Method for producing aln thin film and semiconductor element

Abstract

The application discloses a preparation method of an AlN film and a semiconductor element. The preparation method of the AlN film comprises the following steps: heat treatment on a substrate, pre-treatment of trimethylaluminum (TMAl) at a temperature t0, constant-temperature growth of an AlN buffer 1 buffer layer at a temperature t1, constant-temperature growth of an AlN buffer 2 buffer layer at a temperature t2, constant-temperature growth of an AlN buffer 3 buffer layer at a temperature t3, and constant-temperature growth of an AlN layer at a temperature t4, wherein t1>t0, t2<t1, t3>t1, t4>t3. The application can solve the problems of lattice mismatch caused by the large difference between the AlN lattice constant and the substrate lattice constant and thermal mismatch caused by the difference in the thermal expansion coefficient, and is helpful to improve the surface flatness of the AlN layer and reduce the generation of cracks.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a preparation method of AlN film and a semiconductor element. BACKGROUND

[0002] Aluminum nitride (AlN) is an important third-generation semiconductor material, and its application and development have attracted much attention. Among III-V compound semiconductor materials, AlN has the widest band gap (6.2 eV), and its light-emitting wavelength reaches the deep ultraviolet band, which can be widely used in ultraviolet light-emitting diodes, ultraviolet lasers, and ultraviolet detectors. At the same time, AlN has many excellent properties such as good thermal stability, high thermal conductivity, radiation resistance, strong acid and alkali resistance, high breakdown field, high dielectric breakdown strength, and high electron saturation rate, which makes it have a broad application prospect in the fields of machinery, optics, high-power microwave radio frequency devices, high-efficiency power electronic devices, surface acoustic wave device manufacturing, and high-frequency bandwidth communication.

[0003] Metal organic chemical vapor deposition system (MOCVD) has the advantages of accurate control of thickness and composition during growth, high quality of grown single crystal thin film, and is suitable for large size growth and can meet the needs of large-scale production, which is the main equipment for researching and producing AlN film. At present, the substrates for preparing AlN film mainly include sapphire, SiC and Si. Compared with sapphire and SiC substrates, Si substrate is widely concerned due to its good thermal and electrical conductivity, low price, easy integration with microelectronics, easy large-scale growth, and mature industrialization. However, there are still many difficulties in preparing high-quality AlN single crystal thin film on Si substrate: the large lattice and thermal mismatch between Si substrate and AlN leads to high dislocation density and cracks; the diffusion of Si atoms in Si substrate and Ga atoms in the epitaxial layer leads to poor crystal quality and rough interface; the mobility of Al atoms on the growth surface is very low, and AlN generally tends to grow in three-dimensional island shape, resulting in rough surface and poor crystal quality of AlN film. SUMMARY

[0004] The embodiments of the present application provide a preparation method of AlN film and a semiconductor element, which can solve the problem of poor quality of AlN layer grown on the surface of the substrate.

[0005] In a first aspect, the present application provides a preparation method of AlN film, comprising:

[0006] heat treating the substrate;

[0007] pre-treating the substrate after the heat treatment with TMAl;

[0008] growing an AlN buffer1 buffer layer on the surface of the substrate after the pre-treatment with TMAl is completed.

[0009] An AlN buffer2 buffer layer is grown on the surface of the AlN buffer1 buffer layer;

[0010] An AlN buffer3 buffer layer is grown on the surface of the AlN buffer2 buffer layer;

[0011] An AlN layer is grown on the surface of the AlN buffer3 buffer layer;

[0012] The temperature of the pre-pass TMA1 treatment is t0;

[0013] The growth of the AlN buffer1 buffer layer includes a first isothermal growth stage, where the growth temperature of the first isothermal growth stage is t1, and t1>t0.

[0014] The growth of the AlN buffer2 layer includes a second isothermal growth stage, the growth temperature of which is t2. <t1;

[0015] The growth of the AlN buffer3 buffer layer includes a third isothermal growth stage, and the growth temperature of the third isothermal growth stage is t3, where t3 > t1.

[0016] The growth of the AlN layer includes a fourth isothermal growth stage, where the growth temperature of the fourth isothermal growth stage is t4, and t4 > t3.

[0017] When the temperature is low, the surface of the grown AlN crystal is relatively rough. This application sets an AlN buffer1 layer to connect the substrate, an AlN buffer3 layer to connect the AlN layer, and an AlN buffer2 layer as a transition layer connecting the AlN buffer1 layer and the AlN buffer3 layer. This multi-buffer layer technology can help adjust the lattice mismatch and thermal mismatch between the substrate and AlN, and improve the surface and crystal quality of AlN.

[0018] In some exemplary embodiments, △T1 = t1 - t0, and the range of △t1 is greater than or equal to 20°C and less than or equal to 50°C.

[0019] Within the range of ΔT1, it helps to improve the interface stability at the junction of the AlN buffer layer and the substrate. Preferably, the range of ΔT1 is 20-30°C.

[0020] In some exemplary embodiments, △T2 = t1 - t2, and the range of △T2 is greater than or equal to 20°C and less than or equal to 50°C.

[0021] In the range of △T2, the AlN buffer2 buffer layer is grown to have a proper roughness, and then the AlN buffer2 buffer layer can effectively adjust the stress between the AlN buffer1 buffer layer and the AlN buffer3 buffer layer, and then the stress between the buffer substrate and the AlN layer. Preferably, the range of △T2 is 20-30℃.

[0022] In some exemplary embodiments, △T3=t3-t1, and the range of △T3 is greater than or equal to 20℃ and less than or equal to 50℃.

[0023] In the range of △T3, the AlN buffer3 buffer layer is grown to have a good crystal quality, and the surface quality of the AlN buffer3 buffer layer is also good. Preferably, the range of △T3 is 20-30℃.

[0024] In some exemplary embodiments, △T4=t4-t3, and the range of △T4 is greater than or equal to 20℃ and less than or equal to 50℃.

[0025] In the range of △T4, the AlN layer is further grown to have a better crystal quality and interface flatness. Preferably, the range of △T4 is 30-40℃.

[0026] In some exemplary embodiments, the substrate is a sapphire substrate, a SiC substrate, and a Si substrate; preferably, the substrate is a silicon substrate. The silicon substrate has good thermal and electrical conductivity, low price, easy microelectronic integration, easy large-scale growth, and mature industrialization.

[0027] In the process of growing the AlN buffer1 buffer layer, the AlN buffer2 buffer layer, the AlN buffer3 buffer layer, and the AlN layer on the substrate surface in sequence, the substrate can be placed in a loading tray of a growth reaction chamber, and the loading tray is controlled to rotate, thereby driving the substrate to rotate and improving the growth efficiency of each layer structure. For example, the loading tray is a graphite tray.

[0028] In some exemplary embodiments, the heat treatment of the substrate comprises sequentially performing a first-stage heat treatment and a second-stage heat treatment on the substrate, the first-stage heat treatment controls the temperature range in the growth reaction chamber to be 1150-1250℃, and the second-stage heat treatment controls the temperature range in the growth reaction chamber to be 1050-1150℃.

[0029] The first-stage heat treatment can quickly remove the oxide layer on the substrate surface, and the second-stage heat treatment can slowly remove the remaining oxide layer on the substrate surface, prevent damage to the substrate, and improve the interface stability of the connection between the substrate and the AlN buffer1 buffer layer.

[0030] In some exemplary embodiments, the first stage heat treatment process further comprises: heat treating the silicon substrate in a first carrier gas atmosphere, the first carrier gas atmosphere comprising hydrogen, and the flow rate of the hydrogen being 200 L / min to 250 L / min. The efficiency of removing the surface oxide layer of the substrate can be effectively improved in the first stage heat treatment at a temperature range of 1150°C to 1250°C. At the same time, the processing time is controlled to be 1 min to 2 min to prevent the hydrogen from reacting with the substrate excessively and causing erosion of the substrate.

[0031] In the first stage heat treatment process, the pressure is controlled to be 80 Torr to 120 Torr, and the rotation speed of the carrier disk is controlled to be 900 rpm to 1000 rpm, which can better remove the upper surface oxide layer of the substrate. The first carrier gas further comprises nitrogen, and the flow rate of the nitrogen is 10 L / min to 20 L / min.

[0032] In some exemplary embodiments, the second stage heat treatment process further comprises: heat treating the silicon substrate in a first carrier gas atmosphere, the first carrier gas atmosphere comprising hydrogen, and the flow rate of the hydrogen being 150 L / min to 200 L / min, and the processing time being 2 min to 4 min. Within the above-mentioned range, the remaining surface oxide layer of the substrate can be removed more slowly to prevent damage to the substrate.

[0033] The second stage heat treatment process further comprises: controlling the pressure to be 60 Torr to 100 Torr, and the rotation speed of the carrier disk to be 1000 rpm to 1100 rpm. The first carrier gas further comprises nitrogen, and the flow rate of the nitrogen is 20 L / min to 30 L / min, so as to slow down the rate of removing the oxide layer and protect the substrate.

[0034] In some exemplary embodiments, the temperature t0 of the pre-pass TMAl treatment is 1000°C to 1100°C. The pre-pass TMAl treatment process further comprises: controlling the flow rate of the TMAl to be 100 mL / min to 200 mL / min, and the processing time to be 10 s to 20 s, so as to lay an aluminum layer on the surface of the substrate to prevent the material for growing the subsequent AlN buffer1 buffer layer from directly reacting with the substrate.

[0035] The process of the pre-passing TMAl treatment further comprises: in a first carrier gas atmosphere, and with the first carrier gas passing TMAl, controlling the flow rate of the TMAl to be 100 mL / min-200 mL / min, the carrier gas comprising nitrogen and hydrogen, the flow rate of the nitrogen being 0 L / min-10 L / min, and the flow rate of the hydrogen being 150 L / min-200 L / min, controlling the pressure of the growth reaction chamber to be 60 Torr-100 Torr, controlling the rotation speed of the carrier tray to be 1000 rpm-1100 rpm, and the treatment time being 10 s-20 s, so as to uniformly lay an aluminum layer on the surface of the substrate, for the subsequent uniform and stable growth of the AlN buffer1 buffer layer.

[0036] In some exemplary embodiments, the growth of the AlN buffer1 buffer layer comprises: after the pre-passing TMAl treatment, a first temperature-adjusting growth stage, and after the first temperature-adjusting growth stage, the first constant-temperature growth stage, wherein in the first temperature-adjusting growth stage, various conditions in the growth reaction chamber gradually change to the growth conditions of the first constant-temperature growth stage, and the AlN buffer1 buffer layer starts to grow in the first temperature-adjusting growth stage, and the time of the first temperature-adjusting growth stage is s1, and s1 satisfies 0.5 min≤s1≤1 min.

[0037] In some exemplary embodiments, the growth of the AlN buffer2 buffer layer comprises: after the growth of the AlN buffer1 buffer layer, a second temperature-adjusting growth stage, and after the second temperature-adjusting growth stage, the second constant-temperature growth stage, wherein in the second temperature-adjusting growth stage, various conditions in the growth reaction chamber gradually change to the growth conditions of the second constant-temperature growth stage, and the AlN buffer2 buffer layer starts to grow in the second temperature-adjusting growth stage, and the time of the second temperature-adjusting growth stage is s2, and s2 satisfies 0.5 min≤s2≤1 min.

[0038] In some exemplary embodiments, the growth of the AlN buffer3 buffer layer comprises: after the growth of the AlN buffer2 buffer layer, a third temperature-adjusting growth stage, and after the third temperature-adjusting growth stage, the third constant-temperature growth stage, wherein in the third temperature-adjusting growth stage, various conditions in the growth reaction chamber gradually change to the growth conditions of the third constant-temperature growth stage, and the AlN buffer3 buffer layer starts to grow in the third temperature-adjusting growth stage, and the time of the third temperature-adjusting growth stage is s3, and s3 satisfies 0.5 min≤s3≤1 min.

[0039] In some exemplary embodiments, the growing of the AlN layer comprises: after the growing of the AlN buffer 3 buffer layer, a fourth temperature ramping growth stage is performed, and after the fourth temperature ramping growth stage, the fourth isothermal growth stage is performed, wherein in the fourth temperature ramping growth stage, the various conditions in the reaction chamber are gradually changed to the growth conditions of the fourth isothermal growth stage, and the AlN layer starts to grow in the fourth temperature ramping growth stage, and the time of the fourth temperature ramping growth stage is s4, and s4 satisfies 0.5min≤s4≤1min.

[0040] In some exemplary embodiments, the growth temperature t1 of the first isothermal growth stage ranges from 1050℃ to 1150℃, and the growth conditions of the first isothermal growth stage comprise: in a second carrier gas atmosphere, the flow rate of the TMAl is controlled to be 250mL / min-300mL / min, the flow rate of ammonia is controlled to be 5L / min-10L / min, the pressure is controlled to be 60Torr-90Torr, the rotation speed of the carrier disk is controlled to be 1100r / min-1200r / min, the growth time is controlled to be 5min-18min, and the AlN buffer 1 buffer layer is grown on the surface of the substrate.

[0041] In some exemplary embodiments, the growth temperature t2 of the second isothermal growth stage ranges from 1000℃ to 1100℃, and the growth conditions of the second isothermal growth stage comprise: in a second carrier gas atmosphere, the flow rate of the TMAl is controlled to be 200mL / min-250mL / min, the flow rate of ammonia is controlled to be 10L / min-15L / min, the pressure is controlled to be 90Torr-120Torr, the rotation speed of the carrier disk is controlled to be 1100r / min-1200r / min, the growth time is controlled to be 7min-22min, and the AlN buffer 2 buffer layer is grown on the surface of the AlN buffer 1 buffer layer.

[0042] Compared with the process of growing the AlN buffer 1 buffer layer, in the process of growing the AlN buffer 2 buffer layer, the reaction temperature is reduced, the flow rate of TMAl is reduced, and the flow rate of ammonia is increased, so that the generated AlN buffer 2 buffer layer has relatively coarse crystals, so that the AlN buffer 2 buffer layer can play a better stress buffering role.

[0043] In some example embodiments, the growth temperature t3 of the third isothermal growth stage ranges from 1080°C to 1180°C; the growth conditions of the third isothermal growth stage include: in a second carrier gas atmosphere, the flow rate of the TMAl is controlled to be 250 mL / min to 300 mL / min, the flow rate of the ammonia is controlled to be 3 L / min to 8 L / min, the pressure is controlled to be 50 Torr to 80 Torr, the rotation speed of the carrier disk is controlled to be 1000 rpm to 1100 rpm, the growth time is 10 min to 30 min, and the AlN buffer3 buffer layer is grown on the surface of the AlN buffer2 buffer layer.

[0044] Compared with the process of growing the AlN buffer2 buffer layer, in the process of growing the AlN buffer3 buffer layer, the reaction temperature is increased, and the flow rate of the ammonia, the pressure in the growth reaction chamber, and the rotation speed of the carrier disk are all decreased, which can make the generated AlN buffer3 buffer layer have good crystal quality and a relatively flat surface.

[0045] In some example embodiments, the growth temperature t4 of the fourth isothermal growth stage ranges from 1100°C to 1200°C; the growth conditions of the fourth isothermal growth stage include: in a second carrier gas atmosphere, the first carrier and the second carrier are periodically alternately introduced, the flow rate of the ammonia is controlled to be 3 L / min to 8 L / min, and the AlN layer is grown on the surface of the AlN buffer3 buffer layer; the first carrier includes TMIn, and the second carrier includes TMAl and TMIn.

[0046] In one period, the first carrier is introduced for 10 s to 20 s, and the flow rate of the TMIn is 100 mL / min to 200 mL / min; in one period, the second carrier is introduced for 1 min to 2 min, the flow rate of the TMIn is 50 mL / min to 150 mL / min, and the flow rate of the TMAl is 350 mL / min to 400 mL / min.

[0047] By using the above process, cracks in the AlN layer are prevented, and the flatness and the crystal quality of the AlN layer are improved. Among them, the TMIn plays the role of a surfactant, which can improve the migration rate of Al atoms on the reaction surface and improve the flatness of the reaction surface during the growth of the AlN layer.

[0048] In some example embodiments, in the process of growing the AlN buffer1 buffer layer, the AlN buffer2 buffer layer, the AlN buffer1 buffer layer, and the AlN layer, the second carrier gas includes hydrogen, and the flow rate of the hydrogen is 150 L / min to 200 L / min. The hydrogen can effectively improve the migration rate of Al, and thus improve the surface flatness.

[0049] In a second aspect, the present application provides a semiconductor element, which comprises an AlN buffer1 buffer layer, an AlN buffer2 buffer layer, an AlN buffer3 buffer layer and an AlN layer arranged on a substrate in sequence, and is prepared by the method as described above.

[0050] In some exemplary embodiments, the thickness of the AlN buffer1 buffer layer is 20-40 nm, the thickness of the AlN buffer2 buffer layer is 30-50 nm, and the thickness of the AlN buffer3 buffer layer is 40-60 nm. Controlling the above three buffer layers to meet the above thickness range can realize the stable connection between the substrate and the AlN layer through the three buffer layers, and based on the adjustment of the lattice mismatch, thermal mismatch and surface flatness, the thickness of the AlN buffer1 buffer layer, the AlN buffer2 buffer layer and the AlN buffer3 buffer layer is increased layer by layer.

[0051] The AlN thin film preparation method and the semiconductor element based on the embodiments of the present application have at least the following beneficial effects:

[0052] By performing heat treatment on the substrate in stages, the surface oxide layer of the substrate is first removed quickly, and then the surface oxide layer of the substrate is removed slowly, so as to reduce the damage to the substrate, and then improve the flatness of the subsequently generated AlN layer.

[0053] By generating the AlN buffer1 buffer layer, the AlN buffer2 buffer layer and the AlN buffer3 buffer layer between the substrate and the AlN layer, the stress between the substrate and the AlN layer can be buffered through the three buffer layers, the buffering effect is better, the flatness of the AlN layer can be effectively improved, and the crack of the AlN layer can be reduced.

[0054] By controlling the growth temperature to meet t1>t0, t2<t1, t3>t1 and t4>t3, the surface of the generated AlN buffer2 buffer layer is rougher than that of the AlN buffer1 buffer layer and the AlN buffer3 buffer layer, the AlN buffer2 buffer layer can effectively buffer the stress between the AlN buffer1 buffer layer and the AlN buffer3 buffer layer, and then buffer the stress between the substrate and the AlN layer. BRIEF DESCRIPTION OF DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0056] Figure 1 The flow chart of the preparation method of the AlN film of an embodiment of the present application;

[0057] Figure 2 The structural diagram of sequentially forming the AlN buffer1 buffer layer, the AlN buffer2 buffer layer, the AlN buffer3 buffer layer and the AlN layer on the surface of the substrate of the embodiment one of the present application;

[0058] Figure 3 The atomic force microscope diagram of the surface of the AlN layer of the embodiment one of the present application;

[0059] Figure 4 The optical microscope diagram of the surface of the AlN layer of the embodiment one of the present application;

[0060] Figure 5 The atomic force microscope diagram of the surface of the AlN layer of the embodiment two of the present application;

[0061] Figure 6 The optical microscope diagram of the surface of the AlN layer of the embodiment two of the present application;

[0062] Figure 7 The atomic force microscope diagram of the surface of the AlN layer of the embodiment three of the present application;

[0063] Figure 8 The optical microscope diagram of the surface of the AlN layer of the embodiment three of the present application;

[0064] Figure 9 The atomic force microscope diagram of the surface of the AlN layer of the comparative example one of the present application;

[0065] Figure 10 The optical microscope diagram of the surface of the AlN layer of the comparative example one of the present application;

[0066] Figure 11 The atomic force microscope diagram of the surface of the AlN layer of the comparative example two of the present application;

[0067] Figure 12 The optical microscope diagram of the surface of the AlN layer of the comparative example two of the present application;

[0068] Figure 13 The atomic force microscope diagram of the surface of the AlN layer of the comparative example three of the present application;

[0069] Figure 14 Figure 4 is an optical microscope image of the surface of an AlN layer of Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0070] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0071] As shown in Figure 1, it is a flowchart of the preparation method of the AlN film of the present application, and the preparation method of the AlN film of the present application will be introduced below in combination with specific examples. Figure 1

[0072] Example One

[0073] The silicon substrate was placed into a carrier tray and then transferred into a growth reaction chamber, the carrier tray was a graphite tray, and the silicon substrate was subjected to a first stage heat treatment. In the first stage heat treatment, the temperature in the growth reaction chamber was controlled to be 1150°C, a carrier gas was introduced into the growth reaction chamber, the carrier gas included nitrogen and hydrogen, the flow rate of the nitrogen was 10 L / min, the flow rate of the hydrogen was 200 L / min, the pressure in the growth reaction chamber was controlled to be 80 Torr, the rotation speed of the graphite tray was controlled to be 900 rpm, and the treatment time was 2 min.

[0074] The temperature in the growth reaction chamber was controlled to be 1050°C, and the silicon substrate was subjected to a second stage heat treatment. In the second stage heat treatment, the carrier gas was continuously introduced into the growth reaction chamber, the carrier gas included nitrogen and hydrogen, the flow rate of the nitrogen was 20 L / min, the flow rate of the hydrogen was 150 L / min, the pressure in the growth reaction chamber was controlled to be 60 Torr, the rotation speed of the carrier tray was controlled to be 1000 rpm, and the treatment time was 4 min.

[0075] The temperature in the growth reaction chamber was controlled to be 1000°C, a carrier gas was introduced into the growth reaction chamber, and TMAl was introduced along with the carrier gas to perform a pre-TMAl treatment, the flow rate of the TMAl was controlled to be 100 mL / min, the carrier gas included nitrogen and hydrogen, the flow rate of the nitrogen was 1 L / min, the flow rate of the hydrogen was 150 L / min, the pressure in the growth reaction chamber was controlled to be 60 Torr, the rotation speed of the carrier tray was controlled to be 1000 rpm, and the treatment time was 10 s.

[0076] ​After the TMAl pre-flow, a first temperature ramping growth phase is entered, and the growth conditions are changed to the growth conditions of the first constant temperature growth phase in 1 min. The first temperature ramping growth phase includes: stopping the flow of nitrogen into the growth chamber, and flowing carrier gas, ammonia and TMAl into the growth chamber. The carrier gas includes hydrogen, and the flow rate of the hydrogen is 150 L / min. The flow rate of the ammonia is changed to 5 L / min. The pressure of the growth chamber is controlled to 60 Torr. The rotation speed of the carrier disk is changed to 1100 rpm. The temperature of the growth chamber is changed to 1050 °C. A first constant temperature growth phase is entered, and the growth time of the first constant temperature growth phase is 6 min. The thickness of the AlN buffer 1 buffer layer is 20 nm.

[0077] After the growth of the AlN buffer 1 buffer layer, a second temperature ramping growth phase is entered, and the growth conditions are changed to the growth conditions of the second constant temperature growth phase in 1 min. The second temperature ramping growth phase includes: continuing to flow hydrogen, ammonia and TMAl into the growth chamber. The flow rate of the TMAl is 250 mL / min. The carrier gas includes hydrogen, and the flow rate of the hydrogen is 150 L / min. The flow rate of the ammonia is 5 L / min. The pressure of the growth chamber is changed to 90 Torr. The rotation speed of the carrier disk is 1100 rpm. The temperature of the growth chamber is decreased to 1000 °C. A second constant temperature growth phase is entered, and the growth time of the second constant temperature growth phase is 8 min. The thickness of the AlN buffer 2 buffer layer is 30 nm.

[0078] After the growth of the AlN buffer 2 buffer layer, a third temperature ramping growth phase is entered, and the growth conditions are changed to the growth conditions of the third constant temperature growth phase in 1 min. The third temperature ramping growth phase includes: continuing to flow hydrogen, ammonia and TMAl into the growth chamber. The flow rate of the TMAl is 250 mL / min. The carrier gas includes hydrogen, and the flow rate of the hydrogen is 150 L / min. The flow rate of the ammonia is changed to 3 L / min. The pressure of the growth chamber is changed to 50 Torr. The rotation speed of the carrier disk is changed to 1000 rpm. The temperature of the growth chamber is increased to 1080 °C. A third constant temperature growth phase is entered, and the growth time of the third constant temperature growth phase is 10 min. The thickness of the AlN buffer 3 buffer layer is 40 nm.

[0079] After the AlN buffer layer 3 growth is completed, the fourth temperature-controlled growth stage begins. After 30 seconds, the growth conditions are changed to those of the fourth isothermal growth stage. This fourth temperature-controlled growth stage includes: continuing to introduce hydrogen and ammonia into the growth reaction chamber, controlling the hydrogen flow rate to 200 L / min and the ammonia flow rate to 3 L / min, controlling the pressure in the growth reaction chamber to 50 Torr, and controlling the temperature in the growth reaction chamber to rise to 1100℃, thus entering the fourth isothermal growth stage. The fourth isothermal growth stage includes: periodically and alternately introducing a first and second carrier material into the growth reaction chamber. The first carrier material includes TMIn, and the second carrier material includes TMAl and TMIn. Within one cycle, the first carrier material is introduced for 10 seconds at a TMIn flow rate of 100 mL / min, the second carrier material is introduced for 1 minute at a TMIn flow rate of 50 mL / min, and the TMAl flow rate is 350 mL / min. The growth time for the fourth isothermal growth stage is 90 minutes. The thickness of the grown AlN layer is 300 nm.

[0080] like Figure 2 The diagram shown is a schematic diagram of the structure in which AlN buffer1, AlN buffer2, AlN buffer3 and AlN layers are formed sequentially on the substrate surface in this embodiment.

[0081] like Figure 3 The image shown is an atomic force microscope (AFM) morphology image of the AlN layer surface in this embodiment. Figure 3 As can be seen, the AlN layer surface is relatively flat, exhibiting an island-like morphology, with a root-mean-square (RMS) surface roughness of 0.5 nm. Figure 4 The image shown is an optical microscope (OM) image of the AlN layer in this embodiment. Figure 4 As can be seen, the surface of the AlN layer in this embodiment is relatively smooth and free of cracks. The full width at half maximum (FWHM) of the XRD (002) in this embodiment is 1120 arcsec.

[0082] Example 2

[0083] A silicon substrate is placed in a graphite tray and then transferred to a growth reaction chamber for the first stage of heat treatment. During this first stage, the temperature inside the growth reaction chamber is controlled at 1180°C. Carrier gases, including nitrogen and hydrogen, are introduced into the chamber at a flow rate of 16 L / min and 220 L / min, respectively. The pressure inside the chamber is controlled at 100 Torr, the rotation speed of the graphite tray is controlled at 950 rpm, and the treatment time is 1.5 min.

[0084] The temperature in the growth reaction chamber is controlled to be 1100°C, and the silicon substrate is subjected to a second stage of heat treatment. In the second stage of heat treatment, the carrier gas is continuously introduced into the growth reaction chamber, the carrier gas comprising nitrogen and hydrogen, the flow rate of the nitrogen being 25 L / min, the flow rate of the hydrogen being 180 L / min, the pressure in the growth reaction chamber being controlled to be 80 Torr, the rotation speed of the carrier tray being controlled to be 1050 rpm, and the processing time being 3 min.

[0085] The temperature in the growth reaction chamber is controlled to be 1050°C, the carrier gas is introduced into the growth reaction chamber, and TMAl is introduced into the carrier gas to perform a pre-TMAl treatment, the flow rate of the TMAl being controlled to be 150 mL / min, the carrier gas comprising nitrogen and hydrogen, the flow rate of the nitrogen being 5 L / min, the flow rate of the hydrogen being 180 L / min, the pressure in the growth reaction chamber being controlled to be 80 Torr, the rotation speed of the carrier tray being controlled to be 1050 rpm, and the processing time being 15 s.

[0086] After the pre-TMAl treatment, a first temperature adjustment growth stage is entered, and the growth conditions are changed to the growth conditions of the first constant temperature growth stage in 1 min. The first temperature adjustment growth stage comprises: stopping the introduction of the nitrogen into the growth reaction chamber, and introducing the carrier gas, ammonia and TMAl into the growth reaction chamber, the flow rate of the TMAl being changed to 280 mL / min, the carrier gas comprising hydrogen, the flow rate of the hydrogen being controlled to be 180 L / min, the flow rate of the ammonia being changed to 8 L / min, the pressure in the growth reaction chamber being changed to 75 Torr, the rotation speed of the carrier tray being changed to 1150 rpm, the temperature in the growth reaction chamber being changed to 1100°C, and a first constant temperature growth stage is entered, the growth time of the first constant temperature growth stage being 12 min. The thickness of the AlN buffer1 buffer layer is 32 nm.

[0087] After the growth of the AlN buffer1 buffer layer, a second temperature adjustment growth stage is entered, and the growth conditions are changed to the growth conditions of the second constant temperature growth stage in 1 min. The second temperature adjustment growth stage comprises: continuing to introduce the hydrogen, ammonia and TMAl into the growth reaction chamber, the flow rate of the TMAl being 280 mL / min, the carrier gas comprising hydrogen, the flow rate of the hydrogen being 180 L / min, the flow rate of the ammonia being 8 L / min, the pressure in the growth reaction chamber being changed to 100 Torr, the rotation speed of the carrier tray being 1150 rpm, and the temperature in the growth reaction chamber being lowered to 1050°C, and a second constant temperature growth stage is entered, the growth time of the second constant temperature growth stage being 16 min. The thickness of the AlN buffer2 buffer layer is 40 nm.

[0088] After the growth of the AlN buffer2 buffer layer is completed, a third temperature adjusting growth stage is entered, and the growth conditions are changed to the growth conditions of the third constant temperature growth stage after 1 min. The third temperature adjusting growth stage includes: continuously introducing hydrogen, ammonia and TMAl into the growth reaction chamber, controlling the flow rate of TMAl to be 280 mL / min, the carrier gas including hydrogen, the flow rate of hydrogen being 180 L / min, the flow rate of ammonia being changed to 5 L / min, controlling the pressure of the growth reaction chamber to be changed to 70 Torr, controlling the rotation speed of the carrier disk to be 1050 rpm, and controlling the temperature in the growth reaction chamber to be increased to 1120°C, entering the third constant temperature growth stage, and the growth time of the third constant temperature growth stage being 19 min. The thickness of the AlN buffer3 buffer layer is 48 nm.

[0089] After the growth of the AlN buffer3 buffer layer is completed, a fourth temperature adjusting growth stage is entered, and the growth conditions are changed to the growth conditions of the fourth constant temperature growth stage after 0.5 min. The fourth temperature adjusting growth stage includes: continuously introducing hydrogen and ammonia into the growth reaction chamber, controlling the flow rate of hydrogen to be changed to 220 L / min, the flow rate of ammonia being 5 L / min, controlling the pressure of the growth reaction chamber to be changed to 50 Torr, and controlling the temperature in the growth reaction chamber to be increased to 1150°C, entering the fourth constant temperature growth stage. The fourth constant temperature growth stage includes: periodically and alternately introducing a first carrier and a second carrier into the growth reaction chamber, the first carrier including TMIn, and the second carrier including TMAl and TMIn; in one period, the first carrier is introduced for 15 s, and the flow rate of TMIn is 150 mL / min, the second carrier is introduced for 1.5 min, the flow rate of TMIn is 90 mL / min, and the flow rate of TMAl is 375 mL / min, and the growth time of the fourth constant temperature growth stage is 110 min. The thickness of the AlN layer is 300 nm.

[0090] Figure 5 The atomic force microscope (AFM) topography of the surface of the AlN layer of the present embodiment is shown in FIG. 6, and it can be seen from FIG. 6 that the surface of the AlN layer is very smooth, showing a step flow morphology, and the Root-mean-square (RMS) surface roughness is only 0.3 nm. Figure 5 The optical microscope (OM) of the AlN layer of the present embodiment is shown in FIG. 7, and it can be seen from FIG. 7 that the surface of the AlN layer of the present embodiment is smooth and free of cracks. Figure 6 The optical microscope (OM) of the AlN layer of the present embodiment is shown in FIG. 7, and it can be seen from FIG. 7 that the surface of the AlN layer of the present embodiment is smooth and free of cracks. Figure 6 The XRD (002) half-width of the present embodiment is 960 arcsec.

[0091] Example Three

[0092] The silicon substrate is placed into a graphite boat and then transferred into a growth chamber for a first stage of heat treatment. In the first stage of heat treatment, the temperature in the growth chamber is controlled at 1250 °C, a carrier gas is introduced into the growth chamber, the carrier gas includes nitrogen and hydrogen, the flow rate of the nitrogen is 20 L / min, the flow rate of the hydrogen is 250 L / min, the pressure in the growth chamber is controlled at 120 Torr, the rotation speed of the graphite boat is controlled at 1000 rpm, and the treatment time is 1 min.

[0093] The temperature in the growth chamber is controlled at 1150 °C for a second stage of heat treatment. In the second stage of heat treatment, the carrier gas is continuously introduced into the growth chamber, the carrier gas includes nitrogen and hydrogen, the flow rate of the nitrogen is 30 L / min, the flow rate of the hydrogen is 200 L / min, the pressure in the growth chamber is controlled at 100 Torr, the rotation speed of the graphite boat is controlled at 1100 rpm, and the treatment time is 2 min.

[0094] The temperature in the growth chamber is controlled at 1100 °C, a carrier gas is introduced into the growth chamber, and TMAl is introduced with the carrier gas for a pre-TMAl treatment, the flow rate of the TMAl is controlled at 200 mL / min, the carrier gas includes nitrogen and hydrogen, the flow rate of the nitrogen is 10 L / min, the flow rate of the hydrogen is 200 L / min, the pressure in the growth chamber is controlled at 100 Torr, the rotation speed of the graphite boat is controlled at 1100 rpm, and the treatment time is 20 s.

[0095] After the pre-TMAl treatment, a first temperature adjustment growth stage is entered, and the growth conditions are changed to the growth conditions of a first constant temperature growth stage over 1 min. The first temperature adjustment growth stage includes: stopping the introduction of the nitrogen into the growth chamber, and introducing a carrier gas, ammonia, and TMAl into the growth chamber, the flow rate of the TMAl is controlled at 300 mL / min, the carrier gas includes hydrogen, the flow rate of the hydrogen is controlled at 200 L / min, the flow rate of the ammonia is changed to 10 L / min, the pressure in the growth chamber is changed to 90 Torr, the rotation speed of the graphite boat is changed to 1200 rpm, and the temperature in the growth chamber is changed to 1150 °C, a first constant temperature growth stage is entered, and the growth time of the first constant temperature growth stage is 15 min. The thickness of the AlN buffer 1 buffer layer is 38 nm.

[0096] After the growth of the AlN buffer1 buffer layer is completed, a second temperature adjusting growth stage is entered, and the growth conditions are changed to the growth conditions of the second constant temperature growth stage after 1 min. The second temperature adjusting growth stage includes: continuously introducing hydrogen, ammonia and TMAl into the growth reaction chamber, controlling the flow rate of TMAl to be 300 mL / min, the carrier gas including hydrogen, the flow rate of hydrogen being 200 L / min, the flow rate of ammonia being 10 L / min, controlling the pressure of the growth reaction chamber to change to 120 Torr, controlling the rotation speed of the carrier disk to be 1200 rpm, and controlling the temperature in the growth reaction chamber to decrease to 1100°C, entering the second constant temperature growth stage, and the growth time of the second constant temperature growth stage being 20 min. The thickness of the AlN buffer2 buffer layer is 50 nm.

[0097] After the growth of the AlN buffer2 buffer layer is completed, a third temperature adjusting growth stage is entered, and the growth conditions are changed to the growth conditions of the third constant temperature growth stage after 1 min. The third temperature adjusting growth stage includes: continuously introducing hydrogen, ammonia and TMAl into the growth reaction chamber, controlling the flow rate of TMAl to be 300 mL / min, the carrier gas including hydrogen, the flow rate of hydrogen being 200 L / min, the flow rate of ammonia changing to 8 L / min, controlling the pressure of the growth reaction chamber to change to 80 Torr, controlling the rotation speed of the carrier disk to change to 1100 rpm, and controlling the temperature in the growth reaction chamber to increase to 1180°C, entering the third constant temperature growth stage, and the growth time of the third constant temperature growth stage being 25 min. The thickness of the AlN buffer3 buffer layer is 60 nm.

[0098] After the growth of the AlN buffer3 buffer layer is completed, a fourth temperature adjusting growth stage is entered, and the growth conditions are changed to the growth conditions of the fourth constant temperature growth stage after 1 min. The fourth temperature adjusting growth stage includes: continuously introducing hydrogen and ammonia into the growth reaction chamber, controlling the flow rate of hydrogen to change to 250 L / min, the flow rate of ammonia being 8 L / min, controlling the pressure of the growth reaction chamber to change to 50 Torr, and controlling the temperature in the growth reaction chamber to increase to 1200°C, entering the fourth constant temperature growth stage. The fourth constant temperature growth stage includes: periodically and alternately introducing a first carrier and a second carrier into the growth reaction chamber, the first carrier including TMIn, and the second carrier including TMAl and TMIn; in one period, the first carrier is introduced for 20 s, and the flow rate of TMIn is 200 mL / min, the second carrier is introduced for 2 min, the flow rate of TMIn is 150 mL / min, and the flow rate of TMAl is 400 mL / min, and the growth time of the fourth constant temperature growth stage is 100 min. The thickness of the AlN layer is 300 nm.

[0099] Figure 7The atomic force microscope (AFM) topography of the surface of the AlN layer of this example is shown in Figure 6. It can be seen that the surface of the AlN layer is relatively smooth, with a Root-mean-square (RMS) surface roughness of 1.1 nm. Figure 7 The optical microscope (OM) image of the AlN layer of this example is shown in Figure 7. It can be seen that the surface of the AlN layer of this example is flat and free of cracks. The XRD (002) full width at half maximum of this example is 1250 arcsec. Figure 8 The atomic force microscope (AFM) topography of the surface of the AlN layer of this example is shown in Figure 6. It can be seen that the surface of the AlN layer is relatively smooth, with a Root-mean-square (RMS) surface roughness of 1.1 nm. Figure 8 The optical microscope (OM) image of the AlN layer of this example is shown in Figure 7. It can be seen that the surface of the AlN layer of this example is flat and free of cracks. The XRD (002) full width at half maximum of this example is 1250 arcsec.

[0100] Comparative Example 1

[0101] The differences from Example 2 include:

[0102] Only the first stage of heat treatment was performed on the silicon substrate, and the treatment time was 3 min.

[0103] Figure 9 The atomic force microscope (AFM) topography of the surface of the AlN layer of this example is shown in Figure 6. It can be seen that the surface of the AlN layer is relatively smooth, with a Root-mean-square (RMS) surface roughness of 1.1 nm. Figure 9 The optical microscope (OM) image of the AlN layer of this example is shown in Figure 7. It can be seen that the surface of the AlN layer of this example is flat and free of cracks. The XRD (002) full width at half maximum of this example is 1250 arcsec. Figure 10 The optical microscope (OM) image of the AlN layer of this example is shown in Figure 7. It can be seen that the surface of the AlN layer of this example is flat and free of cracks. The XRD (002) full width at half maximum of this example is 1250 arcsec. Figure 10 The optical microscope (OM) image of the AlN layer of this example is shown in Figure 7. It can be seen that the surface of the AlN layer of this example is flat and free of cracks. The XRD (002) full width at half maximum of this example is 1250 arcsec.

[0104] Comparative Example 2

[0105] The differences from Example 2 include:

[0106] After the growth of the AlN buffer 1 buffer layer was completed, the growth of the AlN buffer 2 and AlN buffer 3 buffer layers was stopped, and the thickness of the AlN buffer 1 buffer layer was 120 nm.

[0107] Figure 11 The atomic force microscope (AFM) topography of the surface of the AlN layer of this example is shown in Figure 6. It can be seen that the surface of the AlN layer is relatively smooth, with a Root-mean-square (RMS) surface roughness of 1.1 nm. Figure 11 The optical microscope (OM) image of the AlN layer of this example is shown in Figure 7. It can be seen that the surface of the AlN layer of this example is flat and free of cracks. The XRD (002) full width at half maximum of this example is 1250 arcsec. Figure 12 The optical microscope (OM) image of the AlN layer of this example is shown in Figure 7. It can be seen that the surface of the AlN layer of this example is flat and free of cracks. The XRD (002) full width at half maximum of this example is 1250 arcsec. Figure 12 The optical microscope (OM) image of the AlN layer of this example is shown in Figure 7. It can be seen that the surface of the AlN layer of this example is flat and free of cracks. The XRD (002) full width at half maximum of this example is 1250 arcsec.

[0108] Comparative Example 3

[0109] The differences from Example 2 include:

[0110] When growing the AlN layer, only AlN monolayers were grown, and the thickness was 300 nm.

[0111] Figure 13 The atomic force microscope (AFM) topography of the surface of the AlN layer of this example is shown in FIG. 4. Figure 13 As can be seen from FIG. 4, the surface of the AlN layer is relatively rough, and the root-mean-square (RMS) surface roughness is only 2.0 nm. Figure 14 The optical microscope (OM) image of the AlN layer of this example is shown in FIG. 5. Figure 14 As can be seen from FIG. 5, the surface of the AlN layer of this example is free of cracks. The XRD (002) full-width-at-half-maximum of the AlN layer of this example is 1220 arcsec.

[0112] The experimental results in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1.

[0113] Table 1

[0114]

[0115] According to the results in Table 1, it can be seen that the interface stability between the AlN layer and the substrate layer and the surface roughness of the AlN film are both optimized in the AlN film prepared in the examples of the present application, relative to the comparative examples.

[0116] In the description of this application, it should be understood that the orientation or positional relationship indicated by the terms “up”, “down”, “left”, “right”, etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms describing the positional relationship in the drawings are only used for exemplary illustration, and cannot be understood as a limitation on the present patent, for those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0117] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing an AlN thin film, characterized in that, include: The substrate is subjected to a first stage heat treatment and a second stage heat treatment in a first carrier gas atmosphere, wherein the first carrier gas atmosphere includes hydrogen and nitrogen. The first stage heat treatment process includes: a hydrogen flow rate of 200 L / min to 250 L / min, a nitrogen flow rate of 10 L / min to 20 L / min, a treatment time of 1 min to 2 min, and a treatment temperature range of 1150℃ to 1250℃; the second stage heat treatment process includes: a hydrogen flow rate of 150 L / min to 200 L / min, a nitrogen flow rate of 20 L / min to 30 L / min, a treatment time of 2 min to 4 min, and a treatment temperature range of 1050℃ to 1150℃. The substrate after the second stage heat treatment is subjected to a pre-pass TMA1 treatment; After the pre-pass TMAl treatment is completed, an AlN buffer1 buffer layer is grown on the substrate surface; An AlN buffer2 buffer layer is grown on the surface of the AlN buffer1 buffer layer; An AlN buffer3 buffer layer is grown on the surface of the AlN buffer2 buffer layer; An AlN layer is grown on the surface of the AlN buffer3 buffer layer; The temperature of the pre-pass TMA1 treatment is t0; The growth of the AlN buffer1 buffer layer includes a first isothermal growth stage, where the growth temperature of the first isothermal growth stage is t1, and t1>t0. The growth of the AlN buffer2 layer includes a second isothermal growth stage, the growth temperature of which is t2. <t1; The growth of the AlN buffer3 buffer layer includes a third isothermal growth stage, and the growth temperature of the third isothermal growth stage is t3, where t3 > t1. The growth of the AlN layer includes a fourth isothermal growth stage, where the growth temperature of the fourth isothermal growth stage is t4, and t4 > t3.

2. The method for preparing AlN thin films according to claim 1, characterized in that, △T1 = t1 - t0, where △T1 is greater than or equal to 20℃ and less than or equal to 50℃; △T2=t1-t2, and the range of △T2 is greater than or equal to 20℃ and less than or equal to 50℃; △T3 = t3 - t1, where △T3 is greater than or equal to 20℃ and less than or equal to 50℃; △T4 = t4 - t3, and the range of △T4 is greater than or equal to 20℃ and less than or equal to 50℃.

3. The method for preparing AlN thin films according to claim 1, characterized in that, The growth of the AlN buffer1 buffer layer includes: after the pre-pass TMAl treatment, a first temperature-controlled growth stage is performed, and after the first temperature-controlled growth stage, a first isothermal growth stage is performed; the time of the first temperature-controlled growth stage is s1, and s1 satisfies 0.5min≤s1≤1min. The growth of the AlN buffer2 buffer layer includes: after the growth of the AlN buffer1 buffer layer is completed, a second temperature-controlled growth stage is performed, and after the second temperature-controlled growth stage, a second isothermal growth stage is performed; the time of the second temperature-controlled growth stage is s2, and s2 satisfies 0.5min≤s2≤1min; The growth of the AlN buffer3 buffer layer includes: after the growth of the AlN buffer2 buffer layer is completed, a third temperature-controlled growth stage is performed, and after the third temperature-controlled growth stage, a third isothermal growth stage is performed; the time of the third temperature-controlled growth stage is s3, and s3 satisfies 0.5min≤s3≤1min. The growth of the AlN layer includes: after the growth of the AlN buffer3 layer is completed, a fourth temperature-controlled growth stage is performed, followed by a fourth isothermal growth stage; the duration of the fourth temperature-controlled growth stage is s4, where s4 satisfies 0.5min≤s4≤1min.

4. The method for preparing AlN thin films according to claim 1, characterized in that, The temperature t0 range of the pre-pass TMAl treatment is 1000℃~1100℃; The pre-pass TMAl treatment process further includes: controlling the flow rate of the TMAl to 100 mL / min to 200 mL / min, and the treatment time to 10 s to 20 s.

5. The method for preparing AlN thin films according to claim 1, characterized in that, The growth temperature t1 of the first isothermal growth stage ranges from 1050℃ to 1150℃. The growth conditions for the first isothermal growth stage include: in a second carrier gas atmosphere, controlling the flow rate of the TMAl to be 250 mL / min to 300 mL / min, the flow rate of ammonia to be 5 L / min to 10 L / min, the pressure to be 60 Torr to 90 Torr, and the growth time to be 5 min to 18 min, and growing the AlN buffer1 buffer layer on the substrate surface.

6. The method for preparing AlN thin films according to claim 1, characterized in that, The growth temperature t2 of the second isothermal growth stage ranges from 1000℃ to 1100℃; The growth conditions for the second isothermal growth stage include: in the second carrier gas atmosphere, controlling the flow rate of the TMAl to be 250 mL / min to 300 mL / min, the flow rate of ammonia to be 5 L / min to 10 L / min, the pressure to be 90 Torr to 120 Torr, the growth time to be 7 min to 22 min, and growing the AlN buffer2 buffer layer on the surface of the AlN buffer1 buffer layer.

7. The method for preparing AlN thin films according to claim 1, characterized in that, The growth temperature t3 of the third isothermal growth stage is in the range of 1080℃~1180℃; The growth conditions for the third isothermal growth stage include: in the second carrier gas atmosphere, controlling the flow rate of the TMAl to be 250 mL / min to 300 mL / min, the flow rate of ammonia to be 3 L / min to 8 L / min, the pressure to be 50 Torr to 80 Torr, and the growth time to be 10 min to 30 min, and growing the AlN buffer3 buffer layer on the surface of the AlN buffer2 buffer layer.

8. The method for preparing AlN thin films according to claim 1, characterized in that, The growth temperature t4 of the fourth isothermal growth stage is in the range of 1100℃~1200℃. The growth conditions for the fourth isothermal growth stage include: in a second carrier gas atmosphere, the first and second carrier materials are periodically and alternately introduced, and the flow rate of ammonia is controlled to be 3L / min~8L / min, and the AlN layer is grown on the surface of the AlN buffer3 buffer layer; the first carrier material includes TMIn, and the second carrier material includes TMAl and TMIn. Within one cycle, the time for introducing the first loading material is 10s~20s, and the flow rate of TMIn is 100mL / min~200mL / min; Within one cycle, the time for introducing the second loading material is 1 min to 2 min, the flow rate of TMIn is 50 mL / min to 150 mL / min, and the flow rate of TMAl is 350 mL / min to 400 mL / min.

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