JPH0387012A - Adhered wafer and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent a wafer from chipping or cracking by chamfering the discontinuous end face of an adhered wafer and then rounding it. CONSTITUTION:An element board 11 is adhered to a supporting board 12 to form an adhered wafer 14. Then, the end face of the wafer 14 is chamfered. The board 11 is ground and polished. Thus, the discontinuous end face of the adhered boards 11, 12 is rounded to provide a rounded continuous face. Since corners to be formed by conventional sharp steps are eliminated, the wafer can be protected against cutting out or cracking.

Description

[Detailed Description of the Invention] [Summary] Bonded wafers and methods of manufacturing the same, particularly high quality silicon on insulators.
Regarding the structure of an SOI wafer and its manufacturing method for obtaining a SOI wafer (ulator, 5ol), in the manufacturing of bonded Sol, chipping of the element substrate and generation of dust due to sharp steps on the end face of the element substrate, and generation of dust on the element substrate. SO with a structure that can prevent cracking
The object of the present invention is to provide a bonded wafer I and a method for manufacturing the same, which is characterized in that a discontinuous end surface of a bonded wafer that occurs after bonding two or more wafers is made into a continuous rounded end surface by an edge grinding process. and a bonded wafer characterized in that the end surface of the bonded wafer obtained by bonding a substrate on which an element is to be formed and a substrate to support the substrate has a continuous curved surface.

[Industrial application field]

The present invention relates to a bonded wafer and a method for manufacturing the same, particularly a high quality silicon-on-insulator (Sil-icon).
on In5lator, 501) relates to the structure of an S○I wafer for obtaining a wafer and its manufacturing method.

In recent years, the field of use of semiconductors has expanded, and higher performance and higher quality are required. In particular, devices with higher speed and environmental resistance are required. For this reason, devices using SOI wafers have been provided, but they do not have the same crystallinity as ordinary silicon substrates (wafers), and the characteristics and yield of the formed elements are poor. There is a need for a method to improve crystallinity.

[Conventional technology]

For conventional SOI wafers, melt method, SI MO
X (Separation by 1wplante
d Oxygen) method, bonding method (bonding method), etc. are known.

However, it is said that it is extremely difficult to obtain high-quality crystals in both the melt method and the SIMOX method due to fundamental problems in their manufacturing methods. On the other hand, the bonding method has the advantage that a high quality Sol substrate can be obtained since high quality crystals are bonded together.

The melting method, which is advantageous for multilayer LSI structures, will be explained with reference to FIG. 4. As shown in the schematic perspective view of FIG. A plurality of islands 33 are formed. Although only six islands 33 are shown to simplify the drawing, more islands are actually formed over the entire surface of the wafer 31. A device is fabricated by forming a single crystal silicon region on this island 33.

FIG. 4(b) is a cross-sectional view of the island 33. In order to make a sor, polycrystalline silicon (polysilicon) 34 is deposited on the entire surface, and then a laser beam is irradiated to melt the polysilicon. As shown in FIG. 4(C), the melted polysilicon flows into the islands 33 and is then recrystallized to become a single crystal silicon layer 36.

In this melt method, crystal defects 37 shown by lines in the figure are generated from the Sin film 32. For example, if the island 33 has a size of 10 holes, the crystal defects 37 from the periphery are about 2.5**. As a result, there is a yield problem in that it is not possible to create single crystal silicon regions at approximately 374 cm in island size.

In the SIMOX method, referring to Figure 5, first of all, Figure 5 (
As shown in a), oxygen ions (○+) are implanted into the silicon substrate (wafer) 41 from above, and the silicon substrate 41
An oxygen implantation layer 42 (shown as crossed by short lines in the figure) is formed by implanting the oxygen implantation layer 42 approximately at the center of the depth.

Then, as shown in FIG. 5(b), 1200-125
When annealing is performed at 0°C, the oxygen implanted layer is made of Sin, and the layer 43
Therefore, 5OI44 is created above it.

However, with this method, oxygen 45 remains in the 5OI 44 as shown by the sandy area, and oxygen in silicon causes crystal defects, so it is difficult to obtain high quality SOI using the SIMOX method.

This led to the development of bonding SO■, which involves bonding an element substrate with an oxidized surface (the substrate on which the element will be formed) and its supporting substrate, and then grinding the surface of the element substrate. Then, the surrounding area is etched and finally polished.

[Problem to be solved by the invention]

The junction Sol will be explained in more detail with reference to FIG.
Since the CZ crystal 51 is rotated during pulling, many lines 52 are formed on the surface of the single-crystal silicon CZ crystal 51 pulled by the CZ method (Fig. 6(a)).
The surface of the CZ crystal 51 is chamfered by cylindrical processing to make the surface uniform and smooth. (Figure 6(b)). Then,
One side of the CZ crystal 51 is removed by orientation flat processing (orientation flat processing) as shown in FIG. 6(C).

Next, a wafer 53 (thickness approximately 0.111 mm) as shown in FIG. 6(d) is made by slicing, and the end surface of the wafer 53 is rounded by chamfering as shown in FIG. 6(e). Then, by lapping, a wafer 53 having a thickness of 500 to 700 μm is made as shown in FIG. 6(f), and then by polishing, the surface of the wafer 53 is made into a mirror surface. In addition to preventing the abrasive grains from stagnation by improving the wraparound of the grains, during the transportation and processing of the finished wafer, if the edges are not chamfered, the corners formed by the almost vertical end faces will be bent and the re-wafers will be removed. This is to avoid cracking.

Next, the surface of the chamfered wafer 53 is oxidized to form Si.
The NG film 54 is applied and two of the wafers 53 are bonded together as shown in FIG. 6(g). In the figure, the upper part is the element substrate 53a, the lower part is the support substrate 53b, and the size of the wafer and the thickness of the oxide film are exaggerated for illustration purposes. Since the surface of the wafer 53 has a mirror surface (mirror finish), the element substrate 53a and the support substrate 5
3b is laminated at room temperature. Next, hydrogen is removed from the moisture contained in the air taken into the SiO□ film 54 by annealing at 1200° C., and the element substrate 53a and the support substrate 53b are firmly bonded by the bond between oxygen and silicon.

Next, the element substrate 53a is polished from above by lapping, and as shown in FIG. 6(h), SiO! Approximately 540.2 to 10 μm of the entire film 54 is left on the element substrate 53a side. Then, a tape 55 serving as a mask material is pasted on the surface of the element substrate 53a, which has been mirror-finished by the rough polishing, in the next etching process.

Subsequently, the peripheral portions not masked by the tape 55 are etched by wet etching (FIG. 6(i)).

At this time, the thickness of the 5i02 film on the adhesive surface is 0.1 to 5 μm.
This Si0g film is the insulator of SOI.

Element substrate 53a after peripheral etching shown in FIG. 6(i)
When observing the wafer, the end surface is almost vertical and there is a sharp step, so if the upper corner hits another object due to vibrations that occur during wafer cleaning or transportation, the corner will chip. It has been experienced that the element substrate 53a cracks in some cases.

Furthermore, in the wrapping of the element substrate 53a shown in FIG. 6(h), since the side surface of the element substrate 53a is at an acute angle with respect to the adhesive surface 56 shown by the dotted line in the figure, the side surface of the element substrate 53a is used for wrapping. Because the abrasive particles accumulate and the flow of the abrasive particles is not uniform overall, problems were also experienced in which the rough lapping was not performed uniformly and the lapped surface did not become a perfect mirror surface.

Therefore, the present invention provides a Sol with a structure that can prevent chipping of the element substrate, generation of dust, and cracking of the element substrate due to the occurrence of sharp steps on the end face of the element substrate in the manufacture of the bonded Sol, and its manufacture. The purpose is to provide a method.

[Means to solve the problem]

In order to achieve the above-mentioned objective, the method for manufacturing a bonded wafer according to the present invention is to turn the discontinuous end face of the bonded wafer that occurs after bonding two or more wafers into a continuous rounded end face by an end face grinding process.

In the method for manufacturing a bonded wafer of the present invention, the edge of the bonded wafer may be ground, and then the substrate on which elements are to be formed may be thinned, or the bonded wafer may be further polished after the edge of the bonded wafer is ground. You can. The substrate on which the element is to be formed may be thinned by polishing, or by grinding and polishing.

In the method for manufacturing a bonded wafer of the present invention, the substrate on which the elements of the bonded wafer are to be formed may be made into a thin film, and then the edge of the bonded wafer may be ground, and the bonded wafer may be further polished after the edge of the bonded wafer is ground. It may be. The substrate on which the element is to be formed may be thinned by polishing, or by grinding and polishing.

In order to achieve the above object, the bonded wafer according to the present invention is obtained by bonding a substrate on which elements are to be formed and a substrate to support the substrate, and the end surface of the bonded wafer has a continuous curved surface.

In the bonded wafer of the present invention, the substrate on which elements are to be formed and the substrate to support the substrate may be bonded via an insulating film, and the end surface of the bonded wafer may be mirror-finished. This may be the case.

[Effect]

FIG. 2 is a diagram showing the principle of the present invention. First, as shown in FIG. (referred to as a supporting substrate) 12 to form a bonded wafer 14.

Next, as shown in FIG. 2(b), the end face of the bonded wafer 14 is chamfered. Subsequently, the element substrate 11 is shown in FIG.
) Grind and polish as shown. Here, the case is that the end face of the bonded wafer 14 is chamfered to form a continuous curved surface, and then the element substrate 11 is made into a thin film. You can.

In other words, according to the present invention, the discontinuous surface formed by the end surfaces of the bonded element substrate 11 and support substrate 12 (bonded wafer) becomes a continuous rounded surface by rounding the end surfaces, and the discontinuous surface formed by the end surfaces of the bonded element substrate 11 and the support substrate 12 (bonded wafer) becomes a continuous rounded surface, and the discontinuous surface formed by the end surface of the bonded element substrate 11 and the support substrate 12 (bonded wafer) becomes a continuous rounded surface, and the discontinuous surface formed by the end surface of the bonded element substrate 11 and the support substrate 12 (bonded wafer) becomes a continuous rounded surface. Since there are no corners to be formed, chipping or cracking can be prevented even if the end face comes into contact with another object due to vibration during cleaning and transportation of the bonded soI, and furthermore, polishing of the element substrate can be performed without any trouble, and the element can be easily polished. The surface of the substrate becomes a highly accurate mirror surface.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to illustrated embodiments.

A first embodiment of the present invention is shown in cross-sectional views in FIGS. 1(a) to (c), and in these figures, the size of the wafer and the thickness of the oxide film are exaggerated and schematically illustrated for the sake of explanation. shown. The end faces of the element substrate 11 and the support substrate 12 are each chamfered, and a Si2 film 13 having a thickness determined depending on the type of element to be formed is formed on each surface. Generally, the combined film thickness of two 5in2 films 13 is 0.1 to 5.
．． It is set within the range of 0 μm. These substrates are first mechanically bonded at room temperature as in the case of the conventional example, and then annealed at 1200°C to remove hydrogen from the moisture taken into the film 13 and to remove oxygen and silicon. The bonded wafer 14 is firmly bonded by bonding.

In this state, the end surface formed by the two substrates becomes a discontinuous surface (FIG. 1(a)).

Next, as shown in FIG. 1(b), the end faces of the bonded wafer 14 of the two substrates are chamfered by an end face grinding process.
Turn a discontinuous end face into a continuous curved end face.

In order to chamfer the discontinuous end face of the bonded wafer 14, use a known grinder shown in FIG. The chuck 21 is moved in the direction of the arrow by the arm 23 to grind the end face. The arm 23 is connected to a drive source (not shown), and this drive source automatically operates the arm 23, so that the chamfering work is mechanically automated.

Next, as shown in FIG. 1(C), the element substrate 11 is ground and polished (roughing). In this lapping, the side surface of the element substrate 11 forms an obtuse angle with respect to the bonding surface 15 of both substrates, so that the flow of abrasive grains is smoothly performed without being obstructed.
The mirror surface is formed uniformly and precisely over the entire surface of the mirror.

Note that the grinding here includes, for example, cutting with a diamond whetstone, and the polishing includes, for example, supplying an aqueous Adan-based solution and colloidal millipower to the polished surface as an abrasive, and using a polishing cloth (polyester nonwoven fabric, etc.). ).

The first embodiment described above is an example in which the element substrate 11 and the support substrate 12 are each chamfered, but in the second embodiment of the present invention, each of them is chamfered as shown in FIG. 1(d). The element substrate 11a and the support substrate 123 that are not used are used. In this second embodiment as well, when the bonded wafer 14 is chamfered by the end face grinding process, the structure shown in FIG. 1(b) is obtained, and by grinding and polishing it, the bonded Sol shown in FIG. 1(c) is obtained. .

In the third embodiment of the present invention, as shown in FIG. 1(e),
It uses a chamfered support substrate 12 (element substrate 11) and a non-chamfered element substrate 11a (support substrate 12a), and when this bonded wafer is chamfered by edge grinding processing, the structure shown in FIG. 1(b) is also obtained. Similar to the first embodiment, the structure shown in FIG. 1(c) is obtained by grinding and polishing.

In the above example, both the element substrate and the support substrate were surface oxidized, but since the support substrate 12 only supports the element substrate, an insulating film (SiOx
Surface oxidation of one of the wafers can be omitted if the thickness of the wafer (film) has sufficient insulating properties for the elements formed on the element substrate. Furthermore, since the element substrate and the support substrate may be chamfered or not chamfered, the following combinations are possible.

(Tree pages, blank spaces below) An example in which the surface of the element substrate of the fourth embodiment is oxidized is shown in Fig. 1<f), in which case the wafer is shown in Fig. 1 (g
), , , (h) are chamfered by end face grinding treatment, ground and polished. Further, examples in which only the surface of the support substrate is oxidized are shown in FIGS. 1(i), (j), and (k).

In the fifth embodiment, as shown in FIG. 1(N), an element substrate 11a (support substrate 12a) whose surface is oxidized and whose surface is not chamfered and a support substrate 12a (device substrate 11a) whose surface is not chamfered are used. When this bonded wafer is chamfered by edge grinding process, it is shown in Fig. 1(g) (Fig. 1(j)).
)) is also ground and polished as shown in Figure 1 (h).
The structure shown in FIG. 1(k) is obtained.

The sixth embodiment is a case where only one side is chamfered and only one side is surface oxidized, as shown in FIG. 1(m) and (n). When the bonded wafer is chamfered, ground, and polished by edge grinding, the structure shown in FIG. 1(h) is obtained, and when the bonded wafer shown in FIG. The structure shown in Figure (k) is obtained.

In the first to sixth embodiments described above, at least one of the element substrate and the support substrate has an oxide film and the adhesive surface has an oxide film, but the element substrate and the support substrate do not have a co-oxide film. This may also be the case with a bonded wafer in which objects are bonded together. In this case, if the support substrate has a large number of defects and the element substrate has almost no defects, the gettering ability can be improved more than when the bonding surface has an oxide film. Each aspect is shown below.

(This page, blank spaces below) In the seventh embodiment, as shown in FIG. 1(o), a bonded wafer in which both the element substrate tJjE 11 and the support substrate 12 are chamfered is bonded to a bonded wafer as shown in FIGS. 1(p) and (q). This is the case where chamfering, grinding, and polishing are performed by end face grinding treatment in this order.

The eighth embodiment uses an element substrate 11a and a support substrate 12a that are not chamfered, as shown in FIG. In this case, only one of them is chamfered, and when both are chamfered by end face grinding, the structure shown in FIG. 1(p) is obtained, and when further grinding and polishing is performed, the structure shown in FIG. 1(q) is obtained.

In the first to ninth embodiments, a case will be described in which a supporting substrate and an element substrate are bonded, chamfering is performed by end face grinding processing to make a discontinuous end face into a continuous curved surface, and then the element substrate is ground and polished. However, as shown in FIGS. 1 (1) to (V), after grinding and polishing the element substrate 11 of the bonded sea urchin fly 4 (this polishing may be performed after the next chamfering), chamfering by end face grinding processing is performed. It may also be the case that the In this case, bonded wafers whose surfaces are oxidized and chamfered are used, but this manufacturing method can be applied to the bonded wafers of each aspect of the second to ninth embodiments. With this method, the chamfered shape of the substrate becomes symmetrical on the front and back surfaces, and a greater effect on preventing cracking and chipping can be expected.

Furthermore, in each of the embodiments described in FIG. 1 above, the discontinuous end face of the bonded wafer is chamfered by end face grinding processing to form a continuous curved surface, but after this end face grinding processing, further polishing is performed. It is also possible to create a mirror surface.

According to the present invention, as shown in FIG. It may be a piece that does not protrude beyond the end face of 13, and in this case, it can be made more difficult to peel off than a piece that protrudes.

〔Effect of the invention〕

As described above, according to the present invention, in the method for manufacturing bonded S○■, chipping and cracking can be prevented by chamfering and rounding the discontinuous end face of a bonded wafer made by bonding two wafers together. This not only reduces the generation of foreign matter and reduces defects and pattern failures due to the generation of dust, but also has the effect that the grinding and polishing of the element substrate can be performed with high precision by chamfering the bonded wafer.

[Brief explanation of drawings]

Figures 1 (a) to (W) are cross-sectional views of embodiments of the present invention, Figure 2 is a cross-sectional view explaining the present invention in detail, Figure 3 is a view showing the chamfering process, and Figure 4 is a view showing the melt method. (a) is a perspective view, (b) and (C) are cross-sectional views, Fig. 5 is a cross-sectional view showing the SIMOX method, and Fig. 6 is a view showing the bonding SOx method. ) is a front view of the CZ crystal, (b) is a front view of the CZ crystal after cylindrical processing,
(c) is a front view of the CZ crystal after orientation flat processing, (d) ~
(f) is a perspective view of the wafer, and (g) to (i) thereof are cross-sectional views of the bonded wafer. 11, 11a...Element substrate 12.12a...Support substrate 13...Sin, film, 14...Bonded wafer, 15... Adhesive surface, 21... Chunk, 22... Grind surface, 23... Arm, 51... CZ crystal, 52... Line, 53...Wafer, 53a...Element substrate, 53b...Support base, 54...Si0g film, 55...Tape, (Substrate on which the element is to be formed), (Substrate on which the element substrate is to be supported) 56... Adhesive surface. Figure 2

Claims (10)

[Claims] (1) Two or more wafers (11, 12, 11a, 12a
) A method for manufacturing a bonded wafer, characterized in that the discontinuous end surface of the bonded wafer (14) produced after bonding is made into a continuous rounded end surface by an edge grinding process. (2) The method for manufacturing a bonded wafer according to claim 1, characterized in that the bonded wafer (14) is subjected to end face grinding, and then the substrate (11, 11a) on which elements are to be formed is thinned. (3) The method for manufacturing a bonded wafer according to claim 2, further comprising polishing the bonded wafer (14) after the end face is ground. (4) The method of manufacturing a bonded wafer according to claim 2 or 3, characterized in that the thinning of the substrate (11, 11a) on which the element is to be formed is performed by polishing, or by grinding and polishing. (5) The substrates (11, 11a) on which the elements of the bonded wafer (14) are to be formed are thinned, and then the bonded wafer (14) is formed into a thin film.
2. The method of manufacturing a bonded wafer according to claim 1, further comprising performing end face grinding of the bonded wafer. (6) The method for manufacturing a bonded wafer according to claim 5, further comprising polishing the bonded wafer (14) after the end face is ground. (7) The method for manufacturing a bonded wafer according to claim 5 or 6, characterized in that the substrate (11, 11a) on which the element is to be formed is thinned by polishing, or by grinding and polishing. (8) The end face of the bonded wafer (14) obtained by bonding the substrate (11, 11a) on which elements are to be formed and the substrate (12, 12a) that should support the substrate has a continuous curved surface. bonded wafer. (9) The substrate (11, 11a) on which the element is to be formed and the substrate (12, 12a) that should support the substrate are connected to the insulating film (13).
9. The bonded wafer according to claim 8, wherein the bonded wafer is bonded via a. (10) The bonded wafer according to claim 8, wherein the end surface of the bonded wafer (14) is a mirror surface.