JP2016074046A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad which prevents peeling during use and can suppress a terminal point detection error in conjunction with deterioration of light transmissivity from an initial use to an end, and provide a manufacturing method of a semiconductor device using the polishing pad.SOLUTION: A polishing pad 1 includes a polishing layer having a polishing region 8 and a light transmission region 11. The light transmission region 11 has a convex curved surface on a front surface side of the polishing region 8. A topmost part 13 of the curved surface of the light transmission region 11 is positioned on the same plane as the front surface 14 of the polishing region or higher than the front surface 14 of the polishing region.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a polishing pad used when planarizing unevenness on a wafer surface by chemical mechanical polishing (CMP), and more specifically, a window (light transmission region) for detecting a polishing state or the like by optical means. The present invention relates to a polishing pad having a semiconductor device and a method for manufacturing a semiconductor device using the polishing pad.

  When manufacturing a semiconductor device, a conductive film is formed on the surface of a semiconductor wafer (hereinafter also referred to as a wafer), and a wiring layer is formed by photolithography, etching, or the like. Processes for forming an insulating film and the like are performed, and unevenness made of a conductor such as metal or an insulator is generated on the wafer surface by these processes. 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, a CMP method 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 an object to be polished (wafer or the like) 4. And a backing material for uniformly pressing the wafer and a supply mechanism for the abrasive 3. 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 object to be polished 4 supported on 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 pressing mechanism for pressing the object to be polished 4 against the polishing pad 1 is provided on the support base 5 side.

  In performing such CMP, there is a problem in determining the wafer surface flatness. In other words, it is necessary to detect when the desired surface characteristics or planar state is reached. Conventionally, with regard to the thickness of the oxide film, the polishing rate, and the like, a test wafer is periodically processed, and after confirming the result, a product wafer is polished.

  However, in this method, the time and cost for processing the test wafer are wasted, and the polishing result differs between the test wafer and the product wafer that have not been processed in advance due to the loading effect peculiar to CMP. If it is not actually processed, it is difficult to accurately predict the processing result.

  Therefore, recently, in order to solve the above-mentioned problems, there is a demand for a method capable of detecting a point in time when desired surface characteristics and thickness are obtained in the CMP process. Various methods are used for such detection, but optical detection means are becoming mainstream in terms of measurement accuracy and spatial resolution in non-contact measurement.

  Specifically, the optical detection means is a method of detecting an end point of polishing by irradiating a wafer with a light beam through a window (light transmission region) through a polishing pad and monitoring an interference signal generated by the reflection. It is.

  In such a method, the end point is determined by monitoring the change in the thickness of the surface layer of the wafer and knowing the approximate depth of the surface irregularities. When such a change in thickness becomes equal to the depth of the unevenness, the CMP process is terminated. Moreover, various things have been proposed about the polishing end point detection method by such optical means and the polishing pad used in the method (Patent Documents 1 to 4).

JP 2014-104521 A Special table 2007-506280 gazette JP 2008-222141 A JP 2003-285259 A

  Since the surface of the light transmission region of the polishing pad described in Patent Documents 1 and 2 is lower than the polishing region, the light transmission region does not contact the object to be polished from the initial use to the final use. Therefore, although there is no possibility that the light transmission region is peeled off, the slurry accumulates in the light transmission region that is lower than the polishing region during polishing, and the light transmittance gradually decreases. Therefore, when the end point is detected by a program corresponding to the initial light transmittance (light reflectance), there is a problem that the light transmittance is lowered from the middle stage of use of the polishing pad to the end stage, and an end point detection error occurs.

  In Patent Document 3, since the light transmission region is roughened by sandblasting or the like, the manufacturing process becomes complicated and the cost increases. Moreover, there is a possibility that foreign matter may be mixed in by sandblasting or the like.

  Since the polishing pad described in Patent Document 4 has a low hardness on the polishing surface side, the conditioner at the time of dressing tends to bite and wear easily. For this reason, the polishing pad described in Patent Document 4 is a convex portion in the initial stage of use, but the window portion becomes a concave portion as the use progresses, and there is a problem that slurry accumulation occurs and the light transmittance is adversely affected. In addition, the polishing pad described in Patent Document 4 has a problem of inferior light transmittance because light scattering is likely to occur in the laminated portion of the soft light-transmitting layer and the hard light-transmitting layer.

  The present invention has been made to solve the above problems, and it is an object of the present invention to provide a polishing pad that can hardly be peeled off during use and can suppress an end point detection error accompanying a decrease in light transmittance from the initial use to the final stage. To do.

  The present invention is a polishing pad comprising a polishing layer having a polishing region and a light transmission region, wherein the light transmission region has a convex curved surface on the surface side of the polishing region, and the curved surface of the light transmission region Is a polishing pad located on the same plane as the surface of the polishing region or above the surface of the polishing region.

  According to the present invention, it is possible to provide a polishing pad that is difficult to peel off during use, and that can suppress an end point detection error accompanying a decrease in light transmittance from the initial use to the final stage.

Schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing Schematic sectional view showing an example of the structure of the polishing pad of the present invention Schematic sectional view showing an example of the structure of the polishing pad of the present invention

  The polishing pad of this embodiment is a polishing pad provided with a polishing layer having a polishing region and a light transmission region, and the light transmission region has a convex curved surface on the surface side of the polishing region, and the light The topmost part of the curved surface of the transmission region is located on the same plane as the surface of the polishing region or above the surface of the polishing region. According to the polishing pad of the present embodiment, it is difficult to peel off during use, and an end point detection error accompanying a decrease in light transmittance can be suppressed from the initial use to the final stage. The reason for such an effect is considered as follows.

  As described above, the optical detection means specifically means that a light beam is irradiated onto a wafer through a window (light transmission region) through a polishing pad and an interference signal generated by the reflection is monitored. This is a method for detecting the end point. In the polishing pad of this embodiment, the light transmission region has a convex curved surface on the surface side of the polishing region, and the top of the light transmission region is flush with the surface of the polishing region or the polishing Since it is located above the surface of the region, the top is also dressed and damaged when the polishing region breaks in (dressing with a pad conditioner). As a result, even when the end point is detected by a program corresponding to the initial light transmittance (light reflectance), the change in light transmittance can be suppressed from the initial use to the end of the polishing pad. An end point detection error due to a change in transmittance can be suppressed. Moreover, since the polishing pad of this embodiment has the surface of the polishing region and the surface of the light transmission region on substantially the same plane during use, the light transmission region is difficult to peel off during use.

  The polishing pad of this embodiment may be only the polishing layer, or may be a laminate of the polishing region and other layers (for example, a cushion layer, an adhesive layer, and a support film).

  FIG. 2 is a schematic cross-sectional view showing an example of the structure of the polishing pad of the present embodiment. As shown in FIG. 2, the polishing pad 1 of this embodiment has a polishing region 8 and a cushion layer 9 laminated, and a light transmission region 11 is provided in an opening 10 of the polishing region 8. The opening 10 is provided so as to overlap with the through hole 12 provided in the cushion layer 9. The light transmission region 11 has a convex curved surface on the surface 14 side (polishing surface side) of the polishing region 8, and the topmost portion 13 of the curved surface of the light transmission region 11 is more than the surface 14 of the polishing region 8. Also located on the top.

  FIG. 3 is a schematic cross-sectional view showing an example of the structure of the polishing pad of the present embodiment. As shown in FIG. 3, the polishing pad 1 of the present embodiment has a polishing region 8 and a cushion layer 9 laminated, and a light transmission region 11 is provided in an opening 10 of the polishing region 8. The opening 10 is provided so as to overlap with the through hole 12 provided in the cushion layer 9. The light transmission region 11 has a convex curved surface on the surface 14 side (polishing surface side) of the polishing region 8, and the topmost portion 13 of the curved surface of the light transmission region 11 is in contact with the surface 14 of the polishing region 8. Located on the same plane.

<Light transmission area>

  The difference in height between the topmost portion 13 of the curved surface of the light transmitting region 11 and the lowest portion 15 of the curved surface damages the light transmitting region 11 due to break-in, and an end point detection error due to a decrease in light transmittance from the initial use to the final stage. 10 to 200 μm is preferable, and 10 to 150 μm is more preferable.

  The lowest part 15 of the curved surface of the light transmission region 11 is scratched on the light transmission region 11 due to break-in, and suppresses an end point detection error due to a decrease in light transmittance from the initial use to the final stage, and scratches during polishing From the viewpoint of suppressing the occurrence, it is preferable to be positioned below the surface 14 of the polishing region 8. From the same viewpoint, the height difference between the lowest surface portion 15 of the curved surface of the light transmission region 11 and the surface 14 of the polishing region is preferably 10 to 200 μm, and more preferably 30 to 200 μm.

  The material for forming the light transmission region 11 is not particularly limited, but a material having a light transmittance of 10% or more at a wavelength of 660 nm is used from the viewpoint of enabling highly accurate optical end point detection in a state where polishing is performed. It is preferable to use a material that is 50% or more. Examples of such materials include polyurethane resins, polyester resins, phenol resins, urea resins, melamine resins, epoxy resins, and acrylic resins, and other thermosetting resins, polyurethane resins, polyester resins, polyamide resins, cellulose resins, Acrylic resins, polycarbonate resins, halogen resins (polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, etc.), polystyrene, olefin resins (polyethylene, polypropylene, etc.), thermoplastic resins, butadiene rubber, isoprene rubber, etc. Examples thereof include rubber, photo-curing resin that is cured by light such as ultraviolet rays and electron beams, and photosensitive resin. These resins may be used alone or in combination of two or more. In addition, in this specification, light transmittance is measured by the method as described in an Example.

  As the material for forming the light transmission region 11, it is preferable to use the same material as that for the polishing region 8 or a material similar to the physical properties of the polishing region 8. In particular, it is preferable to use a polyurethane resin.

  The polyurethane resin comprises an isocyanate component, a polyol component (high molecular weight polyol, low molecular weight polyol, etc.), and a chain extender.

  As the isocyanate component, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, Examples include p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, hexamethylene diisocyanate, 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, and isophorone diisocyanate. . These may be used alone or in combination of two or more.

  Examples of the high molecular weight polyol include a polyether polyol represented by polytetramethylene ether glycol, a polyester polyol represented by polybutylene adipate, a polycaprolactone polyol, a reaction product of a polyester glycol such as polycaprolactone and an alkylene carbonate, and the like. Exemplified polyester polycarbonate polyol, polyester polycarbonate polyol obtained by reacting ethylene carbonate with polyhydric alcohol and then reacting the obtained reaction mixture with organic dicarboxylic acid, and polycarbonate obtained by transesterification reaction between polyhydroxyl compound and aryl carbonate A polyol etc. are mentioned. These may be used alone or in combination of two or more.

  In addition to the high molecular weight polyols described above as polyols, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1, Low molecular weight polyols such as 4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, and 1,4-bis (2-hydroxyethoxy) benzene may be used in combination.

  Chain extenders include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3 -Low molecular weight polyols such as methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene, or 2,4-toluenediamine, 2,6-toluenediamine, 3,5-diethyl-2,4-toluenediamine, 4,4′-di-sec-butyl-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 2,2 ′, 3,3′-tetrachloro-4,4′-diamino Phenylmethane, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 3,3'-diethyl-4,4'-diaminodiphenylmethane, 4,4'-methylene-bis-methyl Anthranilate, 4,4'-methylene-bis-anthranilic acid, 4,4'-diaminodiphenylsulfone, N, N'-di-sec-butyl-p-phenylenediamine, 4,4'-methylene- Bis (3-chloro-2,6-diethylaniline), 4,4′-methylenebis (o-chloroaniline), 3,3′-dichloro-4,4′-diamino-5,5′-diethyldiphenylmethane, 1 , 2-bis (2-aminophenylthio) ethane, trimethylene glycol di-p-aminobenzoate, 3,5-bis (methylthio) -2,4- Polyamines exemplified by toluenediamine and the like can be mentioned. These may be used alone or in combination of two or more. However, since the polyamines are often colored themselves or resins formed using these are colored in many cases, it is preferable to blend them so as not to impair the physical properties and light transmittance. In addition, when a compound having an aromatic hydrocarbon group is used, the light transmittance on the short wavelength side tends to be lowered. Therefore, it is particularly preferable not to use such a compound. In addition, a compound in which an electron donating group such as a halogen group or a thio group or an electron withdrawing group is bonded to an aromatic ring or the like tends to decrease the light transmittance. Therefore, such a compound may not be used. Particularly preferred. However, you may mix | blend to such an extent that the light transmittance requested | required by the short wavelength side is not impaired.

  The ratio of the isocyanate component, the polyol component, and the chain extender in the polyurethane resin can be appropriately changed depending on the molecular weight of each and the desired physical properties of the light transmission region produced therefrom. The number of isocyanate groups of the organic isocyanate relative to the total number of functional groups (hydroxyl group + amino group) of the polyol and the chain extender is preferably 0.95 to 1.15, more preferably 0.99 to 1.10. The polyurethane resin can be manufactured by applying a known urethanization technique such as a melting method or a solution method, but it is preferable to manufacture the polyurethane resin by a melting method in consideration of cost, working environment, and the like.

  As the polymerization procedure of the polyurethane resin, either a prepolymer method or a one-shot method is possible. From the viewpoint of stability and transparency of the polyurethane resin during polishing, an isocyanate-terminated prepolymer from an organic isocyanate and a polyol in advance. Is preferably synthesized, and a prepolymer method in which a chain extender is reacted with this is preferred. Moreover, it is preferable that the NCO weight% of the said prepolymer is about 2 to 8 weight%, More preferably, it is about 3 to 7 weight%. If the NCO wt% is less than 2 wt%, the reaction curing tends to take too much time and the productivity tends to decrease. On the other hand, if the NCO wt% exceeds 8 wt%, the reaction rate becomes too fast. As a result, air entrainment or the like occurs, and physical properties such as transparency and light transmittance of the polyurethane resin tend to deteriorate. When there are bubbles in the light transmission region, the attenuation of the reflected light increases due to light scattering, and the polishing end point detection accuracy and the film thickness measurement accuracy tend to decrease. Therefore, in order to remove such bubbles and make the light transmission region non-foamed, it is preferable to sufficiently remove the gas contained in the material by reducing the pressure to 10 Torr or less before mixing the material. . Moreover, in the stirring process after mixing, in the case of the stirring blade type mixer normally used, it is preferable to stir at the rotation speed of 100 rpm or less so that bubbles may not mix. In addition, the stirring step is preferably performed under reduced pressure. Furthermore, since the rotation and revolution type mixer is difficult to mix bubbles even at high rotation, it is also preferable to perform stirring and defoaming using the mixer.

  The light transmission region 11 has a Asker D hardness of 48 to 75 degrees from the viewpoint of scratching the light transmission region 11 by break-in and suppressing an end point detection error accompanying a decrease in light transmittance from the initial use to the final stage. Is preferable, and 52-75 degree | times is more preferable.

  From the viewpoint of suppressing an end point detection error accompanying a decrease in light transmittance from the initial use to the final stage, the light transmittance at a wavelength of 660 nm of the light transmission region 11 in the polishing pad 1 before use (in a state where no break-in is performed) 10-80% is preferable and 45-80% is more preferable.

  The light transmittance of the light transmission region 11 in the polishing pad 1 that is not used in the polishing step after the break-in is from the viewpoint of suppressing an end point detection error associated with a decrease in light transmittance from the initial use to the final stage. 10 to 45% is preferable, and 15 to 30% is more preferable.

  The light transmittance at a wavelength of 660 nm of the light transmitting region 11 in the polishing pad 1 being used in the polishing step is 10 to 45% from the viewpoint of suppressing an end point detection error accompanying a decrease in light transmittance from the initial use to the final stage. Preferably, 15 to 30% is more preferable.

  The light transmittance change rate from the initial use to the final stage of the polishing pad is preferably 50% or less, more preferably 30% or less, from the viewpoint of suppressing an end point detection error accompanying a decrease in the light transmittance from the initial use to the final stage. . In addition, the change rate of the light transmittance from the initial stage of use of the polishing pad to the final stage can be obtained by the following formula (1).

Change rate of light transmittance (%) = [(A−B) / A] × 100 (1)
(A represents the light transmittance at a wavelength of 660 nm of the light transmitting region in the polishing pad after break-in, and B represents the light transmittance at a wavelength of 660 nm of the light transmitting region in the polishing pad during and / or after use. .)

  The production method of the light transmission region 11 is not particularly limited, and can be produced by a known method. As the method, for example, a resin block is molded into a predetermined shape using a band saw type or canna type slicer, a resin is poured into a predetermined mold and cured, or a centrifugal molding method is used. And a method of punching a resin sheet obtained in a predetermined shape. Among these, a method of punching a resin sheet obtained by molding by a centrifugal molding method into a predetermined shape is preferable. A conventionally well-known thing can be used for the centrifugal molding machine and metal mold | die used for the said centrifugal molding method. As an example of a conventionally known centrifugal molding method, a composition constituting a light transmission region is poured into a heated cylindrical mold that rotates at high speed, and is heated and cured. At the time of the centrifugal molding, the surface (inside) of the resin on the rotating shaft side is an atmosphere, and the resin does not touch the mold or the like. Therefore, the inside surface of the obtained cylindrical resin has a mirror surface (surface roughness Ra 0.5 μm). The following). A light transmission region obtained by punching a sheet obtained by cutting the obtained cylindrical resin in the axial direction into a predetermined shape is a surface (mirror surface (surface roughness Ra 0.5 μm or less )) Is preferably provided on the opposite side of the polished surface, since dispersion of light can be suppressed and an end point detection error associated with a decrease in light transmittance can be further suppressed from the initial use to the final stage. Further, since the resin sheet obtained by molding by the centrifugal molding method has a convex curved surface on the outside at the time of centrifugal molding, the light transmission region 11 is obtained by punching the sheet into a predetermined shape. It is done. Therefore, it is preferable from the viewpoint of manufacturing cost.

  The shape of the light transmission region 11 is not particularly limited except the above, but is preferably the same shape and size as the opening 10 of the polishing region 8.

<Polishing area>
Examples of the material for forming the polishing region 8 include polyurethane resin, polyester resin, polyamide resin, acrylic resin, polycarbonate resin, halogen-based resin (polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, etc.), polystyrene, and olefin resin. (Polyethylene, polypropylene, etc.), epoxy resin, photosensitive resin, and the like. These may be used alone or in combination of two or more. The material for forming the polishing region 8 may be the same as or different from that of the light transmission region 11, but it reduces the wear difference between the polishing region 8 and the light transmission region 11 and improves the durability of the polishing layer. From the viewpoint, it is preferable to use the same material as the forming material used for the light transmission region 11.

  Polyurethane resin is a particularly preferable material for forming the polishing region 8 because it is excellent in abrasion resistance and a polymer having desired physical properties can be easily obtained by variously changing the raw material composition.

  The polyurethane resin comprises an isocyanate component, a polyol component (high molecular weight polyol, low molecular weight polyol, etc.), and a chain extender.

  The isocyanate component to be used is not particularly limited, and examples thereof include an isocyanate component that can be used with the light transmittance.

  The high molecular weight polyol to be used is not particularly limited, and examples thereof include a high molecular weight polyol that can be used with the light transmittance. In addition, the number average molecular weight of these high molecular weight polyols is not particularly limited, but is preferably 500 to 2000 from the viewpoint of the elastic characteristics of the obtained polyurethane. If the number average molecular weight is less than 500, a polyurethane using the number average molecular weight does not have sufficient elastic properties and becomes a brittle polymer. For this reason, the polishing region 8 manufactured from this polyurethane becomes too hard and causes scratches on the wafer surface. Moreover, since it becomes easy to wear, it is not preferable from the viewpoint of the pad life. On the other hand, if the number average molecular weight exceeds 2000, the polyurethane using this becomes too soft, and the polishing region 8 produced from this polyurethane tends to be inferior in flattening characteristics.

  Moreover, as a polyol, the low molecular weight polyol which can be used with the said light transmittance other than high molecular weight polyol can also be used together.

  As chain extenders, 4,4′-methylenebis (o-chloroaniline) (MOCA), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline), 3, 5-bis (methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene- 2,6-diamine, trimethylene glycol-di-p-aminobenzoate, polytetramethylene oxide-di-p-aminobenzoate, 1,2-bis (2-aminophenylthio) ethane, 4,4′-diamino- 3,3′-diethyl-5,5′-dimethyldiphenylmethane, N, N′-di-sec-butyl-4,4′-diaminodiphenylmethane, 4, '-Diamino-3,3'-diethyldiphenylmethane, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 4,4'-diamino-3,3'-diisopropyl-5 5'-dimethyldiphenylmethane, 4,4'-diamino-3,3 ', 5,5'-tetraethyldiphenylmethane, 4,4'-diamino-3,3', 5,5'-tetraisopropyldiphenylmethane, m-xyl Examples include polyamines exemplified by range amine, N, N′-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, and p-xylylenediamine, or the low molecular weight polyol component described above. it can. These may be used alone or in combination of two or more.

  The ratio of the isocyanate component, the polyol component, and the chain extender in the polyurethane resin can be variously changed depending on the molecular weight of each and the desired physical properties of the polishing region 8 produced therefrom. In order to obtain a polishing region 8 having excellent polishing characteristics, the number of isocyanate groups of the isocyanate component relative to the total number of functional groups (hydroxyl group + amino group) of the polyol component and the chain extender is preferably 0.95 to 1.15. More preferably, it is 0.99 to 1.10.

  The polyurethane resin can be produced by the same method as described above. In addition, stabilizers such as antioxidants, surfactants, lubricants, pigments, solid beads, fillers such as water-soluble particles and emulsion particles, antistatic agents, abrasive grains, and other materials as necessary. Additives may be added.

  The polishing region 8 is preferably a fine foam. By using a fine foam, the slurry can be held in the fine pores on the surface, and the polishing rate can be increased.

  The method of finely foaming the polyurethane resin is not particularly limited, and examples thereof include a method of adding hollow beads, a method of foaming by a mechanical foaming method, a chemical foaming method, and the like. In addition, although each method may be used together, the mechanical foaming method using the silicone type surfactant which is a copolymer of polyalkylsiloxane and polyether is especially preferable. Examples of the silicone surfactant include SH-192, L-5340 (manufactured by Toray Dow Corning) and the like as suitable compounds.

An example of a method for producing a micro-bubble type polyurethane foam will be described below. The manufacturing method of this polyurethane foam has the following processes.
1) Foaming process for producing a cell dispersion of isocyanate-terminated prepolymer A silicone-based surfactant is added to an isocyanate-terminated prepolymer (first component) and stirred in the presence of a non-reactive gas. Disperse as fine bubbles to obtain a cell dispersion. When the prepolymer is solid at normal temperature, it is preheated to an appropriate temperature and melted before use.
2) Curing agent (chain extender) mixing step A chain extender (second component) is added to the above-mentioned cell dispersion, mixed and stirred to obtain a foaming reaction solution.
3) Casting step The above foaming reaction liquid is poured into a mold.
4) Curing process The foaming reaction solution poured into the mold is heated and reacted and cured.

  As the non-reactive gas used to form the fine bubbles, non-flammable gases are preferable, and specific examples include nitrogen, oxygen, carbon dioxide, rare gases such as helium and argon, and mixed gases thereof. The use of air that has been dried to remove moisture is most preferable in terms of cost.

  As a stirring device for making non-reactive gas into fine bubbles and dispersing it in an isocyanate-terminated prepolymer containing a silicone-based surfactant, a known stirring device can be used without particular limitation. Specifically, a homogenizer, a dissolver, A two-axis planetary mixer (planetary mixer) is exemplified. The shape of the stirring blade of the stirring device is not particularly limited, but it is preferable to use a whipper-type stirring blade because fine bubbles can be obtained.

  In addition, it is also a preferable aspect to use a different stirring apparatus for the stirring which produces a bubble dispersion liquid in the stirring process, and the stirring which adds and mixes the chain extender in a mixing process. In particular, the stirring in the mixing step may not be stirring that forms bubbles, and it is preferable to use a stirring device that does not involve large bubbles. As such an agitator, a planetary mixer is suitable. There is no problem even if the same stirring device is used as the stirring device for the stirring step and the mixing step, and it is also preferable to adjust the stirring conditions such as adjusting the rotation speed of the stirring blade as necessary. .

  In the production method of polyurethane foam, heating and post-curing the foam that has reacted until the foaming reaction liquid is poured into the mold and no longer flows is effective in improving the physical properties of the foam and is extremely suitable. It is. The foam reaction solution may be poured into the mold and immediately put into a heating oven for post cure, and heat is not immediately transferred to the reaction components under such conditions, so the bubble size does not increase. . The curing reaction is preferably performed at normal pressure because the bubble shape is stable.

  In the production of the polyurethane resin, a catalyst that promotes a known polyurethane reaction such as a tertiary amine type or an organic tin type may be used. The type and addition amount of the catalyst are selected in consideration of the flow time for pouring into a mold having a predetermined shape after the mixing step.

  The polyurethane foam may be produced by a batch method in which each component is metered into a container and stirred, and each component and a non-reactive gas are continuously supplied to the stirring device and stirred to produce bubbles. It may be a continuous production method in which a dispersion is sent out to produce a molded product.

  The average cell diameter of the polyurethane 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 (flatness) of the polished object (wafer) after polishing tends to decrease.

  The specific gravity of the polyurethane foam is preferably 0.5 to 1.3. When the specific gravity is less than 0.5, the surface strength of the polishing region 8 decreases, and the planarity of the object 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 region 8 is reduced and the planarity is good, but the polishing rate tends to decrease.

  The hardness of the polyurethane foam is preferably 45 to 70 degrees as measured by an Asker D hardness meter. When the Asker D hardness is less than 45 degrees, the planarity of the object to be polished is reduced. When the Asker D hardness is more than 70 degrees, the planarity is good but the uniformity of the object to be polished is reduced. There is a tendency.

  The polishing region 8 is produced by cutting the polyurethane foam produced as described above into a predetermined size.

<Cushion layer>
The cushion layer 9 supplements the characteristics of the polishing region 8. The cushion layer 9 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 polishing object having minute irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire polishing object. The planarity is improved by the characteristics of the polishing region 8, and the uniformity is improved by the characteristics of the cushion layer 9. In the polishing pad 1 of the present embodiment, it is preferable to use a cushion layer 9 that is softer than the polishing region 8.

  The material for forming the cushion layer 9 is not particularly limited. For example, 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 such as polyurethane foam and polyethylene foam Examples thereof include rubber resins such as foam, butadiene rubber and isoprene rubber, and photosensitive resins.

<Polishing pad manufacturing method>
The manufacturing method of the polishing pad 1 is not particularly limited. As an example, the polishing region 8 provided with the opening 10 and the cushion layer 9 provided with the through hole 12 are respectively bonded to the adhesive layer of the double-sided adhesive sheet so that the opening 10 and the through hole 12 overlap each other. Then, it can manufacture by bonding the light transmissive area | region 11 to the adhesive bond layer of the double-sided adhesive sheet in the opening part 10. FIG. Further, a double-sided tape may be provided on the surface of the cushion layer 9 to be bonded to the polishing surface plate (platen).

  Examples of means for bonding the polishing region 8 and the cushion layer 9 include a method in which the polishing region 8 and the cushion layer 9 are sandwiched between double-sided adhesive sheets (not shown) and pressed. The double-sided adhesive sheet has a general configuration in which an adhesive layer is provided on both sides of a substrate such as a nonwoven fabric or a film, and is generally called a double-sided tape. 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. Further, since the composition of the polishing region 8 and the cushion layer 9 may be different, the composition of each adhesive layer of the double-sided adhesive sheet can be made different so that the adhesive strength of each layer can be optimized.

  The means for forming the opening 10 and the through-hole 12 are not particularly limited. For example, a method of pressing or grinding with a cutting tool, a method using a laser such as a carbonic acid laser, and the shape of the through-hole are provided. Examples include a method in which a raw material is poured into a mold and cured. In addition, the magnitude | size and shape of the opening part 10 and the through-hole 12 are not restrict | limited in particular.

<Semiconductor device manufacturing method>
The semiconductor device is manufactured through a step of polishing the surface of the semiconductor wafer using the polishing pad 1. 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 the polishing pad 1, a support table 5 (polishing head) that supports the semiconductor wafer 4, and the wafer. This is performed using a backing material for performing uniform pressurization and a polishing apparatus equipped with a polishing agent 3 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 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 pressurizing mechanism for pressing the semiconductor wafer 4 against the 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.

<Evaluation method>
[Level difference between the lowest part of the curved surface of the light transmission area and the surface of the polishing area]
Any six points were measured with a laser displacement meter (LJ-7020K manufactured by Keyence Corporation), and the average was obtained.

[Difference in height between the top of the curved surface of the light transmission area and the minimum of the curved surface]
By performing a three-dimensional analysis with a contact-type digital sensor displacement meter (GT2-H12KLF manufactured by Keyence Corporation), the difference in height between the top of the curved surface of the light transmission region and the minimum of the curved surface was determined.

[Light transmittance of light transmission area before use]
Using a transmission type laser discrimination sensor (IB-01 manufactured by Keyence Corporation), the light transmittance of the light transmission region of the manufactured polishing pad was measured in a measurement wavelength region of 660 nm.

[Light transmittance of light transmission area after break-in]
A polishing pad was attached to the polishing apparatus, and after break-in (dresser: M # 100 dressed by Asahi Diamond Co., Ltd .: 20 minutes in DIW (ultra pure water)), the polishing pad was removed from the polishing apparatus. The light transmittance was measured by the same method as the “light transmittance of the light transmitting region”.

[Change rate of light transmittance]
After the break-in, the light transmittance at a wavelength of 660 nm in the light transmission region is A, and a wafer (8-inch silicon wafer formed with 1 μm of thermal oxide film) is polished for 1 minute per sheet, and this is repeated to 500 The light transmittance at a wavelength of 660 nm in the light transmissive region after polishing the sheet was set as B, and the rate of change was calculated by the following formula. The rate of change is preferably 30% or less. The light transmittance was measured by the same method as described above. Moreover, SPP600S (made by Okamoto Machine Tool Co., Ltd.) was used as a polishing apparatus. As the polishing conditions, silica slurry (SS12 Cabot) was added as a slurry at a flow rate of 150 ml / min during polishing. The polishing load was 350 g / cm ² , the polishing platen rotation speed was 35 rpm, and the wafer rotation speed was 30 rpm.
Change rate of light transmittance (%) = [(A−B) / A] × 100

〔hardness〕
This was performed in accordance with JIS K6253-1997. The produced polyurethane sheet cut into a size of 2 cm × 2 cm (thickness: arbitrary) was used as a sample for hardness measurement, and was allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. At the time of measurement, the samples were overlapped to a thickness of 6 mm or more. The hardness was measured using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D type hardness meter).

[Evaluation of the number of defects]
Scratch evaluation was performed by polishing three 8-inch dummy wafers under the above conditions, then polishing an 8-inch wafer on which a thermal oxide film having a thickness of 10,000 mm was polished for 1 minute, and a defect evaluation apparatus manufactured by KLA Tencor. (Surfscan SP1) was used to measure how many streaks of 0.19 μm or more exist on the polished wafer.

<Production example>
[Production of light transmission region A]
In a reaction vessel, 100 parts by weight of a polyether-based prepolymer (Chemchula: Adiprene L-325: NCO 9.15% by weight) and 4,4′-methylenebis (o-chloroaniline) previously melted at 120 ° C. (Ihara Chemical Co., Ltd. product: Iharacamine MT) was added. The reaction vessel was stirred for 1 minute by a planetary mixer manufactured by Kurabo Industries, and the obtained composition was poured into a mold of a centrifugal molding machine at a temperature of 150 ° C. rotating at 400 rpm. Thereafter, the mold was cured for 10 minutes while rotating at 1200 rpm, and then demolded. Then, post cure was performed at 80 ° C. for 10 hours to obtain a polyurethane elastomer sheet. The post-cure polyurethane sheet was punched out to 57 mm × 20 mm to form a light transmission region A.

[Production of light transmission regions B to D]
The light transmission regions B to D were prepared in the same manner as the light transmission region A except that the thicknesses were different. The thickness of each light transmission region was adjusted by adjusting the thickness of the sheet obtained by centrifugal molding, and the thickness of the sheet was adjusted by the amount of the composition poured into the mold of the centrifugal molding machine.

[Production of light transmission region E]
In a reaction vessel, 100 parts by weight of a polyether-based prepolymer (Chemchula: Adiprene L-325: NCO 9.15% by weight) and 4,4′-methylenebis (o-chloroaniline) previously melted at 120 ° C. (Ihara Chemical Co., Ltd. product: Iharacamine MT) was added. The reaction vessel was stirred for 1 minute with a planetary mixer manufactured by Kurabo Industries, and the obtained composition was poured into a book mold having a length of 200 mm, a width of 150 mm, and a thickness of 2.05 mm. Thereafter, it was cured for 10 minutes and demolded. Then, post cure was performed at 80 ° C. for 10 hours to obtain a polyurethane elastomer sheet. The post-cure polyurethane sheet was punched out to 57 mm × 20 mm to obtain a light transmission region E.

[Production of light transmission region F]
The light transmissive region F was produced in the same manner as the light transmissive region E except that the book mold was 200 mm long × 150 mm wide × 1.93 mm thick.

[Production of polishing area]
In a reaction vessel, 100 parts by weight of a polyether-based prepolymer (Chemchula: Adiprene L-325: NCO 9.15% by weight) and 3% of a silicone-based surfactant (Toray Dow Corning: SH-192) The parts were mixed and the temperature was adjusted to 80 ° C. Using a stirring blade, the mixture was vigorously stirred for about 4 minutes so that bubbles were taken into the reaction system at 900 rpm. 26 parts by weight of 4,4′-methylenebis (o-chloroaniline) (manufactured by Ihara Chemical Co., Ltd .: Iharacamine MT) previously melted at 120 ° C. was added thereto. Thereafter, stirring was continued for about 1 minute, and the reaction solution was poured into a pan-shaped open mold. When the fluidity of this reaction solution disappeared, it was put in an oven and post-cured at 110 ° C. for 6 hours to obtain a polyurethane foam block. This polyurethane foam block was sliced using a band saw type slicer to obtain a polyurethane foam sheet. Next, this sheet was subjected to surface buffing to a predetermined thickness using a buffing machine (manufactured by Amitech Co., Ltd.) to obtain a sheet with adjusted thickness accuracy (thickness: 2.0 mm). This buffed sheet is punched out to a diameter of 61 cm, and a concentric groove having a groove width of 0.40 mm, a groove pitch of 3.1 mm, and a groove depth of 0.76 mm is used on the surface using a groove processing machine (manufactured by Toho Steel Co., Ltd.). Processing was performed. Thereafter, an opening (57 mm × 20 mm) for fitting the light transmission region into a predetermined position of the grooved sheet was punched out. Then, a double-sided tape (manufactured by Sekisui Chemical Co., Ltd .: double tack tape, thickness: 0.10 mm) is attached to the surface of the polishing area opposite to the grooved surface using a laminator, and polishing with double-sided tape is performed. A region was created.

<Example 1>
[Production of polishing pad]
A luffing machine is used to attach one side of the cushion layer made of polyethylene foam (Toray Industries Inc., TORAYPEF, thickness: 0.8 mm) buffed and corona-treated to the polishing surface plate. A double-sided tape for bonding was laminated and punched out to a size of 61 cm in diameter to produce a cushion layer with a double-sided tape. A through hole (50 mm × 14 mm) was formed at a position of about 12 cm from the center of the cushion layer with the double-sided tape. A polishing region with a double-sided tape and a cushion layer with a double-sided tape are bonded so that the opening and the through hole overlap, and further, the light transmission region A is attached to the adhesive layer of the double-sided tape in the opening of the polishing region. A pad was prepared.

<Examples 2 to 4 and Comparative Examples 1 and 2>
The same operation as in Example 1 was performed except that the light transmission region A of Example 1 was changed to light transmission regions B to F. In Comparative Example 1, the surface of the light transmission region is positioned above the surface of the polishing region, and in Comparative Example 2, the surface of the light transmission region is positioned below the surface of the polishing region.

  The evaluation results are shown in Table 1.

  In Examples 1 to 4, the light transmission region has a convex curved surface on the surface side of the polishing region, and the top of the curved surface of the light transmission region is on the same plane as the surface of the polishing region or from the surface of the polishing region. Since it is located above, the light transmission region was damaged at the break-in, and the change rate of the light transmittance was small between the initial use and the final use.

  In Comparative Example 1, since the surface of the light transmission region was positioned above the surface of the polishing region, the surface was caught during polishing, and peeling of the light transmission region occurred. In Comparative Example 2, slurry accumulated in the light transmission region that was lower than the polishing region during polishing, and the light transmittance gradually decreased.

  The polishing pad of the present invention is used to flatten optical materials such as lenses and reflection mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and materials that require high surface flatness such as general metal polishing. It can be used for a polishing pad for processing.

1: 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: Polishing region 9: Cushion layer 10: Opening portion 11: Light transmission region 12: Through hole 13: Topmost portion 14: Surface 15 of polishing region: Minimum portion

Claims (6)

A polishing pad comprising a polishing layer having a polishing region and a light transmission region,
The light transmission region has a convex curved surface on the surface side of the polishing region;
A polishing pad, wherein an uppermost portion of a curved surface of the light transmission region is located on the same plane as the surface of the polishing region or above the surface of the polishing region.   2. The polishing pad according to claim 1, wherein a height difference between a topmost part of the curved surface of the light transmission region and a lowest part of the curved surface is 10 to 200 μm.   The polishing pad according to claim 1 or 2, wherein the light transmittance at a wavelength of 660 nm before use of the light transmission region is 10 to 80%.   The polishing pad according to any one of claims 1 to 3, wherein a D hardness of the light transmission region is 48 to 75 degrees.   The polishing pad according to any one of claims 1 to 4, wherein the light transmission region is manufactured by punching a sheet formed by a centrifugal molding method.   A method for manufacturing a semiconductor device, comprising a step of polishing a surface of a semiconductor wafer using the polishing pad according to claim 1.

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