Epitaxial structure for inhibiting radio frequency loss of Si-based AlN epitaxial wafer and process thereof

Abstract

The invention discloses an epitaxial structure for inhibiting radio frequency loss of a Si-based AlN epitaxial wafer and a process of the epitaxial structure. The process comprises the steps of selecting a substrate, pre-growing an amorphous SiO2 layer, performing ion implantation, annealing and growing an epitaxial layer. The step of pre-growing the amorphous SiO2 layer comprises the steps of pre-growing the amorphous SiO2 layer on the surface of the high-resistance Si through a thermal oxidation method, and performing ion implantation on the Si substrate subjected to thermal oxidation pre-growth. According to the method, H, He, C and N plasmas are pre-injected into the surface of an amorphous SiO2 / high-resistance Si substrate, and a defect layer and n-type doping are formed below the interface of the amorphous SiO2 / Si substrate. The formed defect layer not only can reduce a polarization field formed by stress and reduce the conductivity of an interface channel by relaxation of tensile stress formed by lattice mismatch and thermal mismatch in the epitaxial growth process of the AlN layer, but also can hinder diffusion of Al and Ga and inhibit formation of a p-type parasitic channel near an AlN / Si interface, thereby finally achieving the purpose of reducing radio frequency loss.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor materials, and relates to a preparation process of a heterogeneous epitaxial wafer, in particular to an epitaxial structure and a process thereof for suppressing radio frequency loss of a Si-based AlN epitaxial wafer. Background Art

[0002] Gallium nitride (GaN) is a third-generation wide bandgap semiconductor with characteristics such as direct bandgap, high breakdown electric field, and high thermal conductivity. Therefore, it shows unique advantages in the fields of high power and high frequency, and is widely used in microwave radio frequency (5G communications, radar warning, satellite communications, etc.), power electronics (smart grid, high-speed rail transit, new energy vehicles, etc.) and optoelectronics (LEDs, lasers, photodetectors, etc.) and other fields.

[0003] At present, GaN devices are mainly prepared by heteroepitaxial wafers, and the quality of GaN epitaxial films strongly depends on the properties of heterogeneous substrates, including lattice constant, thermal expansion coefficient, thermal conductivity and surface roughness, etc. In addition, it also has a significant impact on the defect density, crystal orientation, stress strain, surface morphology, polarity, etc. of the GaN epitaxial layer. Therefore, selecting a suitable heteroepitaxial substrate and rationally designing the structural parameters of each layer of the epitaxial wafer are the key to obtaining high-quality GaN epitaxial wafers.

[0004] Si substrates have the advantages of large size, low cost and compatibility with existing CMOS processes, making Si-based GaN radio frequency (RF) electronic materials and their devices the next focus after power electronic devices. However, after epitaxial III-V epitaxial layers, such as AlN and GaN, are grown on Si substrates, Al and Ga elements will diffuse into the high-resistance Si substrate at high temperatures to form parasitic conductive channels, causing the RF loss (RF Loss) of Si-based RF devices to increase significantly.

[0005] In order to solve the above problems, people have adopted a variety of methods to suppress the generation of conductive channels, such as lowering the epitaxial growth temperature, nitriding the AlN / Si interface, and epitaxially growing the 3C-SiC / Si interface structure to suppress the diffusion of Al and Ga elements, thereby weakening the influence of parasitic channels.

[0006] Although the above methods can reduce RF loss to a certain extent, the presence of low-temperature grown III-V epitaxial layers and amorphous SiN will have a negative impact on AlN and subsequent epitaxial growth, and 3C-SiC epitaxy faces the problem of low growth quality. Therefore, a low-cost, simple and effective method is needed to reduce the RF loss of Si-based GaN epitaxial wafers.

[0007] Technical solution of prior art 1 Nitriding AlN / Si surface: Figure 1As shown in (b), nitriding the Si surface before growing AlN can form amorphous SiN with a thickness of nm, thereby inhibiting the diffusion of Al and Ga elements at high temperatures.

[0008] Defects: The generation of amorphous SiN layer will deteriorate the crystallization quality of subsequent epitaxial layers such as AlN and GaN. Although it alleviates the RF loss problem, it also leads to the deterioration of subsequent epitaxial quality.

[0009] Technical solution of prior art 2 Lowering the epitaxial layer temperature: As shown in Table 1, by lowering the growth temperature of each epitaxial layer, the diffusion of Al and Ga elements can be suppressed to a certain extent, so that the RF loss at 28 GHz is reduced from 0.45 dB / mm to 0.2 dB / mm.

[0010] Table 1 GaN on Si low temperature epitaxy data

[0011] Disadvantage: The reduction of RF loss comes at the expense of GaN crystal quality, which will cause new problems for the device later. Summary of the invention

[0012] In view of the above problems of the prior art, the present invention proposes an epitaxial structure and a process for suppressing the radio frequency loss of Si-based AlN epitaxial wafers. This process forms a defect layer structure in the Si (111) substrate through low-energy heavy ion implantation, so as to achieve the purpose of regulating the tensile stress of the AlN layer and suppressing the diffusion of Al atoms, thereby reducing the radio frequency loss caused by the AlN / Si interface.

[0013] The technical solution of the present invention to solve the above technical problems is as follows: An epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, comprising selecting a substrate, pre-growing an amorphous SiO2 layer, ion implantation, annealing, growing an amorphous SiO2 layer, and growing an epitaxial layer; The substrate is selected as follows: a high-resistance Si (111) substrate is selected, and the resistivity of the Si (111) substrate is 1000-10000 Ω·cm; The pre-grown amorphous SiO2 layer is: a 10-500 nm thick amorphous SiO2 layer is pre-grown on a high-resistance Si surface by a thermal oxidation method, wherein Si(111) refers to the (111) crystal plane of a silicon (Si) crystal.

[0014] Based on the above technical solution, the present invention can also be improved as follows.

[0015] Furthermore, in the above-mentioned epitaxial process for suppressing the radio frequency loss of Si-based AlN epitaxial wafer, the ion implantation is as follows: the Si (111) substrate that has been pre-grown by thermal oxidation is implanted with ions, the implantation energy is between 10 and 500 keV, the implantation dose is between 1×10 10 ~1×10 17 / cm 2 , the ion is at least one of H, He, C, N, O, F, Mg, Si, P, Ar, Ca, Ge, As, and Fe.

[0016] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the annealing method is rapid high-temperature thermal annealing, the annealing temperature is 500-1000°C, the annealing atmosphere is N2, and the annealing time is 5-60s.

[0017] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the amorphous SiO2 layer is removed by using an HF solution to completely remove the amorphous SiO2 layer on the annealed substrate.

[0018] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the growing epitaxial layer: using the MOCVD method to epitaxially grow 100-200 nm thick AlN on the surface of the Si (111) substrate.

[0019] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the high-resistance Si (111) substrate is N-type or P-type doped.

[0020] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, after ion implantation, the distribution range of ions is within the range of 0 to 200 nm below the interface between the Si (111) substrate and the epitaxial layer.

[0021] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the thermal oxidation method is dry oxygen oxidation, wet oxygen oxidation or water vapor oxidation.

[0022] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the implantation direction of the ion implantation is perpendicular to the amorphous SiO2 / Si surface.

[0023] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the annealing method is as follows: the substrate after ion implantation is annealed at a temperature of 1000° C., an annealing atmosphere of N2, and an annealing time of 10 s.

[0024] The epitaxial structure obtained by any of the above processes includes a high-resistance Si (111) substrate, a defect layer, and an epitaxial layer. The defect layer is obtained by ion implanting an amorphous SiO2 layer pre-grown on the Si (111) substrate by a thermal oxidation method, annealing, and finally removing the amorphous SiO2 layer. The defect layer is located in the range of 0 to 200 nm below the interface between the Si (111) substrate and the epitaxial layer. The epitaxial structure can suppress radio frequency loss.

[0025] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects: The present invention forms a defect layer and n-type doping below the interface of the amorphous SiO2 / Si (111) substrate by pre-implanting one or more of H, He, C, N, O, F, Mg, Si, P, Ar, Ca, Ge, As, and Fe ions into the surface of the amorphous SiO2 / high-resistance Si (111) substrate. The formation of the defect layer can not only relax the tensile stress formed by lattice mismatch and thermal mismatch during the epitaxial growth of the AlN layer, but also hinder the diffusion of Al and Ga (Ga originates from thermal diffusion in the subsequent epitaxial growth of AlGaN, GaN, etc.), and inhibit the formation of p-type parasitic channels near the AlN / Si (111) interface, thereby ultimately achieving the purpose of reducing radio frequency losses.

[0026] The present invention effectively solves the radio frequency loss caused by the diffusion of Al and Ga elements without affecting the quality of the subsequent epitaxial layer crystal, and provides a feasible technical path for the low-cost and high-quality production of Si-based AlN and Si-based GaN epitaxial materials.

[0027] In summary, the present invention provides a feasible technical path for the realization of low RF loss Si-based AlN epitaxial materials, which can generate considerable economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 TEM images of the AlN / Si cross section of a 200 nm AlN sample of the prior art 1, wherein (a) TMAl pre-flow treatment is adopted, and (b) nitridation treatment is adopted; Figure 2 A flow chart of an epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers provided in an embodiment of the present invention.

[0029] Figure 3 Optical image of the CPW structure used for RF loss testing (a) and the corresponding layout (b). DETAILED DESCRIPTION

[0030] In order to facilitate understanding of the present application, the present application will be described more comprehensively below. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0032] An epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, comprising selecting a substrate, pre-growing an amorphous SiO2 layer, ion implantation, annealing, growing an amorphous SiO2 layer, and growing an epitaxial layer; The substrate is selected as follows: a high-resistance Si (111) substrate is selected, and the resistivity of the Si (111) substrate is 1000-10000 Ω·cm; The pre-grown amorphous SiO2 layer is: pre-growing an amorphous SiO2 layer with a thickness of 10-500nm on the surface of high-resistance Si by a thermal oxidation method.

[0033] Based on the above technical solution, the present invention can also be improved as follows.

[0034] Furthermore, in the above-mentioned epitaxial process for suppressing the radio frequency loss of Si-based AlN epitaxial wafer, the ion implantation is as follows: the Si (111) substrate that has been pre-grown by thermal oxidation is implanted with ions, the implantation energy is between 10 and 500 keV, the implantation dose is between 1×10 10 ~1×10 17 / cm 2 , the ion is at least one of H, He, C, N, O, F, Mg, Si, P, Ar, Ca, Ge, As, and Fe.

[0035] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the annealing method is rapid high-temperature thermal annealing, the annealing temperature is 500-1000°C, the annealing atmosphere is N2, and the annealing time is 5-60s.

[0036] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the amorphous SiO2 layer is removed by using an HF solution to completely remove the amorphous SiO2 layer on the annealed substrate.

[0037] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the growing epitaxial layer: using the MOCVD method to epitaxially grow 100-200 nm thick AlN on the surface of the Si (111) substrate.

[0038] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the high-resistance Si (111) substrate is N-type or P-type doped.

[0039] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, after ion implantation, the distribution range of ions is within the range of 0 to 200 nm below the interface between the Si (111) substrate and the epitaxial layer.

[0040] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the thermal oxidation method is dry oxygen oxidation, wet oxygen oxidation or water vapor oxidation.

[0041] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the implantation direction of the ion implantation is perpendicular to the amorphous SiO2 / Si surface.

[0042] Furthermore, in the above-mentioned epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, the annealing method is as follows: the substrate after ion implantation is annealed at a temperature of 1000° C., an annealing atmosphere of N2, and an annealing time of 10 s.

[0043] The epitaxial structure obtained by any of the above processes includes a high-resistance Si (111) substrate, a defect layer, and an epitaxial layer. The defect layer is obtained by ion implanting an amorphous SiO2 layer pre-grown on the Si (111) substrate by a thermal oxidation method, annealing, and finally removing the amorphous SiO2 layer. The defect layer is located in the range of 0 to 200 nm below the interface between the Si (111) substrate and the epitaxial layer. The epitaxial structure can suppress radio frequency loss.

[0044] The present invention forms a defect layer and n-type doping below the interface of the amorphous SiO2 / Si (111) substrate by pre-implanting one or more of H, He, C, N, O, F, Mg, Si, P, Ar, Ca, Ge, As, and Fe ions into the surface of the amorphous SiO2 / high-resistance Si (111) substrate. The defect layer formed can not only relax the tensile stress formed by lattice mismatch and thermal mismatch during the epitaxial growth of the AlN layer, reduce the polarization field formed by the stress, and reduce the conductivity of the interface channel, but also hinder the diffusion of Al and Ga, and inhibit the formation of p-type parasitic channels near the AlN / Si (111) interface, thereby ultimately achieving the purpose of reducing RF loss.

[0045] The present invention effectively solves the radio frequency loss caused by the diffusion of Al and Ga elements without affecting the quality of the subsequent epitaxial layer crystal, and provides a feasible technical path for the low-cost and high-quality production of Si-based AlN and Si-based GaN epitaxial materials.

[0046] Embodiment 1: The present invention provides an epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers.

[0047] like Figure 2 As shown, the specific preparation steps are as follows: Step 1: Select a 6-inch high-resistance Si (111) substrate with a resistivity of 1000 Ω·cm.

[0048] Step 2: Grow an amorphous SiO2 layer with a thickness of 100 nm on the surface of the Si (111) substrate by thermal oxidation method, where Si (111) refers to the (111) crystal plane of the silicon (Si) crystal.

[0049] Step 3: N ion implantation is performed on the Si (111) substrate after thermal oxidation growth. The implantation energy is between 50 keV and the implantation dose is between 1×10 16 / cm 2 .

[0050] Step 4: The ion-implanted substrate is subjected to rapid high temperature thermal annealing (RTA) at a temperature of 500°C, an annealing atmosphere of N2, and an annealing time of 10s.

[0051] Step 5: Use HF solution to completely remove the amorphous SiO2 layer on the annealed substrate.

[0052] Step 6: Using MOCVD method to epitaxially grow AlN with a thickness of 100 nm on the surface of Si (111) substrate. The MOCVD method can be one of the existing technologies.

[0053] The radio frequency loss test of the prepared Si-based AlN material was carried out. The specific test method was as follows: a CPW transmission line structure (50 nm Ti / 550 nm Au) was prepared on the surface of the AlN / Si(111) sample by electron beam evaporation. Figure 3 As shown, the structure consists of two ground wires and a center wire with a width of , Wire clearance , ground line width The lengths L of the CPW are 53 μm, 30 μm, 160 μm, and 2 mm, respectively. The RF loss of all samples was measured by a Keysight network vector analyzer.

[0054] In this embodiment, the RF loss of the Si-based AlN material is -0.78 dB / mm@30GHz. Compared with the sample without N ion implantation (-0.87 dB / mm@30GHz), the RF loss is reduced by 10.3%.

[0055] Embodiment 2: The present invention provides an epitaxial structure and a process thereof for suppressing radio frequency loss of a Si-based AlN epitaxial wafer.

[0056] The specific preparation steps are as follows: Step 1: Select an 8-inch high-resistance Si (111) substrate with a resistivity of 5000 Ω·cm.

[0057] Step 2: Grow an amorphous SiO2 layer with a thickness of 300 nm on the surface of the Si (111) substrate by thermal oxidation.

[0058] Step 3: P ion implantation is performed on the Si (111) substrate after thermal oxidation growth. The implantation energy is between 200 keV and the implantation dose is between 5×10 11 / cm 2 .

[0059] Step 4: Perform rapid high temperature thermal annealing (RTA) on the ion implanted substrate at a temperature of 800°C, an annealing atmosphere of N2, and an annealing time of 30 seconds.

[0060] Step 5: Use HF solution to completely remove the amorphous SiO2 layer on the annealed substrate.

[0061] Step 6: Use MOCVD method to epitaxially grow 150nm thick AlN on the surface of Si (111) substrate.

[0062] The RF loss test of the prepared Si-based AlN material was carried out. The specific test method is as follows: a CPW transmission line structure (50 nm Ti / 550 nm Au) was prepared on the surface of the AlN / Si(111) sample by electron beam evaporation. The structure consists of two ground wires and a central wire with a width of , Wire clearance , ground line width The lengths L of the CPW are 53 μm, 30 μm, 160 μm, and 2 mm, respectively. The RF loss of all samples was measured by a Keysight network vector analyzer.

[0063] In this embodiment, the RF loss of the Si-based AlN material is -0.43 dB / mm@30GHz. Compared with the sample without P ion implantation (-0.87 dB / mm@30GHz), the RF loss is reduced by 50.6%.

[0064] Embodiment 3: The present invention provides an epitaxial structure and a process thereof for suppressing radio frequency loss of a Si-based AlN epitaxial wafer.

[0065] The specific preparation steps are as follows: Step 1: Select a 12-inch high-resistance Si (111) substrate with a resistivity of 10000 Ω·cm.

[0066] Step 2: Grow an amorphous SiO2 layer with a thickness of 500 nm on the surface of the Si (111) substrate by thermal oxidation.

[0067] Step 3: C ion implantation is performed on the Si (111) substrate after thermal oxidation growth. The implantation energy is between 50 keV and the implantation dose is between 1×10 15 / cm 2 .

[0068] Step 4: The ion-implanted substrate is subjected to rapid high temperature thermal annealing (RTA) at an annealing temperature of 1000° C., an annealing atmosphere of N 2 , and an annealing time of 60 s.

[0069] Step 5: Use HF solution to completely remove the amorphous SiO2 layer on the annealed substrate.

[0070] Step 6: Use MOCVD method to epitaxially grow 200nm thick AlN on the surface of Si (111) substrate.

[0071] The RF loss test of the prepared Si-based AlN material was carried out. The specific test method is as follows: a CPW transmission line structure (50 nm Ti / 550 nm Au) was prepared on the surface of the AlN / Si(111) sample by electron beam evaporation. The structure consists of two ground wires and a central wire with a width of , Wire clearance , ground line width The lengths L of the CPW are 53 μm, 30 μm, 160 μm, and 2 mm, respectively. The RF loss of all samples was measured by a Keysight network vector analyzer.

[0072] The RF loss of the Si-based AlN material in this embodiment is -0.29 dB / mm@30GHz. Compared with the sample without C ion implantation (-0.87 dB / mm@30GHz), the RF loss is reduced by 66.7%.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafers, characterized in that: It includes selecting substrate, pre-growing amorphous SiO2 layer, ion implantation, annealing, removing amorphous SiO2 layer, and growing epitaxial layer; The substrate is selected as follows: a high-resistance Si (111) substrate is selected, and the resistivity of the Si (111) substrate is 1000-10000 Ω·cm; The pre-grown amorphous SiO2 layer is: pre-growing an amorphous SiO2 layer with a thickness of 10-500nm on the surface of high-resistance Si by a thermal oxidation method.

2. The epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafer according to claim 1, characterized in that: The ion implantation is to implant ions into the Si (111) substrate after thermal oxidation pre-growth, with the implantation energy between 10 and 500 keV and the implantation dose between 1×10 10 ~1×10 17 / cm 2 , the ion is at least one of H, He, C, N, O, F, Mg, Si, P, Ar, Ca, Ge, As, and Fe.

3. The epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafer according to claim 1, characterized in that: The annealing method is rapid high temperature thermal annealing, the annealing temperature is 500-1000°C, the annealing atmosphere is N2, and the annealing time is 5-60s.

4. The epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafer according to claim 1, characterized in that: The amorphous SiO2 layer is removed by using an HF solution to completely remove the amorphous SiO2 layer on the annealed substrate.

5. The epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafer according to claim 1, characterized in that: The epitaxial layer is grown by using a MOCVD method to epitaxially grow AlN with a thickness of 100 to 200 nm on the surface of a Si (111) substrate.

6. The epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafer according to claim 1, characterized in that: The high-resistance Si (111) substrate is N-type or P-type doped.

7. The epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafer according to claim 1, characterized in that: After ion implantation, the distribution range of ions is within 0~200nm below the interface between Si (111) substrate and epitaxial layer.

8. The epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafer according to claim 1, characterized in that: The thermal oxidation method is dry oxygen oxidation, wet oxygen oxidation or water vapor oxidation.

9. The epitaxial process for suppressing radio frequency loss of Si-based AlN epitaxial wafer according to claim 1, characterized in that: The ion implantation direction is perpendicular to the amorphous SiO2 / Si surface.

10. The epitaxial structure obtained by the process according to any one of claims 1 to 9, characterized in that: The invention comprises a high-resistance Si (111) substrate, a defect layer and an epitaxial layer. The defect layer is obtained by ion implanting an amorphous SiO2 layer pre-grown on the Si (111) substrate by a thermal oxidation method, then annealing and finally removing the amorphous SiO2 layer. The defect layer is located in the range of 0 to 200 nm below the interface between the Si (111) substrate and the epitaxial layer. The epitaxial structure can suppress radio frequency loss.

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