Mocvd reaction cavity and method for growing algan thin film

Abstract

The application provides an MOCVD reaction cavity and a method for growing an AlGaN film. The MOCVD reaction cavity comprises a gas spray head, a tray and a voltage source. The voltage source is electrically connected with the gas spray head and the tray respectively, and controls the voltage between the gas spray head and the tray. In the process of growing the AlGaN film, a strong electric field is generated between the gas spray head and the tray by the voltage source. The electric field passes through the wafer, changes the surface polarity of the AlGaN film, makes the Al atoms less likely to be adsorbed by N atoms, and further improves the mobility of the Al atoms. The application can quickly change the growth mode of the AlGaN without greatly changing the growth conditions, makes the surface of the AlGaN film more flat, the dislocation density lower and the crystal quality higher. The MOCVD reaction cavity has the advantages of simple structure, convenient operation, low cost and high performance, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to an MOCVD reaction chamber and a method for growing AlGaN thin films. Background Technology

[0002] Metal-organic chemical vapor deposition (MOCVD) is a widely used technique for growing compound semiconductor materials, and it holds an irreplaceable position in the field of nitride semiconductor material growth. Compared to molecular beam epitaxy, MOCVD offers faster growth rates, lower energy consumption and cost, and lower precision requirements for the equipment itself. Compared to plasma sputtering growth, MOCVD boasts higher growth quality and greater flatness.

[0003] Nitride semiconductor materials have extremely wide applications and are an important new type of wide-bandgap semiconductor material. Among them, AlGaN material system has the characteristic of direct bandgap, which is continuously tunable in the range of 3.4 eV to 6.2 eV, making it the best choice for deep ultraviolet LEDs. In addition, AlGaN materials also have broad application prospects in optical communication fields such as full-spectrum lighting, solar-blind band detectors, photodiodes, and ultraviolet lasers.

[0004] However, the quality of AlGaN thin films grown using MOCVD equipment remains low, with high dislocation density and surface roughness. This is primarily due to the low mobility of Al atoms, resulting in high surface roughness and dislocation density in the epitaxially grown AlGaN films. The fundamental reason for the low mobility of Al atoms lies in the high bond energy and short bond length of the Al-N bond. Based on this principle, current methods to increase Al atom mobility include high-temperature growth, reducing the V-III ratio, and reducing growth pressure. High-temperature growth primarily utilizes high temperatures to increase molecular kinetic energy, reducing the probability of Al-N bonding and thus improving Al mobility. However, this method requires high-temperature resistance from the MOCVD chamber and consumes significant energy. Reducing the V-III ratio mainly involves decreasing the N atom density, thereby reducing the probability of Al-N bonding. However, this method leads to a large number of N vacancy defects in the grown AlGaN film, affecting device applications. The main method to reduce growth pressure is to simultaneously reduce the density of Al and N atoms, thereby reducing the probability of Al and N atom collisions and thus reducing the bonding probability. However, this method leads to a slow growth rate and more waste of epitaxial growth raw materials.

[0005] Given the current shortcomings in the growth of AlGaN thin films, it is necessary to improve this process. Summary of the Invention

[0006] In view of this, the present invention proposes an MOCVD reaction chamber and a method for growing AlGaN thin films to solve the technical problems existing in the prior art.

[0007] In a first aspect, the present invention provides an MOCVD reaction chamber, comprising:

[0008] cavity;

[0009] A gas spray head is located within the cavity;

[0010] A tray, located within the cavity and positioned opposite the gas spray head, is rotatable about its central axis;

[0011] A voltage source is electrically connected to the gas spray head and the tray respectively, and the voltage source is used to control the voltage between the gas spray head and the tray.

[0012] Preferably, the MOCVD reaction chamber further includes:

[0013] A rotating shaft is located at the central axis of the tray;

[0014] A drive mechanism, which is connected to the rotating shaft, is used to drive the tray to rotate about its central axis;

[0015] The brush electrode is sleeved on the outer periphery of the rotating shaft and can rotate relative to the rotating shaft;

[0016] The brush electrode is electrically connected to the voltage source, and the tray is electrically connected to the voltage source through the brush electrode.

[0017] Preferably, the MOCVD reaction chamber further includes:

[0018] An insulating component, one end of which is connected to the end of the rotating shaft away from the tray, and the other end of which is connected to the driving mechanism, the driving mechanism driving the insulating component to rotate.

[0019] Preferably, in the MOCVD reaction chamber, the chamber body, the gas spray head, and the voltage source are all grounded.

[0020] Preferably, the rotating shaft of the MOCVD reaction chamber is made of molybdenum.

[0021] Preferably, in the MOCVD reaction chamber, the brush electrode is a carbon brush electrode.

[0022] Secondly, the present invention also provides a method for growing AlGaN thin films using the aforementioned MOCVD reaction chamber, comprising the following steps:

[0023] Place the wafer substrate on the tray;

[0024] The voltage between the gas spray head and the tray is controlled using a voltage source;

[0025] Drive the tray to rotate;

[0026] An Al source, a Ga source, and an N source are introduced into the cavity using a gas spray head, and growth parameters are controlled to grow an AlGaN thin film on the wafer substrate.

[0027] Preferably, in the method for growing AlGaN thin films, the voltage range in the step of controlling the voltage between the gas spray head and the tray using a voltage source is 100V to 40KV.

[0028] Preferably, in the method for growing AlGaN thin films, the step of controlling the voltage between the gas spray head and the tray using a voltage source is any one of a constant voltage mode, a sinusoidal voltage mode, a square wave voltage mode, and a sawtooth wave voltage mode.

[0029] Preferably, in the method for growing AlGaN thin films, the thickness of the AlGaN thin film is 1 nm to 100 μm;

[0030] The AlGaN thin film can be a continuous or discontinuous two-dimensional structure thin film;

[0031] Alternatively, the AlGaN thin film may be a continuous or discontinuous three-dimensional structure thin film.

[0032] The MOCVD reaction chamber and method for growing AlGaN thin films of the present invention have the following advantages over the prior art:

[0033] 1. The MOCVD reaction chamber of this invention includes a gas spray head, a tray, and a voltage source. The voltage source is electrically connected to both the gas spray head and the tray, and controls the voltage between them. During the growth of the AlGaN thin film, a high voltage is generated between the gas spray head and the tray using the voltage source, thereby producing a strong electric field. This electric field passes through the wafer, changing the surface polarity of the AlGaN thin film, making it less likely for Al atoms to be adsorbed by N atoms, thus improving the Al atom mobility. This invention can rapidly change the growth mode of AlGaN without significantly altering the growth conditions, resulting in a smoother AlGaN thin film surface, lower dislocation density, and higher crystal quality. The MOCVD reaction chamber of this invention has a simple structure, is easy to operate, and offers advantages of low cost and high performance, possessing broad application prospects.

[0034] 2. The method for growing AlGaN thin films of the present invention uses the MOCVD reaction chamber of the present invention for film growth. During the growth of AlGaN thin films, the voltage between the gas spray head and the tray is controlled by a voltage source, thus generating an electric field between the tray and the gas spray head. This electric field acts on the wafer substrate, which can adjust the rate of chemical vapor deposition on the substrate surface and increase the atomic mobility of Al atoms, making them less likely to be captured by N atoms and deposited on the surface. When Al atoms migrate to the atomic steps, they are deposited at the steps due to the reduced surface formation energy. This two-dimensional growth mode makes the surface morphology of the AlGaN thin film smoother, the dislocation density lower, and the crystal quality better. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the structure of the MOCVD reaction chamber in one embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0039] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0040] In the description of this invention, it should be understood that the orientation or positional relationship indicated by terms such as "above" is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use, or the orientation or positional relationship in which those skilled in the art are usually understood. It is only for the convenience of describing this invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] This invention provides an MOCVD reaction chamber, such as... Figure 1 As shown, it includes:

[0044] cavity;

[0045] Gas spray head 1, which is located inside the cavity;

[0046] Tray 2, which is located inside the cavity and is positioned opposite to the gas spray head 2, and tray 2 can rotate around its central axis;

[0047] Voltage source 6 is electrically connected to the gas spray head and the tray respectively. Voltage source 6 is used to control the voltage between gas spray head 1 and tray 2.

[0048] It should be noted that the MOCVD reaction chamber of the present invention, such as Figure 1 As shown ( Figure 1(Exploded view) The structure includes a cavity (not shown), a gas spray head 1, a tray 2, and a voltage source 6. The cavity, gas spray head 1, and tray 2 are all conventional cavities, gas spray heads, and trays. This application does not modify these structural components. The gas spray head 1 and tray 2 are both arranged opposite each other within the cavity 1, and the positive and negative terminals of the voltage source 6 are electrically connected to the gas spray head 1 and tray 2, respectively. Thus, the gas spray head 1 and tray 2 form parallel electrode plates arranged opposite each other. The voltage between the gas spray head 1 and tray 2 is controlled by the voltage source 6, that is, the voltage between the electrode plates is controlled by the voltage source 6. Specifically, the voltage source 6 generates a high voltage between the gas spray head 1 and tray 2, thereby generating a strong electric field between the gas spray head 1 and tray 2. This electric field passes through the wafer, thereby changing the surface polarity of the AlGaN thin film, making it more difficult for Al atoms to be adsorbed by N atoms, and thus improving the mobility of Al atoms. By adjusting the voltage applied to the electrodes (i.e., gas spray head 1 and tray 2), the electric field strength between the two electrodes can be changed, which can rapidly change the growth mode of AlGaN without significantly altering the growth conditions, resulting in a smoother AlGaN film surface, lower dislocation density, and higher crystal quality.

[0049] Specifically, in the above embodiments, the tray 2 is used to carry the wafer. For example, a groove can be provided on the tray 2, and the wafer is placed in the groove 2. The tray 2 is a graphite tray; the gas spray head 1 is used to introduce Al source, Ga source and N source into the cavity.

[0050] In some embodiments, it also includes:

[0051] Rotation shaft 3 is located at the central axis of tray 2;

[0052] A drive mechanism, which is connected to the rotating shaft 3, is used to drive the tray 2 to rotate around its central axis;

[0053] The brush electrode 4 is sleeved on the outer periphery of the rotating shaft 3 and can rotate relative to the rotating shaft 3;

[0054] The brush electrode 4 is electrically connected to the voltage source 6, and the tray 2 is electrically connected to the voltage source 6 through the brush electrode 4.

[0055] Specifically, in the above embodiments, a rotating shaft 3 is set at the central axis of the tray 2, and a driving mechanism is connected to the rotating shaft 3. The driving mechanism drives the rotating shaft 3 to rotate, thereby realizing the rotation of the tray 2 around its central axis. The driving mechanism includes, but is not limited to, a motor with adjustable speed, including a servo motor, a stepper motor, or a frequency converter motor. For example, the rotating shaft of the servo motor is connected to the rotating shaft 3, and the rotation of the servo motor drives the tray 2 to rotate around its central axis. At the same time, a brush electrode 4 is set on the outer periphery of the rotating shaft 3. The brush electrode 4 is annular and is sleeved on the outer periphery of the rotating shaft 3 and in contact with the rotating shaft 3. The rotating shaft 3 can rotate relative to the brush electrode 4. The brush electrode 4 is electrically connected to a voltage source 6. The tray 2 is electrically connected to the voltage source 6 through the brush electrode 4. The brush electrode 4 can continuously output high voltage to the rotating shaft 3 and the tray 2 during the high-speed rotation of the rotating shaft 3.

[0056] In some embodiments, it also includes:

[0057] The insulating component 5 has one end connected to the end of the rotating shaft 3 away from the tray 2, and the other end connected to the drive mechanism, which drives the insulating component 5 to rotate.

[0058] In the above embodiments, one end of the insulating member 5 is connected to the rotating shaft 3 and the other end is connected to the driving mechanism. The driving mechanism drives the insulating member 5 to rotate, thereby causing the tray 2 to rotate. By providing the insulating member 5 between the rotating shaft 3 and the cavity, a short circuit between the high voltage electrode and the cavity is prevented. The insulating member 5 of this application is placed between the rotating shaft and the cavity to transmit rotational power and block the conductive circuit between the rotating shaft and the cavity.

[0059] In some embodiments, the gas spray head 1 is made of stainless steel or other conductive and high-temperature resistant materials, the gas spray head 1 is electrically connected to the cavity, and the cavity is grounded.

[0060] In some embodiments, the cavity, the gas spray head 1, and the voltage source 6 are all grounded.

[0061] In some embodiments, the material of the rotating shaft 3 is molybdenum, that is, the rotating shaft 3 is a rotating molybdenum shaft.

[0062] In some embodiments, the brush electrode 4 is made of a conductive material that is wear-resistant and high-temperature resistant. Specifically, the brush electrode 4 is a carbon brush electrode, and preferably, the brush electrode 4 is a graphite brush electrode.

[0063] Based on the same inventive concept, the present invention also provides a method for growing AlGaN thin films using the above-mentioned MOCVD reaction chamber, comprising the following steps:

[0064] S1. Place the wafer substrate on the tray;

[0065] S2. Use a voltage source to control the voltage between the gas spray head and the tray;

[0066] S3, drive the tray to rotate;

[0067] S4. Using a gas spray head, Al, Ga and N sources are introduced into the cavity to control the growth parameters and grow an AlGaN thin film on the wafer substrate.

[0068] The method for growing AlGaN thin films of the present invention uses the aforementioned MOCVD reaction chamber for film growth. Specifically, it includes the following steps: placing a wafer substrate on a tray; controlling the voltage between the gas spray head and the tray using a voltage source; driving the tray to rotate; introducing Al, Ga, and N sources into the chamber using the gas spray head; and controlling the growth parameters to grow the AlGaN thin film on the wafer substrate. Specifically, the growth parameters controlled during the growth process include temperature, pressure, rotation speed, and growth atmosphere. These are all conventional parameters for growing AlGaN thin films. Based on these growth parameters, the present invention further controls the voltage between the gas spray head and the tray using a voltage source. This generates an electric field between the tray and the gas spray head. This electric field, acting on the wafer substrate, can adjust the rate of chemical vapor deposition on the substrate surface and increase the atomic mobility of Al atoms, making them less susceptible to being captured and deposited on the surface by N atoms. When Al atoms migrate to the atomic steps, they deposit at the steps due to the reduced surface formation energy. This two-dimensional growth mode results in a smoother surface morphology, lower dislocation density, and better crystal quality in the AlGaN thin film.

[0069] In some embodiments, the Al source, Ga source, and N source are all conventional Al source, Ga source, and N source. For example, TMAl (trimethylaluminum) is introduced as the Al source, TMGa (trimethylgallium) is introduced as the Ga source, and NH3 is introduced as the N source.

[0070] Specifically, AlGaN thin films are Al x Ga 1-x N, short for x = 0 to 1, refers to AlGaN crystalline thin films with an aluminum content of 0 to 100%.

[0071] In some embodiments, the voltage source can be turned on and the electric field strength and the way the electric field changes can be controlled at any stage of AlGaN film growth.

[0072] In some embodiments, in the step of controlling the voltage between the gas spray head and the tray using a voltage source, the voltage range is 100V to 40KV.

[0073] In some embodiments, in the step of controlling the voltage between the gas spray head and the tray using a voltage source, the voltage mode is any one of constant voltage mode, sinusoidal voltage mode, square wave voltage mode, and sawtooth wave voltage mode.

[0074] In some embodiments, the thickness of the AlGaN film is 1 nm to 100 μm.

[0075] In some embodiments, the AlGaN thin film is a continuous or discontinuous two-dimensional structure thin film.

[0076] In some embodiments, the AlGaN thin film is a continuous or discontinuous three-dimensional structure thin film.

[0077] The following detailed embodiments further illustrate the method for growing AlGaN thin films according to the present invention. This section further describes the present invention in conjunction with specific embodiments, but should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the methods and equipment used in the present invention are conventional methods and equipment in the art.

[0078] Example 1

[0079] This application provides an embodiment of a method. Figure 1 The method for growing AlGaN thin films in an MOCVD reaction chamber, as shown, includes the following steps:

[0080] S1. Place the wafer substrate (specifically a Si substrate) on the tray;

[0081] S2. Use a voltage source to control the voltage between the gas spray head and the tray;

[0082] S3, drive the tray to rotate;

[0083] S4. Using a gas spray head, Al source, Ga source and N source are introduced into the cavity to control the growth parameters and grow AlGaN thin film on the wafer substrate.

[0084] In step S4, the Al source is TMAl, the Ga source is TMGa, and the N source is NH3.

[0085] In step S2, a voltage source is used to control the voltage between the gas spray head and the tray to be 1000V.

[0086] Comparative Example 1

[0087] The method for growing AlGaN thin films provided in this comparative example is the same as that in Example 1, except that in step S2, a voltage source is used to control the voltage between the gas spray head and the tray to be 0V (i.e., there is no electric field between the gas spray head and the tray).

[0088] The AlGaN films grown using the methods in Example 1 and Comparative Example 1 were tested and found that, compared with Comparative Example 1, the AlGaN films grown using the method in Example 1 had a smoother surface morphology, lower dislocation density, and better crystal quality.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for growing AlGaN thin films using an MOCVD reaction chamber, characterized in that, The MOCVD reaction chamber includes: cavity; A gas spray head is located within the cavity; A tray, located within the cavity and positioned opposite the gas spray head, is rotatable about its central axis; A voltage source is electrically connected to the gas spray head and the tray respectively, and the voltage source is used to control the voltage between the gas spray head and the tray; The method for growing AlGaN thin films includes the following steps: Place the wafer substrate on the tray; The voltage between the gas spray head and the tray is controlled using a voltage source; Drive the tray to rotate; An Al source, a Ga source, and an N source are introduced into the cavity using a gas spray head, and growth parameters are controlled to grow an AlGaN thin film on the wafer substrate. In the step of controlling the voltage between the gas spray head and the tray using a voltage source, the voltage range is 100V~40kV; TMAl is used as the Al source, TMGa as the Ga source, and NH3 as the N source.

2. The method for growing AlGaN thin films as described in claim 1, characterized in that, The MOCVD reaction chamber also includes: A rotating shaft is located at the central axis of the tray; A drive mechanism, which is connected to the rotating shaft, is used to drive the tray to rotate about its central axis; The brush electrode is sleeved on the outer periphery of the rotating shaft and can rotate relative to the rotating shaft; The brush electrode is electrically connected to the voltage source, and the tray is electrically connected to the voltage source through the brush electrode.

3. The method for growing AlGaN thin films as described in claim 2, characterized in that, The MOCVD reaction chamber also includes: An insulating component, one end of which is connected to the end of the rotating shaft away from the tray, and the other end of which is connected to the driving mechanism, the driving mechanism driving the insulating component to rotate.

4. The method for growing AlGaN thin films as described in claim 1, characterized in that, The cavity, the gas spray head, and the voltage source are all grounded.

5. The method for growing AlGaN thin films as described in claim 2, characterized in that, The material of the rotating shaft is molybdenum.

6. The method for growing AlGaN thin films as described in claim 2, characterized in that, The brush electrode is a carbon brush electrode.

7. The method for growing AlGaN thin films as described in claim 1, characterized in that, In the step of controlling the voltage between the gas spray head and the tray using a voltage source, the voltage mode is any one of constant voltage mode, sine wave voltage mode, square wave voltage mode, and sawtooth wave voltage mode.

8. The method for growing AlGaN thin films according to any one of claims 1 to 7, characterized in that, The AlGaN thin film has a thickness of 1 nm to 100 μm; The AlGaN thin film can be a continuous or discontinuous two-dimensional structure thin film; Alternatively, the AlGaN thin film may be a continuous or discontinuous three-dimensional structure thin film.

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