Phase-change memory material and device, and array and programming apparatus

Abstract

Disclosed in the present invention are a phase-change memory material and device, and a programming apparatus. The phase-change memory material has a chemical formula of CrxTe100-x, wherein 0<x<100; at -200°C to 200°C, the resistance drift coefficients of amorphous and crystalline thin films of the phase-change memory material are both less than or equal to 0.002; and at -200°C to 200°C, the resistance drift coefficients of different logic states of a phase-change device based on CrxTe100-x and of a device unit in an array are all less than or equal to 0.002. Thus, the data programming accuracy and read-write accuracy over a wide temperature range are effectively improved, and the resistance drift problem in existing phase-change memory technology, particularly the problem of resistance drift behavior being complicated under operating temperatures, is overcome. The programming apparatus comprises a pump laser system, an electrical testing system, a cold and hot temperature control system, and control and monitoring software, thus implementing an "optically controlled electrical-measurement" programming operation of the phase-change memory device in a specific environment; and the programming apparatus can quantitatively control the crystalline-to-amorphous volume ratio during the gradual switching between SET and RESET, thereby achieving linear, continuous and symmetrical variations of the logic states of the device unit.

Description

Phase change memory material, device, array and programming apparatus TECHNICAL FIELD

[0001] The present application relates to the technical field of nonvolatile storage, in particular to a phase change memory material, device, array and programming apparatus. BACKGROUND

[0002] Phase change memory is a nonvolatile storage technology based on phase change materials, and the performance of the memory greatly depends on the intrinsic properties of the materials. Phase change memory uses the different resistance values of phase change materials in different phase structures to identify logical states, and can also obtain multiple resistance values in the same memory cell through gradual phase change switching to realize multi-value storage and storage-computing integrated technology. However, the spontaneous structural relaxation of amorphous phase change materials continuously increases the resistance value over time, i.e. resistance drift, which greatly limits the number of logical states that can be identified by a single node and is one of the main bottlenecks for the storage capacity of phase change multi-value memory chips and the computing power of phase change computing integrated chips. In addition, the service temperature range of chips is extremely wide, for example, the service temperature of vehicle-mounted chips is about -40-165℃, and the external environment of a space station cycles 16 times between -120-120℃ every day. The wide temperature range and diversity of service temperatures make the resistance drift phenomenon more complex and difficult to compensate through algorithms and circuits and other external conditions. Therefore, there is an urgent need to develop a phase change material with intrinsic low resistance drift characteristics in a wide temperature range.

[0003] The gradual switching of phase change memory is achieved by changing the volume ratio of crystals and amorphous materials in the device. In a storage-computing integrated array, the ideal programming method of a single device cell requires the resistance value to remain linear and continuous when switching between SET and RESET, and the resistance values in the two switching processes are mutually symmetrical. However, phase change materials have a large degree of randomness in the processes of nucleation and crystallization and melting and quenching. Phase change memory uses continuous electrical pulses for cumulative writing / iterative erasing programming, which cannot achieve quantitative control of the volume ratio of crystals and amorphous materials in the device, resulting in nonlinear and asymmetric changes in resistance values when switching between SET and RESET. Therefore, there is an urgent need to develop a new phase change memory programming apparatus with linear and continuous and symmetrical changes in resistance values.

[0004] SUMMARY

[0005] To overcome the defects of the prior art, the application provides a phase change storage material, a phase change device, an array and a programming device, the local structure of the amorphous phase of the phase change material is mainly octahedral, no obvious Pears distortion exists, the phase change device and the array based on the material can overcome the resistance drift problem in the prior art.

[0006] To achieve the above object, the application adopts the technical scheme of:

[0007] A phase change storage material, chemical formula is Cr x Te 100-x , wherein 0 < x < 100; the resistance drift coefficients of the amorphous and crystal thin films of the phase change storage material in the temperature range of-200 to 200 DEG C are all less than or equal to 0.002.

[0008] The crystal phase structure of the phase change storage material has a layered structure, the Cr atoms in the layer form [CrTe6] octahedral local structure with the Te atoms, the Cr is at the center of the octahedron, the Te is at the six vertices of the octahedron, and the octahedra are connected in the form of sharing corners and / or edges; the layers are mainly connected by Van der Waals force.

[0009] Most of the Cr atoms and the Te atoms in the amorphous phase structure of the phase change storage material form [CrTe6] octahedral local structure, a small amount of Cr atoms form defect octahedral local structure, the Cr is at the center of the octahedron, the Te is at the six vertices of the octahedron, and the octahedral local structures and / or the defect octahedral local structures are randomly distributed and connected.

[0010] The local structures of the crystal and the amorphous of the phase change storage material are mainly [CrTe6] octahedra, [CrTe6] has stable Cr-Te chemical bonds, the bond lengths of the Cr-Te bonds in the same direction are basically the same, and no obvious Pears distortion exists.

[0011] The preparation method of the phase change storage material includes but is not limited to magnetron sputtering, chemical vapor deposition, atomic layer deposition or electron beam evaporation.

[0012] The crystallization temperature of the amorphous thin film of the phase change storage material is 250 to 300 DEG C, and the ten-year data retention temperature is 130 to 190 DEG C.

[0013] The amorphous phase of the phase-change storage material is in a high resistance state, and the resistance value at room temperature is usually about 5*10 4 Ω to about 1*10 6 Ω; the crystal phase is in a low resistance state, and the resistance value at room temperature is usually about 1*10 3 Ω to about 5*10 4 Ω; the resistance value varies with the temperature and the thickness of the film.

[0014] The phase-change storage material can be applied to a phase-change memory and a phase-change computing and storage integrated array, and specifically, the phase-change storage material is used as a functional layer material of the phase-change memory or a functional layer material of a device unit in the phase-change computing and storage integrated array.

[0015] The phase-change memory device adopts a limited structure, including a substrate such as SiO2 / Si, a bottom electrode layer, an oxide dielectric layer and a top electrode layer arranged in sequence above the substrate; a phase-change storage material layer is arranged in the oxide dielectric layer and simultaneously contacts the bottom electrode layer and the top electrode layer.

[0016] Alternatively, the phase-change memory device adopts a T-shaped structure, including a substrate such as a SiO2 / Si substrate, a bottom electrode layer, an oxide dielectric layer, a phase-change storage material layer and a top electrode layer arranged in sequence above the substrate, and a heating electrode layer arranged in the oxide dielectric layer, which simultaneously contacts the bottom electrode layer and the phase-change storage material layer.

[0017] Further, the materials of the bottom electrode layer, the top electrode layer and the heating electrode layer are high-conductivity and high-thermal-conductivity materials such as TiN or W, Cr or Cu; the oxide dielectric layer is a low-conductivity and low-thermal-conductivity material such as SiO2; the thicknesses of the bottom electrode layer, the oxide dielectric layer, the phase-change storage material layer, the top electrode layer and the heating electrode layer are between 10 nm and 1000 nm; in the limited structure, the phase-change storage material layer is located in the middle of a through hole of the oxide dielectric layer, the through hole is cylindrical or square column-shaped and is arranged concentrically with the oxide dielectric layer, and the corresponding diameter or side length is between 10 nm and 1000 nm; in the T-shaped structure, the heating electrode layer is arranged in the middle of a through hole of the oxide dielectric layer, the through hole is cylindrical or square column-shaped and is arranged concentrically with the oxide dielectric layer, and the corresponding diameter or side length is between 10 nm and 1000 nm.

[0018] The functional layer material of the device is Cr x Te 100-x material; the SET and RESET reversible operations of the device are realized by loading a current or voltage pulse, which respectively correspond to the crystallization and amorphization processes of the functional layer film; adjusting the amplitude and pulse width of the pulse can realize partial crystallization or partial amorphization of the functional layer film, so as to obtain different resistance values corresponding to different logic states.

[0019] The memory-computing integrated array is one of cross-shaped rod structure, transistor-memristor cascade structure or three-dimensional stacked structure, and the device unit structure in the array is one of limiting structure, T-shaped structure or bridge structure;

[0020] The functional layer material of the device unit in the array is the phase change storage material Cr x Te 100-x The logic state programming of the device unit in the array is realized by loading a current or voltage pulse with a certain amplitude and pulse width, and the process corresponds to partial crystallization or partial amorphization of the functional layer film; the logic state reconfiguration of the device unit in the array can be realized by SET or RESET operation, and the process corresponds to complete crystallization or complete amorphization of the functional layer film;

[0021] The resistance drift coefficients of different logic states of the phase change memory device or the device unit in the memory-computing integrated array are all less than or equal to 0.002 in the temperature range of -200 to 200 DEG C, and the resistance drift coefficient can be evaluated by the formula R=R0(t / t0) v , wherein R0 is the resistance at t0, t is the test time, and v is the resistance drift coefficient.

[0022] The phase change memory programming device of the application comprises a pumping laser system, an electrical test system, a cold-hot temperature control system and a control monitoring software;

[0023] The pumping laser system, the electrical test system, the cold-hot temperature control system and the control monitoring software are cooperatively operated, under the unified coordination of the control monitoring software, the pumping laser system emits laser pulses with specified parameters, cooperates with the displacement platform, and realizes gradual crystallization (SET gradual switching) or gradual amorphization (RESET gradual switching) of the phase change storage material in the specified laser irradiation area and path; when the phase change memory is in the RESET state, the phase change storage film in the device is in an amorphous phase, and the specified area of the film is irradiated with laser pulses with specified parameters to cause gradual crystallization, that is, SET gradual switching; when the phase change memory is in the SET state, the phase change storage film in the device is in a crystalline phase, and the specified area of the film is irradiated with laser pulses with specified parameters to cause gradual amorphization, that is, RESET gradual switching; the above two operations can be transformed into each other at any time.

[0024] At the same time, the cold-hot temperature control system reaches a specified environmental temperature at a certain heating rate and is kept for a certain time, and the electrical test system records the electrical response of the phase change memory under the specified test time in real time, so as to realize the "light control and electrical measurement" programming operation of the phase change memory under a specific environment.

[0025] The pumping laser system is used for adjusting the beam size, power and pulse width parameters of the laser pulse, providing light source for the phase change region and acquiring microscopic images in real time.

[0026] The electrical test system is used for real-time monitoring of the electrical signal response of the phase change memory;

[0027] The cold and hot temperature control system is used for precisely controlling the environmental temperature, temperature change and temperature holding time during programming;

[0028] The control and monitoring software is used for integrating all editable control parameters in the entire programming device, including laser pulse parameters, electrical test parameters, displacement platform parameters and temperature control parameters.

[0029] The pump laser system comprises a laser control and focusing module, an illumination module and a camera module; the laser control and focusing module is used for emitting laser pulses and regulating pulse parameters and laser beam spot size; the illumination module is used for providing a visible light source for the phase change memory, the illumination direction being consistent with the laser illumination direction, and cooperating with the camera module to real-time monitor the microscopic image of the phase change region.

[0030] The laser control and focusing module comprises a signal generator and a laser controller; the laser passes through a polarization maintaining single mode fiber, a laser collimator, an optical path calibration unit, a beam expander, a dichroic mirror and an objective lens in sequence after being emitted by a laser generator;

[0031] The output ends of the signal generator and the laser controller are connected to the input end of the laser generator, wherein the signal generator is used for regulating the waveform, pulse width and amplitude parameters of the laser pulse; the laser controller is used for controlling the opening and closing of the laser; and the laser generator is used for generating a laser beam of a specific waveband;

[0032] The polarization maintaining single mode fiber is used for connecting the laser generator and the laser collimator, wherein the polarization maintaining single mode fiber is used for low-loss laser transmission; and the laser collimator is used for converting the laser transmitted by the polarization maintaining single mode fiber into a collimated spatial light;

[0033] The laser beam output by the laser collimator will pass through the optical path calibration unit, the beam expander, the dichroic mirror and the objective lens in sequence; wherein the optical path calibration unit is used for adjusting the laser direction to ensure that the laser is vertically incident to the surface of the functional layer film; the beam expander adopts a double-convex lens imaging to adjust the laser beam spot size before being incident to the objective lens; the dichroic mirror is used for reflecting more than about 85% of the laser output from the beam expander to the objective lens; and the objective lens is used for focusing the laser beam into the phase change memory; the illumination module comprises a fourth convex lens, a beam splitter, a dichroic mirror and an objective lens which are arranged in sequence from the LED light source;

[0034] The LED light source provides LED illumination light, which is used to provide the illumination light source required for microscopic observation. The illumination point light source output from the LED light source is first transmitted into the convex lens to diverge the illumination point light source into parallel light. The beam splitter is located between the convex lens and the dichroic mirror. The beam splitter reflects the parallel light into the dichroic mirror on one hand, and transmits the reflected light generated from the phase change memory to the camera on the other hand. The dichroic mirror allows the illumination light to be transmitted to the objective lens. The objective lens is used to focus the illumination parallel light to the phase change memory.

[0035] The camera module comprises, in sequence from the reflected light of the phase change memory, an objective lens, a dichroic mirror, a beam splitter, a third convex lens and a CMOS camera.

[0036] The electrical test system comprises a source table and a probe. The source table provides voltage and current measurement sources for the phase change memory, and records the resistance values and current values of the response signals before and after laser programming. The probe is used to connect the sample and the source table. The electrical test system can measure the electrical response of the phase change memory in real time, and can also be coupled with a time parameter to test the electrical response within a certain time range before and after laser programming.

[0037] The cold and hot temperature control system comprises a temperature controller and a temperature control probe station. The temperature controller is used to accurately control the environmental temperature, and set a constant temperature or a real-time variable temperature environment for programming.

[0038] The temperature control probe station is used to connect the probe for electrical response testing, and is connected with the temperature controller for environmental temperature and variable temperature rate control. High temperature can be realized by a heater, and low temperature can be realized by liquid nitrogen or liquid helium. The probe station can simultaneously introduce different gas atmospheres, including air, nitrogen, argon, oxygen, vacuum atmosphere, etc.

[0039] The control and monitoring software comprises a laser control module, a signal generator control module, a displacement platform control module, a temperature control probe station control module, an electrical performance monitoring module and a camera monitoring module.

[0040] The laser control module controls the switching and power size of the laser. The signal generator control module controls the signal generator to emit pulses, and sets parameters such as waveform, pulse width and amplitude. The displacement platform control module is used to adjust the relative position of the phase change memory and the laser, control the irradiation path and area of the laser, and realize single-step displacement at a set distance and continuous displacement at a set speed by controlling the displacement platform to move in the X, Y and Z directions with high precision. The temperature control probe station control module is used to adjust the set temperature and variable temperature speed parameters of the temperature controller. The electrical performance monitoring module is used to record the resistance value response of the device unit during switching, including resistance-temperature curve, resistance-time curve, voltage-current characteristic curve, voltage-current curve, etc., and can adjust the test time in real time. The camera monitoring module can monitor and record the microscopic image of the device unit in real time.

[0041] The phase-change memory programming device of this invention achieves precise programming of a quantitative volume and specific region of the phase-change material in the phase-change memory by adjusting the beam size, irradiation area, and irradiation path of a laser. It quantitatively changes the crystal-to-amorphous volume ratio of the effective phase-change region, thereby testing different resistance values ​​and corresponding different logic states of the device. The programming process includes gradually crystallizing the amorphous region (SET step-by-step switching) or gradually amorphizing the crystalline region (RESET step-by-step switching), corresponding to changes in the crystal-to-amorphous volume ratio from 0% to 100% and from 100% to 0%, respectively, obtaining linearly continuous and symmetrically changing resistance value programming results. By changing the switching time and switching volume of the step-by-step crystallization or amorphization, the step size and slope of the linear change in resistance value can be quantitatively controlled, thereby controlling the number of identifiable logic states within the programmed phase-change memory cell.

[0042] The beneficial effects of this invention are:

[0043] Traditional phase change material germanium-antimony-tellurium (CHT) contains numerous germanium tetrahedral defects in its amorphous structure, and the bond lengths of chemical bonds along the same direction vary in local structures, forming long and short bonds. During structural relaxation, significant Pell's distortion occurs, leading to substantial resistivity drift; the drift coefficient of amorphous CHT is approximately 0.11. This invention proposes a Cr... x Te 100-x The phase change material does not contain germanium, and both the local structural units in the amorphous phase and the crystalline phase are dominated by [CrTe6] octahedra, exhibiting no significant Pellère distortion. This effectively decouples the direct relationship between structural relaxation and resistance drift, resulting in a drift coefficient of ≤0.002 for the amorphous thin film. Furthermore, Cr... x Te 100-x The crystallization temperature of its amorphous thin film can reach 250-300℃, which is much higher than that of germanium, antimony and tellurium, which is about 150℃. Therefore, its amorphous phase has excellent thermal stability, and the resistivity drift coefficient is ≤0.002 in the temperature range of -200 to 200℃.

[0044] Phase-change memory and in-memory computing arrays achieve multi-logic-state programming by adjusting the volume ratio of crystalline to amorphous materials in the functional layer thin film. However, the resistance drift of the amorphous material can lead to logic-state decoding errors. The device and array proposed in this invention utilize ultra-low resistance drift Cr... x Te 100-x As a functional layer material, the resistance drift coefficient of different logic states of the device unit is ≤0.002 in the temperature range of -200 to 200℃, effectively improving the programming and read / write accuracy over a wide temperature range. Furthermore, the aforementioned phase-change material, device, and array are compatible with existing CMOS processes. This invention is expected to expand the storage density of phase-change devices and the array scale of in-memory computing, and is easily implemented in engineering integration and fabrication.

[0045] The programming device provided by the application is a light-controlled electrical measurement mode, the volume of the material which undergoes phase change can be precisely controlled by adjusting the beam spot size and the irradiation area of the laser, so that the volume ratio (0%~100%) of the crystal and the amorphous in the programmed device unit can be quantitatively programmed, and linear continuous resistance value programming is realized; the programmed area can be precisely positioned and erased by controlling the laser pulse, so that the volume ratio (100%~0%) of the crystal and the amorphous corresponding to the previous switching process can be obtained, and the symmetrically changed resistance value programming is realized; by jointly adjusting the effective phase change region size and various laser parameters, the step and slope of the linear change of the volume ratio of the crystal and the amorphous can be controlled, and the controllable programming of the number of identifiable logic states in a single phase change memory unit is realized.

[0046] The programming device provided by the application couples physical parameters such as optics, electricity, temperature and time, and can effectively test the performance indicators of the phase change device unit under multiple physical fields, so as to provide reliable evaluation basis for performance preview of the device and array. The various systems and modules are interconnected through software, and automatic programming test can be performed. The device has good compatibility, and new functions and modules can be further developed and expanded according to the programming test requirements. BRIEF DESCRIPTION OF DRAWINGS

[0047] Fig. 1 is a crystal structure atomic model of Cr x Te 100-x .

[0048] Fig. 2 is an amorphous structure atomic model of Cr x Te 100-x .

[0049] Fig. 3 is a resistance-temperature curve of Cr x Te 100-x phase change film.

[0050] Fig. 4 is a resistance drift curve of Cr x Te 100-x phase change film measured at different temperatures.

[0051] Fig. 5 is a ten-year data retention temperature test of Cr x Te 100-x phase change film.

[0052] Fig. 6 is a cross-sectional schematic view of a Cr x Te 100-x limited electronic device unit.

[0053] Fig. 7 is a cross-sectional schematic view of a Cr x Te 100-x T-shaped electronic device unit.

[0054] Fig. 8 is a schematic view of a Cr x Te 100-x phase change device array.

[0055] Figure 9 is a schematic diagram of the photoelectric temperature coupling test device.

[0056] Figure 10 is a partial schematic diagram of the gradual switching of phase change materials in the laser pulse induced device unit. Detailed Implementation

[0057] The present invention will now be described in further detail with reference to the accompanying drawings.

[0058] Figure 1 shows Cr x Te 100-x The crystal atomic model shows that the basic unit of local structure is the [CrTe6] octahedron, and the crystal is composed of multiple [CrTe6] octahedrons connected by sharing corners and edges. The bond lengths of Cr-Te bonds along the same direction are basically the same, and there is no obvious Pell's distortion.

[0059] Figure 2 shows Cr x Te 100-x The amorphous atomic model shows that most Cr and Te form a local [CrTe6] octahedral structure, with the bond lengths of Cr-Te bonds being basically the same along the same direction, and there is no obvious Pearce distortion.

[0060] Figure 3 shows Cr x Te 100-x The resistance-temperature curve of the thin film is shown. The thin film was prepared by magnetron sputtering. The deposited state is low-resistivity. When heated to about 270°C, the resistance increases sharply, at which point the film begins to crystallize. After heating to 350°C, it was naturally cooled to room temperature. The resistance values ​​of crystalline and amorphous films differ by about an order of magnitude, with crystalline films exhibiting a high-resistivity state.

[0061] Figure 4 shows Cr x Te 100-x The resistance drift curves of the deposited thin film at multiple temperatures are used to monitor the change in resistance of the deposited thin film over time (resistance–time). The drift coefficient of the film is ≤0.002 in the range of -150 to 150 °C.

[0062] Figure 5 shows Cr x Te 100-x The ten-year data retention temperature profile of the thin film was obtained by performing resistance-time tests at four known temperatures below the crystallization temperature. The relationship between resistance failure time and temperature was derived, where resistance failure time refers to the time required for the resistance value to decrease to half its initial value when held at a constant temperature. Fitting the resistance failure time and temperature to the Arrhenius equation yielded a ten-year data retention temperature of approximately 162℃ for the thin film.

[0063] Figure 6 shows Cr x Te 100-xA cross-sectional schematic diagram of a confined device unit. The substrate is a SiO2 / Si substrate. Above the substrate, there are, in sequence, a bottom electrode layer 101, an oxide dielectric layer 102, a phase change storage material layer 103, and a top electrode layer 104. The bottom electrode layer and the top electrode layer are typically made of high electrical and thermal conductivity materials such as TiN, W, Cr, and Cu; the oxide dielectric layer is typically made of low electrical and thermal conductivity materials such as SiO2.

[0064] Figure 7 shows Cr x Te 100-x The diagram shows a cross-sectional view of a T-type device unit. The substrate is a SiO2 / Si substrate. Above the substrate, in sequence, are a bottom electrode layer 101, an oxide dielectric layer 102, a heating electrode layer 105, a phase change storage material layer 103, and a top electrode layer 104. The bottom electrode layer, top electrode layer, and heating electrode layer are typically made of high electrical and thermal conductivity materials such as TiN, W, Cr, and Cu; the oxide dielectric layer is typically made of low electrical and thermal conductivity materials such as SiO2.

[0065] Figure 8 shows Cr x Te 100-x This is a schematic diagram of a memory-computing array. The top and bottom electrodes of the device cells are arranged in a cross pattern, forming word lines, bit lines, and source lines. The array size can be expanded in a plane. "Memory" refers to storing data in the device array as resistance values ​​through write operations. "Computation" refers to matrix-vector multiplication: voltage is the input quantity, and according to Ohm's law and Kirchhoff's laws, the output current value is the calculation result. x Te 100-x With wide temperature range and low drift characteristics, its array can realize high-precision in-memory computing applications.

[0066] Figure 9 is a schematic diagram of the photoelectric-temperature-time coupling test device. The device includes a pump laser system, an electrical testing system, a thermal control system, and control and monitoring software.

[0067] The pumped laser system includes a laser control and focusing module, an illumination module, a camera module, and a displacement platform, used to emit laser signals to manipulate the phase change materials in the device for switching. The laser control and focusing module includes a signal generator 1, a laser controller 2, a laser 3, a polarization-maintaining single-mode fiber 4, a laser collimator 5, an optical path calibration unit 6, a first reflecting mirror 61, a second reflecting mirror 62, a beam expander 7, a first convex lens 71, a second convex lens 72, a dichroic mirror 13, and an objective lens 14; the illumination module includes an LED light source 12, a fourth convex lens 11, a beam splitter 10, a dichroic mirror 13, and an objective lens 14; the camera module includes a camera 8, a third convex lens 9, a beam splitter 10, a dichroic mirror 13, and an objective lens 14; the displacement platform includes an XYZ axis displacement platform 18 and an XY axis displacement platform 19.

[0068] The electrical testing system includes probe 16 and source meter 20.

[0069] The cold and hot temperature control system comprises a temperature control probe table 17 and a temperature controller 21.

[0070] The control monitoring software relies on a computer 22 to realize the control and signal monitoring of the test device, including a laser control module, a signal generator control module, a displacement platform control module, a temperature control probe table control module, an electrical performance monitoring module, and a camera monitoring module. Through the linkage of the software to each system and module, automatic programming and real-time recording of electrical response are realized.

[0071] FIG. 10 is a partial schematic view of the gradual switching of the phase change material in the laser pulse-induced device unit. The box area is the effective phase change area, the circular area is the area that undergoes phase change after laser irradiation, and the remaining area in the box is the area that has not been irradiated by laser (no phase change).

[0072] The application will be further described below with specific examples.

[0073] Example 1

[0074] In this example, Cr 30 Te 70 The specific process is as follows:

[0075] A phase change film of the chemical formula Cr 30 Te 70 was prepared by double-target co-sputtering of Cr elemental target and Te elemental target. The sputtering of the Cr elemental target used a direct current power supply with a power of 20 W, and the sputtering of the Te elemental target used a radio frequency power supply with a power of 37 W. The sputtering time was 20 minutes, and the film thickness was about 200 nm. Subsequently, a protective layer with a thickness of about 10 nm was uniformly sputtered on the surface of the film using a ZnS-SiO2 target to avoid damage to the film during subsequent testing.

[0076] A digital source meter and an in-situ cold and hot table were used to test the resistance-temperature of the film. The resistance test was obtained by using a digital source meter to load voltage and test current, and the test voltage was 0.1 V. The temperature was controlled by using an in-situ cold and hot table, and the heating rate was set to 10℃ / min. The film was heated to 350℃ and then cooled to room temperature at a cooling rate of 20℃ / min. The measured resistance-temperature curve is shown in FIG. 3, and it can be seen that the crystallization temperature of the film is about 270℃, and the resistance values of the deposited state and the annealed state are about 8×10 3 Ω and about 9×10 4Ω, the resistance value is inversely changed during the crystallization process. Then, the same batch of thin films is used for ten-year data retention test, resistance-time test is carried out at 245℃, 250℃, 255℃ and 260℃ respectively, and whether the resistance fails is judged by taking 50% resistance change as the standard, and the ten-year data retention of the thin film is obtained by using the Arrhenius formula to fit, which is about 162℃.

[0077] Example 2

[0078] In this embodiment, Cr 30 Te 70 The preparation and electrical performance test of the confined phase change memory cell and the integrated array of storage and calculation are taken as an example, and the specific process is as follows:

[0079] The phase change memory cell is prepared on a substrate (SiO2 / Si, the thickness of SiO2 is about 300nm), which includes a bottom electrode layer (W, the thickness is about 200nm), a dielectric layer (SiO2, the thickness is about 100nm), a functional layer (Cr 30 Te 70 , the thickness is about 50nm) and a top electrode layer (W, the thickness is about 200nm), as shown in FIG. 6. Each layer is deposited by using a magnetron sputtering method, wherein W uses a direct current power source with a power of 80W; SiO2 uses a radio frequency power source with a power of 50W; Cr 30 Te 70 Cr target and Te target are used for co-sputtering, wherein Cr uses a direct current power source with a power of 20W, and Te uses a radio frequency power source with a power of 37W. The integrated array of storage and calculation is connected with each other by word lines, bit lines and source lines between devices, as shown in FIG. 8.

[0080] An electrical performance test of the above device unit is carried out by using an electrical test probe station, a digital source meter and a pulse signal generator. The resistance value of the initial state device unit is about 2×10 3 Ω, the resistance value of the device is changed to about 3×10 5 Ω by SET operation through direct current test; then, the resistance value of the device is changed to about 2×10 3 Ω by RESET operation of the device unit by loading an electrical pulse with a pulse width of 80ns and a voltage of 4.5V; the resistance value of the device is changed to about 3×10 4 Ω by partial SET operation under the RESET state by loading an electrical pulse with a pulse width of 80ns and a voltage of 2.7V, which is the first intermediate resistance state; the resistance value of the device is changed to about 7×10 4 Ω by partial RESET operation under the SET state by loading an electrical pulse with a pulse width of 80ns and a voltage of 4V, which is the second intermediate resistance state.

[0081] The SET state, RESET state and two intermediate resistance states are measured by using the electrical probe station and digital source meter at room temperature, 200℃ and -200℃, respectively, and the duration is 1 hour, and the resistance drift coefficients of the four resistance states at different temperatures are calculated to be less than or equal to 0.002.

[0082] Example 3

[0083] In this embodiment, a germanium-antimony-tellurium bridge structure phase change memory is prepared, and a single device multi-resistance state programming is taken as an example by using the device provided by the application, and the specific process is as follows:

[0084] The effective phase change region in the germanium-antimony-tellurium bridge structure phase change memory has a length of 20 μm, a width of 10 μm and a thickness of 80 nm. The control and monitoring software of the computer 22 is started to ensure that each system is connected normally. The germanium-antimony-tellurium phase change memory is placed on the temperature-controlled probe station 17, and the probe 16 is connected to the device electrode. The source meter is turned on to test the resistance of the sample preliminarily, and it is ensured that the probe and the sample are in good contact. According to the sample micrograph, the XYZ axis displacement platform 18 is adjusted roughly to move the sample to the center of the field of view and focus clearly, and the laser is focused to the smallest spot. The X and Y axes of the XY axis displacement platform 19 are finely adjusted to make the position of the effective phase change region of the device that needs to be irradiated by the laser fall on the position of the laser spot. The temperature controller 21 is adjusted and set, and the temperature is raised to 100℃ at a rate of 10℃ / min, and the holding time is 200 minutes. When the temperature is stable at 100℃, the initial amorphous resistance value and IV curve of the device are collected by using the source meter. Then, the pulse laser parameters are set, the beam spot size is about 1 μm, the power is 80 mW, and the pulse width is 200 ns. The laser irradiates the effective phase change region point by point in a horizontal displacement from right to left, and the irradiated region is crystallized to form a crystal phase. After each point is irradiated by the laser, the resistance value and IV curve of the device are collected by using the source meter, the resistance value is collected for 10 seconds, and the IV curve is tested for 20 seconds. During the test process, the resistance value of the device increases linearly, and 64 different resistance logic states are obtained. Then, the pulse laser parameters are reset, the pulse width is 50 ns, the power is 120 mW, the beam spot size after irradiation is about 1 μm, and the laser irradiates the effective phase change region point by point in the same track. The irradiated region is amorphized to form an amorphous phase. After each point is irradiated by the laser, the resistance value and IV curve of the device are collected by using the source meter, the resistance value is collected for 10 seconds, and the IV curve is tested for 20 seconds. During the test process, the resistance value of the device decreases linearly, and about 64 different resistance logic states are obtained, and the resistance value of each logic state substantially corresponds to the resistance value in the crystallization process.

Claims

1. A phase change memory material having the chemical formula CrxTei-x x where 0 < x < 100. 100-x where 0 < x < 100. The resistance drift coefficient of the amorphous and crystal thin film of the phase change memory material is less than or equal to 0.002 in the temperature range of -200 to 200 DEG C.

2. The phase change memory material of claim 1, wherein, The crystal phase structure of the phase change memory material has a layered structure, in which Cr atoms and Te atoms form [CrTe6] octahedral local structures, Cr is at the center of the octahedron, and Te is at the six vertices of the octahedron, and each octahedral structure is connected in the form of a common angle and / or a common edge; the layers are connected by Van der Waals force. In the amorphous phase structure of the phase change memory material, part of the Cr atoms and Te atoms form [CrTe6] octahedral local structures, Cr is at the center of the octahedron, and Te is at the six vertices of the octahedron, and the remaining Cr atoms form defective octahedral local structures, and each octahedral local structure and / or defective octahedral local structure is randomly connected.

3. The phase change memory material of claim 1, wherein, The local structures of the crystal and amorphous of the phase change memory material are mainly [CrTe6] octahedrons.

4. The phase change storage material of claim 1, wherein, The crystallization temperature of the amorphous thin film of the phase change memory material is 250 to 300 DEG C, and the ten-year data retention temperature is 130 to 190 DEG C.

5. The phase change memory material of claim 1, wherein, The amorphous phase of the phase change memory material is in a high resistance state, with a resistance value of 5 x 10 4 Ω at room temperature. 6 The crystalline phase is in a low resistance state, with a resistance value of 1 x 10 3 Ω at room temperature. 4 Ω.

6. A phase change memory, characterized by, The phase change memory material layer (103) is the phase change memory material according to any one of claims 1 to 5.

7. The phase change memory of claim 6, wherein, The phase change memory is a limited structure, including a substrate, a bottom electrode layer (101), an oxide dielectric layer (102), and a top electrode layer (104) in sequence above the substrate, and a phase change memory material layer (103) arranged in the oxide dielectric layer (102) and simultaneously contacting the bottom electrode layer (101) and the top electrode layer (104). Alternatively, The phase change memory is a T-shaped structure, including a substrate, a bottom electrode layer (101), an oxide dielectric layer (102), a phase change memory material layer (103), and a top electrode layer (104) in sequence above the substrate, and a heating electrode layer (105) arranged in the oxide dielectric layer (102), the heating electrode layer (105) simultaneously contacting the bottom electrode layer (101) and the phase change memory material layer (103).

8. The phase change memory of claim 7, wherein, The thicknesses of the bottom electrode layer (101), the oxide dielectric layer (102), the phase change memory material layer (103), the top electrode layer (104), and the heating electrode layer (105) are between 10 nm and 1000 nm. When the phase change memory is a limited structure, the phase change memory material layer (103) is located in the middle of the through hole of the oxide dielectric layer (102), the through hole is cylindrical or square column-shaped, and is concentrically arranged with the oxide dielectric layer (102), and the corresponding diameter or side length is between 10 nm and 1000 nm. When the phase change memory is a T-shaped structure, the heating electrode layer (105) is arranged in the middle of the through hole of the oxide dielectric layer (102), the through hole is cylindrical or square column-shaped, and is concentrically arranged with the oxide dielectric layer (102), and the corresponding diameter or side length is between 10 nm and 1000 nm.

9. The phase change memory of claim 6, wherein, The SET and RESET reversible operations of the device are realized by loading current or voltage pulse, corresponding to the crystallization and amorphization process of the phase change memory material layer film respectively; the partial crystallization or partial amorphization of the functional layer film is realized by adjusting the amplitude and pulse width of the pulse, and different resistance values corresponding to different logic states are obtained.

10. An opto-electrothermal time-coupled phase change memory programming device, comprising: The system comprises a pumping laser system, an electrical testing system, a cold and hot temperature control system, and a control monitoring software. The pumping laser system, the electrical testing system, the cold and hot temperature control system, and the control monitoring software are cooperatively operated, and under the unified coordination of the control monitoring software, the pumping laser system emits laser pulses with specified parameters, cooperates with the displacement platform, and realizes the gradual crystallization or gradual amorphization of the phase change memory material under the specified laser irradiation area and path. When the phase change memory is in the RESET state, the phase change memory film in the device is in the amorphous phase, and the specified area of the film is irradiated with laser pulses with specified parameters to cause gradual crystallization, i.e., SET gradual switching; when the phase change memory is in the SET state, the phase change memory film in the device is in the crystal phase, and the specified area of the film is irradiated with laser pulses with specified parameters to cause gradual amorphization, i.e., RESET gradual switching; the above two operations can be transformed into each other at any time. At the same time, the cold and hot temperature control system reaches a specified environmental temperature at a certain heating rate and performs a certain length of time for heat preservation, and the electrical testing system records the electrical response of the phase change memory under the specified test time, thereby realizing the "light control and electrical measurement" programming operation of the phase change memory under a specific environment.

11. The opto-thermal time-coupled phase change memory programming device of claim 10, wherein, The pumping laser system is used for adjusting the beam size, power, and pulse width parameters of the laser pulse, and providing light source for the phase change region and obtaining micro images in real time. The electrical testing system is used for real-time monitoring of the electrical signal response of the phase change memory (15). The cold and hot temperature control system is used for accurately controlling the environmental temperature during programming and the temperature change and heat preservation time parameters. The control monitoring software is used for integrating all editable control parameters in the entire programming device, including laser pulse parameters, electrical testing parameters, displacement platform parameters, and temperature control parameters.

12. The opto-thermal time-coupled phase change memory programming device of claim 10, wherein, The pumping laser system comprises a laser control and focusing module, an illumination module, and a camera module; the laser control and focusing module is used for emitting laser pulses and adjusting pulse parameters and laser beam size; the illumination module is used for providing visible light source for the phase change memory (15), and the irradiation direction is consistent with the laser irradiation direction, and cooperates with the camera module to monitor the microscopic image of the phase change region in real time.

13. The opto-thermal time-coupled phase change memory programming device of claim 10, wherein, The laser control and focusing module comprises a signal generator (1), a laser controller (2), a laser (3), a polarization maintaining single mode fiber (4), a laser collimator (5), an optical path calibration unit (6), a beam expanding unit (7), a dichroic mirror (13), and an objective lens (14). The signal generator (1) and the output end of the laser controller (2) are connected with the input end of the laser (3), wherein the signal generator (1) is used for regulating the waveform, pulse width and amplitude parameters of the laser pulse; the laser controller (2) is used for controlling the opening and closing of the laser; and the laser (3) is used for generating laser beams of specific wave bands; The polarization maintaining single mode fiber (4) is used for connecting the laser (3) and the laser collimator (5), wherein the polarization maintaining single mode fiber (4) is used for low-loss laser transmission; and the laser collimator (5) is used for converting the laser transmitted by the polarization maintaining single mode fiber into collimated spatial light; The laser beam output by the laser collimator (5) will pass through the optical path calibration unit (6), the beam expanding unit (7), the dichroic mirror (13) and the objective lens (14) in sequence; wherein the optical path calibration unit (6) is used for adjusting the direction of the laser to ensure that the laser is finally vertically incident on the sample surface; the beam expanding unit (7) adopts double-convex lens imaging and is used for adjusting the spot size of the laser beam before being incident on the objective lens; the dichroic mirror (8) is used for reflecting more than about 85% of the laser output from the beam expanding unit (7) to the objective lens (9); and the objective lens (9) is used for finally focusing the laser beam into the phase change memory (15); the illumination module comprises a fourth convex lens (11), a beam splitter (10), a dichroic mirror (13) and an objective lens (14) arranged in sequence from the LED light source (12); The LED light source (12) provides LED illumination light, which is used for providing an illumination light source for microscopic observation of the sample; the illumination point light source output from the LED light source (12) is first transmitted into the convex lens (11) to diverge the illumination point light source into parallel light; the beam splitter (10) is located between the convex lens (11) and the dichroic mirror (13), wherein the beam splitter (10) reflects the parallel light to the dichroic mirror (13) on one hand and transmits the reflected light generated from the phase change memory (15) to the camera module on the other hand; the dichroic mirror (13) allows the illumination light to be transmitted to the objective lens (14); and the objective lens (14) is used for focusing the illumination parallel light to the phase change memory (15); The camera module comprises an objective lens (14), a dichroic mirror (13), a beam splitter (10), a third convex lens (9) and a CMOS camera (8) arranged in sequence from the reflected light of the phase change memory (15). The electrical test system comprises a source table (20) and a probe (16), wherein the source table (20) provides a voltage and current measurement source for the phase change memory (15), records the electrical response signals of the phase change memory (15) before and after laser programming, and the probe (16) is used for connecting the sample and the source table (20); the electrical test system can measure the electrical response of the phase change memory (15) in real time, can also be coupled with a time parameter, and can test the electrical response of the phase change memory (15) within a certain time range before and after laser programming; 14. The opto-thermal time-coupled phase change memory programming device of claim 13, wherein, The cold and hot temperature control system comprises a temperature controller (21) and a temperature control probe table (17), wherein the temperature controller (21) is used for accurately regulating the environmental temperature of programming, and sets a constant temperature for testing or a real-time variable temperature for testing. ​ The temperature-controlled probe station (17) is used for connecting the test probe (16) to perform the electrical response test, and is connected with the temperature controller (21) to perform the temperature regulation and the temperature variation rate regulation of the test environment. The high-temperature environment can be realized by the heater, the low-temperature environment can be realized by means of liquid nitrogen or liquid helium, the probe station (17) can simultaneously introduce different gas atmospheres according to the test environment requirements, including but not limited to air, nitrogen, argon, oxygen, vacuum atmosphere.

15. The opto-thermal time-coupled phase change memory programming device of claim 14, wherein, The control monitoring software comprises a laser control module, a signal generator control module, a displacement platform control module, a temperature-controlled probe station control module, an electrical performance monitoring module and a camera monitoring module. The laser control module controls the switching and power size of the laser; the signal generator control module controls the signal generator (1) to emit pulses and performs parameter setting of the waveform, pulse width and amplitude; the displacement platform control module is used for adjusting the relative position of the phase change memory (15) and the laser, thereby controlling the irradiation path and area of the laser; the displacement platform is controlled in the X, Y and Z axis directions to perform high-precision displacement, thereby realizing single-step displacement at a set distance and continuous displacement at a set speed; the temperature-controlled probe station control module is used for regulating the set temperature and the temperature variation speed parameters of the temperature controller (21); the electrical performance monitoring module is used for monitoring the electrical response of the device unit in the SET / RESET step-by-step switching process, including the resistance-temperature curve, the resistance-time curve, the volt-ampere characteristic curve and the voltage-current curve; and the camera monitoring module is used for monitoring the microscopic image of the device unit in real time.

Images