A method for preparing self-stripping aluminum nitride film

Abstract

The present invention discloses a method for preparing a self-stripping aluminum nitride film. This method can grow a self-stripping or self-separating aluminum nitride film on a sapphire substrate using metal nitride vapor epitaxy (MNVPE). The method comprises: first, pre-treating the substrate to increase the aluminum nitride nucleation rate on the substrate; then, performing 3D growth of a buffer layer island; then, shutting off all gas sources to prepare the temperature before film growth; then, introducing gas for 2D growth of the film; and, after growth, cooling and removing the film to obtain a self-stripping aluminum nitride film. This method effectively avoids mechanical damage caused by stripping the aluminum nitride film from the substrate, ensures crystal quality, reduces costs, and is highly efficient and environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor single crystal thin film growth and relates to a method for preparing a self-stripping aluminum nitride thin film, and in particular to a process for growing a self-stripping (self-separating) aluminum nitride thin film on a sapphire substrate using metal nitride vapor epitaxy (MNVPE). Background Art

[0002] Aluminum nitride belongs to the III-V nitride family and has an extremely high bandgap (6.2eV). It possesses high thermal conductivity, excellent dielectric properties, acoustic wave transmission characteristics, superior piezoelectric properties, and a large bandgap, making it suitable for use as a new high-density packaging substrate material and a substrate material for high-power circuit modules. Currently, the industrialization and scale-up of high-quality aluminum nitride single crystals remains difficult. Among the key technical difficulties, the ability to peel the grown aluminum nitride single crystal film from the substrate without introducing mechanical damage or further defects that could damage the crystal quality of the aluminum nitride single crystal remains a particularly challenging issue.

[0003] To address this problem, existing researchers have proposed several solutions. Among them, invention patent CN110219050A proposes a method for preparing aluminum nitride single crystal thin films. Conventional HVPE (HVPE) methods for growing AlN typically employ two temperature zones: a source zone and a growth zone. Dangerous gases such as HCl, ammonia (NH3), and hydrogen (H2) are often introduced into the chamber. In the source zone, aluminum chloride is produced by the reaction of Al and HCl, and then in the growth zone, aluminum chloride reacts with ammonia to produce AlN. This invention patent's solution breaks through the traditional approach to growing AlN using HVPE. By employing specialized equipment and corresponding processes, a self-supporting aluminum nitride single crystal thin film with high crystalline quality is successfully produced. However, in this solution, the self-supporting substrate is achieved by decomposing a gallium nitride thin film on a sapphire substrate. This requires the introduction of an expensive gallium nitride thin film into the substrate, hindering cost reduction. Therefore, the present invention proposes a self-stripping aluminum nitride single crystal thin film process that can be grown directly on a sapphire substrate. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies in the prior art and propose a method for preparing a self-stripping aluminum nitride film. This method can effectively avoid mechanical damage caused by stripping the aluminum nitride film from the substrate, ensure crystal quality, reduce costs, and has the characteristics of high efficiency and greenness.

[0005] The technical solution adopted in the present invention is as follows:

[0006] A method for preparing a self-stripping aluminum nitride film, wherein aluminum particles are placed in the source region and a substrate is placed in the growth region in a growth apparatus capable of simultaneously introducing argon and nitrogen and having independent temperature control for the source region and the growth region, the method comprising the following steps:

[0007] In the first step, the temperature of the source region is raised to no less than 1100°C, the temperature of the growth region is controlled to no more than 500°C, nitrogen and argon are introduced, and the gas flow is controlled. The temperature is kept warm to pre-treat the substrate. In the second step, the temperature of the source region is further raised, while the temperature of the growth region is controlled to no less than 1000°C. The nitrogen flow is maintained or increased, the argon flow is reduced, and the temperature is kept warm to perform island-shaped 3D growth of the buffer layer.

[0008] The third step is to turn off the argon and nitrogen gases, and then further increase the temperature of the source area and the growth area to prepare the temperature before film growth.

[0009] The fourth step is to introduce argon and nitrogen, and control the argon gas flow to a low speed to perform thin film 2D growth;

[0010] The fifth step is to quickly cool the sample to room temperature after growth, take out the sample, and the aluminum nitride film can be self-peeled.

[0011] In the above technical solution, further, in the first step, the source zone temperature is 1100-1200°C, the growth zone temperature is increased to 300-500°C, the argon flow rate is 200-500ml / min, the nitrogen flow rate is 1-5L / min, and the temperature is kept for 5-30 minutes.

[0012] Furthermore, in the second step, the temperature of the source zone is raised to 1200-1400° C., the temperature of the growth zone is raised to 1000-1200° C., the argon flow rate is 10-100 ml / min, the nitrogen flow rate is 1-5 L / min, and the temperature is maintained for 5-30 minutes.

[0013] Furthermore, in the third step, after the gas source is turned off, the temperature of the source zone is increased to 1400-1500°C, and the temperature of the growth zone is increased to 1200-1600°C.

[0014] Furthermore, in the fourth step, the argon flow rate is controlled to be 50-200 ml / min, the nitrogen flow rate is controlled to be 1-5 L / min, and the insulation time is controlled to be 1.5 h to 3 h.

[0015] Furthermore, in the fifth step, the cooling rate is 30-60°C / min.

[0016] Furthermore, the substrate is a sapphire substrate.

[0017] Furthermore, the aluminum nitride film was grown using the special equipment in CN110219050A.

[0018] Furthermore, the purity of the aluminum particles is not less than 99.999%.

[0019] Furthermore, the purity of the nitrogen and argon gases introduced is not less than 5N.

[0020] The beneficial effects of the present invention are:

[0021] The present invention enables the growth of self-stripping or self-separating aluminum nitride thin films that can be easily separated from the substrate without subsequent stripping treatment, effectively avoiding mechanical damage and defects introduced by stripping. The self-stripping aluminum nitride single crystal thin films produced by the present invention have high crystal quality and a relatively thick film thickness, making them suitable as substrate materials for homoepitaxial growth and gallium nitride, etc. Furthermore, the method is low-cost and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 , image of the separated aluminum nitride film obtained in Example 1.

[0023] Figure 2 , X-ray diffraction pattern of the aluminum nitride film obtained in Example 1.

[0024] Figure 3 , SEM image of the cross section of the aluminum nitride film obtained in Example 1.

[0025] Figure 4 , SEM image of the surface 3D island structure after the termination of the second step growth in Example 1.

[0026] Figure 5 , SEM image of the cross section of the aluminum nitride film on the substrate finally obtained in Comparative Example 1.

[0027] Figure 6 , in Comparative Example 2, the gas was not turned off in the third step, and the cross-sectional SEM image of the aluminum nitride film was finally obtained.

[0028] Figure 7 , SEM image of the cross section of the unseparated two-dimensional aluminum nitride film on the top of the crystal island obtained in Comparative Example 3. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described in detail below with reference to specific embodiments and accompanying drawings.

[0030] The method for preparing a self-stripping aluminum nitride film of the present invention is implemented in a growth device capable of simultaneously introducing argon and nitrogen and having independent temperature control of the source region and the growth region. Aluminum particles are placed in the source region, and the substrate is placed in the growth region. Specifically, the special equipment described in CN110219050A can be used. The equipment includes a quartz tube and a corundum tube. The corundum tube is coaxially sleeved inside the quartz tube and located at one end of the quartz tube. The inside of the corundum tube serves as the source region, and the other end of the quartz tube serves as the growth region. The temperatures of the source region and the growth region can be independently controlled. The quartz tube can be evacuated, and gases can be introduced into the ends of the quartz tube and the corundum tube respectively (i.e., nitrogen is introduced from the end of the quartz tube, and argon is introduced into the end of the corundum tube). Alternatively, a vent pipe connected to the quartz tube can be provided in the middle of the quartz tube, and nitrogen is introduced through the vent pipe, while argon is still introduced from the end of the corundum tube. In addition, the distance between the substrate and the gas outlet port of the corundum tube can be adjusted.

[0031] According to a specific embodiment of the present invention, a method for directly preparing a self-stripping aluminum nitride film using the above-mentioned device and sapphire as a substrate includes the following steps:

[0032] In the first step, the source zone temperature is raised to 1100-1200°C, the growth zone temperature to 300-500°C, the argon flow rate is 200-500ml / min, the nitrogen flow rate is 1-5L / min, the distance between the argon outlet and the substrate is 2-10cm, and the temperature is maintained for 5-30 minutes. This process is substrate pretreatment. The purpose is to use aluminum vapor to etch the substrate to a certain degree of irregularity, thereby increasing the nucleation rate of aluminum nitride on the substrate.

[0033] In the second step, the source region temperature is further increased to 1200-1400°C (if the source region temperature in the first step is 1200°C, the source region temperature is now increased to above 1200°C, and the endpoint values ​​of the temperature range and flow rate range in the present invention are the same). The growth region temperature is further increased to 1000-1200°C, with an argon flow rate of 10-100 ml / min and a nitrogen flow rate of 1-5 L / min. The distance between the argon outlet and the substrate is 5-10 cm, and the temperature is maintained for 5-30 minutes. This process is the growth of the buffer layer. This process allows aluminum nitride to nucleate and grow on the substrate. The growth time limits its size and forms the basis for self-stripping. This process is island-shaped 3D growth. This step utilizes a slightly lower V / III ratio (lower Al vapor partial pressure) than the fourth step to promote island nucleation and growth, and maintains a shorter time to avoid the complete merging of all islands, which would affect crystal quality.

[0034] The third step is to turn off the argon and nitrogen gases, and continue to increase the temperature of the source area to 1400-1500℃, and the temperature of the growth area to 1200-1600℃.

[0035] In the fourth step, argon gas is turned on at a flow rate of 50-200 ml / min; nitrogen gas is turned on at a flow rate of 1-5 L / min. The distance between the argon outlet and the substrate is 5-10 cm. The temperature is maintained for 1.5 hours or longer. The reason for turning off the gas flow in the third step is to prevent the temperature increase from affecting the already grown grains and affecting their island-like 3D structure. In the fourth step, a low-speed gas flow is used to establish a two-dimensional (2D) growth mode, thereby producing a high-quality film.

[0036] Step 5: Cool down at 30-60℃ / min.

[0037] The above method can make the aluminum nitride film grow in the form of a two-dimensional film on a three-dimensional island. In the rapid cooling mode, the shrinkage rate at the tip of the island is greater than the shrinkage rate of the film. Therefore, when it drops to room temperature, the upper aluminum nitride film falls off naturally.

[0038] Example 1

[0039] In the first type of specialized equipment, CN110219050A, aluminum particles with a purity of no less than 99.999% are placed in the source area. Clean sapphire is placed in the growth area.

[0040] The purity of the nitrogen and argon gases introduced should not be less than 5N.

[0041] First, the temperature of the source zone was raised to 1200°C, the temperature of the growth zone was raised to 400°C, the argon flow rate was 400ml / min, the nitrogen flow rate was 1L / min, the distance from the argon outlet to the substrate was 7cm, and the temperature was kept for 10 minutes.

[0042] Then raise the temperature of the source zone to 1400°C, the temperature of the growth zone to 1200°C, the argon flow rate to 45 ml / min, the nitrogen flow rate to 3 L / min, the distance from the argon outlet to the substrate to 7 cm, and keep warm for 10 minutes.

[0043] After turning off the argon and nitrogen gases, raise the source zone temperature to 1450°C and the growth zone temperature to 1550°C. Once these temperatures are reached, turn on the argon gas flow at a rate of 100 ml / min and the nitrogen flow at a rate of 1 L / min. Keep the distance between the argon outlet and the substrate at 7 cm, and maintain these temperatures for 1.5 hours.

[0044] Cool down at 30°C / min.

[0045] The obtained aluminum nitride film automatically separates from the substrate and falls off. Figure 1 Its XRD and SEM are shown as follows. Figure 2 、 Figure 3 As shown in Figure 2, it can be seen that the film has excellent crystal quality and thick film thickness. Under the same experimental conditions, only the first and second steps of growth are carried out as above, and the sample is taken out after the end. Its SEM is as follows Figure 4As shown, it can be seen that island-shaped 3D structures that are dispersed and independent of each other are formed on the substrate.

[0046] Comparative Example 1

[0047] In the first type of specialized equipment, CN110219050A, aluminum particles with a purity of no less than 99.999% are placed in the source area. Clean sapphire is placed in the growth area.

[0048] The purity of the nitrogen and argon gases introduced should not be less than 5N.

[0049] First, the temperature of the source zone was raised to 1200°C, the temperature of the growth zone was raised to 400°C, the argon flow rate was 400ml / min, the nitrogen flow rate was 1L / min, the distance from the argon outlet to the substrate was 7cm, and the temperature was kept for 10 minutes.

[0050] After turning off the argon and nitrogen gases, raise the source zone temperature to 1450°C and the growth zone temperature to 1550°C. Once these temperatures are reached, turn on the argon gas flow at a rate of 100 ml / min and the nitrogen flow at a rate of 1 L / min. Keep the distance between the argon outlet and the substrate at 7 cm, and maintain these temperatures for 1.5 hours.

[0051] Cool down at 30°C / min.

[0052] The cross-sectional SEM of the obtained samples is as follows Figure 5 As shown in the figure, in this example, no pretreatment process was performed and the aluminum nitride film was grown directly on the substrate, without obvious 3D island structures or peeling gaps. Subsequent peeling treatment is required to separate the film from the substrate.

[0053] Comparative Example 2

[0054] In the first type of specialized equipment, CN110219050A, aluminum particles with a purity of no less than 99.999% are placed in the source area. Clean sapphire is placed in the growth area.

[0055] The purity of the nitrogen and argon gases introduced should not be less than 5N.

[0056] First, the temperature of the source zone was raised to 1200°C, the temperature of the growth zone was raised to 400°C, the argon flow rate was 400ml / min, the nitrogen flow rate was 1L / min, the distance from the argon outlet to the substrate was 7cm, and the temperature was kept for 10 minutes.

[0057] Then raise the temperature of the source zone to 1400°C, the temperature of the growth zone to 1200°C, the argon flow rate to 45 ml / min, the nitrogen flow rate to 3 L / min, the distance from the argon outlet to the substrate to 7 cm, and keep warm for 10 minutes.

[0058] Increase the source zone temperature to 1450°C and the growth zone temperature to 1550°C. Change the argon flow rate to 100 ml / min and the nitrogen flow rate to 1 L / min. Set the distance from the argon outlet to the substrate to 7 cm and maintain the temperature for 0.5 h.

[0059] Cool down at 30°C / min.

[0060] The cross-sectional SEM of the obtained samples is as follows Figure 6 As shown in FIG, since the film growth was carried out directly after the second step growth without closing the gas source, the 3D islands continued to grow and the bottoms were completely merged, making it impossible to create self-stripping conditions.

[0061] Comparative Example 3

[0062] In the first device of CN110219050A, aluminum particles with a purity of not less than 99.999% are placed in the source area. Clean sapphire is placed in the growth area;

[0063] The purity of the nitrogen and argon gases introduced should not be less than 5N.

[0064] First, the temperature of the source zone was raised to 1200°C, the temperature of the growth zone was raised to 400°C, the argon flow rate was 400ml / min, the nitrogen flow rate was 1L / min, the distance from the argon outlet to the substrate was 7cm, and the temperature was kept for 10 minutes.

[0065] Then raise the temperature of the source zone to 1400°C, the temperature of the growth zone to 1200°C, the argon flow rate to 45 ml / min, the nitrogen flow rate to 3 L / min, the distance from the argon outlet to the substrate to 7 cm, and keep warm for 10 minutes.

[0066] After turning off the argon and nitrogen gases, raise the source zone temperature to 1450°C and the growth zone temperature to 1550°C. Once these temperatures are reached, turn on the argon gas flow at a rate of 100 ml / min and the nitrogen flow at a rate of 1 L / min. The distance between the argon outlet and the substrate is 7 cm, and the temperatures are maintained for 0.5 h.

[0067] Cool naturally.

[0068] The film in the sample obtained in this example failed to separate from the substrate by itself, and its cross-sectional SEM is shown in the figure below. Figure 7 As shown, it can be seen that there is an unseparated two-dimensional aluminum nitride film on the top of the crystal island.

[0069] The embodiments described above are merely some preferred embodiments of the present invention and are not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A method for preparing a self-stripping aluminum nitride film, comprising placing aluminum particles in a source region and a substrate in a growth region in a growth apparatus capable of simultaneously introducing argon and nitrogen and having independent temperature control for the source region and the growth region, wherein the substrate is a sapphire substrate, characterized in that: The method further includes: The first step is to raise the temperature of the source region to no less than 1100°C, control the temperature of the growth region to no more than 500°C, introduce nitrogen and argon, control the gas flow, and keep the temperature to pre-treat the substrate; In the second step, the temperature of the source region is further increased while the temperature of the growth region is controlled to be no less than 1000°C. The nitrogen flow rate is maintained or increased, the argon flow rate is reduced, and the temperature is maintained to carry out the island-shaped 3D growth of the buffer layer. The third step is to turn off the argon and nitrogen gases, then further increase the temperature of the source region to 1400-1500°C, and simultaneously increase the temperature of the growth region to 1200-1600°C to prepare the temperature before film growth. In the fourth step, argon and nitrogen are introduced, and the argon gas is controlled to be a low-speed flow with an argon flow rate of 50-200 ml / min to perform thin film 2D growth; the low-speed flow rate is lower than the argon flow rate in the first step; The fifth step is to rapidly cool the sample to room temperature at a rate of 30-60°C / min after growth, remove the sample, and allow the aluminum nitride film to self-strip.

2. The method for preparing a self-stripping aluminum nitride film according to claim 1, wherein: In the first step, the temperature of the source zone is 1100-1200°C, the temperature of the growth zone is increased to 300-500°C, the argon flow rate is 200-500ml / min, the nitrogen flow rate is 1-5L / min, and the temperature is kept for 5-30 minutes.

3. The method for preparing a self-stripping aluminum nitride film according to claim 1, wherein: In the second step, the temperature of the source zone is raised to 1200-1400° C., the temperature of the growth zone is raised to 1000-1200° C., the argon flow rate is 10-100 ml / min, the nitrogen flow rate is 1-5 L / min, and the temperature is kept for 5-30 minutes.

4. The method for preparing a self-stripping aluminum nitride film according to claim 1, wherein: In the fourth step, the nitrogen flow rate is controlled to be 1-5 L / min and the insulation time is 1.5 h to 3 h.

5. The method for preparing a self-stripping aluminum nitride film according to claim 1, wherein: The purity of the aluminum particles is not less than 99.999%.

6. The method for preparing a self-stripping aluminum nitride film according to claim 1, wherein: The purity of the nitrogen and argon gases introduced should not be less than 5N.

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