A gated tube device and a manufacturing method thereof

Abstract

The present invention belongs to the field of micro-nano electronic technology, and particularly relates to a gated tube device and a preparation method thereof. It sequentially includes a first metal electrode layer, a switching layer, and a second metal electrode layer from bottom to top; the switching layer is a metal oxide doped with a metal element, and the metal element is a metal capable of undergoing a redox reaction under the action of an electric field; the specific preparation method is to deposit the first metal electrode layer on a substrate; deposit the switching layer on the first metal electrode layer; then deposit the second metal electrode layer on the switching layer to obtain an initial device; finally, perform an annealing treatment on the initial device to obtain the gated tube device, so as to achieve the technical effects of the prepared gated tube device having low leakage current, large switching ratio, steep switching slope, increased on-state current, and high durability.

Description

Technical Field

[0001] The present invention belongs to the field of micro-nano electronic technology, and particularly relates to a gated tube device and a preparation method thereof. Background Art

[0002] With the rapid development of big data, cloud computing and Internet of Things technologies, the sharp growth of information volume and the continuous expansion of market demand, storage technology is facing unprecedented challenges, especially in terms of the efficiency of data storage and the convenience of data transmission. To address this challenge, the RRAM (resistive random access memory) crossbar array technology has become a forefront technology attracting much attention due to its excellent storage density and fast response performance. The RRAM technology relies on the non-volatile characteristics and high performance of resistive memory devices and has great application potential. However, the storage cells in the RRAM crossbar array often face the problem of leakage current, and the leakage current may affect the reliability of the device through the surrounding cells. Therefore, each storage cell needs to be connected to a gated tube to avoid the interference of leakage current.

[0003] Currently, the more common gated tubes include the two-way threshold switch device based on chalcogenide compounds (Ovonic Threshold Switch, OTS), the threshold switch device based on metal-insulator phase change (Metal Insulator Transition, MIT), and the threshold switch device based on conductive filaments. Among them, compared with the two-way threshold switch device and the threshold switch device based on metal-insulator phase change, the threshold switch device based on conductive filaments has lower leakage current, a larger switching ratio, and a steep switching slope. However, this type of device also has the disadvantages of small on-state current, inability to drive some storage devices, and poor durability. How to prepare a conductive filament type threshold switch device with both low leakage current, large switching, steep switching slope, large on-state current and high durability is an urgent problem to be solved. Summary of the Invention

[0004] Aiming at the defects of the prior art, the present invention provides a gated tube device and a preparation method thereof, aiming to solve the technical problems of the existing gated tube device based on conductive filaments, such as non-low leakage current, small switching ratio, slow switching slope, small on-state current and low durability.

[0005] To achieve the above object, according to the first aspect of the present invention, a gated tube device is provided, which sequentially includes a first metal electrode layer, a switching layer and a second metal electrode layer from bottom to top; the switching layer is a metal oxide doped with a metal element, and the metal element is a metal capable of undergoing a redox reaction under the action of an electric field.

[0006] Preferably, the material of the metal oxide is selected from ScO x 、TiOx , FeO x , NiO x , ZnO x , ZrO x , MoO x , HfO x , TaO x , WO x One or more of them, where the range of x is 1 ≤ x ≤ 2.

[0007] Preferably, the elemental metal is selected from one or more of Ag, Cu, and Co.

[0008] Preferably, in the switching layer, the doping concentration of the elemental metal in the metal oxide increases from bottom to top.

[0009] Preferably, the thickness of the switching layer is 1 - 30 nm.

[0010] Preferably, the materials of the first metal electrode layer and the second metal electrode layer are each independently selected from one or more of Pt, Ti, W, Au, Al, TiN, TaN, TiW, indium tin oxide, indium zinc oxide, and indium silicon oxide.

[0011] According to another aspect of the present invention, a method for manufacturing a gated tube device is provided, and the specific steps include:

[0012] Depositing a first metal electrode layer on a substrate;

[0013] Depositing a switching layer on the first metal electrode layer;

[0014] Then depositing a second metal electrode layer on the switching layer to obtain an initial device;

[0015] Finally, annealing the initial device to obtain a gated tube device.

[0016] Preferably, the annealing time is 30 - 90 s and the temperature is 400 - 600 °C

[0017] Preferably, the methods for depositing the first metal electrode layer, the switching layer, and the second metal electrode layer are each independently selected from chemical vapor deposition, atomic layer deposition, sputtering, pulsed laser deposition, evaporation, or molecular beam epitaxy.

[0018] Generally speaking, compared with the prior art, the above technical solutions conceived by the present invention mainly have the following technical advantages.

[0019] 1. In the present invention, the selectron introduces a specific doped metal into the metal oxide. By using it as a stabilizer for oxygen vacancies, a metal-oxygen vacancy complex is formed, thereby effectively reducing the activation energy required for oxygen vacancy migration and promoting the controllable generation of conductive filaments.

[0020] 2. After introducing a doped metal into the metal oxide in the present invention, annealing is adopted to cause oxygen vacancies in the metal oxide to aggregate along grain boundaries or doping sites of the doped metal, forming a pre-distributed localized high-concentration region, significantly reducing the energy barrier for the formation of conductive filaments in the switching layer. And annealing promotes the reduction of the internal doped metal, forming metal clusters as nucleation points for the generation of conductive filaments. Under the combined action of the two, the device maintains threshold switching characteristics at low voltages. At the same time, by utilizing the high resistance value and sufficient oxygen vacancy concentration provided by the metal oxide, it exhibits the characteristics of low leakage current and steep switching slope.

[0021] 3. The concentration of the metal element in the switching layer of the present invention increases gradually from bottom to top during doping. The gradually increasing doping concentration from bottom to top makes the metal concentration in the bottom doping region of the switching layer relatively low, which can inhibit the random nucleation of oxygen vacancies at the interface, reduce the initial leakage current, and at the same time reduce the breakdown risk caused by local electric field concentration. The large electric field existing in the top high-doping region promotes the orderly migration of oxygen vacancies along the concentration gradient direction, forming a single dominant conductive filament instead of multi-filament competition, thereby improving the stability of the selectron at high on-state current. At the same time, the gradually increasing doping metal concentration gradient from bottom to top in the selectron is equivalent to providing a guiding track for the sufficient migration of oxygen vacancies in the metal oxide. This directional growth method reduces the randomness of its formation and breakage, and will effectively improve the cycle durability. By using a gradually increasing doping concentration from bottom to top, a selectron device with low leakage current, large switching ratio, steep switching slope, large on-state current and high durability is successfully realized after annealing.

[0022] 4. The selectron device provided by the present invention has a simple structure, a wide range of material selections, and at the same time, the preparation method has a simple process, a short process flow and low cost. Therefore, the selectron device of the present invention has the potential to be integrated in series with a storage unit to effectively reduce leakage current, improve storage density and reduce operating power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. is a schematic structural diagram of a selectron unit provided in Embodiment 1 of the present invention.

[0024] Figure 2 FIG. is a flowchart of a preparation method of a selectron unit provided in Embodiment 1 of the present invention.

[0025] Figure 3 FIG. is an actual measurement graph of the current-voltage curve of the selectron device provided in Embodiment 1 of the present invention.

[0026] Figure 4 It is the curve graph of the switching slope part of the strobe tube device provided in Embodiment 1 of the present invention.

[0027] Figure 5 It is the DC durability test graph of the strobe tube device provided in Embodiment 1 of the present invention.

[0028] Figure 6 It is the measured current-voltage curve graph of the strobe tube device provided in Comparative Example 1 of the present invention.

[0029] Figure 7 It is the measured current-voltage curve graph of the strobe tube device provided in Embodiment 2 of the present invention.

[0030] Figure 8 It is the measured current-voltage curve graph of the strobe tube device provided in Embodiment 3 of the present invention.

[0031] Among them, 101 is the first metal electrode layer; 102 is the switching layer; 103 is the second metal electrode layer. Specific Embodiments

[0032] 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.

[0033] Embodiment 1

[0034] This embodiment provides a preparation method of a strobe tube device, wherein the switching layer is metal oxide HfO x doped with metal Cu, where 1 ≤ x ≤ 2, and the doping concentration of metal Cu in the switching layer gradually increases from bottom to top. Its device structure is as Figure 1 shown, and the preparation process is as Figure 2 shown, including the following steps:

[0035] (1) Using a Si and SiO2 semiconductor substrate, the substrate is successively placed in acetone, alcohol, and deionized water for ultrasonic cleaning, each cleaning for 10 min. After cleaning, use a nitrogen gun to blow dry the liquid remaining on the surface for later use;

[0036] (2) Using magnetron sputtering to deposit 10 nm of Ti and 100 nm of Pt on the surface of the substrate as the first metal electrode layer successively, where Ti is used as an adhesion layer to improve the adhesion between Pt and the SiO2 substrate;

[0037] (3) A switching layer is grown on the first metal electrode layer. Using reactive magnetron sputtering, by co-sputtering an Hf target and a Cu target, and introducing oxygen with a flow rate of 10 sccm and argon with a flow rate of 30 sccm, a metal oxide HfO doped with metal Cu is prepared x where 1 ≤ x ≤ 2, and this is used as the switching layer. During the deposition process, the sputtering power of the Cu target is increased every 5 minutes, from 40 W to 70 W, and the sputtering power of the Hf target is kept unchanged at 100 W. The total sputtering time is 20 minutes, and a total of about 25 nm of the switching layer material is deposited;

[0038] (4) 100 nm of Pt is deposited on the functional layer material by magnetron sputtering as the second metal electrode layer material to obtain an initial device;

[0039] (5) The initial device is placed in an annealing furnace for rapid thermal annealing. The annealing atmosphere is a nitrogen atmosphere, the annealing temperature is 500 degrees Celsius, and the annealing time is 30 seconds.

[0040] Figure 3 is the measured current-voltage curve of Example 1 of the present invention. It can be seen that the unannealed device only shows a non-linear current-voltage relationship, while the annealed device shows an obvious threshold switching device, which turns on near 0.7, changes from the off state to the on state, reaching a switching ratio of 10 9 The high switching ratio enables the select tube device to be applied to large-scale memory arrays; the off-state leakage current is less than 1 pA, and the low leakage current can effectively suppress the leakage current in the array, thereby reducing power consumption and reducing misoperations; the on-state current reaches 100 μA, and the high on-state current can enable the device to provide effective current drive for the memory cell. At the same time, when the voltage drops below 0.4 V, the device returns to the off state. The low holding voltage can avoid the voltage division problem after integration on the one hand and achieve low power consumption of the array on the other hand.

[0041] Figure 4 is the current-voltage curve diagram of Specific Example 1 of the present invention under a scanning step of 1 mV. It can be seen that the device has a steep turn-on and turn-off slope, indicating that the device has the ability to turn on and off quickly.

[0042] Figure 5 is the durability test diagram of Example 1 of the present invention under direct current. It can be seen that the device can maintain 1000 direct current cycles without obvious performance degradation at a high on-state current of 100 μA, which indicates that the device has excellent durability and can provide sufficient current drive for the memory cell and maintain excellent durability.

[0043] Comparative Example 1

[0044] This comparative example provides a method for preparing a gated tube device, where the switching layer is metal oxide HfO x , where x = 1.7, and the switching layer does not contain doped metal, including the following preparation steps:

[0045] (1) Using SiO2 and Si semiconductor substrate, the substrate is successively placed in acetone, alcohol, and deionized water for ultrasonic cleaning, each cleaning for 10 min. After cleaning, the residual liquid on the surface is dried with a nitrogen gun for later use;

[0046] (2) Using magnetron sputtering to deposit 10 nm of Ti and 100 nm of Pt on the substrate surface successively as the first metal electrode layer. Among them, Ti serves as an adhesion layer, which can improve the adhesion between Pt and the SiO2 substrate;

[0047] (3) Growing a switching layer on the first metal electrode layer. The material used for the gated tube switching layer is metal oxide HfO x , where 1 ≤ x ≤ 2, with a thickness of 25 nm. The switching layer is grown by magnetron sputtering method, introducing 10 sccm of oxygen and 30 sccm of argon, keeping the sputtering power of the Hf target at 100 W unchanged, and the total sputtering time is 20 minutes, depositing approximately 25 nm of switching layer material in total;

[0048] (4) Using magnetron sputtering to deposit 100 nm of Pt on the functional layer material as the second metal electrode layer material to obtain an initial device;

[0049] (5) Placing the initial device in an annealing furnace for rapid thermal annealing. The annealing atmosphere is a nitrogen atmosphere, the annealing temperature is 500 degrees Celsius, and the annealing time is 30 seconds.

[0050] Figure 6 is the measured current-voltage curve of Comparative Example 1 of the present invention. It can be seen that without doping metal, the device only shows a non-linear voltage-current relationship after annealing. This is because the oxygen vacancies in the metal oxide without doped metal are randomly distributed, and there is no doped metal as the migration center of oxygen vacancies, so it is impossible to form conductive filaments at low voltages. At the same time, there are no metal nanoclusters in the undoped device switching layer as the nucleation sites of conductive filaments, and oxygen vacancies cannot self-organize to form conductive filaments under low electric fields, which all result in the inability of the undoped device to exhibit threshold switching characteristics after annealing.

[0051] Example 2

[0052] This example provides a method for preparing a gated tube device, where the switching layer is metal oxide HfO x doped with metal Cu, where 1 ≤ x ≤ 2, and the doping concentration of metal Cu in the switching layer decreases from bottom to top; including the following steps:

[0053] (1) An Si and SiO2 semiconductor substrate is used. The substrate is successively placed in acetone, alcohol, and deionized water for ultrasonic cleaning for 10 minutes each time. After cleaning, the residual liquid on the surface is dried with a nitrogen gun for standby;

[0054] (2) Using magnetron sputtering, 10 nm of Ti and 100 nm of Pt are successively deposited on the substrate surface as the first metal electrode layer. Among them, Ti is used as an adhesion layer, which can improve the adhesion between Pt and the SiO2 substrate;

[0055] (3) A switching layer is grown on the first metal electrode layer. Using reactive magnetron sputtering, by co-sputtering an Hf target and a Cu target, and introducing oxygen with a flow rate of 10 sccm and argon with a flow rate of 30 sccm, a metal oxide HfO doped with metal Cu is prepared. x In it, where 1 ≤ x ≤ 2, this is used as the switching layer. During the deposition process, the sputtering power of the Cu target is reduced every 5 minutes, from 70 W to 40 W, and the sputtering power of the Hf target is kept at 100 W unchanged. The total sputtering time is 20 minutes, and a total of about 25 nm of switching layer material is deposited;

[0056] (4) Using magnetron sputtering, 100 nm of Pt is deposited on the functional layer material as the second metal electrode layer material to obtain an initial device;

[0057] (5) The initial device is placed in an annealing furnace for rapid thermal annealing. The annealing atmosphere is a nitrogen atmosphere, the annealing temperature is 500 degrees Celsius, and the annealing time is 30 seconds.

[0058] Figure 7 is the measured current-voltage curve diagram of Embodiment 2 of the present invention. It can be seen that the device with the doping metal concentration increasing from top to bottom exhibits threshold switching behavior. It turns on near 0.8 V, changes from the off state to the on state, the leakage current is greater than 100 pA, the on-state current reaches 500 μA, and the switching ratio is about 5 x 10. 6, when the voltage drops below 0.4 V, the device returns to the off state. Compared with Comparative Example 1, the functional layer of this device adopts a bottom-up decreasing Cu element doping concentration distribution, which induces oxygen vacancies to preferentially enrich along the polycrystalline grain boundaries and doping sites during the annealing process, forming a pre-set localized high-concentration defect region. At the same time, Cu doping precipitates metal clusters as the nucleation points of conductive filaments under reducing annealing conditions. The two work together to reduce the activation energy barrier for the formation of the conductive channel, thus achieving threshold switching characteristics at a low driving voltage. Compared with Example 1, the leakage current of this device is larger, and the on-state current is higher. This is because the high doping metal concentration at the bottom causes the electric field to concentrate at the near-bottom electrode interface, accelerating the migration of oxygen vacancies in the metal oxide and the nucleation of conductive filaments, forming a low-resistance path through the dielectric, increasing the leakage current. And the bottom-up concentration decrease may lead to the preferential formation of conductive filaments at the bottom. However, due to the lack of sufficient doped metal or oxygen vacancies in the region of high electric field strength at the top, the filaments may not completely penetrate the dielectric layer, forming an unstable local conduction path. This instability provides a theoretical basis for its larger on-state current.

[0059] Example 3

[0060] This example provides a preparation method of a gated tube device, where the switching layer is metal oxide HfO x doped with metal Cu, where x = 1.3, and metal Cu is uniformly doped in the switching layer; it includes the following steps:

[0061] (1) Use a Si and SiO2 semiconductor substrate, and sequentially place this substrate in acetone, alcohol, and deionized water for ultrasonic cleaning for 10 minutes each time. After cleaning, use a nitrogen gun to blow dry the liquid residues on the surface for later use;

[0062] (2) Use magnetron sputtering to deposit 10 nm of Ti and 100 nm of Pt on the substrate surface successively as the first metal electrode layer. Among them, Ti is used as an adhesion layer, which can improve the adhesion between Pt and the SiO2 substrate;

[0063] (3) Grow the switching layer on the first metal electrode layer. Use reactive magnetron sputtering method. By co-sputtering the Hf target and the Cu target, and introducing 10 sccm of oxygen and 30 sccm of argon, prepare metal oxide HfO x doped with metal Cu as the switching layer. During the deposition process, keep the sputtering power of the Hf target at 100 W and the sputtering power of the Cu target at 40 W unchanged. The total sputtering time is 20 minutes, and a total of about 25 nm of switching layer material is deposited;

[0064] (4) Use magnetron sputtering to deposit 100 nm of Pt on the functional layer material as the second metal electrode layer material to obtain the initial device;

[0065] (5) Place the initial device in an annealing furnace for rapid thermal annealing. The annealing atmosphere is a nitrogen atmosphere, the annealing temperature is 500 degrees Celsius, and the annealing time is 30 seconds.

[0066] Figure 8 It is the measured current-voltage curve diagram of Embodiment 3 of the present invention. It can be seen that the device with a uniform distribution of doped metal concentration also exhibits threshold switching behavior. It turns on near 0.8 V, changes from the off state to the on state, the leakage current is greater than 100 pA, the on-state current can reach 100 μA, and the switching ratio is about 10 6 , and at the same time, when the voltage drops below 0.4 V, the device returns to the off state. Compared with Comparative Example 1, this device uniformly dopes the metal element Cu and combines with the annealing treatment in a nitrogen atmosphere to induce the directional enrichment of oxygen vacancies in the functional layer along the polycrystalline grain boundaries and doping sites, forming a pre-distributed local high-concentration oxygen vacancy region to reduce the activation energy for the formation of conductive filaments. At the same time, annealing synchronously drives the reduction and precipitation of the doped metal to form metal nanoclusters as the nucleation sites for conductive filaments. Due to the synergistic effect of the above-mentioned oxygen vacancy enrichment and metal clusters, the device exhibits threshold switching characteristics at a low driving voltage; compared with Embodiment 1, the leakage current of the device is larger, and at the same time, the on-state current is extremely unstable. After the voltage is greater than the threshold voltage, the current fluctuates at the μA level. This is because the uniform doping of the metal makes the distribution of doped metal atoms and oxygen vacancies provided by the metal oxide in the metal oxide highly randomized. Under the action of an electric field, nucleation may occur simultaneously at multiple positions, forming multiple conductive filaments competing with each other. This multi-filament behavior will lead to jumps in the on-state current and greater randomness in the formation and breakage of filaments. At the same time, uniform doping will introduce a large number of scattering centers, significantly reducing the carrier mobility, thereby resulting in a decrease in the off-state resistance of the switching layer and an increase in the leakage current.

[0067] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A gate tube device, characterized in that: From bottom to top, there are a first metal electrode layer, a switch layer and a second metal electrode layer; the switch layer is a metal oxide doped with a metal element; in the switch layer, the doping concentration of the metal element in the metal oxide increases from bottom to top, and the metal element is a metal that can undergo redox reaction under the action of an electric field.

2. The gate tube device according to claim 1, characterized in that: The material of the metal oxide is selected from ScO x 、TiO x ,FeO x 、NiO x 、ZnO x 、ZrO x 、MoO x , HfO x 、TaO x , WO x One or more of , where x is in the range of 1≤x≤2.

3. The gate tube device according to claim 1, characterized in that: The metal element is selected from one or more of Ag, Cu and Co.

4. The gate transistor device according to claim 1, characterized in that: The thickness of the switch layer is 1-30 nm.

5. The gate transistor device according to claim 4, characterized in that: The materials of the first metal electrode layer and the second metal electrode layer are independently selected from one or more of Pt, Ti, W, Au, Al, TiN, TaN, TiW, indium tin oxide, indium zinc oxide and indium silicon oxide.

6. The method for preparing a gate tube device according to any one of claims 1 to 5, characterized in that: The specific steps include: (1) depositing a first metal electrode layer on a substrate; (2) depositing a switching layer on the first metal electrode layer; (3) then depositing a second metal electrode layer on the switch layer to obtain an initial device; (4) Finally, the initial device is annealed to obtain a gate tube device.

7. The method for preparing a gate tube device according to claim 6, characterized in that: The annealing time is 30-90s and the temperature is 400-600°C.

8. The method for preparing a gate tube device according to claim 6, characterized in that: Methods for depositing the first metal electrode layer, the switch layer and the first metal electrode layer are independently selected from chemical vapor deposition, atomic layer deposition, sputtering, pulsed laser deposition, evaporation or molecular beam epitaxy.

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