Novel semiconductor device and manufacturing method

Abstract

The embodiment of the invention discloses a novel semiconductor device and a manufacturing method, the novel semiconductor device comprises a diamond epitaxial layer, an aluminum nitride epitaxial layer, a source electrode, a grid electrode and a drain electrode, the diamond epitaxial layer is arranged above a diamond substrate; the aluminum nitride epitaxial layer is arranged on the diamond epitaxial layer, and the diamond epitaxial layer is located between the aluminum nitride epitaxial layer and the diamond substrate; a source electrode, a grid electrode and a drain electrode are all arranged on the side, away from the diamond epitaxial layer, of the aluminum nitride epitaxial layer, grid electrode voltage is applied between the source electrode and the grid electrode, and active drain voltage is applied between the source electrode and the drain electrode. The diamond semiconductor device provides a high-performance solution for high-pressure, high-temperature, high-power and intense-radiation application scenes, and has a huge market prospect.

Description

Technical Field

[0001] The present application relates to the field of semiconductor materials, devices and integrated circuits, and in particular to a novel semiconductor device and a manufacturing method thereof. Background Art

[0002] Diamond material has many excellent properties, such as the highest thermal conductivity, ultra-wide bandgap, high breakdown voltage, high carrier mobility, etc. It is called the ultimate semiconductor material and is an important technical route for the further development of semiconductor technology in the "post-Moore era". It has broad application prospects in the development of high-temperature, high-frequency, high-power devices, radiation-resistant devices, ultraviolet detectors, short-wave light-emitting diodes, etc. It is a key electronic device in wireless communications, national defense, new energy, aerospace and other fields.

[0003] Diamond has unique physical and chemical properties that make it particularly attractive for a variety of applications. Diamond has extremely low chemical reactivity, making it useful in highly corrosive environments. Diamond has a room temperature thermal conductivity of over 2000 W / mK, the highest of any known material, 2.5 to 5 times higher than copper, 10 to 20 times higher than silicon, and 3 to 5 times higher than silicon carbide. Diamond is also an electrical insulator at room temperature, with a resistivity of up to 10 6 Diamond is also a wide bandgap semiconductor material with a bandgap width of 5.5 eV and high electron and hole mobility, up to 7000 cm 2 / Vs and 5000cm 2 / Vs and above, it has broad application prospects in semiconductor devices such as high-frequency field effect transistors and high-power switches.

[0004] However, diamond is difficult to dope, especially n-type doping, which limits the production and application of semiconductor devices based on diamond materials. This application solves the problem of difficulty in doping diamond materials and proposes a complete solution for the production of semiconductor devices based on diamond materials.

[0005] Aluminum nitride is a new III-V semiconductor material with the largest bandgap and direct bandgap among III-V compound semiconductors. The bandgap widths of commonly used compound semiconductors are: gallium arsenide 1.43eV, indium phosphide 1.35eV, silicon carbide 3.25eV, gallium nitride 3.44eV, gallium oxide 4.8eV, diamond 5.57eV, aluminum nitride 6.2eV. Compound semiconductor materials have developed rapidly in recent years and are increasingly widely used in lighting, optical communications, power semiconductor devices and wireless communications. As an ultra-wide bandgap semiconductor, it also has excellent properties such as high thermal conductivity, high resistivity, strong breakdown field and small dielectric constant. Aluminum nitride materials will have broad application prospects in the development of high-temperature, high-frequency, high-power microwave devices, radiation-resistant devices, ultraviolet detectors, short-wave light-emitting diodes, etc. It is a key electronic device in the fields of wireless communications, national defense, new energy, aerospace, satellite communication systems, etc.

[0006] In order to overcome the disadvantage of difficult doping of diamond and aluminum nitride materials and make full use of the excellent properties of diamond and aluminum nitride materials, this application proposes a new semiconductor device and its manufacturing method, providing a new technical route and implementation plan for realizing high temperature, high pressure and high power applications. Summary of the invention

[0007] In order to solve the problems existing in the prior art, the present invention provides a novel semiconductor device and a manufacturing method, wherein the novel semiconductor device comprises:

[0008] A diamond epitaxial layer, wherein the diamond epitaxial layer is disposed above a diamond substrate;

[0009] The nitride epitaxial layer is arranged on the diamond epitaxial layer, and the diamond epitaxial layer is located between the nitride epitaxial layer and the diamond substrate; the nitride epitaxial layer material includes aluminum nitride (AlN), boron nitride (BN), aluminum gallium nitride (AlGaN) and the like.

[0010] The source, gate and drain are all arranged on the nitride epitaxial layer at a side away from the diamond epitaxial layer. A gate voltage is applied between the source and the gate, and a source-drain voltage is applied between the source and the drain.

[0011] The present application provides a manufacturing method for manufacturing the above-mentioned novel semiconductor device, the manufacturing method comprising:

[0012] Step 1: Prepare a diamond substrate and remove metal contaminants, impurity particles and organic components on the surface of the diamond substrate;

[0013] Step 2: fabricating a single crystal diamond epitaxial thin film on the diamond substrate;

[0014] Step 3: Fabricating a nitride epitaxial layer on the single crystal diamond epitaxial layer by chemical vapor deposition;

[0015] Step 4: Make source-drain ohmic contacts;

[0016] Step 5: Fabricate a gate on the nitride epitaxial layer.

[0017] Optionally, in some embodiments of the present application, in step 4, the fabrication of the ohmic contact includes a source-drain doping process, and the source-drain doping process includes:

[0018] Step 401: forming a protective layer with a thickness of 100 nm-2 um on the nitride epitaxial layer, wherein the nitride epitaxial layer comprises an aluminum nitride epitaxial layer, and the protective layer comprises one of silicon oxide, silicon nitride and aluminum oxide;

[0019] Step 402: fabricating a mask layer on the protective layer;

[0020] Step 403: Si doping is performed on the source and drain by ion implantation, wherein the ion beam energy range is 10-360keV, the implantation angle is 0-7°, and the implantation dose is 10 14 –10 16 / cm 2 ;

[0021] Step 404: ion activation of silicon doping in aluminum nitride is performed in a nitrogen environment at a high temperature annealing environment of 1200-1600° C. The annealing time is 15-60 minutes.

[0022] Optionally, in some embodiments of the present application, in step 404, the ion activation further includes laser annealing, and the laser annealing includes applying a pulsed laser to the source and drain regions of the aluminum nitride epitaxial layer at room temperature, and the pulsed laser is vertically irradiated to the source and drain regions of the aluminum nitride epitaxial layer to form a source-drain ohmic contact;

[0023] The area outside the source and drain area is protected by the mask layer, the mask layer includes one of a photoresist, a dielectric layer and a metal layer, and the thickness of the mask layer is 100nm-5um;

[0024] After laser annealing is completed, the mask layer is removed, the wafer is cleaned, and high temperature annealing is performed at a temperature of 800-1200C for 30-180 seconds.

[0025] Optionally, in some embodiments of the present application, in step 4, the fabrication of the ohmic contact includes an epitaxial layer regrowth process, and the epitaxial layer regrowth method process includes:

[0026] Step 401′: forming a dielectric layer on the aluminum nitride epitaxial layer, the dielectric layer serving as a mask layer for the epitaxial regrowth process, the thickness of the dielectric layer being 50-500 nm;

[0027] Step 402 ′: etching the mask layer and the nitride film, wherein the nitride film includes an aluminum nitride film;

[0028] Step 403 ′: regrow the aluminum nitride epitaxial layer by chemical vapor deposition to grow material Al x Ga (1-x) N, where 0≤x≤1;

[0029] Step 404 ′: performing n-type doping on the regrown epitaxial material.

[0030] 6. A manufacturing method according to any one of claims 4-5, characterized in that the manufacturing of the ohmic contact comprises:

[0031] Step 405: performing a photolithography process, wherein the photolithography process includes coating, alignment, exposure, and development;

[0032] Step 406: depositing a source-drain metal layer, wherein the source-drain metal layer includes one or more of Ti, Al, Ni, Pt, Au, and Pd;

[0033] Step 407: performing a metal stripping process to remove the photoresist and the metal layer on the photoresist;

[0034] Step 408: Perform a metal annealing process at a temperature between 700-900° C. and a time of 30-90 seconds.

[0035] Optionally, in some embodiments of the present application, in step 5, the gate manufacturing includes:

[0036] Step 501: performing a photolithography process, wherein the photolithography process includes coating, alignment, exposure, and development;

[0037] Step 502: manufacturing a gate metal layer, wherein the manufacturing of the gate metal layer includes metal deposition, metal stripping, degumming, and cleaning.

[0038] Optionally, in some embodiments of the present application, a capping layer is further provided on the aluminum nitride epitaxial layer, the capping layer is located on the source and drain, and the capping layer includes SiN or GaN.

[0039] Optionally, in some embodiments of the present application, in step 1, the removal method includes heated acid treatment, organic solvent ultrasonic cleaning and hydrogen-oxygen plasma etching treatment.

[0040] Optionally, in some embodiments of the present application, in step 3, the nitride epitaxial layer includes an aluminum nitride epitaxial layer, and during the growth of the aluminum nitride epitaxial layer, an Sc evaporation source is added to form a ScAlN material film as the epitaxial layer.

[0041] Compared with the prior art, the beneficial effects of the present invention are:

[0042] The semiconductor device structure proposed in this application combines the unique properties of aluminum nitride and diamond. In a semiconductor device based on this structure, diamond is used as a channel layer and AlN is used as a barrier layer. Because the bandgap widths of AlN and diamond materials are different, the band bending forms a two-dimensional potential well at the heterojunction interface. This two-dimensional potential well confines electrons, and these electrons can only move two-dimensionally in a plane parallel to the interface in the potential well, thus forming a two-dimensional electron gas (2DEG). Based on the high electron mobility transistor made of the two-dimensional electron gas formed by the AlN / Diamond heterojunction, under the action of the source-drain voltage (Vds), the two-dimensional electron gas (2DEG) is transmitted in the channel to form a current (Ids) from the source to the drain. The gate voltage (Vgs) is used to regulate the density of two-dimensional electrons, thereby achieving the purpose of regulating the source-drain current. Based on the semiconductor structure proposed in this application, the problem of difficulty in doping diamond materials has been solved. Since diamond materials have excellent properties such as large bandgap width, high electron mobility, high breakdown voltage, and high thermal conductivity, diamond semiconductor devices will provide high-performance solutions for high-voltage, high-temperature, high-power, and strong radiation application scenarios, and have huge market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 A schematic diagram of the overall structure of a novel semiconductor device provided in an embodiment of the present application;

[0045] Figure 2 Schematic diagram of the source and drain doping process provided in the embodiment of the present application Figure 1 ;

[0046] Figure 3 Schematic diagram of the source and drain doping process provided in the embodiment of the present application Figure 2 ;

[0047] Figure 4 Schematic diagram of the source and drain doping process provided in the embodiment of the present application Figure 3 ;

[0048] Figure 5 Schematic diagram of the source and drain doping process provided in the embodiment of the present application Figure 4 ;

[0049] Figure 6 Schematic diagram of the source and drain doping process provided in the embodiment of the present application Figure 5 ;

[0050] Figure 7 Schematic diagram of the source and drain doping process provided in the embodiment of the present application Figure 6 ;

[0051] Figure 8 A schematic diagram of the process flow of laser annealing provided in an embodiment of the present application;

[0052] Fig. 9 Schematic diagram of the epitaxial regrowth process provided in the embodiment of the present application Figure 1 ;

[0053] Fig.10 Schematic diagram of the epitaxial regrowth process provided in the embodiment of the present application Figure 2 ;

[0054] Fig.11 A schematic diagram of the gradual growth process flow provided in an embodiment of the present application.

[0055] Description of reference numerals:

[0056] 100, diamond substrate; 200, single crystal diamond epitaxial layer; 300, aluminum nitride epitaxial layer; 400, protective layer; 500, source; 600, drain; 700, gate; 800, mask layer; 900, pulsed laser; 1000, dielectric layer. DETAILED DESCRIPTION

[0057] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present application. It is understood that the drawings are only provided for reference and illustration, and are not used to limit the present application. The connection relationship shown in the drawings is only for the convenience of clear description and does not limit the connection method.

[0058] Specifically, Figure 1As shown, a manufacturing method is provided in an embodiment of the present application, and the manufacturing method is used to manufacture a new type of semiconductor device. The new type of semiconductor device is mainly provided with a single crystal diamond substrate 100, a single crystal diamond epitaxial layer 200 and an aluminum nitride epitaxial layer 300, and a source 500, a drain 600 and a gate 700 arranged on the aluminum nitride epitaxial layer 300.

[0059] The above structure is mainly prepared by sequentially preparing each layer structure. First, the single crystal diamond substrate 100 needs to be prepared. The specific preparation process is as follows:

[0060] like Figure 1-2 As shown, the thickness of the substrate may vary depending on the size of the wafer and the device requirements, and is generally between 100-500um.

[0061] In the embodiment of the present application, the single crystal diamond substrate 100 is preferably 50-100 um, and more preferably 80-100 um. The specific thickness of the diamond substrate is designed according to the requirements of the product to be manufactured.

[0062] The size of the single crystal diamond substrate 100 in the present application is 2-6 inches (50-150 mm), and its shape may also be a geometric shape such as a square or a rectangle.

[0063] The single crystal diamond substrate 100 is mainly prepared by a microwave plasma CVD (MPCVD) method.

[0064] When producing the single crystal diamond substrate 100, the present application preferably uses type IIa seed crystals or high-quality CVD diamond seeds, which can reduce the dislocation density and improve the crystal quality of the epitaxial layer.

[0065] In addition to selecting a high-quality seed substrate, pre-treating the seed layer surface to remove surface contaminants can minimize dislocations and cracks caused by the polishing process to obtain a smooth, flat and high-quality initial surface state.

[0066] Since the inherent defects in the seed cannot be eliminated and will extend to the epitaxial layer regardless of the pretreatment technique, the impurity particles and surface damage introduced by polishing and the amorphous carbon layer should be minimized, for example, by using heated acid treatment and ultrasonic cleaning with organic solvents to remove metal contaminants, impurity particles and organic components on the surface.

[0067] Among them, in addition to the above methods, hydrogen-oxygen plasma etching can also be used in the present application. Specifically, under certain temperature and pressure deposition conditions, H2 / O2 plasma selectively etches surface scratches and defects. The specific pretreatment process and method are implemented with reference to the existing technical means.

[0068] The method of selecting and preparing the single crystal diamond substrate 100 is described above.

[0069] In addition, the single crystal diamond substrate can also be made of other materials as a substrate, such as iridium (Ir), metal oxide (such as SrTiO3), silicon substrate, silicon carbide (SiC) substrate, and a substrate formed by a splicing method, and then a new type of single crystal diamond substrate 100 is obtained on these substrates by a heteroepitaxial growth method, which will not be repeated here.

[0070] Secondly, a single crystal diamond epitaxial layer 200 needs to be prepared on the single crystal diamond substrate 100. The purpose of preparing the single crystal diamond epitaxial layer 200 is to prepare a single crystal diamond film with low impurity content, low defect density and high crystallinity for manufacturing diamond semiconductor devices.

[0071] The present application reduces the requirements on the crystal quality of the single crystal diamond substrate 100 by arranging the single crystal diamond epitaxial layer 200 on the single crystal diamond substrate 100. It only needs to grow a layer of high-quality single crystal diamond film on the surface of the single crystal diamond substrate 100 to meet the requirements for the manufacture of diamond devices. Therefore, the manufacturing cost of the single crystal diamond substrate 100 can be reduced.

[0072] In the embodiment of the present application, the thickness of the single crystal diamond epitaxial film may be between 100 nm and 20 um depending on different applications.

[0073] The present application adopts MPCVD to produce the single crystal diamond epitaxial layer 200 .

[0074] In the MPCVD process of making single-crystal diamond films, the main impurity components are nitrogen and silicon, and there are also point defects and hydrogen related to vacancies. Nitrogen impurities may come from the seed substrate, equipment leakage or gas source system. Silicon impurities come from plasma etching of quartz windows. Therefore, to improve the purity of crystals grown by MPCVD, a high-purity gas source and a reliable vacuum system are required. One way to reduce the impurity content is to optimize the growth process under high oxygen concentration of 2% (the flow ratio of O2 to total gas) to achieve a high-purity single-crystal diamond epitaxial film with a nitrogen concentration of less than 1ppb. At the same time, ultraviolet-assisted polishing is used instead of traditional grinding wheel polishing to obtain an ultra-smooth seed crystal surface with a roughness Ra value of less than 0.5nm, thereby effectively reducing the generation of new defects.

[0075] In addition, in the embodiment of the present application, the surface damage on the substrate is eliminated by repeated stripping process, and the dislocation density of the substrate can be obtained to be less than 200 / cm 2 , increased to 500 / cm after epitaxial growth 2 Next, a high-quality single-crystal diamond epitaxial thin film is produced.

[0076] If the selected substrate is other materials, such as iridium (Ir), metal oxide (SrTiO3), silicon substrate, SiC substrate, the single crystal diamond epitaxial layer 200 is manufactured by heteroepitaxy method, which will not be described in detail here.

[0077] After the single crystal diamond epitaxial layer 200 is completed, an aluminum nitride film is prepared on the single crystal diamond epitaxial layer 200. The preparation process mainly realizes an n-type conductive channel layer by growing an aluminum nitride epitaxial layer 300 on the surface of the single crystal diamond epitaxial layer 200 to make a semiconductor device. The method used in this application is a metal organic chemical vapor deposition method (MOCVD-Metal Organic Chemical Vapor Deposition), trimethylaluminum (TMAl, C3H9Al) and ammonia (NH3) are used as aluminum source and nitrogen source respectively, and hydrogen is used as a carrier gas. High-quality single crystal aluminum nitride film can be grown by adjusting the pressure, temperature and gas flow of the reactor. The thickness of the aluminum nitride epitaxial layer 300 is 2-20nm.

[0078] In the present application, in order to reduce the stress and dislocation caused by the lattice mismatch between the diamond material and the aluminum nitride material, a layer of amorphous film, such as silicon oxide, silicon nitride, silicon oxynitride and other materials, can be grown before growing the AlN film. The growth method of the amorphous film includes atomic layer deposition (ALD), chemical vapor deposition (CVD), physical deposition (PVD), etc., and the growth thickness is 0.5-5nm.

[0079] In order to further increase the concentration of two-dimensional electron gas, AlN can be doped to increase the piezoelectric coefficient of the material and achieve the enhanced piezoelectric polarization effect. The production method is: in the above-mentioned AlN growth process, add MO gas source containing Sc element, tri(cyanodieryl) scandium (chemical formula is C 15 H 15 Sc). In this way, while making the AlN film, scandium is doped to form a ScAlN film. The doping concentration can be 5-50%, or even higher, depending on the specific application requirements. Using Sc-doped ScAlN as a barrier layer, due to its strong piezoelectric polarization effect, the concentration of two-dimensional electron gas at the heterojunction interface can be increased, thereby improving the power density of semiconductor devices.

[0080] The aluminum nitride epitaxial layer 300 can also be made by molecular beam epitaxy (MBE) or plasma induced molecular beam (PIMBE), using a conventional evaporation source of Al as an Al source, and a radio frequency plasma source to generate nitrogen radicals, thereby growing a high-quality single-crystalline AlN film on the surface of the diamond. In order to further improve the concentration and mobility of the two-dimensional electron gas, AlN can be doped to increase the piezoelectric coefficient of the material and thereby enhance the piezoelectric polarization effect. The method of production is that in the above-mentioned process of growing AlN, in addition to the Al source, an Sc evaporation source is added to form a ScAlN material. It is also possible to use only one evaporation source, that is, to use an ScAl alloy that has been prepared in a certain proportion, and react with nitrogen radicals generated by a radio frequency plasma source to form a ScAlN film, that is, an Sc-doped AlN film. The doping concentration can be 5-50%, or even higher, determined by the ratio of the ScAl alloy material.

[0081] It should be pointed out that the above-mentioned epitaxial layer, in addition to AlN, can also be boron nitride or aluminum gallium nitride; before making aluminum nitride, boron nitride or aluminum gallium nitride materials, the single crystal diamond substrate 100 needs to be surface treated to remove pollutants, impurity particles, surface damage and amorphous carbon layer; before growing aluminum nitride, boron nitride or aluminum gallium nitride epitaxy, the diamond surface can also be nitrided, such as using N2 plasma treatment, or using CVD (chemical vapor deposition) or ALD (atomic layer deposition) and other methods to make a layer of silicon oxide, silicon nitride, or silicon oxynitride with a thickness of 0.1-5nm.

[0082] In the embodiment of the present application, optionally, a capping layer, such as GaN and SiN, can be formed on the aluminum nitride epitaxial layer 300, and the thickness of the capping layer is 2-10 nm. Among them, the commonly used method for preparing the gallium nitride capping layer is MOCVD, generally using trimethylgallium (TMGa, C3H9Ga) and ammonia (NH3) as gallium source and nitrogen source respectively, and hydrogen as carrier gas. By adjusting the pressure, temperature and gas flow rate of the reactor, high-quality single-crystalline gallium nitride thin film can be grown; the commonly used methods for preparing the silicon nitride capping layer are PECVD and LPCVD.

[0083] The finished material structure is an AlN / Diamond heterostructure. The bandgap width of AlN is 6.2eV, and the bandgap width of diamond is 5.5eV.

[0084] Because the bandgap widths of AlN and diamond materials are different, the bandgap width of AlN is higher than that of Diamond, so there is a step difference between the bottom of the conduction band of the two. This step difference of the conduction band will bend the energy band at the bottom of the conduction band, and the energy band bending will form a two-dimensional potential well at the heterojunction interface. This two-dimensional potential well confines the electrons, and these electrons can only move in two dimensions along the plane parallel to the abrupt junction interface in the potential well, thus forming a two-dimensional electron gas (2DEG). Therefore, in the AlN / Diamond heterojunction structure, even if the AlN barrier layer is not doped, a higher surface density of 2DEG can be obtained by induction of a huge number of polarized positive charges.

[0085] Due to the existence of this two-dimensional electron device, semiconductor devices such as Schottky diodes (SBDs) and diamond high electron mobility transistors (Diamond HEMTs) can be manufactured.

[0086] In this material structure, Diamond serves as the channel layer and AlN serves as the barrier layer.

[0087] The formed AlN / Diamond heterojunction can be used to make a variety of devices, such as light emitting diodes (LEDs), Schottky diodes, and field effect transistors.

[0088] Figure 1 The figure shows a schematic diagram of a field effect transistor (FET) based on an AlN / Diamond heterojunction structure. Diamond is used as a channel layer and AlN is used as a barrier layer. Because the bandgap widths of AlN and diamond materials are different, the band bending forms a two-dimensional potential well at the heterojunction interface. This two-dimensional potential well confines electrons, and these electrons can only move two-dimensionally along a plane parallel to the abrupt junction interface in the potential well, thus forming a two-dimensional electron gas (2DEG), forming a high electron mobility transistor (HEMT) based on the AlN / Diamond heterojunction. Under the action of the source-drain voltage (Vds), the two-dimensional electron gas (2DEG) is transmitted in the channel to form a current (Ids) from the source 500 to the drain 600. The gate voltage (Vgs) is used to control the density of two-dimensional electrons, thereby achieving the purpose of controlling the source-drain current.

[0089] In the on state, the two-dimensional electron gas flows from the source 500 to the drain 600, and the current flows from the drain 600 to the source 500. In order to achieve conduction, the source and drain metals need to achieve good contact with the surface of the barrier layer (AlN), that is, ohmic contact, so that the contact surface presents the minimum resistance. At the same time, the electrons of the source and drain must pass through the barrier layer and connect with the two-dimensional electron gas to realize the current loop.

[0090] There are two prerequisites for forming a good ohmic contact:

[0091] (1) There is a low barrier height between metal and semiconductor;

[0092] (2) The semiconductor has a high concentration of impurities. Since AlN is an ultra-wide bandgap semiconductor material, there are many difficulties in achieving these two conditions.

[0093] This application proposes a variety of methods for solving the above-mentioned problems and achieving ohmic contact, which are described below.

[0094] 1. Source-drain doping, that is, by performing n-type doping on the AlN film at the source and drain positions, the purpose of making a good ohmic contact is achieved.

[0095] The specific process is as follows:

[0096] Step 1: forming a protective layer 400 with a thickness of 100nm-2um on the nitride epitaxial layer, the nitride epitaxial layer includes an aluminum nitride epitaxial layer 300, and the protective layer 400 includes one of silicon oxide, silicon nitride, and aluminum oxide;

[0097] Step 2: forming a mask layer 800 on the protective layer 400;

[0098] Step 3: Si doping is performed on the source and drain by ion implantation, where the ion beam energy range is 10-360keV, the implantation angle is 0-7°, and the implantation dose is 10 14 –10 16 / cm 2 ;

[0099] Step 4: Ion activation of silicon doping in aluminum nitride is performed in a nitrogen environment at a high temperature annealing environment of 1200-1600° C. The annealing time is 15-60 minutes.

[0100] Specifically, in the above step 1, a protective layer 400 is formed to protect the AlN barrier layer from being damaged in the subsequent ion implantation process. The protective layer 400 can be silicon oxide, silicon nitride, aluminum oxide, etc., with a thickness of 100nm-2um. Commonly used methods can be PECVD, LPCVD, ALD, etc. Figure 2 shown.

[0101] The process of making the mask layer 800 in step 2 is mainly carried out by using a photolithography process, including coating, alignment, exposure, and development. The purpose is to implement ion implantation only in the source and drain regions in the subsequent ion implantation process, and to protect the regions outside the source and drain regions with photoresist, such as Figure 3 shown.

[0102] In addition to using photoresist as a mask, other materials, such as silicon oxide, silicon nitride or metal materials, can also be used as a "hard mask" for use in scenarios with higher ion beam energy to prevent damage to the epitaxial material.

[0103] In step 3, an ion implantation process is performed to dope the source and drain with Si, such as Figure 4 The ion beam energy range is 10-360keV, the injection angle is 0-7°, and the injection dose is 10 14 –10 16 / cm 2 , the silicon doping concentration in AlN can be obtained as 10 18 -10 20 / cm 3 .

[0104] During the ion activation process in step 4, the ionization energy of silicon in AlN material is as high as 200-600meV (for comparison, the ionization energy of silicon in GaN is 20-60meV). Therefore, in order to activate the silicon doping in AlN, a higher annealing temperature is required, such as 1200-1600°C, and the annealing is carried out in a nitrogen environment for 15-60 minutes. Figure 5 shown.

[0105] After completing the above process, the source and drain metals are made, specifically:

[0106] (1) First, the protective layer 400 on the AlN surface is removed: generally, an etching method is used, including photolithography, etching, degumming, cleaning and other steps;

[0107] (2) Implementing photolithography process, including coating, alignment, and development;

[0108] (3) Depositing source and drain metal layers. These metals include Ti, Al, Ni, Pt, Au, Pd, etc., which can be a single metal or a combination of multiple metals. They are deposited layer by layer on the aluminum nitride epitaxial layer 300 by metal evaporation. For example, the metal layer can be composed of four metal layers: Ti, Al, Ti, Au, with thicknesses ranging from 2-25 nm, 30-300 nm, 20-100 nm, and 50-500 nm, respectively. For example, Ti 25 nm, Al 50 nm, Ti 100 nm, and Au 250 nm can be selected, respectively, with a total thickness of 450 nm. Figure 6 shown.

[0109] Other combinations and thicknesses of metal layers are possible.

[0110] After the source and drain metal layers are fabricated, the source and drain ohms are fabricated, specifically:

[0111] (1) Performing a metal lift-off process to remove the photoresist and the metal layer on the photoresist;

[0112] (2) Implementing metal annealing process: The annealing process is carried out in an RTA (rapid thermal annealing furnace) at a temperature generally between 700-900°C, usually around 800°C, in an argon or nitrogen environment for 30 seconds to 90 seconds. The purpose is to form an ohmic contact between the metal and the doped AlN, such as Figure 7 shown.

[0113] After the source and drain electrodes are fabricated, the gate 700 is further fabricated. The fabrication steps are described below.

[0114] (1) Photolithography process: coating, alignment, exposure, and development

[0115] (2) Gate metal layer production: metal deposition, metal stripping, degumming, and cleaning, which are not described in detail here.

[0116] The gate metal layer generally uses metals with high work functions, such as Pt, Ni, Au, and Ti. Their work functions are 5.65eV, 5.15eV, 5.1eV, and 4.33eV, respectively. The purpose is to form a Schottky contact with the aluminum nitride epitaxial layer 300. The metal layer can be composed of one layer of metal or 2-4 layers of metal, such as Pt / Au or Ni / Au, with a thickness range of 10-50nm and 50-250nm. The manufacturing method is usually to deposit metal layer by layer on the aluminum nitride epitaxial layer 300 by evaporation or sputtering.

[0117] It should be noted that in the above-mentioned process of manufacturing the source, drain and gate 700, the epitaxial layer does not include a cap layer. When the epitaxial layer includes a cap layer, such as a GaN or SiN cap layer, the process of manufacturing the source, drain and gate 700 needs to be adjusted accordingly, which will not be described in detail here.

[0118] In the above step 4, a good ohmic contact can also be obtained through a laser annealing process, and the specific process is as follows:

[0119] Figure 2-7In the manufacturing process of the source-drain ohmic contact shown in the figure, high-temperature annealing is used to activate the doped ions. In high-temperature processes, such as in a temperature environment of 1300-1600°C, the surface roughness, crystal quality, and residual stress of the material will deteriorate with increasing temperature. At the same time, as the temperature rises, it will also affect the two-dimensional electron gas formed in the heterojunction of AlN and diamond, causing the mobility and concentration of the two-dimensional electron gas to decrease, or even disappear. In order to solve this problem, laser annealing is used to activate the doped ions. Lasers have the characteristics of extremely fast heating, sensitive control, and shallow heat conduction depth. While achieving good ohmic contact, they will not damage the non-annealed area.

[0120] The specific method is as follows:

[0121] according to Figure 2-4 The method described above implements an ion implantation process to dope Si to the source and drain electrodes, wherein the ion beam energy range is 10-360keV, the implantation incident angle is 0-7°, and the implantation dose is 10 14 –10 16 / cm 2 , the silicon doping concentration in AlN is obtained as 10 18 -10 20 / cm 3 .

[0122] Laser annealing is used to activate doped ions: During the laser annealing process, by applying pulsed laser 900 to the sample maintained at room temperature, a higher temperature can be reached instantly and locally, so as to activate the doped ions at the source and drain, increase the concentration of carriers, and thus form the source and drain.

[0123] In the laser annealing process, the purpose of laser annealing to activate ions is achieved by selecting different laser types (pulsed laser or continuous wave laser), different energies, different wavelengths, different times and other parameters, while repairing the crystal defects and damage caused by the ion implantation and doping process.

[0124] For example, an ArF excimer laser with a wavelength of 193 nm can be used for annealing. The energy, voltage and frequency of the laser are set to 50-100 mJ / cm 2 , 15-30kV and 5-20Hz. The pulse duration of the laser is 5-30ns, the number of laser pulses is 200-2000, such as Figure 8 shown.

[0125] In order to protect the area other than the source and drain, a mask layer 800 can be made to protect the non-source and drain area. The mask layer 800 can be a photoresist, a dielectric layer 1000 (silicon oxide and silicon nitride, etc.) or a metal layer, with a thickness ranging from 100nm to 5um.

[0126] After the laser annealing process is completed, the mask layer 800 is removed and the wafer is cleaned. Optionally, a conventional high temperature annealing, such as RTP annealing, at a temperature of 800-1200° C. for 30-180 seconds can be performed to repair crystal defects and damage that may have occurred during the ion implantation and laser annealing process.

[0127] After the laser annealing is completed, the corresponding source 500 and drain 600 metal layers are manufactured.

[0128] The above-mentioned ohmic contact can also be made by an epitaxial regrowth process in the embodiment of the present application. The regrowth method is to remove the AlN epitaxial material at the source and drain positions, and then grow a layer of material that is easy to make ohmic contacts, and make a metal layer and ohmic contacts on the surface of the new material to complete the source and drain. The specific process is:

[0129] Step 401 ′: forming a dielectric layer 1000 on the aluminum nitride epitaxial layer 300 , wherein the dielectric layer 1000 is used as a mask layer 800 for a regrowth process, and the thickness of the dielectric layer 1000 is 50-500 nm;

[0130] Step 402 ′: etching the mask layer and the nitride film in the source and drain regions, wherein the nitride film includes an aluminum nitride film;

[0131] Step 403 ′: Perform epitaxial regrowth process on the substrate by chemical vapor deposition to grow Al x Ga (1-x) N material, wherein 0≤x≤1; preferably, x<0.5. The lower the Al component x in the material, the easier it is to dope and the easier it is to obtain a good ohmic contact.

[0132] Step 404′: Al x Ga (1-x) The N material is doped with n-type.

[0133] In the above, more specifically, a dielectric layer 1000, such as silicon oxide or silicon nitride, is formed on the aluminum nitride epitaxial layer 300 as a mask layer 800 for the epitaxial regrowth process, with a thickness of 50-500nm. There are many manufacturing processes, and commonly used methods include PECVD, LPCVD, etc. Fig. 9 shown.

[0134] (2) Etching process: Etching of mask layer 800 and aluminum nitride film, including photolithography (coating, alignment, development, etc.), etching of mask layer 800, etching of AlN film, degumming, and cleaning. Etching can be done by wet and dry etching methods. For AlN etching, a low-damage etching method is required to avoid damage to the AlN crystal and affect the two-dimensional electron gas on the heterojunction surface. When wet etching is used, commonly used wet etching solutions include: HF, HCl, HNO3 or a combination thereof. When dry etching is used, the etching gas is usually Cl2 and BCl3, or it can be a mixed gas of H2 and one or more etching gases such as CF4, CHF3, CH2F2 or C4F4. According to the requirements of the process formula, inert gas Ar or He can be added to achieve low-rate and low-damage etching. The entire AlN film can be etched directly onto the surface of the single crystal diamond epitaxial layer 200, or a thin layer of AlN with a thickness of 0.5-3 nm can be left at the interface. Fig.10 shown.

[0135] (3) Epitaxial layer regrowth: Epitaxial layer material Al x Ga (1-x) N, where x = 0–1. When x = 0, the epitaxial layer material is GaN; when x = 1, the epitaxial layer is AlN. The epitaxial layer growth method is usually MOCVD (metal organic chemical vapor deposition) and MBE (molecular beam epitaxy), and PVD (physical vapor deposition or sputtering) can also be used. When the MOCVD method is used, trimethylaluminum (TMAl, C3H9Al), trimethylgallium (TMG, C3H9Ga) and ammonia (NH3) are used as aluminum source, gallium source and nitrogen source respectively, and hydrogen is used as the carrier gas. By adjusting the pressure, temperature and gas flow rate of the reactor, high-quality single-crystalline aluminum gallium nitrogen (AlN) with different Al and Ga components can be grown. x Ga (1-x) N) Thin film.

[0136] Furthermore, when growing Al x Ga (1-x) N, it is n-doped, for example, when Al is grown by MOCVD x Ga (1-x) N, in addition to trimethylaluminum (TMA, C3H9Al), trimethylgallium (TMG, C3H9Ga) and NH3, a certain flow of silane (SiH4) is added to the reaction chamber, in which Si atoms replace Al and Ga atoms, forming free electrons in the crystal, and realizing n-type doping of aluminum gallium nitrogen single crystal film. Similarly, when x=0, it is an n-type doped GaN crystal material, and when x=1, it is an n-type doped AlN crystal material.

[0137] Furthermore, the AlN at the source and drain positions can be completely etched and stopped at the surface of the single crystal diamond epitaxial layer 200. Then the above-mentioned epitaxial regrowth process is performed. x Ga (1-x) The Al component in N is between 0 and 1. Preferably, the Al component is selected so that the bandgap of AlGaN is equal to or close to that of diamond, thereby reducing the contact barrier. For example, when x=0.75 is selected, the bandgap of AlGaN is 5.5 eV, which is equal to that of diamond. Furthermore, in the epitaxial regrowth process, AlGaN can be doped to obtain n-AlGaN, further improving the ohmic contact.

[0138] Furthermore, a gradual epitaxial regrowth process can be implemented, that is, from bottom to top, the Al component x decreases from large to small. At the bottom, the component x can be 0.8-1, and at the top, x is 0-0.2, that is, at the bottom, the epitaxial material is AlN or n-AlN, and on the upper surface, it becomes GaN or n-GaN, with multiple layers of Al in the middle. x Ga (1-x) N, x changes gradually, Fig.11 The example shown is a 4-layer gradient structure. The actual number of layers can be more. Such a gradient structure provides multiple advantages:

[0139] 1) The composition of the bottom is the same or similar to that of the original epitaxial layer AlN, which is convenient for growth;

[0140] 2) The top becomes GaN or low-Al AlGaN, the bandgap becomes smaller, and it is easy to form ohmic contact with metal;

[0141] 3) It is possible to heavily dope GaN to form n+GaN, further reducing the ohmic contact resistance.

[0142] Furthermore, the AlN epitaxial layer at the source and drain positions can be completely etched to stop at the surface of the single crystal diamond epitaxial layer 200. Then, the above-mentioned epitaxial layer regrowth process is performed to grow Al x Ga (1-x) N material. Preferably, the Al component x<0.5; preferably, x=0, i.e. GaN material. Further, the regrown material is subjected to n-type doping to form n-AlGaN or n-GaN.

[0143] Further, a gradual regrowth process is implemented, and the Al component in the bottom AlGaN material is between 0.2-0.8. Preferably, the Al component is selected so that the bandgap of AlGaN is equal to or similar to the bandgap of diamond, thereby reducing the contact barrier. For example, x=0.75 is selected, and the bandgap of AlGaN is 5.5eV, which is equal to the bandgap of diamond. The figure shows a 4-layer gradual structure, from bottom to top, x gradually decreases, and the topmost material becomes low-component aluminum gallium nitride (x=0.1-0.2) or x=0. The actual number of layers can be more. Further, n-type doping is implemented on each layer to form n-AlGaN or n-GaN. The advantage of this scheme is that the etching process of the AlN barrier layer is easy to control because the diamond surface can be used as a stop layer for the etching process. At the same time, the Al component can be selected so that the bandgap of the bottom AlGaN material is the same as or similar to that of diamond, thereby reducing the contact barrier and further reducing the resistance.

[0144] After the above regrowth process is completed, the corresponding source 500 , drain 600 metal layers and gate 700 are further manufactured.

[0145] In the present application, the source 500, the gate 700 and the drain 600 are all arranged on the side of the aluminum nitride epitaxial layer 300 away from the single crystal diamond epitaxial layer 200, the gate 700 voltage is applied between the source 500 and the gate 700, and the source-drain voltage is applied between the source 500 and the drain 600.

[0146] The above embodiments are only used to illustrate the technical method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical method of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A novel semiconductor device, characterized in that: include: A diamond epitaxial layer, wherein the diamond epitaxial layer is disposed above a diamond substrate; A nitride epitaxial layer is disposed on the diamond epitaxial layer, and the diamond epitaxial layer is located between the nitride epitaxial layer and the diamond substrate; The source, gate and drain are all arranged on the nitride epitaxial layer at a side away from the diamond epitaxial layer. A gate voltage is applied between the source and the gate, and a source-drain voltage is applied between the source and the drain.

2. A method for manufacturing a novel semiconductor device as claimed in claim 1, characterized in that: The production method comprises: Step 1: Prepare a diamond substrate and remove metal contaminants, impurity particles, surface damage and organic components on the surface of the diamond substrate; Step 2: fabricating a single crystal diamond epitaxial thin film on the diamond substrate; Step 3: forming a nitride epitaxial layer on the single crystal diamond epitaxial layer by chemical vapor deposition to form a nitride film; Step 4: Make source and drain metal and ohmic contact; Step 5: Fabricate a gate on the nitride epitaxial layer.

3. A production method according to claim 2, characterized in that: In step 4, the fabrication of the ohmic contact includes a source-drain doping process, and the source-drain doping process includes: Step 401: forming a protective layer with a thickness of 100nm-2um on the nitride epitaxial layer, wherein the material of the nitride epitaxial layer includes aluminum nitride, boron nitride, aluminum gallium nitride, etc., and the protective layer includes one of silicon oxide, silicon nitride, and aluminum oxide; Step 402: fabricating a mask layer on the protective layer; Step 403: Si doping is performed on the source and drain by ion implantation, wherein the ion beam energy range is 10-360keV, the implantation angle is 0-7°, and the implantation dose is 10 14 –10 16 / cm 2 ; Step 404: ion activation of silicon doping in the nitride is performed in a nitrogen environment at a high temperature annealing environment of 1200-1600° C. The annealing time is 15-60 minutes.

4. A production method according to claim 3, characterized in that: In the step 404, the ion activation further includes laser annealing, wherein the laser annealing includes applying a pulsed laser to the nitride epitaxial layer at room temperature, wherein the pulsed laser is vertically irradiated at the source and drain positions of the nitride epitaxial layer; The area outside the source and drain positions is protected by the mask layer, wherein the mask layer includes one of a photoresist, a dielectric layer and a metal layer, and the thickness of the mask layer is 100nm-5um; After laser annealing is completed, the mask layer is removed, the wafer is cleaned, and high-temperature annealing is performed at a temperature of 800-1200 degrees Celsius for 30-180 seconds.

5. A manufacturing method according to claim 2, characterized in that: In step 4, the fabrication of the ohmic contact includes an epitaxial regrowth process, and the epitaxial regrowth method includes: Step 401′: forming a dielectric layer on the nitride epitaxial layer, the dielectric layer serving as a mask layer for the epitaxial regrowth process, the thickness of the dielectric layer being 50-500 nm; Step 402′: etching the mask layer and the nitride film, wherein the nitride film includes aluminum nitride, boron nitride, and aluminum gallium nitride film; Step 403 ′: Perform a gradual epitaxial regrowth process by chemical vapor deposition to grow an aluminum gallium nitride material Al x Ga (1-x) N, where 0≤x≤1; Step 404 ′: performing n-type doping on the regrown epitaxial material.

6. A production method according to any one of claims 4-5, characterized in that: The production of the ohmic contact comprises: Step 405: performing a photolithography process, wherein the photolithography process includes coating, alignment, exposure, and development; Step 406: depositing a source-drain metal layer, wherein the source-drain metal layer includes one or more of Ti, Al, Ni, Pt, Au, and Pd; Step 407: performing a metal stripping process to remove the photoresist and the metal layer on the photoresist; Step 408: Perform a metal annealing process at a temperature between 700-900° C. and a time of 30-90 seconds.

7. A manufacturing method according to claim 2, characterized in that: In step 5, the gate manufacturing includes: Step 501: performing a photolithography process, wherein the photolithography process includes coating, alignment, exposure, and development; Step 502: manufacturing a gate metal layer, wherein the manufacturing of the gate metal layer includes metal deposition, metal stripping, degumming, and cleaning.

8. A manufacturing method according to claim 7, characterized in that: A cap layer is also disposed on the nitride epitaxial layer, and the cap layer includes SiN or GaN.

9. A manufacturing method according to claim 2, characterized in that: In the step 1, the removal method includes heating acid treatment, organic solvent ultrasonic cleaning and hydrogen-oxygen plasma etching treatment.

10. A manufacturing method according to claim 2, characterized in that: In the step 3, during the growth of the aluminum nitride epitaxial layer, an Sc evaporation source is added to form a ScAlN material, so as to form an aluminum nitride film with the ScAlN material.

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