JPH09109010A - Method and device for polishing mirror surface of wafer periphery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct polishing in a shorter time and in a stablly smooth manner, compared with buff polishing, in polishing the mirror surface of a wafer periphery, by polishing first the peripheral part of the wafer by means of a tape carrying abrasive grains and then polishing the peripheral part of the wafer by means of abrasive. SOLUTION: A mirror surface polishing machine 1 is provided with a tape polishing device 2 and a buff polishing device 3 in order to conduct both tape polishing and buff polishing to a peripheral part of a wafer (W). The tape polishing device 2 is provided with a cassette installing part (A), a wafer positioning part (B), which puts in place the wafer (W) taken out of a cassette, a notch polishing part (C), which polishes a notch part of the wafer (W) an orifla polishing part (D), which polishes an orifla(mme) part of the wafer (W), and a periphery polishing part (E), which polishes the periphery of the wafer (W). ON the other hand, the buff polishing device 3 is provided with a wafer positioning part (G), which positions the wafer (W) sent from a delivery part, a notch polishing part, an orifla polishing part (I) and a periphery polishing part (J).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mirror polishing apparatus suitable for wafers, particularly silicon semiconductor wafers.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of silicon semiconductor wafers, a chamfering process for preventing chipping of the outer peripheral portion of the wafer, a lapping process for eliminating the thickness variation of the wafer, a crushed layer and a contaminated portion are eliminated. After the etching step, mirror polishing of the wafer is performed. This wafer mirror polishing process can be roughly divided into a wafer surface mirror polishing process and a wafer outer peripheral mirror polishing process.

By the way, an orientation flat (hereinafter referred to as "orientation flat") or a notch is provided at a position related to the crystal orientation of the wafer on the outer periphery of the wafer, and these orientation flats or notches are formed on the outer periphery of the wafer by an automated manufacturing apparatus. It is used to detect the position of. Therefore, even in the mirror polishing step of the outer peripheral portion of the wafer, it is necessary to mirror polish the orientation flat or notch and the other portion (hereinafter referred to as “outer periphery”).

Next, a conventional method for mirror-polishing the outer peripheral portion of a silicon single crystal wafer will be described. This method uses a buff made of foamed resin. In this method, the outer circumference and orientation flat of the wafer are mirror-polished with a buff having a groove (grooved groove) matching the shape of the outer circumference and orientation flat.
Use extremely fine SiO ₂ powder etc. for sodium hydroxide (Na
A polishing agent dissolved in an aqueous solution such as OH) is used. A disc-shaped buff is used for mirror-polishing the notch by this method. Of course, an abrasive is used in this case as well.

[0005]

By the way, as a method for etching a silicon semiconductor wafer, there have been conventionally used hydrofluoric acid,
The so-called acid etching was performed by immersing the wafer in a mixed solution of nitric acid and acetic acid, but it is difficult to maintain the flatness of the wafer after lapping with the acid etching, and it is costly to treat the waste solution of the etching solution after use. For this reason, recently, alkali etching has become the mainstream instead of acid etching. However, in the case of alkali etching, the back surface and outer peripheral surface of the wafer are roughened, so that the smoothness is impaired and back surface processing and outer peripheral surface processing are required. Particularly, in the outer peripheral surface processing, the surface roughness is set to a predetermined roughness or less. Therefore, there was a problem that the time required to achieve the target smoothness was several times longer than that of acid etching.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a mirror-polishing method and a mirror-polishing apparatus capable of performing stable polishing in a much shorter time than buffing and stably. Has an aim.

[0007]

In order to achieve such an object, the present inventor has conducted a study on not only polishing by buff but also tape polishing which is currently used in part. This tape polishing is polishing using a tape carrying abrasive grains. The specific method is to press the tape delivered from the tape delivery reel against the outer periphery of the wafer, and wind the tape with the tape take-up reel so that the new surface is always in contact with the processing part, and the tape is wound. By rotating the drum, the relative speed required for mirror polishing is applied between the tape and the wafer to polish the outer periphery of the wafer. In this research on buffing and tape polishing, there was a problem that buffing required several times as long as tape polishing to obtain a polished surface having a predetermined roughness or less, and the time also varied depending on the buff. . On the other hand, it has been found that the surface roughness obtained by tape polishing is limited.

[0008] Therefore, the present inventor, in mirror-polishing the outer peripheral portion of the wafer, polishes the outer peripheral portion using a tape carrying abrasive grains and then buffs it with an abrasive, that is, the tape. An attempt was made to use polishing and buffing together. As a result, it has been found that the mirror surface polishing which uses both tape polishing and buffing can reduce the surface roughness to a predetermined level or less in a much shorter time and more stably than the buffing.

FIG. 1 is a comparison of buffing and tape polishing, in which the vertical axis represents smoothness and the horizontal axis represents polishing time. As shown in FIG. 1, in the tape polishing, the time for polishing to a predetermined smoothness is short, but the obtained smoothness is limited, and in the buff polishing, the time for polishing to a predetermined smoothness is long. Moreover, it can be seen that the polishing time can be smoother than that of tape polishing, although the time varies depending on the buff. A tape having a smaller grain size is used toward the right side of FIG.

The present invention has been made on the basis of such knowledge, and after chamfering the outer peripheral portion of the wafer,
When the outer peripheral portion of the wafer is mirror-polished, the outer peripheral portion is polished with a tape carrying abrasive grains and then buffed with an abrasive.

According to another aspect of the invention, after chamfering the outer peripheral portion of a wafer and performing alkali etching, the outer peripheral portion of the wafer is mirror-polished, and the outer peripheral portion is polished with a tape carrying abrasive grains. After that, the buffing is performed using an abrasive.

Still another aspect of the present invention relates to a mirror polishing apparatus, which comprises a tape polishing apparatus for polishing the outer peripheral portion of a wafer by using a tape carrying abrasive grains, and a buffing polishing apparatus for polishing the outer peripheral portion of a wafer by using a polishing agent. And a buffing device that does this.

According to the above-mentioned means, before the outer peripheral portion of the wafer is polished by the buff, tape polishing having a polishing rate higher than that of the buff polishing can be performed. It will be shortened. Further, after polishing the outer peripheral portion of the wafer with the tape to some extent, buffing which can be performed more densely than the tape polishing can be performed, and therefore polishing with high smoothness becomes possible.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a mirror polishing apparatus according to the present invention. The mirror polishing apparatus 1 includes a tape polishing apparatus 2 and a buff polishing apparatus 3 so that the outer peripheral portion of the wafer can be subjected to tape polishing and buff polishing.

The tape polishing apparatus 2 has a cassette mounting portion A for mounting the cassette 4 containing the wafer W therein.
A wafer positioning part B for positioning the wafer W (FIGS. 3 and 4) taken out from the cassette 4, a notch polishing part C for polishing a notch N (FIG. 3) of the wafer W, and a wafer W It has an orientation flat polishing section D for polishing the orientation flat O (FIG. 4) and an outer peripheral polishing section E for polishing the outer periphery of the wafer W. Further, in this tape polishing apparatus 2, a loader 10 is provided in the cassette mounting portion A, and a wafer transfer device 11 is provided in the center. Also, the notch polishing section C and the orientation flat polishing section D
The notch polishing device 1 and
2, an orientation flat polishing device 13 and an outer peripheral polishing device 14 are provided.

As shown in FIG. 5, the loader 10 lifts and lowers a cassette 4 capable of holding a large number of wafers W in a stacked state (not shown), and takes out the wafers W one by one from the cassette 4. Wafers W that are equipped with a belt conveyor 10a and are held one by one by the belt conveyor 10a in order from the wafer W held under the cassette 4.
Can be taken out.

The wafer transfer device 11 is shown in FIGS.
As shown in FIG. 5, the rotary body 11a includes a rotating body 11a that is driven to rotate about a vertical axis by a motor (not shown), and four arms 11b provided on the rotating body 11a. The air cylinder (not shown) in FIG. 1 pushes outward with a predetermined force for a predetermined time. Further, a suction plate 11c is provided below the tip of each arm 11b as shown in FIG.
Each suction plate 11c is connected to a suction pump (not shown) through an air pipe (not shown) arranged in the arm 11b and the rotating body 11a. The suction plate 11c can be rotated by a motor 11d.

As shown in FIG. 7, the notch polishing device 12 is equipped with a rotary drum 30a and a tape support member 30b. Inside the rotary drum 30a, although not shown,
A reel for feeding the tape T, and the tape T
And a winding reel for winding up.
The tape T delivered from the delivery reel is temporarily guided to the outside of the rotating drum 30a and wound around the outer periphery of the rotating drum 30a in a spiral shape, but the intermediate portion thereof is located outside the rotating drum 30a. Further, the tip of the tape T is guided to the inside of the rotating drum 30a and wound around the winding reel. The rotating drum 30a is reciprocally rotated by a motor 30c,
The take-up reel (not shown) is rotationally driven by the motor 30d. This notch polishing device 12
Then, the tape T hung on the tape support member 30b is pressed against the notch N of the wafer W, and the motor 30d winds the tape T on the take-up reel while
The rotating drum 30a is reciprocally rotated by c and the notch N is polished by the tape T. At that time, the suction plate 11 is so constructed that the entire notch N can be polished.
It is preferable to rotate c back and forth. Further, the rotary drum 30a and the tape support member 30b are configured to be movable in a direction in which they can approach and separate from the notch N, and the tape T
It is preferable to be configured so as to be rotatable about a horizontal axis that passes through the contact portion between the notch N and the notch N and is orthogonal to the above direction.

The orientation flat polishing device 13 and the outer peripheral polishing device 14 have the same structure and are provided with a rotary drum 40a as shown in FIG. 8. The rotary drum 40a has a tape T (not shown). A reel for taking out the tape and a reel for taking up the tape T are provided. The tape T fed from the reel for feeding is once guided to the outside of the rotary drum 40a and wound around the outer periphery of the rotary drum 40a in a spiral shape.
The tip of the tape T is guided inside the rotary drum 40a,
It is wound around the take-up reel. The rotating drum 40a is reciprocally rotated by a motor 40c, and a winding reel (not shown) is rotationally driven by a motor 40d. In the orientation flat polishing device 13 and the outer peripheral polishing device 14, the tape T applied to the rotating drum 40a is pressed against the orientation flat O and the outer periphery of the wafer W, and the wafer W is wound on the winding reel by the motor 40d.
While winding up, the rotary drum 40 is driven by the motor 40c.
By rotating reciprocally a, the orientation flat O and the outer periphery are polished. It is preferable that the rotary drum 40a is configured to be rotatable about a horizontal axis that passes through the contact portion between the tape T and the orientation flat O or the outer periphery and is orthogonal to the above direction so that the entire chamfered portion can be polished.

In the wafer positioning section B, the wafer W is centered by a positioning device (not shown). Further, after the tape polishing is completed, the wafer W returned to the wafer positioning section B is not repositioned, but is sent to the delivery section F of the wafer W by means not shown.

The buffing apparatus 3 includes a wafer positioning section G for positioning the wafer W (FIGS. 3 and 4) sent from the delivery section F by means (not shown) and a notch N (FIG. 3) of the wafer W. The notch polishing section H for polishing, the orientation flat polishing section I for polishing the orientation flat O (FIG. 4) of the wafer W, the outer peripheral polishing section J for polishing the outer periphery of the wafer W, and the wafer W are stored. And a cassette mounting portion K for mounting the cassette 4 for mounting. Further, in the buffing device 3, a wafer transfer device 21 is provided at the center. Further, the notch polishing section H, the orientation flat polishing section I, and the outer peripheral polishing section J are provided with a notch polishing apparatus 22, an orientation flat polishing apparatus 23, and an outer peripheral polishing apparatus 24, respectively. Further, an unloader 25 is provided at the cassette mounting portion K.

The wafer transfer device 21 has substantially the same structure as the wafer transfer device 11, and as shown in FIG. 2, a rotor 21a which is driven to rotate by a motor (not shown) about a vertical axis, and this rotor. 21a, four arms 21b are provided, and each arm 21b is pushed outward by a predetermined force at a predetermined time by a pneumatic cylinder (not shown) inside the rotating body 21a. In addition, the suction plate 21 is provided below the tip of each arm 21b.
c is provided. Each suction plate 21c has an arm 21b.
And an air pipe (not shown) arranged in the rotating body 21a.
Through a suction pump (not shown). The suction plate 21c can be rotated by a motor (not shown).

As shown in FIG. 2, the notch polishing device 22 is provided with a disk-shaped foamed resin buff 22a. The buff 22a has a "U" -shaped arm 22b when viewed from above.
It is supported by. In this notch polishing device 22, the buff 22a is driven to rotate by a motor (not shown), and the outer periphery of the buff 22a is moved to the wafer W.
The notch N of the wafer W is polished by pressing it against the notch N and rotating the wafer W back and forth by a small angle.

As shown in FIG. 9, the orientation flat polishing device 23 is provided with a cylindrical resin buff 23a made of foamed resin. On the outer periphery of the buff 23a, a groove (formal groove) 23b for receiving the orientation flat O of the wafer W is provided. Buff 23
a is rotatably driven by a motor 23c and can be moved up and down by a lifting device (not shown). By pressing the inner surface of the groove 23b of the buff 23a against the orientation flat O of the wafer W, The orientation flat O of W is polished.

As shown in FIG. 10, the peripheral polishing device 24 is provided with a cylindrical resin buff 24a made of foamed resin. On the inner circumference of the buff 24a, a groove (conventional groove) 24b for receiving the outer circumference of the wafer W is provided. The buff 24a is rotatably driven by a motor 24c, and can be moved up and down by an elevating device (not shown) so that the inner surface of the groove 24b of the buff 24a is moved to the wafer W.
The outer periphery of the wafer W is polished by being pressed against the outer periphery of the wafer.

The unloader 25, as shown in FIG.
An elevating device (not shown) for elevating and lowering the cassette 4 capable of holding a large number of wafers W in a stacked state, and a belt conveyor 25a for accommodating the wafers W one by one in the cassette 4, are provided in order from the upper side of the cassette 4. The wafers W can be stored one by one by the belt conveyor 25a.

In the wafer positioning portion G, the wafer W is centered by a positioning device (not shown).

According to the mirror polishing apparatus 1 thus constructed, both tape polishing and buff polishing can be performed, and only one of the tape polishing and the buff polishing can be performed as necessary. When both the tape polishing and the buff polishing are performed, the surface roughness can be made equal to or less than the desired roughness in a much shorter time than the buff polishing and stably.

Although the embodiments of the invention made by the present inventor have been described above, the present invention is not limited to such embodiments, and various modifications can be made without departing from the scope of the invention.

[0030]

The effects of the typical ones of the present invention will be described. Before polishing the outer peripheral portion of the wafer by buffing, tape polishing can be performed at a polishing rate faster than that of buffing. The time required for smoothness is shortened. In addition, after polishing the outer peripheral portion of the wafer with tape to some extent, it is possible to perform buff polishing that allows more precise polishing than tape polishing, so it is difficult to polish with tape alone.
Polishing with a desired roughness or less is possible.

[Brief description of the drawings]

FIG. 1 is a table showing a comparison of smoothness and polishing time between tape polishing and buffing according to the present invention.

FIG. 2 is a plan view of the mirror polishing apparatus according to the embodiment of the present invention.

FIG. 3 is a plan view of a notched wafer.

FIG. 4 is a plan view of a wafer with an orientation flat.

FIG. 5 is a side view of the loader in the tape polishing apparatus according to the embodiment of the present invention.

FIG. 6 is a perspective view showing a part of a wafer transfer device in the polishing apparatus according to the embodiment of the present invention.

FIG. 7 is a perspective view of a notch polishing device in the tape polishing device according to the embodiment of the present invention.

FIG. 8 is a perspective view of an orientation flat polishing device and an outer peripheral polishing device in the tape polishing device according to the embodiment of the present invention.

FIG. 9 is a side view of the orientation flat polishing device in the buffing device according to the embodiment of the present invention.

FIG. 10 is a perspective view of an outer circumference polishing device in the buffing device according to the embodiment of the present invention.

FIG. 11 is a side view of the unloader in the buffing device according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mirror polishing device 2 Tape polishing device 3 Buff polishing device 4 Cassette 10 Loader 11 and 21 Wafer transfer device 12 and 22 Notch polishing device 13 and 23 Orientation flat polishing device 14 and 24 Peripheral polishing device 25 Unloader

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuka Kuroda 150 Odaira, Odakura, Saigo-mura, Nishishirakawa-gun, Fukushima Prefecture Shirakawa Laboratory, Shin-Etsu Semiconductor Co., Ltd. Oji Jono Koshi Nitta 596 Address 2 Naoetsu Electronics Industry Co., Ltd. (72) Inventor Masayoshi Sekizawa Niigata Prefecture Nakakubiki-gun Kikugi Village Oita Jono Koshi Nitta 596 Address 2 Naoetsu Electronics Co., Ltd.

Claims (3)

[Claims] 1. When mirror-polishing the outer peripheral portion of the wafer, after polishing the outer peripheral portion of the wafer with a tape carrying abrasive grains, the outer peripheral portion of the wafer is polished with a buff using an abrasive. A method for mirror-polishing a peripheral portion of a wafer, comprising: 2. A wafer outer peripheral portion is chamfered and alkali-etched, and then the outer peripheral portion of the wafer is mirror-polished. After polishing the outer peripheral portion of the wafer with a tape carrying abrasive grains, an abrasive is applied. A method for mirror-polishing an outer peripheral portion of a wafer, wherein the outer peripheral portion of the wafer is polished with a buff. 3. A tape polishing device for polishing the outer peripheral portion of a wafer using a tape carrying abrasive grains, and a buff polishing device for polishing the outer peripheral portion of the wafer with a buff using an abrasive. Mirror polishing equipment.