JP7276246B2 - Method for manufacturing carrier for double-side polishing machine and method for polishing both sides of wafer - Google Patents

Description

The present invention relates to a method for manufacturing a carrier for a double-sided polishing apparatus and a method for polishing both sides of a wafer using the same.

Since the double-sided polishing machine polishes both sides of about five wafers per batch at the same time, a carrier for the double-sided polishing machine having the same number of holding holes as the number of wafers is placed on the lower surface plate. The wafer is held by the holding holes of the carrier, the wafer is sandwiched from both sides by polishing cloths provided on the upper and lower platens, and polishing is performed while supplying an abrasive to the polishing surface.

Carriers for double-sided polishing apparatuses having holding holes for holding wafers (hereinafter simply referred to as carriers) are mainly made of metal. To protect the outer periphery of the wafer from the metal carrier, the carrier has a resin insert on the inner periphery of the wafer holding hole. Since the resin insert is in contact with the outer periphery of the wafer, it is important in shaping the edge shape of the wafer. One of the parameters regarding the resin insert is the difference in level with the metal substrate (carrier base material). An example of this step will be described below.

FIG. 6 shows a graph of the step profile between the resin insert and the carrier base material after the carrier is polished upright according to the prior art. The upper part is a schematic diagram showing the step between the resin insert and the carrier base material, and the height of the step between the resin insert and the carrier base material is measured by scanning the probe on the front and back sides of the carrier by contact measurement. measured by
The measurement result of the step amount is shown in the middle graph, in which the horizontal axis indicates the distance in the radial direction of the carrier and the vertical axis indicates the step amount. 0 mm on the horizontal axis corresponds to the boundary between the carrier base material (minus) and the resin insert (plus). The step amount is almost 0 μm at the carrier base material portion. In the portion of the resin insert, the step from the front surface or the rear surface of the carrier base material is indicated, and if it is positive, it indicates that it protrudes from the carrier base material, and if it is negative, it indicates that it is recessed from the carrier base material.
The lower graph shows the results of measurement of the amount of step between the front surface and the back surface and the difference between the front and back surfaces at a total of four locations moved by 90° on the resin insert. It can be seen that the difference between the front and back of the step amount is large at any location.

It is known that this step affects the ZDD (radial double derivative of Z-height), which is the edge shape quality of the wafer. In particular, in order to equalize the ZDD on the front and back of the wafer, it is desirable that the amount of level difference between the front and back of the resin insert and the metal substrate be the same. Therefore, in the conventional technology, a resin insert thicker than the metal substrate is adhered, and the number of rotations of the upper and lower surface plates is adjusted to reduce the difference in level difference between the front and back sides (see, for example, Patent Document 1).
In the prior art, the resin-inserted part of the carrier was firmly fixed to prevent it from coming off, such as by bonding with a resin liquid agent or by introducing an anchor into the metal substrate (see, for example, Patent Document 2).

Japanese Patent Application No. 2016-56089 Japanese Patent Application No. 2009-222183

The above method is affected not only by the clogging of the pad (abrasive cloth) and the aggregated state of the slurry (abrasive), but also by the accuracy of the equipment and warping of the carrier. Either the front side or the back side of the resin insert is scraped preferentially, and it is not possible to sufficiently reduce the difference in level difference between the front and back sides, resulting in a difference in ZDD between the front and back sides of the wafer during wafer processing. A case was found. Therefore, there is a demand for a simpler method for start-up polishing of a carrier having a resin insert that is less dependent on the above effects.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a carrier for a double-side polishing machine that can reduce the difference in level between the resin insert and the carrier base material. aim.

In order to solve the above-mentioned problems, the present invention provides a carrier base material for use in a double-sided polishing apparatus having an upper surface plate and a lower surface plate to which polishing cloths are attached, and having holding holes for holding wafers; A method of manufacturing a carrier for a double-sided polishing apparatus, comprising: a carrier base material; a preparation step of preparing the resin insert thicker than the base material; a forming step of forming the resin insert so as to be non-adherent to the inner peripheral surface of the holding hole and having a peel strength of 10 N or more and 50 N or less; A carrier for a double-sided polishing machine, characterized by comprising a rising polishing step in which a carrier comprising a base material and the resin insert is subjected to multi-stage rising polishing with a load of two or more stages using the double-sided polishing machine. to provide a method of manufacturing

If the resin insert is not adhered to the inner peripheral surface of the holding hole and the peel strength is 50 N or less, the surface side and the back side of the step amount between the resin insert and the carrier base material can be removed by performing rising polishing. The vertical position of the resin insert can be adjusted so that the difference becomes smaller, that is, so that the projection of the resin insert becomes more symmetrical. Moreover, if the peel strength is 10 N or more, it is possible to suppress the peeling of the resin insert from the carrier base material due to polishing.
In addition, by increasing the load in two stages or more during the initial polishing, the difference in level between the resin insert and the carrier base material can be reduced in the first stage polishing, and the resin insert can be adjusted to the optimum position. Therefore, the amount of step between the resin insert and the carrier base material can be further reduced in the second and subsequent polishing steps, and the difference between the front and back of the amount of step can be easily reduced. Furthermore, by polishing both sides of the wafer using the carrier thus produced, a polished wafer with a small front-to-back ZDD difference at the edge can be obtained. It should be noted that "the load is applied in two or more steps during the rising polishing" includes the case where the same load is applied and the rising polishing is performed a plurality of times.

Further, in the rising polishing step, the load of the first step of the multi-step of two or more steps can be 150 gf/cm ² or more and 250 gf/cm ^{2 or} less.
A load of 150 gf/cm ² (14.7 kPa) or more on the first stage is sufficient to adjust the position of the resin insert. Further, when the pressure is 250 gf/cm ² (24.5 kPa) or less, it is possible to more effectively suppress the peeling of the non-bonded resin insert from the carrier base material due to the frictional force with the polishing cloth.

Further, in the rising polishing step, the load on the first step of the multi-step of two or more steps can be made larger than the load on the second step.
If the load in the first stage of initial polishing is greater than the load in the second stage, the position of the resin insert adjusted in the first stage polishing will be more effectively prevented from being displaced in the second stage polishing. can be suppressed.

Further, according to the present invention, there is provided a double-side polishing method for a wafer, wherein the wafer is held in the holding hole of the carrier for a double-side polishing apparatus manufactured by the method for manufacturing a carrier for a double-side polishing apparatus, and the wafer is held in the holding hole of the double-side polishing apparatus. By sandwiching between the upper and lower surface plates and rotating the upper and lower surface plates, the double-sided polishing of the wafer is performed, and the difference between the front and back of the ZDD at the edge of the wafer after the double-sided polishing is 5 nm or less. A method for polishing both sides of a wafer is provided.
With such a double-side polishing method for a wafer, the front-back difference in ZDD at the edge of the wafer after double-side polishing is reduced as compared with the conventional method.

Further, in the double-sided polishing, double-sided polishing can be performed in which the load is applied in two or more stages.
By performing double-sided polishing in two or more stages of multistage polishing, the position of the resin insert in the carrier is stabilized in the first stage of polishing, and then the wafer can be polished in the second and subsequent stages of polishing. ZDD can be effectively improved.

Further, in the double-side polishing, the load of the first step of the multi-step of two or more steps can be set to 150 gf/cm ² or more and 250 gf/cm ^{2 or} less.
Such a load is sufficient to stabilize the position of the resin insert, and more effectively prevents the resin insert from peeling off from the carrier base material.

Further, in the double-sided polishing, the load in the first stage of the multiple stages of two or more stages can be made larger than the load in the second stage.
With such a load, it is possible to more effectively prevent the position of the resin insert stabilized in the first step of polishing from being displaced in the second step of polishing.

According to the method for manufacturing a carrier for a double-sided polishing apparatus and the method for double-sided polishing of a wafer according to the present invention, it is possible to easily reduce the difference in level between the resin insert and the carrier base material. can reduce the front-to-back difference in ZDD of the wafer after polishing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart showing an outline of a method for manufacturing a carrier for a double-side polishing apparatus and a method for polishing both sides of a wafer according to the present invention; FIG. 2 is a top view showing an example of a carrier for a double-sided polishing apparatus manufactured by the manufacturing method of the present invention; FIG. 4 is an enlarged view showing measurement points of the peel strength of the resin insert; 1 is a schematic cross-sectional view showing an example of a double-sided polishing machine that can be used in the method of manufacturing a carrier for a double-sided polishing machine according to the present invention; FIG. 5 is a graph showing the measurement results of the difference between the front and back of ZDD at the edge of the wafer after double-sided polishing in Example 1 and Comparative Examples 1-5. FIG. 11 is a graph showing a step profile between a resin insert and a carrier base material after the carrier is polished upright according to the conventional technology; FIG.

As described above, there has been a demand for a method of manufacturing a carrier for a double-sided polishing apparatus that can reduce the difference in level difference between the resin insert and the carrier base material.

As a result of extensive studies on the above problems, the inventors of the present invention have found that by adjusting the number of wedge-shaped fittings and the outer diameter of the resin insert, the resin insert is not glued as in the conventional technology. It was found that the problem can be solved by preparing a carrier having a peel strength of 10 N or more and 50 N or less from the carrier base material, and applying a load in two or more stages during the rising polishing of the resin insert. completed.

Hereinafter, the present invention will be described in detail as an example of embodiments with reference to the drawings, but the present invention is not limited thereto.

FIG. 2 is a top view of a carrier for a double-side polishing machine manufactured by the manufacturing method of the present invention.
The carrier 1 has a carrier base material 3 in which a holding hole 2 for holding a wafer is formed, and a resin insert 4 formed in the inner periphery of the holding hole 2 without bonding. Although the carrier base material 3 with one holding hole 2 is shown here, the present invention is not limited to this, and may have a plurality of holding holes 2 . Also, the material of the carrier base material 3 is not particularly limited, and for example, a metal substrate can be used. As an example of the resin insert 4, for example, as shown in FIG. 3, it may be composed of a ring-shaped portion 4a and a wedge 4b projecting outward from the ring-shaped portion 4a. The number of wedges 4b and the outer diameter of the ring-shaped portion 4a are not particularly limited. However, it is formed so that the peel strength, which will be described later, is adjusted to 10 N or more and 50 N or less. Furthermore, the difference between the front and back of the step is small (for example, the amount of step is about 11.034 μm and the difference between the front and back is about 11.77 μm).

Such a carrier 1 is used, for example, when polishing both sides of a wafer W in a four-way type double-side polishing apparatus 10 as shown in FIG. The double-side polishing machine 10 has an upper surface plate 11 and a lower surface plate 12 which are provided facing each other vertically. A polishing cloth 13 is attached to each of the upper and lower surface plates 11 and 12 . A sun gear 14 is provided in the central portion between the upper surface plate 11 and the lower surface plate 12, and an internal gear 15 is provided in the peripheral portion.
The teeth of the sun gear 14 and the internal gear 15 are meshed with the outer peripheral teeth of the carrier 1. As the upper surface plate 11 and the lower surface plate 12 are rotated by a drive source (not shown), the carrier 1 is rotated. It revolves around the sun gear 14 while rotating. At this time, both surfaces of the wafer W held in the holding holes 2 of the carrier 1 are simultaneously polished by the upper and lower polishing cloths 13 . When polishing the wafer W, the slurry 17 is supplied to the polishing surface of the wafer W from the slurry supply device 16 .

A method for manufacturing a carrier for a double-side polishing apparatus and a method for polishing both sides of a wafer using the double-side polishing apparatus 10 shown in FIG. 4 will be described below. FIG. 1 is a flowchart showing an outline of a method for manufacturing a carrier for a double-side polishing apparatus and a method for polishing both sides of a wafer according to the present invention.
First, as in step 1 of FIG. 1, a carrier base material 3 and a thicker resin insert 4 are prepared. Although the carrier base material 3 having one holding hole 2 is used here, the present invention is not limited to this, and may have a plurality of holding holes 2 .
The materials of the carrier base material 3 and the resin insert 4 are not particularly limited, and the carrier base material 3 may be made of metal such as stainless steel or titanium, or may be surface-hardened. . Moreover, the resin insert 4 can be made of hard resin, for example.

Next, as in step 2 of FIG. 1, a resin insert 4 is formed on the inner peripheral surface of the holding hole 2 . The method of forming the resin insert 4 is not particularly limited, and for example, it can be formed by fitting or injection molding.
Here, the resin insert 4 and the carrier base material 3 are not adhered, and the peel strength is adjusted by adjusting the number and shape of the fitting wedges 4b as shown in FIG. is 10N or more and 50N or less.
The peel strength here means the maximum load at which the resin insert 4 peels from the carrier base material 3 when the measurement point 5 as shown in FIG.

If the peel strength is 50 N or less, the vertical position of the resin insert 4 is adjusted so that the difference in level difference between the resin insert 4 and the carrier base material 3 between the front side and the back side becomes small in the next rising polishing step. (the position in the thickness direction with respect to the carrier base material 3) can be adjusted. Moreover, if the peel strength is 10 N or more, it is possible to suppress the peeling of the resin insert 4 from the carrier base material 3 due to polishing.
For example, if the number of wedges 4b is 100 or less and the height is 5 mm or less, a peel strength of 50 N or less can be achieved more reliably.

Next, as in step 3 of FIG. 1, the carrier 1 is subjected to rising polishing to reduce the amount of step between the resin insert 4 and the carrier base material 3, and to manufacture the carrier 1 with a small difference in the amount of step between the front and back sides. do. Stand-up polishing can be performed by mounting the carrier 1 on a double-sided polishing apparatus 10 as shown in FIG. The types of polishing cloth 13 and slurry 17 are not particularly limited, and the same ones as in the conventional method can be used.

At this time, the load during the rising polishing is multi-staged in two stages or more. That is, a load is applied and the rising polishing is performed multiple times. As a result, the amount of step between the resin insert 4 and the carrier base material 3 can be reduced in the first stage of polishing, and the resin insert 4 can be adjusted to the optimum position. Here, the optimum position means, for example, a position where the difference in the degree of protrusion of the resin insert 4 on the front side and the back side is substantially equal. Next, the step amount between the resin insert 4 and the carrier base material 3 can be further reduced in the second and subsequent polishing steps. As a result, it is possible to obtain an excellent carrier in which the difference in level difference between the front surface side and the back surface side is reduced compared to conventional products. It should be noted that the number of stages of the multi-stage load may be plural, and may be only two stages, or may be three or more stages.

At this time, for example, the load of the first stage can be set to 150 gf/cm ² or more and 250 gf/cm ² or less. A load of 150 gf/cm ² or more is sufficient for adjusting the position of the resin insert 4 . Further, if the density is 250 gf/cm ² or less, it is possible to more effectively suppress the peeling of the non-bonded resin insert 4 from the carrier base material 3 due to the frictional force with the polishing cloth.
Also, the load on the first stage can be made larger than the load on the second stage. For example, for the first stage load of 150 gf/cm ² or more and 250 gf/cm ² or less, the second stage load should be 200 gf/cm ² (19.6 kPa) or less, which is smaller than the first stage load. be able to. By doing so, it is possible to more effectively prevent the position of the resin insert 4, which has been adjusted in the first stage of polishing, from being displaced due to movement during the second stage of polishing. can. It should be noted that the load in each stage can be the same value, or conversely, the load in the first stage can be made smaller than the load in the second stage. By making it larger, the difference between the front and back of the step amount can be efficiently reduced.

Through the above steps 1 to 3, it is possible to manufacture the carrier 1 in which the difference between the front and back surfaces of the resin insert 4 and the carrier base material 3 is reduced.

Then, as in step 4 of FIG. 1, the manufactured carrier 1 is used to polish both sides of the wafer. Double-side polishing of the wafer is performed by holding the wafer W in the holding hole 2 of the carrier 1, sandwiching it between the upper surface plate 11 and the lower surface plate 12 of the double-side polishing apparatus 10, and rotating the upper surface plate 11 and the lower surface plate 12. done by The types of polishing cloth 13 and slurry 17 are not particularly limited, and the same ones as in the conventional method can be used. By using the carrier 1 manufactured according to the present invention, it is possible to easily obtain a polished wafer in which the front-to-back difference in ZDD is sufficiently reduced. Specifically, it is possible to obtain a wafer having a ZDD front-to-back difference of 5 nm or less at the edge.

At this time, in the same manner as the rising-up polishing of the carrier in step 3, the load during double-side polishing can be multi-stepped in two or more steps. By doing so, the wafer can be polished while the resin insert 4 is stabilized at the optimum position, and the ZDD can be improved more effectively.
Also, the load of the first stage can be set to 150 gf/cm ² or more and 250 gf/cm ² or less. By doing so, the load is sufficient to stabilize the position of the resin insert 4, and the separation of the resin insert from the carrier base material can be more effectively suppressed.
Also, the load on the first stage can be made larger than the load on the second stage. In this way, the position of the resin insert 4 that has been stabilized in the first stage of polishing can be more effectively suppressed from being displaced due to movement in the second stage of polishing. can be done.

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the examples.

(Example 1)
According to the flow of FIG. 1, a carrier for a double-sided polishing apparatus of the present invention was manufactured and a wafer with a diameter of 300 mm was double-sided polished. As shown in FIGS. 2 and 3, a resin insert 4 (material: FRP) was formed in a non-bonded manner in the inner peripheral portion of the holding hole 2 of the carrier base material 3 (material: titanium). At that time, by setting the number of wedges 4b to 80, the peel strength of the resin insert 4 was manufactured to be 40N.

For start-up polishing of the carrier 1 and double-sided polishing of the wafer, DSP-20B manufactured by Nachi-Fujikoshi Machine Co., Ltd., which is a 4-way type double-sided polishing device, was used as the double-sided polishing device 10 shown in FIG. A urethane foam pad having a Shore A hardness of 90 was used as the polishing cloth 13, and a slurry 17 containing silica abrasive grains, having an average particle diameter of 35 nm, having an abrasive grain concentration of 1.0 wt %, having a pH of 10.5, and a KOH base was used.
In addition, in both the stand-up polishing of the carrier and the double-sided polishing of the wafer, the position of the insert was stabilized by applying a load of 150 gf/cm ² in the first stage, and 100 gf/cm ² (9.8 kPa) in the second stage. It was set as a two-stage load in which polishing was performed by applying a load of .

(Comparative example 1)
Carrier production and wafer double-sided polishing were performed in the same manner as in Example 1, except that a load of 100 gf/cm ² was applied in both the rising polishing and the double-sided polishing, and a one-stage load was applied to perform polishing only once. rice field.

(Comparative example 2)
The carrier was manufactured and the wafer was polished on both sides in the same manner as in Example 1, except that the peel strength was set to 60 N by setting the number of wedges in the resin insert of the carrier to 130.

(Comparative Example 3)
Carrier production and wafer double-sided polishing were carried out in the same manner as in Comparative Example 2, except that a load of 100 gf/cm ² was applied in both the rising polishing and the double-sided polishing, and a one-stage load was applied to perform polishing only once. rice field.

(Comparative Example 4)
As the carrier, an adhesive carrier in which a resin insert (shape: ring-shaped, without wedges) is adhered and fixed to the carrier base material was adopted, and its peel strength was set to 200N. Other than the above, carrier production and wafer double-sided polishing were carried out in the same manner as in Example 1.

(Comparative Example 5)
Carrier production and wafer double-sided polishing were performed in the same manner as in Comparative Example 4, except that a load of 100 gf/cm ² was applied in both the rising polishing and the double-sided polishing, and a one-stage load was applied to perform polishing only once. rice field.

The difference in level between the resin insert and the carrier base material of each carrier is Example 1: 0.932 μm, Comparative Example 1: 7.192 μm, Comparative Example 2: 7.71 μm, Comparative Example 3: 6.286 μm. , Comparative Example 4: 12.272 μm, Comparative Example 5: 14.378 μm.

The wafers W after double-sided polishing of Example 1 and Comparative Examples 1-5 were subjected to SC-1 cleaning under the condition of NH ₄ OH:H ₂ O ₂ :H ₂ O=1:1:15. For flatness, the wafer after cleaning is measured using Wafersight 1 manufactured by KLA, ZDD is calculated by excluding 2 mm from the edge, and the difference between the front part (front side) and the back part (back side) is measured for one batch An average of 5 sheets was taken and plotted. The results are shown in FIG.

In Comparative Example 1 in which rising polishing and double-sided polishing are not performed with a multi-stage load, and in Comparative Example 2-5 in which the peel strength of the resin insert is large, the difference between the front and back of the ZDD at the edge of the wafer after double-sided polishing is large (both are greater than 5 nm big). On the other hand, if rising polishing and double-sided polishing are performed with a multi-stage load and double-sided polishing of the wafer is performed using the carrier of Example 1 having a peel strength of 50 N or less, the difference between the front and back sides of the ZDD at the edge of the wafer is 5 nm or less. (More specifically, it can be reduced to about 1 nm).

(Example 2)
The carrier was manufactured and the wafer was polished on both sides in the same manner as in Example 1, except that the peel strength was set to 50 N by setting the number of wedges in the resin insert of the carrier to 100.

(Example 3)
The carrier was manufactured and the wafer was polished on both sides in the same manner as in Example 1, except that the peel strength was set to 10 N by setting the number of wedges of the resin insert of the carrier to 20.

(Comparative Example 6)
The carrier was manufactured in the same manner as in Example 1, except that the peel strength was set to 5N by setting the number of wedges of the resin insert of the carrier to 10. As a result, the resin insert was removed during start-up polishing. Production has been discontinued because it has fallen off.

The difference in level difference between the resin insert and the carrier base material of each carrier was 3.912 μm for Example 2 and 3.514 μm for Example 3. In addition, the difference between the front and back sides of the ZDD at the edge of the wafer after double-side polishing was 4.7 nm for Example 2 and 4.5 nm for Example 3. Moreover, in Comparative Example 6, in which polishing was performed with a peel strength of less than 10 N, it was confirmed that the resin insert was removed during polishing.

As described above, according to the method for manufacturing a carrier for a double-sided polishing apparatus of the present invention, it is possible to reduce the difference in level between the resin insert and the carrier base material, and as a result, the difference in ZDD of the wafer is reduced. be able to.

It should be noted that the present invention is not limited to the above embodiments. The above embodiment is an example, and any device that has substantially the same configuration as the technical idea described in the claims of the present invention and produces similar effects is the present invention. It is included in the technical scope of the invention.

DESCRIPTION OF SYMBOLS 1... Carrier for double-sided polishing apparatus, 2... Holding hole, 3... Carrier base material,
4... Resin insert 4a... Ring-shaped part 4b... Wedge 5... Measuring point
DESCRIPTION OF SYMBOLS 10... Double-sided polishing apparatus, 11... Upper surface plate, 12... Lower surface plate, 13... Polishing cloth,
14... Sun gear, 15... Internal gear, 16... Slurry feeder,
17... Slurry, W... Wafer.

Claims (7)

A carrier base material, which is used in a double-sided polishing apparatus having an upper surface plate and a lower surface plate to which polishing cloths are attached, and has holding holes for holding wafers, and a carrier base material arranged along the inner peripheral surface of the holding holes. A method for manufacturing a carrier for a double-side polishing apparatus having a resin insert formed with an inner peripheral portion in contact with the outer peripheral portion of the wafer, the method comprising:
a preparation step of preparing the carrier base material and the resin insert thicker than the carrier base material;
a forming step of forming the resin insert on the inner peripheral surface of the holding hole so as to be non-adhesive and have a peel strength of 10 N or more and 50 N or less;
a double-sided polishing apparatus comprising: a rising polishing step in which the carrier comprising the carrier base material and the resin insert is subjected to multi-stage rising polishing with a load of two or more stages using the double-sided polishing apparatus. A method of manufacturing a carrier for 2. Manufacturing a carrier for a double-side polishing apparatus according to claim 1, wherein in said rising polishing step, the load of said first stage of said multi-stage of said two or more stages is 150 gf/cm ^<2> or more and 250 gf/cm ^<2> or less. Method. 3. The carrier for a double-side polishing apparatus according to claim 1, wherein in the rising polishing step, the load of the first stage of the multi-stage of two or more stages is made larger than the load of the second stage. Production method. A method for polishing both sides of a wafer,
The wafer is held in the holding hole of the carrier for a double-sided polishing machine manufactured by the method for manufacturing a carrier for a double-sided polishing machine according to any one of claims 1 to 3, and the vertical position of the double-sided polishing machine is adjusted. By sandwiching between the plates and rotating the upper and lower surface plates, the wafer is polished on both sides, and the difference between the front and back of the ZDD at the edge of the wafer after the double-side polishing is 5 nm or less. Double-sided polishing method. 5. The method of polishing both sides of a wafer according to claim 4, wherein in the double-side polishing, the load is applied in multiple stages of two or more stages. 6. The double-side polishing method of a wafer according to claim 5, wherein in the double-side polishing, the load of the first stage of the two or more stages is 150 gf/cm ^<2> or more and 250 gf/cm ^<2> or less. 7. The double-sided polishing method of a wafer according to claim 5, wherein in said double-sided polishing, the load in the first stage of said multiple stages of two or more stages is made larger than the load in the second stage.

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