CN106801258A - A kind of preparation method with hexa-prism aluminium nitride whisker - Google Patents

Abstract

The present invention relates to a kind of preparation method with hexa-prism aluminium nitride whisker, the preparation method with hexa-prism aluminium nitride whisker, using physical vapor transport, raw material A lN is heated into by gas phase by Frequency Induction Heating mode, it it is 1,700 1750 DEG C by controlling growth temperature, control growth pressure for 200 300 Torr, crystallization forms the AlN whiskers of hexa-prism.The present invention at a lower temperature, six prism AlN whiskers is obtained by Controlling Growth Rate.

Description

A preparation method with hexagonal aluminum nitride whiskers

technical field

The invention belongs to the field of preparation of one-dimensional wide bandgap semiconductor materials, in particular to a method for preparing hexagonal prism-shaped AlN whiskers based on a physical vapor transport (Physical vapor transport, PVT) method.

Background technique

With the development of semiconductor science and technology, people have been pursuing semiconductor materials with excellent performance. The first-generation semiconductor materials represented by silicon (Si) crystals support the development of the entire semiconductor industry, and the second-generation semiconductor materials represented by gallium arsenide (GaAs) crystals are the supporting materials for the development of the electronic communication industry. Wide bandgap semiconductors represented by silicon carbide (SiC) and gallium nitride (GaN) have received extensive attention and have initially achieved certain applications. In recent years, aluminum nitride (AlN) crystals with larger band gaps have received extensive attention.

Compared with other semiconductor materials, AlN crystal material has the following advantages: (1) Compared with wide bandgap semiconductor SiC (3.2eV) and GaN (3.4eV) materials, AlN crystal has a larger bandgap width (6.2 eV); (2) AlN crystal has excellent thermal conductivity, and the thermal conductivity at room temperature is 319W/(m.K); (3) AlN crystal and its congener compounds GaN and indium nitride (InN) all have direct band gaps Semiconductors have high photoelectric conversion efficiency. The alloy material of AlN and GaN can realize the control of the forbidden band width (3.4-6.2eV) in a certain range by adjusting the ratio of elements.

The excellent material properties of AlN crystals can be widely used in the manufacture of high-temperature, high-frequency, high-power, and radiation-resistant electronic devices, and can be widely used in new energy-saving power electronic devices, microwave communications, and high-efficiency semiconductor lighting. At present, the PVT method is the main method for preparing AlN crystals. Due to the strong anisotropy of AlN crystal growth, the controllable preparation of AlN crystals by PVT method is still one of the difficulties.

Contents of the invention

The invention utilizes the characteristics of high-temperature sublimation of AlN and crystallization anisotropy of different crystal phases, and controls the crystallization temperature and pressure through a physical gas phase transport mechanism to prepare AlN whiskers with a hexagonal prism shape.

The present invention hereby provides a method for preparing hexagonal aluminum nitride whiskers. The method is to use the physical vapor phase transport method to heat the raw material AlN into the gas phase by means of medium frequency induction heating, and control the growth temperature to 1700-1750 ° C. , control the growth pressure to 200-300Torr, and crystallize to form hexagonal AlN whiskers. The invention obtains the hexagonal AlN whisker by controlling the growth rate at a lower temperature.

Preferably, the raw material AlN is AlN powder with a particle size of 100-300 mesh and a purity greater than 99.99%.

Preferably, a material inert to Al vapor is selected as the first crucible to hold the AlN raw material, such as graphite crucible, tungsten crucible, tantalum carbide crucible and the like. Preferably two crucibles are used, ie a first crucible encases a second crucible. The second crucible can be a graphite crucible, a tungsten crucible, or a tantalum carbide crucible.

Preferably, the growth time of the AlN whiskers is 25-35 hours, such as about 30 hours.

Preferably, the AlN whiskers are 300-400 μm wide and 2-3 cm long.

Preferably, the growth atmosphere can be nitrogen.

Preferably, 4H-SiC with a thickness of 1.0-1.5 mm can be used as the seed crystal.

Description of drawings

Fig. 1 is a schematic diagram of a PVT method growth device for preparing hexagonal AlN whiskers;

Fig. 2 is the AlN whisker physical photo that embodiment 1 prepares;

Fig. 3 is the scanning electron micrograph of the single whisker of the AlN whisker of embodiment 1;

Fig. 4 is the AlN whisker physical photo that embodiment 2 prepares;

Fig. 5 is the optical micrograph of the single whisker of the AlN whisker of embodiment 2;

Fig. 6 is a graph of Raman spectrum test results of AlN whiskers prepared by PVT method.

detailed description

The present invention will be further described below in conjunction with specific examples. It should be understood that the following embodiments are only used to illustrate the present invention, not to limit the present invention.

The invention utilizes the characteristics of high-temperature sublimation of AlN and crystallization anisotropy of different crystal phases, and controls the crystallization temperature and pressure through the physical gas phase transport mechanism to prepare AlN whiskers with a hexagonal prism shape, the whiskers are 300-400um wide and 2-3cm long .

Referring to FIG. 1 , which shows a schematic diagram of a growth device, AlN raw material powder is put into a crucible. Among them, the AlN raw material powder can be AlN powder with a particle size of 100-300 mesh and a purity greater than 99.99%. The crucible can be selected from materials that are inactive to Al vapor, such as graphite crucible, tungsten crucible, and tantalum carbide crucible. Preferably, two crucibles can be selected, that is, the first crucible is used to hold the AlN raw material powder, and the second crucible is covered with the first crucible. The second crucible, like the first crucible, is made of materials inactive to Al vapor, such as graphite crucibles, tungsten crucibles, and tantalum carbide crucibles. More preferably, graphite carbon felt is wound outside the second crucible, and the double crucible is beneficial to improve the stability of radial temperature gradient and temperature field. The seed crystal is fixed under the top cover of the first crucible, a 4H-SiC seed crystal can be used, and the thickness of the seed crystal can be 1.0-1.5 mm. The distance between the seed crystal and the AlN powder can be controlled to be 25-35mm. Graphite carbon felt can be set on the top cover of the crucible as the heat preservation top cover.

Place the crucible in the middle of the induction coil, use a mechanical pump and a molecular pump to evacuate the growth chamber to <1x 10 ^{- 3} Pa, then fill it with nitrogen to 200-300 Torr, and heat it through medium-frequency induction to control the heating rate to 15-20°C per minute, heated to 1700-1750°C, kept warm and kept under pressure for 25-35 hours. Then continue to fill with nitrogen gas to 600-800 Torr, control the cooling rate to 3-5° C./min, and cool to room temperature to obtain AlN whiskers with a width of 300-400 μm and a length of 2-3 cm.

Example 1:

1. Put the 200-mesh AlN powder into the tantalum carbide crucible, cover the tantalum carbide crucible with a graphite crucible, wrap graphite carbon felt on the outside of the graphite crucible, fix a 1mm thick 4H-SiC seed crystal under the top cover of the tantalum carbide crucible, Control the distance between the seed crystal and the AlN powder to 30mm, and use graphite carbon felt as the insulation top cover on the tantalum carbide crucible;

2. Place the crucible in the middle of the induction coil, the experimental device is shown in Figure 1, and then start to grow. The preparation is mainly as follows: Use a mechanical pump and a molecular pump to pump the vacuum of the growth chamber to <1x 10 ^-3 Pa, then fill it with nitrogen to 200 Torr, and heat it at 15-20°C/min to 1700°C to start growing AlN whiskers;

3. The growth time is about 30 hours, filled with nitrogen to 700 Torr, and then the temperature is lowered at 3-5°C/min, and the sample is taken out when the temperature drops to room temperature. The photo of the AlN whisker sample is shown in Attachment 2;

4. Carry out SEM test on the prepared sample. Attachment 3 is the test result. From the SEM picture, it can be seen that the AlN whiskers are in the shape of a hexagonal column;

See Figure 6, which shows the results of Raman spectrum testing of AlN whiskers. The Raman spectrum peaks in the figure correspond to the characteristic peaks of AlN crystals, and the half-maximum width of the E2 peak is 10.6cm ^-1 , indicating that AlN whiskers have Good crystalline quality.

Example 2:

1. Put 300 mesh AlN powder into a tungsten crucible, wrap graphite carbon felt on the outside of the tungsten crucible, fix a 1mm thick 4H-SiC seed crystal under the top cover of the tantalum carbide crucible, and control the distance between the seed crystal and the AlN powder The thickness is 30mm, and the graphite carbon felt is used as the insulation top cover on the tantalum carbide crucible;

2. Place the crucible in the middle of the induction coil, use a mechanical pump and a molecular pump to evacuate the growth chamber to <1x 10 ^{- 3} Pa, then fill it with nitrogen to 300 Torr, and heat it at 15-20°C/min to 1750°C to start growth AlN whiskers;

3. The growth time is about 30 hours, filled with nitrogen gas to 700 Torr, and then the temperature is lowered at 3-5°C/min. When the temperature drops to room temperature, the sample is taken out. The photo of the AlN whisker sample is shown in Figure 4;

4. Perform an optical microscope test on the prepared sample, and accompanying drawing 5 is the test result. From the optical microscope photos, it can be seen that the AlN whiskers are in the shape of hexagonal columns.

Claims (9)

1. a kind of preparation method with hexa-prism aluminium nitride whisker, it is characterised in that

Using physical vapor transport, raw material A lN is heated into by gas phase by Frequency Induction Heating mode, by controlling growth temperature It is 1700-1750 DEG C to spend, and controls growth pressure for 200-300 Torr, and crystallization forms the AlN whiskers of hexa-prism.

2. preparation method according to claim 1, it is characterised in that the raw material A lN is AlN powders, and particle diameter is 100- 300 mesh, purity is more than 99.99%.

3. preparation method as claimed in any of claims 1 to 2, it is characterised in that selection is to Al steam torpescence Material hold the raw material A lN as the first crucible.

4. preparation method according to claim 3, it is characterised in that first crucible is graphite crucible, tungsten crucible, carbon Change tantalum crucible.

5. the preparation method according to claim 3 or 4, it is characterised in that first crucible is placed in the second crucible, institute It is graphite crucible, tungsten crucible, carbonization tantalum crucible to state the second crucible.

6. preparation method as claimed in any of claims 1 to 5, it is characterised in that during the growth of the AlN whiskers Between about 25~35 hours.

7. preparation method as claimed in any of claims 1 to 6, it is characterised in that the AlN whiskers 300- wide 400 μm, 2-3cm long.

8. preparation method as claimed in any of claims 1 to 7, it is characterised in that growth atmosphere is nitrogen.

9. preparation method as claimed in any of claims 1 to 8, it is characterised in that with thickness be 1.0~1.5mm 4H-SiC as seed crystal.