Source: http://www.google.com/patents/US7140088?dq=6,998,619
Timestamp: 2014-07-13 09:12:16
Document Index: 664278924

Matched Legal Cases: ['art 58', 'art 58', 'art 58', 'art 58', 'art 58', 'art 58', 'art 58', 'arts 58', 'arts 58', 'arts 58', 'art 58', 'arts 58', 'arts 58', 'arts 58', 'arts 79', 'art 79', 'art 79', 'arts 79', 'arts 79', 'art 82', 'art 82']

Patent US7140088 - Turning tool for grooving polishing pad, apparatus and method of producing ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsDisclosed is a turning tool for cutting circumferential grooves into a surface of a polishing pad formed of a resin material and utilized for polishing semiconductor devices. The turning tool comprising a cutting part arranged to have a tooth width within a range of 0.005�1.0 mm, a wedge angle within...http://www.google.com/patents/US7140088?utm_source=gb-gplus-sharePatent US7140088 - Turning tool for grooving polishing pad, apparatus and method of producing polishing pad using the tool, and polishing pad produced by using the toolAdvanced Patent SearchPublication numberUS7140088 B2Publication typeGrantApplication numberUS 11/360,441Publication dateNov 28, 2006Filing dateFeb 23, 2006Priority dateJul 8, 1999Fee statusPaidAlso published asUS6869343, US7017246, US7104868, US20030119425, US20040198199, US20040198204, US20040209551, US20060137170Publication number11360441, 360441, US 7140088 B2, US 7140088B2, US-B2-7140088, US7140088 B2, US7140088B2InventorsTatsutoshi SuzukiOriginal AssigneeToho Engineering Kabushiki KaishaExport CitationBiBTeX, EndNote, RefManPatent Citations (54), Non-Patent Citations (1), Referenced by (3), Classifications (35), Legal Events (1) External Links: USPTO, USPTO Assignment, EspacenetTurning tool for grooving polishing pad, apparatus and method of producing polishing pad using the tool, and polishing pad produced by using the toolUS 7140088 B2Abstract Disclosed is a turning tool for cutting circumferential grooves into a surface of a polishing pad formed of a resin material and utilized for polishing semiconductor devices. The turning tool comprising a cutting part arranged to have a tooth width within a range of 0.005�1.0 mm, a wedge angle within a range of 15�35 degrees, and a front clearance angle within a range of 65�45 degrees. A polishing pad effectively formed by using the turning tool, and an apparatus and a method of producing such a polishing pad by utilizing the turning tool are also disclosed.
1. A method of producing a polishing pad formed of a resin material for polishing semiconductor devices, said method comprising a step of:
cutting circumferential grooves into a surface of the resin polishing pad by using a turning tool including at least one plate-like shaped tool tip and at least one cutting part extending from one side of the at least one tool tip,
wherein the at least one cutting part has a width within a range of 0.005�1.0 mm, a wedge angle within a range of 15�35 degrees, and a front clearance angle within a range of 65�45 degrees, for cutting circumferential grooves into the surface of the resin polishing pad.
2. A method of producing a polishing pad according to claim 1, wherein said at least one cutting part has a rake angle within a range of 20�10 degrees.
3. A method of producing a polishing pad according to claim 1, wherein said at least one cutting part has a side clearance angle with respect to a radially outer wall of each of said grooves, which is held within a range of 0�3 degrees.
4. A method of producing a polishing pad according to claim 1, wherein said at least one tool tip includes a multiple number of the cutting parts arranged in a predetermined direction and spaced apart by a pitch within a range of 0.2�2.0mm.
5. A method of producing a polishing pad according to claim 4, wherein the cutting parts are arranged in the predetermined direction with regular pitches.
6. A method of producing a polishing pad according to claim 4, wherein said cutting parts are integrally formed at one edge portion of said at least one tool tip so as to protrude outwardly from said one edge portion.
7. A method of producing a polishing pad according to claim 6, wherein said turning tool further includes a multiple number of said tool tips, said tool tips being fixedly arranged with each other so as to be aligned in a width direction thereof.
8. A method of producing a polishing pad according to claim 7, wherein said turning tool further includes a tool-tip holder detachably holding said tool tips.
9. A method of producing a polishing pad according to claim 1, wherein said turning tool further includes a multiple number of said tool tips, each of the tool tips having said at least one cutting part, said tool tips being detachably fixed to each other.
10. A method of producing a polishing pad according to claim 9, wherein said tool tips are superposed on and integrally fixed to one another with spacers interposed between the tool tips so that the spacers function to keep a pitch of said tool tips.
11. A method of producing a polishing pad according to claim 9, wherein said turning tool further includes a tip holder detachably holding said tool tips.
12. A method of producing a polishing pad according to claim 10, wherein said turning tool further includes a tip holder detachably holding said tool tips.
13. A method of producing a polishing pad according to claim 1, wherein said at least one cutting part has a serrated tip portion.
14. A method of producing a polishing pad according to claim 1. wherein said at least one cutting part has at least one serrated side surface.
15. A method of producing a polishing pad according to claim 1, wherein said at least one tool tip includes a multiple number of the cutting parts arranged in a predetermined direction and the cutting parts are spaced apart by a pitch given by integral multiples of a pitch of concentric grooves to be formed into the surface of the polishing pad.
16. A method of producing a polishing pad according to claim 1, wherein said at least one tool tip includes a multiple number of the cutting parts arranged in a predetermined direction and the cutting parts are spaced apart by double a pitch of concentric grooves to be formed into the surface of the polishing pad.
This application is a Continuation of U.S. patent application Ser. No. 10/828,911 filed Apr. 21, 2004, now U.S. Pat. No. 7,017,246, which itself is a Division of U.S. patent application Ser. No. 10/026,504 filed Dec. 19, 2001, now U.S. Pat. No. 6,869,343.
In the semiconductor fabrication processes, a substrate, e.g., a silicon wafer, may undergo multiple masking, etching, implantation, and dielectric and conductor deposition processes, to thereby form a lamination of various kinds of thin layers such as metallic layers and insulative layers. Between each processing steps, it is usually necessary to polish or planarize an outer or upper most surface of the wafer to obtain a substrate surface having a high degree of planarity. Chemical mechanical polishing (hereinafter referred to as �CMP�) is one of known methods of planarization. CMP typically involves placing the wafer mounted on and rotated about an axis of a carrier against a polishing pad mounted on and rotated about an axis of a platen, and pushing the wafer against the polishing pad while supplying a polishing slurry at an interface between the upper most surface of the wafer and the polishing pad. The polishing slurry consists of fine abrasive particles and suitable kind of liquid in which the abrasive particles are dispersed. Typically, the polishing pad is made of a foamed rigid-resin material, so that a surface of the polishing pad has a cellular structure of independent-cell type in which cells are independent of each other or of open-cell type in which cells are communicated with each other, in order to facilitate conditioning of the slurry distribution between the wafer and the polishing pad.
Another known example of conventionally employed polishing pad for CMP is disclosed in U.S. Patent Publication Nos. U.S. Pat. Nos. 5,921,855 and 5,984,769. The disclosed polishing pad is provided with a plurality of annular grooves open in its polishing surface. The plurality of annular grooves are arranged in a generally concentric or coaxial relationship with each other, and are dimensioned to have a width of not smaller than 0.38 mm and a depth of not smaller than 0.51 mm, and are uniformly spaced with a pitch of 2.29 mm in a radial direction of the polishing pad. However, the disclosed polishing pad suffers from inherent structural problems, namely, difficulty in forming grooves extending in a circumferential direction in the polishing pad and difficulty in ensuring a sufficient dimensional accuracy of the grooves.
More specifically described, the annular grooves may be formed on the polishing surface of the polishing pad by embossing with a die, or alternatively may be formed by milling with a saw blade on a mill. In the former case, each of the formed annular grooves is prone to have a dull shape, especially at its open-end edge portions, so that the width of the groove varies in its depth direction. This causes undesirable variation of the groove width, especially when the polishing surface of the polishing pad is worn or is conditioned by the dressing process, resulting in unstable polishing conditions. In the latter case, since the annular grooves are formed by milling of the saw blade on the mill, the formed annular grooves is likely to extend straightly to some extent, making it difficult to form a groove having a small width and a small radius of curvature. This makes it impossible to form a desired polishing pad in which annular grooves having a relatively small width are formed on a radially inner portion of its polishing surface as well as a radially intermediate and a radially outer portion of its polishing surface. In view of a recent tendency of employing a large-diameter wafer, e.g., a wafer having a diameter within a range of 200 mm�300 mm or more, the presence of useless area in the radially inner portion of the polishing surface of the polishing pad undesirably causes an enlargement in size of the polishing pad. Therefore, the problem of the radially inner useless area of the polishing pad becomes very significant.
Moreover, the conventionally employed polishing pad disclosed in the above-mentioned U.S. Patents has the generally concentric annular grooves that have a relatively large width and are uniformly spaced at the relatively large pitch. Further, the disclosed polishing pad includes a backside pad made of a compressed felt fibers leached with urethane, which has an elasticity larger than that of the polishing pad and which is fixed the backside of the urethane pad. Thus, the disclosed polishing pad is mounted on a platen of an optional CMP system via the backside pad. This type of conventional polishing pad has been developed to be applied to planarization of a substrate having multilevel interconnections in which metallic interconnect has a width of 0.25 μm, that is a most advanced technology at the time when applications for the above-mentioned U.S. Patents were filed (i.e., 1997�1998). Namely, the type of polishing pad has been developed to provide the substrate surface having a planarity at a level of 0.3 μm. In the light of the fact that the substrates having multilevel interconnections whose metallic interconnect has a width approximately of 0.18 μm, 0.15 μm and 0.1 μm dominate the recent market, it is apparent that the CMP is now required very sophisticated techniques, i.e., to provide the substrate surface having a high planarity at a level of 0.25 μm or lower. Thus, the conventional polishing pad disclosed in the above U.S. Patents is insufficient for ensuring currently required polishing accuracy and polishing efficiency, and accordingly is unsuitable to be used for CMP for a planarization of a currently developed substrate of multilevel interconnection, which includes interconnect metal layers made of a soft cupper or gold.
SUMMARY OF THE INVENTION It is therefore a first object of the invention to provide a novel turning tool for cutting circumferential grooves, e.g., a multiplicity of generally concentric annular grooves into a surface of a polishing pad formed of a resin material and utilized for polishing semiconductor devices. The turning tool is capable of forming the fine circumferential grooves with a sufficiently small width and with high dimensional accuracy and high stability. The turning tool enables to form the small-width circumferential grooves in the radially inner portion of the polishing surface of the polishing pad, with ease.
The above-indicated first object of the invention may be achieved according to a first aspect of the invention which provides a turning tool for cutting circumferential grooves into a surface of a polishing pad formed of a resin material and utilized for polishing semiconductor devices, the turning tool comprising: a cutting part arranged to have a tooth width within a range of 0.005�1.0 mm, a wedge angle within a range of 15�35 degrees, and a front clearance angle within a range of 65�45 degrees.
The turning tool constructed according to the present invention is capable of cutting into the polishing pad made of the resin material the circumferential grooves having a width of 1.0 mm or smaller, with high dimensional accuracy and without occurrence of burrs in the walls of the grooves. Namely, the turning tool of the present invention makes it possible to stably cut the circumferential grooves into the surface of the polishing pad with a slight infeed rate, and to accurately form the desired grooves in the very inner circumferential portion of the circular work piece. It should be appreciated that the term �circumferential grooves� should be interpreted to mean grooves extending in a circumferential direction of the polishing pad, e.g., a multiplicity of generally annular generally concentric grooves, and a spiral groove or grooves. Preferably, the tooth width is held within a range of 0.1�1.0 mm.
The turning tool constructed according to the present invention may be made of known materials such as hard metal, high speed steel, carbon steel, ceramics, cermet, and diamonds. In the turning tool of the present invention, actual values of the wedge angle and the front clearance angle may be suitably determined within the above-indicated range, taking into account a hardness or other specific physical properties of the work piece, i.e., the polishing pad made of the resin material. It is noted that, if the wedge angle of the turning tool is set to 15 degrees or smaller, the life of the turning tool is shorten, although the cutting ability of the tool is improved. If the wedge angle of the turning tool is set to 35 degrees or larger, the cutting ability of the tool is deteriorated, resulting in a high possibility of occurrence of defects, such as burrs, in the surface of the grooves. The turning tool of the present invention has the wedged angle arranged within a range of 15�35 degrees, thus making it possible to produce a fine cutting into the polishing pad formed of the solid resin material or the foamed rigid-resin material. Therefore, the turning tool of the present invention is capable of preventing occurrence of burrs on the surface of the grooves, while assuring high processing accuracy. It is also noted that if the front clearance angle of the turning tool is set to 45 degrees or smaller in the case where the cutting grooves have relatively small radius of curvatures, the side surfaces of the cutting part of the turning tool is likely to interface with the radially outer walls of the cutting grooves. This results in deterioration of a dimensional accuracy of the grooves, due to occurrence of burrs, recesses and/or protrusions in the surface of the groove walls, and dulled open-end edges of the grooves. Further, the front clearance angle of 65 degrees or larger may adversely effect on the life of the cutting parts of the turning tool.
According to a first preferred form of the turning tool of the invention, the cutting part of the turning tool has a rake angle within a range of 20�10 degrees. It is noted that if the rake angle is set to 20 degrees or larger, the cutting part of the turning tool is prone to cut undesirably into the inside of the polishing pad. On the other hand, if the rake angle is set to 10 degrees or smaller, the cutting ability of the turning tool is deteriorated.
According to a second preferred form of the turning tool of the invention, the cutting part has a side clearance angle with respect to a radially outer wall of each of said grooves, which is held within a range of 0�3 degrees. This arrangement enables to prevent or avoid interface between the radially outer wall of each groove and the cutting part of the turning tool with high stability, thus making it possible to form the grooves with high dimensional accuracy of its radially outer wall portion, even if a radius of curvature of the groove is relatively small. An actual values of the side clearance angle may be suitably determined within the above-indicated range, taking into account a hardness or other specific physical properties of the work piece, i.e., the polishing pad made of the resin material, and the value of the front clearance angle of the tool, so that the cutting part of the turning tool is less likely to interface or cut into the radially outer wall of the each groove. If the side clearance angle exceeds 3 degrees, durability or processability of the cutting part of the tool may be deteriorated, so that the side clearance is preferably set to 2 degrees or smaller. On the other hand, the side clearance angle of the cutting part with respect to a radially inner wall of each of the grooves can be set at around 0 degrees, since an interfere between the cutting part of the turning tool and the radially inner wall of the each groove is less likely to occur.
According to a third preferred form of the turning tool of the invention, the turning tool includes a plurality of cutting parts which are arranged in a predetermined direction with a pitch within a range of 0.2�2.0 mm. The turning tool according to this preferred form makes it possible to cut a plurality of generally concentric grooves with a width within a range of 0.005�1.0 mm and with a radial pitch of 0.2�2.0 mm with high efficiency. Preferably, the cutting parts are arranged in a predetermined direction with a generally constant pitch. According to the actual experiment conducted by the inventor of the present invention, a tool having a single cutting part according to the present invention needs one hour or more for cutting an optional number of generally concentric annular grooves into an optional base for the polishing pad, while a multi edged tool having a plurality of cutting parts constructed according to this preferred form of the turning tool of the invention can do the same work in minuets. It should be appreciated that such a multi-edged tool may be provided by utilizing a toll tip or a plurality of tool tips each having a plurality of cutting parts integrally formed thereon, or alternatively by utilizing a plurality of cutting-part chips each having a single cutting part, which are fixed together. Specific preferred form of the multi-edged tool will be described hereinafter.
According to a second preferred form of the method of the invention, the turning tool is adapted to cut the circumferential grooves into the surface of the base for the polishing pad at a feed per revolution of 0.005�0.05 mm/rev in a depth direction of the base. This arrangement establish an excellent turning condition for cutting the grooves by the present turning tool into the base for the polishing pad which is made of a resin material in a solid state or a foamed state, e.g., a foamed urethane pad. Since the cutting of the grooves is performed at the above-indicated slight feed per revolution, it is possible to sequentially cut the surface of the base for the polishing pad without pressing the surface of the base for the polishing pad. Further, this method permits a smooth cutting of the fine circumferential grooves into the base for the polishing pad with high stability, without any defects such as undesirable cutting of the turning tool into the base and occurrence of burrs in the surface of the formed grooves. Preferably, the cutting parts and the base are rotated relative to each other at a speed of 50�300 rev/min. It is noted that the speed in the turning or cutting method according to the present invention may be desirably determined, taking into account physical properties of the base, quality of the cutting part and/or radius of curvatures of grooves to be formed.
The above-indicated third object of the invention may be achieved according to a third aspect of the invention, which provides a polishing pad, which is effectively formed by using the turning tool constructed according to a first aspect of the invention, the polishing pad comprising: (a) a base made of a resin material; and (b) circumferential grooves open in a surface of the base, wherein the grooves have a width within a range of 0.005�1.0 mm, a depth of 0.2�2.0 mm, and a pitch of 0.2�2.0 mm, and wherein radially inner most one of the circumferential grooves has a radius of curvature of not larger than 10 mm.
In the polishing pad constructed according to the present invention, the circumferential grooves have a relatively small width and a sufficiently small pitch, in comparison with the known polishing pads as disclosed in the above-indicated U.S. Patent Publication Nos. U.S. Pat. Nos. 5,921,855 and 5,984,769. This specific structure of the polishing pad of the present invention, which is distinguishable from that of the conventional polishing pads, enables that the surface of the polishing pad is deformed along a surface of a semiconductor device, e.g., a wafer with improved accuracy, thus ensuring an excellent surface polishing with high accuracy. Described more specifically, the conventional polishing pad requires an elastic backside pad fixed to the backside of a base for the conventional polishing pad so as to absorb or compensate a relatively large local deformation in the front surface of the base caused by bending of grooved portions of the base. Namely, the wall thickness of the base for the conventional polishing pad is decreased at the grooved portion. Since the grooves have a relatively large width, the grooved portion is likely to bent, resulting in the large local deformation of the front surface of the base. Therefore, the conventional polishing pad needs the elastic backside pad to be deformed along the surface of the wafer with desired accuracy. On the other hand, the polishing pad according to the present invention is effectively arranged to sufficiently decrease a width of partitions interposed between adjacent ones of the grooves and a width of each groove, thereby minimizing an amount of local deformation in the surface of the polishing pad due to bending of the grooved portions, while allowing elastic deformation of the partitions so as to expand toward the respective grooves disposed opposite sides of the partitions (i.e., expand in its radially opposite directions). This makes it possible that the surface of the polishing pad is deformed along the surface of the wafer with high accuracy, owing to the elastic deformations of the partitions, thus ensuring a significantly high accurate polishing of the semiconductor devices, that is never achieved by the conventional polishing pad. The polishing pad of the present invention is capable of suitably polishing semiconductor devices having interconnects made of soft metallic materials and arranged with a slight spacing therebetween. For instance, the polishing pad of the present invention enables for the first time to polish and planarize a substrate having multilevel interconnections whose interconnect line has a width of 0.18 μm, 0.15 μm and/or 0.1 μm, with a high planarity level of 0.25 μm or lower.
Preferably, the width of the each groove is arranged within a range of 0.1�0.3 μm so that the polishing pad can be deformed along the surface of the wafer with further improved accuracy, owing to the elastic deformation of the partitions interposed between adjacent ones of the grooves. More preferably, the depth of the each grooves is arranged within a range of 0.1�0.4 μm, thereby improving durability of the polishing pad and minimizing an amount of change of properties of the polishing pad due to a dressing process or the like.
It is noted that if the groove width is smaller than 0.005 mm, it becomes difficult to form such a fine groove by turning and to control the distribution of the slurry desirably. If the groove width is larger than 1 mm, the polishing pad is likely to be excessively bent at its grooved portions, resulting in deterioration of polishing accuracy. Preferably, the groove width is set within a range of 0.1�1.0 mm. Further, if the generally concentric grooves are formed with a pitch of smaller than 0.2 mm, the polishing pad is likely to suffer from a hydroplane phenomenon depending upon a viscosity of the slurry. If the generally concentric grooves are formed with a pitch of larger than 2.0 mm, the polishing pad is less likely to deform accurately along with the surface of the wafer, resulting in deterioration of polishing accuracy. The pitch of the grooves may be desirably determined, taking into account a required polishing accuracy, a kind of material of interconnects of the semiconductor device, or the like. Generally, the pitch of the grooves is determined within a range of 1.0�2.0 mm.
According to another preferred form of the polishing pad of the present invention, the base for the polishing pad is made of a rigid urethane foam and the circumferential grooves are formed with a width of 0.20�0.30 mm, a depth of 0.1�1.0 mm, more preferably 0.1�0.4 mm and a pitch of 1.0�2.0 mm. In this form of the polishing pad, kinds of the rigid urethane foam are not particularly limited. Preferably, the base is formed of a rigid urethane foam having a density at around 700 kg/m3 and a tensile strength of 50 kg/cm3 or more. More preferably, the rigid-urethane foam includes cells having a diameter at around 0.02 mm at the volume ratio of 30%. In this respect, a rigid urethane foam used as packing material, generally has a density at around 100 kg/m3 and a tensile strength at around 15 kg/cm3. It should be appreciated that a solid resin member may also form the base.
In one advantageous form of the second preferred form of the machine of the invention, the milling cutter unit includes at least one milling cutter fixedly supported by a tool shaft extending along a center axis thereof, wherein the at least one cutter includes a disk-shaped body member and a plurality of cutting edges disposed at an outer peripheral portion of said body member at regular angular intervals, and each having a wedge angle within a range of 20�40 degrees, and a front clearance angle within a range of 30�40 degrees, a tooth width within a range of 0.3�2.0 mm, and a side cutting edge angle of 0�2 degree. The use of the milling cutter having a special construction as described above enables the machine to process the base for the polishing pad with increased degree of freedom. For instance, the use of this special milling cutter permits the present machine to form with ease grooves arranged in a grid pattern, a spiral pattern, a spoke-wise pattern and other formable patterns.
In another advantageous form of the second preferred form of the machine of the invention, the drill unit comprises a single-spindle type or a multiple-spindle type drill unit, the drill unit including a drill having a drill diameter of 0.5�1.5 mm, a drill length of 20�30 mm two cutting edges of helix angle of 1�10 degrees, wherein the drill is a straight drill having no back-tapered portion at cutting edges thereof and having a shape edge that has a conical angle with no chisel portion of 55�65 degrees. The use of this drilling unit permits the present machine to cut holes into or through the base for the polishing pad, resulting in an increased degree of freedom in processing the base for the polishing pad. In particular, the drill of the drilling unit is specifically arranged as described above, in other words, the drill has the sharp edge in the conical shape so as to facilitate entrance of the drill into the base, and the cutting edges arranged at its body portion with a relatively dull helical angle so as to perform cutting of the base with a slight amount of feed per revolution. This arrangement minimizes a possibility that the end of the drill damages the base. Thus, the machine equipped with the drilling unit can form a hole at a desired diameter with high accuracy.
According to a fourth preferred form of the machine of the invention, the machine includes two of the saddles, wherein at least one of the tool holders of the two saddles is adapted to detachably support the fixed tool comprising the turning tool comprising a cutting part arranged to have a tooth width within a range of 0.005�1.0 mm, a wedge angle within a range of 15�35 degrees, and a front clearance angle within a range of 65�45 degrees, and an other one of the tool holders of the two saddles is adapted to detachably support the rotative tool selected from a group consisting of the milling cutter unit and the drilling unit. In this arrangement the machine is equipped with both of the turning tool and the rotative tool with high efficiency, whereby the machine is able to execute various kinds of processing with improved operation efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS The forgoing and/or other objects features and advantages of the invention will become more apparent from the following description of preferred embodiments with reference to the accompanying drawings, in which like numerals are used to represent like elements and wherein:
FIG. 4A is a plane view of a platen of the grooving machine of FIG. 1, and FIG. 4B is a cross sectional view of the platen of FIG. 4A taken along line B�B of FIG. 4A;
FIG. 5A is a plane view of a suction plate of the grooving machine of FIG. 1, FIG. 5B is an axial cross sectional view of the suction plate, FIG. 5C is a fragmentally enlarged view of the suction plate, FIG. 5D is an enlarged view of a X portion of FIG. 5C, and FIG. 5E is an enlarged cross sectional view taken along line E�E of FIG. 5D;
FIGS. 17A, 17B and 17C are bottom, side and front views of a turning tool having a plurality of cutting parts, which is usable in the grooving machine of FIG. 1;
FIG. 24A is a side view of one example of a cutting device usable in the grooving machine of FIG. 1, FIG. 24B is a front elevational view of the cutting device, and FIG. 24C is a cross sectional view of the cutting device, taken along line C�C of FIG. 24B;
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring first to FIGS. 1A�1C, there is shown a schematic construction of a grooving machine according to one preferred embodiment of the present invention. The grooving machine is equipped with a turning tool for cutting grooves, which is constructed according to one preferred embodiment of the invention. The grooving machine is used for producing a polishing pad according to one preferred embodiment of the invention in accordance with a method according to one preferred embodiment of the invention.
(a) a circular platen 1 rotatable under control about C-axis extending in a vertical direction as seen in FIG. 1A; (b) a gate-shaped column 11 reciprocatory movable under control in a direction of X-axis; (c) two saddles 8A, 8B mounted on a cross rail 7 and reciprocatory movable along a screw-thread 10 (Y1-axis) and a screw-thread 14 (Y2-axis); (d) two tool holders 18, 19 mounted on the two saddles 8A, 8B; respectively, and reciprocatory movable along a screw-thread 12A (Z1-axis) and a screw-thread 12B (Z2-axis); (e) a numerical control device 102 (see FIGS. 13, 14) adapted to control operation of motor and a control axis; (f) an ion blower 114 as an ion blowing device (see FIG. 15) for neutralizing charged components; (g) a fixed tool 69 as a turning tool in the form of a single cutting edge tool 58 and a multiple cutting edges tool 74 (see FIG. 12) for cutting grooves; (h) a cutting device (see FIG. 24); and (i) a rotative tool 57 in the form of a milling tool 59 and a drill unit 65 (see FIGS. 10, 11). There will be described in detail a general construction of the grooving machine and specific construction of the respective components listed above, with reference to the accompanying drawings, sequentially.
FIGS. 1A�1C shows an entire construction of the grooving machine according to the present embodiment. The circular platen 1 is fixedly mounted on a bed 3 so as to extend parallel to an upper surface of the bed 3. The circular platen 1 is rotatable about the C-axis extending perpendicular to the upper surface of the bed 3, i.e., extending in the vertical direction as seen in FIG. 1A. The bed 3 further supports a pair of first guide rails 5A, 5B horizontally mounted on opposite sides of its upper surface. The first guide rails 5A, 5B extend parallel to each other in a longitudinal direction of the bed 3 while being spaced apart from each other with the circular platen 1 interposed therebetween. The gate-shaped column 11 is mounted on the first guide rails 5A, 5B so that the gate-shaped column 11 is movable along the first guide rails 5A, 5B in the horizontal direction. The gate-shaped column 11 includes a pair of legs in the form of column portions 4A, 4B mounted on the first guide rails 5A, 5B, respectively, and a cross rail 7 extending between the column portions 4A, 4B so as to connect the column portions 4A, 4B to each other. The thus formed gate-shaped column 11 is driven by a pair of screw shaft 6A (first X axis) and 6B (second X axis) disposed on the bed 3 so as to extend along the guide rails 5A, 5B, respectively, in a direction of an X-axis as indicated by an arrow in FIG. 1B. The pair of screw shafts 6A, 6B are synchronously rotated by a drive motor 40 which will be described later with reference to FIG. 7B. The drive of the gate-shaped column 11 is controlled by a suitable control device that will be described later. A pair of second guide rails 9A, 9B are disposed on one of opposite side faces of the cross rail 7 so as to extend in a direction of a Y-axis as indicated by an arrow in FIGS. 1A and 1B, which is perpendicular to the X-axis. On the second guide rails 9A, 9B, the two saddles 8A, 8B are mounted so as to be movable along the guide rails 9A, 9B, i.e., in the direction of the Y-axis. The two saddles 8A, 8B are driven by respective screw shafts 10, 14 disposed on the side face of the cross rail 7 so as to extend along the guide rails 9A, 9B. The screw shafts 10, 14 are rotated by suitably electric drive motors (not shown) under control of the suitable control device. The two saddles 8A, 8B support tool rests 18, 19 mounted thereon, respectively, such that the tool rests 18, 19 are movable in a direction of a Z-axis extending in the vertical direction as seen in FIG. 1A (as indicated by an arrow). The tool rests 18, 19 are driven by respective ball-screws 12A, 12B disposed on the saddles 8A, 8B so as to extend along the Z-axis. The screw shafts 12A, 12B are rotated by respective electric motors 13A, 13B so that the tool rests 18, 19 are moved in the direction of the Z-axis independently of each other. The gate shaped column 11, the saddles 8A, 8B, and the tool rests 18, 19 may be formed by desired metallic materials, preferably rigid light metallic materials such as a hard aluminum alloy or the like.
(a) Circular Platen (C-Axis) Referring next to FIG. 2, the circular platen 1 and a housing member of the circular platen 1 are both shown in their axial cross sections. FIG. 2 also shows a driving mechanism for rotating the circular platen 1 and an air suction device in the form of a suction blower 25 installed within the bed 3 so as to apply a vacuum to an upper surface of the circular platen 1 to thereby attract the base for a desired polishing pad for the CMP, in the form of the foamed urethane pad 15, on the upper surface of the circular platen 1. FIG. 3 shows an enlarged view in axial cross section of a position holding member 38 adapted to place the circular platen at its suitable angular position about the C-axis, which is determined based on the angular position of the circular platen 1 detected by controlling the rotation of the circular platen 1 about the C-axis. FIG. 4 shows a plane view and an axial cross sectional view of the circular platen 1 in which a plurality of air flow passages are evenly formed therethrough so that the vacuum delivered from the suction blower 25 is evenly applied to a rear surface of the foamed urethane pad 15. FIG. 5 shows a suction plate 16 assembled in the surface of the circular platen 1. The suction plate 16 has a plurality of tiny air holes 16 a formed therethrough and tiny grooves 16 b, 16 c connecting the air holes 16 a so that the vacuum is evenly applied to the rear surface of the foamed urethane pad 15, thus preventing deformation of the surface of the urethane pad due to stress concentrated at a local portion of the foamed urethane pad upon cutting grooves on the urethane pad.
The hollow center shaft 17 has a bore 17 b serving as an air passage. The bore 17 b is held in fluid-tight communication at its upper end with a plurality of communication holes 1 a formed through the central portion of the circular platen 1, and at its lower end with an air hose 28 of the suction blower 25 via a coupling 27 supported by a support 26 fixed to a seat portion 3 b of the bed 3. In this condition, the vacuum generated in the suction blower 25 is applicable to the rear surface of the foamed urethane pad placed on the upper surface of the circular platen 1 through the bore 17 b of the center shaft 17 and the communication holes 1 a of the circular platen 1. Therefore, the vacuum application needed for holding the foamed urethane pad on the surface of the circular plate 1 can be executed during the rotation of the center shaft 17. In this respect, the upper open end of the communication holes 1 a are closed by a suction plate 16 which is placed on the upper surface of the circular platen 1. As shown in FIG. 5, the suction plate 16 is formed with a plurality of suction holes in the form of air holes 16 a and grooves 16 b, so that the vacuum is evenly applied in the upper surface of the suction plate 16 through the communication holes 1 a and the air holes 16 a and the grooves 16 b, thus assuring firmly holding of the foamed urethane pad 15 on the surface of the suction plate 16. As is understood from the aforementioned description, the position holding member 38, the drive motor 21 and the suitable power transmittal members cooperates to form a drive mechanism adapted to rotate the circular platen 1 and place the circular platen 1 at a suitable angular position, in the present embodiment.
FIG. 4A shows a plane view of the circular platen 1, while the FIG. 4B shows a cross sectional view of the circular platen 1 taken along line B�B of FIG. 4A. A material for producing the circular platen 1 may be preferably selected from light metals including aluminum alloy, titanium and the like, thereby lowing a moment of inertia of the circular platen 1, thus permitting a prompt startup or stop of the rotation of the circular platen. In particular, the material of the circular platen 1 is desired to be less likely to cause the secular change of the circular platen 1, like strain, to exhibit a heat resistance, and to have sufficient stiffness and strength. While the communication holes 1 a is formed through the central portion of the circular platen 1 for introducing the suction force applied from the suction blower 25 into the upper surface of the circular platen 1 through, the circular platen 1 is also formed with a plurality of leading grooves 1 c, 1 d for leading the suction force into the outer circumferential portion of the circular platen 1. The circular platen 1 is further provided with a plurality of generally concentric grooves 1 e, through which the plurality of leading grooves 1 c, 1 d extending in the radial directions are held in communication with each other. A plurality of circumferential walls 1 f defined between adjacent ones of the annular grooves 1 e serve as supports on which the suction plate 16 is placed.
Referring next to FIGS. 5A, 5B, 5C, there are shown a plane view, an axial cross sectional view, and a fragmentally enlarged view of the suction plate 16. In addition, FIG. 5D shows an enlarged view of an X part of FIG. 5C, and FIG. 5E shows a cross sectional view taken along line E�E of FIG. 5D. As shown in FIG. 5E, the suction plate 16 functions to support the foamed urethane pad 15 to be placed thereon. The suction plate 16 is provided with the multiplicity of tiny air holes 16 a evenly dispersed over the entire surface of the suction plate 16, so that the foamed urethane pad 15 is fixed onto the surface of the suction plate 16 by the suction force evenly applied to the back surface thereof through the air holes 16 a. Like the circular platen 1, the suction plate 16 is made of a material preferably selected from light metals including hard aluminum alloy, titanium, and the like, and ceramic materials.
(b) Gate-Shaped Column (X-Axis) Referring next to FIGS. 6A and 6B, there are shown a plane view and a side view of the gate-shaped column 11 that is placed on the first guide rails 5A, 5B, which are disposed on the bed 3 with the circular platen 1 interposed therebetween. FIGS. 7A and 7B show drive mechanism for driving the gate-shaped column 11 in the direction of the X-axis as shown in FIG. 7A. Namely, FIG. 7A is a plane view of the bed 3 on which the pair of screw shafts 6A, 6B are disposed so as to extend along with the guide rails 5A, 5B, respectively. The motions of the screw shafts 6A, 6B in their axial direction i.e., in the direction of X-axis, are controllable. FIG. 7B shows a power transmitting system for controlling the rotation of the screw shaft 6A, 6B by using a single belt 43.
(c) Two Saddles 8A, 8B Mounted on a Cross Rail (Y1-Axis, Y2-Axis) Referring back to FIG. 6A, there is shown a front view of two saddles 8A, 8B. Two saddles 8A, 8B are mounted on the second guide rails 9A, 9B disposed on the cross rail 7 so as to extend over the two symmetrical columns 4A, 4B in the direction of Y-axis perpendicular to the Z-axis and the X-axis, as shown by arrows in FIGS. 6A and 6B. Therefore, the two saddle systems 8A, 8B are movable in the direction of Y-axis along the second guide rails 9A, 9B. The two saddle systems 8A, 8B are driven by respective drive motors whose operation is controllable so as to place the saddles 8A, 8B at respective desired positions. FIG. 8A is a view corresponding to that of FIG. 6A, in which the two saddles 8A, 8B are removed from the second guide rails 9A, 9B. As is apparent from FIG. 8A, ball-screw shafts 10, 14 are disposed on the cross rail 7 so as to extend along with the second guide rails 9A, 9B, i.e., in the Y-axis direction. The screw shaft 10 is driven by an Y1-axis control motor 47, while the ball-screw shaft 14 is driven by an Y2-axis control motor 48. FIG. 8B shows power transmittal members constituting the motors 47, 48.
(d) Tool Rests Disposed on the Two Saddles (Z1 Axis, Z2 Axis) FIG. 6A shows the tool rests 18, 19 mounted on the saddles 8A, 8B on the front side of the cross rail 7. FIGS. 9A, 9B show a front elevational view and a side elevational view of tool-rest support mechanism in which the tool rest 19 are indicated by a two-dot chain line. Further, FIG. 10 shows one example of the operating state of the tool rest 19 in which a milling cutter unit 59 as a rotative tool 57 is fixed to the tool rest 19. FIG. 11 shows another example of the operating state of the tool rest 19 in which a drill 82 as the rotative tool 57 is fixed to the tool rest 19. FIG. 12 shows yet another example of the operating state of the tool rest 19 in which a single edged tool 58 or a multi-edged tool 74 as a fixed tool 69 is fixed to the tool rest 19. It should be noted that both of the tool rests 18, 19 may be provided with various kinds of rotative tools and fixed tools in a possible variety of combinations. The tool rests 18, 19 may also be provided with the cutting device 77 which will be described later or various kinds of groove cutting tools. For instance, the tool rests 18, 19 may be provided with the rotative tool 57 and the fixed tool 69, respectively. The tool rests 18, 19 may otherwise be provided with different fixed tools, e.g., the single edged tool 58 and the multi edged tool 74, respectively. Alternatively, the tool rests 18, 19 may be provided with different rotative tools 57, namely, the tool rest 18 is provided with one of the milling cutter unit 59 and the drill unit 65, while the tool rest 19 is provided with the other.
In the present embodiment, the gate-shaped column 11 is guided to move in the X-axis direction by the first guide rails 5A, 5B, and the saddles 8A, 8B are guided to move in the Y-axis direction by the second guide rails 9A, 9B, while the tool rests 18, 19 are guided to move in the z-axial direction by the third guide rails 52A, 52B, as described above. Therefore, the cutting edges of the tools fixed to the tool rests 18, 19 can be accurately positioned in the above-indicated X, Y and Z-axis directions by utilizing a numerical control device (hereinafter referred to as �NC� device) 102. Namely, the NC device controls the operations of the drive motors 21, 40, 47, 48, 13A, 13B so that the positions of the gate-shaped column 11, the saddles 8A, 8B and the tool rests 18, 19 are accurately controlled. Further, the milling cutter unit 59 and the drill unit 65 are selectively detachably fixed to the tool rest 19. FIG. 10 shows one operation state of the grooving machine 10 in which the rotative tool 57 consisting of the milling cutter unit 59 having a milling cutter 81 (see FIG. 25) is fixed to the tool rest 19. FIG. 11 shows another operation state of the grooving machine 10 in which drill unit 65 having a drill 82 (see FIG. 26) is fixed to the tool rest 19.
There will be described a manner of operation of the grooving machine of the present invention when the grooving machine is operated under control of the NC device 102 for producing the polishing pad multiplicity of straight grooves arranged in the grid pattern, by way of example. First, the milling cutter units 59 are fixed to the tool rest 18 (19). Subsequently, the motor 21 is operated under control of the NC device 102 for detecting the current angular position of the circular platen 1 and then fixing the circular platen 1 in a predetermined angular position. The motor 40 is also operated under control of the NC device 102 for driving the gate-shaped column 11 to a desired position in the X-axial direction, while the motor 47, 48 are operated under control of the NC device 102 for driving the saddles 8A, 8B in the Y-axial direction, while the motors 13A, 13B are operated under control of the NC device 102 for driving the tool rests 18, 19 to a desired position in the Z-axial direction. Thus, the milling cutting unit 59 is accurately positioned on a desired portion of the foamed urethane pad, which portion is to be processed. With the milling groove cutting unit 59 being positioned as described above, the grooving process is performed according to a suitable processing program stored in a storage device of the NC device 102. Namely, a desired amount of depth of cut of the milling cutter 81 in the Z-axial direction are provided by the operation of the motor 13A, 13B under control of the NC device 102, while a desired amount of displacement of feed per revolution of the saddles 8A, 8B in the Y-axial direction are provided by the operation of the motors 47, 48 under control of the NC device 102.
(e) Numerical Control Device to Control Motor and Control Axis Numerical control device 102 is adapted to control operation of the motors 13A, 13B, 21, 40, 47, 48, so that the circular platen 1, the gate-shaped column 11, the saddle 8A, 8B, the tool rests 18, 19 are accurately and smoothly positioned in the C, X, Y and X axes, respectively. The numerical control device 102 permits to control the motors 13A, 13B to regulate the feed per revolution of the tool rests 18, 19 at minute units. The numerical control device 102 enables an automatic synchronizing control operation of the plurality of motors, according to a suitable control program that is stored in its storage device in advance. In this storage device of the NC device 102, a plurality of grooving patterns to be reproduced on the surface of the foamed urethane pad 15 are stored in advance. A suitable grooving pattern is selected from the stored grooving patterns, then the operations of the processing program for the selected grooving patterns with respect to the respective control axes C, X, Y, Z are prepared. According to this predetermined processing program, the grooving machine of this embodiment is automatically operated so as to reproduce the selected grooving pattern on the surface of the polishing pat.
Referring next to FIG. 13, there is shown a block diagram schematically showing a control system of the NC device 102 adapted to control operation of the grooving machine. Described in detail, the NC device 102 includes data input section 101, a central processing unit (CUP) 103, a data storage section 104 and an I/O interface. Upon starting the grooving process under control of the NC device 102, a tool command representing a kind of required tool, and dimensional information of the required tool is applied to the numerical control device 102 through the data input section 101. The required tool is suitably determined depending upon a desired groove pattern, e.g., a grid pattern or a generally concentric annular groove pattern. This tool command is stored in the data storage section 104 via the CPU 103. Once an operation command is applied from the input section 101, the CPU 103 controls operation of the respective motors 13A, 13B, 21, 40, 47, 48, and the cutting device 77 according to a suitable processing program with reference to data stored in the storage section 104, so that the operations of the circular platen 1, the gate-shaped column 11, the saddles 8A, 8B, the tool rests 18,19 and the milling cutter unit 59, the drill unit 65 are accurately controlled. Each motor is equipped with an encoder. An amount of rotation of the motor detected by the encoder is applied to the NC device so that the NC device controls the operation of the grooving machine in a feedback control fashion. The CPU 103 also controls operation of the suction blower 25, the position holding member 38 of the circular platen 1, the ion blower 114, and a chip collection device 115.
(f) Ion Blowing Device Referring next to FIGS. 15A, 15B, there is shown the ion-blowing device 114 adapted to generate and blow positive ions formed by corona discharge. The ion-blowing device 114 includes a compressed air generator (not shown) and a blower nozzle 76, so that the generated positive ions are discharged through the blower nozzle 76 together with the compressed air. Alternatively, the positive ions are discharged through holes 71(a), 72(a) which will be described later. This ion-blowing device 114 is disposed in a portion of the grooving machine such that a protruded open-end portion of the blower nozzle 76 is located in the vicinity of the attached cutting tool, e.g., the fixed tool 69 or the rotative tool 57 (the multi-edged tool 74 is attached in FIGS. 15A�15C by way of example). When the foamed urethane pad 15 is subjected to the grooving process, cut fragments or chips of the foamed urethane pad 15 are likely to be electrically charged due to friction between the cutting tools and the urethane pad 15, and stick to the surface of the urethane pad 15 and the cutting tools, resulting in difficulty in removing the charged chips from the surfaces of the cutting tool and the urethane pad. To cope with this problem, the ion blowing device 114 is operated to blow the positive ions on the chips stuck to the cutting tool and the foamed urethane pad 15, while the grooving process is executed for the foamed urethane pad 15, whereby the chips are effectively neutralized and removed from the cutting tool and the urethane pad 15. When the multi-edged tool 74 of the fixed tool is used for forming simultaneously a plurality of grooves on the foamed urethane pad 15, in which a plurality of cutting edges are juxtaposed to each other, it is required to evenly blow the positive ions on the respective cutting edges so that the positive ions forcedly come into collision with the charged chips. To meet this requirement, the protruded open-end portion of the nozzle 76 may be suitably arranged.
FIGS. 15A�15C show a front, a side and a bottom elevational view of the ion-blowing device 114 that is fixed to a tool holder 71. The tool holder 71 has a rectangular block shape and detachably fixed to the side face of the tool rest 18 (19) by means of suitable fastening means such as a bolt. The tool holder 71 has the above mentioned through hole 71 a formed therethrough in the vertical direction as seen in FIG. 15A through which positive ions are discharged. To the bottom face of the tool holder 71, a rectangular block shaped tool cartridge is fixed such that the tool cartridge 72 is supported by tapered bush 73 so as to be positioned in the vertical direction as seen in FIG. 15A. The tool cartridge 72 has the above-indicated plurality of straight holes 72 a extending therethrough in the vertical direction as seen in FIG. 15A. These straight holes 72 a are held in communication with the through hole 71 a of the tool holder 71, so that the lower end of the through holes 71 a is exposed to the atmosphere through the straight holes 72 a. As shown in FIG. 15A, the multi edged tool 74 is fixed to the tool holder 71 by way of example. The multi edged tool 74 may be a tool detachably installable on the tool holder 71 with high accuracy. For instance, the multi edged tool 74 is fixed to the tool cartridge 72. The cartridge 72 is positioned relative to the tool holder 71 by means of tapered bushes 73, 73. The cartridge 72 is guided by the side walls of the tool holder 71, and is firmly fitted to the tool holder 71 by means of a pressing plate 75 that is bolted to the tool holder 71. The positive ions can be discharged from the side of the attached tool through the nozzle 76. In the case where the multi edged tool 74 is attached to the tool holder 71 as described above with the compressed air, the ion blowing device 114 may be arranged to blow the positive ion through the through hole 71 a formed through the tool holder 71 and the straight holes 72 a formed through the cartridge 72 instead of or in addition to the nozzle 76. In the ion-blowing device 114, the compressed air generator may be disposed within the nozzle 76, or the straight holes 72 a, for example. Alternatively, the compressed air generator may be constituted by utilizing an external compressed air source that is held in fluid communication with the nozzle 76 or the like via an air conduit. It should be appreciated that the compressed air generator is interpreted to mean the overall structure thereof including the air conduit connecting between the external compressed air source and the nozzle 76 or the like.
(g) Fixed Tool (Turning Tool/Cutting Tool) (1) Turning Tool (Single Edged Tool and Multi Edged Tool) FIGS. 16A and 16B show a front and a side elevational view of the single edged tool 58 as one example of the fixed tool 69. FIGS. 17A�17C shows a bottom, a front and a side elevational view of the multi edged tool 74 as another example of the fixed turning tool 69. The single edge tool 58 and the multi edged tool 74 are suitably used for the grooving process in which the plurality of generally concentric annular grooves are formed on the surface of the foamed urethane pad 15.
The single edged tool 58 has a cutting part 58 a that is arranged as follows so that the single edged tool 58 is suitable for cutting a working piece made of a resin material, e.g., a foamed urethane pad. Namely, the cutting part 58 a of the single edged tool 58 has a tooth width: W1 within a range of 0.005�1.0mm, a side clearance angle: θ1 within a range of 0�3 degrees, as shown in FIG. 16A. Further, the cutting tooth of the single edged tool 58 has a wedge angle: θ2 within a range of 15 �35 degrees, a rake angle: θ3 within a range of 10�20, and a front clearance angIe θ4 within a range of 45�65 degrees, as shown in FIG. 16B. These angles of respective parts of the cutting part 58 a of the single edged part 58 a are determined taking into account a problem of interface between the cutting part 58 a and walls of the foamed grooves and a required strength of the cutting part 58 a. Preferably, the single edged part 58 a is made of a rigid material, such as hard metal, high speed steel, carbon steel, ceramics, cermet, and diamonds.
As shown in FIGS. 17A�17C, the multi-edged tool 74 has a thin rectangular plate-like shape and includes a plurality of cutting parts 58 a integrally formed on and protruding from its bottom end as seen in FIG. 17A, such that the plurality of cutting parts 58 a are arranged in a longitudinal direction of the multi-edged tool 74 at regular intervals within a range of 0.2�2.0 mm, over a substantially entire area of the bottom end of the multi-edged tool 74. It is noted that each of the plurality of cutting parts 58 a of the multi-edged tool 74 is dimensioned identically with the cutting part 58 a of the single edged tool 58. That is, the multi-edged tool 74 serves as a tool tip having a plurality of cutting parts 58 a integrally formed in the end portion thereof.
Referring next to FIGS. 18 and 19, there is shown by way of example the multi-edged tool 74 in the form of the tool tip, which is fixed to the bottom end portion of the tool holder 71, such that the multi-edged tool 74 is gripped by and between the tool holder 71 and the pressing plate 75. Positioning pins 73 fitted to the multi-edged tool 74 is used for positioning the multi-edged tool 74 relative to the tool holder 71. The tool holder 71 equipped with the multi-edged tool 74 as shown in FIG. 19, may be solely fixed to the tool holder 18 (19). Alternatively, a plurality of tool holders 71 each equipped with the multi-edged tool 74 may be fixed to the tool holder 18 (19), as shown FIG. 20. In this case, the cutting parts 58 a of the plurality of multi-edged tools 74 may be arranged at regular intervals, thus permitting high efficiency in cutting a plurality of grooves on the foamed urethane pad 15. As is apparent from FIG. 21, it may be possible to fixed a plurality of multi-edged tools 74 to the tool holder 71 such that the cutting parts 58 a are arranged at regular intervals. This arrangement facilitates the formation of the plurality of grooves on the foamed urethane pad 15, likewise.
(2) Cutting Tool Referring next to FIGS. 24A�24C, there are respectively shown a side elevational view, a front elevational view and a cross sectional view taken along line C�C of FIG. 24B of the cutting device 77 which is adapted to be mounted on the tool rest 18 (19) disposed on the saddle 8A (8B) of the cutting machine constructed according to the present embodiment. The cutting device 77 is operable to cut primary peripheral portion of the foamed urethane pad 15 to shape the external form of the foamed urethane pad 15 desirably. More specifically described, the cutting device 77 includes: a base 78; a fourth guide rails 63A, 63B disposed on the base 78 so as to extend parallel to each other in the Z-axis direction; a tool rest 64 disposed on the base 78 via the pair of fourth guide rails 63A. 63B so as to be movable in the Z-axis direction; a cutting tool holder 66 mounted on the tool rest 64; and a power source 62 disposed on the base 78 so as to generate a drive power by which the tool rest 64 is moved in the Z-axis direction. A cutting tool 61 is fixed to the cutting tool holder 66 such that a base portion of the cutting tool 61 is fitted into a cutting tool base 83 formed in the cutting tool holder 66, while being supported by the a pair of tool supports 65 with its protruding end portion supported by a stopper pin 80. An output member of the power source 62 is connected to a support member 67 disposed on the tool rest 64 via a connecting metal member 68, thus transmitting output power of the power source 62 to the tool rest 64. Thus, the cutting tool 61 is driven in the Z-axis direction. It should be understood that the power source 62 may comprises a piston-cylinder mechanism of pneumatics type or hydraulic type, or a solenoid-type actuator. It should be further understood that the cutting tool 61 may otherwise be constituted by a suitable turning tool for assuring further improved cutting ability of the cutting device 77.
(h) Rotative Tool (Milling Cutter and Drill) (1) Milling Cutter FIG. 25A shows a front view of one example of a milling cutter 81 for forming a fine groove, which is fixed to the grooving milling cutter unit 59. FIG. 25B shows an enlarged view of cutting parts 79 of the milling cutter 81 of FIG. 25A. The milling cutter 81 is a thin circular disk member, which has a center hole 81 a formed therethrough and a plurality of cutting part 79 integrally formed in its outer peripheral portion such that the plurality of cutting part 79 are arranged in a circumferential direction of the grooving milling cutter 81 with a uniform pitch. Each of the cutting parts 79 is dimensioned to have a wedge angle: θ5 within a range of 20�45 degrees, since the wedge angle: θ5 smaller than 20 degrees may cause undesirable shortening of the life of the grooving milling cutter 81, while the wedge angle: θ5 larger than 45 degrees may cause deterioration of cutting capability of the cutting tooth 79. Further, the each cutting parts 79 is dimensioned to have a rake angle: θ6 within a range of 30�40 degrees, more preferably at around 30 degrees, since the rake angle: θ6 smaller than 30 degrees may cause deteriorated stability of the milling cutter 81, while the rake angle: θ6 larger than 40 degrees may cause deterioration of cutting capability of the cutting tooth 79. Yet further, the each cutting tooth 79 is dimensioned to have a side cutting edge angle within a range of 0�2 degrees and a tooth width within a range of 0.3 mm�2.0 mm. The thus formed milling cutter 81 is disposed radially outwardly on a tool shaft formed on the lower portion of the grooving milling cutter unit 59 and rotated in a predetermined circumferential direction by the drive motor 126. The number of the milling cutter 81 fixed to the tool shaft is not particularly limited. For instance, a plurality of grooving milling cutters 81 may be fixed to the tool shaft with constant intervals within a range of 0.1 mm or more, so that a plurality of grooves arranged in a grid pattern are formed on the foamed urethane pad 15 with improved efficiency.
(2) Drill FIG. 26A shows a front elevational view of one example of a drill 82 to be fixed to the drill unit 65, and FIG. 26B shows an exploded view of a cutting part 82 a of the drill 82. As shown in FIG. 26A, the drill 82 has a diameter: D1 within a range of 0.5 mm�1.5 mm and a length: L1 within a range of 20�30 mm. As shown in FIG. 26B, the cutting part 82 a of the drill 81 includes two cutting edges 83, 83. The end edge portion of the drill 82 has a cone angle θ8 within a range of 55�65 degrees, more preferably at around 60 degrees, thus assuring a smooth inserting of the drill 81 into the work piece. A helix angle: θ7 of the two cutting edges 83, 83 is arranged to be held within a range of 1�10 degrees, preferably at about 5 degrees. This arrangement makes it possible to gradually cut a part of the foamed urethane pad 15 located around the edge of the drill 82, thereby forming a desired hole having a predetermined diameter. The number of the drill 82 fixed to the drill unit 65 is not particularly limited. For instance, a plurality of drill 82 may be fixed to the drill unit 65 to form a multi-shaft type drill unit, so that a plurality of holes are formed into the foamed urethane pad 15 with improved efficiency.
(i) Concentric Fine Grooves Referring next to FIGS. 27A, 27B, there is shown a polishing pad fabricated according to one preferred embodiment of the invention by way of example. The polishing pad is formed by cutting a multiplicity of generally concentric grooves into the surface of the foamed urethane pad 15 having a thickness: T1 within a range of 1.0 mm�2.0 mm. The generally concentric grooves have a width: W1 within a range of 0.005�1.0 mm, a depth: D1 within a range of 0.2�2.0 mm, and a pitch: L2 within a range of 0.2�2.0 mm. For producing the polishing pad of the present invention, initially, the single-edged cutting tool 58 or the multi-edged cutting tool 74 is fixed to the tool rest 18 (19), while a base for desired polishing pad, e.g., the foamed urethane pad 15 is placed on the suction plate 16 of the circular platen 1. Preferably, the foamed urethane pad 15 is shaped to have a circular-disk shape identical in size with the circular platen 1 in advance, by cutting. The cutting of the foamed urethane pad 15 may be executed by means of cutting device 77 fixed to the tool rest 18 (19). In the case where the foamed urethane pad 15 has a diameter smaller than the suction plate 16, an annular covering member may be placed on the outer peripheral portion of the suction plate 16 located radially outward of the foamed urethane pad 16, so that the air holes 16 a open in the outer peripheral portion of the suction plate 16 is effectively closed by the annular covering member. The suction plate 16 may be modified so that only a portion of the suction plate 16 serving for suctioning the urethane pad 15 is provided with the air holes 16 a. Alternatively, the communication grooves 16 b formed in the suction plate 16 may be partially closed so that distribution of the suction force on the suction plate 16 is divided into local sections.
The tool rest 18 and the saddle 8A is subsequently displaced in the Y-axis direction so as to subsequently form the multiplicity of grooves. When the formed urethane pad has a relatively large area and a great number of grooves are required to be formed, the multi-edged tool 74 is preferably employed. The multi-edged tool 74 may consist of 10�30 single-edged tools juxtaposed to each other, for example. The use of the multi-edged tool 74 makes it possible to form a great number of grooves with high efficiency.
(j) Grid Patterned Fine Grooves Referring next to FIG. 28, there is shown one example of a polishing pad having a plurality of grooves arranged in the grid pattern. This polishing pad is formed by cutting a multiplicity of straight grooves arranged in the grid pattern into the base for the polishing pad, e.g., the foamed urethane pad 15 having a thickness of 1.4 mm. Each of the straight grooves has a width of 0.8 mm, a depth of 0.5 mm and a pitch of 6.35 mm. For producing this grid grooved polishing pad, initially, the rotative tool unit 57 equipped with the milling cutter 81 is fixed to the tool rest 19 disposed on the saddle 8B, while the urethane pad 15 as a working piece is placed on the circular platen 1. Subsequently, the angular position of the circular platen 1 about the C-axis is detected, and then the circular platen 1 is held in its initial angular position, under control of suitable control device, e.g., the NC device 102 or the sequencer 110. For forming the grooves in the grid pattern, the circular platen 1 placed in its initial angular position is then rotated about the X-axis by 90 degrees to be held in its first processing angular position. The gate-shaped column 11, the saddle 8B and the tool rest 19 are moved to be placed in their initial positions in the X-axis, Y-axis and Z-axis directions, respectively, under control of the control device. A predetermined pitch of displacement of the gate-shaped column in the X-axis in the grid pattern is set in advance, thus eliminating a need for a surplus displacement of the tool rest 19 in the Y-axis direction.
(k) Radial Grooves The grooving machine constructed according to the present invention may form radially arranged grooves on the base for the polishing pad, e.g., the foamed urethane pad 15. Described more specifically, the circular platen 1 on which the foamed urethane pad 15 as the work piece is fixedly placed, is held in a processing angular position, and then the milling cutter 81 fixed to the tool rest 19 is moved by a predetermined amount in the Y-axis direction so as to form a single straight groove extending in a radial direction of the urethane pad 15. After the single radial groove is formed, the circular platen 1 is rotated by a predetermined angle so as to be held in a next processing angular position thereof. The grooving milling cutter 81 is moved again by the predetermined amount in the Y-axis direction so as to form another single straight grooves extending in a radial direction of the urethane pad 15. The above described reciprocating motion of the grooving milling cutter 81 in the Y-axis direction and the rotation of the circular platen 1 about the C-axis are repeated until a desired number of grooves are formed on the urethane pad 15. Thus, the polishing pad having the radial grooves is obtained. In this case, the use of the ion blower is preferable.
(m) Drilling The obtained polishing pads as described above, may be subjected to a drilling process as needed. The drilling process makes it possible to form a plurality of fine holes through the polishing pads. The drilling process may be performed on a working piece that is not subjected to any grooving process. In order to perform the drilling process, a special drill 82 is fixed to the drill unit 65 mounted on the tool rest 19, initially, Subsequently, the circular platen 1 is positioned about the C-axis, and the gate-shaped column 11, the saddle 8B and the tool rest 19 are respectively positioned in the X-axis, Y-axis and Z-axis directions. Then, the tool rest 19 is moved downwardly in the Z-axis direction by a predetermined amount of feed, assuring a predetermined amount of depth of cut of the drill 82. Thus, a desired hole is formed through the grooved urethane pad or the work piece.
While the grid patterned grooves are formed on the surface of the base for the polishing pad by using a milling cutter 81 in the grooving machine of the illustrated embodiment, the grid patterned grooves may be formed more efficiently by utilizing a single edged tool or a multi edged tool that is fixed to the tool rest 18 (19) that is reciprocally movable in the Y-axis direction at a relatively high speed, e.g., 50�180 m per minute. More specifically described, the grooving machine is modified such that the saddles 8A, 8B are reciprocally moved in the Y-axis direction by means of linear motors disposed so as to extend along the guide rails 9A, 9B, in stead of the ball-screw shafts 10, 14. The use of the linear motors enables the above-indicated high-speed reciprocal motion of the saddles 8A, 8B and the tool rest 18, 19 in the Y-axis direction, in comparison with the ball-screw shafts 10, 14 which permits the reciprocal movement of the saddles 8A, 8B at 10 m per minute at most. Thus, the modified grooving machine, which has the linear motors as a drive power source of the saddles 8A, 8B in the Y-axis direction, is capable of cutting the grid patterned grooves into the base for the polishing pad with significantly improved efficiency. In addition, the modified grooving machine utilizes the single or multi edged tool rather than the milling cutter 81. This arrangement is effective to prevent undesirable melt of the base of the polishing pad due to heat caused by frictional contact of the milling cutter 81 with the base for the polishing pad, depending upon kinds of materials of the base for the polishing pad.
EXAMPLES To further illustrate the present invention, there will be described some examples of the invention. It is to be understood that the invention is not limited to the details of these examples, but may be embodied with various changes, modifications and improvements, which may occur to those skilled in the art, without departing from the spirit and scope of the invention defined in the appended claims.
To further clarify technical advantages of the present invention, a relationship between variation in a groove width and a variation of an abutting pressure of a polishing pad with respect to a work, i.e., a wafer, were obtained by conducting a simulation using a static model as shown in FIG. 37. Where a groove width: �a� varies among four values: 0.2 mm, 0.2375 mm, 0.2625 mm and 0.3 mm while a groove pitch is made constant, a variation of the abutting pressure of the polishing pad applied on a surface of the wafer were calculated according to the finite element method. The obtained result as shown in graphs of FIGS. 38 and 39.
As is understood from the graph of FIG. 38, the abutting pressure of the polishing pad applied on the surface of the wafer is significantly increased at open-end edge portions of each groove. Namely, a significantly high peak pressure is generated at the open-end edge portions of the each groove. As is also understood from the graph of FIG. 39, the peak pressure varies over 1.0 gf/mm2 or more under the condition of a groove width variation or error of �20%. In the case where the each groove has a relatively small width selected from a predetermined groove width range of 0.005�1.0 mm of the present invention, the groove width error of �20% means a dimensional difference within a range of 0.002�0.40 mm. This clearly shows that a high dimensional accuracy of the grooves is significantly important to assure a desired polishing ability of the polishing pad with high stability. It should be appreciated that conventional technique for grooving the polishing pad is absolutely insufficient to form such a fine multiplicity of circumferential grooves on the base for the polishing pad with high dimensional accuracy. The aforementioned high dimensional accuracy of the grooving technique of the present invention should be appreciated as a prominence effect of the present invention, which is distinguishable from the conventional grooving techniques.
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(Partial Translation).Referenced byCiting PatentFiling datePublication dateApplicantTitleUS7234224 *Nov 3, 2006Jun 26, 2007Rohm And Haas Electronic Materials Cmp Holdings, Inc.Curved grooving of polishing padsUS7516536 *Dec 12, 2005Apr 14, 2009Toho Engineering Kabushiki KaishaMethod of producing polishing padUS8496512 *Oct 10, 2012Jul 30, 2013Iv Technologies Co., Ltd.Polishing pad, polishing method and method of forming polishing pad* Cited by examinerClassifications U.S. Classification29/557, 82/1.11, 407/67, 407/113, 407/69, 407/70, 407/117International ClassificationB23C5/08, B23C5/10, B24D18/00, B23Q1/52, B24D13/14, B23Q16/04, B24B37/26, B23P13/00, B23B27/16, B23B27/04Cooperative ClassificationB23B27/04, B23B2210/022, B24D18/00, B23Q16/04, B23C5/10, B23Q1/52, B23B2210/02, B24B37/26, B23B2251/50, B23C5/08, B23B2220/12European ClassificationB24B37/26, B23Q1/52, B23Q16/04, B23C5/10, B23B27/04, B24D18/00, B23C5/08Legal EventsDateCodeEventDescriptionMay 28, 2010FPAYFee paymentYear of fee payment: 4RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google