CN116516487A - Method for improving crystal quality of multi-element III-nitride-based semiconductor material - Google Patents
Method for improving crystal quality of multi-element III-nitride-based semiconductor material Download PDFInfo
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Classifications
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/40—AIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi
- C30B29/403—AIII-nitrides
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
- C30B25/02—Epitaxial-layer growth
- C30B25/18—Epitaxial-layer growth characterised by the substrate
- C30B25/183—Epitaxial-layer growth characterised by the substrate being provided with a buffer layer, e.g. a lattice matching layer
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
- C30B25/02—Epitaxial-layer growth
- C30B25/18—Epitaxial-layer growth characterised by the substrate
- C30B25/186—Epitaxial-layer growth characterised by the substrate being specially pre-treated by, e.g. chemical or physical means
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
- C30B33/08—Etching
- C30B33/12—Etching in gas atmosphere or plasma
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention discloses a method for improving the crystal quality of a multi-element III-nitride-based semiconductor material. Firstly, growing an etching preparation layer, and carrying out in-situ etching on the etching preparation layer by using a halogen-based source so as to form etching pits in dislocation areas on the surface of the etching preparation layer; and growing a merging layer on the surface of the etching preparation layer, and merging at least part of the etching pit by the merging layer, wherein the etching preparation layer and the merging layer are made of the same material and are all made of multi-element III-nitride. The method provided by the embodiment of the invention can realize preferential etching of the area around dislocation and almost no etching of the plane area by controlling the temperature and other conditions of the reaction chamber, thereby realizing high-efficiency and selective etching of the multi-element III-nitride-based semiconductor materials such as AlGaN and the like, and avoiding the problems of impurity pollution and the like caused by mask medium decomposition in the conventional ELOG growth by generating etching pits in situ.
Description
Technical Field
The invention particularly relates to a method for improving the crystal quality of a multi-element III-nitride-based semiconductor material, belonging to the technical field of semiconductors.
Background
The AlGaN-based semiconductor is a direct wide-bandgap material, the forbidden band width of which is continuously adjustable between 3.4eV and 6.2eV, is an ideal material for preparing ultraviolet light electronic devices (such as ultraviolet LEDs, detectors and lasers) with the working wavelength of 200nm to 365nm, and has wide application prospects in the fields of ultraviolet light solidification, sterilization and disinfection, biomedical treatment, solar blind detection and the like.
AlGaN-based semiconductor materials are typically heteroepitaxially grown on sapphire, silicon carbide, etc. substrates due to the lack of large-size, low-cost AlN single crystal substrates. Heteroepitaxially growing AlGaN typically requires first growing an AlN buffer layer to reduce the lattice mismatch between the substrate and the epitaxial layers. Nevertheless, the lattice mismatch between the substrate/AlN semiconductor material may also result in a high density of threading dislocation defects in the AlN material, and thus the threading dislocation density in the AlGaN material epitaxially grown on AlN is high. In addition, epitaxial growth of AlGaN material on AlN material, relaxation of in-plane lattice mismatch strain will further increase threading dislocation density in the AlGaN material. Therefore, the threading dislocation density in the AlGaN material is generally higher at present, the crystal quality of the material is poor, and the crystal quality of other nitride semiconductor materials (such as GaN and the like) epitaxially grown on the material is difficult to be greatly improved.
In the conventional lateral epitaxial growth method (ELOG) for improving the quality of the AlGaN crystal, a mask pattern is prepared on the surface of an AlGaN semiconductor material or a substrate, then the lateral growth and combination of nitride semiconductor materials in a mask window area are controlled by using epitaxial growth conditions, and dislocation tilt turning is pulled by using the mirror force of an inclined plane, so that the annihilation of the threading dislocation in the window area is promoted, the threading dislocation density is further reduced, and the material quality is improved. Still another method is a method of forming holes and recombining by in-situ etching or growth condition control, which reduces dislocation density in a similar manner to ELOG, except that no masking medium is needed, but dislocation turning is pulled by mirror force of inclined plane in the in-situ hole combining process.
The prior art also discloses a method for improving the crystal quality of the Al (Ga) N-based semiconductor material by adopting the lateral epitaxy ELOG, which mainly comprises the steps of preparing a mask pattern on a nucleation layer, shielding a part of growth area by using the mask pattern, then carrying out secondary epitaxial growth on the Al (Ga) N-based semiconductor material in a window area without a mask medium, and reducing the threading dislocation density in the material by utilizing turning and annihilation of dislocation when the window area material is laterally epitaxially grown and combined. Although the method can reduce the threading dislocation density, the method faces the problem that impurities in the Al (Ga) N semiconductor material are polluted due to pyrolysis of a mask medium, and the optical and electrical properties of the material are affected. More importantly, during the lateral epitaxial growth process, interaction force exists between the Al (Ga) N semiconductor material laterally grown on the mask medium and the mask medium, so that the Al (Ga) N semiconductor material on the mask medium generates an inclined Tilt angle. Adjacent flanking region semiconductor materials with oblique tin angles inevitably form new dislocations and even grain boundary defects during the merging process. In addition, the ELOG technology needs masking, patterning and secondary epitaxial growth, is complex in process and low in production efficiency, and is difficult to be practically applied to large-scale commercial production.
Holes are formed by hydrogen in-situ etching or regulating Al (Ga) N growth conditions, and then lateral growth is performed to promote hole combination, so that the method is a method for reducing dislocation density of AlGaN materials more efficiently. This approach is implemented in two ways:
the first way is to create holes inside the AlN film by controlling the growth conditions such as temperature, V/III ratio, etc., and then merge to reduce the threading dislocation density in the AlGaN material grown thereon by reducing the threading dislocation density in the AlN material. This method can reduce the threading dislocation density in AlN material to some extent, but has two problems: 1) The thick AlN material is needed to combine the holes, so that the overall stress of the AlN material is large; the AlN growth rate is low, so that the epitaxial cost is improved, and the production efficiency is also greatly reduced; 2) This approach suppresses threading dislocations in AlN from extending into the AlGaN material, but fails to suppress new dislocations due to lattice mismatched strain relaxation at the AlN/AlGaN interface. Therefore, the method is adopted to reduce threading dislocation in the AlGaN material, and has very limited effect;
the second mode is that hydrogen is adopted to etch the surface of the AlGaN material in situ at high temperature, the dislocation line position is corroded to form a plurality of discontinuously distributed holes, then an island-shaped SiNx insertion layer is deposited in situ to fill the holes and form a micro mask, and the subsequent lateral epitaxial growth of the AlGaN material is utilized to reduce the threading dislocation density; this approach can be combined with approach one while suppressing threading dislocations from the AlN and AlGaN materials, thereby improving material quality. However, this approach has problems in that it is very difficult to etch AlGaN with hydrogen at high temperature because al—n bond energy is extremely strong, and it is not only long-lasting but also poor in effect; meanwhile, the difficulty of filling holes by accurately controlling the in-situ SiNx islands is very high, so that the repeatability and the uniformity face a great test; it follows that it is not practical to reduce the crystal quality of AlGaN materials in this way.
Disclosure of Invention
The invention mainly aims to provide a method for improving the crystal quality of a multi-element group III nitride based semiconductor material, so as to overcome the defects in the prior art.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides a method for improving the crystal quality of a multi-element group III nitride based semiconductor material, which comprises the following steps:
growing a first semiconductor material layer on a substrate in a reaction chamber;
inputting a halogen-based source into the reaction chamber to etch the first semiconductor material layer, so that a plurality of concave parts are formed on the surface of the first semiconductor material layer;
and inputting a nitrogen source and a metal source into the reaction chamber, and growing a second semiconductor material layer on the first semiconductor material layer.
Compared with the prior art, the invention has the advantages that:
1) The method for improving the crystal quality of the multi-element group III nitride-based semiconductor material provided by the embodiment of the invention has the advantages of simple process, repetition and controllability, and is completely suitable for large-scale production;
2) The method for improving the crystal quality of the multi-element III-nitride-based semiconductor material can avoid the problems of impurity pollution and the like caused by mask medium decomposition in the traditional ELOG growth;
3) According to the method for improving the crystal quality of the multi-element group III nitride-based semiconductor material, provided by the embodiment of the invention, the adopted halogen-based source can be completely compatible with MOCVD equipment, so that the process flow is greatly simplified, and the cost is saved.
Drawings
FIG. 1 is a schematic flow chart of a method for preparing high quality AlGaN material by in-situ etching and recombination provided in an exemplary embodiment of the invention;
FIG. 2a is a schematic diagram of the selective etching of Al using halogen-based atoms/groups in example 1 of the present invention 0.6 Ga 0.4 N etching the scanning electron microscope image after preparing the layer surface;
FIG. 2b shows the Al after the combination of the etched holes in inventive example 1 0.6 Ga 0.4 Surface scanning electron microscope images of the N combined layers;
FIG. 3 is the Al after etching in comparative example 1 0.6 Ga 0.4 N etching prepares Al grown on the surface of the layer 0.6 Ga 0.4 Surface atomic force microscope images of the N merged layers;
FIG. 4 is a schematic diagram of the TBCl treated Al in comparative example 2 0.6 Ga 0.4 N etching is carried out to prepare an atomic force microscope image of the surface of the layer;
FIG. 5 is Al in comparative example 3 0.4 Ga 0.6 N incorporates atomic force microscopy images of the layer surface.
Detailed Description
In view of the shortcomings in the prior art, the inventor of the present invention has long studied and practiced in a large number of ways to propose the technical scheme of the present invention. The technical scheme, the implementation process, the principle and the like are further explained as follows.
The embodiment of the invention mainly provides a method for improving the crystal quality of a multi-element group III nitride based semiconductor material, such as AlGaN, aiming at the existing method for improving the crystal quality of the multi-element group III nitride based semiconductor material, and the like: in the growth process of the multi-element group III nitride based semiconductor materials such as AlGaN, a halogen-based source is introduced in situ, and etching pits (or called as concave parts or holes or etching dislocation pits) are generated in situ by utilizing the advantages of low activation energy of the chemical reaction of the halogen-based atoms/groups and the multi-element group III nitride based semiconductor materials such as AlGaN (chemical decomposition process) and the characteristics of high density of dangling bonds near dislocation cores and easy chemical reaction; then annihilating threading dislocation by lateral epitaxial growth and combination of the multi-element III-nitride-based semiconductor materials such as AlGaN, thereby greatly improving the crystal quality of the multi-element III-nitride-based semiconductor materials such as AlGaN; in addition, the size and density of the etching pit can be controlled by controlling the conditions of the temperature of the reaction chamber, the flow of the halogen-based source and the like, so that the process flow is greatly simplified, the cost is saved, the yield is improved, and the method is very suitable for commercial application.
The embodiment of the invention provides a method for improving the crystal quality of a multi-element group III nitride based semiconductor material, which comprises the following steps:
growing a first semiconductor material layer on a substrate in a reaction chamber;
inputting a halogen-based source into the reaction chamber to etch the first semiconductor material layer, so that a plurality of concave parts are formed on the surface of the first semiconductor material layer;
and inputting a nitrogen source and a metal source into the reaction chamber, and growing a second semiconductor material layer on the first semiconductor material layer.
In some more specific embodiments, the first semiconductor material layer and the second semiconductor material layer comprise a multi-element group III nitride.
In some of the more specific embodiments of the present invention,the multi-system group III nitride includes In x Al y Ga 1-x-y N、B x Al 1-x N or B x Al y Ga 1-x-y N，0≤x≤1，0≤y≤1。
In some more specific embodiments, the conditions such as the temperature and the pressure of the etching of the first semiconductor material layer by using the halogen-based source are generally lower than the growth temperature of the second semiconductor material layer, and the etching pressure is higher than the growth pressure of the second semiconductor material layer, which can be the same as the growth temperature and the pressure of the second semiconductor material layer.
In some more specific embodiments, the method comprises: etching the first semiconductor material layer under the first temperature and first pressure conditions, and growing the second semiconductor material layer under the second temperature and second pressure conditions; the first temperature is lower than the second temperature and the first pressure is higher than the second pressure.
In some more specific embodiments, the first temperature is 500-1300 ℃, and the first pressure is 10-500Torr.
In some more specific embodiments, the first temperature is 800-900 ℃, and the first pressure is 50-200Torr.
In some more specific embodiments, the method comprises: and controlling the flow of the nitrogen source to be 0-100slm when etching the first semiconductor material layer.
In some more specific embodiments, the flow rate of the nitrogen source is controlled to be 0.1 to 10slm when etching the first semiconductor material layer.
In some more specific embodiments, the second temperature is 500-1300 ℃, and the second pressure is 10-500Torr.
In some more specific embodiments, the second temperature is 1000-1300 ℃, and the second pressure is 50-100Torr.
In some more specific embodiments, the method comprises: and controlling the flow of the nitrogen source to be 0.1-100slm when the second semiconductor material layer is grown.
In some more specific embodiments, 100< v/III <3000 is controlled when growing the second semiconductor material layer.
In some more specific embodiments, the halogen-based source is introduced at a flow rate of 10-1000sccm.
In some more specific embodiments, the halogen-based source is passed over for a period of time ranging from 0.1 to 120 minutes.
In some more specific embodiments, the halogen-based source includes any one or a combination of two or more of chloro, fluoro, bromo, but is not limited thereto.
In some more specific embodiments, the chloro compound includes any one or a combination of two or more of tert-butyl chloride, hydrogen chloride, chlorine gas, and tetrachloromethane, but is not limited thereto.
In some more specific embodiments, the first semiconductor material is formed on a stress transition layer formed on a bottom layer, wherein the stress transition layer and the bottom layer are both group III nitrides.
In some more specific embodiments, the method further comprises: an epitaxial layer is grown on the second semiconductor material layer.
The technical scheme, implementation process, principle and the like will be further explained with reference to the accompanying drawings, and the apparatus for epitaxially growing each structural layer in the embodiments of the present invention may be known to those skilled in the art unless specifically explained.
In order to achieve the above object, as shown in fig. 1, for example, an AlGaN material is shown as an example, a method for improving the crystal quality of a multi-element group III nitride semiconductor material according to an embodiment of the present invention may include the following steps:
(1) Firstly, epitaxially growing AlN, an AlGaN stress transition layer and an AlGaN etching preparation layer (namely the first semiconductor material layer and the same below) on a substrate in a reaction chamber in sequence by adopting a metal chemical vapor deposition (MOCVD) method and the like;
(2) Stopping introducing Al, ga goldIs a source, the pressure of the reaction chamber is regulated to 10to 500Torr, the temperature is regulated to 500to 1300 ℃, and NH 3 The flow is regulated to be 0-100slm; preferably, the pressure in the reaction chamber is adjusted to 50-200Torr, the temperature is adjusted to 800-900 ℃, and NH 3 The flow is regulated to be 0.1-10slm;
(3) Introducing a halogen base source into the reaction chamber, wherein the flow rate of the halogen base source is 10-1000sccm, the introduction time is 0.1-120min, so as to perform in-situ etching on the surface of the AlGaN etching preparation layer, and an etching pit (namely the concave part and the same below) with a certain size is formed, and the depth of the etching pit is more than 50nm;
(4) Stopping the supply of the halogen-based source, adjusting the pressure of the reaction chamber to 10-500Torr, adjusting the temperature to 900-1300 ℃, and NH 3 The flow is regulated to be 0.1-100slm; preferably, the pressure of the reaction chamber is adjusted to 50-100Torr, and the temperature is adjusted to 1000-1300 ℃;
(5) Al and Ga metal sources are led into the reaction chamber again, the growth of an AlGaN merging layer (namely a second semiconductor material layer and the same below) is carried out under the conditions of low pressure (< 100 Torr), lower V/III ratio (100 < V/III < 3000) and high temperature (more than or equal to 900 ℃), and the transverse/longitudinal growth rate ratio of the AlGaN merging layer is 0.04-1, so that etching pits are gradually merged within the thickness range of 0.1-2 mu m, and long and narrow cavities are formed in the AlGaN merging layer, and the purpose of the AlGaN merging layer is to induce dislocation corner annihilation by utilizing the mirror force of crystal faces on the inner wall of the etching pits, and simultaneously inhibit a large number of new dislocations generated by the orientation difference of adjacent mesa crystal grains in the AlGaN merging process;
(6) And continuously growing an AlGaN epitaxial layer with a certain thickness on the surface of the combined AlGaN layer after combination, and finally obtaining the AlGaN thick-layer film material with a flat surface and high quality.
The key point of the method provided by the embodiment of the invention is that a halogen-based source is introduced in the epitaxial growth process of the AlGaN material, the surface of the AlGaN material is etched in situ by utilizing the advantage of low activation energy of the chemical reaction of halogen-based active atoms/groups and the AlGaN material, the conditions of the temperature of a reaction chamber and the like are controlled, the surrounding area of dislocation is etched preferentially, other areas of a plane are not etched almost, thus forming an in-situ etching pit, and then dislocation turning annihilation is driven by utilizing a lateral growth combination mode, so that the crystal quality of the AlGaN material is greatly improved.
The method provided by the embodiment of the invention utilizes the technical method of in-situ etching AlGaN material by utilizing halogen-based active atoms/groups, can avoid the defects of large damage, impurity pollution and the like of the traditional dry etching, also eliminates the defects of low in-situ etching AlGaN by utilizing hydrogen at high temperature, long time consumption and poor etching anisotropy, effectively utilizes the advantages of low chemical reaction activation energy of the halogen-based active atoms and the AlGaN material, and the characteristics of high suspension bond density and easy chemical reaction near dislocation cores, etches the AlGaN material surface in situ, ensures that the areas around dislocation are preferentially etched and the other areas of the plane are hardly etched by controlling the temperature and the like of a reaction chamber, thereby forming in-situ etching pits, and then drives dislocation turning annihilation by utilizing a lateral growth merging mode, thereby obviously reducing the threading dislocation density in the AlGaN material.
The method provided by the embodiment of the invention is used for forming etching pits in situ in the AlGaN material, and then combining to improve the material quality; the method provided by the embodiment of the invention has the advantages that the AlGaN is subjected to in-situ etching by the halogen-based active atoms/groups to generate etching pits, the generated etching pits are favorable for promoting dislocation turning annihilation in the merging process, meanwhile, a closed cavity structure is formed in the AlGaN material after the etching pits are merged, and the cavity structure can be subjected to micro deformation under the influence of material stress, so that part of stress is relaxed, the stress in the AlGaN material is reduced, and the uneven components in the AlGaN material and stress-induced surface roughness are inhibited.
In addition, the method provided by the embodiment of the invention is not only used for improving the crystal quality of the AlGaN-based semiconductor material, but also greatly improves the crystal quality of other nitride semiconductor materials such as GaN and the like which are continuously epitaxially grown on the high-quality AlGaN material prepared by the method.
Example 1
In situ etching of Al using t-butyl chloride (TBCl) 0.6 Ga 0.4 N forms holes and then is combined to prepare high-quality Al 0.6 Ga 0.4 N deep ultraviolet optoelectronic material:
s1: by metalChemical vapor deposition MOCVD equipment for sequentially growing 1 mu m AlN bottom layer and 500nm Al on common sapphire substrate 0.7 Ga 0.3 N stress transition layer, 300nm Al 0.6 Ga 0.4 N etching preparation layer;
s2: stopping introducing TMAL and TMGa metal sources, increasing the pressure of the reaction chamber to 200Torr, reducing the temperature to 900 ℃, and reducing the NH 3 The flow is reduced to 2slm;
s3: introducing TBCl source into the reaction chamber, wherein the flow rate of the TBCl source is 10sccm, continuously introducing 120min to obtain the final product 0.6 Ga 0.4 Performing in-situ etching on the surface of the N etching preparation layer to form etching pits with a certain density, wherein the average depth of the etching pits is about 90nm;
s4: stopping TBCl source supply, reducing the pressure in the reaction chamber to 60Torr, raising the temperature to 1100 ℃, and raising the NH value 3 The flow rate is increased to 10slm;
s5: introducing TMAL and TMGa metal sources into the reaction chamber again, and carrying out Al under the conditions that the pressure is 60Torr, the V/III is 2000 and the temperature is 1100 DEG C 0.6 Ga 0.4 Growth of N-merged layer and Al 0.6 Ga 0.4 The growth rate ratio of the N merging layers in the transverse direction/longitudinal direction reaches 0.1, so that etching pits are gradually merged within the thickness range of 1 mu m, and the aim is to induce dislocation turning annihilation by utilizing the mirror force of the crystal face on the inner wall of the etching pit and inhibit Al at the same time 0.6 Ga 0.4 The adjacent mesa grains generate a large amount of new dislocation due to orientation difference during the N merging layer merging process, and the void generated during the merging process also contributes to relaxation stress, thereby suppressing the high Al component Al 0.6 Ga 0.4 The surface of the N merging layer is rough;
s6: al after combining 0.6 Ga 0.4 The surface of the N merging layer is continuously grown with the thickness of 2 mu m 0.6 Ga 0.4 An N epitaxial layer to finally obtain the Al with flat surface and high quality 0.6 Ga 0.4 N thin film material.
Using a scanning electron microscope to etch the Al in the step S3 0.6 Ga 0.4 Observing the N etching preparation layer, and etching the etched Al 0.6 Ga 0.4 Electron microscope image of N etching preparation layer surfaceAs shown in fig. 2a, hexagonal pits can be observed under a scanning electron microscope, and the areas without pits remain relatively flat; combining the 2 μm Al obtained in step S6 with a scanning electron microscope 0.6 Ga 0.4 Observing the N film material, al 0.6 Ga 0.4 An electron microscope image of the surface of the N film material is shown in FIG. 2b, and Al can be observed under a scanning electron microscope 0.6 Ga 0.4 The surface of the N film material is flat; by X-ray diffraction (XRD) of the obtained Al 0.6 Ga 0.4 The N film material is subjected to scanning test, the half-height width of the (0002) plane rocking curve is 243 arsec, the half-height width of the (10-12) plane is 291 arsec, and the half-height width is far lower than that of direct epitaxial growth Al 0.6 Ga 0.4 N (0002) and (10-12) plane bicrystals 362arcsec, 452arcsec, which demonstrate that the method provided by the invention can significantly improve Al 0.6 Ga 0.4 Crystal quality of N material.
Example 2
In situ etching of Al using t-butyl chloride (TBCl) 0.6 Ga 0.4 N forms holes and then is combined to improve Al 0.6 Ga 0.4 N material mass:
s1: sequentially growing a 1 mu m AlN bottom layer and 500nm Al on a common sapphire substrate by using metal object chemical vapor deposition MOCVD equipment 0.7 Ga 0.3 N stress transition layer, 300nm Al 0.6 Ga 0.4 N etching preparation layer;
s2: stopping introducing Al and Ga metal sources, increasing the pressure of the reaction chamber to 200Torr, increasing the temperature to 1300 ℃, and raising the NH 3 The flow is reduced to 10slm;
s3: introducing TBCl source into the reaction chamber, wherein the introduction flow of the TBCl source is 1000sccm, and continuously introducing for 0.1min to obtain the product 0.6 Ga 0.4 Performing in-situ etching on the surface of the N etching preparation layer to form etching pits with a certain density, wherein the average depth of the etching pits is about 90nm;
s4: stopping TBCl source supply, reducing the pressure in the reaction chamber to 60Torr, reducing the temperature to 1100 ℃, and NH 3 The flow rate is increased to 15slm;
s5: re-introducing TMAL and TMGa metal sources into the reaction chamber under the pressure of 60 DEG CAl is carried out under the conditions of Torr, V/III of 2000 and temperature of 1100 DEG C 0.6 Ga 0.4 Growth of N-merged layer and Al 0.6 Ga 0.4 The growth rate ratio of the N merging layers in the transverse direction/longitudinal direction reaches 0.3, so that etching pits are gradually merged within the thickness range of 1 mu m, and the aim is to induce dislocation turning annihilation by utilizing the mirror force of the crystal face on the inner wall of the etching pit and inhibit Al at the same time 0.6 Ga 0.4 The adjacent mesa grains during the merging of the N-merged layer generate a large number of new dislocations due to the orientation difference, and voids generated during the merging also contribute to relaxation stress, thereby suppressing the high Al composition Al 0.6 Ga 0.4 The surface of the N merging layer is rough;
s6: al after combining 0.6 Ga 0.4 The surface of the N merging layer is continuously grown with the thickness of 2 mu m 0.6 Ga 0.4 An N epitaxial layer to finally obtain the Al with flat surface and high quality 0.6 Ga 0.4 N thin film material.
In the embodiment 2, the hexagonal etching pit can be observed on the AlGaN surface after the etching of S3 under a scanning electron microscope, and the area without the etching pit is relatively flat; s6 2 μm Al after combination 0.6 Ga 0.4 The surface of the N material is smooth; the full width at half maximum of the (0002) plane rocking curve is 243 arsec, the full width at half maximum of the (10-12) plane is 291 arsec, which is far lower than that of the direct epitaxial growth Al by X-ray diffraction (XRD) 0.6 Ga 0.4 N (0002) and (10-12) plane bicrystals 362arcsec, 452arcsec, which demonstrate that the method provided by the invention can significantly improve Al 0.6 Ga 0.4 Crystal quality of N material.
Example 3
On the basis of preparing high-quality AlN by using a nano-patterned sapphire NPSS substrate, in-situ etching Al by using TBCl 0.4 Ga 0.6 N forms holes and then is combined to further improve Al 0.4 Ga 0.6 Crystal quality of the N deep ultraviolet photoelectron material;
s1: a4 μm high quality AlN underlayer is first epitaxially grown on an NPSS substrate using MOCVD equipment, and then 500nm AlN/Al is epitaxially grown 0.5 Ga 0.5 N superlattice transition layer, 300nm Al 0.4 Ga 0.6 N etching preparation layer;
s2: stopping introducing Al and Ga metal sources, increasing the pressure of the reaction chamber to 100Torr, reducing the temperature to 850 ℃, and reducing the NH 3 The flow is reduced to 5slm;
s3: introducing TBCl source into the reaction chamber, wherein the introduction flow rate of the TBCl source is 500sccm, and maintaining for 40min to obtain a reaction product containing Al 0.4 Ga 0.6 Performing in-situ etching on the surface of the N etching preparation layer to form etching pits with a certain density, wherein the average depth of the etching pits is about 150nm;
s4: stopping the TBCl source supply and raising the pressure in the reaction chamber to 150Torr, raising the temperature to 1050℃and NH 3 The flow rate is increased to 15slm;
s5: introducing TMAL and TMGa metal sources into the reaction chamber again, and carrying out Al under the conditions that the pressure is 150Torr, the V/III is 2500 and the temperature is 1050 DEG C 0.4 Ga 0.6 Growth of N-merged layer and Al 0.4 Ga 0.6 The growth rate ratio of the N merging layers in the transverse direction/longitudinal direction reaches 0.06, so that etching pits are gradually merged within the thickness range of 1.2 mu m, and the aim is to induce dislocation turning annihilation by utilizing the mirror force of the crystal face of the etching inner wall and inhibit Al at the same time 0.4 Ga 0.6 In the merging process of the N merging layers, a large number of new dislocation is generated by the adjacent mesa crystal grains due to orientation difference;
s6: al after combining 0.4 Ga 0.6 The surface of the N merging layer is continuously grown with the thickness of 2 mu m 0.4 Ga 0.6 An N epitaxial layer to finally obtain the Al with flat surface and high quality 0.4 Ga 0.6 N thin film material.
The obtained Al is subjected to optical microscopy 0.4 Ga 0.6 The N film material is observed, and Al can be observed under an optical microscope 0.4 Ga 0.6 The N film material has smooth surface and no visible etching pit, the (0002) surface rocking curve half-width is 236 arsec, the (10-12) surface half-width is 353 arsec, which is far lower than that of direct epitaxial growth Al 0.4 Ga 0.6 Bicrystals 369arcsec and 510arcsec on N (0002) and (10-12) surfaces show that the method provided by the invention can obviously improve Al 0.4 Ga 0.6 Crystal quality of N material.
Example 4
By means of carbon tetrachloride (CCl) 4 ) And (3) in-situ etching BAlN to form holes, and then merging to prepare the high-quality BAlN deep ultraviolet optoelectronic material:
s1: sequentially growing a 1 mu m AlN bottom layer and 500nm Al on a common sapphire substrate by using metal object chemical vapor deposition MOCVD equipment 0.7 Ga 0.3 N stress transition layer, 100nm B 0.3 Al 0.7 N etching preparation layer;
s2: stopping introducing TMAL and TEB metal sources, increasing the pressure of the reaction chamber to 50Torr, reducing the temperature to 800 ℃, and reducing the NH 3 The flow is reduced to 5slm;
s3: introducing CCl into the reaction chamber 4 Source, CCl 4 The source flow rate was 600sccm and maintained for 30min for B 0.3 Al 0.7 Performing in-situ etching on the surface of the N etching preparation layer to form etching pits with a certain density, wherein the average depth of the etching pits is about 150nm;
s4: stopping CCl 4 A source supply for raising the pressure of the reaction chamber to 200Torr, raising the temperature to 1100 ℃, and NH 3 The flow rate is increased to 10slm;
s5: introducing TMAL and TEB metal sources into the reaction chamber again, and carrying out B under the conditions of pressure of 200Torr, V/III of 2000 and temperature of 1100 DEG C 0.3 Al 0.7 Growth of N-merged layer and B 0.3 Al 0.7 The growth rate ratio of the N merging layers in the transverse direction/longitudinal direction reaches 0.1, so that etching pits are gradually merged within the thickness range of 1 mu m, and the aim is to induce dislocation turning annihilation by utilizing the mirror force of the crystal face on the inner wall of the etching pit and inhibit B 0.3 Al 0.7 The adjacent mesa grains during the N-merged layer merge generate a large number of new dislocations due to the orientation difference, and voids generated during the merge also contribute to relaxation stress, thereby suppressing high B 0.3 Al 0.7 The surface of the N material is rough;
s6: b after combining 0.3 Al 0.7 The surface of the N merging layer is continuously grown with the thickness of 200nm 0.3 Al 0.7 An N epitaxial layer to finally obtain the B with flat surface and high quality 0.3 Al 0.7 N thin film material.
The obtained B is subjected to optical microscopy 0.3 Al 0.7 The N film material is observed, and B can be observed under an optical microscope 0.3 Al 0.7 The N film material has smooth surface and no visible etching pit, the half-height width of the (0002) plane rocking curve obtained by XRD scanning is 466 arsec, the half-height width of the (10-12) plane is 651 arsec, and the half-height width is far lower than that of the direct epitaxial growth B 0.3 Al 0.7 The bicrystals 590arcsec and 839arcsec of the N (0002) and (10-12) surfaces show that the method provided by the invention can obviously improve B 0.3 Al 0.7 Crystal quality of N material.
Example 5
And (3) in-situ etching AlN by using tertiary butyl chloride (TBCl) to form holes, and then merging to prepare the high-quality AlN deep ultraviolet photoelectron material:
s1: firstly epitaxially growing a 1 mu m high-quality AlN bottom layer on a SiC substrate by using MOCVD equipment;
s2: stopping introducing TMAL metal source, reducing pressure of the reaction chamber to 10Torr, reducing temperature to 980 ℃, and NH 3 The flow is reduced to 5slm;
s3: introducing a TBCl source into the reaction chamber, wherein the introduction flow of the TBCl source is 200sccm, and maintaining for 80min so as to perform in-situ etching on the surface of the AlN bottom layer, and forming etching pits with a certain density, wherein the average depth of the etching pits is about 70nm;
s4: stopping TBCl source supply, increasing the pressure in the reaction chamber to 50Torr, increasing the temperature to 1090 ℃, and raising the NH temperature 3 The flow is maintained at 5slm;
s5: introducing TMAL metal source into the reaction chamber again, growing an AlN merging layer under the conditions that the pressure is 50Torr, the V/III is 1500, the temperature is 1090 ℃, and enabling the transverse/longitudinal growth rate ratio of the AlN merging layer to reach 0.04, so that etching pits are gradually merged within the thickness range of 2 mu m, and the aim is to induce dislocation turning annihilation by utilizing mirror force of crystal faces of etching inner walls, and simultaneously inhibit a large number of new dislocation generated by adjacent mesa crystal grains due to orientation difference in the merging process of the AlN merging layer;
s6: and (3) continuously growing an AlN epitaxial layer with the thickness of 1 mu m on the surface of the combined AlN layer after the combination, and finally obtaining the AlN thin film material with a flat surface and high quality.
The AlN film material obtained is observed by an optical microscope, the surface of the AlN film is smooth, no etching pit is visible under the optical microscope, the full width at half maximum of a (0002) surface rocking curve is 85 arsec, the full width at half maximum of a (10-12) surface is 90 arsec, and the full width at half maximum is far lower than that of bicrystal 92arcsec and 140arcsec of directly epitaxially growing AlN (0002) and (10-12) surfaces, which shows that the crystal quality of the AlN material can be obviously improved by adopting the method provided by the invention.
Comparative example 1
One of Al in comparative example 1 0.6 Ga 0.4 The preparation method of the N film material is basically the same as that of the example 1, except that: in step S3 of comparative example 1, al was reacted with TBCl 0.6 Ga 0.4 When the N etching preparation layer is etched, the inflow rate of the TBCl source is 1050sccm.
Tests show that even if the etching treatment time is only short for 5s, al 0.6 Ga 0.4 The surface of the N etching preparation layer can be coarsened rapidly, and subsequently grown Al 0.6 Ga 0.4 The N merging layers are difficult to merge; scanning electron microscope is used for carrying out the etching treatment on the Al 0.6 Ga 0.4 N etching prepares Al grown on the surface of the layer 0.6 Ga 0.4 Observation of the N-merged layer to obtain Al 0.6 Ga 0.4 The surface electron microscope image of the N merging layer is shown in fig. 3.
Comparative example 2
One of Al in comparative example 2 0.6 Ga 0.4 The preparation method of the N film material is basically the same as that of the example 1, except that: in step S3 of comparative example 2, al was reacted with TBCl 0.6 Ga 0.4 When the N etching preparation layer is etched, the temperature in the reaction chamber is 450 ℃.
Experiments show that when the temperature in the reaction chamber is lower than 500 ℃, NH 3 Is extremely low, so that Al 0.6 Ga 0.4 The N etching preparation layer loses the protection of partial pressure of nitrogen (N), thereby making Al 0.6 Ga 0.4 Accelerating decomposition of TBCl on the surface of the N etching preparation layer to lead to Al 0.6 Ga 0.4 The surface of the N etching preparation layer is very roughEtching of time-selective areas to generate etching holes is impossible, and further Al is not effectively improved by utilizing combination of holes 0.6 Ga 0.4 Crystal quality of N thin film. Etching the etched Al with a scanning electron microscope 0.6 Ga 0.4 Observing the N etching preparation layer, and etching the etched Al 0.6 Ga 0.4 The surface electron microscope image of the N etch preparation layer is shown in fig. 4.
Comparative example 3
After the TBCl source is introduced, the growth of the aluminum gallium nitride material is not carried out in a specific V/III ratio
One Al of comparative example 3 0.4 Ga 0.6 The preparation method of the N film material is basically the same as that of the example 3, except that: the comparison of Al is performed in step S5 of comparative example 3 0.4 Ga 0.6 When the N merging layer grows, controlling the V/III in the reaction chamber to be 3500; it has been found through experiments that the V/III ratio affects the growth rate, the atomic mobility (surface morphology) and the formation of impurities and vacancy point defects of AlGaN materials. Since V/III is greater than 3000, al is grown 0.4 Ga 0.6 The lateral growth rate of the N-merged layer is severely reduced, and the lateral/longitudinal growth rate ratio is lower than 0.01, so that Al 0.4 Ga 0.6 The N merging layers still cannot be merged within the thickness of 4 mu m, the surface is quite rough, and a large number of hexagonal hillocks and step stacks appear; scanning electron microscope for Al 0.4 Ga 0.6 N-merged layer was observed, al 0.4 Ga 0.6 The surface electron microscope image of the N-merged layer is shown in fig. 5.
It should be noted that the above embodiments are only exemplary, and are only used to explain and illustrate the technical solution of the present invention, and of course, the method for epitaxially growing AlGaN material adopted in the embodiments of the present invention may also be Molecular Beam Epitaxy (MBE), hydride Vapor Phase Epitaxy (HVPE), pulse Laser Deposition (PLD), etc.; and is not limited to metal chemical vapor deposition (MOCVD).
The halogen-based source used for in-situ etching in the embodiments of the present invention includes, but is not limited to, various chlorides, such as various fluorides, bromides, and any combination thereof.
Embodiments of the invention are used for engravingThe material for etching and growing includes but is not limited to AlGaN material, and can be In x Al y Ga 1-x-y The N quaternary system nitride semiconductor material is that x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1; may also be B x Al 1-x The range of the component x of the N and the Al is more than or equal to 0 and less than or equal to 1; may also be B x Al y Ga 1-x-y N and other materials, x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1.
The etching pit formed by etching in the embodiment of the invention does not necessarily need to form a closed cavity structure in the subsequent AlGaN material growth process, and can be filled with AlGaN and other materials so as to be completely combined.
Substrates used in the epitaxial AlGaN of embodiments of the present invention include, but are not limited to, sapphire, silicon, self-supporting AlN single crystal, self-supporting GaN single crystal, silicon carbide, diamond, and the like.
Compared with the prior art, the method for improving the crystal quality of the AlGaN-based semiconductor material provided by the embodiment of the invention has the advantages that the halogen-based source is introduced in the growth process of the AlGaN-based semiconductor material such as the multi-element group III nitride, and the problems of impurity pollution and the like caused by mask medium decomposition in the traditional ELOG growth can be avoided by utilizing the advantages of low activation energy of the chemical reaction between halogen-based atoms and the AlGaN multi-element group III nitride (chemical decomposition process) and the characteristics of high suspension bond density and easy chemical reaction near dislocation cores, and by controlling the conditions such as the temperature of a reaction chamber, the like, the preferential etching of the area around the dislocation can be realized, the etching of the planar area is hardly realized, and thus the high-efficiency and selective etching of the AlGaN-based semiconductor material such as the multi-element group III nitride is realized.
The method for improving the crystal quality of the AlGaN-based semiconductor material provided by the embodiment of the invention has the advantages of simple process, repeated controllability and complete suitability for large-scale production; the halogen-based source adopted by the embodiment of the invention can be fully compatible with MOCVD equipment, and after the growth of the multi-element III-nitride-based semiconductor materials such as AlGaN is completed, the complex process flows such as cooling, photoetching mask, secondary epitaxy and the like are not needed, the size of an in-situ etching pit can be accurately controlled by only introducing the halogen-based source and controlling the conditions such as source flow, reaction chamber pressure, temperature and the like, so that the process flow is greatly simplified, and the cost is saved.
The invention provides a method for improving the crystal quality of an AlGaN-based semiconductor material, which can overcome the defects of the prior art scheme, has the outstanding advantages of simple process, stability, controllability, no mask medium and the like, and is completely suitable for mass production.
It should be understood that the above embodiments are merely for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the present invention and implement the same according to the present invention without limiting the scope of the present invention. All equivalent changes or modifications made in accordance with the spirit of the present invention should be construed to be included in the scope of the present invention.
Claims (10)
1. A method for improving the crystal quality of a multi-element group III nitride based semiconductor material, comprising:
growing a first semiconductor material layer on a substrate in a reaction chamber;
inputting a halogen-based source into the reaction chamber to etch the first semiconductor material layer, so that a plurality of concave parts are formed on the surface of the first semiconductor material layer;
and inputting a nitrogen source and a metal source into the reaction chamber, and growing a second semiconductor material layer on the first semiconductor material layer.
2. The method according to claim 1, characterized in that: the materials of the first semiconductor material layer and the second semiconductor material layer comprise multi-element III-group nitrides; preferably, the multi-group III nitride includes In x Al y Ga 1-x-y N、B x Al 1-x N or B x Al y Ga 1-x-y N，0≤x≤1，0≤y≤1。
3. A method according to claim 1, characterized by comprising: etching the first semiconductor material layer under the first temperature and first pressure conditions, and growing under the second temperature and second pressure conditions to form a second semiconductor material layer; the first temperature is lower than the second temperature and the first pressure is higher than the second pressure.
4. A method according to claim 3, characterized in that: the first temperature is 500-1300 ℃, and the first pressure is 10-500Torr;
preferably, the first temperature is 800-900 ℃, and the first pressure is 50-200Torr.
5. A method according to claim 3, characterized by comprising: controlling the flow of the nitrogen source to be 0-100slm when etching the first semiconductor material layer;
preferably, when etching the first semiconductor material layer, the flow rate of the nitrogen source is controlled to be 0.1-10slm.
6. A method according to claim 3, characterized in that: the second temperature is 500-1300 ℃, and the second pressure is 10-500Torr;
preferably, the second temperature is 1000-1300 ℃, and the second pressure is 50-100Torr.
7. A method according to claim 3, characterized by comprising: and controlling the flow of the nitrogen source to be 0.1-100slm when the second semiconductor material layer is grown.
8. A method according to claim 3, characterized in that: when growing to form the second semiconductor material layer, 100< V/III <3000 is controlled.
9. The method according to claim 1, characterized in that: the flow rate of the halogen-based source is 10-1000sccm;
preferably, the halogen-based source is introduced for 0.1 to 120 minutes.
Preferably, the halogen-based source comprises any one or more than two of chloro, fluoro and bromo;
preferably, the chloro compound comprises any one or more than two of tert-butyl chloride, hydrogen chloride, chlorine and tetrachloromethane.
10. The method according to claim 1, characterized in that: the first semiconductor material is formed on the stress transition layer, and the stress transition layer is formed on the bottom layer, wherein the stress transition layer and the bottom layer are both made of III-nitride;
preferably, the method further comprises: an epitaxial layer is grown on the second semiconductor material layer.
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Effective date of registration: 20231115 Address after: 215400 No.168, Changsheng North Road, Taicang City, Suzhou City, Jiangsu Province Applicant after: Suzhou Liyu Semiconductor Co.,Ltd. Address before: 215123, Suzhou, Jiangsu province Suzhou Industrial Park alone villa lake high Parish, if the waterway 398 Applicant before: SUZHOU INSTITUTE OF NANO-TECH AND NANO-BIONICS (SINANO), CHINESE ACADEMY OF SCIENCES |