Background
With the continuous development of integrated circuits, high-speed, high-density, and novel electrically accessible non-volatile memories (NVM) have been recognized as the key to the development of future information technology. Existing NVMs include molecular, random access, flash and ferroelectric NVMs, of which ferroelectric NVMs are of great interest for their low power consumption, high write-erase speed and high endurance performance. However, there are several obstacles to commercialization of perovskite ferroelectric NVM, such as low storage density, high integration cost, etc.;
a Topological Insulator (TI) is a material that is an insulator (or semiconductor) in the bulk, with the surface protected in the metallic state by time-reversal symmetry. Due to the quantum confinement effect of the TI material sub-surface, a two-dimensional electron gas (2DEG) is formed on the surface, making the surface band-gap-free. The electrons in the 2DEG can be viewed as a mass-free dirac fermi. Therefore, the electrons of the TI surface have higher mobility and response speed. However, there is currently little research on the polarization of TI materials and their application to memory.
Disclosure of Invention
The invention discloses a nonvolatile memory device based on topological insulator polarization, which comprises: a substrate; the buried gate is formed in the substrate, and the upper surface of the buried gate is flush with the upper surface of the substrate; the first high-K dielectric layer/topological insulator layer/second high-K dielectric layer lamination covers the buried gate, wherein the topological insulator layer is packaged between the two high-K dielectric layers, and the length of the topological insulator layer is equivalent to that of the buried gate; a two-dimensional channel layer formed on the second high-K dielectric layer, completely covering the topological insulator layer; and the source electrode and the drain electrode are respectively formed on the substrate and two sides of the two-dimensional channel layer, partially cover the two-dimensional channel layer and are not overlapped with the buried gate, and nonvolatile storage is realized based on polarization inversion of the topological insulator layer.
In the nonvolatile memory device based on the topological insulator polarization according to the present invention, preferably, the topological insulator layer is Bi2Se3Or Bi2Te3。
In the topological insulator polarization based nonvolatile memory device of the present invention, preferably, the first high-K dielectric layer and the second high-K dielectric layer are formed of a single dielectric materialThe K dielectric layer is BN or Al2O3、HfO2Or ZrO2。
In the non-volatile memory device based on topological insulator polarization according to the present invention, preferably, the two-dimensional channel layer MoS2Or WS2。
The invention also discloses a preparation method of the nonvolatile memory device based on the topological insulator polarization, which comprises the following steps: forming a buried gate in the substrate to enable the upper surface of the buried gate to be flush with the upper surface of the substrate; forming a first high-K dielectric layer on the buried gate, wherein the first high-K dielectric layer covers the buried gate; forming a topological insulator layer on the first high-K dielectric layer, wherein the length of the topological insulator layer is equivalent to that of the buried gate; forming a second high-K dielectric layer on the topological insulator layer, covering the topological insulator layer; forming a two-dimensional channel layer on the second high-K dielectric layer, which completely covers the topological insulator layer; and forming a source electrode and a drain electrode on the substrate and on two sides of the two-dimensional channel layer, wherein the source electrode and the drain electrode respectively partially cover the two-dimensional channel layer and are not overlapped with the buried gate, and nonvolatile storage is realized based on polarization inversion of the topological insulator layer.
In the method for manufacturing a non-volatile memory device based on topological insulator polarization, preferably, the third-generation topological insulator layer is Bi2Se3Or Bi2Te3。
In the method for manufacturing the nonvolatile memory device based on the topological insulator polarization, the first high-K dielectric layer and the second high-K dielectric layer are preferably BN and Al2O3、HfO2Or ZrO2。
In the method for manufacturing the non-volatile memory device based on the topological insulator polarization, preferably, the two-dimensional channel layer MoS2Or WS2。
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly and completely understood, the technical solutions in the embodiments of the present invention will be described below with reference to the accompanying drawings in the embodiments of the present invention, and it should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. The described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "upper", "lower", "vertical", "horizontal", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
Furthermore, numerous specific details of the invention, such as structure, materials, dimensions, processing techniques and techniques of the devices are described below in order to provide a more thorough understanding of the invention. However, as will be understood by those skilled in the art, the present invention may be practiced without these specific details. Unless otherwise specified below, each part in the device may be formed of a material known to those skilled in the art, or a material having a similar function developed in the future may be used.
Fig. 1 is a flow chart of a method for fabricating a non-volatile memory device based on topological insulator polarization. As shown in fig. 1, the method comprises the following steps:
step S1, cleaning the Si100/SiO 2101 Substrate (SiO)2 Layer 101 thickness 285nm) and a series of 160 μm by 160 μm gate electrode (pad) patterns were lithographed; then, the SiO is etched by Reactive Ion Etching (RIE)2101 and the etching gas is CHF3The volume flow rate is 30sccm, the pressure is 1.3Pa, the RF power is 90W, and the etching rate is 20 nm/min; the etching process was continued for 4min15s, and then 85nm trenches were obtained. Ellipsometry measurements were performed with the coupons with errors within 2 nm. Next, Ti/Pt is deposited to form a buried gate 102 having an upper surface that is level with the upper surface of the substrate, and the resulting structure is shown in FIG. 2. Wherein the thickness of the Ti layer is 15nm, and the thickness of the Pt layer is 70 nm.
Step S2, depositing a first high-K dielectric HfO with a thickness of 30nm on a substrate at 300 ℃ by using an Atomic Layer Deposition (ALD) method 2103. First high-K dielectric HfO2103 completely cover the buried gate 102. Then, a mechanical stripping method is adopted to remove the two-dimensional topological insulator Bi2Se3104 to the first high-K dielectric HfO 2103 and making Bi2Se3104 in horizontal projection is within the range of the buried gate 102, and Bi2Se3104 are of a length comparable to the length of the buried gate 102. Next, a second high-K dielectric HfO with a thickness of 30nm was again deposited by ALD at 300 deg.C 2105, covering it with Bi2Se3104, the resulting structure is shown in fig. 3.
Step S5, adopting a mechanical stripping method to remove the MoS of the two-dimensional material 2106 are transferred to the second high-K dielectric 105 as a channel. The two-dimensional material 106 is sized and positioned to completely cover the topological insulator Bi2Se3104, and the resulting structure is shown in fig. 4.
In step S6, the source and drain regions are patterned by electron beam lithography, and then Ti/Au with a thickness of 15 nm/70 nm is deposited as the source electrode 107 and the drain electrode 108 by Physical Vapor Deposition (PVD), and the resulting structure is shown in fig. 5. A source electrode 107 and a drain electrode 108 formed on the substrate respectivelySeparately covering MoS 2106 and has no overlap with the projection of the buried gate 102 in the horizontal plane direction.
As shown in FIG. 5, the non-volatile memory device based on topological insulator polarization comprises a substrate of Si100/SiO 2101, a first electrode and a second electrode; a buried gate 102 formed in the substrate, the upper surface of which is flush with the upper surface of the substrate; the first high-K dielectric layer 103, the topological insulator layer 104 and the second high-K dielectric layer 105 are stacked to cover the buried gate 102, wherein the topological insulator layer 104 is packaged between the two high-K dielectric layers, the projection of the topological insulator layer 104 on the horizontal plane is positioned in the range of the buried gate 102, and the length of the topological insulator layer 104 is equivalent to that of the buried gate; a two-dimensional channel layer 106 formed on the second high-K dielectric layer 105 and completely covering the topological insulator layer 104; and a source electrode 107 and a drain electrode 108 which are respectively formed on the substrate and on both sides of the two-dimensional channel layer 106, and partially cover the two-dimensional channel layer 106 without overlapping the buried gate 102. Non-volatile storage is achieved based on polarization reversal of the topological insulator material by integrating the topological insulator material in the gate dielectric stack structure.
Although the back-gate structured nonvolatile memory device based on topological insulator polarization has been described as an example, the present invention is not limited thereto, and may be a top-gate structure. Furthermore, the topological insulator can also be Bi2Te3The high-K dielectric layer can also be BN or Al2O3、ZrO2Etc., the two-dimensional channel layer may also be WS2。
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.