JP2000082642A - Method for bonding substrates together - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a laminated substrate from which curvature is reduced even when either one of paired substrates is curved so that its bonding surface may become a protruding surface or recessed surface. SOLUTION: Semiconductor substrates 11 and 12 are successively bonded together from one parts by fixing the substrate 11 in a flat state when the bonding surface 11a of the substrate 11 is protruding or fixing the flat substrate 12 in a flat state when the bonding surface 11a is protruding. When the bonding surface 11a is protruding, such forces that work to protrude the bonding surfaces 11a and 12a of the substrates 11 and 12 are applied and, when the surface 11a is a protruding surface, such forces that work to protrude the bonding surface 11a are applied. In either cases, the forces offset each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of bonding substrates for bonding a pair of substrates together to form a bonded substrate.

[0002]

2. Description of the Related Art For example, as one method for manufacturing a semiconductor device having an SOI structure, a concave portion is formed on one surface of one semiconductor substrate, and an insulating film or the like is formed on this one surface. One semiconductor substrate is bonded to the other semiconductor substrate via a film or the like, and one semiconductor substrate is ground from the back side until the insulating film is exposed, so that a bonded SOI having an island-shaped semiconductor layer on the insulating film is formed. There is a method of forming a substrate.

FIG. 3 shows a general method for forming such a bonded SOI substrate. In this method, as shown in FIG. 3A, a concave portion (not shown), an insulating film (not shown), and the like are formed on one surface, and the surface of the insulating film and the like is formed on the bonding surface 11a. A semiconductor substrate 11, which is referred to as a bond substrate, and a semiconductor substrate 12, which is referred to as a base substrate, to be bonded to the semiconductor substrate 11 at a bonding surface 12a are prepared.

Then, the semiconductor substrate 11 is sucked by a flat vacuum chuck 13, for example.
Is fixed in a flat state, and the semiconductor substrate 12 is dropped onto the semiconductor substrate 11 from a position where the bonding surfaces 11a and 12a face each other in parallel but are not in contact with each other, for example, 1 mm or more.

However, when the distance between the bonding surfaces 11a and 12a becomes several μm, the semiconductor substrate 12 further approaches the semiconductor substrate 11 due to viscous resistance of air and electrostatic force between the semiconductor substrates 11 and 12. Instead, the semiconductor substrate 12 floats on the semiconductor substrate 11.

For this reason, the bonding surfaces 11a and 12a are merely opposed to each other and are not bonded. Therefore,
As shown in FIG. 3B, the diameter of the pressure rod 14 is 1 to 10 mm.
Through the contact portion, for example, 15
By applying a pressure of about 0 g / cm ² , the bonding surface 12a
Is brought into contact with the center of the bonding surface 11a.

[0007] Then, the contact portions of the semiconductor substrates 11 and 12 are adhered to each other by a hydrogen bonding force or a van der Waals force by the action of water or a hydroxyl group present on the bonding surfaces 11a and 12a. 11a, 12
Self-adhesion that progresses to the periphery of a occurs. As a result, as shown in FIG. 3C, a bonded SOI substrate 15 in which the semiconductor substrates 11 and 12 are bonded to each other is formed.

In the above description of FIG. 3, the semiconductor substrate 11 as a bond substrate is fixed in a flat state by the vacuum chuck 13, but conventionally, either the bond substrate or the base substrate is fixed to the vacuum chuck. It is not determined whether the semiconductor substrate 12 is fixed in a flat state with the semiconductor substrate 13 or the semiconductor substrate 12 as a base substrate is fixed in a flat state with the vacuum chuck 13 in some cases.

[0009]

By the way, an insulating film is formed on a semiconductor substrate 11 as a bond substrate at a temperature higher than room temperature by a CVD method or the like, and thereafter, the semiconductor substrate 11 and the insulating film are cooled to room temperature. . However, a semiconductor substrate and an insulating film generally have different heat shrinkage coefficients. For example, an SiO ₂ film has a smaller heat shrinkage coefficient than a Si substrate.
The SiN film has a larger heat shrinkage coefficient than the Si substrate.

Therefore, when the semiconductor substrate 11 is a Si substrate and the insulating film 16 is a SiO ₂ film, the surface of the insulating film 16, that is, the bonding surface 11 a of the semiconductor substrate 11, as shown in FIG. The semiconductor substrate 11 is curved so that is convex. As a result, as shown in FIG. 4B, even if the semiconductor substrate 12 is fixed to a flat state by the flat vacuum chuck 13 and the semiconductor substrates 11 and 12 are bonded to each other, When the fixing of the substrate 12 is released, a force acts on the semiconductor substrate 11 to return the bonding surface 11a to a convex shape.

When the semiconductor substrate 11 is a Si substrate and the insulating film 16 is a SiN film, as shown in FIG. 5A, the surface of the insulating film 16, that is, the bonding surface 11a of the semiconductor substrate 11 has a concave shape. The semiconductor substrate 11 is curved so that As a result, as shown in FIG. 5B, even if the semiconductor substrate 11 is fixed in a flat state by the flat vacuum chuck 13,
After bonding, the semiconductor substrate 11 by the vacuum chuck 13 is used.
Is released, a force acts on the semiconductor substrate 11 to return the bonding surface 11a to a concave shape.

On the other hand, in the method of FIG. 3, which utilizes the contact between the central portions of the bonding surfaces 11a and 12a by the pressure from the pressing rod 14 and the progress of the adhesion by the attraction force between the semiconductor substrates 11 and 12, As is clear from FIG. 3B, the bonding surface 12a of the semiconductor substrate 12 is bonded to the bonding surface 11a of the semiconductor substrate 11 while being extended.

For this reason, after the bonding, a force for shrinking acts on the bonding surface 12a, so that a force for making the bonding surface 11a concave is applied to the semiconductor substrate 11a.
As a result, the semiconductor substrate 12 has the bonding surface 1
A force acts to make 2a convex.

Accordingly, when bonding is performed as shown in FIGS. 4A and 4B and then the fixing of the semiconductor substrate 12 by the vacuum chuck 13 is released, the difference in the heat shrinkage coefficient between the semiconductor substrate 11 and the semiconductor substrate 11 is reduced. Therefore, both the force for returning the bonding surface 11a to the convex shape due to this and the force for making the bonding surface 11a to the convex shape due to the elongation at the time of bonding work, and these forces reinforce each other. Therefore, as shown in FIG. 4C, only the bonded SOI substrate 15 whose curvature is larger than that of the semiconductor substrate 11 before bonding can be formed.

Further, even if the bonding is performed as shown in FIGS. 5A and 5B, and then the fixing of the semiconductor substrate 11 by the vacuum chuck 13 is released, the semiconductor substrate 11 has a heat shrinkage coefficient. The force acting to return the bonding surface 11a to a concave shape due to the difference acts, and the force causing the bonding surface 12a to project into a convex shape due to elongation at the time of bonding acts on the semiconductor substrate 12. As shown in FIG. 5C, only the bonded SOI substrate 15 having a larger curvature than the semiconductor substrate 11 before bonding can be formed because the forces reinforce each other.

Even if an attempt is made to manufacture a semiconductor device on a bonded SOI substrate 15 having a large curvature, the bonded SOI substrate 15 cannot be reliably fixed by a vacuum chuck or the like during transportation or CVD, or cannot be bonded during exposure in lithography. For example, it is difficult to manufacture a semiconductor device with a high yield because a part of the region of the combined SOI substrate 15 is out of the depth of focus.

Even if the semiconductor substrate 11 of the bonded SOI substrate 15 is ground and an island-like semiconductor layer is formed on the insulating film 16 from the semiconductor substrate 11, the semiconductor substrate 11 is not In comparison, when the semiconductor substrate 11 of the bonded SOI substrate 15 in FIG. 4C is ground, the pattern of the island-shaped semiconductor layer and the insulating film 16 is extended.
When the semiconductor substrate 11 of the bonded SOI substrate 15 shown in (c) is ground, the pattern of the island-shaped semiconductor layer and the insulating film 16 shrinks.

Bonded SOI with large pattern expansion and contraction
Even if an attempt is made to manufacture a semiconductor device on the substrate 15, the misalignment of the mask during exposure in lithography is large, and it is particularly difficult to manufacture a semiconductor device having a fine SOI structure. In the bonded SOI substrate 15 formed by the conventional method, the pattern of the island-like semiconductor layer and the insulating film 16 was expanded and contracted in the range of about -4 ppm to 25 ppm.
In order to manufacture a semiconductor device having a minimum dimension of 0.13 μm, it is necessary to reduce the absolute value of the expansion and contraction of the pattern to 3 ppm or less.

Accordingly, the invention of the present application is such that even if one of the pair of substrates is curved such that the bonding surface becomes convex or concave, the substrate is more curved than the substrate that was curved before bonding. It is an object of the present invention to provide a method for bonding substrates, which can form a bonded substrate in which is reduced.

[0020]

According to a first aspect of the present invention, there is provided a method of bonding substrates, wherein one of a pair of substrates is fixed to a flat surface and another of the other substrates is fixed to a flat surface. A part is brought into contact with a part of the bonding surface of one of the substrates, and the bonding between the pair of substrates proceeds from the contact portion to a portion other than the contact portion by the attraction force between the pair of substrates. It is adhered to the bonding surface of one substrate while being stretched.

For this reason, after the bonding, a force for shrinkage acts on the bonding surface of the other substrate, so that
A force to make the bonding surface of one substrate concave is applied to the one substrate, and as a result, a force to make the bonding surface convex is applied to the other substrate.

Then, one of the substrates curved so that the bonding surface becomes convex is fixed in a flat state, and the other flat substrate is bonded to the one substrate. Is released, a force acts on one of the substrates to return the bonding surface to a convex shape. That is, after the bonding, the forces acting on both of the pair of substrates weaken each other.

Therefore, even if one of the pair of substrates is curved so that the bonding surface becomes convex, a force for reducing the curvature acts on the bonded substrate formed by bonding the pair of substrates. .

According to a second aspect of the present invention, one of the substrates is a semiconductor substrate, and an insulating film having a smaller thermal contraction coefficient than the semiconductor substrate is formed on one surface of the semiconductor substrate. Then, the surface of the insulating film is used as a bonding surface of the semiconductor substrate. After the insulating film having a smaller heat shrinkage coefficient than the semiconductor substrate is formed on one surface of the semiconductor substrate at a temperature higher than room temperature, when the semiconductor substrate and the insulating film are cooled to room temperature, the bonding surface becomes convex. Thus, the semiconductor substrate and the insulating film are curved.

However, even if the semiconductor substrate and the insulating film are curved so that the bonding surface becomes convex, after the pair of substrates are bonded, a force for reducing the bending of the semiconductor substrate and the insulating film is applied. Work on laminated substrates. Therefore, when the pair of substrates is attached to each other, an insulating film can be interposed between the pair of substrates by using a semiconductor substrate on which an insulating film having a smaller heat shrinkage coefficient than a semiconductor substrate is formed.

According to the third aspect of the present invention, the concave portion is formed on one surface of the semiconductor substrate, and the insulating film is formed on this one surface, so that one surface of the semiconductor substrate is formed. Are filled with an insulating film. For this reason,
If the semiconductor substrate is ground until the insulating film is exposed after bonding the pair of substrates, a bonded SOI substrate having an island-shaped semiconductor layer over the insulating film can be formed.

Even if the semiconductor substrate and the insulating film are curved, a force for reducing the curvature of the semiconductor substrate and the insulating film acts on the bonded substrate formed by bonding the pair of substrates together. Even when the thermal contraction coefficient is smaller than that of the semiconductor layer, a bonded SOI substrate in which expansion and contraction of the pattern of the semiconductor layer and the insulating film is reduced can be formed.

In the method for bonding substrates according to a fourth aspect of the present invention, a part of a bonding surface of another substrate different from one of the pair of substrates fixed in a flat state is formed on the one substrate. A part of the bonding surface of the one substrate, and the adhesion of the pair of substrates proceeds from the contact part to the part other than the contact part by the attraction force, so that the bonding surface of the other substrate is extended while the other substrate is stretched. Is bonded to the bonding surface.

For this reason, after the bonding, a force for shrinking acts on the bonding surface of the other substrate, so that
A force to make the bonding surface of one substrate concave is applied to the one substrate, and as a result, a force to make the bonding surface convex is applied to the other substrate.

Then, one of the flat substrates is fixed in a flat state, and the other substrate which is curved so that the bonding surface becomes concave is bonded to the one substrate. When the fixing is released, a force acts on the other substrate to return the bonding surface to a concave shape. That is, after the bonding, the forces acting on the other substrate weaken each other.

Accordingly, even if one of the pair of substrates is curved so that the bonding surface becomes concave, a force for reducing the curvature acts on the bonded substrate formed by bonding the pair of substrates.

According to a fifth aspect of the present invention, the other substrate is a semiconductor substrate, and an insulating film having a larger thermal contraction coefficient than the semiconductor substrate is formed on one surface of the semiconductor substrate. Then, the surface of the insulating film is used as a bonding surface of the semiconductor substrate. After the insulating film having a larger heat shrinkage coefficient than the semiconductor substrate is formed on one surface of the semiconductor substrate at a temperature higher than room temperature, when the semiconductor substrate and the insulating film are cooled to room temperature, the bonding surface becomes concave. Thus, the semiconductor substrate and the insulating film are curved.

However, even if the semiconductor substrate and the insulating film are curved so that the bonding surface becomes concave, after bonding the pair of substrates, the force for reducing the curvature of the semiconductor substrate and the insulating film is bonded. Work on the substrate. Therefore, when the pair of substrates is attached to each other, an insulating film can be interposed between the pair of substrates by using a semiconductor substrate on which an insulating film having a higher heat shrinkage coefficient than a semiconductor substrate is formed.

In the method for bonding substrates according to the sixth aspect, since the concave portion is formed on one surface of the semiconductor substrate and the insulating film is formed on this one surface, one surface of the semiconductor substrate is formed. Are filled with an insulating film. For this reason,
If the semiconductor substrate is ground until the insulating film is exposed after bonding the pair of substrates, a bonded SOI substrate having an island-shaped semiconductor layer over the insulating film can be formed.

Even if the semiconductor substrate and the insulating film are curved, a force for reducing the curvature of the semiconductor substrate and the insulating film acts on the bonded substrate formed by bonding a pair of substrates. Even when the heat shrinkage coefficient is larger than that of the semiconductor layer, a bonded SOI substrate in which expansion and contraction of the pattern of the semiconductor layer and the insulating film is reduced can be formed.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the first and second embodiments of the present invention will be described.
An embodiment will be described with reference to FIGS. FIG.
Shows the first embodiment. In the first embodiment, as shown in FIG. 1A, an insulating film 16 and the like are formed on one surface, and are bonded to a semiconductor substrate 11 that is a bond substrate and a semiconductor substrate 11 that is a base substrate. A semiconductor substrate 12 to be formed is prepared.

The semiconductor substrates 11 and 12 are, for example, Si substrates, and the insulating film 16 is, for example, an SiO ₂ film.
6 has a smaller heat shrinkage coefficient than the semiconductor substrate 11. Therefore, as shown in FIG. 1A, the semiconductor substrate 12 is flat, but the semiconductor substrate 11 is curved so that the surface of the insulating film 16, that is, the bonding surface 11a of the semiconductor substrate 11 becomes convex. I have. That is, the prepared semiconductor substrates 11 and 12 are substantially the same as the conventional example shown in FIG.

However, in the first embodiment, the object to be fixed in a flat state by the flat vacuum chuck 13 is shown in FIG.
Instead of the semiconductor substrate 12 as shown in FIG.
The semiconductor substrate 11 is as shown in FIG. After the semiconductor substrate 11 is fixed by the vacuum chuck 13, the same steps as in the method shown in FIG. 3 are performed to bond the semiconductor substrates 11 and 12 together.

When the fixing of the semiconductor substrate 11 by the vacuum chuck 13 is released after the bonding, a force is applied to the semiconductor substrate 11 to return the bonding surface 11a to a convex shape due to the difference in the heat shrinkage coefficient. A force is applied to the substrate 12 to make the bonding surface 12a convex due to elongation at the time of bonding.

That is, after bonding, the semiconductor substrate 1
The forces acting on both 1 and 12 weaken each other, and FIG.
As shown in (c), a bonded SOI substrate 15 having a reduced curvature than the semiconductor substrate 11 before bonding is formed.

FIG. 2 shows a second embodiment. Also in the second embodiment, as shown in FIG. 2A, an insulating film 16 and the like are formed on one surface and are bonded to the semiconductor substrate 11 as a bond substrate and the semiconductor substrate 11 as a base substrate. A semiconductor substrate 12 to be formed is prepared.

However, the semiconductor substrates 11 and 12 are, for example, Si substrates as in the first embodiment described above.
Reference numeral 6 denotes, for example, a SiN film, and the insulating film 16
The heat shrinkage coefficient is larger than 1. Therefore, as shown in FIG. 2A, the semiconductor substrate 12 is flat, but the semiconductor substrate 11 is curved such that the surface of the insulating film 16, that is, the bonding surface 11a of the semiconductor substrate 11 is concave. . That is,
The prepared semiconductor substrates 11 and 12 are substantially the same as the conventional example shown in FIG.

However, in the second embodiment, the object to be fixed in a flat state by the flat vacuum chuck 13 is shown in FIG.
Instead of the semiconductor substrate 11 as shown in FIG.
The semiconductor substrate 12 is as shown in FIG. After the semiconductor substrate 12 is fixed by the vacuum chuck 13, the same steps as those in the method shown in FIG.

When the fixing of the semiconductor substrate 12 by the vacuum chuck 13 is released after the bonding, the semiconductor substrate 11 has a force for returning the bonding surface 11a to a concave shape due to a difference in heat shrinkage coefficient, and an elongation during bonding. This causes both the force to make the bonding surface 11a convex.

That is, after bonding, the semiconductor substrate 1
As shown in FIG. 2 (c), the forces acting on the substrates 1 weaken each other to form a bonded SOI substrate 15 having a smaller curvature than the semiconductor substrate 11 before bonding.

In each of the conventional examples shown in FIGS. 4 and 5, the pattern of the island-like semiconductor layer and the insulating film 16 formed by grinding the semiconductor substrate 11 of the bonded SOI substrate 15 is as described above. It expanded and contracted in the range of about 4 ppm to 25 ppm. However, in the first and second embodiments shown in FIGS. 1 and 2, even if a recess is formed on one surface of the semiconductor substrate 11, the island formed by grinding the semiconductor substrate 11 of the bonded SOI substrate 15 is formed. The pattern of the semiconductor layer and the insulating film 16 expands and contracts only in an absolute value range of 3 ppm or less.

In the first and second embodiments described above,
Although the pressure is applied to the semiconductor substrate 12 and the semiconductor substrate 11 by the pressure rod 14, if the pressure is applied to the semiconductor substrate 12 and the semiconductor substrate 11 by a compressed gas or the like, the semiconductor substrate 12 or the It is possible to prevent the semiconductor substrate 11 from being contaminated, and to prevent bubbles from remaining on the bonding surfaces 11 and 12 by uniform surface pressure.

In the first and second embodiments, the semiconductor substrate 11 which is curved because the insulating film 16 and the like are formed on one surface is bonded to another flat semiconductor substrate 12. Although the invention of the present application is applied to the present invention, the invention of the present application can also be applied to bonding of a substrate other than a semiconductor substrate, which is curved for some reason, to another flat substrate. .

[0049]

According to the method for bonding substrates according to the first aspect of the present invention, a pair of substrates are bonded to each other even if one of the pair of substrates is curved so that the bonding surface becomes convex. Since a force for reducing the curvature acts on the bonded substrate, a bonded substrate having a reduced curvature than the substrate that has been curved before bonding can be formed.

In the method for bonding substrates according to a second aspect, when bonding a pair of substrates, a pair of substrates is formed by using a semiconductor substrate on which an insulating film having a smaller heat shrinkage coefficient than a semiconductor substrate is formed. Since an insulating film can be interposed therebetween, a bonded SOI substrate having an insulating film having a smaller heat shrinkage coefficient than a semiconductor substrate can be formed.

According to the third aspect of the present invention, there is provided a bonded SOI substrate in which the expansion and contraction of the pattern of the semiconductor layer and the insulating film is reduced even if the insulating film has a smaller heat shrinkage coefficient than the semiconductor layer. Since it can be formed, a bonded SOI substrate which can manufacture a semiconductor device having a fine SOI structure with a small misalignment of a mask during exposure in lithography can be formed.

In the method for bonding substrates according to claim 4, a bonded substrate formed by bonding a pair of substrates to each other even if one of the pair of substrates is curved so that the bonding surface becomes concave. Since the force for reducing the curvature acts on the substrate, a bonded substrate having a reduced curvature than the substrate that has been curved before bonding can be formed.

According to a fifth aspect of the present invention, when bonding a pair of substrates, a semiconductor substrate having an insulating film having a larger heat shrinkage coefficient than the semiconductor substrate is used. Since an insulating film can be interposed therebetween, a bonded SOI substrate having an insulating film having a larger heat shrinkage coefficient than a semiconductor substrate can be formed.

In the method for bonding substrates according to claim 6, a bonded SOI substrate in which the expansion and contraction of the pattern of the semiconductor layer and the insulating film is reduced even if the insulating film has a larger heat shrinkage coefficient than the semiconductor layer. Since it can be formed, a bonded SOI substrate which can manufacture a semiconductor device having a fine SOI structure with a small misalignment of a mask during exposure in lithography can be formed.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a first embodiment of the present invention in the order of steps.

FIG. 2 is a side sectional view showing a second embodiment of the present invention in the order of steps.

FIG. 3 is a side sectional view showing a general method for bonding substrates in the order of steps.

FIG. 4 is a side sectional view showing a conventional example of the invention of the present application in the order of steps.

FIG. 5 is a side sectional view showing another conventional example of the present invention in the order of steps.

[Explanation of symbols]

11: semiconductor substrate (substrate), 11a: bonding surface, 1
2: semiconductor substrate (substrate), 12a: bonding surface, 16
… Insulating film

Claims (6)

[Claims] 1. A pair of substrates, one of which is fixed in a flat state, the bonding surfaces of the pair of substrates are opposed to each other, and one of the bonding surfaces of the other substrate of the pair of substrates is Contacting a part of the bonding surface of the one substrate, the adhesion by the attraction force of the pair of substrates is advanced from the contact portion to a portion other than the contact portion, the pair of substrates to each other In the method of bonding substrates, a substrate curved so that the bonding surface becomes convex is used as the one substrate, and a flat substrate is used as the other substrate. Matching method. 2. The semiconductor device according to claim 1, wherein the one substrate is a semiconductor substrate, and an insulating film having a smaller thermal contraction coefficient than the semiconductor substrate is formed on one surface of the semiconductor substrate. The method for bonding substrates according to claim 1, wherein the bonding surface of the substrate is used. 3. The method according to claim 2, wherein a concave portion is formed on the one surface. 4. One of the pair of substrates is fixed in a flat state, the bonding surfaces of the pair of substrates are opposed to each other, and one of the bonding surfaces of the other substrate of the pair of substrates is fixed. Contacting a part of the bonding surface of the one substrate, the adhesion by the attraction force of the pair of substrates is advanced from the contact portion to a portion other than the contact portion, the pair of substrates to each other In the method of bonding substrates to be bonded, a flat substrate is used as the one substrate, and a substrate curved so that the bonding surface is concave is used as the other substrate. Method. 5. The semiconductor device according to claim 1, wherein the other substrate is a semiconductor substrate, an insulating film having a larger thermal contraction coefficient than the semiconductor substrate is formed on one surface of the semiconductor substrate, and the surface of the insulating film is 5. The method for bonding substrates according to claim 4, wherein the bonding surface of the substrate is used. 6. The method according to claim 5, wherein a concave portion is formed on the one surface.