Preparation method of epitaxial wafer structure and LED chip prepared by the same

Abstract

The application discloses a preparation method of an epitaxial wafer structure and an LED chip prepared by the method. The preparation method comprises the following steps: providing a substrate, placing the substrate on a graphite disc of a MOCVD device, then introducing a reaction gas, and growing an epitaxial layer. When the epitaxial layer is grown, the gas introduced into a regional air flow compensation pipeline of the MOCVD device comprises NH3, the generation of pre-reaction is reduced by reducing the flow of NH3 introduced into the regional air flow compensation pipeline, and then the brightness and electrical consistency of the inner circle and the outer circle of the epitaxial wafer are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor devices, and particularly relates to a preparation method of an epitaxial wafer structure and an LED chip prepared by the method. BACKGROUND

[0002] When GaN-based LED epitaxial layers are grown by using MOCVD equipment, with the increase of the use cycle of the MOCVD equipment, the following problems exist: because the linear speed of the inner ring area (the area close to the center of the graphite disc) of the graphite disc is lower than that of the outer ring (the area close to the edge of the outer ring of the graphite disc) under the same rotation speed, the heat dissipation efficiency of the inner ring area is much lower than that of the outer ring, so that the actual temperature of the inner ring area is higher than that of the outer ring. The higher inner ring temperature reduces the density of V-pits (V-pits are crucial for improving the efficiency of hole injection quantum wells) in the area, and further leads to lower electron-hole recombination efficiency in the inner ring area, so that the luminance of the epitaxial wafer in the inner ring area is reduced, and the yield of ESD (electrostatic discharge) is low, and further, the luminance and electrical properties of the inner ring and the outer ring of the epitaxial wafer are significantly different. SUMMARY

[0003] The application aims to provide an epitaxial wafer structure preparation method and an LED chip prepared by the method, which reduces the NH3 flow input of the regional airflow compensation pipeline to reduce the generation of pre-reaction, and further improves the consistency of the luminance and electrical properties of the inner ring and the outer ring of the epitaxial wafer.

[0004] To achieve the above-mentioned purpose, the application provides the following technical scheme:

[0005] The application provides an epitaxial wafer structure preparation method, which comprises the following steps:

[0006] A substrate is provided, the substrate is placed on a graphite disc of MOCVD equipment, and then reaction gas is input to grow an epitaxial layer; when the epitaxial layer is grown, the gas input by a regional airflow compensation pipeline of the MOCVD equipment comprises NH3, and the generation of pre-reaction is reduced by reducing the NH3 flow input of the regional airflow compensation pipeline.

[0007] Optionally, the gas input by the regional airflow compensation pipeline further comprises N2 and / or H2, the flow input of N2 and / or H2 of the regional airflow compensation pipeline is increased while the flow input of NH3 of the regional airflow compensation pipeline is reduced, and the increased flow of N2 and / or H2 is equal to the reduced flow of NH3.

[0008] Optionally, the gas input by the regional airflow compensation pipeline further comprises N2, the flow input of N2 of the regional airflow compensation pipeline is increased while the flow input of NH3 of the regional airflow compensation pipeline is reduced, and the increased flow of N2 is equal to the reduced flow of NH3.

[0009] Optionally, during the growth of the epitaxial layer, the flow of NH3 into the regional gas flow compensation pipeline is controlled to be reduced by 25%-100%, including the end point value.

[0010] Optionally, during the growth of the epitaxial layer, the flow of NH3 into the regional gas flow compensation pipeline is controlled to be reduced by 50%.

[0011] Optionally, during the growth of the epitaxial layer, the gas flowing into the regional gas flow compensation pipeline includes NH3, N2 and H2, wherein the total flow is 10 slm-100 slm, the original flow of NH3 and N2 is 3 slm-20 slm, the flow of NH3 is controlled to be reduced by 3 slm-20 slm, and the flow of N2 is increased by 3 slm-20 slm, including the end point value.

[0012] Optionally, during the growth of the epitaxial layer, the temperature of the inner ring of the graphite disc is controlled to be lower than the temperature of the middle ring or the outer ring.

[0013] Optionally, during the growth of the epitaxial layer, the temperature of the inner ring, the middle ring and the outer ring of the graphite disc is 800℃-1200℃, and the temperature of the inner ring is 10℃-50℃ lower than that of the middle ring or the outer ring, including the end point value.

[0014] Optionally, the epitaxial layer includes N-type semiconductor layer, active layer and P-type semiconductor layer stacked from bottom to top, during the growth of each epitaxial layer, or during the growth of one or more epitaxial layers including the active layer, the flow of NH3 into the regional gas flow compensation pipeline is controlled to be reduced by 25%-100%, and the flow of N2 into the regional gas flow compensation pipeline is increased, and the increased flow of N2 is the same as the reduced flow of NH3.

[0015] Optionally, only during the growth of the active layer, the flow of NH3 into the regional gas flow compensation pipeline is controlled to be reduced, and the flow of N2 into the regional gas flow compensation pipeline is increased, and the active layer includes shallow quantum well layer and multi-quantum well light emitting layer.

[0016] During the growth of the shallow quantum well layer, the growth temperature is controlled as follows: the temperatures of the inner ring, the middle ring and the outer ring of the graphite disc are 880℃, 900℃ and 900℃ respectively, and GaN and In x Ga 1-x N are grown in multiple cycles to form the shallow quantum well layer, wherein x=0.15, the thickness of a single layer of GaN is 8 nm, and the thickness of a single layer of In x Ga 1-x N is 0.5 nm, and the flow of N2 / H2 / NH3 into the regional gas flow compensation pipeline is changed from the original 8 / 0 / 10 slm to 10.5-18 / 0 / 0-7.5 slm.

[0017] In growing the multi-quantum well light emitting layer, the growth temperature is controlled as follows: the inner, middle and outer circle temperatures of the graphite disc are 800℃, 820℃ and 820℃ respectively, and a plurality of cycles of GaN and In x Ga 1-x N are grown to form the multi-quantum well light emitting layer, wherein x is 0.15, the thickness of a single layer of GaN is 20 nm, and the thickness of a single layer of In x Ga 1-x N is 3 nm, and the flow rate of N2 / H2 / NH3 introduced by the regional gas flow compensation pipeline is changed from the original 8 / 0 / 10 slm to 10.5-18 / 0 / 0-7.5 slm.

[0018] Optionally, the epitaxial layer further comprises a low-temperature nucleation layer and a buffer layer, and when each layer of the epitaxial layer is grown, the regional gas flow compensation pipeline is controlled to reduce the flow rate of NH3 introduced and increase the flow rate of N2 introduced, and the growth steps of the epitaxial layer comprise:

[0019] S1, growing a low-temperature nucleation layer on the substrate: annealing the substrate in a hydrogen atmosphere, then reducing the temperature, controlling the inner, middle and outer circle temperatures of the graphite disc to be 830℃, 850℃ and 850℃ respectively, and growing a 20 nm thick low-temperature GaN nucleation layer, wherein the growth pressure is 500 Torr, the rotation speed of the graphite disc is 600 rpm, the V / III molar ratio is 500, and the flow rate of N2 / H2 / NH3 in the regional gas flow compensation pipeline is changed from the original 15 / 0 / 10 slm to 17.5-25 / 0 / 0-7.5 slm;

[0020] S2, growing a buffer layer on the low-temperature nucleation layer: after the low-temperature GaN nucleation layer is grown, in-situ annealing treatment is performed, the annealing temperature is increased, the inner, middle and outer circle temperatures of the graphite disc are 1030℃, 1050℃ and 1050℃ respectively, and the annealing time is 5 min; after annealing, the temperature is increased to grow a non-doped u-GaN buffer layer, wherein the growth thickness is 2 um, the growth pressure is 150 Torr, the rotation speed of the graphite disc is 900 rpm, the V / III molar ratio is 300, and the flow rate of N2 / H2 / NH3 in the regional gas flow compensation pipeline is changed from the original 3 / 15 / 10 slm to 5.5-13 / 15 / 0-7.5 slm;

[0021] S3, growing an N-type semiconductor layer on the buffer layer: after the buffer layer is grown, an n-GaN semiconductor layer with stable doping concentration is grown, wherein the growth thickness is 1.5 um, the inner circle, middle circle and outer circle temperatures of the graphite disc are 1030℃, 1050℃ and 1050℃ respectively, the growth pressure is 150 Torr, the rotation speed of the graphite disc is 800 rpm, the V / III molar ratio is 300, and the flow of N2 / H2 / NH3 in the control area airflow compensation pipeline is changed from the original 10 / 3 / 6 slm to 11.5-16 / 3 / 0-4.5 slm;

[0022] S4, growing a shallow quantum well layer on the N-type semiconductor layer: after the N-type semiconductor layer is grown, the temperature is reduced, the inner circle, middle circle and outer circle temperatures of the graphite disc are controlled to be 880℃, 900℃ and 900℃ respectively, the growth pressure is 200 Torr, the rotation speed of the graphite disc is 600 rpm, the V / III molar ratio is 20, and 5 cycles of GaN and In x Ga 1-x N are grown to form a shallow quantum well layer, wherein x=0.15, the thickness of a single layer of GaN is 8 nm, the thickness of a single layer of In x Ga 1-x N is 0.5 nm, and the flow of N2 / H2 / NH3 in the control area airflow compensation pipeline is changed from the original 8 / 0 / 10 slm to 10.5-18 / 0 / 0-7.5 slm;

[0023] S5, growing a multi-quantum well light-emitting layer on the shallow quantum well layer: after the shallow quantum well layer is grown, the temperature is reduced, the inner circle, middle circle and outer circle temperatures of the graphite disc are controlled to be 800℃, 820℃ and 820℃ respectively, the growth pressure is 200 Torr, the rotation speed of the graphite disc is 600 rpm, the V / III molar ratio is 200, and 10 cycles of GaN and In x Ga 1-x N are grown to form a multi-quantum well light-emitting layer, wherein x is 0.15, the thickness of a single layer of GaN is 20 nm, and the thickness of a single layer of In x Ga 1-x N is 3 nm, and the flow of N2 / H2 / NH3 in the control area airflow compensation pipeline is changed from the original 8 / 0 / 10 slm to 10.5-18 / 0 / 0-7.5 slm;

[0024] S6, growing a P-type semiconductor layer on the multi-quantum well light emitting layer: after the multi-quantum well light emitting layer is grown, the temperature is increased, the temperature of the inner ring, the middle ring and the outer ring of the graphite disc is controlled to be 930 DEG C, 950 DEG C and 950 DEG C respectively, the growth pressure is 200 Torr, the rotation speed of the graphite disc is 1200 revolutions per minute, and the V / III molar ratio is 1000, so that a P-type GaN semiconductor layer with a thickness of 50 nm is formed, wherein the flow rate of N2 / H2 / NH3 in the regional gas flow compensation pipeline is changed from the original 5 / 19 / 6 slm to 6.5-11 / 19 / 0-4.5 slm.

[0025] The application also provides an LED chip comprising an epitaxial wafer structure prepared by the above-mentioned method for preparing an epitaxial wafer structure; the LED chip is any one of a horizontal structure, a vertical structure, a normal structure and a flip structure.

[0026] After the above scheme is adopted, the application has the following advantages:

[0027] 1. In the MOCVD equipment, the central region of the top cover of the Showerhead (used for introducing the reaction gas) is designed as a regional gas flow compensation pipeline, and the regional gas flow compensation pipeline only introduces 5%-10% of the total gas flow as a supplementary gas flow; other gases are introduced by other regions of the Showerhead as a main gas flow. The applicant finds that the main gas flow has a large flow rate and is not easy to produce a pre-reaction product, but the flow rate of the regional gas flow compensation pipeline is small, and the NH3 introduced by the regional gas flow compensation pipeline is easy to pre-react with the nearby Ga source (such as TMGa) in the gas phase due to the high temperature of the inner ring, to generate a GaN pre-reaction product. The growth of the pre-reaction product will block the gas holes of the Showerhead, thereby affecting the uniform and stable introduction of the reaction gas, resulting in uneven growth of the epitaxial layer in the inner ring and the outer ring region, leading to a significant difference in the luminous brightness and electrical properties of the LED epitaxial wafer in the inner ring and the outer ring region, and seriously reducing the overall yield of the device.

[0028] However, when growing the epitaxial layer, by reducing or even closing the flow rate of NH3 introduced in the regional gas flow compensation pipeline, the generation of the pre-reaction product can be effectively reduced, the gas holes of the Showerhead can be avoided from being blocked, the reaction gas can be uniformly and stably introduced into the reaction chamber, the consistency of the growth of the epitaxial layer in the inner ring and the outer ring can be improved, and the brightness and electrical consistency of the inner ring and the outer ring of the epitaxial wafer can be effectively improved, thereby improving the overall yield of the device.

[0029] 2、The application reduces the flow of NH3 in the regional air flow compensation pipeline while increasing the flow of N2 in the regional air flow compensation pipeline, and the reduced flow of NH3 is the same as the increased flow of N2, so that the total flow of the regional air flow compensation pipeline is unchanged, and the molecular mass of N2 is relatively close to that of NH3, so the performance is also relatively close, the supplementary air flow has the functions of supplementing the center air pressure, assisting temperature control, and adjusting the uniformity of epitaxial layer growth, and increasing the same amount of N2 can ensure that the function of the supplementary air flow is not affected, while also improving the consistency of the growth of the inner and outer circles of the epitaxial layer.

[0030] 3、The application also controls the temperature of the inner circle of the graphite disc to be lower than that of the middle circle or the outer circle when growing the epitaxial layer, which can effectively improve the problem of low brightness caused by the actual high temperature of the inner circle, further improve the brightness and electrical consistency of the inner and outer circles of the epitaxial layer, and improve the overall yield of the device. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The process flow chart of the preparation method of the application is shown in the figure.

[0032] Figure 2 The structure diagram of the epitaxial wafer of the application is shown in the figure.

[0033] Label explanation:

[0034] 1, substrate; 2, low-temperature nucleation layer; 3, buffer layer; 4, N-type semiconductor layer; 5, active layer; 51, shallow quantum well layer; 52, multi-quantum well light emitting layer; 6, P-type semiconductor layer. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application, and all the range values of the application include the end point values. The reaction gas described in the application includes gas that is easy to participate in chemical reaction and inert gas that is not easy to participate in chemical reaction.

[0036] Please refer to Figure 1 The application provides a preparation method of an epitaxial wafer structure, comprising:

[0037] A substrate is provided, and the substrate 1 is placed on a graphite tray of a MOCVD device, and then a reaction gas including a Ga source, an In source, NH3, N2, H2, etc. is introduced into a reaction chamber to grow an epitaxial layer. When the epitaxial layer is grown, the gas introduced by a regional gas flow compensation pipeline of the MOCVD device includes NH3. The regional gas flow compensation pipeline is a Pyropurge, which is a gas management system integrated in the MOCVD device, and realizes active regulation of the local atmosphere by injecting high-purity reaction gas into the reaction chamber. In this application, the regional gas flow compensation pipeline is located in the central region of the top cover of the Showerhead (a showerhead used to introduce reaction gas). The regional gas flow compensation pipeline only introduces 5%-10% of the total gas flow as a supplementary gas flow; other gases are introduced by other regions of the Showerhead as a main gas flow. The applicant found that the main gas flow is large and not easy to produce a pre-reaction product, but the flow of the regional gas flow compensation pipeline is small, and it is directly opposite to the inner ring region of the graphite tray. Because the temperature of the inner ring is high, the NH3 introduced by the regional gas flow compensation pipeline is easy to pre-react with the nearby Ga source (such as TMGa) in the gas phase to generate a GaN pre-reaction product. The growth of the pre-reaction product will block the gas holes of the Showerhead, thereby affecting the uniform and stable introduction of the reaction gas, causing the epitaxial layer to grow unevenly in the inner and outer ring regions, resulting in a significant difference in the luminous brightness and electrical properties of the LED epitaxial wafer between the inner and outer ring regions, and severely reducing the overall yield of the device.

[0038] Therefore, by reducing the NH3 flow introduced by the regional gas flow compensation pipeline, the present application can reduce the reaction between NH3 and the Ga source to produce a GaN pre-reaction product, effectively reduce the generation of the pre-reaction product, avoid blocking the gas holes of the Showerhead, enable the reaction gas to be uniformly and stably introduced, improve the consistency of the growth of the epitaxial layer in the inner and outer rings, and further effectively improve the brightness and electrical consistency of the inner and outer rings of the epitaxial wafer, and improve the overall yield of the device. The NH3 flow introduced by the regional gas flow compensation pipeline can be reduced during the growth of each layer of the epitaxial layer; or the NH3 flow introduced by the regional gas flow compensation pipeline can be reduced during the growth of a certain layer or at least two layers of the epitaxial layer.

[0039] Specifically, the gas introduced by the regional gas flow compensation pipeline further includes N2 and / or H2. While reducing the NH3 flow introduced by the regional gas flow compensation pipeline, the flow of other gases introduced by the regional gas flow compensation pipeline is increased, that is, the flow of N2 and / or H2 is increased, and the increased flow of N2 and / or H2 is equal to the reduced flow of NH3. In this way, the total flow of the supplementary gas flow introduced by the regional gas flow compensation pipeline remains unchanged, and the effect of the supplementary gas flow on the growth of the epitaxial layer is not affected.

[0040] Preferably, while reducing the flow of NH3 in the regional gas flow compensation pipeline, only the flow of N2 in the regional gas flow compensation pipeline is increased, and the increased flow of N2 is equal to the reduced flow of NH3. Since the molecular mass of N2 is close to that of NH3, the performance is also close. Selecting the same amount of N2 can ensure that the function of the compensation gas flow is not affected, and at the same time can improve the consistency of the growth of the inner and outer rings of the epitaxial layer.

[0041] Optionally, when growing an epitaxial layer, the flow of NH3 in the regional gas flow compensation pipeline is reduced by 25%-100%, that is, the original flow of NH3 in the regional gas flow compensation pipeline is reduced by 25%-100%, which can effectively improve the brightness and electrical consistency of the inner and outer rings of the epitaxial wafer. Reducing the flow of NH3 by 50% has the best effect. It should be noted that the flow of NH3 can be reduced by 100%, that is, the flow of NH3 can be controlled to 0, which is equivalent to directly closing the flow of NH3. This setting can also improve the brightness and electrical consistency of the inner and outer rings of the epitaxial wafer.

[0042] Optionally, in the case of growing an epitaxial layer, the reaction gas includes NH3, N2 and H2, the total flow of the gas introduced by the regional gas flow compensation pipeline is 10 slm-100 slm, and the original flow of NH3 and N2 is 3 slm-20 slm. The flow of NH3 can be controlled to reduce 3 slm-20 slm, and at the same time, the flow of N2 can be increased by 3 slm-20 slm.

[0043] Preferably, when growing an epitaxial layer, the temperature of the inner ring of the graphite disc is controlled to be lower than that of the middle ring or the outer ring, so as to effectively improve the problem of low brightness caused by the actual high temperature of the inner ring, further improve the brightness and electrical consistency of the inner and outer rings of the epitaxial wafer, and improve the overall yield of the device.

[0044] Optionally, the temperature difference between the inner and outer rings of the graphite disc can be adjusted according to the actual temperature difference. When growing an epitaxial layer, the temperature of the inner, middle and outer rings of the graphite disc is 800℃-1200℃, and the temperature of the inner ring is controlled to be 10℃-50℃ lower than that of the middle ring or the outer ring.

[0045] Specifically, as Figure 2As shown, the epitaxial layer includes, from bottom to top, a low-temperature nucleation layer 2, a buffer layer 3, an N-type semiconductor layer 4, an active layer 5, and a P-type semiconductor layer 6, which is sequentially grown in layers. The active layer 5 is the main light-emitting region. The flow of NH3 in the regional gas flow compensation pipeline can be reduced by 25%-100% only when the active layer 5 is grown. Of course, the flow of NH3 in the regional gas flow compensation pipeline can also be reduced by 25%-100% when each layer of the epitaxial layer is grown, or when one or at least two layers of the epitaxial layer are grown. The above growth methods can effectively improve the brightness and electrical consistency of the inner and outer rings of the epitaxial layer. Preferably, the flow of NH3 in the regional gas flow compensation pipeline is reduced by 25%-100% when one or more layers of the epitaxial layer, including the active layer, are grown.

[0046] The following is further illustrated by way of examples and multiple embodiments:

[0047] Example 1:

[0048] This example is a conventional method for growing an epitaxial layer, without reducing the flow of NH3 in the regional gas flow compensation pipeline, as shown in Figure 1 The preparation method specifically includes the following steps:

[0049] S1, growing a low-temperature nucleation layer 2 on a substrate 1: the substrate 1 can be a sapphire substrate. The sapphire substrate is annealed in a hydrogen atmosphere to clean the surface of the substrate 1. At this time, the temperature is 1050°C. Then, the temperature is lowered to 850°C (i.e., the inner, middle, and outer rings of the graphite disc are all at 850°C). TMGa (Ga and other reaction gases) is introduced to grow a 20-nm-thick low-temperature GaN nucleation layer. The growth pressure is 500 Torr, the graphite disc rotation speed is 600 rpm, the V / III molar ratio is 500 (i.e., the molar ratio of NH3 / TMGa is 500), and the flow rates of N2 / H2 / NH3 introduced into the regional gas flow compensation pipeline are 15 / 0 / 10 slm, respectively.

[0050] S2, growing a buffer layer 3 on the low-temperature nucleation layer 2: after the growth of the low-temperature GaN nucleation layer is completed, in-situ annealing is performed. The annealing temperature is raised to 1050°C (i.e., the inner, middle, and outer rings of the graphite disc are all at 1050°C). The annealing time is 5 min. After annealing, the temperature is raised to 1100°C to grow a non-doped u-GaN buffer layer. The growth thickness is 2 um. The growth process temperature is 1120°C. The growth pressure is 150 Torr. The graphite disc rotation speed is 900 rpm. The V / III molar ratio is 300. The flow rates of N2 / H2 / NH3 introduced into the regional gas flow compensation pipeline are 3 / 15 / 10 slm, respectively.

[0051] S3, growing an N-type semiconductor layer 4 on the buffer layer 3: after the buffer layer 3 is grown, an n-GaN semiconductor layer with stable doping concentration is grown, wherein the growth thickness is 1.5 um, the growth temperature is 1050 °C (i.e. the inner, middle and outer rings of the graphite disc are all at 1050 °C), the growth pressure is 150 Torr, the rotation speed of the graphite disc is 800 rpm, the V / III molar ratio is 300, and the flow rates of N2 / H2 / NH3 in the regional gas flow compensation pipeline are 10 / 3 / 6 slm respectively;

[0052] S4, growing a shallow quantum well layer 51 on the N-type semiconductor layer 4: after the N-type semiconductor layer 4 is grown, the temperature is reduced to 900 °C (i.e. the three rings of the graphite disc are all at 900 °C), the growth pressure is 200 Torr, the rotation speed of the graphite disc is 600 rpm, the V / III molar ratio is 20, and 5 cycles of GaN and In x Ga 1-x N are grown to form the shallow quantum well layer 51, wherein x = 0.15, the thickness of a single layer of GaN is 8 nm, the thickness of a single layer of In x Ga 1-x N is 0.5 nm, and the flow rates of N2 / H2 / NH3 in the regional gas flow compensation pipeline are 8 / 0 / 10 slm respectively;

[0053] S5, growing a multiple quantum well light-emitting layer 52 on the shallow quantum well layer 51: after the shallow quantum well layer 51 is grown, the temperature is reduced to 820 °C (i.e. the three rings of the graphite disc are all at 820 °C), the growth pressure is 200 Torr, the rotation speed of the graphite disc is 600 rpm, the V / III molar ratio is 200, and 10 cycles of GaN and In x Ga 1-x N are grown to form the multiple quantum well light-emitting layer 52, wherein x is 0.15, the thickness of a single layer of GaN is 20 nm, and the thickness of a single layer of In x Ga 1-x N is 3 nm, and the flow rates of N2 / H2 / NH3 in the regional gas flow compensation pipeline are 8 / 0 / 10 slm respectively;

[0054] S6, growing a P-type semiconductor layer 6 on the multiple quantum well light-emitting layer 52: after the multiple quantum well light-emitting layer 52 is grown, the temperature is increased to 950 °C (i.e. the three rings of the graphite disc are all at 950 °C), the growth pressure is 200 Torr, the rotation speed of the graphite disc is 1200 rpm, the V / III molar ratio is 1000, the mole component content of Mg is 0.3%, and a P-type GaN semiconductor layer with a thickness of 50 nm is formed, wherein the flow rates of N2 / H2 / NH3 in the regional gas flow compensation pipeline are 5 / 19 / 6 slm respectively.

[0055] Example 1:

[0056] Compared with Comparative Example 1, each layer of the epitaxial layer in the present example reduces the NH3 flow rate in the regional airflow compensation pipeline by 50%, increases the N2 flow rate, and controls the inner ring temperature of the graphite disc to be less than the middle ring and outer ring temperatures. The specific steps are as follows:

[0057] S1, growing a low-temperature nucleation layer 2 on a substrate 1: the substrate 1 can be selected as a sapphire substrate, the sapphire substrate is annealed in a hydrogen atmosphere, the substrate surface is cleaned, at this time the temperature is 1050°C, then the temperature is lowered, the inner ring, middle ring and outer ring temperatures of the graphite disc are controlled to be 830°C, 850°C and 850°C respectively, and a 20 nm thick low-temperature GaN nucleation layer is grown, wherein the growth pressure is 500 Torr, the graphite disc rotation speed is 600 rpm, the V / III molar ratio is 500, and the N2 / H2 / NH3 flow rate in the regional airflow compensation pipeline is changed from the original 15 / 0 / 10 slm to 20 / 0 / 5 slm, that is, the NH3 flow rate is reduced by 5 slm, which is reduced by 50%;

[0058] S2, growing a buffer layer 3 on the low-temperature nucleation layer 2: after the low-temperature GaN nucleation layer is grown, in-situ annealing treatment is performed, the annealing temperature is increased, the inner ring, middle ring and outer ring temperatures of the graphite disc are 1030°C, 1050°C and 1050°C respectively, and the annealing time is 5 min; after annealing, the temperature is increased to 1100°C, and a non-doped u-GaN buffer layer is grown, wherein the growth thickness is 2 um, the growth process temperature is 1120°C, the growth pressure is 150 Torr, the graphite disc rotation speed is 900 rpm, the V / III molar ratio is 300, and the N2 / H2 / NH3 flow rate in the regional airflow compensation pipeline is changed from the original 3 / 15 / 10 slm to 8 / 15 / 5 slm;

[0059] S3, growing an N-type semiconductor layer 4 on the buffer layer 3: after the buffer layer 3 is grown, an n-GaN semiconductor layer with stable doping concentration is grown, wherein the growth thickness is 1.5 um, the inner ring, middle ring and outer ring temperatures of the graphite disc are 1030°C, 1050°C and 1050°C respectively, the growth pressure is 150 Torr, the graphite disc rotation speed is 800 rpm, the V / III molar ratio is 300, and the N2 / H2 / NH3 flow rate in the regional airflow compensation pipeline is changed from the original 10 / 3 / 6 slm to 13 / 3 / 3 slm;

[0060] S4, growing a shallow quantum well layer 51 on the N-type semiconductor layer 4: after the N-type semiconductor layer 4 is grown, the temperature is lowered, the inner ring, middle ring and outer ring temperatures of the graphite disc are controlled to be 880°C, 900°C and 900°C respectively, the growth pressure is 200 Torr, the graphite disc rotation speed is 600 rpm, the V / III molar ratio is 20, and 5 cycles of GaN and Inx Ga 1-x N, forming the shallow quantum well layer 51, wherein x = 0.15, the thickness of a single layer of GaN is 8 nm, and the thickness of a single layer of In x Ga 1-x N is 0.5 nm, and the flow rate of N2 / H2 / NH3 in the compensation pipeline of the control region is changed from the original 8 / 0 / 10 slm to 13 / 0 / 5 slm.

[0061] S5, growing the multi-quantum well light-emitting layer 52 on the shallow quantum well layer 51: after the growth of the shallow quantum well layer 51 is completed, the temperature is lowered, the temperatures of the inner, middle, and outer circles of the graphite disc are controlled to be 800℃, 820℃, and 820℃ respectively, the growth pressure is 200 Torr, the rotation speed of the graphite disc is 600 rpm, the V / III molar ratio is 200, and 10 cycles of GaN and In x Ga 1-x N are grown, forming the multi-quantum well light-emitting layer 52, wherein x is 0.15, the thickness of a single layer of GaN is 20 nm, and the thickness of a single layer of In x Ga 1-x N is 3 nm, and the flow rate of N2 / H2 / NH3 in the compensation pipeline of the control region is changed from the original 8 / 0 / 10 slm to 13 / 0 / 5 slm.

[0062] S6, growing the P-type semiconductor layer 6 on the multi-quantum well light-emitting layer 52: after the growth of the multi-quantum well light-emitting layer 52 is completed, the temperature is raised, the temperatures of the inner, middle, and outer circles of the graphite disc are controlled to be 930℃, 950℃, and 950℃ respectively, the growth pressure is 200 Torr, the rotation speed of the graphite disc is 1200 rpm, the V / III molar ratio is 1000, the mole fraction of Mg is 0.3%, and a P-type GaN semiconductor layer with a thickness of 50 nm is formed, wherein the flow rate of N2 / H2 / NH3 in the compensation pipeline of the control region is changed from the original 5 / 19 / 6 slm to 8 / 19 / 3 slm.

[0063] Example 2:

[0064] Compared with Example 1, in this example, only when the shallow quantum well layer 51 and the multi-quantum well light-emitting layer 52 are grown, the flow rate of NH3 in the compensation pipeline of the region is reduced by 50%, and the same flow rate of N2 is introduced, the flow rate of NH3 in the compensation pipeline of the other epitaxial layer region remains unchanged, and the other steps are the same as those in Example 1.

[0065] Example 3:

[0066] Compared with Example 1, in this example, the flow of NH3 supplied by the compensation pipe in the controlled area is reduced by 25% and the same flow of N2 is supplied when each layer of the epitaxial layer is grown, and other steps are the same as those in Example 1.

[0067] Example 4:

[0068] Compared with Example 1, in this example, the flow of NH3 supplied by the compensation pipe in the controlled area is reduced by 75% and the same flow of N2 is supplied when each layer of the epitaxial layer is grown, and other steps are the same as those in Example 1.

[0069] Example 5:

[0070] Compared with Example 1, in this example, the flow of NH3 supplied by the compensation pipe in the controlled area is reduced by 100% and the same flow of N2 is supplied when each layer of the epitaxial layer is grown, and other steps are the same as those in Example 1.

[0071] Example 6:

[0072] Compared with Example 1, in this example, the temperature of the three circles of the graphite disc is the same, and the temperature is the same as that in Comparative Example 1, and other steps are the same as those in Example 1.

[0073] The samples of the epitaxial wafers prepared in the above examples and comparative examples are each taken 10 pieces to perform a brightness test at a current of 60 mA and an ESD of 4000 V, and the average brightness and ESD of 4000 V are calculated, wherein the brightness of the outer circle of the epitaxial wafer is 214 mW, and the ESD of 4000 V is 98%, and the calculation results of the inner circle are as shown in Table 1.

[0074] Table 1-Test results of the inner circle of the examples and comparative examples

[0075]

[0076] From the above data, it can be seen that reducing or even closing the flow of NH3 supplied by the compensation pipe in the controlled area and controlling the temperature of the inner circle of the graphite disc to be lower than the temperature of the middle circle and the outer circle can improve the brightness and ESD of 4000 V of the inner circle of the epitaxial wafer, and the effect obtained by reducing the flow of NH3 by 50% is the best. Moreover, in Example 2, the flow of NH3 supplied by the compensation pipe in the controlled area is reduced only when the active layer 5 is grown, and the brightness and yield obtained by the test are not much different from those in Example 1, so that reducing the flow of NH3 supplied by the compensation pipe in the controlled area only when the active layer 5 is grown can also effectively improve the brightness and electrical properties of the inner circle of the epitaxial wafer, and the preparation process is simpler, of course, the effect obtained by controlling the flow of NH3 supplied by the compensation pipe in the controlled area when each layer of the epitaxial layer is grown is better, and a suitable process can be selected according to actual needs.

[0077] The application further provides an LED chip comprising an epitaxial wafer structure prepared by the preparation method of the epitaxial wafer structure.

[0078] It is worth noting that the thickness of the substrate 1, the low-temperature nucleation layer 2, the buffer layer 3, the N-type semiconductor layer 4, the active layer 5 and the P-type semiconductor layer 6 shown in the drawings of the present application are only examples and do not represent the true thickness. Moreover, the true proportions between the substrate 1, the low-temperature nucleation layer 2, the buffer layer 3, the N-type semiconductor layer 4, the active layer 5 and the P-type semiconductor layer 6 are not as shown in the drawings, but are only for reference.

[0079] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be mutually referred to.

[0080] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of producing an epitaxial wafer structure, characterized by, The application relates to a method for growing an epitaxial layer on a substrate, comprising: providing a substrate, placing the substrate on a graphite disc in a MOCVD device, and then introducing reaction gas to grow the epitaxial layer; during the growth of the epitaxial layer, the temperature of the inner circle of the graphite disc is controlled to be lower than the temperature of the middle circle or the outer circle, and the gas introduced by the regional gas flow compensation pipeline of the MOCVD device comprises NH3, and the generation of pre-reaction substances is reduced by reducing the flow of NH3 introduced by the regional gas flow compensation pipeline; The gas introduced by the regional gas flow compensation pipeline further comprises N2 and / or H2, and the flow of N2 and / or H2 introduced by the regional gas flow compensation pipeline is increased while the flow of NH3 introduced by the regional gas flow compensation pipeline is reduced, and the increased flow of N2 and / or H2 is equal to the reduced flow of NH3.

2. The method of claim 1, wherein: During the growth of the epitaxial layer, the flow of NH3 introduced by the regional gas flow compensation pipeline is controlled to be reduced by 25%-100%, including the end point value.

3. The method of claim 1, wherein: During the growth of the epitaxial layer, the flow of NH3 introduced by the regional gas flow compensation pipeline is controlled to be reduced by 50%.

4. The method of claim 1, wherein: During the growth of the epitaxial layer, the gas introduced by the regional gas flow compensation pipeline comprises NH3, N2 and H2, wherein the total flow introduced is 10 slm-100 slm, the original flow of NH3 and N2 is 3 slm-20 slm, the flow of NH3 is controlled to be reduced by 3 slm-20 slm, and the flow of N2 is controlled to be increased by 3 slm-20 slm, including the end point value.

5. The method of claim 1, wherein: During the growth of the epitaxial layer, the temperature of the inner circle, the middle circle and the outer circle of the graphite disc is 800-1200 DEG C, and the temperature of the inner circle is 10-50 DEG C lower than that of the middle circle or the outer circle, including the end point value.

6. The method of claim 1, wherein: The gas introduced by the regional gas flow compensation pipeline comprises NH3, N2 and H2, and the epitaxial layer comprises a N-type semiconductor layer, an active layer and a P-type semiconductor layer which are sequentially stacked and grown from bottom to top, during the growth of each epitaxial layer or one or more epitaxial layers including the active layer, the flow of NH3 introduced by the regional gas flow compensation pipeline is controlled to be reduced by 25%-100%, and the flow of N2 introduced by the regional gas flow compensation pipeline is controlled to be increased, and the increased flow of N2 is equal to the reduced flow of NH3.

7. The method of claim 6, wherein: Only during the growth of the active layer, the flow of NH3 introduced by the regional gas flow compensation pipeline is controlled to be reduced, and the flow of N2 introduced by the regional gas flow compensation pipeline is controlled to be increased, and the active layer comprises a shallow quantum well layer and a multi-quantum well light-emitting layer; In growing the shallow quantum well layer, the growth temperature is controlled as follows: the inner, middle and outer circle temperatures of the graphite disc are 880℃, 900℃ and 900℃ respectively, GaN and In x Ga 1-x N are grown for multiple cycles, forming a shallow quantum well layer, wherein x=0.15, the thickness of a single layer of GaN is 8 nm, the thickness of a single layer of In x Ga 1-x N is 0.5 nm, and the flow rate of N2 / H2 / NH3 supplied by the flow compensation pipeline of the control area is changed from the original 8 / 0 / 10 slm to 10.5-18 / 0 / 0-7.5 slm. In the growth of the multi-quantum well light emitting layer, the growth temperature is controlled as follows: the inner, middle and outer circle temperatures of the graphite disc are 800℃, 820℃ and 820℃ respectively, and a plurality of cycles of GaN and In x Ga 1-x N are grown to form the multi-quantum well light emitting layer, wherein x is 0.15, the thickness of a single layer of GaN is 20 nm, the thickness of a single layer of In x Ga 1-x N is 3 nm, and the flow rate of N2 / H2 / NH3 introduced by the flow compensation pipeline of the control area is changed from the original 8 / 0 / 10 slm to 10.5-18 / 0 / 0-7.5 slm.

8. The method of claim 6, wherein: The epitaxial layer further comprises a low-temperature nucleation layer and a buffer layer, during the growth of each layer of the epitaxial layer, the flow of NH3 introduced by the regional gas flow compensation pipeline is controlled to be reduced, and the flow of N2 introduced by the regional gas flow compensation pipeline is controlled to be increased, and the growth steps of the epitaxial layer comprise: S1, growing a low-temperature nucleation layer on a substrate: annealing the substrate in a hydrogen atmosphere, then lowering the temperature, controlling the temperatures of the inner, middle and outer circles of the graphite disc to be 830 DEG C, 850 DEG C and 850 DEG C respectively, growing a 20 nm thick low-temperature GaN nucleation layer, wherein the growth pressure is 500 Torr, the rotation speed of the graphite disc is 600 rpm, the V / III molar ratio is 500, and the flow rate of N2 / H2 / NH3 in the regional gas flow compensation pipeline is changed from the original 15 / 0 / 10 slm to 17.5-25 / 0 / 0-7.5 slm; S2, growing a buffer layer on the low-temperature nucleation layer: after the low-temperature GaN nucleation layer is grown, in-situ annealing treatment is performed, the annealing temperature is increased, the temperatures of the inner, middle and outer circles of the graphite disc are controlled to be 1030 DEG C, 1050 DEG C and 1050 DEG C respectively, and the annealing time is 5 min; after annealing, the temperature is increased to grow a non-doped u-GaN buffer layer, wherein the growth thickness is 2 um, the growth pressure is 150 Torr, the rotation speed of the graphite disc is 900 rpm, the V / III molar ratio is 300, and the flow rate of N2 / H2 / NH3 in the regional gas flow compensation pipeline is changed from the original 3 / 15 / 10 slm to 5.5-13 / 15 / 0-7.5 slm; S3, growing an n-type semiconductor layer on the buffer layer: after the buffer layer is grown, an n-GaN semiconductor layer with stable doping concentration is grown, wherein the growth thickness is 1.5 um, the temperatures of the inner, middle and outer circles of the graphite disc are 1030 DEG C, 1050 DEG C and 1050 DEG C respectively, the growth pressure is 150 Torr, the rotation speed of the graphite disc is 800 rpm, the V / III molar ratio is 300, and the flow rate of N2 / H2 / NH3 in the regional gas flow compensation pipeline is changed from the original 10 / 3 / 6 slm to 11.5-16 / 3 / 0-4.5 slm; S4, growing a shallow quantum well layer on the N-type semiconductor layer: after the N-type semiconductor layer is grown, the temperature is reduced, the temperatures of the inner circle, the middle circle and the outer circle of the graphite disc are controlled to be 880℃, 900℃ and 900℃ respectively, the growth pressure is 200 Torr, the rotation speed of the graphite disc is 600 rpm, the V / III mole ratio is 20, and GaN and In x Ga 1-x N are grown for 5 cycles to form a shallow quantum well layer, wherein x=0.15, the thickness of a single layer of GaN is 8 nm, the thickness of a single layer of In x Ga 1-x N is 0.5 nm, and the flow rate of N2 / H2 / NH3 introduced by the flow compensation pipeline is changed from the original 8 / 0 / 10 slm to 10.5-18 / 0 / 0-7.5 slm. S5, growing a multi-quantum well light emitting layer on the shallow quantum well layer: after the growth of the shallow quantum well layer is completed, the temperature is reduced, the temperature of the inner circle, middle circle and outer circle of the graphite disc is controlled to be 800℃, 820℃ and 820℃ respectively, the growth pressure is 200 Torr, the rotation speed of the graphite disc is 600 rpm, the V / III molar ratio is 200, and 10 cycles of GaN and In x Ga 1-x N are grown to form a multi-quantum well light emitting layer, wherein x is 0.15, the thickness of a single layer of GaN is 20 nm, the thickness of a single layer of In x Ga 1-x N is 3 nm, and the flow rate of N2 / H2 / NH3 introduced by the control area gas flow compensation pipeline is changed from the original 8 / 0 / 10 slm to 10.5-18 / 0 / 0-7.5 slm. S6, growing a p-type semiconductor layer on the multiple quantum well light-emitting layer: after the multiple quantum well light-emitting layer is grown, the temperature is increased, the temperatures of the inner, middle and outer circles of the graphite disc are controlled to be 930 DEG C, 950 DEG C and 950 DEG C respectively, the growth pressure is 200 Torr, the rotation speed of the graphite disc is 1200 rpm, the V / III molar ratio is 1000, a 50 nm thick p-type GaN semiconductor layer is formed, and the flow rate of N2 / H2 / NH3 in the regional gas flow compensation pipeline is changed from the original 5 / 19 / 6 slm to 6.5-11 / 19 / 0-4.5 slm.

9. An LED chip, characterized by: The LED chip is any one of a horizontal structure, a vertical structure, a normal structure and a flip structure. The LED chip is any one of a horizontal structure, a vertical structure, a normal structure and a flip structure.

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