KR20150039576A - Membrane, polishing head, apparatus and method of polishing work, and silicon wafer - Google Patents

Abstract

The purpose of the present invention is to provide an apparatus and a method of polishing a work, which is capable of obtaining a work having high flatness, a polishing head for the polishing apparatus, and a membrane for the polishing head. Also, the purpose of the prevent invention is to provide a silicon wafer having a preset flatness. In the membrane of the present invention, the maximum thickness of the outer part is thinner than the minimum thickness of the inner part. The polishing head of the present invention and the polishing apparatus use the membrane. Also, the method of polishing a work is a method using the membrane, and the diameter of the silicon wafer is 450mm or more. GBIR defined by a SEMI standard is 0.2μm or less. In addition, the maximum value of SFQR except a ring-shaped region of 2mm from the edge of the work to the inner diameter direction is 0.01μm or less.

Description

[0001] DESCRIPTION [0002] MEMBRANE, POLISHING HEAD, APPARATUS AND METHOD OF POLISHING WORK, AND SILICON WAFER [0002]

The present invention relates to a polishing apparatus and a polishing method for polishing a disc-like work such as a semiconductor wafer, a polishing head for the polishing apparatus, a membrane for the polishing head, and a silicon having a predetermined flatness To a wafer.

In the production of semiconductor wafers such as silicon wafers, which is a typical example of a work to be provided for polishing, there has recently been a demand for a flattening of a semiconductor wafer at the time of exposure from the background of miniaturization of semiconductor elements and large- Demands for the province are becoming more stringent.

BACKGROUND ART Conventionally, as a technique for polishing one surface of a work, there is known a polishing method of a work for pressing a work from a back surface by a membrane. For example, Patent Document 1 discloses that the flatness of the membrane bonded to the rigid ring is 40 占 퐉 or less so that the machining allowance of polishing on the entire surface of the work is made uniform and the flatness of the work to be polished is made uniform Is proposed.

Japanese Patent Application Laid-Open No. 2010-247254

However, as a result of repeated investigations made by the inventors of the present invention, it has been found that the polishing process margin of the outer circumferential portion of the workpiece tends to be small in the technique described in Patent Document 1, and the flatness of the workpiece after polishing is not sufficient . In addition, in the technique described in Patent Document 1, when a membrane having a desired flatness is manufactured, since a mold is integrally formed with the rigid ring, it is necessary to re-manufacture each rigid ring at the time of membrane replacement There is a problem that the cost is increased.

An object of the present invention is to solve the above problems, and an object of the present invention is to provide a polishing apparatus and a polishing method for a work capable of obtaining a highly flat work, a polishing head for the polishing apparatus, and a membrane for the polishing head . It is also an object of the present invention to provide a silicon wafer having a predetermined flatness.

The present inventors have conducted intensive studies to solve the above problems. As a result, the inventors of the present invention have found that the thickness of a membrane provided for polishing is effective because a film having a predetermined nonuniformity in the radial direction thereof is effective for obtaining a work having a higher level of flatness. And the present invention has been accomplished.

The structure of the present invention is as follows.

A membrane for a polishing head of the present invention is a membrane made of a flexible material which is attached to a lower surface of a polishing head used for polishing a disc-shaped work, As the membrane,

Wherein an area of the membrane in the contact area with the workpiece from the outer edge of the contact area to 20 mm inward in the radial direction of the membrane is an outer peripheral part of the membrane and an outer side in the radial direction from the center of the membrane When an area of up to 20 mm is used as the inner peripheral part of the membrane,

And the maximum thickness at the outer peripheral portion of the membrane is thinner than the minimum thickness at the inner peripheral portion of the membrane.

Here, the " contact area of the membrane with the workpiece " refers to a circle-surrounding area having a radius of the same size as the radius of the workpiece provided for polishing, with the center of the disk- shaped membrane as the center of the circle.

In the membrane for a polishing head of the present invention, the maximum thickness in the radial direction of the membrane is Trmax, the minimum thickness is Trmin, and the average thickness is Trave, (1), (2), (3), and (4)

hr = {(Trmax-Trmin) / Trave} x 100

, Hr is preferably 2.8% or more.

The maximum thickness in the diametral direction of the membrane is Trmax, the minimum thickness is Trmin, and the average thickness is Trave. The maximum thickness, the minimum thickness and the average thickness in the diameter of the membrane are referred to.

In the membrane for a polishing head of the present invention, it is preferable that the thickness of the membrane gradually decreases from the center of the membrane toward the outer edge of the contact region toward the outer side in the radial direction.

In the membrane for a polishing head of the present invention, the maximum thickness in the circumferential direction of the membrane is Tcmax and the minimum thickness is Tcmin in the circumferential direction of 5 mm inward in the radial direction from the outer edge of the contact region of the membrane. , The average thickness is Tcave, and the thickness uniformity hc (%) in the circumferential direction of the membrane is expressed by the following relational expressions (2) and

hc = {(Tcmax-Tcmin) / Tcave} x 100

, Hc is preferably 10.2% or less.

Here, the polishing head of the present invention is a polishing head used for polishing a disk-shaped work, and has a holding plate for holding the membrane, an outer edge portion of the membrane, and a pressure supply unit for supplying pressure to the membrane .

A polishing apparatus for a workpiece according to the present invention is a polishing apparatus for a disk-shaped workpiece, comprising: a polishing table having a polishing plate on the upper surface thereof and a polishing head provided above the polishing table; .

Here, the method of polishing a work of the present invention is a method of polishing a disk-

Supplying a pressure to a membrane made of a flexible material attached to a lower surface of a polishing head to contact and hold the back surface of the work with the membrane to press the polishing pad;

And polishing the workpiece by rotating the polishing head,

An outer circumferential portion of the membrane in an area from the outer periphery of the contact region to the workpiece to 20 mm inward in the radial direction of the membrane is defined as an outer circumferential portion of the membrane and 20 mm to the outer side in the radial direction from the center of the membrane Is an inner peripheral portion of the membrane,

And the maximum thickness at the outer peripheral portion of the membrane is thinner than the minimum thickness at the inner peripheral portion of the membrane.

The silicon wafer of the present invention is a silicon wafer having a diameter of 450 mm or more and has a GBIR of 0.2 占 퐉 or less as defined by the SEMI standard and a region of 2 mm inward in the radial direction from the outer edge of the silicon wafer, And the maximum value of the SFQR defined by the specification is 0.04 占 퐉 or less.

Specifically, the GBIR (Groov Backside Ideal Focal Plane Range), specifically, assumes that the back surface of the silicon wafer when it is assumed that the back surface of the silicon wafer is completely absorbed, And the difference between them is calculated.

In addition, SFQR (Site Front Least Squares Range) is defined as a plane in the site where the data is calculated by the least squares method in the set site as a reference plane, and the positive side (i.e., the main surface of the wafer) (Upper side in the case of horizontally oriented upward) and - (side in the lower side), and the maximum value of the SFQR is the maximum value among the SFQRs of the entire site of the wafer Value. The flatness SFQRmax specified in the present invention is measured using a flatness meter (WaferSight, manufactured by KLA-Tencor Corporation) Is the value measured within the site size of the sample.

According to the present invention, it is possible to provide a polishing apparatus and a polishing method for a work capable of obtaining a highly flat work, a polishing head for the polishing apparatus, and a membrane for the polishing head. Further, according to the present invention, it is possible to provide a silicon wafer having a predetermined flatness.

1 is a schematic cross-sectional view showing a double-side polishing apparatus for a work according to an embodiment of the present invention.
2 (a) to 2 (c) are schematic views showing a state in which the membrane is in pressure contact with a silicon wafer.
3 is a diagram showing the relationship between the uniformity in the circumferential direction of the membrane and the uniformity of the machining allowance.
4 is a view showing a three-dimensional distribution of abrasive machining allowances.
Figs. 5 (a) to 5 (e) are views showing the cross-sectional shape of the surface of the membrane (lower figure) and the sectional shape (upper figure) of the polishing allowance of the silicon wafer.
6 is a diagram showing the evaluation result of the SFQR.
7 is a diagram showing the evaluation result of GBIR.

(Mode for carrying out the invention)

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

1 is a schematic sectional view showing a double-side polishing apparatus 1 for a work according to an embodiment of the present invention. As shown in Fig. 1, this double-side polishing apparatus 1 has a polishing head 2 and a platen 3. The polishing head 2 is formed above the surface plate 3 and the polishing pad 4 is attached to the upper surface of the surface plate 3. [ The base 3 is connected to a motor (not shown) for rotating the base 3.

1, the polishing head 2 is provided with a housing portion (top portion) 5a and a housing side portion 5b surrounding other components, and a motor (not shown) for rotating the polishing head 2 And a shaft 6 connected to a rotating shaft (not shown). The housings 5a and 5b prevent internal components from being undesirably exposed or abraded.

As shown in Fig. 1, the polishing head 2 has a retainer ring 7 surrounding a disc-shaped work (silicon wafer in this example). The retainer ring 7 holds the silicon wafer W so as not to come off from the polishing head 2. Further, as shown in Fig. 1, the retainer ring 7 is connected to the lower side of the housing side portion 5b.

1, the polishing head 2 includes a disk-like member 8, a ring-shaped member 9, and a disk-shaped holding plate 10 inside the housings 5a and 5b And an inner head 12 having an inner surface 12a. The lower surface of the inner head 12 serving as the lower surface of the polishing head 2 is provided with a membrane (not shown) for holding the back surface of the silicon wafer W 11 are attached. This membrane 11 is made of a flexible material. 1, the ring-shaped member 9 is connected to the lower surface of the disc-shaped member 8, and the holding plate 10 is screwed and connected to the lower surface of the ring- have. The outer edge of the membrane 11 is held and fixed so as to be sandwiched between the ring-like member 9 and the holding plate 10. [

1, the housing side portion 5b and the inner head 12 are connected by a flexible member 13. [ The first pressure supply section 14 is partitioned by the housing section 5a, the housing side section 5b, the disk-like member 8, and the flexible member 13. [ 1, a first air supply line 15 is formed in the shaft 6 and the housing part 5a, and the first pressure supply part 14 is connected to the first air supply line 15 And is connected to a first air supply device (not shown). With this configuration, the volume of the first pressure supply portion 14 is expanded by the supply of air from the first air supply device, the flexible member 13 is bent, and the flexible member 13 is connected to the flexible member 13 The inner head 12 is pressed downward as shown. In addition, the downward movement of the inner head 12 is limited by the stopper 18 to a predetermined range, and therefore, the pressing force to the silicon wafer W is also limited within a predetermined range.

As shown in Fig. 1, the outer periphery of the membrane 11 is held above the holding plate 10, and a region in contact with the silicon wafer W is extended below the holding plate 10 have. 1, the second pressure supply part 16 is partitioned by the disk-shaped member 8, the ring-shaped member 9, the holding plate 10, and the membrane 11 .

1, a second air supply line 17 is formed in the shaft 6, the housing 5a, the disk-like member 8, and the holding plate 10, (16) is connected to a second air supply device (not shown) via the second air supply line (17). With this configuration, by the supply of air from the second air supply device, the volume in the second pressure supply part 16 expands and the membrane 11 is bent. In this way, the inner pressure of the inner head (11) formed with the membrane (11) by the first pressure supply part (14) while applying the pressure to elastically support the membrane (11) The membrane 11 can be brought into pressure contact with the back surface of the silicon wafer W by applying pressure to elastically support the silicon wafer W in the direction of the silicon wafer W. [ As a result, the silicon wafer W can be pressed downward as shown in the figure where the polishing pad 4 is disposed.

By thus rotating the polishing head 2 and the table 3 while supplying the polishing slurry onto the polishing pad 4 while applying pressure to the silicon wafer W as described above, It is possible to slide the surface of the wafer W side to polish one side of the silicon wafer W. [

In the present embodiment, a region of the membrane 11 in contact with the silicon wafer W from the outer edge of the contact region to 20 mm inward in the radial direction of the membrane 11, The maximum thickness at the outer peripheral portion of the membrane 11 is set to be larger than the maximum thickness at the outer peripheral portion of the membrane 11 when the membrane 11 is an inner peripheral portion of the membrane 11 up to 20 mm outward in the radial direction from the center of the membrane 11. [ It is important to be thinner than the minimum thickness in the inner margin.

Hereinafter, the operation and effect of the present embodiment will be described.

2 (a) to 2 (c) show a state in which when the air is supplied to the second pressure supply unit 16, the membrane 11 held by the outer plate 10 on the holding plate 10 is pressed against the silicon wafer W Fig.

Fig. 2 (a) shows a case where the thickness of the membrane 11 is substantially equal to that of the outer peripheral portion and the inner peripheral portion. 2 (a), the outer edge of the membrane 11 is held and fixed by the holding plate 10, so that the outer peripheral edge of the holding plate 10 ) Is deformed to form a circular arc in a cross-sectional shape when a certain pressure is applied by the supply of air. In addition, the downward movement of the inner head 12 is limited to a certain range by the stopper 18. [ As a result, the pressure of the membrane 11 to the inner peripheral portion of the silicon wafer W becomes relatively large while the pressure to the outer peripheral portion of the silicon wafer W becomes relatively small. Therefore, when one side of the silicon wafer W is polished, the polishing allowance of the outer peripheral portion of the silicon wafer W tends to be small.

2 (b) shows the case where the thickness of the outer peripheral portion of the membrane 11 is reduced compared to the inner peripheral portion. Fig. 2 (c) As compared with that of the housewife. Here, the membrane 11 has a high stretchability at a thin portion, and therefore, when the same pressure is applied, the thin portion of the membrane 11 is stretched well. 2 (b), the thickness of the outer peripheral portion of the membrane 11 is small, so that the elongation of the outer peripheral portion when the pressure is applied is larger than that of the inner peripheral portion where the thickness of the membrane 11 is thick, The membrane 11 is brought into contact more evenly with the inner peripheral portion and the outer peripheral portion. Therefore, the difference between the pressure at the outer peripheral portion and the pressure at the inner peripheral portion when the membrane 11 is pressed against the silicon wafer W becomes small. 2 (c), when the thickness of the outer peripheral portion of the membrane 11 is made relatively thinner than the thickness of the inner peripheral portion, the outer peripheral portion of the membrane 11 becomes relatively more elongated, 11) are more evenly contacted to the inner and outer peripheries. Therefore, the pressure to the outer peripheral portion of the silicon wafer W can be made substantially equal to the pressure to the central portion of the silicon wafer W. [

The maximum thickness of the membrane 11 in the outer peripheral portion of the membrane 11 is thinner than the minimum thickness of the inner peripheral portion of the membrane 11, And the polishing can be performed in this state. Thus, a silicon wafer having a higher level of flatness can be obtained. Further, at the time of replacing the membrane 11, it is sufficient to use a mold provided for the production of the membrane 11 once, and it is not necessary to integrally form the membrane 11 with another member, It becomes. According to the polishing apparatus of the present embodiment, it is possible to obtain the above effect by using a simple method in which no steel ball is required in the apparatus itself and the thickness of the membrane 11 having a predetermined non-uniformity in the radial direction is used Can be obtained.

Here, in the present invention, the thickness uniformity hr (%) in the radial direction of the membrane defined by the relational expression (1) in the contact region is preferably 2.8% or more, more preferably 22% , And still more preferably at least 34%. As described above (as will also be described later in the embodiment), the uniformity in the radial direction of the membrane is low (the value of hr is large), so that the expansion of the membrane at the outer peripheral portion of the work can be ensured, This is because the flatness of the work after polishing becomes higher.

On the other hand, if the uniformity of the thickness in the outer peripheral direction of the membrane 11 is excessively low (the value of hr becomes large), the elongation at the outer peripheral portion of the membrane becomes excessively large and therefore the polishing amount at the outer peripheral portion of the work becomes large, Hr (%) is preferably 37% or less from the standpoint that the shape of the work may become uneven.

In the present invention, it is preferable that the thickness of the membrane 11 gradually decreases from the center of the membrane 11 to the outer edge of the contact area toward the outside in the radial direction. 2 (a), since the pressure gradually decreases from the center of the membrane 11 to the outer edge thereof, the elongation of the membrane 11 is adjusted so as to cancel out the center of the membrane 11 The membrane 11 can press the entire surface of the work W more evenly.

In the present invention, in the circumferential phase of 5 mm inward in the radial direction from the outer edge of the contact region of the membrane 11, the thickness in the circumferential direction of the membrane 11 defined by the above-mentioned relational expression (2) Is preferably 10.2% or less, more preferably 6.5% or less, and even more preferably 1.4% or less. This is because the flatness of the workpiece W after polishing becomes higher when the uniformity of the thickness in the circumferential direction of the membrane 11 is high (the value of hc is small) as described later in the embodiment .

Further, the higher the uniformity in the circumferential direction (the smaller the value of hc is), the better, so the lower limit of hc is not particularly limited.

Here, in the present invention, it is preferable that the membrane 11, which is a flexible material, has a JIS-A hardness of 30 to 90 DEG, and a specific material is not particularly limited. For example, ethylene propylene rubber , Silicone rubber, butyl rubber and the like are preferably used.

Further, the membrane 11 of the present invention can be basically manufactured by a known method. For example, silicone rubber or the like, which is a material of a membrane, is injected into a mold for molding, and the flatness of the mold and the pressure distribution of the press machine are adjusted so that the maximum value of the thickness of the outer peripheral portion is Membranes thinner than the minimum value can be fabricated.

In the present invention, the thickness of the membrane 11 is preferably 0.5 to 1.5 mm. In the present invention, the thickness of the outer peripheral portion of the membrane 11 is preferably 1.3% to 66% of the thickness of the inner peripheral portion.

The pressure at the outer peripheral portion of the membrane 11 against the work W can be brought closer to the pressure at the inner peripheral portion and is made 66% This is because in the outer peripheral portion having characteristics that it is hard to elongate, by thinning the thickness, the inner peripheral portion can be uniformly pressed so as to extend well in the surface.

In order to reduce the thickness of the membrane 11, the thickness of the side on which the work W is pressed may be reduced, or the thickness of the side receiving the pressure from the second pressure supply part 16 may be reduced or both may be reduced .

According to the present invention, as described later in detail, the present invention can provide a wafer which achieves high flatness even in a silicon wafer of a large diameter of 450 mm or more in diameter, A maximum value of SFQR of 450 mm or more, a GBIR defined by the SEMI standard of 0.2 占 퐉 or less and a rounded area of 2 mm inward from the outer edge of the work in the radial direction is 0.04 占 퐉 or less, A silicon wafer can be obtained.

Thus, the yield in the device manufacturing process and the like can be improved.

Next, a polishing method of a work according to an embodiment of the present invention will be described.

In the method of polishing a work of the present embodiment, polishing is performed using the apparatus shown in Fig. Since the device configuration shown in Fig. 1 has already been described, the description will be omitted.

The first air supply device supplies air to the first pressure supply part 14 through the first air supply line 15 and supplies the air to the first pressure supply part 14. In this way, And pushes the inner head 12 downward.

The second air supply device supplies air to the second pressure supply part 16 through the second air supply line 17 and expands the volume of the second pressure supply part 16 to supply the air to the membrane 11, So as to elastically support the membrane 11 downward.

The inner head 12 with the membrane 11 is pressed in the direction of the lower silicon wafer W and the pressure is supplied to the membrane 11 so that the silicon wafer W is held by the membrane 11, .

The polishing slurry is supplied onto the polishing pad 4 and the polishing head 2 and the polishing head 4 are driven by a driving means such as a motor in a state in which the membrane 11 is in pressure contact with the silicon wafer from the back surface of the silicon wafer W. The polishing surface of the silicon wafer W can be polished by sliding the polishing surface of the polishing pad 4 and the silicon wafer W by rotating the surface plate 3. [

The polishing method of the present embodiment is characterized in that the maximum thickness of the outer peripheral portion of the membrane 11 is smaller than the minimum thickness of the inner peripheral portion of the membrane 11.

As a result, the membrane 11 can be pressed sufficiently uniformly over the entire surface of the silicon wafer W, and polishing is performed in this state, whereby a silicon wafer with a higher level of flatness can be obtained. Further, at the time of replacement of the membrane 11, it is sufficient to use a mold provided for the production of the membrane 11 once, and it is not necessary to integrally form the membrane 11 with another member, so that exchange at low cost is possible. According to the polishing method of the present embodiment, there is no need to add steps or the like, and the above effect can be obtained by a simple technique using the membrane 11 having a predetermined nonuniformity in the thickness direction .

Although the embodiments of the present invention have been described above, the present invention can be applied to a polishing head, a polishing apparatus, a polishing apparatus, and a polishing apparatus that presses the back surface of a work W using a membrane 11, And the present invention is not limited to the above-described embodiments at all. For example, in the above embodiment, the method of pressing the membrane 11 by air has been described. However, the membrane 11 may be pressed by the pressurized fluid. In the above embodiment, an example in which the membrane 11 directly presses the work W is shown. In the apparatus shown in Fig. 1, a backing pad made of foamed polyurethane is attached to the lower surface of the membrane 11 , And the work W may be pressed through the backing pad. In the above-described embodiment, the first pressure supply unit 14 has been described as an example in which the air-flexible member is bent. However, the inner head 12 may be elastically supported by another elastic member or the like.

Hereinafter, the embodiments of the present invention are described, but the present invention is not limited to these embodiments.

[Example]

≪ Example 1 >

In order to evaluate the relationship between the uniformity in the circumferential direction of the membrane and the abrasion machining allowance, a plurality of membranes having different uniformities in the circumferential direction were prepared, and a test was performed to measure each abrasion machining allowance. Here, EPDM rubber was used as the membrane. A p-type silicon wafer having a diameter of 450 mm, a thickness of 925 占 퐉, and a crystal orientation of 100 was used as a disk-shaped work. The polishing was carried out by using the apparatus shown in Fig. In this test, an aqueous alkaline solution containing potassium hydroxide (KOH) containing abrasive grains (fine colloidal silica) as a polishing slurry was used as a main agent, the pressure was set to 10 kPa, The number of revolutions of the head was 30 rpm, the number of revolutions of the platen was 30 rpm, and the polishing time was 240 sec.

Here, the uniformity in the circumferential direction of the membrane is defined by the above formula (2), and the smaller the value, the higher the uniformity is. In addition, the uniformity U (%) of the machining allowance was calculated by dividing the maximum machining allowance by the maximum machining allowance dmax, the minimum machining allowance The margin is dmin, the average machining allowance is dave,

U = {(dmax-dmin) / (2 x dave)} x 100

, And the smaller the value, the higher the uniformity.

The thickness of the membrane was measured by using a contact-type thickness measuring instrument. Each of the above machining spare parts was measured using a nano-meter manufactured by Guro-Dasai Co., Ltd., and three-dimensional distribution was also measured using a nano-meter manufactured by Guro-Dasai.

3 is a view showing the relationship between the uniformity in the circumferential direction of the membrane and the machining allowance. 4 is a diagram showing the three-dimensional distribution of the abrasion machining allowances in the case where the uniformity in the circumferential direction of the membrane is 15.2%, 11.1%, 10.2%, 6.5% and 1.4%, respectively.

As shown in Figs. 3 and 4, it can be seen that the higher the uniformity in the circumferential direction of the membrane is, the higher the uniformity of the polishing processing allowance of the silicon wafer is. Particularly, in the range of the uniformity of the circumferential direction of the membrane in the range of 1.4% to 10.2%, the abrasive machining allowance was 20% or less. In this case, the uniformity in the radial direction (defined by the above formula (1)) was 1.5% to 2%.

≪ Example 2 >

Next, a test was conducted to evaluate the relationship between the uniformity in the diametrical direction of the membrane and the abrasion machining allowance. The polishing conditions are the same as in the above test. Here, the uniformity in the radial direction of the membrane is defined by the above formula (1), and the smaller the value, the higher the uniformity is.

5 (a) to 5 (e) show the cross-sectional shape of the membrane surface in the case where the uniformity in the diameter direction of the membrane is 37%, 34%, 22%, 2.8% Sectional view (top view) of the abrasive machining allowance of the silicon wafer.

As shown in Figs. 5 (a) to 5 (e), it can be seen that the uniformity of the polishing allowance of the silicon wafer is higher as the uniformity in the diameter direction of the membrane is lower. Particularly, in the range of the uniformity of the diameter of the membrane in the range of 2.8% to 37%, the uniformity of the abrasive machining allowance became 20% or less. In this case, the uniformity in the circumferential direction (defined by the formula (2)) was 12% to 15%.

≪ Example 3 >

Next, a test was conducted to compare the flatness and the surface roughness (RMS) of the silicon wafer obtained by the present invention with the silicon wafer of the conventional example. As the silicon wafer of the present invention, the polished silicon wafer obtained by the above test was used. This silicon wafer was obtained by polishing with a diameter of 450 mm, uniformity in the diameter direction of the membrane of 20% and uniformity in the circumferential direction of 7%.

The silicon wafer according to the conventional example was prepared by polishing using a polishing apparatus having a membrane formed integrally with a rigid ring. The membrane used for polishing according to the conventional example had a substantially uniform thickness in the radial direction.

Here, the flatness of the silicon wafer was measured by measuring the maximum values of GBIR and SFQR. First, GBIR was measured using a WaferSight (manufactured by KLA-Tencor Corporation). The maximum value of the SFQR was determined by using a Nanometer450TT manufactured by Kuroda Seikasu Co., Ltd. and measuring a rectangular sample of 26 mm x 8 mm in an area excluding the annular area of 2 mm inward in the radial direction from the outer edge of the silicon wafer Multiple measurements were taken.

Further, regarding the surface roughness (RMS) of the silicon wafer, the surface roughness of the silicon wafer was measured using ChapmanMPS manufactured by Chapman Instruments.

The evaluation results will be described below.

6 is a diagram showing the evaluation result of the maximum value of the SFQR. As shown in Fig. 6, the silicon wafer obtained by the present invention has a maximum value of SFQR in a range of 0.04 m or less, which is higher than that of the conventional silicon wafer.

7 is a diagram showing the evaluation result of GBIR. As shown in Fig. 7, it can be seen that the silicon wafer obtained by the present invention has a lower GBIR and higher flatness than the conventional silicon wafer.

Therefore, it can be seen that the silicon wafer obtained by the present invention achieves a high flatness such that GBIR is 0.2 탆 or less and the maximum value of SFQR is 0.04 탆 or less, even though it is a silicon wafer of a large diameter of 450 mm or more in diameter .

The surface roughness (RMS) of the silicon wafer is preferably such that the surface roughness of the polished surface is not more than 2 nm and the ratio of the surface roughness (A) of the surface to the surface roughness (B) Was less than 0.4.

According to the present invention, it is possible to provide a polishing apparatus and a polishing method for a work capable of obtaining a highly flat work, a polishing head for the polishing apparatus, and a membrane for the polishing head. Further, according to the present invention, it is possible to provide a silicon wafer having a predetermined flatness.

1: Double-side polishing machine
2: Polishing head
3: Plate
4: Polishing pad
5a:
5b: housing side
6: Axis
7: retainer ring
8: disk-shaped member
9: ring member
10: Retaining plate
11: Membrane
12: Inner head
13: Flexible member
14: first pressure supply part
15: first air supply line
16: second pressure supply part
17: second air supply line
18: Stopper

Claims (8)

A membrane made of a flexible material which is attached to a lower surface of a polishing head used for polishing a disc-like work and which is pressed against the polishing pad by contacting and holding the back surface of the work,
Wherein an area of the membrane in a contact area with the work from the outer edge of the contact area to 20 mm inward in the radial direction of the membrane is an outer peripheral part of the membrane, When an area of up to 20 mm radially outward is defined as an inner peripheral portion of the membrane,
Wherein a maximum thickness at an outer peripheral portion of the membrane is thinner than a minimum thickness at an inner peripheral portion of the membrane. The method according to claim 1,
The thickness uniformity hr (%) in the diametral direction of the membrane is expressed by the following formula (1), where Trmax is the maximum thickness in the radial direction of the membrane, Trmin is the minimum thickness, (One),
hr = {(Trmax-Trmin) / Trave} x 100
, Wherein hr is at least 2.8%. 3. The method according to claim 1 or 2,
Wherein the thickness of the membrane gradually decreases from the center of the membrane toward the outer edge of the contact region toward the outer side in the radial direction. 3. The method according to claim 1 or 2,
Wherein a circumferential surface of the membrane in a circumferential direction of 5 mm from the outer periphery of the contact region of the membrane in the radial direction has a maximum thickness Tcmax, a minimum thickness Tcmin, and an average thickness Tcave, (2), (3), (4), and (5)
hc = {(Tcmax-Tcmin) / Tcave} x 100
, Hc is 10.2% or less. As a polishing head used for polishing a disc-shaped work,
The membrane according to claim 1 or 2,
A holding plate for holding an outer edge of the membrane,
And a pressure supply unit for supplying pressure to the membrane. As a disk-like workpiece polishing apparatus,
A polishing pad on the upper surface,
The polishing apparatus for a workpiece according to claim 5, further comprising a polishing head according to claim 5, wherein the polishing table is formed above the polishing table. As a method of polishing a disc-shaped work,
Supplying a pressure to a membrane made of a flexible material attached to a lower surface of a polishing head to contact and hold the back surface of the work with the membrane to press the polishing pad;
And polishing the workpiece by rotating the polishing head,
An outer circumferential portion of the membrane in a region from the outer periphery of the contact region to the workpiece in the radial direction of the membrane to 20 mm in the radial direction of the membrane is 20 mm to the outer side in the radial direction from the center of the membrane Is an inner peripheral portion of the membrane,
Wherein the maximum thickness at the outer peripheral portion of the membrane is thinner than the minimum thickness at the inner peripheral portion of the membrane. As a silicon wafer having a diameter of 450 mm or more,
Wherein the maximum value of SFQR defined by the SEMI standard is 0.04 탆 or less except for a region of GBIR of 0.2 탆 or less defined by the SEMI standard and a region of 2 mm radially inward from the outer edge of the silicon wafer. wafer.

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