CN219350147U - Epitaxial structure - Google Patents

Abstract

The application provides epitaxial structures. The epitaxial structure comprises a substrate, and a buffer layer and an epitaxial layer which are sequentially stacked on one side of the substrate, wherein the buffer layer is made of P-GaN, and the epitaxial layer is made of GaN, alN or InN. The P-GaN buffer layer is arranged, atoms can be promoted to gather on the surface along the arrangement direction perpendicular to the substrate and the epitaxial layer by the P-GaN buffer layer, so that the buffer layer and/or the epitaxial layer can be promoted to preferentially grow along the arrangement direction perpendicular to the substrate and the epitaxial layer, and the longitudinal growth of the buffer layer and/or the epitaxial layer is restrained, so that the thickness of the buffer layer and/or the epitaxial layer is reduced, the surface roughness and the crystal quality meeting the device requirements are realized by the epitaxial layer with the submicron thickness, the specific device structure requirement with the limited epitaxial layer thickness is met, the preparation efficiency is effectively improved, and the production cost is reduced.

Description

Epitaxial structure

Technical Field

The application belongs to the technical field of semiconductors, and particularly relates to an epitaxial structure.

Background

In the field of semiconductor technology, it is often necessary to epitaxially prepare thin films with device design requirements. Because of the different lattice constants and thermal expansion coefficients, the thicker the epitaxial layer is, the more easily the epitaxial layer is cracked, and the requirement of the epitaxial structure of a specific device with the limited thickness of the epitaxial layer cannot be met.

Disclosure of Invention

In the technical field of semiconductors, the prepared epitaxial layer has larger thickness due to different lattice constants and thermal expansion coefficients of the epitaxially prepared thin film, so that the epitaxial layer with larger thickness is easy to crack and can not meet the requirement of an epitaxial structure of a specific device.

In view of this, the application provides an epitaxial structure, the epitaxial structure includes the substrate, and in proper order range upon range of setting up in buffer layer and epitaxial layer of substrate one side, the material of buffer layer is P-GaN, the material of epitaxial layer is GaN, or AlN, or InN.

The application provides an epitaxial structure, which consists of a substrate, a buffer layer and an epitaxial layer. The substrate provides a preparation basis for forming the buffer layer and the epitaxial layer. The buffer layer provides a preparation basis for the subsequent formation of the epitaxial layer.

Specifically, the buffer layer and/or the epitaxial layer are laterally grown under the action of the P-GaN buffer layer, and longitudinal growth is inhibited. Wherein, the longitudinal growth refers to that the direction of epitaxial growth is parallel to the arrangement direction of the substrate and the epitaxial layer; lateral growth refers to the direction of epitaxial growth perpendicular to the alignment direction of the substrate and epitaxial layers. In other words, the P-GaN buffer layer can promote atoms to gather on the surface along the direction perpendicular to the arrangement direction of the substrate and the epitaxial layer, thereby promoting the buffer layer and/or the epitaxial layer to preferentially grow along the direction perpendicular to the arrangement direction of the substrate and the epitaxial layer, and inhibit the longitudinal growth of the buffer layer and/or the epitaxial layer, thereby reducing the thickness of the buffer layer and/or the epitaxial layer. Because the buffer layer and/or epitaxial layer in the present application have a smaller overall thickness than the related art, the specific device process requirements with limited epitaxial layer thickness can be met.

Therefore, the lateral growth of the buffer layer and/or the epitaxial layer is enabled under the action of the P-GaN buffer layer, the longitudinal growth is restrained, the thickness of the buffer layer and/or the epitaxial layer is reduced, the surface roughness and the crystal quality meeting the device requirements are realized by the epitaxial layer with the submicron thickness, and therefore the specific device process requirements with the limited thickness of the epitaxial layer are met.

Wherein, in the arrangement direction of the substrate and the buffer layer, the thickness of the epitaxial layer is 200nm-990nm.

Wherein, the doping concentration c of magnesium element and/or antimony element in the buffer layer satisfies the following conditions: 1X 10 ¹⁷ cm ^-3 ≤c≤3×10 ¹⁹ cm ^-3 。

Wherein, when the buffer layer has at least one of magnesium element and antimony element, the buffer layer comprises a plurality of second nuclear islands arranged at intervals.

Wherein the density ρ2 of the second nuclear island satisfies the following condition: 4.2X10 ⁶ cm ^-2 ≤ρ2≤4.8×10 ⁸ cm ^-2 。

Wherein, in an arrangement direction perpendicular to the substrate and the buffer layer, a height h2 of the second nuclear island satisfies the following condition: h2 is more than or equal to 50nm and less than or equal to 250nm.

Wherein the spacing between at least some adjacent second nuclear islands is unequal.

Wherein, the root mean square RMS of the surface roughness of the epitaxial layer facing away from the substrate satisfies the following conditions: RMS is more than or equal to 0.2nm and less than or equal to 5nm.

Wherein the epitaxial structure satisfies at least one of:

in the epitaxial structure, the epitaxial structure has a hexagonal system, and the swing curve half width of XRD along the diffraction angle of the (0002) plane of the hexagonal system is not more than 200 arc seconds;

in the epitaxial structure, the epitaxial structure has a hexagonal system, and a rocking curve half width at diffraction angle of XRD along a (10-12) plane of the hexagonal system is not more than 400 arcsec.

Drawings

In order to more clearly describe the technical solutions in the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be described below.

Fig. 1 is a process flow diagram of a method of fabricating an epitaxial structure in an embodiment of the present application.

Fig. 2 is a schematic diagram of an epitaxial structure corresponding to S300 in fig. 1.

Fig. 3 is a process flow chart included in S200 in an embodiment of the present application.

Fig. 4 is a schematic diagram of an epitaxial structure corresponding to S210 in fig. 3.

Fig. 5 is a schematic diagram of an epitaxial structure corresponding to S220 in fig. 3.

Fig. 6 is a process flow chart included in S300 in an embodiment of the present application.

Fig. 7 is a schematic diagram of an epitaxial structure corresponding to S310 in fig. 6.

Fig. 8 is a process flow chart included in S320 in an embodiment of the present application.

Fig. 9 is a schematic structural view of an epitaxial structure according to an embodiment of the present application.

Description of the reference numerals:

the semiconductor device comprises an epitaxial structure-1, a substrate-11, a buffer layer-12, a second nuclear island-121, an epitaxial layer-13, a first nuclear island-141 and a third nuclear island-151.

Detailed Description

The following are preferred embodiments of the present application and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present application and are intended to be within the scope of the present application.

The application provides a preparation method of an epitaxial structure 1. Referring to fig. 1 and fig. 2 together, fig. 1 is a process flow chart of a method for preparing an epitaxial structure according to an embodiment of the present application. Fig. 2 is a schematic diagram of an epitaxial structure corresponding to S300 in fig. 1. The present embodiment provides a method for manufacturing an epitaxial structure 11, where the method for manufacturing the epitaxial structure 11 includes S100, S200, and S300. Among them, S100, S200, S300 are described in detail as follows.

S100, a substrate 11 is provided.

The epitaxial structure 1 in this embodiment provides a substrate 11 that can provide a load bearing basis for the preparation of other layers. The shape, material, and thickness of the substrate 11 are not limited in this application. Alternatively, the material of the substrate 11 includes, but is not limited to, sapphire, silicon carbide, gallium nitride, aluminum nitride, and the like.

Further alternatively, the material of the substrate 11 is sapphire. When the material of the substrate 11 is sapphire and the material of the epitaxial layer 13 is gallium nitride, the defect of the epitaxial layer 13 can be reduced due to relatively low lattice mismatch between gallium nitride and sapphire, and the sapphire has wide availability, good thermal stability, mature manufacturing process and relatively low cost, so that the sapphire is selected as the material of the substrate 11, and the gallium nitride is selected as the material of the epitaxial layer 13, so that the epitaxial structure 1 with higher crystal quality can be obtained, and the preparation cost can be reduced.

It should be noted that epitaxial growth in the following text of the present application includes lateral growth and longitudinal growth. Longitudinal growth refers to the direction of epitaxial growth parallel to the alignment direction of the substrate 11 and the buffer layer 12 (as shown in the direction D in fig. 2); lateral growth refers to the direction of epitaxial growth perpendicular to the alignment direction of the substrate 11 and the buffer layer 12.

S200, forming a buffer layer 12 on the substrate 11 side.

The buffer layer 12 provided by the epitaxial structure 1 in this embodiment can provide a preparation basis for the subsequent formation of the epitaxial layer 13. The shape, material, and thickness of the buffer layer 12 are not limited in this application. Optionally, the material of the buffer layer 12 includes, but is not limited to GaN, alN, inN and the like. Preferably, the material of the buffer layer 12 is GaN. In one embodiment, the GaN buffer layer 12 containing magnesium element may also be understood as a P-GaN buffer layer 12.

Alternatively, in the arrangement direction of the substrate 11 and the buffer layer 12, the thickness d1 of the buffer layer 12 satisfies the following condition: d1 is less than or equal to 120nm and less than or equal to 200nm. Preferably, the thickness d1 of the buffer layer 12 satisfies the following condition: d1 is more than or equal to 140nm and less than or equal to 190nm. Further preferably, the thickness d1 of the buffer layer 12 satisfies the following condition: d1 is less than or equal to 160nm and less than or equal to 180nm.

The thickness of the buffer layer 12 is designed to be in the above range, so that not only can a preparation foundation be provided for the subsequent formation of the epitaxial layer 13 to grow the epitaxial layer 13 with a smaller thickness, but also the defect of the substrate 11 can be shielded to play a role of buffering. If the thickness of the buffer layer 12 is too small, the distribution of the nuclear islands is loose, which is unfavorable for the lateral growth and combination of GaN seed crystals, so that the buffer layer 12 cannot play the defect of the shielding substrate 11, play the buffer function between the substrate 11 and other layers, and is unfavorable for the preparation of the subsequent layers. If the thickness of the buffer layer 12 is too large, the production efficiency of the buffer layer 12 is too low, and the production cost increases. Therefore, the thickness of the buffer layer 12 is 120nm-200nm, which not only can provide a preparation foundation for the subsequent formation of the epitaxial layer 13 to grow the epitaxial layer 13 with smaller thickness, but also can shield the defect of the substrate 11 to play a role of buffering.

As shown in fig. 2, S300, an epitaxial layer 13 is formed on a side of the buffer layer 12 facing away from the substrate 11; wherein at least one of a magnesium-containing source and an antimony source is added during the formation of the buffer layer 12 and/or the epitaxial layer 13.

The magnesium source in the present embodiment includes at least one of magnesium ions and magnesium atoms. The antimony source in this embodiment includes at least one of antimony ions and antimony atoms.

The epitaxial structure 1 of the present embodiment provides the epitaxial layer 13 with a smaller thickness to meet the specific device process requirements of the limited thickness of the epitaxial layer 13. The shape, material, and thickness of the epitaxial layer 13 are not limited in this application. Optionally, epitaxial layer 13 comprises a III-V nitride. The material of epitaxial layer 13 includes, but is not limited to GaN, alN, inN and the like. Preferably, the material of the epitaxial layer 13 is GaN.

Alternatively, in the arrangement direction of the substrate 11 and the buffer layer 12, the thickness of the epitaxial layer is 200nm to 990nm in the arrangement direction of the substrate and the buffer layer. Alternatively, the thickness d2 of the epitaxial layer 13 satisfies the following condition: d2 is more than or equal to 300nm and less than or equal to 900nm. Preferably, the thickness d2 of the epitaxial layer 13 satisfies the following condition: d2 is more than or equal to 400nm and less than or equal to 800nm. Further preferably, the thickness d2 of the epitaxial layer 13 is 600nm.

The thickness of the epitaxial layer 13 is designed to be in the above range, so that not only can the specific device process requirement of the epitaxial layer 13 with limited thickness be met, but also the crystal quality of the epitaxial layer 13 can be ensured to be higher, so as to meet the requirement of users or products. If the thickness of the epitaxial layer 13 is too small, the epitaxial layer 13 cannot completely cover the buffer layer 12, and the crystal quality of the epitaxial layer 13 is low, which is unfavorable for the preparation of subsequent layers. If the thickness of the epitaxial layer 13 is too large, the space occupied by the epitaxial layer 13 is too large, which is not beneficial to the subsequent device structure layers, and the manufacturing cost is increased. Therefore, the thickness of the epitaxial layer 13 is 200nm-990nm, which not only can meet the process requirements of specific devices with limited thickness of the epitaxial layer 13, but also can ensure that the crystal quality of the epitaxial layer 13 is higher so as to meet the requirements of users or products.

The epitaxial structure 1 includes a device structure layer disposed on a side of the epitaxial layer 13 facing away from the buffer layer 12. The device structure layers include, but are not limited to, active layers, confinement layers, refractive layers, and the like. The device structure layer can be prepared according to the needs of users or products.

The embodiment provides a preparation method of the epitaxial structure 1, which is simple in process and high in operability. First, a buffer layer 12 is formed on one side of a substrate 11. Then, an epitaxial layer 13 is formed on the side of the buffer layer 12 facing away from the substrate 11. Wherein at least one of a magnesium-containing source and an antimony source is added during the formation of the buffer layer 12 and/or the epitaxial layer 13, so that the buffer layer 12 has at least one of a magnesium element and an antimony element therein.

Specifically, the incorporation of magnesium and/or antimony promotes the lateral growth of the buffer layer 12 and/or the epitaxial layer 13, in other words, the incorporation of magnesium and/or antimony promotes the aggregation of atoms at the surface in the direction perpendicular to the arrangement direction of the substrate 11 and the epitaxial layer 13, thereby promoting the preferential growth of the buffer layer 12 and/or the epitaxial layer 13 in the direction perpendicular to the arrangement direction of the substrate 11 and the epitaxial layer 13, and suppressing the longitudinal growth of the buffer layer 12 and/or the epitaxial layer 13, thereby reducing the thickness of the buffer layer 12 and/or the epitaxial layer 13. Because the buffer layer 12 and/or the epitaxial layer 13 in the present application have a smaller thickness than the related art, the specific device process requirements of the epitaxial layer 13 with a limited thickness can be satisfied.

Therefore, in this embodiment, when the buffer layer 12 and/or the epitaxial layer 13 are prepared, the magnesium source and/or the antimony source is introduced to promote the lateral growth of the crystal, so as to reduce the thickness of the buffer layer 12 and/or the epitaxial layer 13, thereby reserving more growth space for the device structure layer growing on one side of the epitaxial layer 13, and realizing the surface roughness and crystal quality meeting the device requirements with the epitaxial layer 13 with submicron thickness, so that the device structure layer can better exert its performance, and the working performance of the epitaxial structure 1 is improved.

Optionally, during the formation of the buffer layer 12 and/or the epitaxial layer 13, the magnesium source comprises biscyclopentadienyl magnesium (Cp ₂ Mg), bis-methylcyclophenyldienylmagnesium (MeCp) ₂ At least one of Mg, the antimony source comprises triethylantimony (TESb), and tri-diethylaminoantimony [ (CH) ₃ ) ₂ N] ₃ At least one of Sb.

Referring to fig. 3-5 together, fig. 3 is a process flow chart included in S200 in an embodiment of the present application. Fig. 4 is a schematic diagram of an epitaxial structure corresponding to S210 in fig. 3. Fig. 5 is a schematic diagram of an epitaxial structure corresponding to S220 in fig. 3. In one embodiment, S200, the step of forming the buffer layer 12 on the substrate 11 side includes:

as shown in fig. 4, S210, the buffer layer 12 is formed on one side of the substrate 11; wherein at least one of the magnesium source and the antimony source is added during the formation of the buffer layer 12.

Optionally, during the process of forming the buffer layer 12, the reaction temperature is 510 ℃ to 560 ℃, the reaction chamber pressure is 380torr to 420torr, and the flow of the magnesium source and/or the antimony source is 130sccm to 170sccm.

Preferably, during the formation of the buffer layer 12, the reaction temperature is 520-550 ℃, the reaction chamber pressure is 390-410 torr, and the flow rate of the magnesium source and/or the antimony source is 140-160 sccm.

It is further preferred that the reaction temperature is 535 deg.c, the reaction chamber pressure is 400torr, and the flow rate of the magnesium source and/or the antimony source is 150sccm during the formation of the buffer layer 12.

Designing the reaction temperature of the buffer layer 12 to the above-described range can ensure not only that the carrier mobility is high but also that the surface roughness of the buffer layer 12 is low to meet the subsequent manufacturing requirements. If the reaction temperature is too high or too low, the carrier mobility of the buffer layer 12 becomes low, and the surface roughness of the buffer layer 12 is large, which is unfavorable for the subsequent preparation of the epitaxial layer 13.

The pressure of the reaction chamber of the buffer layer 12 is designed in the above range, so that not only can the higher migration capability of the atomic groups be ensured, but also the higher crystal quality of the buffer layer 12 can be ensured, so as to meet the subsequent preparation requirements. If the reaction pressure is too high or too low, the radical mobility is reduced, dislocations in the buffer layer 12 are increased, and the crystal quality is lowered.

Designing the flow rate of the magnesium source and/or the antimony source to the above-described range not only ensures that the amount of the magnesium source and/or the antimony source is sufficient to promote lateral growth of the buffer layer 12, but also provides cost savings. If the flow rate of the magnesium source and/or the antimony source is too small, the effect of promoting the lateral growth of the buffer layer 12 may be affected, and even the subsequent preparation of the epitaxial layer 13 with a smaller thickness may be disadvantageous. If the flow of the magnesium source and/or antimony source is too large, the cost of preparation increases.

Optionally, when the material of the buffer layer 12 is gallium nitride, a nitrogen source and a gallium source are added in the process of forming the buffer layer 12, wherein the nitrogen source includes nitrogen gas, and the gallium source includes trimethylgallium.

As shown in fig. 5, S220 is performed to anneal the buffer layer 12 at a high temperature.

Optionally, in the process of performing high-temperature annealing treatment on the buffer layer 12, the annealing temperature is 1040-1080 ℃, and the annealing time is 2-5 min.

The annealing temperature and the annealing time of the buffer layer 12 are designed in the above ranges, so that not only the crystal defect density of the buffer layer 12 can be reduced, but also the surface roughness of the buffer layer 12 can be ensured to be low, so as to meet the subsequent preparation requirements. If the reaction temperature is too high or too low; or, too long or too short annealing time may result in higher crystal defect density of the buffer layer 12, and larger surface roughness of the buffer layer 12, which is not beneficial to the subsequent preparation of the epitaxial layer 13.

In this embodiment, the buffer layer 12 is formed first, and then subjected to high-temperature annealing. Firstly, in the process of forming the buffer layer 12, magnesium element and/or antimony element can be doped in the buffer layer 12, so as to promote the lateral growth of the buffer layer 12, reduce the defects of the buffer layer 12, improve the crystal quality of the buffer layer 12, and provide a foundation for the subsequent preparation of the epitaxial layer 13 with higher crystal quality. Then, the buffer layer 12 is annealed at a high temperature, and at this time, the amorphous structure of the buffer layer 12 is recrystallized, so as to further reduce the crystal defect density of the buffer layer 12, further improve the crystal quality of the buffer layer 12, and further provide a basis for the subsequent preparation of the epitaxial layer 13 with higher crystal quality. Therefore, the buffer layer 12 has lower thickness and higher crystal quality, and provides a basis for the subsequent preparation of the epitaxial layer 13.

Optionally, during the formation of the epitaxial layer 13 on the side of the buffer layer 12 facing away from the substrate 11, the reaction temperature is the same as the annealing temperature. Further alternatively, the reaction temperature is 1040-1080 ℃ during the formation of the epitaxial layer 13 on the side of the buffer layer 12 facing away from the substrate 11.

The annealing in this embodiment can not only recrystallize the amorphous structure to improve the crystal quality, but also because the annealing temperature is the same as the temperature at which the epitaxial layer 13 is formed. After forming the buffer layer 12, high temperature annealing is performed, and then in the process of forming the epitaxial layer 13 at high temperature, the temperature is raised from low temperature to high temperature, so that the epitaxial structure 1 is better and more suitable for the temperature change, and the crystal quality is improved.

Referring again to fig. 4 and 5, in one embodiment, as shown in fig. 4, the buffer layer 12 includes a plurality of connected first core islands 141.

As shown in fig. 5, the plurality of first nuclear islands 141 are subjected to a high temperature annealing process to merge portions of the plurality of first nuclear islands 141 with each other to transform into a plurality of second nuclear islands 121 arranged at intervals. And the height of the first nuclear island 141 is smaller than the height of the second nuclear island 121.

In the present embodiment, the buffer layer 12 includes a plurality of first core islands 141, and the size, dimension, and arrangement of the first core islands 141 are not limited in the present embodiment. Since the plurality of first nuclear islands 141 are closely connected, the plurality of first nuclear islands 141 can also be approximately regarded as one plane.

Specifically, the pressure of the reaction chamber of the buffer layer 12 is designed to be 380torr-420torr, which can ensure that the migration capability of atomic groups is high, and ensure that the crystal quality of the buffer layer 12 is high, so as to meet the subsequent preparation requirement. If the reaction chamber pressure is too small, the size of the islands in the initial nucleation stage is too small, the density is high, and when the islands merge, the merge speed is high, a large number of edge dislocations are generated, and the crystal quality of the buffer layer 12 is lowered. If the reaction chamber pressure is too high, that is, the reaction chamber pressure is relatively increased, although the size of the nuclear islands can be increased, resulting in a decrease in the density of the nuclear islands, when the nuclear islands merge, the merging speed will be slowed down, and the generated edge dislocation annihilates with the mixed dislocation to improve the crystal quality of the buffer layer 12, but the conventional MOCVD equipment cannot work normally under the excessive reaction chamber pressure.

In one embodiment, the height h1 of the first nuclear island 141 satisfies the following condition: h1 is less than or equal to 15nm and less than or equal to 35nm. Preferably, the height h1 of the first nuclear island 141 satisfies the following condition: h1 is more than or equal to 20nm and less than or equal to 30nm.

The height of the first nuclear island 141 is designed to be within the above range to ensure that the high temperature annealing process can produce the second nuclear island 121 with a moderate size to meet the requirement of the subsequent preparation of the epitaxial layer 13. If the height of the first nuclear island 141 is too large or too small, the crystal quality is reduced, and the subsequent requirement for preparing the epitaxial layer 13 cannot be satisfied. The first nuclear islands 141, which are too small in height, result in thinner buffer layer 12, which is detrimental to lateral growth and incorporation, and the nucleation centers are more evacuated after annealing, resulting in insufficient coverage. The first nuclear island 141 having an excessively large height causes the buffer layer 12 to be thicker, which is disadvantageous for the subsequent epitaxial layer 13 growth. So the height of the first nuclear island 141 is designed to be 15nm-35nm, so that the high-temperature annealing treatment can be ensured to generate the second nuclear island 121 with moderate size so as to meet the requirement of preparing the epitaxial layer 13 later.

Optionally, the pitch between the nuclear islands of two adjacent first nuclear islands 141 is not greater than 91nm.

In the present embodiment, the buffer layer 12 after the high temperature annealing treatment includes a plurality of second nuclear islands 121, and the size, dimension, and arrangement of the second nuclear islands 121 are not limited in the present embodiment. After the buffer layer 12 is subjected to the rollback processing, the plurality of first core islands 141 are converted into the plurality of second core islands 121. Wherein the second nuclear island 121 is formed by the combined growth of part of the first nuclear island 141. For example, 3 first core islands 141 merge to form 1 second core island 121.

In one embodiment, the height h2 of the second nuclear island 121 satisfies the following condition: h2 is more than or equal to 50nm and less than or equal to 250nm. Preferably, the height h2 of the second nuclear island 121 satisfies the following condition: h2 is less than or equal to 100nm and less than or equal to 150nm.

The height of the second nuclear island 121 is designed to be within the above range, so that the crystal quality of the buffer layer 12 after the high-temperature annealing treatment can be ensured to be higher, and the requirement of preparing the epitaxial layer 13 later can be met. If the height of the second core island 121 is too large or too small, the crystal quality is reduced, and the subsequent requirement for preparing the epitaxial layer 13 cannot be satisfied. The second core islands 121 with too small or too large height may cause the buffer layer 12 after the high-temperature annealing treatment to be thinner or thicker, so that the crystal defect density of the buffer layer 12 is larger, and further the crystal quality of the buffer layer 12 is reduced, which is not beneficial to the subsequent preparation of the epitaxial layer 13. So the height of the second nuclear island 121 is designed to be 50nm-250nm, the second nuclear island 121 can be ensured to be moderate in size, so that the crystal quality of the buffer layer 12 is higher, and the requirement of the subsequent preparation of the epitaxial layer 13 is met.

The size of the second core islands 121 is designed in the above-described range to ensure a high crystal quality of the buffer layer 12, meeting the subsequent requirements for preparing the epitaxial layer 13. If the size of the second core island 121 is too large or too small, the crystal quality is reduced, and the subsequent requirement for preparing the epitaxial layer 13 cannot be satisfied. The undersize or oversized second core islands 121 may result in a larger crystal defect density of the buffer layer 12, thereby reducing the crystal quality of the buffer layer 12, which is detrimental to the subsequent preparation of the epitaxial layer 13. The second core island 121 is designed to have a size of 50nm-250nm, so that the second core island 121 can be ensured to have a moderate size, so that the crystal quality of the buffer layer 12 is higher, and the requirement of preparing the epitaxial layer 13 later can be met.

In one embodiment, the density of the first nuclear islands 141 is greater than the density of the second nuclear islands 121.

Alternatively, the density ρ1 of the first nuclear island 141 and the density ρ2 of the second nuclear island 121 satisfy the following conditions: 4.2X10 ¹⁰ cm ^-2 ≤ρ1≤4.8×10 ¹⁰ cm ^-2 、4.2×10 ⁶ cm ^-2 ≤ρ2≤4.8×10 ⁸ cm ^-2 。

In the process of performing the high-temperature annealing treatment on the buffer layer 12, part of the first nuclear islands 141 are merged and converted into the second nuclear islands 121, so that as the high-temperature annealing treatment is performed, the density components of the first nuclear islands 141 of the buffer layer 12 are reduced, so that the buffer layer 12 formed by the second nuclear islands 121 after the high-temperature annealing is obtained, and a basis is provided for growing the epitaxial layer 13 with higher crystal quality in the next step.

Alternatively, the pitch between the core islands of two adjacent second core islands 121 is not more than 1 μm.

Optionally, at least a portion of the spacing between adjacent second nuclear islands 121 is unequal.

Specifically, in one embodiment, the buffer layer 12 incorporating magnesium and/or antimony elements can promote lateral growth during formation of the buffer layer 12 because the presence of the nuclear island sidewalls, which can be considered as highly inclined facets consisting of high density basal plane steps, each of which serves as an effective site for trapping adsorbed atoms, thereby allowing epitaxial growth to proceed preferentially in that direction. The addition of magnesium element and/or antimony element promotes adsorption of atoms on the side wall R plane (1011) of the C plane (0001), which occurs so as to promote growth of the buffer layer 12 in the direction of the R plane (1011), i.e., lateral growth. Wherein the C plane (0001) and the R plane (1011) are perpendicular to each other. Growth along the C-plane (0001) is longitudinal growth, and growth along the R-plane (1011) direction is lateral growth.

Referring to fig. 2 again and fig. 6-7, fig. 6 is a process flow chart included in S300 in an embodiment of the present application. Fig. 7 is a schematic diagram of an epitaxial structure corresponding to S310 in fig. 6.

In one embodiment, S300, the step of forming the epitaxial layer 13 on the side of the buffer layer 12 facing away from the substrate 11 includes:

as shown in fig. 7, S310, a plurality of third nuclear islands 151 are epitaxially formed on a side of the buffer layer 12 facing away from the substrate 11.

The size, dimension, and arrangement of the third nuclear island 151 are not limited in this embodiment. Optionally, the third nuclear islands 151 are interconnected. Since the plurality of third nuclear islands 151 are closely connected, the plurality of third nuclear islands 151 may also be approximately regarded as one plane. In one embodiment, the height h3 of the third nuclear island 151 satisfies the following condition: h3 is more than or equal to 250nm and less than or equal to 700nm. Further alternatively, the height h3 of the third nuclear island 151 satisfies the following condition: h3 is more than or equal to 300nm and less than or equal to 600nm. Still further alternatively, the height h3 of the third nuclear island 151 satisfies the following condition: h3 is more than or equal to 350nm and less than or equal to 550nm.

Alternatively, the third nuclear island 151 in the present embodiment can also be understood as a 3D nuclear island, meaning that the growth direction of the third nuclear island 151 can be parallel to the alignment direction of the substrate and the buffer layer, i.e., longitudinal growth; but also can grow transversely, which is perpendicular to the arrangement direction of the substrate and the buffer layer. Wherein the main growth direction of the third nuclear island 151 is longitudinal.

Designing the height of the third nuclear island 151 to the above-described range can ensure that the demand for the subsequent production of the epitaxial layer 13 is satisfied. If the height of the third nuclear island 151 is too small, lateral growth and incorporation will be detrimental. The third nuclear island 151 having an excessively large height increases the thickness of the epitaxial layer 13 to be obtained later, increasing the manufacturing cost. The height of the third nuclear island 151 is designed to be 250nm to 700nm, so that it is possible to ensure that the requirement for the subsequent preparation of the epitaxial layer 13 is satisfied.

In one embodiment, the buffer layer 12 is formed on one side of the substrate 11, and the buffer layer 12 does not have at least one of magnesium element and antimony element. I.e., during formation of the buffer layer 12, at least one of a magnesium-containing source and an antimony source is not added. In the process of forming the buffer layer 12, the first nuclear islands 141 do not have magnesium and antimony elements, and the second nuclear islands 121 of the buffer layer do not have magnesium and antimony elements.

As shown in fig. 2, S320, the plurality of third nuclear islands 151 are epitaxially grown to obtain the epitaxial layer 13, and at least one of the magnesium source and the antimony source is added during the process of forming the epitaxial layer 13.

In the present embodiment, a plurality of third nuclear islands 151 are formed first, and then the epitaxial layer 13 is formed continuously. In continuing to form epitaxial layer 13, a source containing at least one of the magnesium source and the antimony source is added. In the process of continuously forming the epitaxial layer 13, magnesium element and/or antimony element can be doped in the epitaxial layer 13, so that the epitaxial layer 13 is promoted to transversely grow, the thickness of the epitaxial layer 13 is reduced, the specific device process requirement of the epitaxial layer 13 with limited thickness is met, the device structure layer can better exert the performance, and the working performance of the epitaxial structure 1 is improved.

Referring to fig. 8 again, fig. 8 is a process flow chart included in S320 in an embodiment of the present application. In one embodiment, S320, the step of performing epitaxy on the plurality of third nuclear islands 151 includes:

s321, performing epitaxy on the plurality of third nuclear islands 151, where the plurality of third nuclear islands 151 are combined with each other; at least one of the magnesium source and the antimony source is added during the process of combining the plurality of third nuclear islands 151 with each other.

And S322, carrying out epitaxy on the combined plurality of third nuclear islands 151 to obtain the epitaxial layer 13.

The present embodiment adds at least one of the magnesium source and the antimony source in the process of merging the long and flat third nuclear islands 151 to promote the lateral growth of the crystal, providing a basis for reducing the thickness of the epitaxial layer 13. Subsequently, after the plurality of third nuclear islands 151 are combined and flattened, the addition of at least one of the magnesium source and the antimony source is stopped, and the epitaxy is continued, thereby obtaining the epitaxial layer 13 having a submicron thickness. By adopting the preparation method, the epitaxial layer 13 with submicron thickness can be ensured, materials can be saved, and energy loss can be reduced.

In one embodiment, in forming the plurality of third nuclear islands 151, a growth direction of the plurality of third nuclear islands 151 is parallel to an arrangement direction of the substrate 11 and the buffer layer 12; in the process of forming the epitaxial layer 13, the growth direction of the epitaxial layer 13 is perpendicular to the arrangement direction of the substrate 11 and the buffer layer 12.

In the present embodiment, during the formation of the plurality of third nuclear islands 151, the main growth direction of the plurality of third nuclear islands 151 is parallel to the alignment direction of the substrate 11 and the buffer layer 12, in other words, the majority of the plurality of third nuclear islands 151 are longitudinally-extended, and the minority of the plurality of third nuclear islands 151 are laterally-extended. In the process of forming the epitaxial layer 13, the main growth direction of the plurality of third nuclear islands 151 is perpendicular to the alignment direction of the substrate 11 and the buffer layer 12, in other words, most of the epitaxial layer 13 is subjected to lateral epitaxy, and a small part of the epitaxial layer 13 is subjected to longitudinal epitaxy.

By arranging a plurality of third nuclear islands 151 which are longitudinally epitaxial in the main epitaxial direction, and continuing to epitaxially grow a plurality of third nuclear islands 151 which are transversely epitaxial in the main epitaxial direction on the basis, the probability that crystal defects are brought to the epitaxial layer 13 from bottom to top can be reduced, so that the crystal defect density of the epitaxial layer 13 is reduced, and the crystal quality of the epitaxial layer 13 is improved. At the same time, since at least one of the magnesium source and the antimony source is added during the formation of the epitaxial layer 13, the thickness of the epitaxial layer 13 is also ensured to be small.

In one embodiment, the molar flow ratio of the group V source and the group iii source satisfies the following conditions during the lateral growth to form the epitaxial layer 13: V/III is less than or equal to 500 and less than or equal to 1000, and the pressure of the reaction cavity meets the following conditions: p is more than or equal to 50torr and less than or equal to 100torr.

In this embodiment, epitaxial growth is performed under a condition that the V/III ratio is 500 to 1000 and the reaction chamber pressure is 50to 100torr, so that lateral epitaxy can be promoted and the crystal quality of the epitaxial layer 13 can be improved.

Here, the V/III ratio may be used to form the third nuclear island 151 by epitaxy, and/or to perform epitaxy on the plurality of third nuclear islands 151, and/or to perform external delay on the plurality of third nuclear islands 151 after merging, so as to promote lateral epitaxy.

Optionally, the substrate 11 is subjected to a desmear treatment.

Optionally, in the process of decontaminating the substrate 11, the reaction temperature is 1050-1100 ℃, the reaction time is 12-18 min, and the clean atmosphere is hydrogen.

In one embodiment, after the substrate 11 is decontaminated at a high temperature of 1050-1100 ℃, the substrate 11 is naturally cooled to 510-560 ℃, and at this time, a crystal nucleus of aluminum oxynitride is formed on the surface of one side of the substrate 11, which is close to the buffer layer 12, so as to provide a foundation for the preparation of a subsequent layer structure.

In this embodiment, the substrate 11 is subjected to desmutting treatment to remove the contamination on the surface of the substrate 11, so as to facilitate formation of crystal nuclei of aluminum oxynitride, and provide a basis for reducing the degree of mismatch between the substrate 11 and the subsequently prepared epitaxial layer 13, so as to improve the crystal quality of the epitaxial structure 1.

In addition, the second core islands 121 of the buffer layer 12 are scattered and sparse in the related art, and the second core islands 121 can reach up to 615nm in the related art, so that a large amount of atoms are consumed to fill gaps between the second core islands 121 when the epitaxial layer 13 grows on the buffer layer 12, and as the second core islands 121 grow larger, the gaps to be filled are also larger and larger, so that the thickness of the epitaxial layer 13 with higher crystal quality is larger. The epitaxial layer 13 in the related art needs to reach the micron level to meet the preparation requirement of the subsequent device structure layer.

In one embodiment, during the preparation of the epitaxial structure 1, the buffer layer 12 is formed on one side of the substrate 11, i.e. the first nuclear island 141 is formed first. The buffer layer 12 is then subjected to a high temperature annealing treatment. During this high temperature annealing process of the buffer layer 12, most of the first nuclear islands 141 merge with each other to be transformed into second nuclear islands 121, i.e., from smaller first nuclear islands 141 merge to larger second nuclear islands 121. The epitaxial layer 13 is then formed, and during this process of forming the epitaxial layer 13, the second nuclear islands 121 continue to grow and transition to third nuclear islands 151, i.e., from larger second nuclear islands 121 to larger third nuclear islands 151. The growth is then continued on the basis of the third nuclear islands 151 to obtain the epitaxial layer 13, and during this formation of the epitaxial layer 13, the third nuclear islands 151 are connected to form a grid, which is flattened to form the epitaxial layer 13.

However, in this embodiment, when the buffer layer 12 is prepared, the magnesium source and/or the antimony source is introduced to form the buffer layer 12 containing the magnesium element and/or the antimony element, so as to reduce the thickness of the buffer layer 12, thereby reducing the thickness of the epitaxial layer 13, so that the thickness of the epitaxial layer 13 which has higher crystal quality and is smooth and flat in the related art needs to be more than 2 μm to be reduced to submicron, further meeting the specific device process requirement of the epitaxial layer 13 with limited thickness, facilitating the device structure layer to better exert the performance thereof, and improving the working performance of the epitaxial structure 1.

In addition to the above-provided method for manufacturing the epitaxial structure 1, the present application also provides an epitaxial structure 1. The preparation method of the epitaxial structure 1 and the epitaxial structure 1 provided in the embodiments of the present application can achieve the technical effects of the present application, and the two can be used together, or can be used alone, which is not particularly limited in the present application. For example, as an embodiment, the following epitaxial structure 1 may be prepared using the above preparation method of the epitaxial structure 1.

Referring to fig. 9, fig. 9 is a schematic structural diagram of an epitaxial structure according to an embodiment of the present application. The application also provides an epitaxial structure 1, wherein the epitaxial structure 1 comprises a substrate 11, and a buffer layer 12 and an epitaxial layer 13 which are sequentially stacked on one side of the substrate 11, and the buffer layer 12 and/or the epitaxial layer 13 has at least one of magnesium element and antimony element.

The substrate 11, the buffer layer 12, and the epitaxial layer 13 are described in detail above, and are not described here again. In the present embodiment, the magnesium element includes at least one of magnesium ions and magnesium atoms. The antimony element in this embodiment includes at least one of antimony ions and antimony atoms.

The epitaxial structure 1 provided in this embodiment is composed of a substrate 11, a buffer layer 12, and an epitaxial layer 13. The buffer layer 12 and/or the epitaxial layer 13 are doped with magnesium element and/or antimony element to promote the lateral growth of crystals, so as to reduce the thickness of the buffer layer 12 and/or the epitaxial layer 13, thereby meeting the specific device process requirement of the epitaxial layer 13 with limited thickness, realizing the surface roughness and crystal quality meeting the device requirement by the epitaxial layer 13 with submicron thickness, facilitating the device structure layer to better exert the performance thereof, and improving the working performance of the epitaxial structure 1.

Referring again to fig. 9, in one embodiment, the thickness of the epitaxial layer 13 is 200nm-990nm in the alignment direction of the substrate 11 and the buffer layer 12.

Alternatively, as shown in fig. 9, in the arrangement direction D of the substrate 11 and the buffer layer 12, the thickness D1 of the buffer layer 12 satisfies the following condition: d1 is less than or equal to 120nm and less than or equal to 200nm. The thickness d2 of the epitaxial layer 13 satisfies the following condition: d2 is more than or equal to 200nm and less than or equal to 990nm.

The thicknesses of the buffer layer 12 and the epitaxial layer 13 are already described in detail, and will not be described in detail herein. Because the thickness of the epitaxial layer 13 is smaller in the embodiment, the specific device process requirement of the epitaxial layer 13 with limited thickness can be met, the device structure layer can better exert the performance, and the working performance of the epitaxial structure 1 is improved.

In one embodiment, the doping concentration c of magnesium and/or antimony in the buffer layer 12 satisfies the following condition: 1X 10 ¹⁷ cm ^-3 ≤c≤3×10 ¹⁹ cm ^-3 。

Designing the doping concentration of the magnesium element and/or the antimony element to the above-described range not only ensures that the amount of the magnesium element and/or the antimony element is sufficient to promote lateral growth of the buffer layer 12, but also enables cost saving. If the doping concentration of the magnesium element and/or the antimony element is too small, the magnesium element and/or the antimony element cannot be fully utilized to promote the lateral growth of the buffer layer 12, which is disadvantageous for the subsequent preparation of the epitaxial layer 13 with smaller thickness. If the doping concentration of magnesium and/or antimony is too high, the preparation cost is increased and even the growth of the buffer layer 12 is not favored. Therefore, the doping concentration of the magnesium element and/or the antimony element is 1×10 ¹⁷ cm ^-3 -3×10 ¹⁹ cm ^-3 Both to ensure that the amount of magnesium and/or antimony is sufficient to promote lateral growth of the buffer layer 12 and to save costs.

In one embodiment, the buffer layer 12 includes a plurality of second core islands 121 disposed at intervals. Optionally, provided thatThe density ρ2 of the second nuclear island 121 satisfies the following condition: 4.2X10 ⁶ cm ^-2 ≤ρ2≤4.8×10 ⁸ cm ^-2 . Optionally, at least a portion of the spacing between adjacent second core islands 121 is not equal. Alternatively, the pitch between two adjacent second nuclear islands 121 is not more than 1 μm. Alternatively, the size h2 of the second nuclear island 121 in the arrangement direction perpendicular to the substrate and the buffer layer satisfies the following condition: it should be noted that h2 is 50nm or less and 250nm or less, and the schematic structure of the buffer layer 12 can be referred to fig. 5.

In the present embodiment, the second nuclear islands 121 are unevenly distributed on the surface of the substrate 11 side, and the density of the second nuclear islands 121 is maintained at: 4.2X10 ⁶ -4.8×10 ⁸ cm ^-2 Between them. If the density of the second core islands 121 is too high or too low, the crystal defect density of the buffer layer 12 is reduced, so that the crystal quality of the buffer layer 12 is reduced, and the subsequent requirement for preparing the epitaxial layer 13 cannot be met.

Optionally, in one embodiment, the root mean square RMS of the surface roughness of the epitaxial layer 13 facing away from the substrate 11 satisfies the following condition: RMS is more than or equal to 0.2nm and less than or equal to 5nm. In other words, the epitaxial structure 1 in this embodiment has both a thinner thickness of the epitaxial layer 13 and a lower roughness, which provides a basis for the subsequent preparation of the device structure layer.

Optionally, the surface roughness r of the epitaxial layer 13 facing away from the substrate 11 satisfies the following condition: r is more than or equal to 0.20nm and less than or equal to 5.50nm.

Optionally, in one embodiment, the epitaxial structure 1 satisfies at least one of the following conditions:

in the epitaxial structure 1, the epitaxial structure 1 has a hexagonal system, and the half width of a rocking curve of an XRD along a diffraction angle of a (0002) plane of the hexagonal system is not more than 200 arcseconds;

in the epitaxial structure 1, the epitaxial structure 1 has a hexagonal system, and the rocking curve half width of the diffraction angle of XRD along the (10-12) plane of the hexagonal system is not more than 400 arcsec.

In other words, the epitaxial structure 1 in this embodiment has both a thinner thickness of the epitaxial layer 13 and a higher crystal quality, which provides a basis for the subsequent preparation of the device structure layer.

Optionally, in an embodiment, the FWHM value of the crystal plane in the epitaxial structure 1 is not greater than 400 arcsec in an extension direction along the (0002) plane and the (1012) plane in the epitaxial structure 1. Wherein the FWHM value is the full width at half maximum (Full Wave at Half Maximum, FWHM). The FWHM value of the epitaxial structure 1 in the present embodiment is not more than 400 arcsec, in other words, the epitaxial structure 1 in the present embodiment has fewer threading dislocations and mixed dislocations, so the crystal quality of the epitaxial structure 1 is high.

The foregoing has outlined rather broadly the more detailed description of the embodiments of the present application in order that the principles and embodiments of the present application may be explained and illustrated herein, the above description being provided for the purpose of facilitating the understanding of the method and core concepts of the present application; meanwhile, as those skilled in the art will have modifications in the specific embodiments and application scope in accordance with the ideas of the present application, the present description should not be construed as limiting the present application in view of the above.

Claims (8)

1. The epitaxial structure is characterized by comprising a substrate, and a buffer layer and an epitaxial layer which are sequentially stacked on one side of the substrate, wherein the buffer layer is made of P-GaN, and the epitaxial layer is made of GaN, alN or InN.

2. The epitaxial structure of claim 1, wherein a thickness of the epitaxial layer is 200nm-990nm in an alignment direction of the substrate and the buffer layer.

3. The epitaxial structure of claim 1 wherein said buffer layer comprises a plurality of second nuclear islands disposed in spaced apart relation.

4. The epitaxial structure of claim 3 wherein the density ρ2 of the second nuclear islands satisfies the following condition: 4.2X10 ⁶ cm ^-2 ≤ρ2≤4.8×10 ⁸ cm ^-2 。

5. The epitaxial structure of claim 3, wherein a height h2 of said second nuclear island in an alignment direction perpendicular to said substrate and said buffer layer satisfies the following condition: h2 is more than or equal to 50nm and less than or equal to 250nm.

6. The epitaxial structure of claim 3 wherein the spacing between at least some of the adjacent second nuclear islands is unequal.

7. The epitaxial structure of any one of claims 1-6, wherein a root mean square RMS of a surface roughness of a side of the epitaxial layer facing away from the substrate satisfies the following condition: RMS is more than or equal to 0.2nm and less than or equal to 5nm.

8. The epitaxial structure of any one of claims 1-6, wherein the epitaxial structure satisfies at least one of:

in the epitaxial structure, the epitaxial structure has a hexagonal system, and the swing curve half width of XRD along the diffraction angle of the (0002) plane of the hexagonal system is not more than 200 arc seconds;

in the epitaxial structure, the epitaxial structure has a hexagonal system, and a rocking curve half width at diffraction angle of XRD along a (10-12) plane of the hexagonal system is not more than 400 arcsec.

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