Random access memory based on vertical ultra-wide forbidden band semiconductor device and preparation method thereof

Abstract

The invention relates to a random access memory based on a vertical ultra-wide forbidden band semiconductor device and a preparation method of the random access memory, and belongs to the field of semiconductor devices. The device comprises a substrate, an AlN buffer layer, an n < + >-AlGaN layer, an n <->-AlGaN drift layer, an n < + >-AlGaN insertion layer and an Al component gradual change p-AlGaN layer from bottom to top in sequence, an anode is arranged on the upper portion of the Al component gradual change p-AlGaN layer, a groove is etched in the upper portion of the n < + >-AlGaN layer, and a cathode is arranged on the groove. According to the invention, the high-temperature stability and radiation resistance of the memory are effectively improved, and the application range is expanded; a diode structure with a self-rectification characteristic is adopted, the problem of current leakage in a large-scale integrated RRAM array is effectively solved, and data crosstalk is remarkably reduced. The RRAM based on the III-nitride shows greater potential in the aspect of monolithic integration with an HEMT (High Electron Mobility Transistor) and an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), and is beneficial to the preparation of 1T1R.

Description

Technical Field

[0001] The invention relates to a random access memory based on a vertical ultra-wide bandgap semiconductor device and a preparation method thereof, belonging to the technical field of semiconductor devices. Background Art

[0002] Memory plays a vital role in modern computers and electronic devices. Its main function is to store and quickly access data, which directly affects the performance and operating efficiency of the system. As a core component that supports the normal operation of operating systems, applications and various advanced technologies (such as artificial intelligence, cloud computing and the Internet of Things), memory not only ensures the efficiency of data processing, but also plays a key role in data reliability and security. Resistive random access memories (RRAM) have the advantages of high-speed operation, large storage density and low power consumption, and are gradually becoming a strong competitor in the next generation of non-volatile memory. At present, RRAM is mostly based on oxides such as NiOx, TiOx, HfOx, ZnOx, and CuOx. Generally speaking, a storage unit of RRAM usually consists of a transistor and an RRAM resistor, that is, a 1T1R (one-transistor-one-resistor) structure. III-nitride semiconductors have shown significant advantages in electronic devices due to their adjustable wide bandgap characteristics. Compared with oxide-based materials, III-nitride-based memories are easier to be monolithically integrated with III-nitride-based high electron mobility transistors (HEMTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs) to form 1T1R memory cells, thereby realizing large-scale array memory modules. This integrated module is of great significance in the development and application of integrated storage and computing chips and brain-like neural chips.

[0003] In the prior art, RRAM has limitations in application under high temperature and harsh environments, and it is difficult to achieve efficient monolithic integration when integrating traditional RRAM devices with HEMT and MOSFET. In addition, in large-scale integrated RRAM arrays, leakage current at the intersection may cause crosstalk problems, affecting the performance of the memory. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a random access memory based on a vertical ultra-wide bandgap semiconductor device and a preparation method thereof, which effectively improves the high temperature stability and radiation resistance of the memory and expands the scope of application; a storage diode structure with self-rectification characteristics is adopted to effectively solve the leakage current problem that may occur in the large-scale integrated RRAM array, significantly reduce data crosstalk, and improve the reliability and data fidelity of the storage device. Compared with traditional oxide-based RRAM, III-nitride-based RRAM shows greater potential in monolithic integration with HEMT and MOSFET, which is conducive to the preparation of 1T1R.

[0005] The present invention adopts the following technical solution:

[0006] On the one hand, the present invention provides a random access memory based on a vertical ultra-wide bandgap semiconductor device, which comprises, from bottom to top, a substrate, an AlN buffer layer, an n + -AlGaN layer, n - -AlGaN drift layer, n + -AlGaN insertion layer and Al composition gradient p-AlGaN layer, an anode is arranged on the Al composition gradient p-AlGaN layer, and the n + A groove is etched on the upper part of the -AlGaN layer, and a cathode is arranged on the groove.

[0007] Preferably, n + -AlGaN layer is preferably n + -Al 0.5 Ga 0.5 N layer, thickness is 1-3μm, doping element is Si, doping concentration is 1E19cm -3 ~3E19cm -3 ;

[0008] Further, + -Al 0.5 Ga 0.5 The thickness of the N layer is 2 μm and the doping concentration is 1E19 cm -3 .

[0009] Preferably, the n + -AlGaN insertion layer is preferably n + -Al 0.5 Ga 0.5 N insertion layer, thickness is 280~320nm, doping element is Si, doping concentration is 1E19cm -3 ~3E19cm -3 ;

[0010] Further, + -Al 0.5 Ga 0.5N insertion layer, thickness is 300nm, doping concentration is 1E19cm -3 .

[0011] Preferably, the thickness of the AlN buffer layer is 2-3 μm, preferably 2.5 μm.

[0012] Preferably, the n - -AlGaN drift layer is n - -Al 0.5 Ga 0.5 N drift layer, with a thickness of 2.5 to 3.5 μm, preferably 3 μm;

[0013] The - -Al 0.5 Ga 0.5 The doping element of the N drift layer is Si, and the doping concentration is 1E16~3E16cm -3 , preferably 2E16cm -3 .

[0016] Preferably, the Al composition gradient p-AlGaN layer includes a lower portion of Al 0.5→0 Ga 0.5→1 N layer and the p-GaN layer on the upper part.

[0017] Preferably, the Al 0.5→0 Ga 0.5→1 The thickness of the N layer is 100nm, the doping element is Mg, and the doping concentration is 1E19~2E19cm -3 .

[0018] Preferably, the thickness of the p-GaN layer is 300 nm, the doping element is Mg, and the doping concentration is 2E19-3E19 cm -3 .

[0019] The Al composition gradient p-AlGaN layer of the present invention is arranged in this way, which has the following effects:

[0020] 1) Generate three-dimensional hole gas to increase the carrier concentration of the device. 2) The ohmic contact process of p-AlGaN is difficult, while the ohmic contact process of p-GaN is relatively simple; directly on Al 0.5 Ga 0.5 When growing GaN on N, the epitaxial wafer is prone to cracks due to the large lattice mismatch. The use of p-AlGaN with a gradient Al composition can reduce the lattice mismatch.

[0021] The memory device in the present invention is made based on the ultra-wide bandgap semiconductor material AlGaN. The material has an ultra-wide bandgap width, excellent thermal stability and radiation resistance, and is suitable for use in extreme environments such as aerospace, deep-sea exploration and nuclear industry.

[0022] When traditional RRAM devices are integrated with HEMT and MOSFET, it is difficult to achieve efficient monolithic integration. The present invention uses III-nitride to prepare RRAM, which is compatible with III-nitride-based HEMT and MOSFET preparation processes, making 1T1R storage units possible and significantly improving the integration and functional diversity of the device.

[0023] The present invention proposes a storage diode design with self-rectification characteristics, which reduces the influence of crosstalk current and improves the reliability and data integrity of a large-scale integrated storage array.

[0024] On the other hand, the present invention provides a method for preparing the random access memory based on the vertical ultra-wide bandgap semiconductor device, comprising the following steps:

[0025] (1) Growth of epitaxial structure: AlN buffer layer, n + -AlGaN layer, n - -AlGaN drift layer, n + -AlGaN insertion layer and Al composition graded p-AlGaN layer;

[0026] (2) Perform trench etching on the epitaxial structure until the n + - AlGaN layer;

[0027] (3) using electron beam evaporation to deposit metal to form an ohmic contact cathode on the groove;

[0028] (4) Finally, electron beam evaporation of metal is used to form an ohmic contact anode on the upper portion of the Al composition gradient p-AlGaN layer.

[0029] In the present invention, the Al component in AlGaN is adjustable, and a metal organic chemical vapor phase epitaxy method is used, trimethylaluminum, trimethylgallium and ammonia are used as reaction sources to epitaxially grow AlGaN. During the growth process, the Al component in AlGaN can be adjusted by adjusting the molar flow rate ratio of trimethylaluminum to trimethylgallium per minute. The larger the Al component of AlGaN, the larger the band gap width.

[0030] Preferably, in step (2), SiO2 is used as a hard mask for trench etching.

[0031] It should be noted that the preparation material of the RRAM in the present invention is not limited to III-nitride (AlGaN).

[0032] For any details not provided in the present invention, please refer to the prior art.

[0033] The beneficial effects of the present invention are:

[0034] 1. The present invention introduces an n at the pn junction interface + -AlGaN insertion layer, forming AlGaN vertical pn diode. Its advantages are: a) n + -AlGaN insertion layer increases the free carrier density of the device in this area. When voltage is applied to the cathode of the device, the electric field gathers faster at the pn junction, reducing the breakdown voltage. + -AlGaN insertion layer makes the drift region (n - -AlGaN layer) depletion width is narrowed, the pressure-bearing area is reduced, the breakdown voltage of the device is reduced, and the induced voltage of the memory device is significantly reduced, so that the device exhibits excellent performance in high-efficiency storage and low-power operation. b) Introduction of n + -The AlGaN insertion layer increases the carrier concentration in the device, reduces the on-resistance of the device, optimizes the current density and conductivity characteristics of the memory, and is suitable for high-performance computing and low-energy consumption applications.

[0035] 2. The present invention uses III-nitride semiconductor materials to prepare RRAM, which has the following advantages: a) The band gap can be adjusted by adjusting the Al component in AlGaN to optimize its electron mobility and conductivity. b) It provides excellent characteristics of wide band gap and high electron mobility, ensuring the stability of the device under high temperature and harsh environment. c) AlGaN material is not only suitable for storage devices, but also can be monolithically integrated with HEMT and MOSFET, thereby improving the integration and application flexibility of the device.

[0036] 3. The successful growth of n-type and p-type AlGaN layers by MOCVD ensures the high quality and precise control of the materials, ensures the stability of the device under high temperature and harsh environment, provides higher thermal stability and radiation resistance, and is suitable for demanding applications such as aerospace and nuclear industries. By precisely controlling the doping and growth conditions of the materials, the performance of the device can be optimized to ensure its reliability and consistency under extreme conditions.

[0037] The present invention is based on the RRAM structure of III-nitride (such as AlGaN) materials, which effectively improves the high temperature stability and radiation resistance of the memory and is suitable for storage applications in harsh environments such as aerospace and nuclear industries. +-AlGaN insertion layer, optimizes the device structure of AlGaN pn diode, so that it can show excellent performance in storage applications, including low turn-on voltage and low on-resistance, which not only reduces power consumption but also improves data processing speed and efficiency. In addition, the invention adopts a storage diode structure with self-rectification characteristics, which effectively solves the leakage current problem that may occur in large-scale integrated RRAM arrays, significantly reduces data crosstalk, and improves the reliability and data fidelity of storage devices. Compared with traditional oxide-based RRAM, III-nitride-based RRAM shows greater potential in monolithic integration with HEMT and MOSFET, which is conducive to the preparation of 1T1R. In general, the present invention has shown significant advantages in improving storage performance, reducing power consumption, and enhancing environmental adaptability by optimizing the materials and structure of RRAM, providing strong technical support for the research and development and application of a new generation of non-volatile memory. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0039] Figure 1 It is a schematic structural diagram of a random access memory based on a vertical ultra-wide bandgap semiconductor device of the present invention;

[0040] Figure 2 The present invention is a process flow for preparing a random access memory based on a vertical ultra-wide bandgap semiconductor device, wherein (a) is a schematic diagram of a grown epitaxial structure; (b) is a schematic diagram of a structure after trench etching; (c) is a schematic diagram of a structure after forming an ohmic contact cathode; (d) is a schematic diagram of a structure after forming an ohmic contact anode;

[0041] Figure 3 The AlGaN-based RRAM has a rectification characteristic curve of a power diode before breakdown, where (a) is a forward IV characteristic curve and (b) is a reverse IV characteristic curve;

[0042] Figure 4 AlGaN-based RRAM has hysteresis and storage behavior after breakdown, where (a) is the reverse IV characteristic before and after breakdown, (b) is the forward IV characteristic before and after breakdown, and (c) is the bidirectional scanning forward IV characteristic before and after breakdown;

[0043] Figure 5 The IV characteristics of the random access memory based on vertical ultra-wide bandgap semiconductor devices at the first cycle and the 100th cycle in the voltage range of 15V to 25V;

[0044] Among them, 1. substrate, 2. AlN buffer layer, 3. n + -AlGaN layer, 4, n - -AlGaN drift layer, 5, n + -AlGaN insertion layer, 6. Al composition gradient p-AlGaN layer, 7. anode, 8. cathode. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the drawings in the implementation of this specification, but are not limited to this. Anything not fully described in the present invention shall be based on the conventional technology in the art.

[0046] Example 1

[0047] A random access memory based on a vertical ultra-wide bandgap semiconductor device, such as Figure 1 As shown, from bottom to top, it includes a substrate 1, an AlN buffer layer 2, and an + -AlGaN layer 3, n - -AlGaN drift layer 4, n + -AlGaN insertion layer 5 and Al composition gradient p-AlGaN layer 6, an anode 7 is arranged on the Al composition gradient p-AlGaN layer 6, n + A groove is etched on the upper part of the AlGaN layer 3, and a cathode 8 is arranged on the groove.

[0048] n + -AlGaN layer 3 is n + -Al 0.5 Ga 0.5 N layer, thickness 2μm, doping element is Si, doping concentration is 1E19cm -3 ;

[0049] n + -AlGaN insertion layer 5 is n + -Al 0.5 Ga 0.5 N insertion layer, thickness is 300nm, doping element is Si, doping concentration is 1E19cm -3 ;

[0050] The thickness of the AlN buffer layer 2 is 2.5 μm.

[0051] n - -AlGaN drift layer 4 is n - -Al 0.5 Ga 0.5 N drift layer, thickness is 3μm, doped with Si, doping concentration is 2E16cm -3 .

[0052] The Al composition graded p-AlGaN layer 6 includes a lower portion of Al 0.5→0 Ga 0.5→1 N layer and the p-GaN layer on the upper part.

[0053] Al 0.5→0 Ga 0.5→1 The thickness of the N layer is 100nm, the doping element is Mg, and the doping concentration is 1E19~2E19cm -3 .

[0054] The thickness of the p-GaN layer is 300nm, the doping element is Mg, and the doping concentration is 2E19~3E19cm -3 .

[0055] In this embodiment, the Al composition gradient p-AlGaN layer is arranged in this way, which has the following effects:

[0056] 1) Generate three-dimensional hole gas to increase the carrier concentration of the device. 2) The ohmic contact process of p-AlGaN is difficult, while the ohmic contact process of p-GaN is relatively simple; directly on Al 0.5 Ga 0.5 When growing GaN on N, the epitaxial wafer is prone to cracks due to the large lattice mismatch. The use of p-AlGaN with a gradient Al composition can reduce the lattice mismatch.

[0057] The memory device in the present invention is made based on the ultra-wide bandgap semiconductor material AlGaN. The material has an ultra-wide bandgap width, excellent thermal stability and radiation resistance, and is suitable for use in extreme environments such as aerospace, deep-sea exploration and nuclear industry.

[0058] When traditional RRAM devices are integrated with HEMT and MOSFET, it is difficult to achieve efficient monolithic integration. The present invention uses III-nitride to prepare RRAM, which is compatible with III-nitride-based HEMT and MOSFET preparation processes, making 1T1R storage units possible and significantly improving the integration and functional diversity of the device.

[0059] The present invention proposes a storage diode design with self-rectification characteristics, which reduces the influence of crosstalk current and improves the reliability and data integrity of a large-scale integrated storage array.

[0060] Example 2

[0061] A method for preparing the random access memory based on the vertical ultra-wide bandgap semiconductor device, as follows Figure 2 As shown, the following steps are included:

[0062] (1) Growing an epitaxial structure, sequentially growing AlN buffer layer 2, n +-AlGaN layer 3, n - -AlGaN drift layer 4, n + - AlGaN insertion layer 5 and Al composition graded p-AlGaN layer 6;

[0063] (2) Use SiO2 as a hard mask to perform trench etching on the epitaxial structure until the n + - AlGaN layer 3;

[0064] (3) using electron beam evaporation to deposit metal to form an ohmic contact cathode 7 on the groove;

[0065] (4) Finally, an ohmic contact anode 8 is formed on the upper portion of the Al composition gradient p-AlGaN layer by electron beam evaporation of metal.

[0066] In the present invention, the Al component in AlGaN is adjustable, and a metal organic chemical vapor phase epitaxy method is used, trimethylaluminum, trimethylgallium and ammonia are used as reaction sources to epitaxially grow AlGaN. During the growth process, the Al component in AlGaN can be adjusted by adjusting the molar flow rate ratio of trimethylaluminum to trimethylgallium per minute. The larger the Al component of AlGaN, the larger the band gap width.

[0067] Figure 3 In (a), the horizontal axis is the voltage applied to the anode, and the vertical axis is the current density flowing between the cathode and anode of the device. Figure 3 In (b), the horizontal axis is the voltage applied to the cathode, and the vertical axis is the current density flowing between the cathode and anode of the device (the current density is obtained by dividing the current flowing through the device by the anode area); I on Represents the current after the device is turned on, I off Indicates the current when the device is not turned on, I on / I off It indicates the switching ratio of the device. The larger the switching ratio, the better the rectification effect of the device.

[0068] Figure 3 (a) shows that the device has the rectification effect of a power pn diode, and the device switching ratio is 1E9; Figure 3 (b) shows that the breakdown voltage of the device, that is, the induced voltage is 47 V. Before the device breaks down, voltage is applied to the anode and the IV curve is measured, such as Figure 3 (a), similar to a power diode, it does not yet have storage performance. The anode of the device is grounded, and a voltage is applied to the cathode of the device. The measured IV curve is as follows: Figure 3 (b) As the applied voltage increases, the current of the device suddenly increases, inducing the storage performance of the device. Therefore, the voltage applied to the cathode of the device that causes the device current to suddenly increase is called the induced voltage.

[0069] Figure 4In (a), the horizontal axis is the voltage applied to the cathode, and the vertical axis is the current flowing between the cathode and anode of the device; the horizontal axis of (b) is the voltage applied to the anode, and the vertical axis is the current flowing between the cathode and anode of the device; in (c), set means that the voltage is swept from 0 to 25V, and reset means that the voltage is swept from 25V to 0.

[0070] from Figure 4 It can be seen that:

[0071] 1) Before breakdown: Under reverse bias, the current of RRAM is small, and the IV curve shows a typical insulating or high resistance state. This is due to the high resistivity of AlGaN material and the strong electron blocking effect. The current is limited by space charge, which manifests as a lower leakage current. After breakdown: After breakdown, the current of the reverse IV curve will increase significantly, showing a larger reverse current. This indicates that a conductive channel has been formed in the material, especially local defects, cracks or conductive paths caused by electric fields are generated in the device. The conductive mechanism switches from the insulating state to the low-resistance conductive state, and the reverse current shows a strong linear or exponential increase with the increase of bias voltage. This shows that after the device breaks down, the insulating layer in the device is broken down, forming a low-resistance conductive channel, resulting in a significant increase in the reverse current.

[0072] 2) Before breakdown: Under forward bias, the IV curve exhibits nonlinearity. At this time, the device still exhibits a high resistance state, and no obvious conductive channel is formed. After breakdown: After breakdown, the current in the forward IV curve increases sharply, indicating that a conductive channel has been formed and the device has switched to a low resistance state (LRS). This current increase is directly related to the formation of a conductive path and may be dominated by tunneling current or ohmic conductance. (b) It shows that after the device is broken down, the conductive properties switch from a high resistance state (HRS) to a low resistance state (LRS), which corresponds to the state switching in the memory write or erase operation (the high resistance state and the low resistance state can be regarded as "0" and "1" of the stored information). The large current after breakdown indicates the stability of the conductive channel and its good response to the external voltage.

[0073] 3) Before breakdown: During bidirectional scanning, IV exhibits a symmetrical high impedance state (the IV curves obtained when the voltage is scanned from 0 to 25V and from 25V to 0 are almost the same). After breakdown: The IV curves of bidirectional scanning do not overlap, indicating that the electric field-induced conductive channel in the device can exist stably under voltages of different polarities. The device has different current responses to different voltage application methods, which indicates that the device has storage performance.

[0074] Figure 5In the study, after 100 cycles, the IV characteristics of the AlGaN-based RRAM showed stable durability. The IV curve of the random access memory remained consistent after 100 cycles, indicating that the IV characteristics of the memory did not change significantly after multiple write and erase cycles, indicating excellent cycle durability, material and structural stability, and good data retention. This shows that the performance of the device is reliable and suitable for long-term use.

[0075] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A random access memory based on a vertical ultra-wide bandgap semiconductor device, characterized in that: From bottom to top, it includes substrate, AlN buffer layer, n + -AlGaN layer, n - -AlGaN drift layer, n + -AlGaN insertion layer and Al composition gradient p-AlGaN layer, an anode is arranged on the Al composition gradient p-AlGaN layer, and the n + A groove is etched on the upper part of the -AlGaN layer, and a cathode is arranged on the groove.

2. The random access memory based on vertical ultra-wide bandgap semiconductor device according to claim 1, characterized in that: n + -AlGaN layer is preferably n + -Al 0.5 Ga 0.5 N layer, thickness is 1-3μm, doping element is Si, doping concentration is 1E19cm -3 ~31E19cm -3 ; Further, + -Al 0.5 Ga 0.5 The thickness of the N layer is 2 μm and the doping concentration is 1E19 cm -3 .

3. The random access memory based on vertical ultra-wide bandgap semiconductor device according to claim 2, characterized in that: The + -AlGaN insertion layer is preferably n + -Al 0.5 Ga 0.5 N insertion layer, thickness is 280~320nm, doping element is Si, doping concentration is 1E19cm -3 ~31E19cm -3 ; Further, + -Al 0.5 Ga 0.5 N insertion layer, thickness is 300nm, doping concentration is 1E19cm -3 .

4. The random access memory based on vertical ultra-wide bandgap semiconductor device according to claim 3, characterized in that: The thickness of the AlN buffer layer is 2-3 μm, preferably 2.5 μm.

5. The random access memory based on vertical ultra-wide bandgap semiconductor device according to claim 4, characterized in that: The - -AlGaN drift layer is n - -Al 0.5 Ga 0.5 N drift layer, with a thickness of 2.5 to 3.5 μm, preferably 3 μm; The - -Al 0.5 Ga 0.5 The N drift layer is doped with Si at a concentration of 1E16 to 3E16 cm -3 , preferably 2E16cm -3 .

6. The random access memory based on vertical ultra-wide bandgap semiconductor device according to claim 5, characterized in that: The Al composition graded p-AlGaN layer includes a lower portion of Al 0.5→0 Ga 0.5→1 N layer and the p-GaN layer on the upper part.

7. The random access memory based on vertical ultra-wide bandgap semiconductor device according to claim 6, characterized in that: The Al 0.5→0 Ga 0.5→1 The thickness of the N layer is 100 nm, the doping element is Mg, and the doping concentration is 1E19~2E19 cm -3 .

8. The random access memory based on vertical ultra-wide bandgap semiconductor device according to claim 7, characterized in that: The thickness of the p-GaN layer is 300 nm, the doping element is Mg, and the doping concentration is 2E19-3E19 cm -3 .

9. A method for preparing a random access memory based on a vertical ultra-wide bandgap semiconductor device according to claim 8, characterized in that: The steps include: (1) Growth of epitaxial structure: AlN buffer layer, n + -AlGaN layer, n - -AlGaN drift layer, n + -AlGaN insertion layer and Al composition graded p-AlGaN layer; (2) Perform trench etching on the epitaxial structure until the n + - AlGaN layer; (3) using electron beam evaporation to deposit metal to form an ohmic contact cathode on the groove; (4) Finally, electron beam evaporation of metal is used to form an ohmic contact anode on the upper portion of the Al composition gradient p-AlGaN layer.

10. The method for preparing a random access memory based on a vertical ultra-wide bandgap semiconductor device according to claim 9, characterized in that: In step (2), SiO2 is used as a hard mask for trench etching.

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