CN112397646B - Threshold voltage adjusting method of three-terminal superlattice storage and calculation all-in-one device - Google Patents
Threshold voltage adjusting method of three-terminal superlattice storage and calculation all-in-one device Download PDFInfo
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Abstract
The invention provides a threshold voltage regulating method of a three-terminal superlattice storage and calculation all-in-one machine, wherein inverse piezoelectric layers are respectively arranged between a lower electrode layer and a superlattice film and between the superlattice film and an upper electrode layer; different tensile deformations generated by the two inverse piezoelectric layers when different voltages are applied are utilized to generate different tensile stresses on the contacted superlattice film, so that the energy barrier of atomic layer overturning of the phase change material in the superlattice film is adjusted. The invention also provides a method for realizing AND logic operation by the threshold voltage adjusting method, when the upper electrode layer of the superlattice storage integrator, the first inverse piezoelectric layer and the second inverse piezoelectric layer simultaneously apply voltage pulses, the superlattice thin film generates abrupt change of resistance value, namely the output is 1.
Description
Technical Field
The invention belongs to the technical field of microelectronic devices, and particularly relates to a threshold voltage adjusting method of a three-terminal superlattice storage and calculation all-in-one device and a method for realizing AND logic operation of the three-terminal superlattice storage and calculation all-in-one device.
Background
At present, the development of various artificial intelligence techniques is underway, and particularly, the research of brain-like devices is taken as a representative. The brain-like device is characterized in that storage and operation are realized in the same device, namely, the storage and operation are integrated. Most computers currently employ von Neumann architectures, i.e., the CPU is separated from the memory, which are connected by data lines. Not only does this von Neumann architecture result in very high power consumption due to frequent data exchanges between the CPU and the memory, but it also greatly limits the speed of computer data processing due to the limited rate at which data lines transmit signals. Therefore, developing new storage-integration devices will profoundly change the existing computer architecture: (1) reducing energy waste in computers due to frequent data exchanges, (2) increasing the speed at which computers process data, (3) operating systems based on existing von neumann architectures will also make corresponding changes. Therefore, the development of new type of integrated storage devices will bring far-reaching positive impact on our existing information technology.
Superlattice materials are multi-layer films in which two different components alternately grow in thin layers of a few nanometers to a dozen nanometers and maintain strict periodicity, and are layered fine composites in fact in a specific form. Superlattice phase-change memory devices have attracted considerable attention as memory devices because they can rapidly achieve a reversible transition between a low resistance state and a high resistance state by applying an electric or optical pulse, and the process of changing the high resistance state to the low resistance state is referred to as a SET process and the reverse process is referred to as a RESET process. And compared with the traditional phase change memory material, the superlattice phase change memory material has more excellent performances in the aspects of SET speed, RESE power consumption, cyclic erasing and writing stability and the like (Simpson R E, Fons P, Kolobov A V, et al. interfacial phase-change memory [ J ]. Nature nanotechnology,2011,6(8): 501.).
The phase change process of a superlattice phase change memory device can be realized based on the atomic layer inversion of a phase change material, and the energy barrier of the atomic layer inversion can be regulated and controlled by the tensile stress applied to the crystal lattice (Kalikka J, Zhou X, Dilcher E, et al, strong-engineered differential switching in two-dimensional crystals [ J ]. Nature communications,2016,7: 11983.).
If in-plane tensile stress can be applied by an electrical operation method, the energy barrier of atomic layer inversion in the phase change process is adjusted, and the threshold voltage (the threshold voltage is the corresponding critical voltage when the phase change material is subjected to two-state transition after voltage is applied) in the phase change process is changed, the superlattice phase change memory device can be used for realizing simple logic operation, and the superlattice phase change memory device can be expected to be developed into a novel electronic device integrating storage and calculation.
Disclosure of Invention
Aiming at least one defect or improvement requirement in the prior art, the invention provides a three-terminal superlattice memory all-in-one device with adjustable threshold voltage and a preparation method thereof, wherein reverse piezoelectric layers are respectively arranged between a lower electrode layer and a superlattice film and between the superlattice film and an upper electrode layer; different tensile deformations generated by the two inverse piezoelectric layers when different voltages are applied are utilized to generate different tensile stresses on the contacted superlattice film, so that the energy barrier of atomic layer overturning of the phase change material in the superlattice film is adjusted. The threshold voltage of the superlattice phase change unit with the structure in the phase change process can be regulated by externally applied voltage, and the adjustable threshold voltage enables the superlattice phase change memory unit to execute simple logic operation and realize integration of storage and calculation.
In order to achieve the above object, according to one aspect of the present invention, there is provided a threshold voltage adjusting method of a three-terminal superlattice storage integrated device, the three-terminal superlattice storage integrated device includes an upper electrode layer, a superlattice thin film, a lower electrode layer, a first inverse piezoelectric layer formed between the lower electrode layer and the superlattice thin film, and a second inverse piezoelectric layer formed between the superlattice thin film and the upper electrode layer; different tensile deformations generated by the two inverse piezoelectric layers when different voltages are applied are utilized to generate different tensile stresses on the contacted superlattice film, so that an energy barrier for atomic layer overturning of the phase change material in the superlattice film is adjusted, and finally, a regulating effect is generated on the threshold voltage of the superlattice phase change unit in the phase change process.
Further, a voltage or current pulse is applied between the upper electrode layer and the lower electrode layer, and a control pulse is simultaneously applied to the first and second inverse piezoelectric material layers.
Further, a heating layer for communicating the lower electrode layer and the superlattice thin film is partially filled in the first inverse piezoelectric layer;
further, the materials of the first inverse piezoelectric layer and the second inverse piezoelectric layer are piezoelectric ceramic materials, and the piezoelectric ceramic materials are selected from PbNb 2 O 6 、PbTiO 3 、PbZrO 3 、BaTiO 3 Any one of them.
Further, the superlattice thin film comprises a first phase change layer and a second phase change layer which are alternately grown, and the lattice mismatch ratio between the two phase change materials is 0.1-10%.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
(1) the invention provides a three-terminal superlattice storage and calculation all-in-one device with adjustable threshold voltage and a preparation method thereof.A reverse piezoelectric layer is respectively arranged between a lower electrode layer and a superlattice film and between the superlattice film and an upper electrode layer, and different electric pulses are applied to the two reverse piezoelectric layers to enable the superlattice film to generate different tensile stresses so as to adjust an energy barrier of atomic layer overturning of a phase change material in the superlattice film; the threshold voltage of the superlattice phase change unit with the structure in the phase change process can be regulated by externally applied voltage, and the adjustable threshold voltage enables the superlattice phase change memory unit to execute simple logic operation and realize integration of storage and calculation, so that the calculation process and the storage process are integrated into the same superlattice phase change memory, the power consumption of an existing computer is reduced, and the data processing speed is improved.
(2) The three-terminal superlattice storage and calculation all-in-one machine with the adjustable threshold voltage and the preparation method thereof provided by the invention have the advantages that the used preparation process is compatible with the existing CMOS processing process, the process is mature, and the process is simple and easy to implement.
The invention also provides a method for realizing AND logic operation by any one of the threshold voltage adjusting methods, wherein the voltage pulse applied to the upper electrode layer in the three-terminal superlattice storage integrator and the voltage pulse applied to the first and second inverse piezoelectric layers are two input signals, the voltage of the sampling resistor connected with the lower electrode layer of the three-terminal superlattice storage integrator is an output signal, wherein the input signal is 0 or 1, the output signal can be 1 only when the two input signals are 1 simultaneously, and the output signal is 0 at other times, namely when the upper electrode layer of the superlattice storage integrator and the first inverse piezoelectric layer and the second inverse piezoelectric layer simultaneously apply the voltage pulses, the superlattice thin film has abrupt change of resistance, namely the output is 1.
Further, when a voltage of 1.5V is applied to the upper electrode layer, it is written as "1", and when no voltage pulse is applied, it is written as "0"; when a voltage of 3V is applied to the first and second reverse piezoelectric layers, "1" is recorded, and when no electric pulse is applied, "0" is recorded; when the voltage on the sampling resistor reaches 1V, the voltage is marked as 1, and when the voltage is lower than 1V, the voltage is marked as 0.
Drawings
FIG. 1 is one of schematic cross-sectional views of a stage in the fabrication process of a three-terminal superlattice memory integrated device with adjustable threshold voltage according to an embodiment of the invention;
FIG. 2 is a second schematic cross-sectional view of a stage in the fabrication process of a three-terminal superlattice memory integrated device with adjustable threshold voltage according to an embodiment of the present invention;
FIG. 3 is a third schematic cross-sectional view of a third stage in the fabrication process of a three-terminal superlattice memory integrated device with adjustable threshold voltage according to an embodiment of the invention;
FIG. 4 is a fourth schematic diagram of the cross-sectional view of the three-terminal superlattice memory integrated device with adjustable threshold voltage according to the embodiment of the invention;
FIG. 5 is a schematic cross-sectional diagram of a third-end superlattice one-body device with adjustable threshold voltage according to an embodiment of the invention;
FIG. 6 is a sixth schematic cross-sectional view of a third embodiment of a three-terminal superlattice integrator with adjustable threshold voltage according to the present invention;
FIG. 7 is a seventh schematic cross-sectional diagram illustrating a stage in the fabrication process of a three-terminal superlattice memory integrated device with adjustable threshold voltage according to an embodiment of the present invention;
FIG. 8 is an eighth schematic cross-sectional view of a stage in the fabrication of a three-terminal superlattice memory integrated device with adjustable threshold voltage provided by an embodiment of the present invention;
FIG. 9 is a ninth schematic sectional view of a stage in the fabrication of a three-terminal superlattice memory integrated device with adjustable threshold voltage according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of an I-V curve of a three-terminal superlattice storage integrator before and after applying a voltage to a first inverse piezoelectric layer and a second inverse piezoelectric layer according to an embodiment of the present invention;
fig. 11 is a schematic diagram of input and output voltage waveforms when an and logic operation is performed by using a three-terminal superlattice storage integrated device according to an embodiment of the present invention;
in all the figures, the same reference numerals denote the same features, in particular: 1-substrate, 2-substrate thermal growth layer; 3-a lower electrode layer; 4-a first reverse piezoelectric layer; 5, heating a layer; 6-a second inverse piezoelectric layer; 7-upper electrode layer; 8-a first phase change layer; 9-second phase change layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides a three-terminal superlattice storage and calculation all-in-one machine with adjustable threshold voltage, which comprises a substrate layer, and a lower electrode layer, a superlattice film and an upper electrode layer which are sequentially deposited on the substrate layer; the piezoelectric device also comprises a first inverse piezoelectric layer and a second inverse piezoelectric layer;
the first inverse piezoelectric layer is formed between the lower electrode layer and the superlattice film, and a heating layer for communicating the lower electrode layer and the superlattice film is partially filled in the first inverse piezoelectric layer;
the second inverse piezoelectric layer is formed between the superlattice thin film and the upper electrode layer, the upper electrode layer is provided with a convex structure, and the convex structure penetrates through the second inverse piezoelectric layer and is contacted with the surface of the superlattice thin film;
the lattice constants of the materials of the first inverse piezoelectric layer and the second inverse piezoelectric layer can be increased in response to an externally applied voltage, so that in-plane tensile stress is generated on the superlattice thin film in contact with the first inverse piezoelectric layer and the second inverse piezoelectric layer, and the threshold voltage of the superlattice thin film in the phase change process is adjusted under the action of the in-plane tensile stress.
In this embodiment, when an electric pulse is applied to the first and second inverse piezoelectric layers, the first and second inverse piezoelectric layers can be deformed by stretching, thereby generating an in-plane tensile stress on the superlattice thin film sandwiched between the first and second inverse piezoelectric layers; under the action of the in-plane tensile stress, the energy barrier of the phase change material in the superlattice film for atomic layer turnover is reduced; different electric pulses can be applied to the first inverse piezoelectric layer and the second inverse piezoelectric layer to enable the superlattice film to generate different in-plane tensile stresses, so that an energy barrier of atomic layer inversion of the phase change material in the superlattice film is adjusted; the threshold voltage of the superlattice phase change memory cell with the structure in the phase change process can be regulated by externally applied voltage, and the adjustable threshold voltage enables the superlattice phase change memory cell to execute simple logic operation, so that the integration of the operation is realized.
The three-terminal superlattice storage integrated device provided by the embodiment is combined with a resistor and a capacitor to form a simple circuit, so that the logical operation function can be realized.
In this embodiment, the first inverse piezoelectric layer and the second inverse piezoelectric layer are made of piezoelectric ceramic materials, and can generate tensile stress by applying voltage; the piezoelectric ceramic material is selected from PbNb 2 O 6 、PbTiO 3 、PbZrO 3 、BaTiO 3 Any one of the above; the thicknesses of the first inverse piezoelectric layer and the second inverse piezoelectric layer affect the magnitude of the in-plane tensile stress generated by the superlattice film, and further affect the adjustment amplitude of the threshold voltage of the superlattice film in the phase change process, in this embodiment, the thicknesses of the first inverse piezoelectric layer and the second inverse piezoelectric layer are 2-50 nm.
The superlattice thin film comprises a first phase change layer and a second phase change layer which are alternately grown, and the superlattice structure is [ A ] m B n ] z Wherein A represents the phase change material of the first phase change layer, and B represents the phase change material of the second phase change layer; m and n respectively represent the thicknesses of the first phase change layer and the second phase change layer, the unit default is nanometer, and z is the periodicity of the superlattice; in this embodiment, 1/10<m/n<10/1, and 2<m+n<10，5<z<100, m and n are real numbers, and z is an integer. Preferably, the lattice constant mismatch between the two phase change materials A, B should not be too large to ensure that a superlattice structure is more easily formed between the two crystal lattices. More preferably, two phasesThe lattice mismatch between the metamaterials should be between 0.1% and 10%.
The two phase-change materials A, B are elementary substance materials or compound materials, and any two materials with different chemical formulas after the elementary substance and the compound are doped; wherein the elementary substance material is Sb elementary substance; the compound material comprises: Ge-Te binary alloys, Ge-Sb binary alloys, Sb-Te binary alloys, Bi-Te binary alloys, In-Se binary alloys, and Ge-Sb-Te ternary alloys, Ge-Bi-Te ternary alloys, Ge-Sb-Bi-Te quaternary alloys; more preferably GeTe, GeSb, Sb 2 Te 3 、Bi 2 Te 3 、Ge 2 Sb 2 Te 5 、Ge 1 Sb 2 Te 4 Two of which are different. The doped element can be at least one of C, Cu, N, O, Si, Sc and Ti; proper doping can improve the stability of cyclic erasing and writing of the superlattice phase change unit and the SET speed, and reduce the RESET power consumption. In this embodiment, the upper and lower electrode layers are made of Al; in other embodiments, the material of the upper and lower electrode layers can also be W, Ag, Cu, Au, Pt, Ti 3 W 7 Any one of the above; the heating layer is made of W, TiN or Ti 3 W 7 Any one of the above; the substrate layer comprises a silicon wafer and a thermal growth layer deposited on the silicon wafer, and the material of the thermal growth layer is generally amorphous SiO 2 The silicon wafer is mainly used for isolating the monocrystalline silicon wafer from the lower electrode layer and releasing the stress of the substrate.
The embodiment also provides a preparation method of the three-terminal superlattice storage and calculation all-in-one device with adjustable threshold voltage, which comprises the following steps:
s1: providing a substrate layer, and sequentially depositing a lower electrode layer and a first inverse piezoelectric layer on the substrate layer; the substrate layer comprises a silicon wafer and a thermal growth layer deposited on the silicon wafer, and a lower electrode layer and a first inverse piezoelectric layer are sequentially deposited on the thermal growth layer;
s2: forming a first through hole which penetrates through the first inverse piezoelectric layer to be in contact with the surface of the lower electrode layer, and filling a heating layer in the first through hole; the shape of the first through hole is not limited, and the cross section of the first through hole can be a circle, a square or other regular polygons, and the embodiment is preferably a circle; in the deposition process, a heating layer is inevitably formed on the surface of the first inverse piezoelectric layer, the redundant heating layer on the surface of the first inverse piezoelectric layer is removed by utilizing a chemical mechanical polishing method, and the heating layer in the first through hole is reserved;
s3: alternately growing a first phase change layer and a second phase change layer on the surfaces of the heating layer and the first inverse piezoelectric layer to form a superlattice film;
s4: depositing a second inverse piezoelectric layer on the surface of the superlattice thin film;
s5: forming a second through hole which penetrates through the second inverse piezoelectric layer to be in contact with the surface of the superlattice thin film; the shape of the second through hole is not limited, and the cross section of the second through hole can be a circle, a square or other regular polygon; this embodiment is preferably the same circular shape as the first through hole;
s6: and depositing an upper electrode layer inside the second through hole and on the surface of the second inverse piezoelectric layer, wherein the upper electrode layer is of a T-shaped structure due to the existence of the second through hole.
In this embodiment, the first phase change layer, the second phase change layer, the first inverse piezoelectric layer, and the second inverse piezoelectric layer may be prepared by a magnetron sputtering method, an atomic layer deposition method, a molecular beam epitaxy method, a pulsed laser deposition method, a physical vapor deposition method, a chemical vapor deposition method, a thermal evaporation method, or an electrochemical growth method.
The structure and the preparation method of the three-terminal superlattice memory integrator with adjustable threshold voltage provided by the invention are explained in detail in the following by combining the embodiment and the accompanying drawings.
FIGS. 1-9 are schematic diagrams of stages in the fabrication of a three-terminal superlattice integrator in accordance with embodiments of the present invention; the three-terminal superlattice storage integrator prepared in this example employs a "mushroom-type" structure commonly used in phase change memories. In this embodiment, the phase change material A of the first phase change layer is GeTe, and the phase change material B of the second phase change layer is Sb 2 Te 3 M/n is 2/2, z is 12, and the material of the first inverse piezoelectric layer and the second inverse piezoelectric layer is BaTiO 3 The deposition thickness is 10 nm; the specific implementation method comprises the following steps:
(1) referring to FIG. 1, a thickness of 500 μm is selectedAnd (100) oriented silicon wafer as a substrate 1, and SiO with a thickness of 1 μm is formed on the surface of the silicon substrate 1 by thermal growth method 2 The thin film layer serves as a substrate thermal growth layer 2. Cutting a silicon wafer into the size of 1cm multiplied by 1cm, putting the silicon wafer into a beaker, injecting a proper amount of acetone, and ultrasonically cleaning for 10 minutes; after cleaning, cleaning the fabric for 10 minutes by using absolute ethyl alcohol, cleaning the fabric for ten minutes by using deionized water, and drying the fabric by using a nitrogen gun; the impurities on the surface of the substrate can be removed by cleaning, and the stability of the device can be improved. Then, an Al lower electrode layer 3 is formed on the thermally grown layer 2 by magnetron sputtering.
(2) As shown in fig. 2, taking a piece of the substrate 1 on which the lower electrode layer 3 has been formed in step (1), growing a first reverse piezoelectric material layer 4 on the lower electrode layer 3 of the substrate 1 by using a chemical vapor deposition method, wherein the thickness of the first reverse piezoelectric material layer 4 is 10 nm.
(3) As shown in fig. 3, a first through hole is etched inside the first inverse piezoelectric material layer 4 formed in step (2) by using a photolithography and etching process, and the first through hole penetrates through the first inverse piezoelectric material layer 4 and contacts with the lower electrode layer 3, in this embodiment, the first through hole is a circular hole with a diameter of 130 nm.
(4) As shown in fig. 4, the structure formed in step (3) has a surface deposited heating layer 5, and the heating layer 5 falls into the first through-hole to contact the lower electrode layer 3.
(5) As shown in fig. 5, the heating layer 5 on the surface of the first inverse piezoelectric material layer 4 is removed by chemical mechanical polishing, the heating layer 5 in the first through hole is remained, and the upper surface of the heating layer 5 in the first through hole is flush with the upper surface of the first inverse piezoelectric material layer 4.
(6) As shown in fig. 6, a first phase change layer 8 and a second phase change layer 9 are alternately deposited on the surfaces of the heating layer 5 and the first inverse piezoelectric material layer 4 formed in step (5) by using a magnetron sputtering method until a required superlattice period is reached, and a superlattice thin film is formed.
(7) As shown in fig. 7, a second inverse piezoelectric material layer 6 is grown on the surface of the superlattice thin film that has been formed in step (6) by using a chemical deposition method, and the thickness of the second inverse piezoelectric material layer 6 is also 10 nm.
(8) As shown in fig. 8, a second through hole is etched in the surface of the structure formed in step (7) by using the photolithography and etching process, the second through hole penetrates through the second inverse piezoelectric material layer 6 to be in contact with the superlattice thin film, and the second through hole is also a circular hole with a diameter of 130 nm.
(9) As shown in fig. 9, the upper electrode layer 7 is deposited on the surface of the structure formed in step (8), and the upper electrode layer 7 falls into the second through hole to contact the superlattice film.
In an actual use process, voltage is applied to the first reverse piezoelectric material layer 4 and the second reverse piezoelectric material layer 6 at the same time, so that the first reverse piezoelectric material layer 4 and the second reverse piezoelectric material layer 6 are subjected to tensile deformation, and further in-plane tensile stress is generated on the superlattice thin film between the first reverse piezoelectric material layer 4 and the second reverse piezoelectric material layer 6. Under the action of in-plane tensile stress, the energy barrier of Ge and Te atomic layer inversion (both SET and RESET processes in the superlattice are caused by the atomic layer inversion) in the superlattice thin film is reduced. Therefore, the phase change process of the superlattice phase change memory cell shows the characteristic that the threshold voltage is reduced when a sufficiently large control voltage is applied to the first reverse piezoelectric material layer 4 and the second reverse piezoelectric material layer 6, the in-plane tensile stress generated by the superlattice thin film disappears when the control voltage is removed, and the threshold voltage of the superlattice phase change memory cell is restored to the original value.
Voltage or current pulses used for SET, RESET and read operations of the superlattice phase-change memory cell need to be applied between the upper electrode layer 7 and the lower electrode layer 3; the control pulse for controlling the threshold voltage transition of the superlattice phase change memory cell needs to be simultaneously applied to the first and second inverse piezoelectric material layers 4 and 6.
Next, a method of implementing and logic operation using the three-terminal superlattice storage integrator manufactured in this embodiment is described, in which a voltage pulse applied to the upper electrode layer of the three-terminal superlattice storage integrator and voltage pulses applied to the first and second inverse piezoelectric layers are two input signals, and a voltage of a sampling resistor connected to the lower electrode layer of the three-terminal superlattice storage integrator is an output signal. In the and logic operation, the input signal can take two values of 0 or 1, and the output signal can take 1 only when the two input signals take 1 simultaneously, and can take 0 at other times.
In order to realize the AND logic operation, the resistance values of the superlattice storage integrated device are unified to a high-resistance state by applying RESET pulse to the three-terminal superlattice storage integrated device.
When a voltage of 1.5V is applied to the upper electrode layer of the three-terminal superlattice integrator, it is described as "1", and when no electric pulse is applied, it is described as "0". When a control pulse of 3V is applied to the first and second reverse piezoelectric layers in the device, it is described as "1", and when no electric pulse is applied, it is described as "0". When the voltage on the sampling resistor reaches 1V, it is marked as "1", and when it is lower than 1V, it is marked as "0".
FIG. 10 is a schematic view of the I-V curve of a three-terminal superlattice storage integrator before and after applying a voltage to a first inverse piezoelectric layer and a second inverse piezoelectric layer; wherein, curve 1 is the I-V curve of the superlattice phase change memory cell before the voltages are applied on the first inverse piezoelectric layer and the second inverse piezoelectric layer, and curve 2 is the I-V curve of the superlattice phase change memory cell after the voltages are applied on the first inverse piezoelectric layer and the second inverse piezoelectric layer. Fig. 11 is a schematic diagram showing input and output voltage waveforms when the and logic operation is performed by the three-terminal superlattice integrated device. The input pulse 1 is a voltage pulse applied to an upper electrode layer of the three-terminal superlattice storage integrator, the input pulse 2 is a voltage pulse applied to the first inverse piezoelectric layer and the second inverse piezoelectric layer, and the output pulse is a voltage of a sampling resistor connected with a lower electrode layer of the three-terminal superlattice storage integrator.
As shown in fig. 10, when a gradually increasing voltage is applied to the superlattice integrator in the high resistance state, the resistance value (the inverse of the slope) changes abruptly. After mutation, the three-terminal superlattice storage integrator is converted into a stable low-resistance state, and the voltage corresponding to the mutation position is the threshold voltage.
Referring to fig. 10 and 11, before applying the 3V control voltage to the first and second inverse piezoelectric layers (curve 1, the threshold voltage is 2V), the corresponding superlattice thin film cell still maintains the high resistance state even if the 1.5V voltage is applied to the upper electrode layer. At this time, the resistance is large, the current is small, the voltage on the sampling resistor is small and does not reach 1V, so the output is "0".
After applying 3V control voltage to the first and second inverse piezoelectric layers (curve 2, at this time, the threshold voltage is reduced to 1V), and applying 1.5V voltage to the upper electrode layer, the corresponding superlattice thin film unit has undergone abrupt change of resistance value and is converted into a low resistance state. At this time, the resistance is small, the current is large, the voltage on the sampling resistor is large enough to reach 1V, so the output is 1.
As is apparent from fig. 11, when no voltage is applied to the upper electrode layer of the superlattice storage-integrator, the resistance of the superlattice storage-integrator is not likely to change abruptly, but is always maintained in a high resistance state, so that the output is constantly "0" regardless of whether control voltages are applied to the first inverse piezoelectric layer and the second inverse piezoelectric layer.
In summary, if and only if the upper electrode layer of the superlattice storage integrator and the first inverse piezoelectric layer and the second inverse piezoelectric layer simultaneously apply electric pulses with proper sizes (simultaneously input "1"), the superlattice thin film unit may have abrupt change of resistance, that is, the output is "1", which is the principle that the and logic function is realized by using the change of the threshold voltage of the superlattice phase change storage material.
The embodiment also provides a phase change memory, which comprises a memory array consisting of the three-terminal superlattice memory integrator with adjustable threshold voltage, a control circuit, a word line decoder, a bit line decoder, an inverse piezoelectric layer line decoder and other peripheral circuits; the word line decoder is electrically connected with a plurality of word lines arranged along the row direction of the memory array; the bit line decoder is electrically connected with a plurality of bit lines arranged along the column direction of the memory array; the inverse piezoelectric layer circuit decoder is connected with each first inverse piezoelectric layer and each second inverse piezoelectric layer in the storage array through a plurality of inverse piezoelectric layer circuits; the control circuit can be realized by a general processor or a logic circuit commonly used in the field; other peripheral circuits include, but are not limited to, power supply circuits, sensing circuits, and the like. The invention provides a three-terminal superlattice access and calculation all-in-one device with adjustable threshold voltage and a preparation method thereof.A reverse piezoelectric layer is respectively arranged between a lower electrode and a superlattice film and between the superlattice film and an upper electrode, and different electric pulses are applied to the two reverse piezoelectric layers to enable the superlattice film to generate different tensile stress so as to adjust the energy barrier of the phase change material in the superlattice film for atomic layer turnover; the threshold voltage of the superlattice phase change unit with the structure in the phase change process can be regulated by externally applied voltage, and the adjustable threshold voltage enables the superlattice phase change memory unit to execute simple logic operation and realize integration of storage and calculation, so that the calculation process and the storage process are integrated into the same superlattice phase change memory, the power consumption of an existing computer is reduced, and the data processing speed is improved.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (7)
1. A threshold voltage regulating method of a three-terminal superlattice storage and calculation all-in-one device is characterized in that the three-terminal superlattice storage and calculation all-in-one device comprises an upper electrode layer, a superlattice film, a lower electrode layer, a first inverse piezoelectric layer formed between the lower electrode layer and the superlattice film, and a second inverse piezoelectric layer formed between the superlattice film and the upper electrode layer; different tensile deformations generated by the two inverse piezoelectric layers when different voltages are applied are utilized to generate different tensile stresses on the contacted superlattice film, so that the energy barrier of atomic layer overturning of the phase change material in the superlattice film is adjusted, and finally, the threshold voltage of the superlattice phase change unit in the phase change process is regulated and controlled.
2. The method of claim 1, wherein a voltage or current pulse is applied between the upper electrode layer and the lower electrode layer, and a control pulse is simultaneously applied to the first and second inverse piezoelectric material layers.
3. The method for adjusting the threshold voltage of a three-terminal superlattice storage one body as claimed in claim 2, wherein said first inverse piezoelectric layer is partially filled with a heating layer for communicating the lower electrode layer and the superlattice thin film.
4. The method for adjusting the threshold voltage of a three-terminal superlattice integrator as claimed in claim 3, wherein the materials of the first and second inverse piezoelectric layers are piezoelectric ceramic materials selected from PbNb 2 O 6 、PbTiO 3 、PbZrO 3 、BaTiO 3 Any one of them.
5. The method of adjusting threshold voltage of a three-terminal superlattice memory integrated device as claimed in any one of claims 1-4, wherein said superlattice thin film comprises a first phase change layer and a second phase change layer alternately grown, and lattice mismatch ratio between two phase change materials is between 0.1% and 10%.
6. A method for realizing AND logic operation by the threshold voltage adjusting method of any one of claims 2-5 is characterized in that the voltage pulse applied to the upper electrode layer of the three-terminal superlattice storage integrator and the voltage pulse applied to the first and second inverse piezoelectric layers are two input signals, the voltage of the sampling resistor connected with the lower electrode layer of the three-terminal superlattice storage integrator is an output signal, wherein the input signal is '0' or '1', the output signal can be '1' only when the two input signals are simultaneously '1', and the output signal is '0' at other times, namely when the voltage pulses are simultaneously applied to the upper electrode layer of the superlattice storage integrator, the first inverse piezoelectric layer and the second inverse piezoelectric layer, the superlattice thin film has abrupt change of resistance, namely the output is '1'.
7. The method of claim 6, wherein when a voltage of 1.5V is applied to the top electrode layer, it is written as "1", and when no voltage pulse is applied, it is written as "0"; when a voltage of 3V is applied to the first and second reverse piezoelectric layers, "1" is recorded, and when no electric pulse is applied, "0" is recorded; when the voltage on the sampling resistor reaches 1V, the voltage is marked as 1, and when the voltage is lower than 1V, the voltage is marked as 0.
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