Polishing pad and method for making the same

The present invention relates to a polishing pad and a method for making the same. The polishing pad has a grinding layer. The grinding layer includes a plurality of fibers and a main body. The fineness of the fibers is 0.001 den to 6 den. The main body is a foam and encloses the fibers. The main body has a plurality of first pores and a plurality of second pores, wherein the first pores are communicated with each other, and the second pores are independent from each other. The size of the first pores is at least 5 times greater than the size of the second pores. The hardness of the grinding layer is 30 to 90 shore D, and the compression ratio thereof is 1% to 10%.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing pad and a method for making the same, and in particular, to a polishing pad having a fiber substrate and a method for making the same.

2. Description of the Related Art

The conventional polishing pad substantially can be divided into two types: a non-woven polishing pad and a separate foam polishing pad. The conventional non-woven polishing pad includes a plurality of fibers and a resin, and the polishing pad is manufactured by using a composite material of the fibers (such as velvet or suede) and the resin, or impregnating a non-woven fabric formed by the fibers in a thermoplastic polyurethane resin for wet coagulation to form a flexible sheet having high deformability formed. A disadvantage of the polishing pad is that the flexibility thereof may easily lead to poor planarization performance of its grinding surface, and the resin cannot uniformly enclose the fibers, that is, a portion of the fibers are not enclosed by the resin, resulting in that the overall strength is insufficient and the service life is shorter.

The conventional separate foam polishing pad includes a plurality of pores and a resin, and the polishing pad is manufactured by pouring the resin (generally a polymer foam of thermoplastic polyurethane) into a cylindrical mold, cooling the resin for coagulation, and then slicing the resin. The polishing pad has higher rigidity than the first conventional non-woven polishing pad, has separate pore structures, and is usually used for high planarization polishing. However, the major problem of the polishing pad is that since it is difficult to achieve uniform distribution of the concentration of the resin in the cylindrical mold, non-uniform temperature distribution at positions in the cylindrical mold during the molding process may lead to different sizes and non-uniform distribution of the pores, which are not easy to be controlled, and as a result, after the slicing process, the difference between the sizes of the pores on the sliced surface of the polishing pad becomes more significant. Moreover, the pores are not in communication with each other, and polishing slurry may not easily flow therebetween in use, and is apt to scratch a workpiece.

Therefore, it is necessary to provide an innovative and progressive polishing pad and a method for making the same, so as to solve the above problems.

SUMMARY OF THE INVENTION

The present invention provides a polishing pad having a grinding layer, the grinding layer including a plurality of fibers and a main body. The fibers cross each other to form a fiber substrate, and the fineness of the fibers is 0.001 den to 6 den. The main body is a foam and encloses the fibers, the main body has a plurality of first pores and a plurality of second pores, the first pores are communicated with each other, the second pores are independent from each other, and the size of the first pores is at least 5 times greater than the size of the second pores, wherein the hardness of the grinding layer is 30 to 90 shore D, and the compression ratio thereof is 1% to 10%.

The present invention further provides a method for making a polishing pad, including the following steps: (a) placing a fiber substrate in a mold, wherein the fiber substrate includes a plurality of fibers, and the fineness of the fibers is 0.001 den to 6 den; (b) injecting a foaming resin in the mold to permeate the fiber substrate and enclose the fibers, wherein the viscosity of the foaming resin is 2000 cps to 5000 cps; and (c) heating to cure the foaming resin, so as to form a grinding layer, the grinding layer including the fiber substrate and a main body, wherein the main body is a foam formed by curing the foaming resin and encloses the fibers, the main body has a plurality of first pores and a plurality of second pores, the first pores are communicated with each other, the second pores are independent from each other, and the size of the first pores is at least 5 times greater than the size of the second pores, wherein the hardness of the grinding layer is 30 to 90 shore D, and the compression ratio thereof is 1% to 10%.

In the present invention, the polishing pad has preferable rigidity and provides high planarization efficiency, which makes it difficult to scratch a polished workpiece, so that the polished workpiece has preferable surface quality, and has a longer service life. Besides, the polishing pad also has preferable stability and reproducibility in the manufacturing process.

PREFERRED EMBODIMENT OF THE PRESENT INVENTION

FIG. 1is a schematic view of a grinding device according to the present invention. The grinding device1includes a lower base plate11, an adsorption sheet12, a polishing workpiece13, an upper base plate14, a polishing pad15and grinding slurry16. The lower base plate11is opposite to the upper base plate14. The adsorption sheet12adheres onto the lower base plate11by use of an adhesive layer17, and the adsorption sheet12is used for carrying and fixing the polishing workpiece13. The polishing workpiece13is selected from a group consisting of a semiconductor, a storage medium substrate, an integrated circuit, LCD flat panel glass, optical glass and a photoelectric panel. The polishing pad15is fixed to the upper base plate14. For example, the polishing pad15adheres onto the upper base plate14by use of an adhesive layer18. The polishing pad15faces the lower base plate11, for polishing the polishing workpiece13.

The operation mode of the grinding device1is as follows. At first, the polishing workpiece13is placed on the adsorption sheet12, and the polishing workpiece13is adsorbed by the adsorption sheet12. Next, the upper base plate14and the lower base plate11rotate in opposite directions, and the upper base plate14is moved downward, so that a grinding surface223of the polishing pad15contacts a surface of the polishing workpiece13, and the polishing workpiece13can be polished by means of continuous supplement of the grinding slurry16and the action of the polishing pad15.

FIG. 2is a schematic partially enlarged cross-sectional view of an embodiment of a polishing pad according to the present invention. The polishing pad15may be a single-layer structure or a multi-layer structure. In this embodiment, the polishing pad15is a single-layer structure, and has a grinding layer2. The grinding layer2includes a plurality of fibers21and a main body22. The fibers21cross each other to form a fiber substrate20, and the fineness of the fibers21is 0.001 den to 6 den. The material of the fibers21is selected from a group consisting of Polyamide Resin, Polyethylene Terephthalate (PET), Nylon, Polyproylene (PP), Polyester Resin, Acrylic Resin, Polyacrylonitrile Resin and composites thereof. Preferably, the fibers21are short fibers, the length thereof is 30 to 100 mm, and the fiber substrate20is a non-woven fabric. The density of the fiber substrate20is preferably 0.05 to 0.30 g/cm3.

The main body22is a foam and encloses the fibers21. In this embodiment, the main body22is a separate foam, which is a resin composition or copolymer, and the material thereof includes a first component and a second component. The first component is polyuisocyanate, and preferably, the polyuisocyanate is toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI). The second component is a foaming agent, and preferably, the foaming agent is polyol. Preferably, the material of the main body22further includes a cross-linking hardener, for accelerating hardening of the main body22. The cross-linking hardener may be aliphatic amine, alicyclic amine, amide amine or dicyandiamide. The main body22has a plurality of first pores221and a plurality of second pores222. The first pores221are communicated with each other, the second pores222are independent from each other, and the size of the first pores221is at least 5 times, preferably at least 10 times, greater than the size of the second pores222. In this embodiment, the size of the first pores221is 1 to 3 mm, and the size of the second pores222is 100 to 300 μm. The first pores221are physical pores, which are naturally formed in a space located between the fibers21after the raw material of the main body22encloses the fibers21, and the fibers21are not exposed in the first pores221. That is, the first pores221are not pores formed by foaming or impregnation or other chemical processing means. The second pores222are foaming pores, which are formed through a foaming process of the raw material of the main body22.

The hardness of the grinding layer2is 30 to 90 shore D, and preferably is 40 to 70 shore D. The compression ratio of the grinding layer2is 1% to 10%, and preferably is 2% to 5%. As shown inFIG. 2, the main body22has a grinding surface223, and a portion of the fibers21protrude from the grinding surface223.

FIG. 3is a schematic partially enlarged cross-sectional view of another embodiment of the polishing pad according to the present invention. In this embodiment, the fibers21are completely enclosed by the main body22, that is, two ends of each of the fibers21are completely enclosed by the main body22, so that the fibers21are not exposed in the first pores221.

In the present invention, the hardness and the strength (rigidity) of the grinding layer2are moderate, and thus the grinding surface223has preferable planarization performance, which makes it difficult to scratch the polishing workpiece13, and has a longer service life.

FIG. 4toFIG. 8are schematic views of an embodiment of a method for making a polishing pad according to the present invention. The method for making a polishing pad includes the following steps. First, referring toFIG. 4, a fiber substrate20is provided, which is formed of a plurality of fibers21crossing each other. The fineness of the fibers21is 0.001 den to 6 den. The material of the fibers21is selected from a group consisting of Polyamide Resin, Polyethylene Terephthalate (PET), Nylon, Polyproylene (PP), Polyester Resin, Acrylic Resin, Polyacrylonitrile Resin and composites thereof. Preferably, the fibers21are short fibers, the length thereof is 30 to 100 mm, and the fiber substrate20is a non-woven fabric. The weight of the fiber substrate20is 350 g/m2to 1000 g/m2, and the density thereof is preferably 0.05 to 0.30 g/cm3.

Next, the fiber substrate20is placed in a mold3. In this embodiment, the mold3is box-like, which has a length, a width and a depth.

Then, a foaming resin is provided. In this embodiment, the foaming resin is a resin composition or copolymer, and the material thereof includes a first component and a second component. The first component is polyuisocyanate, and preferably, the polyuisocyanate is toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI). The second component is a foaming agent, and preferably, the foaming agent is polyol. Preferably, the material of the foaming resin further includes a cross-linking hardener, for accelerating hardening of the foaming resin. The cross-linking hardener may be aliphatic amine, alicyclic amine, amide amine or dicyandiamide. In the meantime, raw materials (that is, the first component and the second component) of the foaming resin are mixed and stirred to form the foaming resin with a proper viscosity, and preferably, the viscosity of the foaming resin is 2000 cps to 5000 cps.

Referring toFIG. 5, the foaming resin34is injected into the mold3to permeate the fiber substrate20to enclose the fibers21, until the fiber substrate20has been fully immersed in the foaming resin34. At this time, the foaming resin34, after permeating the fiber substrate20, forms a plurality of first pores221(FIG. 2andFIG. 3). The first pores221are physical pores, which are naturally formed in a space located between the fibers21after the foaming resin encloses the fibers21, and the fibers21are not exposed in the first pores221. That is, the first pores221are not pores formed by foaming or impregnation or other chemical processing means. In this embodiment, the foaming resin34enters the fiber substrate20by means of injection or dripping through an injection head32, that is, the foaming resin34downward permeates the fiber substrate20from a location above the fiber substrate20due to gravity, which is different from the conventional impregnation process. Preferably, the injection head32moves in this process, so that the foaming resin34is more uniformly distributed in the fiber substrate20.

Referring toFIG. 6, the foaming resin is cured through heating, so as to form a grinding layer2, the grinding layer2including the fiber substrate20and a main body22(FIG. 2), wherein the main body20is a foam formed by curing the foaming resin34, and encloses the fibers21. At this time, after the foaming resin34is heated, nitrogen (N2) or carbon dioxide (CO2) therein escapes, and a plurality of second pores222is formed. That is, the second pores are foaming pores, which are formed by the raw material (the foaming resin34) of the main body22through a foaming process. Therefore, the main body22has the first pores221and the second pores222, the first pores221are communicated with each other, the second pores222are independent from each other, and the size of the first pores221is at least 5 times greater than the size of the second pores222, wherein the hardness of the grinding layer2is 30 to 90 shore D, and the compression ratio thereof is 1% to 10%.

In this embodiment, the heating and curing process includes two stages: the first stage is a pre-aging step, and the second stage is a hardening and aging step. The pre-aging step is directly heating the foaming resin34and the fiber substrate20in the mold3to form the grinding layer2. Next, the hardening and aging step is taking the grinding layer2out from the mold3and then placing the grinding layer2in an oven or an aging chamber for a long period of time, so as to make the property of the main body22(the foaming resin34) more stable.

Referring toFIG. 7andFIG. 8, a slicing step is performed, so that a portion of the fibers21protrude from a surface of the main body22, so as to manufacture the polishing pad15shown inFIG. 1toFIG. 3. In this embodiment, the slicing step includes two stages: the first stage is transverse slicing, and the second stage is longitudinal slicing. Referring toFIG. 7, the transverse slicing step is shown, and in this step, a cutting tool (not shown in the drawing) removes an upper portion of the grinding layer2along a horizontal direction (as shown by a cutting line36), so as to reduce the thickness of the grinding layer2to expose a portion of the fibers21and form the grinding surface223(FIG. 2). It can be understood that other trimming apparatuses can also be used to remove the upper portion of the grinding layer2. Referring toFIG. 8, the longitudinal slicing step is shown, and in this step, a cutting tool (not shown in the drawing) cuts the grinding layer2into a plurality of portions of a desired size along a vertical direction.

Preferably, next, an adhesive layer18is pasted on the back surface of the grinding layer2, so as to facilitate adhesion of the grinding layer2onto the upper base plate14(FIG. 1).

Examples are given below to describe the present invention in detail, but it does not mean that the present invention is only limited to content disclosed in the examples.

First, a non-woven fiber substrate having a thickness of 5.0 mm is provided, whose weight is 950 g/m2and density is 0.19 g/cm3. The material of fibers of the non-woven substrate is 100% of PET, and the fineness thereof is 1.50 den.

Next, the fiber substrate is placed in a mold, and in this embodiment, the length, the width and the depth of the mold are respectively 100 cm, 100 cm and 1 cm.

Then, diisocyanate (TDI component) with 78.00 wt % and an equivalent number of 200-450 and polyol with 22.00 wt % and an equivalent number of 50-250 are fully mixed to form a foaming resin. In the meantime, the foaming resin is mixed and stirred to form a polymer solution with viscosity of 2250 cps.

Next, the polymer solution of the foaming resin is injected into the mold to permeate the fiber substrate to enclose the fibers.

Then, a pre-aging step is performed, in which the foaming resin and the fiber substrate in the mold are directly heated to 70□, which is maintained for 60 minutes, so as to form the grinding layer. Next, a hardening and aging step is performed, in which the grinding layer is taken out from the mold and then placed in an aging chamber for 12 hours, wherein the temperature of the aging chamber is 70□. The hardness of the grinding layer in the example is 40 shore D, and the compression ratio thereof is 5.33%.

Next, a slicing step is performed, so as to expose a portion of fibers, and the grinding layer is cut into a plurality of portions of a desired size. Afterwards, an adhesive layer is pasted onto the back surface of the grinding layer.

First, a non-woven fiber substrate having a thickness of 4.5 mm is provided, whose weight is 675 g/m2and density is 0.19 g/cm3. The material of fibers of the non-woven substrate is 60% of PET and 40% of Nylon, and the fineness thereof is 3.0 den.

Next, the fiber substrate is placed in a mold, and in this example, the length, the width and the depth of the mold are respectively 90 cm, 170 cm and 5 cm.

Then, diisocyanate (TDI component) with 74.20 wt % and an equivalent number of 200-450, a cross-linking hardener with 20.81 wt % and an equivalent number of 50-250 and polyol with 4.99 wt % and an equivalent number of 50-150 are fully mixed to form a foaming resin. In the meantime, the foaming resin is mixed and stirred to form a polymer solution with viscosity of 3600 cps.

Next, the polymer solution of the foaming resin is injected into the mold to permeate the fiber substrate to enclose the fibers.

Then, a pre-aging step is performed, in which the foaming resin and the fiber substrate in the mold are directly heated to 80□, which is maintained for 75 minutes, so as to form the grinding layer. Next, a hardening and aging step is performed, in which the grinding layer is taken out from the mold and then placed in an aging chamber for 14 hours, wherein the temperature of the aging chamber is 80□. The hardness of the grinding layer in the example is 45 shore D, and the compression ratio thereof is 2.42%.

Next, a slicing step is performed, so as to expose a portion of fibers, and the grinding layer is cut into a plurality of portions of a desired size. Afterwards, an adhesive layer is pasted onto the back surface of the grinding layer.

First, a non-woven fiber substrate having a thickness of 3.0 mm is provided, whose weight is 390 g/m2and density is 0.13 g/cm3. The material of fibers of the non-woven substrate is 50% of PET and 50% of PP, and the fineness thereof is 2.5 den.

Next, the fiber substrate is placed in a mold, and in this embodiment, the length, the width and the depth of the mold are respectively 110 cm, 110 cm and 5 cm.

Then, diisocyanate (TDI component) with 68.90 wt % and an equivalent number of 200-450, aliphatic amine with 28.57 wt % and an equivalent number of 50-250 and polyol with 2.53 wt % and an equivalent number of 50-150 are fully mixed to form a foaming resin. In the meantime, the foaming resin is mixed and stirred to form a polymer solution with viscosity of 4400 cps.

Next, the polymer solution of the foaming resin is injected into the mold to permeate the fiber substrate to enclose the fibers.

Then, a pre-aging step is performed, in which the foaming resin and the fiber substrate in the mold are directly heated to 70□, which is maintained for 80 minutes, so as to form the grinding layer. Next, a hardening and aging step is performed, in which the grinding layer is taken out from the mold and then placed in an aging chamber for 16 hours, wherein the temperature of the aging chamber is 70□. The hardness of the grinding layer in the example is 50 shore D, and the compression ratio thereof is 1.36%.

Next, a slicing step is performed, so as to expose a portion of fibers, and the grinding layer is cut into a plurality of portions of a desired size. Afterwards, an adhesive layer is pasted onto the back surface of the grinding layer.

The above embodiments only describe the principle and the efficacies of the present invention, and are not used to limit the present invention. Therefore, modifications and variations of the embodiments made by persons skilled in the art do not depart from the spirit of the invention. The scope of the present invention should fall within the scope as defined in the appended claims.