Fog chemical vapor deposition system and method for preparing gallium oxide epitaxial thin film

Abstract

The invention discloses a fog chemical vapor deposition system and method for preparing a gallium oxide epitaxial thin film. The system comprises a carrier gas storage tank, an oxygen storage tank, a mixed gas storage tank, a five-channel gas flow controller, a liquid propelling device, a weight sensor, an atomization tank, a gas spraying device and a single-temperature-zone tubular furnace. And the feeding end of the thick quartz tube of the single-temperature-zone tubular furnace is connected with the thin quartz tube. The five-channel gas flow controller is used for controlling the gas flow in the atomization tank, the thin quartz tube and the gas injection device, after the single-temperature-zone tubular furnace reaches the set working temperature, carrier gas directly conveys atomized fog drops to a substrate through the thin quartz tube, and the gallium oxide thin film is formed through deposition at the high temperature. According to the invention, the quartz tube and the vertically downward air injection device are adopted, so that the efficient utilization of raw materials is realized, the liquid level is controlled through the weight sensor, the real-time feedback of fog drops is realized, the atomization uniformity and stability are improved, and finally, the high-quality gallium oxide epitaxial thin film is grown.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor material preparation, and in particular relates to a mist chemical vapor deposition system and method for preparing a gallium oxide epitaxial film. Background Art

[0002] Gallium oxide is a new type of ultra-wide bandgap semiconductor material with a bandgap width of 4.2 to 5.3 eV. It has ultra-high breakdown field strength and radiation resistance, good thermal stability and chemical stability, and very high transmittance in the visible and ultraviolet regions (>80%). To date, many methods have been used to prepare gallium oxide thin films, such as metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), mist chemical vapor deposition (Mist-CVD), etc. Mist-CVD has the advantages of no vacuum, low cost, and diversified raw material selection.

[0003] In general Mist-CVD equipment, the following problems are common: (1) Since the temperature of the front end of the quartz tube wall is very high, a large amount of loss will occur when the droplets are transported there by the carrier gas, so the droplets that can reach the substrate surface become less, and the raw material utilization rate is not high. (2) In general Mist-CVD equipment, the solution in the atomization container will gradually decrease over time. The constant liquid level in the atomization container plays a key role in the stability of the atomization efficiency and the atomization amount. The general Mist-CVD equipment cannot ensure that the atomization amount is uniform over time, so the amount of mist reaching the substrate surface is uneven, which will cause the film surface roughness to be large, the thickness to be uneven, and the crystallinity to be poor during the deposition of the gallium oxide film. CN114059042A discloses a preparation design for preparing gallium oxide film by the Mist method, and provides a method for preparing gallium oxide film, but the equipment used cannot ensure the efficient utilization of raw materials, and the surface roughness of the grown gallium oxide film needs to be improved.

[0004] Since the existing raw materials for growing gallium oxide thin films are relatively expensive, there is an urgent need in the art for a gallium oxide thin film deposition device that has high raw material utilization and grows gallium oxide thin films with small surface roughness, uniform thickness and good crystallinity. Summary of the invention

[0005] One of the objects of the present invention is to provide a mist chemical vapor deposition system for preparing gallium oxide epitaxial thin films.

[0006] The second object of the present invention is to provide a method for preparing gallium oxide epitaxial thin film based on the above system.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a mist chemical vapor deposition system for preparing gallium oxide epitaxial thin films, comprising a carrier gas storage tank, an oxygen storage tank, a mixed gas storage tank, an atomizing tank, and a single temperature zone tubular furnace, the system also comprising a five-channel gas flow controller, a liquid propulsion device, and a weight sensor;

[0009] The upper wall of the coarse quartz tube of the single-temperature zone tubular furnace is provided with a vertical downward air injection device, the feed end of the coarse quartz tube of the single-temperature zone tubular furnace is connected to a thin quartz tube, and one end of the thin quartz tube is provided with two air inlets;

[0010] The carrier gas storage tank and the oxygen storage tank are connected to the atomizing tank through a five-channel gas flow controller and two gas lines, respectively, and then connected to the thin quartz tube through a five-channel gas flow controller and another two gas lines, respectively. The mixed gas storage tank is connected to the jetting device through a five-channel gas flow controller and one gas line;

[0011] The liquid propulsion device is connected to the side wall of the atomizing tank through a communicating vessel, the atomizing tank is connected to another air inlet of the thin quartz tube, and the weight sensor is placed at the bottom end of the atomizing tank.

[0012] Preferably, an inclined substrate base is placed in the middle of the single-temperature zone tube furnace and the inclination angle is adjustable;

[0013] The other end of the thin quartz tube extends into the interior of the thick quartz tube;

[0014] The tail of the thick quartz tube is provided with an exhaust fan, the power of which is adjustable;

[0015] The atomizing tank is provided with an ultrasonic atomizing sheet;

[0016] The liquid propulsion device and the atomization tank are both filled with gallium salt solution.

[0017] Preferably, the five-channel gas flow controller can control the flow of each gas separately;

[0018] The liquid propulsion device is connected to the weight sensor via a start-stop switch.

[0019] In a second aspect, the present invention provides a method for preparing a gallium oxide epitaxial thin film based on the above system, comprising the following steps:

[0020] S1. Adjust the substrate base to be tilted 30 to 60 degrees and place the substrate on the substrate base;

[0021] S2. The pre-prepared gallium salt solution is added to the liquid propulsion device and the atomization tank;

[0022] S3. Turn on the switches of the carrier gas storage tank, the oxygen storage tank and the mixed gas storage tank, and use the five-channel gas flow controller to set the carrier gas flow in the atomizer tank to 0-10 L / min, the carrier gas flow in the fine quartz tube to 0-1 L / min, and the carrier gas flow in the jet device to 0-3 L / min;

[0023] S4. Set the working temperature of the single temperature zone tube furnace to 400-1000°C; set the exhaust fan power to 0-30w; set the atomization frequency of the ultrasonic atomizer;

[0024] S5. After the single-temperature zone tube furnace reaches the set working temperature, turn on the ultrasonic atomizer switch to ultrasonically atomize the gallium salt solution. The carrier gas transports the atomized droplets directly to the substrate through a fine quartz tube, and deposits a gallium oxide film at a high temperature.

[0025] Preferably, the gas in the carrier gas storage tank is high-purity nitrogen (99.99%), and the gas in the oxygen storage tank is high-purity oxygen (99.99%).

[0026] Preferably, the gas in the mixed gas storage tank is a nitrogen and oxygen mixed gas. 2 / N 2 Greater than 0 and less than or equal to 10%.

[0027] Preferably, the atomization frequency of the ultrasonic atomization sheet is 1.7 to 3 MHz.

[0028] Preferably, the gallium salt solution is an aqueous solution of 0.01-0.1 mol / L of gallium acetylacetonate, gallium bromide, and gallium chloride.

[0029] Preferably, the substrate is a sapphire substrate, a silicon carbide substrate, a diamond substrate or a gallium oxide substrate.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention adds a thin quartz tube to the coarse quartz tube of the traditional tube furnace, so that the droplets transported to the single-temperature zone tube furnace can directly reach the substrate base, thereby achieving efficient utilization of raw materials and reducing raw material waste.

[0032] (2) The present invention adds a vertical downward air jet device to the coarse quartz tube of the traditional tube furnace, which can enable the droplets transported to the single-temperature zone tube furnace to better adhere to the substrate, increase the effective contact area between the droplets and the substrate, and make the thin film grown on the substrate more uniform.

[0033] (3) The present invention adds a liquid propulsion device and a weight sensor to the existing tubular furnace mist chemical vapor deposition system to achieve uniform atomization volume over time using ultrasonic atomization sheets in the atomization tank.

[0034] (4) The present invention adds an exhaust fan at the rear of the tubular furnace and adjusts its power to ensure that the droplets in the single-temperature zone tubular furnace can flow evenly on the substrate on the substrate base, thereby effectively reducing the surface roughness of the gallium oxide film and improving the crystallinity of the gallium oxide film.

[0035] (5) The present invention adopts a tubular furnace mist chemical vapor deposition system, which has simple equipment assembly, simple experimental process flow, short preparation cycle, and is conducive to reducing costs, and is very suitable for (semi-)industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the system structure used in the present invention;

[0037] Figure 2 is an XRD diagram of a gallium oxide film grown in the present invention;

[0038] Figure 3 is a transmittance graph of a gallium oxide film grown in the present invention;

[0039] Figure 4 A surface roughness map of a gallium oxide film grown in the present invention;

[0040] In the figure: 1. carrier gas storage tank, 2. oxygen storage tank, 3. mixed gas storage tank, 4. five-channel gas flow controller, 5. liquid propulsion device, 6. weight sensor, 7. ultrasonic atomization sheet, 8. atomization tank, 9. fine quartz tube, 10. jet device, 11. single temperature zone tubular furnace, 12. substrate base, 13. exhaust fan. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the illustrations provided in the present embodiment are only schematic illustrations of the basic concept of the present invention, and although the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation, the form, quantity and proportion of each component in actual implementation may be changed at will, and the component layout may also be more complicated.

[0042] like Figure 1 The mist chemical vapor deposition system for preparing gallium oxide epitaxial thin films shown in the figure comprises a carrier gas storage tank 1 filled with high-purity nitrogen (99.99%), an oxygen storage tank 2 filled with high-purity oxygen (99.99%), and a nitrogen-oxygen mixed gas (O 2 / N 2The invention comprises a mixed gas storage tank 3 (greater than 0 and less than or equal to 10%), a five-channel gas flow controller 4, a liquid propulsion device 5, a weight sensor 6, an atomization tank 8, and a single-temperature zone tubular furnace 11. A vertical downward jet device 10 is arranged on the upper wall of the coarse quartz tube of the single-temperature zone tubular furnace 11, and a substrate base 12 is placed in the middle of the single-temperature zone tubular furnace 11. This position is the temperature measurement position of the single-temperature zone tubular furnace 11, which can ensure the accuracy of the temperature during the experiment. The feed end of the coarse quartz tube of the single-temperature zone tubular furnace 11 is connected to a thin quartz tube 9, and the thin quartz tube 9 is installed in the coarse quartz tube through a quartz flange, and an exhaust fan 13 is arranged at the tail of the coarse quartz tube.

[0043] The carrier gas storage tank 1 and the oxygen storage tank 2 are connected to the atomizing tank 8 through the five-channel gas flow controller 4 and two gas paths, respectively, and then connected to an air inlet of the thin quartz tube 9 through the five-channel gas flow controller 4 and the other two gas paths, respectively. The mixed gas storage tank 3 is connected to the jet device 10 through the five-channel gas flow controller 4 and one gas path. By adjusting the gas flow controller 4, nitrogen, oxygen and nitrogen-oxygen mixed gas with different gas flow rates can enter the atomizing tank 8, the thin quartz tube 9 and the jet device 10. The liquid propulsion device 5 is connected to the atomizing tank 8 through a liquid hose, the weight sensor 6 is placed at the bottom of the atomizing tank 8, and the atomizing tank 8 is provided with an ultrasonic atomizing sheet 7. The liquid propulsion device 5 and the atomizing tank 8 are both filled with a gallium salt solution, and the gallium salt solution can be an aqueous solution of gallium acetylacetonate, gallium bromide and gallium chloride with a concentration of 0.01 to 0.1 mol / L. The ultrasonic atomizing sheet 7 ultrasonically atomizes the solution in the atomizing tank 8 through ultrasonic waves, and after being transported by the carrier gas, enters the single temperature zone tubular furnace 11 through the fine quartz tube 9. The addition of the fine quartz tube 9 can ensure that the atomized droplets in the atomizing tank 8 can be directly transported to the substrate base 12.

[0044] When the weight sensor 6 senses that the solution in the atomization tank 8 is reduced and the weight does not reach the preset weight, the liquid propulsion device 5 will replenish the solution in the atomization tank 8 in time to make the solution in the atomization tank 8 reach liquid level balance, so that the atomization amount of the ultrasonic atomization sheet 7 is uniform over time.

[0045] The exhaust fan 13 has an adjustable power, and can be adjusted to different powers of 0 to 30 W according to the size of the carrier gas of the five-channel gas flow controller 4 to achieve uniform flow of droplets in the single-temperature zone tubular furnace 11.

[0046] Example 1

[0047] The specific steps of growing the gallium oxide epitaxial film based on the above system are as follows:

[0048] S1. The substrate base 12 is adjusted to be inclined at 30 degrees, and the silicon carbide substrate is placed on the substrate base 12;

[0049] S2. The pre-prepared 0.08 mol / L gallium bromide solution is added to the liquid propulsion device 5 and the atomizing tank 8;

[0050] S3. Turn on the switches of the carrier gas storage tank 1, the oxygen storage tank 2 and the mixed gas storage tank 3, and use the five-channel gas flow controller 4 to set the carrier gas flow rate in the atomizer 8 to 6 L / min, the carrier gas flow rate in the thin quartz tube 9 to 0.5 L / min, and the carrier gas flow rate in the jet device 10 to 1.8 L / min;

[0051] S4. Set the operating temperature of the single temperature zone tube furnace 11 to 600 ℃; set the exhaust fan 13 power to 10w;

[0052] S5. Set the atomization frequency of the ultrasonic atomizer 7 to 2 MHz. After the single-temperature zone tubular furnace 11 reaches the set operating temperature, turn on the switch of the ultrasonic atomizer 7 to perform ultrasonic atomization. The carrier gas transports the atomized droplets directly to the silicon carbide substrate on the substrate base 12 through the fine quartz tube 9, and deposits a gallium oxide film at high temperature.

[0053] Example 2

[0054] The specific steps of growing the gallium oxide epitaxial film based on the above system are as follows:

[0055] S1. The substrate base 12 is adjusted to be inclined at 35 degrees, and the diamond substrate is placed on the substrate base 12;

[0056] S2. The pre-prepared 0.09 mol / L gallium chloride solution is added to the liquid propulsion device 5 and the atomizing tank 8;

[0057] S3. Turn on the switches of the carrier gas storage tank 1, the oxygen storage tank 2 and the mixed gas storage tank 3, and use the five-channel gas flow controller 4 to set the carrier gas flow rate in the atomizer 8 to 10L / min, the carrier gas flow rate in the thin quartz tube 9 to 1L / min, and the carrier gas flow rate in the jet device 10 to 3L / min;

[0058] S4. Set the operating temperature of the single temperature zone tube furnace 11 to 800 ℃; set the exhaust fan 13 power to 30w;

[0059] S5. Set the atomization frequency of the ultrasonic atomizer 7 to 3 MHz. After the single-temperature zone tubular furnace 11 reaches the set operating temperature, turn on the switch of the ultrasonic atomizer 7 to perform ultrasonic atomization. The carrier gas transports the atomized droplets directly to the diamond substrate on the substrate base 12 through the fine quartz tube 9, and deposits a gallium oxide film at high temperature.

[0060] Example 3

[0061] The specific steps of growing the gallium oxide epitaxial film based on the above system are as follows:

[0062] S1. The substrate base 12 is adjusted to be tilted 40 degrees, and the sapphire substrate is placed on the substrate base 12;

[0063] S2. The pre-prepared 0.1 mol / L gallium acetylacetonate solution is added to the liquid propulsion device 5 and the atomizing tank 8;

[0064] S3. Turn on the switches of the carrier gas storage tank 1, the oxygen storage tank 2 and the mixed gas storage tank 3, and use the five-channel gas flow controller 4 to set the carrier gas flow rate in the atomizer 8 to 8 L / min, the carrier gas flow rate in the thin quartz tube 9 to 0.7 L / min, and the carrier gas flow rate in the jet device 10 to 2.5 L / min;

[0065] S4. Set the operating temperature of the single temperature zone tube furnace 11 to 700 ℃; set the exhaust fan 13 power to 25w;

[0066] S5. Set the atomization frequency of the ultrasonic atomizer 7 to 2.4 MHz. After the single-temperature zone tube furnace 11 reaches the set working temperature, turn on the switch of the ultrasonic atomizer 7 to perform ultrasonic atomization. The carrier gas transports the atomized droplets directly to the sapphire substrate on the substrate base 12 through the fine quartz tube 9, and deposits a gallium oxide film at a high temperature.

[0067] The gallium oxide film grown in this embodiment is subjected to the following steps: Figure 2 The XRD test shown shows a β-phase gallium oxide single crystal film;

[0068] The gallium oxide film grown in this embodiment is subjected to the following steps: Figure 3 The transmittance test shown shows that the gallium oxide film has a high transmittance of about 80%.

[0069] The gallium oxide film grown in this embodiment is subjected to the following steps: Figure 4 The surface roughness test shown shows that the gallium oxide film has a very flat surface with a surface roughness of 1 nm.

[0070] Therefore, the mist chemical vapor deposition system for preparing gallium oxide epitaxial thin films provided by the present invention is very suitable for growing high-quality gallium oxide epitaxial thin films.

Claims

1. A mist chemical vapor deposition system for preparing gallium oxide epitaxial thin films, comprising a carrier gas storage tank, an oxygen storage tank, a mixed gas storage tank, an atomizing tank, and a single temperature zone tubular furnace, characterized in that: The system also includes a five-channel gas flow controller, a liquid propulsion device, and a weight sensor; The upper wall of the coarse quartz tube of the single-temperature zone tubular furnace is provided with a vertical downward air injection device, the feed end of the coarse quartz tube of the single-temperature zone tubular furnace is connected to a thin quartz tube, and one end of the thin quartz tube is provided with two air inlets; The carrier gas storage tank and the oxygen storage tank are connected to the atomizing tank through a five-channel gas flow controller and two gas lines, respectively, and then connected to an air inlet of the thin quartz tube through a five-channel gas flow controller and another two gas lines, respectively. The mixed gas storage tank is connected to the jet device through a five-channel gas flow controller and one gas line; The liquid propulsion device is connected to the side wall of the atomizing tank through a communicating vessel, the atomizing tank is connected to another air inlet of the thin quartz tube, and the weight sensor is placed at the bottom end of the atomizing tank.

2. A mist chemical vapor deposition system for preparing gallium oxide epitaxial thin films according to claim 1, characterized in that: An inclined substrate base is placed in the middle of the single-temperature zone tubular furnace, and the inclination angle is adjustable; The other end of the thin quartz tube extends into the interior of the thick quartz tube; The tail of the thick quartz tube is provided with an exhaust fan, the power of which is adjustable; The atomizing tank is provided with an ultrasonic atomizing sheet; The liquid propulsion device and the atomization tank are both filled with gallium salt solution.

3. A mist chemical vapor deposition system for preparing gallium oxide epitaxial thin films according to claim 1, characterized in that: The five-channel gas flow controller can control the flow of each gas separately; The liquid propulsion device is connected to the weight sensor via a start-stop switch.

4. A method for preparing a gallium oxide epitaxial thin film based on the system of claim 1, characterized in that: The steps include: S1. Adjust the substrate base to be tilted 30 to 60 degrees and place the substrate on the substrate base; S2. The pre-prepared gallium salt solution is added to the liquid propulsion device and the atomization tank; S3. Turn on the switches of the carrier gas storage tank, the oxygen storage tank and the mixed gas storage tank, and use the five-channel gas flow controller to set the carrier gas flow in the atomizer tank to 0-10 L / min, the carrier gas flow in the fine quartz tube to 0-1 L / min, and the carrier gas flow in the jet device to 0-3 L / min; S4. Set the working temperature of the single temperature zone tube furnace to 400-1000°C; set the exhaust fan power to 0-30w; set the atomization frequency of the ultrasonic atomizer; S5. After the single-temperature zone tube furnace reaches the set working temperature, turn on the ultrasonic atomizer switch to ultrasonically atomize the gallium salt solution. The carrier gas transports the atomized droplets directly to the substrate through a fine quartz tube, and deposits a gallium oxide film at a high temperature.

5. The method for preparing a gallium oxide epitaxial thin film according to claim 4, characterized in that: The gas in the carrier gas storage tank is high-purity nitrogen, the gas in the oxygen storage tank is high-purity oxygen, and the gas in the mixed gas storage tank is a nitrogen-oxygen mixed gas, with O2 / N2 being greater than 0 and less than or equal to 10%.

6. The method for preparing a gallium oxide epitaxial thin film according to claim 4, characterized in that: The frequency of the ultrasonic atomizer is 1.7-3 MHz.

7. The method for preparing a gallium oxide epitaxial thin film according to claim 4, characterized in that: The gallium salt solution is an aqueous solution of 0.01-0.1 mol / L gallium acetylacetonate, gallium bromide and gallium chloride.

8. The method for preparing a gallium oxide epitaxial thin film according to claim 4, characterized in that: The substrate is a sapphire substrate, a silicon carbide substrate, a diamond substrate or a gallium oxide substrate.

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