LED epitaxial wafer and preparation method thereof

Abstract

The present invention provides an LED epitaxial wafer and a preparation method thereof, comprising: providing a substrate; heating the substrate and performing nitridation treatment on the substrate with a nitriding gas to form a warpage control layer on the surface of the substrate, wherein the nitriding gas at least includes ammonia; and sequentially forming an N-type semiconductor layer, a multi-quantum well layer and a P-type semiconductor layer on the surface of the warpage control layer. The substrate is heated and nitrided with a nitriding gas, so that the ammonia combines with some chemical bonds on the surface of the substrate to form a material having a lattice constant between the substrate and the semiconductor layer, namely the warpage control layer, so as to reduce the compressive stress or tensile stress generated by the lattice mismatch between the substrate and the semiconductor layer, thereby reducing and changing the warpage of the LED epitaxial wafer, improving the wavelength uniformity of the LED epitaxial wafer, improving the yield of the LED epitaxial wafer, and saving the sorting cost of the LED chips formed subsequently.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and more specifically, to an LED epitaxial wafer and a preparation method thereof. Background Art

[0002] LED epitaxial wafers refer to epitaxial structures grown on substrates such as sapphire and silicon. LED epitaxial wafers are at the upstream of the LED industry chain, and are the link with the highest technical content in the semiconductor lighting industry, and have the greatest impact on the quality and cost control of the final product. In recent years, the prosperity of the downstream application market has driven the rapid development of the LED industry, and also brought good development opportunities to the LED epitaxial wafer market.

[0003] In order to save production costs, the size of existing LED epitaxial wafers has been expanded from 2 inches to 4 inches, and even 6 inches and 8 inches. However, as the size of LED epitaxial wafers increases, the growth of LED epitaxial wafers also faces many difficulties, such as excessive warping of LED epitaxial wafers due to lattice mismatch, which seriously affects the performance of LED epitaxial wafers. Summary of the invention

[0004] In view of this, the present invention provides an LED epitaxial wafer and a method for preparing the same, so as to solve the problem of excessive warping faced by the LED epitaxial wafer.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing an LED epitaxial wafer, comprising:

[0007] providing a substrate;

[0008] Heating the substrate and performing a nitridation treatment on the substrate using a nitridation gas to form a warpage control layer on the surface of the substrate, wherein the nitridation gas includes at least ammonia;

[0009] An N-type semiconductor layer, a multi-quantum well layer and a P-type semiconductor layer are sequentially formed on the surface of the warpage control layer.

[0010] Optionally, the nitriding gas is a mixed gas of ammonia and hydrogen;

[0011] Alternatively, the nitriding gas is a mixed gas of ammonia and nitrogen;

[0012] Alternatively, the nitriding gas is a mixed gas of ammonia, hydrogen and nitrogen.

[0013] Optionally, the total flow rate of the nitriding gas is 20SLM to 600SLM;

[0014] Wherein, the flow rate of hydrogen is 0SLM to 300SLM, including the endpoint value, the flow rate of nitrogen is 7SLM to 600SLM, including the endpoint value, and the flow rate of ammonia is 1SLM to 220SLM, including the endpoint value;

[0015] Alternatively, the flow rate of hydrogen is 7SLM to 300SLM, including endpoint values, the flow rate of nitrogen is 0SLM to 600SLM, including endpoint values, and the flow rate of ammonia is 1SLM to 220SLM, including endpoint values.

[0016] Optionally, the ratio of ammonia, nitrogen and hydrogen is 1:0:300 to 1:0.1:1;

[0017] Alternatively, the ratio of ammonia, nitrogen and hydrogen is 1:600:0 to 1:0.1:1.

[0018] Optionally, the nitriding treatment time is 0.5min to 20min;

[0019] The temperature of the nitriding treatment is 600°C to 1200°C.

[0020] Optionally, performing nitridation treatment on the substrate includes:

[0021] Performing nitridation treatment on the substrate in a constant temperature manner;

[0022] Alternatively, the substrate is nitrided by gradually increasing the temperature.

[0023] Optionally, before sequentially forming an N-type semiconductor layer, a multi-quantum well layer and a P-type semiconductor layer on the surface of the warpage control layer, the method further comprises:

[0024] forming a buffer layer on the surface of the warpage control layer;

[0025] Alternatively, a buffer layer and a non-doped semiconductor layer are sequentially formed on the surface of the warpage control layer.

[0026] An LED epitaxial wafer comprises a substrate, a warpage control layer located on the surface of the substrate, an N-type semiconductor layer, a multi-quantum well layer and a P-type semiconductor layer located on the surface of the warpage control layer in sequence;

[0027] The warpage control layer is formed by heating the substrate and performing a nitridation treatment on the substrate using a nitriding gas, wherein the nitriding gas includes at least ammonia.

[0028] Optionally, the substrate is a PSS-coated AlN substrate or a sapphire substrate.

[0029] Optionally, it further includes a buffer layer located between the warpage control layer and the N-type semiconductor layer;

[0030] Alternatively, it further includes a buffer layer and a non-doped semiconductor layer which are sequentially located between the warpage control layer and the N-type semiconductor layer.

[0031] Compared with the prior art, the technical solution provided by the present invention has the following advantages:

[0032] The LED epitaxial wafer and the preparation method thereof provided by the present invention heat the substrate and perform nitridation treatment on the substrate using nitriding gas, so that ammonia gas is combined with some chemical bonds on the surface of the substrate to form a material having a lattice constant between that of the substrate and the semiconductor layer, namely, a warp control layer, thereby reducing the compressive stress or tensile stress generated by lattice mismatch between the substrate and the semiconductor layer, thereby reducing and changing the warp of the LED epitaxial wafer, improving the wavelength uniformity of the LED epitaxial wafer, improving the yield of the LED epitaxial wafer, and saving the sorting cost of the LED chips formed subsequently.

[0033] Furthermore, since the present invention only uses atmosphere to nitride the substrate surface to form a warp control layer before epitaxial growth, and no additional gallium source is introduced to grow an additional epitaxial layer, the warping degree of the final epitaxial wafer can be effectively adjusted without increasing the thickness of the epitaxial layer, thereby saving costs.

[0034] In addition, by nitriding the substrate, the low-dimensional oxide on the surface of the substrate can be decomposed to form nitride, thereby reducing the impurity concentration in the substrate, improving the crystal quality of the subsequently formed film layer, and further improving the optoelectronic performance of the LED epitaxial structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0036] Figure 1 A flow chart of a method for preparing an LED epitaxial wafer provided by an embodiment of the present invention;

[0037] Figure 2 Schematic diagram of wavelength distribution of LED epitaxial wafer in the prior art;

[0038] Figure 3 A schematic diagram of wavelength distribution of an LED epitaxial wafer provided in one embodiment of the present invention;

[0039] Figure 4 A schematic diagram of wavelength distribution of an LED epitaxial wafer provided in another embodiment of the present invention;

[0040] Figure 5 A schematic diagram of wavelength distribution of an LED epitaxial wafer provided in another embodiment of the present invention;

[0041] Figure 6 A schematic diagram of wavelength distribution of an LED epitaxial wafer provided in another embodiment of the present invention;

[0042] Figure 7 A schematic diagram of wavelength distribution of an LED epitaxial wafer provided in another embodiment of the present invention;

[0043] Figure 8 A schematic diagram of wavelength distribution of an LED epitaxial wafer provided in another embodiment of the present invention;

[0044] Fig. 9 A schematic diagram of the structure of an LED epitaxial wafer provided by an embodiment of the present invention;

[0045] Fig.10 A schematic diagram of the structure of another LED epitaxial wafer provided by an embodiment of the present invention;

[0046] Fig.11 A schematic diagram of the structure of another LED epitaxial wafer provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The above is the core idea of ​​the present invention. In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] The embodiment of the present invention provides a method for preparing an LED epitaxial wafer, such as Figure 1 As shown, including:

[0049] S101: providing a substrate;

[0050] Optionally, the substrate is a PSS (Patterned Sapphire Substrate) AlN-plated substrate, or the substrate is a sapphire substrate.

[0051] S102: heating the substrate and performing a nitridation treatment on the substrate using a nitridation gas to form a warpage control layer on the surface of the substrate, wherein the nitridation gas includes at least ammonia;

[0052] After the substrate is introduced into the reaction chamber, it is gradually heated and a certain amount of nitriding gas is introduced to perform nitridation treatment on the substrate. The nitriding gas includes at least ammonia. Ammonia can combine with some chemical bonds on the surface of the substrate to form a material with a lattice constant between the substrate and the semiconductor layer, namely, a warp control layer.

[0053] For example, after the temperature rises to 600°C, ammonia gas and the thin film of the ALN / AL2O3 mixture on the surface of the PSS AlN-plated substrate begin to react to form a warpage control layer. After the temperature reaches 1000°C to 1200°C, the nitrogen and / or ammonia gas are turned off for hydrogenation treatment. Among them, the warpage can be controlled by adjusting the flow rate and / or time of ammonia gas, such as increasing the flow rate of ammonia gas can make the LED epitaxial wafer convex, reducing the flow rate of ammonia gas can make the LED epitaxial wafer concave, increasing the time of ammonia gas introduction can make the LED epitaxial wafer convex, and reducing the time of ammonia gas introduction can make the LED epitaxial wafer concave.

[0054] Since the lattice constant of the warp control layer is between the lattice constant of the substrate and the lattice constant of the semiconductor layer to be grown subsequently, the compressive stress or tensile stress caused by lattice mismatch between the substrate and the semiconductor layer can be reduced, thereby reducing and changing the warping of the LED epitaxial wafer, improving the wavelength uniformity of the LED epitaxial wafer, improving the yield of the LED epitaxial wafer, and saving the sorting cost of the subsequently formed LED chips.

[0055] Furthermore, since the present invention only uses atmosphere to nitride the substrate surface to form a warp control layer before epitaxial growth, and no additional gallium source is introduced to grow an additional epitaxial layer, the warping degree of the final epitaxial wafer can be effectively adjusted without increasing the thickness of the epitaxial layer, thereby saving costs.

[0056] In addition, by nitriding the substrate, the low-dimensional oxide on the surface of the substrate can be decomposed to form nitride, thereby reducing the impurity concentration in the substrate, improving the crystal quality of the subsequently formed film layer, and further improving the optoelectronic performance of the LED epitaxial structure.

[0057] S103: forming an N-type semiconductor layer, a multi-quantum well layer and a P-type semiconductor layer in sequence on the surface of the warpage control layer.

[0058] In one embodiment of the present invention, before sequentially forming an N-type semiconductor layer, a multi-quantum well layer and a P-type semiconductor layer on the surface of the warpage control layer, the method further comprises:

[0059] A buffer layer is formed on the surface of the warpage control layer.

[0060] In another embodiment of the present invention, before sequentially forming an N-type semiconductor layer, a multi-quantum well layer and a P-type semiconductor layer on the surface of the warpage control layer, the method further comprises:

[0061] A buffer layer and a non-doped semiconductor layer are sequentially formed on the surface of the warpage control layer.

[0062] It should be noted that the semiconductor layers in the embodiments of the present invention are all gallium nitride layers, that is, the N-shaped semiconductor layer is an N-type gallium nitride layer, the P-type semiconductor layer is a P-type gallium nitride layer, and the undoped semiconductor layer is an undoped gallium nitride layer. Of course, the present invention is not limited to this. In other embodiments, the semiconductor layer can also be a layer of other semiconductor materials.

[0063] In the embodiment of the present invention, the nitriding gas may be a mixed gas of ammonia and hydrogen; or, the nitriding gas may be a mixed gas of ammonia and nitrogen; or, the nitriding gas may be a mixed gas of ammonia, hydrogen and nitrogen.

[0064] Optionally, the total flow rate of the nitriding gas is 20SLM to 600SLM. The flow rate of hydrogen is 0SLM to 300SLM, including the endpoint values, the flow rate of nitrogen is 7SLM to 600SLM, including the endpoint values, and the flow rate of ammonia is 1SLM to 220SLM, including the endpoint values, wherein when the flow rate of hydrogen is 0, the nitriding gas is a mixed gas of ammonia and nitrogen, and when the flow rate of hydrogen is not 0, the nitriding gas is a mixed gas of hydrogen, nitrogen and ammonia.

[0065] Alternatively, the flow rate of hydrogen is 7SLM~300SLM, including endpoint values, the flow rate of nitrogen is 0SLM~600SLM, including endpoint values, and the flow rate of ammonia is 1SLM~220SLM, including endpoint values, wherein, when the flow rate of nitrogen is 0, the nitriding gas is a mixture of ammonia and hydrogen, and when the flow rate of nitrogen is not 0, the nitriding gas is a mixture of hydrogen, nitrogen and ammonia.

[0066] Further optionally, the ratio of ammonia, nitrogen and hydrogen can be 1:0:300 to 1:0.1:1. Similarly, when the ratio of nitrogen is 0, the nitriding gas is a mixed gas of ammonia and hydrogen, and when the ratio of nitrogen is not 0, the nitriding gas is a mixed gas of hydrogen, nitrogen and ammonia. In the mixed gas, the volume of hydrogen is greater than the volume of ammonia and nitrogen.

[0067] Alternatively, the ratio of ammonia, nitrogen and hydrogen is 1:600:0 to 1:0.1:1. Similarly, when the ratio of hydrogen is 0, the nitriding gas is a mixed gas of ammonia and nitrogen, and when the ratio of hydrogen is not 0, the nitriding gas is a mixed gas of hydrogen, nitrogen and ammonia. Among them, the volume of nitrogen in the mixed gas is greater than the volume of ammonia and hydrogen. It should be noted that the order of introducing ammonia, nitrogen and hydrogen into the reaction chamber is not in particular order.

[0068] Optionally, in the embodiment of the present invention, the time of the nitriding treatment is 0.5 min to 20 min; the temperature of the nitriding treatment is 600° C. to 1200° C.

[0069] Furthermore, the temperature of the nitriding treatment can be gradually increased at a fixed heating rate, or it can be kept constant. When gradually increasing the temperature, the temperature can be a step change, such as including multiple nitriding stages, the temperature of different nitriding stages is different, and the temperature increases successively. Specifically, first increase the temperature to 600°C, then gradually increase the temperature to 600°C~800°C for nitriding treatment, and stabilize for 5s~10min; then gradually increase the temperature to 800°C~1000°C for nitriding treatment, stabilize for 5s~10min, and then gradually increase the temperature to 1000°C~1200°C for nitriding treatment, stabilize for 5s~10min. When the temperature is kept constant, directly increase the temperature to a certain temperature in the range of 600°C~1000°C, or increase the temperature to a certain temperature in the range of 800°C~1000°C, and perform nitriding treatment for 0.5min~20min.

[0070] In one embodiment of the present invention, a method for preparing an LED epitaxial wafer comprises the following steps:

[0071] Step 1: Provide a PSS-coated AlN substrate as a substrate.

[0072] Step 2: Place the PSS-coated AlN substrate on a graphite disk, and introduce it into a MOCVD (Metal-organic Chemical Vapor Deposition) reaction chamber, and introduce 200-300 SLM of hydrogen, 20-30 SLM of nitrogen, and 25-35 SLM of ammonia for 5-8 minutes. The temperature of the graphite disk is gradually increased to 900-1100°C by uniform heating.

[0073] Step 3: After heating to 1100-1250°C, perform hydrogenation treatment for 0.5-2 minutes to remove surface impurities.

[0074] Step 4: introduce trimethylgallium to grow a buffer layer with a thickness of 15 to 25 Å and a temperature of 600 to 850°C.

[0075] Step 5: introduce trimethylgallium to grow a non-doped gallium nitride layer with a thickness of 2.0 to 3.0 μm at a temperature of 1100 to 1200° C.

[0076] Step 6: Add trimethylgallium and silane to grow an N-type gallium nitride layer with a thickness of 1.5-2.5 μm, a temperature of 1050-1100°C, and a silane concentration of 7.5E18 / cm 3 ~8.5E18 / cm 3 .

[0077] Step 7: introduce triethylgallium and trimethylindium to grow a multi-quantum well layer with a total thickness of 0.1-0.2 μm, a well temperature of 750-800° C., and a barrier temperature of 830-900° C.

[0078] Step 8: Add triethylgallium and bismuth magnesium to grow a P-type gallium nitride layer with a thickness of 0.3-0.6 μm, a temperature of 900-1000°C, and a Mg concentration of 1.5E19 / cm 3 ~2.5E21 / cm 3 .

[0079] Step 9: Perform cooling annealing treatment to end the growth and test the LED epitaxial wafer. Use a PL tester to test the wavelength. The wavelength distribution of a single wafer is as follows: Figure 3 As shown, the wavelength distribution of a single chip is relatively uniform, which is consistent with Figure 2 Compared with the prior art shown, the concave situation is significantly improved.

[0080] In another embodiment of the present invention, a method for preparing an LED epitaxial wafer comprises the following steps:

[0081] Step 1: Provide a PSS-coated AlN substrate.

[0082] Step 2: Place the PSS-coated AlN substrate on a graphite disk, pass it into the MOCVD reaction chamber, and introduce 200-300 SLM of hydrogen, 20-30 SLM of nitrogen, and 50-70 SLM of ammonia for 5-8 minutes. The temperature of the graphite disk is gradually increased to 900-1100°C at a uniform rate.

[0083] Step 3: After heating to 1050-1200°C, perform hydrogenation treatment for 0.5-2 minutes to remove surface impurities.

[0084] Step 4: introduce trimethylgallium to grow a buffer layer with a thickness of 15 to 25 Å and a temperature of 600 to 850°C.

[0085] Step 5: introduce trimethylgallium to grow a non-doped gallium nitride layer with a thickness of 2.0 to 3.0 μm at a temperature of 1100 to 1200° C.

[0086] Step 6: Add trimethylgallium and silane to grow an N-type gallium nitride layer with a thickness of 1.5-2.5 μm, a temperature of 1050-1100°C, and a silane concentration of 7.5E18 / cm 3 ~8.5E18 / cm 3 .

[0087] Step 7: introducing triethylgallium and trimethylindium to grow a multi-quantum well layer with a total thickness of 0.1-0.2 μm, a well temperature of 750-800° C., and a barrier temperature of 830-900° C.

[0088] Step 8: Add triethylgallium and bismuth magnesium to grow a P-type gallium nitride layer with a thickness of 0.3-0.6 μm, a temperature of 900-1000°C, and a Mg concentration of 1.5E19 / cm 3 ~2.5E21 / cm 3 .

[0089] Step 9: Perform cooling annealing treatment to end the growth and test the LED epitaxial wafer. Use a PL tester to test the wavelength. The wavelength distribution of a single wafer is as follows: Figure 4 As shown, the wavelength distribution of a single chip is relatively uniform, which is consistent with Figure 2 Compared with the prior art shown, the concave situation is significantly improved.

[0090] In another embodiment of the present invention, a method for preparing an LED epitaxial wafer comprises the following steps:

[0091] Step 1: Provide a PSS-coated AlN substrate.

[0092] Step 2: Place the PSS AlN-plated substrate on a graphite plate, pass it into the MOCVD reaction chamber, introduce 200-300 SLM of hydrogen, 20-30 SLM of nitrogen, and 95-110 SLM of ammonia for 2-5 minutes at a temperature of 700-850°C, and perform the first stage of nitridation. After that, gradually increase the temperature to 900-1050°C, keep the gas composition unchanged, and maintain the constant temperature for 2-5 minutes to perform the second stage of nitridation. Step 3: After heating to 1050-1250°C, perform a hydrogenation treatment for 0.5-2 minutes to remove surface impurities.

[0093] Step 4: introduce trimethylgallium to grow a buffer layer with a thickness of 15 to 25 Å and a temperature of 600 to 850°C.

[0094] Step 5: introduce trimethylgallium to grow a non-doped gallium nitride layer with a thickness of 2.0 to 3.0 μm at a temperature of 1100 to 1200° C.

[0095] Step 6: Add trimethylgallium and silane to grow an N-type gallium nitride layer with a thickness of 1.5-2.5 μm, a temperature of 1050-1100°C, and a silane concentration of 7.5E18 / cm 3 ~8.5E18 / cm 3 .

[0096] Step 7: introducing triethylgallium and trimethylindium to grow a multi-quantum well layer with a total thickness of 0.1-0.2 μm, a well temperature of 750-800° C., and a barrier temperature of 830-900° C.

[0097] Step 8: Add triethylgallium and bismuth magnesium to grow a P-type gallium nitride layer with a thickness of 0.3-0.6 μm, a temperature of 900-1000°C, and a Mg concentration of 1.5E19 / cm 3 ~2.5E21 / cm 3 .

[0098] Step 9: Perform cooling annealing treatment to end the growth and test the LED epitaxial wafer. Use a PL tester to test the wavelength. The wavelength distribution of a single wafer is as follows: Figure 5 As shown, the central wavelength of the single-chip wavelength distribution is relatively long, which is different from Figure 2 Compared with the prior art shown, the concave shape is changed to a convex shape.

[0099] In another embodiment of the present invention, a method for preparing an LED epitaxial wafer comprises the following steps:

[0100] Step 1: Provide a PSS-coated AlN substrate.

[0101] Step 2: Place the PSS AlN-plated substrate on a graphite plate, pass it into the MOCVD reaction chamber, introduce 200-300SLM of hydrogen, 20-30SLM of nitrogen, and 7-15SLM of ammonia for 1-3 minutes at a temperature of 700-850°C, and perform the first stage of nitridation. After that, gradually increase the temperature to 900-1050°C, keep the gas composition unchanged, and maintain the constant temperature for 1-3 minutes to perform the second stage of nitridation. Step 3: After heating to 1050-1250°C, perform a hydrogenation treatment for 0.5-2 minutes to remove surface impurities.

[0102] Step 4: introduce trimethylgallium to grow a buffer layer with a thickness of 15 to 25 Å and a temperature of 600 to 850°C.

[0103] Step 5: introduce trimethylgallium to grow a non-doped gallium nitride layer with a thickness of 2.0 to 3.0 μm at a temperature of 1100 to 1200° C.

[0104] Step 6: Add trimethylgallium and silane to grow an N-type gallium nitride layer with a thickness of 1.5-2.5 μm, a temperature of 1050-1100°C, and a silane concentration of 7.5E18 / cm 3 ~8.5E18 / cm 3 .

[0105] Step 7: introducing triethylgallium and trimethylindium to grow a multi-quantum well layer with a total thickness of 0.1-0.2 μm, a well temperature of 750-800° C., and a barrier temperature of 830-900° C.

[0106] Step 8: Add triethylgallium and bismuth magnesium to grow a P-type gallium nitride layer with a thickness of 0.3-0.6 μm, a temperature of 900-1000°C, and a Mg concentration of 1.5E19 / cm 3 ~2.5E21 / cm 3 .

[0107] Step 9: Perform cooling annealing treatment to end the growth and test the LED epitaxial wafer. Use a PL tester to test the wavelength. The wavelength distribution of a single wafer is as follows: Figure 6 As shown, the wavelength distribution of a single chip is relatively uniform, which is consistent with Figure 2 Compared with the prior art shown, the concave situation is significantly improved.

[0108] In another embodiment of the present invention, a method for preparing an LED epitaxial wafer comprises the following steps:

[0109] Step 1: Provide a PSS-coated AlN substrate as a substrate.

[0110] Step 2: Place the PSS-coated AlN substrate on a graphite disk, and introduce it into a MOCVD (Metal-organic Chemical Vapor Deposition) reaction chamber, introduce 200-500 SLM of nitrogen and 20-70 SLM of ammonia for 3-10 minutes, and gradually increase the temperature of the graphite disk to 1050-1250°C by uniform heating.

[0111] Step 3: After heating to 1050-1250°C, perform hydrogenation treatment for 0.5-2 minutes to remove surface impurities.

[0112] Step 4: introduce trimethylgallium to grow a buffer layer with a thickness of 15 to 25 Å and a temperature of 600 to 850°C.

[0113] Step 5: introduce trimethylgallium to grow a non-doped gallium nitride layer with a thickness of 2.0 to 3.0 μm at a temperature of 1100 to 1200° C.

[0114] Step 6: Add trimethylgallium and silane to grow an N-type gallium nitride layer with a thickness of 1.5-2.5 μm, a temperature of 1050-1100°C, and a silane concentration of 7.5E18 / cm 3 ~8.5E18 / cm 3 .

[0115] Step 7: introduce triethylgallium and trimethylindium to grow a multi-quantum well layer with a total thickness of 0.1-0.2 μm, a well temperature of 750-800° C., and a barrier temperature of 830-900° C.

[0116] Step 8: Add triethylgallium and bismuth magnesium to grow a P-type gallium nitride layer with a thickness of 0.3-0.6 μm, a temperature of 900-1000°C, and a Mg concentration of 1.5E19 / cm 3 ~2.5E21 / cm 3 .

[0117] Step 9: Perform cooling annealing treatment to end the growth and test the LED epitaxial wafer. Use a PL tester to test the wavelength. The wavelength distribution of a single wafer is as follows: Figure 7 As shown, the wavelength distribution of a single chip is relatively uniform, which is consistent with Figure 2 Compared with the prior art shown, the concave situation is significantly improved.

[0118] A variation of this embodiment may also be a gradual heating method, specifically: the time is 1 to 3 minutes, the temperature is 700 to 850°C, and the first stage nitriding treatment is carried out. After that, the temperature is gradually increased to 900 to 1000°C, the gas composition remains unchanged, and the constant temperature is maintained for 1 to 3 minutes for the second stage nitriding treatment.

[0119] In another embodiment of the present invention, a method for preparing an LED epitaxial wafer comprises the following steps:

[0120] Step 1: Provide a PSS-coated AlN substrate as a substrate.

[0121] Step 2: Place the PSS-coated AlN substrate on a graphite disk, and introduce it into a MOCVD (Metal-organic Chemical Vapor Deposition) reaction chamber, introduce 200-500 SLM of hydrogen and 20-70 SLM of ammonia for 3-10 minutes, and gradually increase the temperature of the graphite disk to 1050-1250°C by uniform heating.

[0122] Step 3: After heating to 1050-1250°C, perform hydrogenation treatment for 0.5-2 minutes to remove surface impurities.

[0123] Step 4: introduce trimethylgallium to grow a buffer layer with a thickness of 15 to 25 Å and a temperature of 600 to 850°C.

[0124] Step 5: introduce trimethylgallium to grow a non-doped gallium nitride layer with a thickness of 2.0 to 3.0 μm at a temperature of 1100 to 1200° C.

[0125] Step 6: Add trimethylgallium and silane to grow an N-type gallium nitride layer with a thickness of 1.5-2.5 μm, a temperature of 1050-1100°C, and a silane concentration of 7.5E18 / cm 3 ~8.5E18 / cm 3 .

[0126] Step 7: introduce triethylgallium and trimethylindium to grow a multi-quantum well layer with a total thickness of 0.1-0.2 μm, a well temperature of 750-800° C., and a barrier temperature of 830-900° C.

[0127] Step 8: Add triethylgallium and bismuth magnesium to grow a P-type gallium nitride layer with a thickness of 0.3-0.6 μm, a temperature of 900-1000°C, and a Mg concentration of 1.5E19 / cm 3 ~2.5E21 / cm 3 .

[0128] Step 9: Perform cooling annealing treatment to end the growth and test the LED epitaxial wafer. Use a PL tester to test the wavelength. The wavelength distribution of a single wafer is as follows: Figure 8 As shown, the wavelength distribution of a single chip is relatively uniform, which is consistent with Figure 2 Compared with the prior art shown, the concave situation is significantly improved.

[0129] A variation of this embodiment may also be a gradual heating method, specifically: the time is 1 to 3 minutes, the temperature is 700 to 850°C, and the first stage nitriding treatment is carried out. After that, the temperature is gradually increased to 900 to 1100°C, the gas composition remains unchanged, and the constant temperature is maintained for 1 to 3 minutes for the second stage nitriding treatment.

[0130] The method for preparing an LED epitaxial wafer provided in an embodiment of the present invention heats a substrate and performs a nitriding treatment on the substrate using a nitriding gas, so that ammonia combines with some chemical bonds on the surface of the substrate to form a material having a lattice constant between that of the substrate and the semiconductor layer, namely, a warp control layer, thereby reducing the compressive stress or tensile stress caused by lattice mismatch between the substrate and the semiconductor layer, thereby reducing and changing the warping of the LED epitaxial wafer, improving the wavelength uniformity of the LED epitaxial wafer, improving the yield of the LED epitaxial wafer, and saving the sorting cost of the subsequently formed LED chips.

[0131] Furthermore, since the present invention only uses atmosphere to nitride the substrate surface to form a warp control layer before epitaxial growth, and no additional gallium source is introduced to grow an additional epitaxial layer, the warping degree of the final epitaxial wafer can be effectively adjusted without increasing the thickness of the epitaxial layer, thereby saving costs.

[0132] In addition, by nitriding the substrate, the low-dimensional oxide on the surface of the substrate can be decomposed to form nitride, thereby reducing the impurity concentration in the substrate, improving the crystal quality of the subsequently formed film layer, and further improving the optoelectronic performance of the LED epitaxial structure.

[0133] The embodiment of the present invention further provides an LED epitaxial wafer, such as Fig. 9 As shown, it includes a substrate 10, a warpage control layer 11 located on the surface of the substrate 10, an N-type semiconductor layer 12, a multi-quantum well layer 13 and a P-type semiconductor layer 14 located on the surface of the warpage control layer 11 in sequence;

[0134] The warpage control layer 11 is formed by heating the substrate 10 and performing a nitridation treatment on the substrate 10 using a nitridation gas, wherein the nitridation gas at least includes ammonia.

[0135] Optionally, the substrate 10 is a PSS AlN-plated substrate or a sapphire substrate. The warpage control layer 11 is a substance formed on the surface of the substrate 10 after the substrate 10 is nitrided.

[0136] In one embodiment of the present invention, before the N-type semiconductor layer 12, the multi-quantum well layer 13 and the P-type semiconductor layer 14 are sequentially formed on the surface of the warpage control layer 11, as Fig.10 As shown, it also includes:

[0137] A buffer layer 15 is formed on the surface of the warpage control layer 11 .

[0138] In another embodiment of the present invention, before the N-type semiconductor layer 12, the multi-quantum well layer 13 and the P-type semiconductor layer 14 are sequentially formed on the surface of the warpage control layer 11, as Fig.11 As shown, it also includes:

[0139] A buffer layer 15 and a non-doped semiconductor layer 16 are sequentially formed on the surface of the warpage control layer 11 .

[0140] It should be noted that the semiconductor layers in the embodiments of the present invention are all gallium nitride layers, that is, the N-type semiconductor layer 12 is an N-type gallium nitride layer, the P-type semiconductor layer 14 is a P-type gallium nitride layer, and the undoped semiconductor layer 16 is an undoped gallium nitride layer. Of course, the present invention is not limited to this. In other embodiments, the semiconductor layer can also be a layer of other semiconductor materials.

[0141] In the embodiment of the present invention, after the substrate 10 is nitrided with a nitriding gas, ammonia can combine with some chemical bonds on the surface of the substrate 10 to form a material having a lattice constant between that of the substrate 10 and the semiconductor layer 12, namely, the warpage control layer 11.

[0142] Since the lattice constant of the warp control layer 11 is between the lattice constant of the substrate 10 and the lattice constant of the semiconductor layer 12 to be grown subsequently, the compressive stress or tensile stress caused by the lattice mismatch between the substrate 10 and the semiconductor layer 12 can be reduced, thereby reducing and changing the warping of the LED epitaxial wafer, improving the wavelength uniformity of the LED epitaxial wafer, improving the yield of the LED epitaxial wafer, and saving the sorting cost of the subsequently formed LED chips.

[0143] Furthermore, since the present invention only uses atmosphere to nitride the substrate surface to form a warp control layer before epitaxial growth, and no additional gallium source is introduced to grow an additional epitaxial layer, the warping degree of the final epitaxial wafer can be effectively adjusted without increasing the thickness of the epitaxial layer, thereby saving costs.

[0144] In addition, by nitriding the substrate 10, the low-dimensional oxide on the surface of the substrate 10 can be decomposed to form nitride, thereby reducing the impurity concentration in the substrate 10, improving the crystal quality of the subsequently formed film layer, and further improving the optoelectronic performance of the LED epitaxial structure.

[0145] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0146] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an LED epitaxial wafer, characterized in that: include: Providing a substrate, wherein the substrate is a PSS-coated AlN substrate or a sapphire substrate; Heating the substrate and performing a nitridation treatment on the substrate using a nitridation gas, wherein the nitridation gas includes at least ammonia gas, so that the ammonia gas is chemically bonded with the surface of the substrate to form a warpage control layer on the surface of the substrate; An N-type semiconductor layer, a multi-quantum well layer and a P-type semiconductor layer are sequentially formed on the surface of the warpage control layer, and the lattice constant of the warpage control layer is between the crystal constant of the substrate and the lattice constant of the N-type semiconductor layer.

2. The method according to claim 1, characterized in that The nitriding gas is a mixed gas of ammonia and hydrogen; Alternatively, the nitriding gas is a mixed gas of ammonia and nitrogen; Alternatively, the nitriding gas is a mixed gas of ammonia, hydrogen and nitrogen.

3. The method according to claim 2, characterized in that The total flow rate of the nitriding gas is 20SLM to 600SLM; Wherein, the flow rate of hydrogen is 0SLM to 300SLM, including the endpoint value, the flow rate of nitrogen is 7SLM to 600SLM, including the endpoint value, and the flow rate of ammonia is 1SLM to 220SLM, including the endpoint value; Alternatively, the flow rate of hydrogen is 7SLM to 300SLM, including endpoint values, the flow rate of nitrogen is 0SLM to 600SLM, including endpoint values, and the flow rate of ammonia is 1SLM to 220SLM, including endpoint values.

4. The method according to claim 3, characterized in that The ratio of ammonia, nitrogen and hydrogen is 1:0:300 to 1:0.1:1; Alternatively, the ratio of ammonia, nitrogen and hydrogen is 1:600:0 to 1:0.1:

1.

5. The method according to claim 1, characterized in that The nitriding treatment time is 0.5min to 20min; The temperature of the nitriding treatment is 600°C to 1200°C.

6. The method according to claim 1, characterized in that The step of nitriding the substrate comprises: Performing nitridation treatment on the substrate in a constant temperature manner; Alternatively, the substrate is nitrided by gradually increasing the temperature.

7. The method according to claim 1, characterized in that Before sequentially forming an N-type semiconductor layer, a multi-quantum well layer and a P-type semiconductor layer on the surface of the warpage control layer, the method further comprises: forming a buffer layer on the surface of the warpage control layer; Alternatively, a buffer layer and a non-doped semiconductor layer are sequentially formed on the surface of the warpage control layer.

8. An LED epitaxial wafer, characterized in that: It comprises a substrate, a warpage control layer located on the surface of the substrate, an N-type semiconductor layer, a multi-quantum well layer and a P-type semiconductor layer located on the surface of the warpage control layer in sequence; the substrate is a PSS AlN-plated substrate or a sapphire substrate, and the lattice constant of the warpage control layer is between the crystal constant of the substrate and the lattice constant of the N-type semiconductor layer; The warpage control layer is formed by heating the substrate and performing a nitridation treatment on the substrate using a nitriding gas, wherein the nitriding gas includes at least ammonia gas, so that the ammonia gas is chemically bonded to the surface of the substrate.

9. The LED epitaxial wafer according to claim 8, characterized in that: Also included is a buffer layer located between the warpage control layer and the N-type semiconductor layer; Alternatively, it further includes a buffer layer and a non-doped semiconductor layer which are sequentially located between the warpage control layer and the N-type semiconductor layer.

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