JP2006270039A - Laminated wafer and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a laminated wafer efficiently etching an oxide film formed at a terrace of a base wafer without etching the oxide film on a backside of the base wafer. <P>SOLUTION: A method of manufacturing a laminated wafer manufactured by at least laminating a base wafer and a bond wafer comprises the step of etching an oxide film of a terrace of an outer periphery of the laminated wafer. The etching of the oxide film of the terrace is performed by spin etching with the laminated wafer being held and rotated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a bonded wafer and a bonded wafer, and more particularly to a method for etching an oxide film formed on a terrace portion of a bonded wafer.

As a wafer for a high-performance device, a bonded wafer is used in which a semiconductor wafer is bonded to another wafer and then a wafer on the side on which an element is manufactured is thinned.
Specifically, for example, two mirror-polished silicon wafers are prepared, and an oxide film is formed on at least one of the wafers. And after joining these wafers, it heat-processes at the temperature of 200-1200 degreeC, and raises bond strength. Thereafter, a bonded SOI wafer on which an SOI (Silicon On Insulator) layer is formed can be manufactured by grinding and polishing the element fabrication side wafer (bond wafer) to a desired thickness.

  As a method of thinning the bond wafer, in addition to the above-described grinding and polishing methods, an ion implantation layer such as hydrogen ions is previously formed on the bond wafer before bonding, and the ions are bonded to the base wafer. There is also a method (also referred to as Smart Cut (registered trademark)) in which a bond wafer is thinned by peeling at an injection layer.

  In the case of manufacturing a bonded wafer, silicon wafers can be directly bonded without using an oxide film, and an insulating wafer such as quartz, silicon carbide, or alumina may be used as a base wafer.

When manufacturing a bonded wafer as described above, there is a part called a polishing sag and a chamfered part with a slightly reduced thickness at the peripheral part of the two mirror-finished wafers to be bonded, and these parts are not joined together. Or, it remains as an unbonded portion having a weak binding force. If thinning is performed by grinding or the like while such an unbonded portion exists, a part of the unbonded portion is peeled off during the thinning process. Accordingly, the thinned bond wafer has a smaller diameter than the base wafer (base wafer), and minute irregularities are continuously formed in the peripheral portion.
When such a bonded wafer is introduced into the device process, the remaining unbonded portion is peeled off in the device process, generating particles and reducing the device yield.

  Therefore, a method has been proposed in which a remaining unbonded portion is removed in advance by attaching a masking tape so that the peripheral portion is exposed on the upper surface of the bond wafer after thinning, and performing etching (see Patent Document 1). .) The outer peripheral region from which the unbonded portion is removed is called a terrace portion.

  On the other hand, in the method of thinning by peeling off with the ion-implanted layer, the unbonded portion of the polishing sag portion becomes a terrace portion after peeling, and particles are generated from the periphery of the thin film as in the case of thinning by grinding and polishing. There was a problem that it occurred or cracked. Therefore, a method for removing the peripheral portion of the thin film formed on the base wafer after peeling has been proposed (see Patent Document 2).

  However, in the case of thinning by grinding and polishing, there is an oxide film residue formed by heat treatment (bonding heat treatment) to increase the bonding strength in the terrace portion formed by removing the unbonded portion. There was a problem that the film became a source of dust generation during the device fabrication process. In order to solve this problem, an oxide film removing process is performed on the terrace portion. For example, after the unbonded portion is removed, the oxide film is removed by immersing the bonded wafer in hydrofluoric acid. When this method is used, not only the surface of the bonded wafer (including the terrace portion) but also the oxide film on the back surface is removed.

  On the other hand, in the case of an SOI wafer in which an SOI layer is formed on a base wafer via an oxide film, a buried oxide film is formed on one side of the base wafer, and warpage occurs because there is no oxide film on the other side. Sometimes. Therefore, an oxide film may be formed on the back side of the SOI wafer to suppress warpage. In this case, it is necessary to remove the front side oxide film and leave the back side.

  As described above, when only the oxide film on the front side is removed while leaving the oxide film on the back side of the SOI wafer, the SOI wafer is immersed in hydrofluoric acid with the back side of the wafer masked with a masking tape, a photoresist or the like. The method is taken. However, such a method has a problem that it takes time to attach and remove the masking tape or to expose and remove the photoresist, and it is complicated, resulting in poor working efficiency. In addition, since a large amount of etching solution is used, there is a problem that the cost is high.

  In the case of thinning by exfoliating with an ion implantation layer, if an oxide film is formed and bonded to the base wafer, the oxide film remains on the terrace after the exfoliation, but the oxide film is only applied to the bond wafer side. When formed and bonded, an oxide film does not remain on the terrace portion after peeling. However, when a heat treatment for increasing the bond strength is performed in an oxidizing atmosphere thereafter, an oxide film is also formed on the terrace portion.

  In this way, when epitaxial growth is performed on the SOI layer of the SOI wafer in which the oxide film is formed on the terrace portion, polysilicon grows on the terrace portion, which may adversely affect the crystallinity of the SOI layer, It becomes a generation factor.

  By the way, although the thickness of the silicon oxide film which becomes the buried oxide film (BOX) of the SOI wafer varies depending on the device application to be manufactured, a range of about 0.1 to 2 μm is generally used. When used for special applications such as optical waveguides, there is a case where an extremely thick oxide film of 4 μm or more, or 10 μm or more is required. When an SOI wafer having such an extremely thick buried oxide film is to be produced by the method of thinning by peeling off the above-described ion implantation layer, an extremely large ion implantation is required to perform ion implantation through the oxide film. It is not realistic because it requires energy. Therefore, a method is employed in which a thick oxide film is formed on the base wafer side and bonded together. In this case, an extremely thick oxide film remains on the terrace portion after peeling, which causes the above-described problem.

JP-A-3-250616 Republished patent WO01 / 027999

  The present invention has been made in view of the above problems, and is a bonded wafer that efficiently etches an oxide film formed on a terrace portion of a base wafer without removing the oxide film on the back surface of the base wafer. The object is to provide a manufacturing method.

  The present invention has been made to solve the above-described problems, and includes a step of etching an oxide film on a terrace portion of an outer peripheral portion of a bonded wafer, which is produced by bonding at least a base wafer and a bond wafer. There is provided a method for manufacturing a bonded wafer, wherein the etching of the oxide film in the terrace portion is performed by spin etching while holding and rotating the bonded wafer ( Claim 1).

  When the oxide film on the terrace portion is etched by spin etching while holding and rotating the bonded wafer as described above, the etching solution is scattered outward by centrifugal force and does not enter the back surface of the base wafer. Therefore, the oxide film formed on the terrace portion can be efficiently and uniformly etched without removing the oxide film on the back surface of the wafer. In addition, it is not necessary to protect the back surface of the wafer from the etching solution using a masking tape or the like as in the prior art, and the number of steps can be reduced and the working efficiency can be increased.

  In this case, after manufacturing the bonded wafer for etching the oxide film of the terrace portion, at least the base wafer and the bond wafer are closely bonded, and after being subjected to heat treatment in an oxidizing atmosphere and bonded, The outer peripheral portion of the bond wafer is removed by grinding to a predetermined thickness, and then the unbonded portion of the outer peripheral portion of the bond wafer is removed by etching, and then the bond wafer is thinned to a desired thickness. After the bonding portion is etched or the bond wafer is thinned, the oxide film in the terrace portion can be etched by spin etching.

  As described above, the present application relates to the manufacture of a bonded wafer for etching the oxide film on the terrace portion, at least by bonding the base wafer and the bond wafer, and applying heat treatment to the bonded wafer in an oxidizing atmosphere. Thereafter, the outer peripheral portion of the bond wafer is removed by grinding to a predetermined thickness, and then the unbonded portion of the outer peripheral portion of the bond wafer is removed by etching, and then the bond wafer is thinned to a desired thickness. It can be used when the oxide film in the terrace portion is etched by spin etching after the unbonded portion is etched or the bond wafer is thinned.

  In addition, in the manufacture of the bonded wafer for etching the oxide film on the terrace portion, at least after ion implantation is performed on the bond wafer and the bond wafer and the base wafer are brought into close contact with each other, the ion implantation layer is used to form the bonded wafer. This can be done by peeling off the bond wafer to make it thinner (Claim 3).

  As described above, in the present application, the bonded wafer for etching the oxide film in the terrace portion is manufactured by at least implanting ions into the bond wafer and bringing the bond wafer and the base wafer into close contact with each other. It can also be used in the case where the bonding wafer is peeled off from the injection layer to form a thin film.

  In this case, it is preferable to use an HF aqueous solution as the etching solution for the spin etching.

  As described above, the oxide film can be efficiently etched using the HF aqueous solution.

  In this case, it is preferable to use a 50% HF aqueous solution as the HF aqueous solution.

  In this way, when an HF 50% aqueous solution is used as an etching solution for spin etching, high-speed etching can be performed to increase working efficiency.

  In this case, it is preferable that the spin etching is performed by supplying an etching solution directly to the terrace portion.

  When the spin etching is performed by supplying the etching solution directly to the terrace portion in this way, the etching solution does not flow to the central portion of the bonded wafer (for example, the surface of the SOI layer). Even if there is, there is little possibility that the etching solution erodes the BOX through the minute defects in the SOI layer.

  In this case, it is preferable to perform the spin etching while supplying a fluid that protects the central portion from the etching solution to the central portion of the bonded wafer.

  In this way, if the spin etching is performed while supplying a fluid that protects the central portion from the etching solution to the central portion of the bonded wafer, the etching solution flows into the central portion of the bonded wafer (for example, the surface of the SOI layer). Therefore, even if there are micro defects in the SOI layer, the possibility that the etching solution erodes the BOX through the micro defects in the SOI layer is further reduced.

  In this case, any one of water, air, nitrogen gas, and inert gas can be used as the fluid.

  Thus, any of water, air, nitrogen gas, and inert gas can be used as a fluid for protecting the central portion of the bonded wafer from the etching solution.

  In this case, the remaining thickness of the oxide film formed on the terrace portion of the base wafer can be controlled by adjusting the processing time of the spin etching and / or the concentration of the etching solution.

  As described above, the thickness of the oxide film in the terrace portion can be controlled as desired by adjusting the spin etching processing time and / or the concentration of the etching solution.

  Preferably, the base wafer and the bond wafer before bonding are silicon single crystal wafers having an oxide film formed on at least one of them.

  As described above, the method of the present invention can be used for manufacturing a bonded SOI wafer in which a base wafer made of a silicon single crystal wafer and a bond wafer are joined through an insulating film made of an oxide film.

  Further, it is preferable that the bond wafer is thinned and an oxide film is formed on the surface of the bond wafer before the spin etching is performed.

  In this way, even if the etching solution has reached the surface of the bond wafer, BOX erosion can be reliably prevented.

  In addition, it is preferable to supply ozone water to the terrace portion after performing the spin etching.

  In this way, since the terrace portion after removal of the oxide film can be made hydrophilic, adhesion of particles can be suppressed.

  Further, an SOI wafer can be manufactured as the bonded wafer (claim 13).

  As described above, the present invention can be suitably used for manufacturing an SOI wafer.

  In this case, the thickness of the SOI layer of the SOI wafer can be 0.5 μm or less.

  Thus, the present invention is effective for protecting the BOX when the SOI layer of the SOI wafer is as thin as 0.5 μm or less.

  In this case, after manufacturing the SOI wafer, an Si or SiGe epitaxial layer can be formed on the surface of the SOI layer of the SOI wafer.

  Thus, if the SOI wafer from which the oxide film on the terrace portion is removed, even if an epitaxial layer of Si or SiGe is formed, the formation of polysilicon can be prevented, and the crystallinity of the SOI layer is not adversely affected. Generation of particles can be suppressed.

  The present invention also provides a bonded wafer manufactured by the above-described bonded wafer manufacturing method (claim 16).

  In such a bonded wafer, the oxide film on the terrace portion of the base wafer is uniformly etched while leaving the oxide film on the back surface of the base wafer, and the oxide film on the terrace portion is a source of dust generated in the device manufacturing process. Accordingly, a high-quality bonded wafer in which warpage of the wafer is suppressed is obtained. In particular, a bonded wafer in which the remaining thickness of the oxide film in the terrace portion is accurately controlled can be obtained.

  As described above, according to the present invention, the back surface of the base wafer is protected especially by masking tape or the like by holding the bonded wafer and etching the oxide film formed on the terrace portion of the base wafer by spin etching. Without removing the oxide film on the back surface, the oxide film on the terrace portion can be uniformly etched. As a result, the terrace oxide film etching on one side of the wafer can be efficiently performed with a reduced number of processes.

Hereinafter, although this invention is demonstrated in detail, this invention is not limited to these.
Here, FIG. 1 is a schematic view for explaining an example of a method for producing a bonded wafer according to the present invention.

In FIG. 1, first, a bond wafer 2 and a base wafer 3 which are raw material wafers for producing an SOI wafer by bonding are prepared (FIG. 1A). The bond wafer and the base wafer are not particularly limited, and for example, a silicon single crystal wafer can be used.
Next, among the prepared silicon single crystal wafers, the bond wafer 2 is subjected to a heat treatment to form an oxide film 4 on the bond wafer surface (FIG. 1B).

  Next, the bond wafer 2 on which the oxide film is formed and the base wafer 3 are adhered in a clean atmosphere (FIG. 1C). This is subjected to a heat treatment in an oxidizing atmosphere to bond the bond wafer 2 and the base wafer 3 firmly to obtain a bonded wafer 1. As the heat treatment condition, for example, the heat treatment may be performed at a temperature of 200 ° C. to 1200 ° C. in an atmosphere containing oxygen or water vapor (FIG. 1D). At this time, the bond wafer 2 and the base wafer 3 are firmly bonded, and an oxide film (bonded oxide film) 5 is also formed on the entire outer surface of the bonded wafer 1.

  An unbonded portion of the bond wafer 2 and the base wafer 3 is present at about 2 mm on the outer peripheral portion of the bonded wafer 1 thus bonded. Such an unbonded portion cannot be used as an SOI layer for manufacturing a device, and is peeled off in a later process to cause various problems, and thus needs to be removed.

In order to remove the unbonded portion, as shown in FIG. 1E, first, the outer peripheral portion of the bond wafer 2 where the unbonded portion exists is ground and removed to a predetermined thickness t. This is because grinding can be removed at high speed and the processing accuracy is good.
In this case, the predetermined thickness t can be set to 20 to 150 microns, for example.

Next, etching is performed to obtain a wafer from which the unbonded portion of the outer peripheral portion of the bond wafer 2 is removed as shown in FIG. This can be easily performed by immersing the bonded wafer 1 in an etching solution in which the etching rate of the silicon single crystal is significantly higher than that of the oxide film. That is, the outer peripheral portion of the bond wafer 2 is etched by the etching solution because silicon is exposed by grinding, but the other portion of the bonded wafer is not etched because it is covered with the oxide film 5. . Examples of such etching include so-called alkaline etching with KOH, NaOH, or the like.
The terrace portion 7 is formed by such etching.

  Next, as shown in FIG. 1G, the surface of the bond wafer 2 is thinned to a desired thickness. The means for thinning the film is not particularly limited, and for example, it can be performed by grinding / polishing by a normal method.

  Next, spin etching is performed to etch the oxide film formed on the terrace portion 7 of the base wafer 3. The means for holding the wafer in spin etching is not particularly limited. For example, it can be performed by adsorbing and holding the base wafer 3 side. An apparatus for performing the spin etching is not particularly limited, but for example, an apparatus as shown in FIG. 2 can be used. Etching is performed by rotating the bonded wafer 1 at high speed while adhering and holding the bonded wafer 1 by the wafer holding means 10 and supplying the etching solution 9 from the nozzle 8. By performing etching while rotating the wafer in this way, the etching solution 9 is scattered to the outside of the wafer by centrifugal force, and the shaken etching solution 9 is collected through the collection cup 11 and is back of the wafer. There is no wraparound. Therefore, even if the wafer back surface is not masked with a masking tape, photoresist or the like, the oxide film on the wafer back surface side remains without being etched. Therefore, according to the present invention, a step of masking the back surface of the wafer with a masking tape or the like is not required, and the number of steps can be reduced and the terrace oxide film on one side of the wafer can be etched more efficiently.

  As described above, since the etching solution does not circulate to the back surface of the wafer, the adsorption holding during spin etching does not etch the oxide film on the back surface of the wafer even if only a part of the back surface of the wafer is adsorbed. ,No problem. Of course, you may adsorb | suck so that the whole area | region which wants to leave the whole wafer back surface or an oxide film may be covered.

  The etching solution used in the spin etching is not particularly limited as long as it can etch an oxide film, but for example, an HF aqueous solution is preferable. In this case, it is more preferable to use an HF 50% aqueous solution. If it is HF50% aqueous solution, an etching rate is large and can improve working efficiency more. As described above, according to the spin etching, an etching solution having a relatively high concentration can be used. Therefore, even if a thick oxide film is formed on the terrace portion, it can be etched and removed quickly and uniformly.

  Further, instead of removing all the oxide film formed on the terrace portion of the base wafer, there is a case where a bonded wafer having a certain thickness is required. In this case, the remaining thickness of the oxide film in the terrace portion can be controlled with high accuracy by adjusting the processing time of the spin etching and / or the concentration of the etching solution. In the conventional method of immersing the whole in an etching solution, although it is possible to remove the entire oxide film, it is difficult to accurately control the thickness to a predetermined thickness. It is possible to In this case, the etching rate can be controlled more accurately by controlling the temperature of the etching solution.

  As described above, a bonded wafer (FIG. 1 (h)) having the SOI layer 6 according to the present invention, having the oxide film 5 on the base wafer side, and removing the oxide film of the terrace portion 7 is manufactured. be able to.

  In the above method, spin etching was performed after the surface of the bond wafer 2 was thinned, but the present invention is not limited to this. Spin etching may be performed after the unbonded portion is etched, and then thinning may be performed.

  In the above method, the oxide film 4 is formed on the bond wafer 2 and then brought into intimate contact with the base wafer 3. However, the oxide film may be formed in intimate contact with the base wafer 3, or the oxide film is formed on both. In some cases, the contact is made. Further, the bond wafer and the base wafer may be directly adhered without using an oxide film. Further, the base wafer and bond wafer used in the method of the present invention are not limited to silicon single crystal wafers.

  Next, as an example of an embodiment of the present invention different from the above, a case where an SOI wafer is manufactured by a hydrogen ion separation method (smart cut method (registered trademark)) will be described with reference to FIG.

  First, in the step (a) of FIG. 5, two silicon mirror wafers are prepared, and a base wafer 21 serving as a base that meets the device specifications and a bond wafer 22 serving as an SOI layer are prepared.

  Next, in step (b), at least one of the wafers, here, the base wafer 21 is thermally oxidized, and an oxide film 23 having a thickness of about 0.1 μm to 2.0 μm is formed on the surface thereof. Depending on the application, an oxide film of 4.0 μm or more may be formed.

  In the step (c), at least one of hydrogen ions or rare gas ions, here hydrogen ions, is implanted into one surface of the bond wafer 22, and a microbubble layer (encapsulation layer) parallel to the surface at an average ion penetration depth. 24), and the injection temperature is preferably 25 to 450 ° C.

  Step (d) is a step in which the base wafer 21 is superposed and bonded to the hydrogen ion implanted surface of the bond wafer 22 into which hydrogen ions have been implanted through an oxide film, and the two wafers are bonded in a clean atmosphere at room temperature. By bringing the surfaces into contact with each other, the wafers adhere to each other without using an adhesive or the like.

Next, in the step (e), the separation is separated with the encapsulation layer 24 as a boundary to separate the separation wafer 25 and the SOI wafer 26 in which the SOI layer 27 is formed on the base wafer 21 via the oxide film 23. If heat treatment is performed at a temperature of, for example, about 500 ° C. or more in an inert gas atmosphere in the process, the separation wafer 25 and the SOI wafer 26 (SOI layer 27 + oxide film 23 + base wafer 21) are formed by crystal rearrangement and bubble aggregation. To be separated.
In the step (d), if the adhesion strength is increased by plasma-treating the surfaces to be adhered to both wafers, the encapsulating layer 24 can be mechanically peeled off without performing the heat treatment after adhesion. is there.

  Since the bonding force between the wafers bonded in the bonding process and the peeling process in the above steps (d) and (e) is weak to use in the device manufacturing process as it is, a high-temperature heat treatment is applied to the SOI wafer 26 as a bonding heat treatment. To give sufficient bond strength. This heat treatment is preferably performed, for example, in an inert gas atmosphere or an oxidizing gas atmosphere (here, an oxidizing gas atmosphere) at 1050 ° C. to 1200 ° C. for 30 minutes to 2 hours.

  By performing the bonding heat treatment step (f), the oxide film 31 is formed on the surface of the SOI layer 27, and at the same time, the back surface of the base wafer and the oxide film on the terrace portion 30 are also thickened.

  After performing the bonding heat treatment step (f) as described above, the oxide film on the terrace portion 30 is then removed in the spin etching step (g).

  An apparatus for performing spin etching is not particularly limited, and the above-described apparatus can be used. As another example, for example, an apparatus as shown in FIG. 6 can be used. The SOI wafer 26 is adsorbed and held by the wafer holding means 10, the etching solution 9 is directly supplied to the terrace portion from the nozzle 8, and the fluid 12 that protects the central portion of the SOI wafer is supplied from the etching solution 9 to the central portion of the SOI wafer. However, spin etching is performed by rotating the SOI wafer 26 at a high speed.

  When spin etching is performed by directly supplying an etching solution to the terrace portion in this way, the etching solution does not flow on the surface of the SOI layer. Therefore, even if the SOI layer is a thin layer of 0.5 μm or less, the SOI layer There is little possibility that the etching solution erodes the BOX through the minute defects inside. Further, if spin etching is performed in this way while supplying the fluid 12 that protects the central portion from the etching solution to the central portion of the bonded wafer, the possibility of the etching solution flowing to the surface of the SOI layer is further reduced. Even if the SOI layer is a thin layer of 0.5 μm or less, the possibility that the etching solution erodes the BOX through minute defects in the SOI layer is further reduced. Moreover, although such a fluid 12 is not specifically limited, For example, any of water, air, nitrogen gas, and an inert gas can be used.

  Further, as shown in FIG. 6, before performing the spin etching step (g), if the bond wafer is thinned and the oxide film 31 is formed on the surface of the bond wafer (the surface of the SOI layer 27), Even in the case where the etching solution 9 has entered the surface of the SOI layer 27 in the spin etching step (g), BOX erosion can be surely prevented.

  By performing the etching by rotating the wafer by spin etching, the etching solution 9 is scattered to the outside of the wafer by centrifugal force, and the etched etching solution 9 is collected through the collection cup 11 and is removed from the wafer. It does not wrap around to the back side. Therefore, even if the wafer back surface is not masked with a masking tape, photoresist or the like, the oxide film on the wafer back surface side remains without being etched. Therefore, according to the present invention, a step of masking the back surface of the wafer with a masking tape or the like is not required, and the number of steps can be reduced and the terrace oxide film on one side of the wafer can be etched more efficiently.

  In addition, if ozone water is supplied to the terrace part 30 after performing spin etching in this way, the terrace part after oxide film removal can be made hydrophilic, so that adhesion of particles can be suppressed.

Through the steps (a) to (g), an SOI wafer having no oxide film on the terrace portion can be manufactured.
In the above method, an oxide film is formed on the base wafer and then adhered to the bond wafer. However, an oxide film may be formed and adhered to the bond wafer, or an oxide film may be formed on both the base wafer and the bond wafer. Can also be formed.

  In addition, after manufacturing the SOI wafer in this manner, an epitaxial layer of Si or SiGe can be formed on the surface of the SOI layer of the SOI wafer. If the SOI wafer from which the oxide film on the terrace portion is removed as described above, the oxide film is not exposed. Therefore, even if an epitaxial layer of Si or SiGe is formed, the formation of polysilicon can be prevented, and the SOI wafer can be prevented. Generation of particles can be suppressed without adversely affecting the crystallinity of the layer.

  Further, as described above, when the method for manufacturing a bonded wafer according to the present invention is used, even if the SOI layer is a thin layer of 0.5 μm or less, the etching solution passes through the minute defects in the SOI layer in the spin etching. Therefore, it is possible to manufacture a high-quality SOI wafer having an SOI layer thickness of 0.5 μm or less.

  The bonded wafer obtained by the above manufacturing method is a wafer obtained by etching an oxide film formed on the terrace portion of the base wafer while leaving the oxide film on the back surface of the base wafer. Therefore, the oxide film in the terrace portion does not become a dust generation source in the device manufacturing process, and a high-quality bonded wafer in which warpage of the wafer is suppressed can be obtained. Further, a bonded wafer in which the thickness of the oxide film in the terrace portion is set to a desired thickness with high accuracy can be obtained.

Examples of the present invention will be described below, but the present invention is not limited thereto.
(Example 1)
First, a mirror-polished CZ wafer having a diameter of 200 mm, a conductivity type p-type, and a resistivity of 4 to 6 Ω · cm 2 was prepared and used as a base wafer and a bond wafer, respectively. These wafers are brought into close contact according to the steps (a) to (c) of FIG. 1, and bonded heat treatment is performed at 1150 ° C. in an oxygen atmosphere for 3 hours to obtain a bonded wafer as shown in FIG. 1 was produced.

Next, as shown in FIG. 1E, the outer peripheral portion of the bond wafer 2 was ground toward the center from the outer peripheral direction of the wafer using a grinding apparatus. The thickness t was 50 μm.
Next, the unbonded portion on the outer peripheral portion of the bond wafer 2 was removed by etching. Etching was performed by using NaOH as an etching solution for this etching and immersing the entire wafer in NaOH. The etching allowance was 90 μm, and a wafer as shown in FIG.

Next, the surface of the bond wafer 2 was ground and polished using a surface grinding apparatus and a single-side polishing apparatus to form a thin film, thereby forming an SOI layer 6 to obtain a wafer as shown in FIG.
FIG. 3 shows the structure of the oxide film on the terrace portion on the bonded wafer surface at this time. The oxide film in the region a is composed only of the oxide film (buried oxide film) 4 of the bond wafer 2. In the region b, in addition to the buried oxide film 4, there is an oxide film (bonded oxide film) 5 generated during the bonding heat treatment of the bond wafer and the base wafer, and an oxide film thicker than the region a as a whole is formed. The oxide film in the region c is composed only of the combined oxide film 5.

  The base wafer side of such a bonded wafer was held by suction and spin etching was performed. As an etching solution, a 50% HF aqueous solution was used. The etching time was 0 to 80 seconds, and the thicknesses of the oxide films in the regions a to c were examined at regular intervals. The obtained results are shown in FIG. FIG. 4 is an image of the wafer terrace, and shows the thickness of the oxide film for each region from the SOI layer at the bottom of the photo to the chamfer at the top.

  As is clear from the above results, the oxide film formed on the terrace portion of the base wafer can be completely removed by performing spin etching for 80 seconds while adsorbing and holding the base wafer side of the bonded wafer. Also, by changing the processing time of the spin etching, the remaining thickness of the oxide film on the terrace portion of the wafer can be controlled, and a bonded wafer having an arbitrary terrace portion oxide film thickness can be manufactured. it can.

(Example 2)
First, a mirror-polished CZ wafer having a diameter of 200 mm, a conductivity type p-type, and a resistivity of 4 to 6 Ω · cm 2 was prepared and used as a base wafer and a bond wafer, respectively. As shown in FIG. 5, an oxide film having a thickness of 5 μm was formed on the base wafer, and the Si layer of the bond wafer was transferred to the base wafer by a smart cut method (registered trademark) to obtain an SOI wafer. Thereafter, stabilization heat treatment was performed.

  At this time, since a 5 μm oxide film exists on the terrace portion of the SOI wafer, this oxide film was removed by spin etching using the apparatus shown in FIG. A 50% HF aqueous solution was used as an etching solution, and the etching solution was directly supplied to the terrace portion for 5 minutes to remove the oxide film on the terrace portion. During spin etching, pure water was supplied to the central portion of the SOI wafer as a fluid 12 for protecting the SOI layer from the etching solution. Thereafter, the HF aqueous solution was removed by rinsing for 2 minutes. After the rinse treatment, spin drying was performed.

  Thereafter, the oxide film 31 of the SOI layer was removed, the surface was polished, and the SOI layer was planarized to obtain an SOI wafer.

  The SOI wafer obtained in this way was confirmed to be of very high quality without HF eroding the BOX through minute defects in the SOI layer during spin etching.

(Example 3)
First, a mirror-polished CZ wafer having a diameter of 200 mm, a conductivity type p-type, and a resistivity of 4 to 6 Ω · cm 2 was prepared and used as a base wafer and a bond wafer, respectively. As shown in FIG. 5, an oxide film having a thickness of 400 nm was formed on the base wafer, and the Si layer of the bond wafer was transferred to the base wafer by the smart cut method (registered trademark) to obtain an SOI wafer. Thereafter, stabilization heat treatment was performed.

  At this time, since an oxide film having a thickness of 400 nm exists on the terrace portion of the SOI wafer, the oxide film was removed by spin etching using the apparatus shown in FIG. A 50% HF aqueous solution was used as an etching solution, and the etching solution was directly supplied to the terrace portion for 1 minute to remove the oxide film on the terrace portion. During spin etching, pure water was supplied to the central portion of the SOI wafer as a fluid 12 for protecting the SOI layer from the etching solution. Thereafter, HF was removed by rinsing for 30 seconds. After the rinse treatment, spin drying was performed.

Thereafter, the oxide film 31 of the SOI layer was removed, the surface was polished, and the SOI layer was planarized to obtain an SOI wafer having an SOI layer of 200 nm and a BOX layer of 400 nm.
Thereafter, Si epi growth was performed to obtain an SOI wafer having a final SOI layer thickness of 1000 nm.

  Since the SOI wafer obtained in this way was not eroded by HF through minute defects in the SOI layer during spin etching and the epitaxial film was removed by removing the oxide film on the terrace. It was confirmed that an SOI wafer having a very high quality and thick SOI layer can be obtained without forming poly-Si on the terrace portion.

  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.

  For example, in the above-described embodiment, the thinning is performed by grinding / polishing or ion implantation separation, but the thinning may be performed by etching or other methods.

It is the schematic explaining an example of the manufacturing method of the bonding wafer of this invention. 1 is a single wafer type spin etching apparatus that can be used in the method for manufacturing a bonded wafer according to the present invention. It is sectional drawing which illustrates roughly the structure of the oxide film of the terrace part of the surface of a bonding wafer. It is a photograph which shows the remaining thickness according to the site | part of the oxide film of the terrace part for every processing time of spin etching. It is the schematic explaining an example of the manufacturing method of the bonding wafer of this invention. 1 is a single wafer type spin etching apparatus that can be used in the method for manufacturing a bonded wafer according to the present invention.

Explanation of symbols

1 ... Bonded wafer, 2 ... Bond wafer, 3 ... Base wafer,
4 ... oxide film (buried oxide film), 5 ... oxide film (bonded oxide film), 6 ... SOI layer,
7 ... Terrace portion, 8 ... Nozzle, 9 ... Etching solution, 10 ... Wafer holding means,
11 ... Etching solution recovery cup, 12 ... Fluid, 21 ... Base wafer,
22 ... Bond wafer, 23 ... Oxide film (buried oxide film),
24 ... Microbubble layer (encapsulation layer) 25 ... Peeling wafer
26 ... SOI wafer, 27 ... SOI layer, 30 ... Terrace part, 31 ... Oxide film.

Claims (16)

  A method for manufacturing a bonded wafer, comprising: a step of etching an oxide film on a peripheral portion of a bonded wafer produced by bonding at least a base wafer and a bond wafer, wherein the oxide film of the terrace portion is formed. Etching is performed by spin etching while holding and rotating the bonded wafer, and a method for producing a bonded wafer.   In manufacturing the bonded wafer for etching the oxide film on the terrace portion, at least the base wafer and the bond wafer are brought into close contact with each other and subjected to heat treatment in an oxidizing atmosphere, and then bonded. The outer peripheral portion of the unbonded portion is removed by grinding to a predetermined thickness, and then the unbonded portion of the outer peripheral portion of the bond wafer is removed by etching, and then the bond wafer is thinned to a desired thickness. 2. The method for manufacturing a bonded wafer according to claim 1, wherein etching of the oxide film in the terrace portion is performed by spin etching after etching or after thinning the bond wafer.   In manufacturing a bonded wafer for etching the oxide film on the terrace portion, at least ions are implanted into the bond wafer, the bond wafer and the base wafer are brought into close contact, and then the bond wafer is formed with an ion implanted layer. The method for producing a bonded wafer according to claim 1, wherein the method is performed by peeling the film to form a thin film.   The method for manufacturing a bonded wafer according to any one of claims 1 to 3, wherein an HF aqueous solution is used as an etching solution for the spin etching.   The method for producing a bonded wafer according to claim 4, wherein an HF 50% aqueous solution is used as the HF aqueous solution.   6. The method for manufacturing a bonded wafer according to claim 1, wherein the spin etching is performed by supplying an etching solution directly to the terrace portion.   7. The method for producing a bonded wafer according to claim 6, wherein the spin etching is performed while supplying a fluid that protects the central portion from an etching solution to a central portion of the bonded wafer.   The method for producing a bonded wafer according to claim 7, wherein any one of water, air, nitrogen gas, and inert gas is used as the fluid.   9. The remaining thickness of the oxide film formed on the terrace portion of the base wafer is controlled by adjusting the processing time of the spin etching and / or the concentration of the etching solution. The manufacturing method of the bonding wafer of any one of Claims 1.   The bonded wafer according to any one of claims 1 to 9, wherein the base wafer and the bond wafer before bonding are silicon single crystal wafers having an oxide film formed on at least one of them. Manufacturing method.   The bonding according to any one of claims 1 to 10, wherein the bond wafer is thinned and an oxide film is formed on a surface of the bond wafer before the spin etching is performed. A method for manufacturing a laminated wafer.   The method for manufacturing a bonded wafer according to claim 1, wherein ozone water is supplied to the terrace portion after the spin etching is performed.   The method for manufacturing a bonded wafer according to claim 1, wherein an SOI wafer is manufactured as the bonded wafer.   14. The method for producing a bonded wafer according to claim 13, wherein the SOI layer of the SOI wafer has a thickness of 0.5 [mu] m or less.   15. The method for producing a bonded wafer according to claim 13, wherein an epitaxial layer of Si or SiGe is formed on the surface of the SOI layer of the SOI wafer after the production of the SOI wafer.   The bonded wafer manufactured by the manufacturing method of the bonded wafer of any one of Claims 1 thru | or 15.

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