JP2002217149A - Wafer polishing apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer polishing apparatus and method that can stably polish wafers and carry out a uniform dressing of polishing cloths simultaneously and can improve qualitative stability and productivity of wafers although a carrier does not rotate. SOLUTION: In the wafer polishing apparatus in which wafers 10 are polished by polishing cloths 14a, 16a attached on rotating platens 14, 16 after the wafers 10 are set up in wafer holding holes 2 on a carrier 1, dressing rings 4 are fitted in the wafer holding holes 2 so as to turn freely, and the wafers 10 are set up inside the dressing rings 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus and a method for polishing a wafer used as a semiconductor substrate material.

[0002]

2. Description of the Related Art Conventionally, in the production of a silicon wafer used as a semiconductor substrate material, a single crystal ingot is formed by using a Czochralski (CZ) method, a floating zone (FZ) method, or the like. A crystal growth process to be manufactured, a slice process of slicing a single crystal ingot to obtain a thin disk-shaped wafer, and a chamfering of an outer peripheral portion of the wafer obtained by the slicing process in order to prevent cracking or chipping. Process, a lapping process for flattening the wafer, an etching process for removing processing distortion remaining on the chamfered and wrapped wafer, and polishing (polishing) for mirror-polishing the wafer surface (main surface).
And a cleaning step of cleaning the polished wafer and removing abrasives and foreign matter adhering thereto. In addition to these steps, steps such as a heat treatment step are added, the same steps are performed in multiple stages, and the order of the steps is changed.

Among these steps, various types of polishing apparatuses are known in the polishing (polishing) step.
For example, there is a two-way simultaneous polishing apparatus of the four-way type as a wafer polishing apparatus having relatively high accuracy and capable of simultaneously polishing both sides of the wafer. In this device, the upper surface plate and the lower surface plate rotate in opposite directions, and the carrier sandwiched between the upper and lower surface plates engages with the sun gear at the center of the surface plate and the internal gear located around it while rotating. This is a device that revolves in the direction of rotation of the lower platen so that a workpiece in the carrier can be moved in four directions.
JP-A-11-10530).

However, with the recent increase in the diameter of wafers,
In this four-way system, there is a problem that the size of the apparatus is increased, and the installation space and parts of the apparatus are also increased. Therefore, a double-sided simultaneous polishing apparatus instead of the four-way system has been developed recently. For example, JP-A-10-202
Japanese Patent Application Publication No. 511 discloses an apparatus for performing polishing while rotating the carrier in a small turning motion without rotating. This apparatus can stably move the carrier with a simple configuration, can perform good wafer polishing, can reduce the size of the apparatus, and can suitably polish even a large-diameter work. It has the advantage of being able to do so.

[0005] In polishing a wafer, it is important to keep the quality of the polished wafer constant. The quality of the wafer is greatly affected by a change over time of the polishing cloth (mainly, clogging of the polishing cloth and a decrease in the compressibility of the polishing cloth). Therefore, in order to recover the function of the polishing pad, dressing of the polishing pad surface is performed periodically. The dressing is to adjust the polishing cloth surface using a dressing member (dresser) made of ceramics or diamond. Conventionally, such a dressing process has
The polishing apparatus is stopped, a dedicated dressing member is set in the apparatus, a load is applied under the same conditions as when polishing, and dressing is performed using an abrasive or the like.

[0006]

However, since the apparatus is completely stopped as described above, there is a problem that the operation rate of the apparatus is reduced and the productivity is reduced. In order to solve this problem, a polishing apparatus has been developed in which the carrier itself has a dressing function and performs dressing while polishing (see Japanese Patent Application Laid-Open No. 11-10530). In this apparatus, polishing is performed while uniformly dressing the polishing cloth during rotation of the carrier. Such dressing needs to be performed as uniformly as possible in the plane of the polishing pad. This is because if the dressing differs depending on the location, a difference in the polishing rate or the like occurs, and the quality of the wafer cannot be stabilized.

A carrier as disclosed in Japanese Patent Application Laid-Open No. H11-10530 is effective in a four-way type double-side polishing apparatus, but the carrier does not rotate. For example, it is described in Japanese Patent Application Laid-Open No. H10-202511. There is a problem that such a type of polishing apparatus does not work effectively. This is because in a polishing method in which the carrier itself does not rotate, a difference occurs in the relative movement distance depending on each part of the carrier, and a difference occurs in the dressing effect. Therefore, in the polishing method in which the carrier is not rotated, it is difficult to dress the polishing cloth uniformly even if the dressing member is provided on the carrier itself.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and enables stable polishing and uniform dressing of a polishing cloth without rotation of a carrier, stabilization of wafer quality and production. It is an object of the present invention to provide a polishing apparatus and a polishing method for a wafer which can improve the performance.

[0009]

In order to solve the above problems, a wafer polishing apparatus according to the present invention sets a wafer in a wafer holding hole of a carrier, and uses a polishing cloth attached to a rotating platen to polish the wafer. In a wafer polishing apparatus for polishing a main surface, a dressing ring is fitted into the wafer holding hole, and the wafer is set inside the dressing ring.

According to the invention, the dressing ring and the polishing cloth come into frictional contact with each other during wafer polishing by the surface plate,
Dressing of the polishing cloth is always performed. In particular, the portion used for polishing the wafer can be surely dressed. The dressing ring is fixed or rotatable on the carrier. In particular, if the dressing ring is rotatably fitted in the wafer holding hole, the turning force of the dressing ring will be applied by the rotation of the platen, and the dressing ring will rotate in any direction in the wafer holding hole, and evenly spread the abrasive. The polishing cloth can be dressed. As described above, since the dressing is performed while polishing, it is not necessary to stop the apparatus and perform the dressing, and the productivity is improved. Also, since the wafer also rotates inside the dressing ring during polishing,
The wafer can also be polished with high flatness.

Further, the carrier is mounted on a turning mechanism that makes a turning motion without rotating on a plane parallel to the plane of the carrier. According to this invention, the polishing pad can be uniformly dressed by the function of the dressing ring even in a polishing apparatus in which the carrier does not rotate.

Further, the dressing ring is characterized in that a plastic protective material is provided inside the ring-shaped main body. According to this invention, since the wafer protection member having a small coefficient of friction is formed inside the dresser, the wafer can freely rotate inside the dressing ring without damaging the wafer.

Further, a groove is formed on a surface of the dressing ring which contacts the polishing cloth. According to this invention, the grooves form irregularities on the surface of the dressing ring, so that the abrasive is uniformly diffused and the dressing effect is improved.

The present invention also provides a method of polishing a wafer, comprising: setting a wafer in a wafer holding hole of a carrier; and polishing the main surface of the wafer with a polishing cloth attached to a rotating platen. A dressing ring is fitted into a wafer holding hole, a wafer is set inside the dressing ring, and the main surface of the wafer is polished with a polishing cloth by rotating the platen, and the polishing cloth is dressed with the dressing ring at the same time. And According to the invention, since the dressing is performed while the wafer is being polished, it is not necessary to stop and dress the apparatus, and the productivity is improved, and the wafer is rotated during the polishing, so that the wafer is polished with high flatness. Becomes possible. Especially when the dressing ring is rotatably fitted into the wafer holding hole, the dressing effect is also improved,
The wafer is also easy to rotate, which is preferable. Further, the present invention is characterized in that the carrier is rotated so as not to rotate on a plane parallel to the plane of the carrier. According to this invention, the abrasive cloth can be dressed uniformly by the function of the dressing ring even if the polishing cloth is swirled so as not to rotate on a plane parallel to the plane of the carrier.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a wafer polishing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
Unless otherwise specified, shapes, relative arrangements, and the like are not intended to limit the scope of the present invention, but are merely illustrative examples.

FIGS. 1 and 2 show one embodiment of a wafer polishing apparatus according to the present invention, and show a double-side polishing apparatus for polishing a silicon wafer which is a plate-like work.
This double-side polishing apparatus sandwiches a carrier 1 provided with a wafer holding hole 2 from above and below, and also moves an upper platen 14 and a lower platen 16 which are moved relative to the wafer 10 and polished.
And A polishing cloth 14a, 16a is attached to each surface of the upper and lower stools 14, 16, and a polishing surface is formed by the polishing cloth 14a, 16a (see FIG. 2). The wafer 10 is set in a dressing ring 4 (to be described later) loosely fitted in the circular holding hole 2, and the wafer 1 is set in the dressing ring 4.
0 can be freely rotated.

The carrier 1 is caused to make a circular motion (rotational motion) that does not rotate in a plane parallel to its surface, and to give a circular motion to the wafer 10 sandwiched between the upper surface plate 14 and the lower surface plate 16. A mechanism (turning mechanism) 20 is provided. The circular movement mechanism 20 of the carrier 1 has the following configuration. That is, it has a ring-shaped carrier holder 22 composed of a ring main body 22a and a holding ring 22b, and the outer edge of the circular carrier 1 is held by the carrier holder 22 (see FIG. 2).

An eccentric shaft 24a of a drive wheel 24 constituting an arm of a crank mechanism is connected to each of four bearing portions 22c protruding from the outer peripheral surface of the carrier holder 22. The eccentric shaft 24 a is provided eccentrically with respect to a drive shaft 24 b which is parallel to the axis L of the upper and lower platens 14 and 16 and is fixed to the lower center of the drive wheel 24. The eccentric shaft 24a is connected to the bearing 2 of the carrier holder 22.
2c is rotatably inserted. Thus, the eccentric shaft 24a, the drive wheel 24, and the drive shaft 24b constitute a crank mechanism. The drive shafts 24 are arranged at four positions between the base 30 and the carrier holder 22, and the drive shafts 2
A sprocket 25 is attached to 4b, and a timing chain 28 is wound around these sprockets 25. The sprocket 25 is driven by a gear 32 of a motor 31. 35 is the upper platen 14
, A driving means (drive motor) for the upper stool 14, and a driving means (drive motor) for the lower stool 16.

Next, the operation of the polishing apparatus will be described. Eccentric shaft 24a on holder 22 side centering on drive shaft 24b
Is rotated so that the carrier holder 22 makes a circular motion that does not rotate with respect to the base 30. As a result, the carrier 1 rotates eccentrically from the axes of the upper and lower platens 14 and 16 (circular motion that does not rotate). The radius of the circular motion is the same as the distance between the eccentric shaft 24a on the carrier holder 22 side and the drive shaft 24b (the eccentric distance M). Accordingly, all points of the carrier 1 are in a motion of drawing the same small circle locus.

FIGS. 3 and 4 show one configuration example of the carrier 1 and the dressing ring 4 used in the above double-side polishing apparatus. In the figure, a plurality of carriers 1 (5 in the figure) are formed of a disc-shaped carrier body 3 made of a high-strength material such as glass epoxy (epoxy glass, sometimes referred to as EG) as an epoxy resin / glass fiber laminated material. Wafer holding holes 2 are formed. The wafer holding hole 2 is formed sufficiently larger than the diameter of the wafer 10 to be polished, and a ring-shaped dressing ring 4 for dressing a polishing pad is rotatably fitted into the holding hole 2.

The dressing ring 4 is made of alumina,
It is composed of a ring-shaped main body 4a made of ceramics such as zirconia and a protective material 4b fixed inside. Since the protective member 4b is a portion that comes into contact with the wafer 10, a hard plastic having a small coefficient of friction, such as nylon, is used to prevent the wafer 10 from being damaged.

The thickness of the carrier 1 depends on the wafer 1 to be polished.
0 (preferably approximately the same as the finished thickness of the wafer or within -50 μm (0 to −50 μm).
m), and the dressing ring 4 is made substantially the same as or slightly thicker than the finished thickness of the wafer 10. Preferably, it is about ± 30 μm with respect to the finished thickness of the wafer. The width (radial thickness) of the dressing ring 4 may be appropriately selected depending on the problem of strength and the dressing effect, but is preferably about 5 mm to 30 mm.

As described above, the rotatable dressing ring 4 is provided in the portion of the carrier 1 at the wafer holding hole 2, so that the dressing ring 4 and the polishing cloths 14a and 16a are brought into frictional contact during wafer polishing. The dressing is always performed, and even if the carrier 1 does not rotate, the dressing ring 4 is rotated by the rotation of the upper and lower stools 14 and 16 to rotate in an arbitrary direction in the wafer holding hole 2. The polishing pad can be dressed uniformly while the agent is diffused. As described above, since the dressing is performed while polishing, it is not necessary to stop the apparatus and perform the dressing, and the productivity is improved.
Further, since the wafer 10 also rotates during polishing, the wafer can be polished with high flatness. In this case, since the wafer protection member having a small coefficient of friction is formed inside the dresser, it is possible to perform polishing without adversely affecting the wafer.

FIGS. 5 and 6 show another example of the structure of the dressing ring 4 provided on the carrier 1, in which grooves 5 are formed on the front and back of the dressing ring 4 so as to face in the radial direction. With this structure, the surface of the dressing ring 4 is formed with irregularities, whereby the abrasive is more uniformly diffused and the dressing effect is improved. In addition,
The number, groove width, depth, and the like of the grooves 5 are arbitrary. Hereinafter, an example in which the carrier 1 using the dressing ring 4 is mounted on the double-side polishing apparatus shown in FIGS. 1 and 2 and polishing is actually performed will be described.

[Embodiment] The diameter is 1150 mm and the thickness is 7
Eight wafer holding holes 2 were formed in a glass epoxy disk (carrier body 3) of 00 μm. Each wafer holding hole 2 has a diameter of 240 mm, and an inside diameter of 23 mm.
A dressing ring 4 having a diameter of 9 mm and an inner diameter of 203 mm (a thickness of 720 μm) was loosely inserted. The material of the body 4a of the dressing ring 4 is made of alumina ceramic (about 17 m wide).
m), and a nylon protective material 4b (approximately 1
mm). In the dressing ring 4, 36 grooves 5 each having a width of 2 mm and a depth of 100 μm facing in the radial direction were formed at equal intervals on both the front and back surfaces in contact with the polishing pad. The wafer 10 having a diameter of 200mm on the inside of the respective dressing ring 4 charged eight, using a suba600 commercially available from Rodel Nitta Corp. as a polishing cloth, in order polishing pressure 250 g / cm ^2, and containing colloidal silica Polished with an alkaline abrasive, and finished to 7
The thickness was 25 μm.

After repeatedly polishing a plurality of batches (eight wafers as one batch) of wafers repeatedly with the same polishing cloth,
0 was confirmed to be stable. FIG. 7 shows the relationship between the number of polishing batches, the polishing rate, and the flatness. In FIG. 7, curve A indicates the polishing rate (polishing rate), curve B indicates the quality of the wafer 10 (GBIR), and curve C indicates the quality of the wafer 10. (SB
IR).

Here, GBIR (Global Bac)
k Ideal Range has one reference plane in the wafer plane, and is usually defined as the width of the maximum and minimum positional displacements with respect to this reference plane, and is a conventional customary specification of TTV (total thickness). Deviation). FIG. 7 shows the average value of each batch (the average value of eight wafers). In addition, SBIR (Site Back Ideal)
(Range) corresponds to LTV frequently used in the past. When the back surface of the wafer is used as a reference plane, and at each site, the plane including the center point of the site is used as the focal plane, the sum of the absolute values of the maximum displacements on the + side and the − side from the in-site focal plane is calculated for each site. It is evaluated every time. In this experimental example, evaluation was made in a region where the size of the site was 25 mm × 25 mm, and the maximum value (SBIRmax) of all the sites evaluated in one wafer surface was obtained. This is also the average value of each batch (average SBIRmax value of 8 wafers)
It is shown in. As can be seen from the figure, the polishing rate (polishing rate) is stable even after 10 batches of polishing, and the quality (GBIR, SBIR) of the wafer 10 is also stable.

When a conventional carrier having no dressing ring 4 is used and polishing is continued using the same polishing cloth, solids are observed on the polishing cloth surface and the flatness gradually deteriorates in about several batches. In general, in an apparatus for polishing without rotating the carrier, dressing is performed for each batch,
Although the wafer quality is stabilized, by using the dressing ring 4, polishing can be continuously and stably performed for 10 batches or more.

Although the embodiment of the present invention has been described in detail above, the specific configuration is not limited to this embodiment, and there are design changes and the like that do not depart from the gist of the present invention. Is also included in the present invention. For example, the polishing apparatus of the present invention is particularly useful for a polishing apparatus in which the carrier 1 does not rotate, but can also be applied to a conventional four-way polishing apparatus. Further, even if it is not a simultaneous double-side polishing apparatus, a single-side polishing apparatus can be similarly applied as long as it is a polishing apparatus that performs polishing using a carrier holding a wafer.

[0030]

As described above, according to the present invention, the dressing ring is fitted into the wafer holding hole, and the wafer is set inside the dressing ring. Are brought into frictional contact, and the dressing of the polishing pad is always performed. In particular, when the dressing ring is rotatably fitted, the dressing ring also rotates in an arbitrary direction in the wafer holding hole due to the rotation of the dressing ring, so that the abrasive cloth can be dressed uniformly while diffusing the abrasive. . As described above, according to the present invention, since the functional deterioration due to the aging of the polishing pad can be avoided, the quality of the wafer is stabilized and the durability of the polishing pad is improved. Further, there is no need to stop and dress the apparatus, and the productivity is improved by continuous operation, and the wafer is rotated during the polishing, so that the wafer can be polished with high flatness.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a wafer polishing apparatus according to the present invention.

FIG. 2 is a longitudinal sectional side view of the wafer polishing apparatus of FIG.

FIG. 3 is a plan view of a carrier used in the wafer polishing apparatus of the present invention.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a plan view showing another example of the structure of the dressing ring.

FIG. 6 is a sectional view taken along line VI-VI of FIG. 5;

FIG. 7 is a graph showing test results of a polishing apparatus to which a dressing ring is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carrier 2 Wafer holding hole 4 Dressing ring 4a Main body part 4b Protective material 5 Groove 14 Upper surface plate 16 Lower surface plate 14a Polishing cloth 16a Polishing cloth 20 Rotating motion mechanism

Claims (6)

[Claims] 1. A wafer polishing apparatus for setting a wafer in a wafer holding hole of a carrier and polishing a main surface of the wafer with a polishing cloth attached to a rotating platen, wherein a dressing ring is fitted into the wafer holding hole. A wafer polishing apparatus, wherein a wafer is set inside the dressing ring. 2. The wafer polishing apparatus according to claim 1, wherein the carrier is attached to a turning mechanism that turns without rotating on a plane parallel to the plane of the carrier. 3. The wafer polishing apparatus according to claim 1, wherein said dressing ring is provided with a plastic protective material inside a ring-shaped main body. 4. The wafer polishing apparatus according to claim 1, wherein a groove is formed in a surface of the dressing ring that contacts the polishing cloth. 5. A wafer polishing method for setting a wafer in a wafer holding hole of a carrier and polishing a main surface of the wafer with a polishing cloth attached to a rotating platen, wherein a dressing ring is fitted into the wafer holding hole.
A wafer polishing method comprising: setting a wafer inside the dressing ring; rotating the platen to polish the main surface of the wafer with a polishing cloth; and simultaneously dressing the polishing cloth with the dressing ring. 6. The wafer polishing method according to claim 5, wherein the carrier is rotated so as not to rotate on a plane parallel to the plane of the carrier.