High-quality AlN film with buffer layer and preparation method and application thereof

Abstract

The present invention discloses a high-quality AlN film with a buffer layer and a preparation method and application thereof, which belongs to the field of semiconductor material preparation. The method steps include: forming a porphyrin compound coating as a buffer layer on a substrate; physically vapor depositing an AlN seed layer on the buffer layer; and chemically vapor depositing an AlN epitaxial layer on the AlN seed layer to obtain a high-quality AlN film with a buffer layer. The present invention first prepares a porphyrin compound buffer layer on a substrate. The compound has a two-dimensional layered structure and can form a coordination bond with Al of the AlN molecule, which can effectively alleviate the lattice mismatch and thermal adaptation between the AlN film and the substrate; then, an AlN seed layer is deposited on the porphyrin compound buffer layer by PVD, which can provide a better nucleation site for the subsequent growth of AlN; finally, an AlN film with high crystal quality can be grown by MOCVD.

Description

Technical Field

[0001] The invention relates to a high-quality AlN film with a buffer layer and a preparation method and application thereof, belonging to the field of semiconductor material preparation. Background Art

[0002] AlN (aluminum nitride) material is a direct bandgap wide semiconductor material with a bandgap width of 6.2 eV. The interband transition emission wavelength can enter the deep ultraviolet band, making it an ideal material for ultraviolet / deep ultraviolet optoelectronic devices. At the same time, AlN has a high electron mobility (1100 cm 2 / Vs), high breakdown voltage (11.7 MV / cm), and high thermal conductivity (320 W / m K), making it an ideal choice for the preparation of next-generation power electronics and energy harvesting devices operating in harsh environments.

[0003] At present, AlN materials are mainly grown directly on sapphire, SiC (silicon carbide) or Si substrates. There are a series of problems such as lattice mismatch and thermal mismatch between AlN and foreign substrates. The growth of AlN is relatively difficult, and it usually faces the problems of slow growth rate and poor crystal quality. Sapphire substrate has a high melting point, stable physical and chemical properties at high temperature, mature preparation technology, and decreasing price. It is the most widely used substrate. However, sapphire substrate cannot conduct electricity and has low thermal conductivity. At the same time, since sapphire substrate is difficult to peel off, it is not conducive to the preparation of filter devices. The lattice mismatch and thermal mismatch between SiC and AlN are very small, and the chemical properties are stable, and the electrical and thermal conductivity are excellent. It is an ideal foreign substrate material for the growth of AlN thin films. However, due to the high price of SiC and the high cost of device preparation, it is not suitable for commercial large-scale production. The lattice constant of substrates such as silicon and sapphire is greater than that of AlN, which will exert tensile stress on AlN during the growth process; and the thermodynamic expansion coefficient of the silicon substrate is smaller than that of AlN. During the cooling process, the shrinkage rate of AlN is greater than that of the silicon substrate, and the silicon substrate still exerts tensile stress on AlN, resulting in that under normal circumstances, only 200nm~300nm thick AlN can be grown on the silicon substrate. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a high-quality AlN film with a buffer layer and a preparation method and application thereof, which can effectively alleviate the lattice mismatch and thermal adaptation between the AlN film and the substrate.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] In a first aspect, the present application provides a method for preparing a high-quality AlN film with a buffer layer, comprising the following steps:

[0007] forming a porphyrin compound coating as a buffer layer on a substrate;

[0008] Physical vapor deposition of an AlN seed layer on the buffer layer;

[0009] An AlN epitaxial layer is chemically vapor deposited on the AlN seed layer to obtain a high-quality AlN film with a buffer layer.

[0010] The method for preparing a high-quality AlN film with a buffer layer provided in the present application uses porphyrin compounds as the raw materials for the buffer layer. The porphyrin compounds are planar molecules that can form coordination bonds with the Al of the AlN molecules and interact with each other. At the same time, the porphyrin compounds are similar to the graphene plane and have a smaller lattice mismatch with AlN.

[0011] Furthermore, the porphyrin compound has a structure of structural formula I:

[0012]

[0013] Among them, R1, R2, R3, R4, R5, R6, R7, and R8 are independently hydroxyl, thiol, amino, olefinic bond, carboxyl, acyl, hydrogen atom or halogen atom; Ar is independently a benzene ring, a naphthalene ring, anthracene ring, a phenanthrene ring, pyridine, pyrrole, thiophene, thiazole or thiophenol.

[0014] The porphyrin compound is synthesized according to the following steps and reaction formula II:

[0015]

[0016] One or more reaction raw materials having the structure A in reaction formula II are dissolved in a solvent, and then an acid is added. The mixed system is reacted at 150° C. to 200° C. for 8 hours to 24 hours, and then the reaction is stopped. The porphyrin compound is obtained by cooling, filtering, and column chromatography; wherein X is acetoxy, hydroxyl or dimethylamino, and R n and R m It represents four combinations of R1 and R2, R3 and R4, R5 and R6, and R7 and R8.

[0017] Furthermore, the step of forming a porphyrin compound coating as a buffer layer on the substrate includes: dissolving the porphyrin compound in an organic solvent to obtain a porphyrin compound solution, spin-coating the porphyrin compound solution on the substrate, and obtaining the buffer layer after the organic solvent evaporates.

[0018] Furthermore, in the step of physically vapor depositing an AlN seed layer on the buffer layer, the growth pressure is 1×10 -7 ~Torr~6×10 -7 Torr, the growth temperature is 300℃~500℃.

[0019] Furthermore, the thickness of the AlN seed layer is 20 nm to 70 nm, which can be well combined with the buffer layer through coordination bonds and provide a good foundation for the subsequent deposition of high-quality AlN films.

[0020] Furthermore, in the step of chemically vapor depositing an AlN epitaxial layer on the AlN seed layer, a growth pressure is 40 Torr to 60 Torr, and a growth temperature is 1100° C. to 1300° C.

[0021] Furthermore, the thickness of the AlN epitaxial layer is 1000nm-1500nm.

[0022] In a second aspect, the present application provides a high-quality AlN film, which is made by the method for preparing a high-quality AlN film with a buffer layer described in the first aspect.

[0023] In a third aspect, the present application provides an AlN film-based device having a high-quality AlN film as described in the second aspect, wherein both the substrate and the buffer layer have been stripped, or both the substrate and the buffer layer have not been stripped.

[0024] The beneficial effects of the present invention are as follows: the present invention first prepares a porphyrin compound buffer layer on a substrate, the compound has a two-dimensional layered structure and can form a coordination bond with Al of an AlN molecule, and can effectively alleviate the lattice mismatch and thermal adaptation between the AlN film and the substrate; then an AlN seed layer is deposited on the porphyrin compound buffer layer by PVD, and can provide a better nucleation site for the subsequent growth of AlN; finally, an AlN film with high crystal quality can be grown by MOCVD.

[0025] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained by the structures particularly pointed out in the written description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of an AlN film obtained by the method for preparing a high-quality AlN film with a buffer layer provided in an embodiment of the present application.

[0027] Figure 2 This is an image of the AlN film prepared in Example 1 of the present application observed using an atomic force microscope.

[0028] Figure 3 This is an image of the AlN film prepared in Example 1 observed using an atomic force microscope.

[0029] Reference numerals: 10, substrate; 20, buffer layer; 30, AlN seed layer; 40, AlN epitaxial layer. DETAILED DESCRIPTION

[0030] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0031] The disclosure below provides many different embodiments or examples to implement different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed.

[0032] It should be understood that, under the premise of no conflict, any and all embodiments of the present invention can be combined with the technical features in any other embodiment or multiple other embodiments to obtain another embodiment. The present invention includes such a combination to obtain another embodiment.

[0033] In this specification, groups and substituents thereof can be selected by those skilled in the art to provide stable structural moieties and compounds. When substituents are described by conventional chemical formulas written from left to right, the substituents also include chemically equivalent substituents obtained when the structural formula is written from right to left.

[0034] Unless otherwise specified, all technical and scientific terms used herein have the standard meaning in the field to which the claimed subject matter belongs. If there are multiple definitions for a term, the definition herein shall prevail.

[0035] In order to solve a series of problems in the existing growth of AlN and prepare high-quality AlN, the present invention provides a method for preparing a high-quality AlN film with a buffer layer, and provides a high-quality AlN film suitable for devices based on AlN films such as LEDs, filters, and laser detectors.

[0036] Combination Figure 1 The structure shown in the figure, the method for preparing a high-quality AlN film with a buffer layer specifically comprises the following steps:

[0037] S1: forming a porphyrin compound coating as a buffer layer 20 on a substrate 10 .

[0038] S2 : physically vapor depositing an AlN seed layer 30 on the buffer layer 20 .

[0039] S3: chemically vapor depositing an AlN epitaxial layer 40 on the AlN seed layer to obtain a high-quality AlN film with a buffer layer.

[0040] The porphyrin compounds in the buffer layer are planar molecules that can form coordination bonds with the Al of the AlN molecules and interact with each other. At the same time, the porphyrin compounds are similar to the graphene plane and have a smaller lattice mismatch with AlN, which can effectively alleviate the lattice mismatch and thermal adaptation between the AlN film and the substrate. In conjunction with the PVD deposition of the AlN seed layer, it can provide a better nucleation site for the subsequent growth of AlN, and can grow AlN films (epitaxial wafers) with high crystal quality. The substrate of the epitaxial wafer can then be peeled off by physical or chemical methods.

[0041] For example, the physical method includes fixing the substrate on a platform, fixing the two ends of a piece of sticky tape on the platform and the substrate surface respectively, and moving one end of the tape away from the substrate at a constant rate to achieve mechanical separation.

[0042] Chemical methods, for example, can be used to immerse the epitaxial wafer in an organic solvent such as dichloromethane or chloroform to dissolve the buffer layer and separate the aluminum nitride from the substrate.

[0043] The substrate may be a sapphire substrate, a silicon substrate, or the like.

[0044] Porphyrin compounds have the structure of structural formula I:

[0045]

[0046] Among them, R1, R2, R3, R4, R5, R6, R7, and R8 are independently hydroxyl, thiol, amino, olefinic bond, carboxyl, acyl, hydrogen atom or halogen atom; Ar is independently a benzene ring, a naphthalene ring, anthracene ring, a phenanthrene ring, pyridine, pyrrole, thiophene, thiazole or thiophenol.

[0047] Specifically, the porphyrin compound is synthesized according to the following steps and reaction formula II:

[0048]

[0049] One or more reaction raw materials having the structure A in reaction formula II are dissolved in a solvent, and then an acid is added. The mixed system is reacted at 150°C to 200°C for 8 hours to 24 hours, and then the reaction is stopped. After cooling, filtering, and column chromatography, a porphyrin compound is obtained; wherein X is acetoxy, hydroxyl or dimethylamino, and R n and R m It represents four combinations of R1 and R2, R3 and R4, R5 and R6, and R7 and R8.

[0050] Step S1 is specifically as follows: dissolving a porphyrin compound in an organic solvent to obtain a porphyrin compound solution, spin-coating the porphyrin compound solution on a substrate, and obtaining a buffer layer after the organic solvent evaporates. The organic solvent may be, for example, dichloromethane or chloroform. There is no need to volatilize the organic solvent during the preparation process, and the subsequent PVD deposition must be in a negative pressure and heating environment.

[0051] In step S2, the growth pressure is 1×10 -7 ~Torr~6×10 -7 Torr, and the growth temperature is 300℃~500℃. The sputtering power of PVD cannot be too high to prevent the kinetic energy of AlN particles from being too large when they reach the surface of porphyrin compounds, thereby damaging the buffer layer structure. The sputtering power can be set to 0.5kW~1kW, for example.

[0052] Preferably, the thickness of the AlN seed layer is 20 nm to 70 nm, which is beneficial to improving the crystal quality of the AlN epitaxial layer and reducing stress.

[0053] In step S3, the growth pressure is 40Torr~60Torr, and the growth temperature is 1100℃~1300℃. During MOCVD growth, the whole process is accompanied by N2 or Ar gas atmosphere protection to prevent high concentration reaction gas from causing porphyrin compounds to transform. For example, during MOCVD growth, hydrogen is usually required to produce a certain degree of etching. The flow ratio of protective gas to hydrogen can be set to 1:1, which can prevent high-purity H2 from reacting with porphyrin to hydrogen, causing the structure of porphyrin compounds to be destroyed and lose the planar structure.

[0054] AlN epitaxial layers can be grown to a thickness of 1000nm~1500nm with fewer defects, meeting the needs of AlN film-based devices such as LEDs, filters, and laser detectors.

[0055] Example 1

[0056] In a 250mL round-bottom flask, 1-pyrrolylbenzyl alcohol was dissolved in N,N'-dimethylformamide, glacial acetic acid was added, and the mixture was stirred and heated under reflux for 12h. The sample point plate was taken and the reaction progress was judged by thin layer chromatography. After the reaction was completed, the heating was stopped, the reaction was quenched with a saturated NH4Cl solution, and dichloromethane (DCM) was used for extraction three times. The organic phase was combined, dried with anhydrous Na2SO4, filtered, and the filtrate was spin-dried and separated by column chromatography to obtain the porphyrin compound of Example 1. The entire synthesis process can be represented by reaction formula III.

[0057]

[0058] The porphyrin compound of Example 1 was dissolved in dichloromethane, and then the solution was dripped onto a sapphire substrate, and spin-coated at a rotation speed of 4000 rpm to prepare a buffer layer.

[0059] The substrate with the buffer layer was transferred to a magnetron sputtering reaction chamber and deposited by physical vapor deposition at 6×10 -7 A 50 nm AlN seed layer was deposited on the buffer layer at a pressure of 10 Torr.

[0060] The substrate with the AlN seed layer was transferred to the MOCVD reaction chamber, H2 and N2 were introduced into the reaction chamber, the temperature was raised to 1300°C, NH3 and Al sources were introduced, and the ratio of NH3 to Al sources was adjusted. The pressure in the reaction chamber was adjusted to 40 Torr, and an AlN epitaxial layer was grown with a growth thickness of 1250 nm.

[0061] Example 2

[0062] In a 250mL round-bottom flask, dissolve 1-(4-methylpyrrolyl)benzyl alcohol with N,N'-dimethylformamide, add glacial acetic acid, stir and heat under reflux for 15h. Take a sample point plate and judge the progress of the reaction by thin layer chromatography. After the reaction is completed, stop heating, quench the reaction with saturated NH4Cl solution, and extract three times with dichloromethane (DCM). Combine the organic phase, dry with anhydrous Na2SO4, filter with suction, spin dry the filtrate, and separate by column chromatography to obtain the porphyrin compound of Example 2. The entire synthesis process can be represented by reaction formula IV.

[0063]

[0064] The porphyrin compound of Example 2 was dissolved in chloroform, and then the solution was dripped onto a silicon substrate, and spin-coated at a rotation speed of 5000 rpm to prepare a buffer layer.

[0065] The substrate with the buffer layer was transferred to a magnetron sputtering reaction chamber and deposited by physical vapor deposition at 4×10 -7 A 70 nm AlN seed layer was deposited on the buffer layer at a pressure of 10 Torr.

[0066] The substrate with the AlN seed layer was transferred to the MOCVD reaction chamber, H2 and N2 were introduced into the reaction chamber, the temperature was raised to 1200°C, NH3 and Al sources were introduced, and the ratio of NH3 to Al sources was adjusted. The pressure in the reaction chamber was adjusted to 45 Torr, and an AlN epitaxial layer was grown with a growth thickness of 1000 nm.

[0067] Comparative Example 1

[0068] By physical vapor deposition, 6×10 -7 A 50 nm AlN seed layer was deposited on a sapphire substrate at a pressure of 10 Torr.

[0069] The substrate with the AlN seed layer was transferred to the MOCVD reaction chamber, H2 and N2 were introduced into the reaction chamber, the temperature was raised to 1300°C, NH3 and Al sources were introduced, and the ratio of NH3 to Al sources was adjusted. The pressure in the reaction chamber was adjusted to 40 Torr, and an AlN layer was grown with a growth thickness of 1250 nm.

[0070] The AlN film obtained in Example 1 was observed using an atomic force microscope. Figure 2 The AlN film obtained in Comparative Example 1 was observed using an atomic force microscope. Figure 3 As shown. Figure 2 and Figure 3 It can be seen that there are more holes on the surface of the AlN film of Comparative Example 1, and the lateral healing effect of the AlN film is relatively poor; the surface healing degree of the AlN film of Example 1 is better. The embodiment of the present application reduces the lattice mismatch between AlN and the substrate, enhances the migration of Al, and promotes the two-dimensional growth of AlN by introducing a special buffer layer.

[0071] In the description of this specification, the description with reference to the terms "one embodiment", "certain embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0072] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a high-quality AlN film with a buffer layer, characterized in that: The following steps are involved: forming a porphyrin compound coating as a buffer layer on a substrate; Physical vapor deposition of an AlN seed layer on the buffer layer; Chemically vapor depositing an AlN epitaxial layer on the AlN seed layer to obtain a high-quality AlN film with a buffer layer; The structural formula of the porphyrin compound is one of the following two: ； 。 2. The method for preparing a high-quality AlN thin film with a buffer layer according to claim 1, characterized in that: The porphyrin compound is synthesized according to the following steps and reaction formula: ;or ； The reaction raw materials are dissolved in a solvent, and then an acid is added. The mixed system is reacted at 150° C. to 200° C. for 8 hours to 24 hours, and then the reaction is stopped. The porphyrin compound is obtained through cooling, filtering, and column chromatography.

3. The method for preparing a high-quality AlN thin film with a buffer layer according to claim 1, characterized in that: The step of forming a porphyrin compound coating as a buffer layer on the substrate includes: dissolving the porphyrin compound in an organic solvent to obtain a porphyrin compound solution, spin-coating the porphyrin compound solution on the substrate, and obtaining the buffer layer after the organic solvent evaporates.

4. The method for preparing a high-quality AlN thin film with a buffer layer according to claim 1, characterized in that: In the step of physically vapor depositing an AlN seed layer on the buffer layer, the growth pressure is 1×10 -7 ~Torr~6×10 -7 Torr, the growth temperature is 300℃~500℃.

5. The method for preparing a high-quality AlN thin film with a buffer layer according to claim 1, characterized in that: The thickness of the AlN seed layer is 20nm-70nm.

6. The method for preparing a high-quality AlN thin film with a buffer layer according to claim 1, characterized in that: In the step of chemically vapor depositing an AlN epitaxial layer on the AlN seed layer, the growth pressure is 40 Torr-60 Torr, and the growth temperature is 1100° C.-1300° C.

7. The method for preparing a high-quality AlN thin film with a buffer layer according to claim 1, characterized in that: The thickness of the AlN epitaxial layer is 1000nm-1500nm.

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