Wurtzite ferroelectric diode and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor device preparation, in particular to a wurtzite ferroelectric diode and a preparation method thereof, and the method comprises the steps: depositing a bottom electrode layer on a substrate; and depositing a ferroelectric layer on the bottom electrode layer based on a reactive ion co-sputtering mode, heating in the ferroelectric layer deposition process, cooling the substrate, and depositing a top electrode layer on the ferroelectric layer after the cooling of the substrate is completed. According to the method, the ferroelectric layer is deposited in a reactive ion co-sputtering mode, heating is carried out in the ferroelectric layer deposition process, the heating temperature is controlled within 400 DEG C, the dense and uniform ferroelectric layer with high adhesive force is achieved at the low temperature, and the method can be well compatible with the complementary metal oxide semiconductor technology; the bottom electrode layer and the top electrode layer are deposited in a physical vapor deposition mode, uniform and compact metal films are deposited, the method is suitable for deposition of the bottom electrode and the top electrode, and the reliability of the ferroelectric diode is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor device fabrication, and more particularly to a wurtzite ferroelectric diode and a method for fabricating the same. Background Art

[0002] In recent years, due to the excellent ferroelectric properties of wurtzite ferroelectric materials, they are considered to be one of the preferred materials for next-generation novel memories.

[0003] Currently, the methods for fabricating wurtzite ferroelectric diodes generally include molecular beam epitaxy (MBE), metalorganic chemical vapor deposition (MOCVD), or physical vapor deposition (PVD). However, if molecular beam epitaxy or chemical vapor deposition is used, the fabrication temperature usually exceeds 400°C, which is not compatible with complementary metal oxide semiconductor (CMOS) processes, resulting in low-performance ferroelectric diodes. Summary of the Invention

[0004] The purpose of the present invention is to provide a wurtzite ferroelectric diode and a method for fabricating the same. The present invention adopts the following technical means:

[0005] A method for fabricating a wurtzite ferroelectric diode includes:

[0006] Depositing a bottom electrode layer on a substrate;

[0007] Depositing a ferroelectric layer on the bottom electrode layer by reactive ion co-sputtering. During the deposition of the ferroelectric layer, heating is performed, and the selected material corresponds to a heating temperature range of 100 - 400°C;

[0008] Cooling the substrate;

[0009] After cooling the substrate is completed, depositing a top electrode layer on the ferroelectric layer;

[0010] Both the deposition of the bottom electrode layer and the top electrode layer are achieved by physical vapor deposition (PVD).

[0011] In some embodiments of the present application, the constituent material of the bottom electrode layer is one or more of W, Ti, Ta, WN, TiN, TaN, and the thickness of the bottom electrode layer is 20 - 100 nm.

[0012] In some embodiments of the present application, the constituent material of the ferroelectric layer is any one of Al1-xScxN, Al1-xBxN, Zn1-xMgxO, or Ga1-xScxN, where x is 0.05 - 0.95, and the thickness of the ferroelectric layer is 10 - 40 nm.

[0013] In some embodiments of the present application, depositing a ferroelectric layer on the bottom electrode layer based on reactive ion co-sputtering specifically includes: determining a metal and a target, and depositing the ferroelectric layer on the bottom electrode layer by means of co-sputtering using the metal and the target.

[0014] In some embodiments of the present application, the purity of both the metal and the target is 4N9, the deposition power is 100 - 2000W, the deposition pressure is 2 - 40mTorr, the working gas during deposition is nitrogen and argon, the ratio of nitrogen to argon is 10 - 90%, and the working gas flow rate is 100 - 2000sccm.

[0015] In some embodiments of the present application, before depositing the ferroelectric layer, it further includes: depositing a seed on the bottom electrode layer, and the constituent material of the seed is one or more of Pt, Mo, Al, Ru, W, Ta, N, B.

[0016] In some embodiments of the present application, it further includes: after depositing the ferroelectric layer, depositing an oxide on the ferroelectric layer.

[0017] In some embodiments of the present application, cooling is performed using cryo-cooling, cooling the substrate to room temperature, and the temperature of cryo-cooling can be selected as 100k.

[0018] In some embodiments of the present application, the constituent material of the top electrode layer is one or more of W, Ti, Ta, WN, TiN, TaN, and the thickness of the top electrode layer is 20 - 100nm.

[0019] In some embodiments of the present application, a wurtzite ferroelectric diode is also disclosed.

[0020] Compared with the prior art, the wurtzite ferroelectric diode and its preparation method provided by the present invention have the following advantages: The present invention uses reactive ion co-sputtering to deposit the ferroelectric layer, heats during the deposition process of the ferroelectric layer, and controls the heating temperature within 400°C, achieving a dense, uniform, and strongly adherent ferroelectric layer at a relatively low temperature, which can be well compatible with the complementary metal oxide semiconductor process; uses physical vapor deposition to deposit the bottom electrode layer and the top electrode layer, depositing a uniform and dense metal thin film, suitable for the deposition of the bottom electrode and the top electrode, and can improve the reliability of the ferroelectric diode; the ferroelectric diode prepared by the preparation method of the present application can be used to manufacture high-density ferroelectric memories and can improve the storage performance of the ferroelectric memories. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic flow chart of a method for preparing a wurtzite ferroelectric diode in an embodiment of the present invention;

[0022] Figure 2It is a schematic diagram of depositing a ferroelectric layer by reactive ion co-sputtering in an embodiment of the present invention;

[0023] Figure 3 It is a schematic diagram of cooling the substrate in an embodiment of the present invention;

[0024] Figure 4 It is a schematic structural diagram of a wurtzite ferroelectric diode in an embodiment of the present invention. Detailed implementation manners

[0025] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. Hereinafter, the present invention will be described in detail with reference to the drawings and in combination with the embodiments.

[0026] As Figure 1 shown, a method for preparing a wurtzite ferroelectric diode of the present invention includes:

[0027] Step 100: Deposit a bottom electrode layer on a substrate.

[0028] Among them, the substrate is used to provide a physical support platform for semiconductor devices to ensure the structural stability of the devices during manufacturing, use, and testing. The material of the substrate can be selected from silicon, gallium arsenide, silicon carbide, and gallium nitride. The silicon substrate can provide good electrical properties, thermal stability, and mechanical strength. Gallium arsenide is a compound semiconductor material with an electron mobility higher than that of silicon and is suitable for high-frequency and high-speed devices. Silicon carbide is a wide-bandgap semiconductor material with high thermal conductivity, high breakdown electric field, and high saturated electron velocity and is suitable for high-temperature, high-pressure, and high-power applications. When specifically selecting, the material is selected according to the use of the prepared diode.

[0029] Among them, the bottom electrode layer is used to provide electrical connection and structural support for the diode device. In this solution, PVD or CVD methods can be used for deposition. Preferably, PVD deposition is used to deposit a uniform and dense metal thin film, which can improve the reliability of the ferroelectric diode

[0030] Step 200: Deposit a ferroelectric layer on the bottom electrode layer based on the method of reactive ion co-sputtering. During the deposition of the ferroelectric layer, heating is performed, and the heating temperature range corresponding to the selected material during the heating process is 100 - 400 °C.

[0031] Among them, reactive ion sputtering is a thin film deposition technology. The specific implementation method is to use an ion beam to bombard the target material, so that the target atoms or molecules are sputtered out and deposited on the substrate to form a thin film. During the deposition of the ferroelectric layer, heating is carried out, and the heating temperature is controlled between 100°C and 400°C to promote the crystallization and adhesion of the thin film. At the same time, a dense, uniform and strongly adherent ferroelectric layer can be achieved at a temperature below 400°C, which can be well compatible with the complementary metal oxide semiconductor process. The heating temperature is selected based on the material selection.

[0032] Step 300: Cool the substrate.

[0033] Among them, the process of cooling the substrate can ensure the device performance and reliability. During the high-temperature treatment process, thermal stress may be generated in the substrate material. Rapid cooling can help release the stress and prevent the material from cracking or deforming.

[0034] Step 400: After the cooling of the substrate is completed, deposit a top electrode layer on the ferroelectric layer;

[0035] Among them, when the substrate temperature reaches 100K, the cooling is completed. When depositing the top electrode layer, the deposition process needs to be precisely controlled to ensure a stable contact is formed between the top electrode and the ferroelectric layer. The top electrode layer is used to provide a loop path for connection with the external circuit to ensure that current can flow smoothly into and out of the ferroelectric device.

[0036] The deposition of the bottom electrode layer and the top electrode layer are both realized by physical vapor deposition (PVD).

[0037] Among them, physical vapor deposition (PVD) is a thin film deposition technology carried out in a vacuum or low-pressure environment. By directly converting the material from a solid state to a gaseous state and then condensing it on the substrate to form a solid thin film.

[0038] The present invention uses reactive ion co-sputtering to deposit the ferroelectric layer, heats during the deposition of the ferroelectric layer, and controls the heating temperature within 400°C. A dense, uniform and strongly adherent ferroelectric layer can be achieved at a lower temperature, which can be well compatible with the complementary metal oxide semiconductor process; uses physical vapor deposition to deposit the bottom electrode layer and the top electrode layer, deposits a uniform and dense metal thin film, is suitable for the deposition of the bottom electrode and the top electrode, and can improve the reliability of the ferroelectric diode.

[0039] In some embodiments of the present application, the constituent material of the bottom electrode layer is one or more of W, Ti, Ta, WN, TiN, TaN, and the thickness of the bottom electrode layer is 20 - 100nm.

[0040] Among them, tungsten (W) has high thermal stability and electrical conductivity, and also has good wear resistance. Titanium (Ti) is light in weight and high in strength, with good corrosion resistance and biocompatibility. Molybdenum (Ta) has a high melting point and high hardness, with excellent corrosion resistance and chemical stability. Tungsten nitride (WN) has high hardness and wear resistance. Titanium nitride (TiN) is a high-hardness ceramic material, with high thermal stability and corrosion resistance.

[0041] In this embodiment, the bottom electrode is composed of a combination of multiple materials among W, Ti, Ta, WN, TiN, and TaN. Different materials have different conductive properties. By using them in combination, the conductivity of the bottom electrode layer can be optimized, the resistance can be reduced, and the overall performance of the device can be improved. Titanium and molybdenum materials have high resistance to various chemical environments. Using them in combination can improve the corrosion resistance of the bottom electrode layer. The combination of multiple materials can improve the adhesion between the bottom electrode layer and the ferroelectric layer, reduce the risk of delamination and peeling, and improve the device reliability.

[0042] Among them, the thickness of the bottom electrode layer is 20 - 100 nm. For example, 30 nm, 50 nm, 80 nm. A thinner bottom electrode layer can reduce the contact resistance of the device, thereby reducing the overall resistance and improving the efficiency of the electronic device. A lower resistance helps to reduce the power consumption when the device is working.

[0043] In some embodiments of the present application, the composition material of the ferroelectric layer is Al 1-x Sc x N, Al 1-x B x N, Zn 1-x Mg x O or Ga 1-x Sc x N, where x is 0.05 - 0.95, and the thickness of the ferroelectric layer is 10 - 40 nm.

[0044] Among them, Al 1-x Sc x N is formed by the combination of aluminum (Al) and scandium (Sc), which can adjust the bandgap width and polarization characteristics of the material and improve the polarization intensity of the diode. Al 1-x B x N can change the electrical properties of the material, improve the breakdown electric field and reduce the leakage current. The diode prepared by it has high thermal stability and chemical stability. Zn 1-x Mg x O can optimize the dielectric properties and ferroelectric properties of the ferroelectric layer. The diode prepared by it has good thermal stability and low manufacturing cost. Ga 1-x Sc x N supports fast polarization reversal and is suitable for high-frequency applications of diodes. Those skilled in the art can select materials according to the use of the diodes prepared.

[0045] Among them, x is 0.05 - 0.95, for example, 0.2, 0.5, and the thickness of the ferroelectric layer is 10 - 40 nm, for example, 20 nm, 40 nm.

[0046] In some embodiments of the present application, as Figure 2 shown, depositing the ferroelectric layer on the bottom electrode layer based on the reactive ion co - sputtering method specifically includes: determining the metal and the target, and depositing the ferroelectric layer on the bottom electrode layer by means of co - sputtering with the metal and the target.

[0047] Specifically, the bottom heating element is used to heat the substrate, which helps to improve the deposition quality and adhesion of the thin film. Argon gas is introduced into the reaction chamber as the sputtering gas. Argon ions are accelerated under the action of an electric field and strike the target. The argon ions are accelerated under the action of the electric field to form an ion beam. These ion beams strike the surface of the target, sputtering out the target atoms to form an atomic beam. At the same time, reaction gases (nitrogen, oxygen) are introduced into the reaction chamber. The reaction gases react chemically with the sputtered target atomic beam to form a compound, which is deposited on the surface of the bottom electrode layer to form the ferroelectric layer.

[0048] In this embodiment, due to the bombardment of the target by argon ions, the sputtering efficiency is improved, and a relatively fast deposition rate can be obtained, so as to form a uniform ferroelectric thin film on the bottom electrode. The ferroelectric thin film deposited by the reactive ion co - sputtering method has good densification, uniform film formation, and low surface roughness, which can promote the formation of an ideal crystal structure of the thin film, thereby enhancing the comprehensive performance of the fabricated diode.

[0049] In some embodiments of the present application, the purity of the metal and the target is preferably 4N9, the deposition power is 100 - 2000 W, the deposition pressure is 2 - 40 mTorr, the working gases during deposition are nitrogen and argon, the ratio of nitrogen to argon is 10 - 90%, and the working gas flow rate is 100 - 2000 sccm.

[0050] In some embodiments of the present application, before depositing the ferroelectric layer, it further includes: depositing seeds on the bottom electrode layer, and the constituent materials of the seeds are one or more of Pt, Mo, Al, Ru, W, Ta, N, B.

[0051] Among them, different materials have different physical, chemical, and electrical properties. By combining multiple materials, their advantages can be integrated, and the deficiencies of single materials can be compensated, thereby optimizing the working performance of ferroelectric thin films. For example, Pt has good electrical conductivity, thermal stability, and chemical stability, Ru has excellent oxidation resistance and corrosion resistance, and light metals such as Al and B can provide special stress regulation or chemical reactivity. The comprehensive application of multiple materials can achieve the comprehensive regulation of the crystallization orientation, stress state, interface quality, and electrical conductivity of ferroelectric thin films to optimize the comprehensive performance of the ferroelectric layer.

[0052] In some embodiments of the present application, it further includes: after depositing the ferroelectric layer, an oxide is deposited on the ferroelectric layer.

[0053] Among them, the oxide layer can serve as an insulating layer to prevent electrical short circuits between the ferroelectric layer and other layers or electrodes, thereby improving the electrical isolation performance of the device, while reducing the leakage current of the ferroelectric layer and improving the storage stability and retention characteristics of the device.

[0054] Based on the above embodiments, in the embodiments of the present invention, after depositing the ferroelectric layer in the above steps, an oxide layer can also be deposited on the ferroelectric layer. If multiple oxide layers are deposited, large thermal expansion stresses may be generated at the interface, which may cause the device to crack or delaminate. Depositing a single oxide layer can reduce thermal expansion stress and improve the mechanical stability of the device. In addition, a single oxide layer is sufficient to provide the insulation performance and protection effect required by the device, and there is no need to deposit multiple oxide layers.

[0055] In some embodiments of the present application, as Figure 3 shown, cryogenic cooling is used for cooling. The substrate is cooled to room temperature, and the temperature of cryogenic cooling can be selected as 100K.

[0056] Among them, cryogenic cooling (cryo) is usually used after depositing the thin film to rapidly reduce the temperature of the material to improve the stability of the thin film structure. 100K is -173.15°C. During the deposition process, the material may generate thermal stress due to temperature changes. Therefore, cooling the substrate to 100K can reduce thermal stress and prevent the material from cracking or deforming. In this solution, selecting 100K has a higher cost-effectiveness and can achieve the required low-temperature effect at a lower cost.

[0057] In some embodiments of the present application, the composition material of the top electrode layer is one or more of W, Ti, Ta, WN, TiN, TaN, and the thickness of the top electrode layer is 20 - 100nm.

[0058] In some embodiments of the present application, as Figure 4 shown, a wurtzite ferroelectric diode is also disclosed.

[0059] Among them, the diode has a bottom electrode layer, a ferroelectric layer, and a top electrode layer.

[0060] Compared with the prior art, the wurtzite ferroelectric diode and its preparation method provided by the present invention have the following advantages: The present invention uses reactive ion co-sputtering to deposit the ferroelectric layer, heats during the deposition of the ferroelectric layer, and controls the heating temperature within 400 °C, achieving a dense, uniform and strongly adherent ferroelectric layer at a relatively low temperature, which can be well compatible with the complementary metal oxide semiconductor process; The bottom electrode layer and the top electrode layer are deposited by physical vapor deposition, depositing a uniform and dense metal thin film, which is suitable for the deposition of the bottom electrode and the top electrode, and can improve the reliability of the ferroelectric diode; The ferroelectric diode prepared by the preparation method of the present application can be used to manufacture a high-density ferroelectric memory and can improve the storage performance of the ferroelectric memory.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the specific implementation manners of the present invention or make equivalent replacements, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A method for preparing a wurtzite ferroelectric diode, characterized in that: include: depositing a bottom electrode layer on the substrate; Depositing a ferroelectric layer on the bottom electrode layer by reactive ion co-sputtering, wherein heating is performed during the deposition of the ferroelectric layer, and the heating temperature range corresponding to the selected material during the heating process is 100-400° C.; cooling the substrate; After the substrate is cooled, a top electrode layer is deposited on the ferroelectric layer; The deposition of the bottom electrode layer and the top electrode layer are both achieved by physical vapor deposition (PVD).

2. The method for preparing a wurtzite ferroelectric diode according to claim 1, characterized in that: The bottom electrode layer is made of one or more materials selected from the group consisting of W, Ti, Ta, WN, TiN, and TaN, and has a thickness of 20-100 nm.

3. The method for preparing a wurtzite ferroelectric diode according to claim 1, characterized in that: The ferroelectric layer is made of Al 1-x Sc x N, Al 1-x B x N, Zn 1-x Mg x O or Ga 1-x Sc x Any one of N, wherein x is 0.05-0.95, and the thickness of the ferroelectric layer is 10-40 nm.

4. The method for preparing a wurtzite ferroelectric diode according to claim 1, characterized in that: The method of depositing the ferroelectric layer on the bottom electrode layer based on reactive ion co-sputtering specifically includes: determining a metal and a target material, and depositing the ferroelectric layer on the bottom electrode layer by co-sputtering the metal and the target material.

5. The method for preparing a wurtzite ferroelectric diode according to claim 4, characterized in that: The purity of the metal and the target material are both 4N9, the deposition power is 100-2000W, the deposition pressure is 2-40mTorr, the working gas during deposition is nitrogen and argon, the ratio of nitrogen to argon is 10-90%, and the working gas flow rate is 100-2000sccm.

6. The method for preparing a wurtzite ferroelectric diode according to claim 1, characterized in that: Before depositing the ferroelectric layer, the method further includes: depositing seeds on the bottom electrode layer, wherein the constituent material of the seeds is one or more of Pt, Mo, Al, Ru, W, Ta, N, and B.

7. The method for preparing a wurtzite ferroelectric diode according to claim 1, characterized in that: Also includes: After depositing the ferroelectric layer, an oxide is deposited on the ferroelectric layer.

8. The method for preparing a wurtzite ferroelectric diode according to claim 1, characterized in that: The cooling adopts cryo cooling to cool the substrate to room temperature, and the temperature of the cryogenic cooling is 100K.

9. The method for preparing a wurtzite ferroelectric diode according to claim 1, characterized in that: The top electrode layer is made of one or more materials selected from the group consisting of W, Ti, Ta, WN, TiN, and TaN, and has a thickness of 20-100 nm.

10. A wurtzite ferroelectric diode, characterized in that: A wurtzite ferroelectric diode obtained by the preparation method according to any one of claims 1 to 9.

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