JPH10256195A - Silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon wafer which has mirror surfaces on both the front and rear surfaces and the front and rear sides of which can be distinguished easily without causing any problem of dust generation. SOLUTION: On the outer peripheral section of a silicon wafer 1 having mirror surfaces on both the front and rear surfaces, a front-side bevel 2a positioned on the front surface 2 side and a rear-side bevel 3a positioned on the rear surface 3 side are provided. The bevel 2a is formed to have a flat surface and the bevel 3a is formed to have a curved surface. Since the polishing angles of the bevels 2a and 3a are different from each other, the front side and rear side of the wafer 1 can be discriminated easily. When the surface roughness of the bevels 2a and 3a are made different from each other, the front and rear sides of the wafer 1 can also be discriminated easily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon wafer having mirror surfaces on both sides, and more particularly, to a silicon wafer whose front and back can be easily and easily distinguished.

[0002]

2. Description of the Related Art Conventionally, in order to mirror-polish the surface of a silicon wafer, a mechanochemical polishing method in which a physical element using an abrasive and a polishing cloth and a chemical reaction element using an alkali solution are generally used. Have been. In the mechanochemical polishing method, an alkaline polishing liquid containing silicon dioxide (SiO ₂ ) as a main component and having a pH of about 9 to 13 is generally used as a polishing agent. The mirror polishing is performed by rotating.

[0003] Such mirror polishing methods are typically represented by a single-side polishing method and a double-side polishing method. The single-side polishing method is a method in which silicon wafers are bonded one by one or a number of sheets to a polishing block at the same time, and only one side of the silicon wafer is mirror-polished. The double-side polishing method is a method in which both sides of the silicon wafer are simultaneously mirror-polished.

When these two methods are compared, as shown in FIG. 5, a double-sided mirror-polished silicon wafer mirror-polished by a double-sided polishing method is flatter than a single-sided mirror-polished silicon wafer by a single-side polishing method. It turns out that it is excellent. At the same time, as the demand for higher density and higher integration of VLSI and the like is increasing, the necessity of a double-sided mirror-polished silicon wafer having such a high flatness is increasing more than before.

However, a double-sided mirror-polished silicon wafer which is mirror-polished by the double-sided polishing method has a disadvantage that it is difficult to distinguish between the front and back sides. Conventionally, in order to solve such a defect, a method of marking the surface of a silicon wafer with a laser beam (laser marking) and using the laser marking as a mark to discriminate between the front and back sides is generally used.

[0006]

As described above, conventionally, laser marking is provided on the surface of a silicon wafer so that the front and back sides of a double-sided mirror-polished silicon wafer can be distinguished. However, in this method, since dust is generated from the marking portion, there is a problem that the dust causes a disconnection or the like at the time of lithography of the wiring and lowers the element yield.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and a silicon wafer having a mirror surface on both front and rear surfaces can easily and easily determine the front and rear surfaces without causing a problem of dust generation. It is intended to provide a wafer.

[0008]

According to the present invention, there is provided a silicon wafer having a mirror surface on both front and rear surfaces, wherein a front side bevel located on the front side of the silicon wafer and a rear side located on the back side of the silicon wafer are provided on the outer periphery of the silicon wafer. A silicon wafer provided with a side bevel, wherein a polishing angle of the front side bevel with respect to the front surface of the silicon wafer and a polishing angle of the rear side bevel with respect to the back surface of the silicon wafer are provided.

According to the present invention, in a silicon wafer having mirror surfaces on both front and back sides, a front side bevel located on the front side of the silicon wafer and a rear side bevel located on the back side of the silicon wafer are provided on the outer periphery of the silicon wafer. A silicon wafer characterized in that one of the front side bevel and the back side bevel is processed into a flat surface and the other is processed into a curved surface.

Further, according to the present invention, in a silicon wafer having mirror surfaces on both front and back sides, a front side bevel located on the front side of the silicon wafer and a rear side bevel located on the back side of the silicon wafer are provided on the outer periphery of the silicon wafer. ,
A silicon wafer characterized in that the front side bevel and the back side bevel have different surface roughness.

According to the present invention, the polishing angle of the front-side bevel provided on the outer peripheral portion of the silicon wafer with respect to the front surface of the silicon wafer and the polishing angle of the rear-side bevel provided on the outer peripheral portion of the silicon wafer with respect to the back surface of the silicon wafer Therefore, the front and back of the silicon wafer can be easily distinguished from each other by the difference in these polishing angles.

According to the present invention, one of the front bevel and the back bevel provided on the outer peripheral portion of the silicon wafer is processed into a flat surface and the other is processed into a curved surface. It is possible to prevent sharpening at the end of the bevel processed into a curved surface, and to more clearly recognize the difference in the polishing angle compared to a case where both are bevels processed into a flat surface. it can.

Further, according to the present invention, since the surface roughness of the front bevel and the rear bevel provided on the outer peripheral portion of the silicon wafer are made different, the front and back of the silicon wafer can be easily made due to the difference in glossiness. Can be determined.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment FIGS. 1 and 2 show a first embodiment of a silicon wafer according to the present invention. First, FIG. 1 shows a basic configuration of a silicon wafer 1. The silicon wafer 1
As shown in FIG. 1, a front-side bevel 2a having a front surface 2 and a back surface 3 and having an outer peripheral portion located on the front surface 2 side.
And a back side bevel 3a located on the back side 3 side. In the present embodiment, as shown in FIG. 2, the front-side bevel 2a is processed into a flat surface, and the rear-side bevel 3a
Is processed into a curved surface. That is, the polishing is performed so that the polishing angle of the front-side bevel 2a with respect to the front surface 2 and the polishing angle of the rear-side bevel 3a with respect to the rear surface 3 are different from each other.

Here, as for the polishing angle of the surface-side bevel 2a processed into a flat surface, as shown in FIG. , 45 ° or more, the boundary 4 (see FIG. 2) between the front-side bevel 2a and the rear-side bevel 3a becomes sharp and the possibility of causing chipping during the manufacturing process increases. Chipping causes dust and adversely affects the yield of the device.
Considering these, the polishing angle of the front side bevel 2a is 5
It is preferable that the angle is not less than 45 ° and not more than 45 °.

Next, a method for manufacturing a silicon wafer having such a configuration will be described.

First, single crystal silicon is pulled up by the CZ (Chokrasky) method and cut into several blocks.
Thereafter, the outer periphery is ground until the diameter of the block becomes about 150 mmφ, and then slicing is performed to form a plurality of silicon wafer prototypes. In each of these steps, a conventionally well-known method can be used.

Next, the back surface side bevel 3a of the outer peripheral portion of the silicon wafer thus prepared is machined and polished to bevel the surface so that the cross-sectional radius becomes r = 313 μm (round bevel). Processing). afterwards,
Front side bevel 2 located on front side 2 of silicon wafer 1
a is tapered at a polishing angle of 30 °.

Finally, after cleaning, lapping and etching are performed on the front surface 2, the rear surface 3 and the outer peripheral portion of the silicon wafer 1, the front surface 2 and the rear surface 3 of the silicon wafer 1 are polished by the above-mentioned mechanochemical polishing method. Thus, a double-sided mirror-polished silicon wafer having a diameter of 150 mmφ and a thickness of 625 μm is prepared.

Since the silicon wafer 1 thus manufactured has different polishing angles of the front-side bevel 2a and the rear-side bevel 3a, the front and back of the silicon wafer 1 can be easily distinguished by using this. . Both the front-side bevel 2a and the back-side bevel 3a of the silicon wafer 1 may be processed into a flat surface, but as compared with such a case, the silicon wafer 1 as shown in FIG.
Has the following advantages. That is, in the silicon wafer 1 shown in FIG. 2, one of the front-side bevel 2a and the back-side bevel 3a is a taper bevel processed into a flat surface, and the other is a round bevel processed into a curved surface. It is possible to prevent sharpness at the end portions 5 and 6 of the bevel processed into a curved surface shape, and it is possible to more clearly recognize the difference in the polishing angle.

Here, the front and back of the silicon wafer 1 can be visually determined from the difference in polishing angle between the front bevel 2a and the back bevel 3a, and can be automatically determined by the following device. Can also. For example, the discrimination can be made by an automatic discrimination device having a video camera and an image processing device for detecting the amount of inclination with respect to the front surface 2 or the back surface 3 corresponding to each of the front bevel 2a and the back bevel 3a of the silicon wafer 1. In this case, the difference in the amount of inclination can be detected by image recognition of the image processing apparatus, and the front bevel 2a and the back bevel 3a having different polishing angles can be determined.

As shown in FIG. 2, in the silicon wafer 1 in which the front bevel 2a and the back bevel 3a are processed into a flat surface and a curved surface, respectively, the polishing angle of the front bevel 2a and the back bevel 3a is About 3 each
0 ° and 0 °. As described above, since the two polishing angles have a difference in the amount of inclination sufficient to discriminate the front and back of the silicon wafer 1, the front and back of the silicon wafer 1 can be easily distinguished by the above-described automatic discrimination device.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, as shown in FIG. 4A, the front side bevel 2 provided on the silicon wafer 1
a and the surface roughness of the back side bevel 3a are different from each other. Here, the front bevel 2a and the back bevel 3
4 (b) and 4 (c) respectively show the enlarged surface shapes of a.

Next, a method of manufacturing a silicon wafer having such a configuration will be described.

First, a plurality of silicon wafer prototypes are prepared in the same manner as in the first embodiment.

Next, the outer peripheral portion of the silicon wafer is processed and polished with a grindstone having a grain size of # 1000 (average particle size of 10 to 20 μm), and the front-side bevel 2a and the rear-side bevel 3a are beveled into a curved surface. Then, after cleaning, lapping, and etching are performed on the front surface 2, the back surface 3, and the outer peripheral portion of the silicon wafer 1, the front bevel 2a located on the front surface 2 side of the silicon wafer 1 is mirror-finished by buff polishing. By processing under such conditions, the surface roughness of the front-side bevel 2a and the rear-side bevel 3a can be set to 1 to 3 nm and 0.1 to 0.2 μm, respectively.

Finally, the front surface 2 and the back surface 3 of the silicon wafer 1 are polished by the above-mentioned mechanochemical polishing method to produce a double-sided mirror-surface silicon wafer having a diameter of 150 mmφ and a thickness of 625 μm.

Since the silicon wafer 1 thus manufactured has a different surface roughness between the front side bevel 2a and the rear side bevel 3a, it is possible to easily distinguish the front and back of the silicon wafer 1 by using this. it can.

Here, the front and back of the silicon wafer 1 can be automatically determined by the following apparatus. For example, the discrimination can be made by an automatic discriminating apparatus having a gloss meter for detecting the gloss of the front bevel 2a and the back bevel 3a of the silicon wafer 1. In this case, a difference in glossiness can be detected by a photometer to determine the front bevel 2a and the back bevel 3a having different surface roughness.

As shown in FIGS. 4 (a), 4 (b) and 4 (c), a silicon wafer having a front surface bevel 2a and a back surface bevel 3a having surface roughnesses of 1 to 3 nm and 0.1 to 0.2 μm, respectively. In 1, the glossiness of the front bevel 2a and the rear bevel 3a is 1
When it is set to 00%, they are 10% and 100%, respectively.
For this reason, there is a difference in glossiness sufficient to determine the front and back of the silicon wafer 1, and the front and back of the silicon wafer 1 can be easily distinguished by the above-described apparatus.

In the silicon wafer 1 shown in FIGS. 4A, 4B and 4C, both the front bevel 2a and the back bevel 3a are beveled into a curved surface, but the front bevel 2a If the surface roughness of the back side bevel 3a is different, for example, the cross section may be processed to have another shape.

Comparative Example Next, a comparative example with respect to the above-described first embodiment and second embodiment will be described. As a comparative example, a silicon wafer with a laser mark on the surface of a double-sided mirror-polished silicon wafer obtained by subjecting the outer peripheral portion of a silicon wafer to normal bevel processing was used.

In such a silicon wafer, it was possible to determine the front and back of the silicon wafer by obtaining the position of the laser mark by image recognition. However, when particles on the surface of the silicon wafer were measured by a particle counter, dust was found around the laser-marked portion.

As described above, in this comparative example, the front and back of the silicon wafer can be detected, but dust which affects the yield of the element occurs, and a step of forming a laser mark is additionally required.

[0036]

As described above, according to the present invention, in a silicon wafer having mirror surfaces on both front and back surfaces, the front and back surfaces can be distinguished without using a laser mark or the like. Can be prevented, and the element yield can be improved. In addition, it is possible to manufacture a silicon wafer that can be easily distinguished from the front and back without special addition to a conventional processing apparatus, thereby providing a simple, inexpensive, high-quality silicon wafer with high flatness. Therefore, it is possible to sufficiently meet future demands for higher density and higher integration of VLSI and the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing the front and back and the bevel processing range of a silicon wafer according to the present invention.

FIG. 2 is a diagram schematically showing a cross section of a silicon wafer having a front side bevel and a back side bevel having different polishing angles.

FIG. 3 is a diagram showing a relationship between a polishing angle of the silicon wafer shown in FIG. 2 and chipping or visibility.

FIG. 4 is a diagram schematically showing a cross section of a silicon wafer having a front-side bevel and a rear-side bevel having different surface roughnesses.

FIG. 5 is a diagram showing a comparison of flatness between a single-sided mirror-faced silicon wafer and a double-sided mirror-faced silicon wafer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon wafer 2 Front surface 2a Front bevel 3 Back surface 3a Back bevel

Claims (4)

[Claims] 1. A silicon wafer having a mirror surface on both front and back surfaces, wherein a front side bevel located on the front side of the silicon wafer and a back side bevel located on the back side of the silicon wafer are provided on the outer periphery of the silicon wafer. A silicon wafer characterized in that a polishing angle of a side bevel with respect to the front surface of the silicon wafer and a polishing angle of the back side bevel with respect to the back surface of the silicon wafer are different. 2. A silicon wafer having mirror surfaces on both front and rear sides, wherein a front side bevel located on the front side of the silicon wafer and a rear side bevel located on the back side of the silicon wafer are provided on the outer periphery of the silicon wafer. A silicon wafer characterized in that one of the side bevel and the back side bevel is processed into a flat surface and the other is processed into a curved surface. 3. The polishing method according to claim 1, wherein a polishing angle with respect to a front surface or a back surface of the silicon wafer corresponding to the flat surface-processed bevel of the front surface bevel or the rear surface bevel is in a range of 5 ° to 45 °. 3. The silicon wafer according to claim 2, wherein: 4. A silicon wafer having mirror surfaces on both front and back sides, wherein a front side bevel located on the front side of the silicon wafer and a back side bevel located on the back side of the silicon wafer are provided on the outer periphery of the silicon wafer. A silicon wafer characterized in that the side bevel and the back side bevel have different surface roughness.