A method for inhibiting radio frequency loss of a variable temperature aluminum nitride nucleation layer and epitaxial growth

Abstract

This invention discloses a variable-temperature aluminum nitride nucleation layer and its epitaxial growth method for suppressing radio frequency loss. The method involves setting the third-order AlN nucleation layer as a low-temperature-high-temperature-low-temperature layer and introducing in-situ crystalline SiN between the AlN interfaces. x Layer, this in-situ crystalline SiN x The layer effectively blocks Al / Ga interface diffusion, reducing the probability of parasitic conductive channel formation and effectively reducing RF device loss. The introduction of two low-temperature AlN nucleation layers effectively slows down Al / Ga diffusion, avoids the formation of conductive channels in the substrate, reduces leakage current during RF operation, and improves device power-added efficiency (PAE). Through three-stage temperature control, high-density nucleation and diffusion suppression are achieved in the low-temperature seed layer. The medium-high temperature crystallization layer significantly improves crystal quality and compresses dislocation density to a low level. Finally, the low-temperature high-resistivity layer effectively locks carbon atoms and improves resistivity, thereby achieving a synergistic improvement in the electrical and structural properties of the material.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device manufacturing technology, specifically relating to a variable-temperature aluminum nitride nucleation layer and epitaxial growth method for suppressing radio frequency loss. Background Technology

[0002] Gallium nitride high electron mobility transistors (GaN HEMTs), as core devices of third-generation semiconductors, hold an irreplaceable strategic position in high-frequency, high-power applications such as 5G / 6G communication base stations, radar, and satellite communications. Compared to traditional silicon-based LDMOS devices, GaN HEMTs offer higher power density, wider bandwidth support, and superior power conversion efficiency. However, the core factor restricting their large-scale industrialization lies in substrate cost. While mainstream silicon carbide (SiC) substrates offer excellent RF performance and thermal management, their high price and maximum size limitation of 6 inches make them unsuitable for the cost control requirements of the consumer electronics market. Furthermore, SiC-based GaN is difficult to achieve good compatibility with Si CMOS processes. Silicon substrates, with their cost advantages, large size, and good compatibility with Si CMOS processes, have become the ideal choice for promoting the widespread adoption of GaN devices. The wafer cost of 6-inch silicon substrate GaN HEMTs is significantly lower than that of SiC-based devices, which is of great significance for the realization of ultra-large-scale circuits and millimeter-wave base stations. However, the main challenges facing silicon-based gallium nitride (GaN) technology are radio frequency loss and material breakdown: (1) Si-based GaN materials typically have high radio frequency loss, resulting in low power-added efficiency (PAE) of the device, which severely restricts its application in high-frequency systems; (2) Si-based GaN materials generally have poor breakdown, which limits their application in high-voltage and high-power fields.

[0003] The physical causes of radio frequency (RF) losses in Si-based GaN can be attributed to three mechanisms: 1. During high-temperature epitaxy, Al / Ga atoms diffuse into the silicon substrate to form a p-type conductive layer. 2. The traditional AlN nucleation layer has a high dislocation density; through-dislocations act as leakage current channels, leading to increased vertical leakage current, significantly reducing the device breakdown voltage, and increasing RF losses. 3. Amorphous SiN exists at the AlN / Si interface. x The transition layer, with its poor lattice quality, forms additional leakage channels during RF operation, degrading the device's RF performance. The lattice mismatch between the silicon substrate and GaN can lead to the formation of numerous defects during growth, such as dislocations and vacancies. These defects may create leakage paths under an electric field, reducing the material's breakdown voltage. The significant difference in thermal expansion coefficients between silicon and GaN can cause stress during thermal cycling, further exacerbating crystal defects and crack formation. These structural defects reduce the material's breakdown voltage, causing the device to break down prematurely at lower voltages.

[0004] Among existing technologies for reducing radio frequency (RF) loss, one approach is to lower the epitaxial layer temperature. Lowering the growth temperature of each epitaxial layer can suppress the diffusion of Al and Ga elements to some extent, thereby reducing RF loss. However, low-temperature growth deteriorates the crystal quality of epitaxial layers such as AlN and GaN. While alleviating the RF loss problem, it also leads to subsequent deterioration of epitaxial quality. Another approach is to perform high-temperature nitriding pretreatment on the Si surface before AlN growth to form nanometer-thick amorphous SiN. x This approach aims to suppress the diffusion of Al and Ga elements at high temperatures. However, the formation of an amorphous SiN layer deteriorates the crystal quality of subsequent AlN and GaN epitaxial layers. While alleviating RF loss issues, it also leads to subsequent epitaxial quality degradation. The third approach is to reduce RF loss by pre-depositing a 100-500 nm PVD-AlN film on a high-resistivity silicon substrate, followed by GaN epitaxy in an MOCVD reaction chamber. The PVD process is performed at a low temperature of 500-1000℃, far lower than the 1000-1200℃ of MOCVD, significantly weakening the diffusion of Al atoms into the Si substrate. However, this growth method results in high dislocation density, poor breakdown, and a tendency to crack. The fourth approach involves reducing the trimethylaluminum (TMAl) pretreatment flow rate, which significantly suppresses the interfacial Al concentration, weakens the capacitive coupling between the parasitic layer and the 2DEG, and thus reduces RF loss. However, this also carries the risk of deterioration in the quality of the grown materials. Existing methods for increasing breakdown voltage mostly control the C doping concentration of the buffer layer by adjusting the growth temperature, thereby suppressing vertical leakage current and increasing breakdown voltage. However, high C doping concentration may cause the buffer layer to transform into a p-type layer, forming a pn junction and leading to severe current collapse. Furthermore, electrons trapped in the GaN buffer layer may scatter carriers in the channel, resulting in reduced channel mobility. In addition, a method for generating the nucleation layer using different temperatures has been proposed in the prior art. This method improves to some extent the problems of low thermal conductivity and easy formation of parasitic circuits in the SiO2 insulating layer of traditional SOI structures, but it still has the following drawbacks:

[0005] This method has limited effectiveness in suppressing the diffusion of Al and Ga atoms into the silicon substrate during high-temperature epitaxy, and also has limited effectiveness in suppressing radio frequency losses. It is prone to introducing defects such as interface contamination, microcracks, or insufficient bonding during the fabrication process. In particular, during subsequent high-temperature epitaxy or thick-layer growth, it may cause wafer warping and cracking, which restricts device reliability and mass production feasibility. It is difficult to reduce radio frequency losses while simultaneously addressing issues such as high dislocation density and low breakdown voltage. Furthermore, this method has a cumbersome process and poor compatibility with standard MOCVD epitaxy processes, which is not conducive to large-scale integrated circuit manufacturing. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention provides a variable-temperature aluminum nitride nucleation layer for suppressing radio frequency loss and an epitaxial growth method thereof. The technical problem to be solved by this invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a method for growing a variable-temperature aluminum nitride nucleation layer to suppress radio frequency loss, the method comprising:

[0008] A three-stage growth process, consisting of a low-temperature, high-temperature, and low-temperature phase, is employed to grow a three-stage AlN nucleation layer through temporal reconstruction of the temperature field and crystalline deposition. The three-stage AlN nucleation layer comprises, from bottom to top, an AlN seed layer, an AlN crystalline layer, and an AlN high-resistivity layer. A first crystalline SiN layer is disposed between the AlN seed layer and the AlN crystalline layer. x A second crystalline SiN layer is disposed between the AlN crystalline layer and the AlN high-resistivity layer. x layer.

[0009] In one embodiment of the present invention, a three-stage growth process of low temperature-high temperature-low temperature is employed, and a three-stage AlN nucleation layer is grown through temporal reconstruction of the temperature field, including:

[0010] A 20-50 nm AlN seed layer is deposited at a temperature of 700-900℃, and first-state SiN is deposited on the AlN seed layer at a temperature of 800-900℃. x layer;

[0011] Heating to over 1000℃ produces SiN in its first crystalline state. x A 100-200 nm AlN crystalline layer is grown on the AlN crystalline layer, and a second crystalline SiN is deposited on the AlN crystalline layer. x layer;

[0012] Cooling to 650-750℃, in second-crystal SiN x A 50-100 nm high-resistivity AlN layer is deposited on the substrate.

[0013] In one embodiment of the present invention, a 20-50 nm AlN seed layer is deposited at a temperature of 700-900°C, comprising:

[0014] Trimethylaluminum and high-purity ammonia were introduced into the MOCVD reactor as Al and N sources, respectively. TMAl was introduced at 700-900℃ and 70 Torr pressure for a pre-seeding time of 15-25s. The flow rates of trimethylaluminum and ammonia were set to 260-340 sccm and 1300-1700 sccm, respectively, and the growth pressure was set to 50-70 Torr. An AlN seed layer of 20-50 nm was deposited on the substrate.

[0015] In one embodiment of the present invention, the temperature is raised to above 1000°C, and the first crystalline SiN is...x An AlN crystalline layer of 100-200 nm is grown on the layer, including:

[0016] Raise the temperature to over 1000℃, keep the pressure constant, decrease the flow rate of trimethylaluminum, and increase the flow rate of ammonia gas, in the first crystalline state of SiN. x An AlN crystalline layer of 100-200 nm is grown on the layer.

[0017] In one embodiment of the present invention, the temperature is lowered to 650-750°C to form second-crystalline SiN. x A 50-100 nm high-resistivity AlN layer is deposited on the substrate, including:

[0018] Cool to 650-750℃, keep the pressure constant, increase the flow rate of trimethylaluminum and decrease the flow rate of ammonia, and produce second-crystal SiN. x A 50-100 nm high-resistivity AlN layer is deposited on the substrate.

[0019] Secondly, embodiments of the present invention provide an epitaxial growth method for suppressing radio frequency loss, comprising:

[0020] Select a substrate and place it in an MOCVD reactor for pretreatment;

[0021] The method employs the steps of any of the variable-temperature aluminum nitride nucleation layer growth methods for suppressing radio frequency loss as described in the first aspect, wherein a third-order AlN nucleation layer is grown on a substrate by temporal reconstruction of the temperature field and crystalline deposition; the third-order AlN nucleation layer comprises: an AlN seed layer, an AlN crystalline layer, and an AlN high-resistivity layer disposed from bottom to top; a first crystalline SiN is disposed between the AlN seed layer and the AlN crystalline layer. x A second crystalline SiN layer is disposed between the AlN crystalline layer and the AlN high-resistivity layer. x layer;

[0022] An Fe-doped GaN buffer layer is grown on the third-order AlN nucleation layer;

[0023] An unintentionally doped GaN channel layer is grown on the GaN buffer layer;

[0024] An AlGaN barrier layer is grown on the GaN channel layer.

[0025] In one embodiment of the present invention, the substrate is placed in an MOCVD reactor for pretreatment, including:

[0026] The substrate is placed in an MOCVD reactor and thermally cleaned in an H2 atmosphere to remove residual oxides from the surface.

[0027] In one embodiment of the present invention, an Fe-doped GaN buffer layer is grown on the third-order AlN nucleation layer, comprising:

[0028] Ga source, ammonia gas, and Fe source are introduced into the MOCVD reactor; the Ga source includes trimethylgallium, and the Fe source includes ferrocene.

[0029] At a temperature of 1000-1100℃, using H2 as the carrier gas, and by controlling the flow rates of Ga source, ammonia and Fe source, an Fe-doped GaN buffer layer was grown on a third-order AlN nucleation layer.

[0030] In one embodiment of the present invention, an unintentionally doped GaN channel layer is grown on the GaN buffer layer, comprising:

[0031] A Ga source and ammonia gas are introduced into the MOCVD reactor; the Ga source includes trimethylgallium.

[0032] At 1050-1150℃, trimethylgallium and ammonia were used as precursors for Ga and N, respectively, and H2 was used as a carrier gas to grow unintentionally doped GaN channel layers on GaN buffer layers.

[0033] In one embodiment of the present invention, an AlGaN barrier layer is grown on the GaN channel layer, comprising:

[0034] Ga source, Al source and ammonia gas are introduced into the MOCVD reactor; the Ga source includes trimethylgallium; the Al source includes trimethylaluminum.

[0035] At 1050-1150℃, H2 is used as the carrier gas to grow an AlGaN barrier layer on the GaN channel layer.

[0036] The beneficial effects of this invention are:

[0037] In the solution provided by this invention, the AlN seed layer in the third-order AlN nucleation layer is set as a low-temperature seed layer, the AlN crystalline layer is set as a high-temperature crystalline layer, and the AlN high-resistivity layer is set as a low-temperature high-resistivity layer; in-situ crystalline SiN is introduced between the AlN interfaces. x Layer, this in-situ crystalline SiN xThe AlN seed layer effectively blocks Al / Ga atom diffusion at the interface, further reducing the probability of parasitic conductive channel formation and effectively reducing the RF loss of Si-based GaN RF devices. This invention utilizes the low-temperature environment of the AlN seed layer to suppress Al / Ga atom diffusion into the Si substrate, reducing RF loss and ensuring high-density nucleation. The medium-to-high temperature environment of the AlN crystallization layer enhances Al atom mobility, promotes lateral grain merging, and compresses and reduces dislocation density. The low-temperature environment of the AlN high-resistivity layer suppresses carbon desorption, increasing the residence time and incorporation probability of carbon on the growth surface. Simultaneously, the low-temperature layer acts as a stress buffer, offsetting the tensile stress accumulated in the high-temperature layer, supporting the growth of a thicker buffer layer, thereby improving the device breakdown voltage. Two low-temperature AlN seed layers... The introduction of the N nucleation layer effectively slows down the diffusion of Al / Ga atoms into the silicon substrate, effectively avoids the formation of p-type conductive channels in the Si substrate, reduces leakage current during radio frequency operation, and improves the power-added efficiency (PAE) of the device. The AlN high-resistivity layer acts as a stress buffer, effectively offsetting the tensile stress accumulated during the high-temperature growth stage, resulting in a thicker total AlN layer without causing cracks or warping, significantly improving the device breakdown voltage and reliability. Through three-stage temperature control, high-density nucleation and diffusion suppression are achieved in the low-temperature seed layer. The medium- and high-temperature crystallization layer significantly improves the crystal quality and compresses the dislocation density to a lower level. Finally, the low-temperature high-resistivity layer effectively locks carbon atoms, increasing resistivity, thereby achieving a synergistic improvement in the electrical and structural properties of the material. Furthermore, the entire epitaxial process proposed in this invention is completed in one step in an MOCVD device, avoiding substrate transfer or secondary epitaxy required by methods such as PVD-AlN, eliminating interface contamination and microcrack generation, and improving process stability and mass production feasibility. RF loss test results using a coplanar waveguide (CPW) transmission line structure show that the RF loss of the Si-based GaN material prepared by this invention is significantly lower than that of conventional epitaxial structures. Breakdown voltage tests show that the breakdown voltage of devices of the same size is increased by more than 30%, meeting the material performance requirements of high-frequency, high-power RF devices. Attached Figure Description

[0038] Figure 1 This is a schematic diagram illustrating the steps of a variable-temperature aluminum nitride nucleation layer growth method for suppressing radio frequency loss, provided in an embodiment of the present invention.

[0039] Figure 2 This is a schematic flowchart of an epitaxial growth method for suppressing radio frequency loss provided in an embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of an epitaxial structure for suppressing radio frequency loss provided in an embodiment of the present invention.

[0041] Figure 4 Comparison of RF loss in CPW coplanar waveguide transmission lines for an epitaxial growth method to suppress RF loss provided in an embodiment of the present invention;

[0042] Figure 5 This is a breakdown voltage comparison diagram of an epitaxial growth method for suppressing radio frequency loss provided in an embodiment of the present invention. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0044] This invention provides a variable-temperature aluminum nitride nucleation layer for suppressing radio frequency loss and an epitaxial growth method thereof.

[0045] In a first aspect, embodiments of the present invention provide a method for growing a variable-temperature aluminum nitride nucleation layer to suppress radio frequency loss, which may include:

[0046] A three-stage growth process, consisting of a low-temperature-high-low temperature gradient, is employed to grow a three-stage AlN nucleation layer through temporal reconstruction of the temperature field and crystalline deposition. The three-stage AlN nucleation layer comprises, from bottom to top, an AlN seed layer, an AlN crystalline layer, and an AlN high-resistivity layer. A first-stage crystalline SiN layer is placed between the AlN seed layer and the AlN crystalline layer. x A second crystalline SiN layer is disposed between the AlN crystalline layer and the AlN high-resistivity layer. x layer.

[0047] As the first functional layer of the epitaxial structure, the AlN nucleation layer in the radio frequency Si-based GaN material system mainly plays the following roles:

[0048] It alleviates the 16.9% lattice mismatch between Si and GaN and suppresses the extension of penetrating dislocations into the GaN buffer layer and channel layer;

[0049] Preventing Al / Ga atoms from diffusing into the silicon substrate eliminates hole leakage channels;

[0050] It provides high resistivity to ensure the integrity of radio frequency signal transmission.

[0051] However, existing technologies struggle to achieve these three objectives in a coordinated manner, primarily due to three major contradictions:

[0052] The contradiction between dislocation density and resistivity: Although high-temperature growth can improve the crystal quality of AlN, it leads to a decrease in carbon doping efficiency, making it difficult to form a high-resistivity layer. In addition, during high-temperature epitaxy, Al / Ga atoms diffuse into the silicon substrate to form a p-type conductive layer, which becomes the main path for current leakage in radio frequency operation. On the other hand, although low-temperature growth is conducive to carbon doping, it leads to an increase in dislocation density.

[0053] The contradiction between stress control and thickness: Si and AlN have a large difference in thermal expansion coefficients. When the AlN thickness is grown too thick, the thermal mismatch stress is too large, which can cause wafer warping or even cracking.

[0054] The contradiction between doping precision and crystal quality: Carbon doping requires a low-temperature environment, but low temperature will inhibit the surface migration of Al atoms, resulting in the growth of three-dimensional islands, which leads to increased surface roughness and deteriorates the lattice quality of subsequent GaN epitaxial layers.

[0055] To address the aforementioned contradictions, this invention proposes a variable-temperature aluminum nitride nucleation layer growth method to suppress radio frequency losses. By reconstructing the temperature field over time, the material properties are synergistically optimized, resulting in an improvement in breakdown field strength. Furthermore, in-situ crystalline SiN is introduced between the AlN interfaces. x Layer, this in-situ crystalline SiN x The layer effectively blocks the diffusion of Al / Ga atoms at the interface, further reducing the probability of parasitic conductive channels forming and effectively reducing the RF loss of Si-based GaN RF devices. Furthermore, the growth process proposed in this embodiment is completed entirely in an MOCVD reactor, eliminating the need for substrate transfer or complex superlattice design, thus exhibiting good process compatibility. Simultaneously, it suppresses the diffusion of Al / Ga atoms into the Si substrate, reducing dislocation density and effectively lowering the RF loss of Si-based GaN RF devices.

[0056] Specifically, a three-stage growth process of low temperature-high temperature-low temperature is employed, and a three-stage AlN nucleation layer is grown through temporal reconstruction of the temperature field, such as... Figure 1 As shown, it may include:

[0057] S01, at a temperature of 700-900℃, deposit an AlN seed layer of 20-50 nm, and at a temperature of 800-900℃, deposit the first crystalline SiN on the AlN seed layer. x layer;

[0058] SO2, heated to above 1000℃, forms SiN in its first crystalline state. x A 100-200 nm AlN crystalline layer is grown on the AlN crystalline layer, and a second crystalline SiN is deposited on the AlN crystalline layer. x layer;

[0059] SiO3, cooled to 650-750℃, forms second-state SiN. x A 50-100 nm high-resistivity AlN layer is deposited on the substrate.

[0060] For SiO1, a 20-50 nm AlN seed layer is deposited at a temperature of 700-900 °C, and then the first crystalline SiN is deposited on the AlN seed layer at a temperature of 800-900 °C. x Layers may include:

[0061] Trimethylaluminum and high-purity ammonia were introduced into the MOCVD reactor as Al and N sources, respectively. Trimethylaluminum™Al was introduced at 700-900℃ and 70 Torr pressure for a pre-seeding time of 15-25s. The flow rates of trimethylaluminum and ammonia were set to 260-340 sccm and 1300-1700 sccm, respectively, and the growth pressure was 50-70 Torr. An AlN seed layer of 20-50 nm was deposited on the substrate.

[0062] In the process of generating the AlN seed layer, preferably, TMAl with a pre-seedling time of 20s is introduced to prevent amorphous SiN from forming. x Layer formation; the diffusion of Al atoms was suppressed by utilizing a low-temperature environment to ensure high-density nucleation.

[0063] After the AlN seed layer is grown, the temperature is maintained at 800-900℃, and silane (SiH4) and ammonia (NH3) precursors are introduced into the reaction chamber. The flow rate ratio of silane to ammonia is controlled at approximately 1:500-1:1000, and first-state crystalline SiN of 2-5 nm is grown in situ on the surface of the AlN seed layer. x This layer forms a continuous and dense crystalline structure, effectively preventing the downward diffusion of Al atoms during the subsequent high-temperature AlN crystallization process.

[0064] For SO2, heating to above 1000℃ produces first-state SiN x A 100-200 nm AlN crystalline layer is grown on the AlN crystalline layer, and a second crystalline SiN is deposited on the AlN crystalline layer. x Layers may include:

[0065] Raise the temperature to over 1000℃, keep the pressure constant, decrease the flow rate of trimethylaluminum, and increase the flow rate of ammonia gas, in the first crystalline state of SiN. x An AlN crystalline layer of 100-200 nm is grown on the layer.

[0066] In the process of generating the AlN crystal layer, preferably, the temperature can be set to 1000-1100℃, the TMAl gas flow rate is adjusted to 105 sccm, the NH3 gas flow rate is adjusted to 2500 sccm, and an AlN crystal layer of 100-200 nm continues to grow on the AlN seed layer; the medium and high temperature environment is used to improve the Al atom mobility, promote the lateral merging of grains, and compress and reduce the dislocation density.

[0067] After the AlN crystalline layer has grown, the reaction temperature and pressure are kept constant, and SiH4 and NH3 are introduced. The flow ratio of silane to ammonia is controlled at approximately 1:1000-1:2000, and 5-10 nm of second-crystal SiN is deposited in situ. xThe layer further blocks Al / Ga diffusion and suppresses dislocation penetration, providing a stable interface for stress buffering of the upper low-temperature AlN high-resistivity layer.

[0068] For SiO3, cooling to 650-750℃ produces second-state SiN. x A 50-100 nm high-resistivity AlN layer can be deposited on the substrate, which may include:

[0069] Cool to 650-750℃, keep the pressure constant, increase the flow rate of trimethylaluminum and decrease the flow rate of ammonia, and produce second-crystal SiN. x A 50-100 nm high-resistivity AlN layer is deposited on the substrate.

[0070] In the process of generating the AlN high-resistivity layer, preferably, the TMAl gas flow rate is adjusted to 135 sccm and the NH3 gas flow rate is adjusted to 1500 sccm, and a 50-100 nm AlN high-resistivity layer is deposited on the AlN crystalline layer. The low-temperature environment locks carbon atoms in their lattice positions, achieving a higher carbon concentration and improved resistivity. Simultaneously, the low-temperature layer acts as a stress buffer, offsetting the tensile stress accumulated in the high-temperature layer, blocking the upward propagation of dislocations generated in the high-temperature AlN layer, supporting the growth of a thicker GaN buffer layer, and improving the breakdown voltage. The low temperature inhibits carbon desorption, increases the residence time and incorporation probability of carbon on the growth surface, locks carbon atoms in their lattice positions, and simultaneously acts as a stress buffer, offsetting the tensile stress accumulated in the high-temperature layer, resulting in the growth of a thicker, higher-quality buffer layer. Reducing the NH3 flow rate makes the V / III ratio much lower than that of high-temperature AlN growth, creating an Al-rich (N-deficient) surface environment, reducing the supply of H, which is beneficial for the retention and incorporation of carbon-containing groups.

[0071] In this embodiment of the invention, the AlN seed layer in the third-order AlN nucleation layer is set as a low-temperature seed layer, the AlN crystalline layer is set as a high-temperature crystalline layer, and the AlN high-resistivity layer is set as a low-temperature high-resistivity layer; in-situ crystalline SiN is introduced between the AlN interfaces. x Layer, this in-situ crystalline SiN x The layer effectively blocks the diffusion of Al and Ga atoms at the interface, further reducing the probability of parasitic conductive channels forming and effectively reducing the RF loss of Si-based GaN RF devices; combined with in-situ crystalline SiN x Intercalation is performed in a single MOCVD device, completing epitaxy in one step without substrate transfer or bonding, thus avoiding interface contamination and microcrack risks. This is achieved through low-temperature-high-low-temperature temperature field time-series reconstruction and crystalline SiN... xBy leveraging the diffusion-blocking effect of the AlN seed layer, this invention achieves synergistic optimization in suppressing Al / Ga atom diffusion, reducing dislocation density, and increasing resistivity, significantly reducing RF loss and improving breakdown voltage. It also exhibits better process compatibility and potential for high-frequency, high-power applications. The low-temperature environment of the AlN seed layer suppresses Al / Ga atom diffusion into the Si substrate, reducing RF loss and ensuring high-density nucleation. The medium-to-high temperature environment of the AlN crystal layer enhances Al atom mobility, promotes lateral grain merging, and compresses and reduces dislocation density. The low-temperature environment of the AlN high-resistivity layer suppresses carbon desorption, increasing the carbon residence time and incorporation probability on the growth surface. Simultaneously, the low-temperature layer acts as a stress buffer, offsetting the tensile stress accumulated in the high-temperature layer, supporting the growth of a thicker buffer layer, thereby improving device breakdown voltage. Breakdown voltage; the introduction of two low-temperature AlN nucleation layers effectively slows down the diffusion of Al / Ga atoms into the silicon substrate, effectively avoids the formation of p-type conductive channels in the Si substrate, reduces leakage current during RF operation, and improves the device's power-added efficiency (PAE); the AlN high-resistivity layer acts as a stress buffer band, effectively offsetting the tensile stress accumulated during the high-temperature growth stage, resulting in a thicker total AlN layer without inducing cracks or warping, significantly improving the device's breakdown voltage and reliability; through three-stage temperature control, high-density nucleation and diffusion suppression are achieved in the low-temperature seed layer; the medium- and high-temperature crystallization layer significantly improves crystal quality and compresses dislocation density to a lower level; finally, the low-temperature high-resistivity layer effectively locks carbon atoms, increasing resistivity, thereby achieving a synergistic improvement in the material's electrical and structural properties.

[0072] Secondly, embodiments of the present invention provide an epitaxial growth method for suppressing radio frequency losses, such as... Figure 2 As shown, it may include:

[0073] S1. Select a substrate and place it in an MOCVD reactor for pretreatment.

[0074] S2, employing the steps of the variable-temperature aluminum nitride nucleation layer growth method for suppressing radio frequency loss as described in the first aspect, a third-order AlN nucleation layer is grown on the substrate by temporal reconstruction of the temperature field; the third-order AlN nucleation layer includes: an AlN seed layer, an AlN crystalline layer, and an AlN high-resistivity layer arranged from bottom to top; a first crystalline SiN is disposed between the AlN seed layer and the AlN crystalline layer. x A second crystalline SiN layer is disposed between the AlN crystalline layer and the AlN high-resistivity layer. x layer;

[0075] S3, an Fe-doped GaN buffer layer is grown on a third-order AlN nucleation layer;

[0076] S4, grow an unintentionally doped GaN channel layer on the GaN buffer layer;

[0077] S5, an AlGaN barrier layer is grown on the GaN channel layer.

[0078] Specifically, for S1, pretreatment of the substrate in an MOCVD reactor may include:

[0079] The substrate is placed in an MOCVD reactor and thermally cleaned in an H2 atmosphere to remove residual oxides from the surface.

[0080] For S3, growing an Fe-doped GaN buffer layer on a third-order AlN nucleation layer can include:

[0081] A Ga source, ammonia gas, and an Fe source are introduced into the MOCVD reactor; the Ga source may include trimethylgallium, and the Fe source may include ferrocene.

[0082] At a temperature of 1000-1100℃, using H2 as the carrier gas, and by controlling the flow rates of Ga source, ammonia and Fe source, an Fe-doped GaN buffer layer was grown on a third-order AlN nucleation layer.

[0083] Preferably, in step S3, the pressure can be set to 200 mbar, the flow rate of the Ga source can be set to 150 sccm, the flow rate of the Fe source can be set to 150 sccm, and the flow rate of ammonia can be set to 1500 sccm.

[0084] For S4, growing an unintentionally doped GaN channel layer on the GaN buffer layer may include:

[0085] A Ga source and ammonia gas are introduced into the MOCVD reactor; the Ga source may include trimethylgallium.

[0086] At 1050-1150℃, trimethylgallium and ammonia were used as precursors for Ga and N, respectively, and H2 was used as a carrier gas to grow unintentionally doped GaN channel layers on GaN buffer layers.

[0087] Preferably, in step S4, the gas source flow rate of the Ga source can be set to 100 sccm.

[0088] For S5, growing an AlGaN barrier layer on the GaN channel layer can include:

[0089] Ga source, Al source and ammonia gas are introduced into the MOCVD reactor; the Ga source may include trimethylgallium™Ga; the Al source may include trimethylaluminum.

[0090] At 1050-1150℃, H2 is used as the carrier gas to grow an AlGaN barrier layer on the GaN channel layer.

[0091] Understandably, in the process of generating a third-order AlN nucleation layer, the embodiments of the present invention achieve synergistic optimization of material properties through temporal reconstruction of the temperature field:

[0092] First stage (low-temperature AlN seed layer): A 20-50 nm AlN layer is deposited at a low temperature of 700-900℃. The low-temperature environment inhibits the diffusion of Al / Ga atoms into the Si substrate, reduces radio frequency loss, and ensures high-density nucleation.

[0093] Second stage (high-temperature AlN crystallization layer): The temperature is raised to above 1000℃ (preferably 1000-1100℃) to grow a 100-200nm AlN layer. The medium-high temperature environment improves the mobility of Al atoms, promotes lateral grain merging, and compresses and reduces the dislocation density.

[0094] The third stage (low-temperature AlN high-resistivity layer): Deposit a 50-100nm AlN layer at 650-750℃. The low temperature inhibits carbon desorption, increases the residence time and incorporation probability of carbon on the growth surface, and at the same time, the low-temperature layer acts as a stress buffer zone to offset the tensile stress accumulated in the high-temperature layer, supporting the growth of a thicker buffer layer, thereby improving the device breakdown voltage.

[0095] Meanwhile, in this embodiment of the invention, crystalline SiN is grown in situ between the low-temperature AlN seed layer and the high-temperature AlN crystallization layer, and between the high-temperature AlN crystallization layer and the low-temperature AlN high-resistivity layer, respectively. x A layer is used to block the diffusion of Al and Ga atoms and reduce the propagation of penetrating dislocations. This in-situ crystalline SiN x The layer combines good crystallinity and chemical inertness, without disrupting the continuity of AlN growth, thereby significantly reducing radio frequency loss and improving the material's breakdown field strength.

[0096] A schematic diagram of the epitaxial structure for suppressing radio frequency loss prepared by the epitaxial growth method for suppressing radio frequency loss proposed in the embodiments of the present invention is shown below. Figure 3 As shown, the entire epitaxial process proposed in this embodiment of the invention is completed in one step in an MOCVD device, avoiding substrate transfer or secondary epitaxy required by methods such as PVD-AlN, eliminating interface contamination and microcrack generation, and improving process stability and mass production feasibility. This embodiment of the invention uses a coplanar waveguide transmission line structure for RF loss testing. A comparison of RF loss testing using the CPW coplanar waveguide transmission line is shown in the figure. Figure 4 As shown, it can be seen from Figure 4 As can be seen, the results show that the Si-based GaN material grown using the embodiments of the present invention has lower RF loss compared to conventional materials; breakdown voltage tests were performed on devices of the same size made from materials grown using the embodiments of the present invention and conventional methods, and the breakdown voltage comparison graph is shown below. Figure 5 As shown, it can be seen from Figure 5The results show that the Si-based GaN material grown using the method of this invention has a larger breakdown voltage. RF loss testing using a coplanar waveguide (CPW) transmission line structure shows that the RF loss of the Si-based GaN material prepared by this invention is significantly lower than that of conventional epitaxial structures; breakdown voltage testing indicates that the breakdown voltage of devices of the same size is increased by more than 30%, meeting the material performance requirements of high-frequency, high-power RF devices.

[0097] It is understood that the embodiments of the present invention have the following advantages:

[0098] 1) The introduction of two low-temperature AlN nucleation layers effectively slows down the diffusion of Al / Ga atoms into the silicon substrate, effectively avoids the formation of p-type conductive channels in the Si substrate, reduces leakage current during radio frequency operation, and improves the power-added efficiency (PAE) of the device.

[0099] 2) Traditional single-temperature growth processes struggle to balance low dislocation density and high resistivity. This invention employs a three-stage temperature control approach: a low-temperature seed layer achieves high-density nucleation and diffusion suppression; a medium-to-high-temperature crystallization layer significantly improves crystal quality, compressing dislocation density to a lower level; and finally, a low-temperature, high-resistivity layer effectively locks carbon atoms, increasing resistivity, thereby achieving a synergistic improvement in the material's electrical and structural properties.

[0100] 3) The third-stage low-temperature AlN layer acts as a stress buffer zone, effectively offsetting the tensile stress accumulated during the high-temperature growth stage, resulting in a thicker total AlN layer without causing cracks or warping, and significantly improving the device breakdown voltage and reliability.

[0101] 4) The entire epitaxial process is completed in one go in the MOCVD equipment, avoiding substrate transfer or secondary epitaxy required by the PVD-AlN scheme, eliminating interface contamination and microcrack generation, and improving process stability and mass production feasibility.

[0102] 5) In the high-resistivity layer, carbon doping is concentrated at the bottom of the nucleation layer, far away from the GaN channel region. While improving the longitudinal breakdown voltage, it does not affect the transport characteristics of the two-dimensional electron gas in the channel, thus achieving both high breakdown voltage and high electron mobility.

[0103] 6) The RF loss test results of the coplanar waveguide (CPW) transmission line structure show that the RF loss of the Si-based GaN material prepared in this embodiment of the invention is significantly lower than that of conventional epitaxial structures; the breakdown voltage test shows that the breakdown voltage of the device of the same size is increased by more than 30%, which meets the requirements of high-frequency and high-power RF devices for material performance.

[0104] It should be noted that, in the description of this invention, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0105] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for growing a variable-temperature aluminum nitride nucleation layer to suppress radio frequency loss, characterized in that, include: A three-stage growth process of low temperature-high temperature-low temperature was adopted, and a three-stage AlN nucleation layer was grown through temporal reconstruction of the temperature field and crystalline deposition. The third-order AlN nucleation layer comprises, from bottom to top, an AlN seed layer, an AlN crystal layer, and an AlN high-resistivity layer; A first crystalline SiN layer is arranged between the AlN seed layer and the AlN crystalline layer x A second crystalline SiN layer is arranged between the AlN crystalline layer and the AlN high resistance layer x ​ 2. The method for growing a variable-temperature aluminum nitride nucleation layer to suppress radio frequency loss according to claim 1, characterized in that, The method employs a three-stage growth process—low temperature-high temperature-low temperature—to grow a three-stage AlN nucleation layer through temporal reconstruction of the temperature field, including: at a temperature of 700-900 °C, depositing a 20-50 nm AlN seed layer, depositing a first crystalline SiN layer on the AlN seed layer at a temperature of 800-900 °C x at a temperature of 700-900 °C, depositing a 20-50 nm AlN seed layer, depositing a first crystalline SiN layer on the AlN seed layer at a temperature of 800-900 °C Heating to over 1000℃ produces SiN in its first crystalline state. x A 100-200 nm AlN crystalline layer is grown on the AlN crystalline layer, and a second crystalline SiN is deposited on the AlN crystalline layer. x layer; Cooling to 650-750℃, in second-crystal SiN x A 50-100 nm high-resistivity AlN layer is deposited on the substrate.

3. The method for growing a variable-temperature aluminum nitride nucleation layer to suppress radio frequency loss according to claim 2, characterized in that, The deposition of a 20-50 nm AlN seed layer at a temperature of 700-900℃ includes: Trimethylaluminum and high-purity ammonia were introduced into the MOCVD reactor as Al and N sources, respectively. TMAl was introduced at 700-900℃ and 70 Torr pressure for a pre-seeding time of 15-25s. The flow rates of trimethylaluminum and ammonia were set to 260-340 sccm and 1300-1700 sccm, respectively, and the growth pressure was set to 50-70 Torr. An AlN seed layer of 20-50 nm was deposited on the substrate.

4. The method for growing a variable-temperature aluminum nitride nucleation layer to suppress radio frequency loss according to claim 2, characterized in that, The temperature is raised to above 1000℃, in the first crystalline state of SiN x An AlN crystalline layer of 100-200 nm is grown on the layer, including: Raise the temperature to over 1000℃, keep the pressure constant, decrease the flow rate of trimethylaluminum, and increase the flow rate of ammonia, in the first crystalline state of SiN. x An AlN crystalline layer of 100-200 nm is grown on the layer.

5. The method for growing a variable-temperature aluminum nitride nucleation layer to suppress radio frequency loss according to claim 2, characterized in that, The temperature was lowered to 650-750℃, resulting in second-crystal SiN. x A 50-100 nm high-resistivity AlN layer is deposited on the substrate, including: Cool to 650-750℃, keep the pressure constant, increase the flow rate of trimethylaluminum and decrease the flow rate of ammonia, and produce second-crystal SiN. x A 50-100 nm high-resistivity AlN layer is deposited on the substrate.

6. An epitaxial growth method for suppressing radio frequency loss, characterized in that, include: Select a substrate and place it in an MOCVD reactor for pretreatment; The method for growing a temperature-controlled aluminum nitride nucleation layer to suppress radio frequency loss as described in any one of claims 1-5 involves growing a third-order AlN nucleation layer on a substrate by temporal reconstruction of the temperature field and crystalline deposition; the third-order AlN nucleation layer comprises: an AlN seed layer, an AlN crystalline layer, and an AlN high-resistivity layer arranged from bottom to top. A first crystalline SiN is disposed between the AlN seed layer and the AlN crystalline layer. x A second crystalline SiN layer is disposed between the AlN crystalline layer and the AlN high-resistivity layer. x layer; An Fe-doped GaN buffer layer is grown on the third-order AlN nucleation layer; An unintentionally doped GaN channel layer is grown on the GaN buffer layer; An AlGaN barrier layer is grown on the GaN channel layer.

7. The epitaxial growth method for suppressing radio frequency loss according to claim 6, characterized in that, The pretreatment of the substrate by placing it in an MOCVD reactor includes: The substrate is placed in an MOCVD reactor and thermally cleaned in an H2 atmosphere to remove residual oxides from the surface.

8. The epitaxial growth method for suppressing radio frequency loss according to claim 6, characterized in that, A Fe-doped GaN buffer layer is grown on the third-order AlN nucleation layer, comprising: Ga source, ammonia gas, and Fe source are introduced into the MOCVD reactor; the Ga source includes trimethylgallium, and the Fe source includes ferrocene. At a temperature of 1000-1100℃, using H2 as the carrier gas, and by controlling the flow rates of Ga source, ammonia and Fe source, an Fe-doped GaN buffer layer was grown on a third-order AlN nucleation layer.

9. The epitaxial growth method for suppressing radio frequency loss according to claim 6, characterized in that, Growing an unintentionally doped GaN channel layer on the GaN buffer layer includes: A Ga source and ammonia gas are introduced into the MOCVD reactor; the Ga source includes trimethylgallium. At 1050-1150℃, trimethylgallium and ammonia were used as precursors for Ga and N, respectively, and H2 was used as a carrier gas to grow unintentionally doped GaN channel layers on GaN buffer layers.

10. The epitaxial growth method for suppressing radio frequency loss according to claim 6, characterized in that, Growing an AlGaN barrier layer on the GaN channel layer includes: Ga source, Al source and ammonia gas are introduced into the MOCVD reactor; the Ga source includes trimethylgallium; the Al source includes trimethylaluminum. At 1050-1150℃, H2 is used as the carrier gas to grow an AlGaN barrier layer on the GaN channel layer.

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