JP5329199B2 - Laser processing apparatus, laser processing control method, and laser processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform laser beam machining in a state that the condensing point position of a laser beam for machining a workpiece is corrected by always correctly detecting the height position of the upper surface of the workpiece. <P>SOLUTION: Although the range of variations in the height position of the upper surface of a planned dividing line is narrower than the movable range of a second adjusting means for a condensing point position, for example, when a height position of the upper surface of the planned dividing line becomes undetectable because it exists above the movable range of a second adjusting means for a condensing point position, the undetectable position is made detectable by the following: the lowest position of the upper surface height, which exists at the lowest side, is stored; and the positional relation of the second adjusting means for a condensing point position with respect to the upper surface of the workpiece is automatically adjusted so that the position lowest in the movable range of the second adjusting means for a condensing point position is positioned slightly below the above lowest position of the upper surface height by a first adjusting means for a condensing point position. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a laser processing apparatus, a laser processing control method, and a laser processing program for performing laser processing on a workpiece such as a semiconductor wafer.

  In a semiconductor device manufacturing process, a plurality of regions are defined by streets (scheduled division lines) arranged in a lattice pattern on the surface of a semiconductor wafer having a substantially disk shape, and circuits such as IC and LSI are defined in the partitioned regions. Each semiconductor chip is manufactured by cutting the semiconductor wafer on which the semiconductor chip is formed along the street and dividing it into circuits. Cutting along the streets of a semiconductor wafer is usually performed by a cutting device called a dicer, and a processing method of cutting by irradiating a laser beam has also been attempted (see, for example, Patent Document 1).

  However, in general, a plate-like workpiece such as a semiconductor wafer has undulation, and if the thickness varies, the layer is uniformly altered to a predetermined depth due to the refractive index when irradiating a laser beam. Can not form. Therefore, in order to uniformly form a deteriorated layer at a predetermined depth position on a plate-like workpiece such as a semiconductor wafer, the unevenness of the region irradiated with the laser beam is detected in advance, and laser is applied to the unevenness. It is necessary to follow the light beam irradiation means for processing.

  In order to solve the above-described problems, the upper surface of the workpiece held on the chuck table is irradiated with a visible laser beam, and the amount of light corresponding to the area reflected by the upper surface of the workpiece is determined. There has been proposed a laser processing apparatus including a height position detecting means for detecting an upper surface height position (see, for example, Patent Document 2).

JP-A-10-305420 JP 2007-152355 A

  However, the height position detecting means generally has a limited detectable width. The positional relationship between the height position detecting means and the workpiece, even though the variation range of the upper surface height position of the target work piece is within the detectable width of the height position detecting means. Depending on the case, it may not be possible to measure the upper surface height position. In such a case, as a result, the unevenness information for following the laser beam irradiation means cannot be obtained, so that there is a problem that the laser processing cannot be performed and the productivity is remarkably lowered.

  The present invention has been made in view of the above, and always detects the upper surface height position of a workpiece appropriately and performs laser processing with the focusing point position of the processing laser beam with respect to the workpiece being appropriate. An object of the present invention is to provide a laser processing apparatus, a laser processing control method, and a laser processing program.

  In order to solve the above-described problems and achieve the object, a laser processing apparatus according to the present invention includes a chuck table having a holding surface for holding a workpiece partitioned by a division line, and the holding of the chuck table. A processing laser beam oscillating means for oscillating a processing laser beam for laser processing the workpiece held on the surface, and a collecting beam for condensing the processing laser beam oscillated by the processing laser beam oscillating means. A laser beam irradiating means having an optical lens, a processing feed means for relatively moving the chuck table and the laser beam irradiating means in a processing feed direction, and before performing laser processing on the workpiece. In advance, the condensing lens is moved in the direction perpendicular to the holding surface to adjust the condensing point position of the processing laser beam condensed by the condensing lens. 1 focusing point position adjusting means, and a movement that is wider than the range of variation of the upper surface height on the division line of the workpiece and narrower than the movable range of the first focusing point position adjusting means. A second condensing point that is set in a possible range and adjusts the condensing point position of the processing laser beam focused by the condensing lens by moving the condensing lens in the vertical direction using a piezo motor as a drive source Before performing laser processing on the position adjustment means and the target division line, the light beam for detection emitted from the light source for detection is moved while moving the workpiece relatively in the processing feed direction. Condensed by an optical lens and irradiated along the planned division line of the workpiece on the holding surface, and based on the reflected light reflected on the upper surface of the planned division line, the condensing lens and the planned division line Top The distance information is obtained, and the piezo motor is driven so that the obtained distance information becomes a predetermined constant value, and the condenser lens is moved in the vertical direction by the second condenser point position adjusting means, Height position detecting means for detecting the upper surface height position of the planned dividing line by storing the driving information of the piezo motor and acquiring the condenser lens movement information; and control means for controlling the operation of the laser processing apparatus; The control means detects the upper surface height position of the target division line by the height position detection means, and the upper surface height position is the second condensing point position adjustment means. If there is a portion that cannot be detected because it exists above the movable range, the uppermost surface height at the lowermost position on the planned division line detected by the height position detecting means. Down position And storing the lowermost position of the movable range of the second condensing point position adjusting unit below the lowermost position by the first condensing point position adjusting unit. The height position detecting means again detects the upper surface height position on the planned division line, and the upper surface height position is below the movable range of the second condensing point position adjusting means. If there is a possible location, the highest position of the upper surface height existing on the uppermost side on the planned dividing line detected by the height position detecting means is stored, and the first condensing point position adjustment is performed. Means for positioning the uppermost position of the movable range of the second condensing point position adjusting means above the uppermost position, and the height position detecting means enables the upper surface height position on the planned dividing line. Is detected again, and the top surface height position is When there is no place that cannot be detected because it exists within the movable range of the second focusing point position adjusting means, the laser beam irradiating means while relatively moving the workpiece in the processing feed direction Irradiating the target division line with a processing laser beam, and simultaneously driving the piezo motor based on the condenser lens movement information acquired by the height position detecting means. A laser processing is performed on the planned dividing line while adjusting the condensing point position of the condensing lens by the condensing point position adjusting means.

  The laser processing control method according to the present invention includes a chuck table having a holding surface for holding a workpiece partitioned by the division lines, and a laser for the workpiece held on the holding surface of the chuck table. Laser beam irradiating means having processing laser beam oscillating means for oscillating a processing laser beam for processing, and a condenser lens for condensing the processing laser beam oscillated by the processing laser beam oscillating means; A processing feed means for relatively moving the chuck table and the laser beam irradiating means in a processing feed direction; and before performing laser processing on the workpiece, the condenser lens is previously placed on the holding surface. First focusing point position adjusting means for adjusting the focusing point position of the processing laser beam which is moved vertically with respect to the focusing lens and is focused by the focusing lens; It is set to a movable range that is wider than the range of variation of the upper surface height on the division line that the work has and is narrower than the movable range of the first condensing point position adjusting means, and a piezo motor as a drive source, A second condensing point position adjusting means for moving the condensing lens in the vertical direction to adjust a condensing point position of a processing laser beam condensed by the condensing lens; Before the laser processing is performed on the holding surface, the light beam for detection emitted from the light source for detection is condensed by the condensing lens while moving the workpiece relatively in the processing feed direction. The distance information between the condensing lens and the upper surface of the planned division line is acquired based on the reflected light that is irradiated along the planned division line of the workpiece and reflected by the upper surface of the planned division line. The The piezo motor is driven so that the separation information becomes a predetermined constant value, the condensing lens is moved in the vertical direction by the second condensing point position adjusting means, and the driving information of the piezo motor is stored and condensed. Using a laser processing apparatus having a height position detecting means for detecting an upper surface height position of the division planned line by acquiring lens movement information, and the height position detecting means When detecting the upper surface height position, if there is a portion that cannot be detected because the upper surface height position is above the movable range of the second light condensing point position adjusting means, The lowest position of the upper surface height existing on the lowermost side on the planned dividing line detected by the position detecting means is stored, and the second light collecting point is adjusted by the first light collecting point position adjusting means. Point position adjustment hand Positioning the lowermost position of the movable range of the step below the lowermost position and causing the height position detecting means to detect the upper surface height position on the planned dividing line again; and If there is a portion that cannot be detected because the height position is below the movable range of the second focusing point position adjusting means, the division schedule detected by the height position detecting means The uppermost position of the upper surface height existing on the uppermost side on the line is stored, and the uppermost position of the movable range of the second condensing point position adjusting means is stored by the first condensing point position adjusting means. Positioning the upper surface position above the uppermost position, and causing the height position detecting means to detect the upper surface height position on the division-scheduled line again, and the upper surface height position adjusts the second condensing point position. Within the movable range of the means If there is no undetectable part, the laser beam irradiating unit irradiates the target division planned line with the laser beam irradiation means while moving the workpiece relative to the processing feed direction. At the same time, based on the condensing lens movement information acquired by the height position detecting means, the piezo motor is driven and the condensing point of the condensing lens is adjusted by the second condensing point position adjusting means. And performing laser processing on the scheduled division line while adjusting the position.

  The program for laser processing according to the present invention includes a chuck table having a holding surface for holding a workpiece divided by the planned division lines, and a laser for the workpiece held on the holding surface of the chuck table. Laser beam irradiating means having processing laser beam oscillating means for oscillating a processing laser beam for processing, and a condenser lens for condensing the processing laser beam oscillated by the processing laser beam oscillating means; A processing feed means for relatively moving the chuck table and the laser beam irradiating means in a processing feed direction; and before performing laser processing on the workpiece, the condenser lens is previously placed on the holding surface. First focusing point position adjusting means for adjusting the focusing point position of the processing laser beam which is moved vertically with respect to the focusing lens and is focused by the focusing lens; The workpiece is set to a movable range that is wider than the range of variation of the upper surface height on the division line that the workpiece has and that is narrower than the movable range of the first focusing point position adjusting means, and a piezo motor is used as a drive source , Second focusing point position adjusting means for moving the focusing lens in the vertical direction and adjusting the focusing point position of the processing laser beam condensed by the focusing lens, and the target division schedule Before performing laser processing on the line, the light beam for detection emitted from the light source for detection is condensed by the condensing lens while moving the workpiece relatively in the processing feed direction. The distance information between the condensing lens and the upper surface of the division line is acquired based on the reflected light that is irradiated along the division line of the workpiece and reflected from the upper surface of the division line. The piezo motor is driven so that the distance information becomes a predetermined constant value, the condensing lens is moved in the vertical direction by the second condensing point position adjusting means, and the driving information of the piezo motor is stored and collected. A computer provided in a laser processing apparatus having a height position detection means for detecting an upper surface height position of the division planned line by acquiring optical lens movement information, and the division targeted by the height position detection means When detecting the upper surface height position of the planned line, if there is a portion that cannot be detected because the upper surface height position is above the movable range of the second condensing point position adjusting means. , Storing the lowest position of the upper surface height existing on the lowermost side on the planned dividing line detected by the height position detecting means, and the first condensing point position adjusting means causes the first focusing point position adjusting means to store the first position. The lowermost position of the movable range of the two condensing point position adjusting means is positioned below the lowermost position, and the height position detecting means again sets the upper surface height position on the planned dividing line. If there is a function to be detected and a portion that cannot be detected because the upper surface height position is below the movable range of the second focusing point position adjusting means, the height position detecting means The uppermost position of the upper surface height existing on the uppermost side on the planned division line is stored, and the second focusing point position adjusting unit is moved by the first focusing point position adjusting unit. A function of positioning the uppermost position of the possible range above the uppermost position and causing the height position detecting means to detect the upper surface height position on the planned division line again, and the upper surface height position is the first position 2 Focusing position adjustment means If there is no portion that cannot be detected due to the presence of the laser beam, the laser beam irradiating means moves the workpiece relative to the machining feed direction while processing the segmented target line. While irradiating a laser beam, at the same time, based on the condenser lens movement information acquired by the height position detector, the piezo motor is driven and the second condenser point position adjuster adjusts the condenser lens. And a function of performing laser processing on the scheduled division line while adjusting the position of the condensing point.

  According to the present invention, when the variation range of the upper surface height position of the workpiece is within the detectable range but cannot be detected, the first focusing point position adjusting means is controlled to automatically Since it is possible to detect by adjusting the positional relationship of the second focusing point position adjusting means with respect to the upper surface of the workpiece, it is possible to detect the upper surface height position of the workpiece appropriately and always with respect to the workpiece. There is an effect that laser processing can be performed in a state where the condensing point position of the processing laser beam is appropriate.

  Hereinafter, a laser processing apparatus, a laser processing control method, and a laser processing program that are the best mode for carrying out the present invention will be described with reference to the drawings. The present embodiment is a laser processing apparatus that performs laser processing by irradiating a workpiece such as a semiconductor wafer partitioned by a plurality of planned division lines arranged in a grid pattern with a processing laser beam along the planned division lines. An application example is shown.

  First, a workpiece to be processed in the present embodiment will be described. FIG. 1 is an external perspective view showing a workpiece 1. A workpiece 1 to be processed is based on a semiconductor wafer or the like, and is partitioned by a plurality of first division lines 4a and a plurality of second division lines 4b arranged in a lattice pattern on the surface 1a. A plurality of rectangular areas are formed, and the device 5 is formed in the plurality of rectangular areas. The workpiece 1 is not particularly limited. For example, a semiconductor wafer such as a silicon wafer, an adhesive member such as DAF (Die Attach Film) provided on the back surface of the wafer for chip mounting, or a package of a semiconductor product, Examples include ceramic, glass-based or silicon-based substrates, and various processing materials that require accuracy on the order of μm. In addition, such a workpiece 1 is attached to a dicing tape 3 made of a synthetic resin sheet such as polyolefin mounted on an annular frame 2 with the back surface 1b facing upward as shown in FIG. Be prepared.

  Next, a laser processing apparatus for performing laser processing on the workpiece 1 will be described. 2 is an external perspective view showing the main part of the laser processing apparatus of the present embodiment, and FIG. 3 is a schematic side view showing the overall configuration including the optical system configuration such as laser beam irradiation means. These are the schematic side views which expand and show the one part. The laser processing apparatus 20 according to the present embodiment has a chuck table 21 having a holding surface 21a for holding the workpiece 1, and a workpiece 1 held on the holding surface 21a of the chuck table 21 for pulse-like machining. A laser beam irradiating unit 22 that performs laser processing by irradiating a laser beam, an imaging unit 100 that images the workpiece 1 held on the holding surface 21a, and a control unit 200 are provided. The chuck table 21 sucks and holds the workpiece 1 and is rotatably connected to a motor (not shown) in the cylindrical portion 24. Further, the chuck table 21 is provided with a clamp 21 b for fixing the annular frame 2.

  The chuck table 21 is mounted on two stages of sliding blocks 25 and 26. The sliding block 25 is provided so as to be movable in the X-axis direction (machining feed direction) by a machining feed means 27 constituted by a ball screw 27a, a nut (not shown), a pulse motor 27b, and the like, and is mounted on the sliding block 25. The workpiece 1 on the chuck table 21 is moved relative to the pulsed processing laser beam irradiated by the laser beam irradiation means 22 in the X-axis direction. Similarly, the sliding block 26 can be moved in the Y-axis direction (indexing direction) orthogonal to the X-axis direction in the horizontal plane by indexing feeding means 28 constituted by a ball screw 28a, a nut (not shown), a pulse motor 28b, and the like. The workpiece 1 on the chuck table 21 mounted on the slide block 26 is moved relatively in the Y-axis direction with respect to the pulsed processing laser beam irradiated by the laser beam irradiation means 22.

  Here, the machining feed means 27 is provided with a machining feed amount detection means 29 for detecting the machining feed amount of the chuck table 21. The processing feed amount detection means 29 includes a linear scale 29a disposed along the X-axis direction and a reading head (not shown) that is disposed on the sliding block 25 and moves along with the sliding block 25 along the linear scale 29a. Yes. By sending a pulse signal of 1 pulse, for example, every 1 μm from the machining feed amount detection means 29 to the control means 200, the control means 200 counts the input pulse signal and moves the chuck table 21 in the machining feed direction. Is detected.

  Similarly, an index feed amount detecting means 30 for detecting the index feed amount of the chuck table 21 is attached to the index feed means 28. The index feed amount detection means 30 includes a linear scale 30a disposed along the Y-axis direction, and a read head (not shown) that is disposed along the sliding block 26 and moves along the linear scale 30a together with the sliding block 26. Yes. For example, by sending a pulse signal of 1 pulse every 1 μm from the index feed amount detection means 30 to the control means 200, the control means 200 counts the input pulse signals and moves the chuck table 21 in the index feed direction. Is detected.

  Further, the laser beam irradiation means 22 includes a casing 31 arranged substantially horizontally, and the Z-axis direction (by the first focusing point position adjusting means 33 with respect to the support block 32 through the casing 31 ( It is provided to be movable in the vertical direction). The first condensing point position adjusting means 33 includes a ball screw 33a, a nut (not shown), a pulse motor 33b, and the like. A Z-axis feed amount detecting means 34 for detecting the amount of movement of the laser beam irradiating means 22 in the Z-axis feed direction is also attached to the first focusing point position adjusting means 33. The Z-axis feed amount detection means 34 includes a linear scale 34a disposed along the Z-axis direction and a read head (not shown) that is disposed in the casing 31 and moves along with the casing 31 along the linear scale 34a. . For example, by sending a pulse signal of one pulse every 1 μm from the Z-axis feed amount detection means 34 to the control means 200, the control means 200 counts the input pulse signals, and the vertical direction of the laser beam irradiation means 22. The amount of movement is detected.

  Further, as shown in FIGS. 3 and 4, the laser beam irradiation means 22 of the present embodiment includes a processing laser beam oscillation means 22 a and a transmission optical system disposed in the casing 31, and a tip of the casing 31. A condensing lens 22b and a mirror 22c disposed in the condensing part 31a are provided. The processing laser beam oscillation means 22a is for oscillating a pulsed processing laser beam having a wavelength, for example, 1064 nm, which is transmissive to the workpiece 1 held on the holding surface 21a of the chuck table 21. There is a laser beam oscillator composed of a YAG laser oscillator or a YVO4 laser oscillator. The condensing lens 22b condenses and irradiates the pulsed processing laser beam oscillated by the processing laser beam oscillation means 22a toward the workpiece 1 held on the holding surface 21a of the chuck table 21. It consists of a combination lens and the like. The mirror 22c is for reflecting the pulsed processing laser beam oscillated by the processing laser beam oscillation means 22a toward the workpiece 1 (condensing lens 22b).

  Therefore, before laser processing is performed on the workpiece 1, the casing 31 incorporating such a condensing lens 22 b is driven by the first condensing point position adjusting means 33 by driving the pulse motor 33 b and holding surface 21 a. The position of the condensing point of the processing laser beam condensed by the condensing lens 22b can be adjusted by moving in the vertical direction (Z-axis direction).

  Further, the image pickup means 100 mounted on the tip of the casing 31 picks up an image of the upper surface of the workpiece 1 held on the chuck table 21 and is irradiated from the condenser lens 22 b of the laser beam irradiation means 22. This is for detecting a region to be processed by a laser beam. The imaging unit 100 is configured by an imaging device (CCD) or the like, and sends a captured image signal to the control unit 200.

  The control means 200 is composed of a computer having a CPU (not shown) and a RAM (not shown) that execute arithmetic processing according to a control program stored in a ROM (not shown). This control means 200 controls the entire laser processing apparatus 20, and in particular, plays a part of the function of the height position detection means described later and controls the height position detection operation according to the laser processing program. To do.

  Here, the laser processing apparatus 20 according to the present embodiment includes the second condensing point position adjusting means 35 in the casing 31. The second condensing point position adjusting means 35 uses a piezo motor 35a having a fast response speed as a drive source, and at the time of height position detection operation or laser processing, the condensing lens 22b is independently operated at high speed in the vertical direction. This is for adjusting the condensing point position of the processing laser beam condensed by the condensing lens 22b. That is, the second condensing point position adjusting means 35 is for causing the condensing point position of the condensing lens 22b to follow unevenness of the upper surface (back surface 1b) of the workpiece 1. Therefore, the movable range of the second focusing point position adjusting means 35 is the height of the upper surface on the division lines 4a and 4b of the workpiece 1 to be processed as shown in FIG. It is set so as to be wider than the variation range and narrower than the movable range of the first condensing point position adjusting means 33.

  Further, the laser processing apparatus 20 according to the present embodiment uses a part of the laser beam irradiation means 22, the second focusing point position adjusting means 35, and the control means 200 to be processed held on the chuck table 21. A height position detecting means 39 for detecting the upper surface height position of the object 1 is provided. The height position detection means 39 includes a detection light emitting unit 39a, a dichroic mirror 39b, a half mirror 39c, a condenser lens 22b, a half mirror 39d, a cylindrical lens 39e, a slit 39f, and a detection optical system. A first light receiving element 39g and a second light receiving element 39h are provided.

  The detection light emitter 39a is for oscillating a detection beam having a frequency different from the frequency of the processing laser beam oscillated from the processing laser beam oscillation means 22a. In this embodiment, a CW laser light source that oscillates detection light having a wavelength of, for example, 635 nm is used. The dichroic mirror 39b is installed between the processing laser beam oscillation means 22a and the mirror 22c, transmits the processing laser beam emitted from the laser beam oscillation means 41, and detects light emitted from the detection light emitting section 39a. Is reflected toward the mirror 22c (condensing lens 22b) side. In addition, the half mirror 39c transmits the detection light beam emitted from the detection light emitting unit 39a to the dichroic mirror 39b side, while reflecting the detection light beam reflected by the workpiece 1 and reflected by the dichroic mirror 39b. belongs to.

  The condensing lens 22b is used for both processing and detection. The condensing lens 22b condenses the detection light beam that passes through the half mirror 39c and is reflected by the dichroic mirror 39a and the mirror 22c, and is held on the chuck table 21. A lens for irradiating the workpiece 1.

  The half mirror 39c is for splitting the detection light beam reflected by the workpiece 1 into the first optical path Oa and the second optical path Ob. The cylindrical lens 39e and the slit 39f are for restricting a part of the light guided to the first optical path Oa. The cylindrical lens 39e is a lens that is installed in the first optical path Oa and has a condensing function that condenses the detection light beam reflected by the workpiece 1 in one dimension. In the present embodiment, the cylindrical lens 39e is arranged so as to have a light collecting property in the front and back direction of the paper surface in FIG. 4 and not to have a light collecting property in the vertical direction of the paper surface. The slit 39f is positioned between the cylindrical lens 39e and the first light receiving element 39g, and is disposed in the first optical path Oa so that the longitudinal direction of the opening having a predetermined width is orthogonal to the light collection direction of the cylindrical lens 39e. It is a thing.

  Further, the first light receiving element 39g is composed of a photodetector that receives the light, which is guided by the first optical path Oa and regulated by the cylindrical lens 39e and the slit 39f, in the detection light beam reflected by the workpiece 1. The first light receiving element 39g outputs a voltage signal corresponding to the amount of received light to the control means 200. The second light receiving element 39h is made of a photodetector that receives all of the light guided to the second optical path Ob in the detection light beam reflected by the workpiece 1. The second light receiving element 39g outputs a voltage signal corresponding to the amount of received light to the control means 200.

  The detection system function unit as the height position detection unit 39 in the control unit 200 collects the detection light beam by the condensing lens 22b and irradiates the workpiece 1 held on the chuck table 21. First, a detection ratio between the amount of light received by the first light receiving element 39g and the amount of light received by the second light receiving element 39h, and the distance relationship between the upper surface of the workpiece 1 and the condenser lens 22b are set in advance. With reference to a control map stored in a memory (not shown), the upper surface of the workpiece 1 and the condensing lens based on the detection ratio between the received light amount of the first light receiving element 39g and the received light amount of the second light receiving element 39h. The distance information between 22b is acquired. Then, the piezo motor 35a is driven so that the sequentially acquired distance information becomes a predetermined constant value, and the condensing lens 22b is moved in the vertical direction by the second condensing point position adjusting means 35. Then, by storing the drive information of the piezo motor 35a at this time, the upper surface height position of the workpiece 1 is detected by acquiring the condenser lens movement information corresponding to the drive amount of the piezo motor 35a.

  Next, a laser processing control method for the workpiece 1 using such a laser processing apparatus 20 will be described. FIG. 5 is a schematic flowchart showing a laser processing control method executed by the control means 200 in accordance with the laser processing program. In processing, first, the workpiece 1 is placed on the holding surface 21a of the chuck table 21 and sucked and held. Then, the chuck table 21 that sucks and holds the workpiece 1 is positioned immediately below the imaging means 100, and an alignment operation for detecting a machining area of the workpiece 1 to be laser processed is executed. That is, image processing such as pattern matching for aligning the first division line 4a formed in a predetermined direction of the workpiece 1 and the condenser lens 22b is executed to perform alignment. The same applies to the second scheduled division line 4b.

  When alignment is performed in this way, the workpiece 1 on the chuck table 21 is positioned at a coordinate position as shown in FIG. FIG. 6 is an explanatory diagram showing the relationship with the coordinate position in a state where the workpiece 1 is held at a predetermined position of the chuck table 21. FIG. 6B shows a state in which the chuck table 21, that is, the workpiece 1 is rotated 90 degrees from the state shown in FIG. 6A and the second scheduled division line 4b is processed. .

  When the first scheduled division line 4a formed on the workpiece 1 held on the chuck table 21 is detected and the laser machining position is aligned, the control means 200 performs the workpiece in this way. The upper surface height position detection process and the laser processing process are performed along the first division line 4a formed on the workpiece 1 and to be processed. Here, each line of the first division planned line 4a is set to L, and the lowest line is set to L = 1.

  First, the pulse motor 28b is driven and the chuck table 21 is moved by the index feeding means 28, so that the lowest first division planned line 4a in FIG. 6A is positioned directly below the condenser lens 22b. Thereby, the process target line is set to L = 1 (step S1). Then, before the laser processing is performed on the workpiece 1, the pulse motor 33 b is driven on the first division planned line 4 a where L = 1, and the first focusing point position adjusting unit 33 collects in advance. By moving the optical lens 22b in the Z-axis direction, the focal point position of the processing laser beam condensed by the condenser lens 22b is adjusted to be the upper surface position of the first scheduled division line 4a where L = 1. (Step S2).

  Then, the pulse motor 27b is driven, and the machining feed means 27 moves the chuck table 21 (workpiece 1) from the head of the line in the X-axis direction at a predetermined speed (step S3). At the same time, the height position detecting means 39 is operated, and the detection light beam emitted from the detection light emitting section 39a is condensed by the condenser lens 22b and irradiated along the division line 4a of L = 1. Information on the distance between the condensing lens 22b and the upper surface of the division-scheduled line 4a is acquired based on the amount of received light reflected by the upper surface of the line 4a and detected by the first and second light receiving elements 39g and 39h (step S4). ). Then, it is determined whether or not the acquired distance information is a predetermined constant value set in advance (step S5). If the obtained distance information varies according to the unevenness of the upper surface of the planned dividing line 4a and is not constant (step S5: No), the piezo motor 35a is driven so as to cancel the variation and the second focusing point is obtained. The condenser lens 22b is moved in the vertical direction by the position adjusting means 35 (step S6). And it returns to step S4, S5 again, distance information of the condensing lens 22b and the upper surface of the division | segmentation scheduled line 4a is acquired, and it repeats until distance information becomes a predetermined fixed value (step S5: Yes).

  The piezo motor drive information at each coordinate position in the X-axis direction accompanying the movement in the X-axis direction is stored in the memory, including the footback control operation of the distance information by driving the piezo motor 35a (step S7), and the stored piezo motor By acquiring the condenser lens movement information corresponding to the drive information, the upper surface height position at each coordinate position on the planned division line 4a is detected (step S8).

  In such an operation of detecting the upper surface height position, it is determined whether or not a state in which the upper surface height position cannot be detected has occurred at all times (step S9). As a case where the upper surface height position cannot be detected, for example, as shown in FIG. 7A, the variation range of the upper surface height position of the planned dividing line 4a is the second condensing point position adjusting means. Although it is narrower than the movable range of 35, the upper surface height position of the planned dividing line 4a may be present above the movable range of the second condensing point position adjusting means 35.

  As described above, when there is a portion that cannot be detected because the upper surface height position is located above the movable range of the second condensing point position adjusting means 35 (step S9: Yes, step S10: Yes). ), The lowest position of the upper surface height existing on the lowest side on the division planned line 4a of L = 1 detected by the height position detecting means 39 is stored (step S11). Then, by driving the pulse motor 33b, the first condensing point position adjusting unit 33 causes the lowest condensing range of the second condensing point position adjusting unit 35 as shown in FIG. 7B. The position is positioned below the lowermost position by a slight dimension Δh (step S12). Then, the process returns to step S3, and the height position detection means 39 detects the upper surface height position on the division line 4a where L = 1 again. This process is repeated until no upper surface height position is detected (step S9: No).

  In addition, as a case where a location where the upper surface height position cannot be detected occurs, for example, as shown in FIG. 8A, the variation range of the upper surface height position of the planned dividing line 4a is the second condensing point position. In some cases, the upper surface height position of the planned division line 4a is present below the movable range of the second light condensing point position adjusting unit 35, although it is narrower than the movable range of the adjusting unit 35.

  As described above, when there is a portion that cannot be detected because the upper surface height position is below the movable range of the second condensing point position adjusting means 35 (step S9: Yes, step S10: No), the highest position of the upper surface height existing on the uppermost side on the division line 4a of L = 1 detected by the height position detecting means 39 is stored (step S13). Then, as shown in FIG. 8B, the uppermost position of the movable range of the second condensing point position adjusting means 35 is driven by the first condensing point position adjusting means 33 by driving the pulse motor 33b. Is positioned above the uppermost position by a slight dimension Δh (step S14). Then, the process returns to step S3, and the height position detection means 39 detects the upper surface height position on the division line 4a where L = 1 again. This process is repeated until no upper surface height position is detected (step S9: No).

  Then, when the upper surface height position is within the movable range of the second condensing point position adjusting means 39 and no detection is impossible (step S9: No), division with L = 1 It is determined whether or not the height position detection process for the planned line 4a is maintained (step S15). If not completed (step S15: No), the process from step S4 is repeated until the process is completed. .

  If completed (step S15: Yes), the laser beam irradiation means 22 while driving the pulse motor 27b and processing the workpiece 1 in the X-axis direction from the head of the line in the division planned line 4a with L = 1. Irradiating the target division planned line 4a with L = 1 by the processing laser beam and driving the piezo motor 35a based on the condenser lens movement information acquired by the height position detecting means 39. Laser processing is performed on the planned division line 4a while adjusting the condensing point position of the condensing lens 22b by the second condensing point position adjusting means 35 (step S16). That is, as in the case of detecting the height position, by driving the piezo motor 35a based on the condensing lens movement information corresponding to the piezo motor driving information, the condensing point position of the condensing lens 22b becomes the upper surface of the division planned line 4a. Following the unevenness variation, the processing laser beam is always focused at a predetermined depth from the upper surface, and a modified layer is formed inside along the first scheduled dividing line 4a. At this time, the height position of the first condensing point position adjusting means 33 remains fixed.

  In the detection operation of the upper surface height position of the planned division line 4a by the height position detection means 39, there is a time lag in the following operation of the piezo motor 35b and the condenser lens 22b when the distance information varies. Therefore, when driving the piezo motor 35a based on the condensing lens movement information corresponding to the piezo motor drive information in actual laser processing, the time lag may be taken into account for correction.

  Such laser processing is repeated until the processing is completed for the division planned line 4a with L = 1 (step S17: No). When the processing on the division planned line 4a with L = 1 is completed (step S17: Yes), it is determined whether or not the processing target line L is the final line in the division planned line 4a (step S18). If the processing target line L is not the final line (step S18: No), the processing target line L is incremented by +1 and the target is moved to the next line in the division planned line 4a (step S19), and the processing after step S3 is performed. Repeat in the same way. If the processing target line L is the final line (step S18: Yes), the processing for the division planned line 4a is finished, the workpiece 1 is rotated 90 degrees, and the upper surface for each line of the division planned line 4b The height position detection process and the laser processing process are executed in the same manner.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the present embodiment, the processing laser beam having a wavelength that passes through the workpiece 1 is irradiated by aligning the focal point irradiation position from the upper surface (back surface 1b) of the workpiece 1 to a predetermined depth position. As described in the case of laser processing for forming a modified layer, by aligning the focal point irradiation position with the upper surface (surface) of the workpiece and irradiating the processing laser beam with a wavelength absorbed by the workpiece. Even in the case of laser processing for forming a laser processing groove, the same can be applied.

  Further, since films of various materials may be formed on the device surface side or there may be irregularities, it may be necessary to irradiate a processing laser beam from the back side of the workpiece during laser processing. In such a case, only a surplus area around the device where no device is formed on the workpiece so that the protective tape is not attached to the device surface side that is not touched or held on the chuck table. In order to hold and process the chuck table, a chuck table having a concave cross section may be used.

  FIG. 9 is a perspective view illustrating a modified example, and FIG. 10 is a cross-sectional view illustrating a holding state of a workpiece in the modified example. First, as shown in FIG. 9, the workpiece 1 is formed with a plurality of devices 5 that are commercialized in a rectangular area defined by the first and second scheduled division lines 4 a and 4 b in the vicinity of the center. The device area 9a is surrounded by a surplus area 9b surrounding the device area 9a. The workpiece 1 thus formed and mounted on the annular frame 2 is held by a chuck table 41 having a holding surface 41a.

  Here, the chuck table 41 is formed in a substantially circular shape with a size corresponding to the workpiece 1, and the holding surface 41 a is formed by the upper surface of an annular rib portion 41 b formed integrally with the outer periphery of the upper surface of the chuck table 41. ing. The annular rib portion 41b and the chuck table 41 are formed with a suction hole 41d communicating with a suction groove 41c formed on the holding surface 41a. The suction hole 41d communicates with the suction means 42. Here, the holding surface 41a is formed at a position corresponding to the surplus area 9b of the workpiece 1. When the holding surface 41a is held, as shown in FIG. 10, the holding surface 41a is brought into contact with only the surplus area 9b. The workpiece 1 is set to be sucked and held. That is, in the holding state of the workpiece 1, the device 5 in the device region 9a is held without touching anywhere. The chuck table 41 has a pair of clamps 43 positioned around the chuck table 41, and is configured to hold the annular frame 2 in a detachable manner.

  The laser processing of the present embodiment is particularly effective when using the chuck table 41 having such a concave cross section. In the case of holding by such a chuck table 41, if the modified layer is formed along the division lines 4a and 4b, the strength of the workpiece 1 is lowered and the deflection is increased as the processing proceeds, and the collection is increased. This is because the upper surface of the workpiece 1 may move outside the focus adjustment range of the optical lens.

1 is an external perspective view showing a workpiece to be processed in an embodiment of the present invention. It is an external appearance perspective view which shows the principal part of the laser processing apparatus of this Embodiment. It is a schematic side view which shows the whole structure including optical system structures, such as a laser beam irradiation means. It is a schematic side view which expands and shows a part of FIG. It is a schematic flowchart which shows the laser processing control method performed by a control means according to the program for laser processing. It is explanatory drawing which shows the relationship with the coordinate position in the state by which the to-be-processed object was hold | maintained at the predetermined position of the chuck table. It is explanatory drawing about the case where the upper surface height position of a division | segmentation planned line exists above the movable range of the 2nd condensing point position adjustment means. It is explanatory drawing about the case where the upper surface height position of a division | segmentation planned line exists below the movable range of the 2nd condensing point position adjustment means. It is a perspective view which shows a modification. It is sectional drawing which shows the holding state of the to-be-processed object in a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Workpiece 4a, 4b Planned division line 20 Laser processing apparatus 21 Chuck table 21a Holding surface 22 Laser beam irradiation means 22a Laser beam oscillation means for processing 22b Condensing lens 27 Processing feed means 33 First focusing point position adjusting means 35 Second focusing point position adjusting means 35a Piezo motor 39 Height position detecting means 41 Chuck table 200 Control means

Claims (3)

A chuck table having a holding surface for holding a workpiece defined by the division lines,
Processing laser beam oscillation means for oscillating a processing laser beam for laser processing the workpiece held on the holding surface of the chuck table, and a processing laser oscillated by the processing laser beam oscillation means A laser beam irradiating means having a condensing lens for condensing the light beam;
A machining feed means for relatively moving the chuck table and the laser beam irradiation means in a machining feed direction;
Before performing laser processing on the workpiece, the focusing point position of the processing laser beam focused by the focusing lens by moving the focusing lens in a direction perpendicular to the holding surface in advance is determined. First focusing point position adjusting means to be adjusted;
The piezo motor is driven by the piezo motor that is set to a movable range that is wider than the range of variation of the upper surface height on the division line that the workpiece has and that is narrower than the movable range of the first focusing point position adjusting means. A second condensing point position adjusting means for moving the condensing lens in the vertical direction and adjusting a condensing point position of a processing laser beam condensed by the condensing lens;
Before performing laser processing on the target division line, the detection light beam emitted from the detection light source is condensed by the condensing lens while moving the workpiece relative to the processing feed direction. Then, the distance information between the condensing lens and the upper surface of the planned division line based on the reflected light that is irradiated along the planned division line of the workpiece on the holding surface and reflected on the upper surface of the planned division line The piezo motor is driven so that the acquired distance information becomes a predetermined constant value, and the condensing lens is moved in the vertical direction by the second condensing point position adjusting means. A height position detecting means for detecting the upper surface height position of the planned dividing line by storing the driving information and acquiring the condenser lens movement information;
Control means for controlling the operation of the laser processing apparatus;
With
When the control means detects the upper surface height position of the division planned line to be targeted by the height position detection means,
If there is a portion that cannot be detected because the upper surface height position is above the movable range of the second focusing point position adjusting means, the division detected by the height position detecting means The lowest position of the upper surface height existing on the lowermost side on the planned line is stored, and the first condensing point position adjusting means is the most movable range of the second condensing point position adjusting means. The lower position is positioned below the lowest position, and the upper surface height position on the division planned line is detected again by the height position detecting means,
If there is a portion that cannot be detected because the upper surface height position is below the movable range of the second focusing point position adjusting means, the height position detecting means The uppermost position of the upper surface height existing on the uppermost line on the division planned line is stored, and the uppermost position of the movable range of the second condensing point position adjusting unit is stored by the first condensing point position adjusting unit Is positioned above the uppermost position, and the height position detecting means again detects the upper surface height position on the division planned line,
If the upper surface height position is within the movable range of the second focusing point position adjusting means and there is no place that cannot be detected, the workpiece is moved relative to the machining feed direction. The laser beam irradiating unit irradiates the target division planned line with a processing laser beam, and at the same time, based on the condenser lens movement information acquired by the height position detecting unit, the piezo motor The laser processing apparatus is characterized in that laser processing is performed on the planned division line while adjusting the condensing point position of the condensing lens by the second condensing point position adjusting means. A chuck table having a holding surface for holding a workpiece defined by the division lines,
Processing laser beam oscillation means for oscillating a processing laser beam for laser processing the workpiece held on the holding surface of the chuck table, and a processing laser oscillated by the processing laser beam oscillation means A laser beam irradiating means having a condensing lens for condensing the light beam;
A machining feed means for relatively moving the chuck table and the laser beam irradiation means in a machining feed direction;
Before performing laser processing on the workpiece, the focusing point position of the processing laser beam focused by the focusing lens by moving the focusing lens in a direction perpendicular to the holding surface in advance is determined. First focusing point position adjusting means to be adjusted;
The piezo motor is driven by the piezo motor that is set to a movable range that is wider than the range of variation of the upper surface height on the division line that the workpiece has and that is narrower than the movable range of the first focusing point position adjusting means. A second condensing point position adjusting means for moving the condensing lens in the vertical direction and adjusting a condensing point position of a processing laser beam condensed by the condensing lens;
Before performing laser processing on the target division line, the detection light beam emitted from the detection light source is condensed by the condensing lens while moving the workpiece relative to the processing feed direction. Then, the distance information between the condensing lens and the upper surface of the planned division line based on the reflected light that is irradiated along the planned division line of the workpiece on the holding surface and reflected on the upper surface of the planned division line The piezo motor is driven so that the acquired distance information becomes a predetermined constant value, and the condensing lens is moved in the vertical direction by the second condensing point position adjusting means. A height position detecting means for detecting the upper surface height position of the planned dividing line by storing the driving information and acquiring the condenser lens movement information;
Using a laser processing apparatus having
When detecting the upper surface height position of the division planned line as a target by the height position detection means,
If there is a portion that cannot be detected because the upper surface height position is above the movable range of the second focusing point position adjusting means, the division detected by the height position detecting means The lowest position of the upper surface height existing on the lowermost side on the planned line is stored, and the first condensing point position adjusting means is the most movable range of the second condensing point position adjusting means. Positioning the lower position below the lowermost position and causing the height position detecting means to detect the upper surface height position on the planned dividing line again;
If there is a portion that cannot be detected because the upper surface height position is below the movable range of the second focusing point position adjusting means, the height position detecting means The uppermost position of the upper surface height existing on the uppermost line on the division planned line is stored, and the uppermost position of the movable range of the second condensing point position adjusting unit is stored by the first condensing point position adjusting unit Positioning the position above the uppermost position, and again detecting the upper surface height position on the planned dividing line by the height position detecting means;
If the upper surface height position is within the movable range of the second focusing point position adjusting means and there is no place that cannot be detected, the workpiece is moved relative to the machining feed direction. The laser beam irradiating unit irradiates the target division planned line with a processing laser beam, and at the same time, based on the condenser lens movement information acquired by the height position detecting unit, the piezo motor Performing laser processing on the planned dividing line while adjusting the condensing point position of the condensing lens by the second condensing point position adjusting means,
A laser processing control method comprising: A chuck table having a holding surface for holding a workpiece defined by the division lines,
Processing laser beam oscillation means for oscillating a processing laser beam for laser processing the workpiece held on the holding surface of the chuck table, and a processing laser oscillated by the processing laser beam oscillation means A laser beam irradiating means having a condensing lens for condensing the light beam;
A machining feed means for relatively moving the chuck table and the laser beam irradiation means in a machining feed direction;
Before performing laser processing on the workpiece, the focusing point position of the processing laser beam focused by the focusing lens by moving the focusing lens in a direction perpendicular to the holding surface in advance is determined. First focusing point position adjusting means to be adjusted;
The piezo motor is driven by the piezo motor that is set to a movable range that is wider than the range of variation of the upper surface height on the division line that the workpiece has and that is narrower than the movable range of the first focusing point position adjusting means. A second condensing point position adjusting means for moving the condensing lens in the vertical direction and adjusting a condensing point position of a processing laser beam condensed by the condensing lens;
Before performing laser processing on the target division line, the detection light beam emitted from the detection light source is condensed by the condensing lens while moving the workpiece relative to the processing feed direction. Then, the distance information between the condensing lens and the upper surface of the planned division line based on the reflected light that is irradiated along the planned division line of the workpiece on the holding surface and reflected on the upper surface of the planned division line The piezo motor is driven so that the acquired distance information becomes a predetermined constant value, and the condensing lens is moved in the vertical direction by the second condensing point position adjusting means. A height position detecting means for detecting the upper surface height position of the planned dividing line by storing the driving information and acquiring the condenser lens movement information;
In a computer provided in a laser processing apparatus having
When detecting the upper surface height position of the division planned line as a target by the height position detection means,
If there is a portion that cannot be detected because the upper surface height position is above the movable range of the second focusing point position adjusting means, the division detected by the height position detecting means The lowest position of the upper surface height existing on the lowermost side on the planned line is stored, and the first condensing point position adjusting means is the most movable range of the second condensing point position adjusting means. A function of positioning the lower position below the lowest position and detecting the upper surface height position on the planned dividing line again by the height position detecting means;
If there is a portion that cannot be detected because the upper surface height position is below the movable range of the second focusing point position adjusting means, the height position detecting means The uppermost position of the upper surface height existing on the uppermost line on the division planned line is stored, and the uppermost position of the movable range of the second condensing point position adjusting means is stored by the first condensing point position adjusting means. A position of the upper position above the uppermost position, and the height position detecting means again detects the upper surface height position on the planned dividing line,
If the upper surface height position is within the movable range of the second focusing point position adjusting means and there is no place that cannot be detected, the workpiece is moved relative to the machining feed direction. The laser beam irradiating unit irradiates the target division planned line with a processing laser beam, and at the same time, based on the condenser lens movement information acquired by the height position detecting unit, the piezo motor A function of performing laser processing on the planned dividing line while adjusting the condensing point position of the condensing lens by the second condensing point position adjusting means,
The program for laser processing characterized by performing this.

Images