JPS61182239A - Bonding device for semiconductor substrate - Google Patents

Abstract

PURPOSE:To allow two semiconductor wafers to be bonded without leaving bubbles on the adhesive surface between the wafers by, while bending one semiconductor water so as to make its center portion a recess, contacting the semiconductor wafer with the other semiconductor wafer and bonding the former to the latter. CONSTITUTION:A rubber chuck 15 for loading a semiconductor wafer is provided with a plurality of vents 18. An exhausting pipe 19 is provided just under a pedestal 16. The outer periphery of the semiconductor wafer is pulled by vacuum-sucking via the exhausting pipe 19 and the chuck 15 is bent according to the shape of the surface of the pedestal 16. Consequently, the semiconductor wafer is held with its center portion made convex. The semiconductor wafer held in this way is contacted with another semiconductor wafer held by a holder 13 and air or the like is introduced into the chuck 15, thereby to recover the bending in the semiconductor wafer gradually. This makes the adhesive surface spread from its center portion to its peripheral portion, thereby allowing the two semiconductor wafers to be bonded without taking in bubbles therein.

Description

DETAILED DESCRIPTION OF THE INVENTION [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 mirror-polished semiconductor wafers, such as silicon,
When the polished surfaces are brought into contact under clean conditions, a strong bonded wafer is obtained. In this method, there is no need to interpose a different substance such as an adhesive between the wafers, so that the subsequent high-temperature treatment and various chemical treatments can be performed in exactly the same way as for a single semiconductor wafer.゛According to this method, two semiconductor wafers having sufficient impurity concentration, thickness, diffusion layer, etc. are directly bonded at a relatively low temperature (200C or higher), and 1
Since it can be made into a single semiconductor wafer, it has become possible to realize element structures that are difficult to manufacture or impossible to manufacture using conventional methods such as epitaxial growth.

However, when bonding semiconductor wafers using this method, there is a problem in that the peripheral area adheres first due to wafer warping, and air bubbles are left behind in the bonded area. When gluing was performed, uniform adhesion could not be achieved. Therefore, in the past, only one semiconductor wafer was patterned, and it was impossible to bond two patterned semiconductor wafers.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus for aligning two patterned semiconductor wafers and bonding them together without leaving any air bubbles on the bonding surfaces.

[Summary of the invention]

In the apparatus of the present invention, when aligning and bonding two patterned semiconductor wafers to each other, one semiconductor wafer is bent so that its central portion is convex. The convex surface is brought into contact with the other semiconductor wafer, and both wafers are bonded together.

The support stand, which is a component of the device of the present invention, is used to hold the semiconductor wafer by bending the central part of the semiconductor wafer in a convex shape on one side, as in the first generation, and the central part of the surface is convex. A base is formed with a taper rjAt or curved direction and has an exhaust hole opening on its surface, and a groove is formed on the outer periphery of the curve which is stacked on the base and on which a semiconductor wafer is placed. The chuck is made of an elastic body and has a plurality of exhaust holes formed therein that communicate with the exhaust holes of the base. By vacuum suctioning the semiconductor wafer placed on the chuck through the chuck's exhaust hole and the base's exhaust hole,
Together with the chuck, the wafer is held in a state in which the central portion is convex, reflecting the surface shape of the base, which is a semiconductor wafer.

In such an operation to adjust the relative position of one semiconductor wafer held in a convexly bent state on a support base and the other semiconductor wafer held in a non-deformed state in a holder, it is necessary to Several problems arise that need to be solved that are not present in the case of semiconductor wafers that do not have a semiconductor wafer. The first problem is that when a semiconductor wafer is bent into a convex shape, the position of the alignment mark moves inward when viewed from above. Therefore, if alignment marks are simply placed at the same position on each semiconductor wafer, mutual alignment will not be possible due to this deviation. The second problem is that when one semiconductor wafer is held on the support stand, if the center of the semiconductor wafer deviates from the apex of the convex part of the support stand, the shape of the alignment mark seen from above will be distorted, making it difficult to accurately This means that it will not be possible to match. In order to solve these problems, the apparatus of the present invention takes several measures. The following is a step-by-step explanation.

First, in order to prevent alignment marks from shifting due to deflection, the alignment marks can be fixed by a method such as making at least one of the corresponding alignment marks on two semiconductor wafers to be bonded into a long shape in the radial direction of the semiconductor wafers. This can be countered by making at least a portion of the corresponding alignment marks overlap even if the alignment marks are moved. Second, distortion of alignment marks due to deflection can be avoided by introducing an operation that aligns the center of the support stand with the center of the semiconductor wafer held on the support stand before the two semiconductor wafers to be bonded together. Eliminate. To explain this operation in detail, first, hold one semiconductor wafer in a holder on the adhesive side of the semiconductor wafer that will ultimately be held on the support stand, and place the alignment mark on the semiconductor wafer with the holder and support stand close together. The semiconductor wafer is aligned with the marks provided on the support base, and then the semiconductor wafer and the support base are brought into contact, and the vacuum suction on the holder side is released and the vacuum suction on the support base side is started. Hold it on a support stand in a flexed state. As mentioned above, when holding a semiconductor wafer on the adhesive side, in order to prevent contamination of the adhesive surface, the central part of the semiconductor wafer should not come into contact with the holder, and only the peripheral part of the semiconductor wafer should be held by vacuum suction. is desirable. Alternatively, a support column having a cylindrical sliding mechanism having an inner diameter larger than that of the support base may be provided separately, and the support column may be held on a non-adhesive surface such as a semiconductor wafer.

Eighth, in order to improve alignment accuracy in a convexly bent state, alignment is performed at at least eight locations. The amount of movement of the alignment mark due to deflection is determined by the shape of the support base, so if the alignment mark is formed taking this size into account, it is possible to align with just two locations, but this amount of movement is It is difficult to keep the alignment accuracy within a specified thermal range because it varies slightly depending on the thickness of the wafer and other factors. If alignment is performed at 8 points, even if alignment marks are designed without taking into consideration radial movement of alignment marks due to deflection, it will be possible to accurately adjust the alignment marks in the circumferential direction. Relative positions can be adjusted.

Furthermore, in the present invention, as a separate method for solving the problems that arise when alignment is performed in a convexly warped state, the semiconductor wafer is placed on a support stand in two states: a state in which the semiconductor wafer is warped in a convex shape and a state in which it is not warped. A holding mechanism is provided to align two semiconductor wafers without bending, and then the semiconductor wafer held on the support is bent into a convex shape and held in the holder. To provide a method for bonding two semiconductor wafers by bringing them into contact with each other and releasing vacuum suction on a support stand. According to this method, it is possible to align the two semiconductor chips without bending them, so that they can be bonded together without leaving any air bubbles on the bonding surface in exactly the same way as a conventional mask aligner. Therefore, since alignment only needs to be done once, it is possible to significantly shorten the time. However, after alignment, the semiconductor wafer held on the support stage must be bent into a convex shape and then returned to its original position. The alignment accuracy is lower than the above-mentioned method of immediate adhesion.

〔Effect of the invention〕

By using the apparatus of the present invention, two patterned semiconductor wafers are aligned with each other, and
For the first time, it is possible to bond without leaving any air bubbles on the adhesive surface.

[Embodiments of the invention]

The present invention will be explained in detail below.

FIG. 1 is a diagram showing an apparatus according to an embodiment of the present invention. In the figure, reference numeral 14 denotes a support base for bending and holding the first semiconductor wafer to be bonded, 13 is a holder for holding the second semiconductor wafer to be bonded, and 22 is a holder. It is moved up and down by a drive mechanism, and the distance from the support base 13 can be set arbitrarily. 23 is support stand 1
Position 4 in the X and Y directions.

A stage for finely adjusting v4 in the 0 direction, 20 is a light source that generates light with a wavelength that passes through the semiconductor wafer, 21
is an optical system that detects the light that has passed through the semiconductor wafer. The light generated from the light source 2o passes through the exhaust hole 18, passes through the semiconductor wafer held on the support stand 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 by the optical system 21. The position can be adjusted by finely adjusting the stage 23 while looking at the image.

The support stand 14 is composed of a base 16 and a rubber chuck 15. The base 16 is made of metal or the like, has a curved surface in a convex central portion, and has an exhaust hole 18 opening in the surface.

Reference numeral 15 denotes a rubber chuck 9 placed on the base 16 for placing a semiconductor wafer thereon. This rubber chuck 15 has a plurality of exhaust holes 18 formed therein. Base 1
An exhaust pipe 19 is provided below 6, and this exhaust pipe 19
By vacuum suction through the exhaust hole 8, the outer circumference of the semiconductor wafer is pulled and the rubber f kick 15 is bent according to the surface shape of the base 16, and as a result,
The semiconductor wafer is held with its center portion convex. The semiconductor wafer thus held is brought into contact with the other semiconductor wafer, and air or the like is introduced little by little into the rubber chuck 15 to gradually recover the deflection of the semiconductor wafer. As a result, the bonding surface spreads from the center toward the periphery, making it possible to bond two semiconductor wafers without introducing air bubbles. In the case of the apparatus described in claim 6, for example, the periphery of the wafer is supported by the support table 14.
It is also possible to hold the wafer in an undeflected state by mechanically holding it above the wafer and bending the wafer by pressing the center. Alternatively, a shape memory alloy may be used in place of the rubber chuck 15, and the wafer may be held in two states, a bent state and an undeflected state, by heating with a heater.

FIG. 2 is a diagram for explaining a first method of bonding using the apparatus of the present invention. In these figures, 11
．． 12 is two semiconductor wafers to be bonded; 13 is a boulder equipped with a driving mechanism for moving up and down; and 14 is a support base for holding the semiconductor wafer in a convex shape. The holder 13 rotates around the supporting axis and holds the wafer 1.
Practically speaking, it is desirable to have a mechanism for holding the sea urchin 1 with the adhesive surface facing upward, and then rotating it again to hold the sea urchin downward. In this way, the wafer 11 is held in the holder 13 with the adhesive surface facing downward (Figure (a)),
Move the holder 13 downward to hold the wafer 11 and the support stand 14.
Align the centers of the wafer 11 and the support stand 14 with their surfaces brought close to each other (Figure (B)), then bring the wafer 11 and the support stand 14 into contact (Figure (C)), and align the holder 13. The vacuum suction is stopped and the vacuum suction of the support table 14 is started, the wafer 11 is held on the support table 14 in a convexly bent state, and the holder 13 is moved upward (FIG. (d)).

Next, hold the second wafer 12 on the boulder 13 with the adhesive side facing downward (Figure (e)), and move the holder 13 downward to bring the surfaces of the wafers 11 and 12 closer together and align them (Figure (f)). ), then wafer 11 and wafer 1
2 (Figure (g)), and place the wafer 1 on the support stand 14.
By releasing the hold on wafers 11 and 12, the wafers 11 and 12 are bonded. According to this method, the semiconductor wafers 11 and 12 that have been patterned can be reliably bonded all over without residual gas, and a strong bonded wafer can be obtained.

FIGS. 8(a) and 8(b) are diagrams showing examples of alignment marks formed on semiconductor wafers bonded by the method described above. In these figures, alignment marks 24 are used to increase the accuracy of aligning the convex-shaped wafer.
．． 25 are formed at eight locations.

FIG. 8(c) is a diagram showing how the alignment marks overlap when two wafers are stacked and aligned. As described above, when one wafer is bent into a convex shape, the alignment mark moves in the radial direction, so an alignment mark having the shape shown in FIG. 8 is sufficient.

FIG. 4 is a diagram for explaining a second method of bonding using the apparatus of the present invention. In the method described above, the wafers were aligned with one semiconductor wafer bent in a convex shape, whereas in the method described below, the two semiconductor wafers to be bonded are aligned without bending. The operation is extremely simple since there is no need to align the two. First, wafer 1
Hold the wafer 12 on the support stand 14 without bending with the adhesive side facing upward (Figure a)), and hold the wafer 12 on the holder 13 with the wafer facing downward (Figure b)). 13
is moved downward to bring the surface areas of the wafers 11 and 12 close together and align them ((1). Then, the support base 14 is made into a convex shape and the wafer 11 is warped (FIG. (d)). The wafer 11 and the wafer 12 are brought into contact with each other (Figure (e)), and the support table 1 is
4 is flattened and wafers 11 and 12 are bonded. According to this method, it is possible to bond the mask aligner very easily in the same manner as with a normal mask aligner.

The present invention is not limited to the above embodiments. For example, in the method shown in FIG. 2, the semiconductor wafer 12 is supported flatly, but like the semiconductor wafer 11, it may also be held in a bent manner so that the central portion is convex. Furthermore, in the support base 14 of FIG. 1, the rubber m-chuck 15 can be constructed using other elastic materials. Further, the surface of the base 16 does not necessarily have to be a curved surface, and may be a tapered surface with a convex central portion, for example.

[Brief explanation of drawings]

FIG. 1 shows an apparatus according to an embodiment of the present invention, FIGS. 2 and 4 are diagrams for explaining a method of bonding using the apparatus of the present invention, and FIG. 8 shows an apparatus according to the present invention. FIG. 3 is a diagram illustrating an example of alignment marks formed on a semiconductor wafer to which bonding is performed using. 11.12... Semiconductor wafer 13... Holder 14... Support stand ■5... Rubber chuck 16... Base 17.18... Exhaust hole 19... Exhaust pipe 20...・Light source 21...Optical system 22...Holder drive@mechanism 23..."+ Yr θ stage control...Positioning mark 25 on semiconductor wafer 11.
...Alignment mark agent on semiconductor wafer 12 Patent attorney Noriyuki Chika (and one other person) Figure 4 (α) (C) (b) (d) (e) (f)

Claims (6)

[Claims] (1) A support stand that holds one semiconductor wafer by bending it so that its central portion is convex, a holder that holds the other semiconductor wafer facing the support stand, and a support stand and a holder. a mechanism for finely adjusting the position of at least one of the support stand and the holder; and a mechanism for finely adjusting the position of at least one of the support stand and the holder; and a mechanism for finely adjusting the position of at least one of the support stand and the holder; 1. A semiconductor substrate bonding apparatus comprising: a light source that generates a light beam; and means for detecting the light emitted from the light source. (2) The support table consists of a base, a chuck, and a light source, and the base has a tapered or curved surface so that the central part of the surface is convex, and has an exhaust hole that opens on the surface. The elastic body is stacked on the base and has a plurality of exhaust ports formed on the outer periphery of the surface on which the one semiconductor wafer is held, communicating with the exhaust holes of the base, and the light source passes through the semiconductor wafer. The semiconductor wafer placed on the chuck is vacuum-suctioned through the chuck's exhaust hole and the base's exhaust hole to hold the semiconductor wafer in a convex shape at its center. 2. A semiconductor substrate bonding apparatus according to claim 1, wherein the semiconductor substrate bonding apparatus is characterized in that: (3) The semiconductor substrate according to claim 2, further comprising means for adjusting the relative position between the one semiconductor wafer and the support stand when holding the one semiconductor wafer on the support stand. gluing device. (4) There is at least one alignment mark on each semiconductor wafer, and when one semiconductor wafer is held in a convex state on the support stand, the alignment mark of the one semiconductor wafer is placed on the holder. an alignment mark is formed on the other semiconductor wafer held by the semiconductor wafer, such that a figure obtained by projecting from a direction perpendicular to the surface of the other semiconductor wafer and an alignment mark on the other semiconductor wafer overlap. A method for bonding semiconductor substrates, characterized in that bonding is performed using the apparatus according to claim 1. (5) The semiconductor substrate bonding apparatus according to claim 2, wherein the one semiconductor wafer and the other semiconductor wafer are aligned at at least eight locations. (6) The support stand is configured to hold the semiconductor wafer in two states: a state in which the central portion of the semiconductor wafer is convex, and a state in which the semiconductor wafer does not bend. The semiconductor substrate bonding device according to scope 1.