A memristor that realizes the shaping and positioning of conductive filament channels

Abstract

The present invention belongs to the technical field of microelectronic devices, and discloses a memristor for realizing the shaping and positioning of a conductive filament channel. The device includes an upper electrode, a functional layer and a lower electrode. The functional layer is based on the same metal oxide memristor material, wherein the oxygen content thereof changes in a gradient, and the oxygen content in the direction from the lower electrode to the upper electrode shows a trend of first increasing and then decreasing. Since the minimum value of the oxygen vacancy concentration appears in the middle of the functional layer, the fracture position of the conductive filament channel in the memristor can be positioned in the middle of the functional layer. The present invention improves the detailed structure and composition of the functional layer of the memristor device, and the obtained memristor can realize the shaping of the conductive filament channel morphology and the positioning of the conductive filament channel on-off position. Compared with the existing memristor structure, it is conducive to realizing low power consumption, high consistency, and multi-resistance state memristor performance, and can effectively solve the problems of the size of the conductive filament of the memristor device and the randomness of the formation position in the prior art.

Description

Technical Field

[0001] The present invention belongs to the technical field of microelectronic devices, and more specifically, relates to a memristor for realizing shaping and positioning of a conductive filament channel. The shaping and positioning of the conductive filament channel can be realized by regulating a multi-layer functional layer structure. Background Art

[0002] Memristors are composed of a "sandwich" structure of upper and lower electrodes and a functional layer. The dielectric functional layer is used as a medium for ion transmission and storage. Different selections of functional layers will introduce different resistance switching mechanisms, and thus have different applications. External voltage or current excitation causes ion movement and structural changes in the functional layer, which in turn causes changes in the device resistance, and further stores data through resistance differences.

[0003] Memristors, as one of the favorable candidates for new non-volatile memory, have never been widely used in actual industrial development. The fundamental reason is the randomness and diversity of their resistance switching mechanism. The formation of conductive filaments is seriously affected by the non-uniformity of the film itself. In the structure of conventional conductive filament-type memristors, the randomness of the size and formation position of the conductive filaments causes the randomness of device performance. The randomly generated conductive filaments are accompanied by the randomness and uncontrollability of the migration of oxygen vacancies or active metal ions, which will cause the overgrowth of the conductive filaments and make the device difficult to reset and thus fail. Therefore, to improve the performance of memristors, it is essentially necessary to control the location, quantity, and evolution of the conductive filaments.

[0004] Beijing Keyida Intellectual Property Service Co., Ltd. (A high consistency memristor and its preparation method, CN110165050A) discloses a high consistency memristor and its preparation method. Its principle is to insert a layer of active metal nano-intercalation between the electrode and the resistive material to regulate the formation position of the metal conductive filament to improve the device performance. However, this method makes the memristor have a high consistency (high resistance fluctuation range is 10 5 ~10 8 There are some deficiencies in the device cycle characteristics and window value. In 2012, Ryu et al. inserted a Ni interface layer between the NiO and Pt top electrodes to control the oxygen conductive filament path to break at the interface, effectively reducing the reset current, but this method also made the consistency of the high and low resistance values ​​of the device poor (the high and low resistance values ​​fluctuated within a 10-fold window). These methods only narrow the range of the conductive filament generation position, and the randomness of the conductive filament generation position still exists.

[0005] Therefore, a memristor preparation method that has both a simple preparation process and can achieve the shaping and positioning of the conductive filament path can be studied to improve the overall performance of the device.

[0006] The inventors of the present invention have previously studied and obtained "High-performance memristor device based on metal oxide oxygen concentration gradient and its preparation" (see Chinese patent document CN108807668A), which discloses a memristor based on metal oxide oxygen concentration gradient, in which the functional layer is metal oxide, and the oxygen content in the functional layer increases or decreases along the direction from the lower electrode to the upper electrode. Although a conical conductive channel can be formed, the top of the conductive channel with a high oxygen content has the characteristic of easy switching, and can achieve high-speed resistance change under low-voltage operation, but because the conical tip of the conical conductive channel is close to the electrode interface, if the conductive channel is to be broken, it is necessary to overcome the potential barrier between the electrode and the functional layer, and there is poor consistency (large high resistance fluctuation range) and a small window range (about 100). Summary of the invention

[0007] In view of the above defects or improvement needs of the prior art, the purpose of the present invention is to provide a memristor that realizes the shaping and positioning of the conductive filament channel, wherein by improving the detailed structure and composition of the functional layer of the memristor device, the obtained memristor can realize the shaping of the conductive filament channel morphology and the positioning of the conductive filament channel on-off position. Compared with the existing memristor structure, it is conducive to achieving low power consumption, high consistency, and multi-resistance state memristor performance, and can effectively solve the problems of the size of the conductive filament of the memristor device in the prior art and the randomness of the formation position. In addition, the present invention uses homogeneous metal oxide materials to stack and form a resistive functional layer to ensure a simple preparation process.

[0008] To achieve the above-mentioned purpose, according to the present invention, there is provided a memristor for realizing the shaping and positioning of a conductive filament channel, characterized in that the device unit of the memristor comprises an upper electrode, a functional layer and a lower electrode from top to bottom, the functional layer is based on the same metal oxide memristor material, the oxygen content in the functional layer changes in a gradient, and the oxygen content in the functional layer shows a trend of first increasing and then decreasing along the direction from the lower electrode to the upper electrode, and since the minimum oxygen vacancy concentration appears in the middle of the functional layer, the breaking position of the conductive filament channel in the memristor can be positioned in the middle of the functional layer.

[0009] As a further preferred embodiment of the present invention, the functional layer is composed of at least three sub-functional layers, the oxygen content in each sub-functional layer is kept constant, and the thickness of each sub-functional layer is 1 to 20 nm.

[0010] As a further preferred embodiment of the present invention, the total number of the sub-functional layers is an odd number, and the total number of the sub-functional layers is denoted as (2n+1), where n is an integer and n≥1. Then, along the direction from the lower electrode to the upper electrode, the oxygen content of the 1st sub-functional layer to the (n+1)th sub-functional layer increases successively, and the oxygen content of the (n+1)th sub-functional layer to the (2n+1)th sub-functional layer decreases successively; preferably, the absolute value of the difference between the N(O) / N(M) ratios of two adjacent sub-functional layers is 0.1 to 1;

[0011] Wherein, M represents a metal element, N(M) represents the amount of the metal element in a certain sub-functional layer, and N(O) represents the amount of the oxygen element in the same sub-functional layer.

[0012] As a further preference of the present invention, the total number of the sub-functional layers is an odd number, denoted as (2n+1), where n is an integer and n≥1. Then, along the direction from the lower electrode to the upper electrode, the thicknesses of the 1st sub-functional layer to the (n+1)th sub-functional layer decrease successively, and the thicknesses of the (n+1)th sub-functional layer to the (2n+1)th sub-functional layer increase successively; the absolute value of the difference in thickness between two adjacent sub-functional layers is 0 to 10 nm.

[0013] As a further preferred embodiment of the present invention, the functional layer is composed of 3 to 10 sub-functional layers.

[0014] As a further preferred embodiment of the present invention, the metal oxide memristor material is HfO a 、TiO b 、AlO c 、TaO d 、NiO e 、ZrO f Any one of <a<2,0<b<2,0<c<1.5,0<d<2.5,0<e<1,0<f<2。

[0015] As a further preferred embodiment of the present invention, the material used for the upper electrode is Pt, TiN, TaN, TiW or Au; the material used for the lower electrode is Ti, Pt, TiN, TaN, TiW, Hf, Ta or Al.

[0016] As a further preferred embodiment of the present invention, the total thickness of the functional layer is 5 nm to 500 nm.

[0017] Through the above technical scheme conceived by the present invention, compared with the prior art, the present invention constructs a functional layer with an oxygen vacancy concentration distribution in an "hourglass" shape (this is because in the device of the present invention, along the direction from the lower electrode to the upper electrode, the chemical ratio of the oxygen element shows a trend of first increasing and then decreasing; correspondingly, the distribution of the oxygen vacancy concentration will show a trend of first decreasing and then increasing), and the corresponding conductive filaments will also form a shape similar to an "hourglass", which will not change during the on and off process and will be fixed. In addition, since the present invention can control the on and off of the conductive filaments in the middle position of the functional layer, the conductive filament path can be fixed and positioned. The present invention can achieve an "hourglass" shape of oxygen vacancy concentration distribution through the design of a functional layer with a specific oxide oxygen content distribution, so that after voltage is applied, the shape of the oxygen vacancy conductive filament channel is also distributed in an "hourglass" shape, with the least number of oxygen vacancies in the middle position, where the resistivity is high and the partial pressure is large, and at the same time, the thermal conductivity is the smallest at the lowest oxygen vacancy concentration, which means that a large amount of Joule heat will be generated and drive the oxygen vacancies to diffuse laterally, and at the same time, under the dual effects of the electric field driving the longitudinal migration of oxygen vacancies, the conductive filament breaks at the place with the least number of oxygen vacancies, that is, the conductive filament can be controlled to be turned on and off only in the middle position, thereby improving the performance of the memristor.

[0018] The reason why the present invention can achieve the finalization and positioning of the conductive filament channel of the memristor is that the functional layer is composed of homogeneous metal oxide memristor material, and the oxygen concentration changes from less to more and then less along the direction from the lower electrode to the upper electrode, so that the oxygen vacancy concentration distribution is in an "hourglass" shape. Compared with the prior art memristor in which the conical tip of the conical conductive channel is close to the electrode interface, if the memristor of this prior art is to achieve the break of the conductive channel, it is necessary to overcome the potential barrier between the electrode and the functional layer; while in the device of the present invention, the break of the conductive channel is between the same functional materials, there is no barrier to overcome, and the break is controlled in the middle of the functional layer, which improves the consistency of the high and low resistance values ​​of the device, and the window value is greatly improved (window value>100).

[0019] Secondly, the functional layer of the memristor of the present invention uses homogeneous materials, the preparation process is simple, and the problem of interface adaptation between different materials can be avoided, which has great advantages in terms of cost, process complexity, etc.

[0020] Specifically, the present invention can achieve the following beneficial effects:

[0021] (1) The present invention constructs a functional layer with an oxygen vacancy concentration distribution in an "hourglass" shape, with the least number of oxygen vacancies in the middle position, where the resistivity is high and the partial pressure is large. At the same time, the thermal conductivity is the lowest at the oxygen vacancy concentration. Driven by the electric field and Joule heat, the on and off of the conductive filaments can be controlled at the middle weak position, thereby achieving the shaping and positioning of the conductive filament path; the total number of sub-functional layers is preferably an odd number, so that the position of the oxygen vacancy concentration minimum value can be located in the sub-functional layer in the middle, further improving the device performance;

[0022] (2) The present invention constructs a functional layer with an oxygen vacancy concentration distribution in an "hourglass" shape. The on-off of the conductive filament path determines the high and low resistance states of the device. When a voltage is applied, the on-off of the conductive filament path occurs only in the middle position, which reduces the randomness of the on-off position, is beneficial to improving the window value and consistency of the device, and reduces power consumption;

[0023] (3) The present invention is a single ion path, the electrode does not participate in the formation of the conductive filament, and only relies on the regulation of the oxygen concentration in the functional layer to form the conductive filament path, which is conducive to analysis;

[0024] (4) In addition, the functional layer of the present invention has a homogeneous structure and does not require the addition of other materials during the preparation process. It only needs to change the sputtering atmosphere and oxygen content, which ensures the consistency of the preparation environment, reduces the complexity of the process, and avoids contamination by other ions during preparation. It has great advantages in terms of cost, process complexity, etc.

[0025] (5) For the "hourglass-shaped" oxygen vacancy conductive filament path formed by the device structure, considering that the pre-conduction voltage and operating voltage of the layer with more oxygen vacancies are smaller than those of the layer with less oxygen vacancies, in order to further ensure that the oxygen vacancy conductive filament path is broken in the part with the lowest oxygen vacancy concentration in the middle, the thickness of the layer with more oxygen vacancies can be preferably designed to be greater than the thickness of the layer with less oxygen vacancies, which is more conducive to the formation of the "hourglass" shape. At the same time, the greater the difference in the N(O) / N(M) ratio between two adjacent sub-functional layers, that is, the greater the difference in oxygen vacancy concentration, the more conducive to the formation of the "hourglass" shape. Considering that in actual preparation, a larger error can be allowed, it is preferred in the present invention to control the absolute value of the difference in the N(O) / N(M) ratio between two adjacent sub-functional layers to be not less than 0.1.

[0026] In summary, the memristor device obtained based on the present invention can realize the shaping and positioning of oxygen vacancy conductive filaments, thereby fundamentally improving the performance of the device, improving the consistency and window value, reducing power consumption, process complexity and cost, and laying a foundation for the device to be widely used in actual industrial development. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1It is a cross-sectional schematic diagram of the memristor unit that realizes the shaping and positioning of the conductive filament channel provided in Embodiments 1 and 2 of the present invention.

[0028] Figure 2 It is the memristance characteristic curve of the memristor unit that realizes the shaping and positioning of the conductive filament channel provided in Embodiment 1 of the present invention.

[0029] Figure 3 It is a schematic diagram of the resistive switching mechanism of the memristor unit that realizes the shaping and positioning of the conductive filament channel provided in Example 1 of the present invention.

[0030] Figure 4 When depositing HfO by magnetron sputtering process x It is the corresponding relationship diagram of different argon-oxygen ratios and different oxygen-hafnium ratios obtained by XPS.

[0031] Figure 5 It is the memristance characteristic curve of the memristor unit that realizes the shaping and positioning of the conductive filament channel provided in Embodiment 2 of the present invention.

[0032] Figure 6 It is the multi-resistance characteristic diagram of the memristor device prepared in Embodiment 2 of the present invention under a 20 ns pulse stimulation.

[0033] Figure 1 The meanings of the reference numerals in the figure are as follows: 1 is the upper electrode Pt, 2 is the 5-layer structure HfO x functional layer (with different x values), 3 is the lower electrode Ti, 4 is the passivation layer SiO2, 5 is the substrate Si; A, B, C, D, and E respectively refer to sub-functional layers with different oxygen contents. Specific Embodiments

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] Generally speaking, the memristor that realizes the shaping and positioning of the conductive filament channel in the present invention has a functional layer with a multi-layer structure and is based on a homogeneous metal oxide memristive material. The functional layer with the multi-layer structure is stacked in the order of decreasing, increasing, and then decreasing oxygen concentration. Taking the functional layer with a 5-layer structure as an example, as Figure 1 shown, the oxygen concentration distribution is A layer < B layer < E layer, and E layer > C layer > D layer.

[0036] Embodiment 1: A memristor that realizes the shaping and positioning of the conductive filament channel and its preparation

[0037] The present invention realizes an oxygen vacancy conductive filament passage similar to an "hourglass" shape by using a homogeneous metal oxide layer. Under the control of the electric field and Joule heat, the on and off positions of the conductive filaments are controlled in the middle of the functional layer (especially the middle of the functional layer), thereby realizing the shaping and positioning of the conductive filament channel, which is specifically explained below with reference to the accompanying drawings.

[0038] Figure 1 A schematic diagram of the structure of a memristor for realizing the shaping and positioning of a conductive filament channel provided by an embodiment of the present invention, specifically, the memristor device structure includes an electrode layer and a multi-layered functional layer, and the functional layer is sandwiched between two electrodes. The functional layer is composed of a homogeneous metal oxide memristor material, and the chemical ratio of the oxygen element shows a trend of first increasing and then decreasing along the direction from the lower electrode to the upper electrode.

[0039] The functional layer is composed of a homogeneous metal oxide memristor material, the material is HfO x 、TiO x 、AlO x 、TaO x 、NiO x 、ZrO x Any material in the present invention, more specifically, HfO x ; The thickness of the single functional layer (i.e., sub-functional layer) is 1 to 20 nm, and the number of stacked layers is 3 to 10. More specifically, in the present embodiment, the thickness of the single functional layer is 20 nm, and the number of stacked layers is 5. The material used for the upper electrode layer is Pt, TiN, TaN, TiW or Au, more specifically, in the present embodiment, it is Pt. The material used for the lower electrode layer is Ti, Pt, TiN, TaN, TiW, Hf, Ta or Al, more specifically, in the present embodiment, it is Ti. The thickness of the functional layer is 5 nm to 500 nm. More specifically, in the present invention, the thickness of the functional layer is 100 nm.

[0040] That is to say, in this embodiment, the HfO x Memristor, the upper electrode is Pt, the thickness is 100nm, the lower electrode is Ti, the thickness is 100nm, the functional layer is a 5-layer structure, each layer is 20nm, the total thickness is 100nm, among which the O / Hf ratio in the A layer and the D layer is 1.71 (O / Hf ratio, that is, the atomic ratio of the O element to the Hf element, that is, the ratio of the amount of matter); the O / Hf ratio in the B layer and the C layer is 1.83; the O / Hf ratio in the E layer is 1.99; its structure is as follows Figure 1 It can be seen that along the direction from the lower electrode to the upper electrode, the chemical ratio of oxygen element increases first and then decreases, that is, the oxygen concentration in layer A is less than that in layer B, the oxygen concentration in layer B is less than that in layer E, the oxygen concentration in layer D is less than that in layer C, and the oxygen concentration in layer C is less than that in layer E, presenting an inverted "V" distribution.

[0041] Since the functional layer with oxygen vacancy concentration distribution in the shape of an "hourglass" is constructed, the middle layer has the least oxygen vacancies, where the resistivity is high and the partial pressure is large. At the same time, the thermal conductivity is the lowest where the oxygen vacancy concentration is the lowest. Therefore, driven by the electric field and Joule heat, the conductive filaments will be switched on and off at the weak position in the middle, thereby achieving the shaping and positioning of the conductive filament pathway and the change of the device resistance.

[0042] The following specifically describes the embodiment HfO x The preparation method of the memristor; the specific steps are as follows:

[0043] Preparation of lower electrode:

[0044] A Ti electrode with a thickness of 100 nm was prepared on a Si substrate with an insulating layer of SiO2 by electron beam evaporation.

[0045] Preparation of functional layer:

[0046] The functional layer can be prepared by magnetron sputtering process. x When the oxygen content is controlled, the HfO x In x. Figure 4 As shown, for the preparation of HfO x For example, its x value increases first and then decreases with the oxygen content introduced. XPS (X-ray photoelectron spectroscopy) can be used multiple times to measure the product HfO under different oxygen content. x The value of x in the experiment is used to determine the amount of oxygen used in the experiment. At the same time, temperature and sputtering power will also change the product HfO x The x value is medium, so the same temperature state and sputtering power can be maintained during preparation. Other memristor materials TiO x 、AlO x 、TaO x 、NiO x 、ZrO x Similarly, deposition can be performed similarly.

[0047] In this embodiment, the functional layer is prepared by magnetron sputtering, with a total of five layers, each layer is 20 nm, and the total thickness is 100 nm. The O / Hf ratio in the A and D layers is 1.71, and the volume ratio of Ar to O2 is 21:29; the O / Hf ratio in the B and C layers is 1.83, and the volume ratio of Ar to O2 is 16:31; the O / Hf ratio in the E layer is 1.99, and the volume ratio of Ar to O2 is 18:29; the process conditions of sputtering are: the background vacuum is 5*10 -3 Pa, the working pressure is 0.67Pa, the DC sputtering power is 100W, and the sputtering time for each layer is 22 minutes;

[0048] Preparation of upper electrode:

[0049] Photolithography: Photolithography is used to etch out the square upper electrode pattern, such as Figure 1 As shown;

[0050] Sputtering: The Pt top electrode was prepared on the photolithography pattern by magnetron sputtering with a thickness of 100 nm. The process conditions for sputtering were: background vacuum 5*10 -4 Pa, working pressure is 0.5Pa, DC sputtering power is 35W, and sputtering time is 700s;

[0051] Stripping: The obtained sample is immersed in acetone and shaken until the pattern is completely clear. Then, it is washed with anhydrous ethanol and deionized water in turn and blown dry with nitrogen to obtain a memristor device with the desired structure.

[0052] Figure 2 This is a DC scanning cycle characteristic diagram of the memristor device prepared in Example 1. The high resistance of the device is stable at 33k, the low resistance is stable at 218Ω, and the window value is about 105, which is beneficial to the analog characteristics of the device. After multiple DC cycles, the device can still operate normally, indicating that the device has good consistency and cycle characteristics.

[0053] Figure 3 It is a mechanism model diagram of the memristor device prepared in Example 1. The XPS test results can be used to predict the prepared device. After applying the set voltage, the oxygen vacancy conductive filaments form an "hourglass" shaped path. The test results show that the prepared device does have a significant improvement in the performance of the memristor, and the device has improvements in consistency, window value, stability, etc.

[0054] Example 2: A memristor capable of realizing the shaping and positioning of a conductive filament channel and its preparation

[0055] The present invention realizes an oxygen vacancy conductive filament passage similar to an "hourglass" shape by using a homogeneous metal oxide layer. Under the control of the electric field and Joule heat, the on and off positions of the conductive filaments are controlled in the middle of the functional layer (especially the middle of the functional layer), thereby realizing the shaping and positioning of the conductive filament channel, which is specifically explained below with reference to the accompanying drawings.

[0056] Figure 1 A schematic diagram of the structure of a memristor for realizing the shaping and positioning of a conductive filament channel provided by an embodiment of the present invention, specifically, the memristor device structure includes an electrode layer and a multi-layered functional layer, and the functional layer is sandwiched between two electrodes. The functional layer is composed of a homogeneous metal oxide memristor material, and the chemical ratio of the oxygen element shows a trend of first increasing and then decreasing along the direction from the lower electrode to the upper electrode.

[0057] The functional layer is composed of a homogeneous metal oxide memristor material, the material is HfO x 、TiOx 、AlO x 、TaO x 、NiO x 、ZrO x Any material in the present invention, more specifically, HfO x ; The thickness of a single functional layer (i.e., a sub-functional layer) is 1 to 20 nm, and the number of stacked layers is 3 to 10. More specifically, in this embodiment, the thickness of layers A and D is 15 nm, the thickness of layers B and C is 10 nm, the thickness of layer E is 5 nm, and the number of stacked layers is 5. The material used for the upper electrode layer is Pt, TiN, TaN, TiW or Au, more specifically, in this embodiment, it is Pt. The material used for the lower electrode layer is Ti, Pt, TiN, TaN, TiW, Hf, Ta or Al, more specifically, in this embodiment, it is Ti. The thickness of the functional layer is 5 nm to 500 nm. More specifically, in the present invention, the thickness of the functional layer is 55 nm.

[0058] That is to say, in this embodiment, the HfO x Memristor, the upper electrode is Pt, the thickness is 100nm, the lower electrode is Ti, the thickness is 100nm, the functional layer is a 5-layer structure, the thickness of the A and D layers is 15nm, the thickness of the B and C layers is 10nm, the thickness of the E layer is 5nm, the total thickness is 55nm, among which the O / Hf ratio in the A and D layers is 1.53; the O / Hf ratio in the B and C layers is 1.71; the O / Hf ratio in the E layer is 1.9; its structure is as follows Figure 1 It can be seen that along the direction from the lower electrode to the upper electrode, the chemical ratio of oxygen element increases first and then decreases, that is, the oxygen concentration in layer A is less than that in layer B, the oxygen concentration in layer B is less than that in layer E, the oxygen concentration in layer D is less than that in layer C, and the oxygen concentration in layer C is less than that in layer E, presenting an inverted "V" distribution.

[0059] Since the functional layer with oxygen vacancy concentration distribution in the shape of an "hourglass" is constructed, the middle layer has the least oxygen vacancies, where the resistivity is high and the partial pressure is large. At the same time, the thermal conductivity is the lowest where the oxygen vacancy concentration is the lowest. Therefore, driven by the electric field and Joule heat, the conductive filaments will be switched on and off at the weak position in the middle, thereby achieving the shaping and positioning of the conductive filament pathway and the change of the device resistance.

[0060] The following specifically describes the embodiment HfO x The preparation method of the memristor; the specific steps are as follows:

[0061] Preparation of lower electrode:

[0062] A Ti electrode with a thickness of 100 nm was prepared on a Si substrate with an insulating layer of SiO2 by electron beam evaporation.

[0063] Preparation of functional layer:

[0064] The functional layer was prepared by magnetron sputtering. There were five layers in total. The thickness of each layer was 15 nm, 10 nm, 5 nm, 10 nm, and 15 nm, respectively. The total thickness was 55 nm. The O / Hf ratio in the A and D layers was 1.53, and the volume ratio of Ar to O2 was 4:37; the O / Hf ratio in the B and C layers was 1.71, and the volume ratio of Ar to O2 was 21:29; the O / Hf ratio in the E layer was 1.9, and the volume ratio of Ar to O2 was 22:25; the process conditions of sputtering were: the background vacuum was 5*10 -3 Pa, the working pressure was 0.67Pa, the DC sputtering power was 100W, and the sputtering time was 15 minutes, 10 minutes, 5 minutes, 10 minutes, and 15 minutes respectively;

[0065] Preparation of upper electrode:

[0066] Photolithography: Photolithography is used to etch out the square upper electrode pattern, such as Figure 1 As shown;

[0067] Sputtering: The Pt top electrode was prepared on the photolithography pattern by magnetron sputtering with a thickness of 100 nm. The process conditions for sputtering were: background vacuum 5*10 -4 Pa, working pressure is 0.5Pa, DC sputtering power is 35W, and sputtering time is 700s;

[0068] Stripping: The obtained sample is immersed in acetone and shaken until the pattern is completely clear. Then, it is washed with anhydrous ethanol and deionized water in turn and blown dry with nitrogen to obtain a memristor device with the desired structure.

[0069] Figure 5 This is a DC scanning cycle characteristic diagram of the memristor device prepared in Example 2. The high resistance of the device is stable at 1M, the low resistance is stable at 820Ω, and the window value is about 1000, which is beneficial to the analog characteristics of the device. After multiple DC cycles, the device can still operate normally, indicating that the device has good consistency and cycle characteristics.

[0070] Figure 6 The multi-resistance characteristic diagram of the memristor device prepared in Example 2 under 20ns pulse stimulation shows that 70 resistance state changes can be achieved within the small resistance range of 15k to 7k, and the resistance state changes have excellent linearity, which is beneficial to the later neuromorphic simulation and calculation.

[0071] The above embodiment only uses a 5-layer structure of HfO x The functional layers are examples. In addition to 5 layers, according to actual conditions, there can also be functional layers with other numbers of sub-functional layers (such as an odd or even number greater than or equal to 3 in total number of sub-functional layers, of course an odd number has better effects).

[0072] In addition to hafnium oxide, memristor materials can be titanium oxide, aluminum oxide, tantalum oxide, nickel oxide, zirconium oxide and other metal oxides known in the prior art to have memristor function; accordingly, since oxygen vacancies are required, the chemical ratio of oxygen elements must be less than the chemical ratio of oxygen elements in the standard chemical formula. Taking hafnium oxide as an example, the standard chemical formula is HfO2 (i.e., hafnium dioxide). Accordingly, if hafnium oxide HfO is used a To construct the functional layer in the device of the present invention, a needs to satisfy a<2; similarly, TiO b 、AlO c 、TaO d 、NiO e 、ZrO f Medium, 0 <b<2,0<c<1.5,0<d<2.5,0<e<1,0<f<2。

[0073] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An application of a memristor for realizing the shaping and positioning of a conductive filament channel in shaping the conductive filament channel morphology and positioning the conductive filament channel on-off position to improve the memristor window value and cycle characteristics, characterized in that: The device unit of the memristor includes an upper electrode, a functional layer and a lower electrode from top to bottom. The functional layer is based on the same metal oxide memristor material. The oxygen content in the functional layer changes in a gradient. The oxygen content in the functional layer increases first and then decreases along the direction from the lower electrode to the upper electrode. Since the minimum value of the oxygen vacancy concentration appears in the middle of the functional layer, the fracture position of the conductive filament channel in the memristor can be located in the middle of the functional layer. The total number of sub-functional layers is an odd number, and the total number of sub-functional layers is denoted as (2n+1), where n is an integer and n≥1. Then, along the direction from the lower electrode to the upper electrode, the thickness of the first sub-functional layer to the (n+1)th sub-functional layer decreases in sequence, and the thickness of the (n+1)th sub-functional layer to the (2n+1)th sub-functional layer increases in sequence; the absolute value of the difference in thickness between two adjacent sub-functional layers is less than or equal to 10 nm; Moreover, compared with devices with the same thickness of each sub-functional layer, the memristor has a higher window value and better cycling characteristics; Furthermore, along the direction from the lower electrode to the upper electrode, the oxygen content of the first sub-functional layer to the (n+1)th sub-functional layer increases successively, and the oxygen content of the (n+1)th sub-functional layer to the (2n+1)th sub-functional layer decreases successively; the absolute value of the difference between the N(O) / N(M) ratios of two adjacent sub-functional layers is 0.1 to 1; Wherein, M represents a metal element, N(M) represents the amount of the metal element in a certain sub-functional layer, and N(O) represents the amount of the oxygen element in the same sub-functional layer.

2. The use according to claim 1, characterized in that: The functional layer is composed of at least three sub-functional layers, the oxygen content in each sub-functional layer is kept constant, and the thickness of each sub-functional layer is 1-20 nm.

3. The use according to claim 1, characterized in that: The functional layer is composed of 3 to 10 sub-functional layers.

4. The use according to claim 1, characterized in that: The metal oxide memristor material is HfO a 、TiO b 、AlO c 、TaO d 、NiO e 、ZrO f Any one of <a<2,0<b<2,0<c<1.5,0<d<2.5,0<e<1,0<f<2。 5. The use according to claim 1, characterized in that: The material used for the upper electrode is Pt, TiN, TaN, TiW or Au; the material used for the lower electrode is Ti, Pt, TiN, TaN, TiW, Hf, Ta or Al.

6. The use according to claim 1, characterized in that: The total thickness of the functional layer is 5nm to 500nm.

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