MAGNETIC RANDOM ACCESS MEMORY and manufacture method thereof
Technical field
The present invention relates to a kind of MAGNETIC RANDOM ACCESS MEMORY (MRAM), more specifically, relate to a kind of MRAM that utilizes magnetic domain retardance and giant magnetoresistance (GMR) or tunnel magnetoresistive (TMR).
Background technology
MRAM is nonvolatile semiconductor memory member and novel solid magnetic store, it utilized based on nanometer magnetic material the magnetoresistance of unique spin correlation conduction (spin dependent conduction).MRAM utilizes GMR or TMR, and GMR or TMR take place because of spin (electronic degree of freedom) applies great influence to electron transport.
GMR is that the spin that forms between two kinds of ferromagnetic materials is arranged the spin that forms between identical situation and the two kinds of ferromagnetic materials and arranged between the opposite situation, has the phenomenon of resistance difference in ferromagnetic material/non-ferromagnetic metallics/ferromagnetic material sandwich construction.TMR be with two kinds of ferromagnetic materials between the spin that forms arrange opposite situation and compare, the easier phenomenon of passing of electric current in ferromagnetic material/megohmite insulant/ferromagnetic material sandwich construction is arranged in the identical situation in the spin that forms between two kinds of ferromagnetic materials.In utilizing the MRAM situation of GMR, since little corresponding to the difference between the resistance value of direction of magnetization, so the difference between the magnitude of voltage can not increase.In addition, utilize the MRAM of GMR to have shortcoming on the size that increases MOSFET, this MOSFET combines with gmr film to form a unit.Therefore, carried out more research so that utilize the MRAM practicability of tmr film.
In traditional MRAM during record data, the vector sum on X and the Y direction is used to select the concrete unit in an array, and this array has the matrix structure of unit mram cell.Also promptly, according to existing asteroid method, the direction of magnetization of magnetic thin film with respect to the external magnetic field sum considered in the record of data.In traditional MRAM, electric current is applied on the electrode wires intersected with each other of data storage cell (GMR or TMR) top, with because of the reversing magnetic field that forms across this electrode wires is induced to direction of magnetization in the free layer of data storage cell, and this direction of magnetization is as a message unit.
For realize can be practical memory device, the work energy consumption need be reduced to minimum, this has limited the selection of the material that is used for data storage cell.In traditional MRAM, in order to produce reversing magnetic field, i.e. power consumption, permalloy (NiFe) is used most widely for the free layer of magnetoresistance device.Importantly increase magnetic resistance,, and make chip structure efficiently with the travelling speed of raising MRAM.For this reason, the magnetic thin film that is used for free layer must have ferromagnetic characteristic and high polarization characteristic.In order to obtain these characteristics, can use NiCoFe alloy, semimetal alloy, magnetic non-crystaline amorphous metal or the like, but these magnetic materials has big reversing magnetic field, so they can not easily be applied among traditional MRAM.Also promptly, because reversing magnetic field is big,, therefore be difficult to above magnetic material need to be used to the memory device of high density of integration so the width of electrode wires and thickness need be greater than existing methods.
Simultaneously, the vector on utilizing X and Y direction and recording information in the array of memory device, or when from the array of memory device, duplicating out, need two and independently write source electrode, this makes the structure of chip become complicated.
Summary of the invention
In order to address the above problem, the purpose of this invention is to provide a kind of miniature MAGNETIC RANDOM ACCESS MEMORY (MRAM) device and array, this device and array do not need reversing magnetic field, power consumption is reduced to minimum, has simple structure, can increase travelling speed, and have size, thereby realize the micro memory device corresponding to domain size.
In order to realize above purpose of the present invention, a kind of MAGNETIC RANDOM ACCESS MEMORY is provided, comprising: a data storage cell, this unit comprise a fixed bed, a nonmagnetic layer and a free layer; One data input cell, this unit are electrically connected with the two ends of this free layer so that data are inputed in the data storage cell; And a data output unit, this unit is electrically connected with free layer and fixed bed will be stored in the data output in the data storage cell.
Preferably, fixed bed and free layer are formed by ferromagnetic material, and free layer comprises at least one neticdomain wall.
Preferably, data input cell comprises: a Data In-Line, and electric current is loaded on the free layer through this line, to determine direction of magnetization; And a data input selector switch, this switch is formed between the end and Data In-Line of free layer.Preferably, the data output unit comprises: be formed on the bit line on the free layer; And the data output selector switch that is connected to the fixed bed bottom.
Preferably, each in data input selector switch and the data output selector switch is a diode, a MOS transistor or a bipolar transistor.
A kind of MAGNETIC RANDOM ACCESS MEMORY array also is provided, and this array has a matrix structure of cell memory device, and each cell memory device comprises: a data storage cell, this unit comprise a fixed bed, a nonmagnetic layer and a free layer; One data input cell, this unit are electrically connected with the two ends of this free layer so that data are inputed in the data storage cell; And a data output unit, this unit is electrically connected with free layer and fixed bed will be stored in the data output in the data storage cell.The input that data input cell and data output unit are electrically connected to respectively in the MAGNETIC RANDOM ACCESS MEMORY array selects demoder and output to select on the demoder, to select concrete cell memory device.
Preferably, data input cell comprises: a Data In-Line, and electric current is loaded on the free layer through this line, to determine direction of magnetization; And a data input selector switch, this switch is formed between the end and Data In-Line of free layer, and selects the demoder electricity to drive by input.The data output unit comprises: be formed on the bit line on the free layer; And be connected to the fixed bed bottom and select the electrically driven (operated) data output selector switch of demoder by output.
Preferably, MAGNETIC RANDOM ACCESS MEMORY also comprises a reference column that is formed by the benchmark memory unit, and in each benchmark memory unit, the direction of magnetization of the free layer of data storage cell is fixed.The bit line of the bit line of cell memory device and benchmark memory unit is connected to comparer.
A kind of method of moving the MAGNETIC RANDOM ACCESS MEMORY array also is provided, input selection demoder and output selection demoder that this MAGNETIC RANDOM ACCESS MEMORY array comprises an array and is electrically connected with data input part part and data output section part respectively, to select cell memory device concrete in this array, this array has a matrix structure of cell memory device, each cell memory device comprises: a data storage cell, this unit comprise a fixed bed, a nonmagnetic layer and a free layer; Data input cell, this unit is electrically connected with the two ends of this free layer, so that data are inputed in the data storage cell; And the data output unit, this unit is electrically connected with free layer and fixed bed, will be stored in the data output in the data storage cell.The method comprising the steps of: (a) utilize input to select demoder to select concrete cell memory device, and by utilizing data input cell that electric current is loaded on the selected cell memory device, the spin that forms predetermined direction in the magnetic domain of the free layer of data storage cell is arranged; And (b) utilize output to select demoder to drive the output selector switch that is connected on the concrete cell memory device, and utilize the data output unit that data are read from data storage cell.
Data input cell comprises: a Data In-Line, and electric current is loaded on the free layer through this line, to determine direction of magnetization; And a data input selector switch, this switch is formed between the end and Data In-Line of free layer, and selects the demoder electricity to drive by input.Herein, step (a) comprises step: utilize input to select demoder driving data input selector switch; And the spin that forms predetermined direction by Data In-Line in the magnetic domain of free layer is arranged.
The data output unit comprises: be formed on the bit line on the free layer; And be connected to the fixed bed bottom and select the electrically driven (operated) data output selector switch of demoder by output.Herein, step (b) comprises step: utilize output to select demoder driving data output selector switch; And the fixed bed of measurement data storage unit and the resistance value between the free layer, with sense data.
This array also comprises a reference column that is formed by the benchmark memory unit, in each benchmark memory unit, the direction of magnetization of the free layer of data storage cell is fixed, and the bit line of the bit line of cell memory device and benchmark memory unit is connected to comparer.Herein, step (b) comprises the resistance value of the data storage cell of cell memory device and fixed resistance value corresponding to the data storage cell of the benchmark memory unit of cell memory device compared, and is stored in data in the cell memory device with output.
Description of drawings
In conjunction with the drawings to a preferred embodiment of the present invention will be described in detail, above purpose of the present invention and advantage will become more clear, wherein:
Figure 1A to 1B describes the synoptic diagram of the data input principle of MAGNETIC RANDOM ACCESS MEMORY (MRAM) device according to an embodiment of the invention;
Fig. 2 A to 2B is the synoptic diagram that is used to illustrate according to the data output principle of the MRAM device of this embodiment of the invention;
Fig. 3 A is the equivalent circuit diagram according to the unit mram cell of this embodiment of the invention;
Fig. 3 B and 3C are the viewgraph of cross-section according to the MRAM device of this embodiment of the invention; And
Fig. 4 is the equivalent circuit diagram of MRAM array according to an embodiment of the invention.
Embodiment
Record data and describe with reference to Figure 1A to 2B in the used data storage cell in MAGNETIC RANDOM ACCESS MEMORY (MRAM) according to an embodiment of the invention from the principle of copy data wherein.This MRAM device comprises: as giant magnetoresistance (GMR) device or tunnel magnetoresistive (TMR) device of data storage cell; Two switches are used on whole array selecting a unit cell with at the data storage cell record data or from copy data wherein; And an electric connection line, this line is the path that data-signal inputs or outputs.
Constitute by a plurality of layers as GMR or TMR device: a fixed bed, a nonmagnetic layer and a free layer according to the data storage cell of the MRAM of this embodiment of the invention.Data I/O value changes with the conversion direction of free layer.
Nonmagnetic layer 15 forms on fixed bed 13, and in this this fixed bed, direction of magnetization is fixed on a specific direction.Free layer 12 is formed on the nonmagnetic layer 15.Nonmagnetic layer 15 is non-magnetic metal layer or oxide skin(coating), and is formed between fixed bed 13 and the free layer 12, so that their magnetic is separated.Free layer 12 has a neticdomain wall.This neticdomain wall is that nature forms, and perhaps the type or the mode of deposition of the ferromagnetic material that its width can be by forming free layer 12 are regulated.Fixed bed 13 is made of ferromagnetic layer and anti-ferromagnetic layer.
The principle of data recording will at first be illustrated.Usually, there is several different methods to change the direction of magnetization of magnetic domain.At first, the direction of magnetization of the free layer of information memory cell can utilize magnetoresistance device to determine with respect to the reversing magnetic field of free layer.Secondly, direction of magnetization can utilize electron spin and magnetization to interact to determine.The 3rd, direction of magnetization can utilize the direction of current that is applied on the magnetic domain to determine.MRAM according to the present invention adopts the third method.
If apply direct current or alternating current at the two ends of free layer 12, then electric current flows with the form of pulse 10.Herein, the magnetic domain of free layer 12 changes according to sense of current corresponding to the direction of magnetization of fixed bed 13.Direction of magnetization 11 representative data values 0 or 1.If electric current applies on the reverse direction of Figure 1A, then direction of magnetization 11 and Figure 1A's is opposite, shown in Figure 1B.Herein, direction of magnetization 11 representatives are different from the data value of representative among Figure 1A.Also promptly, when direction of magnetization 11 is represented " 0 " in Figure 1A, then in Figure 1B, represent " 1 ".
The data output principle is with reference to Fig. 2 A and 2B explanation.Identical according to the data output principle of MRAM of the present invention and traditional MRAM.
Electric current is applied to the bottom of fixed bed of data storage cell and the top of free layer 22 respectively, and the resistance value between fixed bed 23 and the free layer 22 is measured.Fixed bed 23 is identical in Fig. 2 A with 21 with free layer 22 direction of magnetization 24 separately, and they are opposite in Fig. 2 B.Therefore, identical with common magnetoresistance device, the resistance among Fig. 2 B is greater than among Fig. 2 A, and the data value of this resistance official post storage is discerned.
MRAM device according to the present invention describes with reference to Fig. 3 A to 3C.Fig. 3 A is the equivalent circuit diagram according to MRAM device of the present invention.Fig. 3 B and 3C are the cut-open views of the MRAM device among Fig. 3 A of respectively A-A ' along the line and B-B ' intercepting.
MRAM device according to the present invention comprises: a data storage cell 31, information are recorded in wherein or wherein duplicate certainly; Two switches 32 and 36 are used for selecting predetermined data storage cell 31 in whole memory arrays; And an electric connection line, data-signal is input in the data storage cell 31 by this line, or from wherein output.Need data input cell and data output unit with data storage in data storage cell 31, or from sense data wherein.Therefore, in order in whole array, to select a unit cell, need input selector switch 36 and output selector switch 32 with input and output.
As mentioned above, be magnetoresistance device according to the data storage cell 3 of MRAM device of the present invention, and make GMR or TMR device.It has the sandwich construction of fixed bed/nonmagnetic layer/free layer.This free layer comprises a plurality of magnetic domains.The switch of MRAM device can be made the device such as diode, MOS transistor or bipolar transistor, and this device can be carried out switching function.
In an embodiment of the present invention, use two switches.One is connected in series on the free layer.Another is vertically connected on the free layer and fixed bed of data memory unit, forms electric access node structure.
Has operation according to the unit cell of MRAM structure of the present invention with reference to Fig. 3 A explanation.The operation of MRAM device is divided into: select units corresponding in the array of the matrix structure with a plurality of unit cells 30; And data are recorded in the selected unit, or from copy data wherein.
When the input data, the single unit cell 30 in the MRAM array is transfused to selection wire 37 and Data In-Line 38 is selected.Then, be recorded in the data storage cell 31 by input selector switch 36 from the data message that Data In-Line 38 provides.As mentioned above, in the free layer of data storage cell 31, direction of magnetization is determined according to the sense of current that flows in Data In-Line 38.According to direction of magnetization, the data value of " 0 " or " 1 " is determined and record.Herein, Reference numeral 39 expression data input paths.
Then, when output data, read resistance difference by utilizing detecting amplifier (S/A) etc. corresponding to the direction of magnetization of each fixed bed of data storage cell 31 and free layer, data are read from the MRAM unit cell, this unit cell is selected by output selection wire 33 (that is word line) and bit line 34.
Fig. 4 is the equivalent circuit diagram of array with matrix structure of a plurality of above-mentioned MRAM unit cells.Connect a plurality of unit cells forming a plurality of row 41, and adopt reference column 42.Select the MRAM unit cell in the concrete memory column, utilize comparer 44 that the signal of selected MRAM unit cell and the signal that is arranged in the reference cell of the reference column in the delegation 42 are compared, to read " 0 " or " 1 " data value in the data storage cell that is stored in selected MRAM unit cell.In the free layer of each reference cell 43, the initial spin direction is fixed, and is used as the benchmark of the data value of storing in the common MRAM unit cell.
With reference to Fig. 4, data input process, i.e. data writing process will be described at first.Select in the whole M array ram under the situation of unit cell A, input selects demoder that power supply is supplied to the input selection wire 45 that links to each other with unit cell A, with conducting data input selector switch 46.Input source electrode/ground imposes on unit cell A with electric current by Data In-Line 47, with the direction of magnetization in the magnetic domain of the free layer of specified data storage unit 48.Data In-Line 47 is electrically connected to the both sides of the free layer of each unit cell.Spin in the data based free layer is arranged (that is direction of magnetization) and is stored in the data storage cell.This is a data writing process.
Then the data output procedure will be described, i.e. the data readout.Output selects demoder that power supply is offered the output selection wire 49 that is connected to unit cell A, i.e. word line.Also promptly, required unit cell A chooses by output selection wire 49, and data output selector switch 50 conductings of unit cell A.Then, power supply is loaded on the bit line 51, and the free layer of data storage cell 48 and the resistance difference between the fixed bed are read.
Preferred MRAM array according to the present invention is provided with reference cell, and this reference cell has the structure identical with the MRAM unit cell, and has fixing direction of magnetization in its free layer, and promptly fixing spin is arranged.Also promptly, when selecting required MRAM unit cell, in the reference column 42, the reference cell that is formed on the row identical with required MRAM unit cell is selected simultaneously, and reads its resistance value.Herein, the resistance value of required MRAM unit cell compares by the resistance value of comparer 44 with selected reference cell.Comparer 44 is connected to the bit line of common MRAM unit cell, and is connected to the bit line of the reference cell in the reference column 42.
As shown in Figure 4, when reading of data value in MRAM unit cell A, the reference cell B that shares an output ground with this MRAM unit cell A is selected in reference column 42, and the resistance value of reference cell B and MRAM unit cell A by comparer 44 relatively.The direction of magnetization of the free layer of reference cell B is fixed.By the comparison resistance value, the data value that is stored among the MRAM unit cell A is confirmed as " 0 " or " 1 ".
The present invention has eliminated the problem in the conventional art that utilizes reversing magnetic field, and a kind of MRAM is provided, and this MRAM can utilize the thin magnetic film with high polarization characteristic and low driving power consumption.In addition, the invention provides a kind of MRAM unit cell, it has and magnetic domain size of the same size, thereby data can be stored in the very simple data storage cell of structure, or from wherein reading.Therefore, the present invention can realize having the MRAM of high density of integration.