Fine-adjustment thread arrangement and machining device

Abstract

A fine adjustment thread assembly for coupling a first part (56) and a second part (70) together while maintaining the first part and the second part spaced apart from each other, for adjusting a distance between the first part and the second part, and for detecting a load applied to the second part, comprising: a first external thread (83) which can be brought into threaded engagement with a first internal thread (452, 562) formed in the first part; a second external thread (85) arranged on an extension of an axial direction of the first external thread (83) and axially spaced from the first external thread (83), which has a thread pitch different from that of the first internal thread (452, 562) and which can be brought into threaded engagement with a second internal thread (302, 712) formed in the second part; a connecting portion (87) through which the first external thread (83) and the second external thread (85), which are spaced apart from each other, are integrally connected to each other; and a load sensor (89) housed under a compressive load in the connecting section (87).

Description

BACKGROUND ARTTechnical FieldThe present invention relates to a fine adjustment screw assembly and a machining apparatus.DESCRIPTION OF THE RELATED ARTSome grinding apparatuses grind a workpiece held on a holding surface of a chuck table with an annular array of grinding stones attached to a grinding unit. In such a grinding apparatus, the chuck table and the grinding unit are positioned relative to each other so that the grinding stones pass through the center of the workpiece when the workpiece is ground by the grinding stones on the grinding apparatus.The workpiece held on the holding surface of the chuck table is ground in a radial region extending from the center to an outer peripheral edge of the workpiece. In the radial region, the holding surface and the lower surfaces of the grinding stones are parallel to each other. Moreover, the extent of parallelism between the holding surface and the lower surfaces of the grinding stones is adjusted based on a measured thickness of the workpiece being ground. Therefore, the grinding apparatus has a tilt adjusting mechanism for adjusting the amount of parallelism between the holding surface and the lower surfaces of the grinding stones.The inclination adjusting mechanism inclines a spindle unit supported on a spindle supporting housing for rotating the grinding stones. Alternatively, the inclination adjusting mechanism inclines a chuck shaft unit supported on a device base for rotating the chuck table.In recent years, the need has arisen for shortened grinding times required to grind workpieces. In order to shorten a grinding time, the grinding stones are pressed against a workpiece under an increased load when the grinding stones grind the workpiece. If the load on the grinding stones is too large, a band interposed between the workpiece and the holding surface is broken, making it difficult to uniformly form the thickness of the workpiece which has been ground.Attempts have been made to make uniform the thickness of a ground workpiece by controlling the load applied to the grinding stones based on the load measured when the workpiece is ground. In order to measure the load, a load sensor is disposed between the jig base and the chuck shaft unit or between the spindle support housing and the spindle unit, i.e., between jig members as disclosed in Japanese Laid-Open Patent No. 2003-326456.Further information helpful for understanding the present invention can be found in the following documents:JP 5 805 347 B2 relates to a coupling element which has a supporting structure and a sensor unit, wherein the sensor unit is capable of measuring an axial prestress applied in the coupling element.DE 10 2017 103 212 A1 relates to a semiconductor structure bonding device which can comprise a leveling system.JP 2013-119 123 A relates to a grinding apparatus provided with a holding means capable of holding and rotating a plate-shaped workpiece, an abrasive having a lifting mechanism and grinding the plate-shaped workpiece held by the holding means, and a thickness measurement device.JP 2016-203 290 A relates to a processing machine capable of achieving efficient processing.SUMMARY OF THE INVENTIONAccording to the arrangement disclosed in Japanese Laid-Open Patent No. 2013-119123, when the inclination of the chuck shaft unit or the spindle unit is varied by the inclination adjusting mechanism, the distance between the device members with the load sensor interposed therebetween is also varied. When the distance between the device elements is increased, the load is less likely to be applied to the load sensor, and thus becomes difficult to be measured by the load sensor.It is therefore an object of the present invention to provide a machining apparatus capable of appropriately measuring a load applied to a machining tool even after a tilt adjustment operation is performed to adjust the extent of parallelism between the holding surface of a chuck table and the lower surface of the machining tool.According to an aspect of the present invention, there is provided a fine adjustment screw assembly for coupling a first part and a second part to each other while maintaining the first part and the second part spaced apart from each other, adjusting a distance between the first part and the second part, and detecting a load applied to the second part, comprising: a first external thread that can be brought into threaded engagement with a first internal thread formed in the first part; a second external thread that is disposed on an extension of an axial direction of the first external thread and is spaced apart axially from the first external thread, that has a thread pitch different from that of the first internal thread, and that can be brought into threaded engagement with a second internal thread formed in the second part; a connection portion through which the first external thread and the second external thread spaced apart from each other, integrally connected to each other and a load sensor housed in the connecting portion under a compressive load.According to another aspect of the present invention, there is provided a machining apparatus comprising: a holding unit for holding a workpiece on a holding surface thereof; a machining unit comprising a spindle and a machining tool attached to the spindle; a vertical movement mechanism for moving a supporting housing supporting the machining unit thereon in vertical directions perpendicular to the holding surface; and a machining unit inclination adjusting mechanism for adjusting an inclination of the machining unit with respect to the holding unit, wherein the machining unit inclination adjusting mechanism comprises: a fine adjustment screw assembly for coupling a first part and a second part to each other while keeping the first part and the second part spaced apart from each other, for adjusting a distance between the first part and the second part and detecting a load applied to the second part, wherein the fine adjustment thread assembly includes: a first external thread that can be brought into threaded engagement with a first internal thread formed in the first part; a second external thread that is disposed on an extension of an axial direction of the first external thread and is axially spaced apart from the first external thread, that has a thread pitch different from that of the first internal thread and that can be brought into threaded engagement with a second internal thread formed in the second part; a connection portion by which the first external thread and the second external thread spaced apart from each other can be integrally connected to each other; and a load sensor accommodated in the connection portion under a compressive load; and the first part includes the support housing and the second part includes the machining unit.According to another aspect of the present invention, there is provided a machining apparatus comprising: a holding unit for holding a workpiece on a holding surface thereof; a base supporting the holding unit thereon; a machining unit comprising a spindle and a machining tool attached to the spindle; a vertical movement mechanism for moving a supporting housing supporting the machining tool thereon in vertical directions perpendicular to the holding surface; and a holding unit inclination adjusting mechanism for adjusting an inclination of the holding unit with respect to the machining unit, wherein the holding unit inclination adjusting mechanism comprises: a fine adjustment thread assembly for holding a first part and a second part while the first part and the second part are held apart from each other, for adjusting a distance between the first part and the second part and detecting a load applied to the second part, wherein the fine adjustment thread assembly includes: a first external thread that can be brought into threaded engagement with a first internal thread formed in the first part; a second external thread that is disposed on an extension of an axial direction of the first external thread and is axially spaced apart from the first external thread, that has a thread pitch different from that of the first internal thread, and that can be brought into threaded engagement with a second internal thread formed in the second part; a connection portion by which the first external thread and the second external thread spaced apart from each other are integrally connected to each other; and a load sensor accommodated in the connection portion under a compressive load; and the first part includes the base and the second part includes the holding unit.The fine adjustment screw assembly according to the present invention is capable of adjusting the distance between the first part and the second part and detecting a load applied to the second part.The machining apparatus according to the present invention is capable of easily adjusting the inclination of the holding unit and the machining unit with respect to each other by rotating the fine adjustment screw assembly, thereby easily adjusting the amount of parallelism between the holding surface of the holding unit and the machining tool of the machining unit.The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and the appended claims with reference to the appended drawings showing a preferred embodiment of the invention.BRIEF DESCRIPTION OF THE FIGURESFIG. 1 is a perspective view of a grinding apparatus as a machining apparatus according to a preferred embodiment of the present invention; FIG. 2 is a cross-sectional cross-sectional view of the grinding apparatus illustrated in FIG. 1 ; FIG. 3 is a cross-sectional view of a fine adjustment screw assembly incorporated in the grinding apparatus shown in FIGS. 1 and 2; FIG. 4 is a cross-sectional view of a retainer tilt adjustment mechanism and components in the vicinity thereof; and FIG. 5 is a cross-sectional view of a machining unit inclination adjusting mechanism and components in the vicinity thereof.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTAs illustrated in FIG. 1, a grinding apparatus 1 functions as a processing apparatus according to a preferred embodiment of the present invention to grind a wafer 100 as a workpiece, and includes a main housing 10 shaped as a rectangular parallelepiped and a column 11 extending upward from the main housing 10.The wafer 100 could be, for example, a circular semiconductor wafer. The wafer 100 has a surface side 101 directed downward in FIG. 1, which has a plurality of components formed thereon, which are protected by a protective tape 105 fastened thereto. The wafer 100 is to be ground on a back side 104 thereof, which is arranged opposite to the surface side 101.The main housing 10 has an opening 13 defined in an upper surface thereof. The grinding device 1 has a holding unit 30 arranged in the opening 13. The holding unit 30 includes a chuck table 31 having a holding surface 32 for holding the wafer 100 thereon and a support member 33 that supports the chuck table 31. As shown in FIG. 2, the support member 33 and the chuck table 31 are fixed to each other by bolts 37.The holding surface 32 of the chuck table 31 illustrated in FIG. 1 is held in fluid communication with a suction source, not illustrated, to hold the wafer 100 under suction with the protective tape 105 disposed between the surface 101 side of the wafer 100 and the holding surface 32. The holding surface 32 thus holds the wafer 100 on the holding surface 32 of the chuck table 31.The chuck table 31 having the wafer 100 held on the holding surface 32 is rotatable about a central table axis 301 (see FIG. 2 ) extending in the Z-axis directions through the center of the holding surface 32 by a rotation mechanism 34 disposed below the support member 33. Therefore, the wafer 100 held on the holding surface 32 is rotated about an axis aligned with the center of the holding surface 32.As shown in FIG. 1, a cover plate 39 is horizontally disposed around the chuck table 31. A bellows cover 12 expandable and contractable in the Y-axis directions is coupled to both ends of the cover plate 39. The holding unit 30 is disposed above and supported on a Y-axis moving mechanism 40.The Y-axis moving mechanism 40 is an example of a horizontal moving mechanism. The Y-axis moving mechanism 40 functions to move the holding unit 30 and a grinding unit 70 acting as a processing means on the column 11 relative to each other in the Y-axis directions parallel to the holding surface 32. According to the present embodiment, the Y-axis moving mechanism 40 functions to move the holding unit 30 relative to the grinding unit 70 in the Y-axis directions. Another example of the horizontal movement mechanism could be a turntable with a plurality of holding units 30 arranged thereon.The Y-axis moving mechanism 40 includes a pair of Y-axis guide rails 42 parallel to the Y-axis directions, a Y-axis moving table 45 slidable on and along the Y-axis guide rails 42, a Y-axis ball screw 43 extending parallel to the Y-axis guide rails 42, a Y-axis servo motor 44 connected to one end of the Y-axis ball screw 43, and a support base 41 supporting thereon the Y-axis guide rails 42, the Y-axis ball screw 43, and the Y-axis servo motor 44.The Y-axis movable table 45 is slidably disposed on the Y-axis guide rails 42. A nut 451 (see FIG. 2 ) is fixed to a lower surface of the Y-axis movable table 45 and operatively screwed over the Y-axis ball screw 43.As illustrated in FIG. 1, when energized, the Y-axis servo motor 44 rotates the Y-axis ball screw 43 about its central axis extending horizontally, causing the nut 451 to move the Y-axis movable table 45 in one of the Y-axis directions along the Y-axis guide rails 42. The support member 33 of the holding unit 30 is disposed on the table 45 movable along the Y axis. Therefore, when the Y-axis movable table 45 moves in one of the Y-axis directions, the holding unit 30 including the chuck table 31 also moves with the Y-axis movable table 45 in the same Y-axis direction. The Y-axis movable table 45 thus constitutes an example of a base supporting the holding unit 30 thereon.According to the present embodiment, the holding unit 30 is moved along the Y-axis directions by the Y-axis moving mechanism 40 substantially between a wafer placement region as a front region in the -Y direction where the wafer 100 is placed on the chuck table 31 and a grinding region as a rear region in the +Y direction where the wafer 100 is ground on the holding surface 32.Moreover, as illustrated in FIG. 1, the pillar 11 is erected on the main housing 10 in a rear portion in the +Y direction. The grinding unit 70 for grinding the wafer 100 on the chuck table 31 and a grinding feed mechanism 50 are mounted on a front surface of the column 11.The grinding feed mechanism 50 functions to move the holding unit 30 and the grinding unit 70 relative to each other in the Z-axis directions, i.e., grinding feed directions, perpendicular to the holding surface 32. According to the present embodiment, the grinding feed mechanism 50 functions to move the grinding unit 70 relative to the holding unit 30 in the Z-axis directions.The grinding feed mechanism 50 includes a pair of Z-axis guide rails 51 parallel to the Z-axis directions, a Z-axis movable plate 53 slidable on and along the Z-axis guide rails 51, a Z-axis ball screw 52 extending parallel to the Z-axis guide rails 51, a Z-axis servo motor 54, and a support sheath 56 attached to a front surface, i.e., a surface side, of the Z-axis movable plate 53 supporting the grinding unit 70 thereon.The Z-axis movable plate 53 is slidably disposed on the Z-axis guide rails 51. A nut 501 (see FIG. 2 ) is fixed to a rear surface, i.e., a rear side, of the Z-axis movable plate 53 and operatively screw-mounted over the Z-axis ball screw 52. The Z-axis servo motor 54 is connected to one end of the Z-axis ball screw 52.When the Z-axis servomotor 54 is energized, it rotates the Z-axis ball screw 52 about its central axis extending vertically, causing the nut 501 to move the Z-axis movable plate 53 in one of the Z-axis directions along the Z-axis guide rails 51. Therefore, when the Z-axis movable plate 53 moves in one of the Z-axis directions, the support housing 56 attached to the Z-axis movable plate 53 and the grinding unit 70 supported on the support housing 56 also move in the same Z-axis direction with the Z-axis movable plate 53. The grinding feed mechanism 50 thus represents an example of a vertical movement mechanism for moving the support housing 56 that supports the grinding unit 70 in vertical directions perpendicular to the holding surface 32.The grinding unit 70 is an example of a processing means. As shown in FIG. 1, the grinding unit 70 includes a spindle housing 71 fixed to the support housing 56, a spindle 72 rotatably supported by the spindle housing 71, a rotation motor 73 for rotating the spindle 72 about its central axis extending vertically, a disc mount 74 mounted on a lower end of the spindle 72, and a grinding disc 75 supported on the disc mount 74.The spindle housing 71 is held in the support housing 56 and extends in the Z-axis directions. The spindle 72 extends perpendicularly to the holding surface 32 of the chuck table 31 in the Z-axis directions and is rotatably supported by the spindle housing 71.The rotation motor 73 is coupled to an upper end of the spindle 72. When the rotary motor 73 is energized, it rotates the spindle 72 about a spindle central axis 701 (see FIG. 2 ) and its central axis extending in the Z-axis directions.The disc mount 74 is shaped as a circular plate and fixed to a lower end, i.e., a distal end, of the spindle 72. The disk mount 74 supports the grinding disk 75 on a lower surface thereof.The grinding wheel 75 has substantially the same diameter as the wheel mount 74, and the grinding wheel 75 has an annular wheel base 76 made of a metallic material such as aluminum alloy or the like, and an annular array of grinding stones 77 fixed to a lower surface of the wheel base 76 along an entire circumferential edge thereof. When the annular array of grinding stones 77 is held in contact with the back surface 104 of the wafer 100 held on the chuck table 31 disposed in the grinding area and is rotated about its central axis by the rotating motor 73 through the spindle 72, the disc mount 74, and the disc base 76, the grinding stones 77 grind the back surface 104 of the wafer 100. The grinding stones 77 are an example of a machining tool. As described above, the grinding unit 70 has the spindle 72, and the spindle 72 supports the grinding stones 77 as a machining tool thereon and rotates the grinding stones 77 to grind the wafer 100.As illustrated in FIG. 1, a thickness measurement unit 60 is disposed on the upper surface of the main housing 10 along the opening 13. The thickness measurement unit 60 is capable of measuring the thickness of the wafer 100 held on the holding surface 32 while making contact with the wafer 100.Specifically, the thickness measurement unit 60 includes a first probe 61 and a second probe 62, which contact the holding surface 32 of the chuck table 31 and the wafer 100, respectively, for measuring the height of the holding surface 32 of the chuck table 31 and the height of the wafer 100. The thickness measuring unit 60 could alternatively include a contactless range finding device, i.e., a laser range finding device, for example, instead of the first probe 61 and the second probe 62.Moreover, as shown in FIG. 1, a linear scale 65 for measuring the vertical position of the grinding unit 70 is disposed on the column 11. The linear scale 65 has a reading device 66 mounted on the Z-axis movable plate 53 for movement therewith in the Z-axis directions, and a scale member 67 disposed on a front surface of one of the Z-axis guide rails 51. When the linear scale 65 is in operation, the reading means 66 reads divisions of the scale member 67 to detect the vertical position of the grinding unit 70 while being moved by the grinding feed mechanism 50.As illustrated in FIG. 2, the holding unit 30 includes holding unit inclination adjusting mechanisms 35. According to the present embodiment, the support member 33 of the holding unit 30 is placed on the Y-axis movable table 45 with the holding unit inclination adjusting mechanisms 35 and a fixed coupling member, not shown, interposed therebetween. According to the present embodiment, specifically, the Y-axis movable table 45 supports the holding unit 30 thereon with the holding unit inclination adjusting mechanisms 35 and the fixed coupling member interposed therebetween.The holding unit inclination adjusting mechanisms 35 have fine adjustment screw assemblies that couple the Y-axis movable table 45 and the holding unit 30 to each other. According to the present embodiment, a fixed link member and two holding unit inclination adjusting mechanisms 35 are disposed between the Y-axis movable table 45 and the holding unit 30 at equal angular intervals of 120 degrees in circumferential directions around the central table axis 301, for example.The fixed coupling member is provided to couple the Y-axis movable table 45 and the holding unit 30 to each other with a fixed distance maintained therebetween at a location where the fixed coupling member is disposed. The holding unit inclination adjusting mechanisms 35 are also provided to couple the Y-axis movable table 45 and the holding unit 30 to each other with a distance maintained therebetween. However, the holding unit inclination adjusting mechanisms 35 are capable of adjusting the distance between the table 45 moved along the Y axis and the holding unit 30 at locations where the holding unit inclination adjusting mechanisms 35 are disposed.With the distance adjustment function, the holding unit inclination adjustment mechanisms 35 can vary the inclination of the holding unit 30 with respect to the table 45 movable along the Y axis, i.e., the inclination of the central table axis 301. The holding unit inclination adjusting mechanisms 35 are thus capable of adjusting the inclination of the holding unit 30 with respect to the grinding unit 70 positioned above the holding unit 30 when the wafer 100 is to be ground on the holding unit 30, and thus adjusting, for example, the amount of parallelism between the holding surface 32 of the holding unit 30 and the lower surfaces of the grinding stones 77 of the grinding unit 70.Moreover, each of the holding unit inclination adjusting mechanisms 35 also serves as a load detecting means for detecting a load applied to the holding surface 32 of the chuck table 31 in directions perpendicular to the holding surface 32, i.e., in the Z-axis directions, or a load applied to the holding unit 30 when the wafer 100 is ground at the holding unit 30.Structural details of the holding unit inclination adjusting mechanisms 35 will be described below. as illustrated in FIG. 3, each of the holding unit inclination adjusting mechanisms 35 includes a bolt 81 having a cylindrical shape and a load sensor, i.e., a force sensor, 89 accommodated in the bolt 81.The bolt 81 has, on its outer circumferential surface, a first external thread 83 having a first thread pitch and a second external thread 85 having a second thread pitch different from the first thread pitch. The second external thread 85 is disposed on an extension of an axial direction, i.e., a longitudinal direction of the bolt 81, of the first external thread 83 and axially spaced apart from the first external thread 83. The bolt 81 also has a connecting portion that connects the first external thread 83 and the second external thread 85 axially spaced apart from each other.As shown in FIG. 4, the first external thread 83 of the bolt 81 can be brought into screw engagement with the table internal thread 452 formed in the table 45 movable along the Y axis, which is also referred to as a first part. The table inner thread 452 is an example of a first inner thread and has a first thread pitch that is the same as the first outer thread 83. a nut, not shown, that can be screwed over the first outer thread 83 could be added, and the first outer thread 83 held in screw engagement with the table inner thread 452 in the first part could be fastened by the nut screwed over it.The second external thread 85 can be brought into screw engagement with an internal holding unit thread 302 formed in the supporting element 33 of the holding unit 30, which is also referred to as a second part. The retainer inner thread 302 is an example of a second inner thread and has a second thread pitch that is the same as the second outer thread 85, but different from the first thread pitch of the table inner thread 452. A nut, not shown, that can be threaded over the second external thread 85 could be added and the second external thread 85, which is held in threaded engagement with the retainer inner thread 302 in the second part, could be fastened by the nut threaded over it.To adjust the inclination of the holding unit 30 with respect to the grinding unit 70, the operator of the grinding apparatus 1 rotates the bolt 81 of one of the holding unit inclination adjusting mechanisms 35 or the bolts 81 of both holding unit inclination adjusting mechanisms 35. Therefore, the Y-axis movable table 45 and the holding unit 30 are moved with respect to the bolt 81 or the bolts 81.As described above, the first pitch of the table inner thread 452 and the second pitch of the holding unit inner thread 302 are different from each other. Therefore, when the pin 81 of one of the holding unit inclination adjusting mechanisms 35 or the pins 81 of both the holding unit inclination adjusting mechanisms 35 are rotated, the distance by which the Y-axis movable table 45 is moved with respect to the pin 81 or the pins 81 and the distance by which the holding unit 30 is moved with respect to the pin 81 or the pins 81 are different from each other. Accordingly, the operator can increase or decrease the distance between the Y-axis movable table 45 and the holding unit 30 at the location where one of the holding unit inclination adjusting mechanisms 35 is disposed or at the locations where both the holding unit inclination adjusting mechanisms 35 are disposed by changing the direction in which the bolt 81 or the bolts 81 are rotated.In this way, the operator can change the distance between the Y-axis movable table 45 and the holding unit 30 at the location where one of the holding unit inclination adjusting mechanisms 35 is disposed or at the locations where both the holding unit inclination adjusting mechanisms 35 are disposed by rotating one of the holding unit inclination adjusting mechanisms 35 or both the holding unit inclination adjusting mechanisms 35 by which the Y-axis movable table 45 and the holding unit 30 are coupled to each other. The operator can thus vary the inclination of the holding unit 30 on the table 45 movable along the Y direction, thereby adjusting the inclination of the holding unit 30 with respect to the grinding unit 70.According to the present embodiment, in order to place the holding unit inclination adjusting mechanisms 35 between the Y-axis movable table 45 and the holding unit 30 and also to rotate the pins 81 of the holding unit inclination adjusting mechanisms 35, the holding unit 30 has openings 303 defined therein, where the pins 81 have ends that are exposed (see FIG. 4 ). In addition, the Y-axis movable table 45 has openings 453 defined therein where the pins 81 have other exposed ends. The other ends of the bolts 81 have respective heads 811 over which a tool such as a wrench or the like can be fitted. The operator inserts the tool into the apertures 453 and causes the tool to act on the heads 811 to thereby rotate the bolts 81.Moreover, as illustrated in FIG. 3, each of the holding unit inclination adjusting mechanisms 35 has an opening 82 defined in an end portion of the bolt 81 where the second external thread 85 is formed. The connecting portion 87 has a load sensor accommodating space 84 defined therein behind the opening 82 for accommodating the load sensor 89 therein.As shown in FIG. 3, the load sensor 89 is inserted into the bolt 81 through the opening 82 therein as indicated by the arrow 401, and accommodated under a compressive load in the load sensor accommodating space 84 in the connecting portion 87. The compressive load is applied as follows. The load sensor 89 has an external thread formed at an upper portion thereof held in screw engagement with an internal thread formed in an upper portion of the load sensor accommodation space 84 to press a lower distal end of the load sensor 89 against the bottom of the load sensor accommodation space 84, thereby applying a pressing load to a piezoelectric element, not shown, disposed centrally in the load sensor 89 with respect to the longitudinal directions in which the load sensor 89 extends. The load sensor 89 thus placed in the load sensor accommodation space 84 is capable of measuring a load applied to the holding unit inclination adjustment mechanism 35, i.e., the bolt 81, in the Z-axis directions representing longitudinal directions of the bolt 81, or in other words, measuring a load applied to the holding unit 30.As shown in FIG. 2, the grinding unit 70 includes machining unit inclination adjusting mechanisms 78. According to the present embodiment, the spindle housing 71 of the grinding unit 70 is placed on a bottom plate 561 (see FIG. 5 ) of the support housing 56 having the machining unit inclination adjusting mechanisms 78 and a fixed coupling member, not illustrated, interposed therebetween. In particular, according to the present embodiment, the support housing 56 supports the grinding unit 70 thereon with the machining unit inclination adjusting mechanisms 78 and the fixed coupling member interposed therebetween.The machining unit tilt adjustment mechanisms 78 include fine adjustment screw assemblies that couple the support housing 56 and the grinding unit 70 together. According to the present embodiment, a fixed coupling member and two machining unit inclination adjusting mechanisms 78 are disposed between the support housing 56 and the grinding unit 70, for example, at equal angular intervals of 120 degrees in circumferential directions about the spindle central axis 701.The fixed coupling member is provided to couple the support housing 56 and the grinding unit 70 to each other with a fixed distance maintained therebetween at a location where the fixed coupling member is disposed.The machining unit inclination adjusting mechanisms 78 are also provided to couple the support housing 56 and the grinding unit 70 to each other with a distance maintained therebetween. However, the machining unit inclination adjusting mechanisms 78 are capable of adjusting the distance between the support housing 56 and the grinding unit 70 at locations where the machining unit inclination adjusting mechanisms 78 are disposed.With the distance adjustment function, the machining unit inclination adjustment mechanisms 78 can vary the inclination of the grinding unit 70 with respect to the support housing 56, i.e., the inclination of the spindle central axis 701. The processing unit inclination adjusting mechanisms 78 are thus capable of adjusting the inclination of the grinding unit 70 with respect to the holding unit 30 disposed below the grinding unit 70 when the wafer 100 is to be ground on the holding unit 30, and thus adjusting, for example, the amount of parallelism between the holding surface 32 of the holding unit 30 and the lower surfaces of the grinding stones 77 of the grinding unit 70.Each of the fine adjustment screw arrangements of the machining unit inclination adjusting mechanisms 78 is identical in structure to the fine adjustment screw arrangement of the holding unit inclination adjusting mechanism 35 shown in FIG. 3.As shown in FIG. 5, the first external thread 83 of the bolt 81 can be brought into threaded engagement with a support housing internal thread 562 formed in the bottom plate 561 of the support housing 56, which is also referred to as a first part. The support housing internal thread 562 is an example of the first internal thread and has a first thread pitch which is the same as the first external thread 83. a nut, not shown, which can be screwed over the first external thread 83 could be added, and the first external thread 83 held in screw engagement with the support housing internal thread 562 in the first part could be fastened by the nut screwed over it.The second external thread 85 can be brought into a screw engagement with an internal grinding unit thread 712 formed in the spindle housing 71 of the grinding unit 70, which is also referred to as a second part. The grinding unit internal thread 712 is an example of the second internal thread and has a second thread pitch that is the same as the second external thread 85, but is different from the first thread pitch of the support housing internal thread 562. A nut, not shown, that may be threaded over the second external thread 85 could be added, and the second external thread 85, held in threaded engagement in the grinding unit internal thread 712 in the second part, could be fastened by the nut threaded over it.To adjust the inclination of the grinding unit 70 with respect to the holding unit 30, the operator rotates the bolt of one of the machining unit inclination adjusting mechanisms 78 or the bolts 81 of both the machining unit inclination adjusting mechanisms 78, When the bolt 81 or the bolts 81 are rotated, the first external thread 83 is axially moved with respect to the support case internal thread 562, and the second external thread 85 is axially moved with respect to the grinding unit internal thread 712. Therefore, the support housing 56 and the grinding unit 70 are moved with respect to the bolt 81 or the bolts 81.As described above, the first pitch of the support housing internal thread 562 and the second pitch of the grinding unit internal thread 712 are different from each other. Therefore, when the bolt 81 of one of the machining unit inclination adjusting mechanisms 78 or the bolts 81 of both the machining unit inclination adjusting mechanisms 78 are rotated, the distance by which the support housing 56 is moved with respect to the bolt 81 or the bolts 81 and the distance by which the grinding unit 70 is moved with respect to the bolt 81 or the bolts 81 are different from each other. Accordingly, the operator can reduce the distance between the support housing 56 and the grinding unit 70, i.e., the distance between the bottom plate 561 of the support housing 56 and the spindle housing 71 of the grinding unit 70 at the location where one of the holding unit inclination adjusting mechanisms 35 is disposed or at the locations where both the holding unit inclination adjusting mechanisms 35 are disposed, by changing the direction in which the bolt 81 or the bolts 81 are rotated.In this way, the operator can change the distance between the support housing 56 and the grinding unit 70 at the location where one of the machining unit inclination adjusting mechanisms 78 is disposed or at the locations where both the machining unit inclination adjusting mechanisms 78 are disposed by rotating one of the machining unit inclination adjusting mechanisms 78 or both the machining unit inclination adjusting mechanisms 78 through which the support housing 56 and the grinding unit 70 are coupled to each other. The operator can thus change the inclination of the grinding unit 70 on the support housing 56, thereby adjusting the inclination of the grinding unit 70 with respect to the holding unit 30.The bolt 81 has a lower end corresponding to the other end of the bolt 81 illustrated in FIG. 4 exposed in a space below the bottom plate 561 of the support case 56, i.e., in a gap between the bottom plate 561 and the disk mount 74 (see FIG. 2 ). The operator inserts the tool into the gap and causes the tool to act on the head 811 at the exposed end of the bolt 81 to thereby rotate the bolt 81.In each of the machining unit inclination adjusting mechanisms 78, the load sensor 89 under a compressive load is accommodated in the load sensor accommodating space 84 in the connecting portion 87 of the bolt 81. The compressive load is applied as follows. The load sensor 89 has an external thread formed at an upper portion thereof held in threaded engagement with an internal thread formed in an upper portion of the load sensor accommodation space 84 to press a lower distal end of the load sensor 89 against the bottom of the load sensor accommodation space 84, thereby applying a pressing load to a piezoelectric element, not shown, disposed centrally in the load sensor 89 with respect to the longitudinal directions in which the load sensor 89 extends. The load sensor 89 thus placed in the load sensor accommodation space 84 is capable of measuring a load applied to the machining unit inclination adjustment mechanism 78, i.e., the bolt 81, in the Z-axis directions representing longitudinal directions of the bolt 81, or in other words, measuring a load applied to the grinding unit 70.Each of the load sensors 89 included in the holding unit inclination adjusting mechanisms 35 and the machining unit inclination adjusting mechanisms 78 is capable of measuring both a negative load applied when the load sensor 89 is expanded and a positive load applied when the load sensor 89 is compressed. The load sensor 89 can measure a load with an adjusting bolt that is compressed when a machining load is applied thereto and that is expanded when no machining load is applied thereto.According to the present embodiment, as described above, the inclination of the holding unit 30 and the grinding unit 70 with respect to each other can be adjusted simply by rotating the holding unit inclination adjusting mechanisms 35 or the machining unit inclination adjusting mechanisms 78, making it easy to adjust the degree of parallelism between the holding surface 32 of the holding unit 30 and the lower surfaces of the grinding stones 77. Moreover, the holding unit inclination adjusting mechanisms 35 and the processing unit inclination adjusting mechanisms 78 can measure loads applied to the holding unit 30 and the grinding unit 70 with the load sensors 89 accommodated in the holding unit inclination adjusting mechanisms 35 and the processing unit inclination adjusting mechanisms 78, respectively.Each of the holding unit inclination adjusting mechanisms 35 has a fine adjustment screw assembly screwed into both the Y-axis movable table 45 and the holding unit 30. Similarly, each of the machining unit tilt adjustment mechanisms 78 includes a fine adjustment threaded assembly threaded into both the support housing 56 and the grinding unit 70. Therefore, even if the distance between members coupled to the holding unit 30 and the grinding unit 70 is increased to adjust the inclination of the holding unit 30 and the grinding unit 70 with respect to each other, the holding unit inclination adjusting mechanisms 35 and the machining unit inclination adjusting mechanisms 78 are less likely to be separated from these members.According to the present embodiment, accordingly, the load sensors 89 of the holding unit inclination adjusting mechanisms 35 and the processing unit inclination adjusting mechanisms 78 are inhibited from becoming load free. The load sensors 89 are thus capable of appropriately measuring loads applied to the holding unit 30 or the grinding unit 70 even after the inclination of the holding unit 30 and the grinding unit 70 with respect to each other is adjusted.According to the present embodiment, while grinding performed on the wafer 100 by the grinding apparatus 1 is interrupted, the inclination of the holding unit 30 and the grinding unit 70 with respect to each other is adjusted, and a load applied to the holding unit 30 or the grinding unit 70 is measured, so that the load applied before the adjustment of the inclination and the load applied after the adjustment of the inclination can be adjusted to prevent the wafer 100 from suffering thickness defects after the adjustment of the inclination.According to the present embodiment, the operator rotates the bolts 81 of the holding unit inclination adjusting mechanisms 35 and the machining unit inclination adjusting mechanisms 78 using a tool. However, the bolts 81 could be rotated by a drive source such as an electric motor or the like.Moreover, the holding unit 30 according to the present embodiment includes the two holding unit inclination adjusting mechanisms 35, and the grinding unit 70 includes the two processing unit inclination adjusting mechanisms 78. However, if the inclination of the holding unit 30 and the grinding unit 70 with respect to each other can be adjusted appropriately, the holding unit 30 may include three or more holding unit inclination adjusting mechanisms 35, and the grinding unit 70 may include three or more processing unit inclination adjusting mechanisms 78.Moreover, the holding unit 30 according to the present embodiment includes the holding unit inclination adjusting mechanisms 35 for adjusting the inclination of the holding unit 30 with respect to the grinding unit 70 and measuring a load applied to the holding unit 30, and the grinding unit 70 includes the processing unit inclination adjusting mechanisms 78 for adjusting the inclination of the grinding unit 70 with respect to the holding unit 30 and measuring a load applied to the grinding unit 70. Instead, the grinding apparatus 1 may be arranged to include either the holding unit inclination adjusting mechanisms 35 or the machining unit inclination adjusting mechanisms 78. With this arrangement, it is possible to adjust the inclination of the holding unit 30 and the grinding unit 70 with respect to each other and also to measure loads.According to the example illustrated in the present embodiment, the grinding apparatus 1 grinds the wafer 100 by feed grinding with the grinding unit 70 having the annular array of grinding stones 77. Instead, the grinding apparatus 1 may grind a workpiece held on the holding surface 32 of the holding unit 30 by means of deep grinding with the grinding unit 70 having the annular array of grinding stones 77.Moreover, the grinding apparatus 1 as a machining unit may include a rotating unit including a single-point cutting tool as a machining tool, and the inclination of the rotating unit and the holding unit 30 with respect to each other may be changed by the holding unit inclination adjusting mechanisms 35 and / or the machining unit inclination adjusting mechanisms 78, and loads applied to the holding unit 30 and / or the rotating unit may be measured by the holding unit inclination adjusting mechanisms 35 and / or the machining unit inclination adjusting mechanisms 78.Alternatively, the grinding apparatus 1 as a machining unit may include a polishing unit including a disk-shaped or an annular polishing pad, and the inclination of the polishing unit and the holding unit 30 with respect to each other may be changed by the holding unit inclination adjusting mechanisms 35 and / or the machining unit inclination adjusting mechanisms 78, and loads applied to the holding unit 30 and / or the polishing unit may be measured by the holding unit inclination adjusting mechanisms 35 and / or the machining unit inclination adjusting mechanisms 78.According to the present embodiment, the holding unit inclination adjusting mechanisms 35 each having the shape of the fine adjustment screw assembly illustrated in FIG. 3 couple the Y-axis movable table 45 as the first part and the holding unit 30 as the second part to each other, and the machining unit inclination adjusting mechanisms 78 each having the shape of the fine adjustment screw assembly illustrated in FIG. 3 couple the support housing 56 as the first part and the grinding unit 70 as the second part to each other.However, the first part is not limited to the Y-axis movable table 45 and the support case 56, and the second part is not limited to the holding unit 30 and the grinding unit 70. Regardless of the nature and characteristics of the first part and the second part, the fine adjustment screw assemblies that couple the first part and the second part together while maintaining them spaced apart from each other are capable of adjusting the distance between the first part and the second part and detecting loads applied to the second part.The present invention is not limited to the details of the preferred embodiment described above. The scope of the invention is defined by the appended claims and all changes and modifications that fall within the equivalents of the scope of the claims are therefore intended to be embraced by the invention.

Claims

A fine adjustment screw assembly for coupling a first part (56) and a second part (70) to each other while maintaining the first part and the second part spaced apart from each other, for adjusting a distance between the first part and the second part and detecting a load applied to the second part, comprising: a first external thread (83) that can be brought into threaded engagement with a first internal thread (452, 562) formed in the first part; a second external thread (85) that is disposed on an extension of an axial direction of the first external thread (83) and is axially spaced apart from the first external thread (83), that has a thread pitch different from that of the first internal thread (452, 562), and that can be brought into threaded engagement with a second internal thread (302, 712) formed in the second part; a connecting portion (87) by which the first male thread (83) and the second male thread (85) spaced apart from each other are integrally connected to each other; and a load sensor (89) accommodated in the connecting portion (87) under a compressive load.A machining apparatus comprising: a holding unit (30) for holding a workpiece (100) on a holding surface (32) thereof; a machining unit (70) including a spindle (72) and a machining tool (77) attached to the spindle (72); a vertical movement mechanism (50) for moving a support housing supporting the machining unit (70) thereon in vertical directions perpendicular to the holding surface (32); and a machining unit inclination adjusting mechanism (78) for adjusting an inclination of the machining unit (70) with respect to the holding unit (30), wherein the machining unit inclination adjusting mechanism (78) includes a fine adjustment screw arrangement for coupling a first part (56) and a second part (70) to each other while keeping the first part (56) and the second part (70) spaced apart from each other, for adjusting a distance between the first part (56) and the second part (70) and detecting a load applied to the second part (70), the fine adjustment thread assembly comprising: a first external thread (83) that can be threadably engaged with a first internal thread (562) formed in the first part; a second external thread (85) that is disposed on an extension of an axial direction of the first external thread (83) and is axially spaced from the first external thread (83), that has a thread pitch different from that of the first internal thread (562), and that can be threadably engaged with a second internal thread (712) formed in the second part; a connecting portion (87) by which the first external thread (83) and the second external thread (85) spaced apart from each other are integrally connected to each other, and a load sensor (89) accommodated in the connecting portion (87) under a compressive load, and wherein the first part includes the support housing (56) and the second part includes the machining unit (70).A machining apparatus comprising: a holding unit (30) for holding a workpiece (100) on a holding surface (32) thereof; a base (45) supporting the holding unit (30) thereon; a machining unit (70) comprising a spindle (72) and a machining tool (77) attached to the spindle (72); a vertical movement mechanism (50) for moving a supporting housing supporting the machining tool (77) thereon in vertical directions perpendicular to the holding surface (32); and a holding unit inclination adjusting mechanism (35) for adjusting an inclination of the holding unit (30) with respect to the machining unit (70), wherein the holding unit inclination adjusting mechanism (35) includes a fine adjustment screw assembly for holding a first part (45) and a second part (30), while maintaining the first part (45) and the second part (30) spaced apart from each other, for adjusting a distance between the first part (45) and the second part (30) and detecting a load applied to the second part (30), the fine adjustment thread assembly comprising: a first external thread (83) that can be brought into threaded engagement with a first internal thread (452, 562) formed in the first part; a second external thread (85) that is arranged at an extension of an axial direction of the first external thread (83) and is axially spaced apart from the first external thread (83), that has a thread pitch different from that of the first internal thread (452, 562), and that can be brought into threaded engagement with a second internal thread (302, 712) formed in the second part; a connecting portion (87), by which the first male thread (83) and the second male thread (85) spaced apart from each other are integrally connected to each other, and a load sensor (89) accommodated in the connecting portion (87) under a compressive load, and wherein the first part includes the base (45) and the second part includes the holding unit (30).

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