CN112164739B - Growth method of micro light-emitting diode epitaxial wafer - Google Patents

Growth method of micro light-emitting diode epitaxial wafer Download PDF

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CN112164739B
CN112164739B CN202011040907.2A CN202011040907A CN112164739B CN 112164739 B CN112164739 B CN 112164739B CN 202011040907 A CN202011040907 A CN 202011040907A CN 112164739 B CN112164739 B CN 112164739B
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layer
growth
growth stage
temperature buffer
gas
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CN112164739A (en
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姚振
从颖
董彬忠
李鹏
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HC Semitek Suzhou Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/4401—Means for minimising impurities, e.g. dust, moisture or residual gas, in the reaction chamber
    • C23C16/4408—Means for minimising impurities, e.g. dust, moisture or residual gas, in the reaction chamber by purging residual gases from the reaction chamber or gas lines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
    • H01L33/007—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound comprising nitride compounds

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Abstract

The present disclosure provides a growth method of a micro light emitting diode epitaxial wafer, the growth method comprising: growing an epitaxial layer on a substrate; when an epitaxial layer grows on the substrate, blowing purge gas into the cavity cover of the reaction cavity, and purging by-products generated in the reaction cavity to the tail gas end of the reaction cavity so as to discharge the by-products out of the reaction cavity; the usage amount of the purging gas is positively correlated with the usage amount of the MO source required by each layer, the flow rate of the reaction gas required by each layer, the growth thickness of each layer and the doping concentration of each layer; the usage amount of the purge gas is also related to the growth stage of each layer of the epitaxial layer, the growth stage of each layer of the epitaxial layer is divided into an initial growth stage, an intermediate growth stage and an end growth stage, and the usage amount of the purge gas in the intermediate growth stage is larger than that in the initial growth stage and the end growth stage. The growth method can reduce the generation of surface particles in the growth process of the epitaxial wafer, form a good surface and ensure the light-emitting effect of the micro light-emitting diode.

Description

Growth method of micro light-emitting diode epitaxial wafer
Technical Field
The disclosure relates to the technical field of semiconductors, in particular to a growth method of a micro light-emitting diode epitaxial wafer.
Background
A Light Emitting Diode (LED) is a semiconductor electronic component capable of Emitting Light. As a novel high-efficiency, environment-friendly and green solid-state illumination light source, the LED is a new generation light source with a wide prospect, and is rapidly and widely applied to the fields such as traffic signal lamps, automobile interior and exterior lamps, urban landscape illumination, indoor and outdoor display screens, small-distance display screens and the like.
The epitaxial wafer is a primary finished product in the LED manufacturing process. In the related art, when growing an LED epitaxial wafer, methods are generally used that: providing a substrate, and growing a low-temperature buffer layer, a high-temperature buffer layer, an N-type layer, an active layer, an electron blocking layer and a P-type layer on the substrate in sequence. Wherein, above-mentioned epitaxial wafer is at the in-process of reaction intracavity growth, and the accessory substance that produces when part grows can deposit at the lateral wall of reaction chamber for the impurity content in the reaction chamber increases, can drop to the epitaxial wafer finally, produces the particulate matter on the epitaxial wafer surface, influences the crystal quality of epitaxial wafer. Especially for micro LEDs with small volume, the sum of the volume of particles falling onto the surface of the micro LED may be larger than the volume of the micro LED, resulting in failure of the micro LED.
Disclosure of Invention
The embodiment of the disclosure provides a growth method of a micro light-emitting diode epitaxial wafer, which can reduce the generation of surface particles in the growth process of the epitaxial wafer, form a good surface and ensure the light-emitting effect of the micro light-emitting diode. The technical scheme is as follows:
the embodiment of the disclosure provides a growth method of a micro light-emitting diode epitaxial wafer, which comprises the following steps:
providing a substrate;
growing an epitaxial layer on the substrate, wherein the epitaxial layer comprises a low-temperature buffer layer, a high-temperature buffer layer, an N-type layer, an active layer, an electron blocking layer and a P-type layer which are sequentially grown;
when an epitaxial layer grows on the substrate, blowing purge gas into a cavity cover of the reaction cavity, and purging by-products generated in the reaction cavity to a tail gas end of the reaction cavity so that the by-products are discharged out of the reaction cavity;
the usage amount of the purge gas is positively correlated with the usage amount of the MO source required by each layer, the flow of the reaction gas required by each layer, the growth thickness of each layer and the doping concentration of each layer;
the usage amount of the purge gas is also related to the growth stage of each epitaxial layer, the growth stage of each epitaxial layer is divided into an initial growth stage, an intermediate growth stage and an end growth stage, and the usage amount of the purge gas in the intermediate growth stage is larger than that in the initial growth stage and the end growth stage.
Optionally, the low-temperature buffer layer and the high-temperature buffer layer are grown in the initial growth stage, the N-type layer and the active layer are grown in the intermediate growth stage, and the electron blocking layer and the P-type layer are grown in the final growth stage.
Optionally, when a low-temperature buffer layer, a high-temperature buffer layer, an N-type layer, an active layer, an electron blocking layer and a P-type layer are sequentially grown on the substrate, the used amounts of the purge gas of the reaction chamber cover are M1, M2, M3, M4, M5 and M6;
wherein M5 is more than M1 is more than M2 is more than M3, M5 is more than M4 is more than M3, and M5 is more than M6 is more than M3.
Optionally, the amount of the purge gas used is 10L to 30L.
Optionally, M1 is 15-20L, M2 is 20-25L, M3 is 25-30L, M4 is 16-20L, M5 is 15-18L, and M6 is 18-25L.
Optionally, MO sources required for growth of each layer include TEGa/TMGa/TMIn/TMAl/CP2At least one of Mg.
Optionally, the reactant gas required for growth of each layer comprises SiH4/H2/NH3/N2At least one of (1).
Optionally, the thickness of low temperature buffer layer is 15 ~ 30nm, the thickness of high temperature buffer layer is 2 ~ 3.5um, the thickness of N type layer is 2 ~ 3um, the thickness of active layer is 130 ~ 160nm, the thickness of electron barrier layer is 30 ~ 50nm, the thickness of P type layer is 50 ~ 80 nm.
Optionally, the low-temperature buffer layer is an Al-doped GaN layer, the N-type layer is an Si-doped GaN layer, and the electron blocking layer is Mg-doped AlyGa1-yAnd the N layer, y is 0.15-0.25, and the P layer is a GaN layer doped with Mg.
Optionally, the doping concentration of Al in the low-temperature buffer layer is 1 × 103cm-3～3*103cm-3The doping concentration of Si in the N-type layer is 1019cm-3～6*1019cm-3The doping concentration of Mg in the electron blocking layer is 1018cm-3～1019cm-3The doping concentration of Mg in the P-type layer is 1020cm-3～1021cm-3。
The technical scheme provided by the embodiment of the disclosure has the following beneficial effects:
the amount of the purging gas for limiting the chamber cover of the reaction chamber is set according to the amount of the MO source required for growing each layer, the flow rate of the reaction gas required for growing each layer, the growth thickness of each layer, the doping concentration of each layer and the growth stage of each layer. Because the reaction chamber is swept to the sweeping gas of reaction chamber lid to the tail gas end of reaction chamber is reached to the accessory substance of quickening the reaction, with outside discharging the accessory substance to the reaction chamber, reduces the deposit of accessory substance at the reaction chamber lateral wall, and then reduces the impurity content in the reaction chamber, can reduce the production of reaction in-process surface particulate matter finally. Therefore, according to the MO source usage amount required by each layer, the reaction gas flow required by each layer, the growth thickness of each layer, the doping concentration of each layer and the growth stage of each layer, the usage amount of the purging gas of the reaction cavity cover can be more reasonably set when each layer grows, and byproducts generated when each layer grows can be guaranteed to be discharged out of the reaction cavity, so that the generation of surface particles in the epitaxial wafer growth process is reduced, a good surface is formed, and the light emitting effect of the micro LED is guaranteed.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a flowchart of a method for growing a micro light emitting diode epitaxial wafer according to an embodiment of the present disclosure;
fig. 2 is a flowchart of another method for growing a micro light emitting diode epitaxial wafer according to an embodiment of the present disclosure;
FIG. 3 is a schematic illustration of a purging of a chamber lid purge gas in a reaction chamber provided by an embodiment of the disclosure.
Detailed Description
To make the objects, technical solutions and advantages of the present disclosure more apparent, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
Fig. 1 is a flowchart of a method for growing a micro light emitting diode epitaxial wafer according to an embodiment of the present disclosure, where as shown in fig. 1, the method for growing includes:
step 101, a substrate is provided.
Wherein the substrate may be a sapphire substrate.
And 102, growing an epitaxial layer on the substrate, and when the epitaxial layer grows on the substrate, introducing purging gas into the cavity cover of the reaction cavity, purging by-products generated in the reaction cavity to a tail gas end of the reaction cavity, so that the by-products are discharged out of the reaction cavity.
In this embodiment, the epitaxial layer includes a low temperature buffer layer, a high temperature buffer layer, an N-type layer, an active layer, an electron blocking layer, and a P-type layer, which are sequentially grown.
The usage amount of the purging gas is positively correlated with the usage amount of the MO source required by each layer, the flow rate of the reaction gas required by each layer, the growth thickness of each layer and the doping concentration of each layer.
The usage amount of the purge gas is also related to the growth stage of each layer of the epitaxial layer, the growth stage of each layer of the epitaxial layer is divided into an initial growth stage, an intermediate growth stage and an end growth stage, and the usage amount of the purge gas in the intermediate growth stage is larger than that in the initial growth stage and the end growth stage.
If the usage amount of the purge gas of the reaction chamber cover is too large, the gas flow inside the reaction chamber is unstable, and the normal reaction in the reaction chamber is affected. If the amount of purge gas used for the reaction chamber cover is too small, the reaction by-product cannot be blown out of the reaction chamber.
Optionally, the purge gas of the reaction chamber cover is nitrogen. The nitrogen can accelerate the separation of the side reactant from the cavity of the reaction cavity, and the stability of the reaction environment of the cavity is ensured.
In the disclosed embodiment, a low temperature buffer layer and a high temperature buffer layer are grown at an initial growth stage, an N-type layer and an active layer are grown at an intermediate growth stage, and an electron blocking layer and a P-type layer are grown at an end growth stage.
In the embodiment, the low-temperature buffer layer is an Al-doped GaN layer with a thickness of 15-30 nm. The high-temperature buffer layer is a GaN layer, and the thickness is 2-3.5 um. The N-type layer is a GaN layer doped with Si and has a thickness of 2-3 um. The active layer comprises multiple InGaN well layers alternately grown in periodsAnd a GaN barrier layer. The thickness of the InGaN well layer is 2-3 nm, and the thickness of the GaN barrier layer is 8-11 nm. The number of layers of the InGaN well layer and the GaN barrier layer is 11-13, and the total thickness of the InGaN well layer and the GaN barrier layer is 130-160 nm. The electron barrier layer is Mg-doped AlyGa1-yAnd an N (y is 0.15-0.25) layer having a thickness of 30-50 nm. The P-type layer is a GaN layer doped with Mg, and the thickness of the P-type layer is 50-80 nm.
Wherein the doping concentration of Al in the low-temperature buffer layer is 1 x 103cm-3～3*103cm-3Doping concentration of Si in N type layer is 1019cm-3～6*1019cm-3The doping concentration of Mg in the electron blocking layer is 1018cm-3～1019cm-3Doping concentration of Mg in P type layer is 1020cm-3～1021cm-3。
Optionally, MO sources required for growth of each layer include TEGa/TMGa/TMIn/TMAl/CP2At least one of Mg.
Optionally, the reactant gas required for growth of each layer comprises SiH4/H2/NH3/N2At least one of (1).
Illustratively, when a low-temperature buffer layer, a high-temperature buffer layer, an N-type layer, an active layer, an electron blocking layer and a P-type layer are sequentially grown on a substrate, the used amounts of purge gases of a reaction chamber cover are M1, M2, M3, M4, M5 and M6, respectively;
wherein M5 is more than M1 is more than M2 is more than M3, M5 is more than M4 is more than M3, and M5 is more than M6 is more than M3.
At this time, when the N-type layer is grown, the usage amount of the purge gas of the reaction chamber cover is the largest, and when the electron blocking layer is grown, the usage amount of the purge gas of the reaction chamber cover is the smallest.
In the embodiment of the present disclosure, the used amount of the purge gas of the reaction chamber cover when each layer in the epitaxial layer grows can be determined by the following two methods:
1. debugging method
The method comprises the steps of firstly obtaining the values of the MO source usage amount, the reaction gas flow rate, the growth thickness and the Al doping concentration parameter during the growth of the low-temperature buffer layer, and then presetting the usage amount M1 of the purging gas of the reaction cavity cover during the growth of the low-temperature buffer layer by a technician according to experience. At this time, since the low-temperature buffer layer is grown at the initial growth stage, M1 can be set small.
Then obtaining the use amount of the MO source, the flow rate of reaction gas and the growth thickness when the high-temperature buffer layer grows, and comparing the parameters with the corresponding parameters of the low-temperature buffer layer. For example, the MO source is used in the following amount: the flow rate of TMGa is 300-800 sccm, and the use amount of the MO source during the growth of the low-temperature buffer layer is as follows: the flow rate of TMGa is 30-100 sccm. At the moment, the use amount of the MO source during the growth of the high-temperature buffer layer is larger than that of the MO source during the growth of the low-temperature buffer layer. And the flow of reaction gas when the high temperature buffer layer grows is the same with the flow of reaction gas when the low temperature buffer layer grows, and the thickness of high temperature buffer layer is 15 ~ 30nm for 2 ~ 3.5um is greater than the thickness of low temperature buffer layer far away. Therefore, although the high-temperature buffer layer is not doped with other elements, the usage amount of the MO source is greater than that of the low-temperature buffer layer during growth of the high-temperature buffer layer, the thickness of the MO source is also much greater than that of the low-temperature buffer layer, and the high-temperature buffer layer is closer to the middle growth stage than the low-temperature buffer layer, so that the usage amount of the purge gas can be increased on the basis of M1, and a value with a larger value is selected as the usage amount of the purge gas M2 of the reaction chamber cover during growth of the low-temperature buffer layer, that is, M1 is less than M2.
According to the principle, by analogy, the usage amount of the purge gas can be finally determined when each layer in the epitaxial layer grows.
It should be noted that, in particular, when the N-type layer is grown, the amount of MO source used and the flow rate of the reactant gas required are relatively large in each layer, and at the same time, the electron-providing substance silane is additionally added to the N-type layer, so that the doping concentration is large. And in order to ensure the effect of supplying electrons, the thickness of the N-type layer is also set to be thicker. Therefore, when the N-type layer is grown, the used amount of the purge gas of the reaction cavity cover is the largest. When the electron blocking layer is grown, the required amount of the MO source and the required flow rate of the reaction gas are relatively small in each layer. Although the electron blocking layer is doped with Al and Mg, the thickness of the electron blocking layer is thin, and the influence of the doping concentration on the using amount of the purging gas of the reaction cavity cover is small. And the electron blocking layer is grown at the end of the growth stage, so that the use amount of the purging gas of the reaction cavity cover is minimum when the electron blocking layer is grown.
Then, the determined amounts of the purge gas used during the growth of each layer, M1, M2, M3, M4, M5 and M6, are inputted into programs of the respective devices, and the respective devices are controlled by the programs, so that the purge gas is blown out from the reaction chamber lid in a set amount during the growth of each layer of the epitaxial layer. And after the epitaxial wafer grows, manufacturing the epitaxial wafer into a micro LED chip, and detecting the average value of the surface particle number of the single micro LED chip.
The method comprises the steps of combining M1, M2, M3, M4, M5 and M6 with different values for multiple times to respectively manufacture different micro LED chips, and then selecting a combination mode with the minimum mean value of the surface particle number of a single micro LED chip as the final values of M1, M2, M3, M4, M5 and M6.
For example, in this embodiment, the finally determined combination manner is: M1-15L, M2-20L, M3-30L, M4-25L, M5-10L, and M6-25L.
2. And (4) weight method.
Namely, the corresponding relation between each parameter influencing the value of the usage M of the purge gas and the usage M of the purge gas is determined. For example, the amount of purge gas used is positively correlated with the amount of MO source used a required for growth of each layer, the flow rate B of reaction gas required for growth of each layer, the growth thickness C of each layer, and the doping concentration D of each layer. At this time, A, B, C, D are preset to four fixed values respectively, and the usage amount of the purge gas is selected as an initial value M0. Then, the control value B, C, D is kept constant, and different A and different M are selected0Growing the epitaxial layer, finally manufacturing the grown epitaxial layer into a chip, and detecting whether the average number of the surface particle number on the surface of the chip meets the requirement. If the requirements are met, acquiring a group of A and M0The value combination of (1). Through multiple experiments, a plurality of groups of A and M meeting the requirements can be obtained0To obtain A and M0Curve K1. Then, based on the relationship curve K1, it can be determinedWhen each epitaxial layer is grown by adopting different MO source usage amounts, the corresponding purge gas usage amount M01。
Likewise, using the above method, parameters B and M can be obtained0Curve K2, parameters C and M0Curve K3, parameters D and M0Curve K4. According to the relation curve K2, the usage amount M of the corresponding purge gas can be determined when each layer of the epitaxial layer is grown by adopting the reaction gases with different flow rates02. According to the relation curve K3, the usage amount M of the corresponding purge gas of each epitaxial layer under different growth thicknesses can be determined03. According to the relation curve K4, the usage amount M of the corresponding purge gas of each epitaxial layer under different doping concentrations can be determined04。
And then matching weights for all the parameters, wherein the weight corresponding to the parameter A is a, the weight corresponding to the parameter B is B, the weight corresponding to the parameter C is C, and the weight corresponding to the parameter D is D.
And the amount of purge gas used is also related to the growth stage of each layer of the epitaxial layer, so that the correction coefficient e related to the growth stage parameters can be setrAnd r is 1, 2 or 3. Wherein the layer grown in the primary growth stage has a correction coefficient of e1The layer grown in the intermediate growth stage has a correction coefficient of e2The layer grown at the end of the growth phase has a correction factor of e3。
Wherein a + b + c + d is 1, e1＜e2，e3＜e2，a、b、c、d、e1、e2And e3The specific value of (A) can be set manually.
Finally, the usage M of the purge gas during the growth of each epitaxial layer under each parameter can be calculated according to the following formulax：
Mx＝(M01*a+M02*b+M03*c+M04*d)er
Where x represents the number of epitaxial layers.
The growing method provided by the embodiment of the disclosure limits the usage amount of the purge gas of the reaction cavity cover to be set according to the usage amount of the MO source required by each layer, the flow rate of the reaction gas required by each layer, the growth thickness of each layer, the doping concentration of each layer and the growth stage of each layer. Because the reaction chamber is swept to the sweeping gas of reaction chamber lid to the tail gas end of reaction chamber is reached to the accessory substance of quickening the reaction, with outside discharging the accessory substance to the reaction chamber, reduces the deposit of accessory substance at the reaction chamber lateral wall, and then reduces the impurity content in the reaction chamber, can reduce the production of reaction in-process surface particulate matter finally. Therefore, according to the MO source usage amount required by each layer, the reaction gas flow required by each layer, the growth thickness of each layer, the doping concentration of each layer and the growth stage of each layer, the usage amount of the purging gas of the reaction cavity cover can be more reasonably set when each layer grows, and byproducts generated when each layer grows can be guaranteed to be discharged out of the reaction cavity, so that the generation of surface particles in the epitaxial wafer growth process is reduced, a good surface is formed, and the light emitting effect of the micro LED is guaranteed.
The embodiment of the present disclosure describes specific growth steps of a light emitting diode epitaxial wafer when each layer is grown, fig. 2 is a flowchart of another growth method of a light emitting diode epitaxial wafer provided in the embodiment of the present disclosure, and as shown in fig. 2, the growth method includes:
step 201, a substrate is provided.
The substrate can be a sapphire flat sheet substrate.
Further, step 201 may further include:
and processing the substrate at high temperature for 5-6 min in a hydrogen atmosphere. Wherein the temperature of the reaction chamber is 1000-1100 deg.C, and the pressure of the reaction chamber is controlled at 200-500 torr.
In this embodiment, a Veeco K465i or C4 or RB MOCVD (Metal Organic Chemical Vapor Deposition) apparatus is used to realize the epitaxial wafer growth method. By using high-purity H2(Hydrogen) or high purity N2(Nitrogen) or high purity H2And high purity N2The mixed gas of (2) is used as a carrier gas, high-purity NH3As nitrogen source, trimethyl gallium (TMGa) and triethyl gallium (TEGa) as gallium source, and trimethyl indium (TMIn) asIndium source, silane (SiH4) as N-type dopant, Si source, trimethylaluminum (TMAl) as aluminum source, magnesium diclocene (CP)2Mg) as a P-type dopant, i.e., a Mg source. The pressure in the reaction chamber is 100-600 torr.
Step 202, growing a low temperature buffer layer on the substrate.
Wherein the low-temperature buffer layer is an Al-doped GaN layer, and the doping concentration of Al is 1 x 103～3*103cm-3。
Illustratively, TMGa and TMAl are introduced into the reaction cavity as a gallium source and an aluminum source, and N is introduced2、H2And NH3Controlling the temperature in the reaction chamber to be 530-560 ℃, the pressure to be 200-500 torr, and the reaction temperature in the reaction chamber is [0001 ] of sapphire]And growing a low-temperature buffer layer with the thickness of 15-30 nm on the surface.
Wherein, the flow rate of TMGa introduced into the reaction cavity is 30-100 sccm, the flow rate of TMAl is 60-150 sccm, and N is2The gas flow rate of (A) is 30-80L, H2The gas flow rate of (2) is 80-160L, NH3The gas flow rate of (2) is 30-80L.
Optionally, when the low-temperature buffer layer grows, the usage amount M1 of the purge gas of the reaction chamber cover is 15-20L. If M1 is less than 15L, the use amount is small, which affects the smoothness of the flow field (i.e. the spatial distribution of the airflow formed by the MO sources and the gas in the chamber during the high-speed rotation of the reaction chamber), and thus the effect of reducing the generation of particles cannot be achieved. Since the low-temperature buffer layer is the initial stage of diode epitaxial wafer growth, the amount of each MO source and gas used is small, and if M1 is greater than 20L, the growth cost is increased.
Illustratively, when the low-temperature buffer layer is grown, the using amount M1 of the purge gas of the reaction cavity cover is 15-18L. At the moment, the subsequent flow field can be ensured to be smooth and reasonable in production cost.
Fig. 3 is a schematic diagram illustrating purging of a purge gas of a reaction chamber cover according to an embodiment of the disclosure, and as shown in fig. 3, at this time, a purge gas Q is introduced into the reaction chamber cover 300a, and the purge gas Q may purge the reaction chamber S, so as to accelerate a byproduct of a reaction to reach a tail gas end 300b of the reaction chamber S, so as to discharge the byproduct to the outside of the reaction chamber S, reduce deposition of the byproduct on a sidewall of the reaction chamber S, and further reduce an amount of impurities in the reaction chamber S.
Step 203, growing a high temperature buffer layer on the low temperature buffer layer.
Wherein, the high-temperature buffer layer is an undoped GaN layer.
Illustratively, TMGa is introduced into the reaction cavity as a gallium source, and N is introduced2、H2And NH3And controlling the temperature in the reaction cavity to be 1000-1100 ℃ and the pressure to be 200-600 torr, and growing a high-temperature buffer layer with the thickness of 2-3.5 um on the low-temperature buffer layer.
Wherein the flow rate of TMGa introduced into the reaction cavity is 300-800 sccm, and N2The gas flow rate of (A) is 30-80L, H2The gas flow rate of (2) is 80-160L, NH3The gas flow rate of (2) is 30-80L.
Optionally, when the high-temperature buffer layer grows, the usage amount M2 of the purge gas of the reaction chamber cover is 20-25L. Because the layer is a filling and restoring layer, the growth temperature, the needed MO source and the air flow are large, the usage amount of the purging gas of the reaction cavity cover needs to be large, good heat flow distribution is formed, the growth temperature distribution on the surface of the epitaxial wafer is more uniform, smooth and uniform air flow is formed, and the unevenness of the surface of the epitaxial layer caused by the falling of particles on the top is reduced. If M2 is less than 20L, the use of relatively small amount will affect the smoothness of the laminar airflow, and thus may increase the risk of particle shedding on the top of the epitaxial wafer. If M2 is larger than 25L, the gas flow rate of normal reaction is affected due to the larger amount of M2.
Illustratively, when the high-temperature buffer layer is grown, the using amount M2 of the purge gas of the reaction cavity cover is 21-24L. At this time, stable and smooth airflow can be ensured, and the gas flow rate of normal reaction can not be influenced.
Step 204, growing an N-type layer on the high-temperature buffer layer.
Wherein the N-type layer is a GaN layer doped with Si with a doping concentration of 1019cm-3～6*1019cm-3。
Illustratively, TMGa is introduced into the reaction chamberFor gallium source, introducing N2、H2、NH3And SiH4And controlling the temperature in the reaction cavity to be 1000-1100 ℃ and the pressure to be 150-300 torr, and growing an N-type layer with the thickness of 2-3 um on the high-temperature buffer layer.
Wherein the flow rate of TMGa introduced into the reaction cavity is 500-100 sccm, N2The gas flow rate of (A) is 20-60L, H2The gas flow rate of (1) is 60-110L, NH3The gas flow rate of (1) is 30-80L, SiH4The gas flow rate of (2) is 100-150L.
Because the N-type layer is the main electron providing layer, the usage amount of the needed MO source and the flow rate of the needed reaction gas are relatively larger in each layer, meanwhile, a substance for providing electrons, namely silane, is additionally added in the N-type layer, the doping concentration is larger, in order to ensure the effect of providing electrons, the thickness of the N-type layer is also set to be thicker, and the usage amount of the purging gas of the reaction cavity cover is the largest when the N-type layer is grown.
Optionally, when the N-type layer is grown, the usage amount M3 of the purge gas of the chamber cover is 25-30L. If M3 is less than 25L, the uniformity and stability of the overall gas flow will be affected due to the relatively low amount of M3, and the worse the uniformity and stability of the overall gas flow, the more particulate matter will be formed on the surface of the epitaxial wafer. If M3 is greater than 30L, the gas flow rate for normal reaction in this layer will also be affected. On the other hand, unnecessary resource waste is also caused.
Illustratively, when the N-type layer is grown, the using amount M3 of the purge gas of the reaction cavity cover is 25-30L. At this time, uniform and stable air flow and appropriate resource utilization can be ensured.
Step 205, an active layer is grown on the N-type layer.
The active layer comprises a plurality of InGaN well layers and GaN barrier layers which are alternately grown in a period. The number of active layers can be 11-13, and the total thickness of the active layers is 130-160 nm.
Illustratively, TEGa and TMIn are introduced into the reaction cavity as a gallium source and an indium source, and N is introduced2And NH3Controlling the temperature in the reaction chamber to be 760-780 ℃, the pressure to be 200torr, and growing an InGaN well layer with the thickness of 2 nm-3 nm.
Wherein the flow rate of TEGa introduced into the reaction cavity is 50-200sccm, the flow rate of TMIn is 500-1000sccm, and N is2The gas flow rate of (2) is 50-100L, NH3The gas flow rate of (2) is 30-80L.
Introducing TEGa as a gallium source into the reaction cavity, and introducing N2And NH3Controlling the temperature in the reaction cavity to be 860-890 ℃, the pressure to be 200torr, and growing a GaN barrier layer with the thickness of 8-11 nm.
Wherein the flow rate of TEGa introduced into the reaction cavity is 50-200sccm, N2The gas flow rate of (2) is 50-100L, NH3The gas flow rate of (2) is 30-80L.
Since the layer is a region where electrons and holes perform combined light emission, and the well layer and the barrier layer are grown cyclically, in order to ensure the definition of the well-barrier interface in consideration of multiple-cycle switching growth, in this embodiment, the usage amount of the purge gas of the reaction chamber cover is the same when the well layer and the barrier layer of the active layer are grown.
Optionally, when the active layer is grown, the usage amount M4 of the purge gas of the reaction chamber cover is 16-20L. If M4 is less than 16L, the uniformity and stability of In composition distribution In the layer will be affected by the relatively small amount of M4, and the uniformity of light-emitting wavelength and the uniformity of light-emitting brightness will be affected. If M4 is larger than 20L, the gas flow rate of the normal reaction is affected and the distribution uniformity of the In component is adversely affected because the amount used is relatively large and the MO source and the gas flow rate are relatively small.
Illustratively, when the active layer is grown, the using amount M4 of the purge gas of the reaction cavity cover is 16-18L. At the moment, the stability and uniformity of the In doping component can be ensured, and the interface definition of the well layer and the barrier layer and the consistency of wavelength and brightness are improved.
Step 206, an electron blocking layer is grown on the active layer.
Wherein the electron blocking layer is Mg-doped AlyGa1-yN(y＝0.15～0.25)。
Illustratively, TMGa, TMAl and CP are introduced into the reaction chamber2Mg is respectively used as a gallium source, an aluminum source and an Mg source, and N is introduced2And NH3Controlling the temperature in the reaction cavity to be 930-970 ℃ and the pressure to be 100torr, and growing an electron blocking layer with the thickness of 30-50 nm on the active layer.
Wherein, the flow rate of TMGa introduced into the reaction cavity is 30-100 sccm, the flow rate of TMAl is 80-200 sccm, and CP2The flow rate of Mg is 50-200sccm, N2The gas flow rate of (2) is 50-100L, NH3The gas flow rate of (2) is 30-80L.
When the electron blocking layer grows, the needed MO source usage amount and the needed reaction gas flow rate are relatively small in each layer, although the electron blocking layer is doped with Al and Mg, the thickness of the electron blocking layer is small, and the influence of the doping concentration on the usage amount of the purging gas of the reaction cavity cover is small, so that the usage amount of the purging gas of the reaction cavity cover is the minimum when the electron blocking layer grows.
Optionally, when the electron blocking layer grows, the usage amount M5 of the purge gas of the reaction cavity cover is 15-18L. If M5 is less than 15L, the effect of reducing surface particles is not obtained because the purge gas is used in a small amount. If M5 is greater than 18L, the production cost increases.
Illustratively, when the electron blocking layer is grown, the usage amount M5 of the purge gas of the reaction cavity cover is 15-17L, and the usage amount is most suitable.
Step 207, a P-type layer is grown on the electron blocking layer.
Wherein the P-type layer is a GaN layer doped with Mg with a doping concentration of 1020cm-3～1021cm-3Preferably 5 x 1020cm-3。
Illustratively, TMGa and CP are introduced into the reaction chamber2Mg is respectively used as a gallium source and an Mg source, and N is introduced2、H2And NH3Controlling the temperature in the reaction cavity to be 940-980 ℃ and the pressure to be 200-600 torr, and growing a P-type layer with the thickness of 50-80 nm on the electron blocking layer.
Wherein the flow rate of TMGa introduced into the reaction cavity is 1000-2000 sccm, and CP2The flow rate of Mg is 500-2The gas flow rate of (A) is 50-100L, H2Of (2) a gasFlow rate of 100-200L, NH3The gas flow rate of (2) is 30-80L.
Optionally, when the P-type layer is grown, the usage amount M6 of the purge gas of the reaction chamber cover is 18-25L. Since this layer is the main donor layer for holes, maximum activation of Mg atoms is required. If M6 is less than 18L, the required amount of this layer cannot be satisfied, and the activation effect of Mg is affected. If the amount is more than 25L, the production cost is increased because the amount is excessively large.
Illustratively, when a P-type layer grows, the using amount M6 of the purging gas of the reaction cavity cover is 18-23L, and the doping effect of Mg atoms can be guaranteed.
Although the thickness of the P-type layer is slightly thicker than that of the electron blocking layer, the flow of the used MO source and the introduced gas is also larger, the used amount of the purging gas of the reaction cavity cover is set to be smaller than that of the high-temperature buffer layer due to the fact that the thickness of the P-type layer is close to the tail sound of growth.
After the steps are completed, the temperature of the reaction cavity can be reduced to 650-850 ℃, annealing treatment is carried out for 5-15 min in a nitrogen atmosphere, then the temperature is gradually reduced to the room temperature, and the epitaxial growth of the light emitting diode is finished.
The growing method provided by the embodiment of the disclosure limits the usage amount of the purge gas of the reaction cavity cover to be set according to the usage amount of the MO source required by each layer, the flow rate of the reaction gas required by each layer, the growth thickness of each layer, the doping concentration of each layer and the growth stage of each layer. Because the reaction chamber is swept to the sweeping gas of reaction chamber lid to the tail gas end of reaction chamber is reached to the accessory substance of quickening the reaction, with outside discharging the accessory substance to the reaction chamber, reduces the deposit of accessory substance at the reaction chamber lateral wall, and then reduces the impurity content in the reaction chamber, can reduce the production of reaction in-process surface particulate matter finally. Therefore, according to the MO source usage amount required by each layer, the reaction gas flow required by each layer, the growth thickness of each layer, the doping concentration of each layer and the growth stage of each layer, the usage amount of the purging gas of the reaction cavity cover can be more reasonably set when each layer grows, and byproducts generated when each layer grows can be guaranteed to be discharged out of the reaction cavity, so that the generation of surface particles in the epitaxial wafer growth process is reduced, a good surface is formed, and the light emitting effect of the micro LED is guaranteed.
One specific implementation of the method for growing the light emitting diode epitaxial wafer shown in fig. 2 includes: when a low-temperature buffer layer, a high-temperature buffer layer, an N-type layer, an active layer, an electron blocking layer and a P-type layer are sequentially grown on the substrate, the using amounts of the purging gases of the reaction cavity cover are respectively M1, M2, M3, M4, M5 and M6. Wherein, M1-15L, M2-20L, M3-30L, M4-25L, M5-10L, and M6-25L.
Compared with the micro LED chip which is prepared by growth without limiting the usage amount of the purging gas of the reaction cavity cover when each layer grows in the prior art, the average value of the surface particle number of the single micro LED chip is reduced to 100 from 300.
The above description is intended to be exemplary only and not to limit the present disclosure, and any modification, equivalent replacement, or improvement made without departing from the spirit and scope of the present disclosure is to be considered as the same as the present disclosure.

Claims (9)

1. A growth method of a micro light-emitting diode epitaxial wafer comprises the following steps:
providing a substrate;
growing an epitaxial layer on the substrate, wherein the epitaxial layer comprises a low-temperature buffer layer, a high-temperature buffer layer, an N-type layer, an active layer, an electron blocking layer and a P-type layer which are sequentially grown;
the method is characterized in that when an epitaxial layer grows on the substrate, purging gas is introduced into a cavity cover of a reaction cavity, and a by-product generated in the reaction cavity is purged to a tail gas end of the reaction cavity so as to be discharged out of the reaction cavity;
the usage amount of the purge gas is positively correlated with the usage amount of the MO source required by each layer, the flow of the reaction gas required by each layer, the growth thickness of each layer and the doping concentration of each layer;
the usage amount of the purge gas is also related to the growth stage of each layer of the epitaxial layer, the growth stage of each layer of the epitaxial layer is divided into an initial growth stage, an intermediate growth stage and an end growth stage, and the usage amount of the purge gas in the intermediate growth stage is larger than that in the initial growth stage and the end growth stage;
growing the low-temperature buffer layer and the high-temperature buffer layer at the initial growth stage, growing the N-type layer and the active layer at the intermediate growth stage, and growing the electron blocking layer and the P-type layer at the end growth stage.
2. The growth method of claim 1, wherein when a low-temperature buffer layer, a high-temperature buffer layer, an N-type layer, an active layer, an electron blocking layer and a P-type layer are sequentially grown on the substrate, the used amounts of the purge gas of the reaction chamber cover are M1, M2, M3, M4, M5 and M6;
wherein M5 is more than M1 is more than M2 is more than M3, M5 is more than M4 is more than M3, and M5 is more than M6 is more than M3.
3. The growth method according to claim 2, wherein the purge gas is used in an amount of 10L to 30L.
4. The growing method of claim 3, wherein M1 is 15-20L, M2 is 20-25L, M3 is 25-30L, M4 is 16-20L, M5 is 15-18L, and M6 is 18-25L.
5. The growth method according to any one of claims 1 to 4, wherein the MO source required for the growth of each layer comprises TEGa/TMGa/TMIn/TMAl/CP2At least one of Mg.
6. The growth method according to any one of claims 1 to 4, wherein the reaction gas required for the growth of each layer comprises SiH4/H2/NH3/N2At least one of (1).
7. The growth method according to any one of claims 1 to 4, wherein the low-temperature buffer layer has a thickness of 15 to 30nm, the high-temperature buffer layer has a thickness of 2 to 3.5um, the N-type layer has a thickness of 2 to 3um, the active layer has a thickness of 130 to 160nm, the electron blocking layer has a thickness of 30 to 50nm, and the P-type layer has a thickness of 50 to 80 nm.
8. The growth method according to any one of claims 1 to 4, wherein the low-temperature buffer layer is an Al-doped GaN layer, the N-type layer is an Si-doped GaN layer, and the electron blocking layer is Mg-doped AlyGa1-yAnd the N layer, y is 0.15-0.25, and the P layer is a GaN layer doped with Mg.
9. The growth method according to claim 8, wherein the doping concentration of Al in the low-temperature buffer layer is 1 x 103cm-3～3*103cm-3The doping concentration of Si in the N-type layer is 1019cm-3～6*1019cm-3The doping concentration of Mg in the electron blocking layer is 1018cm-3～1019cm-3The doping concentration of Mg in the P-type layer is 1020cm-3～1021cm-3。
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