CN210805810U - Silicon-based gallium nitride epitaxial structure - Google Patents
Silicon-based gallium nitride epitaxial structure Download PDFInfo
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- CN210805810U CN210805810U CN201922056218.XU CN201922056218U CN210805810U CN 210805810 U CN210805810 U CN 210805810U CN 201922056218 U CN201922056218 U CN 201922056218U CN 210805810 U CN210805810 U CN 210805810U
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Abstract
The utility model discloses a silicon-based gallium nitride epitaxial structure, which comprises a silicon substrate, an Al layer, a nitrogen-containing buffer layer, a stripping layer, an N-GaN layer, an active layer and a P-GaN layer which are sequentially arranged on the silicon substrate; the nitrogen-containing buffer layer comprises an AlN layer, an AlGaN layer and a GaN layer, wherein the AlN layer is arranged between the Al layer and the AlGaN layer, and the GaN layer is arranged between the AlGaN layer and the stripping layer; the stripping layer is made of SiO2、SiNx、Al2O3In AlNOne or more of the above. The utility model discloses a peel ply not only can reduce follow-up formation GaN's defect, also can adopt simple wet etching process to corrode the peel ply to get rid of the silicon substrate.
Description
Technical Field
The utility model relates to a light emitting diode technical field especially relates to a silica-based gallium nitride epitaxial structure.
Background
The third-generation semiconductor material mainly includes silicon carbide (SiC), gallium nitride (GaN), diamond, and the like, and compared with the second-generation semiconductor silicon (Si), gallium arsenide (GaAs), and the like, the third-generation semiconductor material gallium nitride (GaN) has a larger bandgap (>3eV), and is also generally referred to as a wide bandgap semiconductor material.
Due to the advantage of forbidden bandwidth, the GaN material is obviously superior to the traditional semiconductor materials such as Si, GaAs and the like in the aspects of breakdown electric field, intrinsic carrier concentration and radiation resistance.
In addition, the GaN material is more excellent than Si in the aspects of carrier mobility, saturated carrier concentration and the like, so that the GaN material is particularly suitable for manufacturing power and microwave electronic devices with high power density, high speed and high efficiency, and has wide application prospects in the fields of 5G communication, cloud computing, fast charging sources, wireless charging and the like.
Meanwhile, GaN is epitaxially grown on the silicon substrate, so that the advantages of high performance of the GaN material and large size and low cost of a mature Si wafer can be effectively combined. However, the lattice mismatch between gallium and silicon is large, and due to the high defect density and the 54% coefficient of thermal expansion, the epitaxial film cracks during the cooling process, and the metal shelf directly ends up chemically melting with the silicon substrate.
Forming high quality gan material on a silicon substrate while facilitating removal of the silicon substrate is a technical problem in the prior art.
Disclosure of Invention
The utility model aims to solve the technical problem that a silicon-based gallium nitride epitaxial structure is provided, forms high-quality gallium nitride material on the silicon substrate, is convenient for get rid of the silicon substrate simultaneously.
In order to solve the technical problem, the utility model provides a silicon-based gallium nitride epitaxial structure, which comprises a silicon substrate, an Al layer, a nitrogen-containing buffer layer, a stripping layer, an N-GaN layer, an active layer and a P-GaN layer, wherein the Al layer, the nitrogen-containing buffer layer, the stripping layer, the N-GaN layer, the active layer and the P-GaN layer are sequentially arranged on the silicon substrate;
the nitrogen-containing buffer layer comprises an AlN layer, an AlGaN layer and a GaN layer, wherein the AlN layer is arranged between the Al layer and the AlGaN layer, and the GaN layer is arranged between the AlGaN layer and the stripping layer;
the stripping layer is made of SiO2、SiNx、Al2O3Or AlN.
As an improvement of the scheme, the stripping layer is provided with a plurality of holes, the holes penetrate through the stripping layer, and the N-GaN layer arranged on the stripping layer is filled in the holes.
As an improvement of the scheme, the thickness of the stripping layer is 10-300 nm.
As an improvement of the above scheme, the shape of the hole is funnel-shaped, the width of the top opening of the hole is a, the width of the bottom opening of the hole is b, wherein,
b＝(0.4～0.6)*a。
in an improvement of the scheme, a is 6-50 μm.
In an improvement of the above scheme, the distance between the holes is c, and c is 5-20 μm.
As an improvement of the above scheme, the thickness of the Al layer is the thickness of one layer of Al atoms;
the AlN layer is 100-500 nm thick, the AlGaN layer is 200-300 nm thick, and the GaN layer is 1-2 μm thick.
Implement the utility model discloses, following beneficial effect has:
the utility model provides a pair of silicon-based gallium nitride epitaxial structure, including the silicon substrate, locate Al layer, nitrogenous buffer layer, peel ply and gallium nitride epitaxial layer on the silicon substrate in proper order, the gallium nitride epitaxial layer is including setting gradually N-GaN layer, active layer and the P-GaN layer on the peel ply.
The utility model discloses a Al layer and nitrogenous buffer layer are used for reducing the lattice mismatch between silicon substrate and the gallium nitride epitaxial layer, improve epitaxial structure's crystal quality. The utility model discloses a peel ply not only can reduce follow-up formation GaN's defect, also can adopt simple wet etching process to corrode the peel ply to get rid of the silicon substrate.
The utility model has a stripping layer made of SiO2、SiNx、Al2O3And one or more of AlN. The material is oxide or nitride, which not only has good adhesion with GaN, but also is easy to be etched by hydrofluoric acid.
The utility model discloses form the hole of infundibulate in the peel ply, can let corrosive liquid enter into the inside of peel ply easily and corrode the peel ply to make silicon substrate and gallium nitride epitaxial layer separation.
Drawings
Fig. 1 is a schematic structural diagram of an epitaxial structure of the present invention;
FIG. 2 is a schematic view of the structure of the hole of the present invention;
fig. 3 is a schematic view of the arrangement of the holes of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings.
Referring to fig. 1, the present invention provides a silicon-based gallium nitride epitaxial structure, including a silicon substrate 10, an Al layer 20, a nitrogen-containing buffer layer 30, a peeling layer 40 and a gallium nitride epitaxial layer 50 sequentially disposed on the silicon substrate 10, wherein the gallium nitride epitaxial layer 50 includes an N-GaN layer 51, an active layer 52 and a P-GaN layer 53 sequentially disposed on the peeling layer 40.
The utility model discloses a Al layer 20 and nitrogenous buffer layer 30 are used for reducing the lattice mismatch between silicon substrate 10 and gallium nitride epitaxial layer 50, improve epitaxial structure's crystal quality.
Specifically, the nitrogen-containing buffer layer 30 of the present invention includes an AlN layer 31, an AlGaN layer 32, and a GaN layer 33, the AlN layer 31 is provided between the Al layer 20 and the AlGaN layer 32, and the GaN layer 33 is provided between the AlGaN layer 32 and the peeling layer 40.
The utility model discloses AlN layer 31, AlGaN layer 32 and GaN layer 33 in the nitrogenous buffer layer 30 all are three five elements, and the crystal lattice is all very close, and combines with the N element, can effectively reduce the lattice mismatch between silicon substrate 10 and the gallium nitride, improves epitaxial structure's crystal quality.
Specifically, the AlN layer 31 has a thickness of 100 to 500nm, the AlGaN layer 32 has a thickness of 200to 300nm, and the GaN layer 33 has a thickness of 1 to 2 μm.
Since the lattice constant of AlN is 0.3112nm, which is smaller than the effective lattice constant 0.3840nm of the Si (111) substrate 10, tensile stress is accumulated in the AlN layer, so that dislocations are bent and annihilated. If the thickness of the AlN layer is less than 100nm, the AlN layer is too thin to be shielded; if the AlN layer has a thickness of more than 500nm, the AlN layer is too thick and easily cracks.
Because the reaction of Si and Ga can form a back melting etching pit, which causes poor electric leakage and antistatic capability of the LED chip, AlN with a certain thickness is grown as a barrier before GaN is grown, and the chemical reaction of Si and Ga can be prevented.
The utility model discloses a AlGaN layer 32 plays the lattice effect of buffering AlN and GaN as the intermediate level.
When the thickness of the GaN layer 33 reaches 1 μm, the GaN layer 33 grows flat throughout; if the thickness of the GaN layer 33 is greater than 2 μm, the thickness becomes too thick, and the gallium nitride epitaxial layer 50 formed later may be stress mismatched and cracked.
The utility model discloses a peel ply 40 is used for separating silicon substrate 10 and gallium nitride epitaxial layer 50. In the process of manufacturing a chip, the epitaxial structure of the present invention needs to remove the silicon substrate 10 to improve the light emitting efficiency of the chip. The stripped silicon substrate 10 can be reused to reduce production cost.
The utility model discloses a peel ply 40 not only can reduce the follow-up defect that forms GaN, also can adopt simple wet etching process to corrode peel ply 40 to get rid of silicon substrate 10.
The peeling layer 40 of the utility model is made of SiO2、SiNx、Al2O3And one or more of AlN. The material is oxide or nitride, which not only has good adhesion with GaN, but also is easy to be etched by hydrofluoric acid.
The peeling layer 40 of the present invention may have a single-layer structure or a double-layer structure. The thickness of the peeling layer 40 affects not only the separation of the silicon substrate 10 but also the crystal quality of the gallium nitride epitaxial layer 50.
Preferably, the thickness of the peeling layer 40 is 10 to 300 nm. If the thickness of the peeling layer 40 is less than 10nm, the thickness is too thin to form a film; if the thickness of the peeling layer 40 is more than 300nm, the thickness is too thick, the peeling layer 40 will be formed in a lump shape, and the internal stress between the lump shape and the gallium nitride is too large, which may cause SiO2Breaking and breaking.
In order to facilitate the peeling layer 40 to be etched by the etchant, the peeling layer 40 is provided with a plurality of holes 41, the holes 41 penetrate through the peeling layer 40, wherein the holes 41 are filled with the N-GaN layer arranged on the peeling layer 40.
Preferably, the holes 41 are funnel-shaped. The utility model discloses form the hole of infundibulate in peel ply 40, can let corrosive liquid enter into the inside of peel ply 40 easily and corrode peel ply 40 to make silicon substrate 10 separate with gallium nitride epitaxial layer 50. It should be noted that the gallium nitride epitaxial layer 50 filled in the hole may be broken during the etching process and separated from the buffer layer, but the quality of the gallium nitride epitaxial layer 50 is not affected.
Referring to fig. 2, the diameter of the top opening of the hole 41 is a, and the diameter of the bottom opening is b, and in order to facilitate the corrosive liquid to enter the peeling layer 40, it is preferable that b is (0.4 to 0.6) × a.
More preferably, a is 6 to 50 μm. If the diameter a of the top opening of the hole is less than 6 microns, the opening is too small, and an epitaxial layer is difficult to form in the hole; if a is larger than 50 μm, the opening is too large and the epitaxial layer in the hole is difficult to break and separate.
Referring to fig. 3, the holes 41 are arranged in an array, and a distance between the holes 41 and the holes 41 is c, preferably, c is 5 to 20 μm. If c is less than 5 μm, the distance is too small and the defect density of the epitaxial layer is increased; if c is greater than 20 μm, the distance is too large, which also affects the epitaxial layer quality.
In order to further improve the crystal quality of the epitaxial structure, a U-GaN layer 54 is further disposed between the peeling layer 40 and the N-GaN layer 51, and a P-type AlGaN layer 55 is further disposed between the P-GaN layer 53 and the active layer 52.
Correspondingly, the utility model also provides a preparation method of silica-based gallium nitride epitaxial structure, including following step:
firstly, forming an Al layer and a nitrogen-containing buffer layer on a silicon substrate;
specifically, the method comprises the following steps:
1. maintaining the temperature of the MOCVD reaction cavity at 1000-1100 ℃ and the pressure at 50-200 torr, and treating the silicon substrate in a hydrogen atmosphere for 1-5 minutes;
because the surface of the silicon substrate is provided with a thin SiO layer2Oxygen atoms and other impurities on the surface of the substrate can be removed by using hydrogen at high temperature, and a good foundation is laid for forming an epitaxial layer with good performance at the later stage.
2. Maintaining the temperature of the reaction chamber at 1100-1100 ℃ and the pressure at 50-200 torr, introducing trimethylaluminum (TMAl) into the MOCVD reaction chamber, and forming an Al layer on the silicon substrate;
the thickness of the Al layer is a thickness of one layer of Al atoms.
The utility model discloses a silicon substrate can effectively be passivated on Al layer, prevents the reaction gas NH of silicon substrate and later stage3React to form amorphous SiNx，SiNxThe growth quality of the later GaN crystal is seriously influenced; meanwhile, the Al layer can also be used as a growth seed of the AlN at the later stage, so that the AlN layer uniformly covers the surface of the matrix.
3. Keeping the temperature of the reaction chamber at 960-1060 ℃ and the pressure at 50-200 torr, and introducing NH into the MOCVD equipment3And TMA, forming an AlN layer on the Al layer;
4. keeping the temperature of the reaction chamber at 960-1060 ℃ and the pressure at 50-200 torr, and introducing NH into the MOCVD reaction chamber3TMA, and trimethylgallium (TMGa), an AlGaN layer is formed on the AlN layer.
Wherein the value range is 0.35-1, and the value is gradually reduced along with the increase of the thickness of the AlGaN layer; or 0.1 to 1; and varies progressively with increasing AlGaN layer thickness. In particular, the decreasing change is a continuous change, a gradient change or a mixed gradient change. Continuous variation means that the thickness of the buffer layer decreases uniformly as it increases; the gradient change means that the value is kept constant in a certain thickness range, and is reduced to a certain specific value and kept constant after the thickness is increased to another thickness range; the mixed gradient change refers to a combination of the two changes. Preferably, the decreasing change is a gradient change.
The AlGaN layer has a thickness of 200-300 nm, preferably 250-300 nm.
It should be noted that if GaN is grown directly on the AlN layer, a large number of dislocations from the AlN layer extend up to the GaN layer, and the compressive stress accumulated in the GaN layer causes the dislocation density to be greatly increased. Thus, an AlGaN layer was prepared, and the Al composition was reduced from 1 to 0.35 or 0.1 in a gradient by controlling TMA flow rate during the growth thereof. Along with the reduction of Al components, AlGaN crystal lattices are continuously increased, compressive stress is continuously accumulated, and under the action of the compressive stress, a large number of dislocations from an AlN layer are bent, combined and annihilated at an AlGaN interface, so that the dislocation density extending to GaN is greatly reduced, and the crystal quality of the GaN is improved.
5. Keeping the temperature of the reaction chamber at 1000-1100 ℃ and the pressure at 100-300 torr, and introducing gas NH3And TMGa, forming a GaN layer on the AlGaN layer.
Secondly, a stripping layer is formed on the buffer layer,
and forming a stripping layer on the GaN layer by adopting an evaporation, sputtering, PECVD or MOCVD process.
Specifically, the release layer has various embodiments, including:
the first embodiment is as follows: maintaining the temperature of the reaction chamber at 200-300 ℃ and the pressure at 450-550 torr, and introducing SiH into the PECVD equipment4And N2And O, forming a stripping layer on the GaN layer.
The second embodiment: maintaining the temperature of the reaction chamber at 200-300 ℃ and the pressure at 450-550 torr, and introducing SiNx and SiH into the PECVD equipment4And N2And O, forming a stripping layer on the GaN layer.
The third embodiment is as follows: maintaining the temperature of the reaction chamber at 200-300 ℃ and the pressure at 450-550 torr, and introducing Al into the PECVD equipment2O3TEMA and N2And O, forming a stripping layer on the GaN layer.
Etching the stripping layer to form a plurality of holes;
and etching the stripping layer by adopting a photoetching process until a plurality of funnel-shaped holes are formed on the surface of the GaN layer.
Specifically, a layer of photoresist is coated on the stripping layer, soft testing is carried out on the photoresist, the soft baking temperature is 90-100 ℃, a photomask covers the photoresist, the photoresist is exposed for 10-15 seconds under the illumination with the wavelength of 365nm, a developer is used for developing to show a pattern, and then hard baking is carried out on the photoresist, the hard baking temperature is 110-130 ℃, and the time is 3-65 min; then, hydrofluoric acid is used to etch the stripping layer, and the etching time is 30-60 min.
The utility model discloses form the hole of infundibulate in the peel ply, can let corrosive liquid enter into the inside of peel ply easily and corrode the peel ply to make silicon substrate and gallium nitride epitaxial layer separation. It should be noted that the gan epitaxial layer filled in the hole may be broken during the etching process and separated from the buffer layer, but the quality of the gan epitaxial layer is not affected.
Referring to fig. 2, the diameter of the top opening of the hole is a, and the diameter of the bottom opening of the hole is b, and in order to facilitate the corrosive liquid to enter the stripping layer, it is preferable that b is (0.4 to 0.6) × a.
More preferably, a is 6 to 50 μm. If the diameter a of the top opening of the hole is less than 6 microns, the opening is too small, and an epitaxial layer is difficult to form in the hole; if a is larger than 50 μm, the opening is too large and the epitaxial layer in the hole is difficult to break and separate.
The holes are arranged in an array, and the distance between the holes is c, preferably, c is 5 to 20 μm. If c is less than 5 μm, the distance is too small and the defect density of the epitaxial layer is increased; if c is greater than 20 μm, the distance is too large, which also affects the epitaxial layer quality.
And fourthly, forming an epitaxial layer in the stripping layer and the holes.
And sequentially forming an N-GaN layer, an active layer and a P-GaN layer in the stripping layer and the holes by adopting an MOCVD (metal organic chemical vapor deposition) process.
The above disclosure is only a preferred embodiment of the present invention, and certainly should not be taken as limiting the scope of the invention, which is defined by the claims and their equivalents.
Claims (7)
1. A silicon-based gallium nitride epitaxial structure is characterized by comprising a silicon substrate, an Al layer, a nitrogen-containing buffer layer, a stripping layer, an N-GaN layer, an active layer and a P-GaN layer, wherein the Al layer, the nitrogen-containing buffer layer, the stripping layer, the N-GaN layer, the active layer and the P-GaN layer are sequentially arranged on the silicon substrate;
the nitrogen-containing buffer layer comprises an AlN layer, an AlGaN layer and a GaN layer, wherein the AlN layer is arranged between the Al layer and the AlGaN layer, and the GaN layer is arranged between the AlGaN layer and the stripping layer;
the stripping layer is made of SiO2、SiNx、Al2O3Or AlN.
2. A GaN-based epitaxial structure according to claim 1 wherein the lift-off layer has a plurality of holes formed therethrough, and the N-GaN layer formed on the lift-off layer fills the holes.
3. The silicon-based gallium nitride epitaxial structure of claim 2, wherein the lift-off layer has a thickness of 10 to 300 nm.
4. Silicon-based gallium nitride epitaxial structure according to claim 2, wherein the shape of the cavity is funnel-shaped, the top opening of the cavity has a width a and the bottom opening has a width b, wherein,
b＝(0.4～0.6)*a。
5. a silicon-based gallium nitride epitaxial structure according to claim 3 wherein a is 6 to 50 μm.
6. A gan-based epitaxial structure according to claim 2 wherein the distance between the holes is c, which is 5-20 μm.
7. A silicon-based gallium nitride epitaxial structure according to claim 1, wherein the thickness of the Al layer is the thickness of a layer of Al atoms;
the AlN layer is 100-500 nm thick, the AlGaN layer is 200-300 nm thick, and the GaN layer is 1-2 μm thick.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110838539A (en) * | 2019-11-25 | 2020-02-25 | 佛山市国星半导体技术有限公司 | Silicon-based gallium nitride epitaxial structure and manufacturing method thereof |
| WO2024045270A1 (en) * | 2022-09-01 | 2024-03-07 | 中国科学院微电子研究所 | Laminated structure and preparation method therefor, pattern transfer method, and reworking method |
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2019
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110838539A (en) * | 2019-11-25 | 2020-02-25 | 佛山市国星半导体技术有限公司 | Silicon-based gallium nitride epitaxial structure and manufacturing method thereof |
| CN110838539B (en) * | 2019-11-25 | 2024-04-30 | 佛山市国星半导体技术有限公司 | Silicon-based gallium nitride epitaxial structure and manufacturing method thereof |
| WO2024045270A1 (en) * | 2022-09-01 | 2024-03-07 | 中国科学院微电子研究所 | Laminated structure and preparation method therefor, pattern transfer method, and reworking method |
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