Substrate for electronic device and method for manufacturing same

Abstract

Provided is a substrate for an electronic device in which a nitride semiconductor film is formed on a bonded substrate of a silicon single crystal in which a first silicon single crystal substrate having a crystal plane orientation {111} and a second silicon single crystal substrate having a crystal plane orientation {111} are bonded with an oxide film interposed therebetween, the oxide film has a film thickness of 2 nm or more and 470 nm or less. As a result, it is possible to provide a substrate for electronic devices in which a nitride semiconductor is formed on a silicon single crystal and which has higher breaking strength.

Description

Technical Field

[0001] The present invention relates to a substrate for electronic devices and a method for manufacturing the same, and in particular to a substrate for electronic devices having a nitride semiconductor formed on a silicon substrate and a method for manufacturing the same. Background Art

[0002] Nitride semiconductors such as GaN and AlN can be used to manufacture high electron mobility transistors (HEMT) and high withstand voltage electronic devices using two-dimensional electron gas.

[0003] It is difficult to produce a nitride semiconductor wafer having the above-mentioned nitride semiconductor grown on a substrate. In the past, sapphire substrates and SiC substrates have been used as growth substrates. However, in order to increase the diameter (larger aperture) of the substrate and reduce the cost of the substrate, epitaxial growth of nitride semiconductors is also performed on silicon single crystal substrates by vapor phase growth. Compared with sapphire substrates and SiC substrates, when an epitaxial growth film of a nitride semiconductor is produced on a silicon single crystal substrate by vapor phase growth, a large diameter substrate can be used, so the device has high productivity and is easy to process, which is advantageous. However, when a nitride semiconductor is vapor-grown on a silicon single crystal substrate, due to the stress caused by the difference in lattice constants and thermal expansion coefficients, an increase in warping, slip, cracking, etc. are likely to occur, and thus the stress is reduced by growth conditions and a relaxation layer.

[0004] For example, when epitaxial growth is performed on a silicon single crystal substrate, an AlN buffer layer is stacked on an exposed Si substrate, and a GaN-HEMT structure epitaxial layer is stacked, thereby producing an epitaxial substrate for power devices and for RF devices. In particular, in order to make the epitaxial substrate for power devices have a high withstand voltage, it is necessary to produce a silicon-based gallium nitride (GaN on Si) (GaN on a silicon single crystal) with a thickened GaN epitaxial layer. To thicken the thickness of the epitaxial layer, it is sufficient to thicken the silicon single crystal substrate used as the growth substrate for epitaxial growth. In addition, as a method for thickening the silicon single crystal substrate, there is a method of bonding two silicon single crystal substrates. Patent document 1 discloses setting the thickness of the bonded substrate to be greater than 2 mm. In addition, patent document 2 discloses the following technology: as a combination of two substrates to be bonded, the surface orientation of the bonding wafer (base wafer) is {111}, and the surface orientation of the base wafer is {100} and the resistivity is less than 0.1Ωcm.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2021-014376

[0008] Patent Document 2: Japanese Patent Application Publication No. 2021-027186 Summary of the invention

[0009] 1. Technical issues to be resolved

[0010] As described above, there is known a technique of using a bonded substrate (laminated substrate) obtained by bonding two substrates as a growth substrate as disclosed in Patent Documents 1 and 2. However, there is still a demand for a substrate for electronic devices having a higher breaking strength.

[0011] The present invention has been made to solve the above-mentioned technical problems, and an object of the present invention is to provide an electronic device substrate and a method for manufacturing the same, wherein the electronic device substrate is an electronic device substrate having a nitride semiconductor formed on a silicon single crystal and having a higher fracture strength.

[0012] (II) Technical solution

[0013] In order to solve the above-mentioned technical problems, the present invention provides a substrate for electronic devices, which is a substrate for electronic devices having a nitride semiconductor film formed on a bonding substrate of a silicon single crystal, characterized in that: the bonding substrate is a substrate formed by bonding a first silicon single crystal substrate with a crystal plane orientation of {111} and a second silicon single crystal substrate with a crystal plane orientation of {111} via an oxide film, and the film thickness of the oxide film is greater than 2nm and less than 470nm.

[0014] In this way, as long as a substrate for electronic devices in which a nitride semiconductor film is formed on a bonding substrate of a silicon single crystal, the bonding substrate is a substrate bonded via an oxide film, and the thickness of the oxide film is as thin as 2 nm to 470 nm, a substrate for electronic devices with higher fracture strength can be made.

[0015] In addition, the present invention provides a substrate for electronic devices, which is a substrate for electronic devices on which a nitride semiconductor film is formed on a bonding substrate of a silicon single crystal, and is characterized in that: the bonding substrate is a substrate formed by bonding a first silicon single crystal substrate with a crystal plane orientation of {111} and a second silicon single crystal substrate via an oxide film, and the film thickness of the oxide film is greater than 2 nm and less than 470 nm.

[0016] In such a scheme, as long as the substrate for electronic devices has a nitride semiconductor film formed on a bonding substrate of a silicon single crystal, the bonding substrate is a substrate bonded via an oxide film, and the thickness of the oxide film is as thin as 2 nm to 470 nm, a substrate for electronic devices with higher fracture strength can be made.

[0017] At this time, the crystal plane orientation of the second silicon single crystal substrate can be set to {100}.

[0018] Even when the first silicon single crystal substrate and the second silicon single crystal substrate are set to such a combination of crystal plane orientations, it is possible to obtain a substrate for an electronic device having high fracture strength.

[0019] Furthermore, in the electronic device substrate of the present invention, the film thickness of the oxide film can be set to be greater than or equal to 2 nm and less than or equal to 190 nm.

[0020] In the electronic device substrate of the present invention, by setting the film thickness of the oxide film to such a range, it is possible to obtain an electronic device substrate having high fracture strength.

[0021] At this time, the combined substrate is preferably a substrate formed by combining the first silicon single crystal substrate and the second silicon single crystal substrate in a state where the notch of the first silicon single crystal substrate and the notch of the second silicon single crystal substrate are rotationally misaligned by 15° to 165°.

[0022] Such a substrate can be used as a substrate for electronic devices having higher fracture strength.

[0023] Furthermore, the diameter of the bonding substrate can be set to 300 mm or more.

[0024] As described above, the substrate having high breaking strength of the present invention is particularly effective for a substrate for electronic devices having a large diameter of 300 mm or more.

[0025] In addition, the present invention provides a method for manufacturing a substrate for electronic devices, which is a method for manufacturing a substrate for electronic devices in which a nitride semiconductor film is formed on a silicon single crystal bonding substrate, and is characterized in that it comprises: a process of preparing a first silicon single crystal substrate having a crystal plane orientation of {111} and a second silicon single crystal substrate having a crystal plane orientation of {111}; a process of forming an oxide film on the surface of at least one of the first silicon single crystal substrate and the second silicon single crystal substrate; a process of superimposing the first silicon single crystal substrate and the second silicon single crystal substrate with the oxide film in between, and performing heat treatment to thereby bond the first silicon single crystal substrate and the second silicon single crystal substrate to produce the bonded substrate; and a process of epitaxially growing the nitride semiconductor film on the surface of the first silicon single crystal substrate of the bonded substrate, so that the film thickness of the oxide film separating the first silicon single crystal substrate and the second silicon single crystal substrate becomes greater than 2 nm and less than 470 nm, thereby forming the film thickness of the oxide film formed in the process of forming the oxide film.

[0026] According to the method for manufacturing an electronic device substrate of the present invention, the bonded substrate can be a substrate bonded via an oxide film, and the oxide film can be made thinner to a thickness of 2 nm to 470 nm, thereby manufacturing an electronic device substrate with higher fracture strength.

[0027] In addition, the present invention provides a method for manufacturing a substrate for electronic devices, which is a method for manufacturing a substrate for electronic devices in which a nitride semiconductor film is formed on a silicon single crystal bonding substrate, and is characterized in that it comprises: a process of preparing a first silicon single crystal substrate and a second silicon single crystal substrate having a crystal plane orientation of {111}; a process of forming an oxide film on the surface of at least one of the first silicon single crystal substrate and the second silicon single crystal substrate; a process of superimposing the first silicon single crystal substrate and the second silicon single crystal substrate with the oxide film in between, and performing heat treatment to thereby bond the first silicon single crystal substrate and the second silicon single crystal substrate to produce the bonded substrate; and a process of epitaxially growing the nitride semiconductor film on the surface of the first silicon single crystal substrate of the bonded substrate, so that the film thickness of the oxide film separating the first silicon single crystal substrate and the second silicon single crystal substrate becomes greater than 2 nm and less than 470 nm, thereby forming the film thickness of the oxide film formed in the process of forming the oxide film.

[0028] Even in such a scheme, if the manufacturing method of the electronic device substrate of the present invention is used, the combined substrate can be a substrate formed by combining through an oxide film, and the film thickness of the oxide film can be made thinner to more than 2nm and less than 470nm, thereby being able to manufacture a substrate for electronic devices with higher breaking strength.

[0029] At this time, the crystal plane orientation of the second silicon single crystal substrate can be set to {100}.

[0030] Even when the first silicon single crystal substrate and the second silicon single crystal substrate are set to such a combination of crystal plane orientations, a substrate for an electronic device having high fracture strength can be manufactured.

[0031] In addition, in the manufacturing method of a substrate for electronic devices of the present invention, the thickness of the oxide film formed in the process of forming the oxide film can be formed in such a way that the thickness of the oxide film separating the first silicon single crystal substrate and the second silicon single crystal substrate is greater than 2 nm and less than 190 nm.

[0032] In the present invention, by setting the film thickness of the oxide film to such a range, a substrate for an electronic device having high fracture strength can be manufactured.

[0033] At this time, the first silicon single crystal substrate and the second silicon single crystal substrate are preferably combined in a state where the notch of the first silicon single crystal substrate and the notch of the second silicon single crystal substrate are rotationally misaligned by 15° to 165°.

[0034] According to such a production method, a substrate for an electronic device having higher fracture strength can be produced.

[0035] Furthermore, the diameters of the prepared first silicon single crystal substrate and the second silicon single crystal substrate can be set to 300 mm or more.

[0036] The electronic device substrate having high breaking strength produced by the production method of the present invention is particularly effective in producing an electronic device substrate having a large diameter of 300 mm or more.

[0037] (III) Beneficial effects

[0038] Since the combined substrate of the electronic device substrate of the present invention is a substrate formed by combining through an oxide film, and the film thickness of the oxide film is as thin as 2 nm or more and 470 nm or less, it is possible to provide an electronic device substrate with higher fracture strength. In addition, the manufacturing method of the electronic device substrate of the present invention can manufacture such an electronic device substrate. Therefore, in addition to improving the quality of the electronic device substrate formed with a nitride semiconductor film, productivity can also be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic cross-sectional view showing an example of the electronic device substrate of the present invention.

[0040] Figure 2 This is a schematic diagram for explaining the positional relationship between the notches of the first silicon single crystal substrate and the second silicon single crystal substrate viewed from the main surface side of the bonding substrate in the electronic device substrate of the present invention.

[0041] Figure 3 This is a flowchart showing an outline of an example of the method for producing the electronic device substrate of the present invention.

[0042] Figure 4 The diagrams are schematic diagrams showing the state of the breaking load test, wherein (a) is a diagram viewed from the upper side in the vertical direction, and (b) is a diagram viewed from the side.

[0043] Figure 5 It is a graph showing the results of Examples 1-1 to 1-9 and Comparative Examples 1-1 and 1-2, and Examples 3-1 to 3-8 and Comparative Examples 3-1 and 3-2.

[0044] Figure 6 It is a graph which shows the results of Examples 2-1 to 2-8 and Examples 4-1 to 4-8. DETAILED DESCRIPTION

[0045] Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

[0046] [Substrates for electronic devices]

[0047] like Figure 1As shown, the electronic device substrate 20 of the present invention has a nitride semiconductor film 21 formed on a silicon single crystal bonding substrate 10. In the description of the present invention, the silicon single crystal bonding substrate 10 is also referred to as a "bonding substrate". In this case, the bonding substrate 10 is a substrate formed by bonding a first silicon single crystal substrate 11 with a crystal plane orientation of {111} and a second silicon single crystal substrate 12 with a crystal plane orientation of {111} via an oxide film 13. Figure 1 As shown, the nitride semiconductor film 21 is formed on the first silicon single crystal substrate 11. The electronic device substrate 20 of the present invention is characterized in that the oxide film 13 has a film thickness of 2 nm or more and 470 nm or less.

[0048] In addition, the bonding substrate 10 may be a substrate formed by bonding a first silicon single crystal substrate 11 and a second silicon single crystal substrate 12 having a crystal plane orientation of {111} via an oxide film 13. Figure 1 As shown, the nitride semiconductor film 21 is formed on the first silicon single crystal substrate 11. The electronic device substrate 20 of the present invention is characterized in that the oxide film 13 has a film thickness of 2 nm or more and 470 nm or less.

[0049] At this time, the crystal plane orientation of the second silicon single crystal substrate 12 can be set to {100}.

[0050] In addition, the description of Miller index is as generally shown. That is, {} refers to the general term for equivalent crystal plane orientations, and () refers to each direction of the crystal plane orientation. In addition, <> represents the general term for equivalent crystal axis directions, and [] refers to each direction of the crystal axis direction.

[0051] Furthermore, the crystal plane orientations of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 may each have an off angle of several degrees (about 5° or less).

[0052] Here, as described above, in order to make the epitaxial substrate for power devices have a high withstand voltage, it is necessary to produce a substrate for electronic devices in which a nitride semiconductor film is formed thicker on a silicon single crystal substrate (for example, GaN on Si (silicon-based gallium nitride) in which the thickness of the GaN epitaxial layer is thickened). In order to thicken the thickness of the epitaxial layer, it is sufficient to thicken the silicon single crystal substrate and then perform epitaxial growth. In addition, as a method for thickening the silicon substrate, a method of making a combined substrate in which two silicon single crystal substrates are bonded together is implemented, but when using such a combined substrate (bonded substrate), a substrate with stronger fracture strength is still desired.

[0053] In order to produce a substrate 20 for electronic devices with stronger fracture strength, the present invention sets the film thickness of the oxide film 13 to be greater than 2 nm and less than 470 nm as described above. By using a combined substrate 10 separated by an oxide film 13 having a film thickness in this range, the fracture strength of the combined substrate 10 can be improved compared to the case where the oxide film is not formed. Therefore, even if the nitride semiconductor film 21 is formed on the combined substrate 10, the fracture strength can still be improved. It is believed that the oxide film 13 can play the role of a buffer layer when stress is applied by separating the oxide film 13. From the perspective of the amount of effect and the ease of controlling the thickness of the oxide film, it is preferred to set the film thickness of the oxide film 13 to be greater than 2 nm and less than 190 nm. Even if the film thickness of the oxide film 13 is thickened in a manner that the film thickness exceeds 470 nm, the effect of forming the oxide film 13 will steadily decrease, and the oxidation time used to form the oxide film 13 will also be prolonged, so it is not helpful.

[0054] Furthermore, in the present invention, the silicon single crystal bonding substrate 10 is preferably a substrate formed by bonding a first silicon single crystal substrate 11 and a second silicon single crystal substrate 12 in a state where the notch of the first silicon single crystal substrate 11 and the notch of the second silicon single crystal substrate 12 are rotationally misaligned by 15° to 165°. In this way, the fracture strength can be further improved by misaligning the notch position in the bonding substrate 10.

[0055] Furthermore, the diameter of the bonding substrate can be set to 300 mm or more.

[0056] As described above, the substrate having high breaking strength of the present invention is particularly effective for a substrate for electronic devices having a large diameter of 300 mm or more.

[0057] For the electronic device substrate 20 of the present invention, since the substrate strength is high as described above, the diameter of the combined substrate 10 (and the electronic device substrate 20) can also be set to a large diameter of 300 mm or more. In the past, the substrate strength of such a large diameter substrate was not sufficient, and sometimes cracks occurred, but in the present invention, as described above, it is possible to make a substrate 20 for electronic devices with higher fracture strength. The upper limit of the diameter of the combined substrate 10 (and the electronic device substrate 20) is not particularly limited, for example, it can be set to 450 mm or less.

[0058] When the diameter of the bonding substrate 10 (and the electronic device substrate 20) is 300 mm or more, the diameters of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 are also 300 mm or more. The thickness of each of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 is not particularly limited, and a thickness that meets the standard can be appropriately used. In particular, when the diameter is 300 mm, the thickness can be set to 775 μm. This type of silicon single crystal substrate is used as a common device substrate, which is cheap and can be used without any special problems. As the thickness of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12, for example, a thickness of 500 μm to 1500 μm can be used. The thickness of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 can be different, that is, the thickness ratio of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 is not limited to 1. Even if the thickness ratio is not 1, as long as it is the same as the total thickness of the bonding substrate 10, the same effect can be obtained.

[0059] In addition, the thickness of the combined substrate 10 formed by bonding the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 is not limited to 775μm×2. It is known that the thicker the substrate thickness, the stronger the strength against the breaking load. Therefore, in the structure of the present invention, for example, when the thickness of the bonded combined substrate 10 is made equivalent to the standard thickness of 775μm of a substrate with a diameter of 300mm in common circulation, although the strength is not as good as the combined substrate formed by bonding the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 of the same thickness of 775μm in the structure of the present invention (thickness of about 1550μm), the strength is still greatly increased compared to a substrate of the same thickness (775μm). Of course, in this case, the thickness ratio of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 is not limited to 1. As a method for manufacturing such a combined substrate 10 with a thickness of 775μm, two thinner first silicon single crystal substrates 11 and second silicon single crystal substrates 12 can be joined to make a total thickness of 775μm, or two general specification products (thickness 775μm) can be joined and then polished to adjust the thickness to 775μm.

[0060] Reference Figure 2 , illustrating the positional relationship between the notch of the first silicon single crystal substrate 11 and the notch of the second silicon single crystal substrate 12 in the bonding substrate 10. Figure 2 In (a) to (f), the crystal plane orientations of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 are both {111}, and as an example, the notch position is shown as <110> Direction. Figure 2 (a), (b), (c), (d), (e), and (f) respectively show the cases where the notch position is not rotated (rotated 0°), rotated 10°, rotated 15°, rotated 20°, rotated 30°, and rotated 60°. Figure 2In each of Figures (a) to (f), for simplicity, the notch position of the first silicon single crystal substrate 11 is shown facing directly downward, and the notch position of the second silicon single crystal substrate 12 represented by the dotted line is misaligned according to the angle of each figure.

[0061] In addition to the above-described combined substrate 10 having the oxide film 13 interposed therebetween, the electronic device substrate 20 of the present invention can also be formed by making the notch of the first silicon single crystal substrate 11 and the notch of the second silicon single crystal substrate 12 such that Figure 2 The rotational misalignment shown in (b) to (f) can further increase the fracture strength. The rotational misalignment angle is preferably greater than Figure 2 (b) 10°, especially if Figure 2 The notches of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 are preferably rotated at a position displaced by 15° or more as shown in (c) to (f).

[0062] The positions of the notches of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 are not limited to any particular positions. <110> direction, other directions can also be given. Since the strength difference caused by the angular misalignment of the notch occurs from the relative position of the notch, which has the characteristic of being physically weak to the breaking load, even in <110> Even if there are gaps in other directions other than the direction, the present invention still has the same effect.

[0063] In addition, in the electronic device substrate 20 of the present invention, the nitride semiconductor film 21 is formed on the surface of the first silicon single crystal substrate 11 having a {111} crystal plane orientation. Therefore, the electronic device substrate 20 can be formed with a good nitride semiconductor film 21.

[0064] [Method for producing a substrate for electronic devices]

[0065] Below, refer to Figure 3 A method for producing the electronic device substrate 20 of the present invention as described above will be described.

[0066] First, if Figure 3 As shown in S11 of FIG. 1 , a first silicon single crystal substrate 11 and a second silicon single crystal substrate 12 are prepared (step S11). At this time, silicon single crystal substrates having a crystal plane orientation of {111} are prepared as the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12. At this time, the diameters of the prepared first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 can be set to be greater than 300 mm.

[0067] In addition, as another solution, in step S11, a first silicon single crystal substrate 11 having a crystal plane orientation of {111} can be prepared, and a second silicon single crystal substrate 12 having a crystal plane orientation other than {111} can be prepared. In this case, it is preferred that the crystal plane orientation of the second silicon single crystal substrate 12 is set to {100}. Even with such a combination of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12, the subsequent steps can be performed in the same manner.

[0068] In addition, since the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 are bonded to form a bonded substrate 20 of one silicon single crystal substrate, the first silicon single crystal substrate 11 can be called a bonded wafer, and the second silicon single crystal substrate 12 can be called a base wafer.

[0069] The thickness of each of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 is not particularly limited, and a thickness that complies with the standard can be appropriately used. In addition, the resistivity and impurity concentration of each of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 can be appropriately set.

[0070] Then, if Figure 3 As shown in step S12, an oxide film is formed on the surface of at least one of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 (step S12). The oxide film formed here becomes a Figure 1 The oxide film 13 shown. The means for forming the oxide film is not particularly limited, for example, an oxide film (thermal oxide film) can be formed on the surface by performing an oxidation heat treatment. Regarding the thickness of the oxide film, in the step S13 described later, after combining the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12, the oxide film 13 is formed in such a manner that the film thickness of the oxide film 13 separating the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 becomes greater than 2nm and less than 470nm. The oxide film can be formed on each of the two silicon single crystal substrates, or it can be formed on any of the silicon single crystal substrates. In addition, the oxide film formed here can also be formed in the form of a natural oxide film as long as it is greater than 2nm when bonding.

[0071] Then, if Figure 3 As shown in step S13, the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 are combined (step S13). At this time, the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 are superimposed with the oxide film formed in step S12 interposed therebetween, and heat treated to thereby combine them. Thus, the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 are firmly combined to form a combined substrate 10 (see Figure 1 ).

[0072] As described above, by forming the thickness of the oxide film formed in the step of forming the oxide film in step S12 so that the thickness of the oxide film 13 separating the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 is greater than 2 nm and less than 470 nm, it is possible to naturally make the thickness of the oxide film 13 after the two substrates are bonded in step S13 greater than 2 nm and less than 470 nm. It is preferred that the thickness of the oxide film formed in step S12 is formed so that the thickness of the oxide film 13 separating the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 is greater than 2 nm and less than 190 nm.

[0073] The conditions (atmosphere, temperature, time, etc.) of the heat treatment (bonding heat treatment) are not particularly limited as long as the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 can be bonded. The bonding heat treatment temperature can be set, for example, to be performed in a nitrogen atmosphere at 400° C. or higher and 1200° C. or lower for 1 to 12 hours.

[0074] In the step of bonding the two substrates in step S13, it is preferred that the bonding is performed in a state where the notch of the first silicon single crystal substrate 11 and the notch of the second silicon single crystal substrate 12 are rotated by 15° to 165° (see Figure 2 ).

[0075] After the bonding heat treatment and before the epitaxial growth of the nitride semiconductor film described later, the surface of the bonding substrate 10 is preferably cleaned. In particular, it is preferred to remove the oxide film formed on the surface of the bonding substrate 10 (particularly the surface of the first silicon single crystal substrate 11) by hydrofluoric acid spin cleaning or the like.

[0076] In this way, after the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 are combined to form a combined substrate 10, Figure 3 As shown in S14, the nitride semiconductor film 21 (refer to Figure 1 ) epitaxial growth is performed on the surface of the first silicon single crystal substrate 11 of the bonding substrate 10 (step S14). In addition, the first silicon single crystal substrate 11 may be double-sided polished before the bonding. If double-sided polishing is not performed before the bonding, single-sided polishing may be performed in advance on the main surface to be grown after the bonding and before the epitaxial growth. Of course, double-sided polishing may also be performed on the second silicon single crystal substrate 12.

[0077] As the nitride semiconductor film 21, an AlN layer, a GaN layer, an AlGaN layer, etc. can be formed. The nitride semiconductor film 21 can be formed by a common method. In addition, an intermediate layer (buffer layer) can be formed appropriately. In this way, it is possible to manufacture Figure 1 The electronic device substrate 20 is shown.

[0078] Example

[0079] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples; however, the present invention is not limited to the following Examples.

[0080] (Examples 1-1 to 1-9, Comparative Example 1-1)

[0081] according to Figure 3 The method for manufacturing the electronic device substrate of the present invention is as follows: Figure 1 The electronic device substrate 20 is shown.

[0082] First, as the first silicon single crystal substrate 11, a double-sided polished substrate with a diameter of 300 mm, a thickness of 775 μm, a crystal plane orientation of {111}, a p-type, a resistivity of 5000 Ωcm and a <110> A silicon single crystal substrate with a notch formed in the direction of the substrate is prepared as the second silicon single crystal substrate 12, which is double-sided polished, has a diameter of 300 mm, a thickness of 775 μm, a crystal plane orientation of {111}, a p-type, a resistivity of 5000 Ωcm, and is <110> A silicon single crystal substrate having a notch formed in the direction (step S11). In addition, the interstitial oxygen concentration Oi of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 is 16 ppm (JEIDA standard).

[0083] A surface oxide film is formed on the two silicon single crystal substrates prepared above (step S12). Regarding the film thickness of the oxide film, it is formed in a manner to have the following thickness when the two silicon single crystal substrates are bonded together: 2nm (Example 1-1), 23nm (Example 1-2), 80nm (Example 1-3), 150nm (Example 1-4), 190nm (Example 1-5), 220nm (Example 1-6), 280nm (Example 1-7), 350nm (Example 1-8), 470nm (Example 1-9), 600nm (Comparative Example 1-1). Regarding the specific formation method, first, Example 1-1 is formed in the form of a natural oxide film. In addition, the oxidation heat treatment of Examples 1-2 to 1-9 and Comparative Example 1-1 is set to a pyrogenic oxidation method. The conditions of the thermal oxidation method are as follows: 900°C for 15 minutes (Example 1-2), 900°C for 60 minutes (Example 1-3), 900°C for 142 minutes (Example 1-4), 900°C for 199 minutes (Example 1-5), 900°C for 214 minutes (Example 1-6), 900°C for 256 minutes (Example 1-7), 900°C for 301 minutes (Example 1-8), 1000°C for 213 minutes (Example 1-9), and 1000°C for 275 minutes (Comparative Example 1-1).

[0084] Next, the two silicon single crystal substrates are stacked by aligning the notches of the two silicon single crystal substrates, and subjected to a bonding heat treatment at 500° C. in a nitrogen atmosphere to form a bonded substrate 10 (step S13). Then, the bonded substrate 10 is subjected to a hydrofluoric acid spin cleaning to remove the oxide film on the surface of the bonded substrate 10.

[0085] Next, on the surface of the first silicon single crystal substrate 11 combined with the substrate 10, a 150nm AlN layer, a 160nm AlGaN layer, a superlattice structure formed by alternating 25 groups of GaN layers and AlN layers, a 1000nm GaN layer, a 20nm AlGaN layer, and a 3nm GaN layer are epitaxially grown with a total film thickness of 1.8μm to serve as a nitride semiconductor film 21 (process S14).

[0086] As a result, in Examples 1-1 to 1-9, the nitride semiconductor film 21 could be formed without causing cracks, etc. In this manner, the electronic device substrate 20 was manufactured.

[0087] Furthermore, under the same conditions as in Examples 1-1 to 1-9 and Comparative Example 1-1, bonding substrates before forming a nitride semiconductor film were prepared, and the strength of each bonding substrate was measured.

[0088] In the strength measurement of the bonded substrate, Figure 4 As shown, the breaking load was investigated using a precision universal testing machine manufactured by Instron. Figure 4 (a) is a view viewed from the upper side in the vertical direction, Figure 4 (b) is a view observed from the side.

[0089] like Figure 4 As shown in (a) and (b), three fulcrum clamps J are arranged above and below the bonding substrate (the curvature radius R of the crimping point is 15 mm). In the bonding substrate, the strength of the notch position is relatively weak, so the notch position N is set in such a way that it becomes the position directly below the central fulcrum clamp J (refer to Figure 4 (a), (b)).

[0090] (Comparative Example 1-2)

[0091] The preparation of the bonding substrate was carried out in the same manner as in Example 1-1, but the following points were changed. After preparing the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12, the oxide film formation of step S12 was not performed on both substrates. In addition, the natural oxide film on the bonding surface of the two substrates was removed by HF spin washing. Then, the two substrates were bonded in a state where the natural oxide film had been removed. For this substrate (bonded substrate without an oxide film), the fracture load was investigated in the same manner as above.

[0092] (Comparative Examples 1-3)

[0093] A first silicon single crystal substrate 11 similar to that of Example 1-1 was prepared. The breaking load of this substrate was examined in the same manner as above.

[0094] The above-mentioned results of breaking load (strength) are summarized in Table 1. In addition, for Examples 1-1 to 1-9 and Comparative Examples 1-1 and 1-2, the plotted results are shown. Figure 5 ( Figure 5 Examples 3-1 to 3-8 and Comparative Examples 3-1 and 3-2 described later are also shown.

[0095] [Table 1]

[0096]

[0097] Thus, the strength of the combined substrate 10 in Examples 1-1 to 1-9 is higher than that in Comparative Examples 1-1 to 1-3. In addition, the strength of Comparative Example 1-2, which has no oxide film and is combined with two silicon single crystal substrates, is only about twice the strength of a single silicon single crystal substrate that is not joined in Comparative Example 1-3. In contrast, it can be seen that in Examples 1-1 to 1-9 using a combined substrate 10 combined via an oxide film 13, the strength is greatly improved and far exceeds twice the strength of a single silicon single crystal substrate that is not joined. In addition, in Comparative Example 1-1 (600nm) where the thickness of the oxide film exceeds 470nm, not only does the effect of the oxide film decline and fail to obtain sufficient strength, but it also takes time to form the oxide film.

[0098] (Example 2-1)

[0099] Steps S11 to S14 were performed in the same manner as in Example 1-1 (a natural oxide film was formed, and the thickness of the oxide film 13 after bonding was 2 nm), thereby manufacturing the electronic device substrate 20 .

[0100] (Examples 2-2 to 2-8)

[0101] The same method as in Example 2-1 was used, but the positions of the notches of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 were rotated so as to be offset to manufacture the electronic device substrate 20. The magnitude of the rotation offset was set to 10° (Example 2-2), 15° (Example 2-3), 20° (Example 2-4), 30° (Example 2-5), 60° (Example 2-6), 170° (Example 2-7), and 180° (Example 2-8).

[0102] In Examples 2-1 to 2-8, the nitride semiconductor film 21 can be formed without cracking or the like.

[0103] In addition, the bonding substrate 10 before forming the nitride semiconductor film was prepared under the same conditions as in Examples 2-1 to 2-8, and the strength (fracture load) of each bonding substrate was measured. The strength measurement of each bonding substrate 10 was carried out in the same manner as in Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-3. The above fracture load (strength) results are summarized in Tables 2 and Figure 6 ( Figure 6 The following examples 4-1 to 4-8 are also shown.

[0104] [Table 2]

[0105]

[0106] The strength of the bonding substrate 10 of Examples 2-1 to 2-8 is improved compared with Comparative Examples 1-1 to 1-3.

[0107] Among Examples 2-1 to 2-8, the strength of the combined substrates 10 of Examples 2-3 to 2-6 was particularly high, and the strength was also higher than that of Examples 2-1 and 2-2 in which the rotational misalignment of the notches of the two substrates was less than 15°.

[0108] In addition, the rotational misalignment of the notches of the two substrates of Examples 2-7 and 2-8 is 170° and 180°, and the notches are located on the opposite side of the substrate to the notch position when the rotational misalignment of the notch is 10° and 0° (i.e., Examples 2-2 and 2-1). If the strength of Example 2-1 (0°) is compared with that of Example 2-8 (180°), the two show similar values. If the strength of Example 2-2 (10°) is compared with that of Example 2-7 (170°), the two also show similar values. Therefore, it is believed that the rotational misalignment of the notches of the two substrates is 170° and 180°, which is equivalent to the rotational misalignment of the notches of the two substrates is 10° and 0°, respectively. Therefore, for example, it is believed that the rotational misalignment of the notches of the two substrates is 15°, which is also equivalent to the rotational misalignment of the notches of the two substrates is 165°. In summary, it is believed that the rotational misalignment of the notches of the two substrates is preferably set to 15°~165°.

[0109] (Examples 3-1 to 3-8, Comparative Example 3-1)

[0110] according to Figure 3 The method for manufacturing the electronic device substrate of the present invention is as follows: Figure 1 The electronic device substrate 20 shown in FIG. 1-1 is different from the second silicon single crystal substrate 12 in that the second silicon single crystal substrate 12 has a crystal plane orientation of {100} and a <100> A silicon single crystal substrate with a notch formed in the direction.

[0111] First, as the first silicon single crystal substrate 11, a double-sided polished substrate with a diameter of 300 mm, a thickness of 775 μm, a crystal plane orientation of {111}, a p-type, a resistivity of 5000 Ωcm and a <110> A silicon single crystal substrate with a notch formed in the direction of the substrate is prepared, and as the second silicon single crystal substrate 12, a double-sided polished substrate with a diameter of 300 mm, a thickness of 775 μm, a crystal plane orientation of {100}, a p-type substrate, a resistivity of 5000 Ωcm and a <100> A silicon single crystal substrate having a notch formed in the direction (step S11). In addition, the interstitial oxygen concentration Oi of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 is 16 ppm (JEIDA standard).

[0112] A surface oxide film is formed on the two silicon single crystal substrates prepared above (step S12). The oxide film thickness is formed in such a way that the following thickness is achieved when the two silicon single crystal substrates are bonded together: 2nm (Example 3-1), 25nm (Example 3-2), 83nm (Example 3-3), 148nm (Example 3-4), 189nm (Example 3-5), 223nm (Example 3-6), 295nm (Example 3-7), 468nm (Example 3-8), 599nm (Comparative Example 3-1). Regarding the specific formation method, first, Example 3-1 is formed in the form of a natural oxide film. In addition, the oxidation heat treatment of Examples 3-2 to 3-8 is set as a pyrolysis oxidation method. The conditions of the thermal oxidation method are as follows: 900°C for 15 minutes (Example 3-2), 900°C for 60 minutes (Example 3-3), 900°C for 142 minutes (Example 3-4), 900°C for 199 minutes (Example 3-5), 900°C for 214 minutes (Example 3-6), 900°C for 256 minutes (Example 3-7), 1000°C for 213 minutes (Example 3-8), and 1000°C for 275 minutes (Comparative Example 3-1).

[0113] Next, the two silicon single crystal substrates are stacked by aligning the notches of the two silicon single crystal substrates, and subjected to a bonding heat treatment at 500° C. in a nitrogen atmosphere to form a bonded substrate 10 (step S13). Then, the bonded substrate 10 is subjected to a hydrofluoric acid spin cleaning to remove the oxide film on the surface of the bonded substrate 10.

[0114] Next, on the surface of the first silicon single crystal substrate 11 combined with the substrate 10, a 150nm AlN layer, a 160nm AlGaN layer, a superlattice structure formed by alternating 25 groups of GaN layers and AlN layers, a 1000nm GaN layer, a 20nm AlGaN layer, and a 3nm GaN layer are epitaxially grown with a total film thickness of 1.8μm to serve as a nitride semiconductor film 21 (process S14).

[0115] As a result, in Examples 3-1 to 3-8, the nitride semiconductor film 21 could be formed without cracking, etc. In this way, the electronic device substrate 20 was manufactured.

[0116] Furthermore, a bonding substrate before forming a nitride semiconductor film was prepared under the same conditions as in Examples 3-1 to 3-8 and Comparative Example 3-1, and the strength was measured in the same manner as above.

[0117] (Comparative Example 3-2)

[0118] The preparation of the bonding substrate was carried out in the same manner as in Example 3-1, but the following points were changed. After preparing the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12, the oxide film formation of step S12 was not performed on both substrates. In addition, the natural oxide film on the bonding surface of the two substrates was removed by HF spin washing. Then, the two substrates were bonded in a state where the natural oxide film had been removed. For this substrate (bonded substrate without an oxide film), the fracture load was investigated in the same manner as above.

[0119] The above results of the breaking load (strength) are summarized in Table 3. In addition, for Examples 3-1 to 3-8 and Comparative Examples 3-1 and 3-2, the results are plotted and shown in Figure 5 .

[0120] [Table 3]

[0121]

[0122] Thus, the strength of the bonded substrate 10 in Examples 3-1 to 3-8 is higher than that in Comparative Examples 3-1 and 3-2. In addition, the strength of Comparative Example 3-2 when there is no oxide film and two silicon single crystal substrates are bonded is only about twice the strength of a single silicon single crystal substrate that is not bonded in Comparative Example 1-3. In contrast, it can be seen that in Examples 3-1 to 3-8 using the bonded substrate 10 bonded via the oxide film 13, the strength is greatly improved and far exceeds twice the strength of a single silicon single crystal substrate that is not bonded.

[0123] (Example 4-1)

[0124] Steps S11 to S14 were performed in the same manner as in Example 3-1 (a natural oxide film was formed, and the thickness of the oxide film 13 after bonding was 2 nm), thereby manufacturing the electronic device substrate 20 .

[0125] (Examples 4-2 to 4-8)

[0126] The same method as in Example 4-1 was used, but the positions of the notches of the first silicon single crystal substrate 11 and the second silicon single crystal substrate 12 were rotated so as to be offset to manufacture the electronic device substrate 20. The magnitude of the rotation offset was set to 10° (Example 4-2), 15° (Example 4-3), 20° (Example 4-4), 30° (Example 4-5), 60° (Example 4-6), 170° (Example 4-7), and 180° (Example 4-8).

[0127] Examples 4-1 to 4-8 can form the nitride semiconductor film 21 without causing cracks or the like.

[0128] In addition, the bonding substrate 10 before forming the nitride semiconductor film was prepared under the same conditions as in Examples 4-1 to 4-8, and the strength (fracture load) of each bonding substrate was measured. The strength measurement of each bonding substrate 10 was carried out in the same manner as in Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-3. The above fracture load (strength) results are summarized in Table 4 and shown in Figure 6 middle.

[0129] [Table 4]

[0130]

[0131] The strength of the bonding substrate 10 of Examples 4-1 to 4-8 is improved compared with Comparative Examples 3-1, 3-2, and 1-3. In addition, Example 4-1 is under the same conditions as Example 3-1, but the data difference caused by experimental deviation occurs.

[0132] Among Examples 4-1 to 4-8, the strength of the combined substrates 10 of Examples 4-3 to 4-6 is particularly high, and the strength is also higher than that of Examples 4-1 and 4-2 in which the rotational misalignment of the notches of the two substrates is less than 15°.

[0133] In addition, the rotational misalignment of the notches of the two substrates of Examples 4-7 and 4-8 is 170° and 180°, and the notches are located on the opposite side of the substrate to the notch position when the rotational misalignment of the notch is 10° and 0° (i.e., Examples 4-2 and 4-1). If the strength of Example 4-1 (0°) is compared with that of Example 4-8 (180°), the two show similar values. If the strength of Example 4-2 (10°) is compared with that of Example 4-7 (170°), the two also show similar values. Therefore, it is believed that the rotational misalignment of the notches of the two substrates is 170° and 180°, which is equivalent to the rotational misalignment of the notches of the two substrates is 10° and 0°, respectively. Therefore, for example, it is believed that the rotational misalignment of the notches of the two substrates is 15°, which is also equivalent to the rotational misalignment of the notches of the two substrates is 165°. In summary, it is believed that the rotational misalignment of the notches of the two substrates is preferably set to 15°~165°.

[0134] (Example 5)

[0135] After bonding the combined substrate 10 manufactured under the conditions of Example 2-5, the thickness is adjusted to 775μm by grinding, polishing, and etching. The strength (breaking load) of the combined substrate 10 is measured in the same manner as in Example 1-1 to Example 1-9 and Comparative Examples 1-1 to 1-3. As a result, the breaking load (strength) of Example 5 is 912N. The breaking load (strength) of Comparative Example 1-3 (i.e., an example in which the total thickness is 775μm and is the same as Example 5, but is composed of a single substrate) is 305N as shown in Table 1, so the breaking load of Example 5 is improved compared to Comparative Example 1-3.

[0136] The present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any technical solution having substantially the same configuration and having the same function and effect as the technical concept described in the claims of the present invention is included in the technical scope of the present invention.

Claims

1. A substrate for electronic devices, wherein a nitride semiconductor film is formed on a silicon single crystal bonding substrate, characterized in that: The combined substrate is a substrate formed by combining a first silicon single crystal substrate having a crystal plane orientation of {111} and a second silicon single crystal substrate having a crystal plane orientation of {111} via an oxide film. The oxide film has a thickness of not less than 2 nm and not more than 470 nm.

2. An electronic device substrate, wherein a nitride semiconductor film is formed on a silicon single crystal bonding substrate, characterized in that: The combined substrate is a substrate formed by combining a first silicon single crystal substrate and a second silicon single crystal substrate with a crystal plane orientation of {111} through an oxide film. The oxide film has a thickness of not less than 2 nm and not more than 470 nm.

3. The electronic device substrate according to claim 2, wherein: The crystal plane orientation of the second silicon single crystal substrate is {100}.

4. The electronic device substrate according to claim 1 or 2, characterized in that: The oxide film has a thickness of not less than 2 nm and not more than 190 nm.

5. The electronic device substrate according to claim 1 or 2, characterized in that: The combined substrate is a substrate formed by combining the first silicon single crystal substrate and the second silicon single crystal substrate in a state where the notch of the first silicon single crystal substrate and the notch of the second silicon single crystal substrate are rotationally misaligned by 15° to 165°.

6. The electronic device substrate according to claim 1 or 2, characterized in that: The diameter of the combined substrate is greater than 300 mm.

7. A method for manufacturing a substrate for an electronic device, which is a method for manufacturing a substrate for an electronic device, wherein a nitride semiconductor film is formed on a bonding substrate of a silicon single crystal, characterized in that: have: A step of preparing a first silicon single crystal substrate having a crystal plane orientation of {111} and a second silicon single crystal substrate having a crystal plane orientation of {111}; forming an oxide film on a surface of at least one of the first silicon single crystal substrate and the second silicon single crystal substrate; The process of laminating the first silicon single crystal substrate and the second silicon single crystal substrate via the oxide film and performing heat treatment to thereby combine the first silicon single crystal substrate and the second silicon single crystal substrate to manufacture the combined substrate; and a step of epitaxially growing the nitride semiconductor film on the surface of the first silicon single crystal substrate of the bonding substrate, The thickness of the oxide film formed in the step of forming the oxide film is formed so that the thickness of the oxide film separating the first silicon single crystal substrate and the second silicon single crystal substrate is greater than or equal to 2 nm and less than or equal to 470 nm.

8. A method for manufacturing a substrate for an electronic device, wherein a nitride semiconductor film is formed on a bonding substrate of a silicon single crystal, characterized in that: have: The step of preparing a first silicon single crystal substrate and a second silicon single crystal substrate having a crystal plane orientation of {111}; forming an oxide film on a surface of at least one of the first silicon single crystal substrate and the second silicon single crystal substrate; The process of laminating the first silicon single crystal substrate and the second silicon single crystal substrate via the oxide film and performing heat treatment to thereby combine the first silicon single crystal substrate and the second silicon single crystal substrate to manufacture the combined substrate; and a step of epitaxially growing the nitride semiconductor film on the surface of the first silicon single crystal substrate of the bonding substrate, The thickness of the oxide film formed in the step of forming the oxide film is formed so that the thickness of the oxide film separating the first silicon single crystal substrate and the second silicon single crystal substrate is greater than or equal to 2 nm and less than or equal to 470 nm.

9. The method for manufacturing an electronic device substrate according to claim 8, wherein: The crystal plane orientation of the second silicon single crystal substrate is set to {100}.

10. The method for producing a substrate for an electronic device according to claim 7 or 8, characterized in that: The thickness of the oxide film formed in the step of forming the oxide film is formed so that the thickness of the oxide film separating the first silicon single crystal substrate and the second silicon single crystal substrate is greater than or equal to 2 nm and less than or equal to 190 nm.

11. The method for producing a substrate for an electronic device according to claim 7 or 8, characterized in that: The first silicon single crystal substrate and the second silicon single crystal substrate are combined in a state where the notch of the first silicon single crystal substrate and the notch of the second silicon single crystal substrate are rotationally misaligned by 15° to 165°.

12. The method for producing a substrate for an electronic device according to claim 7 or 8, characterized in that: The diameters of the prepared first silicon single crystal substrate and the second silicon single crystal substrate are set to be 300 mm or more.

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