JPH0997755A - Mirror-surface wafer bonding method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable two mirror-surface wafers to be bonded together through a comparatively simple method without using a complicated and large device by a method wherein the mirror-surface wafers are placed on a sloping support, and the chamfered corner of the wafer is pressed under prescribed conditions. SOLUTION: When two mirror-surface wafers W1 and W2 of the same shape are bonded together making their mirror surfaces confront each other, the wafer W1 is rested on a support 4 which is previously fixed as tilted forming an angle of 70 deg. to 90 deg. with a horizontal direction and making its mirror surface face upwards, and the wafer W2 is made to gently overlap the wafer W1 making the mirror surfaces of the wafers W1 and W2 confront each other so as not to impose a load larger than the component force of its own weight on the wafer W1 . Then, the ridge of a convex curved-surface pressing member 7 of plastic body is made to bear against the one end of the chamfered corner 10 of the wafer W2 and slightly pressed against it, and the pressing member 7 is made to start bonding the wafers W1 and W2 together. By this setup, two mirror-surface wafers are bonded together through a comparatively simple device preventing voids from occurring in a bonded surface without the manual operation of a skilled operator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding technique for semiconductor substrate wafers, and more particularly to a method and apparatus for bonding two mirror-shaped wafers of the same shape.

[0002]

2. Description of the Related Art Conventionally, when two mirror-polished silicon wafers, or at least one of the silicon wafers having a silicon oxide film or a nitride film formed thereon, are brought into contact with each other under a clean condition, an adhesive agent, etc. The wafers are adhered to each other without using (hereinafter, this state is referred to as bonding). However, since this bonded state is not perfect, the wafers are strongly bonded to each other by heat treatment thereafter (hereinafter, this state is referred to as bonding). An SOI (Silicon On Insulator) wafer is obtained by bonding two silicon wafers of which the surface of at least one of the latter wafers is oxidized through the oxide film.

In such an SOI wafer, since it is not necessary to interpose a different substance such as an adhesive between the wafers, the subsequent high temperature treatment and various chemical treatments can be freely performed, and the pn wafer can be used.
There is an advantage that joining and dielectric embedding can be simplified. In addition to the improvement of thinning technology such as flatness and cleanliness, its practical application is drawing attention.

By the way, when two mirror-finished wafers are bonded as described above, air bubbles are taken into a part of the bonded surfaces due to a slight warp of the wafers, etc., resulting in defective bonding (void).
Therefore, as shown in Japanese Patent Publication No. 6-1790, for example, one of the semiconductor wafers is placed on a support table that can be bent and held so that the central portion has a convex shape.
The other semiconductor wafer is held by a holder that can be held opposite to the support table, the holder is lowered, and the other semiconductor wafer is brought into contact with the convex portion of the one semiconductor wafer, and then one of the support boards is provided. A method of joining both wafers by releasing the holding of the semiconductor wafers is disclosed.

On the other hand, as another example of the joining method described above,
There is a method disclosed in JP-A-5-152549. As shown in FIG. 4, this method uses a base wafer 1a and a bond wafer 1 having an oxide film formed on the bonding surface.
b, at least at room temperature cleanliness class 10 at normal temperature
In a clean bench of 00 or more, after the base wafer 1a is sucked and fixed to the vacuum suction table 2 in a substantially horizontal state, the bond wafer 1b is sucked by the vacuum tweezers 3 at a portion 11b near the OF portion (orientation flat portion) 2b. Let Then, by operating the vacuum tweezers 3, the bond wafer 1b is tilted so that the OF portion 2b of the bond wafer 1b is slightly lowered, and in that state, the bond wafer 1b is lowered from the upper position of the base wafer 1a. Yuki, bond wafer 1
b of the OF surface 2b and the O of the base wafer 1a
The edge on the joining surface side of the F portion 2a is lightly bumped into contact.
Next, the two wafers are brought close to each other until the distance between the end portions 3a and 3b opposite to the OF portions 2a and 2b becomes about 1 mm, and then the bond wafer 1 by the vacuum tweezers 3 is used.
Stop the adsorption of b. Then, the bond wafer 1b has an OF portion 2a which is an initial butting portion with the base wafer 1a.
Is rotated by its own weight with the edge on the side of the bonding surface as a fulcrum, and finally the entire surface of the base wafer 1a and the entire surface of the bond wafer 1b come into contact with each other, and a pressing force is applied to the OF portion, so that the OF portion 2a, 2b is connected to the other side 3a, 3b It is a method of sequentially advancing the bonding toward.

[0006]

However, in the joining method described in the above-mentioned Japanese Patent Publication No. 6-1790, the apparatus for joining is complicated, the scale is large, and the equipment cost accompanying it is high. In addition, there is a problem that one wafer is bent and held on a support table for joining, and thus an excessive force is applied to the wafer to damage or break it. By this method, it was possible to reduce the entrapment of air bubbles on the wafer bonding surface, but it was not always a satisfactory elimination of air bubble entrapment.

Further, the above-mentioned conventional Japanese Patent Laid-Open No. 5-152549.
In the bonding method described in the publication, the edge of the bonding surface of the OF portion 2b of the bond wafer 1b is brought into contact with the bonding surface side edge of the OF portion 2a of the base wafer 1a by operating the vacuum tweezers 3, The distance between the end portions 3a, 3b on the opposite side of the OF portions 2a, 2b of the wafer is set to about 1 mm or less, the suction state of the bond wafer 1b is released and the wafer is brought into contact with itself by its own weight, and then a pressing force is immediately applied. This requires delicate position adjustment and pressing timing to be performed by manual operation by a skilled worker, which is disadvantageous in workability and cannot be mass-produced by mechanization, resulting in poor production efficiency. there were. Also, in this bonding method, it is possible to reduce the entrapment of air bubbles (that is, voids) on the wafer bonding surface,
The self-weight of the bond wafer acts as a pressing force, and the bonding spontaneously starts from multiple locations on the wafer mirror surface, trapping air bubbles, or causing defective bonding (void) near the OF portion of the bonded surface. However, there was a disadvantage that a perfect joint could not be made.

Therefore, in view of the above-mentioned conventional problems, the present invention can perform the joining by a relatively simple method without using a complicated and large-scale device, and requires manual operation by a skilled worker. It is an object of the present invention to provide a method and apparatus for bonding a mirror-finished wafer, which can be automated without the need for the above, have excellent production efficiency, and can prevent the occurrence of voids in the bonded portion.

[0009]

As a result of various studies to solve the above problems, the present inventor has made a mirror surface which is an upper surface placed on an inclined support table when two mirror surface wafers are bonded. The present invention has been completed by finding a method and apparatus for joining mirror-polished wafers that can effectively solve the above problems by pressing the chamfered corners of the wafer under predetermined conditions to perform the joining.

That is, the present invention is a method for superimposing and bonding the mirror surfaces of two mirror-shaped wafers of the same shape, which is preliminarily fixed to a support base at an angle of 70 ° to 90 ° with respect to the horizontal direction. , The first mirror-finished wafer is supported so that the mirror-finished side thereof faces up, and the mirror-finished surface of the second mirror-finished wafer is opposed to the mirror-finished surface of the first wafer by the weight of the second wafer. After gently stacking so that a load equal to or more than the force is not applied to the first wafer, press the ridge line of the pressing member made of a convex curved elastic body to one end of the chamfered corner of the second wafer. The gist of the invention is a method of joining mirror-finished wafers, which is applied and lightly pressed to start joining the two mirror-finished wafers from the pressed portion.

The present invention also provides the above-mentioned joining method,
When the angle of the chamfered portion at the pressing portion of the second mirror-finished wafer with the edge of the wafer being chamfered is θ, the angle between the main surface of the wafer and the ridge of the pressing member is based on 1/2 × θ It is preferable that the pressing portion of the second mirror-finished wafer in which the edge of the wafer is curved in the joining method has an angle β between the main surface of the wafer and the ridgeline of the pressing member. , Β from 0 ° to 10 °
And pressing in that direction is preferable. Further, in the bonding method, the bonding of the mirror surfaces of two mirror-shaped wafers of the same shape to each other is performed in a high-purity inert gas atmosphere. Is also suitable.

Furthermore, there is provided a device for superposing and joining the mirror surfaces of two mirror-shaped wafers of the same shape,
The second mirror-finished wafer is placed on the first mirror-finished wafer so that the mirror-faces thereof face each other, and the second wafer is gently superposed so that a load equal to or greater than the component force due to the self-weight of the second wafer is not applied to the first wafer. For supporting the fixed base at an angle of 70 ° to 90 ° with respect to the horizontal direction, a pressing drive unit attached to one end of the supporting base, a pressing arm extending from the pressing drive unit, and a pressing arm of the pressing arm. A gist of an apparatus for joining mirror-finished wafers, comprising a convex curved surface-shaped pressing member which is attached to the tip and is pressed against the chamfered corner portions of the second mirror-finished wafers in the both mirror-finished wafers.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The method and apparatus for bonding mirror-finished wafers of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is an explanatory diagram showing an example of the apparatus of the present invention. As shown in this figure, a device 1 of the present invention is a device for superposing and joining the mirror surfaces of _two mirror-shaped wafers W ₁ and W ₂ of the same shape, and the first mirror-surface wafer (here, , A base wafer) W ₁ and a second mirror surface wafer (here, a bond wafer) W ₂ ,
The mirror surfaces are opposed to each other, and the bond wafer W ₂
A load larger than the component force due to the self-weight of the base wafer W
_1. A support base 4 for gently overlapping so as not to cover ₁ , a pressing drive unit 5 attached to one end of the support base 4, a pressing arm 6 extending from the pressing drive unit 5, and a tip of the pressing arm 6. It is mainly composed of a convex curved surface-shaped pressing member 7 which is attached and presses against the chamfered corners of the bond wafer W ₂ in the both mirror-finished wafers.

The support 4 is a flat plate on which the base wafer W ₁ can be placed, and is supported by a base 8 so as to be inclined at a predetermined angle with respect to the horizontal direction. In this device, the inclination angle of the support table is important, and the inclination angle is 70 ° to 9 ° with respect to the horizontal direction.
If the angle is within the range of 0 ° and is smaller than the angle of 70 °, the bond wafer W bonded to the base wafer W _1
It is difficult to mechanize because self-weight joining with ₂ starts immediately,
In addition, there is a problem that voids are likely to occur. On the contrary, if the angle is larger than 90 °, the base wafer W ₁ is below the support base 4 and the wafer cannot be held, which is not preferable.

In order to hold both wafers within this angle range, a holding member 9 for holding the wafer is provided at a predetermined position on the support base.
9'is attached in two symmetry. The holding members 9 and 9'are usually composed of rod-shaped members, especially pins, which are mounted almost vertically from the supporting base so that both wafers can be supported so as not to slip off the supporting base.

At one end of the support 4, particularly near the lower end,
A pressing drive unit 5 is attached, and a pressing arm 6 extending from this drive unit can be moved in the front-rear and left-right directions.

The pressing arm 6 is usually a long rod-shaped body and is made of a metal material such as aluminum or stainless steel, and its tip end is vertically hit against the pressing part of the wafer, or a force is applied thereto. It is formed in such a shape. A pressing member 7 for pressing the bond wafer W ₂ is attached to the tip of the pressing arm 6.

The vicinity of the pressing member 7 in contact with the wafer has a convex curved surface shape, which is a convex curved surface formed as a rotating body, for example, a spherical shape, a cylindrical body, a conical shape, or Part of that shape is used. The pressing member 7 is an elastic body having the above-mentioned shape, and for example,
Rubber or synthetic resin molding is used. The pressing arm 6 operates so that the ridgeline of the pressing member 7 can be pressed against the chamfered corner portion 10 of the bond wafer W ₂ .

In the present invention, the chamfered corner portion refers to the corner portion of a wafer whose edge is chamfered.
When the edge of the wafer is curved, this means including the starting point of the curved surface.

With the apparatus having such a structure, the two mirror-finished wafers W ₁ and W ₂ can be bonded together.
The specular wafer used in the present invention refers to a specular wafer made of a usual semiconductor material, and as its material,
Semiconductor materials (silicon, compound semiconductors), oxide single crystals and ceramic materials (quartz and other ceramics)
Is included. Therefore, the bonded body has a silicon-silicon direct bonding, a silicon-SiO ₂ film-silicon bonding (SO
I), or silicon-SiO ₂ (quartz) bonding and the like.

The term "bonding" as used in the present invention means, as described in the above-mentioned prior art, two silicon wafers that have been mirror-polished, or a silicon wafer having a silicon oxide film or a nitride film formed on at least one of them. That is, the mirror surfaces are brought into contact with each other under clean conditions to bond the wafers to each other without using an adhesive or the like. Furthermore, the term "bonding" as used in the present invention means that the wafers in a bonded state are subjected to heat treatment or the like to firmly bond the wafers to each other, as described in the above-mentioned prior art.

In the present invention, the first mirror surface wafer and the second mirror surface wafer, that is, the base wafer and the bond wafer are bonded as two mirror surface wafers. In the case of a semiconductor material, the base wafer is a bond wafer. When a semiconductor element is formed, it refers to a wafer that supports it, and a bond wafer is a wafer that is bonded to the upper surface of the base wafer and serves as a layer that forms a semiconductor element. In the present invention, as described above, the first
Bonding was performed using the mirror-finished wafer of No. 1 as a base wafer and the second mirror-finished wafer as a bond wafer, but reversely, the first mirror-finished wafer was used as a bond wafer, and the second mirror-finished wafer was used as a base wafer. You may join.

Next, a method of joining two mirror-finished wafers using the above apparatus of the present invention will be described. Using the apparatus of the present invention as shown in FIG. 1, two mirror-shaped wafers of the same shape, that is, a first mirror-surface wafer (here, a base wafer) W ₁ and a second mirror-surface wafer (here, This is a method of bonding W ₂ mirror surfaces on top of each other, which is used as a bond wafer.
The base wafer W ₁ is supported by a support base 4 fixed at an angle of 0 ° to 90 ° so that the mirror surface side of the base wafer W ₁ faces up, and the bond wafer W _{2 has} the mirror surface of the base wafer W ₁ mirror surface. And the bond wafer W facing each other.
Component force load or greater by ₂ its own weight, after gently overlaid so as not to the base wafer W _1, one end of the chamfered corner 10 of the bond wafer W _2, made of an elastic material of convex curved surface The ridge line of the pressing member 7 is pressed and lightly pressed, and the two mirror-finished wafers are joined from the pressed portion to join the _two wafers W ₁ and W ₂ .

In such a joining method, the inclination angle of the support base 4 is important as described above, and when the angle is smaller than the angle of 70 ° with respect to the horizontal direction, it is joined to the base wafer W _1. There is a problem that self-weight bonding with the bond wafer W ₂ will start immediately and it will be difficult to mechanize, and voids will easily occur. Conversely, if the angle is larger than 90 °, the base wafer W ₁ will be below the support table. Since the wafer cannot be held, which is not preferable, the inclination angle is set in the range of 70 ° to 90 °.

The above-mentioned two wafers W ₁ and W ₂ are arranged on a support base so as to face each other, and a holding member provided on the support base fixed at a predetermined inclination angle separates both the wafers from _{each other.} The base wafer W ₁ is gently overlapped and held so that a load larger than the component force due to its own weight is not applied to the base wafer W ₁ . Here, bond wafer W ₂
The load equal to or greater than the component force due to its own weight is a load in a state in which the joining with the base wafer W ₁ is not immediately started due to its own weight, and this load causes the inclination angle of the support base to fall from 70 ° to 70 °.
The condition is satisfied when the angle is set within the range of 90 °.

In this way, one end of the chamfered corner portion 10 of the above-mentioned wafer W ₂ (if the wafer edge is curved surface processing, the wafer edge curved surface processing start point) is pressed. The pressing position at this one end may be any point near the chamfered corner and in the vicinity thereof, and the pressing position is lightly pressed by the ridge of the pressing member 7 to bond the _two wafers W ₁ and W ₂ . Let it start. Although the pressing force at this time varies depending on the surface roughness and cleanliness of each mirror-finished wafer, it is usually 1
The amount is about 00 g to 1000 g, preferably about 500 g.

Next, the joining method of the present invention will be described in more detail. 2 and 3 are enlarged side views of the wafer pressing portion showing the method for joining mirror-finished wafers of the present invention. As shown in FIG. 2, in the method of the present invention, a method is adopted in which the ridgeline of the pressing member 7 is pressed against the chamfered corner portion 10 of the bond wafer W ₂ and lightly pressed to start the bonding from there. However, particularly by specifying the pressing direction of the pressing member 7, more preferable joining is possible.

The pressing direction differs depending on the curved surface shape of the wafer edge. First, in the case of a wafer in which the edge of the wafer is chamfered, the chamfered portion angle at the pressing portion of the bond wafer W ₂ is θ, and the angle between the main surface of the wafer and the ridge of the pressing member is α, α = 1 It is important to press in the direction based on / 2 × θ. This chamfer angle θ is 8 for a wafer with a normal edge chamfered.
Are 11 ° and 22 °. After the chamfer angle θ is determined, the angle α in the pressing direction is based on ½ × θ, but this range is preferably adopted if it is within ± 30% thereof. For example, when θ is 22 °, α
Is in the range of 7.7 ° to 14.3 °.

Further, in the case of a wafer whose edge is curved, as shown in FIG. 3, the vicinity of the edge curved surface processing start point 11 of the bond wafer W ₂ is pressed. Β in the pressing direction
Is in the range of 0 ° to 10 °, and more preferably in this range. In this way, by setting the angle α in the pressing direction within the predetermined range with respect to the chamfered angle θ,
Further, by setting the angle β in the pressing direction within a predetermined range, it is possible to perform complete joining without the occurrence of voids.

By the method of the present invention as described above, it is possible to carry out bonding with less generation of voids, but it is preferable to carry out the bonding in a high-purity inert gas atmosphere using the apparatus and method described above. In this case, the high-purity inert gas is, for example, N ₂ or Ar which is usually used as an ultra-high-purity inert gas for semiconductor manufacturing, and has a cleanliness of US Federal Standard Class 10 or higher. It is desirable to do it in a clean bench. By performing the bonding in this atmosphere, it is possible to prevent contamination of the bonding interface of boron (B), which is a chemical contaminant, in particular.

[0031]

EXAMPLES Next, examples and comparative examples of the present invention will be described. (Examples 1 to 3 and Comparative Examples 1 and 2) A bond wafer made of a silicon single crystal with an oxide film having a diameter of 8 inches and a base wafer made of a silicon single crystal having a diameter of 8 inches and having the same shape as the base wafer were provided for each 20 pieces. I prepared them one by one. Each wafer was a mirror-finished wafer having a surface roughness of 10 nm or less, and a chamfered portion of the wafer edge was chamfered at an angle of 22 °.

Using each of the above-mentioned wafers and using a device having a structure as shown in FIG. 1, the base wafer is placed on a pre-inclined support stand so that its mirror surface side is the front side, and the above-mentioned base wafer is placed on the support wafer. After gently laminating the bond wafers, the bond wafers were allowed to stand for 3 minutes, and then the ridge line of the pressing member made of a rubber cylinder attached to the tip of the aluminum pressing arm was attached to one end of the chamfered corner of the bond wafer. Pressing with the pressing direction angle α as shown in Fig.
Bonding of the mirror-finished wafers was started to complete the bonding. Regarding the inclination angle of the support base in this case, 80 ° (Example 1), 70 ° (Example 2), 85 ° (Example 3),
Bonding was performed at an angle of 60 ° (Comparative Example 1) and 45 ° (Comparative Example 2), respectively.

Next, with respect to each of the bonded wafers, the amount of voids was observed by an ultrasonic flaw detection method using a void inspection device My Scope i (trade name, manufactured by Hitachi Construction Machinery Co., Ltd.), and the results are shown. The results are shown in Table 1. In addition, the size of the void was determined to be a defective product if any one of the circular shapes of 1 to 20 mm was detected, and a product that was not detected was determined to be an acceptable product.

For each of the above wafers, the elapsed time until the self-weight bonding is started after the bond wafer is superposed on the base wafer is also measured, and the results are shown in Table 1.
It was shown to. The suitability for mechanization at this time was evaluated as follows. (Evaluation) ◎ ... Mechanization compatibility is particularly excellent. ○: Mechanization compatibility is available ×: Mechanization compatibility is not available

[0035]

[Table 1]

(Embodiment 4) A wafer similar to the wafers used in the above-mentioned Embodiments 1 to 3 is used, and the pressing portion is set at an angle as shown in FIG.
The joining was completed by pressing in the same manner with a support base tilted at the same angle as described above. Table 1 shows the results regarding the occurrence of voids and the suitability for mechanization of this wafer as described above.

(Embodiment 5) A bond wafer consisting of a silicon single crystal with an oxide film having a diameter of 8 inches and 20 base wafers consisting of a silicon single crystal with an oxide film having a diameter of 8 inches and having the same shape were prepared for each 20 sheets. Each wafer was a mirror-finished wafer having a surface roughness of 10 nm or less, and a wafer whose wafer edge was curved was used.

Using each of the above wafers, the pressing portion is shown in FIG.
In the first embodiment, the angle as shown in FIG.
Press in the same way with a tilted support,
The joining was completed. With respect to this wafer, the results on the compatibility of void generation and mechanization are shown in Table 1 as described above.
It was shown to.

(Embodiments 6 to 8) A method similar to that of Embodiment 1 was carried out by using the apparatus having the structure shown in FIG. 1 in a clean room in an N ₂ gas atmosphere (in this case, the cleanliness level was US Federal Standard Class 10). Example 6), a method similar to Example 4 (Example 7), and a method similar to Example 5 (Example 8) were respectively joined, and joining was completed. Table 1 shows the results regarding the occurrence of voids and the suitability for mechanization of this wafer as described above.

(Test Results) As is clear from the results shown in Table 1, the wafers of Examples 1 to 3 had fewer defective wafers and the void generation rate was higher than those of Comparative Examples 1 and 2 as conventional examples. In regard to compatibility of mechanization, those of Comparative Examples 1 and 2 are not suitable because self-weight bonding starts immediately because the inclination angle of the support base is low.
No. 3 is suitable for automation because the self-weight joining does not start for a proper period. In addition, Examples 4 to 8 were not only suitable for automation, but also obtained favorable results with respect to the occurrence rate of voids.

[0041]

According to the device of the present invention, since it is mainly composed of a support base that can be fixed at a predetermined inclination angle, a drive unit attached to one end of the support base, a pressing arm, and a pressing member, it is possible to use the conventional structure. It is possible to use a relatively simple device rather than a complicated and large-scale device, and it is possible to automate without requiring manual operation by a skilled worker. Furthermore, it is possible to completely prevent the occurrence of voids at the joint.

Further, according to the method of the present invention, by pressing one end of the chamfered corner portion of the bond wafer fixed to the support table having a predetermined inclination angle with the pressing member, the voids that are often generated conventionally are completely eliminated. Can be prevented. Especially,
By specifying the pressing direction of the pressing member against the bond wafer, it is possible to further prevent the generation of voids. Furthermore, according to another method of the present invention, by bonding the mirror-finished wafers to each other in an atmosphere of high-purity inert gas, it is possible to prevent contamination of the bonding interface such as boron (B).

[Brief description of drawings]

FIG. 1 is an explanatory view showing a mirror-wafer bonding apparatus of the present invention.

FIG. 2 is an enlarged side view of a pressing portion showing the mirror-like wafer bonding method of the present invention.

FIG. 3 is an enlarged side view of a pressing portion showing another bonding method for the mirror-finished wafer of the present invention.

FIG. 4 is an explanatory view showing a conventional wafer bonding method.

[Explanation of Codes] 1 ... Joining device 2 ... Vacuum suction table 3 ... Vacuum tweezers 4 ... Support table 5 ... Pushing drive section 6 ... Pushing arm 7 ... Pushing member 8 ... Base 9, 9 '... Holding member 10 ... Chamfering angle part 11 ... edge curved machining start point W ₁ ... first mirror wafer W ₂ ... second mirror wafer theta ... chamfer angle alpha, beta ... pressing direction angle 1a ... base wafer 1b ... bond wafer 2a, 2b ... oF section 3a , 3b ... End portion on the opposite side of the OF portion 11b ... Near portion of the OF portion

Claims (5)

[Claims] 1. A method for joining mirror surfaces of two mirror-shaped wafers of the same shape by superimposing and bonding the mirror surfaces to each other, wherein a first support is fixed to a support base fixed at an angle of 70 ° to 90 ° with respect to the horizontal direction.
The mirror surface of the second wafer with the mirror surface side facing up, and the mirror surface of the second mirror surface wafer facing each other with the mirror surface of the first wafer above the component surface of the second wafer due to its own weight. After gently stacking so that the load is not applied to the first wafer, lightly press the ridge line of the pressing member made of an elastic body with a convex curved surface shape against one end of the chamfered corner of the second wafer A method for joining mirror-finished wafers, comprising the step of pressing and starting the joining of two mirror-finished wafers from the pressed portion. 2. An angle α formed between the main surface of the wafer and the ridgeline of the pressing member, where θ is the chamfered angle of the pressed portion of the second mirror-finished wafer having the edge of the wafer chamfered.
Is pressed in a direction with ½ × θ as a reference, the method of bonding a mirror-finished wafer according to claim 1, wherein 3. When the pressing portion of the second mirror-finished wafer with the edge of the wafer being curved is the angle β between the main surface of the wafer and the ridge of the pressing member, β is in the range of 0 ° to 10 °. 2. The method for joining mirror-finished wafers according to claim 1, wherein the pressing is performed in that direction. 4. The method for joining mirror-finished wafers according to claim 1, wherein the mirror-like surfaces of two mirror-like wafers of the same shape are joined together in an atmosphere of high-purity inert gas. . 5. An apparatus for laminating and joining mirror surfaces of two mirror-shaped wafers of the same shape, wherein the first mirror-surface wafer and the second mirror-surface wafer are opposed to each other, 70 ° to 9 ° with respect to the horizontal direction for gently stacking so that a load equal to or greater than the component force due to the own weight of the second wafer is not applied to the first wafer.
A support base fixed at an angle of 0 °, a pressing drive unit attached to one end of the support base, a pressing arm extending from the pressing drive unit, and a tip end of the pressing arm attached to both mirror surface wafers. A mirror-surface wafer bonding apparatus, comprising: a convex curved surface-shaped pressing member that presses and presses a chamfered corner portion of a second mirror-surface wafer.