Manufacturing method of silicon substrate for quantum computer, silicon substrate for quantum computer and semiconductor device

Abstract

To provide a silicon substrate for a quantum computer which can suppress the influence of 29Si and suppress the influence of a nuclear spin, and a method for manufacturing the same.SOLUTION: A method for manufacturing a silicon substrate for a quantum computer includes the steps of: forming an Si epitaxial layer on a silicon substrate as a silicon-based raw material gas by performing epitaxial growth using an Si source gas in which the total content of 28Si and 30Si in the whole silicon in the silicon-based raw material gas is 99.9% or more; forming an δ-doped layer of oxygen (O) by oxidizing a surface of the Si epitaxial layer; and forming the Si epitaxial layer on the δ-doped layer by performing epitaxial growth using the Si source gas in which the total content of 28Si and 30Si in the whole silicon in the silicon-based raw material gas is 99.9% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a silicon substrate for a quantum computer, a silicon substrate for a quantum computer, and a semiconductor device. [Background technology]

[0002] Quantum computers, which utilize quantum effects such as superposition and entanglement, are expected to be able to solve calculations that conventional computers cannot solve in a realistic amount of time. The elements used in quantum computers are also mounted on semiconductor substrates such as silicon substrates.

[0003] There are several methods for using elements for quantum computing, but the main ones are those that use the Josephson effect using superconductors, and those that use electron spin resonance (ESR) to convert quantum effects into electrical signals.

[0004] In a device using electron spin on a silicon substrate, the quantum effect is read out by irradiating electron spin placed in a magnetic field with microwaves and sweeping the frequency to cause resonance (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-025657 [Patent Document 2] Patent Publication No. 2021-111696 Summary of the Invention [Problem to be solved by the invention]

[0006] When using electron spin in this way, if there are unnecessary spin components in the vicinity, the electron spin energy is split by the Zeeman effect, and quantum effects cannot be used in calculations.29 Si content reduced as much as possible 28 It is necessary to form a Si-rich Si layer.

[0007] For this purpose, isotope enrichment was carried out 28 Using SiH4 gas 28 A silicon substrate with a Si epitaxial layer is used. In addition, in order to create a single-electron layer (the presence of multiple electrons makes calculations difficult due to spin interactions between electrons), electron confinement (single-electron transistor) is required.

[0008] To achieve this, a fin structure is often fabricated to confine electrons at the tip of the fin, or an SOI (Silicon On Insulator) structure is often used. The fin structure has the advantage of being formed using only silicon, but it is difficult to control the surface state of the silicon surface. On the other hand, with an SOI structure, the influence of the silicon and oxide film interface is small, but it is difficult to form an insulating layer. That is, 28 Even if Si is oxidized, the diffusion of silicon during the heat treatment causes the formation of a 29 The influence of Si occurs.

[0009] In addition, the same problem occurs during the heat treatment during the formation of SOI using conventional bonding methods. 28 Diffusion of Si occurs, 28 The isotope effect of Si cannot be fully utilized.

[0010] The present invention has been made to solve the above problems, 29 The present invention provides a silicon substrate for quantum computers that can suppress the influence of Si and the influence of nuclear spin, and a method for manufacturing the same. [Means for solving the problem]

[0011] The present invention has been made to achieve the above object, and is a method for manufacturing a silicon substrate for a quantum computer, the method comprising: forming a silicon substrate on a silicon substrate using a silicon-based source gas; 28Si and 30 The present invention includes a step of forming a Si epitaxial layer by epitaxial growth using a Si source gas having a total Si content of 99.9% or more, a step of oxidizing the surface of the Si epitaxial layer to form a δ-doped layer of oxygen (O), and a step of depositing a δ-doped layer on the δ-doped layer containing 99.9% or more of the total silicon contained in the silicon-based source gas. 28 Si and 30 and forming a Si epitaxial layer by performing epitaxial growth using a Si source gas having a total Si content of 99.9% or more.

[0012] According to this method for manufacturing a silicon substrate for a quantum computer, it is possible to manufacture a silicon substrate for a quantum computer that can suppress the influence of nuclear spin, and it is possible to manufacture a silicon substrate that fully exhibits the isotope effect suitable for a quantum computer and on which single-electron transistors can be easily formed.

[0013] In this case, the method for manufacturing a silicon substrate for a quantum computer can be one in which monosilane gas is used as the Si source gas.

[0014] This allows silicon substrates suitable for quantum computers to be manufactured at lower temperatures.

[0015] In this case, the process of forming the oxygen (O) delta-doped layer and the process of forming the Si epitaxial layer on the delta-doped layer can be repeated to form multiple pairs of the delta-doped layer and the Si epitaxial layer on the delta-doped layer, resulting in a method for manufacturing a silicon substrate for a quantum computer.

[0016] This makes it possible to manufacture silicon substrates that are more suitable for quantum computers.

[0017] In this case, the method for manufacturing a silicon substrate for a quantum computer can be such that the thickness of the outermost Si epitaxial layer of the silicon substrate for a quantum computer is thicker than the thickness of Si epitaxial layers other than the outermost Si epitaxial layer.

[0018] This makes it possible to manufacture silicon substrates that are more suitable for quantum computers.

[0019] In this case, by heat treating the silicon substrate for a quantum computer, the plurality of δ-doped layers can be integrated to form an SOI structure, thereby forming a method for manufacturing a silicon substrate for a quantum computer.

[0020] This makes it possible to manufacture a silicon substrate having an SOI structure suitable for quantum computers.

[0021] In this case, the method for manufacturing a silicon substrate for a quantum computer can use a silicon substrate having a resistivity of 1000 Ω·cm or more.

[0022] This makes it possible to manufacture a silicon substrate for a quantum computer that can stably extract signals obtained by spin resonance without distortion.

[0023] The present invention also provides a method for manufacturing a silicon substrate for a quantum computer, comprising: 28 By performing epitaxial growth using Si source gas, 28 forming a Si epitaxial layer; 28 A step of oxidizing the surface of the Si epitaxial layer to form a δ-doped layer of oxygen (O); and 28 By performing epitaxial growth using Si source gas, 28 and forming a silicon epitaxial layer.

[0024] According to this method for manufacturing a silicon substrate for a quantum computer, it is possible to manufacture a silicon substrate for a quantum computer that can suppress the influence of nuclear spin, and it is possible to manufacture a silicon substrate that fully exhibits the isotope effect suitable for a quantum computer and on which single-electron transistors can be easily formed.

[0025] At this time, the above 28 As a Si source gas 28 The method can be a method for manufacturing a silicon substrate for a quantum computer using Si monosilane gas.

[0026] This allows silicon substrates suitable for quantum computers to be manufactured at lower temperatures.

[0027] At this time, the step of forming the δ-doped layer of oxygen (O) and the step of forming the δ-doped layer on the δ-doped layer 28 The step of forming a Si epitaxial layer is repeated, and the δ-doped layer and the step of forming a Si epitaxial layer on the δ-doped layer are 28 The method can be a method for manufacturing a silicon substrate for a quantum computer in which multiple pairs of Si epitaxial layers are formed.

[0028] This makes it possible to manufacture silicon substrates that are more suitable for quantum computers.

[0029] At this time, the outermost layer of the silicon substrate for quantum computers 28 The thickness of the Si epitaxial layer is 28 Other than the Si epitaxial layer 28 The method for manufacturing a silicon substrate for a quantum computer can be made thicker than the thickness of a Si epitaxial layer.

[0030] This makes it possible to manufacture silicon substrates that are more suitable for quantum computers.

[0031] In this case, the method for manufacturing a silicon substrate for a quantum computer can be such that the plurality of δ-doped layers are integrated by heat treating the silicon substrate for a quantum computer to form an SOI structure.

[0032] This makes it possible to manufacture a silicon substrate having an SOI structure suitable for quantum computers.

[0033] In this case, the method for manufacturing a silicon substrate for a quantum computer can use a silicon substrate having a resistivity of 1000 Ω·cm or more.

[0034] This makes it possible to manufacture a silicon substrate for a quantum computer that can stably extract signals obtained by spin resonance without distortion.

[0035] The present invention has also been made to achieve the above object, and provides a silicon substrate for a quantum computer, comprising a silicon substrate and an epitaxial layer on the silicon substrate, wherein the silicon in the epitaxial layer is occupied by 28 Si and 30 A Si epitaxial layer having a composition in which the total content of Si is 99.9% or more, and an SiO2 layer on the Si epitaxial layer, 28 Si and 30 An SiO2 layer having a composition in which the total content of Si is 99.9% or more, and an epitaxial layer on the SiO2 layer, 28 Si and 30 and a Si epitaxial layer having a composition in which the total Si content is 99.9% or more.

[0036] Such a silicon substrate for a quantum computer can be used as a silicon substrate for a quantum computer that can suppress the influence of nuclear spin, fully exhibits the isotope effect suitable for a quantum computer, and is a silicon substrate on which single-electron transistors can be easily formed.

[0037] In this case, the silicon substrate for quantum computers can be one in which the SiO2 layer is a δ-doped layer of oxygen (O).

[0038] This results in a silicon substrate with a δ-doped layer suitable for quantum computing.

[0039] In this case, the silicon substrate for quantum computers can be one in which the SiO2 layer is a buried oxide film (BOX) layer in an SOI structure.

[0040] This results in a silicon substrate with an SOI structure suitable for quantum computers.

[0041] In this case, the semiconductor device can be one that includes an element on a silicon substrate for a quantum computer.

[0042] This results in a semiconductor device in which the influence of nuclear spins is suppressed.

[0043] The present invention also provides a silicon substrate for a quantum computer, comprising: a silicon substrate; 28 A Si epitaxial layer and the 28 on the Si epitaxial layer 28 The SiO2 layer and the 28 On top of the SiO2 layer 28 A silicon substrate for quantum computers is provided, which comprises a Si epitaxial layer.

[0044] Such a silicon substrate for a quantum computer can be used as a silicon substrate for a quantum computer that can suppress the influence of nuclear spin, fully exhibits the isotope effect suitable for a quantum computer, and is a silicon substrate on which single-electron transistors can be easily formed.

[0045] At this time, the above 28 The silicon substrate for quantum computers can be formed by using an SiO2 layer as a δ-doped layer of oxygen (O).

[0046] This results in a silicon substrate with a δ-doped layer suitable for quantum computing.

[0047] At this time, the above 28 The SiO2 layer can be a buried oxide film (BOX) layer in an SOI structure, making it a silicon substrate for quantum computers.

[0048] This results in a silicon substrate with an SOI structure suitable for quantum computers.

[0049] In this case, the semiconductor device can be characterized as having an element on a silicon substrate for a quantum computer.

[0050] This results in a semiconductor device in which the influence of nuclear spins is suppressed. [Effects of the Invention]

[0051] As described above, the method for manufacturing a silicon substrate for a quantum computer of the present invention makes it possible to manufacture a silicon substrate for a quantum computer that can suppress the influence of nuclear spin, and to manufacture a silicon substrate that fully exhibits the isotope effect suitable for a quantum computer and on which single-electron transistors can be easily formed. The silicon substrate for a quantum computer of the present invention makes it possible to manufacture a silicon substrate for a quantum computer that can suppress the influence of nuclear spin, and to manufacture a silicon substrate that fully exhibits the isotope effect suitable for a quantum computer and on which single-electron transistors can be easily formed. [Brief explanation of the drawings]

[0052] [Figure 1] 1 is a schematic diagram illustrating an example of the structure of a silicon substrate for a quantum computer according to the present invention. [Figure 2] 10A and 10B are schematic diagrams illustrating another example of the structure of a silicon substrate for a quantum computer according to the present invention. [Figure 3] 1A and 1B are schematic diagrams illustrating the flow of a method for manufacturing a silicon substrate for a quantum computer according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0053] The present invention will be described in detail below, but the present invention is not limited thereto.

[0054] As mentioned above, 29 There has been a demand for a silicon substrate for quantum computers that can suppress the influence of Si and the influence of nuclear spin, as well as a method for manufacturing such a substrate.

[0055] As a result of intensive research into the above-mentioned problems, the present inventors have discovered a method for manufacturing a silicon substrate for a quantum computer, which comprises: supplying a silicon-based source gas onto a silicon substrate; 28 Si and 30 The present invention includes a step of forming a Si epitaxial layer by epitaxial growth using a Si source gas having a total Si content of 99.9% or more, a step of oxidizing the surface of the Si epitaxial layer to form a δ-doped layer of oxygen (O), and a step of depositing a δ-doped layer on the δ-doped layer containing 99.9% or more of the total silicon contained in the silicon-based source gas. 28 Si and 30 The present inventors have found that a method for manufacturing a silicon substrate for a quantum computer, which includes a step of forming a Si epitaxial layer by performing epitaxial growth using a Si source gas having a total Si content of 99.9% or more, can manufacture a silicon substrate for a quantum computer that can suppress the influence of nuclear spin, and can manufacture a silicon substrate that fully exhibits the isotope effect suitable for a quantum computer and on which single-electron transistors can be easily formed, and have completed the present invention.

[0056] The present inventors have also discovered a method for manufacturing a silicon substrate for a quantum computer, which comprises: 28 By performing epitaxial growth using Si source gas, 28 forming a Si epitaxial layer; 28A step of oxidizing the surface of the Si epitaxial layer to form a δ-doped layer of oxygen (O); and 28 By performing epitaxial growth using Si source gas, 28 The present inventors have found that a silicon substrate for a quantum computer that can suppress the influence of nuclear spin can be manufactured by a method for manufacturing a silicon substrate for a quantum computer, which includes a step of forming a Si epitaxial layer, and that a silicon substrate that fully exhibits the isotope effect suitable for a quantum computer and on which single-electron transistors can be easily formed can be manufactured, thereby completing the present invention.

[0057] Furthermore, as a result of intensive research into the above-mentioned problems, the present inventors have discovered a silicon substrate for a quantum computer, comprising a silicon substrate and an epitaxial layer on the silicon substrate, wherein the silicon in the epitaxial layer accounts for 28 Si and 30 A Si epitaxial layer having a composition in which the total content of Si is 99.9% or more, and an SiO2 layer on the Si epitaxial layer, 28 Si and 30 An SiO2 layer having a composition in which the total content of Si is 99.9% or more, and an epitaxial layer on the SiO2 layer, 28 Si and 30 The inventors have found that a silicon substrate for a quantum computer having a Si epitaxial layer with a composition in which the total Si content is 99.9% or more can be used to form a silicon substrate for a quantum computer that can suppress the influence of nuclear spin, that fully exhibits the isotope effect suitable for a quantum computer, and that can easily form a single-electron transistor, and have completed the present invention.

[0058] The present inventors have also discovered a silicon substrate for a quantum computer, comprising: a silicon substrate; 28 A Si epitaxial layer and the 28 on the Si epitaxial layer 28 The SiO2 layer and the 28 On top of the SiO2 layer28 The inventors have found that a silicon substrate for a quantum computer having a Si epitaxial layer can be used to suppress the influence of nuclear spin, and can provide a silicon substrate that fully exhibits the isotope effect suitable for a quantum computer and on which single-electron transistors can be easily formed, thereby completing the present invention.

[0059] The following description will be made with reference to the drawings.

[0060] below," 28 The definition of the term will be explained using "Si" as an example, but other isotopes ( 30 Similar expressions may also be used for other materials (e.g., Si).

[0061] In this specification, the silicon-based source gas " 28 "Si source gas" refers to the gas containing silicon that accounts for 28 It means a gas having a composition in which the Si content is 99.9% or more. 28 Si monosilane gas (" 28 SiH4) is the silicon content of monosilane (SiH4) gas. 28 It refers to monosilane gas with a composition containing 99.9% or more Si. Stable isotopes of silicon include: 28 Si, 29 Si, 30 There are three types of Si, and their natural abundance ratios are 92.23%, 4.67%, and 3.1%. For example, by centrifuging silicon-containing gas (silane-based gas) consisting of natural Si isotope composition, 28 Si source gas can be produced. 30 Si source gas and "silicon source gas" 28 Si and 30 A "Si source gas" having a total Si content of 99.9% or more can be produced in the same manner.

[0062] In this specification, " 28 The "Si epitaxial layer" refers to the area of the silicon in the epitaxial layer. 28It means an epitaxial layer having a composition in which the Si content is 99.9% or more. For example, 28 It can be obtained by epitaxial growth using a Si source gas.

[0063] In this specification, " 28 "SiO2" refers to the percentage of SiO2 in the total silicon. 28 It means SiO2 having a composition with a Si content of 99.9% or more. For example, 28 It can be obtained by oxidizing a Si epitaxial layer.

[0064] In this specification, the term "δ-doped layer" refers to a layer in which an element different from the base material is introduced to a monoatomic layer. For example, a δ-doped layer of oxygen (O) is formed by doping a monoatomic layer (1.36 × 10 15 atoms / cm 2 ) is included. As for the δ-doping method, for example, there is a method described in Patent Document 2.

[0065] [Silicon substrates for quantum computers] (First embodiment) As a result of extensive investigation into the above-mentioned problems, the present inventors have discovered a method for manufacturing a silicon substrate and an epitaxial layer on the silicon substrate, the method comprising: 28 Si and 30 A Si epitaxial layer having a composition in which the total content of Si is 99.9% or more, and an SiO2 layer on the Si epitaxial layer, 28 Si and 30 An SiO2 layer having a composition in which the total content of Si is 99.9% or more, and an epitaxial layer on the SiO2 layer, 28 Si and 30 and a silicon epitaxial layer having a composition in which the total content of silicon is 99.9% or more. 29 We found that this could be used as a silicon substrate for quantum computers, which can suppress the effects of Si and nuclear spin.

[0066] The Si epitaxial layer in the silicon substrate for quantum computers according to the present invention is 28 Si and 30 It is sufficient that the total Si content is 99.9% or more. 28 Si and 30 The epitaxial layer does not necessarily contain both silicon and silicon. 28 When the Si content is 99.9% or more, 30 The Si content may be 99.9% or more.

[0067] In this case, the SiO2 layer is preferably a δ-doped layer of oxygen (O). Such a silicon substrate for a quantum computer is a silicon substrate having a δ-doped layer suitable for a quantum computer.

[0068] Furthermore, it is preferable that the SiO2 layer is a buried oxide film (BOX) layer in an SOI structure. Such a silicon substrate for a quantum computer is a silicon substrate having an SOI structure suitable for quantum computers.

[0069] Furthermore, it is preferable that the element is provided on the silicon substrate for quantum computers. Such a semiconductor device is a semiconductor device in which the influence of nuclear spin is suppressed.

[0070] Regarding a more detailed embodiment, in the silicon substrate for a quantum computer according to the first embodiment, 28 This will be explained in the second embodiment below, which corresponds to a composition in which the Si content is 99.9% or more.

[0071] (Second embodiment) The present inventors also discovered a silicon substrate and a 28 a Si epitaxial layer; 28 on the Si epitaxial layer 28 an SiO2 layer;28 On top of the SiO2 layer 28 and a Si epitaxial layer, 29 As described above, the silicon substrate for a quantum computer according to the second embodiment of the present invention is a silicon substrate for a quantum computer according to the first embodiment, in which the proportion of the total silicon in the epitaxial layer is reduced by 100%. 28 This corresponds to a composition with a Si content of 99.9% or more.

[0072] 1 shows an example of the structure of a silicon substrate for a quantum computer according to the present invention. The silicon substrate for a quantum computer according to the second embodiment comprises a silicon substrate 1 and a 28 a Si epitaxial layer 2; 28 on the Si epitaxial layer 2 28 an SiO2 layer 3; 28 On top of the SiO2 layer 3 28 The semiconductor device is provided with a Si epitaxial layer 2.

[0073] The silicon substrate for quantum computers shown in Figure 1 28 The SiO2 layer 3 can be a δ-doped layer of oxygen (O). FIG. 2 shows a δ-doped layer 3A of oxygen (O) with a plurality of layers (a δ-doped layer 3A of oxygen (O) and adjacent layers 28 1 shows an example in which a plurality of Si epitaxial layers 2 are provided, but the oxygen (O) δ-doped layer is 28 It may be a single layer (one layer) like the SiO2 layer 3.

[0074] In addition, in the silicon substrate for quantum computers shown in Figure 1, 28 The SiO2 layer 3 can be a buried oxide (BOX) layer in an SOI structure. In this case, the buried oxide (BOX) layer ( 28 The thickness of the SiO2 layer can be set to about 0.01 to 1 μm.

[0075] The silicon substrate 1 used in the silicon substrate for quantum computers according to the present invention will be described. The silicon substrate 1 is not particularly limited. 28 Any substrate capable of depositing a Si epitaxial layer is sufficient. There are no particular restrictions on the diameter, thickness, dopants, etc. In quantum computers, microwaves are used to read the spin state of electrons and other elements that exhibit quantized behavior. For this reason, it is preferable to use a high-resistivity substrate to reduce signal distortion in the electrical transmission path. In particular, a substrate with a resistivity of approximately 1000 Ω·cm or higher is preferable. This results in a silicon substrate for quantum computers that can stably extract signals obtained by spin resonance without distortion.

[0076] A semiconductor device in which elements are provided on the silicon substrate for quantum computers according to the present invention described above is a semiconductor device in which the influence of nuclear spins is suppressed.

[0077] [Method of manufacturing silicon substrates for quantum computers] (Third embodiment) Next, a method for manufacturing a silicon substrate for a quantum computer according to a third embodiment of the present invention will be described. The method for manufacturing a silicon substrate for a quantum computer according to the present invention comprises: forming a silicon-based source gas on a silicon substrate; 28 Si and 30 The method includes the steps of forming a Si epitaxial layer by epitaxial growth using a Si source gas having a total Si content of 99.9% or more, oxidizing the surface of the Si epitaxial layer to form a δ-doped layer of oxygen (O), and depositing a δ-doped layer on the δ-doped layer containing 99.9% or more of the total silicon contained in the silicon-based source gas. 28 Si and 30 and forming a Si epitaxial layer by epitaxial growth using a Si source gas having a total Si content of 99.9% or more.

[0078] The silicon-based source gas in the method for manufacturing a silicon substrate for a quantum computer according to the third embodiment of the present invention is a silicon-based source gas containing silicon atoms. 28 Si and 30 It is sufficient that the total Si content of the Si source gas is 99.9% or more. 28 Si and 30 The silicon content of the silicon-based source gas does not necessarily have to be both SiO2 and Si. 28 When the Si content is 99.9% or more, 30 This includes cases where the Si content is 99.9% or more.

[0079] It is preferable to use monosilane gas as the Si source gas, which allows silicon substrates suitable for quantum computers to be manufactured at lower temperatures.

[0080] It is preferable to repeat the steps of forming an oxygen (O) delta-doped layer and forming a Si epitaxial layer on the delta-doped layer to form multiple pairs of delta-doped layers and Si epitaxial layers on the delta-doped layers, thereby manufacturing a silicon substrate more suitable for quantum computers.

[0081] Furthermore, it is preferable that the thickness of the outermost Si epitaxial layer of the silicon substrate for quantum computers is thicker than the thickness of the Si epitaxial layers other than the outermost Si epitaxial layer, thereby enabling the manufacture of a silicon substrate that is even more suitable for quantum computers.

[0082] In this case, it is preferable to use a silicon substrate with a resistivity of 1000 Ω·cm or more, which makes it possible to manufacture a silicon substrate for quantum computers that can stably extract signals obtained by spin resonance without distortion.

[0083] As for a more detailed embodiment, in a method for manufacturing a silicon substrate for a quantum computer according to a third embodiment, 28This will be explained in the following fourth embodiment, which corresponds to a composition in which the Si content is 99.9% or more.

[0084] (Fourth embodiment) Furthermore, in a method for manufacturing a silicon substrate for a quantum computer according to a fourth embodiment of the present invention, a silicon-based raw material gas is applied to a silicon substrate. 28 By performing epitaxial growth using Si source gas, 28 forming a Si epitaxial layer; 28 A step of oxidizing the surface of the Si epitaxial layer to form a δ-doped layer of oxygen (O); and 28 By performing epitaxial growth using Si source gas, 28 As described above, the method for manufacturing a silicon substrate for a quantum computer according to the fourth embodiment of the present invention is the same as the method for manufacturing a silicon substrate for a quantum computer according to the third embodiment, except that the amount of silicon contained in the silicon-based source gas is reduced by 100%. 28 This corresponds to a composition with a Si content of 99.9% or more. This will be explained in detail below.

[0085] First, a silicon substrate 1 is prepared as shown in FIG. 3(A).

[0086] Next, as shown in FIG. 3(B), epitaxial growth (deposition) is performed on the silicon substrate 1. 28 A Si epitaxial layer 2 is formed. In this case, the CVD method can form an epitaxial layer with good crystallinity. In the epitaxial growth, silicon-based raw material gas is, for example, silicon obtained by isotope enrichment. 28 A Si source gas is used. 28 As a Si source gas, 28 Si monosilane gas ( 28 It is preferable to use SiH4), which allows epitaxial growth at a lower temperature.

[0087] Also, at this time 28The thickness of the Si epitaxial layer 2 is not particularly limited, but a thickness of about 0.01 to 1 μm is sufficient. This is reasonable considering that, as can be seen from the example of Si NMR, the influence of adjacent electron spin-nuclear spin interactions is strongest and the influence decreases when the distance is several atoms.

[0088] Next, as shown in Figure 3(C), an oxide film for electron confinement is formed. 28 An SiO2 layer is formed. In the example of Fig. 3, an oxygen (O) delta doping method is used to form an oxygen (O) delta doped layer 3A.

[0089] Using the δ-doping method, 28 By oxidizing the surface of the Si epitaxial layer to form a δ-doped layer 3A of oxygen (O), the silicon of the insulating film is converted into silicon oxide ( 28 SiO2), which makes it possible to avoid the effects of electron-nuclear spin interactions.

[0090] Next, as shown in Figure 3(D), on top of this δ-doped layer 28 The Si epitaxial layer 2 is deposited. 28 As in the case of the Si epitaxial layer 2, the CVD method can form an epitaxial layer with good crystallinity. 28 SiH4 etc. 28 The thickness of the epitaxial layer is 1 / 2 of the first layer. 28 It does not have to be as thick as the Si epitaxial layer 2, and can be adjusted as needed to allow electron confinement. For example, the thickness can be set to about 0.001 to 0.5 μm.

[0091] Although it is possible to fabricate a device with this structure as it is, the insulating layer formed in the process up to this point is called δ-doped, and oxygen is only inserted at the atomic level, so there is a possibility that the insulation is insufficient. Therefore, we will introduce the process of forming the oxygen (O) δ-doped layer 3A in Figure 3(C) and the process of forming the δ-doped layer on top of the δ-doped layer in Figure 3(D). 28The process of forming the Si epitaxial layer 2 is repeated, and as shown in FIG. 3(E), a δ-doped layer 3A of oxygen (O) and a layer on the δ-doped layer 28 It is also preferable to form multiple pairs of Si epitaxial layers, which makes the silicon substrate even more suitable for quantum computers.

[0092] As shown in Figure 3(F), multiple delta-doped layers can be further oxidized and integrated by heat treatment to form a thick insulating layer. The resulting thick insulating layer can form an SOI structure that functions as a buried oxide (BOX) layer 3B. This makes the silicon substrate even more suitable for quantum computers.

[0093] On top of the oxygen (O) δ-doped layer 3A and δ-doped layer 28 The number of times the Si epitaxial layer 2 is stacked can be changed as needed depending on the characteristics and design of the device. 28 The Si epitaxial layer 2 is the outermost layer. 28 Other than the Si epitaxial layer 28 It is preferable to set the thickness to be thicker than the Si epitaxial layer. For example, the thickness can be set to about 0.002 to 1 μm. In this way, even if oxidation is performed, the outermost layer 28 The Si epitaxial layer 2 never disappears.

[0094] Like this 28 Si-rich silicon layer ( 28 By using a silicon epitaxial layer, the insulating layer 28 Si-rich oxide film ( 28 It is possible to form a thin SiO2 layer. [Example]

[0095] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0096] (Example) A boron-doped silicon substrate with a diameter of 300 mm (resistivity: 1000 Ω·cm) was prepared. 28 Silicon epitaxial growth was carried out using SiH4 (isotope 99.94%) as the raw material. The temperature was 850°C and the pressure was 100 Torr (13332 Pa) under reduced pressure conditions to form a 1 μm film. Next, the substrate was left in the atmosphere for 2 hours. 28 After forming a natural oxide film of SiO2 composition (δ-doping of oxygen), 28 Using SiH4 (isotope 99.94%) as the raw material, a silicon epitaxial layer of 3 nm was formed at a temperature of 850°C and a pressure of 100 Torr (13332 Pa). 28 After forming a natural oxide film of SiO2 composition (δ-doping of oxygen), 28 Using SiH4 (isotope 99.94%) as the raw material, a silicon epitaxial layer of 3 nm was grown under reduced pressure conditions of 850°C and 100 Torr (13,332 Pa). This process was repeated four times. 28 Using SiH4 (isotope 99.94%) as the raw material, a silicon epitaxial layer of 100 nm was formed at a temperature of 850°C and a pressure of 100 Torr (13,332 Pa). Finally, a heat treatment was performed at 800°C for 10 minutes to oxidize the oxygen delta-doped layer and form a single oxide film (buried oxide film (BOX) layer). 28 We fabricated SOI substrates with a Si epitaxial layer on top.

[0097] As described above, according to the examples of the present invention, it is possible to obtain a silicon substrate for a quantum computer that can suppress the influence of nuclear spin, that fully exhibits the isotope effect suitable for a quantum computer, and that can easily form a single-electron transistor.

[0098] The present specification includes the following aspects. [A]: A method for manufacturing a silicon substrate for a quantum computer, A silicon-based source gas is applied to a silicon substrate. 28 Si and 30forming a Si epitaxial layer by epitaxial growth using a Si source gas having a total Si content of 99.9% or more; oxidizing the surface of the Si epitaxial layer to form an oxygen (O) δ-doped layer; On the δ-doped layer, a silicon-based source gas containing 28 Si and 30 and forming a Si epitaxial layer by epitaxial growth using a Si source gas having a total Si content of 99.9% or more. [B]: The method for producing a silicon substrate for a quantum computer according to [A] above, in which monosilane gas is used as the Si source gas. [C]: A method for manufacturing a silicon substrate for a quantum computer according to [A] or [B] above, in which the step of forming the oxygen (O) delta-doped layer and the step of forming the Si epitaxial layer on the delta-doped layer are repeated to form multiple pairs of the delta-doped layer and the Si epitaxial layer on the delta-doped layer. [D]: A method for manufacturing a silicon substrate for a quantum computer according to [C] above, in which the thickness of the outermost Si epitaxial layer of the silicon substrate for a quantum computer is made thicker than the thickness of Si epitaxial layers other than the outermost Si epitaxial layer. [E]: The method for producing a silicon substrate for a quantum computer according to [D] above, wherein the silicon substrate for a quantum computer is heat-treated to integrate the plurality of δ-doped layers to form an SOI structure. [1]: A method for manufacturing a silicon substrate for a quantum computer, On a silicon substrate, silicon-based raw material gas 28 By performing epitaxial growth using Si source gas, 28 forming a Si epitaxial layer; The aforementioned 28 oxidizing the surface of the Si epitaxial layer to form an oxygen (O) δ-doped layer; On top of the δ-doped layer, 28 By performing epitaxial growth using Si source gas,28 and forming a silicon epitaxial layer. [2]: The above 28 As a Si source gas 28 The method for manufacturing silicon substrates for quantum computers described above [1] uses Si monosilane gas. [3]: forming a δ-doped layer of oxygen (O), and 28 The step of forming a Si epitaxial layer is repeated, and the δ-doped layer and the step of forming a Si epitaxial layer on the δ-doped layer are 28 The method for manufacturing a silicon substrate for a quantum computer according to [1] or [2] above, in which multiple pairs of Si epitaxial layers are formed. [4]: The outermost layer of the silicon substrate for quantum computers 28 The thickness of the Si epitaxial layer is 28 Other than the Si epitaxial layer 28 The manufacturing method of the silicon substrate for quantum computers described above [3], which is thicker than the thickness of the Si epitaxial layer. [5]: The method for manufacturing a silicon substrate for a quantum computer according to [4] above, wherein the silicon substrate for a quantum computer is heat-treated to integrate the plurality of δ-doped layers to form an SOI structure. [6]: The method for manufacturing a silicon substrate for a quantum computer according to [A], [B], [C], [D], [E], [1], [2], [3], [4] or [5], wherein the silicon substrate has a resistivity of 1000 Ω·cm or more. [F]: A silicon substrate for a quantum computer, A silicon substrate; an epitaxial layer on the silicon substrate, the epitaxial layer comprising: 28 Si and 30 a Si epitaxial layer having a composition in which the total Si content is 99.9% or more; an SiO2 layer on the Si epitaxial layer, the SiO2 layer occupying the entire silicon 28 Si and 30an SiO2 layer having a composition in which the total content of Si is 99.9% or more; an epitaxial layer on the SiO2 layer, the epitaxial layer comprising silicon 28 Si and 30 A silicon substrate for quantum computers comprising a Si epitaxial layer having a composition with a total Si content of 99.9% or more. [G]: The silicon substrate for quantum computers according to [F] above, wherein the SiO2 layer is a δ-doped layer of oxygen (O). [H]: The silicon substrate for quantum computers according to [F] above, wherein the SiO2 layer is a buried oxide film (BOX) layer in an SOI structure. [7]: A silicon substrate for a quantum computer, A silicon substrate; On the silicon substrate 28 a Si epitaxial layer; Applicable 28 on the Si epitaxial layer 28 an SiO2 layer; Applicable 28 On top of the SiO2 layer 28 A silicon substrate for quantum computers comprising a Si epitaxial layer. [8]:The above 28 The silicon substrate for quantum computers described above [7], in which the SiO2 layer is a delta-doped layer of oxygen (O). [9]: The above 28 The silicon substrate for quantum computers [7], in which the SiO2 layer is the buried oxide (BOX) layer in the SOI structure.

[10] : A semiconductor device characterized by comprising an element on a silicon substrate for a quantum computer according to [F], [G], [H], [7], [8] or [9].

[0099] The present invention is not limited to the above-described embodiments, which are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that provides similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0100] 1...Silicon substrate, 2... 28 Si epitaxial layer, 3… 28 SiO2 layer, 3A...Oxygen (O) δ-doped layer ( 28 SiO2 layer), 3B: Buried oxide film (BOX) layer ( 28 SiO2 layer), 10, 10A...Silicon substrate for quantum computers.

Claims

1. A method for manufacturing a silicon substrate for a quantum computer, comprising: A silicon-based source gas is applied to a silicon substrate. ２８ Si and ３０ forming a Si epitaxial layer by epitaxial growth using a Si source gas having a total Si content of 99.9% or more; oxidizing the surface of the Si epitaxial layer to form an oxygen (O) δ-doped layer; On the δ-doped layer, a silicon-based source gas containing ２８ Si and ３０ and forming a Si epitaxial layer by epitaxial growth using a Si source gas having a total Si content of 99.9% or more.

2. 2. The method for manufacturing a silicon substrate for a quantum computer according to claim 1, wherein monosilane gas is used as the Si source gas.

3. 2. The method for manufacturing a silicon substrate for a quantum computer according to claim 1, wherein the step of forming the oxygen (O) delta-doped layer and the step of forming the Si epitaxial layer on the delta-doped layer are repeated to form multiple pairs of the delta-doped layer and the Si epitaxial layer on the delta-doped layer.

4. 4. The method for manufacturing a silicon substrate for a quantum computer according to claim 3, wherein the thickness of the outermost Si epitaxial layer of the silicon substrate for a quantum computer is made thicker than the thicknesses of Si epitaxial layers other than the outermost Si epitaxial layer.

5. 5. The method for manufacturing a silicon substrate for a quantum computer according to claim 4, wherein the plurality of δ-doped layers are integrated by heat-treating the silicon substrate for a quantum computer to form an SOI structure.

6. A method for manufacturing a silicon substrate for a quantum computer, comprising: On a silicon substrate, silicon-based raw material gas ２８ By performing epitaxial growth using a Si source gas, ２８ forming a Si epitaxial layer; The aforementioned ２８ oxidizing the surface of the Si epitaxial layer to form an oxygen (O) δ-doped layer; On top of the δ-doped layer, ２８ By performing epitaxial growth using a Si source gas, ２８ and forming a silicon epitaxial layer.

7. The aforementioned ２８ As a Si source gas ２８ 7. The method for manufacturing a silicon substrate for a quantum computer according to claim 6, wherein Si monosilane gas is used.

8. forming a δ-doped layer of oxygen (O); ２８ The step of forming a Si epitaxial layer is repeated to form the δ-doped layer and the δ-doped layer on the ２８ 7. The method for manufacturing a silicon substrate for a quantum computer according to claim 6, wherein a plurality of pairs of Si epitaxial layers are formed.

9. The outermost layer of the silicon substrate for quantum computers ２８ The thickness of the Si epitaxial layer is ２８ Other than Si epitaxial layer ２８ 9. The method for manufacturing a silicon substrate for a quantum computer according to claim 8, wherein the thickness of the silicon epitaxial layer is made thicker than that of the Si epitaxial layer.

10. 10. The method for manufacturing a silicon substrate for a quantum computer according to claim 9, wherein the plurality of δ-doped layers are integrated by heat-treating the silicon substrate for a quantum computer to form an SOI structure.

11. 11. The method for manufacturing a silicon substrate for a quantum computer according to claim 1, wherein the silicon substrate has a resistivity of 1000 Ω·cm or more.

12. A silicon substrate for a quantum computer, A silicon substrate; an epitaxial layer on the silicon substrate, the epitaxial layer comprising: ２８ Si and ３０ a Si epitaxial layer having a composition in which the total Si content is 99.9% or more; SiO on the Si epitaxial layer ２ layer, ２ of the total silicon in the layer ２８ Si and ３０ SiO having a composition in which the total content of Si is 99.9% or more ２ Layers and The SiO ２ an epitaxial layer on the layer, the epitaxial layer occupying the entire silicon of the epitaxial layer; ２８ Si and ３０ and a Si epitaxial layer having a composition in which the total Si content is 99.9% or more.

13. The SiO ２ 13. The silicon substrate for quantum computers according to claim 12, wherein the layer is a delta-doped layer of oxygen (O).

14. The SiO ２ 13. The silicon substrate for quantum computers according to claim 12, wherein the layer is a buried oxide (BOX) layer in an SOI structure.

15. A silicon substrate for a quantum computer, A silicon substrate; On the silicon substrate ２８ a Si epitaxial layer; Applicable ２８ On the Si epitaxial layer ２８ SiO ２ Layers and Applicable ２８ SiO ２ Above the layer ２８ A silicon substrate for a quantum computer, comprising: a silicon epitaxial layer;

16. The aforementioned ２８ SiO ２ 16. The silicon substrate for quantum computers according to claim 15, wherein the layer is a δ-doped layer of oxygen (O).

17. The aforementioned ２８ SiO ２ 16. The silicon substrate for quantum computers according to claim 15, wherein the layer is a buried oxide (BOX) layer in an SOI structure.

18. A semiconductor device comprising an element on the silicon substrate for a quantum computer according to any one of claims 12 to 17.

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