JP2010184348A - Polishing pad and method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad which is used in a polishing step of flattening very small unevenness of a very small pattern formed on a surface of an object to be polished such as a semiconductor wafer, and capable of enhancing the uniformity of the polishing amount in the entire surface of the object such as wafer, and a method for manufacturing a semiconductor device by using the polishing pad. <P>SOLUTION: Concentric grooves are formed in a surface of a polishing pad, the groove pitches of the grooves are different in the radial direction of the polishing pad, and the groove pitches are continuously changed in the surface of the polishing pad. Further, concentric grooves are formed in the surface of the polishing pad, the groove widths of the grooves are different in the radial direction of the polishing pad, and the groove widths are continuously changed in the surface of the polishing pad. In the method for manufacturing the semiconductor device, the polishing pad is used. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polishing pad for use in planarizing unevenness of a surface of an object to be polished such as a semiconductor wafer by chemical mechanical polishing (CMP), and more particularly, a semiconductor wafer having excellent polishing rate and having been polished. The present invention relates to a polishing pad excellent in surface uniformity of an object to be polished such as a semiconductor device and a method of manufacturing a semiconductor device using the polishing pad.

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

  As a method for flattening irregularities on the surface of a semiconductor wafer, a CMP method is generally employed. CMP is a technique in which a polishing surface of a semiconductor wafer is pressed against a polishing surface of a polishing pad, and polishing is performed using a slurry in which abrasive grains are dispersed (hereinafter referred to as slurry).

  A polishing apparatus generally used in CMP performs, for example, uniform pressing of a polishing surface plate that supports a polishing pad, a support table (polishing head) that supports an object to be polished (such as a semiconductor wafer), and the semiconductor wafer. And a polishing agent supply mechanism. For example, the polishing pad is attached to the polishing surface plate by pasting with a double-sided tape. The polishing surface plate and the support base are arranged so that the polishing pad supported by the polishing table and the object to be polished are opposed to each other, and each has a rotating shaft. Further, the support base is provided with a pressurizing mechanism for pressing the object to be polished against the polishing pad.

  Until now, various attempts have been made to improve the uniformity of the polishing rate over the entire surface of the semiconductor wafer during polishing. For example, the configuration of the entire pad includes the following.

1. A synthetic leather layer as a polishing layer is laminated on an elastic polyurethane layer (see Patent Document 1).
2. A configuration in which a polyurethane-impregnated nonwoven fabric is bonded to a foamed polyurethane layer (see Patent Document 2).
3. A polishing surface is provided and a rigid element of selected thickness and stiffness is provided adjacent to the polishing surface and adjacent to the rigid element to impart a substantially uniform force to the rigid element. And an elastic element is provided, and the rigid element and the elastic element impart an elastic bending force to the polishing surface to induce a controlled bending on the polishing surface, which is the entire surface of the workpiece. A polishing pad characterized by conforming to a specific shape and maintaining controlled rigidity with respect to a local shape of the workpiece surface (see Patent Document 3).

4). A large - surface A of the longitudinal elastic modulus E _A, and a small lower layer B modulus of longitudinal elasticity E _B, both layers A, a large middle layer M of at least longitudinal elastic modulus than the layer B between the B provided A polishing cloth characterized in that (see Patent Document 4).
5). A pad (see Patent Document 5) in which the intermediate layer is divided by a configuration of a polishing layer, an intermediate layer having higher elasticity than the polishing layer, and a soft underlayer is exemplified.
Some have attempted to devise a groove shape on the pad surface in order to improve uniformity. For example,
6). A polishing pad using a pad having a different groove shape between the center portion and the outside of the pad surface (see Patent Document 6).

7). A polishing pad formed by combining a plurality of grooves and holes (see Patent Document 7).
8). A polishing pad in which the groove-shaped center having a geometrical center and the center of the polishing pad are provided eccentrically (see Patent Document 8).
9. A polishing pad having a first region having a plurality of concentric grooves and a second region having a second pitch (see Patent Document 9).
10. A polishing pad having grooves with different densities in adjacent regions (see Patent Document 10).
11. Examples thereof include a polishing pad having an annular groove and a streamline groove (see Patent Document 11).

US Pat. No. 3,504,457 Japanese Patent Laid-Open No. 06-021028 Japanese Patent Application Laid-Open No. 06-077185 Japanese Patent Laid-Open No. 10-156724 JP-A-11-048131 Japanese Patent No. 2647046 Japanese Patent No. 3042593 JP-A-10-249710 Japanese Patent Application Laid-Open No. 11-070463 JP 2000-943039 A JP 2000-198061 A

The above-described polishing pad has the following problems.
In the above system 1, the elastic polyurethane layer plays a role of making the load applied to the semiconductor wafer uniform with respect to the uniformity of the entire surface. However, since the outermost polishing layer uses soft synthetic leather, scratches, etc. However, there is a problem that the flattening characteristics in a minute region are not good.

  Even in the lamination of polyurethane and nonwoven fabric in 2 above, the nonwoven fabric layer plays the same role as the elastic polyurethane layer 1 described above, and the uniformity is obtained. In addition, since the polishing layer also has a hard foamed polyurethane layer, it has superior planarization characteristics compared to synthetic leather. In polishing, the required level has not been reached. Further, the planarization characteristics can be improved by further increasing the hardness of the hard urethane layer, but in this case, the occurrence of scratches is not practical.

  The structure of the polishing layer, the rigid layer, and the elastic layer in 3 above has an appropriate hardness that does not cause scratches in the surface polishing layer, and has a flattening characteristic that deteriorates without increasing the hardness. It is the thing of the structure improved by. This solves the problem of the above-mentioned two methods. In this case, the thickness of the polishing layer is specified to be 0.003 inches or less, and when this thickness is actually used, the polishing layer is used. There is also a drawback that the product life is short.

  In the method 4 described above, the basic idea is the same as that in the method 3 described above, and the range of the elastic modulus of each layer is limited to obtain a more efficient range. There is no means to realize it, and it is difficult to manufacture a polishing pad.

The basic idea of the method 5 is the same as that of the method 3 described above, but the intermediate rigid layer is divided into a predetermined size in order to further improve the uniformity within the wafer surface. However, this dividing step is costly and an inexpensive polishing pad cannot be supplied.
In addition, there are the following problems with respect to the groove shape.

  In the method of 6 above, the central part and the peripheral part are concentric grooves, and the part between them is shaped like a punch hole. In general, punching is performed by punching a wide area at once using punches arranged in one or several rows. However, in this method, a general processing method cannot be used and it is difficult to manufacture.

  In the method of 7 above, in the configuration in which a plurality of holes and grooves are combined, the slurry supply is abundant and the uniformity is improved to some extent, but the slurry actively enters the central portion of the wafer where the slurry tends to be insufficient. Rather, the effect is limited.

  In the above method 8, the center of the polishing pad and the center of the concentric groove are shifted, so that the problem that the groove shape is transferred to the silicon wafer to be processed and the uniformity is deteriorated is solved. It is impossible to prevent a decrease in the polishing rate at the portion.

  In the method 9 described above, there are two regions having different groove pitches, and the uniformity is improved to some extent, but the slurry is not actively taken into the central portion of the wafer, and high uniformity cannot be expected.

  The above ten methods can be said to be improved versions of the above nine methods. However, in this method, as described above, the slurry is not actively taken into the central portion of the wafer, and high uniformity cannot be expected.

  In the method of 11 above, an attempt is made to positively control the flow of the slurry by making the groove shape a streamline groove. However, in this method, necessary slurry flows out along the streamline grooves, and sufficient uniformity cannot be obtained.

  The present invention provides a polishing pad used in a polishing process in which a fine pattern is formed on a semiconductor wafer, which is an object to be polished, and planarizes fine irregularities of the pattern, and has an excellent polishing rate and a semiconductor wafer. It is an object of the present invention to provide a polishing pad that is particularly useful in the manufacture of semiconductor devices, which is excellent in the flatness of the respective microregions and in the uniformity of the polishing amount over the entire surface of the semiconductor wafer.

  That is, according to the present invention, a plurality of concentric grooves are formed on the surface of the polishing region (polishing layer) of the polishing pad, and the groove pitch (p) is an interval between adjacent grooves in the radial direction of the polishing pad. ), And the groove pitch continuously changes in the surface of the polishing pad. In the present invention, a plurality of concentric grooves are formed on the surface of the polishing region (polishing layer) of the polishing pad, and the grooves have different groove widths (w) in the radial direction of the polishing pad. A polishing pad characterized by continuously changing in a plane is provided.

  Further, in the polishing pad, the concentric groove width (w) to be formed is in the range of 0.05 mm to 2.0 mm, and the concentric groove pitch (p) to be formed is 0.1 mm to 20 mm. is there.

Furthermore, the material for forming the polishing region is the above-described polishing pad that is a fine foam, the average foam diameter of the fine foam is 70 μm or less, and the specific gravity of the fine foam is 0. The polishing pad is 0.5 to 1.0 g / cm ³ , the hardness of the fine foam is 45 to 65 degrees in Asker D hardness, and the compression ratio of the fine foam is The above-mentioned polishing pad that is 0.5 to 5.0%, and the compression recovery rate of the fine foam is the above-mentioned polishing pad that is 50 to 100%, and the storage elasticity of the fine foam at 40 ° C. and 1 Hz. The polishing pad has a rate of 200 MPa or more.

  Furthermore, it is a manufacturing method of a semiconductor device including the process of grind | polishing the surface of a semiconductor wafer using the polishing pad in any one of the said.

In the present invention, the pitch of the concentrically formed grooves is continuously changed depending on the location of the circular polishing pad in the radial direction, thereby controlling the polishing rate at each location, resulting in uniform polishing of the wafer to be polished. Increases nature. In the present invention, “groove pitch (p)” means the distance of the shortest portion between adjacent grooves as shown in FIG. 1 and is “continuous” when the groove pitch (P) changes. the amount of change in groove pitch (absolute value of the difference between FIG. 1, p ₁ and p) is at 5mm or less, if the amount of change exceeds 5mm, groove pitch is not a continuous change, stepwise As a result, the uniformity of the polishing amount cannot be improved.

Further, in the present invention, in order to improve the uniformity, in addition to the groove pitch, concentric grooves formed on the surface of the polishing pad have different groove widths in the radial direction of the polishing pad, and the groove width is within the surface of the polishing pad. In the polishing pad, the polishing pad is continuously changed. In the present invention, the groove width (w) is the width of the groove itself, as shown in FIG. 1, and the “continuous change” of the groove width is the amount of change when the groove width changes. 1.95 mm or less (in FIG. 1, the absolute value of the difference between w ₁ and w). When this amount of change exceeds 1.95 mm, the groove width is not a continuous change but a stepwise change, and improvement in the uniformity of the polishing amount cannot be expected.

  In the present invention, the pitch and width of the concentric grooves described above may be changed continuously at the same time.

  When the concentric grooves are specifically illustrated as a preferable form in which the pitch and the groove width are continuously changed in the radial direction of the polishing pad, the pitch of the concentric grooves is the radial direction of the circular polishing pad. In the center and the outer periphery, respectively, and formed so as to increase asymptotically toward the center (approximately half the radius), and The width of the concentric grooves has first and second maximum values at the center and the outer periphery in the radial direction of the circular polishing pad, and is asymptotic toward the center (approximately half the radius). Are formed so as to decrease.

  For example, as shown in FIG. 2, the central portion, the outer peripheral portion, and the central portion correspond to the central portion where 0 position in the “partial pad position in contact in the (semiconductor) wafer radial direction” on the horizontal axis corresponds to the central portion. Corresponds to the central portion, and the 100 position corresponds to the outer peripheral portion.

  The concentric groove width formed in the present invention is preferably in the range of 0.05 mm to 2.0 mm. When the groove width is less than 0.05 mm, the slurry is difficult to enter the groove, the effect as a slurry flow path is reduced, and the polishing rate is also reduced. Also, a groove width of less than 0.05 mm is very difficult to process and lacks productivity.

  When the groove width exceeds 2.0 mm, the effective area where the polishing pad contacts the semiconductor wafer to be polished is reduced, and the polishing rate is reduced.

  In the present invention, the concentric groove pitch formed is preferably in the range of 0.1 mm to 20 mm. When the groove pitch is less than 0.1 mm, an extremely large number of grooves are formed on the pad, the effective area where the polishing pad comes into contact with the wafer to be polished is reduced, and the polishing rate is lowered. In addition, when the groove pitch exceeds 20 mm, the area of the polishing pad that contacts the semiconductor wafer increases, the frictional resistance between the semiconductor wafer and the pad increases, and the semiconductor wafer comes off the wafer holder (polishing head). Dechuck occurs.

  When the groove pitch and groove width are continuously changed, the groove width and groove pitch at the pad location are preferably determined by the following method.

  First, a reference polishing pad having a fixed groove width and groove pitch is prepared, polishing is performed with the pad, and the polishing rate profile of the polished wafer is examined. Next, when the groove pitch is changed from the obtained polishing profile, for example, the groove pitch at each point of the polishing pad is changed based on the following formula 1.

[Where Px is the groove pitch in the radial direction, RR is the desired polishing rate, RRh is the point in a certain radial direction when polishing with a reference pad with a fixed groove pitch and width. RRa is: polishing rate constant (1500-2500 Å / min arbitrary), and Ap is a groove pitch constant (50-100 arbitrary). ]

  When the groove width is changed, the groove width at each point of the polishing pad is changed based on Equation 2.

[Wx is the groove width in the radial direction, RR is the desired polishing rate, and RRh is a point in a certain radial direction when polishing with a reference pad with a fixed groove pitch and width. RRb is a polishing rate constant (2500-3500 Å / min arbitrary), and Aw is a groove width constant (1500-2500 arbitrary). ]

  Moreover, it is preferable that the forming material of the polishing region constituting the polishing surface of the polishing pad is a fine foam.

  The average cell diameter of the fine foam is preferably 70 μm or less, more preferably 50 μm or less. If the average bubble diameter is 70 μm or less, planarity (flatness; small number of irregularities in each minute region of the semiconductor wafer) is good.

The specific gravity of the fine foam is preferably 0.5 to 1.0 g / cm ³ , more preferably 0.7 to 0.9 g / cm ³ . When the specific gravity is less than 0.5 g / cm ^3, the strength of the surface of the polishing region decreases, the planarity of the object to be polished decreases, and when the specific gravity is greater than 1.0 g / cm ³ , The number of fine bubbles is reduced and the planarity is good, but the polishing rate tends to be low.

  The fine foam preferably has an Asker D hardness of 45 to 65 degrees, more preferably 45 to 60 degrees. When the Asker D hardness is less than 45 degrees, the planarity of the object to be polished decreases. When the Asker D hardness is greater than 65 degrees, the planarity is good, but the uniformity of the object to be polished (uniformity; semiconductor wafer) There is a tendency that the amount of polishing amount on the entire surface is small).

  The compression ratio of the fine foam is preferably 0.5 to 5.0%, more preferably 0.5 to 3.0%. If the compression ratio is within the above range, both planarity and uniformity can be sufficiently achieved. The compression rate is a value calculated by the following formula.

[In the formula, T1 is the thickness of the fine foam when a stress load of 30 KPa (300 g / cm ² ) is maintained for 60 seconds from the unloaded state to the fine foam, and T2 is 180 KPa (1800 g / This is the thickness of the fine foam when a stress load of cm ² ) is held for 60 seconds. ]

  The compression recovery rate of the fine foam is preferably 50 to 100%, more preferably 60 to 100%. When it is less than 50%, as the repeated load is applied to the polishing region during polishing, a large change appears in the thickness of the polishing region, and the stability of the polishing characteristics tends to decrease. The compression recovery rate is a value calculated by the following formula.

［式中、Ｔ１は微細発泡体に無負荷状態から３０ＫＰa （３００ｇ／ｃｍ^２）の応力の負荷を６０秒間保持した時の微細発泡体の厚みであり、Ｔ２はＴ１の状態から１８０ＫＰa （１８００ｇ／ｃｍ^２）の応力の負荷を６０秒間保持した時の微細発泡体の厚みであり、Ｔ３はＴ２の状態から無負荷状態で６０秒間保持し、その後、３０ＫＰa（３００ｇ／ｃｍ^２）の応力の負荷を６０秒間保持した時の微細発泡体の厚みである。］

[In the formula, T1 is the thickness of the fine foam when a stress load of 30 KPa (300 g / cm ² ) is maintained for 60 seconds from the unloaded state to the fine foam, and T2 is 180 KPa (1800 g / The thickness of the fine foam when a stress load of cm ² ) is held for 60 seconds, T3 is held for 60 seconds from the T2 state in an unloaded state, and then a stress load of 30 KPa (300 g / cm ² ) Is the thickness of the fine foam when held for 60 seconds. ]

  It is preferable that the storage elastic modulus at 40 ° C. and 1 Hz of the fine foam is 200 MPa or more, and more preferably 250 MPa or more. When the storage elastic modulus is less than 200 MPa, the strength of the surface of the polishing region decreases, and the planarity of the object to be polished tends to decrease. The storage elastic modulus is an elastic modulus measured by applying a sinusoidal vibration to a fine foam using a dynamic viscoelasticity measuring device and using a tensile test jig.

  The polishing pad used in the CMP of the present invention has concentric grooves formed on the surface of the polishing pad, and the grooves have different groove pitches in the radial direction of the polishing pad, and the groove pitch is within the polishing pad surface. The polishing pad is characterized by being continuously changed, and concentric grooves are formed on the surface of the polishing pad. The grooves have different groove widths in the radial direction of the polishing pad. Is a polishing pad characterized by continuously changing in the surface of the polishing pad, and in polishing a wafer or the like to be polished by making such a polishing pad formed with a groove. It is understood that the in-plane polishing uniformity after polishing of the object to be polished while maintaining the polishing rate, that is, polishing uniformity where the flatness in the surface after polishing of the object to be polished is uniform can be achieved, Semiconductor device Chair is very effective in the production of.

It is a figure explaining groove pitch (p) and groove width (w) of the present invention. The outline of the width (w) and pitch (p) of the concentric groove | channel which can be set in Example 1 is shown. The outline of the width (w) and pitch (p) of the concentric groove | channel which can be set in Example 2 is shown. The outline of the width (w) and pitch (p) of the concentric groove | channel which can be set in the comparative example 1 is shown.

  Examples of the material for forming the polishing region include polyurethane resin, polyester resin, polyamide resin, acrylic resin, polycarbonate resin, halogen resin (polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, etc.), polystyrene, olefin resin ( Polyethylene, polypropylene, etc.), epoxy resins, and photosensitive resins. These may be used alone or in combination of two or more.

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

  The polyurethane resin contains an organic isocyanate, a polyol, and a chain extender.

  The organic isocyanate to be used is not particularly limited, and examples thereof include the organic isocyanate.

  The polyol to be used is not particularly limited, and examples thereof include the polyol. In addition, although the number average molecular weight of these polyols is not specifically limited, It is preferable that it is 500-2000 from viewpoints, such as the elastic characteristic of the polyurethane obtained. 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. Therefore, the polishing pad manufactured from this polyurethane becomes too hard and causes scratches on the polishing surface of the object to be polished. Moreover, since it becomes easy to wear, it is not preferable from the viewpoint of the life of the polishing pad. On the other hand, when the number average molecular weight exceeds 2000, polyurethane using the same becomes soft, so that a polishing pad produced from this polyurethane tends to have poor planarization characteristics.

  In addition to the high molecular weight polyols described above, the polyols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol. 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-beads (2-hydroxyethoxy) benzene and other low molecular weight polyols can be used in combination.

  Further, the ratio of the high molecular weight component to the low molecular weight component in the polyol is determined by the characteristics required for the polishing region produced therefrom.

  Examples of chain extenders include polyamines exemplified by 4,4′-methylenebis (o-chloroaniline), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline) and the like. Or the low molecular weight polyols mentioned above. These may be used alone or in combination of two or more.

  The ratio of the organic isocyanate, polyol, and 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 produced therefrom. In order to obtain a polishing region having excellent polishing characteristics, 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, and more preferably Is 0.99 to 1.10.

  The polyurethane resin can be produced by a method similar to the above method. If necessary, stabilizers such as antioxidants, surfactants, lubricants, pigments, fillers, antistatic agents, and other additives may be added to the polyurethane resin.

  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 and does not have an active hydrogen group is preferable. Examples of the silicone surfactant include SH-192 (manufactured by Toray Dow Corning Silicon) and the like as a suitable compound.

  An example of a method for producing a closed cell type polyurethane foam used in the polishing region will be described below. The manufacturing method of this polyurethane foam has the following processes.

Stirring step for preparing a cell dispersion of isocyanate-terminated prepolymer A silicone-based surfactant is added to the isocyanate-terminated prepolymer and stirred with a non-reactive gas to disperse the non-reactive gas as fine bubbles, To do. When the isocyanate-terminated prepolymer is solid at room temperature, it is preheated to an appropriate temperature and melted before use.
Curing Agent (Chain Extender) Mixing Step A chain extender is added to the above cell dispersion and mixed and stirred.
Curing Step An isocyanate-terminated prepolymer mixed with a chain extender is cast and cured by heating.

  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 method for producing the polyurethane fine foam, it is extremely preferable to heat and post-cure the reacted foam until the foam dispersion does not flow by pouring the cell dispersion into the mold, which has the effect of improving the physical properties of the foam. It is. The bubble dispersion may be poured into the mold and immediately placed in a heating oven for post-cure. Under such conditions, heat is not immediately transferred to the reaction components, and the bubble diameter 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 tertiary amine or organotin 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 can be produced in a batch system in which each component is weighed into a container and stirred. Alternatively, each component and a non-reactive gas are continuously supplied to a stirrer 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 polishing area to be the polishing layer is manufactured by cutting the polyurethane foam prepared as described above into a predetermined size.

  In the polishing region made of the fine foam of the present invention, it is preferable that a groove for holding and renewing the slurry is provided on the polishing side surface in contact with the object to be polished. Since the polishing region is formed of a fine foam, it has a large number of openings on the polishing surface and has a function of holding the slurry. However, in order to efficiently further maintain the slurry and renew the slurry. Also, in order to prevent destruction of the object to be polished due to adsorption with the object to be polished, it is preferable to have concentric grooves on the surface on the polishing side.

  The method of forming the groove is not particularly limited. For example, a method of machine cutting using a jig such as a tool of a predetermined size, a method of pouring and curing a resin in a mold having a predetermined surface shape , A method of pressing a resin with a press plate having a predetermined surface shape, a method of forming using photolithography, a method of forming using a printing technique, and a laser beam using a carbon dioxide gas laser, etc. The method of doing is mentioned.

  Although the thickness of a grinding | polishing area | region is not specifically limited, Preferably it is 0.6-3.5 mm. As a method of producing the polishing region of the thickness, a method of making the block of the fine foam a predetermined thickness using a band saw type or a canna type slicer, pouring resin into a mold having a cavity of a predetermined thickness, and curing And a method using a coating technique or a sheet forming technique.

  Further, the variation in the thickness of the polishing region is preferably 100 μm or less, and particularly preferably 50 μm or less. When the thickness variation exceeds 100 μm, the polishing region has a large undulation, and there are portions where the contact state with the object to be polished is different, which tends to adversely affect the polishing characteristics. In order to eliminate the variation in the thickness of the polishing region, the surface of the polishing region is generally dressed with a dresser in which diamond abrasive grains are electrodeposited or fused in the initial stage of polishing, but the above range is exceeded. Things will increase dressing time and reduce production efficiency. Further, as a method of suppressing the thickness variation, there is a method of buffing the surface of the polishing region having a predetermined thickness. When buffing, it is preferable to carry out stepwise with abrasive sheets having different particle sizes.

As the polishing pad in the present invention, at least two of a single layer type pad generally used conventionally or a polishing layer which is a polishing region in contact with an object to be polished such as a wafer, and a cushion layer positioned between the polishing layer and the platen. It may be a laminated pad having layers, or may be a laminated polishing pad such as a multilayer polishing pad in which other layers are stacked. From the viewpoint of production and performance, those having at least two cushion layers located between the polishing layer and the platen (surface plate) are preferable.
Thus, the present invention is not limited to a single-layer or multi-layer polishing pad.

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

  A material for forming the cushion layer 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 a polyurethane foam and a polyethylene foam Examples thereof include rubber resins such as foam, butadiene rubber and isoprene rubber, and photosensitive resins.

  Examples of means for bonding the polishing layer and the cushion layer used in the polishing region include a method of sandwiching the polishing region and the cushion layer with a double-sided tape and pressing.

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

  Examples of means for attaching the cushion layer and the double-sided tape include a method of pressing and bonding the double-sided tape to the cushion layer.

  The double-sided tape has a general configuration in which an adhesive layer is provided on both surfaces of a base material such as a nonwoven fabric or a film as described above. In consideration of peeling from the platen after using the polishing pad, it is preferable to use a film as the base material because the tape residue and the like can be eliminated. The composition of the adhesive layer is the same as described above.

  The semiconductor device is manufactured through a step of polishing the surface of the semiconductor wafer using the polishing pad. A semiconductor wafer is generally a laminate of a wiring metal and an oxide film on a silicon wafer. The method and apparatus for polishing a semiconductor wafer are not particularly limited. For example, a polishing surface plate for supporting a polishing pad, a support table (polishing head) for supporting an object to be polished such as a semiconductor wafer, and uniform pressure on the wafer. This is performed using a backing material to be performed and a polishing apparatus equipped with an abrasive supply mechanism. For example, the polishing pad is attached to the polishing surface plate by pasting with a double-sided tape. The polishing surface plate and the support base are disposed so that the polishing pad and the semiconductor wafer supported by each surface face each other, and each has a rotation shaft. Further, a pressure mechanism for pressing the semiconductor wafer against the polishing pad is provided on the support base side. In polishing, the semiconductor wafer is pressed against the polishing pad while rotating the polishing surface plate and the support base, 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 object to be polished such as a semiconductor wafer 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.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. The evaluation items in Examples and the like were measured as follows.

(Average bubble diameter measurement)
A polishing region cut in parallel with a microtome cutter as thin as possible to a thickness of about 1 mm was used as a sample for measuring average bubble diameter. The sample was fixed on a slide glass, and the total bubble diameter in an arbitrary 0.2 mm × 0.2 mm range was measured using an image processing apparatus (Image Analyzer V10, manufactured by Toyobo Co., Ltd.), and the average bubble diameter was calculated.

(Specific gravity measurement)
This was performed according to JIS Z8807-1976. A polished area cut into a 4 cm × 8.5 cm strip (thickness: arbitrary) was used as a sample for measuring specific gravity, and the sample was allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

(Asker D hardness measurement)
This was performed in accordance with JIS K6253-1997. A polished region cut out to 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 a temperature of 23 ° C. ± 2 ° C. and a humidity of 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).

(Measurement of compression rate and compression recovery rate)
A polishing area (polishing layer) cut into a 7 mm diameter circle (thickness: arbitrary) is used as a sample for measuring the compression rate and compression recovery rate, and left for 40 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. did. For the measurement, a thermal analysis measuring instrument TMA (manufactured by SEIKO INSTRUMENTS, SS6000) was used to measure the compression rate and the compression recovery rate. Moreover, the calculation formula of a compression rate and a compression recovery rate is shown below.

[T1 is the thickness of the polishing layer when a stress load of 30 KPa (300 g / cm ² ) is maintained for 60 seconds from the unloaded state to the polishing layer, and T2 is the stress of 180 KPa (1800 g / cm ² ) from the state of T1. This is the thickness of the polishing layer when the load is held for 60 seconds. ]

(Storage elastic modulus measurement)
This was performed in accordance with JIS K7198-1991. A polishing region cut into a 3 mm × 40 mm strip (thickness; arbitrary) was used as a sample for dynamic viscoelasticity measurement, and the sample was allowed to stand for 4 days in a container containing silica gel under an environmental condition of 23 ° C. The accurate width and thickness of each sheet after cutting was measured with a micrometer. For measurement, a storage elastic modulus E ′ was measured using a dynamic viscoelastic spectrometer (manufactured by Iwamoto Seisakusho, present IS Engineering Co., Ltd.). The measurement conditions at that time are shown below.

<Measurement conditions>
Measurement temperature: 40 ° C
Applied strain: 0.03%
Initial load: 20g
Frequency: 1Hz

(Evaluation of polishing characteristics)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, polishing characteristics were evaluated using the prepared polishing pad.

The evaluation of the polishing rate was carried out by polishing about 0.5 μm of an 8 inch silicon wafer formed with a thermal oxide film of 1 μm and calculating from the time at this time. An interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the thickness of the oxide film. As polishing conditions, silica slurry (SS12, manufactured by 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 number was 35 rpm, and the wafer rotation number was 30 rpm.

  The evaluation of uniformity was calculated by the following formula from film thickness measurement values at arbitrary 25 points of the wafer after polishing. Note that the smaller the uniformity value, the higher the uniformity of the wafer surface.

  The planarization characteristics are evaluated by depositing a thermal oxide film of 0.5 μm on an 8-inch silicon wafer, performing predetermined patterning, depositing an oxide film of 1 μm by p-TEOS, and providing a pattern with an initial step of 0.5 μm. A wafer was produced. This wafer was polished under the above conditions, and after polishing, each step was measured to evaluate the planarization characteristics. Two steps were measured as the flattening characteristics. One is a local step, which is a step in a pattern in which lines having a width of 270 μm are arranged in a space of 30 μm, and the step after one minute was measured. The other is the amount of scraping. In the pattern in which lines with a width of 270 μm are arranged in a space of 30 μm and the pattern in which lines with a width of 30 μm are arranged in a space of 270 μm, the level difference between the above two patterns is 2000 mm or less. The amount of scraping of the 270 μm space was measured. If the numerical value of the local step is low, it indicates that the unevenness of the oxide film caused by the pattern dependency on the wafer is flattened at a certain time. Further, when the amount of scraping of the space is small, the amount of shaving of the portion that is not desired to be shaved is small and the flatness is high.

Preparation of polishing region In a fluorine-coated reaction vessel, 100 parts by weight of a filtered polyether-based prepolymer (Uniroy, Adiprene L-325, NCO concentration: 2.22 meq / g), and a filtered silicone-based nonionic interface 3 parts by weight of an activator (manufactured by Toray Dow Silicone, SH192) was mixed, and the temperature was adjusted to 80 ° C. Using a fluorine-coated stirring blade, the mixture was vigorously stirred for about 4 minutes so that air bubbles were taken into the reaction system at a rotation speed of 900 rpm. Thereto, 26 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical amine, manufactured by Ihara Chemical Co., Ltd.) previously melted and filtered at 120 ° C. was added. Thereafter, stirring was continued for about 1 minute, and the reaction solution was poured into a pan-type open mold coated with fluorine. When the reaction solution lost its fluidity, it was placed in an oven and post-cured at 110 ° C. for 6 hours to obtain a polyurethane resin foam block. This polyurethane resin foam block was sliced using a band saw type slicer (manufactured by Fecken) to obtain a polyurethane resin foam sheet.

Next, this sheet was subjected to surface buffing to a predetermined thickness using a buffing machine (Amitech Co., Ltd.) to obtain a sheet with adjusted thickness accuracy (sheet thickness: 1.27 mm). This buffed sheet is punched into a predetermined diameter (61 cm), and a groove processing machine (manufactured by Toho Koki Co., Ltd.) is used to make a groove width of 0.25 mm, groove pitch of 1.50 mm, and groove depth of 0.40 mm. Concentric grooves were processed. Using a laminator on the surface opposite to the grooved surface of this sheet, a double-sided tape (Sekisui Chemical Co., Ltd., double tack tape) is applied, and then a light transmission area is formed at a predetermined position of the grooved sheet. A hole for fitting (thickness 1.27 mm, 57.5 mm × 19.5 mm) was punched out to prepare a polishing region with a double-sided tape. The physical properties of the produced polishing region were an average bubble diameter of 45 μm, a specific gravity of 0.86 g / cm ³ , an Asker D hardness of 53 degrees, a compression rate of 1.0%, a compression recovery rate of 65.0%, and a storage elastic modulus of 275 MPa. .

Polishing pad preparation
Example 1
In the production of the polishing region, the condition of the groove machining portion was changed, and a pad was produced in which the groove pitch was continuously changed as shown in FIG . Table 1 shows the polishing characteristics when polishing is performed using this pad. It was confirmed that the uniformity of the polishing pad thus produced was extremely high.

Example 2
In the production of the polishing region, the condition of the groove processing portion was changed, and a pad was produced in which the groove width was continuously changed as shown in FIG . Table 1 shows the polishing characteristics when polishing is performed using this pad. It was confirmed that the uniformity of the polishing pad thus produced was extremely high.

Comparative Example 1
A polishing pad was produced in the same groove shape produced in the production of the polishing region. FIG. 4 shows the groove pitch and groove width at each location in the polishing pad warp direction, and is constant at any location. Table 1 shows the polishing characteristics when polishing is performed using this pad. The uniformity of the polishing pad produced in this way was not high.
Further, the flattening characteristics of Examples 1 and 2 and Comparative Example 1 were both excellent.

Claims (8)

A plurality of concentric grooves are formed on the surface of the polishing area of the polishing pad, and the groove pitch (p), which is the distance between adjacent grooves in the radial direction of the polishing pad, is different. and at 1mm or more, der variation of the adjacent groove pitch is 5mm or less in the radial direction of the polishing pad is, the pitch of the concentric circular grooves, in the radial direction of the circular polishing pad, the respective central portion and the peripheral portion 1 the polishing pad second has a minimum value, and is formed so as to asymptotically increases towards the central portion is 1/2 sites radius and said Rukoto.   The polishing pad according to claim 1, wherein the groove pitch of the plurality of concentric grooves is 0.1 mm to 20 mm. A plurality of concentric grooves are formed on the surface of the polishing region of the polishing pad, the groove width (w) is different, the groove width is 0.05 mm or more, and grooves adjacent in the radial direction of the polishing pad change amount der less 1.95mm groove width is, a width of the concentric circular grooves, in the radial direction of the circular polishing pad, the first respectively the central portion and the peripheral portion and the second maximum value, and polishing pad, wherein Rukoto formed to asymptotically decrease toward the center is 1/2 portion of the radius.   The polishing pad according to claim 3, wherein the groove width of the plurality of concentric grooves is in the range of 0.05 mm to 2 mm. A plurality of concentric grooves are formed on the surface of the polishing area of the polishing pad, and the groove pitch (p), which is the distance between adjacent grooves in the radial direction of the polishing pad, is different. 1 mm or more, the change amount of the groove pitch adjacent in the radial direction of the polishing pad is 5 mm or less, the groove width (w) of the groove is different, the groove width is 0.05 mm or more, and the diameter of the polishing pad Ri change amount der less 1.95mm groove width of the adjacent grooves in the direction,
The pitch of the concentric grooves has first and second minimum values in the central portion and the outer peripheral portion in the radial direction of the circular polishing pad, respectively, and asymptotically toward the central portion that is a ½ portion of the radius. Formed to increase,
The width of the concentric grooves has first and second maximum values in the central portion and the outer peripheral portion in the radial direction of the circular polishing pad, respectively, and asymptotically toward the central portion that is a half portion of the radius. polishing pad, wherein Rukoto formed to decrease manner.   The polishing pad according to any one of claims 1 to 5, wherein the forming material of the polishing region is a fine foam.   The polishing pad according to claim 6, wherein the fine foam has an average cell diameter of 70 μm or less.   The manufacturing method of a semiconductor device including the process of grind | polishing the surface of a semiconductor wafer using the polishing pad of any one of Claims 1-7.

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