A method and device for preparing a transition metal chalcogenide single crystal thin film

Abstract

The invention discloses a method and device for preparing a transition metal sulfide compound single crystal film. The preparation method comprises the following steps: obtaining a gaseous metal source by in-situ surface reaction between a highly active reaction gas and a solid metal source, and then performing a gas phase reaction with a gas source containing a sulfide element on a substrate surface to grow a transition metal sulfide compound single crystal film; achieving rapid growth of the film by high nucleation density and high growth rate; using a device of the preparation method, transferring a substrate from a sample injection chamber to an epitaxial chamber, performing batch material growth in the epitaxial chamber at a constant temperature, transferring a sample from the epitaxial chamber to a sampling chamber for cooling, thereby avoiding time and energy consumption caused by the temperature increase and decrease process of the epitaxial chamber, achieving uninterrupted, batch growth and transmission of the transition metal sulfide compound single crystal film, and improving production efficiency.

Description

Technical Field

[0001] The present invention relates to a method for preparing a transition metal sulfide compound, in particular to a method for preparing a transition metal sulfide compound single crystal film, and also to a device used in the preparation method. Background Art

[0002] Transition metal chalcogenides (TMDCs) have excellent physical and chemical properties, such as band gap structures in the visible light range and high carrier mobility, and have broad application prospects in many fields such as field effect transistors, optoelectronic devices, micro-nanoelectronic devices and large-scale integrated circuits. The existing wafer-level TMDC film preparation method usually uses a transition metal oxide powder source and a single substance powder of a chalcogen element to be prepared by gas phase reaction after sublimation.

[0003] However, the main problem faced by the powder source is that it is difficult to control the volatilization of the powder during the heating and cooling process. The negative effects include: 1) During the substrate heating process, the powder source has begun to volatilize before the substrate reaches the growth temperature; 2) After the growth is completed and the sample is cooled, the powder source cannot be cooled in time and continues to volatilize, which will cause surface contamination and uncontrollable thickness. 3) Batch growth stability cannot be guaranteed. The powder volatilization rate depends on the amount of powder. As the number of uses increases, the amount of powder gradually decreases, and the volatilization rate also decreases. There are differences in growth between different batches, so frequent replenishment is required, which reduces production efficiency. 4) The reaction efficiency of the powder source is low, and the growth of continuous films often requires a reaction time of more than 30 minutes.

[0004] At the same time, the existing TMDC epitaxial equipment only contains a single heatable epitaxial chamber. The epitaxial substrate is heated up, the material is grown, and the temperature is cooled down together with the epitaxial chamber. All processes are completed in the same growth chamber. Among them, the epitaxial process takes up 5-10% of the time of the entire process; while the heating and cooling links consume more than 90% of the total process time. The extra time consumption in the production link greatly prolongs the process flow, resulting in a significant reduction in the film yield. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a method for preparing a transition metal sulfide compound single crystal thin film with controllable operation and high efficiency. The second purpose is to provide an apparatus used in the above preparation method.

[0006] Technical solution: The method for preparing a transition metal chalcogenide single crystal thin film of the present invention comprises the following steps:

[0007] (1) The reaction gas undergoes an oxidation or chlorination reaction on the surface of a solid metal source and volatilizes in situ to obtain a gaseous metal source, wherein the reaction gas is Cl2, HCl or O2, and the gaseous metal source is a metal oxide gaseous source, a metal chloride gaseous source or a metal oxychloride gaseous source;

[0008] (2) The gaseous metal source prepared in step (1) reacts with the gas source containing the chalcogen element on the surface of the substrate in the gas phase to grow a transition metal chalcogenide compound single crystal thin film.

[0009] Preferably, the reaction gas flow rate is 1-50 ml per minute, and the temperature of the solid metal source is 450-950°C.

[0010] Preferably, the solid metal source is a molybdenum source or a tungsten source, and the gas source containing chalcogen elements is hydrogen selenide or hydrogen sulfide.

[0011] Preferably, in step (2), the flow ratio of the gaseous metal source to the gas containing the chalcogen element is 1:1 to 1:50.

[0012] Preferably, the reaction gas is a mixture of Cl2, HCl or O2 gas and an inert gas.

[0013] Preferably, in the mixed gas, the concentration of the reaction gas is 5% to 95%.

[0014] The device used in the above preparation method includes an epitaxial chamber, and also includes a sampling chamber and a sampling chamber respectively connected to the epitaxial chamber. The epitaxial chamber is provided with two air inlets.

[0015] Preferably, the device is further provided with a first manipulator for transferring samples between the injection chamber and the epitaxial chamber, and a second manipulator for transferring samples between the epitaxial chamber and the sampling chamber.

[0016] Preferably, the temperatures of the injection chamber, epitaxial chamber and sampling chamber can be set separately.

[0017] The method for preparing a transition metal sulfide compound single crystal thin film of the present invention obtains a highly active gaseous metal source by allowing a highly active reaction gas, such as Cl2, HCl, or O2, to flow through a heated solid metal source for an in-situ reaction; the supply rate of the gaseous metal source can be precisely controlled by the reaction gas flow rate and the temperature of the solid metal source, and can be switched on and off instantly.

[0018] The growth of transition metal chalcogenide continuous thin film is formed by the gradual growth of crystal domains nucleated at different positions and splicing each other. Therefore, from the perspective of growth process, the parameters that affect the growth rate of single crystals include the nucleation density of the crystal domain and the growth rate of a single crystal domain. The higher the nucleation density of the crystal domain and the faster the growth rate, the shorter the time to form a continuous film. The nucleation density and growth rate are both related to the reactivity of the growth atmosphere. The gaseous metal source and the gas source containing chalcogen elements react in an ultra-highly active gas phase on the substrate surface to form a transition metal chalcogenide single crystal film; therefore, the gas phase reaction can also be controlled in real time by timely switching of the highly active reaction gas; by controlling the growth of the crystal domain under controllable conditions, a batch of continuous film growth can be completed within 1-5 minutes. This changes the usual operation of using transition metal oxide or sulfide powder in the preparation of transition metal chalcogenide single crystal films. The volatilization of the powder at high temperature is difficult to control, and it is impossible to accurately form a film with a specific content on the substrate surface, which affects the growth process and quality of the film.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0020] (1) The method for preparing a transition metal chalcogenide single crystal thin film of the present invention uses a highly active reaction gas solid metal source to perform an in-situ reaction to obtain a high nucleation density and a crystal domain growth rate, thereby achieving rapid growth of a continuous thin film, and the growth rate is accelerated by 10-60 times;

[0021] (2) The equipment of the present invention is designed with a multi-stage chamber structure, which is interconnected and can be set to different temperatures, thereby reducing unnecessary temperature rise and fall processes and energy waste, consuming 90% of the time of the entire process flow, and achieving rapid and large-scale preparation of TMDC wafers. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a physical picture of the wafer-level molybdenum disulfide single crystal of the present invention;

[0023] Figure 2 This is a physical picture of a 2-inch molybdenum diselenide single crystal wafer grown in a single batch according to the present invention;

[0024] Figure 3 This is a second harmonic surface scanning image of the single crystal thin film obtained in Example 1;

[0025] Figure 4 This is a second harmonic surface scanning image of the single crystal thin film obtained in Example 2;

[0026] Figure 5 is the Raman spectrum of the single crystal thin film obtained in Example 2;

[0027] Figure 6 is the photoluminescence spectrum of the single crystal thin film obtained in Example 2;

[0028] Figure 7 is the Raman spectrum of the single crystal thin film obtained in Example 3;

[0029] Figure 8 is the photoluminescence spectrum of the single crystal thin film obtained in Example 3;

[0030] Fig. 9 is the Raman spectrum of the single crystal thin film obtained in Example 4;

[0031] Fig.10 is the photoluminescence spectrum of the single crystal thin film obtained in Example 4;

[0032] Fig.11 It is a structural schematic diagram of the device of the present invention;

[0033] Fig.12 This is an optical microscope detection image of the film surface of Comparative Example 2. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0035] Example 1

[0036] The preparation method of the transition metal chalcogenide single crystal thin film of the present invention is as follows:

[0037] (1) The epitaxial chamber is evacuated to below 10Pa, 200 standard milliliters per minute (sccm) of Ar is introduced, and the temperature is raised to 950°C. The substrate is transferred from the injection chamber to the epitaxial chamber. A solid metal source Mo sheet is placed in the epitaxial chamber, and 10 sccm of reaction gas O2 is introduced for in-situ reaction to generate a MoO3 gaseous source;

[0038] (2) 30 sccm H2S gas is introduced into the sample injection chamber to react with the MoO3 gas source on the substrate surface for 5 minutes to grow a transition metal chalcogenide single crystal thin film MoS2.

[0039] After the reaction is completed, the entire batch of samples is sent to the sampling chamber by the robot for storage and cooling. At the same time, the substrate is transferred from the injection chamber to the epitaxial chamber to start the next batch of thin film growth. After multiple batches of thin film growth are completed, they are merged into the sampling chamber until the cooling is completed and sampling is carried out.

[0040] like Figure 1 Grow 2-inch MoS2 single crystal wafers for one batch; Figure 3 This is the second harmonic generation surface scanning (SHG mapping) characterization result of MoS2 single crystal wafer. It can be seen that the SHG mapping intensity is uniform and continuous, indicating that there is no grain boundary.

[0041] Example 2

[0042] Compared with Example 1, Example 2 changes the type of reaction gas, specifically:

[0043] (1) The epitaxial chamber is heated to 1000°C, evacuated to below 10Pa, and introduced with 200 standard milliliters per minute (sccm) of Ar. The substrate is transferred from the injection chamber to the epitaxial chamber. A solid metal source Mo sheet is placed in the epitaxial chamber. 10 sccm of the reaction gas HCl is introduced for in-situ reaction to generate a MoCl5 gaseous source;

[0044] (2) 30 sccm H2Se was introduced, and a gas phase reaction was carried out on the substrate surface in the injection chamber with a MoCl5 gas source for 5 minutes to grow a transition metal chalcogenide single crystal thin film MoSe2.

[0045] After the reaction is completed, the sample is sent to the sampling chamber by the robot for storage and cooling. At the same time, the substrate is transferred from the injection chamber to the epitaxial chamber to start the next batch of thin film growth. After multiple batches of thin film growth are completed, they are merged into the sampling chamber until the cooling is completed and sampling is carried out.

[0046] like Figure 2 The 2-inch MoSe2 single crystal sample was obtained. SHG surface scanning test was performed at any position of the sample, such as Figure 5 It shows that no grain boundaries exist. Figure 6 and Figure 6 They are the Raman spectrum and photoluminescence spectrum of the MoSe2 single crystal sample. It can be seen from the figure that the prepared sample is a single layer of MoSe2.

[0047] Example 3

[0048] Compared with Example 2, Example 3 changes the type of solid metal source, specifically:

[0049] (1) The epitaxial chamber is heated to 950°C, evacuated to below 10 Pa, and introduced with 200 standard milliliters per minute (sccm) of Ar. The substrate is transferred from the injection chamber to the epitaxial chamber. A solid metal source W sheet is placed in the epitaxial chamber. 10 sccm of the reaction gas HCl is introduced for in-situ reaction to generate a WCl5 gaseous source.

[0050] (2) 30 sccm H2Se gas is introduced to react with WCl5 gas source on the substrate surface in the injection chamber for 5 minutes to grow a transition metal chalcogenide single crystal thin film WSe2.

[0051] After the reaction is completed, the entire batch of samples is sent to the sampling chamber by the robot for storage and cooling. At the same time, the substrate is transferred from the injection chamber to the epitaxial chamber to start the next batch of thin film growth. After multiple batches of thin film growth are completed, they are merged into the sampling chamber until the cooling is completed and sampling is carried out.

[0052] Figure 7 and Figure 8 They are the Raman spectrum and photoluminescence spectrum of the single crystal WSe2 sample. It can be seen from the figure that the prepared sample is a single layer WSe2.

[0053] Example 4

[0054] Compared with Example 3, Example 4 changes the type of reaction gas, specifically:

[0055] (1) The epitaxial chamber is heated to 950°C, evacuated to below 10 Pa, and introduced with 200 standard milliliters per minute (sccm) of Ar. The substrate is transferred from the injection chamber to the epitaxial chamber. A solid metal source W sheet is placed in the epitaxial chamber. 10 sccm of the reaction gas HCl is introduced for in-situ reaction to generate a WCl5 gaseous source.

[0056] (2) 50 sccm H2S gas is introduced, and a gas phase reaction is carried out on the substrate surface in the injection chamber with a WCl5 gas source for 5 minutes to grow a transition metal chalcogenide single crystal thin film WS2.

[0057] After the reaction is completed, the entire batch of samples is sent to the sampling chamber by the robot for storage and cooling. At the same time, the substrate is transferred from the injection chamber to the epitaxial chamber to start the next batch of thin film growth. After multiple batches of thin film growth are completed, they are merged into the sampling chamber until the cooling is completed and sampling is carried out.

[0058] Fig. 9 and Fig.10 They are the Raman spectrum and photoluminescence spectrum of the single crystal WS2 sample. It can be seen from the figure that the prepared sample is a single layer WS2.

[0059] Example 5

[0060] Compared with Example 3, Example 4 changes the type of solid metal source, specifically:

[0061] (1) The epitaxial chamber is heated to 950°C, evacuated to below 10Pa, and introduced with 200 standard milliliters per minute (sccm) of Ar. The substrate is transferred from the injection chamber to the epitaxial chamber. Solid metal source WO3 powder is placed in the epitaxial chamber. 10 sccm of reaction gas HCl is introduced for in-situ reaction to generate WOCl gaseous source;

[0062] (2) 30 sccm H2S gas was introduced, and the substrate surface in the injection chamber was reacted with the WOCl gas source in the gas phase for 5 minutes to grow a transition metal chalcogenide single crystal thin film WS2.

[0063] After the reaction is completed, the entire batch of samples is sent to the sampling chamber by the robot for storage and cooling. At the same time, the substrate is transferred from the injection chamber to the epitaxial chamber to start the next batch of thin film growth. After multiple batches of thin film growth are completed, they are merged into the sampling chamber until the cooling is completed and sampling is carried out.

[0064] Example 6

[0065] Compared with Example 1, Example 6 changes the flow rate of the reaction gas, specifically:

[0066] (1) The epitaxial chamber is evacuated to below 10Pa, 200 standard milliliters per minute (sccm) of Ar is introduced, and the temperature is raised to 950°C. The substrate is transferred from the injection chamber to the epitaxial chamber. A solid metal source Mo sheet is placed in the epitaxial chamber, and 10 sccm of reaction gas O2 is introduced for in-situ reaction to generate a MoO3 gaseous source;

[0067] (2) 50 sccm H2S gas is introduced into the sample injection chamber to react with the MoO3 gas source on the substrate surface for 5 minutes to grow a transition metal chalcogenide single crystal thin film MoS2.

[0068] After the reaction is completed, the entire batch of samples is sent to the sampling chamber by the robot for storage and cooling. At the same time, the substrate is transferred from the injection chamber to the epitaxial chamber to start the next batch of thin film growth. After multiple batches of thin film growth are completed, they are merged into the sampling chamber until the cooling is completed and sampling is carried out.

[0069] Comparative Example 1

[0070] The growth system using a single chamber takes more than 30 times longer to produce single crystal thin films of transition metal chalcogenides:

[0071] (1) The growth chamber was evacuated to below 10 Pa, 200 standard milliliters per minute (sccm) of Ar was introduced, and the temperature was raised to 950°C, which took about 30 minutes; 10 sccm of reaction gas O2 was introduced to react with the solid metal source Mo sheet in situ to generate MoO3 gaseous source;

[0072] (2) 30 sccm H2S gas was introduced into the substrate surface in the injection chamber to react with the MoO3 gas source in the gas phase for 5 minutes to grow a transition metal chalcogenide single crystal thin film MoS2. Then, the epitaxial chamber was cooled down, which took 2.5 hours.

[0073] The preparation time using this method is 3 hours, which is more than 30 times longer than the preparation method of the present invention.

[0074] Comparative Example 2

[0075] It is difficult to obtain a clean film with strict uniform thickness when using transition metal oxide powder and sulfur powder to prepare transition metal chalcogenide film:

[0076] (1) The growth chamber was evacuated to below 10 Pa, 200 standard milliliters per minute (sccm) of Ar was introduced, and the temperature was raised to 950°C, which took about 30 minutes;

[0077] (2) 30 mg / min of S vapor was introduced to react with the MoO3 gas source on the substrate surface in the sample inlet chamber for 40 minutes to grow a transition metal chalcogenide single crystal thin film MoS2. Then, the temperature was lowered for 2.5 hours.

[0078] After repeating the experiment three times, optical microscopy revealed that a thick layer of MoS2 and incompletely reacted particles appeared on the film surface, such as Fig.12 This phenomenon is caused by the premature volatilization of MoO3 during the heating process and the continued volatilization of MoO3 during the cooling process, which proves that the volatilization of the powder is difficult to control to form a stable film.

Claims

1. A method for preparing a transition metal chalcogenide single crystal thin film, characterized in that: The following steps are involved: (1) The reaction gas is oxidized or chlorinated on the surface of the solid metal source, and volatilized in situ to obtain a gaseous metal source, wherein the reaction gas is Cl2, HCl or O2, and the gaseous metal source is a metal oxide gaseous source, a metal chloride gaseous source or a metal oxychloride gaseous source, and the flow rate of the reaction gas is 1-50 ml per minute, and the temperature of the solid metal source is 450-950° C.; (2) The gaseous metal source prepared in step (1) reacts with the gas source containing the chalcogen element on the surface of the substrate in the gas phase to grow a transition metal chalcogenide compound single crystal thin film.

2. The preparation method according to claim 1, characterized in that: The solid metal source is a molybdenum source or a tungsten source, and the gas source containing chalcogen elements is hydrogen selenide or hydrogen sulfide.

3. The preparation method according to claim 1, characterized in that: In step (2), the flow ratio of the gaseous metal source to the gas containing the chalcogen element is 1:1 to 1:

50.

4. The preparation method according to claim 1, characterized in that: In step (1), the reaction gas is a mixture of Cl2, HCl or O2 gas and an inert gas.

5. The preparation method according to claim 4, characterized in that: In the mixed gas, the concentration of Cl2, HCl or O2 gas is 5% to 95%.

6. The preparation method according to claim 1, characterized in that: The growth time in step (2) is at least 1 minute.

7. An apparatus used in the preparation method according to claim 1, comprising an epitaxial chamber (2), characterized in that: The invention also comprises a sample injection chamber (1) and a sampling chamber (3) which are interconnected with the epitaxial chamber (2); the epitaxial chamber (2) is provided with two air inlets; a first manipulator (4) for transferring samples between the sample injection chamber (1) and the epitaxial chamber (2); and a second manipulator (5) for transferring samples between the epitaxial chamber (2) and the sampling chamber (3); the sample injection chamber (1), the epitaxial chamber (2) and the sampling chamber (3) are independently temperature-controlled.

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