JPH061790B2 - Bonding device for semiconductor substrates - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an apparatus for directly bonding semiconductor wafers such as silicon to each other.

[Technical background of the invention and its problems]

Two semiconductor wafers, such as mirror-polished silicon,
A strong bonded wafer can be obtained by bringing the polished surfaces into contact with each other under clean conditions. In this method, 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 performed in exactly the same manner as one semiconductor wafer. Further, according to this method, two semiconductor wafers having various impurity concentrations, thicknesses, diffusion layers, etc. can be directly bonded at a relatively low temperature (200 ° C. or higher) to form one semiconductor wafer. Therefore, it is possible to realize a device structure which is difficult or impossible to manufacture by the conventional method such as the epitaxial growth method.

However, when a semiconductor wafer is bonded by this method, there is a problem that the peripheral part is bonded first due to the warp of the wafer and air bubbles are left in the bonded part, and it is not possible to use a device such as a mask aligner used for lithography. When adhesion was performed, uniform adhesion could not be achieved. Therefore, conventionally, it was limited to the case where only one semiconductor wafer was patterned, and it was impossible to bond two patterned semiconductor wafers.

[Object of the Invention]

It is an object of the present invention to provide a device that bonds two semiconductor wafers, which are each patterned, to each other by aligning the positional relationship with each other and without leaving bubbles on the bonding surface.

[Outline of Invention]

In the apparatus of the present invention, when two patterned semiconductor wafers are aligned and bonded to each other, one of the semiconductor wafers is bent so that its central portion has a convex shape. In this state, the convex surface is brought into contact with the other semiconductor wafer to bond both wafers.

The support base, which is a component of the device of the present invention, is for holding the semiconductor wafer central portion by bending it convexly on one side as described above, so that the surface central portion is convex. A base having a tapered surface or a curved surface and having an exhaust hole opened on the surface thereof, and a groove formed in the outer peripheral portion of the surface on which the semiconductor wafer is placed and which is stacked on the base, and the base is formed along the groove. A chuck made of an elastic body having a plurality of exhaust holes communicating with the exhaust holes of the table is provided. Then, the semiconductor wafer placed on the chuck is vacuum-sucked through the exhaust hole of the chuck and the exhaust hole of the base, so that the semiconductor wafer together with the chuck has a convex central part reflecting the surface shape of the base. It is designed to be held in the state of.

In the operation of adjusting the relative position of one semiconductor wafer held in such a state that it is bent in a convex shape on the support table and the other semiconductor wafer held in the holder without bending, There are several problems to be solved that are not the case for semiconductor wafers without. First, the first problem is that when the semiconductor wafer is bent in a convex shape, the position of the alignment mark moves inward when viewed from above. Therefore, even if the alignment marks are provided at the same positions on the respective semiconductor wafers, they cannot be aligned with each other due to the displacement. The second problem is that when one of the semiconductor wafers is held on the support base and the center of the semiconductor wafer deviates from the apex of the convex portion of the support base, the shape of the alignment mark seen from above is distorted, and accurate alignment becomes difficult. It is not possible. In order to solve these problems, some measures are considered in the device of the present invention. Hereinafter, description will be made step by step.

First of all, with respect to the movement of the alignment mark due to the bending, at least one of the corresponding alignment marks of the two semiconductor wafers to be bonded is made to have a shape long in the radial direction of the semiconductor wafer. Even if they move, at least a part of the corresponding alignment marks can be overlapped so that they can be matched. Secondly, the alignment mark distortion due to the deflection is caused by introducing an operation of aligning the center of the supporting table with the center of the semiconductor wafer held by the supporting table before the two semiconductor wafers to be brought into contact with each other. Will be resolved. This operation will be described in detail. First, one semiconductor wafer to be finally held on the supporting table is held on the holder on the adhesive surface side, and the alignment mark of the semiconductor wafer is set in the state where the holder and the supporting table are in close proximity. And the marks provided on the support base are aligned, then the semiconductor wafer and the support base are brought into contact with each other, the vacuum suction on the holder side is released, the vacuum suction on the support base side is started, and the convex shape is obtained. Hold it in a bent state on a support. As described above, when holding the semiconductor wafer on the adhesive surface side, in order to prevent contamination of the adhesive surface, the central portion of the semiconductor wafer should not be in contact with the holder, and should be held by vacuum suction only on the peripheral portion of the semiconductor wafer. Is desirable. Alternatively, a supporting column having a cylindrical movable mechanism having an inner diameter larger than that of the supporting base may be separately provided to hold the semiconductor wafer on the non-bonding surface.

Thirdly, in order to improve the alignment accuracy in the state of being bent in a convex shape, alignment is performed at at least three places. The amount of movement of the alignment mark due to flexure is determined by the shape of the support base. Therefore, if the alignment mark is formed in consideration of this size, it is possible to perform alignment at only two locations. Is slightly changed depending on the thickness of the semiconductor wafer, etc., so that it is difficult to keep the alignment accuracy within the specified heat range. If the alignment is performed at three points, even if the alignment mark is designed without considering the radial movement of the alignment mark due to bending, it is possible to accurately adjust the alignment mark by adjusting the deviation of the alignment mark in the circumferential direction. The position can be adjusted.

Further, according to the present invention, as a separate method for solving the problems caused by performing the alignment in the state of being bent in the convex shape, there are two states, that is, a state in which the semiconductor wafer is bent in the convex shape on the support base and a state in which the semiconductor wafer is not bent. With a mechanism that can hold the two semiconductor wafers, the two semiconductor wafers are aligned in a non-deflected state, and then the semiconductor wafers held by the support are flexed in a convex shape and held by the holder. Provided is a method of bringing semiconductor wafers into contact with each other, releasing vacuum suction of a support base, and adhering two semiconductor wafers. According to this method, since the two semiconductor wafers can be aligned without bending, the bonding can be performed without leaving bubbles on the bonding surface in the same manner as the conventional mask aligner. Therefore,
Since the positioning is done only once, it is possible to significantly reduce the time. However, since the operation of bending the semiconductor wafer held on the support base once after convex alignment and then returning it again, the alignment is performed in the convex flexure state. The alignment accuracy is lower than that of the above-mentioned method of immediately bonding.

〔The invention's effect〕

By using the apparatus of the present invention, two patterned semiconductor wafers are aligned with each other,
It is possible for the first time to bond without leaving bubbles on the bonding surface.

Example of Invention

 Examples of the present invention will be described below.

FIG. 1 is a diagram showing an apparatus according to an embodiment of the present invention. In the figure, 14 is a support for bending and holding the first semiconductor wafer to be bonded in a convex shape, 13 is a holder for holding the second semiconductor wafer to be bonded, and 22 is a holder. It can be moved up and down by the drive mechanism, and the interval with the support base 13 can be set arbitrarily. 23 is the position of the support base 14 in the x direction,
A stage for fine adjustment in the y direction and the θ direction, and 20 is a light source that generates light having a wavelength that passes through the semiconductor wafer,
Reference numeral 21 is an optical system for detecting the light transmitted through the semiconductor wafer. The light generated from the light source 20 passes through the exhaust hole 18, passes through the semiconductor wafer held by the support base 14 or the holder 13, and is detected by the optical system 21, so that the alignment mark formed on the semiconductor wafer is detected. Watching the stage
23 can be finely adjusted for alignment.

The support base 14 is composed of a base 16 and a rubber chuck 15. The base 16 is made of metal or the like, and is curved so that the central portion of the surface is convex, and an exhaust hole 18 that opens to the surface is formed. 15 is put on the base 16,
A rubber chuck for mounting semiconductor wafers. The rubber chuck 15 has a plurality of exhaust holes 18 formed therein. An exhaust pipe 19 is provided under the base 16,
By vacuum suction through this exhaust pipe 19, the exhaust hole
The outer periphery of the semiconductor wafer is stretched via 18 and the rubber chuck 15 bends according to the surface shape of the base 16, and as a result, the semiconductor wafer is held with the central portion being convex. . The semiconductor wafer held in this way is brought into contact with the other semiconductor wafer, and air or the like is gradually introduced into the rubber chuck 15 to gradually recover the deflection of the semiconductor wafer. As a result, the bonding surface spreads from the central part toward the peripheral part, and the two semiconductor wafers can be bonded together without taking in air bubbles. Claim 6
In the case of the apparatus described in the item 1, for example, the periphery of the wafer is supported by
It is also possible to hold it in a non-deflected state by using a method of mechanically holding it on 14 and bending the wafer by pushing the center part. Alternatively, a shape memory alloy may be used instead of the rubber chuck 15, and a method of holding the wafer in two states, that is, a state where the wafer is warped and a state where the wafer is not warped, by heating with a heater may be adopted.

FIG. 2 is a diagram for explaining a first method of performing bonding using the device of the present invention. In these figures, 11,
Reference numeral 12 is two semiconductor wafers to be bonded, 13 is a holder equipped with an up-and-down driving mechanism, and 14 is a support base that holds the semiconductor wafer in a convex shape. Holder 13
It is practically desirable to have a mechanism such as rotating around a supporting axis to hold the wafer 11 with the adhesive surface facing upward, and then rotating again to hold the wafer downward. In this way, the wafer 11 is held on the holder 13 with the adhesive surface facing downward ((a) figure), and the holder 13 is moved downward to support the wafer 11 and the support base 14 in a state where the surfaces of the wafer 11 and the support base 14 are close to each other. The center of the base 14 is aligned (Fig. (B)), and then the wafer 11 and the support 14 are brought into contact with each other (Fig. (C)), the vacuum suction of the holder 13 is stopped, and the vacuum suction of the support 14 is stopped. Then, the wafer 11 is held in a convex shape on the support base 14 and the holder 13 is moved upward ((d)).
Figure). Next, hold the wafer 12 with the adhesive side facing down in the holder 13
(Fig. (E)), the holder 13 is moved downward to align the surfaces of the wafer 11 and the wafer 12 (Fig. (F)), and then the wafer 11 and the wafer 12 are aligned. The wafers 11 and 12 are adhered by bringing them into contact with each other (Fig. (G)) and releasing the holding of the wafer 11 by the support base 14. According to this method, the patterned semiconductor wafers 11 and 12 can be reliably bonded over the entire surface without residual gas to obtain a strong bonded wafer.

FIGS. 3 (a) and 3 (b) are views showing examples of alignment marks formed on a semiconductor wafer to be bonded by the method described above. In these figures, the alignment marks 24 and 25 are 3 in order to improve the precision of aligning the convex wafer.
It is formed in the place. FIG. 3 (c) is a diagram showing a state in which the alignment marks are overlapped when the two wafers are superposed and aligned with each other. As described above, when one of the wafers is bent in a convex shape, the alignment mark moves in the radial direction. Therefore, the alignment mark having the shape shown in FIG. 3 is sufficient.

FIG. 4 is a diagram for explaining a second method of performing bonding using the device of the present invention. In the method described above, the wafers are aligned in a state where one semiconductor wafer is bent in a convex shape, whereas in the method described below, the two semiconductor wafers to be bonded are aligned without bending. It is extremely easy to operate. First, the wafer 11
Is held on the support base 14 with the adhesive surface facing upward (FIG. (A)), and the wafer 12 is held in the holder 13 with the adhesive surface facing downward (FIG. (B)). When the wafers 11 and 12 are moved downward and the surfaces of the wafers 11 and 12 are brought close to each other to perform alignment (FIG. (C)), the support base 14 is then formed in a convex shape to bend the wafer 11 (FIG. (D)), The wafer 11 and the wafer 12 are brought into contact with each other (Fig. (E)), the support base 14 is flattened, and the wafers 11 and 12 are bonded. According to this method, the bonding can be performed very easily by the same operation as that of a normal mask aligner.

The present invention is not limited to the above embodiment. For example, in the method shown in FIG. 2, the semiconductor wafer 12 is supported flat, but like the semiconductor wafer 11, this may also be held by being bent so that the central portion has a convex shape. Further, in the support base 14 of FIG. 1, the rubber chuck 15 can be constructed by using another elastic material. The surface of the base 16 does not necessarily have to be a curved surface, and may be, for example, a tapered surface having a convex central portion.

[Brief description of drawings]

FIG. 1 is a diagram showing an apparatus according to an embodiment of the present invention, FIGS. 2 and 4 are diagrams for explaining a method of mounting using the apparatus of the present invention, and FIG. 3 is an apparatus of the present invention. It is a figure which shows the example of the alignment mark formed in the semiconductor wafer which adhere | attaches using. 11, 12 ... Semiconductor wafer 13 ... Holder 14 ... Support 15 ... Rubber chuck 16 ... Base 17,18 ... Exhaust hole 19 ... Exhaust pipe 20 ... Light source 21 ... Optical system 22 ... Holder drive mechanism 23 ... x, y, θ stage 24 ... Alignment mark on semiconductor wafer 11 ... Alignment mark on semiconductor wafer 12 ...

Claims (6)

[Claims] 1. A support base for holding one semiconductor wafer by bending it so that its central portion is convex, a holder for holding the other semiconductor wafer facing the support base, and a support base. A mechanism for changing the distance to the holder, a mechanism for finely adjusting the position of at least one of the support and the holder,
A light source for generating a long-wavelength light beam capable of extremely reducing the light absorption coefficient of the semiconductor wafer when the semiconductor wafer is irradiated with light; and a means for detecting light emitted from the light source and transmitted through the semiconductor wafer. An apparatus for bonding a semiconductor substrate, comprising: 2. The support base comprises a base, a chuck, and a light source, and the base is formed into a tapered surface or a curved surface so that the central portion of the surface is convex, and has an exhaust hole opening on the surface thereof. The chuck is formed of an elastic body that is stacked on the base and has a plurality of exhaust ports communicating with the exhaust holes of the base on the outer periphery of the surface on which the one semiconductor wafer is held. A state in which a light having a wavelength that passes through the chuck is generated, and the one semiconductor wafer placed on the chuck is vacuum-sucked through the exhaust hole of the chuck and the exhaust hole of the base to form a convex portion at the center thereof. The semiconductor substrate adhering device according to claim 1, wherein the device is adhered to the semiconductor substrate. 3. The method according to claim 2, further comprising means for adjusting a relative position between the one semiconductor wafer and the supporting base when holding the one semiconductor wafer on the supporting base. Bonding device for semiconductor substrates. 4. At least one on each semiconductor wafer.
When there is one alignment mark, and one semiconductor wafer is held on the support in a convex state, the alignment mark of the one semiconductor wafer is placed on the other semiconductor wafer held by the holder and the other The alignment mark is formed so that the figure obtained by projecting from the direction perpendicular to the surface of the semiconductor wafer and the alignment mark of the other semiconductor wafer are overlapped with each other, and the apparatus according to claim 1 is used. A method for adhering a semiconductor substrate, the method comprising: adhering the semiconductor substrate. 5. The semiconductor substrate bonding apparatus according to claim 2, wherein the one semiconductor wafer and the other semiconductor wafer are aligned in at least three positions. 6. The support base holds the semiconductor wafer in two states, that is, the central portion of the semiconductor wafer is convex and the semiconductor wafer is not warped. The semiconductor substrate bonding apparatus according to claim 1.