JP2018182144A - Manufacturing method of multilayer film soi wafer and multilayer film soi wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a multilayer film SOI wafer which has no chipping and cracking in an end surface of a second active layer.SOLUTION: A manufacturing method of a multilayer film SOI wafer, includes: a step of preferring a SOI wafer 30 having a terrace part; a step of reducing the thickness of an outer peripheral region of a wafer 40 of a second active layer, forming a shape of an upper layer part 42 of the wafer for the second active layer as a circle in a cross section in parallel to a wafer surface, and reducing a diameter of a front surface 40A of the upper layer part with respect to that of the wafer 40 of the second active layer; a step of forming a second oxidation film 24 onto the SOI wafer 30 and/or the front surface of the wafer 40 of the second active layer; a step of forming an adhesion wafer 46 by performing a combining heating processing by overlapping the SOI wafer 30 and the wafer 40 for the second active layer through the second oxidation film 24; and a step of reducing the thickness of the adhesion wafer 46, and obtaining the multilayer film SOI wafer 100 having the second active layer 48.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of manufacturing a multilayer SOI wafer and a multilayer SOI wafer.

  An SOI (Silicon on Insulator) wafer has a structure in which an oxide film and an active layer (SOI layer) are stacked on a supporting substrate. Also, as an advantage to highly integrated devices, there is a multilayer film SOI wafer. The multilayer SOI wafer has a structure in which at least a first oxide film, a first active layer, a second oxide film, and a second active layer are stacked on a support substrate. That is, the multilayer film SOI wafer has a plurality of active layers on the support substrate.

  Patent Document 1 describes the following technology as a method of manufacturing a multilayer film SOI wafer. First, oxygen ions are implanted from the surface of the first active layer wafer to form an oxygen ion implanted layer in the first active layer wafer, and then the oxygen ion implanted layer is formed from the surface to which oxygen ions are implanted by thermal oxidation. A first oxide film is formed by then. Next, the supporting substrate wafer and the first active layer wafer are overlapped via the first oxide film, and bonding heat treatment is performed to bond the supporting substrate wafer and the first active layer wafer. Next, the wafer for the first active layer is thinned to obtain an SOI wafer having the first active layer. Next, oxygen ions are implanted from the surface of the wafer for the second active layer to form an oxygen ion implanted layer inside the wafer for the second active layer, and then oxygen ions are implanted from the surface to which oxygen ions are implanted by thermal oxidation. A second oxide film is formed up to the layer. Next, the second active layer wafer is superimposed on the first active layer side of the SOI wafer through the second oxide film, and bonding heat treatment is performed to bond the SOI wafer and the second active layer wafer. Match. Next, the wafer for the second active layer is thinned to obtain a multilayer SOI wafer having a second active layer of a desired thickness.

JP, 2007-109961, A

  In the process of producing a multilayer film SOI wafer based on an SOI wafer, patent document 1 does not describe at all about the end face of the wafer. However, generally, a wafer used as the supporting substrate wafer 10 or the first active layer wafer 20 has a chamfered portion on the end face of the wafer as shown in FIG. The SOI wafer is manufactured through the following steps. As shown in FIGS. 4A to 4D, the supporting substrate wafer 10 having a chamfer on the end face is bonded to the first active layer wafer 20 with the first oxide film 12 in between. Then, the non-adhesion area | region which the chamfers do not adhere | attach will arise outside the outer periphery of a bonding surface. If this unbonded area is left, the wafer may be chipped or broken in a later process. Therefore, the non-adhered area is removed by chamfering or etching the outer peripheral area of the first active layer wafer 20. Specifically, as shown in FIG. 4 (D), after the wafer for support substrate 10 and the wafer 20 for the first active layer are bonded via the first oxide film 12, the wafer 20 for the first active layer is obtained. The peripheral region is reduced in thickness by chamfering. As a result, the silicon residual portion 14 remains in the lower part of the outer peripheral region of the first active layer wafer 20 (FIG. 4E). Subsequently, the silicon residual portion 14 is removed by etching (FIG. 4F). When the non-bonded area is removed by such a procedure, a terrace 32 is formed above the outer peripheral area of the support substrate 10. That is, the terrace portion 32 means a region above the outer peripheral region of the support substrate 10 from which the outer peripheral region of the first active layer wafer 20 has been removed so that the first active layer wafer 20 does not exist. Here, the “peripheral region of the support substrate” refers to a region of 1 to 3 mm radially inward from the outermost periphery of the support substrate, and the “peripheral region of the first active layer wafer” refers to the first active layer. Points from 1 to 3 mm radially inward from the outermost edge of the wafer. In addition, in this specification, the process demonstrated with reference to FIG.4 (D)-(F) is called "terrace process." Thereafter, the wafer for the first active layer is ground and polished to produce an SOI wafer 30 having the first active layer 22 of a desired thickness (FIG. 4 (G)).

  The present inventors found that when a multilayer film SOI wafer is produced based on the SOI wafer 30 produced in this manner, there is a problem that a chipping or a crack is generated at the end face of the second active layer. . Below, the experiment which led to this knowledge is demonstrated.

  Referring to FIGS. 5A to 5D, in order to obtain a multilayer film SOI wafer, first, an SOI wafer 30 having a terrace portion 32 and a wafer 40 for the second active layer are interposed via the second oxide film 24. to paste together. Thereafter, the outer peripheral region of the second active layer wafer 40 is thinned by chamfering. As a result, the silicon residual portion 16 remains in the lower part of the outer peripheral region of the second active layer wafer 40 (FIG. 5E). Subsequently, the silicon residual portion 16 is removed by etching (FIG. 5F). Thus, a terrace 33 shown in FIG. 5F is formed. The “peripheral region of the second active layer wafer” refers to a region of 1 to 3 mm radially inward from the outermost peripheral end of the second active layer wafer.

  However, in practice, when the SOI wafer 30 having the terrace portion 32 and the wafer 40 for the second active layer are bonded via the second oxide film 24, as shown in FIG. 5D, the wafer 40 for the second active layer The lower side of the outer peripheral region is not supported by the first active layer 22 of the SOI wafer. That is, the non-supporting region in which the wafer 40 for the second active layer is not supported by the first active layer 22 is formed on the radially outer side of the portion of the wafer 40 for the second active layer as at least the second active layer 48. Be done. In such a state, as shown in FIG. 5E, if the outer peripheral region of the second active layer wafer 40 is chamfered, the silicon residual portion 16 may be peeled off during the chamfering, or during the etching process, It was found that the silicon residual portion 16 peeled off during the transfer of the wafer. As a result, as shown in FIG. 5G, it was found that there is a problem that chipping or cracking occurs on the end face of the second active layer 48 obtained by grinding and polishing the wafer 40 for the second active layer. .

  Therefore, in view of the above problems, it is an object of the present invention to provide a method for manufacturing a multilayer SOI wafer having no chipping or cracking at the end face of the second active layer, and a multilayer SOI wafer.

The essential features of the present invention for solving the above-mentioned problems are as follows.
(1) Preparing an SOI wafer having a first oxide film and a first active layer stacked on a support substrate, and having a terrace portion where the first active layer does not exist above the outer peripheral region of the support substrate One step,
The outer peripheral region of the second active layer wafer is reduced in thickness to make the shape of the upper layer portion of the second active layer wafer circular in a cross section parallel to the wafer surface, and the diameter of the surface of the upper layer portion is the second 2) a second step of reducing the diameter of the wafer for the active layer,
Forming a second oxide film on the surface of the first active layer or the surface of the upper layer, or the surface of the first active layer and the surface of the upper layer;
The SOI wafer and the wafer for the second active layer are superposed and subjected to bonding heat treatment such that the second oxide film is located between the surface of the first active layer and the surface of the upper layer portion. And bonding the SOI wafer and the wafer for the second active layer to form a bonded wafer.
A fifth step of thinning the bonded wafer from the wafer side for the second active layer to obtain a multilayer film SOI wafer having a second active layer of a desired thickness;
A manufacturing method of a multilayer film SOI wafer characterized by having.

  (2) In the fifth step, a portion of the silicon remaining portion produced in the outer peripheral region of the wafer for the second active layer due to the thickness reduction in the second step is centered on the outer periphery of the wafer for the second active layer. The method for manufacturing a multilayer film SOI wafer according to the above (1), wherein the bonded wafer is reduced in thickness from the wafer side for the second active layer after grinding and removal toward the.

  (3) The method for producing a multilayer SOI wafer according to (1) or (2), wherein in the second step, the diameter of the surface of the upper layer portion is equal to or less than the diameter of the first active layer.

  (4) The method for manufacturing a multilayer SOI wafer according to any one of (1) to (3), wherein in the second step, the diameter of the upper layer portion is gradually increased toward the surface of the upper layer portion.

(5) A multilayer SOI wafer in which a first oxide film, a first active layer, a second oxide film, and a second active layer are stacked on a supporting substrate,
A multilayer film SOI wafer having a terrace portion where the first active layer does not exist above a peripheral region of the support substrate.

  (6) The multilayer film SOI wafer according to (5), in which there is no chipping or cracking on the end face of the second active layer.

  (7) The multilayer film SOI wafer according to (5) or (6) above, wherein the surface of the terrace portion is not scratched.

  (8) The multilayer film SOI wafer according to any one of the above (5) to (7), wherein the diameter of the second active layer is equal to or less than the diameter of the first active layer.

  According to the present invention, it is possible to obtain a multilayer film SOI wafer having no chipping or cracking at the end face of the second active layer.

FIG. 7 is a schematic cross-sectional view illustrating the method of manufacturing the multilayer film SOI wafer 100 according to the first embodiment of the present invention. FIG. 13 is a schematic cross-sectional view illustrating the method of manufacturing the multilayer film SOI wafer 200 according to the second embodiment of the present invention. (A) is a schematic cross section showing the shape of the second active layer wafer 40 obtained by the processing of the second step in the first and second embodiments, and (B) is a portion I of (A). FIG. It is a schematic cross section which shows the manufacturing method of SOI wafer 30 which has the terrace part 32 which can be used for this invention. FIG. 16 is a schematic cross-sectional view illustrating the method of manufacturing the conventional multilayer film SOI wafer 300. (A) is an enlarged photograph of the multilayer SOI wafer as viewed from above according to the invention example, (B) according to the comparative example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each embodiment, the same reference numeral is attached to the same component in principle, and the description thereof will not be repeated. Also, in FIGS. 1 to 5 for convenience of explanation, the ratio of the actual thickness is different from that of the wafer for support substrate 10, the wafer 20 for the first active layer, the SOI wafer 30 and the wafer 40 for the second active layer. The thicknesses of the first oxide film 12 and the second oxide films 24 and 26 are exaggeratedly shown.

(Manufacturing method of multilayer film SOI wafer)
A first embodiment of the method for manufacturing a multilayer SOI wafer according to the present invention is shown in FIG. 1, and a second embodiment is shown in FIG.

First Embodiment
First, with reference to FIG. 1, a method of manufacturing a multilayer SOI wafer 100 according to a first embodiment of the present invention will be described. In the present embodiment, first, the first oxide film 12 and the first active layer 22 are stacked on the support substrate 10, and the terrace portion 32 in which the first active layer 22 does not exist above the outer peripheral region of the support substrate 10. An SOI wafer 30 is prepared (first step). Next, the outer peripheral region of the second active layer wafer 40 is reduced to make the shape of the upper layer portion 42 of the second active layer wafer 40 a circle in a cross section parallel to the wafer surface, and the surface of the upper layer portion 42 Is smaller than the diameter of the second active layer wafer 40 (second step). The silicon remaining portion 44 remains in the outer peripheral region of the second active layer wafer 40 by this processing. Next, a second oxide film 24 is formed on the surface 22A of the SOI wafer 30 on the side of the first active layer 22 (third step). Next, the SOI wafer 30 and the second active layer wafer 40 are placed on the second oxide film 24 so that the second oxide film 24 is positioned between the surface 40A of the upper layer portion and the surface 22A of the first active layer. Overlap. Thereafter, bonding heat treatment is performed to bond the SOI wafer 30 and the wafer 40 for the second active layer to form a bonded wafer 50 (fourth step). Next, a portion 44 a of the silicon remaining portion is ground and removed from the outer periphery of the wafer 40 for the second active layer. Next, the bonded wafer 50 is reduced in thickness from the side of the second active layer wafer 40 to form a multilayer SOI wafer 100 having the second active layer 48 of a desired thickness (fifth step).

  In the multilayer film SOI wafer 100, a first oxide film 12, a first active layer 22, a second oxide film 24, and a second active layer 48 are stacked on a support substrate 10.

Second Embodiment
Next, with reference to FIG. 2, a method of manufacturing the multilayer SOI wafer 200 according to the second embodiment of the present invention will be described. In the present embodiment, first, the first oxide film 12 and the first active layer 22 are stacked on the support substrate 10, and the terrace portion 32 in which the first active layer 22 does not exist above the outer peripheral region of the support substrate 10. An SOI wafer 30 is prepared (first step). Next, the outer peripheral region of the second active layer wafer 40 is reduced to make the shape of the upper layer portion 42 of the second active layer wafer 40 a circle in a cross section parallel to the wafer surface, and the surface of the upper layer portion 42 Is smaller than the diameter of the second active layer wafer 40 (second step). The silicon remaining portion 44 remains in the outer peripheral region of the second active layer wafer 40 by this processing. Next, a second oxide film 26 is formed on the surface of the second active layer wafer 40 (third step). Next, the SOI wafer 30 and the wafer 40 for the second active layer are combined with the second oxide film 26 so that the second oxide film 26 is positioned between the surface 40A of the upper layer portion and the surface 22A of the first active layer. Overlap. Thereafter, bonding heat treatment is performed to bond the SOI wafer 30 and the wafer 40 for the second active layer to form a bonded wafer 50 (fourth step). Next, a portion 44a of the silicon remaining portion is removed by grinding from the outer periphery of the second active layer wafer 40 toward the center. Next, the bonded wafer 50 is reduced in thickness from the side of the second active layer wafer 40 to form a multilayer SOI wafer 200 having the second active layer 48 of a desired thickness (fifth step).

  In the multilayer film SOI wafer 200, a first oxide film 12, a first active layer 22, a second oxide film 26, and a second active layer 48 are stacked on a support substrate 10.

(First step: formation of an SOI wafer having a terrace portion)
In the first step, as shown in FIGS. 1 and 2, the first oxide film 12 and the first active layer 22 are stacked on the support substrate 10, and the first active layer 22 is formed over the outer peripheral region of the support substrate 10. Form a SOI wafer 30 having a terrace 32 which does not exist. Here, the method of forming the SOI wafer 30 is not particularly limited. For example, with reference to FIG. 4, the method described below can be used.

  First, the first oxide film 12 is formed on the surface of the supporting substrate wafer 10 (FIGS. 4A and 4B). The thickness of the first oxide film 12 is preferably 0.1 μm or more and 3.0 μm or less. Here, the method of forming the first oxide film 12 is not particularly limited, and, for example, a known thermal oxidation method can be suitably used. The thermal oxidation conditions in this case are preferably 900 ° C. or more and 1200 ° C. or less, and 30 minutes or more and 2 hours or less in an oxygen atmosphere. The first oxide film may be formed on the surface of the first active layer wafer 20, or may be formed on the surfaces of both the supporting substrate wafer 10 and the first active layer wafer 20.

  Next, the supporting substrate wafer 10 and the first active layer wafer 20 are superimposed via the first oxide film 12 (FIG. 4C). Next, bonding heat treatment is performed to bond the supporting substrate wafer 10 and the first active layer wafer 20 (FIG. 4D). Here, the bonding heat treatment is preferably performed under conditions of a wafer temperature of 400 ° C. or more and 1200 ° C. or less and 10 minutes or more and 6 hours or less in an oxidizing gas or inert gas atmosphere. By setting the wafer temperature to 400 ° C. or more, sufficient bonding strength can be obtained, and by setting the wafer temperature to 1200 ° C. or less, the occurrence of slip can be suppressed.

  Here, as shown in FIG. 4D, an unbonded region is generated outside the outer periphery of the bonding surface of the supporting substrate wafer 10 and the first active layer wafer 20. If this unbonded area is left, the wafer may be chipped or broken in a later step, so the unbonded area is removed as follows. That is, as shown in FIG. 4D, after bonding the support substrate wafer 10 and the first active layer wafer 20 via the first oxide film 12, the outer peripheral region of the first active layer wafer 20 is obtained. Reduce the thickness by chamfering. As a result, the silicon residual portion 14 remains in the lower part of the outer peripheral region of the first active layer wafer 20 (FIG. 4E). The thickness of the silicon residue portion 14 is preferably about 5 to 50 μm from the bonding surface of the supporting substrate wafer 10 and the first active layer wafer 20 toward the first active layer wafer 20. Subsequently, the silicon residual portion 14 is removed by etching (FIG. 4F). When the non-bonded area is removed by such a procedure, a terrace portion from which the outer peripheral area of the first active layer wafer 20 is removed so that the first active layer wafer 20 does not exist above the outer peripheral area of the support substrate 10 32 are formed. In addition, an alkaline etching solution can be used suitably for an etching. In addition, a scaly oxide film residue derived from the first oxide film 12 may remain on the surface of the terrace portion 32, but this oxide film residue is removed by sticking and peeling off an adhesive tape. You may

  Next, as shown in FIG. 4G, the thickness of the first active layer wafer 20 is reduced to obtain an SOI wafer 30 having a first active layer 22 of a desired thickness. The thickness of the first active layer 22 is preferably 0.1 μm to 100 μm. In addition, in the case of thickness reduction, publicly known or arbitrary methods can be used suitably, for example, the surface grinding method and the mirror surface polishing method are mentioned. Also, other techniques such as the well-known Smart Cut method (registered trademark) may be used.

(Second step: processing of wafer for second active layer)
In the second step, as shown in FIGS. 1 and 2, the outer peripheral region of the second active layer wafer 40 is reduced in thickness, and the shape of the upper layer portion 42 of the second active layer wafer 40 is a cross section parallel to the wafer surface. And the diameter of the upper layer portion 42 is smaller than the diameter of the wafer 40 for the second active layer. Below, the technical significance which employ | adopts a 2nd process is demonstrated.

  With reference to FIGS. 1 and 2, even though the bonded wafer 50 is formed in the fourth step through the second step, a portion of the wafer 40 for the second active layer which is to be at least the second active layer 48. On the radially outer side, an unsupported area as shown in FIG. 5 (D) is not formed. Further, when the bonded wafer is formed, the end face of the portion to be the second active layer 48 in the second active layer wafer 40 is finished in advance. Therefore, in the fifth step, only the portion of the second active layer wafer 40 which is not to be the second active layer 48 may be ground and removed. Therefore, even if silicon in a portion not to be the second active layer 48 peels off in the fifth step, the end face of the second active layer formed in advance is not affected and no chipping or cracking occurs. .

  First, the height of the upper layer portion 42 will be described in detail. Referring to FIGS. 3A and 3B, the height of the upper layer portion 42 is not particularly limited as long as it exceeds the desired thickness a of the second active layer 48. Here, a is preferably 5 μm to 100 μm. In addition, when performing the X-axis process and Y-axis process which are mentioned later, it is preferable to set b shown in FIG. 3 (B) to 30 micrometers or more and 100 micrometers or less. Although the details will be described later, the purpose is to secure a gap necessary for performing the X-axis processing.

  Next, the shape of the upper layer portion 42 will be described in detail. The shape of the upper layer portion 42 is a circle in a cross section parallel to the wafer surface, and the diameter d of the upper layer portion 42 is smaller than the diameter of the second active layer wafer 40. More preferably, the diameter d of the surface of the upper layer portion is designed to be equal to or less than the diameter of the first active layer 22, and specifically, smaller than the diameter of the first active layer 22 by about 1 mm. When the diameter d is larger than the diameter of the first active layer 22, the outer edge of the second active layer 48 protrudes outside the first active layer 22 from the side portion of the multilayer SOI wafer. A gap of micron order is formed between the substrate 10 and the supporting substrate wafer 10. If the gap is formed as described above, it is not preferable because the problem of dry residue or foreign material residue may occur in the gap in the cleaning process of the multilayer SOI wafer.

  Further, the shape of the side surface of the upper layer portion 42 can be appropriately designed in accordance with the desired shape of the end surface of the second active layer 48. For example, when it is desired to make the end face of the second active layer 48 an end face parallel to the wafer thickness direction, a portion of the side surface of the upper layer 42 to be the second active layer 48 later is designed to be parallel to the wafer thickness direction. Do. Also, when it is desired to gradually reduce the diameter of the second active layer 48 toward the upper side of the wafer, the diameter of the upper layer portion 42 is designed to be gradually increased toward the surface 40A of the upper layer portion. In this case, the angle between the surface 40A of the upper layer portion and the side surface of the upper layer portion 42 is preferably 45 ° or more and 90 ° or less. In addition, a well-known chamfering apparatus can be used suitably for the process of a 2nd process. At this time, for convenience of processing, the lower shape of the side surface of the upper layer portion 42 becomes a round shape as shown in FIG. 3B in the cross section in the wafer thickness direction.

(Third step: formation of second oxide film)
In the third step, as shown in FIG. 1, the second oxide film 24 is formed on the surface of the SOI wafer 30. That is, the second oxide film 24 is formed on the surface 22 A on the first active layer side of at least the surface of the SOI wafer 30. Alternatively, as shown in FIG. 2, the second oxide film 26 is formed on the surface of the second active layer wafer 40. That is, the second oxide film 26 is formed at least on the surface 40 A of the upper layer portion 42. The thickness of the second oxide films 24 and 26 is preferably 0.1 μm or more and 3.0 μm or less. Here, the method for forming the second oxide films 24 and 26 is not particularly limited, and for example, a known thermal oxidation method can be suitably used. The thermal oxidation conditions in this case are preferably 900 ° C. or more and 1200 ° C. or less, and 30 minutes or more and 2 hours or less in an oxygen atmosphere. As another embodiment of the present invention, the second oxide film may be formed on both the surface of the SOI wafer and the surface of the wafer for the second active layer.

(Fourth Process: Formation of Bonded Wafer)
In the fourth step, as shown in FIGS. 1 and 2, the SOI wafer 30 and the wafer 40 for the second active layer are overlapped via the second oxide films 24 and 26. That is, the second oxide films 24 and 26 are located between the surface 40A of the upper layer portion and the surface 22A of the first active layer. Thereafter, bonding heat treatment is performed to bond the SOI wafer 30 and the wafer 40 for the second active layer to form a bonded wafer 46. The bonding heat treatment is preferably performed under conditions of a wafer temperature of 400 ° C. or more and 1200 ° C. or less for 10 minutes or more and 6 hours or less in an oxidizing gas or inert gas atmosphere. By setting the wafer temperature to 400 ° C. or more, sufficient bonding strength can be obtained, and by setting the wafer temperature to 1200 ° C. or less, the occurrence of slip can be suppressed.

(Fifth step: thinning of wafer for second active layer)
Next, in the fifth step, the thickness of the bonded wafer 50 is reduced from the side of the second active layer wafer 40 to obtain multilayer SOI wafers 100 and 200 having the second active layer 48 of a desired thickness. Here, when the bonded wafer 50 is ground in the thickness direction from the second active layer wafer 40 side, a portion 44a of the silicon remaining portion has a sharp knife-like shape with a sharp cross-sectional shape, and a knife edge It will When the silicon in the knife-edgeed portion is peeled off, the surface of the terrace portion 32 may be damaged. Therefore, it is preferable to reduce the thickness of the second active layer wafer 40 after the following steps from the viewpoint of preventing the terrace portion 32 from being damaged. In the present specification, grinding in the thickness direction is referred to as “Y-axis processing”.

(X axis processing)
In order to prevent generation of flaws on the surface of the terrace portion 32, grinding is performed from the outer periphery to the center of the wafer 40 for the second active layer before performing Y-axis processing to make a knife edge of the silicon remaining portion 44 It is preferable to remove in advance the portion 44a of the silicon remaining portion that may be concerned. In the present specification, a direction from the outer periphery to the center of the second active layer wafer is defined as “X-axis direction”, and grinding along the X-axis direction is referred to as “X-axis processing”. Here, in order to perform the X-axis processing, it is necessary to secure a sufficient space in which the grindstone can be inserted in the X-axis direction below the wafer 40 for the second active layer. In the present embodiment, since the second active layer wafer 40 is processed in the second step, as shown in FIGS. 1 and 2, between the upper portion of the support substrate 10 and the lower portion of the silicon remaining portion 44. In addition, it is possible to secure a sufficient space for inserting the grindstone in the X-axis direction. Therefore, the portion 44a of the silicon remaining portion can be easily removed by X-axis processing. Here, the size of the gap for inserting the grindstone can be suitably determined by appropriately adjusting the size of b shown in FIG. 3 (B) described above for the shape of the upper layer portion 42. The portion 44 a of the silicon remaining portion that may be knife-edge is 80% to 90% of the radial width of the terrace portion 32 from the end face of the wafer 40 for the second active layer toward the center. is there. Moreover, arbitrary or well-known grindstones can be used for X-axis processing.

(Y-axis processing)
After X-axis processing, Y-axis processing is performed on the bonded wafer 50 from the second active layer wafer 40 side to obtain a second active layer 48 having a desired thickness. At this time, since a part 44a of the silicon remaining portion is removed in advance by the X-axis processing, the surface of the terrace portion 32 is not damaged. The thickness a of the second active layer 48 is preferably 5 μm to 100 μm. In addition, arbitrary or well-known grindstone can be used for Y-axis process. In addition, after the grinding, polishing such as mirror polishing may be performed. Further, the oxide film or the like present on the end face of the second active layer 48 may be removed by an etching process or the like after the fifth step.

(Wafer for supporting substrate, wafer for first active layer, wafer for second active layer)
As the support substrate wafer 10, the first active layer wafer 20, and the second active layer wafer 40 of the present invention, a single crystal silicon wafer made of silicon single crystal can be used. As the single crystal silicon wafer, a single crystal silicon ingot grown by the Czochralski method (CZ method) or the floating zone melting method (FZ method) can be sliced by a wire saw or the like. Furthermore, any impurity may be added to these wafers to make them n-type or p-type.

  Preferably, at least one of the support substrate 10, the first active layer wafer 20, and the second active layer wafer 40 is a polished wafer. Here, a polished wafer can be obtained by polishing the above-mentioned single crystal silicon wafer with abrasive grains and performing surface treatment by a chemical method.

  As mentioned above, although the manufacturing method of the multilayer film SOI wafer of this invention was demonstrated taking the 1st and 2nd embodiment as an example, the manufacturing method of the multilayer film SOI wafer of this invention is not limited to the said embodiment, Modifications can be made as appropriate within the scope of the claims.

(Multilayer film SOI wafer)
Next, multilayer film SOI wafers 100 and 200 obtained by the above manufacturing method will be described with reference to FIGS. In the multilayer SOI wafers 100 and 200, the first oxide film 12, the first active layer 22, the second oxide films 24 and 26, and the second active layer 48 are stacked on the supporting substrate 10. Further, a terrace portion 32 where the first active layer 22 does not exist is formed above the outer peripheral region of the support substrate 10. The above description is incorporated for this reason.

  In addition, it is preferable that the end face of the second active layer 48 be free of chipping and cracking, and the terrace 32 be free of flaws. The diameter of the second active layer 48 is preferably equal to or less than the diameter of the first active layer 22. The above description is also incorporated for these reasons. Preferably, at least one of the support substrate 10, the first active layer 22, and the second active layer 48 is made of a polished wafer.

  As mentioned above, although multilayer film SOI wafer 100, 200 was made into an example and explained about a multilayer film SOI wafer of the present invention, a multilayer film SOI wafer of the present invention is not limited to this, and changes suitably in a claim. It can be added.

(Invention example)
First, polished wafers prepared from silicon wafers obtained from CZ single crystal silicon ingots were prepared as supporting substrate wafers, first active layer wafers, and second active layer wafers. The diameter of these wafers was 200 mm, and the thickness was 725 μm.

  Next, referring to FIG. 4, a first oxide film was formed on the surface of the supporting substrate wafer by thermal oxidation. The thickness of the first oxide film was 1 μm. Next, after the supporting substrate wafer and the first active layer wafer were stacked via the first oxide film, bonding heat treatment was performed to bond the supporting substrate wafer and the first active layer wafer. . The conditions of the bonding heat treatment were 1150 ° C. and 2 hours in an oxygen atmosphere. Next, a terrace portion was formed above the outer peripheral region of the support substrate by the above-described chamfering process and etching process. Thereafter, the wafer for the first active layer was ground and polished from the surface to produce an SOI wafer having the first active layer. The surface of the first active layer had a diameter of 197 mm and a thickness of 5 μm.

  Next, the outer peripheral region of the second active layer wafer was reduced in thickness, and the second active layer wafer was processed into the shape shown in FIGS. 3 (A) and 3 (B). Here, the height of the upper layer portion (total value of a and b) is 45 μm, and the shape of the upper layer portion is a circle in a cross section parallel to the wafer surface. Further, the diameter d of the surface of the upper layer portion is smaller than the diameter (200 mm) of the wafer for the second active layer, and specifically, d is 196 mm.

  Next, a second oxide film was formed on the surface on the first active layer side of the surface of the SOI wafer by thermal oxidation. The thickness of the second oxide film was 1 μm.

  Next, the SOI wafer and the wafer for the second active layer are stacked via the second oxide film, and a bonding heat treatment is performed to bond the SOI wafer and the wafer for the second active layer together, thereby forming a bonded wafer. Formed. The conditions of the bonding heat treatment were 1150 ° C. and 2 hours in an oxygen atmosphere.

  Next, after removing in advance part of the silicon remaining portion that may become knife edged by X-axis processing, the bonded wafer is thinned from the wafer side for the second active layer by Y-axis processing, and the diameter of the surface is A multilayer SOI wafer having a second active layer of 196 mm and a thickness of 5 μm was formed.

(Comparative example)
The multilayer film SOI wafer 300 of the comparative example was manufactured by the method shown in FIGS.

  First, as the wafer for support substrate, the wafer for the first active layer, and the wafer for the second active layer, the same wafer as that of the invention example is prepared, and the SOI wafer shown in FIG. Obtained.

  Next, a second oxide film was formed on the surface on the first active layer side of the surface of the SOI wafer (FIGS. 5A and 5B). The thickness of the second oxide film was 1 μm. Next, after the SOI wafer and the wafer for the second active layer are superimposed via the second oxide film, bonding heat treatment is performed to bond the SOI wafer and the wafer for the second active layer, and a bonded wafer is obtained. Were formed (FIG. 5 (C), (D)). The conditions of the bonding heat treatment were 1150 ° C. and 2 hours in an oxygen atmosphere. Next, the unsupported area shown in FIG. 5D was removed by chamfering and etching (FIGS. 5E and 5F). Next, grinding and polishing were performed to obtain a multilayer SOI wafer 300 having a second active layer with a thickness of 5 μm (FIG. 5 (G)).

(Evaluation method)
In the invention examples and the comparative examples, the presence or absence of a chip or crack at the end face of the second active layer was examined by visual observation. Moreover, the presence or absence of the flaw in the surface of a terrace part was investigated by magnification 50x using the microscope. FIGS. 6 (A) and 6 (B) show enlarged photographs of the end face of the second active layer and the surface of the terrace in the inventive example and the comparative example.

(Explanation of evaluation results)
In the invention example, no chipping or cracking was found on the end face of the second active layer, and no flaw was found on the surface of the terrace. On the other hand, in the comparative example, chips and cracks were also found on the end face of the second active layer, and scratches were also found on the surface of the terrace. In the enlarged photographs shown in FIGS. 6A and 6B, if a chip or crack is present on the end face of the second active layer, the boundary between the end face of the second active layer and the terrace portion is jagged. It becomes.

  According to the present invention, it is possible to obtain a multilayer film SOI wafer having no chipping or cracking at the end face of the second active layer.

100, 200 Multilayer film SOI wafer 10 Wafer for support substrate (support substrate)
12 first oxide film 14, 16 silicon residual portion 20 wafer for first active layer 22 first active layer 22A surface of first active layer 24, 26 second oxide film 30 SOI wafer 32 terrace portion 40 wafer for second active layer 40A Upper surface side surface 42 upper layer 44 silicon remaining part 44a part of silicon remaining part 48 second active layer 50 bonded wafer

Claims (8)

A first step of preparing an SOI wafer having a first oxide film and a first active layer stacked on a support substrate, and having a terrace portion where the first active layer does not exist above the outer peripheral region of the support substrate; ,
The outer peripheral region of the second active layer wafer is reduced in thickness to make the shape of the upper layer portion of the second active layer wafer circular in a cross section parallel to the wafer surface, and the diameter of the surface of the upper layer portion is the second 2) a second step of reducing the diameter of the wafer for the active layer,
Forming a second oxide film on the surface of the first active layer or the surface of the upper layer, or the surface of the first active layer and the surface of the upper layer;
The SOI wafer and the wafer for the second active layer are superposed and subjected to bonding heat treatment such that the second oxide film is located between the surface of the first active layer and the surface of the upper layer portion. And bonding the SOI wafer and the wafer for the second active layer to form a bonded wafer.
A fifth step of thinning the bonded wafer from the wafer side for the second active layer to obtain a multilayer film SOI wafer having a second active layer of a desired thickness;
A manufacturing method of a multilayer film SOI wafer characterized by having.   In the fifth step, a portion of the silicon remaining portion formed in the outer peripheral region of the wafer for the second active layer by the thickness reduction in the second step is directed from the outer periphery of the wafer for the second active layer toward the center The method for manufacturing a multilayer SOI wafer according to claim 1, wherein the bonded wafer is thinned from the side of the second active layer wafer after grinding and removal.   The method for manufacturing a multilayer SOI wafer according to claim 1, wherein in the second step, a diameter of a surface of the upper layer portion is equal to or less than a diameter of the first active layer.   The method for manufacturing a multilayer SOI wafer according to any one of claims 1 to 3, wherein the diameter of the upper layer portion is gradually increased toward the surface of the upper layer portion in the second step. A multilayer SOI wafer in which a first oxide film, a first active layer, a second oxide film, and a second active layer are stacked on a support substrate,
A multilayer film SOI wafer having a terrace portion where the first active layer does not exist above a peripheral region of the support substrate.   6. The multilayer SOI wafer according to claim 5, wherein the end face of the second active layer is free from chipping and cracking.   The multilayer film SOI wafer according to claim 5, wherein the surface of the terrace portion is not scratched.   The multilayer film SOI wafer according to any one of claims 5 to 7, wherein a diameter of the second active layer is equal to or less than a diameter of the first active layer.