Aluminum nitride doped scandium ferroelectric film memristor and preparation method thereof

Abstract

The invention provides an aluminum nitride doped scandium ferroelectric film memristor and a preparation method thereof. The memristor structurally comprises a Si substrate, a Pt bottom electrode layer, an Al < 0.84 > Sc < 0.16 > N functional layer and a Pt top electrode layer from bottom to top. The preparation method of the memristor comprises the following steps: preprocessing the Si substrate; forming a Pt bottom electrode layer on the Si substrate by adopting a direct current magnetron sputtering method; forming an Al < 0.84 > Sc < 0.16 > N functional layer on the Pt bottom electrode layer by sputtering an aluminum-scandium alloy target material in a nitrogen atmosphere by adopting a direct-current magnetron sputtering method; and forming a Pt top electrode layer on the Al < 0.84 > Sc < 0.16 > N functional layer by adopting a direct current magnetron sputtering method. The prepared aluminum nitride doped scandium ferroelectric film memristor has excellent ferroelectric characteristics, the resistance value stability is outstanding in the resistance state conversion process, the high / low resistance state shows reliable durability in a cycle test, the working current can be stably maintained at a submicroampere level, the operation power consumption is low, the remanent polarization is very high, and the performance of the memristor is greatly improved. The ferroelectric memristor is more prominent in storage performance, high in durability and wider in application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of memristors, and in particular to a scandium-doped aluminum nitride ferroelectric thin film memristor and a preparation method thereof. Background Art

[0002] The von Neumann architecture can no longer support the rapid improvement of chip computing power. Inspired by the high interconnectivity and efficiency of biological neural networks, neuromorphic computing has emerged. This mode has great advantages in traditional data processing, storage, etc., and is expected to solve this problem. A memristor is a component required to implement such a mode, so it shows significant application prospects in the field of storage technology. A memristor is a non-linear element with the ability to remember resistance and is also one of the basic circuit components, proposed by Professor Leon O. Chua in 1971. In 2008, the journal "Nature" published a study by HP Labs. The Pt / TiO2 / Pt three-layer structure they discovered marked the birth of the memristor model. This has triggered extensive research on memristors, which are mainly applied in fields such as artificial synaptic devices and neuromorphic computing. Among the candidate materials for memristors, ferroelectric materials have received attention due to the regulation of their polarization state by an electric field, fast switching speed, and strong stability. A ferroelectric memristor is to introduce a ferroelectric material into the memristor structure as a dielectric layer. Under the action of an external electric field, the central atom of the ferroelectric material can cross the potential barrier and migrate between different internal regions. The ferroelectric material undergoes polarization reversal and is set to the polarization state "1"; when a reverse electric field is applied, the ferroelectric material undergoes polarization reversal in the opposite direction and is set to the polarization state "0", so that the data storage function can be realized relying on this characteristic. The combination of this ferroelectric material and the memristor has both non-volatility of storing information and fast response ability, and can be applied to high-performance electronic synaptic devices and neuromorphic computing and other fields. However, in the prior art, ferroelectric memristors based on hafnium-based (such as HfO2) have problems such as insufficient ferroelectric phase stability, poor compatibility between high-temperature processes and CMOS production lines, and the device resistance state switching durability and energy efficiency are difficult to meet the hardware requirements of neuromorphic computing. The wurtzite-structured group III nitride AlScN has a more stable ferroelectric phase compared with hafnium-based ferroelectric materials, and its unique low-temperature preparation characteristic (<400 °C) ensures good compatibility with complementary metal oxide semiconductor processes. This advantage opens up new possibilities for the application of AlScN materials in storage devices. Summary of the Invention

[0003] The purpose of the present invention is to provide a scandium-doped aluminum nitride ferroelectric thin film memristor and a preparation method thereof, so as to provide a memristor that can be prepared at low temperature and has excellent storage performance.

[0004] The present invention is implemented as follows: A scandium-doped aluminum nitride ferroelectric thin film memristor is provided, specifically, a Pt bottom electrode layer, Al 0.84 Sc 0.16 N functional layer, and a Pt top electrode layer are sequentially formed on an Si substrate; the Al 0.84 Sc 0.16 N functional layer is obtained by magnetron sputtering an aluminum scandium alloy target in a nitrogen atmosphere.

[0005] Furthermore, the thickness of the Al 0.84 Sc 0.16 N functional layer is 42 nm; the thickness of the Pt bottom electrode layer is 60 nm; the thickness of the Pt top electrode layer is 20 nm.

[0006] The present invention also provides a preparation method for a scandium-doped aluminum nitride ferroelectric thin film memristor, including the following steps:

[0007] (1) Pretreat the Si substrate;

[0008] (2) Form a Pt bottom electrode layer on the Si substrate by DC magnetron sputtering;

[0009] (3) Form an Al 0.84 Sc 0.16 N functional layer on the Pt bottom electrode layer by sputtering an aluminum scandium alloy target in a nitrogen atmosphere by DC magnetron sputtering;

[0010] (4) Form a Pt top electrode layer on the Al 0.84 Sc 0.16 N functional layer by DC magnetron sputtering.

[0011] Furthermore, step (1) is specifically: ultrasonically clean the Si substrate in acetone, absolute ethanol, and deionized water in sequence, then put the Si substrate into a diluted hydrofluoric acid solution for cleaning for 30 s, then clean with deionized water, and finally dry the substrate with nitrogen.

[0012] Furthermore, step (2) is specifically: fix the Si substrate to the sample stage, fix the Pt target to the DC target stage, evacuate the cavity to below 1.5×10 -4 Pa, introduce argon into the cavity to maintain the pressure in the cavity at 3 Pa, and perform sputtering to form a Pt bottom electrode layer.

[0013] Furthermore, the sputtering time is 6 min, and the thickness of the Pt bottom electrode layer is 60 nm.

[0014] Furthermore, step (3) is specifically: fix the aluminum scandium alloy target to the DC target stage, fix the Pt bottom electrode layer to the sample stage, evacuate the cavity to 1.5×10 -4Pa, introduce nitrogen gas into the cavity to maintain the pressure in the cavity at 0.3 Pa, raise the temperature of the sample stage, and perform sputtering to form Al on the Pt bottom electrode. 0.84 Sc 0.16 N functional layer.

[0015] Furthermore, the aluminum scandium alloy target is an Al 0.7 Sc 0.3 alloy target.

[0016] Furthermore, in step (3), the sputtering time is 15 min, and the thickness of the Al 0.84 Sc 0.16 N functional layer is 42 nm.

[0017] Furthermore, in step (3), raise the temperature of the sample stage to 350 °C.

[0018] The present invention has the following beneficial effects:

[0019] The ferroelectric memristor preparation process proposed by the present invention is simple and easy to implement. Through performance testing, it is proved that the memristor has excellent ferroelectric characteristics, outstanding resistance stability during the resistance state conversion process, and reliable durability is shown in both the high / low resistance states during the cycle test. The working current of the device can be stably maintained at the sub-microampere level, realizing low operating power consumption. In addition, the ferroelectric memristor prepared by this method has a very high remanent polarization intensity, indicating that it has a good storage window, and it is a ferroelectric memristor with more prominent storage performance, strong durability, and broader application prospects. Description of the Drawings

[0020] Figure 1 is a schematic structural diagram of the memristor provided by the present invention.

[0021] Figure 2 is the EDS spectrum of the Al 0.84 Sc 0.16 N functional layer of the memristor prepared in Example 2 of the present invention.

[0022] Figure 3 is the I-V characteristic curve of the memristor prepared in Example 2 of the present invention.

[0023] Figure 4 is the retention and endurance characteristic results of the memristor prepared in Example 2 of the present invention.

[0024] Figure 5 is the pulse regulation characteristic result of the memristor prepared in Example 2 of the present invention.

[0025] Figure 6 is the PFM test of the ferroelectric characteristics of the memristor prepared in Example 2 of the present invention. Detailed Embodiments

[0026] Example 1

[0027] As Figure 1 shown, the aluminum nitride-doped scandium ferroelectric thin film memristor provided by the present invention has a structure including an Si substrate 1, a Pt bottom electrode layer 2, an Al 0.84 Sc 0.16 N functional layer 3, and a Pt top electrode layer 4, which are sequentially arranged from bottom to top.

[0028] Among them, the thickness of the Pt bottom electrode layer 2 is 60 nm, and the thickness of the Al 0.84 Sc 0.16 N functional layer 3 is 42 nm, and the thickness of the Pt top electrode layer 4 is 20 nm. The preparation process of the Pt top electrode layer 4 is specifically as follows: A number of mask plates are placed on the Al 0.84 Sc 0.16 N functional layer, and sputtering is carried out using a Pt target to form cylindrical electrodes with a diameter of 100 μm uniformly distributed on the Al 0.84 Sc 0.16 N functional layer.

[0029] Example 2

[0030] The preparation method of the memristor based on the aluminum nitride-doped scandium ferroelectric thin film provided by the present invention includes the following steps:

[0031] (1) The Si substrate is ultrasonically cleaned for 10 min to sequentially remove residual grease with acetone solution, residual acetone with absolute ethanol, and ethanol residue with deionized water. Silicon will undergo natural oxidation in the air. Therefore, before use, the oxide layer needs to be removed first. The cleaned Si substrate is placed in a hydrofluoric acid dilution solution (hydrofluoric acid: deionized water = 1:3) and cleaned for 30 s to remove the SiO2 layer on the substrate, then placed in deionized water and cleaned thoroughly to remove the residual hydrofluoric acid dilution solution, and finally the substrate is dried with a high-purity nitrogen gun.

[0032] (2) Preparation of the bottom electrode layer: Using a magnetron sputtering coating system, open the cavity of the magnetron sputtering equipment, take out the tray, polish the impurities on the target table and the tray with sandpaper, then clean the organic matter attached to the surface of the target table and the tray with acetone, and finally wipe it clean with an alcohol cotton ball. Apply silver glue evenly on the tray, and then place the treated Si substrate flatly on the place where the silver glue is applied for bonding to ensure uniform growth of the thin film during sputtering. Place the tray on the sample stage in the cavity and rotate it to fix it, place the Pt metal target on the DC target table and fix it and install the target sleeve, close the cavity, turn on the vacuum mechanical pump and the molecular pump power supply of the equipment, and pump the cavity vacuum to 1.5×10 -4Pa. Then, argon gas is introduced into the cavity as the sputtering gas. The intake valve is adjusted to maintain the pressure in the cavity at 3 Pa. The DC power supply for controlling the ignition of Pt is turned on, and the power of the DC power supply is adjusted to 60 W to ignite the Pt target. Pre-sputtering is carried out for 5 min to clean the impurities on the surface of the target. During the pre-sputtering process, the Si substrate needs to be blocked by a baffle to prevent the formation of an unwanted material film on the substrate. After that, the baffle is opened, and formal sputtering is carried out for 6 min to form a Pt bottom electrode layer with a thickness of 60 nm on the Si substrate.

[0033] (3) Preparation of the functional layer: The atmosphere is introduced through the intake valve. The cavity of the magnetron sputtering equipment is opened, and the target table is taken out and polished with sandpaper to remove impurities. The organic impurities attached to the surface are cleaned with acetone, and then wiped clean with an alcohol cotton ball. The target is replaced, and the Al 0.7 Sc 0.3 alloy target is fixed on the DC target table and the target sleeve is installed. The air pressure in the cavity is evacuated to 1.5×10 -4 Pa. Nitrogen gas is introduced into the cavity through the inflation valve. The DC power supply is turned on, and the power of the DC power supply is adjusted to 100 W to ignite the Al 0.7 Sc 0.3 alloy target. The intake valve is adjusted to maintain the pressure in the cavity at 0.3 Pa. The temperature of the tray is raised to 350 °C. Pre-sputtering is carried out for 5 min. The baffle is opened, and formal sputtering is carried out for 15 min to form a scandium-doped aluminum nitride functional layer with a thickness of 42 nm on the Pt bottom electrode layer.

[0034] (4) Preparation of the top electrode layer: The atmosphere is introduced through the intake valve. The cavity of the magnetron sputtering equipment is opened, and the grown Al 0.84 Sc 0.16 N functional layer is taken out. The organic matter attached to the surface of the mask plate is cleaned with acetone using an ultrasonic cleaner and finally wiped clean with an alcohol cotton ball. The mask plate is pasted on the grown Al 0.84 Sc 0.16 N functional layer. The mask plate is evenly distributed with round holes with a diameter of 50 μm. The circular hole area is the size of the effective working area of the memristor after the sputtering of the electrode layer is completed.

[0035] The target table is taken out and polished with sandpaper to remove impurities, wiped with acetone to remove the organic matter attached to the surface, and finally wiped clean with alcohol. The target is replaced, and the Pt target is fixed on the target table and the target sleeve is installed. The cavity is evacuated to 1.5×10 -4 Pa. Argon gas is introduced into the cavity. The intake valve is adjusted to maintain the pressure in the cavity at 3 Pa. The DC power supply for controlling the ignition of the Pt target is turned on, and the power of the DC power supply is adjusted to 60 W. The Pt target is ignited, and pre-sputtering is carried out for 5 min; then formal sputtering is carried out for 2 min to form a cylindrical Pt top electrode layer with a thickness of 20 nm on the Al 0.84 Sc 0.16 N functional layer.

[0036] For the scandium-doped aluminum nitride ferroelectric thin film memristor prepared by the present invention, the key point is to prepare a scandium-doped aluminum nitride thin film on a Pt bottom electrode layer by using magnetron sputtering technology.

[0037] The above-described embodiments are any one of the preparation methods protected by the present invention. As long as it is within the range of process parameters described in the claims and the specification (such as the bottom electrode layer being metal Pt, the chamber vacuum degree of magnetron sputtering, the DC source power, the pre-sputtering time, and the formal sputtering time, etc.), the memristor to be protected by the embodiments of the present invention can be obtained, and the prepared memristor has basically similar performance to the device prepared in this embodiment.

[0038] Performance Test

[0039] Perform energy dispersive X-ray spectroscopy (EDS) test on the scandium-doped aluminum nitride ferroelectric thin film prepared in Example 2 of this embodiment. The results are shown in Figure 2 . Figure 2 (a) is the elemental surface distribution map, showing the uniform elemental distribution at the film height. Figure 2 (b) shows the EDS analysis results, and the data fitting ratio reaches 98.98%, with high credibility. Through the calculation of the relative elemental content obtained by testing, the Sc doping ratio is 16%. The content of Sc in the film is lower than that in the target. There may be the following reasons: 1) During the sputtering process, the sputtering yields of different elements may be different, and there may be differences in the sputtering efficiencies of Al and Sc, resulting in a higher content of Al in the film than in the target. 2) During the film growth process, Sc elements may be more likely to segregate or diffuse on the surface, thus affecting the final composition. 3) The influence of process parameters Process parameters such as sputtering power, gas pressure, and substrate temperature may affect the composition of the film.

[0040] Perform I-V characteristic curve test on the scandium-doped aluminum nitride ferroelectric thin film memristor prepared in Example 2 of this embodiment. The test data is presented in logarithmic form to more clearly observe the detailed changes in the microcurrent region. The results are shown in Figure 3 . From Figure 3 it can be seen that the I-V curve of the device can maintain stable performance during multiple cycle tests, has a large memory window, and has better storage characteristics.

[0041] Perform durability and retention characteristic tests on the scandium-doped aluminum nitride ferroelectric thin film memristor prepared in Example 2. As Figure 4 shown, the device can stably maintain 10 8 times of durability fatigue tests, as well as the retention characteristics of up to 16 resistance states, demonstrating the potential of the device for multi-level storage applications and long-term operation.

[0042] The scandium-doped aluminum nitride ferroelectric thin film memristor prepared in Example 2 was used to study the biomimetic characteristics of neural synapses. By adjusting the electrical pulse parameters, the change trend of the device conductance value was measured, and it was found that it could precisely regulate the change of the conductance value and had the potential to simulate the plasticity of biological synapses. The pulse amplitude was set to 8 V, the interval and pulse width were 2 μs, and the conductance regulation behaviors with different numbers of pulses (1, 5, 10, 15, 20) were explored, as Figure 5 (a) The results show that the conductance increases with the increase in the number of pulses. Subsequently, as Figure 5 (b) shows, under the conditions of 20 consecutive pulses, 2 μs pulse width and interval, by changing the pulse amplitude (3 V - 10 V), it was found that the conductance increases with the increase in amplitude. As Figure 5 (c) shows, at an amplitude of 8 V and an interval of 2 μs, by adjusting the pulse width (2 μs, 4 μs, 6 μs, and 8 μs), the conductance of the device increases with the increase in pulse width and finally reaches a saturation value. On the contrary, as Figure 5 (d) shows, at an amplitude of 8 V and a pulse width of 2 μs, the conductance decreases with the increase in pulse interval. The above research results fully demonstrate that the scandium-doped aluminum nitride ferroelectric thin film memristor prepared by the present invention can precisely regulate its conductance characteristics by adjusting electrical pulse parameters (including number, amplitude, pulse width, and interval), thereby effectively simulating the plasticity behavior of biological synapses.

[0043] The Al 0.84 Sc 0.16 N functional layer prepared in Example 2 was subjected to piezoelectric testing using a piezoresponse force microscope (PFM). As Figure 6 (a) shows, when a +10 V forward bias voltage was applied to the device, the Al 0.84 Sc 0.16 N thin film underwent downward polarization flipping. After scanning with a -10 V reverse bias voltage, the Al 0.84 Sc 0.16 N thin film underwent upward polarization flipping. Figure 6 (b)'s amplitude and phase hysteresis loop diagram reveals that the scandium-doped aluminum nitride ferroelectric thin film memristor has a low coercive voltage, facilitating the flipping of ferroelectric polarization, and the phase flipping is close to 180°.

[0044] The structural form of the novel high-performance ferroelectric memristor prepared by the present invention can be expressed as Pt / Al 0.84 Sc 0.16 N / Pt / Si, showing typical bipolar non-volatile storage performance. The above Example 2 is a preferred embodiment of the present invention, but the embodiments of the present invention are not limited by the described embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. An aluminum nitride doped scandium ferroelectric thin film memristor, characterized in that: A Pt bottom electrode layer, an Al 0.84 Sc 0.16 N functional layer and Pt top electrode layer; the Al 0.84 Sc 0.16 The N functional layer is prepared by sputtering an aluminum-scandium alloy target in a nitrogen atmosphere through a magnetron sputtering method.

2. The aluminum nitride doped scandium ferroelectric thin film memristor according to claim 1, characterized in that: The Al 0.84 Sc 0.16 The thickness of the N functional layer is 42 nm; the thickness of the Pt bottom electrode layer is 60 nm; and the thickness of the Pt top electrode layer is 20 nm.

3. A method for preparing an aluminum nitride-doped scandium ferroelectric thin film memristor, characterized in that: The following steps are involved: (1) Pretreatment of Si substrate; (2) forming a Pt bottom electrode layer on a Si substrate by using a DC magnetron sputtering method; (3) DC magnetron sputtering was used to form Al on the Pt bottom electrode layer by sputtering an aluminum-scandium alloy target in a nitrogen atmosphere. 0.84 Sc 0.16 N functional layers; (4) DC magnetron sputtering was used to deposit Al 0.84 Sc 0.16 A Pt top electrode layer is formed on the N functional layer.

4. The method for preparing the aluminum nitride doped scandium ferroelectric thin film memristor according to claim 3, characterized in that: Step (1) specifically comprises: ultrasonically cleaning the Si substrate in acetone, anhydrous ethanol and deionized water in sequence, then placing the Si substrate in a hydrofluoric acid dilution solution for cleaning for 30 seconds, then cleaning with deionized water, and finally blowing the substrate dry with nitrogen.

5. The method for preparing the aluminum nitride doped scandium ferroelectric thin film memristor according to claim 3, characterized in that: Step (2) specifically includes: fixing the Si substrate on the sample stage, fixing the Pt target on the DC target stage, and evacuating the chamber to a vacuum of 1.5×10 -4 Pa, argon gas is introduced into the chamber to maintain the pressure in the chamber at 3Pa, and sputtering is performed to form a Pt bottom electrode layer.

6. The method for preparing the aluminum nitride doped scandium ferroelectric thin film memristor according to claim 5, characterized in that: The sputtering time is 6 minutes, and the thickness of the Pt bottom electrode layer is 60 nm.

7. The method for preparing the aluminum nitride doped scandium ferroelectric thin film memristor according to claim 3, characterized in that: Step (3) specifically includes: fixing the aluminum-scandium alloy target on the DC target stage, fixing the Pt bottom electrode layer on the sample stage, and evacuating the chamber to a vacuum of 1.5×10 -4 Pa, nitrogen was introduced into the chamber to maintain the pressure in the chamber at 0.3 Pa, the sample stage temperature was increased, and sputtering was performed to form Al on the Pt bottom electrode. 0.84 Sc 0.16 N functional layers.

8. The method for preparing the aluminum nitride doped scandium ferroelectric thin film memristor according to claim 7, characterized in that: The aluminum-scandium alloy target is Al 0.7 Sc 0.3 Alloy target.

9. The method for preparing the aluminum nitride doped scandium ferroelectric thin film memristor according to claim 7, characterized in that: The sputtering time in step (3) is 15 min, and the Al 0.84 Sc 0.16 The thickness of the N functional layer is 42 nm.

10. The method for preparing the aluminum nitride doped scandium ferroelectric thin film memristor according to claim 8, characterized in that: In step (3), the sample stage temperature is raised to 350°C.

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