Method for multi-step continuous regulation and control of direct growth self-stripping gallium nitride
阅读说明：本技术 一种多步连续调控直接生长自剥离氮化镓的方法 (Method for multi-step continuous regulation and control of direct growth self-stripping gallium nitride ) 是由 张保国 邵永亮 胡海啸 郝霄鹏 吴拥中 吕洪 于 2021-06-24 设计创作，主要内容包括：本发明公开了一种多步连续调控直接生长自剥离氮化镓的方法,包括如下步骤：生长用GaN衬底在多温区多气氛的管式生长炉中的装配；GaN衬底在高温下氧化性气氛中氧化制备表面具有氧化镓层的衬底；具有氧化镓层的GaN衬底在腐蚀气体气氛中干刻蚀制备多孔GaN衬底；多孔GaN衬底上生长GaN单晶；生长工艺结束后控制氨气通入量实现界面出GaN分解；降温后烘箱静置得到自剥离GaN单晶。(The invention discloses a method for multi-step continuous regulation and control of direct growth self-stripping gallium nitride, which comprises the following steps: assembling a GaN substrate for growth in a multi-temperature-zone and multi-atmosphere tubular growth furnace; oxidizing the GaN substrate in an oxidizing atmosphere at high temperature to prepare a substrate with a gallium oxide layer on the surface; preparing a porous GaN substrate by dry etching the GaN substrate with the gallium oxide layer in a corrosive gas atmosphere; growing GaN single crystal on the porous GaN substrate; controlling the ammonia gas introduction amount to realize the decomposition of the GaN at the interface after the growth process is finished; and cooling and standing the obtained product in an oven to obtain the self-stripping GaN monocrystal.)
1. A method for multi-step continuous regulation and control of direct growth self-stripping gallium nitride is characterized by comprising the following steps:
(1) selecting a substrate for GaN single crystal growth, and loading the substrate into a GaN crystal growth furnace;
(2) heating according to the GaN crystal growth operating specification, heating to a certain oxidation temperature, keeping the temperature for a period of time, and introducing a certain amount of oxidizing gas;
(3) continuously heating to a certain etching temperature, preserving the temperature for a period of time, and introducing hydrogen chloride gas for etching;
(4) continuously heating to the growth temperature of the GaN single crystal, and carrying out normal process growth;
(5) after the growth is finished, cooling to a certain nitridation protection temperature, preserving the temperature for a period of time and controlling the introduction amount of ammonia;
(6) and cooling the growth furnace to room temperature, opening the furnace, taking out the GaN crystal, cleaning the GaN crystal, blow-drying the GaN crystal by using high-purity nitrogen, standing the GaN crystal in a baking oven at a certain temperature, and taking out the GaN crystal after a period of time to obtain the self-stripped GaN.
2. The method according to claim 1, wherein the substrate for GaN single crystal growth in step (1) comprises Si, Al deposited with a GaN seed layer2O3And SiC, wherein the thickness of the seed layer is 5-20 μm.
3. The method according to claim 1, wherein the GaN crystal growth furnace in the step (1) is a vertical or horizontal growth furnace and has a multi-temperature zone multi-atmosphere function which can provide three or more temperature zones and four or more atmospheres.
4. The method as claimed in claim 1, wherein the oxidation temperature in the step (2) is set to 600 to 800 ℃; setting the oxidation time to be 30-60 min; the oxidizing gas is oxygen or standard gas prepared by oxygen according to a certain proportion (0.01-99.99%); the amount of the oxidizing gas is set to 100 to 1000 sccm.
5. The method according to claim 1, wherein the etching temperature in the step (3) is set to 800-1100 ℃; setting the etching time to be 10-30 min; the amount of hydrogen chloride gas introduced is set to 10 to 200 sccm.
6. The method as claimed in claim 1, wherein the nitridation protection temperature in step (5) is set to 800-1100 ℃, the nitridation time is set to 60-120 min, and the ammonia gas is continuously introduced in an amount of 200-1000 sccm, or is introduced in pulses at certain time intervals of 5-30 s.
7. The method according to claim 1, wherein the oven of the GaN crystal after the standing growth in step (6) is set to have a temperature of 50-100 ℃ and a standing time of 30-60 min.
Technical Field
The invention relates to a method for directly growing self-stripping gallium nitride by multi-step continuous regulation, which is simple, convenient, direct and easy to operate, can grow and obtain self-stripping GaN single crystals, and belongs to the technical field of semiconductors.
Background
GaN has the characteristics of large forbidden band width, high electron mobility, high electron saturation velocity, acid and alkali resistance, high temperature resistance and the like. These excellent properties make GaN materials widely used in LED lighting, semiconductor lasers, solar cells, transistors, microwave devices, phased array radars, full color displays, and data storage. Since the melting point of GaN is as high as 2791K, the decomposition pressure is only 4.5GPa and is 10 GPa5In the atmosphere of Pa, the decomposition temperature of GaN is only about 900 ℃, so that a naturally existing GaN crystal cannot be found for preparing a substrate for homoepitaxial growth. Because of the lack of a homoepitaxial substrate for GaN crystal growth, most GaN crystals are heteroepitaxial growth, and the thermal mismatch and lattice mismatch brought by the heteroepitaxial growth inevitably cause the grown GaN crystals to have high dislocation density and internal stress, thereby greatly reducing the quality of the GaN single crystals and further limiting the wide application of the GaN single crystals. Meanwhile, the existence of the foreign substrate also influences the performance of the later-stage GaN preparation device, so that the GaN single crystal is urgently needed to be stripped from the foreign substrate.
The current common stripping methods are mechanical stripping and laser stripping, but the mechanical stripping operation procedure is complex, a large amount of impurities can be introduced in the stripping process, and larger processing stress is generated; the laser stripping equipment is expensive, the maintenance cost is high, the requirement on growing the crystal is higher, and the laser stripping equipment is not suitable for large-scale popularization. And the yield of the two methods is difficult to achieve expectation, and the subsequent operation is carried out after the GaN growth is finished, so that the phase change increases the preparation cost. Therefore, a simple, convenient, direct and easy-to-operate method for preparing the self-peeling GaN single crystal is urgently needed, and the aim is well achieved by the method for continuously regulating and controlling the direct growth of the self-peeling GaN in multiple steps.
Disclosure of Invention
The invention provides a method for directly growing self-stripping gallium nitride by multi-step continuous regulation and control to solve the problems.
A method for multi-step continuous regulation and control of direct growth self-stripping gallium nitride is characterized by comprising the following steps:
(1) selecting a substrate for GaN single crystal growth, and loading the substrate into a GaN crystal growth furnace;
(2) heating according to the GaN crystal growth operating specification, heating to a certain oxidation temperature, keeping the temperature for a period of time, and introducing a certain amount of oxidizing gas;
(3) continuously heating to a certain etching temperature, preserving the temperature for a period of time, and introducing hydrogen chloride gas for etching;
(4) continuously heating to the growth temperature of the GaN single crystal, and carrying out normal process growth;
(5) after the growth is finished, cooling to a certain nitridation protection temperature, preserving the temperature for a period of time and controlling the introduction amount of ammonia;
(6) and cooling the growth furnace to room temperature, opening the furnace, taking out the GaN crystal, cleaning the GaN crystal, blow-drying the GaN crystal by using high-purity nitrogen, standing the GaN crystal in a baking oven at a certain temperature, and taking out the GaN crystal after a period of time to obtain the self-stripped GaN.
The substrate for GaN single crystal growth in the step (1) comprises Si and Al deposited with a GaN seed layer2O3And the thickness of the seed layer of the SiC can be between 5 and 20 mu m.
The GaN crystal growth furnace in the step (1) can be a vertical or horizontal growth furnace, the substrate can be fixed in a suspension mode or a lifting mode, the GaN crystal growth furnace has the functions of multiple temperature zones and multiple atmospheres, the number of the temperature zones can be more than or equal to three, and the number of the atmospheres can be more than or equal to four.
The oxidation temperature in the step (2) is set to be 600-800 ℃; the oxidation time can be set to be 30-60 min; the oxidizing gas can be oxygen or standard gas prepared by oxygen according to a certain proportion (0.01-99.99%); the amount of the oxidizing gas to be introduced may be set to 100 to 1000 sccm.
The etching temperature in the step (3) is set to be 800-1100 ℃; the etching time can be set to be 10-30 min; the amount of the hydrogen chloride gas introduced can be set to 10 to 200 sccm.
In the step (5), the nitriding protection temperature can be set to 800-1100 ℃, the nitriding time can be set to 60-120 min, the amount of the introduced ammonia gas can be continuously introduced into 200-1000 sccm, and the ammonia gas can be introduced into the reactor in a pulse mode at certain time intervals (5-30 s).
The temperature of the oven of the GaN crystal after standing and growing in the step (6) can be set to be 50-100 ℃, and the standing time can be set to be 30-60 min.
The principle of the invention is as follows: firstly, oxidizing a substrate seed layer at a low temperature to generate a thin layer with gallium oxide; then, etching the thin gallium oxide layer on the surface of the substrate at high temperature by means of hydrogen chloride gas to generate a seed layer with a hole structure; then, a growth process of the GaN crystal is used for growth, the introduction of ammonia gas is continuously introduced and controlled after the growth is finished, the GaN at the interface (the porous seed layer in the previous step) is heated and decomposed to generate nitrogen and metal gallium due to the fragile structure, and the decomposition phenomenon of the integrally grown GaN crystal is not obvious due to the inhibition effect of the introduced ammonia gas; and finally, taking out the GaN crystal cooled to room temperature, cleaning, and standing in a low-temperature oven, wherein gallium decomposed at the interface is melted to obtain the self-stripped GaN crystal.
Drawings
FIG. 1 shows the surface morphology of a seed layer of a porous structure generated on the surface of a GaN substrate after hydrogen chloride gas etching at high temperature in example 1 of the present invention after being enlarged by 2000 times under a scanning electron microscope;
FIG. 2 is a cross-sectional view of a seed layer of a porous structure generated on the surface of a GaN substrate after hydrogen chloride gas etching at high temperature in example 1 of the present invention after being enlarged by 10000 times under a scanning electron microscope;
FIG. 3 is a photograph of a Ga face of a GaN crystal grown in example 1 of the present invention (in the drawing, one cell of a graph paper is 1 mm);
FIG. 4 is a photograph of an N face of a GaN crystal grown in example 1 of the present invention;
FIG. 5 is a self-peeling GaN crystal obtained after the oven was left standing in example 1 of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples.
Example 1
(1) Selecting GaN/Al prepared by MOCVD2O3As the substrate for GaN single crystal growth, the thickness of the GaN seed layer on the substrate is 5 μm, and the substrate is arranged in a vertical GaN single crystal growth furnace with five temperature zones capable of supplying four gas atmospheres in a lifting manner;
(2) heating according to the GaN crystal growth operating specification, keeping the temperature for 30min when the temperature is raised to 800 ℃, introducing high-purity oxygen of 200sccm, and oxidizing the GaN seed layer to generate a gallium oxide thin layer;
(3) continuing to heat to 1000 ℃, preserving the temperature for 20min, introducing 100sccm hydrogen chloride gas for etching, removing the gallium oxide thin layer generated in the step (2), and etching to prepare a seed layer of the hole structure;
(4) continuously heating to the growth temperature of the GaN single crystal, and carrying out normal process growth;
(5) after the growth is finished, cooling to 900 ℃, preserving heat for 120min to ensure the decomposition of the interface hole-shaped GaN, and introducing 300sccm ammonia gas in a pulse mode with 10s as an interval to inhibit the decomposition of the growing GaN crystal;
(6) and cooling the growth furnace to room temperature, opening the furnace, taking out the GaN crystal, cleaning the GaN crystal, drying the GaN crystal by using high-purity nitrogen, standing the GaN crystal in an oven at 80 ℃ for 60min, and taking out the GaN crystal to obtain the self-stripped GaN.
FIG. 1 shows the surface of a gallium oxide thin layer grown at low temperature in a growth furnace after high temperature hydrogen chloride etching, resulting in a large number of hexagonal etch pits of about 1 μm in size, and the surface becoming rough providing a large number of nucleation growth sites; FIG. 2 is a cross-section of the substrate after high temperature etching, showing that the etched hexagonal pits have a depth of about 5 μm and substantially penetrate the entire seed crystal layer of GaN; FIGS. 3, 4 and 5 show that the grown GaN single crystal has a good peeling effect, and the sapphire substrate is broken by stress and is easily separated from the crystal.
Example 2
As described in example 1, except that: the GaN growth substrate selected in the step (1) is Si or SiC deposited with a GaN seed layer, and the thickness of the seed layer can be between 5 and 20 mu m.
Example 3
As described in example 1, except that: the GaN crystal growth furnace in the step (1) is a horizontal growth furnace, and the substrate can be fixed in a suspension mode.
Example 4
As described in example 1, except that: the oxidation temperature in the step (2) is set to 700 ℃; the oxidation time can be set to 60 min; standard gas of oxygen configured at 50%; the amount of the oxygen standard gas introduced may be set to 1000 sccm.
Example 5
As described in example 1, except that: the etching temperature in the step (3) is set to 900 ℃; setting the etching time to be 30 min; the amount of hydrogen chloride gas introduced was set to 200 sccm.
Example 6
As described in example 1, except that: in the step (5), the nitridation protection temperature can be set to 1000 ℃, the nitridation protection time is set to 60, and 500sccm of ammonia gas is continuously introduced.
Example 7
As described in example 1, except that: the oven of the GaN crystal after standing and growing in the step (6) can be at 100 ℃ and the standing time can be 30 min.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.