Method for manufacturing bonded wafer

Abstract

A method for manufacturing a bonded wafer using a base wafer which is an epitaxial wafer produced by a method including at least one of: (1) setting a chamfer width of a wafer for epitaxial growth to be 0.20 mm or less on an epitaxial growth side; (2) preparing a wafer for epitaxial growth having a rise shape on an epitaxial growth side periphery, thereby adjusting the wafer to have an amount of sag within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2 on a bonding surface side periphery; and (3) adjusting epitaxial growth conditions so a change in amount of sag before and after growth becomes a positive value, thereby adjusting the wafer to have sag within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2. The method can manufacture a bonded wafer with a small terrace width even when an epitaxial wafer is used as the base wafer.

Claims

1. A method for manufacturing a bonded wafer having a thin-film on a base wafer, comprising: ion-implanting at least one gas ion selected from a hydrogen ion and a rare gas ion from a surface of a bond wafer, thereby forming an ion-implanted layer into the inside of the bond wafer; bonding the ion-implanted surface of the bond wafer and a surface of the base wafer directly or through an insulating film; and then delaminating the bond wafer along the ion-implanted layer; wherein the base wafer is an epitaxial wafer produced by a method including at least one of the following conditions (1) to (3): (1) setting a chamfer width of a wafer for epitaxial growth to be 0.20 mm or less on an epitaxial growth side; (2) preparing a wafer for epitaxial growth having a periphery shape adjusted to a rise shape on an epitaxial growth side, thereby adjusting the epitaxial wafer to have an amount of sag within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2 on a periphery of a bonding surface side; and (3) adjusting epitaxial growth conditions such that a change of an amount of sag before and after the epitaxial growth becomes a positive value, thereby adjusting the epitaxial wafer to have an amount of sag within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2 on a periphery of a bonding surface side.

2. The method for manufacturing a bonded wafer according to claim 1, wherein the chamfer width in (1) is set to 0.05 mm or more.

3. The method for manufacturing a bonded wafer according to claim 1, wherein the bond wafer is a wafer adjusted to have an amount of sag within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2 on a periphery of a bonding surface side.

4. The method for manufacturing a bonded wafer according to claim 2, wherein the bond wafer is a wafer adjusted to have an amount of sag within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2 on a periphery of a bonding surface side.

5. The method for manufacturing a bonded wafer according to claim 1, wherein the bonded wafer is manufactured to have a terrace width of 1 mm or less.

6. The method for manufacturing a bonded wafer according to claim 2, wherein the bonded wafer is manufactured to have a terrace width of 1 mm or less.

7. The method for manufacturing a bonded wafer according to claim 3, wherein the bonded wafer is manufactured to have a terrace width of 1 mm or less.

8. The method for manufacturing a bonded wafer according to claim 4, wherein the bonded wafer is manufactured to have a terrace width of 1 mm or less.

9. The method for manufacturing a bonded wafer according to claim 1, wherein the amount of sag is a value in ZDD expressed by second order differential of a displacement of a surface of the wafer with respect to a radius of the wafer.

10. The method for manufacturing a bonded wafer according to claim 2, wherein the amount of sag is a value in ZDD expressed by second order differential of a displacement of a surface of the wafer with respect to a radius of the wafer.

11. The method for manufacturing a bonded wafer according to claim 3, wherein the amount of sag is a value in ZDD expressed by second order differential of a displacement of a surface of the wafer with respect to a radius of the wafer.

12. The method for manufacturing a bonded wafer according to claim 4, wherein the amount of sag is a value in ZDD expressed by second order differential of a displacement of a surface of the wafer with respect to a radius of the wafer.

13. The method for manufacturing a bonded wafer according to claim 5, wherein the amount of sag is a value in ZDD expressed by second order differential of a displacement of a surface of the wafer with respect to a radius of the wafer.

14. The method for manufacturing a bonded wafer according to claim 6, wherein the amount of sag is a value in ZDD expressed by second order differential of a displacement of a surface of the wafer with respect to a radius of the wafer.

15. The method for manufacturing a bonded wafer according to claim 7, wherein the amount of sag is a value in ZDD expressed by second order differential of a displacement of a surface of the wafer with respect to a radius of the wafer.

16. The method for manufacturing a bonded wafer according to claim 8, wherein the amount of sag is a value in ZDD expressed by second order differential of a displacement of a surface of the wafer with respect to a radius of the wafer.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a flowchart showing an example of the method for manufacturing a bonded wafer of the present invention;

(2) FIG. 2 is a cross-sectional view showing an example for producing an epitaxial wafer by a method including the condition (1);

(3) FIG. 3 is a cross-sectional view showing an example for producing an epitaxial wafer by a method including the condition (2);

(4) FIG. 4 is a cross-sectional view showing an example for producing an epitaxial wafer by a method including the condition (3);

(5) FIG. 5 are explanatory diagrams to explain (a) the chamfer width and (b) the terrace width; and

(6) FIG. 6 is an explanatory diagram to explain the ZDD.

DESCRIPTION OF EMBODIMENTS

(7) As described above, it has been desired to develop a method for manufacturing a bonded wafer which can manufacture a bonded wafer with a small terrace width even when an epitaxial wafer is used as the base wafer.

(8) The inventors have diligently investigated on the foregoing problem and found that the bonded wafer with a small terrace width can be manufactured by using an epitaxial wafer produced by a method including at least one of the following conditions (1) to (3) as the base wafer; thereby brought the present invention to completion.

(9) That is, the present invention is a method for manufacturing a bonded wafer having a thin-film on a base wafer, comprising: ion-implanting at least one gas ion selected from a hydrogen ion and a rare gas ion from a surface of a bond wafer, thereby forming an ion-implanted layer into the inside of the bond wafer; bonding the ion-implanted surface of the bond wafer and a surface of the base wafer directly or through an insulating film; and then delaminating the bond wafer along the ion-implanted layer; wherein

(10) the base wafer is an epitaxial wafer produced by a method including at least one of the following conditions (1) to (3):

(11) (1) setting a chamfer width of a wafer for epitaxial growth to be 0.20 mm or less on an epitaxial growth side;

(12) (2) preparing a wafer for epitaxial growth having a periphery shape adjusted to a rise shape on an epitaxial growth side, thereby adjusting the epitaxial wafer to have an amount of sag within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2 on a periphery of a bonding surface side; and

(13) (3) adjusting epitaxial growth conditions such that a change of an amount of sag before and after the epitaxial growth becomes a positive value, thereby adjusting the epitaxial wafer to have an amount of sag within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2 on a periphery of a bonding surface side.

(14) Hereinafter, the present invention will be described specifically, but the present invention is not limited thereto.

(15) Herein, the chamfer width and the terrace width will be described with reference to FIG. 5.

(16) The chamfer width of a wafer 1 for epitaxial growth on the epitaxial growth side is expressed by the length of X1 in FIG. 5(a).

(17) The terrace width is the length expressed by X3 in FIG. 5(b), and is expressed by the sum of the chamfer width X1 and the width X2 from the end of the chamfer portion to the end of the thin film (SOI layer) 6 in the bonded wafer 7 having the thin film (SOI layer) 6 formed on the base wafer 3.

(18) In the present invention, the amount of sag can be ZDD (Z-Height Double Differentiation), which is a commonly used indication.

(19) Definition of ZDD will now be described with reference to FIG. 6. An abscissa in FIG. 6 represents a distance from a peripheral end of a wafer, and an ordinate in the same represents a displacement of a shape of a wafer surface. In general, ZDD means second order differential of a displacement of a surface of the wafer with respect to a radius of the wafer. A positive value of ZDD represents that a surface is displaced in a rising direction, whereas a negative value of the same represents that the surface is displaced in a sagging direction.

(20) Hereinafter, the inventive method for manufacturing a bonded wafer will be described with reference to FIG. 1. FIG. 1 is a flowchart showing an example of the method for manufacturing a bonded wafer of the present invention.

(21) In the method for manufacturing a bonded wafer of FIG. 1, to provide an epitaxial wafer to be a base wafer, a wafer 1 for epitaxial growth is prepared (FIG. 1 (A1)), and onto the prepared wafer 1 for epitaxial growth, an epitaxial layer 2 is formed to produce an epitaxial wafer 3 (FIG. 1 (A2)). In this case, the epitaxial wafer is produced by a method including at least one of the foregoing conditions (1) to (3). Thus produced epitaxial wafer 3 is used as the base wafer (hereinafter, referred to as a base wafer 3).

(22) Then, a bond wafer 4 is prepared (FIG. 1 (B1)), and the bond wafer 4 is subjected to ion-implanting of at least one gas ion selected from a hydrogen ion and a rare gas ion to form an ion-implanted layer 5 into the inside of the bond wafer (FIG. 1 (B2)).

(23) Subsequently, the ion-implanted surface of the bond wafer 4 and the surface of the base wafer 3 are bonded (FIG. 1 (C)). Then, the bond wafer 4 is delaminated along the ion-implanted layer 5 to form a thin film 6 on the base wafer 3, thereby producing a bonded wafer 7 (FIG. 1 (D)).

(24) Hereinafter, each step will be described more specifically.

(25) [Preparation of Base Wafer (Produce of Epitaxial Wafer)]

(26) In the present invention, the base wafer is an epitaxial wafer produced by a method including at least one of the following conditions (1) to (3):

(27) (1) setting a chamfer width of a wafer for epitaxial growth to be 0.20 mm or less on the epitaxial growth side;

(28) (2) preparing a wafer for epitaxial growth having a periphery shape adjusted to a rise shape on the epitaxial growth side, thereby adjusting the epitaxial wafer to have an amount of sag within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2 on the periphery of the bonding surface side; and

(29) (3) adjusting epitaxial growth conditions such that a change of an amount of sag before and after the epitaxial growth becomes a positive value, thereby adjusting the epitaxial wafer to have an amount of sag within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2 on the periphery of the bonding surface side.

(30) It is to be noted that the wafer that is performed epitaxial growth is not particularly limited. It is suitable, however, to use a mirror-polished silicon single crystal wafer, etc.

(31) Hereinafter, each of the conditions (1) to (3) will be described more specifically.

(32) <Condition (1)>

(33) FIG. 2 is a cross-sectional view showing an example for producing an epitaxial wafer by a method including the condition (1). In the method of FIG. 2, first, a wafer with the chamfer width X1 of 0.15 mm (0.20 mm or less) on the side that is performed epitaxial growth is prepared as the wafer 1 for epitaxial growth (FIG. 2 (1-A1)). Then, onto the surface of this wafer 1 for epitaxial growth, an epitaxial layer 2 is formed to produce an epitaxial wafer 3 (FIG. 2 (1-A2)).

(34) By using a wafer with the chamfer width X1 of 0.20 mm or less on the epitaxial growth side as the wafer 1 for epitaxial growth, the terrace width can be reduced remarkably in manufacturing a bonded wafer.

(35) In this case, the chamfer width X1 of 0.05 mm or more makes it possible to prevent a crack and chipping during the processing, and is preferable.

(36) <Condition (2)>

(37) FIG. 3 is a cross-sectional view showing an example for producing an epitaxial wafer by a method including the condition (2). In the method of FIG. 3, first, a wafer having a periphery shape adjusted to a rise shape on the side that is performed epitaxial growth is prepared as the wafer 1 for epitaxial growth (FIG. 3 (2-A1)). Then, onto the surface of this wafer 1 for epitaxial growth, an epitaxial layer 2 is formed to produce an epitaxial wafer 3 while adjusting an amount of sag of the epitaxial wafer 3 on the periphery of the bonding surface side to be within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2 (FIG. 3 (2-A2)).

(38) It is to be noted that the adjustment of the periphery shape to the rise shape on the epitaxial growth side of the wafer 1 for epitaxial growth can be carried out by appropriately adjusting the polishing conditions such as a load and a rotation speed of a polishing cloth in mirror-polishing.

(39) <Condition (3)>

(40) FIG. 4 is a cross-sectional view showing an example for producing an epitaxial wafer by a method including the condition (3). In the method of FIG. 4, a wafer 1 for epitaxial growth is prepared (FIG. 4 (3-A1)). Then, onto the surface of this wafer 1 for epitaxial growth, an epitaxial layer 2 is formed to produce an epitaxial wafer 3 while adjusting the epitaxial growth conditions such that a change of an amount of sag before and after the epitaxial growth becomes a positive value, and an amount of sag of the epitaxial wafer 3 on the periphery of the bonding surface side falls within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2 (FIG. 4 (3-A2)).

(41) It is to be noted that the adjustment in such a way that a change of an amount of sag before and after the epitaxial growth becomes a positive value means that when the wafer has a sag shape before the epitaxial growth, it is adjusted to reduce the sag shape or to have a flat or rise shape after the epitaxial growth; when the wafer is flat before the epitaxial growth, it is adjusted to have a rise shape after the epitaxial growth; and when the wafer has a rise shape before the epitaxial growth, it is adjusted to enlarge the rise shape after the epitaxial growth.

(42) It is possible to selectively produce the epitaxial layer in a rise shape or a sag shape by appropriately adjusting the growth conditions in the epitaxial growth (growth rate, growth temperature, power balance of a heating lump, etc.).

(43) In condition (2) and condition (3), the chamfer width of the wafer 1 for epitaxial growth on the epitaxial growth side is not particularly limited, and can be an ordinary width (about 0.30 to 0.50 mm).

(44) In the inventive method for manufacturing a bonded wafer, an epitaxial wafer is produced by a method including at least one of the foregoing conditions (1) to (3) described above. That is, an epitaxial wafer may be produced by a method including one of the conditions (1) to (3) as described above, or may be produced by a method including two of or all three of these conditions.

(45) As a method including the two conditions, the following three methods are enumerated.

(46) (Conditions (1)+(2))

(47) A method in which a wafer having a chamfer width of 0.20 mm or less on the epitaxial growth side and a periphery shape adjusted to a rise shape on the epitaxial growth side is prepared as a wafer for epitaxial growth, and an epitaxial layer is formed on the surface of the wafer while adjusting an amount of sag of the epitaxial wafer on the periphery of the bonding surface side to be within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2.

(48) (Conditions (1)+(3))

(49) A method in which a wafer having a chamfer width of 0.20 mm or less on the epitaxial growth side is prepared as a wafer for epitaxial growth, and an epitaxial layer is formed on the surface of the wafer while adjusting the epitaxial growth conditions such that a change of an amount of sag before and after the epitaxial growth becomes a positive value, and an amount of sag of the epitaxial wafer on the periphery of the bonding surface side falls within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2.

(50) (Conditions (2)+(3))

(51) A method in which a wafer having a periphery shape adjusted to a rise shape on the epitaxial growth side is prepared as a wafer for epitaxial growth, and an epitaxial layer is formed on the surface of the wafer while adjusting the epitaxial growth conditions such that a change of an amount of sag before and after the epitaxial growth becomes a positive value, and an amount of sag of the epitaxial wafer on the periphery of the bonding surface side falls within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2.

(52) As a method including all of the three conditions, the following method is enumerated.

(53) (Conditions (1)+(2)+(3))

(54) A method in which a wafer having a chamfer width of 0.20 mm or less on the epitaxial growth side and a periphery shape adjusted to a rise shape on the epitaxial growth side is prepared as a wafer for epitaxial growth, and an epitaxial layer is formed on the surface of the wafer while adjusting the epitaxial growth conditions such that a change of an amount of sag before and after the epitaxial growth becomes a positive value, and an amount of sag of the epitaxial wafer on the periphery of the bonding surface side falls within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2.

(55) It is to be noted that when including still more conditions, the terrace width of a produced bonded wafer can be smaller. Accordingly, it is preferable to include two of the conditions (1) to (3), and is more preferable to include all of the three conditions.

(56) An epitaxial wafer used as a base water can be manufactured by a method described above.

(57) [Preparation of Bond Wafer]

(58) As a bond wafer used in the present invention, which is not particularly limited, a mirror-polished silicon single crystal wafer can be suitably used, for example. Incidentally, although the chamfer width of the bond wafer on the bonding surface side may be an ordinary width (about 0.30 to 0.50 mm), it is preferable that the bond wafer be adjusted to have an amount of sag within a range of 30 nm/mm.sup.2 to +10 nm/mm.sup.2 on the periphery of the bonding surface side. The use of such a bond wafer makes it easy to coordinate with the periphery shape of the base wafer, which is an epitaxial wafer, thereby improving the effect of reducing a chamfer width, and makes it possible to produce a bonded wafer with a small terrace width more easily.

(59) The bond wafer may have an oxide film formed thereon to be a buried oxide film.

(60) Then, at least one gas ion selected from a hydrogen ion and a rare gas ion is ion-implanted from above the surface of a bond wafer or an oxide film with an ion implanter to form an ion-implanted layer into the inside of the wafer. An accelerating voltage of the ion implantation (acceleration energy) can be selected such that a thin film having a target thickness can be obtained.

(61) [Bonding]

(62) Subsequently, the base wafer (an epitaxial wafer) prepared as described above and the bond wafer having an ion-implanted layer formed therein are bonded. The ion-implanted surface of the bond wafer and the surface of the base wafer is bonded directly or through an insulating film.

(63) [Formation of Thin Film (Delamination of Bond Wafer)]

(64) Then, in the wafers thus bonded, the bond wafer is delaminated along the ion-implanted layer to form a thin film on the base wafer. The delamination can be performed by a known method such as a delamination heat treatment.

(65) The inventive method for manufacturing a bonded wafer described above can manufacture a bonded wafer with a small terrace width (e.g., 1 mm or less, more preferably 0.5 mm or less) even when an epitaxial wafer is used as the base wafer. Such a bonded wafer has a large effective area, and even its periphery can be used for forming a device.

EXAMPLE

(66) The present invention will be specifically described below with reference to Examples and Comparative Example, but the present invention is not limited thereto.

Example 1

(67) As a wafer for epitaxial growth, a PW wafer (a mirror-polished wafer composed of silicon single crystal) with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.20 mm was prepared. The amount of sag of this wafer at this time was set to 20 nm/mm.sup.2 (a sag shape) in a value measured as an amount of inclination (ZDD) at a point of 148 mm from the center (a point of 2 mm from the peripheral end). Then, onto this wafer, an epitaxial layer with a thickness of 3.5 m was formed. The epitaxial growth conditions were adjusted to make the amount of sag after the epitaxial growth be 60 nm/mm.sup.2. Thus prepared epitaxial wafer was used as a base wafer.

(68) For a bond wafer, a PW wafer with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.35 mm and an amount of sag on the periphery of the bonding surface side of 20 nm/mm.sup.2 was prepared. To this PW wafer, a BOX oxide film with a film thickness of 200 nm was formed. This was then subjected to hydrogen ion-implantation on conditions of acceleration energy of 50 keV and a dose amount of 5.010.sup.16/cm.sup.2. Thus prepared wafer was used as a bond wafer.

(69) Subsequently, the bond wafer and the base wafer were bonded, and subjected to a delamination heat treatment at 500 C. for 30 minutes. As a result, the bond wafer was delaminated, and an SOI wafer could be obtained. In the produced SOI wafer, the chamfer width was 0.20 mm, the width from the end of the chamfer portion to the end of the SOI layer was 0.80 mm, and the sum of these (the terrace width) was 1.00 mm.

(70) The chamfer widths and the amounts of sag of the base wafer and the bond wafer are shown in Table 1. Table 2 shows the chamfer width, the width from the end of the chamfer portion to the end of the SOI layer, and the terrace width of the produced SOI wafer.

Example 2

(71) As a wafer for epitaxial growth, a PW wafer (a mirror-polished wafer composed of silicon single crystal) with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.35 mm was prepared. The amount of sag of this wafer at this time was set to +20 nm/mm.sup.2 (a rise shape) in a value measured as an amount of inclination (ZDD) at a point of 148 mm from the center (a point of 2 mm from the peripheral end). Then, onto this wafer, an epitaxial layer with a thickness of 3.5 m was formed. The epitaxial growth conditions were adjusted to make the amount of sag after the epitaxial growth be 30 nm/mm.sup.2. Thus prepared epitaxial wafer was used as a base wafer.

(72) For a bond wafer, a PW wafer with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.35 mm and an amount of sag on the periphery of the bonding surface side of 20 nm/mm.sup.2 was prepared. To this PW wafer, a BOX oxide film with a film thickness of 200 nm was formed. This was then subjected to hydrogen ion-implantation on conditions of acceleration energy of 50 keV and a dose amount of 5.010.sup.6/cm.sup.2. Thus prepared wafer was used as a bond wafer.

(73) Subsequently, the bond wafer and the base wafer were bonded, and subjected to a delamination heat treatment at 500 C. for 30 minutes. As a result, the bond wafer was delaminated, and an SOI wafer could be obtained. In the produced SOI wafer, the chamfer width was 0.35 mm, the width from the end of the chamfer portion to the end of the SOI layer was 0.65 mm, and the sum of these (the terrace width) was 1.00 mm.

(74) The chamfer widths and the amounts of sag of the base wafer and the bond wafer are shown in Table 1. Table 2 shows the chamfer width, the width from the end of the chamfer portion to the end of the SOI layer, and the terrace width of the produced SOI wafer.

Example 3

(75) As a wafer for epitaxial growth, a PW wafer (a mirror-polished wafer composed of silicon single crystal) with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.35 mm was prepared. The amount of sag of this wafer at this time was set to 40 nm/mm.sup.2 (a sag shape) in a value measured as an amount of inclination (ZDD) at a point of 148 mm from the center (a point of 2 mm from the peripheral end). Then, onto this wafer, an epitaxial layer with a thickness of 3.5 m was formed. The epitaxial growth conditions were adjusted to make the amount of sag after the epitaxial growth be 30 nm/mm.sup.2. Thus prepared epitaxial wafer was used as a base wafer.

(76) For a bond wafer, a PW wafer with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.35 mm and an amount of sag on the periphery of the bonding surface side of 20 nm/mm.sup.2 was prepared. To this PW wafer, a BOX oxide film with a film thickness of 200 nm was formed. This was then subjected to hydrogen ion-implantation on conditions of acceleration energy of 50 keV and a dose amount of 5.010.sup.16/cm.sup.2. Thus prepared wafer was used as a bond wafer.

(77) Subsequently, the bond wafer and the base wafer were bonded, and subjected to a delamination heat treatment at 500 C. for 30 minutes. As a result, the bond wafer was delaminated, and an SOI wafer could be obtained. In the produced SOI wafer, the chamfer width was 0.35 mm, the width from the end of the chamfer portion to the end of the SOI layer was 0.60 mm, and the sum of these (the terrace width) was 0.95 mm.

(78) The chamfer widths and the amounts of sag of the base wafer and the bond wafer are shown in Table 1. Table 2 shows the chamfer width, the width from the end of the chamfer portion to the end of the SOI layer, and the terrace width of the produced SOI wafer.

Example 4

(79) As a wafer for epitaxial growth, a PW wafer (a mirror-polished wafer composed of silicon single crystal) with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.15 mm was prepared. The amount of sag of this wafer at this time was set to +20 nm/mm.sup.2 (a rise shape) in a value measured as an amount of inclination (ZDD) at a point of 148 mm from the center (a point of 2 mm from the peripheral end). Then, onto this wafer, an epitaxial layer with a thickness of 3.5 m was formed. The epitaxial growth conditions were adjusted to make the amount of sag after the epitaxial growth be 20 nm/mm.sup.2. Thus prepared epitaxial wafer was used as a base wafer.

(80) For a bond wafer, a PW wafer with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.35 mm and an amount of sag on the periphery of the bonding surface side of 20 nm/mm.sup.2 was prepared. To this PW wafer, a BOX oxide film with a film thickness of 200 nm was formed. This was then subjected to hydrogen ion-implantation on conditions of acceleration energy of 50 keV and a dose amount of 5.010.sup.16/cm.sup.2. Thus prepared wafer was used as a bond wafer.

(81) Subsequently, the bond wafer and the base wafer were bonded, and subjected to a delamination heat treatment at 500 C. for 30 minutes. As a result, the bond wafer was delaminated, and an SOI wafer could be obtained. In the produced SOI wafer, the chamfer width was 0.15 mm, the width from the end of the chamfer portion to the end of the SOI layer was 0.65 mm, and the sum of these (the terrace width) was 0.80 mm.

(82) The chamfer widths and the amounts of sag of the base wafer and the bond wafer are shown in Table 1. Table 2 shows the chamfer width, the width from the end of the chamfer portion to the end of the SOI layer, and the terrace width of the produced SOI wafer.

Example 5

(83) As a wafer for epitaxial growth, a PW wafer (a mirror-polished wafer composed of silicon single crystal) with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.15 mm was prepared. The amount of sag of this wafer at this time was set to 20 nm/mm.sup.2 (a sag shape) in a value measured as an amount of inclination (ZDD) at a point of 148 mm from the center (a point of 2 mm from the peripheral end). Then, onto this wafer, an epitaxial layer with a thickness of 3.5 m was formed. The epitaxial growth conditions were adjusted to make the amount of sag after the epitaxial growth be 10 nm/mm.sup.2. Thus prepared epitaxial wafer was used as a base wafer.

(84) For a bond wafer, a PW wafer with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.35 mm and an amount of sag on the periphery of the bonding surface side of 20 nm/mm.sup.2 was prepared. To this PW wafer, a BOX oxide film with a film thickness of 200 nm was formed. This was then subjected to hydrogen ion-implantation on conditions of acceleration energy of 50 keV and a dose amount of 5.010.sup.16/cm.sup.2. Thus prepared wafer was used as a bond wafer.

(85) Subsequently, the bond wafer and the base wafer were bonded, and subjected to a delamination heat treatment at 500 C. for 30 minutes. As a result, the bond wafer was delaminated, and an SOI wafer could be obtained. In the produced SOI wafer, the chamfer width was 0.15 mm, the width from the end of the chamfer portion to the end of the SOI layer was 0.60 mm, and the sum of these (the terrace width) was 0.75 mm.

(86) The chamfer widths and the amounts of sag of the base wafer and the bond wafer are shown in Table 1. Table 2 shows the chamfer width, the width from the end of the chamfer portion to the end of the SOI layer, and the terrace width of the produced SOI wafer.

Example 6

(87) As a wafer for epitaxial growth, a PW wafer (a mirror-polished wafer composed of silicon single crystal) with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.35 mm was prepared. The amount of sag of this wafer at this time was set to +5 nm/mm.sup.2 (a rise shape) in a value measured as an amount of inclination (ZDD) at a point of 148 mm from the center (a point of 2 mm from the peripheral end). Then, onto this wafer, an epitaxial layer with a thickness of 3.5 m was formed. The epitaxial growth conditions were adjusted to make the amount of sag after the epitaxial growth be +10 nm/mm.sup.2. Thus prepared epitaxial wafer was used as a base wafer.

(88) For a bond wafer, a PW wafer with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.35 mm and an amount of sag on the periphery of the bonding surface side of 20 nm/mm.sup.2 was prepared. To this PW wafer, a BOX oxide film with a film thickness of 200 nm was formed. This was then subjected to hydrogen ion-implantation on conditions of acceleration energy of 50 keV and a dose amount of 5.010.sup.16/cm.sup.2. Thus prepared wafer was used as a bond wafer.

(89) Subsequently, the bond wafer and the base wafer were bonded, and subjected to a delamination heat treatment at 500 C. for 30 minutes. As a result, the bond wafer was delaminated, and an SOI wafer could be obtained. In the produced SOI wafer, the chamfer width was 0.35 mm, the width from the end of the chamfer portion to the end of the SOI layer was 0.25 mm, and the sum of these (the terrace width) was 0.60 mm.

(90) The chamfer widths and the amounts of sag of the base wafer and the bond wafer are shown in Table 1. Table 2 shows the chamfer width, the width from the end of the chamfer portion to the end of the SOI layer, and the terrace width of the produced SOI wafer.

Example 7

(91) As a wafer for epitaxial growth, a PW wafer (a mirror-polished wafer composed of silicon single crystal) with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.15 mm was prepared. The amount of sag of this wafer at this time was set to +5 nm/mm.sup.2 (a rise shape) in a value measured as an amount of inclination (ZDD) at a point of 148 mm from the center (a point of 2 mm from the peripheral end). Then, onto this wafer, an epitaxial layer with a thickness of 3.5 m was formed. The epitaxial growth conditions were adjusted to make the amount of sag after the epitaxial growth be +10 nm/mm.sup.2. Thus prepared epitaxial wafer was used as a base wafer.

(92) For a bond wafer, a PW wafer with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.35 mm and an amount of sag on the periphery of the bonding surface side of 20 nm/mm.sup.2 was prepared. To this PW wafer, a BOX oxide film with a film thickness of 200 nm was formed. This was then subjected to hydrogen ion-implantation on conditions of acceleration energy of 50 keV and a dose amount of 5.010.sup.16/cm.sup.2. Thus prepared wafer was used as a bond wafer.

(93) Subsequently, the bond wafer and the base wafer were bonded, and subjected to a delamination heat treatment at 500 C. for 30 minutes. As a result, the bond wafer was delaminated, and an SOI wafer could be obtained. In the produced SOI wafer, the chamfer width was 0.15 mm, the width from the end of the chamfer portion to the end of the SOI layer was 0.25 mm, and the sum of these (the terrace width) was 0.40 mm.

(94) The chamfer widths and the amounts of sag of the base wafer and the bond wafer are shown in Table 1. Table 2 shows the chamfer width, the width from the end of the chamfer portion to the end of the SOI layer, and the terrace width of the produced SOI wafer.

Comparative Example 1

(95) As a wafer for epitaxial growth, a PW wafer (a mirror-polished wafer composed of silicon single crystal) with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.35 mm was prepared. The amount of sag of this wafer at this time was set to 20 nm/mm.sup.2 (a sag shape) in a value measured as an amount of inclination (ZDD) at a point of 148 mm from the center (a point of 2 mm from the peripheral end). Then, onto this wafer, an epitaxial layer with a thickness of 3.5 m was formed. The epitaxial growth conditions were adjusted to make the amount of sag after the epitaxial growth be 60 nm/mm.sup.2. Thus prepared epitaxial wafer was used as a base wafer.

(96) For a bond wafer, a PW wafer with a diameter of 300 mm having a chamfer shape with a chamfer width of 0.35 mm and an amount of sag on the periphery of the bonding surface side of 20 nm/mm.sup.2 was prepared. To this PW wafer, a BOX oxide film with a film thickness of 200 nm was formed. This was then subjected to hydrogen ion-implantation on conditions of acceleration energy of 50 keV and a dose amount of 5.010.sup.16/cm.sup.2. Thus prepared wafer was used as a bond wafer.

(97) Subsequently, the bond wafer and the base wafer were bonded, and subjected to a delamination heat treatment at 500 C. for 30 minutes. As a result, the bond wafer was delaminated, and an SOI wafer could be obtained. In the produced SOI wafer, the chamfer width was 0.35 mm, the width from the end of the chamfer portion to the end of the SOI layer was 0.80 mm, and the sum of these (the terrace width) was 1.15 mm.

(98) The chamfer widths and the amounts of sag of the base wafer and the bond wafer are shown in Table 1. Table 2 shows the chamfer width, the width from the end of the chamfer portion to the end of the SOI layer, and the terrace width of the produced SOI wafer.

(99) TABLE-US-00001 TABLE 1 Base wafer Amount of Amount of sag before sag after Bond wafer Chamfer epitaxial epitaxial Chamfer Amount Conditions of method width growth growth width of sag for manufacturing (mm) (nm/mm.sup.2) (nm/mm.sup.2) (mm) (nm/mm.sup.2) epitaxial wafer Example 1 0.20 20 60 0.35 20 (1) Example 2 0.35 +20 30 0.35 20 (2) Example 3 0.35 40 30 0.35 20 (3) Example 4 0.15 +20 20 0.35 20 (1) + (2) Example 5 0.15 20 10 0.35 20 (1) + (3) Example 6 0.35 +5 +10 0.35 20 (2) + (3) Example 7 0.15 +5 +10 0.35 20 (1) + (2) + (3) Comparative 0.35 20 60 0.35 20 Example 1

(100) TABLE-US-00002 TABLE 2 Chamfer Width from the end of the Terrace width chamfer portion to the end width (mm) of the SOI layer (mm) (mm) Example 1 0.20 0.80 1.00 Example 2 0.35 0.65 1.00 Example 3 0.35 0.60 0.95 Example 4 0.15 0.65 0.80 Example 5 0.15 0.60 0.75 Example 6 0.35 0.25 0.60 Example 7 0.15 0.25 0.40 Comparative 0.35 0.80 1.15 Example 1

(101) As shown in Table 2, each Examples 1 to 7, which used an epitaxial wafer manufactured by a method including at least one of the conditions (1) to (3) as a base wafer, could manufacture a bonded wafer with a terrace width of 1 mm or less. On the other hand, Comparative example 1, which used an epitaxial wafer manufactured by a method without including any of the conditions (1) to (3) as a base wafer, could not manufacture a bonded wafer with a terrace width of 1 mm or less. Moreover, the terrace width could be reduced smaller by using an epitaxial wafer produced by a method including two or more conditions of the conditions (1) to (3) as a base wafer.

(102) From the results described above, it was revealed that the inventive method for manufacturing a bonded wafer can manufacture a bonded wafer with a small terrace width (e.g., 1 mm or less) even when an epitaxial wafer is used as a base wafer.

(103) It is to be noted that the present invention is not limited to the foregoing embodiment. The embodiment is just an exemplification, and any examples that have substantially the same feature and demonstrate the same functions and effects as those in the technical concept described in claims of the present invention are included in the technical scope of the present invention.