Method for manufacturing bonded SOI wafer

Abstract

A method for manufacturing a bonded SOI wafer using a base oxidation method is provided, which can suppress the occurrence of slip dislocations and the formation of oxygen precipitates on the base wafer. The method for manufacturing a bonded SOI wafer is characterized by comprising: a step of preparing a single crystal silicon wafer having an initial interstitial oxygen concentration of 15 ppma ('79 ASTM) or more as a base wafer; when a silicon oxide film is formed on the surface of the base wafer by heat treating the base wafer in an oxidizing atmosphere, setting the temperature of the base wafer to be placed in a heat treatment furnace for the heat treatment to be 800°C or more, and performing the heat treatment of the base wafer at a temperature above the temperature to form a silicon oxide film; a step of bonding the base wafer to a bonding wafer via the silicon oxide film; and a step of thinning the bonded bonding wafer to form an SOI layer.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a bonded SOI wafer, and more particularly to a method for manufacturing a bonded SOI wafer by forming a silicon oxide film on a base wafer which is a supporting substrate of an SOI layer and bonding the wafer. Background Art

[0002] In addition to high-performance CPUs, SOI (Silicon On Insulator) is also used in the fields of RF components and SiPhotonics. Technology has been developed to integrate functions that were previously implemented by a combination of discrete components into Si chips, significantly improving their functionality.

[0003] As the use of bonded SOI expands, the required range of variation becomes wider when the required SOI layer thickness / BOX layer (buried oxide film layer) thickness is thinner or thicker than before.

[0004] Si Photonics uses the SOI layer as an optical waveguide, and the BOX layer and the surrounding SiO2 layer as a reflective layer. In order to ensure a higher reflectivity corresponding to the wavelength used, the required thickness of the BOX layer is increased, and the time for the BOX oxidation heat treatment used to form the BOX layer is correspondingly increased.

[0005] In the manufacturing method of a thin film bonded SOI wafer using an ion implantation layer for peeling, when a thicker BOX layer is formed on the bonding wafer side where the SOI layer is formed, the ions forming the peeling layer need to be implanted more deeply, and the depth is restricted by the upper limit of the acceleration voltage of the ion implanter. Therefore, in order to manufacture an SOI wafer with a BOX layer thickness of more than a certain degree, a method is adopted in which the BOX layer is formed on the base wafer side instead of the bonding wafer side where the ion implantation is performed and bonded to manufacture the SOI wafer. This method is called the base oxidation SOI method (hereinafter also referred to as the base oxidation method).

[0006] When the BOX layer is formed by the base oxidation method, a BOX oxidation heat treatment process is performed on the base wafer side before the heat treatment in the SOI process for strengthening the bonding force after peeling and further for adjusting the surface roughness and film thickness, so the base wafer is added with the corresponding heat treatment thermal history. In particular, in the manufacture of SOI wafers with a thick BOX layer, the BOX oxidation heat treatment sometimes takes a very long time.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2017-69240

[0010] Patent Document 2: Japanese Patent Application Publication No. 2006-80461 Summary of the invention

[0011] 1. Technical issues to be resolved

[0012] When etching is performed on the base wafer of the SOI wafer to form structures such as vertical holes and grooves, the oxygen precipitates of the base wafer may hinder the etching and affect the formation of the structure. Therefore, for this purpose, it is desired to make the density and size of the oxygen precipitates of the base wafer as small as possible. However, if the base wafer is subjected to a long BOX oxidation heat treatment in order to form a thicker BOX layer, the density and size of the oxygen precipitates of the base wafer will also increase. In this way, suppressing and reducing the oxygen precipitation of the base wafer in the SOI wafer using the base oxidation method has become a major issue.

[0013] On the other hand, as a method for suppressing the density and size of oxygen precipitates formed when performing BOX oxidation heat treatment for a long time, it is possible to consider using a single crystal silicon wafer with a low oxygen concentration (for example, less than 15 ppma ('79ASTM)) as a base wafer. For example, Patent Document 1 describes a technology for making a thicker BOX SOI wafer by a base oxidation method, and describes a method for oxidizing a base wafer with Oi (initial interstitial oxygen concentration) ≤ 10 ppma ('79ASTM) at a temperature of 700°C to 1000°C for more than 5 hours. However, this type of wafer with a low oxygen concentration has the problem of slip dislocations caused by heat treatment. In addition, Patent Document 1 does not record any content related to the input temperature and BMD during oxidation.

[0014] Furthermore, Patent Document 2 (Claim 8) describes a method of performing RTO as a nucleation heat treatment performed before a bonding heat treatment. However, Patent Document 2 is about a method for manufacturing a bonded SOI wafer in which a BOX layer is formed on the bonding wafer side.

[0015] The present invention aims to solve the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing a bonded SOI wafer using a base oxidation method, which method can suppress the occurrence of slip dislocations and the formation of oxygen precipitates on the base wafer.

[0016] (II) Technical solution

[0017] In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a bonded SOI wafer, which is a method for manufacturing a bonded SOI wafer by bonding a bonding wafer and a base wafer both composed of single crystal silicon via a silicon oxide film, characterized in that it comprises: a process of preparing a single crystal silicon wafer with an initial interstitial oxygen concentration of 15 ppma ('79ASTM) or more as the base wafer; when a silicon oxide film is formed on the surface of the base wafer by subjecting the base wafer to a heat treatment furnace for performing the heat treatment in an oxidizing atmosphere, setting the temperature of the base wafer to be placed in a heat treatment furnace for performing the heat treatment to be above 800°C, and performing the heat treatment of the base wafer at a temperature above the placement temperature to form a silicon oxide film; a process of bonding the base wafer to the bonding wafer via the silicon oxide film; and a process of thinning the bonded bonding wafer to form an SOI layer.

[0018] Thus, by setting the input temperature to 800° C. or higher, it is possible to reduce oxygen precipitation nuclei or suppress their growth. In addition, by using a wafer having an appropriately high initial interstitial oxygen concentration as a base wafer, the occurrence of slip dislocations can be suppressed.

[0019] At this time, the diameter of the base wafer can be greater than 200 mm.

[0020] Even when the base wafer has such a large diameter, the present invention can suppress the occurrence of slip dislocations.

[0021] At this time, it is preferred that the base wafer is subjected to RTA heat treatment at a temperature of 800° C. or higher before the heat treatment.

[0022] This can reduce oxygen precipitation nuclei or suppress their growth, resulting in a reduction in the density and size of oxygen precipitates.

[0023] Furthermore, in the step of forming the silicon oxide film,

[0024] The thickness of the silicon oxide film formed on the surface of the base wafer may be greater than 1 μm.

[0025] As described above, according to the present invention, it is possible to suppress the formation of slip dislocations and oxygen precipitates and form a thick BOX layer (silicon oxide film).

[0026] (III) Beneficial effects

[0027] As described above, the method for manufacturing a bonded SOI wafer of the present invention can utilize the basic oxidation method to suppress slip dislocations, reduce oxygen precipitation nuclei or inhibit their growth, resulting in a reduction in the density and size of oxygen precipitates. In addition, a bonded SOI wafer having a BOX layer of a desired thickness can be efficiently manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is an explanatory diagram showing an example of the process of the method for manufacturing a bonded SOI wafer of the present invention.

[0029] Description of Reference Numerals

[0030] 1…base wafer, 2…silicon oxide film, 3…bonding wafer, 4…ion implantation layer, 5…SOI layer, 6…peeling wafer, 7…bonding SOI wafer. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below, but the present invention is not limited thereto.

[0032] As described above, the thickness required for the BOX layer of the bonded SOI wafer increases. However, the BOX oxidation heat treatment is performed for a long time, which causes the oxygen precipitates in the base wafer to grow and increase in density and size. Therefore, it is necessary to develop a method for manufacturing a bonded SOI wafer that can suppress the formation of oxygen precipitates in the base wafer.

[0033] Even in the heat treatment in the SOI wafer manufacturing process for adjusting the surface roughness and film thickness after stripping, the density and size of oxygen precipitates will change, and if the conditions are selected, the density of oxygen precipitates can be reduced. However, in the base wafer where the SOI layer of the base oxidation method, especially the BOX layer, becomes thicker and has undergone a long BOX oxidation heat treatment (heat treatment under an oxidizing atmosphere), the heat treatment in the SOI wafer manufacturing process after stripping has a relatively small effect on oxygen precipitates, and it can be seen that the oxygen precipitates formed during the initial BOX oxidation heat treatment dominate. Therefore, the inventors of this case have found that it is important to suppress the formation of oxygen precipitates as much as possible during the initial BOX oxidation heat treatment.

[0034] As a method thereof, by starting the heat treatment from the highest possible temperature during the initial BOX oxidation heat treatment, the formation of oxygen precipitation nuclei at low temperatures is suppressed and the density and size of the precipitates are suppressed. In this way, the density and size of the oxygen precipitates can be suppressed even after subsequent heat treatment. More specifically, the input temperature to the heat treatment furnace is set to a higher temperature of 800°C or above, and the heat treatment furnace is used for BOX oxidation heat treatment of the base wafer, and it is further preferred that the base wafer is subjected to RTA heat treatment at a higher temperature of 800°C or above before being treated with the heat treatment furnace. The inventors of this case have found that this can reduce oxygen precipitation nuclei or inhibit their growth, and as a result, the density and size of oxygen precipitates can be reduced, thereby completing the present invention.

[0035] However, when the initial interstitial oxygen concentration of the base wafer is less than 15 ppma ('79 ASTM), the problem of slip dislocation is that the input temperature is above 800°C. The larger the diameter of the wafer, the more likely it is for such slip dislocation to occur. Such slip dislocation is likely to occur when heat treating a wafer having a diameter of more than 200 mm, especially a wafer having a diameter of more than 300 mm. In addition, when heat treating such a large-diameter wafer, the input temperature into the heat treatment furnace is usually set to a low temperature of about 500°C to 700°C to avoid slip dislocation.

[0036] In contrast, the present invention suppresses the occurrence of slip dislocations by using a wafer having an appropriately high oxygen concentration in the wafer, since it is difficult to suppress the occurrence of slip dislocations due to setting the input temperature to 800° C. or higher.

[0037] That is, the present invention is a method for manufacturing a bonded SOI wafer, which is a method for manufacturing a bonded SOI wafer by bonding a bonding wafer and a base wafer both made of single crystal silicon via a silicon oxide film, and is characterized by having:

[0038] A process of preparing a single crystal silicon wafer having an initial interstitial oxygen concentration of 15 ppma ('79 ASTM) or more as the base wafer;

[0039] When a silicon oxide film is formed on the surface of the base wafer by subjecting the base wafer to a heat treatment in an oxidizing atmosphere, the temperature at which the base wafer is introduced into a heat treatment furnace for performing the heat treatment is set to be 800° C. or higher, and the heat treatment of the base wafer is performed at a temperature higher than the introduction temperature to form the silicon oxide film;

[0040] a step of bonding the base wafer to the bonding wafer via the silicon oxide film;

[0041] The step of thinning the bonded wafers to form an SOI layer.

[0042] The method for manufacturing the bonded SOI wafer of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

[0043] like Figure 1 As shown, first, a single crystal silicon wafer having an initial interstitial oxygen concentration of 15 ppma ('79 ASTM) or more is prepared as a base wafer 1 ( Figure 1 , SP1).

[0044] In addition, a single crystal silicon wafer is prepared as the bonded wafer 3. The oxygen concentration of the bonded wafer 3 is not particularly limited.

[0045] As the base wafer of Si Photonics, a wafer with a normal resistivity (1-20Ω·cm) used as a standard and an oxygen concentration of more than 15ppma ('79ASTM) can generally be selected. There is no upper limit on the oxygen concentration, but 25ppma is sufficient. In such an oxygen concentration, a high-resistance wafer is sometimes selected from the perspective of improving RF characteristics. In this case, a low oxygen concentration is selected to suppress the decrease in resistivity caused by oxygen donors. However, in the case of forming a thicker BOX layer, in order to suppress the occurrence of slip during the BOX oxidation heat treatment, it is desirable to select a wafer with a higher oxygen concentration to a certain extent. However, if the oxygen concentration increases, it can be expected that the density and size of the oxygen precipitates formed by the heat treatment will also increase.

[0046] When the initial interstitial oxygen concentration of the base wafer 1 is less than 15 ppma ('79 ASTM), slip dislocations are likely to occur when the temperature of the base wafer 1 placed in the heat treatment furnace described later is 800° C. or higher. On the other hand, if the initial interstitial oxygen concentration of the base wafer 1 is 15 ppma ('79 ASTM) or higher, the occurrence of such slip dislocations can be suppressed.

[0047] The diameter of the base wafer 1 may be 200 mm or more. As described above, the larger the diameter of the wafer, the more likely slip dislocations will occur. However, in the present invention, a base wafer having a high initial interstitial oxygen concentration of 15 ppma ('79 ASTM) or more is used to suppress such slip dislocations.

[0048] Next, the base wafer 1 is subjected to a heat treatment (BOX oxidation heat treatment) in an oxidizing atmosphere to form a silicon oxide film 2 ( Figure 1 , SP2).

[0049] When forming the silicon oxide film 2, if the oxidation heat treatment temperature is high and the treatment time is long, there is a tendency that the density and size of the oxygen precipitates become larger, and this tendency depends largely on the density of the oxygen precipitation nuclei formed during the low-temperature thermal history before reaching the oxidation heat treatment temperature. Therefore, in order to reduce the low-temperature thermal history, the input temperature into the furnace is increased in the present invention (in the case of a batch type vertical furnace, it is the temperature when the boat is placed in the furnace).

[0050] Usually, the base wafer is put into the furnace while waiting at 500°C or 600°C. In the present invention, the temperature is set to 800°C or higher. By starting the above-mentioned heat treatment at a higher temperature, it is possible to reduce oxygen precipitation nuclei or inhibit their growth. This effect cannot be obtained if the input temperature is lower than 800°C. The upper limit of the input temperature is not particularly limited as long as it can inhibit slip dislocations, and is preferably below 1050°C, and more preferably below 1000°C.

[0051] The BOX oxidation heat treatment for forming the silicon oxide film 2 is performed at a temperature equal to or higher than the input temperature.

[0052] Batch type vertical furnaces are generally used for BOX oxidation heat treatment. Steam oxidation is often selected to increase the oxide film growth rate, and the oxidation heat treatment temperature is often set at a high side.

[0053] Furthermore, before the heat treatment in the batch type vertical furnace, the base wafer 1 is preferably subjected to RTA heat treatment at a temperature of 800° C. or higher.

[0054] Specifically, a single-chip lamp-heated RTA device can be used to perform a preheat treatment (RTO heat treatment) at a temperature of 800°C or higher, for example, at 1000°C in an oxidizing atmosphere. In this case, the generation of oxygen precipitation nuclei can be suppressed, and the oxygen precipitation nuclei can be eliminated to reduce the density. Thereafter, even if heat treatment is performed in a batch-type vertical furnace, the density will not increase as long as the preheat treatment (RTO heat treatment) is performed.

[0055] In addition, the use of an oxidizing atmosphere can suppress the roughness of the wafer surface.

[0056] In the step of forming the silicon oxide film 2 (SP2), the thickness of the silicon oxide film 2 formed on the surface of the base wafer 1 can be set to 1 μm or more. Thus, the present invention can suppress the formation of slip dislocations and oxygen precipitates and form the silicon oxide film 2 (BOX layer) of a desired thickness.

[0057] On the other hand, ion implantation can be performed on the prepared bonding wafer 3 to form an ion implantation layer 4 for peeling, and cleaning can be performed before bonding. The ion types for ion implantation include hydrogen ions and helium ions. The ion implantation conditions such as dose and acceleration voltage can be appropriately determined according to the required final SOI layer thickness, SOI layer thickness processing allowance thickness (layer thickness processing replacement thickness) in the SOI manufacturing process, etc.

[0058] The base wafer 1 is subjected to an oxidation heat treatment to form a silicon oxide film 2 on the surface of the base wafer 1, and then the base wafer 1 is bonded to the bonding wafer 3 via the silicon oxide film 2 ( Figure 1 , SP3).

[0059] Next, the bonded wafer 3 is thinned to form an SOI layer 5 ( Figure 1 , SP4).

[0060] More specifically, if the bonded wafers 1 and 3 are subjected to a peeling heat treatment and peeled off through the ion implantation layer 4, a thin film bonded SOI wafer 7 is formed with a silicon oxide film 2 and an SOI layer 5 formed on the base wafer 1. In addition, although a peeling wafer 6 is derived at this time, it can be reused as a new bonded wafer 3.

[0061] After that, the following may be performed: a bonding heat treatment to improve the bonding strength between the SOI layer 5 and the base wafer 1; a heat treatment to adjust the surface roughness and the thickness of the SOI layer. Although these heat treatments are sometimes performed at a higher temperature than the initial BOX oxidation heat treatment, the heat treatment time is not as long as the BOX oxidation heat treatment.

[0062] According to the method for manufacturing a bonded SOI wafer of the present invention as described above, it is possible to suppress the occurrence of slip dislocations and suppress the formation of oxygen precipitates on the base wafer 1. In addition, it is possible to efficiently manufacture a bonded SOI wafer 7 having a BOX layer of a desired thickness.

[0063] In addition, the above example illustrates the process of thinning the bonded wafer 3 by forming the ion implantation layer 4 and peeling off the ion implantation layer 4, but the present invention is not limited thereto. For example, the bonded wafer 3 may be thinned by combining grinding, polishing, etching, etc.

[0064] Example

[0065] The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0066] The method for manufacturing a bonded SOI wafer according to the present invention is as follows: Figure 1 The bonded SOI wafer 7 was manufactured using the following materials and conditions as shown in the explanatory diagram.

[0067] (Example 1)

[0068] A single crystal silicon wafer with a diameter of 300 mm, a crystal orientation of <100>, and an initial interstitial oxygen concentration of 21 ppma ('79 ASTM) was prepared as the base wafer 1. The base wafer 1 was subjected to an oxidation heat treatment at 1000°C in an oxidizing atmosphere using a batch type vertical oxidation furnace, thereby forming a 2 μm silicon oxide film (BOX layer) 2 on the surface of the base wafer 1. At this time, the input temperature to the vertical furnace was set to 800°C.

[0069] The base wafer 1 was bonded to the ion-implanted bonding wafer 3 (single crystal silicon wafer with a diameter of 300 mm and a crystal orientation of <100>) via a 2 μm silicon oxide film 2, and peeled off by peeling heat treatment, thereby forming a bonded SOI wafer 7 with an SOI structure. After peeling, an oxidation heat treatment was performed to improve the bonding strength, and an RTA heat treatment was performed to adjust the surface roughness. The oxygen precipitate density of the base wafer 1 was measured using LST (Laser Scattering Tomography) for the bonded SOI wafer 7 adjusted to the final film thickness, and the result was 1×10 8 pcs / cc.

[0070] Furthermore, the back surface of the base wafer 1 of the fabricated bonded SOI wafer 7 was observed under a spotlight, and no slip dislocation was observed.

[0071] (Example 2)

[0072] As the base wafer 1, a single crystal silicon wafer with a diameter of 300 mm, a crystal orientation of <100>, and an initial interstitial oxygen concentration of 21 ppma ('79 ASTM) was prepared. The base wafer 1 was heat treated at 1000°C for 60 seconds using a single-wafer lamp-heated RTA device in an oxygen atmosphere. Thereafter, an oxidation heat treatment was performed at 1000°C in an oxidizing atmosphere using a batch-type vertical oxidation furnace, thereby forming a 2μm silicon oxide film 2 on the surface of the base wafer 1. At this time, the input temperature to the vertical furnace was set to 800°C.

[0073] The base wafer 1 was bonded to the ion-implanted bonding wafer 3 (single crystal silicon wafer with a diameter of 300 mm and a crystal orientation of <100>) via a 2 μm silicon oxide film 2, and peeled off by a peeling heat treatment, thereby forming a bonded SOI wafer 7 with an SOI structure. After peeling off, an oxidation heat treatment was performed to improve the bonding strength, and an RTA heat treatment was performed to adjust the surface roughness. The oxygen precipitate density of the base wafer 1 was measured using LST for the bonded SOI wafer 7 adjusted to the final film thickness, and the result was 1×10 7 pcs / cc.

[0074] Furthermore, the back surface of the base wafer 1 of the fabricated bonded SOI wafer 7 was observed under a spotlight, and no slip dislocation was observed.

[0075] (Comparative Example 1)

[0076] A single crystal silicon wafer with a diameter of 300 mm, a crystal orientation of <100>, and an initial interstitial oxygen concentration of 21 ppma ('79 ASTM) was prepared as a base wafer 1. The base wafer 1 was subjected to an oxidation heat treatment at 1000°C in an oxidizing atmosphere using a batch type vertical oxidation furnace, thereby forming a 2 μm silicon oxide film 2 on the surface of the base wafer 1. At this time, the input temperature to the vertical furnace was set to 600°C.

[0077] The base wafer 1 was bonded to the ion-implanted bonding wafer 3 (single crystal silicon wafer with a diameter of 300 mm and a crystal orientation of <100>) via a 2 μm silicon oxide film 2, and peeled off by a peeling heat treatment, thereby forming a bonded SOI wafer 7 with an SOI structure. After peeling off, an oxidation heat treatment was performed to improve the bonding strength, and an RTA heat treatment was performed to adjust the surface roughness. The oxygen precipitate density of the base wafer 1 was measured using LST for the bonded SOI wafer 7 adjusted to the final film thickness, and the result was 7×10 8 pcs / cc.

[0078] Furthermore, the back surface of the base wafer 1 of the fabricated bonded SOI wafer 7 was observed under a spotlight, and no slip dislocation was observed.

[0079] (Comparative Example 2)

[0080] A single crystal silicon wafer with a diameter of 300 mm, a crystal orientation of <100>, and an initial interstitial oxygen concentration of 12 ppma ('79 ASTM) was prepared as a base wafer 1. The base wafer 1 was subjected to an oxidation heat treatment at 1000°C in an oxidizing atmosphere using a batch type vertical oxidation furnace, thereby forming a 2 μm silicon oxide film 2 on the surface of the base wafer 1. At this time, the input temperature to the vertical furnace was set to 800°C.

[0081] The base wafer 1 was bonded to the ion-implanted bonding wafer 3 (single crystal silicon wafer with a diameter of 300 mm and a crystal orientation of <100>) via a 2 μm silicon oxide film 2, and peeled off by a peeling heat treatment, thereby forming a bonded SOI wafer 7 with an SOI structure. After peeling off, an oxidation heat treatment was performed to improve the bonding strength, and an RTA heat treatment was performed to adjust the surface roughness. The oxygen precipitate density of the base wafer 1 was measured using LST for the bonded SOI wafer 7 adjusted to the final film thickness, and the result was 1×10 7 pcs / cc.

[0082] However, when the back surface of the base wafer 1 of the fabricated bonded SOI wafer 7 was observed under a spotlight, many slip dislocations were observed.

[0083] These results are shown in Table 1.

[0084] Table 1

[0085]

[0086] From the results shown in Table 1, it can be seen that in Examples 1 and 2 in which the initial interstitial oxygen concentration of the base wafer 1 is set to 15 ppma ('79 ASTM) or more and the temperature of introduction into the heat treatment furnace is set to 800° C., even when a base wafer with a diameter of 300 mm is used, slip dislocations can be suppressed and the density of oxygen precipitates can be suppressed compared to Comparative Examples 1 or 2.

[0087] In Example 2, unlike Example 1, RTA heat treatment is performed before the oxidation heat treatment for forming the silicon oxide film 2, but even if this preheating treatment is performed, it will not affect the effect of suppressing the occurrence of slip dislocations of the present invention. In addition, in Example 2, the density of oxygen precipitates in the base wafer can also be suppressed.

[0088] In addition, in all the embodiments and comparative examples, after the silicon oxide film 2 is formed, the base wafer 1 is subjected to the following: peeling heat treatment, oxidation heat treatment for improving bonding strength, and RTA heat treatment for adjusting surface roughness, so it can also be considered that the heat treatment time of the base wafer 1 is prolonged and the density of oxygen precipitates is increased. However, according to the results of embodiments 1, 2 and comparative example 2, it can be seen that the initial heat treatment temperature (input temperature) of the base wafer 1 is dominant for the formation of oxygen precipitates.

[0089] On the other hand, in Comparative Example 1, although the initial interstitial oxygen concentration of the base wafer 1 was 15 ppma ('79 ASTM) or more, the temperature of introduction into the heat treatment furnace was less than 800° C., and therefore it is considered that the density of oxygen precipitates could not be suppressed.

[0090] In Comparative Example 2, although the temperature introduced into the heat treatment furnace was 800° C., since the initial interstitial oxygen concentration of the base wafer 1 was less than 15 ppma ('79 ASTM), it is considered that many slip dislocations occurred.

[0091] As can be seen from the above, the method for manufacturing a bonded SOI wafer of the present invention can suppress the occurrence of slip dislocations and reduce the density of oxygen precipitates in the base wafer.

[0092] The present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are for illustrative purposes only, and any solution having substantially the same structure and producing the same effects 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 method for manufacturing a bonded SOI wafer, which is a method for manufacturing a bonded SOI wafer by bonding a bonding wafer and a base wafer both made of single crystal silicon via a silicon oxide film, characterized in that: have: A process of preparing a single crystal silicon wafer having an initial interstitial oxygen concentration of 15 ppma ('79 ASTM) or more as the base wafer; When a silicon oxide film is formed on the surface of the base wafer by subjecting the base wafer to a heat treatment in an oxidizing atmosphere, the temperature at which the base wafer is introduced into a heat treatment furnace for performing the heat treatment is set to be 800° C. or higher, and the heat treatment of the base wafer is performed at a temperature higher than the introduction temperature to form the silicon oxide film; a step of bonding the base wafer to the bonding wafer via the silicon oxide film; as well as a step of thinning the bonded wafers to form an SOI layer, The diameter of the base wafer is greater than 200 mm.

2. The method for manufacturing a bonded SOI wafer according to claim 1, characterized in that: Before the heat treatment, the base wafer is subjected to RTA heat treatment at a temperature above 800° C.

3. The method for manufacturing a bonded SOI wafer according to claim 1 or 2, characterized in that: In the step of forming the silicon oxide film, The thickness of the silicon oxide film formed on the surface of the base wafer is set to be greater than 1 μm.

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