JP4802624B2 - Manufacturing method of bonded SOI wafer - Google Patents

Description

  The present invention relates to a method for manufacturing a bonded SOI wafer by bonding a bond wafer made of a silicon single crystal wafer and a base wafer through an oxide film, and then thinning the bond wafer.

  As one method for manufacturing SOI wafers, two silicon single crystal wafers (bond wafer and base wafer) are bonded together through a silicon oxide film, and then the bonded wafer is thinned to form an SOI layer. The law is well known. The SOI wafer manufactured as described above has an SOI structure in which an SOI (Silicon On Insulator) layer is formed on a base wafer via a buried oxide film (BOX).

  When an SOI wafer is manufactured using the wafer bonding method, there is a problem that warpage occurs in the SOI wafer due to a difference in thermal expansion coefficient between the silicon single crystal and the silicon oxide film.

  In order to solve this problem, in the method described in Patent Document 1, a bonded wafer is manufactured as follows. That is, a silicon oxide film is formed on at least one main surface of any one of two wafers (bond wafer and base wafer), and the other wafer is formed such that the oxide film is an intermediate layer. After bonding to the wafer and forming the bonded wafer, the wafer is heated to a predetermined temperature and subjected to a bonding heat treatment for bonding the bond wafer and the base wafer, and then the bonded wafer is subjected to a thermal oxidation process (also serving as a bonding heat treatment). A thermal oxide film is formed on the entire surface, and one wafer (bond wafer), preferably, the surface of the wafer on which the silicon oxide film is formed before bonding heat treatment is polished to reduce the thickness, thereby bonding SOI. Manufacture wafers.

  As a result, when the upper wafer (bond wafer) is polished and thinned, the upper and lower surfaces of the other wafer (base wafer) are covered with silicon oxide films. The amount is substantially the same (that is, the residual stress distribution is substantially equal on the upper and lower surfaces), and the deformation of the wafer is prevented. As a result, a bonded SOI wafer with high flatness without warping can be obtained. It is said that.

  Further, according to Patent Document 2, the bonding is strengthened as a method other than the method of forming a thermal oxide film on the entire surface by thermally oxidizing the bonded wafer as in the method described in Patent Document 1. The bonding heat treatment itself is performed in a nitrogen atmosphere, and then a method of obtaining a bonded SOI wafer by depositing an oxide film on the main surface opposite to the bonded surface of the base wafer by a CVD method is disclosed. . And it is supposed that curvature can be suppressed by this.

  By the way, although the thickness of the silicon oxide film used as the buried oxide film (BOX) of the SOI wafer varies depending on the device application to be manufactured, a thickness in the range of about 0.1 to 2 μm is generally used. However, when used for a special purpose such as an optical waveguide in an optical integrated device or the like, it may be required to have a very thick buried oxide film of 4 μm or more, or 10 μm or more.

  In order to form such a thick buried oxide film by thermally oxidizing a silicon wafer, the silicon wafer must be put in a high-temperature heat treatment furnace for many days, and the production efficiency is extremely poor. Cost factor.

  Therefore, if an oxide film (hereinafter referred to as a CVD oxide film) is deposited and formed by CVD instead of the thermal oxide film, it is beneficial because a thick oxide film can be formed efficiently in a short time. In order to manufacture an SOI wafer in which this CVD oxide film becomes a BOX, a CVD oxide film having a predetermined thickness is deposited on one main surface (mirror surface side) of the bond wafer, and the CVD oxide film on the main surface as necessary. After polishing, a method of bonding to the base wafer, applying a bonding heat treatment for increasing the bonding strength, and then thinning the bond wafer side can be used.

  However, when an SOI wafer having a very thick BOX is manufactured in this way, the warpage of the SOI wafer and the occurrence of slip dislocations cannot be sufficiently suppressed only by the methods described in Patent Documents 1 and 2 above. There was a problem.

Japanese Patent Publication No. 6-80624 JP-A-11-97320

  The present invention has been made in view of such a problem, and even a bonded SOI wafer having a thick BOX can be manufactured efficiently and with sufficiently suppressed warpage. An object of the present invention is to provide a method for manufacturing a laminated SOI wafer.

  The present invention has been made to solve the above problems, and in the method for manufacturing a bonded SOI wafer, at least a bonded surface of at least one of a bond wafer composed of a silicon single crystal wafer and a base wafer is formed. A first silicon oxide film is formed on the main surface on the side by a CVD method, and the bonded wafer and the base wafer are bonded together via the first silicon oxide film to form a bonded wafer, and then the bonded wafer A second silicon oxide film is formed by CVD on the main surface opposite to the bonding surface of the base wafer constituting the substrate, the bond wafer is thinned, and then the first and second silicon oxide film forming temperatures are formed. Provided is a method for manufacturing a bonded SOI wafer characterized in that bonding heat treatment is performed at a higher temperature than (Claim 1).

  According to the present invention, in the method for manufacturing a bonded SOI wafer, at least one kind of hydrogen ion or rare gas ion is implanted from at least one main surface of a bond wafer made of a silicon single crystal wafer to form an ion implantation layer. Forming a first silicon oxide film by a CVD method on the main surface on the bonding surface of at least one of the base wafer composed of a bond wafer and a silicon single crystal wafer formed with the ion implantation layer; After the bonded wafer and the base wafer are bonded to each other through the first silicon oxide film to form a bonded wafer, the main surface opposite to the bonded surface of the base wafer constituting the bonded wafer A second silicon oxide film is formed on the substrate by CVD, and then the bond wafer is A method for manufacturing a bonded SOI wafer, comprising: bonding heat treatment at a temperature higher than the first and second silicon oxide film forming temperatures after the bond wafer is thinned by peeling at an on-implant layer. (Claim 2).

As described above, even in the conventional method, an oxide film is formed on the main surface opposite to the bonded surface of the base wafer in order to reduce the warpage of the SOI wafer. However, since the method of Patent Document 1 forms a thermal oxide film by a thermal oxidation process that also serves as a bonding heat treatment, when manufacturing an SOI wafer having a very thick BOX thickness, the thickness is equivalent to the BOX thickness. In order to form the thermal oxide film, heat treatment for a long time at a high temperature is required, and slip dislocation occurs frequently. On the other hand, the method of Patent Document 2 forms a CVD oxide film on the main surface opposite to the bonded surface of the base wafer after performing a high-temperature bonding heat treatment for firmly bonding the bond wafer and the base wafer. Is. For this reason, when manufacturing an SOI wafer having a very large BOX thickness, since a thick oxide film is formed only on one wafer after the high-temperature bonding heat treatment is completed, the silicon single crystal and the silicon oxide are formed. Large warpage occurs due to the difference in thermal expansion coefficient between the film and the slip dislocations frequently occur.
In contrast, according to the present invention, a second silicon oxide film is formed on the main surface opposite to the bonded surface of the base wafer by a CVD method, separately from the first silicon oxide film to be a BOX. For this reason, during the bonding heat treatment, the upper and lower surfaces of the base wafer are covered with the second silicon oxide film and the BOX. Even when an SOI wafer having a very large BOX thickness is manufactured, the base wafer The difference in heat shrinkage rate between the upper and lower surfaces can be reduced. In addition, since the bond wafer is thinned before the high temperature bonding heat treatment, the stress acting on the base wafer when the bond wafer shrinks during the cooling process after the bonding heat treatment is reduced, and warping after the bonding heat treatment is suppressed. As a result, the occurrence of slip dislocation can be suppressed.
Further, in the present invention, the first and second silicon oxide films are formed by the CVD method. Therefore, even a thick oxide film can be formed efficiently in a short time.

  In this case, it is preferable that the separation at the ion implantation layer is performed by performing a heat treatment at a temperature higher than the formation temperature of the second silicon oxide film.

  In the case of the ion implantation separation method, it is preferable to form the oxide film at such a low temperature that does not cause separation, and then perform separation at the ion implantation layer by heat treatment at a temperature higher than the oxide film formation temperature.

  In the method for manufacturing a bonded SOI wafer according to the present invention, the thickness of the first silicon oxide film can be 4 μm or more.

  As described above, in the method for manufacturing a bonded SOI wafer according to the present invention, even when the thickness of the first silicon oxide film is very thick, such as 4 μm or more, warping can be sufficiently suppressed.

  In the method for manufacturing a bonded SOI wafer according to the present invention, it is preferable that the difference between the thickness of the second silicon oxide film and the thickness of the first silicon oxide film is within 1 μm.

  Thus, if the difference between the thickness of the second silicon oxide film and the thickness of the first silicon oxide film is within 1 μm, the difference in thermal shrinkage between the upper and lower surfaces of the base wafer can be reduced. Thereby, even if the thickness of the BOX is extremely thick, the warp generated during the bonding heat treatment can be more reliably suppressed.

  As described above, according to the bonded SOI wafer manufacturing method of the present invention, even a bonded SOI wafer having a thick BOX can be manufactured efficiently and with less warpage. Is possible.

Hereinafter, the present invention will be described in more detail.
First, when manufacturing an SOI wafer having a very thick BOX, the present inventors have investigated, in order to find out the cause that the conventional method could not sufficiently suppress the occurrence of warpage of the SOI wafer. I did research.

As described above, in the case of forming a very thick buried oxide film (BOX) of 4 μm or more, or 10 μm or more, since it is not efficient to form by thermal oxidation, it may be formed by a CVD method.
In this case, the inventors of the present invention do not have a large warp even when the CVD oxide film is thick when a CVD oxide film having a predetermined thickness is deposited on one main surface of the bond wafer. I noticed that would occur. This is considered to be caused by the fact that the bonding heat treatment is performed at a temperature higher than the formation temperature of the CVD oxide film, so that a large shrinkage occurs in the CVD oxide film (the CVD oxide film formation temperature is usually 800 ° C.). The following is the low temperature).

Thus, when the BOX is thick, even if thermal oxidation treatment (bonding heat treatment) is performed to form an oxide film on the entire surface as in the method described in Patent Document 1, thermal oxidation is formed. Since the film is thinner than the thickness of the BOX, the effect is suppressed to a small level. For this reason, generation | occurrence | production of the curvature of a SOI wafer cannot fully be suppressed.
On the other hand, in the case of a method of forming a CVD oxide film on the main surface opposite to the bonding surface of the base wafer after the bonding heat treatment as in the method described in Patent Document 2, the wafer is formed by the bonding heat treatment as described above. Has already largely warped. For this reason, even if a CVD oxide film is formed on the main surface opposite to the bonded surface of the base wafer, warping of the SOI wafer cannot be sufficiently suppressed. In addition, if an SOI wafer that has been warped is flattened in this way, an additional high-temperature heat treatment is required, which is not efficient, and a stress is applied to the wafer that has already warped in the opposite direction. As a result, slip dislocation is likely to occur, and the mechanical strength of the wafer is reduced.

  Therefore, as a result of intensive studies, the present inventors have determined that, prior to the bonding heat treatment, apart from the first silicon oxide film that becomes the BOX, the side opposite to the bonding surface of the base wafer constituting the bonded wafer If the second silicon oxide film is formed on the main surface of the substrate by CVD and the bond wafer is further thinned, the upper and lower surfaces of the base wafer are covered with the second silicon oxide film and the buried oxide film (BOX). Therefore, the difference in thermal shrinkage between the upper and lower surfaces of the base wafer can be reduced, and since the bond wafer is thinned, the bond wafer shrinks in the cooling process of the bonding heat treatment. The acting stress is reduced. As a result, it was conceived that an SOI wafer with less slip dislocations can be produced efficiently and with sufficient warpage, and the present invention was completed.

Hereinafter, although embodiment of this invention is described, this invention is not limited to these.
FIG. 1 is an explanatory view showing an example of a method for manufacturing a bonded SOI wafer according to the present invention.
First, in the first step (see FIG. 1A), a base wafer 11 and a bond wafer 14 made of a silicon single crystal wafer are prepared.

In the next step (see FIG. 1B), the bond wafer 14 is held by the susceptor 12 of the CVD apparatus (not shown), and the first silicon is formed on the main surface on the bonding surface side of the bond wafer 14 by the CVD method. An oxide film 13 is formed. Then, if necessary, a step of flattening the surface of the first silicon oxide film 13 by polishing is added.
When the bonded SOI wafer is used for a special application such as an optical waveguide in an optical integrated device or the like, an extremely thick buried oxide film of 4 μm or more, or 10 μm or more is required. If the 1 silicon oxide film is formed by the CVD method in this way, even a thick oxide film can be formed efficiently and in a short time.
At this time, the first silicon oxide film may be formed not on the bond wafer 14 but on the base wafer 11 or on both wafers.

  In the next step (see FIG. 1C), a bonded wafer 15 is formed by bonding the bond wafer 14 and the base wafer 11 through the first silicon oxide film 13. For example, by bringing the surface of the first silicon oxide film 13 and one main surface of the base wafer 11 into contact with each other in a clean atmosphere at room temperature, the wafers are bonded without using an adhesive or the like.

In the next step (see FIG. 1D), the bonded wafer 15 is again held by the susceptor 12 of the CVD apparatus (not shown), and a CVD method is applied to the main surface opposite to the bonded surface of the base wafer 11. Thus, the second silicon oxide film 16 is formed. The thickness of the second silicon oxide film 16 is preferably the same as that of the first silicon oxide film to be a BOX, but if the difference between these thicknesses is 1 μm or less, the BOX thickness is 4 μm or more. Even so, the warp caused by the difference in oxide film thickness can be made 100 μm or less (in the case of a diameter of 200 mm).
In this case, since the main surface opposite to the bonding surface of the bond wafer 14 is in contact with the susceptor 12, the problem of contamination is a concern. However, according to the method of FIG. 1, the portion that comes into contact with the susceptor is removed in the subsequent thinning process, so that the problem of contamination does not need to be so much concerned.

  In the next step (see FIG. 1E), the bond wafer 14 is thinned by a method such as surface grinding, polishing, or etching. If the thickness of the bond wafer 14 after thinning is 100 μm or less, preferably 50 μm or less, the stress acting on the base wafer when the bond wafer shrinks during the cooling process after the bonding heat treatment is sufficiently small, and warping is sufficient. Can be suppressed.

  In the next step (see FIG. 1F), the bonding heat treatment is performed at a temperature higher than the formation temperature of the first and second silicon oxide films 13 and 16. Before the bonding heat treatment, the bonding strength is insufficient, so it cannot be used in the device manufacturing process as it is. For this reason, the bonded SOI wafer 15 is subjected to a high-temperature heat treatment as a bonding heat treatment so that the bonding strength is sufficient. For example, the heat treatment can be performed in an inert gas atmosphere at 1050 ° C. to 1200 ° C. for 30 minutes to 2 hours.

  At this time, if an oxide film is provided only on one surface of the base wafer, the wafer is not bonded during the bonding heat treatment due to the difference in thermal expansion coefficient between the silicon single crystal and the silicon oxide film. It will be greatly warped. However, according to the method of the present invention of FIG. 1, the upper and lower surfaces of the base wafer 11 are covered with the second silicon oxide film 16 and the first silicon oxide film 13, that is, the buried oxide film (BOX). For this reason, even when the difference in thermal shrinkage between the upper and lower surfaces of the base wafer 11 is small and the thickness of the BOX is extremely thick, it is possible to sufficiently suppress the warpage that occurs during the bonding heat treatment.

  Then, after the bonding heat treatment, the surface of the bond wafer 14 thinned as necessary is polished to finally form the first silicon oxide film 13 as a buried oxide film (BOX), on which the SOI layer 18 is formed. The bonded SOI wafer 10 formed with is manufactured.

Next, FIG. 2 is explanatory drawing which shows another example of the manufacturing method of the bonding SOI wafer of this invention. This method is called a so-called ion implantation separation method.
First, in the first step (see FIG. 2A), a base wafer 21 and a bond wafer 24 made of a silicon single crystal wafer are prepared. Then, at least one of hydrogen ions or rare gas ions is implanted from one main surface of the bond wafer 24. Thereby, the ion implantation layer 27 parallel to the surface can be formed inside the bond wafer 24 at the average ion penetration depth. At this time, a thin oxide film may be formed in advance on the ion implantation surface of the bond wafer in order to prevent channeling. The depth of the ion implantation layer 27 at this time is reflected in the thickness of the finally formed SOI layer 28. Therefore, the thickness of the SOI layer can be controlled by performing ion implantation while controlling the implantation energy and the like.

In the next step (see FIG. 2B), the bond wafer 24 is held on the susceptor 22 of the CVD apparatus (not shown), and the first main surface on the side that becomes the bonding surface of the bond wafer 24 is formed by the CVD method. After the formation of the silicon oxide film 23, the surface of the first silicon oxide film 23 is polished as necessary. The bonded surface of the bond wafer 24 is usually the same as the surface on which ion implantation has been performed.
At this time, the first silicon oxide film may be formed on the base wafer 21 instead of the bond wafer 24, or may be formed on both wafers.

  In the next step (see FIG. 2C), a bonded wafer 25 is formed by bonding the bond wafer 24 and the base wafer 21 with the first silicon oxide film 23 interposed therebetween.

  In the next step (see FIG. 2D), the bonded wafer 25 is again held on the susceptor 22 of the CVD apparatus (not shown), and the CVD method is applied to the main surface opposite to the bonded surface of the base wafer 21. Thus, the second silicon oxide film 26 is formed.

  In the next step (see FIG. 2E), the bond wafer 24 is thinned by peeling off the bond wafer 24 with the ion implantation layer 27. For example, if heat treatment is applied to the bonded wafer 25 at a temperature of about 500 ° C. or higher in an inert gas atmosphere, the bond wafer 24 is peeled off by the ion implantation layer 27 due to crystal rearrangement and bubble aggregation. Can do.

At this time, the separation at the ion implantation layer 27 is preferably performed by performing a heat treatment at a temperature higher than the formation temperature of the second silicon oxide film 26. This is because the second silicon oxide film is formed at a low temperature that does not cause peeling, and then the ion implantation layer is peeled off by heat treatment at a temperature higher than the oxide film forming temperature.
Note that, when the peeling heat treatment is performed at a temperature higher than the formation temperature of the second silicon oxide film, a large shrinkage occurs in the silicon oxide film, but according to the method of FIG. Since it is covered with the second silicon oxide film and the first silicon oxide film, the difference in thermal shrinkage between the upper and lower surfaces of the base wafer is reduced. In addition, since peeling occurs in the ion-implanted layer during the heat treatment, the bond wafer is already thinned in the cooling process, and warpage can be sufficiently prevented.

In the next step (see FIG. 2F), the bonding heat treatment is performed at a temperature higher than the temperature at which the first and second silicon oxide films 23 and 26 are formed.
Also at this time, the upper and lower surfaces of the base wafer 21 are covered with the second silicon oxide film 26 and the first silicon oxide film 23, that is, the buried oxide film (BOX). For this reason, the warp generated during the bonding heat treatment can be sufficiently suppressed as described in the method of FIG.

  In the last step (see FIG. 2G), polishing or heat treatment for planarizing the SOI layer is performed, and finally the first silicon oxide film 23 is formed as a buried oxide film (BOX). The bonded SOI wafer 20 having the SOI layer 28 formed thereon is manufactured.

  Here, in any of the methods shown in FIGS. 1 and 2, it is preferable that the thickness of the second silicon oxide film is equal to the thickness of the first silicon oxide film. Thus, if the thickness of the second silicon oxide film is made equal to the thickness of the first silicon oxide film, the difference in thermal shrinkage rate between the upper and lower surfaces of the base wafer can be made substantially the same. Thereby, even if the thickness of the BOX is extremely large, the warp generated during the bonding heat treatment can be further suppressed.

  According to the methods shown in FIGS. 1 and 2, even if the bonded BOX is a very thick bonded SOI wafer having a BOX thickness of 4 μm or more, particularly 10 μm or more, the generation of warpage is suppressed efficiently. Can be manufactured.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited to these.
Example 1
A bonded SOI wafer 10 was manufactured according to the method of FIG.
First, as shown in FIG. 1A, a base wafer 11 and a bond wafer 14 made of a silicon single crystal wafer having a diameter of 200 mm, a plane orientation (100), a p-type, 10 Ωcm, and a thickness of 725 μm and single-side mirror polished. Got ready.
Next, as shown in FIG. 1B, the bond wafer 14 is held on the susceptor 12 of the CVD apparatus, and the first surface by the CVD method is formed on the main surface (mirror surface side) that becomes the bonding surface of the bond wafer 14. A silicon oxide film 13 was formed. The deposition conditions for the first silicon oxide film 13 are as follows. Source gas: SiH ₄ , O ₂ , Deposition temperature: 700 ° C., Deposition pressure: normal pressure, Deposition film thickness: 10 μm, Surface polishing: Polishing allowance 100 nm by CMP. The warpage amount of the bond wafer 14 after forming the first silicon oxide film 13 was 30 μm.
Next, as shown in FIG. 1C, the surface of the first silicon oxide film 13 of the bond wafer 14 and the mirror surface of the base wafer 11 were bonded together at room temperature to form a bonded wafer 15.

Next, as shown in FIG. 1D, a second silicon oxide film 16 was formed by a CVD method on the main surface opposite to the bonding surface of the base wafer 11 constituting the bonded wafer 15. The deposition conditions of the second silicon oxide film 16 were the same as the deposition conditions of the first silicon oxide film 13 except that the surface polishing was not performed.
Next, as shown in FIG. 1E, the bond wafer 14 was thinned by surface grinding and surface polishing. The grinding allowance for surface grinding at this time was 680 μm, and the allowance for surface polishing was 15 μm.
Finally, as shown in FIG. 1 (f), bonding heat treatment was performed at 1100 ° C. for 2 hours in an Ar 100% atmosphere. The temperature of this bonding heat treatment is higher than the formation temperature of the first and second silicon oxide films 13 and 16.
In this way, a bonded SOI wafer 10 was manufactured. The warpage amount of the manufactured bonded SOI wafer was 15 μm.

(Comparative Example 1)
A bonded SOI wafer was manufactured in the same manner as in Example 1 except that the second silicon oxide film was not formed on the base wafer by the CVD method. However, the bond wafer was thinned after the bonding heat treatment.
The warpage amount of the manufactured bonded SOI wafer was 800 μm.

  Table 1 below summarizes the manufacturing conditions of the bonded SOI wafer manufactured in Example 1 and Comparative Example 1.

Looking at Comparative Example 1, the warpage amount of the bond wafer when forming the first silicon oxide film was 10 μm, whereas the warpage amount of the bonded SOI wafer after the bonding heat treatment was 800 μm. That is, when a high-temperature bonding heat treatment is performed without forming a second silicon oxide film on the base wafer by a CVD method before the high-temperature bonding heat treatment, and the bond wafer is thinned, the bonded SOI wafer is greatly warped. I understand that.
On the other hand, in Example 1, before the high-temperature bonding heat treatment, the second silicon oxide film is formed on the base wafer by the CVD method, whereby the upper and lower surfaces of the base wafer are respectively formed with the second silicon oxide film. Since it is covered with the first silicon oxide film and thinned before the bonding heat treatment, it can be seen that the warpage generated during the high-temperature bonding heat treatment and the cooling process can be sufficiently suppressed.

(Example 2)
A bonded SOI wafer was manufactured according to the method of FIG.
First, as shown in FIG. 2 (a), a base wafer 21 and a bond wafer 24 made of a silicon single crystal wafer having a diameter of 200 mm, a plane orientation (100), a p-type, 10 Ωcm, and a thickness of 725 μm and polished on one side. Got ready. Then, hydrogen ions were implanted from the main surface on the mirror surface side of the bond wafer 24 to form an ion implantation layer 27. The ion implantation conditions are as follows. Injection energy: 40 keV, injection amount: 8E16 / cm ² (8 × 10 ¹⁶ / cm ² ), injection angle: 7 degrees.
Next, as shown in FIG. 2B, the bond wafer 24 is held on a susceptor 22 of a CVD apparatus (not shown), and CVD is performed on the main surface on the side (mirror surface side) that becomes the bonding surface of the bond wafer 24. A first silicon oxide film 23 was formed by the method. The deposition conditions for the first silicon oxide film 23 are as follows. Source gas: SiH ₄ , O ₂ , deposition temperature: 400 ° C., deposition pressure: normal pressure, deposition film thickness: 10 μm, surface polishing: 100 nm polishing cost by CMP. The warpage amount of the bond wafer 24 after forming the first silicon oxide film 23 was 10 μm.
Next, as shown in FIG. 2C, the surface of the first silicon oxide film 23 of the bond wafer 24 and the mirror surface of the base wafer 21 were bonded together at room temperature to form a bonded wafer 25.

Next, as shown in FIG. 2D, a second silicon oxide film 26 was formed on the main surface opposite to the bonding surface of the base wafer 21 constituting the bonded wafer 25 by the CVD method. The deposition conditions of the second silicon oxide film 26 were the same as the deposition conditions of the first silicon oxide film 23 except that the surface polishing was not performed.
Next, as shown in FIG. 2 (e), the bond wafer 24 was thinned by peeling the bond wafer 24 with an ion implantation layer 27. The conditions for the peeling heat treatment are as follows. Heat treatment temperature: 500 ° C., heat treatment time: 30 minutes, heat treatment atmosphere: Ar 100%, post-peeling SOI layer thickness: about 350 nm.
Next, as shown in FIG. 2F, bonding heat treatment was performed at 1100 ° C. for 2 hours in an Ar 100% atmosphere. The temperature of the bonding heat treatment is higher than the formation temperature of the first and second silicon oxide films 23 and 26 and the peeling heat treatment temperature.
Finally, as shown in FIG. 2G, polishing for planarizing the SOI layer was performed. The polishing allowance at this time was 100 nm.
In this way, a bonded SOI wafer 20 was manufactured. The warpage amount of the manufactured bonded SOI wafer was 12 μm.

(Comparative Example 2)
A bonded SOI wafer was manufactured in the same manner as in Example 2 except that the second silicon oxide film was not formed on the base wafer by the CVD method.
The warpage amount of the manufactured bonded SOI wafer was 790 μm.

  Table 2 below summarizes the manufacturing conditions of the bonded SOI wafer manufactured in Example 2 and Comparative Example 2.

In Comparative Example 2, the warpage amount of the bond wafer when forming the first silicon oxide film was 10 μm, whereas the warpage amount of the bonded SOI wafer after the high-temperature bonding heat treatment was 790 μm. . That is, it can be seen that when the high-temperature bonding heat treatment is performed without forming the second silicon oxide film on the back surface of the base wafer constituting the bonded wafer by the CVD method, the bonded SOI wafer is greatly warped.
On the other hand, in Example 2, since the second silicon oxide film is formed on the base wafer by the CVD method before the peeling heat treatment and the bonding heat treatment, the warp generated during the high-temperature bonding heat treatment is sufficiently suppressed. You can see that

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

It is explanatory drawing which shows an example of the manufacturing method of the bonding SOI wafer of this invention. It is explanatory drawing which shows another example of the manufacturing method of the bonding SOI wafer of this invention.

Explanation of symbols

10, 20 ... Bonded SOI wafer, 11, 21 ... Base wafer,
12, 22 ... susceptor, 13, 23 ... first silicon oxide film,
14, 24 ... Bond wafer, 15, 25 ... Bonded wafer,
16, 26 ... second silicon oxide film, 27 ... ion implantation layer,
18, 28 ... SOI layer.

Claims (5)

  In the method for manufacturing a bonded SOI wafer, a first silicon oxide film is formed by a CVD method on at least a main surface on a bonding surface of at least one of a bond wafer made of a silicon single crystal wafer and a base wafer. The bonded wafer and the base wafer are bonded to each other through the first silicon oxide film to form a bonded wafer, and then the main wafer opposite to the bonded surface of the base wafer constituting the bonded wafer is formed. A bonded SOI, wherein a second silicon oxide film is formed on the surface by a CVD method, the bond wafer is thinned, and then a bonding heat treatment is performed at a temperature higher than the first and second silicon oxide film forming temperatures. Wafer manufacturing method.   In a method for manufacturing a bonded SOI wafer, at least one kind of hydrogen ion or rare gas ion is implanted from at least one main surface of a bond wafer made of a silicon single crystal wafer to form an ion implantation layer, and the ion implantation is performed. A first silicon oxide film is formed by a CVD method on a principal surface on the side to be a bonding surface of at least one of a base wafer made of a bond wafer and a silicon single crystal wafer formed with a layer, and the first silicon oxide film The bonded wafer and the base wafer are bonded to each other through a wafer to form a bonded wafer, and then a second surface is formed on the main surface opposite to the bonded surface of the base wafer constituting the bonded wafer by a CVD method. A silicon oxide film is formed, and then the bond wafer is peeled off by the ion implantation layer. By the after the bond wafer is thinned, the first and method for producing a bonded SOI wafer characterized by bonding heat treatment at a temperature higher than the second silicon oxide film formation temperature. 3. The method for manufacturing a bonded SOI wafer according to claim 2, wherein the second silicon oxide film is formed at a temperature that does not cause peeling at the ion implantation layer .   4. The method for manufacturing a bonded SOI wafer according to claim 1, wherein a thickness of the first silicon oxide film is 4 μm or more. 5.   5. The bonded SOI wafer according to claim 1, wherein a difference between the thickness of the second silicon oxide film and the thickness of the first silicon oxide film is set to 1 μm or less. Manufacturing method.

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