A multi-bit memory based on homojunction and its preparation method

Abstract

The present invention discloses a multi-bit memory based on a homojunction and a method for preparing the same. The multi-bit memory based on a homojunction comprises: a substrate; a bottom electrode formed on the substrate; a functional layer, which is a multilayer amorphous oxide thin film with different oxygen contents, formed on the bottom electrode; and a top electrode formed on the functional layer. When a voltage is applied to the top electrode, each layer of the amorphous oxide thin film sequentially forms an oxygen vacancy conductive channel from top to bottom, achieving step-by-step modulation of the resistance state, allowing a single device to have the function of multi-state storage.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a multi-bit memory based on a homojunction and a preparation method thereof. Background Art

[0002] With the development of the information age, the ever-increasing amount of data and information has placed higher demands on memory. In particular, traditional three-terminal flash memory faces the challenge of scaling. The development of two-terminal resistive random access memory with improved scalability has become an important development direction for next-generation high-density storage.

[0003] On the other hand, as device integration continues to increase, memory storage capacity is gradually being limited by physical limitations. Simply increasing chip storage capacity by integrating more memory cells on the same chip is no longer enough to meet future high-density storage needs. There is an urgent need to explore new methods to increase device storage capacity. Against this backdrop, multi-bit memory has emerged. By achieving adjustable multi-bit storage within the same device unit, the storage capacity of a single device and the storage capacity of the entire memory module can be greatly improved. Therefore, the development of high-performance multi-bit memory is of great value.

[0004] Existing multi-bit memories face problems such as poor stability, unclear polymorphic distinction, and relatively random switching between different resistance states. Therefore, it is necessary to start from the working mechanism of polymorphic resistive switching and design a multi-bit memory with reliable resistance state transition from the source. Summary of the Invention

[0005] The present invention discloses a multi-bit memory based on a homojunction, comprising: a substrate; a bottom electrode formed on the substrate; a functional layer, which is a multilayer amorphous oxide film with different oxygen contents, formed on the bottom electrode; and a top electrode formed on the functional layer. When a voltage is applied to the top electrode, each layer of the amorphous oxide film sequentially forms an oxygen vacancy conductive channel from top to bottom, thereby realizing step-by-step modulation of the resistance state.

[0006] In the homojunction-based multi-bit memory of the present invention, preferably, the amorphous oxide film is three-layered.

[0007] In the multi-bit memory based on homojunction of the present invention, preferably, the oxygen content concentration gradually decreases from the first layer of amorphous oxide film to the second layer of amorphous oxide film to the third layer of amorphous oxide film, so that the functional layer forms a step-by-step oxygen vacancy state.

[0008] In the multi-bit memory based on homojunction of the present invention, preferably, when no voltage is applied, the device is in an initial logic resistance state 00; when voltage is applied to the top electrode, when the oxygen vacancy channel in the third amorphous oxide film is formed, the oxygen vacancy conductive channel in the second amorphous oxide film and the first amorphous oxide film has not yet been formed, so the device is in a resistance state lower than the initial state, that is, logic resistance state 01; when voltage is further applied, oxygen vacancy channels in the third amorphous oxide film and the second amorphous oxide film are formed, and the resistance state of the device is reduced again, that is, logic resistance state 10; voltage is continued to be applied, and oxygen vacancy channels in the third amorphous oxide film, the second amorphous oxide film and the first amorphous oxide film are all formed, and the resistance state of the device becomes the lowest, that is, logic resistance state 11, so the device has a continuously adjustable 4-level multi-bit resistance state.

[0009] In the multi-bit memory based on homojunction of the present invention, preferably, the amorphous oxide film is TiN x O 2-x ,TaN x O 2-x , HfN x O 2-x or ZnN x O 2-x .

[0010] The present invention also discloses a method for preparing a multi-bit memory based on a homojunction, comprising the following steps: forming a bottom electrode on a substrate; forming a multilayer amorphous oxide film with different oxygen contents as a functional layer on the bottom electrode; forming a top electrode on the functional layer, applying voltage to the top electrode, and forming oxygen vacancy conductive channels in each layer of the amorphous oxide film from top to bottom in sequence, thereby realizing step-by-step modulation of the resistance state.

[0011] In the homojunction-based multi-bit memory preparation method of the present invention, preferably, the amorphous oxide film is three-layered.

[0012] In the homojunction-based multi-bit memory preparation method of the present invention, it is preferred that the oxygen content concentration gradually decreases from the first layer of amorphous oxide film to the second layer of amorphous oxide film to the third layer of amorphous oxide film, so that the functional layer forms a step-by-step oxygen vacancy state.

[0013] In the preparation method of a multi-bit memory based on a homojunction of the present invention, preferably, when no voltage is applied, the device is in an initial logic resistance state 00; when voltage is applied to the top electrode, when the oxygen vacancy channel in the third oxide film is formed, the oxygen vacancy conductive channel in the second amorphous oxide film and the first amorphous oxide film has not yet been formed, so the device is in a resistance state lower than the initial state, that is, logic resistance state 01; when voltage is further applied, oxygen vacancy channels in the third amorphous oxide film and the second amorphous oxide film are formed, and the resistance state of the device is reduced again, that is, logic resistance state 10; voltage is continued to be applied, and oxygen vacancy channels in the third amorphous oxide film, the second amorphous oxide film and the first amorphous oxide film are all formed, and the resistance state of the device becomes the lowest, that is, logic resistance state 11, so the device has a continuously adjustable 4-level multi-bit resistance state.

[0014] In the method for preparing a multi-bit memory based on a homojunction of the present invention, preferably, the amorphous oxide film is TiN x O 2-x ,TaN x O 2-x , HfN x O 2-x or ZnN x O 2-x .

[0015] Beneficial effects:

[0016] (1) Using amorphous oxide thin film stacks with different oxygen ratios as the resistive switching functional layer, the device characteristics can be controlled by designing the device material system.

[0017] (2) The oxygen defect concentrations in different layers of the functional layer are regulated to achieve segmented accumulation of conductive filaments, thereby realizing the multi-bit storage function from a mechanistic perspective.

[0018] (3) A single device is given the function of polymorphic storage, avoiding the physical limitations of high-density integration and solving the problem of limited storage capacity of traditional devices from a hardware perspective. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of the method for preparing multi-bit memory based on homojunction.

[0020] Figure 2 It is a schematic diagram of the device structure after the bottom electrode is formed.

[0021] Figure 3 It is a schematic diagram of the device structure after the first layer of amorphous oxide film is formed.

[0022] Figure 4 It is a schematic diagram of the device structure after the second layer of amorphous oxide film is formed.

[0023] Figure 5 This is a schematic diagram of the device structure after the third layer of amorphous oxide film is formed.

[0024] Figure 6 Schematic diagram of the device structure after the top electrode is formed.

[0025] Figure 7 This is a schematic diagram of the working principle of multi-bit memory based on homojunction. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. 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. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be noted that the terms "upper," "lower," "vertical," and "horizontal," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In addition, many specific details of the present invention are described below, such as device structure, materials, dimensions, processing techniques, and technologies, to facilitate a clearer understanding of the present invention. However, as will be appreciated by those skilled in the art, the present invention may be practiced without following these specific details. Unless otherwise noted below, various components of the device may be constructed from materials known to those skilled in the art, or materials with similar functions developed in the future may be used.

[0029] Figure 1 This is a flow chart of the method for preparing an artificial heterogeneous synaptic device with a two-dimensional / zero-dimensional hybrid structure according to the present invention. Figure 1 As shown, the following steps are included:

[0030] Step S1: prepare a 4-inch silicon wafer as a substrate 100 for preparing a multi-bit memory based on a homojunction. The substrate may also be made of silicon oxide wafer, glass, aluminum oxide, etc.

[0031] Step S2, using physical vapor deposition to grow a bottom electrode Pt101 with a thickness of 80nm on the substrate 100, the structure is as follows Figure 2 As shown in the figure, the growth process uses a power of 60W, Ar2 gas at a flow rate of 30sccm. The bottom electrode material can also be Pd, Au, TiN, etc.; the thickness can range from 50nm to 150nm; and the preferred power range is 50W to 120W.

[0032] Step S3, growing TiN on the bottom electrode 101 by physical vapor deposition x O 2-x Amorphous oxide films serve as three functional layers. The oxygen concentration in the three layers gradually decreases from the first to the second and then to the third, resulting in a step-by-step pattern of oxygen vacancies in the functional layers.

[0033] In the process of growing the first layer of amorphous oxide film 102, the flow rates of Ar2, O2 and N2 are 30 sccm, 10 sccm and 0 sccm respectively, the power is controlled at 60 W, the sputtering time is controlled at 200 s, and the obtained structure is as follows: Figure 3 shown.

[0034] During the growth of the second layer of amorphous oxide film 103, the flow rates of Ar2, O2 and N2 are 30 sccm, 5 sccm and 5 sccm respectively, the power is controlled at 60 W, the sputtering time is controlled at 200 s, and the obtained structure is as follows Figure 4 shown.

[0035] During the growth of the third layer of amorphous oxide film 104, the flow rates of Ar2, O2 and N2 are 30 sccm, 1 sccm and 9 sccm respectively, the power is controlled at 60 W, the sputtering time is controlled at 200 s, and the obtained structure is as follows Figure 5 shown.

[0036] However, the present invention is not limited to this, and the number of functional layers is not limited to three. The material of the functional layer can also be TaN x O 2-x , HfN x O 2-x , ZnN x O 2-x etc.; the power selection range is 50W to 100W; the sputtering time is preferably 100s to 300s.

[0037] Step S4, using UV lithography to define a 100 μm × 100 μm rectangular top electrode shape on the sample, and using physical vapor deposition to grow 50 nm thick Al as the top electrode 105, the resulting structure is as follows Figure 6As shown, the growth process uses 60W power, Ar2 gas, and a flow rate of 30 sccm. The top electrode can also be made of Au, TaN, etc.; the thickness is preferably 30nm to 80nm; and the power is preferably 50W to 120W.

[0038] like Figure 6 As shown, the multi-bit memory based on homojunction of the present invention includes: a substrate 100; a bottom electrode 101, formed on the substrate 100; a functional layer, which is a multi-layer amorphous oxide film with different oxygen contents formed on the bottom electrode, and in this embodiment, there are three layers, including a first amorphous oxide film 102, a second amorphous oxide film 103 and a third amorphous oxide film 104; a top electrode 105, formed on the functional layer.

[0039] When a voltage is applied to the top electrode 103 , the three layers of amorphous oxide thin films sequentially form oxygen vacancy conductive channels from top to bottom, thereby obtaining different resistance states and realizing step-by-step modulation of the resistance state. Figure 7 This is a cross-sectional diagram of a single device, showing the working principle of multi-bit memory based on homojunction. Figure 7 As shown, when no voltage is applied, the device is in an initial logic resistance state of 00. When voltage is applied to the top electrode 105, and oxygen vacancy channels form in the third amorphous oxide film 104, oxygen vacancy conductive channels have not yet formed between the second amorphous oxide film 103 and the first amorphous oxide film 102, resulting in a lower resistance state than the initial state, namely, logic resistance state 01. Further voltage application causes oxygen vacancy channels to form in the third amorphous oxide film 104 and the second amorphous oxide film 102, further lowering the device's resistance to logic resistance state 10. Further voltage application causes oxygen vacancy channels to form in the third amorphous oxide film 104, the second amorphous oxide film 103, and the first amorphous oxide film 102, resulting in the device's lowest resistance state, namely, logic resistance state 11. Thus, the device has a continuously adjustable four-level multi-bit resistance state.

[0040] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with this technical field within the technical scope disclosed in the present invention should be covered by the scope of protection of the present invention.

Claims

1. A multi-bit memory based on a homojunction, characterized in that: include: substrate; a bottom electrode formed on the substrate; a functional layer, which is a multilayer amorphous oxide thin film with different oxygen contents, formed on the bottom electrode; a top electrode formed on the functional layer, When voltage is applied to the top electrode, each layer of amorphous oxide film forms oxygen vacancy conductive channels from top to bottom, realizing step-by-step modulation of the resistance state. Wherein, the amorphous oxide film is TiN x O 2-x ,TaN x O 2-x , HfN x O 2-x or ZnN x O 2-x .

2. The multi-bit memory based on homojunction according to claim 1, characterized in that: The amorphous oxide film comprises three layers.

3. The multi-bit memory based on homojunction according to claim 2, characterized in that: The oxygen content concentration gradually decreases from the first amorphous oxide film layer to the second amorphous oxide film layer and then to the third amorphous oxide film layer, so that the functional layer forms a step-wise oxygen vacancy state.

4. The multi-bit memory based on homojunction according to claim 2, characterized in that: When no voltage is applied, the device is in the initial logic resistance state 00; Applying a voltage to the top electrode, when the oxygen vacancy channel is formed in the third amorphous oxide film, the oxygen vacancy conductive channel in the second amorphous oxide film and the first amorphous oxide film has not yet been formed, so the device is in a lower resistance state than the initial state, that is, a logic resistance state 01; When voltage is further applied, oxygen vacancy channels are formed in the third and second amorphous oxide films, and the resistance state of the device decreases again, that is, the logical resistance state 10; Continuing to apply voltage, oxygen vacancy channels are formed in the third amorphous oxide film, the second amorphous oxide film, and the first amorphous oxide film, and the resistance state of the device becomes the lowest, that is, the logical resistance state 11. Therefore, the device has a continuously adjustable 4-level multi-bit resistance state.

5. A method for preparing a multi-bit memory based on a homojunction, characterized in that: The following steps are involved: forming a bottom electrode on the substrate; forming a multilayer amorphous oxide thin film with different oxygen contents as a functional layer on the bottom electrode; forming a top electrode on the functional layer, When voltage is applied to the top electrode, each layer of amorphous oxide film forms oxygen vacancy conductive channels from top to bottom, realizing step-by-step modulation of the resistance state. Wherein, the amorphous oxide film is TiN x O 2-x ,TaN x O 2-x , HfN x O 2-x or ZnN x O 2-x .

6. The method for preparing a multi-bit memory based on a homojunction according to claim 5, characterized in that: The amorphous oxide film comprises three layers.

7. The method for preparing a multi-bit memory based on a homojunction according to claim 6, characterized in that: The oxygen content concentration gradually decreases from the first amorphous oxide film layer to the second amorphous oxide film layer and then to the third amorphous oxide film layer, so that the functional layer forms a step-wise oxygen vacancy state.

8. The method for preparing a multi-bit memory based on a homojunction according to claim 6, wherein: When no voltage is applied, the device is in the initial logic resistance state 00; A voltage is applied to the top electrode. When the oxygen vacancy channel is formed in the third oxide film, the oxygen vacancy conductive channel in the second amorphous oxide film and the third amorphous oxide film has not yet been formed. Therefore, the device is in a lower resistance state than the initial state, that is, a logic resistance state 01. When voltage is further applied, oxygen vacancy channels are formed in the third and second amorphous oxide films, and the resistance state of the device decreases again, that is, the logical resistance state 10; Continuing to apply voltage, oxygen vacancy channels are formed in the third amorphous oxide film, the second amorphous oxide film, and the first amorphous oxide film, and the resistance state of the device becomes the lowest, that is, the logical resistance state 11. Therefore, the device has a continuously adjustable 4-level multi-bit resistance state.

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