JP7026942B2 - Underlay for polishing pad and polishing method using the underlay - Google Patents

Description

The present invention relates to an auxiliary member used for a polishing pad used in polishing work of semiconductor parts, electronic parts and the like. More specifically, the present invention relates to an underlay for a polishing pad, which is a new auxiliary member installed between the surface plate and the polishing pad when the polishing pad having a predetermined adsorption layer is fixed to the surface plate.

In the manufacturing process of semiconductor parts such as semiconductor wafers, glass substrates for displays, and substrates for hard disks, and electronic parts, a polishing step for flattening or mirroring the surface of the substrate or the like is included. The polishing step is performed by fixing the polishing pad to the surface plate of the polishing device and sliding the member to be polished and the polishing pad in a pressurized state while supplying the polishing slurry to the surface of the polishing layer of the polishing pad.

In the past, the mainstream method for fixing the polishing pad to the surface plate was to use an adhesive material such as adhesive tape, but this method requires time and effort to replace and fix the polishing pad, and the work efficiency of the polishing process is high. Was greatly reduced. To solve this problem of fixing the polishing pad, we have developed a polishing pad that can be easily fixed and replaced (Patent Documents 1 and 2).

Utility Model Registration No. 3166396 Japanese Patent No. 5765858

FIG. 4 shows the appearance of the polishing pad provided with such an adsorption layer. This polishing pad is provided with an adsorption layer made of a predetermined silicone compound having an adsorption action on the back surface side of the base material that supports the polishing layer. The silicone compound constituting this adsorption layer has an adsorption action regardless of the material such as glass or metal, and its holding power is also good. Regarding the holding force due to this adsorption, there is a characteristic that the shearing force (fixing strength in the horizontal direction) is high, while the peeling force (fixing strength in the vertical direction) is low. This property is suitable for fixing the polishing pad to the surface plate. This is because in the polishing work, the polishing pad is continuously subjected to the stress in the horizontal direction, so that a high holding force is required in the shearing force. Regarding the holding force in the vertical direction, since the polishing pad is pressed against the surface plate, a large holding force is not always required. The adsorption effect of the adsorption layer made of this silicone compound is uniform in the surface of the polishing pad, and a uniform holding force can be exhibited from the central portion to the end portion. Therefore, stable polishing work can be expected.

Further, this polishing pad has an advantage that it can be smoothly fixed to the surface plate and the replacement work can be efficiently performed. As described above, since the adsorption layer of the polishing pad has a lower peeling force than the shearing force, the polishing pad can be fixed by lightly pressing the polishing pad in the vertical direction on the surface plate, and can be easily attached and detached. Therefore, the polishing pad by the applicant of the present application is also useful from the viewpoint of improving the efficiency of the polishing work.

As described above, the polishing pad provided with the predetermined adsorption layer by the applicant of the present application has good convenience in the replacement work and also has excellent fixing ability to the surface plate. However, according to the study by the present inventors, even when such a useful polishing pad is used, although rarely, the polishing pad may be displaced or partially peeled off due to the progress of the polishing work. It has been confirmed that there is.

The deviation or peeling of the polishing pad that occurs in this case is not necessarily due to deterioration of the adsorption layer due to the length of the polishing time or the frequency of replacement of the polishing pad. In addition, it is not a problem that always occurs, and the polishing work can be performed without any problem in most polishing environments and conditions. However, in order to make this polishing pad more popular than ever, it is preferable to eliminate problems such as peeling even if there is a slight possibility.

The present invention has been made based on the above background, and in a polishing method using a polishing pad having an adsorption layer made of a predetermined silicone composition, deviation from the surface plate, peeling, etc. are suppressed. Provides a method for. Specifically, an auxiliary member useful for a polishing pad having an adsorption layer and a polishing method using the auxiliary member will be disclosed.

For the above purpose, the present inventors have decided to investigate factors such as peeling from the surface plate during polishing work with respect to a polishing pad provided with a predetermined adsorption layer. As a result, it was considered that the polishing slurry may invade the interface between the adsorption layer of the polishing pad and the surface plate, which may cause peeling or the like. The polishing slurry is a suspension having a basic composition in which polishing abrasive grains made of colloidal silica, alumina, ceria, diamond, etc. are dispersed in a solvent. As a result of the study, the present inventors have considered that the penetration into the interface between the polishing pad and the surface plate may increase depending on the composition and composition of the polishing slurry. In particular, it was considered that the penetration into the interface would be improved in the polishing slurry having low viscosity by adjusting the components.

The low-viscosity polishing slurry penetrates the interface relatively easily due to the influence of the capillary phenomenon due to the minute gap between the polishing pad and the surface plate. The state in which the slurry is accumulated at the interface is not preferable for the adsorption layer made of the silicone composition, and the adsorption force is lowered. Due to this decrease in suction force, the polishing pad may be peeled off or displaced from the surface plate.

However, even if the polishing slurry is the cause of the decrease in the capacity of the adsorption layer of the polishing pad, it is difficult to easily change its composition and composition. The components and configurations of the polishing abrasive grains, the solvent, and the like that make up the polishing slurry are generally optimized based on the material of the member to be polished, the required polishing accuracy, and the like. Even if there is a concern that the polishing slurry may affect a specific polishing pad, it is not easily acceptable to make changes that affect the polishing accuracy or the like.

In addition, there seems to be a limit to the improvement on the polishing pad side. In particular, it can be said that it is almost impossible to enhance the resistance to a specific polishing slurry while maintaining the advantages of the composition and structure of the adsorption layer described above.

Therefore, the present inventors have studied the application of an auxiliary member capable of adjusting the fixed state to the surface plate while using the conventional polishing pad provided with the adsorption layer as it is. Then, he came up with a thin plate-shaped underlay to be installed under the polishing pad, which is provided with a groove for capturing and discharging the polishing slurry leaching from the surface of the polishing pad.

That is, the present invention is a thin plate-shaped underlay installed between the polishing pad and the surface plate when the polishing pad is fixed to the surface plate, and the outer edge of the underlay is placed on the surface in contact with the polishing pad. At least one annular groove is formed along the outer edge, and at least one discharge groove extending from the annular groove formed on the outermost edge side toward the outer edge of the underlay and having an opening at the outer edge end is formed. , An underlay for polishing pads.

FIG. 1 is a diagram showing the appearance of a specific example of an underlay for a polishing pad according to the present invention. The underlay for the polishing pad illustrated in FIG. 1 is a disk-shaped thin plate, and an annular groove is formed along the outer periphery thereof. In the example of FIG. 1, two concentric annular grooves are formed. The annular groove on the outermost edge side is a groove toward the outer edge of the underlay, and a discharge groove having an opening is formed.

Then, FIG. 2 illustrates a state when the underlay for the polishing pad according to the present invention exemplified in FIG. 1 is applied and the polishing pad is fixed to the surface plate. When installing the underlay according to the present invention, the underlay is brought into close contact with the surface plate without any gaps. On the other hand, when the polishing pad is brought into close contact with the underlay, a gap is formed at the interface between the two due to the annular groove. In this way, with the polishing pad fixed to the surface plate via the underlay, the polishing slurry is supplied to the surface of the polishing pad, and the polishing pad is rotated to perform the polishing work.

As shown in FIG. 2, during the polishing operation, the polishing slurry reaches the side surface of the polishing pad by centrifugal force and gradually permeates the interface between the adsorption layer and the underlay. In the present invention, first, the polishing slurry that permeates this interface is stored in the annular groove. As a result, the polishing slurry is suppressed from spreading over the entire surface at the interface of the adsorption layer, and the influence of the polishing slurry becomes local. Then, the polishing slurry in which the annular groove is stored is discharged to the outside via the discharge groove by the rotation of the polishing pad. By the above process, the close contact state near the edge of the polishing pad is maintained, so that it is possible to suppress the deviation and peeling that are likely to occur from there.

Next, the configuration of the underlay for the polishing pad according to the present invention having the above-mentioned action will be described in more detail.

The overall shape and dimensions of the polishing pad underlay according to the present invention are substantially the same as the applied polishing pad. Generally, the polishing pad is circular, so the underlay is often disk-shaped. The thickness of the underlay is not particularly limited, but it does not need to be excessively thick. The thickness of the underlay is preferably a thin plate of about 150 μm to 1000 μm, and more preferably 150 μm to 500 μm.

As the constituent material of the underlay, various resin materials are applied in consideration of chemical stability to the polishing slurry in addition to the material cost and strength. Specifically, it is a resin such as polyester, polyethylene, polystyrene, polypropylene, nylon, urethane, polyvinylidene chloride, and polyvinyl chloride. A polyester-based resin material is preferable, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are preferable, and PET is particularly preferable.

As described above, the feature of the underlay for the polishing pad according to the present invention is that an annular groove for storing and discharging the polishing slurry is formed. The annular groove is an annular groove along the outer edge of the underlay. At least one annular groove is formed at a position slightly distant from the outer edge of the underlay toward the center. One or two or more annular grooves are formed, and one to four annular grooves are preferably formed.

Further, in order to discharge the polishing slurry stored in the annular groove to the outside, a discharge groove extending from the annular groove toward the outer edge of the underlay is formed in the underlay. The drainage ditch has an opening at the outer edge of the underlay, from which the polishing slurry is discharged. The drainage ditch may be linear or curved. At least one drainage ditch is formed, but it is preferable to form a plurality of drainage ditches. It is preferable to form 2 to 8 drainage ditches, and it is preferable to form them at equal intervals.

Further, when two or more annular grooves are formed, a communication groove that communicates the adjacent annular grooves is formed in order to effectively discharge the polishing slurry from the annular grooves other than the annular groove on the outermost edge side. Is preferable. It is preferable that at least one communication groove is formed for each combination of adjacent annular grooves. The communication groove may also be linear or curved. Further, like the discharge grooves, it is preferable to form 2 to 8 grooves, and it is preferable to form them at equal intervals.

The position of forming the annular groove is not particularly limited. Preferably, the annular groove located on the outermost edge side is formed at a distance of 5 mm or more from the outer edge of the underlay. This is because if this interval is excessively large, the polishing slurry may stay at the interface between the underlay and the polishing pad before reaching the annular groove. Further, two or more annular grooves are formed, and it is preferable that the distance between the adjacent annular grooves is 1.5 mm or more and 15 mm or less. More preferably, the interval is set to 1.5 mm or more and 5 mm or less. When forming two or more annular grooves, it is preferable to form them concentrically at equal intervals. The position of the groove described above is shifted with reference to the center line of the groove width.

The depth (height) of the groove is preferably in the range of 20% or more and 80% or less with respect to the thickness of the underlay. The width of the groove is preferably in the range of 2 mm or more and 10 mm or less. The dimensions of these grooves are set in consideration of suitable storage and discharge of the polishing slurry. The underlay of the present invention is formed with three types of grooves, an annular groove, a discharge groove, and a communication groove, all of which are preferably within the above range. Further, it is preferable that the depths of these grooves are the same.

Further, the underlay for the polishing pad according to the present invention has a surface roughness (Ra) of 0.01 to 0.7 μm in a region serving as a contact surface with the adsorption layer, that is, a region in which no groove is formed. Is preferable. The surface roughness of this underlay is a regulation for improving the fixed state of the polishing pad. According to the study by the present inventors, if the surface roughness of the contact surface with the adsorption layer of the underlay exceeds 0.7 μm, instability occurs in the fixed state of the polishing pad, although it is minute, and the polishing accuracy is lowered. May occur. In addition, if the surface of the underlay is excessively rough, the polishing pad may peel off. As described above, in consideration of the adhesion between the underlay and the polishing pad, the preferable range of the surface roughness of the underlay was set to 0.7 μm or less. This surface roughness is preferably reduced as much as possible, but from a practical point of view, the lower limit is preferably 0.01 μm. The surface roughness of the underlay is more preferably 0.01 to 0.25 μm.

The underlay for the polishing pad according to the present invention has a groove formed on the surface in contact with the adsorption layer of the polishing pad, but the configuration of the other surface, that is, the surface joined to the surface plate is particularly limited. There is no such thing. The material of the underlay may be exposed without any special processing or coating on this surface. Further, a bonding layer for fixing the underlay to the surface plate may be formed on this surface. This is to firmly fix the underlay. The bonding layer is preferably composed of an adhesive or an adhesive. Specific adhesives and adhesives include acrylic and rubber adhesives, silicone adhesives, and epoxy adhesives. By providing the joint layer on the underlay in advance, it can be quickly fixed to the surface plate during polishing work. However, since fixing is possible by applying an adhesive or an adhesive to the surface plate or the underlay at the stage of fixing the underlay, the bonding layer is not essential. If the polishing slurry permeates the bonding interface between the underlay and the surface plate, the underlay may be peeled off or displaced. Therefore, the pressure-sensitive adhesive / adhesive is required to be resistant to the polishing slurry. It is also required that the joint between the underlay and the surface plate does not create a gap.

The underlay for the polishing pad described above is useful for the polishing pad (Patent Documents 1 and 2) provided with a predetermined adsorption layer. Here, the configuration of a suitable polishing pad will be described. This polishing pad has an essential configuration of a polishing layer for polishing a member to be polished and an adsorption layer composed of a silicone composition.

The polishing layer is a member that appropriately holds the supplied polishing slurry and polishes the surface of the member to be polished. As the polishing layer, a polishing cloth applied to a conventional general polishing pad can be applied. For example, a non-woven fabric made of nylon, polyurethane, polyethylene terephthalate or the like, a foam molded product or the like is applied.

The adsorption layer is a member for fixing the polishing pad by the adsorption action derived from the constituent material. This adsorption layer is composed of a silicone composition, and is basically the same as that applied to the conventional polishing pads (Patent Documents 1 and 2) by the present inventors described above. That is, the silicone composition constituting the adsorption layer is a silicone composed of a linear polyorganosiloxane having a vinyl group only at both ends, and a silicone composed of a linear polyorganosiloxane having a vinyl group at both ends and a side chain. A composition obtained by cross-linking at least one silicone selected from a silicone composed of a branched polyorganosiloxane having a vinyl group only at the terminal and a silicone composed of a branched polyorganosiloxane having a vinyl group at the terminal and side chains. be.

Specific examples of the above-mentioned silicone include the compound of Chemical formula 1 as an example of the linear polyorganosiloxane. Further, as an example of the branched polyorganosiloxane, the compound of Chemical formula 2 can be mentioned.

（式中Ｒは下記有機基、ｎは整数を表す）

(R in the formula represents the following organic group, n represents an integer)

（式中Ｒは下記有機基、ｍ、ｎは整数を表す）

(In the formula, R represents the following organic group, and m and n represent integers)

Specific examples of the substituent (R) in Chemical formulas 1 and 2 include an alkyl group such as a methyl group, an ethyl group and a propyl group, an aryl group such as a phenyl group and a trill group, or a carbon atom of these groups. Examples thereof include monovalent hydrocarbon groups excluding homozygous or heterologous unsubstituted or substituted aliphatic unsaturated groups in which a part or all of hydrogen atoms are substituted with halogen atoms, cyano groups and the like. Preferably, at least 50 mol% thereof is a methyl group. The substituents may be different or the same. Further, this polysiloxane may be used alone or as a mixture of two or more kinds.

The silicone constituting the adsorption layer having a number average molecular weight of 30,000 to 100,000 has a suitable adsorption action. However, in adjusting the surface roughness, the number average molecular weight of the applied silicone and the firing temperature at the manufacturing stage have an influence. The number average molecular weight of silicone is preferably 30,000 to 60,000 in order to easily exhibit suitable surface roughness.

The polishing pad is composed of the polishing layer and the adsorption layer described above. Normally, these are not directly bonded, and an appropriate base material is used to form an adsorption layer on one surface of the base material, and a polishing layer is bonded to the other surface to form a polishing pad. The base material is composed of a resin material such as polyester (PET, PEN), polyethylene, polystyrene, polypropylene, nylon, urethane, polyvinylidene chloride, and polyvinyl chloride.

Next, a polishing method using an underlay for a polishing pad according to the present invention will be described. The polishing method according to the present invention basically has the same steps as the polishing method using the polishing pad having the above-mentioned predetermined adsorption layer. That is, the polishing pad is adsorbed and fixed to the surface plate, the polishing pad is rotated while supplying the polishing slurry, and the member to be polished is pressed against the polishing pad to perform the polishing work. The present invention is characterized in that the polishing pad is fixed to the surface plate via the underlay according to the present invention.

That is, the polishing method according to the present invention is a polishing method in which a polishing pad including at least a polishing layer and an adsorption layer is fixed to a platen and a member to be polished is slid on the polishing layer of the polishing pad. The adsorption layer is a silicone composed of a linear polyorganosiloxane having a vinyl group only at both ends, a silicone composed of a linear polyorganosiloxane having a vinyl group at both ends and a side chain, and a branch having a vinyl group only at the end. It is composed of a composition obtained by cross-linking at least one kind of silicone selected from silicones made of polyorganosiloxane and silicones made of branched polyorganosiloxane having vinyl groups at the ends and side chains. After fixing the underlay for the polishing pad of the present invention, the polishing pad is fixed to the underlay for polishing.

In this polishing method, when the underlay for the polishing pad of the present invention is fixed to the surface plate, if the above-mentioned bonding layer is provided on the surface plate, the underlay is fixed by adhering and adhering the surface of the bonding layer to the surface plate. Will be done. In such a case, since the release paper is usually attached to the surface of the joint layer of the underlay, the release paper is peeled off to expose the joint layer and fixed to the surface plate. If the underlay is not provided with the above-mentioned bonding layer, the underlay is fixed by pressing at least one of the underlay and the surface plate after applying an adhesive / adhesive.

On the other hand, when the polishing pad is fixed to the surface plate on which the underlay is fixed, the polishing pad is placed on the underlay and the polishing pad is pressed from the polishing layer side toward the surface plate to complete the process. At this time, it is not necessary to press the entire surface with an even force, and the adsorption action of the adsorption layer is exhibited by pressing the surface of the polishing layer as if stroking it.

As described above, after the polishing pad is adsorbed and fixed to the surface plate via the underlay, normal polishing work can be performed. Here, there are no restrictions on the material, shape, and dimensions of the member to be polished, which is the subject of the present invention.

During the polishing operation, the polishing slurry is supplied between the member to be polished and the polishing pad. There are restrictions on the composition of the polishing slurry supplied during this polishing operation (material and particle size of the abrasive grains, type of solvent, slurry concentration, etc.) and the presence / absence / type of additives (surfactant, thickener, etc.). There is no. However, the present invention is particularly useful for polishing operations that apply a polishing slurry with low viscosity. This is because the polishing slurry having low viscosity easily penetrates into the bonding interface between the adsorption layer and the surface plate. The polishing slurry for which the present invention is effective is a polishing slurry having a viscosity of 10 mPa · s or less at 20 ° C. It is also effective for polishing slurries of 3 mPa · s or less, and is also useful for polishing slurries of 1.5 mPa · s or less. Even with a low-viscosity slurry of 0.01 mPa · s, peeling of the polishing pad is unlikely to occur.

The members to be polished are sequentially polished, and when the polishing pad is worn out, it is replaced. At this time, as in the conventional case, the polishing pad can be easily released by shifting it upward from the polishing pad and injecting air into the interface. Then, the new polishing pad can be fixed to the surface plate to continue the polishing work.

The underlay for a polishing pad according to the present invention is useful as an auxiliary member for polishing work using a polishing pad having an adsorption layer made of a predetermined silicone composition. According to the present invention, it is possible to prevent the polishing pad from being displaced or peeled off due to the permeation of the polishing slurry. As a result, even in a long-time polishing work, efficient work without interruption due to a defect of the polishing pad becomes possible.

The figure explaining the appearance of an example of the underlay for a polishing pad which concerns on this invention. The figure explaining the fixed state of the polishing pad when the underlay for the polishing pad which concerns on this invention is applied. The schematic diagram of the polishing apparatus used in this embodiment. The figure explaining the structure of the conventional polishing pad provided with the adsorption layer.

Hereinafter, preferred embodiments of the present invention will be described. In the present embodiment, it is a figure which manufactures the underlay which has the same structure as the underlay for the polishing pad which concerns on this invention exemplified in FIG. 1, and shows the appearance and the cross-sectional structure of. The underlay of the present embodiment is a disk-shaped thin plate (dimensions: diameter 743 mm, thickness 250 μm) made of a resin material (PET). On the surface of this underlay (the surface on the polishing pad side), two annular grooves along the outer peripheral shape are formed concentrically. The outer annular groove on the outermost edge side is formed at a distance of 15 mm from the edge of the underlay, and the inner annular groove is formed at a distance of 5 mm from the outer annular groove. Further, in the annular groove on the outermost edge, a discharge groove is formed in the direction of the outer edge of the underlay. Further, a communication groove for communicating these is formed between the two annular grooves. The depth of each of these grooves is 150 μm. The surface roughness (Ra) of the PET plate material constituting the underlay of the present embodiment was 0.4 μm.

The underlay for the polishing pad of the present embodiment was manufactured by cutting out a circular sheet having the above-mentioned dimensions from a PET sheet and forming an annular groove or the like at a predetermined position. Each groove was formed by cutting with a router.

In the present embodiment, the silicon wafer is polished by using the polishing pad underlay and the polishing pad provided with the adsorption layer.

The polishing pad used in this embodiment is a silicone (molecular weight) composed of linear polyorganosiloxane having vinyl groups only at both ends on one surface of a circular base material (thickness 50 μm, size φ800 mm) made of PET. It is a bond of an adsorption layer (thickness 25 μm) made of 30000). A suede-like polishing cloth (model number 7355-000F: nap length 450 μm, thickness 1.37 mm) is adhered to the other surface of the base material.

A polishing test was performed using the polishing pad and the underlay described above. In this polishing test, the underlay for the polishing pad of the present embodiment was adhered and fixed to the surface plate (outer diameter 800 mm, manufactured by SUS) of the polishing apparatus shown in FIG. 3 with a rubber-based adhesive. Then, after the polishing pad was adsorbed and fixed on the underlay, a silicon wafer (φ8 inch) was polished as a member to be polished. In the polishing work, the silicon wafer was rotated while being pressed on the polishing layer, and at the same time, the polishing slurry was dropped onto the polishing layer (flow rate 150 ml / min) to perform the polishing work.

The polishing slurry used was a commercially available polishing agent containing colloidal silica as polishing particles (trade name: Glanzox, manufactured by Fujimi Incorporated Co., Ltd.) diluted with pure water and a surfactant (abrasive: pure water: surfactant). Agent = 70:25: 5). This polishing slurry had a viscosity of 0.7 mPa · s.

Other polishing conditions were as follows.
・ Polishing pressure: 0.163kgf / cm ²
・ Rotation speed of polishing pad: 45 rpm
-Rotation speed of the member to be polished: 47 rpm
・ Head swing speed: 250 mm / min
・ Number of wafers to be polished, polishing time: 200 wafers are polished for 3 minutes per wafer.

After the polishing work in each of the above time intervals, the state of adhesion between the polishing pad and the surface plate was visually confirmed, and the presence or absence of misalignment or peeling of the polishing pad was examined. As a result, no deviation or peeling of the polishing pad was observed even after polishing 200 wafers. Further, when the wafer after the polishing work was washed with pure water and dried, and then the surface to be polished was observed, no remarkable scratches were observed.

Comparative Example : In order to confirm the effect of the underlay for the polishing pad of the present embodiment, the polishing test was performed by fixing the polishing pad to the surface plate without using the underlay as in the conventional case. At this time, when polishing was performed under the same polishing conditions as above, there was no problem until after 50 wafers were polished. However, the polishing pad was displaced from around 50 sheets, and even after that, partial peeling occurred. Therefore, the effect of the underlay in the present invention was confirmed.

As described above, the underlay for the polishing pad according to the present invention acts as an auxiliary member for suppressing the displacement or peeling of the polishing pad in the polishing work by the conventional polishing pad having an adsorption layer. According to the present invention, the fixed state of the polishing pad can be maintained even in the polishing work for a long time. INDUSTRIAL APPLICABILITY The present invention can form a highly accurate polished surface even for a wafer or a display panel whose diameter and area are increasing.

Claims (6)

In a polishing method in which a polishing pad including a polishing layer and an adsorption layer is fixed to a surface plate and a member to be polished is slid on the polishing layer of the polishing pad.
The adsorption layer of the polishing pad is a silicone composed of a linear polyorganosiloxane having a vinyl group only at both ends, a silicone composed of a linear polyorganosiloxane having a vinyl group at both ends and a side chain, and a silicone having a vinyl group only at the ends. It comprises a composition obtained by cross-linking at least one silicone selected from a silicone composed of a branched polyorganosiloxane having a vinyl group and a silicone composed of a branched polyorganosiloxane having a vinyl group at the terminal and side chains. can be,
When fixing the polishing pad to the surface plate
An underlay for a thin plate-shaped polishing pad, at least one annular groove along the outer edge of the underlay is formed on the surface in contact with the polishing pad, and the annular groove formed on the outermost edge side. An underlay for a polishing pad, which extends from the bottom toward the outer edge of the underlay and has at least one discharge groove having an opening at the outer edge end, is fixed to the surface plate.
Then, a polishing method in which the adsorption layer of the polishing pad is fixed to the underlay and polished. The polishing method according to claim 1, wherein two or more annular grooves are formed in the underlay for the polishing pad, and at least one communication groove that communicates the adjacent annular grooves is formed . The polishing method according to claim 1 or 2, wherein the annular groove located on the outermost edge side of the underlay for the polishing pad is formed at a distance of 5 mm or more from the outer edge of the underlay . One of claims 1 to 3, wherein two or more annular grooves are formed in the underlay for the polishing pad, and the distance between the adjacent annular grooves is 1.5 mm or more and 15 mm or less. The polishing method described in. Claims 1 to claim that the depth of the groove formed on the surface of the underlay for the polishing pad is 20% or more and 80% or less with respect to the thickness of the underlay, and the width of the groove is 2 mm or more and 10 mm or less. Item 4. The polishing method according to any one of Items 4. The polishing method according to any one of claims 1 to 5, wherein the surface roughness (Ra) of the region where the groove on the surface of the underlay for the polishing pad is not formed is 0.01 to 0.7 μm .

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