• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    In a preliminary grinding step, a plate-like workpiece held on a chuck table is ground using a grinding unit until the thickness of the plate-like workpiece is reduced to a thickness greater than a final thickness. In a strength measuring step subsequent to the preliminary grinding step, the thickness of the plate-like workpiece held on the chuck table is measured using a thickness measuring unit at a plurality of measuring positions at different distances from the axis of rotation of the chuck table. In a determining step subsequent to the starch measuring step, the difference between a maximum value and a minimum value of plural strengths measured in the starch measuring step is calculated, and it is determined whether the above calculated difference between the maximum value and the minimum value is less than or equal to the difference between a maximum allowable strength and a minimum allowable strength for the final strength is or not.
    公开号:AT515950A2
    申请号:T50580/2015
    申请日:2015-07-03
    公开日:2016-01-15
    发明作者:
    申请人:Disco Corp；
    IPC主号:
    专利说明:

    STATE OF THE ART
    Field of the invention
    The present invention relates to a grinding method for grinding a plate-like or plate-shaped workpiece for reducing the thickness of the plate-like workpiece.
    Description of the Related Art
    When grinding a plate-like workpiece for
    Reducing the thickness of the plate-like workpiece, the thickness of the plate-like workpiece is measured during grinding. At the time when the thickness of the plate-like workpiece is reduced to a target thickness, the grinding is terminated. A method for measuring the thickness of the plate-like workpiece includes a method using contact strength measurement as described in Japanese Patent Publication No. 5025200 and a method using non-contact strength measuring devices as described in Japanese Patent Laid-Open Publication No. 2009-50944.
    However, there is a case where the thickness of the ground plate-like workpiece varies according to the radial position on the plate-like workpiece, i. according to the distance to the axis of rotation of a clamping turntable which holds the plate-like workpiece. In order to cope with such thickness variations of the plate-like workpiece, Japanese Patent Laid-Open No. 2011-235388 discloses a technique of measuring the thickness of a plate-like workpiece held on a clamping turntable at a plurality of positions different distances from the axis of rotation of the chuck table, storing the measured data to the thickness of the plate-like Workpiece and use the measurement data as management data for determining whether or not any device (chip) obtained by dividing the plate-like workpiece is good. Further, Japanese Patent Laid-Open Publication No. 2008-264913 discloses a technique of measuring the thickness of a plate-like workpiece held on a clamping turntable at a plurality of positions different distances from the axis of rotation of the chuck table and adjusting the inclination of the chuck table according to the measurement data of the thickness of the plate-like workpiece thereby reducing thickness variations of the plate-like workpiece.
    BRIEF SUMMARY OF THE INVENTION
    In the method described in Japanese Patent Laid-Open Publication No. 2011-235388, the thickness-of-plate-type workpiece measured data can be used to determine whether each chip is good or not. However, there is no guarantee that the Strength of each chip is within a target tolerance, so that the yield can not be improved.
    Further, in the method described in Japanese Patent Laid-Open No. 2008-264913,
    Thickness variations of the plate-like workpiece are reduced according to the distance to the rotation axis of the chuck table by adjusting the inclination of the chuck table. However, there is no guarantee that the strength of each chip will be within a target tolerance.
    It is therefore an object of the present invention to provide a grinding method for a plate-like workpiece which maximizes the number of chips whose thickness is within the tolerance, the chips being obtained by dividing a plate-like workpiece, thereby improving the yield.
    According to one aspect of the present invention, there is provided a grinding method for a plate-like workpiece using a grinding apparatus comprising a chuck table for holding a plate-like workpiece, rotating means for rotating the chuck table, and abrasive with an abrasive member for grinding the upper surface of the plate-like workpiece held on the chuck table the thickness of the plate-like workpiece is reduced, starch measuring means for non-contact measuring the thickness of the plate-like workpiece ground by the abrasive, and measuring position moving means for moving the starch measuring means in the radial direction of the chuck table, the grinding method for a plate-like workpiece initiating a grinding step of grinding the plate-like workpiece; on the
    A chuck table is held, using the abrasive, until the thickness of the plate-like workpiece is reduced to a thickness greater than a predetermined final thickness, a strength measuring step of measuring the thickness of the plate-like workpiece held on the chuck table using the thickness-measuring means at a plurality Measuring positions at different distances from the axis of rotation of the chuck table when moving the starch measuring means in the chucking table radial direction after performing the preliminary grinding step, a determining step of calculating the difference between a maximum value and a minimum value of a plurality of thicknesses measured in the starch measuring step, and determining whether the above-calculated difference between the maximum value and the minimum value is less than or equal to the difference between a maximum allowable strength and a minimum allowable strength for the predetermined final thickness ; and a finishing grinding step of adjusting a grinding amount for the plate-like workpiece according to the determination result in the determining step and then grinding the plate-like workpiece according to the grinding amount using the abrasive, thereby reducing the thickness of the plate-like workpiece to the predetermined final thickness.
    Preferably, if it is determined in the determining step that the difference between the maximum value and the minimum value is less than or equal to the difference between the allowable maximum strength and the allowable minimum thickness, the plate-like workpiece is ground in the finishing grinding step until the minimum value becomes greater than or equal to the minimum thickness and the maximum value less than or equal to the maximum strength.
    Preferably, if it is determined in the determining step that the difference between the maximum value and the minimum value is greater than the difference between the allowable maximum strength and the allowable minimum thickness, the plate-like workpiece is ground in the finishing grinding step until the range of portions in which the thickness of the plate-like workpiece is within the range from the maximum allowable strength to the minimum allowable strength.
    According to the grinding method of the present invention, the final thickness in the finishing grinding step is controlled according to whether or not the thickness variation range of the plate-like workpiece ground in the initial grinding step is less than or equal to the final thickness tolerance. Accordingly, the range of portions where the thickness of the plate-like Workpiece within the tolerance for final strength. As a result, of the number of chips obtained by dividing the plate-like workpiece, the number of chips whose thickness is within the tolerance for the final thickness can be maximized, thereby improving the yield.
    In the case where the range of thickness variations of the plate-like workpiece ground in the initial grinding step is less than or equal to the final thickness tolerance, the plate-like workpiece is ground until the minimum value becomes greater than or equal to the minimum thickness and the maximum value decreases than or equal to the maximum strength. Accordingly, the thickness of the plate-like workpiece can be made to be within the tolerance at all positions. As a result, the thicknesses of all of the chips obtained by dividing the plate-like workpiece can be made to be within the tolerance, whereby the yield is improved.
    In the case where the range of thickness variations of the plate-like workpiece ground in the initial grinding step is greater than the final thickness tolerance, the plate-like workpiece is ground until the range of portions where the thickness of the plate-like workpiece is within the tolerance becomes maximum becomes. Accordingly, of the number of chips obtained by dividing the plate-like workpiece, the number of chips whose strengths are within the tolerance for the final thickness can be maximized, whereby the yield is improved.
    The above and other objects, features and advantages of the present invention and the manner of carrying out the same will become apparent from a consideration of the following description and appended claims with reference to the appended claims
    Drawings which illustrate some preferred embodiments of the invention will be more apparent and best illustrate the invention itself.
    BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a grinding apparatus; FIG. Fig. 2 is a perspective view showing a chuck table, abrasives and starch measuring means; FIG. Fig. 3 is a partial sectional side view showing the chuck table, abrasives, starch measuring means and
    Measuring position moving means; FIG. 4 is a top view showing measurement positions against which the thickness of the plate-like workpiece is measured; FIG. 5 is a graph showing the distribution of the
    Measuring positions with respect to the distance from the center of the plate-like workpiece and the rotation angle of the plate-like workpiece shows; FIG. 6 is a graph showing the distribution of the
    Measuring positions with respect to the distance from the center of the plate-like workpiece and the distance of a measuring path shows; FIG. Fig. 7 is a graph showing the thickness of the plate-like workpiece measured in a measuring step; FIG. Fig. 8 is a graph showing a first example of the thickness of the plate-like workpiece ground in a final grinding step; FIG. Fig. 9 is a graph showing a second example of the thickness of the plate-like workpiece ground in the finishing grinding step; and FIG. Fig. 10 is a diagram showing a third example of the thickness of the plate-like workpiece which was ground in the final grinding step.
    DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
    With reference to FIG. 1, a grinding apparatus 10 is shown. The grinding apparatus 10 is a device for grinding a plate-like workpiece, such as a wafer, on which a plurality of components are formed, whereby the thickness of the plate-like workpiece is reduced to a predetermined thickness. The grinding apparatus 10 includes a robot 111 for loading / unloading the plate-like workpiece, positioning means 12 for positioning the plate-like workpiece before grinding, feeding means 112 for transferring the plate-like workpiece positioned by the positioning means 12, three chuck tables 14a, 14b and 14c for holding the plate-like workpiece transferred by the feed means 112, a turn table 13 for moving the chuck tables 14a to 14c, two pieces of grinding means 15a and 15b for grinding the plate-like work held on the chuck tables 14a to 14c, two pieces of feed means 16a and 16b for respectively moving the abrasives 15a and 15b, two pieces of thickness measuring means 171 and 172 for measuring the thickness of the plate-like workpiece held on the chuck tables 14a to 14c, return means 113 for transferring the plate-like workpiece after grinding and cleaning means 18 for cleaning the plate-like workpiece which has been transferred by the return means 113.
    The robot 111 functions to take out the plate-like workpiece stored in a cassette 21a before grinding and transferring it to the positioning means 12, and also functions to transfer the plate-like workpiece cleaned by the cleaning means 18 to a cassette 21b and after grinding Store it in the cassette 21b. Each of the chuck tables 14a to 14c has a holding surface parallel to an XY plane defined by the ± X direction and the ± Y direction. The holding surface is suitable for holding the plate-like workpiece under suction. Each of the chuck tables 14a to 14c is rotatable by rotation means 19 (see FIG. 3) for rotation about an axis parallel to the ± Z direction perpendicular to the XY plane.
    The turntable 13 is rotatable about an axis parallel to the ± Z direction. The chuck tables 14a to 14c are located on an upper surface of the turntable 13 parallel to the XY plane at three positions equally spaced from the center (axis) of the turntable 13 in the radial direction and equidistant from each other in the circumferential direction. By the rotation of the turntable 13, each of the chuck tables 14a to 14c is selectively taken
    Loading / unloading position in which the plate-like workpiece is loaded before the grinding by the feeding means 12 or unloaded after grinding by the returning means 113, a first grinding position in which the plate-like workpiece is ground by the grinding means 15a, and a second grinding position in which the plate-like workpiece by the abrasive 15b is ground.
    The feed means 112 functions to transfer the plate-like workpiece positioned by the positioning means 12 to one of the chuck tables 14a to 14c arranged at the loading / unloading position. Accordingly, the plate-like workpiece is held on one of the chuck tables 14a to 14c in the state where the center of the plate-like workpiece coincides with the center (axis) of the chuck table set at the loading / unloading position.
    Each of the abrasives 15a and 15b includes a rotating shaft that extends in the ± Z direction, a mount 150 attached to the lower end of the rotating shaft, and a grinding wheel 151 attached to the lower surface of the mount 150. A plurality of abrasion members 22 are attached to the lower surface of the grinding wheel 151. Abrasive members 22 in abrasive 15a are intended for rough grinding, while abrading members 22 are intended for finish grinding in abrasive 15b. Although the grinding apparatus 10 shown in FIG. 1, which includes two pieces of abrasives 15a and 15b, the grinding apparatus useful in the present invention may include a single abrasive. In this case, the turntable 13 may be omitted.
    Each of the feeding means 16a and 16b includes a ball screw 160 extending in the ± Z direction, a guide rail 161 parallel to the ball screw 160, a motor 162 for rotating the ball screw 160, and a movable member 163 formed by the rotation of the ball screw 160 as shown in FIGS Guide rail 161 is guided in the ± Z-direction is movable. The movable member 163 of the feeding means 16a is fixed to the abrasive 15a, and the movable member 163 of the feeding means 16b is fixed to the abrasive 15b. Accordingly, when the motor 162 is operated to rotate the ball screw 160, the movable member 163 is moved in the ± Z direction to thereby move each of the abrasives 15a and 15b vertically. More specifically, when the applying means 16a is operated to move the abrasive 15a in the -Z direction, the abrasion members 22 in the abrasive 15 are abutted against the upper surface of the plate-like workpiece held on one of the chuck tables 14a to 14c attached to the first one Grinding position is set, wherein the grinding wheel 151 is rotated in the abrasive 15a and the chuck table 14 (which constitutes one of the chuck tables 14a to 14c) set at the first grinding position is also rotated, whereby rough grinding is performed on the plate-like workpiece. Likewise, when the applying means 16b is operated to move the abrasive 15b in the -Z direction, the abrasion members 22 in the abrasive 15b are abutted against the upper surface of the plate-like workpiece held on one of the chuck tables 14a to 14c at the second grinding position is set, wherein the grinding wheel 151 is rotated in the abrasive 15b and the chuck table 14, which is set at the second grinding position, is also rotated, whereby finish grinding is performed on the plate-like workpiece.
    The starch measuring means 171 is a contact strength measuring agent as described, for example, in Japanese Patent Publication No. 5025200. The starch measuring means 171 has two contact members with one of the two contact members passing with the upper surface of the plate-like workpiece and the other contact member passing with the upper surface of the chuck table 14 set at the first grinding position. The height difference between the two contact members is determined as the thickness of the plate-like workpiece held on the chuck table 14 set at the first grinding position. The starch measuring means 171 can measure the thickness of the plate-like workpiece during grinding of the plate-like workpiece by the abrasive means 15a.
    The starch measuring means 172 is a non-contact starch measuring agent as described in, for example, Japanese Patent Laid-Open Publication No. 2009-50944. The starch measuring means 172 functions to measure the thickness of the plate-like workpiece held on the chuck table 14 set at the second grinding position. The starch measuring means 172 can measure the thickness of the plate-like workpiece during grinding of the plate-like workpiece by the abrasive 15b. Since the starch measuring means 172 is non-contact, scratching of the upper surface of the plate-like workpiece can be avoided.
    As shown in FIG. 2, the thickness measuring means 172 includes a measuring portion 721 for measuring the thickness of a plate-like workpiece 30 held on the chuck table 14, an arm portion 722 for supporting the measuring portion 721, and a shaft portion 723 for supporting the arm portion 722. The chuck table 14 constitutes one of the chuck tables 14a to 14c represented in FIG. 1 are shown.
    The shaft portion 723 is rotatable about an axis 729 (see FIG.3) parallel to the ± Z direction. The shaft portion 723 is moved by measuring position moving means 173 (see FIG. 3), thereby pivoting the arm portion 722. As a result, there is a change in the measuring position where the measuring portion 721 located at the front end of the arm portion 722 measures the thickness of the plate-like workpiece 30. Accordingly, by operating the measuring-position moving means 173, the distance between the measuring position and the rotational axis of the chuck table 14 is changed.
    The measuring section 721 is configured to measure the thickness of the plate-like workpiece 30, for example, according to the interference of light. More specifically, the measuring section 721 generates light having a transmission wavelength to the plate-like workpiece 30, and supplies this light to the plate-like workpiece 30. This light is reflected on the plate-like workpiece 30, and resulting reflected light from the plate-like workpiece 30 is detected by the measuring section 721. The light to be supplied from the measuring section 721 has a relatively wide spectrum, and the light is reflected both on the upper surface of the plate-like workpiece 30 and on the lower surface of the plate-like workpiece 30, so that interference between the reflected light from the upper surface of the plate-like By analyzing the spectral distribution of the interference light due to this interference, the thickness of the plate-like workpiece 30 is measured. This measuring method does not require measuring the height of the holding surface of the chuck table 14. Accordingly, the thickness of the plate-like workpiece 30 at any measuring position can be accurately measured even if the holding surface of the chuck table 14 has unevenness.
    The abrasion members 22 included in the abrasive 15b are annularly arranged along the outer periphery of the grinding wheel 151. When the grinding wheel 151 is rotated, the abrasion members 22 are also rotated so as to pass through the rotational axis of the chuck table 14. The measuring portion 721 in the area where the abrasion members 22 do not abut the upper surface of the plate-like workpiece 30. Accordingly, the thickness of the plate-like workpiece 30 during grinding of the plate-like workpiece 30 by the abrasive 15b can be measured.
    As shown in FIG. 3, the measuring position moving means 173 includes a motor 731 capable of operating in the forward and reverse directions, and a belt 732 for transmitting the torque to the shaft portion 723, so that the shaft portion 723 can be rotated by the operation of the motor 731. When the measuring position moving means 173 is operated to rotate the shaft portion 723, the measuring position of the measuring portion 721 in the radial direction of the chuck table 14 is moved. On the other hand, when the rotating means 19 is operated to rotate the chuck table 14, the plate-like workpiece 30 held on the chuck table 14 is rotated. Accordingly, the measuring portion 721 can measure the thickness of the plate-like workpiece 30 at almost all positions other than the central position of the plate-like workpiece 30.
    A grinding method for grinding the plate-like workpiece 30 using the grinding apparatus 10 will now be described. (1) holding step
    The plate-like workpiece 30 is taken out of the cassette 21 a by the robot 111 and then transferred to the positioning means 12. Thereafter, the plate-like workpiece 30 is set by the positioning means 12 at a predetermined position and next transferred by the feeding means 112 to the chuck table 14 at the loading / unloading position. The plate-like workpiece 30, which is disposed on the chuck table 14, is held thereon by suction. (2) First grinding step
    Thereafter, the turntable 13 is rotated to the first grinding position for moving the chuck table 14 holding the plate-like workpiece 30. Thereafter, the plate-like workpiece 30 held on the chuck table 14 is rough ground by the grinding means 15a. During this rough grinding, the thickness of the plate-like workpiece 30 is measured by the thickness measuring means 171. When the thickness of the plate-like workpiece 30 becomes a predetermined thickness greater than a predetermined final thickness, the first grinding step is completed. (3) Second grinding step
    Thereafter, the turntable 13 for moving the chuck table 14 holding the plate-like workpiece 30 which has been ground by the grinding means 15a is rotated to the second grinding position. Thereafter, the plate-like workpiece 30 held on the chuck table 14 is ground at the second grinding position by the abrasive 15b. During this grinding, the thickness of the plate-like workpiece 30 is measured by the thickness measuring means 172. When the thickness of the plate-like workpiece 30 becomes the predetermined final thickness, the second grinding step is completed. The second grinding step is described in more detail. The second grinding step is composed of an initial grinding step of grinding the plate-like workpiece 30 until the thickness of the plate-like workpiece 30 becomes a predetermined thickness greater than the final thickness, a strength measuring step of measuring the thickness of the plate-like workpiece 30 at a plurality of positions different from the axis of rotation of the plate A chuck table 14, a determining step of determining how to finish grinding according to the thickness measured in the starch measuring step, and a finishing grinding step of carrying out the finishing grinding according to the determination result in FIG
    Determination step together. (3-1) Introductory grinding step
    The plate-like workpiece 30 held on the chuck table 14 is ground by the abrasive 15b for reducing the thickness of the plate-like workpiece 30. During this initial grinding, the thickness of the plate-like workpiece 30 is measured by the thickness measuring means 172. When the starch measured by the starch measuring means 172 becomes a predetermined thickness greater than the final thickness, the initial grinding step is completed. (3-2) Amount of starch
    The thickness of the plate-like workpiece 30 ground in the preliminary grinding step is measured at a plurality of positions by the thickness measuring means 172. For example, as shown in FIG. 4, a plurality of measuring positions 41a, 41b, 41c, and 41d are arranged on a plurality of concentric circles of different diameter respectively around the center of the plate-like workpiece 30, and the thickness of the plate-like workpiece 30 at these measuring positions 41a to 41d is measured by the thickness measuring means 172. More specifically, the measuring section 721 of the starch measuring means 172 is positioned by the measuring position moving means 173 at a predetermined distance from the center of the chuck table 14. In this state, the chuck table 14 is rotated by the rotating means 19, and the thickness of the plate-like workpiece 30 is predetermined
    Time intervals measured by the starch measuring means 172. Since the center of the plate-like workpiece 30 coincides with the center of the
    Clamping table 14 coincides, the thickness of the plate-like workpiece 30 can be measured at a plurality of positions, which are arranged on a first circle around the center of the plate-like workpiece 30.
    Thereafter, the measuring portion 721 of the starch measuring means 172 is moved by the measuring position moving means 173 in the radial direction of the chuck table 14, whereby the distance between the center of the measuring table 14 and the measuring position of the
    Measuring section 172 is changed. In this state, the turntable 14 is rotated by the rotating means 19, and the thickness of the plate-like workpiece 30 is measured at predetermined time intervals by the thickness measuring means 172. Accordingly, the thickness of the plate-like workpiece 30 can be measured at a plurality of positions set on a second circle of different diameter from the first circle around the center of the plate-like workpiece 30. This process is repeated predetermined times. As a result, the thickness of the plate-like workpiece 30 can be measured at a plurality of positions set on each of a plurality of concentric circles of different diameter around the center of the plate-like workpiece 30e. In FIG. 4, the plurality of concentric circles are denoted by the various radial positions 41a to 41d.
    When the time intervals of measuring the thickness of the plate-like workpiece 30 are determined by the measuring means 172 and the rotational speed of the chuck table 14 to be rotated by the rotating means 19 is also set, the measuring positions 41a to 41d at which the thickness measuring means 172 is the thickness of the plate-like workpiece 30, as shown in FIG. 5, all of the measuring positions 41 a to 41 have the same angular intervals (horizontal axis) from circumferential measuring positions irrespective of the distance (vertical axis) to the center of the plate-like workpiece 30.
    However, as shown in FIG. 6, the distance (horizontal axis) of a measurement path on each of the concentric circles is different. That is, the longer the distance (vertical axis) to the center of the plate-like workpiece 30, the greater the length of each circle, i. of the measurement path, and therefore the spacing between any adjacent one of the circumferential measurement positions is greater. In other words, the longer the distance to the center of the plate-like workpiece 30, the larger the range of portions of the plate-like workpiece 30 at which the thickness at the circumferential measuring positions is measured and represented by measured values. Conversely, the distance to the center of the plate-like workpiece 30 is shorter, the smaller the range of such portions of the plate-like workpiece 30. Considering this fact, the following determining step is carried out according to the range of such portions of the plate-like workpiece 30 which is measured by the measured values Number of measurements is shown. Alternatively, such control may be performed that the spacing between the circumferential measurement positions on the measurement path becomes equal among the concentric circles. More specifically, this control can be performed by changing the rotational speed of the chuck table 14 for the measuring positions 41a to 41d or by changing the scanning time for the measuring positions 41a to 41d. For example, the rotational speed of the chuck table 14 is increased as the distance to the center of the chuck table 14 increases. Alternatively, the sampling time decreases as the distance to the center of the chuck table 14 increases. As a result, the measurement density on the measurement path among the concentric circles becomes equal. In this case, it is not necessary to multiply the distance from the center of the chuck table 14 to each measurement position in calculating the median or average of measurement values of the strength in the following determination step. For example, in the case where there are five measurement positions, the third value at count from the largest value and from the smallest value is defined as the median value. In the case where the number of measurement positions is even, the average of the two middle values is defined as the median value. For example, in the case where there are six measurement positions, the average of the third value in counting becomes the largest value and the third value counts from the smallest value defined as the median value. (3-3) Determination step
    According to the plurality of measured values of the thickness measured in the above-mentioned strength measuring step, a control section (not shown) such as a calculator incorporated in the grinding apparatus 10 determines a grinding amount by which finish grinding should be performed in the next step. For example, reference numeral 431 in FIG. 7 of the more measured values of starch measured in the starch measuring step. A minimum value 432 and a maximum value 433 are extracted from the plurality of measurement values 431 to calculate a difference 434 between the maximum value 433 and the minimum value 432.
    Reference numeral 421 in FIG. 7 denotes a target end thickness of the plate-like workpiece 30. The target end thickness 421 may have a predetermined tolerance. Reference numerals 422 and 423 denote a permissible minimum value (permissible minimum thickness) or. a permissible maximum value (maximum permissible strength). A difference (tolerance) 424 between the allowable maximum value 423 and the allowable minimum value 422 is stored in advance and compared with the difference 434 calculated above.
    On the assumption that the finishing grinding step is performed under the same conditions as those of the previous step, the thickness of the plate-like workpiece 30 can be reduced by the same amount as a whole. Accordingly, under this condition, the difference between a maximum value and a minimum value for the thickness of the plate-like workpiece 30 at the end of the Finish loop equal to the difference 434.
    With reference to FIG. 8, the thickness of the plate-like workpiece 30 at the end of finish grinding is indicated by reference numeral 441. The magnitude 441 has a maximum 443 and a minimum 442, and the difference therebetween is indicated by reference 444. In the case where the difference 434, FIG. 7, is less than or equal to the tolerance 424, the difference 444 shown in FIG. 8, less than or equal to tolerance 444, as shown in FIG. 8gezeigt. Accordingly, the following finish grinding step is performed such that the minimum value 442 becomes greater than or equal to the minimum allowable strength 422 and the maximum value 443 becomes less than or equal to the allowable maximum strength 423. As a result, the thickness 441 of the plate-like workpiece 30 can be made to be within the tolerance 424 at all positions on the plate-like workpiece 30. The difference obtained by subtracting the allowable minimum strength 422 from the minimum value 432 shown in FIG. 7 is defined as a maximum grinding amount, and the difference obtained by subtracting the allowable maximum strength 423 from the maximum value 433 shown in FIG. 7 is defined as a minimum grinding amount. Then the
    For example, the average of the minimum grinding amount and the maximum grinding amount will be selected as the grinding amount in the case of finish grinding in the range from the minimum grinding amount to the maximum grinding amount
    Finish grinding used. Accordingly, even if the thickness of the plate-like workpiece 30 at any position where the measurement was not made is smaller than that
    Minimum value 432 or larger than the maximum value 433, it is possible to minimize the possibility that the thickness 441 of the plate-like workpiece 30 at the end of finish grinding could be outside the tolerance 424 at any position.
    In the case where the difference 434 between the maximum value 433 and the minimum value 432 is greater than the tolerance 424, the difference 444 between the maximum value 443 and the minimum value 442 of the thickness 441 of the plate-like workpiece 30 at the end of finish grinding also becomes larger than the tolerance 424. Accordingly, in this case, the thickness 441 of the plate-like workpiece 30 may be out of tolerance 424 at some positions. In this case, the grinding amount in the finishing grinding step to be executed later is determined such that the range of portions of the plate-like workpiece 30 in which the thickness 441 is within the tolerance 424 becomes maximum.
    For example, in the case where the plate-like workpiece 30 is ground until the minimum value 442 of the thickness 441 of the plate-like workpiece 30 reaches the minimum allowable thickness 422 at the end of finish grinding, as shown in FIG. 9, portions at which the thickness 441 of the plate-like workpiece 30 becomes larger than the allowable maximum thickness 423. Further, in the case where the plate-like workpiece 30 is ground, the maximum value 443 of the thickness 441 of the plate-like workpiece 30 is at the end of finish grinding The permissible maximum value 423, as shown in FIG. 10, reaches portions at which the thickness 441 of the plate-like workpiece 30 becomes smaller than the allowable minimum thickness 422.
    In this way, the strength of the plate-like
    Workpiece 30, which was ground in the preliminary grinding step, measured by the strength measuring means 172 for obtaining the measured data 431. In the case where the difference 434 between the minimum value 432 and the maximum value 433 of the measurement data 431 is larger than the tolerance 424, the grinding amount becomes
    Finishing grinding is controlled with reference to the measurement data 431 so that the range of portions where the thickness of the plate-like workpiece 30 at the end of finish grinding is within the tolerance becomes maximum.
    For example, the control of the grinding amount is performed as follows: 1. Of the measurement data 431 obtained in the preliminary grinding step, the median value of the measurement data at the measurement position 41a, the median value of the measurement data at the measurement position 41b, the median value of the measurement data at the measurement position 41c, and the median value of the Measurement data determined at the measuring position 41d. 2. The median value at each measurement position is multiplied by the distance from the center of the plate-like workpiece 30 to the measurement position for obtaining a product. Then, the products for all the measurement positions are added to obtain a total. Then, this sum is divided by the sum of the distances from the center of the plate-like workpiece 30 to all the measuring positions, whereby the median value of the starch is obtained. More specifically, assuming that the measuring positions are the plural measuring positions 41a to 41d on the concentric circles around the center of the plate-like workpiece 30, and the distances from the center of the plate-like workpiece 30 to these measuring positions 41a, 41b, 41c and 41d are denoted by the reference signs ra, rb, rc and rd respectively, the median value of the magnitude is represented by the following expression.
    Median value of the thickness of the plate-like workpiece 30 ground in the preliminary grinding step = (median value of the strength at the measuring position 41a χ ra + median value of the strength at the measuring position 41b χ rb + median value of the strength at the measuring position 41c χ rc + median value of the strength at the measuring position 41d χ rd) / (ra + rb + rc + rd). 3. In the finish grinding step of grinding the plate-like workpiece 30 after performing the preliminary
    Grinding step, the plate-like workpiece 30 is ground until the median value obtained above becomes a target value 425 for the final thickness. The target value 425 is set to an intermediate value in the tolerance 424.
    In fact, the difference between the above-obtained median value and a measured value measured by the strength measuring means 172 at the beginning of finish grinding is calculated. At this time, the measured value on one of the concentric circles is obtained by the starch measuring means 172. For example, in the case where the measurement is performed at the measurement position 41c, the difference between the median value obtained above and the median value of the measurement values obtained at the measurement position 41c is calculated.
    Thereafter, the abrasion members 22 are brought into contact with the upper surface of the plate-like workpiece 30 for grinding the upper surface of the plate-like workpiece 30, while measuring the thickness of the plate-like workpiece 30 using the starch measuring means 172. When the sum of the measured value by the strength measuring means 172 and the difference obtained above becomes equal to the target value 425, the grinding is completed. As a result, the range of portions of the plate-like workpiece 30 where the strength is within the tolerance 424 becomes maximum. While the median value of the measurement values obtained by the thickness measurement means 172 at the measurement positions 41a to 41d is used, the average of the measurement values at each measurement position may be used.
    In the case of using the median value, a measured value that is locally large due to dust trapped between the upper surface of the chuck table and the lower surface of the plate-like workpiece 30 may be regarded as an abnormal value, and this measurement may be excluded from the calculation. (3-4) finish grinding step
    The plate-like workpiece 30 held on the chuck table 14 is ground again by the abrasive article 15b under the same conditions. When the plate-like workpiece 30 is ground by the grinding amount determined in the determining step, the finish grinding is completed. For example, when the thickness of the plate-like workpiece 30 measured by the starch measuring means 172 in the finishing grinding step becomes a value that is finished by subtracting the grinding amount determined in the determining step from the thickness measured at the same measuring position in the thickness measuring step, finish grinding is finished.
    In this way, the thickness of the plate-like workpiece, which is ground in the initial grinding step, is measured at a plurality of positions, and the grinding amount at the finish grinding is accordingly determined whether the difference between the maximum value and the minimum value of the measured strength is less than or equal to the tolerance for the As a result, the range of portions where the thickness of the plate-like workpiece at the end of finish grinding is within the tolerance can be maximized. As a result, of all the chips obtained by dividing the plate-like workpiece, the number of chips whose strengths are within the tolerance can be maximized. In the case where the difference between the maximum value and the minimum value of the measured strength is less than or equal to the final thickness tolerance, the grinding amount in finish grinding is determined such that the minimum value becomes greater than or equal to the minimum allowable strength and the maximum value lower than or equal to the maximum allowable strength. Accordingly, the thickness of the plate-like workpiece at all the positions can be made to be within the tolerance so that the number of chips whose strengths are within the tolerance can be maximized.
    On the other hand, in the case where the difference between the maximum value and the minimum value of the measured strength is larger than the tolerance for the final thickness, the grinding amount at the finish grinding is determined such that the range of portions where the strength is outside the tolerance becomes minimum. Accordingly, the number of chips that are within the tolerance can be maximized.
    Therefore, the number of chips whose strengths are within the tolerance can be easily changed by changing the amount of grinding in
    Finish grinding to be maximized. Accordingly, in comparison with the method described in Japanese Patent Laid-Open Publication No. 2008-264913, in which the inclination of the chuck table is adjusted, a calculation amount for facilitating the adjustment can be reduced, so that the time required for grinding can be shortened , More specifically, in the case where the chips obtained by dividing the plate-like workpiece are power device chips, the tolerance for the final strength is tens of microns, for example, which is larger than the tolerance (for example, several microns) in the case of ordinary device chips. In such a case where the final thickness tolerance is large, the thickness of the plate-like workpiece can be easily made by changing the grinding amount in finish grinding so as to be within the tolerance at all positions.
    Further, the past method including the step of adjusting the chuck table may not support the strength variation due to any factors other than the distance to the center of the plate-like workpiece, such as unevenness on the chucking surface of the chuck table. In contrast, the method of the present invention can support strength variations due to any factors other than the distance to the center of the plate-like workpiece, not only by measuring the thickness of the plate-like workpiece at a plurality of radial positions at different distances to the center of the plate-like workpiece, but also by measuring the thickness of the plate-like workpiece several circumferential positions equidistant from the center of the plate-like workpiece.
    In the initial grinding step, the measuring positions at which the starch measuring means measures the thickness of the plate-like workpiece can be any positions, since the accurate measurement of the starch is performed in the subsequent starch measuring step.
    In the starch measuring step, the measuring positions where the thickness measuring means measures the thickness of the plate-like workpiece are not necessarily arranged concentrically, but it is sufficient that the distances to the center of the plate-like workpiece deviate from each other. For example, the measuring position of the starch measuring means may be moved by the measuring position moving means slowly in the radial direction of the plate-like workpiece and the chuck table rotated by the rotating means. In this state, the thickness of the plate-like workpiece is measured by the starch measuring means at predetermined time intervals so that the measuring positions are spirally arranged in this case.
    In the determination step, in the above description, the two values or the minimum grinding amount and the maximum grinding amount are used for calculating the range of portions where the strength is outside the tolerance. As a modification, two or more values selected in the range from the minimum amount of grinding to the maximum amount of grinding may be used to calculate the range of portions where the strength is outside the tolerance. Then, the grinding amount corresponding to the calculated minimum area may be set as the grinding amount for finish grinding.
    The present invention is not limited to the details of the above-described preferred embodiments. The scope of the invention is defined by the appended claims, and all changes and modifications which come within the equivalence of the scope of the claims are therefore intended to be embraced by the invention.
    权利要求:
    Claims (3)
    [1]
    1. Abrasive method for a plate-like workpiece using a grinding apparatus comprising a chuck table for holding a plate-like workpiece, rotating means for rotating the chuck table, abrasive with an abrasive member for grinding the upper surface of the plate-like workpiece held on the chuck table, thereby reducing the thickness of the plate-like workpiece is, strength measuring means for non-contact measurement of the thickness of the plate-like workpiece, which is ground by the abrasive, and measuring position moving means for moving the starch measuring means in the radial direction of the clamping table, the grinding method for a plate-like workpiece comprising: an initial grinding step of grinding the plate-like workpiece, which on the chuck table is maintained, using the abrasive, until the thickness of the plate-like workpiece is reduced to a magnitude, the greater is a given final strength; a thickness measuring step of measuring the thickness of the plate-like workpiece held on the chuck table using the thickness measuring means at a plurality of measuring positions different in the distance to the axis of rotation of the chuck table when moving the starch measuring means in the radial direction of the chuck table after performing the preliminary grinding step; a determining step of calculating the difference between a maximum value and a minimum value of a plurality of strengths measured in the starch measuring step and determining whether the above calculated difference between the maximum value and the minimum value is less than or equal to the difference between an allowable maximum strength and a minimum allowable strength for the predetermined final strength is not or not; and a finishing grinding step of adjusting a grinding amount for the plate-like workpiece according to the determination result in the determining step and then grinding the plate-like workpiece in accordance with the grinding amount using the abrasive, thereby reducing the thickness of the plate-like workpiece to the predetermined final thickness.
    [2]
    A method of grinding a plate-like workpiece according to claim 1, wherein, when it is determined in the determining step that the difference between the maximum value and the minimum value is less than or equal to the difference between the allowable maximum strength and the allowable minimum thickness, the plate-like workpiece is ground in the finish grinding step Minimum value is greater than or equal to the minimum strength and the maximum value is less than or equal to the maximum strength.
    [3]
    A method of grinding a plate-like workpiece according to any one of claims 1 or 2, wherein when determined in the determining step that the difference between the maximum value and the minimum value is greater than the difference between the allowable maximum strength and the allowable minimum thickness, the plate-like workpiece is ground in the finishing grinding step until the range of portions in which the thickness of the plate-like workpiece is within the range of the allowable maximum strength to the minimum allowable strength becomes the maximum.
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    同族专利:
    公开号 | 公开日
    DE102015212289A1|2016-01-07|
    JP2016016457A|2016-02-01|
    AT515950A3|2019-02-15|
    AT515950B1|2019-11-15|
    JP6389660B2|2018-09-12|
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    JP2014138329A|JP6389660B2|2014-07-04|2014-07-04|Grinding method|
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