Patent Publication Number: US-2011070807-A1

Title: Machining apparatus using rotary grinder

Description:
CROSS-REFERENCE TO RELATED ART 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2009-218427, filed on Sep. 24, 2009; the entire contents of which are incorporated herein by reference. 
     FIELD 
     The present embodiment relates to a machining apparatus for cutting or grooving a workpiece by pressing a rotary grinder on the workpiece such as a semiconductor wafer. 
     BACKGROUND 
     A machining apparatus for cutting or grooving a workpiece by pressing a rotary grinder, which rotates with a high speed, on the workpiece such as a semiconductor wafer described in Patent Publication 1 (U.S. Pat. No. 7,101,256) has been known. 
     The grinder in the machining apparatus described in Patent Publication 1 is a machine tool to cut the workpiece such as a semiconductor wafer, in which a width dimension of the grinder is configured to be small, having a size approximately between 10 μm to 100 μm. 
     With respect to the grinder in process, it is required to supply a cutting fluid in order to cool the grinder or remove working dust. Moreover, it is required to discharge the cutting fluid with high pressure in order to certainly supply the cutting fluid to a contacting portion between the grinder and the workpiece. 
     Therefore, the cutting fluid is supplied by use of a round nozzle having a small diameter, such as a diameter of approximately 1 mm. 
     The nozzle is arranged adjustably to face the cutting portion of the grinder. In order to improve machining accuracy, the nozzle is adjusted to position so that a center of the nozzle and a center of the grinder in a width direction face each other in the same plane. 
     The relationship between the position adjustment of the nozzle and the improvement of the machining accuracy is as follows. Fluid pressure of the cutting fluid discharged from the nozzle is the highest in the center of the nozzle, and gradually lowered outward from the center of the nozzle. Therefore, when the center of the nozzle is shifted from the center of the grinder in the width direction, the fluid pressure of the cutting fluid discharged toward the grinder differs on both sides of the grinder in the width direction, the grinder is distorted due to the fluid pressure difference acting on the both sides of the grinder in the width direction, and the machining accuracy is lowered because the grinder is rotated while being distorted. 
     As described in Patent Publication 1, a position adjustment mechanism with high accuracy is required in order to adjust the position of the nozzle so that the center of the nozzle and the center of the grinder in the width direction face each other on the same plane. As a result, the cost for the machining apparatus has been high. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view illustrating a whole constitution of a first embodiment. 
         FIG. 2  is a perspective view illustrating a part of the first embodiment. 
         FIG. 3  is a perspective view illustrating a part of a second embodiment. 
         FIG. 4  is a partially sectional perspective view of a nozzle according to a third embodiment. 
         FIG. 5  is a partially sectional perspective view of a nozzle according to a fourth embodiment. 
         FIG. 6  is a partially sectional perspective view of a nozzle according to a fifth embodiment. 
         FIG. 7  is a partially sectional perspective view of a nozzle according to a sixth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a machining apparatus includes a disk-like grinder, and a nozzle for discharging a cutting fluid to the grinder. The grinder cuts or grooves a workpiece by rotating. The grinder is provided with a cutting portion at a periphery of the grinder. The nozzle faces the cutting portion in a radial direction of the grinder, and is arranged adjustably in a width direction of the cutting portion. A cross-section shape of the nozzle has a rectangular shape or an elliptic shape in which a dimension in a width direction of the cutting portion is larger than a dimension in a peripheral direction of the cutting portion. 
     Hereinafter, embodiments will be described with reference to the drawings. 
     (First Embodiment) 
     A first embodiment will be described with reference to  FIGS. 1 and 2 . A machining apparatus according to the first embodiment is a dicing apparatus for cutting or grooving a workpiece W such as a semiconductor wafer, and includes a thin disk-like grinder  1 . The grinder  1  is held between two flanges  2 . A rotating shaft  4  of an actuator  3  is approximately horizontally connected to a center of each flange  2  in a radial direction. 
     A periphery of the grinder  1  is provided with a cutting portion  5  that performs cutting and grooving while intervening the workpiece W. The cutting portion  5  is formed to have a width dimension of 10 to 100 μm in a thickness direction of the cutting portion  5 . 
     A chuck table  6  is provided underneath to the grinder  1  connected to the rotating shaft  4 . The chuck table  6  detachably hold the workpiece W by applying a vacuum force or by using a wax. 
     A nozzle  7  is arranged facing the cutting portion  5  in a radial direction of the grinder  1 . The nozzle  7  discharges a cutting fluid L toward an intervening portion between the cutting portion  5  and the workpiece W. The nozzle  7  is held by a holding member  8  being movable in an X direction, a Y direction, and a Z direction, and pivotable in a θ direction. The holding member  8  is driven by an actuator  9 . The nozzle  7  is appropriately adjusted in the X direction, the Y direction, the Z direction, and the θ direction by driving the holding member  8  by the actuator  9 . 
     The actuator  9  may be a screw feeding mechanism, a gear drive mechanism, a piezoelectric actuator, and the like. The X direction as one of the moving directions of the nozzle  7  is a width direction of the grinder  1 . As for the cutting fluid L, pure water or a fluid in which a rust inhibitor is added to pure water is adopted. 
     The holding member  8  is attached with a light source  10  to direct light toward the grinder  1 . The light source  10  is positioned so that a center of a cross-section of light corresponds to a center of the grinder  1  in the width direction in the cutting fluid L discharged from the nozzle  7 . As for the light source  10 , a semiconductor laser and the like is adopted. 
     A light sensor  11  is arranged to face the light source  10  on an opposite side of the grinder  1 , as a detector to detect light emitted from the light source  10 . The light sensor  11  detects an intensity distribution of the light emitted from the light source  10  and outputs the detected intensity distribution to a controller  12 . 
     The light emitted from the light source  10  is blocked by the grinder  1 , or diffusely reflected by the cutting fluid L. Therefore, the intensity distribution of the light that reaches the opposite side of the grinder  1  changes according to a position and angle of the nozzle  7 , i.e. the position and angle of the light source  10 . That is, the position and angle of the nozzle  7  can be expected by detecting the intensity distribution of the light emitted from the light source  10  by the light sensor  11 . 
     The controller  12  controls the actuator  9  based on both the intensity distribution of the light output from the light sensor  11  and an optimum intensity distribution preliminarily stored in a memory device  13 , so as to move the nozzle  7  to an optimum position. 
     The above-mentioned “optimum position of the nozzle  7 ” is the position where the nozzle  7  discharges the cutting fluid so as to machine the workpiece W optimally. In addition, the “optimum intensity distribution” is the light intensity distribution detected by the light sensor  11  when the nozzle  7  is positioned at the optimum position. Namely, when the light sensor  11  detects the optimum intensity distribution, the nozzle  7  can be presumed to be positioned at the optimum position. 
     The memory device  13  stores the optimum position of the nozzle  7  as coordinate data (X, Y, Z, θ). The coordinate data is stored in the memory device  13  by inputting the data through an external terminal  14 . 
     The cross-section of the nozzle  7  when the nozzle  7  is cut in a plane parallel to an opening  7   a  of the nozzle  7  is formed to have a rectangular shape in which a dimension “a” in the width direction of the grinder  1  (in the X direction) is larger than a dimension “b” in the peripheral direction of the grinder  1  (in the Z direction) perpendicular to the X direction. Therefore, when the cutting fluid L is discharged from the nozzle  7  toward the intervening portion between the cutting portion  5  and the workpiece W, the cutting fluid L is discharged widely in the width direction of the grinder  1 . 
     In such a configuration, when the workpiece W is cut or grooved by use of the machining apparatus, the workpiece W is held on the chuck table  6 , the grinder  1  is rotated together with the rotating shaft  4  of the actuator  3 , and the grinder  1  is moved so as to bring the rotating cutting portion  5  to the workpiece W. Then, the cutting fluid L is discharged from the nozzle  7 , and the intensity distribution of light emitted from the light source  10  is detected by the light sensor  11 . 
     The light intensity distribution detected by the light sensor  11  is output to the controller  12 , and compared to the light intensity distribution stored in the memory device  13 . Based on the comparison result, the controller  12  outputs a drive signal to the actuator  9  so as to conform the light intensity distribution detected by the light sensor  11  to the light intensity distribution stored in the memory device  13 . Accordingly, the nozzle  7  is adjusted to be positioned at the optimum position, and the cutting fluid L discharged from the nozzle  7  is supplied optimally for machining. 
     After the nozzle  7  is positioned at the optimum position, the grinder  1  is further moved downward to start cutting or grooving the workpiece W. 
     The machining apparatus according to the first embodiment is operated such that the nozzle  7  is automatically positioned at the optimum position by detecting light emitted from the light source  10  by the light sensor  11  and driving the actuator  9  based on the detected result. 
     Thus, the nozzle  7  can be accurately and repeatably positioned at the optimum position. Also, cutting or grooving of the workpiece W can be carried out with almost the same precision regardless of skill levels of operators who operate the machining apparatus. As a result, chipping or cracking is reduced, and a uniformity of a machining surface quality can be achieved. 
     In addition, the cross-section of the nozzle  7  is formed to have a rectangular shape in which the dimension “a” in the width direction of the grinder  1  (in the X direction) is larger than the dimension “b” in the peripheral direction of the grinder  1  (in the Z direction) perpendicular to the X direction. Accordingly, a range in which fluid pressure of the cutting fluid L discharged from the nozzle  7  is the highest becomes wide in the width direction of the grinder  1 . 
     Thus, even if the nozzle  7  is roughly positioned, the cutting fluid L with the highest fluid pressure to be discharged from the nozzle  7  can be easily positioned at the center position in the width direction of the grinder  1 . Therefore, even if the nozzle  7  is roughly positioned, the fluid pressure of the cutting fluid L discharged from the nozzle  7  can become equal on both sides of the cutting fluid L in the width direction of the grinder  1 . As a result, the fluid pressure of the cutting fluid L acting on the both sides of the grinder  1  in the width direction is prevented from being different from each other caused by the rough positioning of the nozzle  7 . Moreover, the grinder  1  can be prevented from being distorted and rotating while being distorted due to such a fluid pressure difference. Accordingly, the machining apparatus can be maintained with high machining accuracy. Consequently, the actuator  9  may have a lowered positioning function in performance, which results in achievement of low cost of the machining apparatus. 
     The first embodiment was described above explaining the example of the case where the cross-section of the nozzle  7  has a rectangular shape. However, the rectangular shape is not limited to a quadrilateral shape with four right angles. 
     The rectangular shape may be a trapezoidal shape as long as the dimension “a” in the width direction of the grinder  1  is larger than the dimension “b” in the peripheral direction of the grinder  1 . 
     (Second Embodiment) 
     A second embodiment will be described with reference to  FIG. 3 . Note that, in the second embodiment and the other embodiments described below, the same constituent elements as the constituent elements of the aforementioned embodiments are indicated by the same reference numerals, and explanations thereof will not be repeated. 
     The fundamental constitution of the second embodiment is the same as the first embodiment illustrated in  FIGS. 1 and 2 . Meanwhile, the second embodiment includes a nozzle  7 A having a different shape from the nozzle of the first embodiment. 
     The cross-section of the nozzle  7 A when the nozzle  7 A is cut in a plane parallel to the opening  7   a  of the nozzle  7 A is formed to have an elliptic shape in which the dimension “a” in the width direction of the grinder  1  (in the X direction) is larger than the dimension “b” in the peripheral direction of the grinder  1  (in the Z direction) perpendicular to the X direction. Therefore, when the cutting fluid L is discharged from the nozzle  7 A toward the intervening portion between the cutting portion  5  of the grinder  1  and the workpiece W, the cutting fluid L is discharged widely in the width direction of the grinder  1 . 
     In such a configuration, since the cross-section of the nozzle  7 A is formed to have an elliptic shape in which the dimension “a” in the width direction of the grinder  1  (in the X direction) is larger than the dimension “b” in the peripheral direction of the grinder  1  perpendicular to the X direction (in the Z direction), a range in which fluid pressure of the cutting fluid L discharged from the nozzle  7 A is the highest becomes wide in the width direction of the grinder  1 . 
     Thus, even if the nozzle  7 A is roughly positioned, the cutting fluid L with the highest fluid pressure to be discharged from the nozzle  7 A can be easily positioned at the center position in the width direction of the grinder  1 . Therefore, even if the nozzle  7 A is roughly positioned, the fluid pressure of the cutting fluid L discharged from the nozzle  7 A can become equal on both sides of the cutting fluid L in the width direction of the grinder  1 . As a result, the fluid pressure of the cutting fluid L acting on the both sides of the grinder  1  in the width direction is prevented from being different from each other caused by the rough positioning of the nozzle  7 A. Moreover, the grinder  1  can be prevented from being distorted and rotating while being distorted due to such a fluid pressure difference. Accordingly, the machining apparatus can be maintained with high machining accuracy. Consequently, the actuator  9  may have a lowered positioning function in performance, which results in achievement of low cost of the machining apparatus. 
     (Third Embodiment) 
     A third embodiment will be described with reference to  FIG. 4 . The fundamental constitution of the third embodiment is the same as the first embodiment illustrated in  FIGS. 1 and 2 . Meanwhile, the third embodiment includes a nozzle  7 B having a different inside shape from the nozzle in the first embodiment. 
     A peripheral shape of the nozzle  7 B is formed to have a rectangular shape similarly to the nozzle  7  in the first embodiment. The nozzle  7 B in the third embodiment is provided inside with a plurality of flow-straightening plates  15  along a longitudinal direction (the X direction) of a cross-section of the nozzle  7 B. The flow-straightening plates  15  are arranged that the flow-straightening plates  15  straighten flow of the cutting fluid L discharged from the opening  7   a  of the nozzle  7 B in the width direction of the grinder  1  that is the longitudinal direction of the opening  7   a.    
     In such a configuration, the cutting fluid L discharged from the opening  7   a  of the nozzle  7 B toward the grinder  1  is straightened by the flow-straightening plates  15 , so that a disturbed flow when the cutting fluid L is discharged from the opening  7   a  of the nozzle  7 B is prevented. Therefore, the fluid pressure of the cutting fluid L acting on the both sides of the grinder  1  in the width direction can be prevented from being different from each other due to the disturbed flow caused when the cutting fluid L is discharged from the opening  7   a  of the nozzle  7 B. Accordingly, the occurrence of the fluid pressure difference of the cutting fluid L on the both sides of the grinder  1  in the width direction caused by the disturbed flow of the cutting fluid L discharged from the nozzle  7 B can be prevented. Moreover, the grinder  1  can be prevented from being distorted and rotating while being distorted due to such a fluid pressure difference of the cutting fluid L. As a result, high machining accuracy in the machining apparatus can be achieved. 
     (Fourth Embodiment) 
     A fourth embodiment will be described with reference to  FIG. 5 . The fundamental constitution of the fourth embodiment is the same as the third embodiment illustrated in  FIG. 4 . Meanwhile, the fourth embodiment includes a nozzle  7 C having a different peripheral shape from the nozzle in the third embodiment. 
     The peripheral shape of the nozzle  7 C is formed to have an elliptic shape similarly to the nozzle  7 A in the second embodiment. The nozzle  7 C in the fourth embodiment having the elliptic peripheral shape is provided inside with a plurality of flow-straightening plates  15  in a longitudinal direction (the X direction) of a cross-section of the nozzle  7 C. The flow-straightening plates  15  are arranged that the flow-straightening plates  15  straighten flow of the cutting fluid L discharged from the opening  7   a  of the nozzle  7 C in the width direction of the grinder  1  that is the longitudinal direction of the opening  7   a.    
     In such a configuration, the cutting fluid L discharged from the opening  7   a  of the nozzle  7 C toward the grinder  1  is straightened by the flow-straightening plates  15 , so that a disturbed flow when the cutting fluid L is discharged from the opening  7   a  of the nozzle  7 C is prevented. Therefore, the fluid pressure of the cutting fluid L acting on the both sides of the grinder  1  in the width direction can be prevented from being different from each other due to the disturbed flow caused when the cutting fluid L is discharged from the opening  7   a  of the nozzle  7 C. Accordingly, the occurrence of the fluid pressure difference of the cutting fluid L on the both sides of the grinder  1  in the width direction caused by the disturbed flow of the cutting fluid L discharged from the nozzle  7 C can be prevented. Moreover, the grinder  1  can be prevented from being distorted and rotating while being distorted due to such a fluid pressure difference of the cutting fluid L. As a result, high machining accuracy in the machining apparatus can be achieved. 
     (Fifth Embodiment) 
     A fifth embodiment will be described with reference to  FIG. 6 . The fundamental constitution of the fifth embodiment is the same as the third embodiment illustrated in  FIG. 4 . Meanwhile, the fifth embodiment includes a nozzle  7 D, which is different from the third embodiment, and is provided with disturbed flow restrainers  16  formed in a streamlined shape in a flowing direction of the cutting fluid L at end portions of the flow-straightening plates  15  in the opening  7   a  of the nozzle  7 D. 
     In such a configuration, by providing the disturbed flow restrainers  16  at the end portions of the flow-straightening plates  15 , the occurrence of the disturbed flow when the cutting fluid L is discharged from the opening  7   a  of the nozzle  7 D can be further prevented. Accordingly, the fluid pressure difference of the cutting fluid L on the both sides of the grinder  1  in the width direction caused by the disturbed flow can be prevented. Moreover, the grinder  1  can be prevented from being distorted and rotating while being distorted due to such a fluid pressure difference of the cutting fluid L. As a result, high machining accuracy in the machining apparatus can be achieved. 
     (Sixth Embodiment) 
     A sixth embodiment will be described with reference to  FIG. 7 . The fundamental constitution of the sixth embodiment is the same as the fifth embodiment illustrated in  FIG. 6 . Meanwhile, the sixth embodiment includes a nozzle  7 E having a different peripheral shape from the nozzle in the fifth embodiment. 
     The peripheral shape of the nozzle  7 E is formed to have an elliptic shape similarly to the nozzle  7 A in the second embodiment. The nozzle  7 E in the sixth embodiment having the elliptic peripheral shape is provided inside with the flow-straightening plates  15  in a longitudinal direction (the X direction) of a cross-section of the nozzle  7 E. The nozzle  7 D is provided with the disturbed flow restrainers  16  formed in a streamlined shape in a flowing direction of the cutting fluid L at the end portions of the flow-straightening plates  15  in the opening  7   a  of the nozzle  7 E. 
     In such a configuration, by providing the disturbed flow restrainers  16  at the end portions of the flow-straightening plates  15 , the occurrence of the disturbed flow when the cutting fluid L is discharged from the opening  7   a  of the nozzle  7 E can be further prevented. Accordingly, the fluid pressure difference of the cutting fluid 
     L on the both sides of the grinder  1  in the width direction caused by the disturbed flow can be prevented. Moreover, the grinder  1  can be prevented from being distorted and rotating while being distorted due to such a fluid pressure difference of the cutting fluid L. As a result, high machining accuracy in the machining apparatus can be achieved. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.