Method for vertical heteroepitaxial high orientation of metal platinum based on single crystal tungsten diselenide

Abstract

The application discloses a method for preparing high-oriented metal platinum based on single-crystal tungsten diselenide vertical hetero-epitaxy, and the gap between the obtained metal platinum and tungsten diselenide is less than the Van der Waals spacing, so that better two-dimensional material and metal contact is formed. The tungsten diselenide is located at the bottom layer, and the metal platinum is located at the upper layer, and the two are vertically stacked. By using oxygen annealing, longitudinal induction is formed to form high-oriented metal platinum epitaxy, so that the contact resistance of the heterojunction is reduced. The method provided by the application solves the problems of high-oriented metal thin film preparation difficulty, thin film size limitation and high cost. The tungsten diselenide field effect transistor is PMOS, high-quality contact between the semiconductor two-dimensional material and the metal is realized through the method, which is beneficial to reducing the contact resistance, and the NMOS field effect transistor is formed to be complementary, which is beneficial to improving the performance of the nanosheet CMOS device.

Description

Technical Field

[0001] This invention relates to a method for epitaxial metal thin films, specifically a method for forming high-quality contacts by inducing the epitaxial growth of highly oriented platinum metal thin films based on p-type two-dimensional materials. Background Technology

[0002] As silicon-based process dimensions continue to shrink, the short-channel effect is increasingly impacting the performance of transistor devices. To further reduce the size of complementary logic circuits while maintaining device performance, two-dimensional semiconductor channel materials with high mobility and high on / off ratios and atomic layer thickness are needed. Among these, n-type two-dimensional materials (molybdenum sulfide) transistors already exhibit excellent performance. One obstacle to the further development of CMOS devices is the low mobility and high contact resistance of p-type two-dimensional materials. Therefore, it is necessary to develop a method for inducing highly oriented epitaxial contacts in metals using p-type two-dimensional materials to achieve p-type transistor devices with lower resistance and higher mobility.

[0003] Currently, the main methods for preparing metal thin films are deposition or sputtering. However, deposited polycrystalline metal thin films contain numerous grain boundaries, which significantly degrade the properties of the metal film and increase contact resistance. In recent years, using single-crystal two-dimensional materials as substrates for epitaxial growth of single-crystal metal materials has provided a simple and cost-effective method for preparing single-crystal metal materials. Summary of the Invention

[0004] To address the current challenges of fabricating highly oriented metal thin films, including difficulties in film size limitations and high costs, this invention aims to provide a non-destructive, vertical heteroepitaxial deposition method for platinum thin films based on single-crystal two-dimensional tungsten diselenide, thereby offering a simple method for fabricating high-performance p-type transistors. Specifically, by improving the contact between platinum and tungsten diselenide, and optimizing the contact through vertical heteroepitaxial deposition, a heterojunction smaller than the van der Waals pitch is formed, achieving a lower contact resistance than existing p-type devices.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for vertical heteroepitaxial high-orientation platinum thin film is characterized by using single-crystal tungsten diselenide as an epitaxial substrate, epitaxially depositing platinum on it to obtain a polycrystalline platinum thin film, and then inducing the platinum to form a high-orientation platinum thin film along tungsten diselenide through oxygen annealing. The spacing of the platinum-tungsten diselenide heterojunction is smaller than the van der Waals spacing, forming a better p-type ohmic contact.

[0007] This invention relates to a highly oriented platinum film obtained by induced epitaxy of single-crystal tungsten diselenide, wherein the thickness of the platinum film is preferably 5-20 nanometers. Tungsten diselenide is located at the bottom layer, and platinum is located at the top layer, stacked vertically. The highly oriented platinum epitaxy is formed by oxygen annealing, thereby reducing the contact resistance of the heterojunction. Preferably, the single-crystal tungsten diselenide is a single layer to ten layers, grown by chemical vapor deposition on the surface of any substrate (amorphous substrate or single-crystal substrate is acceptable), which can be an amorphous silicon oxide or silicon nitride substrate, or a single-crystal sapphire substrate. The substrate itself does not affect the formation of the highly oriented film by induced metal crystallization.

[0008] Preferably, the method for vertical heteroepitaxial highly oriented metal thin films includes the following steps:

[0009] The first step is to grow single-crystal tungsten diselenide on a substrate using chemical vapor deposition.

[0010] The second step is to epitaxially grow a polycrystalline platinum film on the obtained single-crystal tungsten diselenide substrate.

[0011] The third step involves annealing a tungsten diselenide-polycrystalline platinum thin film in oxygen. Tungsten diselenide induces the polycrystalline platinum to form a highly oriented platinum thin film, resulting in a heterojunction with a spacing smaller than the van der Waals spacing, thus forming a better p-type ohmic contact.

[0012] Preferably, in the above method, the method for growing tungsten diselenide in the first step is chemical vapor deposition. In one embodiment of the present invention, the substrate is placed in a chemical vapor deposition system, tungsten dioxide and a selenium source are heated, argon gas at 100 standard milliliters per minute and hydrogen gas at 10 standard milliliters per minute are introduced, and the reaction pressure is maintained between 1000 and 2000 Pa. Growth is carried out at 890 degrees Celsius on the substrate surface for 10-15 minutes. After growth, the heating power is turned off, and the substrate is allowed to cool naturally to room temperature using an inert gas as a protective gas, thereby growing high-quality, large-size single-crystal tungsten diselenide on the substrate surface.

[0013] Preferably, in the above method, the method for epitaxializing the polycrystalline platinum thin film in the second step is electron beam evaporation, and the evaporation rate can be 0.04 nanometers per second. The thickness of the platinum thin film is preferably 5-20 nanometers.

[0014] Preferably, in the above method, the method for inducing the formation of a highly oriented platinum thin film in the third step is oxygen annealing, with an annealing temperature of 200°C to 300°C and an annealing time of 1 hour to 6 hours. During oxygen annealing, argon is used as the carrier gas, and a mixture of argon and oxygen is introduced. The argon flow rate is 100 to 1000 sccm, the oxygen flow rate is 10 to 100 sccm, and the pressure is 19 to 760 torr. In one embodiment of the invention, the substrate with deposited platinum is placed in a quartz boat and then placed in a tube furnace. Argon gas is introduced at a flow rate of 100 standard milliliters per minute, and then the temperature is raised to 300°C. Oxygen is then introduced at a flow rate of 10 standard milliliters per minute and maintained at 300°C for 2 hours. After annealing, the substrate is cooled to room temperature to obtain a highly oriented platinum thin film on tungsten diselenide. The platinum on the surface of the substrate without tungsten diselenide remains a polycrystalline thin film. The spacing between tungsten diselenide and highly oriented platinum is smaller than the van der Waals spacing. The p-type tungsten diselenide transistors prepared using the above method have better contact.

[0015] The beneficial effects of this invention are:

[0016] (1) This invention is the first to propose the deposition of highly oriented platinum metal thin films on the surface of single-crystal two-dimensional materials.

[0017] (2) The present invention can select mature silicon oxide / p-type silicon wafer substrates and use chemical vapor deposition to grow single crystal tungsten diselenide on amorphous silicon oxide, which results in low cost and simple process for obtaining tungsten diselenide.

[0018] (3) The present invention uses the common electron beam evaporation method to deposit polycrystalline metal platinum thin films on tungsten diselenide, and a highly oriented metal platinum thin film can be obtained by simple high-temperature oxygen annealing in a tube furnace.

[0019] (4) The method of the present invention can improve the contact quality of platinum and tungsten diselenide, reduce the contact resistance, and realize high-performance p-type transistor devices. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a p-type transistor structure with a vertical heteroepitaxial contact of platinum-tungsten diselenide prepared for an example, wherein 1 is a silicon substrate, 2 is a silicon dioxide layer, 3 is a tungsten diselenide layer, and 4 is a platinum thin film.

[0021] Figure 2The following is a process flow diagram for fabricating a p-type transistor with a vertical heteroepitaxial contact of platinum-tungsten diselenide as an example. In step 1, the silicon wafer is cleaned using a standard RCA cleaning process and then rapidly annealed to remove organic residues. In step 2, WSe2 is grown using a chemical vapor deposition process. In step 3, a platinum electrode is fabricated using a micro / nano fabrication process or a shutter mask evaporation process. In step 4, a highly oriented platinum thin film is obtained by oxygen annealing in a tube furnace.

[0022] Figure 3 Scanning electron microscope cross-sectional image of highly oriented metallic platinum prepared for the example. Detailed Implementation

[0023] To make the content of this invention easier to understand, the technical solutions of this invention will be further described below through specific embodiments. However, the following examples are merely examples in this invention and do not represent the scope of protection of this invention. The scope of protection of this invention is determined by the claims.

[0024] The method for vertical heteroepitaxial single-crystal platinum thin films based on three-layer tungsten diselenide is described in [reference]. Figure 2 It includes the following steps:

[0025] Step 1: Using a SiO2 / Si(111) substrate, clean the particles, organic matter, oxides, etc. on the substrate using the standard RCA cleaning process. After cleaning, dry the substrate with high-purity nitrogen gas and set it aside for later use.

[0026] Step 2: Chemical vapor deposition to grow three layers of tungsten diselenide material on a silicon dioxide layer.

[0027] Step 3: Preparation of platinum metal electrodes including spin coating of photoresist, baking, photolithography, development, metal evaporation and stripping: (1) Spin coating of PMMA, spin coating parameters are 3000rpm, 60s, and baking at 180℃ for 90s after spin coating; (2) Electron beam exposure to pattern the photoresist for stripping metal; (3) Development: the developer is MIBK:IPA = 1:3, development for 45s, clean with deionized water, and dry with N2; (4) Evaporation of 20nm thick Pt; (5) Metal stripping: heating at 120℃ for 30min in NMP, cleaning with isopropanol, and drying with nitrogen.

[0028] Step 4: Annealing is carried out in a tube furnace at a pressure of 19 torr, with 10 sccm of oxygen / 100 sccm of argon, an annealing temperature of 300℃, and a time of 120 minutes. After annealing, the tube is allowed to cool naturally to room temperature before being removed.

[0029] Step 5: Perform cross-sectional characterization of the sample using scanning electron microscopy. The results are as follows: Figure 3 As shown, this is a highly oriented (111) platinum.

Claims

1. A method for vertical heteroepitaxial highly oriented platinum thin films, characterized in that, Using single-crystal tungsten diselenide as an epitaxial substrate, metallic platinum is epitaxially deposited on it to obtain a polycrystalline metallic platinum thin film. Then, the metallic platinum is induced to form a highly oriented metallic platinum thin film along the tungsten diselenide by oxygen annealing. During annealing, a mixture of argon and oxygen is introduced, with an argon flow rate of 100~1000 sccm and an oxygen flow rate of 10~100 sccm. The annealing temperature is 200~300℃ and the pressure is 19~760 torr.

2. The method as described in claim 1, characterized in that, The thickness of the platinum thin film is 5-20 nanometers.

3. The method as described in claim 1, characterized in that, The single-crystal tungsten diselenide is a two-dimensional material ranging from one to ten layers.

4. The method as described in claim 1, characterized in that, Includes the following steps: 1) Single-crystal tungsten diselenide was grown on a substrate using chemical vapor deposition; 2) A polycrystalline platinum thin film is epitaxially grown on a single-crystal tungsten diselenide substrate; 3) Annealing tungsten diselenide-polycrystalline platinum thin films in oxygen induces the formation of highly oriented platinum thin films by tungsten diselenide, resulting in heterojunctions with a spacing smaller than the van der Waals spacing, thus forming good p-type ohmic contacts.

5. The method as described in claim 4, characterized in that, The substrate mentioned in step 1) is an amorphous substrate or a single-crystal substrate.

6. The method as described in claim 4, characterized in that, Step 1) Single-crystal tungsten diselenide is grown in a chemical vapor deposition system using tungsten dioxide and a selenium source.

7. The method as described in claim 4, characterized in that, Step 2) Epitaxial polycrystalline platinum thin films are produced using electron beam evaporation.

8. The method as described in claim 4, characterized in that, Step 3) Annealing in oxygen for 1 to 6 hours.

9. The method as described in claim 4, characterized in that, Step 3) is carried out in a tubular furnace.

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