Semiconductor structure capable of reducing defect density and manufacturing method

Abstract

The invention discloses a semiconductor structure capable of reducing defect density and a manufacturing method. The manufacturing method comprises the following steps: growing a BNO buffer layer on a substrate; sequentially growing a first transition layer of BxAl (1-x) NO and a second transition layer of GaxAl (1-x) N on the BNO buffer layer; when the first transition layer is grown, the value of x is gradually reduced from 1 to 0, and the growth temperature is gradually increased from the first temperature to the second temperature; when the second transition layer is grown, the value of x is gradually increased from 0 to 1, the growth temperature is gradually reduced from a second temperature to a third temperature, and the second temperature is higher than the first temperature and the third temperature; and growing an epitaxial layer on the second transition layer to form a semiconductor structure. According to the invention, the BNO buffer layer, the first transition layer of BxAl (1-x) NO and the second transition layer of BxAl (1-x) NO are arranged between the substrate and the epitaxial layer, and the concentration of Al in the first transition layer of BxAl (1-x) NO and the concentration of Al in the second transition layer of GaxAl (1-x) N are gradually increased and then gradually reduced to carry out linear change, so that the defect density is effectively reduced.

Description

Technical Field

[0001] The invention relates to the field of semiconductors, and in particular to the structure and manufacture of light emitting diodes. Background Art

[0002] GaN materials are widely used in many fields such as LED light-emitting diodes and power electronic devices, which are important application directions in the field of nitride semiconductor research. With the development of science and technology and the needs of life, the pursuit of display effects in the display field continues to rise. From LCD TVs, LED backlight TVs to Mini LED backlight TVs, and then to Mini / Mcro LED direct display TVs, we can see the market's pursuit of true full-color display. In order to promote the goal of MicroLED ultimate display, in recent years, MicroLED direct display has become the key layout direction of nitride semiconductor leading companies. China, South Korea, Japan, the United States, Germany and other countries have also given strong support to MicroLED display in terms of system, funding, technology and other aspects.

[0003] The blue-green epitaxial structure of the Micro LED light-emitting diode includes a substrate, and a buffer layer, an undoped GaN layer, a Si-doped nGaN layer, an active layer InGaN, an electron blocking layer EBL and a Mg-doped pGaN layer sequentially grown on the substrate. The substrate is a sapphire substrate, a Si substrate or a SiC substrate.

[0004] When growing GaN epitaxial layer on sapphire substrate, although there is a buffer layer, the buffer layer is mostly AlGaN material, which can relieve the stress between epitaxial layer and substrate to a certain extent. However, due to the large lattice mismatch and thermal mismatch between sapphire substrate and GaN layer, the lattice adaptation is as high as 13% or more. The lattice constant of Al2O3 on sapphire substrate is a=0.4758nm (lattice used for LED epitaxy), and the lattice constant of GaN is C=0.5185nm (lattice used for LED epitaxy). Therefore, GaN material grown on sapphire substrate is subject to large compressive stress from sapphire substrate, and only one buffer layer cannot completely buffer stress; and because Al atoms pre-react severely and the diffusion barrier of Al atoms at the same position is very high, the AlGaN layer generates relatively more nucleation points during epitaxial growth, and each nucleation point forms islands as the core and merges with each other, resulting in a large number of defects in the material during the merging process. At the same time, in order to buffer the stress, the thickness of the AlGaN layer will be relatively thick, and the sapphire substrate will exert strong tensile stress on the thick AlGaN layer, which will cause the AlGaN layer to break and produce a large number of crack defects. In summary, during the epitaxial growth of GaN materials on sapphire substrates, due to the high stress, a large number of threading dislocations are easily generated, which in turn leads to a high density of material defects. After being made into Micro LED blue-green chips through the chip process, poor photoelectric properties such as low quantum efficiency, severe leakage, and poor ESD resistance will appear.

[0005] Therefore, there is an urgent need for a semiconductor structure and a manufacturing method that can solve the above problems and reduce defect density. Summary of the invention

[0006] The purpose of the present invention is to provide a semiconductor structure and a manufacturing method for reducing defect density, wherein a BNO buffer layer, a BNO layer and a BNO layer are provided between a substrate and an epitaxial layer. x Al (1－x) The first transition layer of NO and Ga x Al (1－x) The concentrations of Al in the second transition layer of N, the first transition layer, and the second transition layer gradually increase and then decrease to perform a linear change, thereby effectively reducing the defect density.

[0007] In order to achieve the above object, the present invention provides a method for manufacturing a semiconductor structure with reduced defect density, comprising: providing a substrate; growing a BNO buffer layer on the substrate; and sequentially growing B x Al (1－x) The first transition layer of NO and Ga x Al (1－x)N second transition layer; when growing the first transition layer, the flow rate of the reaction material of B gradually decreases from the preset M concentration to 0, and the flow rate of the reaction material of Al gradually increases from 0 to M, so that the value of x gradually decreases from 1 to 0, so that the concentration of B in the first transition layer gradually decreases from bottom to top, and the concentration of Al gradually increases, and the first transition layer gradually transitions from BNO material to BAlNO material and then to AlNO material; when growing the second transition layer, the flow rate of the reaction material of AL gradually decreases from the preset M concentration to 0, and the flow rate of the reaction material of Ga gradually increases from 0 to M, so that the value of x gradually increases from 0 to 1, so that the concentration of Al in the second transition layer gradually decreases from bottom to top, and the concentration of Ga gradually increases, and the second transition layer gradually transitions from AlN material to GaAlN material and then to GaN material; growing an epitaxial layer on the second transition layer to form a semiconductor structure.

[0008] Preferably, when growing the first transition layer, the growth temperature gradually increases from the first temperature to the second temperature; when growing the second transition layer, the growth temperature gradually decreases from the second temperature to the third temperature, and the second temperature is greater than the first temperature and the third temperature. The change in the growth temperature of different transition layers can improve the mobility of Al atoms. The migration energy of Al atoms is higher but the mobility is lower. The diffusion length of the Al atom surface is smaller than that of Ga atoms. During the epitaxial growth process, the lateral diffusion ability of Al atoms is weak. They tend to occupy the position where the substrate is initially adsorbed and will no longer move to the lattice point with the lowest energy. The growth temperature changes linearly according to the concentration of Al, which can increase the migration rate of Al atoms, increase the diffusion length of the Al atom surface, and reduce the island nucleation density formed by the parasitic reaction of Al atoms, thereby further reducing the linear defect density.

[0009] More preferably, the first temperature is equal to the third temperature. Of course, the first temperature may not be equal to the third temperature. The first temperature is preferably selected to adapt to the BNO buffer layer, and the third temperature is preferably selected to adapt to the epitaxial layer.

[0010] Specifically, the first temperature is 1000 degrees Celsius, the second temperature is 1200 degrees Celsius, and the third temperature is 1000 degrees Celsius.

[0011] Preferably, during the growth of the first transition layer, the carrier gas is nitrogen and no hydrogen is passed, the reaction gas is NH3, and the amount of NH3 used is 2 / 5 to 1 / 2 of that of nitrogen.

[0012] Preferably, during the growth of the second transition layer, the carrier gas is nitrogen and no hydrogen is passed, the reaction gas is NH3, and the amount of NH3 used is 1 / 2 to 3 / 5 of that of nitrogen.

[0013] Preferably, the BNO buffer layer is deposited on the substrate by PVD sputtering coating.

[0014] Specifically, when the BNO buffer layer is grown, the coating temperature is controlled between 700° C. and 750° C., and the oxygen gas flow rate is controlled between 2 sccm and 3 sccm.

[0015] Preferably, the total thickness of the BNO buffer layer is 30 nm-50 nm.

[0016] Preferably, the epitaxial layer includes, from bottom to top, an undoped GaN layer, an n-type semiconductor layer, an active layer, an electron blocking layer, a p-type semiconductor layer, and a p-type contact layer, which are sequentially grown on the second transition layer.

[0017] The present invention also provides a semiconductor structure with reduced defect density, which is manufactured by the above-mentioned method for manufacturing a semiconductor structure with reduced defect density. The semiconductor structure is a light emitting diode structure or other semiconductor structure.

[0018] The present invention also provides a semiconductor structure with reduced defect density, comprising a substrate, a BNO buffer layer, a first transition layer and a second transition layer sequentially grown on the substrate, wherein the first transition layer is B x Al (1－x) NO and its x value gradually decreases from 1 to 0, so that the concentration of B in the first transition layer gradually decreases from bottom to top, and the concentration of Al gradually increases. The first transition layer gradually transitions from BNO material to BAlNO material and then to AlNO material; the second transition layer is Ga x Al (1－x) N and its x value gradually increases from 0 to 1, so that the concentration of Al in the second transition layer gradually decreases from bottom to top, and the concentration of Ga gradually increases, and the second transition layer gradually transitions from AlN material to GaAlN material and then gradually transitions to GaN material.

[0019] Compared with the prior art, the present invention provides a BNO buffer layer and a B x Al (1－x) The first transition layer of NO and Ga x Al (1－x) The second transition layer of N makes the concentration of B in the first transition layer gradually decrease from bottom to top, and the concentration of Al gradually increase. The first transition layer gradually transitions from BNO material to BAlNO material and then to AlNO material, which can effectively adjust the stress. The lattice adjustment of the BNO buffer layer, the first transition layer and the second transition layer can reduce and interrupt the dislocation along the growth direction, reduce the defect density in the material growth process, reduce leakage, and improve the quantum efficiency of the light-emitting diode. On the other hand, the use of B x Al (1－x) NO as a transition layer also makes the first transition layer and the BNO buffer layer better adapted, further reducing dislocations along the growth direction and lowering defect density. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a flow chart of a method for manufacturing a semiconductor structure with reduced defect density.

[0021] Figure 2 1 is a structural diagram of a semiconductor structure for reducing defect density according to the present invention.

[0022] Figure 3 It is a flow chart for the production of epitaxial layers on semiconductor structures.

[0023] Figure 4 FIG. 4 is another structural diagram of the semiconductor structure with low defect density according to the present invention. DETAILED DESCRIPTION

[0024] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the implementation methods and the accompanying drawings.

[0025] refer to Figure 1 The present invention discloses a method for manufacturing a semiconductor structure with reduced defect density, comprising steps S1 to S4.

[0026] S1, providing a substrate 10.

[0027] The substrate 10 is a sapphire substrate, and other types of substrates 10 may also be used.

[0028] S2 , growing a BNO buffer layer 20 on the substrate 10 .

[0029] The BNO buffer layer 20 is deposited on the substrate 10 by PVD sputtering. Specifically, when the BNO buffer layer 20 grows, the coating temperature is controlled between 700°C and 750°C, and the oxygen gas flow rate is controlled between 2sccm and 3sccm. The total thickness of the BNO buffer layer 20 is 30nm-50nm.

[0030] S3, growing B on the BNO buffer layer 20 in sequence x Al (1－x) The first transition layer 31 of NO and Ga x Al (1－x) The second transition layer 32 of N.

[0031] When the first transition layer 31 is grown, the flow rate of the reaction material of B gradually decreases from the preset M concentration to 0, the flow rate of the reaction material of Al gradually increases from 0 to M, and the growth temperature gradually increases from the first temperature to the second temperature, that is, the concentration of B gradually decreases, the concentration of Al gradually increases, and the first transition layer 31 gradually transitions from BNO material to BAlNO material and then to AlNO material; when the second transition layer 32 is grown, the flow rate of the reaction material of Al gradually decreases from the preset M concentration to 0, the flow rate of the reaction material of Ga gradually increases from 0 to M, and the growth temperature gradually decreases from the second temperature to the third temperature, that is, the concentration of Al gradually decreases, the concentration of Ga gradually increases, and the second transition layer 32 gradually transitions from AlN material to GaAlN material and then to GaN material, and the second temperature is greater than the first temperature and the third temperature. M is the preset flow rate.

[0032] When the first transition layer 31 is grown, the growth temperature gradually increases linearly, the flow rate of the reaction material of B gradually decreases linearly, and the flow rate of the reaction material of Al gradually increases linearly. When the second transition layer 32 is grown, the growth temperature gradually decreases linearly, the flow rate of the reaction material of Al gradually decreases linearly, and the flow rate of the reaction material of Ga gradually increases linearly.

[0033] In this embodiment, the reaction materials input when growing the first transition layer 31 are: trimethylboron, trimethylaluminum, NH3, and oxygen. During the growth, the material flow rates of trimethylboron and trimethylaluminum are gradually adjusted to gradually change their concentrations. Similarly, when growing the second transition layer 32, the flow rates of the reaction materials containing Al and the flow rates of the reaction materials containing Ga are adjusted to gradually change their concentrations.

[0034] The first temperature is equal to the third temperature. Of course, the first temperature may not be equal to the third temperature. The first temperature is preferably selected to adapt to the BNO buffer layer 20, and the third temperature is preferably selected to adapt to the epitaxial layer 40. In this embodiment, the first temperature is 1000 degrees Celsius, the second temperature is 1200 degrees Celsius, and the third temperature is 1000 degrees Celsius.

[0035] During the growth of the first transition layer 31 and the second transition layer 32, the growth temperature of different transition layers changes, which can improve the migration ability of Al atoms. The migration energy of Al atoms is higher but the mobility is lower. The diffusion length of the Al atom surface is smaller than that of Ga atoms. During the epitaxial growth process, the lateral diffusion ability of Al atoms is weak. They tend to occupy the position of initial substrate adsorption and will no longer move to the lattice point with the lowest energy. The growth temperature changes linearly according to the concentration of Al, which can improve the migration rate of Al atoms, increase the diffusion length of the Al atom surface, and reduce the island nucleation density formed by the parasitic reaction of Al atoms, thereby reducing linear defects.

[0036] Specifically, during the growth of the first transition layer 31, the carrier gas is nitrogen without hydrogen, the reaction gas is NH3, and the amount of NH3 is 2 / 5 to 1 / 2 of that of nitrogen. During the growth of the second transition layer 32, the carrier gas is nitrogen without hydrogen, the reaction gas is NH3, and the amount of NH3 is 1 / 2 to 3 / 5 of that of nitrogen.

[0037] S4, growing an epitaxial layer 40 on the second transition layer 32 to form a semiconductor structure.

[0038] refer to Figure 3 , step S4 specifically includes: S41, growing an undoped GaN layer 41 on the transition layer 30; S42: growing an n-type semiconductor layer 42 (n-GaN) on the undoped GaN layer 41; S43, growing an active layer 43 (InGaN, MQW layer) on the n-type semiconductor layer 42; S44, growing an electron blocking layer 44 (EBL) on the active layer 43; S45, growing a p-type semiconductor layer 45 (p-GaN) on the electron blocking layer 44; S46, growing a p-type contact layer 46 (GaN contact layer) on the p-type semiconductor layer 45. Among them, the undoped GaN layer 41 is an undoped u-GaN layer. Among them, the specific production process and structure of the GaN epitaxial layer 40 are not limited to this.

[0039] In this embodiment, the epitaxial layer 40 includes, from bottom to top, an undoped U-GaN layer 41, an n-type semiconductor layer 42 (n-GaN), an active layer 43 (MQW layer of InGaN), an electron blocking layer 44 (EBL), a p-type semiconductor layer 45 (P-GaN layer), and a P-type contact layer (GaN contact layer), which are sequentially grown on the second transition layer 32.

[0040] refer to Figure 2 The present invention also discloses a semiconductor structure with reduced defect density, 100, which is manufactured by the above-mentioned method for manufacturing a semiconductor structure with reduced defect density.

[0041] refer to Figure 2 The semiconductor structure for reducing defect density includes a substrate 10, a BNO buffer layer 20 grown on the substrate 10, a first transition layer 31 grown on the BNO buffer layer 20, a second transition layer 32 grown on the first transition layer 31, and an epitaxial layer 40 grown on the second transition layer 32.

[0042] refer to Figure 4The epitaxial layer 40 includes, from bottom to top, an undoped U-GaN layer 41, an n-type semiconductor layer 42 (n-GaN), an active layer 43 (MQW layer of InGaN), an electron blocking layer 44 (EBL), a p-type semiconductor layer 45 (P-GaN layer), and a P-type contact layer (GaN contact layer), which are sequentially grown on the second transition layer 32.

[0043] Compared with the prior art, the present invention provides a BNO buffer layer 20, a BNO buffer layer 20 and a BNO layer 40 between the substrate 10 and the epitaxial layer 40. x Al (1－x) The first transition layer 31 of NO and Ga x Al (1－x) N's second transition layer 32, B x Al (1－x) After the x of NO gradually increases from 0 to 1 to form the first transition layer 31, Ga x Al (1－x) The x of N is gradually reduced from 1 to 0 to form the second transition layer 32, which can effectively adjust the stress, and use the lattice adjustment of the BNO buffer layer 20, the first transition layer 31 and the second transition layer 32 to reduce and interrupt the dislocation along the growth direction, reduce the defect density in the material growth process, reduce leakage, and improve the quantum efficiency of the light-emitting diode. x Al (1－x) The first transition layer 31 of NO and Ga x Al (1－x) The growth temperature of the second transition layer 32 of N changes linearly according to the concentration of Al during growth, which can improve the migration rate of Al atoms, increase the diffusion length of the Al atom surface, reduce the island nucleation density formed by the parasitic reaction of Al atoms, and further reduce the linear defect density.

[0044] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention are still within the scope covered by the present invention.

Claims

1. A method for manufacturing a semiconductor structure with reduced defect density, characterized in that: include: providing a substrate; growing a BNO buffer layer on the substrate; On the BNO buffer layer, B x Al (1－x) The first transition layer of NO and Ga x Al (1－x) N second transition layer; when growing the first transition layer, the flow rate of the reaction material of B gradually decreases from the preset M concentration to 0, and the flow rate of the reaction material of Al gradually increases from 0 to M, so that the value of x gradually decreases from 1 to 0, the concentration of B gradually decreases from bottom to top in the first transition layer, and the concentration of Al gradually increases, and the first transition layer gradually transitions from BNO material to BAlNO material and then gradually transitions to AlNO material; when growing the second transition layer, the flow rate of the reaction material of AL gradually decreases from the preset M concentration to 0, and the flow rate of the reaction material of Ga gradually increases from 0 to M, so that the value of x gradually increases from 0 to 1, the concentration of Al gradually decreases from bottom to top in the second transition layer, and the concentration of Ga gradually increases, and the second transition layer gradually transitions from AlN material to GaAlN material and then gradually transitions to GaN material; An epitaxial layer is grown on the second transition layer to form a semiconductor structure.

2. The method for manufacturing a semiconductor structure with reduced defect density according to claim 1, wherein: When growing the first transition layer, the growth temperature gradually increases from the first temperature to the second temperature; when growing the second transition layer, the growth temperature gradually decreases from the second temperature to the third temperature, and the second temperature is greater than the first temperature and the third temperature.

3. The method for manufacturing a semiconductor structure with reduced defect density according to claim 2, wherein: The first temperature is equal to the third temperature.

4. The method for manufacturing a semiconductor structure with reduced defect density according to claim 3, wherein: The first temperature is 1000 degrees Celsius, the second temperature is 1200 degrees Celsius, and the third temperature is 1000 degrees Celsius.

5. The method for manufacturing a semiconductor structure with reduced defect density according to claim 1, wherein: During the growth of the first transition layer, the carrier gas is nitrogen and no hydrogen is passed, the reaction gas is NH3, and the amount of NH3 is 2 / 5 to 1 / 2 of that of nitrogen; During the growth of the second transition layer, the carrier gas is nitrogen and no hydrogen is passed, the reaction gas is NH3, and the amount of NH3 used is 1 / 2 to 3 / 5 of that of nitrogen.

6. The method for manufacturing a semiconductor structure with reduced defect density according to claim 1, wherein: The BNO buffer layer is deposited on the substrate by PVD sputtering coating. When the BNO buffer layer grows, the coating temperature is controlled between 700° C. and 750° C., and the oxygen gas flow rate is controlled between 2 sccm and 3 sccm.

7. The method for manufacturing a semiconductor structure with reduced defect density according to claim 1, wherein: The total thickness of the BNO buffer layer is 30nm-50nm.

8. The method for manufacturing a semiconductor structure with reduced defect density as claimed in claim 1, wherein: The epitaxial layer includes, from bottom to top, an undoped GaN layer, an n-type semiconductor layer, an active layer, an electron blocking layer, a p-type semiconductor layer, and a p-type contact layer which are sequentially grown on the second transition layer.

9. A semiconductor structure with reduced defect density, characterized in that: The semiconductor structure is manufactured by the method for manufacturing a semiconductor structure with reduced defect density according to any one of claims 1 to 8.

10. A semiconductor structure with reduced defect density, characterized in that: The invention comprises a substrate, a BNO buffer layer, a first transition layer and a second transition layer sequentially grown on the substrate, wherein the first transition layer is B x Al (1－x) NO and its x value gradually decreases from 1 to 0, so that the concentration of B in the first transition layer gradually decreases from bottom to top, and the concentration of Al gradually increases. The first transition layer gradually transitions from BNO material to BAlNO material and then to AlNO material; the second transition layer is Ga x Al (1－x) N and its x value gradually increases from 0 to 1, so that the concentration of Al in the second transition layer gradually decreases from bottom to top, and the concentration of Ga gradually increases, and the second transition layer gradually transitions from AlN material to GaAlN material and then gradually transitions to GaN material.

Images