Aluminum nitride film and preparation method thereof

Abstract

The present invention discloses a method for preparing an aluminum nitride film, which comprises: pre-treating the surface of a sapphire substrate to increase the oxygen vacancy concentration on the surface of the sapphire substrate; and depositing an aluminum nitride film on the surface of the pre-treated sapphire substrate. The present invention also discloses a method for preparing an aluminum nitride film using the preparation method. The present invention increases the oxygen vacancies on the surface of the sapphire substrate by pre-treating the sapphire substrate. The increase in oxygen vacancies increases the electrical conductivity of Al ions, reduces the migration barrier of Al ions at the interface, and promotes the lateral migration of Al ions, so that AlN tends to grow in two dimensions in the early stage. Therefore, not only can the dislocation and stress caused by the original three-dimensional growth be avoided, but also the time for AlN to cover the sapphire PSS substrate is reduced, thereby improving the mass production efficiency.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor technology, and in particular, relates to an aluminum nitride film and a preparation method thereof. Background Art

[0002] In the manufacturing process of light-emitting diodes (LEDs), in order to alleviate the mismatch between the sapphire (Al2O3) substrate and gallium nitride (GaN), a layer of aluminum nitride (AlN) is usually plated on the sapphire substrate as a buffer layer, which can effectively improve the performance of LED optoelectronic devices, increase the throughput of subsequent metal organic chemical vapor deposition (MOCVD), and reduce production costs. At present, sapphire substrates usually use patterned substrates (PSS), which can reduce the dislocation defects between sapphire and GaN, improve the epitaxial quality, and improve the internal quantum efficiency of LEDs and increase light extraction efficiency.

[0003] However, there are some problems in growing AlN on sapphire PSS substrates. Specifically, the migration barrier of Al ions on sapphire PSS substrates is high, the wettability is poor, and the adhesion coefficient is high. These lead to the initial three-dimensional island growth (Volmer-Weber) of AlN, which is easy to produce high-density dislocations and large stress during nucleation, and it is very easy to propagate upward. Moreover, in this growth mode, AlN takes a long time to cover the sapphire PSS substrate, the coverage speed is slow, and the mass production efficiency is low. Summary of the invention

[0004] In order to solve the technical problems existing in the above-mentioned prior art, an embodiment of the present invention provides an aluminum nitride film and a preparation method thereof which can increase the coverage speed and improve the film quality.

[0005] According to one aspect of an embodiment of the present invention, a method for preparing an aluminum nitride film includes: pretreating a surface of a sapphire substrate to increase the oxygen vacancy concentration on the surface of the sapphire substrate; and depositing an aluminum nitride film on the surface of the pretreated sapphire substrate.

[0006] In an example of the preparation method provided in the above aspect, the method of pretreating the surface of the sapphire substrate includes: replacing aluminum ions on the surface of the sapphire substrate with divalent ions to increase the oxygen vacancy concentration on the surface of the sapphire substrate.

[0007] In an example of the preparation method provided in the above aspect, the divalent ions include at least one of magnesium ions and tin ions.

[0008] In an example of the preparation method provided in the above aspect, the method for pretreating the surface of the sapphire substrate includes: using a metal organic chemical vapor deposition process, passing a divalent ion source and a carrier gas into a reaction chamber where the sapphire substrate is placed, and pretreating the surface of the sapphire substrate at a predetermined reaction chamber temperature and a predetermined reaction chamber pressure.

[0009] In an example of the preparation method provided in the above aspect, the divalent ion source is tetrakis(dimethylamino)tin, and the carrier gas is a reducing gas.

[0010] In an example of the preparation method provided in the above aspect, the reducing gas is hydrogen.

[0011] In an example of the preparation method provided in the above aspect, the predetermined reaction chamber temperature is 1000°C~1200°C.

[0012] In an example of the preparation method provided in the above aspect, the predetermined reaction chamber pressure is 140 Torr~160 Torr.

[0013] In an example of the preparation method provided in the above aspect, the method for depositing an aluminum nitride film on the surface of a pretreated sapphire substrate includes: using a physical vapor deposition process, the sputtering power supply is a 5kW pulse power supply, the purity of the aluminum target is 99.999%, the reaction chamber pressure is 5mtorr, and argon gas with a flow rate of 150sccm, nitrogen gas with a flow rate of 50sccm, and oxygen gas with a flow rate of 2.3sccm are introduced into the reaction chamber, and sputtering is performed on the surface of the pretreated sapphire substrate for 50s to form an aluminum nitride film.

[0014] The aluminum nitride thin film provided according to one aspect of an embodiment of the present invention is prepared by the above-mentioned method for preparing the aluminum nitride thin film.

[0015] Beneficial effect: The present invention increases oxygen vacancies on the surface of the sapphire substrate by pre-treating the sapphire substrate. The increase in oxygen vacancies will increase the conductivity of Al ions, reduce the migration barrier of Al ions at the interface, promote the lateral migration of Al ions, and make AlN tend to grow in two dimensions in the early stage. Therefore, not only can the dislocation and stress caused by the original three-dimensional growth be avoided, but also the time for AlN to cover the sapphire PSS substrate is reduced, and the mass production efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other aspects, features and advantages of the embodiments of the present invention will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0017] Figure 1 is a flow chart of a method for preparing an aluminum nitride thin film according to an embodiment of the present invention;

[0018] Figure 2 2 are XRD rocking curve diagrams of the example film and the comparative example film. DETAILED DESCRIPTION

[0019] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention may be implemented in many different forms, and the present invention should not be construed as being limited to the specific embodiments set forth herein. On the contrary, these embodiments are provided to explain the principles of the present invention and their practical applications, so that other persons skilled in the art can understand the various embodiments of the present invention and various modifications suitable for specific intended applications.

[0020] As used herein, the term "including" and its variations represent open terms, meaning "including but not limited to". The terms "based on", "according to", etc. mean "based at least in part on", "based at least in part on". The terms "embodiment", "one example", "one embodiment" and "an embodiment" mean "at least one embodiment". The terms "another embodiment", "another embodiment", "another example", "yet another example" mean "at least one other embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other definitions may be included below, whether explicit or implicit. Unless the context clearly indicates otherwise, the definition of a term is consistent throughout the specification.

[0021] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the drawings, while other details that are not very relevant are omitted.

[0022] Figure 1 is a flow chart of a method for preparing an aluminum nitride thin film according to an embodiment of the present invention.

[0023] Reference Figure 1 In step S110, the surface of the sapphire substrate is pretreated to increase the oxygen vacancy concentration on the surface of the sapphire substrate.

[0024] In one example, the sapphire substrate may be a sapphire PSS substrate.

[0025] As an example of pre-treating the surface of a sapphire substrate, divalent ions can be used to replace aluminum ions on the surface of the sapphire substrate to increase the oxygen vacancy concentration on the surface of the sapphire substrate. This is because the formation energy of intrinsic oxygen vacancies in the Al2O3 of the sapphire substrate is high, it is not easy to form and the concentration is low, and the addition of divalent ions is conducive to the formation of oxygen vacancies. Taking Sn as an example, after Sn atoms replace Al atoms, they still form bonds with the inherent 6 oxygen atoms. When Sn is 2+ and Al is 3+, after Sn replaces Al, oxygen vacancies will be generated on the basis of maintaining electrical neutrality.

[0026] The divalent ions include at least one of magnesium ions and tin ions, but the present invention is not limited thereto, and other suitable monovalent or divalent ions may be used.

[0027] In step S120, an aluminum nitride film is deposited on the surface of the pre-treated sapphire substrate.

[0028] The following is a further detailed description of the method for preparing the aluminum nitride film according to the embodiment of the present invention by taking divalent tin ions as an example.

[0029] The first step is Sn pretreatment: using metal organic chemical vapor deposition (MOCVD) process, using tetrakis(dimethylamino)tin (TDMASn) as the Sn source, the carrier gas is high-purity hydrogen, the reaction chamber temperature is set to 1000°C ~ 1200°C (preferably 1100°C), the reaction chamber pressure is 140Torr ~ 160Torr (preferably 150Torr), the Sn source flow rate is 180sccm, the Sn source and the carrier gas are introduced into the reaction chamber where the sapphire PSS substrate is placed, and Sn pretreatment is performed for 15 minutes to complete the surface pretreatment of the sapphire PSS substrate.

[0030] The second step is to grow AlN: using physical vapor deposition (PVD) technology, the sputtering power supply is a 5kw pulse power supply, the purity of the aluminum target is 99.999%, the reaction chamber pressure is set to 5mtorr, and argon, nitrogen and oxygen are introduced into the reaction chamber where the Sn pre-treated sapphire PSS substrate is placed for sputtering for 50s to form an aluminum nitride film. Among them, the flow rates of argon, nitrogen and oxygen are 150sccm, 50sccm and 2.3sccm respectively.

[0031] The aluminum nitride film prepared by the preparation method of the embodiment (hereinafter referred to as the "embodiment film") is completed above. It should be understood that the preparation of the aluminum nitride film of the present invention is not limited thereto. For verification and comparison, an aluminum nitride film prepared by the preparation method of a comparative example (hereinafter referred to as the "comparative example film") is provided below.

[0032] Preparation of comparative film (without Sn pretreatment, AlN is directly grown on sapphire PSS substrate):

[0033] The physical vapor deposition (PVD) process was adopted, the sputtering power supply was a 5kw pulse power supply, the purity of the aluminum target was 99.999%, the reaction chamber pressure was set to 5mtorr, and argon, nitrogen and oxygen were introduced into the reaction chamber where the sapphire PSS substrate without Sn pretreatment was placed for sputtering for 50s to form an aluminum nitride film. The flow rates of argon, nitrogen and oxygen were 150sccm, 50sccm and 2.3sccm respectively.

[0034] The thickness of the embodiment film and the comparative film was measured by ellipsometer. With the same sputtering time, the thickness of the embodiment film was 168nm, while the thickness of the comparative film was 152nm. This is because the embodiment film was pretreated with Sn during preparation, the lateral migration ability of Al atoms was enhanced, the time for AlN to cover the sapphire PSS substrate was shortened, and the overall coverage growth rate of the AlN film was improved.

[0035] Figure 2 2 are XRD rocking curve diagrams of the example film and the comparative example film.

[0036] The film of the example ( Figure 2 Example 1) and the comparative film ( Figure 2 The comparative example 1) in the test was carried out. Figure 2 As shown in the figure, the half width of AlN (002) of the embodiment film is 0.19°, which is significantly smaller than the half width of AlN (002) of the comparative film (which is 0.32°). At the same time, the XRD diffraction intensity of the embodiment film is also significantly higher than that of the comparative film. This shows that the AlN crystal quality of the embodiment film is significantly better than that of the comparative film, which is attributed to the fact that the sample of the embodiment film has been pretreated with Sn, avoiding the dislocation and stress caused by the original three-dimensional growth, and improving the overall quality of AlN.

[0037] The comparison between the above embodiment films and the comparative example films shows that when AlN is grown on a sapphire PSS substrate after Sn pretreatment at high temperature in an MOCVD chamber with high-purity hydrogen as the carrier gas, not only can the dislocation and stress caused by the original three-dimensional growth be avoided, thereby improving the quality of the AlN crystal; it also reduces the time for AlN to cover the sapphire PSS substrate, thereby improving mass production efficiency.

[0038] In summary, according to the aluminum nitride film and preparation method thereof of the embodiment of the present invention, the increase of oxygen vacancies will increase the Al ion conductivity, reduce the migration barrier of Al ions at the interface, promote the lateral migration of Al ions, and make AlN tend to grow in two dimensions in the early stage. Therefore, not only can the dislocation and stress caused by the original three-dimensional growth be avoided, but also the time for AlN to cover the sapphire PSS substrate is reduced, and the mass production efficiency is improved.

[0039] The terms "exemplary," "example," and the like used throughout this specification mean "used as an example, instance, or illustration" and do not mean "preferred" or "advantageous" over other embodiments. The detailed description includes specific details for the purpose of providing an understanding of the described techniques. However, these techniques can be implemented without these specific details. In some instances, in order to avoid obscuring the concepts of the described embodiments, well-known structures and devices are shown in block diagram form.

[0040] The optional implementation modes of the embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above implementation modes. Within the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all belong to the protection scope of the embodiments of the present invention.

[0041] The above description of the contents of this specification is provided to enable any person of ordinary skill in the art to implement or use the contents of this specification. Various modifications to the contents of this specification will be apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other variations without departing from the scope of protection of the contents of this specification. Therefore, the contents of this specification are not limited to the examples and designs described herein, but are consistent with the widest range of principles and novel features disclosed herein.

Claims

1. A method for preparing an aluminum nitride thin film, characterized in that: include: Pre-treating the surface of a sapphire substrate to increase the oxygen vacancy concentration on the surface of the sapphire substrate; Depositing an aluminum nitride film on the surface of the pre-treated sapphire substrate; The method for pretreating the surface of the sapphire substrate comprises: using a metal organic chemical vapor deposition process, introducing a divalent ion source and a carrier gas into a reaction chamber in which the sapphire substrate is placed, and pretreating the surface of the sapphire substrate at a predetermined reaction chamber temperature and a predetermined reaction chamber pressure, thereby replacing aluminum ions on the surface of the sapphire substrate with divalent ions to increase the oxygen vacancy concentration on the surface of the sapphire substrate; Wherein, the divalent ions include at least one of magnesium ions and tin ions, the predetermined reaction chamber temperature is 1000° C. to 1200° C., and the predetermined reaction chamber pressure is 140 Torr to 160 Torr.

2. The preparation method according to claim 1, characterized in that: The divalent ion source is tetrakis(dimethylamino)tin, and the carrier gas is a reducing gas.

3. The preparation method according to claim 2, characterized in that: The reducing gas is hydrogen.

4. The preparation method according to claim 1, characterized in that: The method for depositing an aluminum nitride film on the surface of a pretreated sapphire substrate comprises: A physical vapor deposition process was adopted, the sputtering power source was a 5 kW pulse power source, the purity of the aluminum target was 99.999%, the pressure of the reaction chamber was 5 mtorr, argon with a flow rate of 150 sccm, nitrogen with a flow rate of 50 sccm, and oxygen with a flow rate of 2.3 sccm were introduced into the reaction chamber, and sputtering was performed for 50 seconds on the surface of the pretreated sapphire substrate to form an aluminum nitride film.

5. An aluminum nitride film prepared by the preparation method according to any one of claims 1 to 4.

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