Manufacturing method of laminate structure, laminate structure, and semiconductor device

Abstract

To provide a manufacturing method of a laminate structure having a semiconductor layer formed of a gallium oxide-based semiconductor, containing a step of forming a thin single crystal film formed o the gallium oxide-based semiconductor and capable of suppressing the generation of a crack at the time of forming the single crystal film and after the formation, and a laminate structure and a semiconductor device that are manufactured by using the method.SOLUTION: A manufacturing method of a laminate structure 1, comprises the steps of: forming a single crystal film 10 formed of a gallium oxide-based semiconductor onto a support substrate 11 using an ion cut technique; forming an amorphous film 120 formed of the gallium oxide-based semiconductor onto the single crystal film 10; and crystallizing the amorphous film 120. In the step of forming the amorphous film 120 and the step of crystallizing the amorphous film 120 are executed in a state where a temperature of the support substrate 11 is kept at 300°C or less.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a laminated structure, a laminated structure, and a semiconductor device.

Background Art

[0002] Conventionally, as a method for manufacturing a semiconductor device having a semiconductor layer made of a gallium oxide-based semiconductor, a manufacturing method such as a Schottky barrier diode including a step of thinning a substrate made of a gallium oxide-based semiconductor by polishing is known (see Patent Document 1).

[0003] Since the thermal conductivity of a gallium oxide-based semiconductor is lower than that of other semiconductor materials such as Si and GaAs, a semiconductor device using a substrate made of a gallium oxide-based semiconductor generates more heat with respect to the magnitude of current than a semiconductor device using a substrate made of other semiconductor materials such as Si having the same thickness. Therefore, by thinning the substrate made of a gallium oxide-based semiconductor, the amount of heat generation can be suppressed, and the heat generated in the semiconductor device can be efficiently dissipated from the substrate side.

[0004] Conventionally, a method for manufacturing a semiconductor device such as a Schottky barrier diode including a step of bonding a thin single crystal film made of a gallium oxide-based semiconductor onto a different substrate using ion cut (also called Smart Cut (registered trademark)) technology is known (see Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] According to the method for manufacturing a semiconductor device described in Patent Document 1, when attempting to reduce the thickness of a substrate made of a gallium oxide-based semiconductor from several hundred μm to several tens of μm or less, there is a risk of cracks occurring in the wafer including the substrate during processing.

[0007] In the method for manufacturing a semiconductor device described in Patent Document 2, a film made of a gallium oxide-based semiconductor is formed by epitaxial crystal growth on a single crystal film bonded on the above-mentioned heterogeneous substrate. This is because the maximum thickness of the single crystal film formed by ion cutting is about 2 μm, and the thickness of the layer made of the gallium oxide-based semiconductor is insufficient with only the single crystal film formed by ion cutting for manufacturing a vertical power device that requires a drift layer thicker than 2 μm.

[0008] However, in order to epitaxially grow a film made of a gallium oxide-based semiconductor, it is necessary to raise the substrate temperature to approximately 600 °C or higher. Furthermore, in order to epitaxially grow a high-quality film made of a gallium oxide-based semiconductor with few crystal defects, it is necessary to raise the substrate temperature to about 1000 °C. Therefore, due to the difference in the linear expansion coefficients between the single crystal film made of the gallium oxide-based semiconductor and the heterogeneous substrate, there is a risk of cracks occurring in the single crystal film during epitaxial growth.

[0009] An object of the present invention is to provide a method for manufacturing a laminated structure having a semiconductor layer made of a gallium oxide-based semiconductor, including a step of forming a thin single crystal film made of a gallium oxide-based semiconductor, and a method capable of suppressing the occurrence of cracks during and after the formation of the single crystal film, and a laminated structure and a semiconductor device manufactured using the method.

Means for Solving the Problems

[0010] One aspect of the present invention provides the following method for manufacturing a laminated structure, laminated structure, and semiconductor device in order to achieve the above object.

[0011] [1] A step of forming a single crystal film made of a gallium oxide-based semiconductor on a support substrate made of a material having a higher thermal conductivity than the gallium oxide-based semiconductor using an ion cut technique, a step of forming an amorphous film made of a gallium oxide-based semiconductor on the single crystal film, and a step of crystallizing the amorphous film, wherein the step of forming the amorphous film and the step of crystallizing the amorphous film are carried out while maintaining the temperature of the support substrate at 300 ° C or lower. A method for manufacturing a laminated structure. [2] The method for manufacturing a laminated structure according to [1] above, wherein in the step of crystallizing the amorphous film, the amorphous film is crystallized by performing laser annealing on the amorphous film. [3] A support substrate made of a material having a higher thermal conductivity than a gallium oxide-based semiconductor, and a single crystal film made of a gallium oxide-based semiconductor provided on the support substrate, having a thickness of 2 μm or less and a donor impurity concentration of 1 × 10 18 cm -3 or more, and a crack-free epitaxial film made of a gallium oxide-based semiconductor provided on the single crystal film, having a donor impurity concentration of 1 × 10 17 cm -3 or less. A laminated structure. [4] The laminated structure according to [3] above, wherein the main surface of the single crystal film is a (100) plane. [5] The laminated structure according to [4] above, wherein the support substrate is made of Si, SiC, W, or Mo. [6] The laminated structure according to [3] above, wherein the main surface of the single crystal film is a surface other than the (100) plane, (-201) plane, and (101) plane. [7] The laminated structure according to [6] above, wherein the main surface of the single crystal film is a (010) plane or a (-102) plane. [8] A semiconductor device including the laminated structure according to any one of [3] to [7] above.

Advantages of the Invention

[0012] According to the present invention, there is provided a method for manufacturing a stacked structure having a semiconductor layer made of a gallium oxide-based semiconductor, the method including a step of forming a thin single crystal film made of a gallium oxide-based semiconductor, and capable of suppressing the generation of cracks during and after the formation of the single crystal film, and a stacked structure and a semiconductor device manufactured using the method can be provided.

Brief Description of Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0014] (Configuration of Stacked Structure) FIG. 1 is a vertical cross-sectional view of a stacked structure 1 according to an embodiment of the present invention. The stacked structure 1 includes a support substrate 11, a single crystal film 10 made of a gallium oxide-based semiconductor provided on the support substrate 11, and an epitaxial film 12 made of a gallium oxide-based semiconductor provided on the single crystal film 10.

[0015] The gallium oxide-based semiconductor constituting the single crystal film 10 and the epitaxial film 12 is Ga2O3, or Ga2O3 added with one or both of Al and In. Ideally, (Ga x Al y In (1-x-y))It has a composition represented by Ga2O3(0 < x ≤ 1, 0 ≤ y < 1, 0 < x + y ≤ 1). When Al is added to Ga2O3, the bandgap widens, and when In is added, the bandgap narrows. The crystal of the above gallium oxide-based semiconductor typically has a β-type crystal structure.

[0016] Since the single crystal film 10 is formed using the ion-cutting technique, it has a thickness of 2 μm or less. Details of the ion-cutting technique will be described later.

[0017] Also, since the single crystal film 10 is formed using the ion-cutting technique, the in-plane film thickness variation is smaller compared to the substrate thinned by polishing, and the value obtained by dividing the difference between the maximum and minimum values of the film thickness by the intermediate value thereof is 10% or less.

[0018] Also, since the single crystal film 10 is separated from a substrate made of a gallium oxide-based semiconductor using the ion-cutting technique, it contains donor impurities with a concentration of 1 × 10 18 cm -3 or more. The substrate from which the single crystal film 10 is separated is cut out from a single crystal ingot of a gallium oxide-based semiconductor grown by the melt growth method, and the single crystal ingot contains a large amount of donor impurities (1 × 10 18 cm -3 or more) derived from its raw materials.

[0019] Also, as will be described later, by forming the epitaxial film 12 while suppressing the temperature rise of the support substrate 11, the generation of cracks in the single crystal film 10 can be suppressed. Therefore, it is possible to manufacture the laminated structure 1 including the single crystal film 10 without cracks.

[0020] The epitaxial film 12 is formed by solid-phase epitaxial crystal growth with the single crystal film 10 as the base. Specifically, after forming an amorphous film of a gallium oxide-based semiconductor on the single crystal film 10, this amorphous film is crystallized by heat treatment using laser annealing or the like to obtain the epitaxial film 12.

[0021] The formation of an amorphous film of a gallium oxide-based semiconductor can be carried out by vacuum evaporation, sputtering, etc. while maintaining the temperature of the support substrate 11 at 300°C or lower. Further, according to laser annealing, since only the amorphous film on the substantially single-crystalline film 10 can be locally heated, the amorphous film can be crystallized while maintaining the temperature of the support substrate 11 at 300°C or lower.

[0022] Therefore, it is possible to suppress the generation of cracks in the single-crystalline film 10 caused by the difference in the linear expansion coefficients between the single-crystalline film 10 made of a gallium oxide-based semiconductor and the support substrate 11 in the film formation process of the epitaxial film 12.

[0023] The epitaxial film 12 is formed to have a thickness corresponding to the use of the laminated structure 1, for example, a thickness of 2 μm or more and 100 μm or less. For example, when the laminated structure 1 is used for a vertical power device such as a Schottky barrier diode or a field effect transistor, a drift layer with a thickness of usually 2 μm or more is required, so it is preferable to form the epitaxial film 12 to have a thickness of 2 μm or more. On the other hand, in order to suppress the amount of heat generated when an electric current flows and to improve the heat dissipation property, for example, it is preferable to make the thickness of the epitaxial film 12 100 μm or less.

[0024] In the solid-phase epitaxial crystal growth of the epitaxial film 12, by forming an amorphous film by vacuum evaporation or sputtering using a high-purity raw material, the donor impurity concentration of the epitaxial film 12 can be suppressed to 1×10 17 cm -3 or less. Therefore, the donor impurity concentration of the epitaxial film 12 is lower than that of the single-crystalline film 10 divided from the substrate.

[0025] The support substrate 11 is made of a material that has a higher thermal conductivity than the gallium oxide-based semiconductor and has heat resistance such that melting or deformation does not occur at the heat treatment temperature in ion cutting (approximately 300 °C at the lowest temperature). For example, it is made of any one of Si, SiC, C, Mg, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Sr, Zr, Nb, Mo, Rh, Pd, Ag, Sn, Sb, Hf, Ta, W, Ir, Pt, Au, Bi, or a material formed by mixing two or more of the above with N, Ga, and In added thereto. Note that a material with a higher thermal conductivity than the gallium oxide-based semiconductor is used for the support substrate 11 in order to reduce the amount of heat generated and improve heat dissipation by using the single crystal film 10 and the epitaxial film 12, which are thinner than the substrate made of the gallium oxide-based semiconductor, as layers made of the gallium oxide-based semiconductor.

[0026] When forming a film made of a gallium oxide-based semiconductor by vapor phase epitaxial crystal growth, generally, a substrate temperature of 600 °C or higher is required. However, as described above, the epitaxial film 12 is formed by solid phase epitaxial crystal growth while maintaining the temperature of the support substrate 11 at 300 °C or lower. Therefore, the support substrate 11 does not need to have heat resistance that can withstand heat of 600 °C or higher, and it is sufficient to have heat resistance that can withstand heat treatment in ion cutting, for example, heat treatment at 300 °C. Therefore, inexpensive metals such as W, Mo, and Cu, which are likely to be deformed by heat, can be used as the material of the support substrate 11.

[0027] The linear expansion coefficient has relatively large anisotropy, with a small difference between the value in the b-axis direction (

[0010] direction) and the value in the c-axis direction (

[0001] direction), and a large difference between these values and the value in the a-axis direction (

[0100] direction). For example, the linear expansion coefficient of β-Ga2O3, which is a typical gallium oxide-based semiconductor, has a value of 1.54×10 -6 / K in the a-axis direction, a value of 3.37×10 -6 / K in the b-axis direction, and a value of 3.15×10 -6It is / K. Since it is easier to handle when the anisotropy of the in-plane linear expansion coefficient is small, the main plane of the single crystal film 10 made of a gallium oxide-based semiconductor is preferably a (100) plane including the b-axis and the c-axis in the plane.

[0028] Among the materials of the above-mentioned support substrate 11, those with a small difference in linear expansion coefficient from the (100) plane of the gallium oxide-based semiconductor are those with a linear expansion coefficient of 2.6 to 4.15×10 -6 / K for Si, a linear expansion coefficient of 4.4×10 -6 / K for SiC, a linear expansion coefficient of 4.3×10 -6 / K for W, a linear expansion coefficient of 4.9×10 -6 / K for Mo. By using these as the material of the support substrate 11, the generation of cracks in the single crystal film 10 due to the difference in linear expansion coefficient between the single crystal film 10 having the (100) plane as the main plane and the support substrate 11 can be suppressed. Furthermore, among Si, SiC, W, and Mo, W and Mo are excellent in terms of cost.

[0029] That is, from the viewpoint of more effectively suppressing the generation of cracks in the single crystal film 10, it is preferable that the main plane of the single crystal film 10 is a (100) plane and the support substrate 11 is made of Si, SiC, W, or Mo, and it is more preferable that the main plane of the single crystal film 10 is a (100) plane and the support substrate 11 is made of W or Mo.

[0030] The epitaxial film 12 preferably has few defects in order to function as an operating layer of a semiconductor device manufactured using the laminated structure 1. Defects mainly occur when an amorphous film is crystallized by laser annealing or the like. The epitaxial film 12 is required to suppress the generation of defects during crystallization and become a single crystal that inherits the crystallinity of the single crystal film 10.

[0031] The (100) plane and (-201) plane of the gallium oxide-based semiconductor are likely to be twin planes of twin defects, and stacking defects are likely to occur on the (101) plane. Therefore, it is preferable to use a plane other than the (100) plane, (-201) plane, and (101) plane, for example, the (010) plane, (001) plane, or (-102) plane as the main plane of the single crystal film 10.

[0032] In particular, when the (010) plane and the (-102) plane are the main planes of the single crystal film 10, since the (100) plane with a small surface energy is perpendicular to the main plane, when manufacturing a semiconductor device having a trench structure such as a trench MOSFET using the laminated structure 1, it is easy to form a vertical trench along the (100) plane.

[0033] Also, when the main plane of the single crystal film 10 is the (010) plane, the heat dissipation property in the direction perpendicular to the main plane is excellent. Therefore, from the viewpoint of the heat dissipation property of the laminated structure 1, it is preferable that the main plane of the single crystal film 10 is the (010) plane.

[0034] When the laminated structure 1 is used for manufacturing a vertical semiconductor device, since the support substrate 11 also becomes a part of the current path, it is preferable that the support substrate 11 has a low resistivity, for example, a resistivity of 50 mΩcm or less.

[0035] Since the contact portion of the support substrate 11 with the single crystal film 10 made of a gallium oxide-based semiconductor may be oxidized, its surface may be coated with Pt, Au, or the like.

[0036] (Manufacturing method of the laminated structure) Figs. 2(a) to (d) and Figs. 3(a) to (c) are vertical cross-sectional views showing the manufacturing process of the laminated structure 1 according to the embodiment of the present invention. Hereinafter, an example of the flow of the manufacturing process of the laminated structure 1 will be shown using these figures.

[0037] First, a single crystal substrate 100 made of a gallium oxide-based semiconductor and a support substrate 11 are prepared, and planarization treatment such as CMP (chemical mechanical polishing) and mechanical polishing is performed on the surfaces to be joined (hereinafter referred to as the joining surfaces) of each. The thickness of the single crystal substrate 100 is, for example, 300 μm or more.

[0038] Next, as shown in Fig. 2(a), hydrogen ions or helium ions are ion-implanted into a position at a predetermined depth from the bonding surface of the single-crystalline substrate 100 to form an ion-implanted layer 101. The hydrogen ions or helium ions are, for example, 1×10 16 ~5×10 17 cm -2 or so.

[0039] As will be described later, since the film peeled from the single-crystalline substrate 100 using the ion-implanted layer 101 as a peeling surface becomes the single-crystalline film 10, the depth of the ion-implanted layer 101 from the bonding surface of the single-crystalline substrate 100 is determined according to the thickness of the target single-crystalline film 10. Since the maximum implantation depth of hydrogen ions and helium ions is 2 μm, the maximum film thickness of the single-crystalline film 10 is 2 μm.

[0040] Next, as shown in Fig. 2(b), the bonding surfaces of the single-crystalline substrate 100 and the support substrate 11 are altered to form amorphous layers 102 and 110, respectively.

[0041] When the bonding surfaces of the single-crystalline substrate 100 and the support substrate 11 are irradiated with a neutral atom beam of Ar using an FAB gun 50 or the like in a vacuum chamber, the surface is damaged and the crystalline state is altered to amorphous, and the amorphous layers 102 and 110 are formed.

[0042] In the process of forming the amorphous layers 102 and 110, the oxide film and the adsorption layer on the bonding surfaces of the single-crystalline substrate 100 and the support substrate 11 can be removed to expose and activate the bonding hands. Further, since this process is carried out in a vacuum, oxidation or the like does not occur on the activated surface, and the activated state can be maintained.

[0043] Next, as shown in Fig. 2(c), the amorphous layer 102 of the single-crystalline substrate 100 and the amorphous layer 110 of the support substrate 11 are brought into contact in a vacuum. After bringing the single-crystalline substrate 100 and the support substrate 11 into contact, they may be fixed by a jig or the like so as not to peel off.

[0044] Next, as shown in FIG. 2(d), a heat treatment is performed on the single crystal substrate 100 and the support substrate 11 in a state where the amorphous layer 102 and the amorphous layer 110 are in contact with each other, and the single crystal substrate 100 and the support substrate 11 are bonded together. This heat treatment is performed at a temperature of 300°C or higher and 600°C or lower for about several minutes. Further, this heat treatment may be performed under reduced pressure in a vacuum chamber, or may be performed in another furnace outside the vacuum chamber.

[0045] By this heat treatment, the amorphous layer 102 and the amorphous layer 110 are each recrystallized, and the single crystal substrate 100 and the support substrate 11 are firmly bonded by covalent bonding. At the same time, by this heat treatment, the single crystal substrate 100 can be broken by the ion implantation layer 101.

[0046] Next, as shown in FIG. 3(a), the single crystal substrate 100 is separated by the ion implantation layer 101 that has been broken. As a result, the layer bonded to the support substrate 11 on the support substrate 11 side of the ion implantation layer 101 of the single crystal substrate 100 remains on the support substrate 11. The portion remaining on the support substrate 11 of this single crystal substrate 100 becomes the single crystal film 10.

[0047] Note that the single crystal film 10 can be separated again from the remaining single crystal substrate 100 after separating the single crystal film 10 by repeating the same process using the ion cutting technique. Therefore, compared with the method of polishing the substrate to form a thin single crystal film, the raw material loss can be significantly reduced. All of the gallium oxide-based semiconductor scraped off by the polishing process will be discarded.

[0048] Before the step of forming the next amorphous film 120, a chemical mechanical polishing (CMP) treatment may be performed on the surface of the single crystal film 10. By performing the CMP treatment, the surface of the single crystal film 10 becomes flatter. As a result, the surface flatness of the amorphous film 120 and the epitaxial film 12 is also improved. Further, by performing the CMP treatment, the damage generated in the ion cutting process of the single crystal film 10 is removed. As a result, an improvement in the crystallinity of the epitaxial film 12 formed thereon is expected. The amount of material removed by the CMP treatment is typically about 10 to 300 nm.

[0049] Next, as shown in FIG. 3(b), an amorphous film 120 made of a gallium oxide-based semiconductor is formed on the single-crystalline film 10. The formation of the amorphous film 120 is carried out by vacuum evaporation or sputtering while maintaining the temperature of the support substrate 11 at 300° C. or lower.

[0050] Therefore, it is possible to suppress the generation of cracks in the single-crystalline film 10 due to the difference in the linear expansion coefficients between the single-crystalline film 10 made of the gallium oxide-based semiconductor and the support substrate 11 in the film formation process of the amorphous film 120.

[0051] Next, as shown in FIG. 3(c), the amorphous film 120 is crystallized to obtain an epitaxial film 12. The crystallization of the amorphous film 120 is carried out by laser annealing or the like while maintaining the temperature of the support substrate 11 at 300° C. or lower.

[0052] Therefore, it is possible to suppress the generation of cracks in the single-crystalline film 10 due to the difference in the linear expansion coefficients between the single-crystalline film 10 made of the gallium oxide-based semiconductor and the support substrate 11 in the process of crystallizing the amorphous film 120.

[0053] According to laser annealing, since it is possible to locally heat only the amorphous film 120 on the single-crystalline film 10, the amorphous film 120 can be crystallized while maintaining the temperature of the support substrate 11 at 300° C. or lower.

[0054] Laser annealing is carried out, for example, by an excimer laser annealing (ELA) method using a KrF excimer laser with a wavelength of 248 nm. While scanning by moving the laser irradiation spot on the surface of the amorphous film 120, the entire surface of the amorphous film 120 is irradiated with the laser. The laser irradiation is carried out, for example, in air at room temperature (approximately 20° C.).

[0055] In addition, any method other than laser annealing, such as heat treatment using the light of a lamp, may be used as long as the amorphous film 120 can be crystallized while maintaining the temperature of the support substrate 11 at 300°C or lower.

[0056] When an amorphous film made of a gallium oxide-based semiconductor is directly formed on a support substrate 11 made of a material different from the gallium oxide-based semiconductor and crystallized by laser annealing or the like, a polycrystalline film rather than a single crystal film is obtained. The polycrystalline film has more crystal defects than the single crystal film and cannot be used, for example, in the manufacture of vertical high-voltage power devices.

[0057] When an amorphous film made of a gallium oxide-based semiconductor is formed on a substrate made of a general gallium oxide-based semiconductor instead of the thin single crystal film 10 and crystallized by laser annealing or the like, the substrate must be thinned by polishing or the like thereafter, and the above-mentioned problems such as the occurrence of cracks in the wafer during processing occur.

[0058] (Configuration of semiconductor device) Figs. 4(a) and (b) are vertical cross-sectional views of a Schottky barrier diode 2 and a FinFET 3, which are examples of semiconductor devices manufactured using the stacked structure 1, respectively.

[0059] The Schottky barrier diode 2 shown in Fig. 4(a) is a vertical semiconductor device and includes a stacked structure 1 composed of a single crystal film 10, a support substrate 11, and an epitaxial film 12, an anode electrode 21 connected to the epitaxial film 12, and a cathode electrode 22 connected to the support substrate 11.

[0060] The single crystal film 10 has a thickness of, for example, 0.1 to 2 μm and contains donor impurities with a concentration of 1×10 18 ~1×10 20 cm -3 As described above, since the single crystal film 10 is separated from a substrate made of a gallium oxide-based semiconductor containing donor impurities using the ion cut technique, 1×10 18 cm-3 It contains donor impurities at the above concentrations.

[0061] The higher the donor impurity concentration in the single crystal film 10, the lower the conduction loss. However, if the addition amount is too large, crystal defects may occur. Therefore, it is preferably set within the range of 3×10 18 ~5×10 20 cm -3 .

[0062] The support substrate 11 has a thickness of, for example, 50 to 1000 μm.

[0063] The epitaxial film 12 has a thickness of, for example, 2 to 100 μm and contains donor impurities at a concentration of 1×10 14 ~1×10 17 cm -3 . If the donor concentration of the epitaxial film 12 is within the range not exceeding 1×10 17 cm -3 , donor impurities such as Si and Sn may be intentionally added to the epitaxial film 12.

[0064] The anode electrode 21 has a laminated structure of, for example, Ni / Ti / Au and forms a Schottky contact with the epitaxial film 12. In this case, the thicknesses of the Ni layer, Ti layer, and Au layer are, for example, 15 nm, 5 nm, and 200 nm, respectively.

[0065] The cathode electrode 22 has a laminated structure of, for example, Ti / Au and forms an ohmic contact with the support substrate 11. In this case, the thicknesses of the Ti layer and Au layer are, for example, 50 nm and 200 nm, respectively.

[0066] In the Schottky barrier diode 2, by applying a forward voltage (the anode electrode 21 side is at a positive potential) between the anode electrode 21 and the cathode electrode 22, the energy barrier at the interface between the anode electrode 21 and the epitaxial film 12 as seen from the epitaxial film 12 is reduced, and current flows from the anode electrode 21 to the cathode electrode 22. On the other hand, when a reverse voltage (the anode electrode 21 side is at a negative potential) is applied between the anode electrode 21 and the cathode electrode 22, the flow of current is blocked by the Schottky barrier.

[0067] The FinFET (Fin Field-Effect Transistor) 3 shown in FIG. 4(b) is a vertical field-effect transistor, and includes a stacked structure 1 composed of a single-crystalline film 10, a support substrate 11, and an epitaxial film 12; a channel layer 31 and a contact layer 32 stacked on the epitaxial film 12; a gate electrode 34 embedded in a trench 33 provided in the channel layer 31 and the contact layer 32 and covered with a gate insulating film 35; a source electrode 36 connected to the contact layer 32; and a drain electrode 37 connected to the support substrate 11.

[0068] The single-crystalline film 10 has a thickness of, for example, 0.1 to 2 μm and contains donor impurities with a concentration of 1×10 18 ~1×10 20 cm -3 . As described above, since the single-crystalline film 10 is divided from a substrate made of a gallium oxide-based semiconductor containing donor impurities using the ion-cut technique, it contains donor impurities with a concentration of 1×10 18 cm -3 or more without intentional addition.

[0069] The higher the donor impurity concentration of the single-crystalline film 10, the lower the conduction loss. However, if the addition amount is large, crystal defects may occur. Therefore, it is preferably set within the range of 5×10 18 ~5×10 19 cm -3 .

[0070] The support substrate 11 has a thickness of, for example, 50 to 1000 μm.

[0071] The epitaxial film 12 has a thickness of, for example, 2 to 100 μm and contains donor impurities at a concentration of 1×10 14 ~1×10 17 cm -3 . If the donor concentration of the epitaxial film 12 does not exceed 1×10 17 cm -3 , donor impurities such as Si and Sn may be intentionally added to the epitaxial film 12.

[0072] The channel layer 31 and the contact layer 32 are made of a gallium oxide-based semiconductor and are formed on the epitaxial film 12 by the same solid-phase epitaxial crystal growth as the epitaxial film 12. The channel layer 31 and the contact layer 32 have a trench 33 that opens on the upper surface of the contact layer 32.

[0073] The channel layer 31 is a layer in which a gate electrode 34 is embedded and a channel is formed when a gate voltage is applied. The epitaxial film 12 under the channel layer 31 functions as a drift layer for maintaining breakdown voltage. The contact layer 32 is used to make an ohmic connection between the source electrode 36 and the semiconductor layer.

[0074] The channel layer 31 has a thickness of, for example, 0.1 to 5 μm and contains donor impurities at a concentration of 2×10 15 ~1×10 17 cm -3 . The contact layer 32 has a thickness of, for example, 10 nm to 5 μm and contains donor impurities at a concentration of 1×10 18 ~1×10 21 cm -3 .

[0075] The gate electrode 34 is made of a conductor, that is, a metal such as Ni or a semiconductor containing a high concentration of donors. The gate insulating film 35 has, for example, a portion 35a covering the side surface and the bottom surface of the gate electrode 34 and a portion 35b covering the upper surface of the gate electrode 34. The portion 35a and the portion 35b of the gate insulating film 35 are made of, for example, HfO2 and SiO2, respectively. The thicknesses of the portion 35a and the portion 35b of the gate insulating film 35 are, for example, 10 nm or more and 100 nm or less, and 50 nm or more and 2000 nm or less, respectively.

[0076] The source electrode 36 and the drain electrode 37 are ohmically connected to the contact layer 32 and the support substrate 11, respectively. The source electrode 36 and the drain electrode 37 have, for example, a Ti / Au laminated structure.

[0077] The FinFET 3 may be normally-off type or normally-on type, but when used as a power device, it is usually manufactured as a normally-off type from the viewpoint of safety. This is to prevent the source electrode 36 and the drain electrode 37 from conducting during a power failure.

[0078] In the normally-off type FinFET 3, by applying a voltage equal to or higher than the threshold voltage between the gate electrode 34 and the source electrode 36, a channel is formed in the fin-shaped region between the adjacent trenches 33 of the channel layer 31 and the contact layer 32, and current flows from the drain electrode 37 to the source electrode 36.

[0079] Semiconductor devices manufactured using a stacked structure 1 such as a Schottky barrier diode 2 or a FinFET 3 are obtained, for example, by forming a plurality of device structures in an array on a wafer-shaped stacked structure 1 and then singulating this by dicing. The device structures of semiconductor devices such as Schottky barrier diodes 2 and FinFETs 3 can all be formed on the stacked structure 1 by known methods. Note that the stacked structure 1 is not suitable for the manufacture of elements that require an impurity implantation layer by ion implantation. This is because cracks occur in the single crystal film 10 due to the difference in the linear expansion coefficients of the single crystal film 10 and the support substrate 11 during the heat treatment accompanying ion implantation.

[0080] (Effects of the Embodiment) In the stacked structure 1 according to the embodiment of the present invention, and semiconductor devices such as a Schottky barrier diode 2 and a FinFET 3 using the same, a single crystal film 10 and an epitaxial film 12 are used as semiconductor layers made of a gallium-based semiconductor. Since the total value of the thicknesses of the single crystal film 10 and the epitaxial film 12 is significantly smaller than the thickness (several hundred μm) of a substrate made of a general gallium oxide-based semiconductor, compared with a stacked structure and a semiconductor device using the substrate as it is, the amount of heat generated when a current is passed can be suppressed low, and the heat dissipation performance can be improved.

[0081] Further, according to the embodiment of the present invention, by using an ion cut technique, a thin single crystal film 10 can be formed while suppressing the generation of cracks. Further, by forming the epitaxial film 12 by solid phase epitaxial crystal growth using laser annealing, the generation of cracks in the single crystal film 10 due to the difference in the linear expansion coefficients of the single crystal film 10 and the support substrate 11 can be suppressed.

[0082] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention. Further, the components of the above embodiments can be arbitrarily combined without departing from the gist of the invention.

[0083] In addition, the embodiments described above do not limit the invention according to the claims. It should also be noted that not all combinations of features described in the embodiments are essential means for solving the problems of the invention.

Description of Reference Numerals

[0084] 1... Stacked structure, 10... Single crystal film, 11... Support substrate, 12... Epitaxial film, 2... Schottky barrier diode, 3... FinFET

Claims

1. A step of forming a single crystal film made of a gallium oxide-based semiconductor on a support substrate made of a material having a higher thermal conductivity than the gallium oxide-based semiconductor using an ion cutting technique; A step of forming an amorphous film made of a gallium oxide-based semiconductor on the single crystal film; A step of crystallizing the amorphous film; comprising: The step of forming the amorphous film and the step of crystallizing the amorphous film are carried out while maintaining the temperature of the support substrate at 300 °C or lower. A method for manufacturing a laminated structure.

2. In the step of crystallizing the amorphous film, the amorphous film is crystallized by performing laser annealing on the amorphous film. The method for manufacturing a laminated structure according to Claim 1.

3. A support substrate made of a material having a higher thermal conductivity than the gallium oxide-based semiconductor; A single crystal film made of a gallium oxide-based semiconductor, which is provided on the support substrate, has a thickness of 2 μm or less, a donor impurity concentration of 1 × 10 １８ cm －３ or more, and does not contain cracks, and An epitaxial film made of a gallium oxide-based semiconductor, provided on the single-crystal film and having a donor impurity concentration of 1×10 １７ cm －３ or less, and comprising: A laminated structure.

4. The main surface of the single crystal film is a (100) plane. The laminated structure according to Claim 3.

5. The support substrate is made of Si, SiC, W, or Mo. The laminated structure according to Claim 4.

6. The main surface of the single crystal film is a plane other than the (100) plane, (-201) plane, and (101) plane. The laminated structure according to Claim 3.

7. The main surface of the single crystal film is a (010) plane or a (-102) plane. The laminated structure according to Claim 6.

8. Comprising the laminated structure according to any one of Claims 3 to 7. A semiconductor device.

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