[Operation] Since the present invention uses abnormal Hall voltage as a read signal, it is possible to read with a good S/N ratio, and a part of the current line for reproduction and the voltage line for reproduction can be shared, or the current line, using at least one of the voltage lines for recording,
Since a common voltage line is used for reproducing magnetic thin film memory elements in stacked layers or in the same position, this is particularly useful for increasing memory density. Furthermore, since a resistor is inserted between the magnetic thin film memory element and the read voltage line, the current flowing to the magnetic thin film memory element that is not being read is restricted. Furthermore, since the abnormal Hall voltage is stored in the capacitor, power consumption is reduced. Furthermore, if the current direction is the same, “0”
"," and "1" can be recorded, thereby improving the data transfer speed.Furthermore, since pulse current is passed through the current line for reproduction, power consumption is reduced.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram showing the configuration of an embodiment of the present invention. In this figure, 1 is a magnetic thin film memory element, and suffixes such as 1aa, 1ab, . The same applies to other symbols. 2 is a current line attached to the magnetic thin film memory element 1, and 3 is a voltage line attached to the magnetic thin film memory element 1. The magnetic thin film memory element 1 uses a magnetic thin film having perpendicular magnetic anisotropy. Further, GND indicates grounding.

Now, when it is desired to read information from the magnetic thin film memory element 1cb magnetized downward, a current I is passed through the current line 2c, and the voltage change on the voltage line 3b at that time is VHJ'.
Just read. Similarly, when it is desired to read information from the upwardly magnetized magnetic thin film memory element 1ac, a current I is passed through the current line 2a, and the voltage change at that time on the voltage line 3c is V.
Just read HJ. The voltage at this time is the voltage line 3.
This is an abnormal Hall voltage that occurs between the current line 2 and the grounded point of the current line 2, and a voltage of ± is generated between the downwardly magnetized magnetic thin film memory element and the upwardly magnetized magnetic thin film memory element. Therefore, it can be read out as a memory based on the difference in the recorded magnetization direction.

Next, FIG. 2 shows the relationship between the current I applied to the current line 2 and the voltage (abnormal Hall voltage) VH of the voltage line 3. The larger the applied current I, the larger the voltage change VH, the better the S/N ratio of the reproduced signal, and the higher the degree of integration of the magnetic thin film memory element 1. However, if the current I flowing through the current line 2 increases, the temperature of the wiring will increase, and in extreme cases, the wiring may break. Further, due to the temperature rise, the temperature of the magnetic thin film memory element 1 itself also rises. Since the abnormal Hall voltage VH decreases as the temperature of the element itself increases, the applied current I cannot be made too large. In order to improve this, the current applied to the current line 2 is applied as a pulse current. The shorter the pulse width, the better, as long as the Hall voltage VH changes so that it can be read out. In addition, pulsed current leads to a reduction in the power consumption of the entire memory.

Next, the recording method will be explained. FIG. 3 is a conceptual diagram showing the configuration of another embodiment of the present invention. In FIG. 3, 4 and 5 are horizontal and vertical recording lines. The horizontal and vertical recording lines 4 and 5 are orthogonal to each other,
It is arranged at a position slightly shifted from the magnetic thin film memory element 1, so that a magnetic field is applied to the magnetic thin film memory element 1 in the perpendicular direction when currents Ix and Iy are applied. As an example, a case will be described in which the magnetization of the magnetic thin film memory element 1bb is recorded downward. When a current Ix is applied to the horizontal recording line 4b in the → direction, the perpendicular magnetic field applied to the magnetic thin film memory element 1bb is Hix, and when a current Iy is applied to the vertical recording line 5b in the ↑ direction, the magnetic thin film memory Element Ibb
The perpendicular magnetic field applied to is Hiy. Furthermore, when the current Iα is passed in the → direction through the reproduction current line 2b, the perpendicular magnetic field applied to the magnetic thin film memory element 1bb is Hiα, and when the current Iβ is passed in the ↑ direction through the reproduction voltage line 3b, The perpendicular magnetic field applied to the magnetic thin film memory element 1bb is Hiβ
shall be. Assuming that the coercive force of the magnetic thin film memory element 1bb is Hc, the following relationship is established when recording. If Hc<Hix+Hiy+Hiα+Hiβ (1), the magnetization of the magnetic thin film memory element 1bb is reversed and recording is completed. Furthermore, in equation (1), if it holds even if Hix=0, the horizontal recording line 4b can be omitted. Similarly, even if Hiy=0, if it holds true, the vertical recording line 5b can be omitted. Furthermore, Hix=Hiy
Even if = 0, if it holds true, the horizontal and vertical recording lines 4b, 5b
Both are not necessary. That is, the current line 2 and voltage line 3 for reproduction can also serve as recording lines. This example is
The current line 2 and voltage line 3 for reproduction are also used as recording lines, and both the horizontal and vertical recording lines 4 and 5 are omitted in Figure 1, and the grounding GND side of the current line 2 is This is shared with the voltage line 3, and the overall configuration is significantly simplified.

[0014] Regarding the reproduction and recording methods, the following ideas may be considered. FIG. 4 is an explanatory diagram showing an embodiment of a reproduction method different from that of FIG. 1, and the following three points are different from the embodiment of FIG. 1.
It is a point. (1) The abnormal Hall voltage VH is read out as a potential difference generated between terminals A and B of the voltage line 3 arranged on both sides of the magnetic thin film memory element 1. In such a configuration, the direction in which the reproducing current I flows is perpendicular to the straight line connecting AB, so when there is no abnormal Hall effect, no potential difference is generated between the terminals A and B due to the current I. Therefore, only a potential difference due to the abnormal Hall effect occurs between terminals AB. For example, signals having different polarities and equal absolute values can be obtained depending on the magnetization direction of the magnetic thin film memory element 1. (2) Resistors R are provided at both ends of the magnetic thin film memory element 1, and the resistors R can reduce the flow of current to the magnetic thin film memory element 1 that is not being read, thereby reducing noise caused by them. (3) Install a capacitor C between terminals AB. For example, when a reproducing current is passed through the current line 2a, all the magnetic thin film memory elements 1aa, 1ab, 1ac, ... in that row are read out, and the corresponding terminals Ai, Bi (i=a, b
, c, . . .), an abnormal Hall voltage VH is generated between them. These are stored in capacitor C after a certain charging time. After capacitor C is charged, the regeneration current is stopped. One by one Aa-Ba, Ab-B without using capacitor C
When reading out the potential difference between b, Ac-Bc, . . . , it is necessary to keep the reproducing current flowing throughout the reading, resulting in a large loss in power consumption. The charged capacitor is opened and read after the reproduction current stops.

Next, FIG. 5 is an explanatory diagram showing one embodiment of the recording method. In the example of FIG. 3, it was considered that the current line 2 and voltage line 3 used for reproduction are also used for recording. This is also possible here, but to simplify the explanation, recording and reproduction are considered independently, and only the lines necessary for recording are shown in FIG. For example, in order to record the magnetization of the magnetic thin film memory element 1ac in an upward direction, current is passed through the recording lines 4aU and 3cU in the direction shown in the figure. Furthermore, in order to record downward, current is passed through the recording lines 4aD and 3cD in the direction shown in the figure. Different recording lines are used to perform upward and downward recording in this way. This eliminates the need to reverse the direction of the current in the recording line and the time required to reverse it. That is, the data transfer speed during recording can be increased.

Next, a method for manufacturing a magnetic thin film memory according to the present invention will be explained. A mask 1 as shown in FIG. 6 is placed on the substrate.
0 in close contact with Cu, Au,
A conductor such as Al is formed through the through hole 11 by sputtering or the like (the dotted line portion will be described later). moreover,
The upper and lower sides of the rectangular through hole 21 of the mask 20 as shown in FIG. A film is formed by a sputtering method or the like. An insulating film is formed in areas other than the magnetic thin film memory element 1 by a lift-off method or the like. Furthermore, a mask 3 as shown in FIG.
0, and a conductor such as Cu, Au, Al, etc. is formed by sputtering or the like through the through hole 31 as a reproduction voltage line 3 so as to be in contact with the previously formed magnetic thin film memory element 1. A dielectric film such as SiNx is formed on the magnetic thin film memory element 1 and the voltage line 3 as a protective film. As recording lines, Cu strip lines are formed so as to be orthogonal to each other.
Each of them is formed at a position slightly shifted from the rectangular magnetic thin film memory element 1 (see FIG. 3). Finally, apply a protective coating with resin. The coercive force Hc of the HoCo film of this example is 30 (Oe) [Oersted], the pattern period is 2 μm, and the magnetic thin film memory element 1 is 0.5 μm.
It is a corner. The distance between the recording line and the center of the magnetic thin film memory element 1 is 1 μm. Recording currents Ix, Iy, Iα, Iβ
A constant current is applied as shown in Table 1.

[0017]

[Table 1]

In all of Experimental Examples 1 to 6, the coercive force of 30 (Oe) of the magnetic thin film memory element 1 was sufficiently exceeded, and good recording was performed. Furthermore, when a pulse current with a pulse width of 50 (nsec) is applied to the current line 2 so that a voltage of about 20 mV is applied across one of the magnetic thin film memory elements 1, a voltage of about 20 μV is applied to the voltage line 3. A change appeared, and a good read operation was performed.

Next, still another embodiment will be explained with reference to FIG. After forming the lead-out portions of the current line 2 for reproduction and the voltage line 3 for reproduction from the magnetic thin film memory element 1 on the substrate (not shown), a HoCo film was formed as the magnetic thin film memory element 1 in the same manner as in Example 1. form. Thereafter, the vertical recording line 5 and the horizontal recording line 4 are formed while sandwiching an insulating film such as alumina so that they can be insulated from each other. After that, the same steps are repeated to form the number of laminated layers of magnetic thin film memory, but for the playback lines for each layer, the playback voltage lines that connect each layer are formed by forming through holes and connection conductors. form 3. The coercive force Hc of the HoCo film of this example is 30 (Oe). In FIG. 9, when recording on the magnetic thin film memory element 1aaa, both recording lines 4aa
A constant current of 10 mA was applied to each of the and 5 aa. At this time, the magnetic fields generated by both recording lines 4aa and 5aa at the center of the magnetic thin film memory element 1aaa are each 20
(Oe), and only when both magnetic fields were superimposed, the coercive force of 30 (Oe) of the magnetic thin film memory element 1 was sufficiently exceeded, and good recording was performed. Further, as in the embodiment shown in FIG. 3, the magnetic field may be supplemented by passing a constant current through the current line 2 for reproduction. When reading, a pulse current with a pulse width of 50 (nsec) was applied to the current line 2 so that a voltage of about 20 mV was applied to both ends of one of the magnetic thin film memory elements 1. A voltage change of about 5 μV appeared on the voltage line 3aa, and good reading was possible. The amount of change in this voltage decreases as the number of stacked magnetic thin film memory elements 1 increases, so the number of stacked magnetic thin film memory elements 1 needs to be determined within a detectable range.

[0020]

As described above, according to the present invention, reading is performed using the anomalous Hall effect of the magnetic thin film. At least one of the current line and the voltage line is used for recording, and the voltage line for reading the stacked magnetic thin film memory elements at the same position is made common.
The number of lines can be reduced, the configuration can be simplified, and the degree of memory integration can be significantly improved. Furthermore, since a resistor is inserted between the magnetic thin film memory element and the read voltage line, the current flowing to the magnetic thin film memory element that may be read is limited. Furthermore, since the abnormal Hall voltage is stored in the capacitor, power consumption is reduced. Furthermore, since "0" and "1" can be recorded with the current direction being the same, the data transfer speed is improved. Furthermore, since regeneration is performed by passing a pulsed current through the current line, there are effects such as reduced power consumption.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of reproduction lines and a magnetic thin film memory element showing an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between applied current and abnormal Hall voltage.

FIG. 3 is a conceptual diagram showing another embodiment of the present invention in which recording lines are arranged in FIG. 1;

FIG. 4 is a conceptual diagram showing an embodiment of another reproduction method of the present invention.

FIG. 5 is a conceptual diagram showing an embodiment of another recording method of the present invention.

FIG. 6 is a mask diagram for creating current lines of a magnetic thin film memory used in an embodiment of the present invention.

FIG. 7 is a mask diagram for producing a magnetic thin film memory element used in an example of the present invention.

FIG. 8 is a mask diagram for creating voltage lines of a magnetic thin film memory used in an embodiment of the present invention.

FIG. 9 is a conceptual diagram showing an embodiment of a stacked magnetic thin film memory of the present invention.

FIG. 10 is a schematic diagram of a conventional magnetic thin film memory element assembled.

[Explanation of symbols]

1 Magnetic thin film memory element 2 Current line 3 Voltage line 4 Lateral recording line 5 Vertical recording line

Claims (8)

[Claims] 1. A magnetic thin film memory using a magnetic thin film memory element in which information is recorded by the direction of magnetization of a thin film magnetic material and outputs an abnormal Hall voltage when energized. A reproducing current line for supplying current to output an abnormal Hall voltage, and a reproducing voltage line for deriving the abnormal Hall voltage by using the other end of the current line in common. magnetic thin film memory. 2. The magnetic thin film memory according to claim 1, wherein at least one of a current line and a voltage line for reproduction is used as a recording line. 3. The magnetic thin film memory according to claim 1 is stacked vertically, and voltage lines for reproduction of the magnetic thin film memory elements stacked at the same position are commonly connected. magnetic thin film memory. 4. The magnetic thin film memory according to claim 1, further comprising a resistor inserted between the magnetic thin film memory element and the reproduction voltage line. 5. The magnetic thin film memory according to claim 4, further comprising a capacitor for storing the output abnormal Hall voltage. 6. The magnetic thin film memory according to claim 1, wherein at least one of a current line and a voltage line for reproduction is used as a recording line, and a current is passed during recording to perform recording in the magnetic thin film memory element. Recording method for thin film memory. 7. Corresponding recording lines for recording 2-bit information "0" and "1" are provided, and the "0" and "1" are recorded using the same direction of current flowing through each recording line. A recording method for a magnetic thin film memory characterized by the following. 8. The magnetic thin film memory according to claim 1, wherein a pulse current is applied to a current line for reproduction, and an abnormal Hall voltage excited in the voltage line is read out as a reproduction signal. How to play.