WO2023193636A1

WO2023193636A1 - Method for highly orienting platinum on basis of vertical heteroepitaxy of single crystal tungsten diselenide

Info

Publication number: WO2023193636A1
Application number: PCT/CN2023/084393
Authority: WO
Inventors: 吴燕庆; 王欣; 刘视远
Original assignee: 北京大学
Priority date: 2022-04-07
Filing date: 2023-03-28
Publication date: 2023-10-12
Also published as: CN116926672A

Abstract

A method for highly orienting platinum on the basis of vertical heteroepitaxy of single crystal tungsten diselenide, comprising: using single crystal tungsten diselenide as an epitaxial substrate; depositing a polycrystalline platinum thin film on the epitaxy of the epitaxial substrate; and then, longitudinally inducing, by means of oxygen annealing, platinum to form a highly oriented platinum thin film along tungsten diselenide, wherein a gap between the platinum and the tungsten diselenide is smaller than the Van der Waals distance, so that a better two-dimensional material is formed to contact a metal, thereby reducing the Schottky barrier height for a metal-semiconductor contact. According to the method, the problem that a highly oriented metal thin film is difficult to prepare, limited in size and high in costs is solved. A tungsten diselenide field effect transistor is a PMOS, and achieves high-quality contact between a tungsten diselenide semiconductor and a metal by means of the method, thereby reducing contact resistance, being complementary to an NMOS field effect transistor, and improving the performance of a nanosheet CMOS device.

Description

Method for vertical heteroepitaxial highly oriented metal platinum based on single crystal tungsten diselenide

Technical field

The invention relates to a method for epitaxial metal thin films, and specifically relates to a method for inducing the epitaxial growth of highly oriented metal platinum thin films based on p-type two-dimensional materials to form high-quality contacts.

Background technique

As the size of silicon-based processes gradually shrinks, the short channel effect increasingly affects the performance of transistor devices. In order to further reduce the size of complementary logic circuits while ensuring device performance, high mobility and high switching ratios are needed. Atomic layer-thick two-dimensional semiconductor channel material. Among them, n-type two-dimensional material (molybdenum sulfide) transistors already have excellent performance. One of the obstacles to the further development of CMOS devices is that the p-type two-dimensional material has low mobility and large contact resistance. Therefore, it is necessary to develop a method of using p-type two-dimensional materials to induce metal to form highly oriented epitaxial contacts to achieve p-type transistor devices with lower resistance and higher mobility.

At present, the preparation methods of metal thin films are mainly deposition methods or sputtering methods. The deposited polycrystalline metal thin films have a large number of grain boundaries, which will greatly reduce the properties of the metal thin films and increase the contact resistance. In recent years, single crystal two-dimensional materials have been used as substrates for epitaxial single crystal metal materials, providing a simple and affordable method to prepare single crystal metal materials.

Contents of the invention

In view of the current problems of difficulty in preparing highly oriented metal films, limited film size, and high cost, the purpose of the present invention is to provide a damage-free vertical heterogeneous induced epitaxial noble metal platinum film based on the single crystal two-dimensional material tungsten diselenide. method, thereby providing a simple method to prepare high-performance p-type transistors. Among them, by improving the contact between metal platinum and tungsten diselenide, the vertical heteroepitaxial deposition of metal platinum and tungsten diselenide is used to optimize the contact, forming a heterojunction smaller than the van der Waals distance, achieving a smaller size than the existing p-type device contact resistance.

In order to achieve the above objects, the present invention adopts the following technical solutions:

A method for vertical heteroepitaxy of highly oriented metal platinum films, which is characterized by using single crystal tungsten diselenide as an epitaxial substrate, epitaxially depositing metal platinum on it to obtain a polycrystalline metal platinum film, and then inducing metal through oxygen annealing Platinum forms a highly oriented metal platinum film along tungsten diselenide. The spacing of the metal platinum-tungsten diselenide heterojunction is smaller than the van der Waals spacing, forming a better p-type ohmic contact.

The present invention obtains a highly oriented metal platinum film based on induced epitaxy of single crystal tungsten diselenide. The thickness of the metal platinum film is preferably 5-20 nanometers. Tungsten diselenide is located on the bottom layer and metal platinum is located on the upper layer. The two are stacked vertically. Oxygen annealing is used to form highly oriented metal platinum epitaxy, thereby reducing the contact resistance of the heterojunction. Preferably, the single crystal tungsten diselenide has a single layer to ten layers and is grown on the surface of any substrate (either an amorphous substrate or a single crystal substrate) through chemical vapor deposition. It can be amorphous silicon oxide, The silicon nitride substrate can also be a single crystal sapphire substrate. The substrate itself will not affect the induction of metal crystallization to form a highly oriented film.

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

In the first step, a chemical vapor deposition method is used to grow single crystal tungsten diselenide on the substrate;

In the second step, a polycrystalline metal platinum film is epitaxially grown on the obtained single crystal tungsten diselenide as a substrate;

The third step is to anneal the tungsten diselenide-polycrystalline metal platinum film in oxygen, and use tungsten diselenide to induce the polycrystalline platinum to form a highly oriented platinum film, obtaining a heterojunction with a spacing smaller than the van der Waals spacing, and forming a better p type ohmic contact.

Preferably, in the above method, the method of growing tungsten diselenide in the first step is chemical vapor deposition. In one embodiment of the present invention, the substrate is placed into a chemical vapor deposition system, the tungsten dioxide and selenium sources are heated, 100 standard milliliters per minute of argon gas and 10 standard milliliters per minute of hydrogen gas are introduced, and the reaction gas pressure is maintained Grow at 890 degrees Celsius on the substrate surface for 10-15 minutes between 1000 and 2000 Pa. After the growth is completed, the heating power is turned off, inert gas is used as the protective gas, and the process is naturally cooled to room temperature, and high-quality and large-sized single crystal tungsten diselenide is grown on the surface of the substrate.

Preferably, in the above method, the method for epitaxially growing the polycrystalline metal platinum film in the second step is electron beam evaporation, and the evaporation rate can be 0.04 nanometers per second. The thickness of the metallic platinum film is preferably 5-20 nanometers.

Preferably, in the above method, the method for inducing the formation of a highly oriented metal platinum film in the third step is oxygen annealing, the annealing temperature is 200 degrees Celsius to 300 degrees Celsius, and the annealing time is 1 hour to 6 hours. During oxygen annealing, argon gas is used as the carrier gas and oxygen is mixed. During annealing, a mixture of argon and oxygen is introduced. The argon gas flow rate is 100~1000 sccm, the oxygen flow rate is 10~100 sccm, and the pressure is 19~760 torr. In one embodiment of the present invention, the substrate on which platinum metal is deposited is placed in a quartz boat and placed in a tube furnace. Argon gas is introduced with a flow rate of 100 standard milliliters per minute, and then the temperature begins to rise to 300 degrees Celsius. When oxygen is introduced, the flow rate is 10 standard milliliters per minute, and the temperature is maintained at 300 degrees Celsius for 2 hours. After the annealing is completed, it is cooled to room temperature to obtain a highly oriented metal platinum film on tungsten diselenide. On the lining without tungsten diselenide, The metallic platinum on the bottom surface is still a polycrystalline film. The distance between tungsten diselenide and the highly oriented metal platinum is smaller than the van der Waals distance. The p-type tungsten diselenide transistor prepared by the above method has better contact.

Beneficial effects of the present invention:

(1) This invention proposes for the first time to deposit a highly oriented metal platinum film on the surface of a single crystal two-dimensional material.

(2) The present invention can use a mature silicon oxide/p-type silicon wafer substrate and use chemical vapor deposition to grow single crystal tungsten diselenide on amorphous silicon oxide. The cost of obtaining tungsten diselenide is low and the process is simple. .

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

(4) The method of the present invention can improve the contact quality between metal platinum and tungsten diselenide, reduce contact resistance, and realize high-performance p-type transistor devices.

Description of drawings

Figure 1 is a schematic structural diagram of a p-type transistor with a vertical heteroepitaxial contact of metal platinum and tungsten diselenide prepared in the embodiment, where 1 is a silicon substrate, 2 is a silicon dioxide layer, and 3 is a tungsten diselenide layer. 4 is a metal platinum film.

Figure 2 is a process flow chart for preparing a p-type transistor with a vertical heteroepitaxial contact of metal platinum-tungsten diselenide according to an embodiment. In the first step, the silicon wafer is cleaned using a standard RCA cleaning process and rapidly annealed to remove organic residues; The second step is to grow WSe ₂ using chemical vapor deposition process; the third step is to prepare the metal platinum electrode through micro-nano processing or shutter mask evaporation process; the fourth step is to use tube furnace oxygen annealing to obtain a highly oriented metal platinum film.

Figure 3 is a scanning electron microscope cross-section of the highly oriented metal platinum prepared in the Example.

Detailed ways

In order to make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below through specific examples. However, the following examples are only examples of the present invention and do not mean that the present invention is limited. The scope of rights protection of the present invention shall be determined by the claims.

The method of vertical heteroepitaxial single crystal metal platinum film based on three layers of tungsten diselenide, see Figure 2, includes the following steps:

Step 1: Use a SiO ₂ /Si (111) substrate and use the standard RCA cleaning process to clean particles, organic matter, oxides, etc. on the substrate. After cleaning, blow dry with high-purity nitrogen for use.

Step 2: Chemical vapor deposition grows three layers of tungsten diselenide material on the silicon dioxide layer.

The third step: Preparation of metal platinum electrode including spin coating of photoresist, baking, photolithography, development, metal evaporation and stripping: (1) Spin coating of PMMA, spin coating parameters are 3000 rpm, 60 s, spin Bake at 180°C for 90 s after coating; (2) Electron beam exposure to pattern the photoresist that peels off the metal; (3) Development: The developer solution is MIBK:IPA=1:3, develop for 45 s, and rinse with deionized water Clean and blow dry with N ₂ ; (4) Evaporate 20 nm thick Pt; (5) Strip the metal: heat in NMP at 120°C for 30 minutes, clean with isopropyl alcohol, and blow dry with nitrogen.

Step 4: The pressure in the tube furnace is 19 torr, the gas is 10 sccm oxygen/100 sccm argon, the annealing temperature is 300°C, and the time is 120 minutes for annealing. After annealing, it is naturally cooled to normal temperature and taken out.

Step 5: Conduct cross-sectional characterization of the sample using a scanning electron microscope. The result is shown in Figure 3, which is highly oriented (111) platinum.

Claims

A method for vertical heteroepitaxy of highly oriented metal platinum films, which is characterized by using single crystal tungsten diselenide as an epitaxial substrate, epitaxially depositing metal platinum on it to obtain a polycrystalline metal platinum film, and then inducing metal through oxygen annealing Platinum forms a highly oriented metallic platinum film along tungsten diselenide.
The method of claim 1, wherein the thickness of the platinum metal film is 5-20 nanometers.
The method of claim 1, wherein the single crystal tungsten diselenide is a two-dimensional material with a single layer to ten layers.
The method of claim 1, comprising the following steps:

1) Use chemical vapor deposition method to grow single crystal tungsten diselenide on the substrate;

2) Use single crystal tungsten diselenide as a substrate and epitaxially grow a polycrystalline metal platinum film on it;

3) Anneal the tungsten diselenide-polycrystalline metal platinum film in oxygen, and use tungsten diselenide to induce the polycrystalline platinum to form a highly oriented platinum film, obtaining a heterojunction with a spacing smaller than the van der Waals spacing, and forming a good p-type ohmic contact. .
The method of claim 4, wherein the substrate in step 1) is an amorphous substrate or a single crystal substrate.
The method of claim 4, wherein step 1) uses tungsten dioxide and selenium sources to grow single crystal tungsten diselenide in a chemical vapor deposition system.
The method of claim 4, wherein step 2) uses electron beam evaporation to epitaxially extend the polycrystalline metal platinum film.
The method of claim 4, wherein the temperature of step 3) annealing in oxygen is 200~300°C, and the annealing time is 1 hour~6 hours.
The method according to claim 4, characterized in that step 3) is carried out in a tube furnace. During annealing, a mixture of argon and oxygen is introduced, the argon flow rate is 100~1000 sccm, and the oxygen flow rate is 10~100 sccm. sccm, pressure is 19~760 torr.