JP2022127060A - Silicon wafer and manufacturing method for multilayer wafer using the same - Google Patents

Abstract

To provide a silicon wafer processed to be thin and bonded onto a supporting wafer, in which the occurrence of a crack or chipping at a wafer periphery part can be suppressed, and a manufacturing method for a multilayer wafer using the same.SOLUTION: A silicon wafer 1 processed to be thin in a device manufacturing process includes a handling part 2 with a chamfered peripheral part where first and second inclined surfaces 2a and 2b are formed respectively on front and back peripheral parts, and a device formation part 3 with a disc-like shape formed at one surface side of the handling part on a concentric circle with the handling part so as to have smaller diameter. The peripheral part of the device formation part includes a third inclined surface 3b that is inclined with respect to the wafer surface. A lower edge of the third inclined surface is formed continuously so as to connect to an upper edge of the first inclined surface of the peripheral part of the handling part. The inclination angle of the third inclined surface is 40° or more and 75° or less with respect to the wafer surface.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a silicon wafer and a method for manufacturing a laminated wafer using the same, and particularly to a silicon wafer which is thinned in a device manufacturing process and which is less susceptible to bevel cracking or chipping in a device use region. The present invention relates to a laminated wafer manufacturing method.

In recent years, it has been studied to stack a plurality of semiconductor chips to improve functions, capacity, processing capability, and the like. As one method for realizing this, there is a method of producing a three-dimensional device by stacking a plurality of semiconductor wafers to form a stacked wafer. In the laminated wafer, the thickness of the lowest first semiconductor wafer is formed to some extent thick, and after the second semiconductor wafer having the same thickness is laminated on the top surface of the first semiconductor wafer, heat dissipation is achieved. , or to allow further stacking of semiconductor wafers thereon, the second semiconductor wafer is thinned by grinding the upper surface thereof.

For example, as shown in FIG. 6A, in this laminated wafer 30, a bonded wafer 32 having substantially the same thickness is laminated on a lower layer support wafer 31 (a silicon oxide film or an adhesive agent). are joined by). As shown, the support wafer 31 and the bonded wafer 32 are chamfered. Then, the bonded wafer 32 is ground from the upper surface side (front surface side) in order to improve heat dissipation or to make it possible to stack another semiconductor wafer (not shown) thereon. and thinly processed.

However, since the outer peripheral end surface (chamfered surface) of the bonded wafer 32 before grinding is formed to have a trapezoidal cross section or an arcuate cross section as shown in the figure, the bonded wafer 32 is ground until it becomes thin. When processed, as shown in FIG. 6(b), the outer peripheral end face becomes a sharp-angled shape like a knife edge (knife edge), and as a result, there is a problem that it is easily chipped. In addition, if chipping occurs, cracks will occur from there, and there are problems such as deterioration in the quality of the laminated wafer and the unavailability of use.

In order to address such a problem, Patent Document 1 discloses that a second semiconductor wafer (corresponding to a bonded wafer) 42 is stacked on a first semiconductor wafer (corresponding to a support wafer) 41 as shown in FIG. A processing method is disclosed in which, after removing the outer peripheral end surface of the second semiconductor wafer 42 while rotating it, the upper surface side of the second semiconductor wafer 42 is ground to make it thinner.
As a means for removing the outer peripheral end surface of the second semiconductor wafer 42, as shown in FIG. 1 is brought into contact with the outer peripheral edge of the semiconductor wafer 42 and removed by grinding.

JP 2005-116614 A

According to the method disclosed in Patent Literature 1, when this is carried out, it is possible to prevent the peripheral edge portion (bevel portion) of the second semiconductor wafer (corresponding to the bonded wafer) 42 from becoming knife edge-like.
However, removing only the peripheral edge of the second semiconductor wafer 42 by lowering the grinding wheel 43 rotated at high speed may damage the underlying first semiconductor wafer 41, which is not technically easy. There was a problem.
Moreover, even if the processing is performed, not only the peripheral edge of the second semiconductor wafer 42 but also a part of the surface portion is removed, so there is a problem that the effective area for stacking the semiconductor chips is reduced.
In addition, a deep crushed layer is likely to form on the processed surface, which may cause contamination, cracking, etc. in the subsequent device manufacturing process.

SUMMARY OF THE INVENTION The present invention has been made under the circumstances described above. It is an object of the present invention to provide a silicon wafer capable of producing a silicon wafer and a method for manufacturing a laminated wafer using the silicon wafer.

A silicon wafer according to the present invention, which has been made to solve the above-mentioned problems, is a silicon wafer that is thinned in a device manufacturing process, the peripheral edge portion of which is chamfered, and the front and back peripheral edge portions have first and second silicon wafers, respectively. and a disk-shaped device forming portion formed concentrically with the handling portion and having a smaller diameter on one side of the handling portion, wherein the device forming portion The peripheral portion has a third inclined surface that is inclined with respect to the wafer surface, and is continuously formed such that the lower end of the third inclined surface is connected to the upper end of the first inclined surface of the peripheral portion of the handling portion. , the inclination angle of the third inclined surface is 40° or more and 75° or less with respect to the wafer surface.
In addition, it is desirable that the inclination angles of the first and second inclined surfaces are set to 15° or more and 50° or less with respect to the wafer surface.

As described above, in the silicon wafer according to the present invention, since the inclination angle (bevel angle) of the peripheral portion of the device forming portion is formed to be 40° or more and 75° or less, the corner portion of the peripheral end portion is not an acute angle. It is possible to prevent cracks and chips from occurring. As a result, deterioration in quality of the semiconductor wafer can be suppressed.

Further, a method for manufacturing a laminated wafer using a silicon wafer according to the present invention, which has been made to solve the above problems, is a laminated wafer in which a silicon wafer is bonded to a support wafer, and the silicon wafer is ground and thinned. comprising the steps of: bonding the upper surface side of the device formation portion to the support wafer; and removing the handling portion by grinding, wherein the upper surface side of the device formation portion is attached to the support wafer Before the step of bonding onto the wafer, a sloped surface is formed on the periphery of the device formation portion, and the sloped surface is formed at an angle of inclination of 40° or more and 75° or less with respect to the wafer surface. have.
In addition, before the step of bonding the upper surface side of the device formation portion to the support wafer, an inclined surface is formed in the peripheral portion of the handling portion, and the inclination angle of the inclined surface with respect to the wafer surface is 15° or more and 50°. ° or less.

According to such a method, since only the handling portion arranged on the device forming portion and having a larger diameter than the device forming portion needs to be removed in the grinding process, the grinding process can be easily performed. In addition, no sharp edge is formed on the periphery of the device forming portion remaining after the thinning process, so that cracking or chipping of the wafer can be prevented.

According to the present invention, in a silicon wafer that is thinned and bonded to a support wafer, it is possible to suppress the occurrence of cracks and chips at the peripheral edge of the wafer, and a laminated wafer using the same. A manufacturing method can be provided.

FIG. 1 is a perspective view showing an embodiment of a silicon wafer according to the invention. FIG. 2 is a cross-sectional view showing an enlarged peripheral end portion (bevel portion) of the silicon wafer of FIG. FIG. 3 is a cross-sectional view showing a state in which the peripheral edge of a silicon wafer is ground with a bevel grindstone. 4(a) and 4(b) are cross-sectional views showing a state in which the peripheral end portion of a silicon wafer is ground with another bevel grindstone. 5(a) to 5(c) are cross-sectional views for explaining the steps of manufacturing a laminated wafer using the silicon wafer of the present invention. 6(a) and 6(b) are cross-sectional views for explaining problems of conventional laminated wafers. FIG. 7 is a cross-sectional view for explaining a conventional laminated wafer manufacturing method.

A silicon wafer and a method for manufacturing the same according to the present invention will be described below. The silicon wafer according to the present invention is used after being laminated on a disk-shaped support glass or support wafer and then ground in the thickness direction to be thinned.

FIG. 1 is a perspective view schematically showing an embodiment of a silicon wafer according to the invention. FIG. 2 is a cross-sectional view showing an enlarged peripheral end portion (bevel portion) of the silicon wafer of FIG. In the following description, the top side of the silicon wafer 1 shown in FIG. 1 is called the front side, and the bottom side is called the back side.
A silicon wafer 1 shown in FIG. 1 has a handling portion 2 forming the back side, and a device forming portion 3 formed on the handling portion 2 concentrically with the handling portion 2 and forming the front side.

As shown in FIG. 2, the upper surface portion of the handling portion 2 and the lower surface portion of the device forming portion 3 are connected, and the handling portion 2 and the device forming portion 3 are integrally formed.
In addition, the peripheral end portion of the handling portion 2 is chamfered on both the front side and the back side to have a trapezoidal cross section.
In addition, the device formation portion 3 has a device formation surface 3a on the front side thereof and an inclined surface 3b (third inclined surface) whose peripheral edge is chamfered. The lower end of the inclined surface 3b is continuously formed so as to be connected to the upper end of the inclined surface 2a on the front side of the handling portion 2. As shown in FIG.

The reason for such a shape is that grinding for thinning is performed step by step, and thinning can be easily performed without causing cracks or the like. That is, when manufacturing a laminated wafer, the surface side of the silicon wafer 1 (the surface side of the device forming portion 3) is bonded to a disk-shaped support glass or a support wafer (not shown) (that is, the silicon wafer 1 is 1 and 2), and the handling portion 2 is removed during grinding.

The shape of the silicon wafer 1 before thinning will be described more specifically.
In the handling part 2, the inclination angles (called bevel angles) of the chamfered (beveled) inclined surfaces 2a and 2b (the first inclined surface and the second inclined surface) with respect to the horizontal plane are 15 for both θ1 on the front side and θ2 on the back side. ° or more and 50° or less. The bevel angles .theta.1 and .theta.2 may be the same angle or different angles within the above angle range.
If the bevel angles θ1 and θ2 are less than 15°, the bevel width becomes too large with a standard wafer thickness (for a thickness of 300 mm, the bevel width becomes 775 μm), which is not preferable. Further, when the bevel angles θ1 and θ2 are larger than 50°, chipping, cracking, and dust generation may occur during handling, polishing, and grinding, which is not preferable.

Further, the device forming portion 3 is formed such that the inclination angle (called a bevel angle) θ3 of the inclined surface 3b is 40° or more and 75° or less. That is, the bevel angle .theta.3 is formed to be greater than the bevel angle .theta.1, and a concave step is formed between the inclined surfaces 2a and 3b unless the bevel angles .theta.2 and .theta.3 are equal. The angle .theta.4 of the recessed step is preferably 130.degree.
Moreover, if the bevel angle θ3 is less than 40°, cracks may occur during processing for thinning the wafer, which is not preferable. Further, if the bevel angle θ3 is larger than 75°, there is a risk of cracks occurring during handling, a concern that the film on the device may easily peel off, and a possibility of dust generation due to contact with the wafer carrier (cassette). I don't like it.

Further, as shown in FIG. 2, the thickness A of the device formation portion 3 after grinding is formed in the range of A≦T ₁ ≦100 μm, where T ₁ is the thickness of the device formation portion 3 before grinding. . As a result, it is possible to prevent cracking and chipping of the outer peripheral edge of the thinned silicon wafer 1 . Moreover, if T1 is larger than 500 μm, the peripheral edge of the handling portion 2 of the silicon wafer ₁ becomes too thin, and the bevel portion tends to crack or chip during processing, which is not preferable.

Further, as shown in FIG. 2, in the peripheral end portion of the handling portion ₂ , the radial length (bevel portion width) W1 of the chamfered portion is formed to be 500 μm or less. By satisfying this condition, it is possible to prevent the diameter of the wafer after thinning from becoming too small, and facilitate processing into the intended bevel shape.
Although the thickness _T0 of the silicon wafer 1 is not specified, it is formed to be 775 μm, for example.

In order to form the silicon wafer 1 having such a shape, as shown in FIG. 3, a grindstone 15 for beveling corresponding to the desired shape of the bevel portion is prepared in advance, and the silicon wafer 1 is rotated around the central axis at high speed. The peripheral edge of the wafer may be ground by the bevel whetstone 15 while the beveling grindstone 15 is being used.

Alternatively, as shown in FIG. 4A, for example, a bevel grindstone 16 corresponding to the back surface side shape of the silicon wafer 1 (lower back surface side peripheral edge portion of the handling unit 2) is used to grind only the wafer back surface side peripheral edge portion. Then, as shown in FIG. 4(b), a bevel grindstone 17 corresponding to the shape of the front surface of the silicon wafer 1 (from the upper portion of the handling section 2 to the peripheral edge of the device forming section 3) is used to grind the front peripheral edge of the wafer. part should be ground.

Next, the process of forming the laminated wafer 20 using the silicon wafer 1 having such a shape will be described with reference to FIGS. 5(a) and 5(b).
First, as shown in FIG. 5A, a silicon oxide film of several tens of nanometers or an adhesive (resin ). As a result, the back surface of the silicon wafer 1 (the back surface of the handling unit 2) becomes the top surface of the laminated wafer 20. Next, as shown in FIG. The thickness of the silicon wafer 1 at this time is T ₀ (for example, 775 μm).

Next, as a grinding process, the silicon wafer 1 is ground from above to a target value A (for example, 100 μm) using a grinder, and the handling portion 2 is removed as shown in FIG. 5(b). In this manner, since the grinding process is a step of grinding and removing the handling portion 2 having a larger diameter than the device forming portion 3 on the device forming portion 3, the grinding work can be easily performed.
Here, since the bevel angle θ3 of the device formation portion 3 is 40° or more and 75° or less, it does not have a knife-edge shape.

As described above, in the laminated wafer 20 using the silicon wafer 1 according to the present embodiment, the bevel angle θ3 of the device formation portion 3 on the support wafer 10 is 40° or more and 75° or less with respect to the surface of the support wafer 10. Since the corners of the peripheral edge are not sharp, cracks and chipping can be prevented. As a result, deterioration in quality of the semiconductor wafer can be suppressed.
Further, when forming the laminated wafer 20 using the silicon wafer 1, in the grinding process, only the handling portion 2 arranged on the device forming portion 3 and having a larger diameter than the device forming portion 3 should be removed. Therefore, grinding can be easily performed. In addition, no sharp edge is formed on the periphery of the device forming portion 3 remaining after the thinning process, so that cracking or chipping of the wafer can be prevented.

The silicon wafer according to the present invention and the method for producing a laminated wafer using the silicon wafer will be further described based on examples.
In this example, a silicon wafer having a diameter of 300 mm and a thickness of 775 μm (T ₀ ) was manufactured, and the peripheral edge of the wafer was processed based on the conditions set in Examples 1 to 7 and Comparative Examples 1 to 4. and silicon wafers for verification having device forming portions with smaller diameters and different bevel angles.
Next, the verification silicon wafer is bonded to the support wafer via a silicon oxide film having a thickness of 80 nm, and is ground (using a #8000 whetstone) for stepwise thinning according to the above-described embodiment. Carried out.

The target values (set values) for the stepwise grinding of the silicon wafer for verification were the initial value T ₀ =775 μm and the post-grinding target value A=5 μm for each condition. _In addition, the radial projection length W1 at the peripheral end portion (bevel portion) of the large diameter portion was set to 500 μm.

In each example (Examples 1 to 7, Comparative Examples 1 to 4), 1000 samples were verified, and conditions were set for θ1, θ2, and θ3 shown in FIG.
Table 1 shows the conditions and results of Examples 1 to 7 and Comparative Examples 1 to 4. In Table 1, the evaluation item "bevel cracks and chipping" is indicated by ◯ when no cracking or chipping occurred, and by x when it occurred. Note that bevel cracks and chips include cracks and chips in the peripheral end portion of the handling portion that occur during grinding of the silicon wafer. In addition, the evaluation item "poor bonding" is indicated by ◯ when there is no bonding failure with the support wafer, x when the occurrence rate is 1% or more, and Δ when the occurrence rate is less than 1%. As for "metal contamination", which is an evaluation item, a level equivalent to that of the conventional bevel shape is indicated by Δ, and a good level is indicated by ○. If it was ○ or △, it was judged to be a non-defective product.

(Table 1)

In Example 1, the bevel angle θ1 of the handling portion was 30°, the bevel angle of the handling portion θ2 was 30°, and the bevel angle θ3 of the device forming portion was 40°. , metal contamination was good.
In Example 2, the bevel angle θ1 of the handling portion was 30°, the bevel angle of the handling portion θ2 was 30°, and the bevel angle θ3 of the device forming portion was 60°. , metal contamination was good.

In Example 3, the bevel angle θ1 of the handling portion was 30°, the bevel angle of the handling portion θ2 was 30°, and the bevel angle θ3 of the device formation portion was 75°. , metal contamination was good.
In Example 4, the bevel angle θ1 of the handling portion was 15°, the bevel angle of the handling portion θ2 was 15°, and the bevel angle θ3 of the device formation portion was 60°. , metal contamination was good.

In Example 5, the bevel angle θ1 of the handling portion was 20°, the bevel angle of the handling portion θ2 was 20°, and the bevel angle θ3 of the device formation portion was 65°. , metal contamination was good.
In Example 6, the bevel angle θ1 of the handling portion was 40°, the bevel angle of the handling portion θ2 was 40°, and the bevel angle θ3 of the device formation portion was 60°. , metal contamination was good.
In Example 7, the bevel angle θ1 of the handling portion was 50°, the bevel angle of the handling portion θ2 was 50°, and the bevel angle θ3 of the device forming portion was 60°. , metal contamination was good.

On the other hand, in Comparative Example 1, the bevel angle θ1 of the handling portion was 30°, the bevel angle θ2 of the handling portion was 30°, and the bevel angle θ3 of the device formation portion was 35°.
There was no bonding failure and good metal contamination, but the peripheral edge of the device forming portion became knife-edge, and the bevel portion cracked and chipped.

In Comparative Example 2, the bevel angle θ1 of the handling portion was 30°, the bevel angle θ2 of the handling portion was 30°, and the bevel angle θ3 of the device forming portion was 80°.
No joint failure occurred, and metal contamination was good. Further, there was no bevel cracking or chipping at the peripheral edge of the device forming portion during the thinning process, but cracking or chipping occurred at the bevel portion of the handling portion.

In Comparative Example 3, the bevel angle θ1 of the handling portion was 15°, the bevel angle θ2 of the handling portion was 15°, and the bevel angle θ3 of the device formation portion was 60°.
No joint failure occurred, and metal contamination was good. Further, there was no bevel cracking or chipping at the peripheral edge of the device forming portion during the thinning process, but the bevel portion of the handling portion became edge-like, and cracking or chipping occurred there.

In Comparative Example 4, the bevel angle θ1 of the handling portion was 55°, the bevel angle θ2 of the handling portion was 55°, and the bevel angle θ3 of the device formation portion was 60°.
No joint failure occurred, and metal contamination was good. Further, there was no bevel cracking or chipping at the peripheral edge of the device forming portion during the thinning process, but cracking or chipping occurred at the bevel portion of the handling portion during handling.

From the results of the above examples, it was found that the risk of crack generation during wafer handling can be suppressed by setting the handling portion bevel angles θ1 and θ2 to 15° or more and 50° or less.
Further, it has been found that by setting the bevel angle θ3 of the device formation portion to 40° or more, the peripheral edge portion of the device formation portion does not become edge-like, and the occurrence of cracks can be suppressed. Further, it was confirmed that the risk of crack generation during wafer handling can be reduced by setting the bevel angle θ3 of the device formation portion to 75° or less.

REFERENCE SIGNS LIST 1 silicon wafer 2 handling part 2a inclined surface 2b inclined surface 3 device formation part 3a inclined surface 10 support wafer 20 laminated wafer θ1 bevel angle θ2 bevel angle θ3 bevel angle

Claims (4)

A silicon wafer to be thinned in the device manufacturing process,
a handling part having a chamfered peripheral edge and having first and second inclined surfaces formed on the front and back peripheral edges, respectively;
a disk-shaped device forming portion formed concentrically with the handling portion and having a smaller diameter on one side of the handling portion;
The peripheral portion of the device forming portion has a third inclined surface that is inclined with respect to the wafer surface, and the lower end of the third inclined surface is connected to the upper end of the first inclined surface of the peripheral portion of the handling portion. is continuously formed as
A silicon wafer, wherein the inclination angle of the third inclined surface is set to 40° or more and 75° or less with respect to the wafer surface. A silicon wafer, wherein the inclination angles of the first and second inclined surfaces are set to 15° or more and 50° or less with respect to the wafer surface. A method for manufacturing a laminated wafer, wherein the silicon wafer according to claim 1 or claim 2 is bonded to a support wafer, and the silicon wafer is ground to be thinned,
bonding the upper surface side of the device formation portion onto the support wafer;
grinding and removing the handling portion;
Before the step of bonding the upper surface side of the device formation portion onto the support wafer,
A method of manufacturing a laminated wafer, wherein an inclined surface is formed on the peripheral edge of the device forming portion, and the inclination angle of the inclined surface with respect to the wafer surface is in the range of 40° or more and 75° or less. Before the step of bonding the upper surface side of the device formation portion onto the support wafer,
4. The method for manufacturing laminated wafers according to claim 3, wherein an inclined surface is formed on the peripheral edge of the handling part, and the inclination angle of the inclined surface with respect to the wafer surface is 15[deg.] or more and 50[deg.] or less. .

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