JP5752930B2 - Laser processing equipment - Google Patents

Description

  The present invention relates to a laser processing apparatus that performs laser processing on a workpiece (workpiece) such as a semiconductor wafer.

  In the semiconductor device manufacturing process, devices such as IC and LSI are formed in each of a plurality of regions partitioned by division lines arranged in a lattice pattern on the surface of a work having a substantially disc shape, and along the division lines By cutting the workpiece, it is divided into individual chips. In addition to a processing method using a cutting device called a dicer, a processing method in which a workpiece is cut by irradiating with a laser beam is applied to cutting the workpiece (see, for example, Patent Document 1).

  However, if there are minute irregularities on the workpiece surface (hereinafter referred to as waviness), the thickness of the workpiece will vary, and the laser beam will be uniformly modified to a predetermined depth due to the refractive index. A layer cannot be formed. Therefore, in order to uniformly form the modified layer at a predetermined depth position inside the workpiece having waviness, the unevenness of the region irradiated with the laser beam is detected in advance, and the laser beam irradiation means is made to follow the unevenness. It is necessary to process.

  On the other hand, a height position detecting means for irradiating the surface of the work held by the holding table with a visible light laser beam and detecting the surface height position of the work based on the amount of reflected light reflected by the work surface. An equipped laser processing apparatus has been proposed (see, for example, Patent Document 2).

  In general, such height position detection means has a limited detectable range. For this reason, the height variation of the workpiece surface may not be measured even though the range of the workpiece surface height variation is within the detectable range of the height position detecting means. In such a case, since the height variation cannot be measured, laser processing cannot be performed, and productivity is significantly reduced.

  On the other hand, there has been proposed a laser processing device that automatically adjusts the positional relationship between the height position detection means and the workpiece and continues the measurement and machining when the workpiece surface height variation cannot be measured. (For example, see Patent Document 3).

JP-A-10-305420 JP 2007-152355 A JP 2010-142819 A

  However, if the workpiece surface height variation cannot be measured, the workpiece surface will be divided in a laser processing device that automatically adjusts the positional relationship between the height position detection means and the workpiece and continues measurement and processing. When the height variation on the line cannot be measured, it is necessary to measure again the division planned line that could not be measured. Accordingly, there has been a problem that productivity decreases as the number of automatic adjustments increases.

  This invention is made | formed in view of this point, and it aims at providing the laser processing apparatus which can suppress the fall of productivity resulting from the measurement of the height variation of the workpiece | work surface.

The laser processing apparatus according to the present invention includes a holding unit that holds a workpiece on which a division line is set, an oscillator that oscillates a laser beam on the workpiece held by the holding unit, and a laser beam oscillated by the oscillator. A condensing lens, and can be moved in a direction perpendicular to the holding surface of the holding means within a range larger than the height variation on the division line of the workpiece, A first condensing point position adjusting unit that adjusts a condensing point position of the laser beam by moving the condensing lens by a predetermined amount in a vertical direction while irradiating the laser beam to the scheduled division line; The moving range in the direction is wider than that of the first focusing point position adjusting means, and before the laser beam is irradiated to the division planned line, the first By moving the condensing point position adjusting means in the vertical direction, the condensing point position of the laser beam condensed by the condensing lens is positioned at an appropriate position, and the laser beam is irradiated to the division planned line. And the second condensing point position adjusting means for keeping the position of the first condensing point position adjusting means in the vertical direction fixed while the light for detection is condensed by the condensing lens. The condensing lens is moved in the vertical direction by the first condensing point position adjusting means so that the amount of the reflected light reflected on the upper surface of the work is irradiated with the work held by the holding means is constant. Based on the lens position information obtained by the height position detecting means and the height position detecting means for measuring the height variation by acquiring the lens movement information of the condenser lens A laser processing apparatus comprising: a control unit that controls the first focusing point position adjusting unit, the second focusing point position adjusting unit, and the processing unit, wherein the control unit includes the height When the height variation is measured by the position detection means, the center position calculated from the highest position and the lowest position of the height variation detected by the height position detection means is the first condensing point. when the position adjusting means does not match the machining area reference value is the median of a predetermined amount that can be moved, before measuring the height variation of the next of said dividing line, the center position of the height variation is the working After the vertical position of the first focus point position adjusting means is adjusted by the second focus point position adjusting means so as to match the range reference value, the detection is performed along the next scheduled division line. Shine light And the height variation on the next scheduled division line is measured by moving the condensing lens in the vertical direction by the first condensing point position adjusting means .

According to this laser processing apparatus, the center position calculated from the uppermost position and the lowermost position of the height variation detected by the height position detecting means is a predetermined amount by which the first focusing point position adjusting means can move. If it does not match the machining range reference value, which is the median value of the second , before measuring the height variation of the next scheduled dividing line, the second position is adjusted so that the center position of the height variation matches the machining range reference value. by adjusting the position in the vertical direction of the first focal position adjusting means by point position adjusting means, departing from the measurement range of the height variation in height position detecting means of the workpiece surface comprising the following dividing line It is the structure which can reduce the probability to do. As a result, the frequency of occurrence of measuring the division line to be detected again without measuring the workpiece surface height variation can be reduced, thereby suppressing the decrease in productivity due to the workpiece surface height variation measurement. It is possible to provide a laser processing apparatus that can be used.

  ADVANTAGE OF THE INVENTION According to this invention, the laser processing apparatus which can suppress the fall of productivity resulting from the measurement of the workpiece surface height variation can be provided.

1 is a perspective view showing an entire laser processing apparatus according to an embodiment. It is a schematic side view which shows the whole structure including the optical system structure of the said laser processing apparatus. It is a figure which expands and shows a part of optical system shown in FIG. It is a schematic flowchart which shows the laser processing method performed by a control means according to the program for laser processing. It is a schematic flowchart which shows the laser processing method performed by a control means according to the program for laser processing. It is explanatory drawing about the case where the highest position of the height variation on the division | segmentation planned line of a workpiece | work exceeds the upper limit of the movable range of the 1st condensing point position adjustment means. It is explanatory drawing about the case where the lowest position of the height variation on the division | segmentation line of a workpiece | work exceeds the lower limit of the movable range of the 1st condensing point position adjustment means. It is explanatory drawing about the case where the center position where the height variation on the division | segmentation planned line of a workpiece | work does not correspond with the process range reference value of a 1st condensing point position adjustment means.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a perspective view showing an entire laser processing apparatus 1 according to an embodiment of the present invention. As shown in FIG. 1, the laser processing apparatus 1 moves the chuck table 4 holding the workpiece W and the laser irradiation unit 5 relative to each other and irradiates the workpiece W with a detection light beam so as to irradiate the surface of the workpiece W. The height variation is measured, and the workpiece W after the height variation is detected is irradiated with a laser beam, and laser processing is performed along a planned division line on the workpiece W.

  Here, the workpiece | work W which is a workpiece of the laser processing apparatus 1 is demonstrated. The workpiece W is formed in a substantially disc shape, and division lines are arranged in a lattice pattern on the surface, and devices (not shown) are formed in each of a plurality of regions partitioned by the division lines. The workpiece W is supported by the annular frame 3 via the support tape 2 with the surface on which the device is formed facing downward.

In the present embodiment, a semiconductor wafer such as a silicon wafer will be described as an example of the workpiece W. However, the workpiece W is not particularly limited. For example, silicon (Si), gallium arsenide (GaAs) is used. The workpiece W may be a semiconductor wafer such as silicon carbide (SiC), a sapphire (Al ₂ O ₃ ) -based inorganic material substrate, or various processing materials that require micron-order processing position accuracy.

  In the laser processing apparatus 1, a pair of X-axis guide rails 7 a and 7 b formed in the X-axis direction are disposed on a processing table 6. The X-axis table 8 is placed so as to be movable in the X-axis direction along the X-axis guide rails 7a and 7b. A nut portion (not shown) is formed on the back side of the X-axis table 8, and a ball screw 9 is screwed to the nut portion. A drive motor 10 is connected to the end of the ball screw 9, and the ball screw 9 is rotationally driven by the drive motor 10.

  On the X-axis table 8, a pair of Y-axis guide rails 11a and 11b formed in the Y-axis direction are disposed. The Y-axis table 12 is placed so as to be movable in the Y-axis direction along the Y-axis guide rails 11a and 11b. A nut portion (not shown) is formed on the back side of the Y-axis table 12, and a ball screw 13 is screwed to the nut portion. A driving motor 14 is connected to the end of the ball screw 13, and the ball screw 13 is rotationally driven by the driving motor 14.

  On the Y-axis table 12, a chuck table 4 as a holding means is installed. The chuck table 4 includes a table support portion 4a, a work holding portion 4b that holds and holds a work W on which a scheduled division line is provided, and a frame holding portion 4c that holds the annular frame 3. With. Inside the table support part 4a, a suction source for sucking and holding the work W on the work holding part 4b is provided.

  Further, a support column 15 is erected on the processing table 6, and a pair of Z-axis guide rails 16 a and 16 b formed in the Z-axis direction (vertical direction) are disposed on the support column 15. An arm 17 extending above the chuck table 4 from the upper end of the support column 15 is attached to be movable in the Z-axis direction along the Z-axis guide rails 16a and 16b. The arm 17 supports the laser irradiation unit 5 and the imaging means 19 as processing means. The laser irradiation unit 5 performs laser processing by irradiating the workpiece W held on the workpiece holding portion 4b of the chuck table 4 with a pulsed processing laser beam. The laser irradiation unit 5 houses an optical system to be described later, and is provided so as to be movable in the Z-axis direction by the second condensing point position adjusting means 18 via the arm 17. The second focusing point position adjusting means 18 includes a ball screw 18a, a nut portion (not shown), and a drive motor 18b.

  The second condensing point position adjusting means 18 is arranged so that the first condensing point position adjusting means 21 disposed in the arm 17 is Z-axis before irradiating the laser beam to the division line of the work W. The condensing point position of the laser beam that moves in the direction (vertical direction) and is condensed by the condensing lens 5c provided in the laser irradiation unit 5 is positioned at an appropriate position, and further, the laser beam is with respect to the division line of the workpiece W During the irradiation, the position of the first focusing point position adjusting means 21 in the Z-axis direction is kept fixed.

  The imaging unit 19 images the surface of the workpiece W held on the workpiece holding unit 4 b and detects a region to be processed by the laser beam emitted from the laser irradiation unit 5. The imaging unit 19 is configured by an imaging device (CCD) or the like, and sends the captured image signal to the control unit 20.

  Next, an optical system driving mechanism in the laser processing apparatus 1 will be described with reference to FIG. FIG. 2 is a schematic side view showing the overall configuration including the optical system configuration. The optical system according to the present embodiment is configured to reflect the laser beam emitted from the laser beam oscillation means 5a by the mirror 5b and to collect the reflected light on the workpiece W by the condenser lens 5c.

  The laser beam oscillation means 5 a oscillates a laser beam having a wavelength that is transmissive to the workpiece W held on the workpiece holding portion 4 b of the chuck table 4. The laser beam oscillation means 5a is composed of, for example, a YAG laser oscillator or a YVO4 laser oscillator, and oscillates a pulsed laser beam having a wavelength of 1064 nm.

  In the arm 17, first focusing point position adjusting means 21 is disposed. The first condensing point position adjusting means 21 uses a drive motor such as a piezo motor as a drive source, and simultaneously irradiates a laser beam to a division line of the work W, and simultaneously shows the work on the chuck table 4 as indicated by an arrow A. The condensing lens 5c is moved in the Z-axis direction (vertical direction) with respect to the holding unit 4b, and the condensing point position of the laser beam condensed by the condensing lens 5c is adjusted. In addition, the movable range in the Z-axis direction of the condensing lens 5c by the first condensing point position adjusting unit 21 is larger than the height variation of the surface of the workpiece W.

  The arm 17 moves in the Z-axis direction (vertical direction) with respect to the work holding portion 4b of the chuck table 4 as indicated by an arrow B, using the drive motor 18b of the second focusing point position adjusting means 18 as a drive source. . The movable range in the Z-axis direction is wider in the second condensing point position adjusting unit 18 than in the first condensing point position adjusting unit 21 (that is, B> A).

  The control means 20 is composed of hardware resources such as a CPU, ROM, and RAM, and the CPU reads control software stored in the ROM and executes processing according to the program. The control unit 20 inputs control signals to the first focusing point position adjusting unit 21, the second focusing point position adjusting unit 18, and the laser irradiation unit 5.

  The arm 17 is provided with a height position detecting means 22 for detecting the height position of the surface of the workpiece W held on the chuck table 4. Next, the height position detecting means 22 will be described with reference to FIG. FIG. 3 is an enlarged view showing a part of the optical system shown in FIG. The height position detection means 22 shown in FIG. 3 includes a detection light emitting unit 22a, photodetectors 22b and 22c, a cylindrical lens 22d, a slit 22e, half mirrors 22f and 22g, and a dichroic mirror 22h as a detection optical system. And a condensing lens 5c.

  The detection light emitting unit 22a oscillates a detection light beam having a frequency different from that of the laser beam oscillated from the laser beam oscillation means 5a. The detection light emitting unit 22a is composed of, for example, a CW laser oscillator, and oscillates a detection light beam having a wavelength of 635 nm. The detection light beam emitted from the detection light emitting unit 22a passes through the half mirror 22g, and then is reflected by the dichroic mirror 22h and the mirror 5b. The reflected light is collected on the work W by the condenser lens 5c. The half mirror 22g transmits the detection light beam oscillated from the detection light emitting unit 22a to the dichroic mirror 22h side, and reflects the light reflected from the dichroic mirror 22h side to the half mirror 22f side. The dichroic mirror 22h reflects the light transmitted through the half mirror 22g to the mirror 5b side, and transmits the laser beam oscillated from the laser beam oscillation means 5a to the mirror 5b side.

  The half mirror 22f splits the detection light beam reflected on the surface of the workpiece W into the optical paths Oa and Ob. The photodetector 22b receives all the light guided to the optical path Oa and outputs a voltage signal corresponding to the amount of received light to the control means 20.

  On the other hand, the photodetector 22c receives the light guided to the optical path Ob, and regulated by the cylindrical lens 22d and the slit 22e, and outputs a voltage signal corresponding to the amount of received light to the control means 20. The cylindrical lens 22d disposed on the optical path Ob condenses the detection light beam reflected by the workpiece W in a linear shape. In the present embodiment, the cylindrical lens 22d is arranged so as to have a condensing property in the Y-axis direction but not to have a condensing property in the Z-axis direction. In addition, the slit 22e positioned between the cylindrical lens 22d and the photodetector 22c is arranged so that the longitudinal direction of the opening with a predetermined width is orthogonal to the condensing direction of the cylindrical lens 22d.

  In the detection system function section of the height position detection means 22 in the control means 20, the relationship between the detection ratio of the amount of light received by the photodetectors 22b and 22c and the distance between the upper surface of the workpiece W and the condenser lens 5c is stored in advance in the memory. Stored. Accordingly, distance information between the upper surface of the workpiece W and the condensing lens 5c can be acquired based on the detection ratio of the amount of light received by the photodetectors 22b and 22c of the detection light beam reflected on the surface of the workpiece W. That is, the height position of the surface of the workpiece W is driven by the first condensing point position adjusting means 21 so that the distance information between the upper surface of the workpiece W and the condensing lens 5c that are sequentially acquired becomes a predetermined constant value. Then, the condensing lens 5c is moved in the Z-axis direction (vertical direction), the drive information of the first condensing point position adjusting means 21 at this time is stored, and the movement information of the condensing lens 5c is acquired and detected. it can.

  Then, the laser processing method of the workpiece | work W which uses the laser processing apparatus 1 is demonstrated. 4 and 5 are schematic flowcharts showing a laser processing method executed by the control means 20 in accordance with the laser processing program. In the processing, first, the workpiece W is placed on the chuck table 4 and is attracted to the workpiece holding portion 4b by a suction source (not shown). Thereafter, the chuck table 4 that sucks and holds the workpiece W is positioned immediately below the imaging means 19, and an alignment operation for detecting an area of the workpiece W to be laser processed is executed. That is, a division planned line formed on the workpiece W is detected, and alignment of the laser processing position is performed. After the alignment work is completed, the control means 20 performs a height variation detection process and a laser processing process along the division line of the workpiece W. Here, each line of the division planned lines arranged in the X-axis direction of the workpiece W is defined as L, and the first line to be processed is defined as L = 1.

  First, the chuck table 4 is moved directly below the laser irradiation unit 5 by driving the drive motor 14 of the laser processing apparatus 1 and moving the Y-axis table 12. At this time, the division line L = 1 is positioned immediately below the condenser lens 5c, and the processing target line is set to L = 1 (step ST1).

  Subsequently, by moving the arm 17 by driving the drive motor 18b of the second focusing point position adjusting means 18, the focusing point position of the laser beam condensed by the focusing lens 5c of the laser irradiation unit 5 is changed. It adjusts so that it may be on the division | segmentation planned line L = 1 (step ST2).

  Subsequently, by driving the drive motor 10 and moving the X-axis table 8, the chuck table 4 is moved at a predetermined speed in the X-axis direction. Thereby, the workpiece W sucked and held by the workpiece holding portion 4b of the chuck table 4 is processed and fed at a predetermined speed in the X-axis direction from the head of the scheduled division line L = 1 (step ST3).

  Simultaneously with step ST3, a detection light beam is oscillated from the detection light emitting unit 22a of the height position detection means 22, condensed by the condensing lens 5c, and irradiated along the planned division line L = 1. Then, the detection light beam reflected on the surface of the workpiece W is detected by the photodetectors 22b and 22c, and the detection ratio of the amount of received light is acquired (step ST4).

  Subsequently, whether or not the detection ratio of the amount of received light acquired in step ST4 is a predetermined constant value set in advance, more specifically, the amount of reflected light detected by the photodetector 22c is a constant value. Is determined (step ST5). That is, the amount of reflected light detected by the photodetector 22c fluctuates due to the influence of the waviness on the surface of the workpiece W, whereas the amount of reflected light detected by the photodetector 22b is affected by the influence. Absent. In step ST4, it is determined whether or not the detection ratio of the amount of reflected light reflected from the surface of the workpiece W is constant by determining whether or not the amount of reflected light detected by the photodetector 22c is a constant value. Judgment.

  If the detection ratio of the amount of received light received does not match a predetermined constant value because the amount of reflected light detected by the photodetector 22c varies due to the waviness of the surface of the workpiece W (step ST5: No), the first condensing point position adjusting means 21 is driven, and the condensing lens 5c is moved in the Z-axis direction (vertical direction) so as to cancel the fluctuation in the amount of reflected light (step ST6). Then, the process returns to step ST4 again, and the processes after step ST4 are repeated until the detection ratio of the amount of received light detected by the photodetectors 22b and 22c matches a predetermined constant value.

  In this way, when the detection processing of the entire planned division line L = 1 is completed while driving the first condensing point position adjusting unit 21, the first condensing point position adjusting unit at each coordinate position in the X-axis direction is completed. 21 including the feedback control operation by driving the first light condensing point position adjusting means 21 is stored in the memory in the control means 20, and the stored first light condensing point position adjusting means 21 is stored. The movement information of the condenser lens 5c is acquired from the driving information. And based on the movement information of this condensing lens 5c, the surface height position in each coordinate position on the division | segmentation scheduled line L = 1 of the workpiece | work W is measured (step ST7). If necessary, in addition to the drive information of the first condensing point position adjusting means 21 at each coordinate position in the X-axis direction, the detection ratio information of the received light amount detected by the photodetectors 22b and 22c is also provided. It may be used to measure the surface height position at each coordinate position on the planned division line L = 1.

  Subsequently, in the measurement process of step ST7, it is determined whether or not there is a surface height position that cannot be detected in the division line L = 1 of the workpiece W (step ST8).

  As a case where there is a coordinate position where the surface height position cannot be detected, as shown in FIG. 6A, the distribution of the surface height position at each coordinate position on the division line L = 1 of the workpiece W is shown. An example is when the height varies. FIG. 6 is an explanatory diagram of a case where the uppermost position of the height variation on the division line L of the workpiece W exceeds the upper limit value of the movable range of the first condensing point position adjusting unit 21. In FIG. 6A, the width (Z2) from the lowest position to the uppermost position of the height variation on the division line L = 1 of the workpiece W is the movable range of the first condensing point position adjusting means 21. Despite being smaller than (Z1) (that is, Z1> Z2), the uppermost position with the height variation on the division line L = 1 of the workpiece W is the movable range of the first condensing point position adjusting means 21. It shows a case where the upper limit value is exceeded (step ST8: No, step ST9: Yes). In this case, the lowest position with the height variation on the division line L = 1 of the workpiece W is stored (step ST10), and then, as shown in FIG. When the adjusting unit 18 is driven, the lower limit value of the movable range of the first condensing point position adjusting unit 21 is lower by Δh than the lowest position with the height variation of the division line L = 1 of the workpiece W. (Step ST11). And it returns to step ST3 again and repeats the process after step ST3 until it can detect the surface height position in all the coordinate positions. In FIG. 6, the vertical axis represents the surface height position of the workpiece W, and the horizontal axis represents the coordinate position on the planned division line L. Further, in FIG. 6, the curve C indicates the height variation corresponding to the undulation on the division planned line L. The same applies to FIGS. 7 and 8 shown below.

  Further, as another case where there is a coordinate position where the surface height position cannot be detected, as shown in FIG. 7A, the surface height position at each coordinate position on the division line L = 1 of the workpiece W. The case where the height variation which shows distribution of this generate | occur | produces is mentioned. FIG. 7 is an explanatory diagram of a case where the lowest position of the height variation on the division line L of the workpiece W exceeds the lower limit value of the movable range of the first condensing point position adjusting means 21. In FIG. 7A, the width (Z2) from the lowest position to the uppermost position of the height variation on the division line L = 1 of the workpiece W is the movable range of the first condensing point position adjusting means 21. Despite being smaller than (Z1) (that is, Z1> Z2), the lowermost position of the height variation on the division line L = 1 of the work W is movable by the first focusing point position adjusting means 21. The case where the lower limit value of the range is exceeded is shown (step ST8: No, step ST9: No). In this case, the uppermost position with the height variation on the division line L = 1 of the workpiece W is stored (step ST12), and then, as shown in FIG. The means 18 is driven so that the upper limit value of the movable range of the first condensing point position adjusting means 21 is higher by Δh than the uppermost position with the height variation of the division line L = 1 of the workpiece W. Position (step ST13). And it returns to step ST3 again and repeats the process after step ST3 until it can detect the surface height position in all the coordinate positions.

  And the width (Z2) from the lowest position to the highest position of the height variation on the division line L = 1 of the work W is all within the movable range (Z1) of the first light condensing point position adjusting means 21. By doing so, when the surface height position can be detected at all coordinate positions (step ST8: Yes), the chuck table 4 is moved by moving the X axis table 8 by driving the drive motor 10. The laser beam is oscillated from the laser beam oscillation means 5a of the laser irradiation unit 5 while moving at a predetermined speed in the X-axis direction and processing and feeding at a predetermined speed in the X-axis direction from the head of the division planned line L = 1. The light is condensed by the optical lens 5c and irradiated along the division line L = 1. At this time, based on the movement information of the condensing lens 5c acquired by the height position detecting means 22, the first condensing point position adjusting means 21 is driven to adjust the condensing point position of the condensing lens 5c. Then, a laser beam is irradiated (step ST14). That is, by causing the condensing point position of the condensing lens 5c to follow the height variation on the division line L = 1 of the work W, the laser beam is always condensed to a predetermined depth from the surface of the work W, thereby A modified layer is formed along the predetermined division line L = 1 from the W surface to a predetermined depth. In addition, during execution of step ST15, the 2nd condensing point position adjustment means 18 is not moved, but the height position is fixed.

  Note that, in the detection operation of the height variation of the planned division line L = 1 of the workpiece W by the height position detection unit 22, the first condensing point position adjusting unit when the movement information of the condensing lens 5c varies. A time lag occurs in the follow-up operation of the lens 21 and the condenser lens 5c. Therefore, when driving the first condensing point position adjusting means 21 based on the movement information of the condensing lens 5c at the time of laser processing, the time lag may be taken into account for correction.

  Such laser processing is repeated until the processing of the division line L = 1 of the workpiece W is completed (step ST15: No). When the laser processing of the division line L = 1 of the workpiece W is completed (step ST15: Yes), it is determined whether the processing target line L = 1 is the final line (step ST16).

  If the machining target line L = 1 is not the final line (step ST16: No), then the height variation calculated from the uppermost position and the lowermost position of the height variation on the division planned line L = 1 of the workpiece W will be described. It is determined whether or not the center position coincides with a processing range reference value that is a median value of the movable range of the first condensing point position adjusting means 21 (step ST17). When the center position of the height variation on the planned division line L = 1 matches the processing range reference value of the first condensing point position adjusting means 21 (step ST17: Yes), the processing target line L is incremented by +1. Increment and move the processing object to the next division line L = L + 1 (step ST19), and repeat the processing after step ST3.

  As shown in FIG. 8A, the center position of the height variation on the division line L = N of the workpiece W does not match the processing range reference value of the first condensing point position adjusting means 21, and the height is high. When the center position of the unevenness exists by the size Z3 above the processing range reference value, when the height unevenness is measured on the next division line L = N + 1, the highest position of the height unevenness is the first position. There is a tendency to exceed the upper limit of the movable range Z1 of the condensing point position adjusting means 21. In this case, according to the flowchart shown in FIG. 4, it is necessary to measure the height variation on the division line L = N + 1 again.

  Therefore, when the center position of the height variation on the planned division line L = N does not coincide with the processing range reference value of the first condensing point position adjusting means 21 (step ST17: No), FIG. ), The second collection is performed so that the center position of the height variation on the division line L = N of the workpiece W coincides with the processing range reference value of the first focusing point position adjusting means 21. The light spot position adjusting unit 18 is driven to adjust the lower limit value and the upper limit value of the movable range of the first condensing point position adjusting unit 21 so as to move upward by the size Z3. Accordingly, the condensing point position of the condensing lens 5c is also adjusted (step ST18). By adjusting in this way, when the height variation on the next division line L = N + 1 is measured, from the lowest position of the height variation on the division line L = N + 1 of the workpiece W to the uppermost position. It is possible to reduce the probability that the width (Z2) deviates from the movable range (Z1) of the first focusing point position adjusting means 21.

  After the adjustment in step ST18, the processing target line L is incremented by +1, the processing target is moved to the next division line L = L + 1 (step ST19), and the processing after step ST3 is repeated.

  When the processing target line L is the final line (step ST16: Yes), the laser processing for the division planned lines arranged in the X-axis direction of the workpiece W is finished. Similarly, in order to execute the height variation detection process and the laser processing process along the planned division lines arranged in the Y-axis direction of the workpiece W, the process is started by rotating the chuck table 4 by 90 °.

  As described above, according to the laser processing apparatus 1 according to the present embodiment, from the uppermost position and the lowermost position with height variations on the division planned line that is the processing target detected by the height position detecting means 22. If the calculated center position does not coincide with the processing range reference value, which is a predetermined amount of median value that the first focusing point position adjusting means 21 can move, the height variation of the next division line to be processed is changed. Prior to the measurement, the position of the first condensing point position adjusting unit 21 in the vertical direction is adjusted by the second condensing point position adjusting unit 18 so that the center position of the height variation matches the processing range reference value. Thus, the probability that the height variation of the surface of the workpiece W including the division line to be processed next deviates from the measurement range of the height position detecting means 22 can be reduced. For this reason, the frequency of occurrence of a situation where the division line to be detected cannot be measured again without measuring the height variation on the surface of the workpiece W can be reduced, resulting in a decrease in productivity due to the measurement of the height variation on the workpiece W surface. It is possible to provide a laser processing apparatus capable of suppressing the above.

  In addition, this invention is not limited to the said embodiment, It can implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited thereto, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, in the above embodiment, it is configured to determine whether or not the center position of the height variation on the processing target division planned line of the workpiece W matches the processing range reference value in step ST18 of the laser processing step. The matching here is not limited to perfect matching, and a configuration that allows a certain amount of width is also possible. In the determination of whether or not they match, by allowing a certain amount of width, the condensing point position is adjusted by the second condensing point position adjustment so that the center position of the height variation matches the processing range reference value. The frequency of executing step ST19 can be reduced. Therefore, it is possible to further suppress a decrease in productivity due to the measurement of height variation.

  The present invention is applicable to a laser processing apparatus that performs laser processing on a workpiece (workpiece) such as a semiconductor wafer.

DESCRIPTION OF SYMBOLS 1 Laser processing apparatus 2 Support tape 3 Annular frame 4 Chuck table 4a Table support part 4b Work holding part 4c Frame holding part 5a Laser beam oscillation means (oscillator)
5b Mirror 5c Condensing lens 6 Processing table 7a, 7b X-axis guide rail 8 X-axis table 9 Ball screw 10 Drive motor 11a, 11b Y-axis guide rail 12 Y-axis table 13 Ball screw 14 Drive motor 15 Supporting part 17 Arm 18 First 2 focusing point position adjusting means 18a ball screw 18b drive motor 19 imaging means 20 control means 21 first focusing point position adjusting means 22 height position detecting means 22a detection light emitting sections 22b and 22c photo detector 22d cylindrical lens 22e Slit 22f, 22g Half mirror 22h Dichroic mirror

Claims (1)

Holding means for holding a work set with a division line,
Processing means comprising: an oscillator that oscillates a laser beam on the workpiece held by the holding means; and a condenser lens that condenses the laser beam oscillated by the oscillator;
The condenser lens can be moved in a direction perpendicular to the holding surface of the holding means within a range larger than the height variation on the division line of the workpiece, and the laser beam is applied to the division line. The first condensing point position adjusting means for adjusting the condensing point position of the laser beam by moving the condensing lens by a predetermined amount in the vertical direction,
The moving range in the vertical direction is wider than that of the first focusing point position adjusting unit, and the first focusing point position adjusting unit is set in the vertical direction before irradiating the laser beam to the division planned line. When the laser beam focused by the condenser lens is moved to an appropriate position, and the laser beam is irradiated to the planned division line, the first laser beam in the vertical direction is irradiated. Second condensing point position adjusting means for keeping the position of the condensing point position adjusting means fixed;
The first condensing point is such that the detection light beam is condensed by the condensing lens and irradiated onto the workpiece held by the holding means, and the amount of reflected light reflected by the upper surface of the workpiece is constant. A height position detecting means for measuring the height variation by moving the condenser lens in a vertical direction by a position adjusting means and acquiring lens movement information of the condenser lens;
Control means for controlling the first focusing point position adjusting means, the second focusing point position adjusting means, and the processing means based on the lens movement information obtained by the height position detecting means; ,
A laser processing apparatus comprising:
When the height variation is measured by the height position detection unit, the control unit has a center position calculated from the uppermost position and the lowermost position of the height variation detected by the height position detection unit. , when said first focal position adjusting means does not match the machining area reference value is the median of a predetermined amount that can be moved, before measuring the height variation of the next of said dividing line, the high After adjusting the position in the vertical direction of the first focus point position adjusting means by the second focus point position adjusting means so that the center position of the unevenness coincides with the processing range reference value, Irradiate the detection light beam along the scheduled division line, and move the condenser lens in the vertical direction by the first focal point position adjusting means to measure the height variation on the next planned division line. Leh Over processing equipment.

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