JP2016124043A - Abrasive pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive pad enabled to reduce a polishing failure by suppressing the occurrence of a particle or scratch while suppressing the reduction of a polishing rate.SOLUTION: A circular polishing sheet 8 or a circular abrasive pad includes a circular abrasive layer. The circular abrasive layer includes a concentric circular groove 10 and one cross-shaped groove 11, and said cross-shaped groove 11 intersects orthogonally at the center of the circular abrasive layer.SELECTED DRAWING: Figure 2

Description

  The present invention is used for flattening optical materials such as lenses and reflecting mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and materials that require high surface flatness such as general metal polishing. The present invention relates to a polishing pad and a method for manufacturing a semiconductor device using the same.

  When manufacturing a semiconductor device, a process of forming a conductive film on the wafer surface and forming a wiring layer by photolithography, etching, or the like, a process of forming an interlayer insulating film on the wiring layer, etc. These steps are performed, and irregularities made of a conductor such as metal or an insulator are generated on the wafer surface. In recent years, miniaturization of wiring and multilayer wiring have been advanced for the purpose of increasing the density of semiconductor integrated circuits, and along with this, technology for flattening the irregularities on the wafer surface has become important.

  As a method for flattening the irregularities on the wafer surface, chemical mechanical polishing (hereinafter referred to as CMP) is generally employed. CMP is a technique of polishing using a slurry-like abrasive (hereinafter referred to as slurry) in which abrasive grains are dispersed in a state where the surface to be polished of a wafer is pressed against the polishing surface of a polishing pad. As shown in FIG. 1, for example, a polishing apparatus generally used in CMP includes a polishing surface plate 2 that supports a polishing pad 1 and a support base (polishing head) 5 that supports a material to be polished (semiconductor wafer) 4. And a backing material for uniformly pressing the wafer, and a slurry supply mechanism. The polishing pad 1 is attached to the polishing surface plate 2 by attaching it with a double-sided tape, for example. The polishing surface plate 2 and the support base 5 are disposed so that the polishing pad 1 and the material to be polished 4 supported by each of the polishing surface plate 2 and the support base 5 are opposed to each other, and are provided with rotating shafts 6 and 7 respectively. Further, a pressurizing mechanism for pressing the workpiece 4 against the polishing pad 1 is provided on the support base 5 side.

  In order to improve polishing characteristics such as polishing speed and planarization characteristics, it is important to uniformly disperse new slurry over the entire surface of the polishing pad and to efficiently discharge used slurry. In view of cost, it is preferable to keep the new slurry on the polishing pad as much as possible to reduce the consumption of the slurry. Therefore, normally, the polishing surface that comes into contact with the material to be polished of the polishing pad has a groove for holding and renewing the slurry (for example, Patent Documents 1 to 3).

JP 2010-234458 A JP 2011-177844 A JP2011-235425A

  Usually, the polishing surface is dressed before and during polishing. Dress debris often remains on the surface of the polishing pad immediately after the dress, and the dress debris generates particles and scratches. Further, since polishing scraps are generated when polishing is continued, particles and scratches are also generated by the polishing scraps. By providing a large number of grid-like and / or radial grooves on the surface of the polishing pad, it is possible to discharge polishing dust and dress waste and prevent particles and scratches (Patent Documents 1 to 3). The surface area of the polished surface is reduced and the polishing rate is lowered. On the other hand, if the groove width is reduced or the number of grooves is reduced to increase the area of the polishing surface, polishing waste and dress waste cannot be discharged at a high rate, and particles and scratches are generated. breaking bad. That is, it has been extremely difficult to achieve both a high polishing rate and a low polishing defect.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polishing pad capable of suppressing generation of particles and scratches while suppressing a decrease in polishing rate and reducing polishing defects.

  The present invention is a circular polishing pad including a circular polishing layer, wherein the circular polishing layer has a concentric circular groove and one cross-shaped groove, and the cross-shaped groove is substantially orthogonal to the center of the circular polishing layer. A circular polishing pad.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of a particle | grain and a scratch can be suppressed, suppressing the fall of a polishing rate, and the polishing pad which can reduce polishing defect can be provided. The reason why the present invention has such an effect is not clear, but is considered as follows.

    Since the concentric circular grooves have a high slurry holding power, it is possible to obtain a good polishing rate, but it is difficult to discharge the slurry in the grooves. By providing a single cross groove instead of a plurality of radial grooves, dress waste and polishing waste can be discharged while suppressing a decrease in the polishing rate, and generation of particles and scratches can be reduced. It is done.

Schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing Schematic showing the groove shape of the polishing layer

  The circular polishing pad according to the present embodiment is a circular polishing pad including a circular polishing layer, and the circular polishing layer has a concentric circular groove and one cruciform groove, and the cruciform groove is formed of the circular polishing layer. It is characterized by being substantially orthogonal at the center.

  The polishing material is not particularly limited. For example, polyurethane resin, polyester resin, polyamide resin, acrylic resin, polycarbonate resin, halogen resin (polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, etc.), polystyrene, olefin Examples thereof include resins (polyethylene, polypropylene, etc.), epoxy resins, and photosensitive resins. Polyurethane resin is preferable as a material for the polishing layer because it is excellent in abrasion resistance and can be adjusted to have desired physical properties by variously changing the raw material composition.

  The polishing layer may be a foam or a non-foam, but is preferably formed of a polyurethane resin foam.

  Examples of the method for producing a polyurethane resin foam include a method of adding hollow beads, a mechanical foaming method, and a chemical foaming method.

  The average cell diameter of the polyurethane resin foam is preferably 30 to 80 μm, more preferably 30 to 60 μm. When deviating from this range, the polishing rate tends to decrease, or the planarity of the polished material (wafer) after polishing tends to decrease.

  The specific gravity of the polyurethane resin foam is preferably 0.5 to 1.3. When the specific gravity is less than 0.5, the surface strength of the polishing layer decreases, and the planarity of the material to be polished tends to decrease. On the other hand, when the ratio is larger than 1.3, the number of bubbles on the surface of the polishing layer decreases, and planarity is good, but the polishing rate tends to decrease.

  The hardness of the polyurethane resin foam is preferably 40 to 70 degrees with an Asker D hardness meter. When the Asker D hardness is less than 40 degrees, the planarity of the material to be polished is lowered. When the Asker D hardness is more than 70 degrees, the planarity is good but the uniformity of the material to be polished is lowered. There is a tendency.

  The size of the circular polishing layer is not particularly limited, but is usually about 30 to 100 cm in diameter.

  The circular polishing layer may be provided with an optical end point detection window (light transmission region).

  Although the thickness of a circular polishing layer is not specifically limited, Usually, it is about 0.8-4 mm, and it is preferable that it is 1.5-2.5 mm. As a method for producing the circular polishing layer having the above thickness, a foam block is sliced to a predetermined thickness using a band saw type or canna type slicer, and a resin is poured into a mold having a cavity of a predetermined thickness and cured. Examples thereof include a method and a method using a coating technique or a sheet forming technique.

  Hereinafter, the polishing pad of this embodiment will be described with reference to the drawings. FIG. 2 is a schematic view showing the surface of the polishing layer of the polishing pad of this embodiment. As shown in FIG. 2, the polishing layer 8 has concentric grooves 10 and cross-shaped grooves 11 on the surface thereof.

  The groove pitch of the concentric circular grooves 10 is not particularly limited, but is preferably 1.0 to 6.5 mm, more preferably 1.2 to 4.5 mm from the viewpoint of suppressing the polishing rate reduction and from the viewpoint of dress waste and polishing waste discharge. 1.5 to 4.0 mm is more preferable.

  The width of the outermost peripheral portion 9 of the polishing layer is 1/2 or more of the groove pitch of the concentric grooves 10 from the viewpoint of pad end stability during polishing such as turning up of the polishing layer and stability of fixing to a surface plate, More than groove pitch is preferable and it is more preferable that it is wider than groove pitch.

  The groove width of the concentric groove 10 is not particularly limited, but is preferably 0.15 to 1.2, more preferably 0.2 to 0.7 mm from the viewpoint of suppressing the polishing rate reduction and from the viewpoint of discharging dress debris and polishing debris. 0.25 to 0.5 mm is more preferable.

  The groove depth of the concentric grooves 10 is adjusted as appropriate according to the thickness of the circular polishing layer, but is generally 0.3 to 1.5 mm from the viewpoint of suppressing the polishing rate reduction, and from the viewpoint of discharging dress debris and polishing debris. Is preferable, 0.4 to 1.2 mm is more preferable, and 0.45 to 1.0 mm is more preferable.

  The groove pitch, groove width, and groove depth of the concentric circular grooves 10 are generally constant, but in order to make the slurry retention and renewability desirable, the groove pitch, groove width, The groove depth and the like can be changed. When the groove pitch, groove width, groove depth, etc. are changed for each range, the width of the outermost peripheral portion 9 is 1/2 or more of the groove pitch closest to the outermost peripheral portion 9, and preferably equal to or larger than the groove pitch. More preferably, it is wider than the groove pitch. The upper limit of the width of the outermost peripheral portion 9 is not particularly limited, but is preferably not more than twice the groove pitch of the concentric circular grooves 10 from the viewpoint of not impairing the effect of holding and updating the slurry of the grooves 10.

  The cross-shaped groove 11 has a shape in which two linear grooves are substantially orthogonal to each other. One cross-shaped groove 11 is provided in the polishing layer. In this specification, “substantially orthogonal” means intersecting in the range of 90 ° ± 10 °.

  The groove width of the cross-shaped groove 11 is not particularly limited, but is preferably 2.0 to 8.0 mm, more preferably 2.0 to 6.0 mm from the viewpoint of suppressing the reduction of the polishing rate and the viewpoint of discharging dress waste and polishing waste. Preferably, 2.0 to 4.0 mm is more preferable.

  The groove depth of the cruciform groove 11 is appropriately adjusted according to the thickness of the circular polishing layer 8, but is generally 0.1 to 1. in terms of maintaining the polishing rate and discharging dress debris and polishing debris. 5 mm is preferable, 0.45-1.3 mm is preferable, and 0.45-1.2 mm is more preferable. The groove depth of the cross-shaped groove is preferably the same as the groove depth of the concentric circular groove or deeper than the groove depth of the concentric circular groove from the viewpoint of discharging dress waste and polishing waste.

  When the number of defects is constantly high or when the number of defects tends to increase with time, the depth of the cross-shaped groove is preferably 0.1 mm or more from the viewpoint of promoting the discharge of slurry. Further, when the groove depth is deep, the volume of the groove is increased and the slurry tends to be insufficient, so that the polishing rate is lowered. Accordingly, the depth of the cross-shaped groove is preferably 0.1 mm or less from the viewpoint of suppressing a decrease in the polishing rate.

  When the contact area between the material to be polished and the surface of the polishing layer decreases, the polishing rate decreases. Therefore, the ratio of the area of the polishing layer surface to the groove area (surface groove area / pad surface area × 100) is 5 to 25% from the viewpoint of suppressing the generation of particles and the like while maintaining a high polishing rate. Preferably, 12 to 17% is more preferable. The area of the polishing layer surface is the area of the entire polishing layer, and the area of the groove is the sum of the areas of concentric grooves and the cross-shaped grooves.

  It is preferable that the central part of the concentric circle related to the concentric circular groove 10 and the substantially orthogonal part of the two linear grooves of the cruciform groove 11 are in the substantially central part of the circular polishing layer 8. During polishing, a force is applied to the surface of the polishing layer 8 in the polishing direction, and there is no escape for the force on the surface of the polishing layer 8, particularly the central portion of the polishing layer 8. The central portion of the concentric circles related to the concentric grooves 10 and the substantially orthogonal portions of the two linear grooves of the cruciform groove 11 pass through the center of the polishing layer 8 to handle the surface of the polishing layer 8 generated during polishing. Since it can reduce and curl of the center part of the polishing layer 8 can be suppressed, generation of particles and the like can be suppressed.

  The method for forming the concentric grooves 10 and the cruciform grooves 11 is not particularly limited. For example, a method of machine cutting using a jig such as a predetermined size tool, a mold having a predetermined surface shape, or the like. A method of forming the resin by pouring and curing the resin, a method of pressing and forming the resin with a press plate having a predetermined surface shape, a method of forming using photolithography, a method of forming using a printing technique, Examples thereof include a formation method using a laser beam using a carbon dioxide laser or the like. Further, the corners of the substantially orthogonal portion of the cross-shaped groove 10 may be chamfered.

  The circular polishing pad may be only the circular polishing layer, or may be a laminate of the circular polishing layer and another layer (such as a cushion layer).

  The cushion layer supplements the characteristics of the circular polishing layer. The cushion layer is necessary in order to achieve both planarity and uniformity in a trade-off relationship in CMP. Planarity refers to the flatness of a pattern portion when a material having fine irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire material to be polished. The planarity is improved by the characteristics of the circular polishing layer, and the uniformity is improved by the characteristics of the cushion layer. In the circular polishing pad, the cushion layer is preferably softer than the circular polishing layer.

  Examples of the cushion layer include a fiber nonwoven fabric such as a polyester nonwoven fabric, a nylon nonwoven fabric, and an acrylic nonwoven fabric, a resin-impregnated nonwoven fabric such as a polyester nonwoven fabric impregnated with polyurethane, a polymer resin foam such as polyurethane foam and polyethylene foam, a butadiene rubber, Examples thereof include rubber resins such as isoprene rubber and photosensitive resins.

  Examples of means for attaching the circular polishing layer and the cushion layer include a method in which the circular polishing layer and the cushion layer are sandwiched and pressed with a double-sided tape.

  The double-sided tape has a general configuration in which adhesive layers are provided on both sides of a substrate such as a nonwoven fabric or a film. In consideration of preventing the slurry from penetrating into the cushion layer, it is preferable to use a film for the substrate. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low. In addition, since the circular polishing layer and the cushion layer may have different compositions, the composition of each adhesive layer of the double-sided tape can be made different to optimize the adhesive strength of each layer.

  The circular polishing pad may be provided with a double-sided tape on the surface to be bonded to the platen. As the double-sided tape, a tape having a general configuration in which an adhesive layer is provided on both surfaces of a base material can be used as described above. As a base material, a nonwoven fabric, a film, etc. are mentioned, for example. In consideration of peeling from the platen after use of the circular polishing pad, it is preferable to use a film for the substrate. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low.

  The semiconductor device is manufactured through a step of polishing the surface of the semiconductor wafer using the polishing pad. A semiconductor wafer is generally a laminate of a wiring metal and an oxide film on a silicon wafer. The method and apparatus for polishing the semiconductor wafer are not particularly limited. For example, as shown in FIG. 1, a polishing surface plate 2 that supports a polishing pad (polishing layer) 1 and a support table (polishing head) that supports the semiconductor wafer 4. 5 and a polishing apparatus equipped with a backing material for uniformly pressing the wafer and a supply mechanism of the abrasive 3. The circular polishing pad 1 is mounted on the polishing surface plate 2 by, for example, attaching with a double-sided tape. The polishing surface plate 2 and the support base 5 are disposed so that the polishing pad 1 and the semiconductor wafer 4 supported on each of the polishing surface plate 2 and the support table 5 face each other, and are provided with rotating shafts 6 and 7 respectively. Further, a pressure mechanism for pressing the semiconductor wafer 4 against the circular polishing pad 1 is provided on the support base 5 side. In polishing, the semiconductor wafer 4 is pressed against the polishing pad 1 while rotating the polishing surface plate 2 and the support base 5, and polishing is performed while supplying slurry. The flow rate of the slurry, the polishing load, the polishing platen rotation speed, and the wafer rotation speed are not particularly limited and are appropriately adjusted.

  As a result, the protruding portion of the surface of the semiconductor wafer 4 is removed and polished flat. Thereafter, a semiconductor device is manufactured by dicing, bonding, packaging, or the like. The semiconductor device is used for an arithmetic processing device, a memory, and the like.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

<Measurement and evaluation method>
[Polishing conditions]
ARW-8C1A (manufactured by MAT) was used as a polishing apparatus, and polishing was performed while dressing the polishing pad surface under the following conditions.
・ Monitor wafer: Thermal oxide film 1μm deposited on 8 inch silicon wafer ・ Slurry: SS25 (Cabot) double diluted and used ・ Slurry supply flow rate: 150 ml / min
Polishing load: 5 psi Retainer load: 6 psi
・ Rotation speed: Polishing / wafer = 100/100 rpm
-Dresser: SAESOL 4in dresser 60rpm

[Evaluation of polishing characteristics]
After the break-in, 10 dummy wafers were processed, the monitor wafer was polished, and the monitor wafer was initially evaluated. Thereafter, the monitor wafer was poured into the 50th and 100th wafers, and the fluctuation of the polishing rate and the state of the defect were evaluated. The method for evaluating the fluctuation of the polishing rate and the method for evaluating the defect state are as follows.

[Evaluation of polishing rate]
With respect to the polishing rate of the polishing pad having only concentric grooves, the case where the polishing rate was decreased by less than 5% was rated as ◯, and the case where the polishing rate was 5% or more was rated as x.

[Defect evaluation]
It measured using the defect evaluation apparatus (SP1 TBI). The case where the defect was hardly changed from the initial evaluation was marked with ◯, and the case where the defect was increasing from the initial evaluation was marked with x. Further, when 100 monitor wafers were processed, the case where there was no peeling at the center of the polishing pad was evaluated as ◯, and the case where there was peeling was evaluated as x.

<Production example>
In a container, 1229 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20), 272 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, polytetramethylene ether glycol 1901 having a number average molecular weight of 1018 Part by weight and 198 parts by weight of diethylene glycol were added and reacted at 70 ° C. for 4 hours to obtain an isocyanate-terminated prepolymer A. Also, 100 parts by weight of 1,6-hexamethylene diisocyanate (Sumika Bayer Urethane Co., Ltd., Sumidur N-3300, isocyanurate type) in a container and 16.3 weights of polytetramethylene ether glycol having a number average molecular weight of 250 Part (NCOindex: 4) was allowed to react at 100 ° C. for 3 hours to obtain an isocyanate-terminated prepolymer B (1). 100 parts by weight of the prepolymer A, 23.3 parts by weight of the prepolymer B (1), and 3.7 parts by weight of a silicon-based nonionic surfactant (manufactured by Toray Dow Corning Silicon, SH-192) are added to the polymerization vessel. The mixture was mixed, adjusted to 70 ° C. and degassed under reduced pressure. Then, it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. Thereto was added 36.1 parts by weight (NCOindex: 1.1) of 4,4′-methylenebis (o-chloroaniline) previously melted at 120 ° C. The mixed liquid was stirred for about 70 seconds, and then poured into a pan-shaped open mold (casting container). When the fluidity of the mixed solution disappeared, it was put in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane foam block. The polyurethane foam block heated to about 80 ° C. was sliced using a slicer (AGW Tech, VGW-125) to obtain a polyurethane foam sheet. Next, using a buffing machine (Amitech Co., Ltd.), the surface of the sheet was buffed to a thickness of 2.0 mm to obtain a sheet with an adjusted thickness accuracy. The buffed sheet was punched out with a diameter of 61 cm.

<Example 1>
A groove processing machine (manufactured by Techno Co., Ltd.) is used on the surface of the produced abrasive sheet to form a concentric groove having a width of 0.4 mm, a depth of 0.8 mm, a pitch of 3.1 mm, and a cross groove. A polishing layer was prepared by forming a width of 4.0 mm and a depth of 0.85 mm (size). A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was attached to the surface of the polishing layer opposite to the grooved surface using a laminator. Furthermore, the surface of the cushion sheet (Toray Industries, Inc., polyethylene foam, Torepef, thickness 0.8 mm) subjected to corona treatment was buffed and bonded to the double-sided tape using a laminator. Further, a double-sided tape was attached to the other surface of the cushion sheet using a laminator to prepare a polishing pad.

<Example 2-6>
A polishing pad was prepared in the same manner as in Example 1 except that the shape of the groove was changed to the shape shown in Table 1.

<Comparative Example 1>
A concentric groove having a width of 0.4 mm, a depth of 0.8 mm, and a pitch of 3.1 mm (dimensions) is formed on the surface of the prepared polishing sheet using a groove processing machine (manufactured by Techno). did. The groove pattern on the polished surface was only concentric. Thereafter, a polishing pad was produced in the same manner as in the example.

<Comparative example 2>
Concentric circles and lattice-shaped grooves are formed on the surface of the prepared abrasive sheet using a groove processing machine (manufactured by Techno Co., Ltd.). The concentric circular grooves are 0.4 mm wide, 0.8 mm deep, 3.1 mm pitch, and grid-shaped grooves are And a width of 4.0 mm, a depth of 0.85 mm, and a pitch of 15 mm (dimensions) to produce a polishing layer. Thereafter, a polishing pad was produced in the same manner as in the example.

<Comparative Example 3>
A cross groove was formed with a width of 4 mm and a depth of 0.85 mm (dimensions) on the surface of the prepared polishing sheet using a groove processing machine (manufactured by Techno Corporation) to prepare a polishing layer. Thereafter, a polishing pad was produced in the same manner as in the example.

  From Table 1, the polishing pad of Example 1 maintained the polishing rate even when used for polishing for a long time, and no defects such as particles and scratches were observed.

  The method for producing a laminated polishing pad of the present invention requires high surface flatness such as optical materials such as lenses and reflecting mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and general metal polishing processes. It can be used in a method for manufacturing a polishing pad that performs planarization of a material.

1: Laminated polishing pad 2: Polishing surface plate 3: Abrasive (slurry)
4: Material to be polished (semiconductor wafer)
5: Support base (polishing head)
6, 7: Rotating shaft 8: Circular polishing sheet 9: Convex part 10 on the outermost peripheral part: Concentric circular groove (concave part)
11: Cross-shaped groove (concave)

Claims (7)

A circular polishing pad comprising a circular polishing layer,
The circular polishing layer has concentric circular grooves and one cruciform groove,
A circular polishing pad, wherein the cross-shaped grooves are substantially orthogonal at the center of the circular polishing layer.   The circular polishing pad according to claim 1, wherein the concentric groove has a groove width of 0.15 to 1.2 mm.   The circular polishing pad according to claim 1 or 2, wherein a groove depth of the concentric grooves is 0.3 to 1.5 mm.   The circular polishing pad according to any one of claims 1 to 3, wherein a groove pitch of the concentric grooves is 1.0 to 6.5 mm.   The circular polishing pad according to any one of claims 1 to 4, wherein a groove width of the cruciform groove is 2.0 to 8.0 mm.   The groove depth of the cruciform groove is 0.1 to 1.6 mm, and the groove depth of the cruciform groove is the same as the groove depth of the concentric circular groove or deeper than the groove depth of the concentric circular groove. The circular polishing pad according to any one of the above. A method for manufacturing a semiconductor device, comprising a step of polishing a surface of a semiconductor wafer using the circular polishing pad according to claim 1.

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