Method of manufacturing semiconductor device and semiconductor device

Abstract

To provide a method of manufacturing a semiconductor element which achieves efficient energy supply, and to provide the semiconductor element.SOLUTION: The method of manufacturing a semiconductor device includes forming a tin-containing film (Ga2O3) 212 on a gallium oxide-based compound (β - SnO2) 210, doping the gallium oxide-based compound 210 with tin by irradiating the tin-containing film 212 with ultraviolet light, forming a metallic film 214 of titanium (Ti), chromium (Cr), nickel (Ni), or the like without removing the tin-containing film 212, and forming electrodes 216 by forming a film of gold (Au) or the like thereon. The metal film 214 constitutes a metal electrode together with the electrode 216.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a semiconductor device and a semiconductor device. [Background technology]

[0002] Currently, energy consumption continues to increase along with economic growth, while climate change requires reductions in greenhouse gas emissions. This calls for the development of power electronics technology to achieve efficient energy supply. Power electronics is a technology for converting and controlling electrical energy, and the semiconductors used in its circuits are called power devices (power semiconductors). Silicon (Si) has traditionally been used as a material for power devices, but Si is reaching its performance limits. Research and development has been conducted on alternative materials, such as silicon carbide (SiC) and gallium nitride (GaN), which have larger bandgaps than Si. While these materials can realize devices with higher breakdown voltages and lower loss than Si, they face challenges such as expensive substrates and difficulty in mass production.

[0003] Therefore, beta gallium oxide (β-Ga2O3), which has a larger band gap than 4H-SiC or GaN, is attracting attention as a next-generation power device material. Because of its extremely large band gap, β-Ga2O3 has superior material properties to SiC and GaN. Furthermore, because it is possible to grow single-crystal bulks using the melt growth method, there is a prospect for low-cost mass production of Ga2O3 power devices. However, research and development of devices using this material has been delayed due to the inability to fully utilize its excellent material properties. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 8,207,003 [Patent Document 2] Japanese Patent Publication No. 2020-76153 [Patent Document 3] U.S. Patent No. 5,413,959 [Patent Document 4] Japanese Patent Application Publication No. 8-264468 [Patent Document 5] Summary of JP-A-4-250617

[0005] A method for manufacturing a semiconductor device according to one aspect of the present disclosure includes forming a tin-containing oxide film on a gallium oxide-based compound, irradiating the tin-containing oxide film with ultraviolet laser light to dope the gallium oxide-based compound with tin, and forming a metal electrode on the tin-containing oxide film irradiated with the ultraviolet laser light.

[0006] In a semiconductor device according to another aspect of the present disclosure, a tin-containing oxide film is formed on a gallium oxide-based compound, and the tin-containing oxide film is irradiated with ultraviolet laser light to dope tin into the gallium oxide-based compound, so that the Sn concentration in the tin-containing oxide film is 10 21 atoms / cm 3 The Sn concentration of the tin-doped gallium oxide compound is 10 21 atoms / cm 3 The Sn concentration is less than 10 at a depth of 10 nm from the interface between the tin-containing oxide film and the gallium oxide-based compound. 18 atoms / cm 3 That's all. [Brief explanation of the drawings]

[0007] Some embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 shows a schematic configuration example of a laser doping system. [Figure 2] Figure 2 is a chart showing a comparison of the physical properties of β-Ga2O3 and major semiconductor materials. [Figure 3] FIG. 3 is an explanatory diagram showing an outline of a method for manufacturing a semiconductor device according to a comparative example. [Figure 4] FIG. 4 is a flowchart of a method for manufacturing a semiconductor device according to the embodiment. [Figure 5]FIG. 5 is an explanatory diagram showing an outline of a method for manufacturing a semiconductor device according to an embodiment. [Figure 6] FIG. 6 is a cross-sectional view showing an example of the structure of a semiconductor element manufactured by applying the method for manufacturing a semiconductor element according to the embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing an example of the structure of a power device currently being proposed. [Figure 8] FIG. 8 is a graph showing an example of the distribution of tin (Sn) concentration when Ga2O3 is doped with Sn by the process of the embodiment. Embodiment

[0008] -table of contents- 1. Example of a laser doping system 1.1 Configuration 1.2 Operation 2. Specific examples of semiconductor materials 2.1 Physical properties and crystalline phases of Ga2O3 2.2 Physical properties of β-Ga2O3 2.3 Dopant implantation process into β-Ga2O3 2.3.1 Dopants in β-Ga2O3 2.3.2 Ion implantation 2.3.3 Laser doping method 3. Manufacturing method of semiconductor element according to comparative example 4. Challenges 5. Implementation form 5.1 Configuration 5.2 Operation 5.3 Actions and Effects 6. Application examples for device fabrication 6.1 Application Example 1 6.2 Application Example 2 7. Example of Sn concentration distribution 8. About the Processor 9.Other

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the content of the present disclosure. Furthermore, not all of the configurations and operations described in each embodiment are necessarily essential as the configurations and operations of the present disclosure. Note that the same components are given the same reference symbols, and redundant explanations will be omitted.

[0010] 1. Example of a laser doping system 1.1 Configuration FIG. 1 shows a schematic configuration example of a laser doping system 10. The laser doping system 10 includes a laser device 12, an optical path 13, and a laser irradiation device 14. The laser device 12 is a laser device that outputs pulsed laser light having a photon energy higher than the band gap of the semiconductor material. For example, the laser device 12 may be a discharge-pumped ultraviolet laser device that uses F2, ArF, or KrF as a laser medium. Alternatively, the laser device 12 may be a solid-state laser device that outputs ultraviolet wavelengths.

[0011] The laser system 12 includes an oscillator 20, a monitor module 24, a shutter 26, and a laser control processor 28.

[0012] The oscillator 20 includes a chamber 30 , an optical resonator 32 , a charger 36 , and a pulsed power module (PPM) 38 .

[0013] An excimer laser gas is sealed in the chamber 30. The chamber 30 includes a pair of electrodes 43 and 44, an insulating member 45, and windows 47 and 48.

[0014] The optical resonator 32 is composed of a rear mirror 33 and an output coupler (OC) 34. The rear mirror 33 and the OC 34 each have a flat substrate coated with a highly reflective film and a partially reflective film. The chamber 30 is disposed on the optical path of the optical resonator 32.

[0015] The PPM 38 includes a switch 39 and a charging capacitor (not shown). The switch 39 is connected to a signal line that transmits a control signal from the laser control processor 28.

[0016] The charger 36 is connected to the charging capacitor of the PPM 38. The charger 36 receives charging voltage data from the laser control processor 28 and charges the charging capacitor of the PPM 38.

[0017] The monitor module 24 includes a beam splitter 50 and a light sensor 52 .

[0018] The shutter 26 is disposed on the optical path of the pulsed laser light output from the monitor module 24. The optical path of the pulsed laser light is sealed by a housing and an optical path tube 13 (not shown), and may be purged with an inert gas such as N2 gas.

[0019] The laser irradiation device 14 includes an irradiation optical system 70 , a frame 72 , an XYZ stage 76 , a table 74 , and a laser irradiation control processor 100 .

[0020] The illumination optical system 70 includes high-reflection mirrors 111 , 112 , and 113 , an attenuator 120 , a beam homogenizer 130 , a mask 140 , a transfer optical system 142 , a window 146 , and a housing 150 .

[0021] The high-reflection mirror 111 is disposed so that the pulsed laser light output from the laser device 12 passes through the attenuator 120 and enters the high-reflection mirror 112 .

[0022] Attenuator 120 is disposed on the optical path between high-reflection mirror 111 and high-reflection mirror 112. Attenuator 120 includes two partially reflecting mirrors 121 and 122 and rotation stages 123 and 124 that change the angle of incidence of the pulsed laser light on each mirror.

[0023] High-reflection mirror 112 is disposed so that the pulsed laser light that has passed through attenuator 120 passes through beam homogenizer 130 and mask 140 and is incident on high-reflection mirror 113. Beam homogenizer 130 and mask 140 are disposed on the optical path between high-reflection mirror 112 and high-reflection mirror 113.

[0024] Beam homogenizer 130 includes a fly's eye lens 132 and a condenser lens 134 and is positioned to provide Kohler illumination to mask 140 .

[0025] The high-reflection mirror 113 is positioned so that the pulsed laser light incident via the beam homogenizer 130 is irradiated onto the dopant thin film 160 containing the dopant via the transfer optical system 142 and the window 146. The dopant is an element that is doped (added) into the semiconductor material 162 by laser doping.

[0026] The transfer optical system 142 is positioned so that an image of the mask 140 is focused through a window 146 onto the surface of a dopant thin film 160 formed on a semiconductor material 162 .

[0027] The transfer optical system 142 may be a combination of a plurality of lenses 143 and 144, and may be a reduction projection optical system.

[0028] The window 146 is located on the optical path between the transfer optical system 142 and the object to be irradiated, and is disposed in a hole in the housing 150 via an O-ring or the like (not shown).

[0029] The housing 150 is provided with an inlet 152 and an outlet 154 for N 2 gas, and may be sealed with an O-ring or the like (not shown) to prevent outside air from entering the housing 150.

[0030] An illumination optical system 70 and an XYZ stage 76 are fixed to a frame 72. A table 74 is placed on the XYZ stage 76, and an illumination target is placed on the table 74.

[0031] The semiconductor material 162 may be, for example, Ga2O3. The semiconductor material 162 is held on an XYZ stage 76 via a table 74.

[0032] A dopant thin film 160 containing a dopant is formed on the surface of the semiconductor material 162. The dopant thin film 160 may be, for example, a SnO2 film or an ITO film.

[0033] The radiation shield 170, which surrounds the table 74 including the space between the window 146 and the object to be irradiated, is sealed with, for example, an O-ring (not shown) or the like, and is configured to be able to fill at least the surface of the object to be irradiated in the space between the window 146 and the object to be irradiated with a purge gas. The radiation shield 170 is provided with a purge gas inlet 172 and outlet 174. Instead of using a purge gas, it is also possible to connect the outlet 174 to a vacuum pump (not shown) with the inlet 172 closed, and place the semiconductor material 162 to be irradiated in a vacuum environment.

[0034] The purge gas may be, for example, dry air, oxygen, nitrogen gas, argon, or helium gas. Irradiation may be performed in a vacuum environment or in the air without using a purge gas.

[0035] The window 146 may be made of CaF2 crystal or a synthetic quartz substrate that transmits excimer laser light, and may be coated with an anti-reflection film on both sides.

[0036] 1.2 Operation The operation of the laser doping system 10 will now be described. The laser irradiation control processor 100 reads the irradiation condition parameters for laser doping. Specifically, it reads the fluence Fd for laser doping. Since the fluence Fd varies depending on the material and film thickness of the irradiated object, it is advisable to specify it in advance through experiments, etc.

[0037] The laser irradiation control processor 100 sets the target pulse energy Et and the transmittance Td of the attenuator 120 from the fluence Fd on the surface of the object to be irradiated, and controls the incident angles of the two partial reflection mirrors 121 and 122 using their respective rotation stages 123 and 124 so that the transmittance of the attenuator 120 becomes Td.

[0038] The laser irradiation control processor 100 first controls the XY axes of the XYZ stage 76 so that the image of the mask 140 is positioned in the irradiation region of the semiconductor material 162. Then, the laser irradiation control processor 100 controls the Z axis of the XYZ stage 76 so that the image of the mask 140 is focused on the surface of the dopant thin film 160 formed on the semiconductor material 162.

[0039] The laser irradiation control processor 100 causes the laser device 12 to output pulsed laser light. The laser irradiation control processor 100 transmits a target pulse energy Et and a light emission trigger Tr to the laser control processor .

[0040] The pulsed laser light output from the oscillator 20 is sampled by a beam splitter 50 of the monitor module 24, and the pulse energy E is measured by an optical sensor 52. The laser control processor 28 controls the charging voltage of the charger 36 so that the difference ΔE between the pulse energy E and the target pulse energy Et approaches zero.

[0041] The pulsed laser light transmitted through the beam splitter 50 of the monitor module 24 enters the laser irradiation device 14 via the optical path 13. The pulsed laser light entering the laser irradiation device 14 is reflected by the high-reflection mirror 111, attenuated by the attenuator 120, and reflected by the high-reflection mirror 112.

[0042] The pulsed laser light reflected by the high-reflection mirror 112 is spatially homogenized in light intensity by the beam homogenizer 130 and then incident on the mask 140. Here, it is preferable that the shape of the beam that uniformly illuminates the mask 140 is larger than the hole in the mask 140 and substantially matches the shape of the mask.

[0043] The pulsed laser light transmitted through the mask 140 is reflected by the high-reflection mirror 113, and is transferred and imaged onto the surface of the dopant thin film 160 by the transfer optical system 142. As a result, the dopant thin film 160 and the semiconductor material 162 are heated, and the dopant diffuses into the semiconductor material 162 due to thermal diffusion and thermal shock waves.

[0044] The laser irradiation control processor 100 controls the X and Y axes of the XYZ stage 76 so that the next irradiation region of the semiconductor material 162 is irradiated with the pulsed laser light.

[0045] The above operation is performed for all regions to be irradiated in the semiconductor material 162. The pulsed laser light is irradiated with 1 to 100,000 pulses per irradiation area. In this way, the laser doping system 10 may expose the semiconductor material 162 by a step-and-repeat method.

[0046] 2. Specific examples of semiconductor materials 2.1 Physical properties and crystalline phases of Ga2O3 Ga2O3 has five crystalline polymorphs: α, β, γ, δ, and ε (κ). Of the five crystalline phases, the β phase is the thermodynamically most stable, while the other phases are metastable. Therefore, research and development of Ga2O3 devices has focused on β-Ga2O3. The β phase has a monoclinic β-gallium structure, and is the only one of the five phases that can be grown as a single-crystal bulk by melt growth. Phases other than the β phase have attracted attention in recent years due to their unique properties not found in the β phase. The α phase, which has a corundum structure, can easily be grown as a thin film by heteroepitaxial growth on a sapphire substrate, which also has a corundum structure. For this reason, the α phase is the second most researched phase after the β phase. The γ phase has a defect spinel structure, and the δ phase has a cubic bixbyite structure. Since the ε(κ) phase has spontaneous polarization, it is expected that a high-concentration two-dimensional electron gas (2DEG) will form at the (AlGa)2O3 / Ga2O3 interface, similar to an AlGaN / GaN heterojunction. Thin films of these metastable phases transition to the most stable β phase upon high-temperature treatment, so low-temperature treatment is the only option.

[0047] 2.2 Physical properties of β-Ga2O3 Figure 2 shows a comparison of the physical properties of β-Ga2O3 with those of major semiconductor materials. The most outstanding feature of β-Ga2O3 is its extremely large band gap of approximately 4.5 eV. β-Ga2O3 has a band gap larger than that of wide band gap semiconductors such as 4H-SiC and GaN, and is therefore referred to as an ultra-wide band gap semiconductor. This large band gap predicts a breakdown field of 7 MV / cm or more, more than twice that of 4H-SiC or GaN. A large breakdown field makes it possible to make the drift layer thinner or increase the impurity concentration, thereby reducing resistance.

[0048] The Varigas figure of merit is an index of power device performance when Si is expressed as 1, and is a value determined by the dielectric constant, electron mobility, and dielectric breakdown field. Since the Varigas figure of merit is proportional to the cube of the dielectric breakdown field, the Varigas figure of merit for β-Ga2O3 is larger than that of other materials. The larger the Varigas figure of merit, the smaller the on-resistance can be, and it is expected that low loss will be achieved.

[0049] 2.3 Dopant implantation process into β-Ga2O3 This section explains the dopants implanted into β-Ga2O3 and provides an overview of the ion implantation method and laser doping method, which are the most commonly used methods for implanting dopants into β-Ga2O3.

[0050] 2.3.1 Dopants in β-Ga2O3 The electrical conductivity of a semiconductor can be changed by injecting impurities called dopants into it. Dopants are divided into donors and acceptors. Injecting donors supplies free electrons to the semiconductor, making it an n-type semiconductor, while injecting acceptors supplies holes to the semiconductor, making it a p-type semiconductor. Free electrons and holes are called carriers, and they carry electric charges. Regarding β-Ga2O3, research and development of n-type semiconductors has progressed, but no results have been achieved for p-type semiconductors.

[0051] As mentioned above, the structure of β-Ga2O3 is a monoclinic β-gallium structure, with two types of Ga sites: Ga(1) with a coordination number of 4 and Ga(2) with a coordination number of 6. It is expected that carriers will be generated by injecting dopants and substituting the Ga sites with the dopants.

[0052] The n-type dopants in β-Ga2O3 include Si, Sn, and Ge. Si and Ge tend to substitute for Ga(1), and Sn for Ga(2). Both form shallow donor levels.

[0053] 2.3.2 Ion implantation Ion implantation is a technique widely used to implant dopants into semiconductors. The properties of the substrate can be changed by ionizing dopant atoms or molecules, accelerating them to several keV to several MeV, and implanting them into the substrate. The procedure for ion implantation into β-Ga2O3 involves first implanting the ions at room temperature, followed by annealing at 900-1000°C to activate the implanted dopants. The contact resistivity of devices fabricated using ion implantation is 4.6×10 -6 Ωcm 2 A good value was obtained, and an ohmic contact was formed. In this way, the ion implantation method has produced results that are practical for the fabrication of β-Ga2O3 devices. However, ion implantation requires high-temperature annealing after ion implantation to activate the implanted dopants, which makes the process more complicated.

[0054] 2.3.3 Laser doping method Laser doping is a technique for injecting dopants into semiconductors by laser irradiation. Laser doping can be performed by irradiating a substrate with laser light in a gas atmosphere or solution containing dopant atoms, or by depositing a dopant thin film on a substrate and irradiating it with laser light. The latter method is used in the embodiments of the present disclosure. When a dopant thin film is deposited on a semiconductor substrate and irradiated with laser light, the heat of the laser light diffuses the dopant. The substrate does not melt during this process, and the dopant is injected by solid-phase diffusion. Laser doping has the advantage of simplifying the process, since it does not require high-temperature annealing to activate the dopant. Another advantage is that a highly doped layer can be formed in a shallow region of several tens to hundreds of nanometers.

[0055] 3. Manufacturing method of semiconductor element according to comparative example 3 is an explanatory diagram showing an outline of a manufacturing method of a semiconductor device according to a comparative example. The comparative example of the present disclosure is a form that the applicant recognizes as being known only by the applicant, and is not a publicly known example that the applicant acknowledges. For example, the process of performing laser doping on a β-Ga2O3 semiconductor and then forming an electrode is as follows.

[0056] [Step 1] A dopant thin film 202 serving as a dopant supply source is formed on a β-Ga2O3 semiconductor 200. The dopant thin film 202 is, for example, an a-Si (amorphous silicon) film.

[0057] [Step 2] Pulsed laser light is irradiated onto the dopant thin film 202, and the dopant in the dopant thin film 202 is doped into the semiconductor material (see F3A on the left side of FIG. 3).

[0058] [Step 3] The dopant thin film 202 is removed by etching (see F3B in the upper center of FIG. 3).

[0059] [Step 4] After that, a metal film 204 made of a metal material that is resistant to oxidation, such as titanium (Ti), chromium (Cr), or nickel (Ni), is formed, and then a gold (Au) film is formed as an electrode 206 (see F3C on the right side of FIG. 3).

[0060] 4. Challenges In the manufacturing method of the semiconductor device according to the comparative example, when forming an electrode on the β-GaO semiconductor 200 after doping, it is necessary to remove the dopant thin film 202 formed on the β-GaO semiconductor 200 by a method such as etching, which makes the manufacturing process complicated.

[0061] Furthermore, if the dopant thin film 202 is not made of a material that can be selectively removed, there is a risk that a portion 200D of the surface of the doped β-Ga2O3 layer will also be removed (see F3D in the lower center of Figure 3). This limits the doping range and etching method.

[0062] 5. Implementation form 5.1 Configuration The configuration of the laser doping system used in the method for manufacturing a semiconductor device according to the embodiment may be the same as that of the laser doping system 10 shown in Fig. 1. The pulsed laser light output from the laser device 12 is an example of the "ultraviolet laser light" in the present disclosure.

[0063] 5.2 Operation FIG. 4 shows a flowchart of the method for manufacturing a semiconductor device according to the embodiment, and FIG. 5 shows an outline of the process.

[0064] In step S11, a dopant thin film 212 is formed on a gallium oxide-based compound 210, which is a semiconductor material. The dopant thin film 212 is a tin dioxide (SnO) film with a thickness of 1 nm to 300 nm, formed by, for example, sputtering or pulsed laser deposition (PLD). The gallium oxide-based compound 210 may be, for example, β-GaO, another crystalline polytype of GaO (e.g., α-GaO), (In,Ga)O, or In-Ga-Zn-O. Instead of SnO, tin monoxide (SnO) or SnOx, where x is a non-integer, may also be used. Other oxides containing Sn may also be used, such as InO:Sn (ITO: indium tin oxide or tin-doped indium oxide) or In-Ga-Sn-O. These may be in a single crystal state, polycrystalline, or amorphous.

[0065] In step S12, pulsed laser light is irradiated from above the dopant thin film 212, and tin (Sn) in the SnO2 film is doped as a dopant into the semiconductor material (see F5A on the left side of FIG. 5). The irradiation conditions for the pulsed laser light must be set so that it is below the damage threshold of the underlying Ga2O3 layer and so that the flatness of the SnO2 surface does not interfere with the formation of the upper metal electrode. For example, in the case of KrF excimer laser light (wavelength 248 nm), the laser fluence on the SnO2 film is 400 mJ / cm 2 It is recommended to set it to 100mJ / cm or less. 2 More than 400mJ / cm2 The following range is preferable.

[0066] In step S13, the SnO2 film that is the dopant thin film 212 is not removed, and a metal film 214 of Ti, Cr, Ni, or the like is formed on the SnO2 film. Since the dopant thin film 212 is a thin film that has conductivity, it can be used as part of an electrode.

[0067] After step S13, in step S14, an electrode 216 made of Au or the like is formed on the metal film 214. The electrode 216 is an example of the "metal electrode" in this disclosure. Note that the metal film 214 and the electrode 216 can form a metal electrode.

[0068] After step S14, in step S15, wiring 218 and the like may be arranged by wire bonding or the like (see F5B on the right side of FIG. 5).

[0069] In the semiconductor device 220 thus fabricated, the dopant thin film 212 used as the dopant supply source functions as a contact electrode. A contact electrode is an electrode material used as a combination of materials that generates low electrical resistance (contact resistance) at the interface (contact surface) between different materials.

[0070] 5.3 Actions and Effects The method for manufacturing a semiconductor device according to the embodiment provides the following advantages.

[0071] [1] After the laser doping step (step S12), there is no need to perform a step of removing the dopant thin film 212 by etching or the like. This simplifies the manufacturing process and prevents the surface of the β-Ga2O3 layer from being eroded by the etching process.

[0072] [2] The SnO2 film itself, which serves as a dopant supply source, serves as an ohmic electrode with Ga2O3, so the electrical resistance between the electrode 216 and the Ga2O3 semiconductor is reduced, reducing electrical loss and heat generation.

[0073] [3] A highly doped layer remains on the top surface of β-Ga2O3, reducing contact resistance and power loss in the device.

[0074] 6. Application examples for device fabrication 6.1 Application Example 1 6 shows an example of the structure of a semiconductor device 300 fabricated by applying the method for fabricating a semiconductor device according to the embodiment. Since it is difficult to fabricate a p-type Ga2O3, the device is limited to being configured as only an n-type. For example, in the device structure shown in FIG. 6, as shown in the area surrounded by the dashed circle in FIG. 6, a high concentration n-type GaN is present near the interface between the source (S) electrode 302 and the drain (D) electrode 304. ++ A layer needs to be formed.

[0075] The manufacturing process of the semiconductor device 300 shown in FIG. 6 is as follows.

[0076] [Step 21] An Fe-doped Ga2O3 layer 312, which serves as an insulating layer, is laminated on a substrate material 310. The substrate material 310 may be sapphire or the like other than Ga2O3.

[0077] [Step 22] An undoped (undoped) Ga2O3 layer 314 is deposited on the Fe-doped Ga2O3 layer 312 as a buffer layer.

[0078] [Step 23] A Ga2O3 layer 316 doped with a low concentration of Sn is stacked on the undoped Ga2O3 layer 314. The Sn concentration of the Sn-doped Ga2O3 layer 316 is, for example, approximately 3×10 16 atoms / cm 3 It may be less than.

[0079] [Step 24] A SnO2 layer 318 is deposited on the Sn-doped Ga2O3 layer 316 at positions where the source (S) and drain (D) electrodes 302, 304 will be formed. The SnO2 layer 318 is an example of the "tin-containing oxide film" in this disclosure.

[0080] [Step 25] Laser irradiation is performed from above the SnO2 layer 318 to form a highly Sn-doped n layer near the top surface of the Ga2O3 layer 316. ++ Form layer 316D. ++ The Sn concentration in layer 316D is, for example, approximately 1×10 18 atoms / cm 3 It may be more than that.

[0081] [Step 26] Next, an SiO2 layer 320 is laminated on the Ga2O3 layer 316 as a gate insulating film.

[0082] [Step 27] Then, without removing the SnO2 layer 318, electrodes 302 and 304 are formed, and an electrode 322 is formed on the SiO2 layer 320.

[0083] 6.2 Application Example 2 Figure 7 is a cross-sectional schematic diagram showing an example of the structure of a currently proposed Ga2O3 power device. The structure of the vertical depletion-mode Ga2O3 transistor shown in Figure 7 is based on the following publications: M. H. Wong, K. Goto, H. Murakami, Y. Kumagai, and M. Higashiwaki, "Current aperture vertical β-Ga2O3 MOSFETs fabricated by N- and Si-ion implantation doping," IEEE Electron Device Lett., vol. 40, no. 3, pp. 431-434, March 2019; and Masataka Higashiwaki and Takashi Uemura, "Environmental Control ICT Fundamental Technology - From Foundation to Social Deployment - Research and Development of Gallium Oxide Electronic Devices," National Institute of Information and Communications Technology Report, vol. 66, No. 2 (2020). (https: / / www.nict.go.jp / publication / shuppan / kihou-journal / houkoku66-2_HTML / 2020N-04-01.pdf)

[0084] The process according to the embodiment of the present disclosure can be applied to the source electrode portion surrounded by the dashed circle and the drain electrode portion surrounded by the dashed ellipse in Fig. 7. That is, in the device structure of the field effect transistor (FET) shown in Fig. 7, n-type FETs are provided at the interfaces between the source electrode and the drain electrode and the semiconductor material to reduce contact resistance. ++ In such a portion, the process of the embodiment is applied to form a metal electrode as a source electrode or a drain electrode on the SnO2 layer as a dopant supply source, thereby making the SnO2 layer function as a contact electrode.

[0085] 7. Example of Sn concentration distribution 8 is a graph showing an example of the distribution of Sn concentration when Sn is doped into Ga2O3 by the process of the embodiment. The horizontal axis of FIG. 8 represents depth in nanometers (nm). The vertical axis represents Sn concentration in atoms / cm. 3 8, the solid line indicates the distribution of the Sn concentration before laser light irradiation (before doping), and the dashed line indicates the distribution of the Sn concentration after doping.

[0086] To reduce the contact resistance, the Sn concentration is 10 21 atoms / cm 3 The Sn concentration in the Sn-doped Ga2O3 layer near the interface with the SnO2 layer is 10 18 atoms / cm 3 For example, in the distribution of Sn concentration in a laminated structure of an SnO2 layer and a Ga2O3 layer, the depth at which the depth differential of the concentration reaches a negative maximum value is defined as the interface, and the depth at which the depth differential of the concentration reaches a negative maximum value is 10 18 atoms / cm 3 The Sn concentration at a depth of 10 nm from the interface is preferably 10 19 atoms / cm 3 More preferably, 10 20 atoms / cm 3However, this does not apply when doping is performed to form an n-layer in a deeper region from the interface.

[0087] In Fig. 8, the area up to 10 nm deep from the interface between the SnO2 layer and the Ga2O3 layer is 20 atoms / cm 3 The region at a depth of 10 nm from the interface shown in FIG. 8 corresponds to the "doped region with an Sn concentration of 10 18 atoms / cm 3 This is an example of a "doped region" having the above structure. By adjusting the film thickness of each layer and the laser irradiation conditions according to the application and structure of the device to be fabricated, it is possible to form a doped region having a desired Sn concentration.

[0088] 8. About the Processor Processors such as the laser control processor 28 and the laser irradiation control processor 100 may be physically configured in the form of hardware to execute various processes included in the present disclosure. For example, the processor may be a computer including a memory in which a control program defining various processes is stored and a processing device that executes the control program. The control program may be stored in a single memory, or may be stored separately in multiple physically separate memories, with the various processes defined by the control program as a collection of these memories. The processing device may be a general-purpose processing device such as a CPU (Central Processing Unit) or a processing device for a specific purpose such as a GPU (Graphics Processing Unit).

[0089] The processor may also be programmed in the form of software to perform the various processes described herein, for example, the processor may be a dedicated device such as an ASIC (Application Specific Integrated Circuit) or a programmable device such as an FPGA (Field Programmable Gate Array) that implements the functions of performing the various processes.

[0090] The various processes included in the present disclosure may be performed by a single computer, a single dedicated device, or a single programmable device, or may be performed by cooperation of multiple physically separate computers, multiple dedicated devices, or multiple programmable devices. The various processes may be performed by a combination of at least two of one or more computers, one or more dedicated devices, and one or more programmable devices.

[0091] 9.Other The above description is intended to be illustrative, not limiting. Accordingly, it will be apparent to those skilled in the art that modifications can be made to the embodiments of the present disclosure without departing from the scope of the claims. It will also be apparent to those skilled in the art that the embodiments of the present disclosure can be used in combination. Terms used throughout this specification and claims should be construed as "open-ended" terms unless expressly stated. For example, terms such as "comprise," "have," "comprise," and "equip" should be interpreted as meaning "without excluding the presence of elements other than those listed." The modifier "a" should be interpreted as meaning "at least one" or "one or more." The term "at least one of A, B, and C" should be interpreted as "A," "B," "C," "A+B," "A+C," "B+C," or "A+B+C." It should also be interpreted to include combinations other than "A," "B," and "C."

Claims

1. forming a tin-containing oxide film on the gallium oxide-based compound; doping the gallium oxide compound with tin by irradiating the tin-containing oxide film with ultraviolet laser light; forming a metal electrode on the tin-containing oxide film irradiated with ultraviolet laser light.

2. 2. The method for manufacturing a semiconductor device according to claim 1, The tin-containing oxide film is tin dioxide. A method for manufacturing semiconductor devices.

3. 2. The method for manufacturing a semiconductor device according to claim 1, The tin-containing oxide film is indium tin oxide or tin-doped indium oxide. A method for manufacturing semiconductor devices.

4. 2. The method for manufacturing a semiconductor device according to claim 1, The gallium oxide-based compound is gallium oxide. A method for manufacturing semiconductor devices.

5. 5. The method for manufacturing a semiconductor device according to claim 4, The gallium oxide compound is β-Ga 2 O 3 That is, A method for manufacturing semiconductor devices.

6. 2. The method for manufacturing a semiconductor device according to claim 1, the ultraviolet laser light is a KrF excimer laser light; A method for manufacturing semiconductor devices.

7. 2. The method for manufacturing a semiconductor device according to claim 1, The fluence of the ultraviolet laser light on the tin-containing oxide film is 100 mJ / cm 2 More than 400mJ / cm 2 Below is the A method for manufacturing semiconductor devices.

8. 2. The method for manufacturing a semiconductor device according to claim 1, The tin-containing oxide film is irradiated with the ultraviolet laser light to dope the gallium oxide compound with tin, thereby increasing the Sn concentration to 10 18 atoms / cm 3 forming a doped region in which A method for manufacturing semiconductor devices.

9. 2. The method for manufacturing a semiconductor device according to claim 1, When the tin-containing oxide film is irradiated with the ultraviolet laser light to dope the tin into the gallium oxide-based compound, the Sn concentration in the tin-containing oxide film is 10 21 atoms / cm 3 That's all, The Sn concentration of the tin-doped gallium oxide compound is 10 21 atoms / cm 3 the Sn concentration is less than 10 at a depth of 10 nm from the interface between the tin-containing oxide film and the gallium oxide-based compound 18 atoms / cm 3 That's all. A method for manufacturing semiconductor devices.

10. 10. The method for manufacturing a semiconductor device according to claim 9, The Sn concentration is 10 19 atoms / cm 3 That's all. A method for manufacturing semiconductor devices.

11. 10. The method for manufacturing a semiconductor device according to claim 9, The Sn concentration is 10 20 atoms / cm 3 That's all. A method for manufacturing semiconductor devices.

12. 2. The method for manufacturing a semiconductor device according to claim 1, The tin-containing oxide film is formed by a sputtering method or a pulsed laser deposition method. A method for manufacturing semiconductor devices.

13. 2. The method for manufacturing a semiconductor device according to claim 1, The tin-containing oxide film has a thickness of 1 nm or more and 300 nm or less. A method for manufacturing semiconductor devices.

14. 2. The method for manufacturing a semiconductor device according to claim 1, the metal electrode comprises Au; A method for manufacturing semiconductor devices.

15. 2. The method for manufacturing a semiconductor device according to claim 1, Before forming the metal electrode on the tin-containing oxide film, forming a metal film containing any one of Ti, Cr, or Ni on the tin oxide-containing oxide; A method for manufacturing semiconductor devices.

16. forming a tin-containing oxide film on the gallium oxide-based compound; When the tin-containing oxide film is irradiated with ultraviolet laser light to dope the gallium oxide compound with tin, the Sn concentration in the tin-containing oxide film is 10 21 atoms / cm 3 That's all, The Sn concentration of the tin-doped gallium oxide compound is 10 21 atoms / cm 3 the Sn concentration is less than 10 at a depth of 10 nm from the interface between the tin-containing oxide film and the gallium oxide-based compound 18 atoms / cm 3 That's all. Semiconductor element.

17. 17. The semiconductor device of claim 16, The Sn concentration is 10 19 atoms / cm 3 That's all. Semiconductor element.

18. 17. The semiconductor device of claim 16, The Sn concentration is 10 20 atoms / cm 3 That's all. Semiconductor element.

19. 17. The semiconductor device of claim 16, a metal electrode is formed on the tin-containing oxide film irradiated with the ultraviolet laser light; Semiconductor element.

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