CN105655342A - Ferroelectric nonvolatile memory and preparation method and read/write operation method thereof - Google Patents

Ferroelectric nonvolatile memory and preparation method and read/write operation method thereof Download PDF

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CN105655342A
CN105655342A CN201610098138.9A CN201610098138A CN105655342A CN 105655342 A CN105655342 A CN 105655342A CN 201610098138 A CN201610098138 A CN 201610098138A CN 105655342 A CN105655342 A CN 105655342A
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read
ferroelectric
write
electrode
storage cell
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CN105655342B (en
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江安全
耿文平
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Fudan University
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B53/00—Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory capacitors
    • H10B53/30—Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory capacitors characterised by the memory core region
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
    • G11C11/22—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using ferroelectric elements
    • G11C11/223—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using ferroelectric elements using MOS with ferroelectric gate insulating film
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B69/00—Erasable-and-programmable ROM [EPROM] devices not provided for in groups H10B41/00 - H10B63/00, e.g. ultraviolet erasable-and-programmable ROM [UVEPROM] devices

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Abstract

The invention belongs to the technical field of ferroelectric storage, and particularly relates to a ferroelectric nonvolatile memory and a preparation method and a read/write operation method thereof. The ferroelectric memory comprises a ferroelectric thin film layer, a ferroelectric storage unit etched on the surface of the ferroelectric thin film layer, and in-plane read/write electrode layers prepared at the left and right of the ferroelectric storage unit; and a polarization direction of an electric domain is basically not parallel to a normal direction of the read/write electrode layer. When an in-plane structure of the storage unit is changed, the multi-bit information storage can be realized. A read operation and a write operation can be completed by virtue of a storage unit left/right deposited read/write electrode layer etched on the surface, and an additional read electrode and an additional read/write electrode can be additionally arranged on the top of the etched ferroelectric storage unit so as to realize the read operation. The ferroelectric memory is simple in structure, simple in preparation, low in cost and capable of nondestructively and rapidly reading the stored electric-domain logic information in a large-current way.

Description

Nonvolatile ferroelectric memory and preparation method thereof and read/write operation method
Technical field
The invention belongs to FERROELECTRICS MEMORIES TECHNOLOGY field, it is specifically related to a kind of novel Nonvolatile ferroelectric memory, particularly relates to based on ferroelectric thin-flim materials surface etch memory element and manufacture left and right electrode in the face connecting memory element in ferroelectric cell gap and carry out reading preparation method and the read/write operation method of high density ferroelectric memory and this ferroelectric memory in the face of write operation.
Background technology
Ferroelectric Random Access Memory FRAM (FerroelectricRandomAccessMemory) utilizes ferroelectric domain (or being called " electricdomain ") to keep two kinds of different polarization orientations to store the nonvolatile memory (Non-volatileMemory) of data as logical message (" 0 " or " 1 ") under positive and negative electric field action, and it can also be called " ferroelectric memory ".
The storage medium layer of ferroelectric memory is the ferroelectric thin film layer of the ferroelectric domain with can reverse (or being called " upset "), and at present, the prestissimo of the domain reversal can measured in laboratory can reach 0.2ns, and actually it can also be faster. Normally, the speed reversal of electricdomain determines the access time of memorizer, and the coercive voltage of domain reversal determines the read-write voltage of device, and it almost can reduce in equal proportion along with the reduction of film thickness. Therefore, ferroelectric memory has that reading and writing data speed is fast, driving voltage is low and memory density advantages of higher, obtains in recent years and pays close attention to widely and develop faster.
At present, ferroelectric memory can be divided mainly into by groundwork or operator scheme: the big class of FeFET two of the destructive FRAM reading (DRO) and non-Destructive readout (NDRO). Destructive (DRO) ferroelectric memory that reads is the storage electrostatic capacitor replacing routine as dielectric layer with ferroelectric capacitor (using the electric capacity that ferroelectric thin film layer is formed), and utilizes its polarization reversal to realize write and the reading of data. Up to now, on market, all ferroelectric memorys of application are all adopt this mode of operation, wherein with 1 transistor T and ferroelectric capacitor C(and 1T1C) build memory element, and using this 1T1C memory element as circuit design, in read operation process, by the reference capacitance connected with 1T1C memory element carries out voltage reading, the method adopting charge integration, fetches whether the electricdomain judging ferroelectric thin film layer reverses, thus the logical message in recognition memory cell.This ferroelectric memory is in read operation, and voltage reading can cause the domain reversal of ferroelectric thin film layer, and therefore, its shortcoming is information reading is destructive, and poor reliability needs again to write back original logical message state after read operation. It addition, along with the raising of device integration density, the area of the ferroelectric capacitor C of memory element constantly reduces, and reading electric charge is that the area to ferroelectric capacitor C is directly proportional, and therefore can read electric charge also fewer and feweri; When device memory cell size is less than 130nm, stored logical message in current reading circuit basic None-identified memory element, seriously hinder ferroelectric memory and develop to high density direction.
Non-Destructive readout (NDRO) ferroelectric memory is then utilize ferroelectric thin film layer to replace the gate dielectric layer of conventional MOSFET and constitute the ferro-electric field effect transistor (FeFET) of MFS structure. Leakage current I can be changed by the control of polarised directiondsSize, gap can reach several order of magnitude, and storage information can realize non-demolition under only small voltage and read. It has the features such as High Density Integration, high read or write speed, non-demolition reading and low-power consumption, but owing to the logical message of this device keeps poor performance, generally can only achieve a couple of days, and storage market generally requires to be not less than 10 years. Therefore this structure is at present also in the laboratory research stage, fails practice in memory product.
Therefore, Current commercialization application destructive reads (DRO) ferroelectric memory mainly so that ferroelectric capacitor to be read in charge integration mode, as summarized above, its shortcoming with destructive reading, need after reading to re-write data, thus along with the operation of substantial amounts of erasing and rewriting, causing that the reliability of device reduces, have impact on data reading speed; Further, it is scaled that this reading principle limits ferroelectric capacitor C, and memory density is low, for instance, the maximum only 8MB of ferroelectric memory of current commercial applications.
Adopt the domain wall that formed of ferroelectric domain of two kinds of different orientations and then produce domain wall electric current and can also read the logical message of stored ferrum electricity electricdomain. Thin film micro-zone is applied electric field by the commonly used nanometer pinpoint to atomic force microscope in the world at present, thus changing thin film local electric domain orientation thus forming conduction domain wall. This atomic force needle point technology cannot be compatible with current semiconductor technology, namely cannot realize large-scale production; It addition, read current generally only has pA-nA magnitude, namely electric current is too weak, it is impossible to is stored by high speed readout circuit (ns magnitude) and is identified. Read-write memory cell structure in this technology employing face, completely compatible with semiconductor technology; Additionally read domain wall current signal and can reach 100nA-10 �� A, it is possible to identified by the reading circuit of current high-speed memory.
Summary of the invention
An object of the present invention be in that to provide a kind of can with big electric current reading manner realizes information non-Destructive readout, high density ferroelectric memory in face that memory property is good, the read operation of ferroelectric memory and write operation all can complete by left and right electrode layer in the same face.
For realizing object above or other purposes, the present invention provides techniques below scheme.
It is an aspect of this invention to provide that provide a kind of ferroelectric memory, this ferroelectric memory includes:
The cuboid ferroelectric storage cell (305) that ferroelectric thin film layer (303) and film surface etch, bottom ferroelectric thin film layer, (303) and surface are etched out ferroelectric storage cell (305) actually same entirety, and namely the etching depth of film surface memory element is less than film thickness;
And it is arranged on left and right read-write electrode layer (307) on ferroelectric storage cell (305) both sides, described surface, the ferroelectric storage cell (305) being etched out between described read-write electrode layer (307) is divided into two parts, is electrode to (3071) and (3073);
The polarised direction of the electricdomain (3031 or 3033) of described ferroelectric thin film layer (303) and the electricdomain (3051 or 3053) of ferroelectric storage cell (305) is substantially not parallel to the normal direction of described read-write electrode layer (307) place plane;
Wherein, when reading and writing the write signal biasing first direction between two parts of the adjacent described etching ferroelectric storage cell (305) in electrode layer (307) in described, the electric field formed between (3071) and (3073) is reversed completely by the electricdomain of corresponding described surface etch ferroelectric storage cell (305) by electrode, and and do not reverse bottom ferroelectric thin film layer (303) and between electricdomain, set up domain wall conductive channel (3054).
Such as, when biasing write signal (this signal voltage is more than or equal to the coercive field voltage of ferroelectric storage cell) of first direction between two parts of the adjacent described ferroelectric storage cell (305) in described read-write electrode layer (307), the electricdomain that the surface electricdomain of corresponding described ferroelectric storage cell (305) is not reversed with bottom biock body thin film to be completely reversed forms conduction domain wall passage;
When biasing read signal (this signal voltage is less than the coercive field voltage of ferroelectric storage cell) of first direction between two parts of the adjacent described ferroelectric storage cell (305) in described read-write electrode layer (307), the domain wall conductive channel (3054) that corresponding described ferrum ammeter face is etched between the memory element (305) and ferroelectric thin film bottom (303) that are formed and is formed or do not formed is not destroyed.
Ferroelectric memory according to an embodiment of the invention, wherein, when biasing the write signal of second direction opposite to the first direction between two parts of the adjacent described surface etch ferroelectric storage cell (305) in described read-write electrode layer (307), electricdomain (3053a) reversion of the etching ferroelectric storage cell (305) being completely reversed is made to return to initial polarization direction.
In the ferroelectric memory of described any embodiment before, configure the thickness (h) of described ferroelectric storage cell (305) and/or the width (d) of described ferroelectric storage cell (305), so that the electricdomain of ferroelectric storage cell (305) described between (3071) and (3073) is completely reversed by the counter electrode under voltage effect of writing in biasing predefined size.
In the ferroelectric memory of described any embodiment before, configure the thickness (h) of described ferroelectric storage cell (305) and/or the width (d) of described ferroelectric storage cell (305) so that under the read voltage effect of biasing predefined size corresponding counter electrode ferroelectric storage cell (305) electricdomain described between (3071) and (3073) is completely reversed and and do not reverse bottom ferroelectric thin film layer (303) and between electricdomain, set up domain wall conductive channel (3054).
Alternatively, the width (d) of described ferroelectric storage cell (305) is more than or equal to 2 nanometers and less than or equal to 10 microns.
Alternatively, the length (l) of described ferroelectric storage cell (305) is more than or equal to 2 nanometers and less than or equal to 10 microns.
Alternatively, the thickness (h) of described ferroelectric storage cell (305) is more than or equal to 5nm and less than or equal to 1 micron
Specifically, described ferroelectric nonvolatile memory also includes substrate (301), and described ferroelectric thin film layer (303) is arranged on described substrate (301), simultaneously, substrate (301) and ferroelectric thin film layer (303) can be identical materials, namely use ferrum electricity block materials.
Preferably, described substrate (301) is dielectric base. Consider the compatibility with semiconductor technology, generally choose silicon base.
Alternatively, ferroelectric storage cell (305) the actually same entirety of described ferroelectric thin film layer (303) and surface etch, material is selected from bismuth ferrite BiFeO3, mix bismuth ferrite salt (Bi, the La) FeO of La3, lead zirconate titanate salt (Pb, Zr) TiO3, dawn acid lithium LiTaO3Or niobic acid lithium salts LiNbO3��
Alternatively, described ferroelectric thin film layer (303) thickness is more than or equal to 10 nanometers and less than 100 microns.
Alternatively, the thickness of described read-write electrode layer (307) is more than or equal to 5 nanometers and less than or equal to 100 nanometers.
Alternatively, by controlling the crystal orientation that described ferroelectric thin film layer (303) grows with the ferroelectric storage cell (305) etched, to such an extent as to the electricdomain (3031 of described ferroelectric thin film layer (303), 3033) and electricdomain (3051, the 3053) polarised direction of ferroelectric storage cell (305) be substantially not orthogonal to the plane of described read-write electrode layer (307).
According to another aspect of the present invention, it is provided that the preparation method of more than one described ferroelectric nonvolatile memories, including step:
Substrate (301) is provided;
Substrate (301) is formed ferroelectric thin film (303);
Ferroelectric storage cell (305) is gone out in ferroelectric thin film (303) surface etch; And
Read-write electrode layer (307) in face is formed between described ferroelectric storage cell (305).
Preparation method according to an embodiment of the invention, wherein, described ferroelectric storage cell (305) and read-write electrode layer (307) electron beam process or nano impression or photoetching and dry etching are formed.
Further aspect according to the present invention, the write operation method of more than one described ferroelectric memorys is provided, wherein, the electrode of the adjacent ferroelectric storage cell (305) in described read-write electrode layer (307) to (3071 and 3073) between bias the write signal (V of first directionwrite1), corresponding described ferroelectric storage cell (305) surface electricdomain part is inverted, thus writing the first logical message (" 1 ").
Further, the electrode of the adjacent described ferroelectric storage cell (305) in described read-write electrode layer (307) to (3071 and 3073) between bias the write signal (V of second direction opposite to the first directionwrite2), make corresponding described ferroelectric storage cell (305) surface electricdomain part not be inverted or reverse and return to initial polarization direction, thus writing the second logical message (" 0 ").
Wherein, in described ferroelectric thin film layer (303) with ferroelectric storage cell (305), forming domain wall (3054) between electricdomain (3053a) that ferroelectric storage cell (305) surface is inverted and the electricdomain (3031a) that bottom is not inverted, the read-write electrode of the through described read-write electrode layer (307) of this domain wall (3054) is between (3071 and 3073).
According to another aspect of the invention, the read operation method of more than one described ferroelectric memorys is provided, wherein, the electrode of the adjacent ferroelectric storage cell (305) in described read-write electrode layer (307) to (3071 and 3073) between bias the read signal of first direction (bias field be less than the coercive field of this ferroelectric material, if being equivalent to more than coercive field and perform a write operation), by reading whether the nonreversible electricdomain of size of current between these two parts part electricdomain Yu the described ferroelectric thin film layer in bottom (303) to judge corresponding described surface ferroelectric storage cell (305) sets up domain wall conductive channel, thus reading the logical message of storage.
Read operation method according to an embodiment of the invention, wherein, after removing described read signal, does not destroy the domain wall passage that write operation process is set up, thus the information that writes is not destroyed in read operation process.
Wherein, the read voltage of described read signal should be less than write signal voltage, and the domain wall passage formed between corresponding described surface ferroelectric storage cell (305) and described bottom ferroelectric thin film layer (303) is not destroyed.
The solution have the advantages that, the ferroelectric memory of the embodiment of the present invention utilize the ferroelectric storage cell etched can read-write electrode between electric field action under reverse; Wherein, during write operation, the electricdomain of correspondence ferrum ammeter face memory element is inverted, and after write signal removes, the electricdomain of this reversion can keep; The domain wall conductive channel set up between this surface ferroelectric storage cell and bottom ferroelectric thin film during read operation is obtained in the way of big electric current by read signal, after read signal removes, without influence on domain wall conductive channel, thus can realize non-destructive and read; Therefore, read-write operation is simple, and data retention characteristics is good; It is very beneficial for small size, high-density applications; Simultaneously simple in construction, preparation is simple, cost is low. Can realize, with big current system (100nA-10 �� A), stored electricdomain logical message is carried out non-destructive quickly to read, it is far longer than the pA-nA best level kept in the world at present, is particularly suitable for the application of high density data storage or general-purpose storage.
Accompanying drawing explanation
Fig. 1 is the cross section structure schematic diagram of the non-volatile reading ferroelectric memory according to one embodiment of the invention.
Fig. 2 is the electrode top plan view structure between the ferroelectric storage cell of Nonvolatile ferroelectric memory shown in Fig. 1.
The one writing that Fig. 3 is the ferroelectric memory of embodiment illustrated in fig. 1 is read " 1 " and and writes " 0 " and read " 0 " operating principle schematic diagram.
Fig. 4 is the current-voltage curve under positive and negative cyclical voltage effect. In figure, arrow illustrates voltage cycle direction, and maximum reading domain wall electric current can reach a microampere magnitude. Meanwhile, figure illustrates the structure of 30nm and 150nm surface storage unit, and what measure ferroelectric domain is �� 7V lower piezoelectric imaging at left and right voltage, therefrom it is evident that the on off state of domain wall.
Fig. 5 is the retention performance of the ferroelectric memory of one embodiment of the invention. Switching current read-out under 4V voltage effect changes over. Maximum reading domain wall current on/off ratio is more than 106, read current is stable in time.
Fig. 6 is the fatigue properties of the ferroelectric memory of one embodiment of the invention. Read-out by writing under voltage effect in 1MHz frequency and+8V/-10V cycle, the switching current under 4V voltage is with the change of write cycle time number. Maximum reading domain wall current on/off ratio is more than 106, the read-write cycle is more than 1010��
Fig. 7 is the preparation method process schematic of the ferroelectric memory of further embodiment of this invention.
Fig. 8 is the cross section structure schematic diagram of the non-volatile reading ferroelectric memory of second embodiment of the invention.
The one writing that Fig. 9 is the ferroelectric memory of embodiment illustrated in fig. 8 is read " 1 " and and writes " 0 " and read " 0 " operating principle schematic diagram.
Figure 10 is that further embodiment of this invention produces SEM and the read-write current-voltage curve of the source-drain electrode of nanometer storing unit (in face the first and second read-write electrodes) and gate electrode (i.e. third reading electrode) structure with the LiNbO3 monocrystal material surface of [100] oriented cuts.
Figure 11 be the ferroelectric nano memory element shown in Figure 10 source-drain electrode (in the inner face of face first and second read-write electrode) between electric current and domain reversal coercive field voltage with the change of gate voltage (i.e. third reading electrode voltage) Vg.
Figure 12 is the ferroelectric storage cell top plan view structure of the Nonvolatile ferroelectric memory shown in Fig. 1 and Fig. 8.
Detailed description of the invention
Further describing the present invention below in conjunction with drawings and Examples, wherein, same or analogous key element is adopted and is indicated by the same numeral.
Be described below be the present invention multiple possible embodiment in a part, it is desirable to provide the basic understanding to the present invention, it is no intended to confirm the crucial of the present invention or conclusive key element or limit scope of the claimed.
In the accompanying drawings, for the sake of clarity, exaggerate the thickness in layer and region, it is illustrated that in each several part between dimension scale relation do not reflect reality dimension scale relation.
In the examples below, clear in order to what describe, exemplarily give electricdomain direction or polarised direction it should be appreciated that arrive, the electricdomain direction of ferroelectric memory or polarised direction are not limited to the direction shown in embodiment as shown in the figure.
Fig. 1 show the cross section structure schematic diagram of the Nonvolatile ferroelectric memory according to one embodiment of the invention; Fig. 2 show the top plan view structure of the read-write electrode of the Nonvolatile ferroelectric memory shown in Fig. 1. As shown in Figure 1, illustrated therein is the partial cross section structure of ferroelectric memory 30, it mainly includes substrate 301, ferroelectric thin film layer 303, ferroelectric storage cell 305 and read-write electrode layer 307, wherein, read-write electrode layer 307 is arranged on ferroelectric storage cell 305 both sides and is in contact with it. The multiple possible top plan view structure of the ferroelectric storage cell 305 of Fig. 1 ferroelectric memory. In this embodiment, ferroelectric storage cell structure can be rectangle, it is also possible to be other various structures such as zigzag. The ferroelectric memory 30 of the embodiment of the present invention is different from conventional iron electrical storage, it need not be arranged on the lower electrode layer of read-write electrode layer 307 opposite side, read-write electrode layer 307 both can be used to realize read operation in this ferroelectric memory 30, may also be used for realizing write operation, because of referred to herein as read-write electrode layer 307.
Continue as depicted in figs. 1 and 2, read-write electrode layer 307 is arranged on ferroelectric storage cell 305 both sides, in this example, read-write electrode layer 307 is divided into read-write electrode part 3071 and read-write electrode part 3073 by ferroelectric storage cell 305, read-write electrode part 3071 and read-write electrode part 3073 composition read-write electrode pair, in this embodiment, this read-write electrode read-write electrode layer 307 to mainly constituting this embodiment.
Continue as it is shown in figure 1, substrate 301 can be various base materials conventional in ferroelectric memory, for instance it can be Si, SrTiO3Or LiNbO3. Normally, the material of substrate 301 selects mainly to be together decided on by substrate 301 and ferroelectric thin film layer 303. In this embodiment, substrate 301 can be Si substrate, and it is prone to compatible with semiconductor CMOS process, contributes to large-scale production. It addition, the lattice paprmeter according to ferroelectric thin film layer 303 requires to select SrTiO3Or LiNbO3Deng base material, in order to obtain the epitaxial thin-film layer of excellent performance. Additionally, substrate 301 and ferroelectric thin film layer 303 can be commaterial, i.e. ferroelectric material, including ferrum electricity block ceramic and monocrystalline.
Ferroelectric thin film layer 303 is formed on substrate 301, it is possible to be arbitrary ferroelectric material with suitable domain structure, and it specifically can be selected from following material: bismuth ferrite BiFeO3, mix bismuth ferrite salt (Bi, the La) FeO of La3, lead zirconate titanate salt (Pb, Zr) TiO3, LiTaO3Or niobic acid lithium salts LiNbO3;It is to be understood, however, that arrive, the concrete ferroelectric material type of ferroelectric thin film layer 303 is not restriction, and those skilled in the art can select any ferroelectric material type. The preparation method of ferroelectric thin film layer 305 neither be restrictive, for instance, it is possible to formed by the preparation of the thin-film deposition method such as collosol and gel, sputtering, CVD, PLD.
Ferroelectric storage cell 305 is to be formed after ferroelectric thin film layer 303 in substrate 301, by semiconductor technology photoetching, electron-beam direct writing or the technology such as nano impression or photoetching realize the Graphic transitions of storage organization, then by lithographic technique, form memory cell structure including dry etching and wet etching at film surface. Certainly, in other embodiments, ferroelectric storage cell can form various memory cell structure. The scope of the width d of ferroelectric storage cell 305 can more than or equal to 2 nanometers and less than or equal to 10 microns, it can be such as 10 nanometers, 100 nanometers, 1 micron etc., spacing d is more little, more be conducive to improving the memory density of ferroelectric memory, and be more conducive to reducing read voltage, and it is more little to read power consumption, therefore, ferroelectric storage cell 305 can be the unit of various micron/nano size. Ferroelectric storage cell 305 be shaped as rectangle, it is also possible to for other shapes such as zigzag. The thickness (h) of ferroelectric storage cell (305) is more than or equal to 10nm and less than or equal to 1 micron. Read-write electrode part 3071 and the read-write electrode part 3073 length (namely length dimension of ferroelectric storage cell) on direction, down suction can more than or equal to 2 nanometers and less than or equal to 10 microns, for instance 100 nanometers.
Read and write electrode part 3071 in face and read-write electrode part 3073 can be through continuous print metal film layer in this embodiment and formed by etching part between ferroelectric storage cell, in this article, read-write electrode part 3071 and read-write electrode part 3073 composition read-write electrode pair, herein, " reading " reflects that they at least have the function of read operation, " writes " herein and reflects that they at least have the function of write operation.
Read-write electrode part 3071 and/or read-write electrode part 3073 its can be the conductive material of a kind of low-resistivity, for instance, it can be selected from Pt, SrRuO3��LaNiO3In one or more combination. The thickness of read-write electrode part 3071 and/or read-write electrode part 3073 can be 5-100nm, for instance, 30nm. Read-write electrode part 3071 and/or read-write electrode part 3073 can be, but not limited to be formed by the preparation of the thin-film deposition method such as sputtering, evaporation, CVD, PLD.
Continue as shown in Figure 1, in the present invention, ferroelectric thin film layer 303 and ferroelectric storage cell 305 are required to meet the condition that its ferroelectric domain is important in face, namely there is component in face (projection in the spontaneous polarization of ferrum electricity electricdomain direction on face), ferroelectric thin film layer 303 can form the electricdomain 3031 or 3033 of both direction as shown in Figure 1, ferroelectric storage cell 305 can form the electricdomain 3051 or 3053 of both direction as shown in Figure 1, the polarised direction of electricdomain 3031 and 3051 is completely contrary with the polarised direction of electricdomain 3033 and 3053, after biasing is more than coercive voltage, electricdomain can along direction of an electric field orientation, therefore, during at bias field direction and former electricdomain voltage in opposite direction and more than coercive voltage, electricdomain 3031 and 3051 or 3033 and 3053 can be reversed. in this embodiment, normal (being shown perpendicular to the dotted line of the read-write electrode layer 307) direction of the substantially not parallel read-write electrode layer 307 of the polarised direction of the electricdomain of ferroelectric thin film layer 303 and ferroelectric storage cell 305, or substantially it is not orthogonal to read-write electrode layer 307.Specifically, it is possible to realize by controlling the crystal orientation of ferroelectric thin film layer 303 growth, illustratively, it is possible at the SrTiO that crystal face is (001)3The BiFeO of substrate 301 Epitaxial growth 100 nanometer thickness-3Ferroelectric thin film layer 303, wherein BiFeO-3The polarised direction of the electricdomain of ferroelectric thin film layer 303 is along<111>direction.
Fig. 3 show the one writing of the ferroelectric memory of embodiment illustrated in fig. 1 and reads " 1 " and and write " 0 " and read " 0 " operating principle schematic diagram.
In this embodiment, illustrate with electricdomain 3051 place polarised direction storage logical message " 0 " of ferroelectric storage cell 305 for signal. As shown in Fig. 3 (a), in one writing operating process, biasing write signal V between the read-write electrode part 3073 and read-write electrode part 3071 of read-write electrode layer 307write1, namely constitute read-write electrode to upper offset write signal V in read-write electrode part 3073 and read-write electrode part 3071write1, the direction of write signal biases negative sense for read-write electrode part 3073, read-write electrode part 3071 biases forward, thus they form the substantially electric field E1 in direction as shown in Fig. 3 (a). The electricdomain of ferroelectric storage cell 305 can be produced impact by electric field E1, electric field E1 is when with the electric field component in the polarised direction opposite direction of the electricdomain of ferroelectric storage cell 305 more than the coercive voltage making this electricdomain that upset to occur, and the polarised direction that the electricdomain generation reversion of this unit forms the electricdomain 3053 shown in electricdomain 3053a(electricdomain 3053a and Fig. 1 is essentially identical).
The electricdomain of ferroelectric thin film layer 303 is not substantially affected by electric field E1 impact (or it under-effected is made the raw reversion of its electricdomain by electric field E1), and electricdomain is not reversed, and is correspondingly formed the electricdomain 3031 as shown in Fig. 3 (a), namely electricdomain 3031 is the same reverses. The polarised direction of electricdomain 3053a is basic completely contrary with the polarised direction of electricdomain 3031, therefore, boundary's wall between electricdomain 3031 and electricdomain 3053a or interface, thus charged domain wall or domain boundary 3054 can be produced, but the conductive channel of domain wall 3054 correspondence likely can turn off close to the local of substrate, so that conductive channel turns off and affects the read current in readout. It is therefore preferred that the thickness of ferroelectric thin film layer 303 should much larger than the width (d) of ferroelectric storage cell, substrate 301 can be the dielectric base that various insulant is formed. In embodiments of the present invention, form domain wall 3054 after one writing operation and be through ferroelectric storage cell 305, but can not the upper and lower surface of through ferroelectric thin film layer 303, thus turning off domain wall passage and affecting the read current of readout; The diagram shape that the concrete shape of domain wall 3054 is not also limited by the embodiment of the present invention limits, for instance, two domain walls 3054 can be formed generally cylindrical.
Wherein, owing to electricdomain 3053a utilizes electric field E1 realizing upset with the electric field component in the polarised direction opposite direction of electricdomain 3031, therefore, when the width (d) of ferroelectric storage cell, coercive voltage are known, it is possible to calculate the most small letter voltage V forming electricdomain 3053awrite1��
Fig. 3 (b) show reading " 1 " operating process and the operating principle schematic diagram of the ferroelectric memory of embodiment illustrated in fig. 1.
In this embodiment, read operation principle is totally different from the read operation principle of traditional ferroelectric memory, and wherein, when read operation, substrate 301 does not need offset signal, and it can be unsettled, read signal VreadBe be biased in read-write electrode between, below be biased in read-write electrode part 3071, read-write electrode part 3073 illustrate for example.Read voltage should be less than writing voltage, to prevent write operation by mistake in reading process.
As shown in Figure 3 (b), in reading " 1 " operating process, biasing read signal V between read-write electrode part 3071, read-write electrode part 3073readRead-write electrode part 3073 biases negative sense, read-write electrode part 3071 biases forward, thus reading and writing the electric field E3(E3 forming direction as shown in the figure between electrode part 3073 and read-write electrode part 3071 less than coercive field Ec), owing to electric field E3 is absent from the electric field component that makes electricdomain 3053a reverse, electricdomain 3053a remains unchanged completely, thus the domain wall conductive channel formed is non-switched off, now read-write electrode part 3073 produces read current, read current I with read-write electrode part 3071readFor On state (i.e. ON state), expression reads logical message " 1 ".
It is to be appreciated that read signal VreadRead voltage be necessarily less than write signal Vwrite1Write voltage, so, it is to avoid when read operation produce " mistake " write operation.
As read signal VreadAfter removing, owing in above read operation process, the electricdomain of ferroelectric storage cell does not change, therefore, read signal VreadAfter removing, the electricdomain of ferroelectric storage cell does not also change. Domain wall passage stable existence, until when writing a write operation.
Further, at read current signal IreadAfter, the read voltage signal V between read-write electrode part 3073 and read-write electrode part 3071readRemoving, electric field E3 disappears, and now, the domain wall passage between electricdomain 3053a and electricdomain 3031 is not destroyed. Therefore, ferroelectric memory 30 stored logical message " 1 " before a read operation does not change after read operation, it is achieved that non-destructive reads.
As shown in Figure 3 (c), in writing " 0 " operating process, constitute read-write electrode to upper offset write signal V in read-write electrode part 3073 and read-write electrode part 3071write2, write signal Vwrite2With write signal Vwrite1In opposite direction, wherein read-write electrode part 3073 biases forward, read-write electrode part 3071 biases negative sense, thus they form the electric field E2 in directions substantially as shown in Figure 3 (c). Existence due to ferroelectric storage cell 305, electricdomain corresponding to ferroelectric storage cell 305 can be produced impact by electric field E2, namely such as electricdomain 3053a shown in Fig. 3 (a) can be produced impact, electric field E2 is when with the electric field component in the polarised direction opposite direction of electricdomain 3053a more than the coercive voltage making this electricdomain that upset to occur, this electricdomain 3053a reverses, it is returned to original or initial polarised direction, unified formation electricdomain 3031. Now, logical message is written as " 0 ".
Similarly, based on ferroelectric storage cell 305 at write signal Vwrite2Electric-field intensity distribution under effect is it can be seen that Vwrite2To write voltage more big, make electricdomain 3053a reply the degree of depth of reversion more deep. Therefore, it can the voltage swing by controlling write signal, make electricdomain 3053a full recovery be reversed to electricdomain 3031; Example as shown in Figure 3 (c), has a certain size the write signal V writing voltagewrite2Under effect, the electricdomain 3053a of corresponding ferroelectric storage cell is rotarily formed electricdomain 3051 completely, and domain wall 3054 disappears.
Wherein, write signal Vwrite1And Vwrite2Concrete signal form is not restrictive, for instance it can be the voltage pulse signal etc. of certain frequency.
Fig. 3 (d) show reading " 0 " operating process and the operating principle schematic diagram of the ferroelectric memory of embodiment illustrated in fig. 1.
As shown in Fig. 3 (d), in reading " 0 " operating process, between read electrode part 3071, read electrode part 3073, bias read signal VreadForming the electric field E3 in direction as shown in the figure, owing to electric field E3 is less than the coercive field Ec of ferroelectric storage cell, the electricdomain 3051 of ferroelectric storage cell is reversed, thus not forming domain wall conductive channel, now read-write electrode part 3073 does not produce read current (I with read-write electrode part 3071read=0), read current IreadFor Off state (i.e. OFF state), expression reads logical message " 0 ".
Therefore, above read operation process, it is totally different from the electric charge reading method of the ferroelectric memory of traditional capacitance structure, embodiments herein achieves electric current and reads the mode of logical signal.
It will be appreciated that, although being above storing what logical message " 0 " illustrated for example with the electricdomain 3051 of ferroelectric storage cell 305 and the electricdomain 3031 place polarised direction of ferroelectric thin film layer, it will be understood by the skilled person that, the electricdomain 3051/3053 of ferroelectric storage cell and the electricdomain 3031/3033 place polarised direction of ferroelectric thin film layer can also represent storage logical message " 1 "/" 0 ", voltage signal direction in corresponding write operation and read operation changes with can also carrying out the suitability, to realize similar read-write process as shown in Figure 3.
Fig. 4 show the current-voltage curve of the ferroelectric memory of one embodiment of the invention, is specially the LiNbO of [100] oriented cuts3Monocrystal material surface produces the Nano-structure of different in width, and after the Pt metal electrode of wide 100nm is prepared at two ends, left and right, we can be measured that the current-voltage curve under positive and negative cyclical voltage effect. In figure, arrow illustrates voltage cycle direction, and maximum reading domain wall electric current can reach a microampere magnitude. Figure illustrates the structure of 30nm and 150nm surface storage unit, and what measure ferroelectric domain is �� 7V lower piezoelectric imaging at left and right voltage, therefrom it is evident that the on off state of domain wall.
Fig. 5 show the ferroelectric memory retention performance curve of one embodiment of the invention, is specially the LiNbO of [100] oriented cuts3Monocrystal material surface manufactures the Nano-structure of 150nm width, and after the Pt metal electrode of wide 100nm is prepared at two ends, left and right, we can be measured that switching current read-out under 4V voltage effect changes over. Maximum reading domain wall current on/off ratio is more than 106, read current is stable in time, and namely information keeps functional.
Fig. 6 show the ferroelectric memory fatigue properties curve of one embodiment of the invention. It is specially the LiNbO of [100] oriented cuts3Monocrystal material surface manufactures the Nano-structure of 150nm width, after the Pt metal electrode of wide 100nm is prepared at two ends, left and right, we can be measured that and write under voltage effect read-out switching current under 4V voltage with the change of write cycle time number in 1MHz frequency and+8V/-10V cycle. Maximum reading domain wall current on/off ratio is more than 106, the read-write cycle is more than 1010��
Fig. 7 show the preparation method process schematic of the ferroelectric memory of one embodiment of the invention. In conjunction with shown in Fig. 1 and Fig. 7, first, step S810, it is provided that substrate 310 as shown in Figure 1, the material of substrate 310 selects mainly to be together decided on by ferroelectric thin film layer 303, it is possible to identical with ferroelectric material, is ferroelectric ceramics block or monocrystalline. In this embodiment, substrate 301 can be Si substrate, and it is prone to compatible with semiconductor CMOS process.
Further, step S820, form ferroelectric thin film layer 303. In this embodiment, ferroelectric thin film layer 303 can be, but not limited to be selected from following material: bismuth ferrite BiFeO3, mix bismuth ferrite salt (Bi, the La) FeO of La3, lead zirconate titanate salt (Pb, Zr) TiO3, LiTaO3Or niobic acid lithium salts LiNbO3; Ferroelectric thin film layer 303 can be closed the preparation of the thin-film deposition method such as technology, sputtering, CVD, PLD by ionic bond and be formed.
In other embodiments, it is also possible to formed before ferroelectric thin film layer 303 in substrate, substrate is initially formed one layer of dielectric layer.
Further, step S830, etch ferroelectric storage cell 305 in face.In this embodiment, ferroelectric storage cell 305 can pass through semiconductor lithography, the technology such as electron-beam direct writing and nano impression on Graphic transitions to ferroelectric thin film 303, will then pass through dry etching (reactive ion etching (RIE) or inductively coupled plasma etching (ICP)) or wet etching form ferroelectric storage cell. This memory element can be, but not limited to be obtained by above method.
Further, step S840, reads and writes electrode pair in ferroelectric thin film layer 303 and ferroelectric storage cell 305 in formation face. In this embodiment, read-write electrode is constituted by read-write electrode part 3071 and read-write electrode part 3073, is separated by ferroelectric storage cell 305 between read-write electrode part 3071 and read-write electrode part 3073; Read-write electrode is to being selected from Pt, SrRuO3��LaNiO3In one or more combination; The thickness of read-write electrode part 3071 and/or read-write electrode part 3073 can be 5-100nm, for instance, 30nm; Read-write electrode part 3071 and/or read-write electrode part 3073 can be, but not limited to be formed by the preparation of the thin-film deposition method such as sputtering, CVD, PLD. 307 structures be can be, but not limited to be obtained by electron beam process, nano impression or other photoetching methods by this electrode.
So, basically forming the ferroelectric memory of embodiment as shown in Figure 1, in this embodiment, read-write electrode part 3071 and read-write electrode part 3073 are simultaneously used for being formed the upper electrode layer 307 of this memorizer.
Fig. 8 show the cross section structure schematic diagram of the non-destructive read-out ferroelectric memorizer according to present invention second embodiment of the invention. It mainly includes substrate 401, ferroelectric thin film layer 403, ferroelectric storage cell 405 and electrode layer 407, electrode layer 407 is defined as read-write electrode layer 407, wherein, read-write electrode layer 407 is arranged on ferroelectric thin film layer 403 and ferroelectric storage cell and is in contact with it, such that it is able to ferroelectric storage cell 405 upper offset electric field signal. The ferroelectric memory 40 of the embodiment of the present invention is different from conventional iron electrical storage, it need not be arranged on the lower electrode layer of read-write electrode layer 407 opposite side, read-write electrode layer 407 both can be used to realize read operation in this ferroelectric memory 40, may also be used for realizing write operation, electrode layer 407 is therefore also referred to as read-write electrode layer 407. Namely read-write electrode layer 407 read and write electrode part 4071, read-write electrode part 4073 and read electrode 4075, read-write electrode part 4071 and read-write electrode part 4073 and is formed writing electrode pair, reads and writes electrode part 4071 or 4073 and read electrode 4075 and constitutes read electrode layer. Read in this embodiment, this read-write electrode read-write electrode layer 407 to mainly constituting this embodiment. Herein, " reading " reflects that they at least have the function of read operation, " writes " herein and reflects that they at least have the function of write operation.
Continuing as shown in Figure 8, substrate 401 can be various base materials conventional in ferroelectric memory, for instance it can be Si, SrTiO3��LiTaO3Or LiNbO3. Normally, the material of substrate 401 selects mainly to be together decided on by substrate 401 and ferroelectric thin film layer 403. In this embodiment, substrate 401 can be Si substrate, and it is prone to compatible with semiconductor CMOS process, contributes to large-scale production. It addition, the lattice paprmeter according to ferroelectric thin film layer 403 requires to select SrTiO3��LiTaO3Or LiNbO3Deng base material, in order to obtain the epitaxial thin-film layer of excellent performance. Additionally, substrate 401 and ferroelectric thin film layer 403 can be commaterial, i.e. ferroelectric material, including ferrum electricity block ceramic and monocrystalline.
Ferroelectric thin film layer 403 is formed on substrate 401, it is possible to be arbitrary ferroelectric material with suitable domain structure, and it specifically can be selected from following material: bismuth ferrite BiFeO3, mix bismuth ferrite salt (Bi, the La) FeO of La3, lead zirconate titanate salt (Pb, Zr) TiO3��LiTaO3Or niobic acid lithium salts LiNbO3; It is to be understood, however, that arrive, the concrete ferroelectric material type of ferroelectric thin film layer 403 is not restriction, and those skilled in the art can select any ferroelectric material type. The preparation method of ferroelectric thin film layer 405 neither be restrictive, for instance, it is possible to formed by the preparation of the thin-film deposition method such as ionic bond conjunction, collosol and gel, sputtering, CVD, PLD.
Ferroelectric storage cell 405 is to be formed after ferroelectric thin film layer 403 in substrate 401, by semiconductor technology photoetching, the technology such as electron-beam direct writing or nano impression realizes the Graphic transitions of storage organization, then by lithographic technique, forms memory cell structure including dry etching and wet etching. Certainly, in other embodiments, ferroelectric storage cell can form various memory cell structure. The scope of the width d of ferroelectric storage cell 405 can more than or equal to 2 nanometers and less than or equal to 10 microns, it can be such as 10 nanometers, 100 nanometers, 1 micron etc., spacing d is more little, more be conducive to improving the memory density of ferroelectric memory, and be more conducive to reducing read voltage, and it is more little to read power consumption, therefore, ferroelectric storage cell 405 can be the unit of various micron/nano size. The shape of ferroelectric storage cell 405 can be rectangle, can also be other shapes such as zigzag, the thickness (h) of ferroelectric storage cell (405) is more than or equal to 10nm and less than or equal to 1 micron, read-write electrode part 4071, read-write electrode part 4073 and the read electrode 4075 length (namely length dimension of ferroelectric storage cell) on vertical ferroelectric memory element direction can more than or equal to 2 nanometers and less than or equal to 10 microns, for instance 100 nanometers.
Read-write electrode part 4071, read-write electrode part 4073 and read electrode 4075 can be through continuous print metal film layer in this embodiment and formed by etching part between ferroelectric storage cell, in this article, read-write electrode part 3071 and read-write electrode part 3073 form writing electrode pair, read-write electrode part 4071 or 4073 and read electrode 4075 constitute read electrode layer. Herein, " reading " reflects that they at least have the function of read operation, " writes " herein and reflects that they at least have the function of write operation.
Read-write electrode part 4071, read-write electrode part 4073 and read electrode 4075 its can be the conductive material of a kind of low-resistivity, for instance, it can be selected from Pt, SrRuO3��LaNiO3In one or more combination. The thickness of read-write electrode part 4071 and/or read-write electrode part 4073 can be 5-100nm, for instance, 30nm. Read-write electrode part 4071 and/or read-write electrode part 4073 can be, but not limited to be formed by the preparation of the thin-film deposition method such as sputtering, evaporation, CVD, PLD.
Continue as shown in Figure 8, in the present invention, ferroelectric thin film layer 403 and ferroelectric storage cell 405 are required to meet the condition that its ferroelectric domain is important in face, namely there is component in face (projection in the spontaneous polarization of ferroelectric domain direction on face), ferroelectric thin film layer 403 can form the electricdomain 4031 or 4033 of both direction as shown in Figure 1, ferroelectric storage cell 305 can form the electricdomain 4051 or 4053 of both direction as shown in Figure 1, the polarised direction of electricdomain 4031 and 4051 is completely contrary with the polarised direction of electricdomain 4033 and 4053, after biasing is more than coercive voltage, electricdomain can along direction of an electric field orientation, therefore, during at bias field direction and former electricdomain voltage in opposite direction and more than coercive voltage, electricdomain 4031 and 4051 or 4033 and 4053 can be reversed.In this embodiment, normal (being shown perpendicular to the dotted line of the read-write electrode layer 307) direction of the substantially not parallel read-write electrode layer 407 of the polarised direction of the electricdomain of ferroelectric thin film layer 403 and ferroelectric storage cell 405, or substantially it is not orthogonal to read-write electrode layer 407. Specifically, it is possible to realize by controlling the crystal orientation of ferroelectric thin film layer 303 growth, illustratively, it is possible at the SrTiO that crystal face is (001)3The BiFeO of substrate 301 Epitaxial growth 100 nanometer thickness-3Ferroelectric thin film layer 303, wherein BiFeO-3The polarised direction of the electricdomain of ferroelectric thin film layer 303 is along<111>direction.
Fig. 9 show the one writing of the ferroelectric memory of embodiment illustrated in fig. 8 and reads " 1 " and and write " 0 " and read " 0 ".
In this embodiment, illustrate with electricdomain 4051 place polarised direction storage logical message " 0 " of ferroelectric storage cell 305 for signal. As shown in Fig. 9 (a), in one writing operating process, biasing write signal V between the read-write electrode part 4073 and read-write electrode part 4071 of read-write electrode layer 307write1, namely constitute read-write electrode to upper offset write signal V in read-write electrode part 4073 and read-write electrode part 4071write1, the direction of write signal biases negative sense for read-write electrode part 4073, read-write electrode part 4071 biases forward, thus they form the substantially electric field E1 in direction as shown in Fig. 3 (a). The electricdomain of ferroelectric storage cell 405 can be produced impact by electric field E1, electric field E1 is when with the electric field component in the polarised direction opposite direction of the electricdomain of ferroelectric storage cell 405 more than the coercive voltage making this electricdomain that upset to occur, and the polarised direction that the electricdomain generation reversion of this unit forms the electricdomain 4053 shown in electricdomain 4053a(electricdomain 4053a and Fig. 1 is essentially identical).
The electricdomain of ferroelectric thin film layer 403 is not substantially affected by electric field E1 impact (or it under-effected is made the raw reversion of its electricdomain by electric field E1), and electricdomain is not reversed, namely electricdomain 4031 is the same reverses. The polarised direction of electricdomain 4053a is basic completely contrary with the polarised direction of electricdomain 4031, therefore, boundary's wall between electricdomain 4031 and electricdomain 4053a or interface, thus charged domain wall or domain boundary 4054 can be produced, but the conductive channel of domain wall 4054 correspondence likely can turn off close to the local of substrate, so that conductive channel turns off and affects the read current in readout. It is therefore preferred that the thickness of ferroelectric thin film layer 403 should much larger than the width (d) of ferroelectric storage cell, substrate 401 can be the dielectric base that various insulant is formed. In embodiments of the present invention, forming domain wall 3054 and be through ferroelectric storage cell 305 after one writing operation, the diagram shape that the concrete shape of domain wall 3054 is not also limited by the embodiment of the present invention limits, for instance, two domain walls 3054 can be formed generally cylindrical.
Wherein, owing to electricdomain 4053a utilizes electric field E1 realizing upset with the electric field component in the polarised direction opposite direction of electricdomain 4031, therefore, when the width (d) of ferroelectric storage cell, coercive voltage are known, it is possible to calculate the most small letter voltage V forming electricdomain 4053awrite1��
Fig. 9 (b) show reading " 1 " operating process and the operating principle schematic diagram of the ferroelectric memory of embodiment illustrated in fig. 1.
In this embodiment, read operation principle is totally different from the read operation principle of traditional ferroelectric memory, and wherein, when read operation, substrate 401 does not need offset signal, and it can be unsettled, read signal VreadBe be biased in read-write electrode 407 between, below be biased in read-write electrode part 4071 or read-write electrode part 3073 and read electrode part 4075 illustrate for example.
As shown in Figure 9 (b), in reading " 1 " operating process, read and write biasing read signal V between electrode part 4071 or read-write electrode part 4073 and read electrode part 4075read, read electrode part 4075 biases negative sense, read-write electrode part 4071 biases forward or read electrode part 4073 biases negative sense, read-write electrode part 4075 biases forward. thus reading and writing the electric field E4(E4 forming direction as shown in the figure between electrode part 4071 and read electrode part 4075 or read-write electrode part 4073 and read electrode part 4075 more than coercive field Ec), owing to electric field E4 is absent from the electric field component that makes electricdomain 4053a reverse, electricdomain 3053a remains unchanged completely, thus the domain wall conductive channel not formed between read-write electrode part 4071 and read electrode part 4075 or read-write electrode part 4073 and read electrode part 4075, now do not produce read current between read-write electrode part 4071 and read electrode part 4075 or read-write electrode part 4073 and read electrode part 4075, read current Iread=0, now, the domain wall conductive channel between ferroelectric storage cell 405 and ferroelectric thin film layer 403 is On state (i.e. ON state), and corresponding ferroelectric storage cell represents reading logical message " 1 ". It will be understood by the skilled person that the read voltage signal using any one direction, all can realize the reading " 1 " of the ferroelectric memory to the present invention and read " 0 " operating process.
It is to be appreciated that read signal VreadIt is necessarily less than write signal V unlike read voltage shown in Fig. 3 (b)write1Write voltage, this read-out voltage is not write voltage influence completely, thus without producing by mistake write operation.
As read signal VreadAfter removing, between read-write electrode part 4071 and read electrode part 4075 or read-write electrode part 4073 and read electrode part 4075, the electricdomain of ferroelectric storage cell is reversed, therefore, in read operation process, the electricdomain of ferroelectric storage cell does not change, read signal VreadAfter removing, the electricdomain of ferroelectric storage cell does not also change. Ferroelectric memory 30 stored logical message " 1 " before a read operation does not change after read operation, it is achieved that non-destructive reads.
As shown in Figure 9 (c), in writing " 0 " operating process, constitute read-write electrode to upper offset write signal V in read-write electrode part 4073 and read-write electrode part 4071write2, write signal Vwrite2With write signal Vwrite1In opposite direction, wherein read-write electrode part 4073 biases forward, read-write electrode part 4071 biases negative sense, thus they form the electric field E2 in directions substantially as shown in Figure 9 (c). Existence due to ferroelectric storage cell 405, electricdomain corresponding to ferroelectric storage cell 405 will not be produced impact by electric field E2, namely such as electricdomain 4053a shown in Fig. 9 (a) can be produced impact, electric field E2 is when with the electric field component in the polarised direction opposite direction of electricdomain 4053a more than the coercive voltage making this electricdomain that upset to occur, this electricdomain 4053a reverses, it is returned to original or initial polarised direction, unified formation electricdomain 4051. Now, logical message is written as " 0 ".
Similarly, based on ferroelectric storage cell 405 at write signal Vwrite2Electric-field intensity distribution under effect is it can be seen that Vwrite2To write voltage more big, make electricdomain 4053a reply the degree of depth of reversion more deep. Therefore, it can the voltage swing by controlling write signal, make electricdomain 4053a full recovery be reversed to electricdomain 4031; Example as shown in Figure 9 (c), has a certain size the write signal V writing voltagewrite2Under effect, the electricdomain 4053a of corresponding ferroelectric storage cell is rotarily formed electricdomain 4051 completely, and domain wall 4054 disappears.
Fig. 9 (d) show reading " 0 " operating process and the operating principle schematic diagram of the ferroelectric memory of embodiment illustrated in fig. 1.
As shown in Fig. 9 (d), in reading " 0 " operating process, read and write biasing read signal V between electrode part 4071 or read-write electrode part 4073 and read electrode part 4075read, read electrode part 4075 biases negative sense, read-write electrode part 4071 biases forward or read electrode part 4073 biases negative sense, read-write electrode part 4075 biases forward. Read signal V is biased between read electrode part 4071, read electrode part 4073read, forming the electric field E4 in direction as shown in the figure, the electricdomain 4051 of ferroelectric storage cell is reversed, and forms electricdomain 4053b, thus forming domain wall conductive channel, now read-write electrode part 4071 or read-write electrode part 4073 and read electrode part 4075 produce read current Iread, now, the domain wall conductive channel between ferroelectric storage cell 405 and ferroelectric thin film layer 403 is Off state (i.e. OFF state), represents and reads logical message " 0 ".
Wherein, write signal Vwrite1And Vwrite2With VreadConcrete signal form is not restrictive, for instance it can be the voltage pulse signal etc. of certain frequency.
Therefore, above read operation process, it is totally different from the electric charge reading method of the ferroelectric memory of traditional capacitance structure, embodiments herein achieves electric current and reads the mode of logical signal. Figure 10 and Figure 11 is with LiNbO3Single-crystal iron electric material is nanodevice structural and the concrete data of electrical measurement of the another embodiment of the present invention made by example.
Figure 10 show the LiNbO3 monocrystal material surface of [100] oriented cuts and produces the source-drain electrode (in face the first and second read-write electrodes) of nanometer storing unit and the stereoscan photograph of gate electrode (i.e. third reading electrode) structure. When gate electrode ground connection, between source and drain, domain reversal stupid voltage of spoiling can be reduced to 5.8V from 13V, is at this moment that +/-10V voltage can realize positive and negative electricdomain write between source and drain, is namely stored in logical one/" 0 " operation. Drawing of information can be passed through to read at the endogenous gate voltage of 0-5.8V. Particularly as follows: after+10V source-drain voltage writes logical one information, be in ON state at the endogenous gate voltage read current of 0-5.8V; Otherwise, after-10V source-drain voltage writes logical zero information, the endogenous gate voltage read current of 0-5.8V is in OFF state. Figure 11 be the ferroelectric nano memory element shown in Figure 10 source-drain electrode (in face left and right electrode) between electric current and domain reversal coercive voltage with the change of gate voltage Vg.
Figure 12 show the ferroelectric storage cell top plan view structural representation of ferroelectric memory, and Figure 12 (a) is general memory cell structural representation, but is not limited to rectangle, it is possible to for other shapes multiple such as circular, oval. Figure 12 (b) and (c) are another ferroelectric storage cell structural representation, and this structure can improve the read-write electrode write operation voltage to 307 or 407, thus avoiding missing write information in reading information process; Figure 12 (d), Figure 12 (e) and Figure 12 (f) memory cell structure can realize 4,8,2nThe multidigit read-write storage operations such as position.
Therefore, the FRAM process of the ferroelectric capacitor structure that the ferroelectric memory of the embodiment of the present invention is relatively conventional, it is not necessary to form lower electrode layer, structure is very simple, and preparation process is very simple, and cost is low.
In the above description, use directional terminology (such as " on ", D score etc.) and the parts of various embodiments that describe of similar terms represent the direction shown in accompanying drawing or the direction that can be readily appreciated by one skilled in the art. These directional terminology are used for relative description and clarification, rather than the orientation of any embodiment to be limited to concrete direction or orientation.
Example above primarily illustrates the ferroelectric memory of the present invention and operational approach thereof and preparation method, especially describes read operation method and principle.Although only some of them embodiments of the present invention being described, but those of ordinary skill in the art it is to be appreciated that the present invention can without departing from its spirit with scope in many other form implement. Therefore, the example shown and embodiment are considered illustrative and not restrictive, and when the of the present invention spirit and scope defined without departing from such as appended claims, the present invention is likely to contain various amendments and replacement.

Claims (20)

1. a ferroelectric nonvolatile memory, it is characterised in that including:
The cuboid ferroelectric storage cell (305) that ferroelectric thin film layer (303) and film surface etch, bottom ferroelectric thin film layer, (303) and surface are etched out ferroelectric storage cell (305) actually same entirety;
And it is arranged on left and right read-write electrode layer (307) on ferroelectric storage cell (305) both sides, described surface, the ferroelectric storage cell (305) being etched out between described read-write electrode layer (307) is divided into two parts, is electrode to (3071) and (3073);
The polarised direction of the electricdomain (3031 or 3033) of described ferroelectric thin film layer (303) and the electricdomain (3051 or 3053) of ferroelectric storage cell (305) is substantially not parallel to the normal direction of described read-write electrode layer (307) place plane;
Wherein, when reading and writing the write signal biasing first direction between two parts of the adjacent described etching ferroelectric storage cell (305) in electrode layer (307) in described, the electric field formed between (3071) and (3073) is reversed completely by the electricdomain of corresponding described surface etch ferroelectric storage cell (305) by electrode, and and do not reverse bottom ferroelectric thin film layer (303) and between electricdomain, set up domain wall conductive channel (3054).
2. ferroelectric nonvolatile memory as claimed in claim 1, it is characterized in that, when biasing write signal (this signal voltage is more than or equal to the coercive field voltage of ferroelectric storage cell) of second direction opposite to the first direction between two parts of the adjacent ferroelectric storage cell (305) in electrode layer (307) are read and write in described left and right, the domain reversal that ferroelectric storage cell (305) is completely reversed is made to return to initial polarization direction.
3. Nonvolatile ferroelectric memory as claimed in claim 2, it is characterized in that, in described read-write electrode layer, at least two part of (307) includes the first read-write electrode part (3071) and the second read-write electrode part (3073), described first read-write electrode part and the second read-write electrode part composition read-write electrode pair, described write signal or read signal are biased in described read-write electrode to upper.
4. non-destructive read-out ferroelectric memorizer as claimed in claim 3, it is characterised in that except read-write electrode pair, also include third reading electrode, described third reading electrode is arranged between the first read-write electrode and the second read-write electrode;
Wherein, described third reading electrode and the first read-write electrode or the second read-write electrode constitute read electrode pair, this read electrode is to when biasing read signal, not retrained by the coercive field voltage between third reading writing electrode and the first read-write electrode or the second read-write electrode, to improve signal-obtaining electric current.
5. non-destructive read-out ferroelectric memorizer as claimed in claim 3, it is characterised in that except read-write electrode pair, also reads and writes first simultaneously and arranges third reading electrode and the 4th read electrode between electrode and the second read-write electrode;
Wherein, described third reading electrode and the 4th read electrode constitute read electrode pair, and this read electrode, to when biasing read signal, is not retrained by the coercive field voltage between third reading electrode and the 4th read electrode, to improve signal-obtaining electric current.
6. Nonvolatile ferroelectric memory as claimed in claim 1, it is characterized in that, configure the thickness of described ferroelectric thin film layer (303) and/or the width (d) of described ferroelectric storage cell (305), so that ferroelectric thin film layer (303) bottom electricdomain is not reversed or do not reversed in the way of longitudinally running through described ferroelectric thin film layer (303) the writing under voltage effect that ferroelectric storage cell (305) electricdomain in corresponding described ferroelectric storage cell is completely reversed of biasing predefined size.
7. the Nonvolatile ferroelectric memory as described in claim 1 or 6, it is characterized in that, configure the thickness of described ferroelectric thin film layer (303) and/or the width (d) of described ferroelectric storage cell (305), so that the domain wall conductive channel (3054) between the memory element (305) that corresponding described ferroelectric thin film surface etch is formed under the read voltage effect of biasing predefined size and ferroelectric thin film layer (303) bottom is not destroyed.
8. Nonvolatile ferroelectric memory as claimed in claim 1, it is characterised in that described ferroelectric storage cell (305) is rectangular structure, and its width (d) is more than or equal to 2 nanometers and less than or equal to 10 microns;
The length (l) of described ferroelectric storage cell (305) is more than or equal to 2 nanometers and less than or equal to 10 microns; And described ferroelectric storage cell is as a whole with ferroelectric thin film layer.
9. Nonvolatile ferroelectric memory as claimed in claim 1, it is characterised in that also including substrate (300), described ferroelectric thin film layer (303) is arranged on described substrate (300).
10. Nonvolatile ferroelectric memory as claimed in claim 1, it is characterised in that the material of described ferroelectric thin film layer (303) and ferroelectric storage cell (305) is selected from bismuth ferrite, mixes the bismuth ferrite salt of La, lead zirconate titanate salt, dawn acid lithium or niobic acid lithium salts.
11. Nonvolatile ferroelectric memory as claimed in claim 1, it is characterised in that the thickness of described ferroelectric thin film layer (303) is more than or equal to 10 nanometers and less than or equal to 100 microns; The thickness of described ferroelectric thin film surface storage unit (305) or etching depth are more than or equal to 5nm and less than or equal to 1 micron;
The thickness of described read-write electrode layer (307) is more than or equal to 5 nanometers and less than or equal to 100 nanometers.
12. Nonvolatile ferroelectric memory as claimed in claim 1, it is characterized in that, by controlling the crystal orientation that described ferroelectric thin film layer (303) grows, to such an extent as to the normal direction of the substantially not parallel described read-write electrode layer (307) of polarised direction of the electricdomain (3031,3033) of described ferroelectric thin film layer (303).
13. the preparation method of a Nonvolatile ferroelectric memory as claimed in claim 1, it is characterised in that concrete steps include:
Substrate (301) is provided;
Described substrate (301) is formed ferroelectric thin film (303);
Ferroelectric storage cell (305) is gone out in ferroelectric thin film (303) surface etch; And
Left and right read-write electrode layer (307) in face is formed between described ferroelectric storage cell (305).
14. preparation method as claimed in claim 13, it is characterised in that further comprise the steps of: the left and right sides first in face and read and write formation third reading electrode between electrode and the second read-write electrode, or form third reading electrode and the 4th read electrode.
15. the write operation method of a non-destructive read-out ferroelectric memorizer as claimed in claim 1, it is characterised in that: bias the write signal (V of first direction between two parts (3071 and 3073) of the adjacent described ferroelectric storage cell (305) in read-write electrode layer (307)write1), corresponding described ferroelectric storage cell (305) surface portion electricdomain is inverted, thus writing the first logical message " 1 ";
Write signal (the V of second direction opposite to the first direction is biased between two parts (3071 and 3073) of the adjacent described ferroelectric storage cell (305) in described read-write electrode layer (307)write2), make corresponding described ferroelectric storage cell (305) surface portion not be inverted or electricdomain of reversing returns to initial polarization direction, thus writing the second logical message " 0 ".
16. write operation method as claimed in claim 15, it is characterized in that, bottom ferroelectric thin film layer in (303) and surface ferroelectric storage cell (305), forming domain wall (3054) between described electricdomain (3053a) that ferroelectric storage cell (305) surface is inverted and the described electricdomain (3031a) that bottom is not inverted, the read-write electrode of the through described read-write electrode layer (307) of this domain wall (3054) is between (3071 and 3073).
17. the read operation method of a Nonvolatile ferroelectric memory as claimed in claim 1, it is characterized in that: between two parts on adjacent described surface ferroelectric storage cell (305) in read-write electrode layer (307), bias the read signal of first direction, by reading size of current between these two parts and whether be inverted with the electricdomain judging corresponding described ferroelectric storage cell (305) and then setting up domain wall conductive channel with the electricdomain of ferroelectric thin film layer (303) bottom, thus reading the logical message of storage;
After removing read signal, read operation process is not destroyed the logical message of write during write operation.
18. read operation method as claimed in claim 17, it is characterised in that the read voltage of described read signal writes voltage less than described write signal.
19. the read operation method of a Nonvolatile ferroelectric memory as claimed in claim 1, it is characterized in that: between third reading electrode and the first read-write electrode or the second read-write electrode, or between third reading electrode and the 4th read electrode, bias first direction read signal, by reading the size of current between these two parts, whether the electricdomain to judge corresponding described ferroelectric storage cell (305) is inverted and then sets up domain wall conductive channel with the electricdomain bottom ferroelectric thin film layer (303), thus reading the logical message of storage;
After removing read signal, read operation process is not destroyed the logical message of write during write operation.
20. read operation method as claimed in claim 19, it is characterised in that the read voltage of described read signal is not by the restriction writing voltage of described write signal.
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