JPWO2013011921A1 - Polishing pad - Google Patents

Abstract

The polishing pad is a polishing pad having at least a polishing layer, and the polishing layer includes a groove having a side surface on a polishing surface, and at least one of the side surfaces is continuous from the polishing surface and is an angle formed with the polishing surface. Is formed from a first side surface where α is α, and a second side surface which is continuous from the first side surface and formed by a plane parallel to the polishing surface, and an angle α formed with the polishing surface. Is greater than 95 degrees, the angle β formed with the surface parallel to the polishing surface is greater than 95 degrees, and the angle β formed with the surface parallel to the polishing surface is smaller than the angle α formed with the polishing surface. The bending point depth from the polishing surface to the bending point of the first side surface and the second side surface is greater than 0.2 mm and equal to or less than 3.0 mm.

Description

  The present invention relates to a polishing pad. More specifically, the present invention relates to a polishing pad that is preferably used for forming a flat surface in semiconductors, dielectric / metal composites, integrated circuits, and the like.

  As the density of semiconductor devices increases, the importance of multilayer wiring and the accompanying interlayer insulation film formation, electrode formation of plugs, damascene, and the like is increasing. Along with this, the importance of the flattening process of these interlayer insulating films and electrode metal films has increased, and a polishing technique called CMP (Chemical Mechanical Polishing) has become widespread as an efficient technique for this flattening process. doing.

  In general, a CMP apparatus includes a polishing head that holds a semiconductor wafer that is an object to be processed, a polishing pad for polishing the object to be processed, and a polishing surface plate that holds the polishing pad. The polishing process of the semiconductor wafer uses a slurry to move the semiconductor wafer and the polishing pad relative to each other, thereby removing the protruding portion of the layer on the surface of the semiconductor wafer and flattening the layer on the surface of the wafer. The pad surface is updated by dressing using a diamond dresser or the like to prevent clogging and sharpening.

  2. Description of the Related Art Conventionally, a technique for improving the flatness of a wafer and the polishing rate is known by making a groove pattern formed on the surface of a polishing layer concentrically and making the cross-sectional shape of the groove substantially rectangular (for example, , See Patent Document 1).

  However, in this technique, the burrs formed at the corners due to the corners in the cross-sectional shape of the grooves, dressing performed before and after polishing or during polishing, and the like may cause scratches. In order to solve this problem, a technique of providing an inclined surface at the boundary between the polishing surface and the groove is disclosed (for example, see Patent Documents 2 and 3).

JP 2002-144219 A JP 2004-186392 A JP 2010-45306 A

  Here, the present inventors provide not only scratches by providing an inclined surface at the boundary between the polishing surface and the groove, but also an improvement in suction force and slurry flow between the wafer and the polishing pad, It has been found that the polishing rate is increased. However, it has also been found that the fluctuation of the polishing rate cannot be suppressed depending on the angle of the inclined surface. It has also been found that providing an inclined surface reduces the polishing surface area, increases the pad cut rate, and shortens the life of the pad.

  An object of the present invention is to provide a long-life polishing pad that can suppress fluctuations in the polishing rate while maintaining a high polishing rate, among other polishing characteristics.

  The present inventors considered that the inclination from the polishing surface to the groove bottom has an effect on the pad cut rate, and the angle between the polishing surface and the boundary between the grooves has an influence on the polishing rate. In order to achieve both, we thought that the problem could be solved by combining the angle at which the pad cut rate is reduced and the angle at which the polishing rate fluctuation is reduced.

  Therefore, the present invention employs the following means in order to solve the above problems. That is, a polishing pad having at least a polishing layer, wherein the polishing layer includes a groove having a side surface on a polishing surface, and at least one of the side surfaces is continuous from the polishing surface, and an angle formed with the polishing surface is α The first side surface and the second side surface that is continuous from the first side surface and is parallel to the polishing surface are β, and the angle α formed with the polishing surface is 95. The angle β formed by the surface parallel to the polishing surface is greater than 95 degrees, and the angle β formed by the surface parallel to the polishing surface is smaller than the angle α formed by the polishing surface. A polishing pad, wherein a bending point depth from the polishing surface to a bending point of the first side surface and the second side surface is greater than 0.2 mm and 3.0 mm or less.

  The present invention can provide a long-life polishing pad that can suppress fluctuations in the polishing rate while maintaining a high polishing rate.

FIG. 1 is a partial cross-sectional view showing a configuration of a main part of a polishing pad according to an embodiment of the present invention. FIG. 2 is a partial cross-sectional view showing the configuration (second example) of the main part of the polishing pad according to one embodiment of the present invention. FIG. 3 is a partial cross-sectional view showing the configuration (third example) of the main part of the polishing pad according to one embodiment of the present invention. FIG. 4 is a partial cross-sectional view showing the configuration (fourth example) of the main part of the polishing pad according to one embodiment of the present invention.

Hereinafter, modes for carrying out the present invention will be described.
The inventor has intensively studied a long-life polishing pad that can suppress fluctuations in the polishing rate while maintaining a high polishing rate. As a result, the present inventor is a polishing pad having at least a polishing layer, wherein the polishing layer includes a groove having a side surface on a polishing surface, and at least one of the side surfaces is continuous from the polishing surface, An angle formed between the first side surface having an angle α and a second side surface continuous with the first side surface and having an angle β with the surface parallel to the polishing surface, the angle formed with the polishing surface α is greater than 95 degrees, the angle β formed with the surface parallel to the polishing surface is greater than 95 degrees, and the angle β formed with the surface parallel to the polishing surface is greater than the angle α formed with the polishing surface. A polishing pad that is small and has a bending point depth from the polishing surface to a bending point of the first side surface and the second side surface of greater than 0.2 mm and not greater than 3.0 mm. By configuring, the above-mentioned problems can be solved at once. And investigate the Rukoto.

In the present invention, the polishing pad preferably has a cushion layer separately from at least the polishing layer. When there is no cushion layer, since the distortion due to water absorption or the like of the polishing layer cannot be buffered, the polishing rate and in-plane uniformity of the material to be polished fluctuate unstably. The strain constant of the cushion layer is preferably in the range of 7.3 × 10 ⁻⁶ μm / Pa or more and 4.4 × 10 ⁻⁴ μm / Pa or less. The upper limit is preferably 3.0 × 10 ⁻⁴ μm / Pa or less, and more preferably 1.5 × 10 ⁻⁴ μm / Pa or less, from the viewpoint of polishing rate fluctuations and local flatness of the material to be polished. Further, the lower limit is preferably 1.0 × 10 ⁻⁵ μm / Pa or more, and more preferably 1.2 × 10 ⁻⁵ μm / Pa or more. When the fluctuation of the polishing rate is large, the polishing amount of the material to be polished changes, and as a result, the film thickness of the material to be polished changes and adversely affects the performance of the semiconductor device. Therefore, the polishing rate fluctuation rate is preferably 20% or less, 15% or less is more preferable.

The strain constant in the present invention is such that when a pressure of 27 kPa is applied with a dial gauge for 60 seconds using an indenter with a tip diameter of 5 mm, the thickness is (T1) μm, and then the pressure at 177 kPa is 60 seconds. The thickness when added was (T2) μm and was calculated according to the following formula.
Strain constant (μm / Pa) = (T1-T2) / (177-27) / 1000

  Examples of such cushion layers include natural rubber, nitrile rubber, “neoprene (registered trademark)” rubber, polybutadiene rubber, thermosetting polyurethane rubber, thermoplastic polyurethane rubber, silicone rubber, and “Hytrel (registered trademark)”. Examples include foamed elastomers, polyolefin foams such as “Tolepef (registered trademark, Pef manufactured by Toray Industries, Inc.)”, and non-woven fabrics such as “suba400” manufactured by Nitta Haas Co., but are not limited thereto. is not.

  The strain constant of the cushion layer can be adjusted according to the material. For example, when the cushion layer is a foam, the strain constant tends to increase because the degree of foaming tends to soften. Further, when the cushion layer is non-foamed, the hardness can be adjusted by adjusting the degree of crosslinking in the cushion layer.

  The thickness of the cushion layer is preferably in the range of 0.1 to 2 mm. From the viewpoint of in-plane uniformity over the entire surface of the semiconductor substrate, it is preferably 0.25 mm or more, and more preferably 0.3 mm or more. Moreover, from a viewpoint of local flatness, 2 mm or less is preferable and 1 mm or less is more preferable.

  The polishing layer surface (polishing surface) of the polishing pad in the present invention has a groove. Examples of the shape of the groove viewed from the surface of the polishing layer include, but are not limited to, a lattice shape, a radial shape, a concentric shape, and a spiral shape. The grooves are most preferably lattice-shaped because an open system extending in the circumferential direction can renew the slurry efficiently.

  At least one of the side surfaces of the groove in the present invention is a first side surface that is continuous from the polishing surface and has an angle α with the polishing surface, and a surface that is continuous from the first side surface and is parallel to the polishing surface. It is comprised from the 2nd side surface which the angle | corner made is (beta). Each of the first side surface and the second side surface may be flat (linear in the cross-sectional shape of the groove) or curved surface (curved in the cross-sectional shape of the groove).

  In the present invention, the angle α is larger than 95 degrees, the angle β is larger than 95 degrees, and the angle β is smaller than the angle α. Thereby, the fluctuation | variation of a polishing rate can be suppressed, maintaining a high polishing rate. This is explained as follows. Generally, the fluctuation of the polishing rate is large in the initial to intermediate period, but not only the polishing rate is increased by providing an inclined surface larger than 95 degrees at the boundary between the polishing surface and the groove, but such an initial to intermediate period is also provided. The fluctuation of the polishing rate can be effectively suppressed.

  On the other hand, such a structure has a concern that the contact area between the material to be polished and the surface of the polishing pad is small and the pad cut rate is large. For this reason, it is preferable that the groove has a structure in which the contact area increases after a certain depth. Such an object can be achieved by adjusting the angles α and β as described above. The difference between the angle α and the angle β is more preferably 55 degrees or less, and further preferably 50 degrees or less.

  From the viewpoint of slurry retention and fluidity, the angle α is preferably 105 degrees or more as a lower limit, and more preferably 115 degrees or more. Further, the upper limit of the angle α is preferably 150 degrees or less, and more preferably 140 degrees or less. The opposite side surfaces forming the groove may have the same shape, but since the slurry flows due to centrifugal force, it is better that at least the side surface on the circumferential side is inclined among the opposing side surfaces forming the groove. More effective. The angle β is not particularly limited as long as it is smaller than the angle α, but the upper limit is more preferably less than 150 degrees, and further preferably less than 140 degrees.

  Here, the side surface (side surface 3) may be continuous from the side surface 2 in the opposite direction to the side surface 1, in which case the angle (angle 3) formed by the side surface 3 and the polishing surface is greater than 95 degrees, and the angle β Preferably it is smaller.

  Similarly, n may be a natural number of 3 or more, and may have a side surface (side surface (n + 1)) that is continuous with the side surface n in the opposite direction to the side surface (n−1). The angle (angle (n + 1)) made with the polishing surface is preferably larger than 95 degrees and smaller than the angle n.

  As the material to be polished is polished, the polishing layer is scraped, and the polishing rate fluctuates when the polishing surface passes through the bending point that is the boundary between the first side surface and the second side surface. Further, since the pad cut rate is different between the first side surface and the second side surface of the shallowest groove side surface, the depth from the polishing surface to the bending point is an inclined groove portion on the polishing surface side. It is preferable that the depth is not less than a depth that does not reduce the effect. Considering this point and the point that it is preferable that the polishing pad has a long life, the depth from the polishing surface to the bending point is specifically preferably 10% or more and 95% or less of the entire depth of the groove, More preferably, it is 20% or more and 90% or less.

  Since it is important to achieve both a long pad life and suppression of fluctuations in the polishing rate, the bending point depth from the polishing surface to the bending points of the first side surface and the second side surface is less than 0.2 mm. The range is large and 3.0 mm or less. The polished surface here is a polished surface before the polishing layer is shaved. When the bending point depth is deep, the life of the pad is shortened. When the bending point depth is shallow, the polishing rate varies. The upper limit of the bending point depth from the polished surface to the bending point of the first side surface and the second side surface is preferably 2.5 mm or less, more preferably 2.0 mm or less, and even more preferably 1.8 mm or less. Further, the lower limit of the bending point depth from the polishing surface to the bending point of the first side surface and the second side surface is preferably 0.3 mm or more, more preferably 0.4 mm or more, and further preferably 0.5 mm or more. .

  The specific shape of the groove in the present invention as described above will be described with reference to the drawings. FIG. 1 is a partial cross-sectional view showing a configuration of a main part of a polishing pad according to an embodiment of the present invention. A polishing pad 1 shown in the figure has a polishing layer 10. A groove 12 is formed in the polishing surface 11 of the polishing layer 10. The groove 12 is continuous with the polishing surface 11, is inclined with respect to the polishing surface 11 at an angle α, is continuous with the first side surface 13, and is bent with respect to the first side surface 13. 14 has a second side surface 15 bent through 14 and a deepest groove portion 16. The angle β of the second side surface with respect to the surface parallel to the polishing surface 11 is smaller than the angle α of the first side surface 13 with respect to the polishing surface 11.

  In addition, the shape comprised by the 2nd side surface 15 and the deepest part 16 of a groove | channel is not necessarily restricted to the shape shown in FIG. For example, like the groove 17 of the polishing pad 2 shown in FIG. 2, the deepest portion 18 may have a bottom surface substantially parallel to the polishing surface 11. Further, like the groove 19 of the polishing pad 3 shown in FIG. 3, the boundary portion between the second side surface 15 and the deepest portion 20 may be curved. Moreover, like the groove | channel 21 of the polishing pad 4 shown in FIG. 4, the cross-sectional shape of the 2nd side surface 15 and the deepest part 22 may comprise U shape.

  As the polishing layer constituting the polishing pad, a structure having closed cells is preferable because it forms a flat surface in a semiconductor, a dielectric / metal composite, an integrated circuit, or the like. Further, the hardness of the polishing layer is preferably 45 to 65 degrees as measured by an Asker D hardness meter. When the Asker D hardness is less than 45 degrees, the uniformity of planarization characteristics (planarity) within the wafer surface is reduced as the polishing rate of the material to be polished decreases in the wafer surface uniformity (uniformity). ) Tend to decrease.

  Although not particularly limited, materials for forming such a structure include polyethylene, polypropylene, polyester, polyurethane, polyurea, polyamide, polyvinyl chloride, polyacetal, polycarbonate, polymethyl methacrylate, polytetrafluoroethylene, epoxy resin, ABS resin, AS resin, phenol resin, melamine resin, “neoprene (registered trademark)” rubber, butadiene rubber, styrene butadiene rubber, ethylene propylene rubber, silicon rubber, fluororubber, and resins mainly composed of these. Two or more of these may be used. Even in such a resin, a material mainly composed of polyurethane is more preferable in that the closed cell diameter can be controlled relatively easily.

  Polyurethane is a polymer synthesized by polyaddition reaction or polymerization reaction of polyisocyanate. The compound used as the symmetry of the polyisocyanate is an active hydrogen-containing compound, that is, a compound containing two or more polyhydroxy groups or amino groups. Examples of the polyisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, but are not limited thereto. Two or more of these may be used.

  The polyhydroxy group-containing compound is typically a polyol, and examples thereof include polyether polyol, polytetramethylene ether glycol, epoxy resin-modified polyol, polyester polyol, acrylic polyol, polybutadiene polyol, and silicone polyol. Two or more of these may be used. It is preferable to determine the combination and optimum amount of polyisocyanate and polyol, catalyst, foaming agent, and foam stabilizer depending on the hardness, the cell diameter and the expansion ratio.

  As a method of forming closed cells in these polyurethanes, the chemical foaming method is generally used by blending various foaming agents into the resin during polyurethane production, but it is cured after foaming the resin by mechanical stirring. The method of making it can also be used preferably.

  The average bubble diameter of closed cells is preferably 30 μm or more from the viewpoint of reducing scratches. On the other hand, from the viewpoint of the flatness of the local unevenness of the material to be polished, the average bubble diameter is preferably 150 μm or less, more preferably 140 μm or less, and further preferably 130 μm or less. The average bubble diameter was observed in a circular shape that was missing at the edge of the field among the bubbles observed in one field of view when the sample cross section was observed with a VK-8500 ultra-deep microscope manufactured by Keyence at a magnification of 400 times. The circular bubbles excluding the generated bubbles are obtained by measuring the equivalent circle diameter from the cross-sectional area with an image processing apparatus and calculating the number average value.

  A preferred embodiment of the polishing pad in the present invention is a pad containing a polymer of a vinyl compound and polyurethane and having closed cells. Although the toughness and hardness can be increased only with the polymer from the vinyl compound, it is difficult to obtain a uniform polishing pad having closed cells. Polyurethane becomes brittle when its hardness is increased. By impregnating a polyurethane with a vinyl compound, a polishing pad containing closed cells and having high toughness and hardness can be obtained.

  A vinyl compound is a compound having a polymerizable carbon-carbon double bond. Specifically, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl Methacrylate, 2-hydroxybutyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, acrylic acid, methacrylic acid, fumaric acid, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, maleic acid, maleic Dimethyl acid, diethyl maleate, dipropyl maleate, phenylmaleimide, Hexyl maleimide, isopropyl maleimide, acrylonitrile, acrylamide, vinyl chloride, vinylidene chloride, styrene, alpha-methyl styrene, divinylbenzene, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and the like. Two or more of these may be used.

Among the vinyl compounds described above, CH ₂ = CR ¹ COOR ² (R ¹ : methyl group or ethyl group, R ² : methyl group, ethyl group, propyl group or butyl group) is preferable. Among them, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate are easy to form closed cells in polyurethane, good in impregnation of monomers, easy to polymerize, vinyl compound that has been polymerized and cured The foamed structure containing the polymer and polyurethane is preferred because of its high hardness and good flattening characteristics.

  Polymerization initiators preferably used for obtaining polymers of these vinyl compounds include azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile), azobiscyclohexanecarbonitrile, benzoyl peroxide, lauroyl peroxide. Examples thereof include radical initiators such as oxide and isopropyl peroxydicarbonate. Two or more of these may be used. A redox polymerization initiator, for example, a combination of a peroxide and an amine can also be used.

  Examples of the method for impregnating the polyurethane with the vinyl compound include a method of immersing the polyurethane in a container containing the vinyl compound. In this case, it is also preferable to perform treatments such as heating, pressurization, decompression, stirring, shaking, and ultrasonic vibration for the purpose of increasing the impregnation rate.

  The amount of vinyl compound impregnated in polyurethane should be determined by the type of vinyl compound and polyurethane used and the characteristics of the polishing pad to be produced. The content ratio of the polymer obtained from the vinyl compound in the body and the polyurethane is preferably 30/70 to 80/20 by weight. If the content ratio of the polymer obtained from the vinyl compound is 30/70 or more by weight, the hardness of the polishing pad can be sufficiently increased. Further, if the content ratio is 80/20 or less, the elasticity of the polishing layer can be sufficiently increased.

  The content of the polymer obtained from the polymerized and cured vinyl compound in polyurethane and the content of polyurethane can be measured by a pyrolysis gas chromatography / mass spectrometry method. As an apparatus that can be used in this method, a double shot pyrolyzer “PY-2010D” (manufactured by Frontier Laboratories) is used as a thermal decomposition apparatus, and “TRIO-1” (manufactured by VG) is used as a gas chromatograph / mass spectrometer. ).

  In the present invention, from the viewpoint of flatness of local irregularities of the semiconductor substrate, it is preferable that the polymer phase obtained from the vinyl compound and the polyurethane phase are contained without being separated. Expressed quantitatively, the infrared spectrum of the polishing pad observed with a micro-infrared spectrometer having a spot size of 50 μm has an infrared absorption peak of a polymer polymerized from a vinyl compound and an infrared absorption peak of polyurethane. In addition, it is preferable that the infrared spectra at various locations are substantially the same. As a micro-infrared spectrometer used here, IRμs manufactured by SPECTRA-TEC can be mentioned.

  The polishing pad may contain various additives such as an abrasive, an antistatic agent, a lubricant, a stabilizer, and a dye for the purpose of improving characteristics.

In the present invention, the density of the polishing layer is preferably 0.3 g / cm ³ or more, more preferably 0.6 g / cm ³ or more, and 0.65 g / cm ³ from the viewpoint of reducing local flatness defects and global steps. More preferably, it is cm ³ or more. On the other hand, from the viewpoint of reducing scratches, 1.1 g / cm ³ or less is preferable, 0.9 g / cm ³ or less is more preferable, and 0.85 g / cm ³ or less is more preferable. The density of the polishing layer in the present invention is a value measured using water as a medium using a Harvard pycnometer (JIS R-3503 standard).

  Examples of the material to be polished in the present invention include the surface of an insulating layer or metal wiring formed on a semiconductor wafer. Examples of the insulating layer include an interlayer insulating film of metal wiring, a lower insulating film of metal wiring, and shallow trench isolation used for element isolation. Examples of the metal wiring include aluminum, tungsten, copper, and alloys thereof, and structurally include damascene, dual damascene, and plug. When copper is used as the metal wiring, a barrier metal such as silicon nitride is also subject to polishing. As the insulating film, silicon oxide is currently mainstream, but a low dielectric constant insulating film is also used. In addition to semiconductor wafers, it can also be used for polishing magnetic heads, hard disks, sapphire, SiC, MEMS (Micro Electro Mechanical Systems) and the like.

  The polishing method of the present invention is suitably used for forming a flat surface on glass, semiconductors, dielectric / metal composites, integrated circuits and the like.

  Hereinafter, the details of the present invention will be described with reference to examples. However, the present invention is not construed as being limited by this embodiment. The measurement was performed as follows.

<Bubble diameter measurement>
Of the bubbles observed in one field of view when the cross section of the sample is observed with a Keyence VK-8500 ultra-deep microscope at a magnification of 400 times, the circular shape excluding the bubbles observed in a circular shape missing at the edge of the field of view The equivalent circle diameter was measured from the cross-sectional area of the bubbles with an image processing apparatus, and the calculated number average value was taken as the average bubble diameter.

<Hardness measurement>
This was performed in accordance with JIS K6253-1997. A sample obtained by cutting the produced polyurethane resin 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. Hardness was measured using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D-type hardness meter).

<Micro rubber A hardness measurement>
A sample obtained by cutting out the cushion layer into a size of 3 cm × 3 cm was used as a sample for hardness measurement, and was allowed to stand for 16 hours in an environment of a temperature of 23 ° C. ± 2 ° C. and a humidity of 50% ± 5%. Using a micro rubber hardness meter MD-1 manufactured by Kobunshi Keiki Co., Ltd., three different points were measured in one sample, and the calculated average value was defined as micro rubber A hardness.

<Inclination angle measurement>
A pad with grooves formed on the surface of the polishing layer is placed so that the razor blade is perpendicular to the groove direction and sliced in the groove depth direction, and the cross section of the groove is measured with a VK-8500 ultra-deep microscope manufactured by Keyence. By observing, the angle (angle α) formed between the polishing surface and the side surface continuous with the polishing surface of the groove was measured. The closest groove was measured at the position of 1/3 of the radius and the position of 2/3 from the center of the pad, and the average of the two points in each place was taken as the inclination angle. The angle β was measured in the same manner.

<Bend point depth measurement>
A pad with grooves formed on the surface of the polishing layer is placed so that the razor blade is perpendicular to the groove direction and sliced in the groove depth direction, and the cross section of the groove is measured with a VK-8500 ultra-deep microscope manufactured by Keyence. By observing, the vertical distance from the polished surface to the midpoint of two opposing bending points consisting of the first side surface and the second side surface was measured. The nearest groove was measured at the position of 1/3 and 2/3 of the radius from the center of the pad, and the average of the two points in each place was taken as the bending point depth.

<Initial bending distance measurement>
A pad with grooves formed on the surface of the polishing layer is placed so that the razor blade is perpendicular to the groove direction and sliced in the groove depth direction, and the cross section of the groove is measured with a VK-8500 ultra-deep microscope manufactured by Keyence. Observed, the distance between the two bending points facing each other between the polished surface having the angle α and the side surface 1 was measured and defined as the bending point distance. Further, the distance between the bending points at the initial stage of polishing was defined as the distance between the initial bending points.

<Strain constant calculation>
Using an indenter with a tip diameter of 5 mm, the thickness when a pressure of 27 kPa is applied for 60 seconds with a dial gauge is (T1) μm, and then the thickness when a pressure of 177 kPa is applied for 60 seconds is (T2) The strain constant was calculated as μm according to the following formula.
Strain constant (μm / Pa) = (T1-T2) / (177-27) / 1000

<Average polishing rate calculation>
Polishing was performed while detecting the end point under predetermined polishing conditions using a Mirror 3400 manufactured by Applied Materials. The polishing characteristics were measured in the diameter direction, excluding the outermost periphery of 10 mm of the 8-inch wafer. An average polishing rate (nm / min) was calculated by measuring 37 points every 5 mm within a surface within a radius of 90 mm from the center.

<Polishing rate fluctuation rate calculation>
After polishing 1000 wafers and measuring the average polishing rate for each wafer, the polishing rate fluctuation rate from the first to the 700th wafer was calculated according to the following formula.
Polishing rate fluctuation rate (%) = {(maximum wafer average polishing rate) − (minimum wafer average polishing rate)} / (1000th wafer average polishing rate)

  When the fluctuation of the polishing rate is large, the device may be defective due to insufficient polishing or excessive polishing. Therefore, the fluctuation rate of the polishing rate is preferably small, preferably 30% or less, more preferably 20% or less.

<Average pad cut rate measurement>
Polishing while applying end point detection under a predetermined polishing condition using Mirror 3400 of Applied Materials Co., Ltd., groove depth (D1) mm after polishing 30 sheets with depth gauge, groove depth after polishing 1000 sheets ( D2) mm was measured and calculated know dress by dresser time _{(t d).}
Average pad cut rate (μm / min) = (D1-D2) × 1000 / t _d
The average pad cut rate depends on the distance between the bending points and the angle α and the angle β. The distance between the bending points varies with the progress of polishing. The average pad cut rate is smaller as the average distance between the bending points from the initial polishing to the final polishing is smaller.
Average distance between inflection points (mm) = {(initial polishing cross-sectional area) − (final polishing cross-sectional area)} / {(polishing initial deepest groove depth) − (polishing final deepest groove depth)}

<Calculation of polishing pad life>
The groove depth at the initial stage of polishing was measured, the effective groove depth (D3) mm which was 0.3 mm shallower than the deepest part was calculated, and the wafer was polished from the time (t _p ) and the average pad cut rate.
Life of polishing pad (time) = D3 × 1000 / (average pad cut rate) × t _p / 60
The life of the polishing pad is preferably 15 hours or longer.

  Hereinafter, Examples 1 to 12 and Comparative Examples 1 to 4 will be described.

(Example 1)
30 parts by weight of polypropylene glycol, 40 parts by weight of diphenylmethane diisocyanate, 0.5 parts by weight of water, 0.3 parts by weight of triethylamine, 1.7 parts by weight of a silicone foam stabilizer and 0.09 parts by weight of tin octylate are mixed in a RIM molding machine. Then, it was discharged into a mold and subjected to pressure molding to produce a closed-cell foamed polyurethane sheet.

  The foamed polyurethane sheet was immersed in methyl methacrylate to which 0.2 part by weight of azobisisobutyronitrile was added for 60 minutes. Next, 15 parts by weight of polyvinyl alcohol “CP” (degree of polymerization: about 500, manufactured by Nacalai Tesque), 35 parts by weight of ethyl alcohol (special grade reagent, manufactured by Katayama Chemical), water 50 The foamed polyurethane sheet surface layer was coated with polyvinyl alcohol by being immersed in a solution consisting of parts by weight and then dried.

Next, the foamed polyurethane sheet was sandwiched between two glass plates via a vinyl chloride gasket and polymerized and cured by heating at 65 ° C. for 6 hours and at 120 ° C. for 3 hours. After releasing from between the glass plates and washing with water, vacuum drying was performed at 50 ° C. A polishing layer was prepared by slicing the hard foam sheet thus obtained to a thickness of 2.00 mm. The methyl methacrylate content in the polishing layer was 66% by weight. The D hardness of the polishing layer was 54 degrees, the density was 0.81 g / cm ³ , and the average cell diameter of closed cells was 45 μm.

  The obtained hard foam sheet was ground on both sides to prepare a polishing layer having a thickness of 2.4 mm.

A thermoplastic polyurethane (cushion layer thickness: 0. 0) made by Nippon Matai Co., Ltd. having a strain constant of 0.15 × 10 ⁻⁴ μm / Pa (micro rubber A hardness 89) as a cushion layer was obtained on the polishing layer obtained by the above method. 3 μm) was laminated through a MA-6203 adhesive layer manufactured by Mitsui Chemicals Polyurethane Co., Ltd. using a roll coater, and a double-sided tape 5604TDM manufactured by Sekisui Chemical Co., Ltd. was bonded to the back surface as a back tape. This laminate is punched into a circle having a diameter of 508 mm, and grooves having a groove pitch of 15 mm, an angle α of 135 degrees, an angle β of 120 degrees, and a groove depth of 1.9 mm are formed in an XY lattice pattern on the polishing layer surface. A polishing pad was obtained. At this time, the bending point depth was 0.69 mm, and the distance between the initial bending points was 3 mm.

  The polishing pad obtained by the above method was attached to a surface plate of a polishing machine (“Mirra 3400” manufactured by Applied Materials Co., Ltd.). Retainer ring pressure = 41 kPa (6 psi), inner tube pressure = 28 kPa (4 psi), membrane pressure = 28 kPa (4 psi), platen rotation speed = 76 rpm, polishing head rotation speed = 75 rpm, slurry (Cabot Corporation) Manufactured, SS-25) was flowed at a flow rate of 150 mL / min, and 1000 sheets were polished by in-situ dressing with a Saesol dresser with a load of 17.6 N (4 lbf), a polishing time of 1 minute, and 30 seconds from the start of polishing.

  The average polishing rate of the 1000th oxide film was 192.2 nm / min. The fluctuation rate of the polishing rate in 1000 sheets was 8.5%. The average pad cut rate was 1.22 μm / min, and the polishing pad life was 22 hours.

(Example 2)
Polishing was performed in the same manner as in Example 1 except that the groove angle α on the polishing layer surface was changed to 145 degrees, the polishing layer thickness was changed to 2.25 mm, and the groove depth was changed to 1.75 mm. At this time, the bending point depth was 0.46 mm, and the distance between the initial groove bending points was 3 mm. The average polishing rate was 195.2 nm / min, and the polishing rate fluctuation rate was 13.2%. The average pad cut rate was 1.15 μm / min, and the polishing pad life was 21 hours.

Example 3
Polishing was performed in the same manner as in Example 1 except that the groove angle β on the polishing layer surface was changed to 100 degrees, the polishing layer thickness was changed to 3.15 mm, and the groove depth was changed to 2.65 mm. At this time, the bending point depth was 1.37 mm, and the distance between the initial bending points was 3.4 mm. The average polishing rate was 184.1 nm / min, and the polishing rate fluctuation rate was 17.2%. The average pad cut rate was 1.22 μm / min, and the polishing pad life was 32 hours.

Example 4
Polishing was performed in the same manner as in Example 1 except that the groove angle α on the polishing layer surface was 100 degrees, the angle β was 98 degrees, the polishing layer thickness was 2.0 mm, and the groove depth was 1.5 mm. At this time, the bending point depth was 0.3 mm, and the distance between the initial bending points was 3 mm. The average polishing rate was 187.8 nm / min, and the polishing rate fluctuation rate was 17.8%. The average pad cut rate was 1.20 μm / min, and the polishing pad life was 16 hours.

(Example 5)
Polishing was performed in the same manner as in Example 1 except that the groove angle α on the polishing layer surface was 150 degrees, the angle β was 145 degrees, the polishing layer thickness was 2.0 mm, and the groove depth was 1.5 mm. At this time, the bending point depth was 0.27 mm, and the distance between the initial bending points was 5 mm. The average polishing rate was 201.9 nm / min, and the polishing rate fluctuation rate was 18.9%. The average pad cut rate was 1.24 μm / min, and the polishing pad life was 16 hours.

(Example 6)
Polishing was performed in the same manner as in Example 1 except that the groove angle α on the polishing layer surface was 160 degrees, the angle β was 110 degrees, the polishing layer thickness was 2.5 mm, and the groove depth was 2.05 mm. At this time, the bending point depth was 0.79 mm, and the distance between the initial bending points was 5 mm. The average polishing rate was 183.8 nm / min, and the polishing rate fluctuation rate was 16.4%. The average pad cut rate was 1.35 μm / min and the polishing pad life was 21 hours.

(Example 7)
Polishing was performed in the same manner as in Example 1 except that the groove angle α on the polishing layer surface was 115 degrees, the angle β was 100 degrees, the polishing layer thickness was 2.0 mm, and the groove depth was 1.5 mm. At this time, the bending point depth was 0.27 mm, and the distance between the initial bending points was 3 mm. The average polishing rate was 182.5 nm / min, and the polishing rate fluctuation rate was 17.5%. The average pad cut rate was 1.22 μm / min, and the polishing pad life was 16 hours.

(Example 8)
Polishing was performed in the same manner as in Example 1 except that the groove angle α on the polishing layer surface was 165 degrees, the angle β was 155 degrees, the polishing layer thickness was 2.2 mm, and the groove depth was 1.7 mm. At this time, the bending point depth was 0.5 mm, and the distance between the initial bending points was 5 mm. The average polishing rate was 190.2 nm / min, and the polishing rate fluctuation rate was 15.6%. The average pad cut rate was 1.36 μm / min, and the polishing pad life was 17 hours.

Example 9
Polishing was performed in the same manner as in Example 1 except that the polishing layer thickness was changed to 2.9 mm and the groove depth was changed to 2.4 mm. At this time, the bending point depth was 2.1 mm, and the distance between the initial bending points was 3 mm. The average polishing rate was 185.7 nm / min, and the polishing rate fluctuation rate was 14.4%. The average pad cut rate was 1.23 μm / min, and the polishing pad life was 28 hours.

(Example 10)
Polishing was performed in the same manner as in Example 1 except that the polishing layer thickness was changed to 3.5 mm and the groove depth was changed to 3.0 mm. At this time, the bending point depth was 2.6 mm, and the distance between the initial bending points was 3 mm. The average polishing rate was 183.3 nm / min, and the polishing rate fluctuation rate was 15.1%. The average pad cut rate was 1.24 μm / min, and the polishing pad life was 36 hours.

(Example 11)
Polishing was performed in the same manner as in Example 1 except that the two angles α facing each other across the groove on the polishing layer surface were 135 degrees and 130 degrees, and the two facing angles were changed to be different. At this time, the bending point depth was 0.69 mm, and the distance between the initial bending points was 3 mm. The average polishing rate was 191.8 nm / min, and the polishing rate fluctuation rate was 9.0%. The average pad cut rate was 1.20 μm / min, and the polishing pad life was 22 hours.

(Example 12)
Polishing was performed in the same manner as in Example 1 except that a polyester film having a thickness of 188 μm was bonded to the back surface of the polishing layer via an adhesive and a cushion layer was bonded to the polyester film surface. At this time, the bending point depth was 0.69 mm, and the distance between the initial bending points was 3 mm. The average polishing rate was 192.8 nm / min, and the polishing rate fluctuation rate was 9.3%. The average pad cut rate was 1.22 μm / min, and the polishing pad life was 22 hours.

(Comparative Example 1)
Polishing was performed in the same manner as in Example 1 except that the groove angle α on the polishing layer surface was 93 degrees, the angle β was 90 degrees, the polishing layer thickness was 2.0 mm, and the groove depth was 1.5 mm. At this time, the bending point depth was 0.27 mm, and the distance between the initial bending points was 1.5 mm. The average polishing rate was 180.1 nm / min, the polishing rate fluctuation rate was 45.1%, and the polishing rate fluctuation was large. The average pad cut rate was 1.12 μm / min, and the polishing pad life was 18 hours.

(Comparative Example 2)
Polishing was performed in the same manner as in Example 1 except that the groove angle α on the polishing layer surface was 93 degrees, the angle β was 90 degrees, the polishing layer thickness was 2.0 mm, and the groove depth was 1.5 mm. At this time, the bending point depth was 0.27 mm, and the distance between the initial bending points was 3 mm. The average polishing rate was 189.5 nm / min, the polishing rate fluctuation rate was 30.8%, and the polishing rate fluctuation was large. The average pad cut rate was 1.5 μm / min, the polishing pad life was 13 hours, and the life was short.

(Comparative Example 3)
Polishing was performed in the same manner as in Example 1 except that the angle β was 98 degrees, the polishing layer thickness was 2.0 mm, and the groove depth was 1.5 mm. At this time, the bending point depth was 0.15 mm, and the distance between the initial bending points was 3 mm. The average polishing rate was 190.1 nm / min, the polishing rate fluctuation rate was 36.2%, and the polishing rate fluctuation was large. The average pad cut rate was 1.42 μm / min, the polishing pad life was 14 hours, and the life was short.

(Comparative Example 4)
Polishing was performed in the same manner as in Example 1 except that the groove angle α on the polishing layer surface was 160 degrees, the angle β was 100 degrees, the polishing layer thickness was 2.5 mm, and the groove depth was 2.0 mm. At this time, the bending point depth was 0.60 mm, and the distance between the initial bending points was 4 mm. The average polishing rate was 184.6 nm / min, the polishing rate fluctuation rate was 31.0%, and the polishing rate fluctuation was large. The average pad cut rate was 1.32 μm / min, and the polishing pad life was 21 hours.

  Table 1 shows the results obtained in Examples 1 to 12 and Comparative Examples 1 to 4 described above.

1, 2, 3, 4 Polishing pad 10 Polishing layer 11 Polishing surface 12, 17, 19, 21 Groove 13 First side surface 14 Bend point 15 Second side surface 16, 18, 20, 22 Deepest part

Claims (5)

A polishing pad having at least a polishing layer,
The polishing layer comprises a groove having a side surface on the polishing surface,
At least one of the side surfaces is continuous with the polishing surface, and is formed with a first side surface having an angle α with the polishing surface, and a surface continuous with the first side surface and parallel to the polishing surface. Composed of a second side with an angle β,
The angle α formed with the polishing surface is greater than 95 degrees, the angle β formed with the surface parallel to the polishing surface is greater than 95 degrees, and the angle β formed with the surface parallel with the polishing surface is the polishing surface. Is smaller than the angle α formed by
A polishing pad, wherein a bending point depth from the polishing surface to a bending point of the first side surface and the second side surface is greater than 0.2 mm and 3.0 mm or less.   2. The polishing pad according to claim 1, wherein a difference between an angle α formed with the polishing surface and an angle β formed with a surface parallel to the polishing surface is 55 degrees or less.   The polishing pad according to claim 1, wherein an angle α formed with the polishing surface is 105 degrees or more and 150 degrees or less.   The polishing pad according to any one of claims 1 to 3, wherein an angle β formed by a surface parallel to the polishing surface is greater than 95 degrees and less than 150 degrees.   The polishing pad according to any one of claims 1 to 4, wherein a pattern of grooves on the polishing surface is a lattice pattern.

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