A method for changing the orientation of a growing film

Abstract

A method for changing the orientation of a growing film, which relates to a vacuum evaporation deposition film process. The substrate is cleaned with alcohol, acetone and deionized water at room temperature, cleaned in an ultrasonic cleaner to remove impurities on the substrate surface, and the cleaned sample is placed in a fast sample chamber; a mechanical pump and a turbomolecular pump are used to obtain 10 ‑ 8 After the growth chamber is filled with a vacuum of mbar, the substrate is transferred from the fast sample feed chamber into the growth chamber of the growth equipment, and the sample is annealed in an O atmosphere; at the same time, a plasma-activated Zn metal source and Mg metal source are introduced to grow a MgZnO film for 2 hours. After the growth is completed, the sample is taken out. It can solve the problems related to expensive hexagonal substrates, complex process conditions, and the selection of polarity and non-polarity, and achieve pure, controllable, and precise growth. Under the condition that the temperature, pressure and other process parameters remain unchanged, a growth film with different crystal orientations can be deposited on the same material.

Description

Technical Field

[0001] The invention relates to a vacuum evaporation deposition film process, in particular to a method for changing the orientation of a growing film. Background Art

[0002] In the 21st century, when information technology is highly developed, semiconductors, as a material between conductors and insulators, have received extensive attention. Wide bandgap semiconductor materials have shorter wavelengths than ordinary semiconductor materials and can be well used in short-wavelength light-emitting devices. They have great potential in the fields of communications, electronics, photovoltaics, and lighting, and have received great attention from researchers. Research on semiconductors has a long history, and various semiconductor materials with different properties have come into the sight of researchers. Compared with the first-generation semiconductor materials (Si, Ge) and the second-generation semiconductor materials (GaAs, InP), the third-generation wide bandgap semiconductor materials effectively make up for many shortcomings of the previous two generations of semiconductors. Representative materials include gallium nitride (GaN), silicon carbide (SiC), indium nitride (InN), and zinc oxide (ZnO). These third-generation semiconductor materials have advantages such as wide band gap, high breakdown voltage, and high electron mobility.

[0003] As a third-generation wide bandgap semiconductor material, ZnO is a member of the II-VI compound semiconductors. As an excellent direct bandgap semiconductor material, it has many unique advantages. The bandgap width at room temperature is about 3.37eV; the exciton binding energy of 60meV makes it possible for excitons to recombine stably at room temperature, which means that efficient stimulated emission of excitons can be carried out at room temperature or higher; the high melting point of 1975℃ and high chemical stability; non-toxic and environmentally friendly advantages are all reasons why ZnO has become a popular semiconductor material. MgZnO prepared by doping ZnO with Mg not only inherits the advantages of ZnO, but also has significantly improved electron mobility and bandgap width. In particular, the bandgap size of MgZnO can be controlled by adjusting the Mg content to improve the spectral responsivity. However, from a crystallographic point of view, hexagonal wurtzite ZnO is the most stable. Its growth is achieved by alternating superposition of Zn and O surfaces, thus forming a polar ZnO film with a crystal orientation of (001). This polar film will generate an internal electric field, separating the electrons and holes in the active layer. This phenomenon will have an adverse effect on ZnO optoelectronic devices.

[0004] MgZnO also inherits the lattice structure of ZnO. Studies have shown that crystal orientation always produces a specific atomic structure on the surface. The chemical properties and electronic orbital states of polar and non-polar surfaces are different, which will affect the physical and optoelectronic properties of MgZnO materials. Therefore, it is very valuable to study the different crystal orientations of MgZnO, which is very helpful for expanding the commercial potential of MgZnO. At present, polar and non-polar growth films are mainly formed on substrates with small lattice mismatch, including c-axis ZnO grown on AlN buffer layer, a-axis ZnO grown on r-plane sapphire, and m-plane ZnO grown on LiGaO2 (110). In addition to the choice of substrate, studies have reported that the crystal orientation of ZnO films is controlled by the growth temperature, and temperature plays an important role in controlling the surface morphology of the material. In addition, Zn precursors are used to change the crystal growth orientation. Summary of the invention

[0005] The purpose of the present invention is to provide a method for changing the orientation of a growing thin film in view of the problems existing in the prior art, such as the expensive hexagonal substrate, complicated process conditions, and the selection of polarity and non-polarity.

[0006] The present invention comprises the following steps:

[0007] 1) Clean the substrate with alcohol, acetone and deionized water at room temperature, and clean it in an ultrasonic cleaner to remove impurities on the surface of the substrate. Clean it alternately for 3 times, each time for 5 minutes, and place the cleaned sample into a fast sample chamber;

[0008] 2) Use mechanical pump and turbomolecular pump to obtain 10 -8 After the growth chamber is filled with a vacuum degree of mbar, the substrate is transferred from the fast sample introduction chamber into the growth chamber of the growth equipment, and the sample is annealed in an O atmosphere;

[0009] 3) After annealing, plasma activated Zn metal source and Mg metal source are introduced simultaneously to grow MgZnO film for 2 hours. After the growth is completed, the sample is taken out.

[0010] In step 1), the substrate is made of MgO with different crystal orientations, such as MgO (111), MgO (110) and MgO (100).

[0011] In step 2), the growth equipment may be one of a molecular beam epitaxy growth equipment, a vapor phase epitaxy growth equipment (MOCVE), a physical vapor deposition (PVD), a pulsed laser deposition system (PLD), etc.; preferably, a molecular beam epitaxy (MBE) is used, and the vacuum degree of the growth chamber can reach 10 -9 mbar; the annealing conditions may be: the annealing temperature is maintained at 800 ° C, the O plasma power is 250W, and the O pressure is maintained at 5×10-5 mbar, annealing time 1h.

[0012] In step 3), during the growth process, a reflection high energy electron diffraction device (RHEED) can be used to observe the growth state of the film in real time. The growth process conditions can be: the temperature of the Mg source (Mg, 99.999%) and the Zn source (Zn, 99.999%) are both maintained at 330°C, the substrate temperature is maintained at 275°C, the O plasma power is 180W, and the O pressure is maintained at 1×10 -5 mbar.

[0013] Compared with the prior art, the present invention has the following outstanding advantages:

[0014] Different from the method of changing the substrate material or adding new dopants, the present invention controls the crystal orientation of the epitaxially grown film by changing the crystal orientation of the substrate. The present invention selects an MgO substrate with a lattice constant similar to that of MgZnO, which can solve the problems related to expensive hexagonal substrates, complex process conditions, and the selection of polarity and non-polarity. In addition to selecting an MgO substrate, the substrate of the present invention can also use sapphire, silicon wafers, glass, etc.; the materials available for growth are not limited to MgZnO, and can be expanded to ZnO, SiC, GaN, diamond and other wide bandgap semiconductor materials. Growth is carried out in a molecular beam epitaxy device, and the growth state of the film is monitored in real time using a reflective high-energy electron diffraction device to achieve pure, controllable and precise growth. Under the condition that various process parameters such as temperature and air pressure remain unchanged, a growth film with different crystal orientations can be deposited on the same material, which can be applied in the field of optoelectronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 XRD pattern of MgZnO grown on MgO(111) (2theta scan).

[0016] Figure 2 Schematic diagram of the structure of MgZnO grown on MgO(111).

[0017] Figure 3 XRD pattern (phi scan) of MgZnO grown on MgO(110).

[0018] Figure 4 Schematic diagram of the structure of MgZnO grown on MgO(110).

[0019] Figure 5 XRD pattern of MgZnO grown on MgO(100) (2theta scan).

[0020] Figure 6 Schematic diagram of the structure of MgZnO grown on MgO(100). DETAILED DESCRIPTION

[0021] The following embodiments will further illustrate the present invention in conjunction with the accompanying drawings.

[0022] The present invention uses alcohol, acetone and deionized water to clean the substrate at room temperature, cleans it in an ultrasonic cleaner to remove impurities on the surface of the substrate, and cleans it three times alternately, each time for 5 minutes, and places the cleaned sample into a fast sampling chamber; uses a mechanical pump and a turbomolecular pump to obtain 10 -8 After the growth chamber is filled with a vacuum degree of 100 mbar, the substrate is transferred from the fast sample introduction chamber into the growth chamber of the growth equipment, and the sample is annealed in an O atmosphere; after the annealing treatment, a plasma-activated Zn metal source and a Mg metal source are simultaneously introduced to grow a MgZnO film for 2 hours, and the sample is taken out after the growth is completed. In addition to the MgO substrate, the substrate of the present invention can also be sapphire, silicon wafer, glass, etc.; the materials available for growth are not limited to MgZnO, and can be expanded to ZnO, SiC, GaN, diamond and other wide bandgap semiconductor materials. The following embodiments are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the application of the present invention should still fall within the scope of the patent coverage of the present invention.

[0023] Example 1

[0024] The MgO (111) substrate was cleaned and placed in a molecular beam epitaxy device. The sample was annealed in an O atmosphere for 1 h. During the annealing process, the annealing temperature was maintained at 800 °C, the O plasma power was 250 W, and the O pressure was maintained at 5×10 - 5 After annealing, plasma-activated Zn metal source and Mg metal source were introduced simultaneously to grow MgZnO thin film for 2 h. During the growth process, the temperature of Mg source (Mg, 99.999%) and Zn source (Zn, 99.999%) were maintained at 330°C, the substrate temperature was maintained at 275°C, the O plasma power was 180 W, and the O pressure was maintained at 1×10-5 mbar to obtain a sample.

[0025] Figure 1 The XRD spectrum of the sample (2theta scan) is shown. The diffraction peak at 34.4° in the scan spectrum is the characteristic peak of the ZnO (0001) plane. The film grows along the c-axis. The sample has a hexagonal wurtzite structure and is a polar plane.

[0026] Figure 2 A schematic diagram of the sample structure is shown. It consists of MgZnO in the upper part and MgO(111) substrate in the lower part.

[0027] Example 2

[0028] The MgO (110) substrate was cleaned and placed in a molecular beam epitaxy device. The sample was annealed in an O atmosphere for 1 h. During the annealing process, the annealing temperature was maintained at 800 °C, the O plasma power was 250 W, and the O pressure was maintained at 5×10 - 5 After annealing, plasma-activated Zn metal source and Mg metal source were introduced simultaneously to grow MgZnO thin film for 2 h. During the growth process, the temperature of Mg source (Mg, 99.999%) and Zn source (Zn, 99.999%) were maintained at 330°C, the substrate temperature was maintained at 275°C, the O plasma power was 180 W, and the O pressure was maintained at 1×10-5 mbar to obtain a sample.

[0029] Figure 3 The XRD spectrum (phi scan) of the sample is shown. The growth direction of the film deviates from the c-axis by about 34°, indicating inclined growth.

[0030] Figure 4 A schematic diagram of the sample structure is shown. It consists of MgZnO in the upper part and MgO(110) substrate in the lower part.

[0031] Example 3

[0032] The MgO (100) substrate was cleaned and placed in a molecular beam epitaxy device. The sample was annealed in an O atmosphere for 1 h. During the annealing process, the annealing temperature was maintained at 800 °C, the O plasma power was 250 W, and the O pressure was maintained at 5×10 - 5 After annealing, plasma-activated Zn metal source and Mg metal source were introduced simultaneously to grow MgZnO thin film for 2 h. During the growth process, the temperature of Mg source (Mg, 99.999%) and Zn source (Zn, 99.999%) were maintained at 330°C, the substrate temperature was maintained at 275°C, the O plasma power was 180 W, and the O pressure was maintained at 1×10-5 mbar to obtain a sample.

[0033] Figure 5 The XRD spectrum of the sample (2theta scan) is shown. The diffraction peak at 31.8° in the scanning spectrum is the characteristic peak of the MgZnO (10-10) plane, indicating that the epitaxial film grows along the m-plane.

[0034] Figure 6 A schematic diagram of the sample structure is shown, consisting of MgZnO in the upper part and MgO(100) substrate in the lower part.

[0035] Under the same process conditions, for example, maintaining the gas pressure, deposition time and growth temperature unchanged during the experiment, the present invention successfully prepares MgZnO grown along the c-axis, tilted and m-plane only by changing the crystal orientation of the substrate material, and can be widely used in the field of magnesium zinc oxide optoelectronic devices.

Claims

1. A method for changing the orientation of a growing film, characterized in that The following steps are involved: 1) Cleaning the substrate with alcohol, acetone and deionized water at room temperature, cleaning in an ultrasonic cleaner to remove impurities on the surface of the substrate, and placing the cleaned sample in a fast sample chamber; the cleaning of the substrate with alcohol, acetone and deionized water and cleaning in an ultrasonic cleaner are performed alternately for 3 times, each time for 5 minutes; the substrate is selected from MgO with different crystal orientations; the MgO with different crystal orientations is MgO (111), MgO (110) and MgO (100); 2) Use mechanical pump and turbomolecular pump to obtain 10 -8 After the substrate is placed in a growth chamber with a vacuum degree of mbar, the substrate is transferred from the fast sample introduction chamber into the growth chamber of the growth equipment, and the sample is annealed in an O atmosphere; the growth equipment is one of a molecular beam epitaxial growth equipment, a vapor phase epitaxial growth equipment, a physical vapor deposition system, and a pulsed laser deposition system; 3) After annealing, plasma-activated Zn metal source and Mg metal source were introduced simultaneously to grow MgZnO film for 2 hours. After the growth was completed, the sample was taken out. During the growth process, a reflection high-energy electron diffraction device was used to observe the growth state of the film in real time.

2. A method for changing the orientation of a growing film as claimed in claim 1, characterized in that In step 2), the growth equipment is a molecular beam epitaxial growth equipment, and the vacuum degree of the growth chamber can reach 10 -9 mbar.

3. A method for changing the orientation of a growing film as claimed in claim 1, characterized in that In step 2), the annealing conditions are as follows: the annealing temperature is maintained at 800°C, the O plasma power is maintained at 250W, and the O pressure is maintained at 5×10 -5 mbar, annealing time 1h.

4. A method for changing the orientation of a growing film as claimed in claim 1, characterized in that In step 3), the growth process conditions are: the temperature of the Mg metal source and the Zn metal source are maintained at 330°C, the substrate temperature is maintained at 275°C, the O plasma power is 180W, and the O pressure is maintained at 1×10 -5 mbar.

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