JPH03183130A - Manufacture of semiconductor substrate - Google Patents

Abstract

PURPOSE:To eliminate an unbonded part, at the outer circumference of wafers, caused at a pasting operation and to prevent the breakage produced at the outer circumference part of the wafers by a method wherein two wafers are pasted and, after that, their outer circumference is chamfered. CONSTITUTION:Two wafers 1 and 2 are pasted; after that, the outer circumference part of the two wafers 1 and 2 which have been pasted in advance is chamfered. As a result, when the wafer 1 on one side is polished and processed at a posterior process, the peripheral end edge 1a of the wafer 1 on one side is not levitated from the wafer 11 on the other side. That is to say, since an unbouded part is eliminated, a breakage is not produced at the outer circumference part of the wafer 1 on one side. Consequently, reliability of a semiconductor substrate 1d is increased, and the yield of a device formed on the substrate 16 can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor substrate, and particularly to a method for manufacturing a semiconductor substrate by bonding wafers together to form an SOI (silicon-on-insula).
(tor)) relates to a method of manufacturing a substrate.

[Summary of the Invention] The present invention provides a method for manufacturing a semiconductor substrate formed by bonding two wafers together. By removing the unbonded portion on the outer periphery and preventing chips from occurring on the outer periphery of the wafer when one wafer is thinned by subsequent polishing, it is possible to improve the reliability of the semiconductor substrate and to improve the reliability of the semiconductor substrate. This makes it possible to achieve a high yield of devices to be formed.

In particular, by performing the above-mentioned chamfering with a diamond wheel, and by setting the rotational direction of the wafer and the diamond wheel in the same direction, chipping of the wafer during chamfering can be prevented, thereby improving the reliability of semiconductor substrates and improving the reliability of semiconductor substrates. This makes it possible to further increase the yield of devices formed on the substrate.

[Conventional technology]

BACKGROUND ART Recently, development has been progressing to fabricate a VLSI using a so-called Sol substrate formed by forming a thin single-crystal silicon layer on an insulator. Among the various methods for producing Sol substrates, the bonding method is considered to have the best crystallinity and superior properties.

FIG. 17 shows an example of an SOI substrate using a bonding method. As shown in FIG. 17A, a mirror silicon wafer (51
4) A predetermined pattern of steps is formed on the main surface of 4) using the IJ sogerafy technique so that a plurality of convex portions (52) are formed. Then, on the main surface, an insulating film, for example, 5I0
Two films (53) are formed, and a planarization layer, such as a polycrystalline silicon layer (54), is formed on the entire surface to fill in the steps, and the surface of this polycrystalline silicon layer (54) is polished flat.

Next, as shown in FIG. 17B, another mirror silicon wafer (55) is bonded to the flattened polycrystalline silicon layer (54) to form a bonded wafer (57).
As shown in Figure C, the silicon wafer (51) is polished from the back side using the 5i02 film (53) as a polishing stopper.
An SOI substrate (58) having a plurality of island-like silicon regions (56) separated by a 5in2 film (53) is obtained.

[Problem to be solved by the invention]

However, in the conventional semiconductor substrate manufacturing method, during the polishing process shown in FIG. 17C, the bonded wafer (
There is an inconvenience that chipping occurs on the outer periphery of 57). That is, generally the wafers (51) and (55) have their respective peripheral edges (51a) and <5
5a) has an arcuate cross section, so Figure 17C
When polishing one wafer (51) shown in
When polishing is performed to the vicinity of the bonding interface (j'), the peripheral edge (51a) of one wafer (51) is floating relative to the other wafer (55), and the floating part (unbonded part) (59) becomes very thin and easily chipped. If this portion <59) is missing, it becomes a source of dust and dirt, which is disadvantageous in that it leads to a decrease in the yield in manufacturing devices.

The present invention has been made in view of the above points, and its purpose is to prevent chipping on the outer periphery of a wafer that occurs during polishing, improve the reliability of semiconductor substrates, and improve the reliability of semiconductor substrates. An object of the present invention is to provide a method for manufacturing a semiconductor substrate that can achieve a high yield of devices to be formed.

[Means to solve the problem]

The manufacturing method of the present invention includes two wafers (1) and (process 1)
) (16)
In the manufacturing method, two wafers (1) and (11
), then chamfer the outer periphery.

The chamfering described above is performed using, for example, a diamond wheel (23), and is further performed by setting the rotational direction of the wafers (1) and (11> and the rotational direction of the diamond wheel (23) in the same direction.

[Effect]

According to the manufacturing method of the present invention described above, two wafers (1
) and (11), the outer peripheries of the two wafers (1) and (11) that had been bonded in advance were chamfered, so one of the wafers (1) could be polished in the subsequent process. At this time, the peripheral edge 1 (la
) will no longer float relative to another wafer (11), that is, there will be no unbonded parts, and chipping will no longer occur at the outer periphery of one wafer (1). Therefore, not only can the reliability of the semiconductor substrate (16) be improved, but also the yield of devices formed on the substrate (16) can be increased.

In particular, the chamfering of the outer peripheries of wafers 0] and (11) is performed using a diamond wheel (23),
Furthermore, by setting the rotation direction of the wafers (1) and (11> and the rotation direction of the diamond wheel (23) in the same direction, the grinding waste (25) generated during chamfering can be particularly removed from the grinding wheel (25).
11) and the diamond wheel (23), the wafer (11) is prevented from chipping during chamfering, and the reliability of the semiconductor substrate (16) is improved and the diamond wheel (16) is formed on the substrate (16). Accordingly, it is possible to further increase the yield of manufactured devices.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to FIGS. 1 to 16.

FIG. 1 is a process diagram showing a method of manufacturing a semiconductor substrate (hereinafter referred to as an SO2 substrate) according to this embodiment. The steps will be explained step by step below.

First, as shown in FIG. 1A, a plurality of convex portions (2) with a thickness of 1000 mm are formed on the main surface of a silicon wafer (1) whose both sides are mirror-finished using photolithography technology. A predetermined pattern of steps is formed.

Next, as shown in FIG.
A 5in2 film (3) is formed using the VD (chemical vapor deposition) method, and this S1-hole film (3) is used as a buffer, and a polycrystalline silicon layer (4) is further formed on this film to a thickness of 5 cm using the CVD method.
Deposits are about μm.

Next, as shown in FIG. (4)
Perform flattening polishing on the surface. This polishing produces 1000A
Only the minute pattern protrusions (5) are polished, and the polycrystalline silicon layer (4) is planarized.

Next, as shown in the first diagram, another silicon wafer (
11) is directly bonded to the flattened polycrystalline silicon layer [4] to form a bonded wafer (12).

During this bonding process, both wafers (1) and (11)
After cleaning the surfaces of both wafers (1) and (11) with a mixed solution of ammonia and hydrogen peroxide, they are dried using a spin dryer. Next, bonding is performed in a clean atmosphere. Thereafter, heat treatment is performed at 1100° C. for 2 hours in an oxygen atmosphere or a nitrogen atmosphere to provide adhesion to the bonding interface (A) comparable to that of the bulk.

Next, as shown in Fig. 1E and Fig. 2, the peripheral edges (lla) and (la) of the bonded wafer (12>) are chamfered. As shown in FIG. 3, processing is used to chuck (21a) between the top and bottom of the bonded wafer (12).

(21b) and the bonded wafer (12
) with chucks (21a), (21b) and rotating shaft (
22a) and (22b) at a rotation speed of about lrpm, and a diamond wheel (23
〉 is also rotated at a rotation speed of approximately 280 rpm via the rotating shaft (24), and the peripheral edges (la), (lla) of the bonded wafer (12) and the diamond wheel 〈23
) and the diamond electrodeposited portion (23a) are brought into contact with each other. Then, as shown in FIG. 2B, the peripheral edge (la) of one wafer (1) is polished, and the peripheral edge 1 (lla) of the other wafer (11) is polished at the interface It should be slightly removed. At this time, the bonded wafer (
12) and the diamond wheel (23) are set in the same direction. In addition, one wafer (
The maximum grinding allowance d for 1) was set to about 3 to 4 mm. Normally, profile grinding by rotating a grinding wheel is carried out with the direction of rotation of the workpiece (in this case, the bonded wafer (12)) and the direction of rotation of the grinding wheel (in this case, the diamond wheel (23)) being different. . When this method is applied to the chamfering process, as shown in Fig. 4, the grinding start point a and the grinding (spraying point) can be at different positions, so as shown in Fig. ) gets caught between the bonded wafer, especially another wafer (11), and the diamond electrodeposited part (23a) of the diamond wheel (23), and as a result, grinding debris is generated between the diamond wheel (23) and the wafer (11). (25) is clogged, which causes excessive force to be applied and cracks (26) to appear, or the 6th
As shown in the figure, the outer periphery (flb) of the wafer (11)
There is an inconvenience that a chip (27) occurs. but,
As in this example, if the rotation directions of the bonded wafer (12) and the diamond wheel <23> are set in the same direction, the grinding start point a and the grinding waste ejection point will be at the same position as shown in Fig. 7. Therefore, the grinding waste (25) is transferred to the wafer (11).
) and the diamond wheel (23).Therefore, as shown in Figure 8, the wafer (11)
Chamfering can be performed with high precision without causing any chipping on the outer circumferential portion (Ilb).

Thereafter, as shown in FIG. 1E, the damage layer caused by the grindstone on the grinding surface is removed by etching to remove machining strain.

At this time, R on the other main surface side of one wafer (1)
(Circular arc) (13) is formed.

After that, as shown in FIG. 1F, one of the wafers (1
) from its end face by polishing to make it flat (i.e. selective polishing).
A plurality of island-like silicon regions (15) separated from each other by O□ films (3) are formed to obtain the desired Sol substrate (16).

As described above, according to this example, after bonding two wafers (1) and (11), the bonded wafer (12
Since the outer periphery of the wafer (1) is chamfered, the 9th
As shown in the figure, the peripheral edge (To) of one wafer (1) after grinding no longer floats relative to the other wafer (11), and in other words, the unbonded portion (
14) Since the wafer (indicated by the - dotted chain line) is eliminated, chipping on the outer periphery of one wafer (1) no longer occurs. Therefore, it is possible to improve the reliability of the SOI substrate (16) and to increase the yield of devices formed on the SOI substrate (16).Furthermore, during the chamfering, the bonded wafer (12) ) and the diamond wheel (23〉) were set to rotate in the same direction, so the grinding waste (25) generated during chamfering was removed from the bonded wafer and the wafer (1).
1) and the diamond wheel (23), and chipping of the outer peripheral portion (llb) of the wafer (11) during chamfering can be prevented. Therefore, the reliability of the SOI substrate (16) and the yield of devices can be further improved.

Two wafers (1) and (11) in the above example
In the process of bonding the wafers (see the first diagram), normally two wafers (1) and (1) are bonded together as shown in Figure 10A.
In contrast to 1), they are combined and bonded as is without any forced deformation. In this case, when wafers (1) and (11) self-bond (adsorb) to each other due to hydrogen bonding force and van der Waals force, they are randomly bonded, so as shown in Figure 10B, the bonding There is a disadvantage that air is easily taken into the interface <i>, and as a result, a large number of air bubbles (31) are generated at the bonding interface (I).In addition, as another bonding method, as shown in FIG. , one of the wafers (e.g. wafer (11)
) is held in a vacuum suction check (not shown), and the wafer (11) is deflected into a convex spherical shape by vacuum suction, and then the wafer (11) that has not been forcibly deformed (for example, wafer (1)) and the wafer (11) are After adhering the centers of each wafer (11) to each other, weaken the suction force of the vacuum suction check and use the self-adsorption effect of both wafers (1) and (11) to bond them from the center toward the outer periphery. There is a method of When bonding with wafer (1) while returning the wafer to wafer (1), it is thought that the contact speed near the outer periphery will be faster than the contact speed near the center.Such a bonding interface (1)
For example, if a device is manufactured using a bonded wafer (12) containing air bubbles (31), the air bubbles (31) will be removed during the heat treatment process.
1) rupture occurs, resulting in a decrease in device yield and the inconvenience of becoming a source of contamination in the process due to particles.

Therefore, in this example, the air bubbles (31) generated during bonding are pushed out from the bonding interface <i> by applying pressure from one or both sides of the bonded wafer (12>), and the bonding interface (A>) to obtain a highly reliable Sol substrate (16) with no air bubbles (31) at all. That is, by the above method, two sheets of
) are pasted together, the inclusion of air bubbles is confirmed by transmitting infrared rays, etc. At this time, as shown in FIGS. 12A and 12B, the bonding interface (j'
), if there are bubbles (31) in the wafer (12), use a roller press (41) as shown in FIG. 13 to move the roller (42) from one end surface of the wafer (12) to the other end surface as shown in FIG. Move while applying pressure. At this time, bubbles (3
1) moves as if being pushed by the roller (42>) and is finally pushed out from the bonding interface <i>, thereby obtaining a bonded wafer (12) completely free of air bubbles (31). If the pressure applied by the roller (42) is too high, there is a risk of cracking the wafer (12), so the pressure applied by the roller (42) should be 0.1 kg/
It is sufficient if it is equal to or greater than cut.

Also, something (buffer) to place under the wafer (12) (
43) is preferably a soft material, such as silicone rubber. In addition, the air bubbles (31) are expelled using a roller press machine.
It is preferable to carry out immediately after the bonding in step 11). This is because if this is done after the heat treatment after bonding the wafers (1) and (11), it will be impossible to push out the bubbles (31) because the bonding has been completed in areas other than the bubbles (31). It is from. Bonded wafer (1
The method for applying pressure to 2) is not limited to the roller press machine (41), but a jig (44) having a convex bottom surface may be used as shown in FIG. 15.

That is, the bonded wafer (12) is placed on a soft plate (for example, silicone rubber, etc.) (45), and the jig (4)
When pressure is applied from the center of the wafer (12) in 4), the air bubbles (31) are pushed out from the bonding interface (I2), and the air bubbles (31) are
A bonded wafer (12) completely free of 1) can be obtained. Note that the height h of the convex portion (44a) of this jig (44) is approximately 20 μm to 200 μm, and the size is preferably larger than the diameter of the wafer (12).

The above example shows a method for removing air bubbles (31) when they have entered the bonded wafer (12).
In this example, the following method is used to prevent air bubbles (31) from entering 12).

That is, as shown in FIG. 16A, two wafers (1)
and <11) are sucked into a vacuum suction chuck (not shown) made of an elastic material such as silicone rubber, and deformed into a convex spherical shape. In this state, the wafers (1) and (11) are brought into contact with each other from approximately the center. After that, while controlling the suction pressure of the vacuum suction check, both wafers (1) and (1) are removed by the vacuum suction check.
The wafers (1) and (11) are gradually brought into contact with each other up to their outer peripheries while being pressed against each other, and when the entire surfaces of the wafers (1) and (11) come into contact, the vacuum suction check is returned to normal pressure to complete the bonding.

According to this method, the contact speed near the center between wafers (1) and (11) and the contact speed near each outer periphery are almost the same, so that when bonding, as shown in FIG. 16B, , it is possible to obtain a bonded wafer (12) with no air bubbles mixed into the bonded interface (I).Here, bonding was performed while maintaining the vacuum of a vacuum suction check (not shown). However, as an alternative method, two wafers (1) and (11) deflected into a convex spherical surface are
) The pressure may be slowly returned to normal pressure at the point when the centers of the two areas begin to come into contact with each other. At this time, the wafers (1) and (11) are bonded together due to their self-restoring force, but even in this case, a bonded wafer (12) without air bubbles can be obtained. This is thought to be because the contact speed is slower at the outer periphery than in the normal case (see FIG. 11), so that air bubbles are not captured.

According to the method shown in FIGS. 13 to 16 above, since no air bubbles are mixed into the bonding interface (I!) of the bonded wafer (12), bubble bursting during subsequent heat treatment is prevented, and bubble bursting is prevented. This eliminates contamination of the heat treatment furnace due to contamination of the heat treatment furnace, improving the yield of the device and improving the reliability of the device.In particular, in the case of FIG. In order to prevent this in advance, the roller press machine (41
), jigs (44), etc. are not required, maintenance of the manufacturing equipment is reduced, and workability is improved.

〔Effect of the invention〕

In the method for manufacturing a semiconductor substrate according to the present invention, after bonding two wafers, the outer periphery of the two wafers is chamfered, so that the unbonded portion of the wafer outer circumference that occurs during bonding can be removed, and the subsequent When one wafer is thinned by polishing, it is possible to prevent chipping from occurring on the outer periphery of the wafer, thereby achieving high reliability of the semiconductor substrate and high yield of devices formed on the substrate.

In particular, since the chamfering described above is performed using a diamond wheel, and the rotation direction of the wafer and the diamond wheel are the same, it is possible to prevent grinding particles from getting into the space between the wafer and the diamond wheel that occurs during chamfering, and Chips can be prevented. Therefore,
It is possible to further improve the reliability of the semiconductor substrate and the yield of devices.

[Brief explanation of drawings]

Fig. 1 is a process diagram showing the method for manufacturing the SOI substrate according to this embodiment, Fig. 2 is an explanatory drawing showing chamfering processing, Fig. 3 is an explanatory drawing showing a specific example of the chamfering method, and Figs. 4 to 6 is an explanatory diagram showing the effect when the rotation directions of the wafer and the diamond wheel are different; FIGS. 7 and '58 are explanatory diagrams showing the effect when the rotation direction of the wafer and the diamond wheel are set in the same direction; 10 is an explanatory diagram showing the state of the wafer during selective polishing, FIG. 10 is an explanatory diagram showing a normal bonding method, FIG. 11 is an explanatory diagram showing another example of the normal bonding method, and FIG. 12A and B are a side view and a plan view showing the state of the wafers during bonding; FIG. Explanatory diagram,
FIG. 15 is an explanatory diagram showing another example of the bubble removal method,
Figure 6 is an explanatory diagram showing a bonding method that prevents air bubbles from entering.
FIG. 17 is a process diagram showing an SOI substrate according to a conventional example;
FIG. 8 is an explanatory diagram showing the state of a wafer during conventional selective polishing. (1) and (11>) are silicon wafers, (2) are convex parts, (3) are SiO□ films, (4) are polycrystalline silicon layers, (
12) is a bonded wafer, (15) is an island silicon region, (16) is an SOI substrate, (1) is a bonded interface, (
23) is a diamond wheel. Agent Hidemori Matsukuma This example: 2. Showing the process section Figure 2 1b Pre-requisition right of Shushuk
Tsukikuni Diagram 9 tZU Risome = Wader ＼ How to fix normal Kinutori U A2 Explanation National Policy 10 Diagram 3! The palm of the hand is attached to the six grips #11 and shown in Figure 11. figure

Claims (1)

[Claims] A method for manufacturing a semiconductor substrate by bonding one or two wafers, characterized in that after bonding the two wafers, the outer periphery of the two wafers is chamfered. . 2. The method of manufacturing a semiconductor substrate according to claim 1, wherein the chamfering is performed using a diamond wheel, and the chamfering is performed with the rotational direction of the wafer and the rotational direction of the diamond wheel being the same.