阅读说明：本技术 一种氮化铝模板的制备方法 (Preparation method of aluminum nitride template ) 是由 徐广源 蒋国文 樊怡翔 白城镇 常煜鹏 于 2021-06-15 设计创作，主要内容包括：本发明涉及一种氮化铝模板的制备方法,其包括以下步骤：(1)、在衬底的表面上溅射10～1000nm厚的氮化铝层；(2)、将表面溅射有氮化铝层的衬底进行高温退火处理；(3)、将经过高温退火处理后的表面溅射有氮化铝的衬底进行深冷处理；(4)、将深冷处理后的表面溅射有氮化铝的衬底升温至室温；(5)、将升温至室温的表面溅射有氮化铝的衬底进行低温退火处理；(6)、重复循环上述步骤(3)-步骤(5)两到六次,得到最终的氮化铝模板。其可有效优化AlN和蓝宝石界面的应力状态,改善界面的结合性能,减小AlN的晶格应变,提高用此模板生长不同组分AlGaN的表面形貌和晶体质量。(The invention relates to a preparation method of an aluminum nitride template, which comprises the following steps: (1) sputtering an aluminum nitride layer with the thickness of 10-1000nm on the surface of the substrate; (2) carrying out high-temperature annealing treatment on the substrate with the aluminum nitride layer sputtered on the surface; (3) carrying out subzero treatment on the substrate with the aluminum nitride sputtered on the surface after the high-temperature annealing treatment; (4) heating the subzero treated substrate with the aluminum nitride sputtered on the surface to room temperature; (5) carrying out low-temperature annealing treatment on the substrate with the aluminum nitride sputtered on the surface and heated to room temperature; (6) and (5) repeatedly circulating the steps (3) to (5) for two to six times to obtain the final aluminum nitride template. The template can effectively optimize the stress state of an AlN and sapphire interface, improve the bonding performance of the interface, reduce the lattice strain of AlN, and improve the surface appearance and the crystal quality of AlGaN with different components grown by using the template.)

1. The preparation method of the aluminum nitride template is characterized by comprising the following steps of:

(1) sputtering an aluminum nitride layer with the thickness of 10-1000nm on the surface of the substrate;

(2) carrying out high-temperature annealing treatment on the substrate with the aluminum nitride layer sputtered on the surface;

(3) carrying out subzero treatment on the substrate with the aluminum nitride sputtered on the surface after the high-temperature annealing treatment;

(4) heating the subzero treated substrate with the aluminum nitride sputtered on the surface to room temperature;

(5) carrying out low-temperature annealing treatment on the substrate with the aluminum nitride sputtered on the surface and heated to room temperature;

(6) and (5) repeatedly circulating the steps (3) to (5) for two to six times to obtain the final aluminum nitride template.

2. The method for preparing the aluminum nitride template according to claim 1, wherein in the step (3), when the subzero treatment is performed, the substrate with the aluminum nitride sputtered on the surface after the high-temperature annealing treatment is placed in subzero treatment equipment, the subzero treatment equipment is sealed, and 1-5L of liquid nitrogen is filled into the sealed subzero treatment equipment.

3. The method for preparing the aluminum nitride template according to claim 2, wherein the cryogenic treatment equipment is cooled at a constant cooling rate during the cryogenic treatment in the step (3), wherein the cooling rate is 2 ℃/min to 50 ℃/min, and the temperature is maintained for 0.5 to 10 hours after being cooled to-170 ℃ to-190 ℃.

4. The method for preparing the aluminum nitride template according to claim 2, wherein the cryogenic treatment equipment is cooled in a gradient cooling manner during the cryogenic treatment in the step (3), wherein the temperature is first cooled at a cooling rate of 2 ℃/min to 50 ℃/min, and is kept at-80 ℃ to-150 ℃ for 0.5 to 10 hours, and is then cooled at a cooling rate of 2 ℃/min to 50 ℃/min, and is kept at-170 ℃ to-190 ℃ for 0.5 to 10 hours. .

5. The method for preparing an aluminum nitride template according to claim 3 or 4, wherein the step (5) is specifically: and putting the substrate with the aluminum nitride sputtered on the surface and heated to the room temperature into a low-temperature annealing furnace for low-temperature annealing treatment, wherein the annealing atmosphere is nitrogen, the nitrogen flow is 10-10000 sccm, and the chamber pressure in the annealing furnace is 200-650 torr.

6. The method for preparing the aluminum nitride template according to claim 5, wherein the low-temperature annealing treatment in the step (5) is performed at a constant heating rate, the heating rate is 2-40 ℃/min, and the annealing is performed for 0.2-6h when the temperature is raised to 1000-1480 ℃.

7. The method for preparing the aluminum nitride template according to claim 5, wherein the low-temperature annealing treatment in the step (5) adopts gradient annealing, namely, the temperature is raised at a temperature rise rate of 2-40 ℃/min, and the annealing is carried out for 0.2-3 h after the temperature is raised to 1000-1480 ℃; and then cooling at the cooling rate of 2-20 ℃/min, cooling to 400-980 ℃, and then annealing for 0.2-3 h.

8. The method for preparing an aluminum nitride template according to claim 1, wherein the step (1) is specifically: putting the planar substrate into magnetron sputtering equipment for sputtering, wherein the sputtering process specifically comprises the following steps: the power is 1000-4000W, the nitrogen flow is 80-200 sccm, the oxygen flow is 0.1-2 sccm, the argon flow is 0.1-40 sccm, and the temperature is 400-750 ℃.

9. The method for preparing an aluminum nitride template according to claim 8, wherein the step (2) is specifically: and placing the substrate with the aluminum nitride layer sputtered on the surface into a high-temperature annealing furnace for high-temperature annealing treatment, wherein the annealing temperature is 1500-1800 ℃, the annealing time is 0.2-3 h, the annealing atmosphere is nitrogen, the nitrogen flow is 100-12000 sccm, and the annealing pressure is 200-650 torr.

10. The method for preparing an aluminum nitride template according to claim 9, wherein the step (4) is specifically: after the subzero treatment is finished, directly taking out the subzero treated substrate with the aluminum nitride sputtered on the surface and heating the subzero treated substrate to room temperature under natural conditions, or heating the subzero treated substrate with the aluminum nitride sputtered on the surface to room temperature along with subzero treatment equipment and then taking out the subzero treated substrate.

The technical field is as follows:

the invention belongs to the technical field of semiconductor epitaxial substrate preparation, relates to a preparation method of a substrate for forming a deep ultraviolet LED epitaxial structure, and particularly relates to a preparation method of a high-quality low-stress aluminum nitride template.

Background art:

an aluminum nitride (AlN) template is a substrate material for epitaxial growth of the aluminum gallium nitrogen-based deep ultraviolet LED. The crystal quality of the aluminum nitride template directly determines the crystal quality of the upper layer of aluminum gallium nitrogen. The high-quality aluminum nitride template can effectively reduce the Threading Dislocation Density (TDDs) of the aluminum gallium nitride, improve the radiation recombination efficiency of electrons and holes in an LED structure grown on the basis of the material, and improve the reliability and the service life of the LED.

Currently, AlN templates which can be used as deep ultraviolet LED structures for growth include single crystal AlN substrates and heterogeneous AlN substrates. Single crystal AlN substrates are expensive and have limited supply, limiting applications. Techniques for preparing AlN films via heterogeneous substrates include Metal Organic Chemical Vapor Deposition (MOCVD), magnetron sputtering, Molecular Beam Epitaxy (MBE), Hydride Vapor Phase Epitaxy (HVPE), and the like.

Among them, molecular beam epitaxy has a slow growth rate and a high cost, and the grown thin film has oval defects/long whisker defects on the surface and has problems of polycrystalline growth and the like.

HVPE suffers from the following drawbacks: (1) the growth rate is high, and the film thickness is difficult to accurately control; (2) the reaction gas corrodes the chamber, thereby affecting the quality of the epitaxial film; (3) the growth rate is high, and heteroepitaxy is easy to crack.

MOCVD epitaxial growth processes are complex, require nucleation and coarsening layers of appropriate morphology for crack and morphology control, and have poor crystal quality (where the half-peak width of the (102) plane rocking curve is around 400arc seconds). Meanwhile, the MOCVD equipment is relatively expensive, and coating is deposited around the chamber and on the upper cover during the epitaxial process, which affects the repeatability of the process.

The magnetron sputtering method has high production efficiency and low cost, but the grown film is polycrystalline, has poor crystallization quality, cannot be directly used as a template, and is generally used as a nucleating layer for AlN epitaxial growth.

Meanwhile, aluminum nitride directly grows on the surface of the substrate made of sapphire and is heteroepitaxy, and due to the fact that large thermal mismatch and lattice mismatch exist between sapphire and aluminum nitride, a complex transition layer process needs to be added when the sapphire substrate grows an aluminum nitride single layer or an LED structure in MOCVD equipment, and the Threading Dislocation Density (TDDs) of the grown aluminum nitride or aluminum gallium nitride is high, so that the internal quantum efficiency (EQE) of the LED structure growing on the basis of the material is reduced, meanwhile, yield cracks are easy to generate, LED electric leakage is caused, and the yield of chips is influenced.

Sputtered aluminum nitride is polycrystalline and has a high Threading Dislocation Density (TDDs), and cannot be used directly as an aluminum nitride template, and is generally used as a nucleation layer for MOCVD-grown aluminum nitride templates. The high temperature annealing of sputtered aluminum nitride can significantly improve the twinned quality of sputtered aluminum nitride, causing the sputtered polycrystalline film to recrystallize into a single crystal film. However, high temperature annealing lowers the lattice constant a of aluminum nitride, and a large compressive stress is present therein (after annealing, the lattice constant of aluminum nitride is 0.3097nm c 0.4989nm, and the lattice constant of unstressed aluminum nitride is 0.3112nm c 0.4982 nm). The lattice mismatch between the annealed aluminum nitride and the unstressed gallium nitride is 2.9% (the lattice constant of the unstressed gallium nitride is a 0.31896nm and c is 0.51855nm), the lattice mismatch between the unstressed aluminum nitride and the unstressed gallium nitride is 2.43%, and the lattice mismatch between the aluminum nitride and the aluminum gallium nitride is linearly related to the aluminum component, so that compared with the unstressed aluminum nitride, the lattice mismatch between the aluminum nitride annealed at high temperature and the aluminum gallium nitride with different aluminum components is larger, the lattice mismatch is increased, hillock shapes of the aluminum gallium nitride are increased, the crystal quality is poor, and the aluminum nitride annealed at high temperature cannot be directly used as a template for growing the deep ultraviolet LED.

In view of the above technical defects in the prior art, it is urgently needed to develop a novel preparation method of a high-quality low-stress aluminum nitride template.

The invention content is as follows:

in order to overcome the defects of the prior art, the invention provides a preparation method of an aluminum nitride template, which can effectively optimize the stress state of an AlN and sapphire interface, improve the bonding performance of the interface, reduce the lattice strain of AlN and improve the surface appearance and the crystal quality of AlGaN with different components grown by using the template by carrying out heat treatment (cryogenic treatment and annealing treatment) on a sputtering AlN template after high-temperature annealing.

In order to achieve the above purpose, the invention provides the following technical scheme:

the preparation method of the aluminum nitride template is characterized by comprising the following steps of:

(1) sputtering an aluminum nitride layer with the thickness of 10-1000nm on the surface of the substrate;

(2) carrying out high-temperature annealing treatment on the substrate with the aluminum nitride layer sputtered on the surface;

(3) carrying out subzero treatment on the substrate with the aluminum nitride sputtered on the surface after the high-temperature annealing treatment;

(4) heating the subzero treated substrate with the aluminum nitride sputtered on the surface to room temperature;

(5) carrying out low-temperature annealing treatment on the substrate with the aluminum nitride sputtered on the surface and heated to room temperature;

(6) and (5) repeatedly circulating the steps (3) to (5) for two to six times to obtain the final aluminum nitride template.

Preferably, when the subzero treatment in the step (3) is performed, the substrate with the surface sputtered with the aluminum nitride after the high-temperature annealing treatment is placed into subzero treatment equipment, the subzero treatment equipment is sealed, and 1-5L of liquid nitrogen is filled into the sealed subzero treatment equipment.

Preferably, when the cryogenic treatment is performed in the step (3), the cryogenic treatment equipment is cooled at a constant cooling rate, wherein the cooling rate is 2 ℃/min to 50 ℃/min, and the temperature is maintained for 0.5 to 10 hours after the temperature is reduced to-170 ℃ to-190 ℃.

Preferably, when the cryogenic treatment is performed in the step (3), the cryogenic treatment equipment is cooled in a gradient cooling manner, wherein the temperature is first cooled at a cooling rate of 2 ℃/min to 50 ℃/min, and is kept at-80 ℃ to-150 ℃ for 0.5 to 10 hours, and is then cooled at a cooling rate of 2 ℃/min to 50 ℃/min, and is kept at-170 ℃ to-190 ℃ for 0.5 to 10 hours. .

Preferably, the step (5) is specifically: and putting the substrate with the aluminum nitride sputtered on the surface and heated to the room temperature into a low-temperature annealing furnace for low-temperature annealing treatment, wherein the annealing atmosphere is nitrogen, the nitrogen flow is 10-10000 sccm, and the chamber pressure in the annealing furnace is 200-650 torr.

Preferably, the low-temperature annealing treatment in the step (5) adopts a constant heating rate to heat, the heating rate is 2-40 ℃/min, and the annealing is carried out for 0.2-6h when the temperature is raised to 1000-1480 ℃.

Preferably, the low-temperature annealing treatment in the step (5) adopts gradient annealing, namely, the temperature is raised at the rate of 2-40 ℃/min, and the annealing is carried out for 0.2-3 h after the temperature is raised to 1000-1480 ℃; and then cooling at the cooling rate of 2-20 ℃/min, cooling to 400-980 ℃, and then annealing for 0.2-3 h.

Preferably, the step (1) is specifically: putting the planar substrate into magnetron sputtering equipment for sputtering, wherein the sputtering process specifically comprises the following steps: the power is 1000-4000W, the nitrogen flow is 80-200 sccm, the oxygen flow is 0.1-2 sccm, the argon flow is 0.1-40 sccm, and the temperature is 400-750 ℃.

Preferably, the step (2) is specifically: and placing the substrate with the aluminum nitride layer sputtered on the surface into a high-temperature annealing furnace for high-temperature annealing treatment, wherein the annealing temperature is 1500-1800 ℃, the annealing time is 0.2-3 h, the annealing atmosphere is nitrogen, the nitrogen flow is 100-12000 sccm, and the annealing pressure is 200-650 torr.

Preferably, the step (4) is specifically: after the subzero treatment is finished, directly taking out the subzero treated substrate with the aluminum nitride sputtered on the surface and heating the subzero treated substrate to room temperature under natural conditions, or heating the subzero treated substrate with the aluminum nitride sputtered on the surface to room temperature along with subzero treatment equipment and then taking out the subzero treated substrate.

Compared with the prior art, the preparation method of the aluminum nitride template has the following beneficial technical effects:

1. the sputtering polycrystalline aluminum nitride with poor quality can become a high-quality single crystal aluminum nitride template;

2. the high-quality aluminum nitride template prepared by the preparation method can directly grow aluminum gallium nitride with different components in MOCVD equipment without growing transition layers or superlattices, and the grown aluminum gallium nitride has low threading dislocation density and no cracks.

3. The preparation method of the invention greatly reduces the internal stress of the aluminum nitride template after heat treatment in different procedures, greatly reduces the lattice mismatch with different components of aluminum gallium nitrogen grown in later period, and reduces the number of hills on the surface of the aluminum gallium nitrogen.

4. The used sputtering equipment, annealing furnace and cryogenic treatment equipment are all high-efficiency production equipment, so that the manufacturing cost is low, and the production can be rapidly carried out in large batch.

Drawings

FIG. 1 is a flow chart of a method of preparing an aluminum nitride template of the present invention.

FIG. 2 is a graph of temperature profile for a single temperature cryogenic process of the present invention.

FIG. 3 is a graph of the temperature profile of the gradient temperature cryogenic treatment of the present invention.

FIG. 4 is a temperature profile of a single temperature low temperature anneal process of the present invention

FIG. 5 is a temperature profile of a gradient temperature low temperature annealing process in accordance with the present invention.

Fig. 6 is a temperature profile throughout the process of the method of preparing an aluminum nitride template of the present invention.

The specific implementation mode is as follows:

the present invention is further described with reference to the following drawings and examples, which are not intended to limit the scope of the present invention.

In order to overcome the problems in the prior art, the invention provides a preparation method of an aluminum nitride template, which utilizes the principle that the stress state of a composite material interface and a composition material can be improved by single expansion, contraction or multiple expansion and contraction of crystal lattices to reduce the internal stress of the high-temperature aluminum nitride annealing template. The lattice reduction adopts two different cryogenic treatment processes, and the lattice expansion also adopts two different low-temperature annealing processes, namely, the combined thermal treatment process of cryogenic treatment and annealing treatment optimizes the interface stress state between aluminum nitride and the substrate, improves the interface bonding performance, and reduces the lattice mismatch with later-stage growth aluminum gallium nitrogen.

Fig. 1 shows a flow chart of a method of preparing an aluminum nitride template of the present invention. As shown in fig. 1, the method for preparing the aluminum nitride template of the present invention comprises the following steps:

firstly, sputtering an aluminum nitride layer with the thickness of 10-1000nm on the surface of a substrate.

In the present invention, the substrate may be any planar substrate. Preferably, the substrate is a sapphire substrate.

Wherein, the sputtering of the aluminum nitride layer with the thickness of 10-1000nm on the surface of the substrate can adopt a magnetron sputtering mode. That is, a planar substrate is placed in a magnetron sputtering apparatus for sputtering. When magnetron sputtering is performed, preferably, the sputtering process specifically is: the sputtering power is 1000-4000W, the nitrogen flow during sputtering is 80-200 sccm, the oxygen flow is 0.1-2 sccm, the argon flow is 0.1-40 sccm, and the sputtering temperature is 400-750 ℃. By adopting the sputtering process, the high-quality aluminum nitride film can be formed on the sapphire substrate.

And secondly, carrying out high-temperature annealing treatment on the substrate with the aluminum nitride layer sputtered on the surface.

In the invention, the high-temperature annealing treatment is to place the substrate with the aluminum nitride layer sputtered on the surface into a high-temperature annealing furnace for high-temperature annealing treatment. Wherein the annealing temperature during high-temperature annealing is 1500-1800 ℃, the annealing time is 0.2-3 h, the annealing atmosphere is nitrogen, the nitrogen flow is 100-12000 sccm, and the annealing pressure is 200-650 torr.

Through the high-temperature annealing treatment, the bicrystal quality of the sputtered aluminum nitride film can be obviously improved, so that the sputtered polycrystalline aluminum nitride with poor quality can become a high-quality single crystal aluminum nitride template.

And thirdly, carrying out subzero treatment on the substrate with the aluminum nitride sputtered on the surface after the high-temperature annealing treatment.

Cryogenic treatment is a method of treating materials at temperatures below-130 ℃. The subzero treatment can effectively optimize the stress state of the composite material interface and improve the interface bonding performance.

In the invention, when the subzero treatment is carried out, the substrate with the aluminum nitride sputtered on the surface after the high-temperature annealing treatment is placed in subzero treatment equipment, the subzero treatment equipment is sealed, and a proper amount of liquid nitrogen, for example, 1-5L of liquid nitrogen is filled into the sealed subzero treatment equipment.

Wherein, when the subzero treatment is carried out, two subzero treatment modes can be adopted.

One is single temperature cryogenic treatment, i.e., the cryogenic treatment plant cools at a constant cooling rate. Specifically, as shown in FIG. 2, the cryogenic treatment equipment is cooled at a constant cooling rate of 2 ℃/min to 50 ℃/min, and is kept at the temperature of-170 ℃ to-190 ℃ for 0.5 to 10 hours.

The other is gradient temperature cryogenic treatment, that is, cryogenic treatment equipment performs temperature reduction in a gradient temperature reduction mode. Specifically, as shown in fig. 3, the cryogenic treatment equipment is firstly cooled at a constant cooling rate of 2 ℃/min to 50 ℃/min, and is kept for 0.5 to 10 hours after the temperature is reduced to-80 ℃ to-150 ℃; then cooling at a constant cooling rate of 2-50 ℃/min, and preserving heat for 0.5-10 h after the temperature is reduced to-170-190 ℃.

Fourthly, heating the substrate with the aluminum nitride sputtered on the surface to room temperature after the subzero treatment.

Specifically, after the cryogenic treatment is completed, the substrate with the aluminum nitride sputtered on the surface after the cryogenic treatment can be directly taken out and heated to the room temperature under the natural condition, or the substrate with the aluminum nitride sputtered on the surface after the cryogenic treatment is heated to the room temperature along with the cryogenic treatment equipment and then taken out.

Fifthly, carrying out low-temperature annealing treatment on the substrate with the aluminum nitride sputtered on the surface and heated to room temperature.

Low temperature annealing is a heat treatment process in which a material is held at a certain temperature for a period of time. The low-temperature annealing can ensure that the material is uniformly expanded as a whole, and residual stress existing in the material is released in the uniform expansion process.

In the present invention, when the low-temperature annealing treatment is performed, the substrate whose surface is sputtered with aluminum nitride and which has been heated to room temperature is placed in a low-temperature annealing furnace to perform the low-temperature annealing treatment. Wherein, when the low-temperature annealing treatment is carried out, the annealing atmosphere is nitrogen, the nitrogen flow is 10-10000 sccm, and the chamber pressure in the annealing furnace is 200-650 torr.

Wherein, when the low-temperature annealing treatment is carried out, two annealing processes are adopted.

One is a single temperature low temperature annealing process, that is, annealing at a constant ramp rate. Specifically, as shown in FIG. 4, the temperature is raised to 1000-1480 ℃ at a constant rate of 2-40 ℃/min, and the annealing time is 0.2-6h (i.e., the temperature is maintained for 0.2-6h after the temperature is raised to 1000-1480).

The other is gradient temperature low temperature annealing treatment, namely gradient annealing. Specifically, as shown in FIG. 5, the temperature is raised to 1000-1480 ℃ at a constant temperature rise rate of 2-40 ℃/min, and the annealing time is 0.2-3 h; then reducing the temperature to 400-980 ℃ at a constant cooling rate of 2-20 ℃/min, and the annealing time is 0.2-3 h.

And sixthly, repeatedly circulating the steps (three) to (five) for two to six times to obtain the final aluminum nitride template.

Namely, the aluminum nitride template after high-temperature annealing is circularly subjected to cryogenic treatment and low-temperature annealing treatment for two to six times according to the sequence from the step (three) to the step (five).

Thus, as shown in fig. 6, the temperature of the aluminum nitride template is increased during the whole process of the method for preparing the aluminum nitride template, so as to facilitate the high-temperature annealing treatment. Subsequently, heat treatment, that is, deep cooling treatment and low-temperature annealing treatment are performed a plurality of times. Therefore, by repeatedly carrying out cryogenic treatment and annealing treatment on the sputtered AlN subjected to high-temperature annealing, the stress state of the AlN and sapphire interface can be effectively optimized, the bonding performance of the interface is improved, the lattice strain of the AlN is reduced, and the surface appearance and the crystal quality of AlGaN with different components grown by using the template are improved.

The high-quality aluminum nitride template prepared by the preparation method of the aluminum nitride template can directly grow aluminum gallium nitride with different components in MOCVD equipment without growing transition layers or superlattices, and the grown aluminum gallium nitride has low threading dislocation density and no cracks. In addition, the sputtering equipment, the annealing furnace and the cryogenic treatment equipment are all high-efficiency production equipment, so the manufacturing cost is low, and the production can be rapidly carried out in large batch.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and do not limit the protection scope of the present invention. Those skilled in the art can make modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.