JP2010266407A - Height detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To use all the wavelengths of the diffracted beams of a desired order, when using diffraction. <P>SOLUTION: A height detector includes a height-detecting means 120, having an optic fiber 121 for regulating passage of beam other than the beam forming a focus in the vicinity of a surface of a workpiece 1 among reflected beams; a diffraction optic element 122 for splitting the reflected beam which has passed through the optic fiber 121 into diffraction beam spreading in the same plane; and a primary diffraction beam detecting means 130 for detecting only the primary diffracted beam among the primary diffracted beam and higher-order diffracted beams contained in the diffraction beam. The primary diffracted beam detecting means 130 includes a diffracted beam condenser lens 131 for condensing the diffracted beam; a wavelength dispersion filter 132 for refracting the condensed diffracted beam, in a direction of going out of the same plane, at different angles for each of wavelengths; a wavelength detection sensor 133, having a detecting part only at a portion where the primary diffraction beam is condensed so as to detect the beam intensity of each wavelength of only the primary diffracted beam; and a memory 134 for storing a control map in which focus distances of the respective wavelengths of white beam condensed by a chromatic aberration lens 102 are stored. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a height detection apparatus that measures the height position of a workpiece surface such as a semiconductor wafer to be laser processed, for example.

  In the semiconductor device manufacturing process, a plurality of areas are defined by streets (division lines) arranged in a grid pattern on the surface of a semiconductor work having a substantially disk shape, and circuits such as IC and LSI are defined in the partitioned areas. Each semiconductor chip is manufactured by dividing each semiconductor circuit by cutting the semiconductor work on which the film is formed along the street. Cutting along the streets of a semiconductor work is usually performed by a cutting device called a dicer, but a processing method of cutting by irradiating a laser beam has also been attempted.

  For example, as a method of dividing a workpiece such as an optical device wafer along the street, a laser processing groove is formed by irradiating the workpiece with a pulsed laser beam having a wavelength that absorbs the workpiece along the street. A method of cleaving by applying an external force along the groove has been proposed (see, for example, Patent Document 1).

  In addition, a laser processing method has been attempted in which a pulse laser beam having a wavelength that is transmissive to the workpiece is used, and the pulse laser beam is irradiated with a focused point inside the region to be divided. The dividing method using this laser processing method is to irradiate a pulse laser beam having a wavelength that is transmissive to the workpiece by aligning the condensing point from one side of the workpiece to the inside, along the street along the street. The modified layer is continuously formed, and the work is divided by applying an external force along the street whose strength is reduced by forming the modified layer (see, for example, Patent Document 2). .

  By the way, a plate-like workpiece such as a wafer has undulation, and the surface height position of the workpiece is not constant. Therefore, in any of the above processing methods, in order to be able to divide the workpiece into chips with good quality when external force is applied, the height position of the workpiece surface is detected, and the laser is processed during laser processing based on the detection result. It is necessary to uniformly form the laser processing groove and the modified layer by correcting the focal position of the beam. Thus, for example, a detection device that detects the height position of the workpiece surface using white light has been proposed (see, for example, Patent Document 3). That is, using the fact that white light that has passed through a chromatic aberration lens has a different focal length depending on the wavelength, the focal length is obtained by specifying the wavelength of reflected light that has passed through the pinhole, and the surface height position of the workpiece is measured. It is what I did.

JP-A-10-305420 Japanese Patent No. 3408805 JP 2008-170366 A

  These proposed examples made it possible to accurately measure the height position of the workpiece surface. However, when light is dispersed for each wavelength by using diffraction, a phenomenon in which adjacent order spectra partially overlap occurs, and therefore only wavelengths in the free spectral region where no overlap occurs can be used for detection. That is, the wavelength range that can be used for detection is limited.

  The present invention has been made in view of the above, and an object of the present invention is to provide a height detection device that can use all wavelengths of diffracted light of a desired order for detection when diffraction is used. .

  In order to solve the above-described problems and achieve the object, a height detection device according to the present invention is a height detection device that is mounted on a processing machine and detects the height of a work held by a holding means. A white light source that emits white light, a chromatic aberration lens that condenses each wavelength included in the white light, and forms a plurality of condensing points on the optical axis toward the workpiece, and the chromatic aberration lens collects the light. Height detecting means for detecting reflected light reflected by the workpiece and being reflected by the workpiece, the height detecting means other than light focused on the workpiece surface in the vicinity of the workpiece surface. A light restricting means that restricts the passage of light, a diffractive optical element that branches the reflected light that has passed through the light restricting means into diffracted light that spreads in the same plane, and predetermined nth-order diffracted light (n Is an integer) and the nth order is a different order. N-order diffracted light detecting means for detecting only the n-th order diffracted light out of the folded light, and the n-th order diffracted light detecting means collects the diffracted light including the n-order diffracted light and the different-order diffracted light. The diffracted light collecting lens, and the diffracted light including the nth-order diffracted light and the different-order diffracted light collected by the diffracted light condensing lens at different angles for each wavelength in the direction outside the same plane. A refracting wavelength dispersion filter, and a detection unit only at a location where the n-order diffracted light is condensed among the n-order diffracted light and the different-order diffracted light that are collected at different locations for each wavelength by the wavelength dispersion filter And a control map storing a focal length of each wavelength included in the white light collected by the chromatic aberration lens, and detecting a light intensity for each wavelength of only the n-th order diffracted light. Memory, including And obtaining the height position of the workpiece held by the holding means based on the signal and the control map from the wavelength sensor.

  ADVANTAGE OF THE INVENTION According to this invention, when using diffraction, the height detection apparatus which can utilize for detection all the wavelengths of the diffracted light of a desired order can be provided.

FIG. 1 is an external perspective view showing a main part of a laser processing apparatus equipped with a height detection apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view showing a workpiece used for processing by the laser processing apparatus. FIG. 3 is a block diagram schematically showing the height detection apparatus of the present embodiment. FIG. 4 is a schematic diagram illustrating a state of the light collection position. FIG. 5 is an enlarged configuration diagram illustrating a portion A in FIG. FIG. 6 is an enlarged configuration diagram showing a portion B in FIG. FIG. 7 is an explanatory diagram showing the relationship with the coordinate position in a state where the workpiece is held at a predetermined position of the holding means.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a height detection device that is a mode for carrying out the present invention will be described with reference to the drawings. In this embodiment, a height detection device that detects the height position of a workpiece such as a semiconductor wafer in which devices are formed in a plurality of regions partitioned by a plurality of streets arranged in a lattice shape as a detection target. An application example will be described in which the workpiece is mounted on a laser processing apparatus which is a processing machine that performs laser processing by irradiating a workpiece with a processing laser beam along a street.

  FIG. 1 is an external perspective view showing a main part of a laser processing apparatus equipped with a height detection device of the present embodiment, and FIG. 2 is a perspective view showing a workpiece used for processing by the laser processing apparatus. . The laser processing apparatus 20 according to the present embodiment irradiates a pulsed processing laser beam onto a holding unit 21 having a holding surface 21a for holding the workpiece 1 and the workpiece 1 held on the holding surface 21a of the holding unit 21. Then, a processing laser beam irradiating means 22 for laser processing and a height detecting device 100 for detecting the height position of the surface of the work 1 held on the holding surface 21a of the holding means 21 as a detection target are provided. ing. The holding means 21 sucks and holds the workpiece 1 and is rotatably connected to a motor (not shown) in the cylindrical portion 24.

  First, as shown in FIG. 2, a workpiece 1 to be processed is prepared with a surface 1a facing upward on a dicing tape 3 made of a synthetic resin sheet such as polyolefin mounted on an annular frame 2. Is done. The workpiece 1 is not particularly limited. For example, an adhesive member such as a wafer such as a semiconductor wafer, a DAF (Die Attach Film) provided on the back surface of the wafer for chip mounting, or a package of semiconductor products, ceramic, glass, etc. Examples thereof include various types of processing materials that require accuracy of the order of μm. The workpiece 1 of the present embodiment is based on a semiconductor wafer or the like, and has a plurality of first streets 4a extending in the X-axis direction and a plurality of second streets 4b extending in the Y-axis direction, which are arranged in a lattice pattern on the surface 1a. And a plurality of rectangular areas are formed, and the device 5 is formed in the plurality of rectangular areas.

  The holding means 21 is mounted on two stages of sliding blocks 25 and 26. The holding means 21 is provided and mounted on the sliding block 25 so as to be movable in the X-axis direction, which is the horizontal direction, by a processing feed means 29 constituted by a ball screw 27, a nut (not shown), a pulse motor 28, and the like. The workpiece 1 is processed and fed relative to the pulse laser beam irradiated by the processing laser beam irradiation means 22. Similarly, the holding means 21 is provided so as to be movable in the Y-axis direction, which is the horizontal direction, by an index feeding means 32 constituted by a ball screw 30, a nut (not shown), a pulse motor 31 and the like with respect to the sliding block 26. The mounted workpiece 1 is indexed and sent relative to the pulsed laser beam irradiated by the processing laser beam irradiation means 22.

  Here, the processing feed means 29 is provided with a processing feed amount detection means 33 for detecting the processing feed amount of the holding means 21. The processing feed amount detection means 33 includes a linear scale 33a disposed along the X-axis direction, and a reading head (not shown) disposed along the linear scale 33a along with the sliding block 25. Yes. The machining feed amount detection means 33 sends a pulse signal of 1 pulse to a control means (not shown) for every 1 μm, for example, and this control means counts the input pulse signal and detects the machining feed amount of the holding means 21. To do.

  Similarly, an index feed amount detection means 34 for detecting the index feed amount of the holding means 21 is attached to the index feed means 32. The index feed amount detection means 34 includes a linear scale 34a disposed along the Y-axis direction and a read head (not shown) disposed along the linear block 34a and disposed along the sliding block 26 along the linear scale 34a. Yes. For example, the indexing feed amount detection means 34 sends a pulse signal of one pulse every 1 μm to the control means, so that the control means counts the input pulse signals and detects the indexing feed amount of the holding means 21.

  Further, the processing laser beam irradiation means 22 includes a casing 35 arranged substantially horizontally, and can be moved in the Z-axis direction by a Z-axis moving means (not shown) via the casing 35 with respect to the support block 36. Is provided. The processing laser beam irradiating means 22 includes a laser beam oscillating means and a transmission optical system (not shown) provided in the casing 35, and a pulse-like processing oscillated by the laser beam oscillating means provided at the tip of the casing 35. A condenser 39 for irradiating the workpiece 1 held by the holding means 21 with a laser beam is provided. The laser beam oscillation means is constituted by a laser beam oscillator composed of a YAG laser oscillator or a YVO4 laser oscillator. A condenser lens for processing for condensing and irradiating the workpiece 1 with the laser beam for processing is provided in the condenser 39. For the processing condensing lens, a Z-axis lens actuator that performs fine adjustment of focusing in the Z-axis direction at high speed is provided.

  Further, the height detection device 100 attached to the tip of the casing 35 precedes the processing laser beam irradiation means 22 on the street to be processed of the workpiece 1 held on the holding surface 21a of the holding means 21. The detection light is irradiated to detect the surface height position on the street. In detecting the surface height, even if the height position of the surface 1a of the workpiece 1 fluctuates, a good laser processing groove is formed by matching the focusing position of the laser beam for processing with the height position of the surface 1a. It is. Information on the surface height position detected by the height detection device 100 is sent to the control means, and processing (not shown) in the condenser 39 that irradiates the processing laser beam to the workpiece 1 during laser processing of the street. This is used for control of a Z-axis lens actuator for focusing the condenser lens for use.

  FIG. 3 is a configuration diagram schematically showing the height detection apparatus 100 of the present embodiment, FIG. 4 is a schematic diagram showing the state of the light collecting position, and FIG. 5 is a portion A in FIG. FIG. 6 is an enlarged configuration diagram showing a portion B in FIG. 3. The height detection apparatus 100 of the present embodiment mainly includes a white light source 101, a chromatic aberration lens 102, and a height detection means 120.

  The white light source 101 is a light source that emits white light including light of a plurality of wavelengths, and a tungsten lamp, a halogen lamp, a white LED, or the like can be used. In this embodiment, for example, a halogen lamp is used. The chromatic aberration lens 102 is for condensing and irradiating white light emitted from the white light source 101 toward the holding surface 21 a (work 1) side of the holding means 21. Here, the chromatic aberration lens 102 is a condensing lens that forms a plurality of focal points on the optical axis toward the workpiece 1 for each wavelength included in white light. That is, since the white light collected by the chromatic aberration lens 102 has a different refractive index depending on the wavelength, the focal length differs depending on the wavelength. As such a chromatic aberration lens 102, for example, an aspherical lens having a numerical aperture NA = 0.68 and a viewing angle WD = 1.56 mm is used.

  Here, between the white light source 101 and the chromatic aberration lens 102, a collimating lens 105, a condenser lens 106, an irradiation side optical fiber 107, and a collimating lens 108 are arranged in this order. The irradiation side optical fiber 107 forms a first optical path 109a, and is used to stably propagate only white light necessary for the chromatic aberration lens 102 with respect to white light emitted from the white light source 101. Further, the collimating lens 105 and the condensing lens 106 are lenses for converting the white light emitted from the white light source 101 into a parallel beam and then condensing it so as to efficiently enter the incident end of the irradiation side optical fiber 107. In either case, a lens in which the influence of chromatic aberration is suppressed is used. Further, a fiber coupler 110 that is integrated with the incident end side of the optical fiber 121 is provided on the emission end side of the irradiation side optical fiber 107, and is connected to the common optical fiber 111. The collimating lens 108 provided between the common optical fiber 111 and the chromatic aberration lens 102 converts the white light emitted from the common optical fiber 111 through the irradiation side optical fiber 107 into a parallel beam and guides it to the chromatic aberration lens 102. This lens suppresses the influence of chromatic aberration.

  The height detection means 120 is for detecting the surface height position of the workpiece 1 based on the reflected light of the white light condensed by the chromatic aberration lens 102 and reflected by the surface of the workpiece 1. The height detection unit 120 mainly includes an optical fiber 121, a diffractive optical element 122, and a first-order diffracted light detection unit 130. The optical fiber 121 forms a second optical path 109b different from the first optical path 109a, and light other than the light focused on the surface of the work 1 out of the reflected light of the white light reflected on the surface of the work 1 Is a light regulating means for regulating the passage of light. Here, regulation means not only the case where light does not pass completely but also the case where part does not pass light. As the optical fibers 107, 111, and 121, a multimode fiber having a core and a clad and having a core diameter of 50 μm, for example, is used.

  The diffractive optical element 122 is a diffraction grating for converting into detection diffracted light corresponding to the wavelength component of the reflected light that has passed through the optical fiber 121. For this reason, the diffractive optical element 122 of the present embodiment converts the reflected light, which is guided to the second optical path 109b by the optical fiber 121 and parallelized by the collimating lens 123 at the output end of the optical fiber 121, in the same plane, For example, it is dispersed in diffracted light spreading in the YZ plane. The collimating lens 123 is also a lens that suppresses the influence of chromatic aberration.

  The first-order diffracted light detecting means 130 is a detecting means for detecting only the first-order diffracted light out of the first-order diffracted light and the higher-order diffracted light such as the second-order diffracted light included in the diffracted light branched by the diffractive optical element 122. And is provided as n-th order diffracted light detection means. The first-order diffracted light detection means 130 mainly includes a diffracted light condensing lens 131, a wavelength dispersion filter 132, a wavelength detection sensor 133, a memory 134, and a surface height position calculation unit 135.

  The diffracted light condensing lens 131 condenses diffracted light including first-order diffracted light (n-order diffracted light) and higher-order diffracted light (different-order diffracted light) branched by the diffractive optical element 122 toward the wavelength detection sensor 133. belongs to. Further, the wavelength dispersion filter 132 is a direction outside the YZ plane (same plane) where the diffractive optical element 122 branches the diffracted light including the first order diffracted light and the higher order diffracted light collected by the diffracted light condensing lens 131. That is, it is an optical element for refracting at different angles for each wavelength so as to have a spread in the X-axis direction. For example, a prism or the like can be used.

  In addition, the wavelength detection sensor 133 has a detection unit only at a location where the first-order diffracted light is condensed among the first-order diffracted light and the high-order diffracted light that are collected at different locations for each wavelength by the wavelength dispersion filter 132. And it is for detecting the light intensity for every wavelength of only 1st-order diffracted light. That is, the wavelength detection sensor 133 is branched by the diffractive optical element 122 and received by the detection unit only the first-order diffracted light among the diffracted light that is incident on different positions according to the wavelength by the diffraction condensing lens 131, The light intensity for each wavelength is detected. As the wavelength detection sensor 133, a CCD line sensor, a CMOS sensor, or the like that can detect the wavelength of the diffracted light condensed by the diffraction condensing lens 131 can be used.

  Here, the state of the condensing position of the diffracted light condensed on the wavelength detection sensor 133 through the diffractive optical element 122, the diffractive condensing lens 131, and the wavelength dispersion filter 132 will be described with reference to FIG. For example, when a wavelength region of 400 to 1000 nm is to be used as the first-order diffracted light based on the self-colored light, each wavelength light 400, 500, 600, 700 in the first-order diffracted light that has passed through the diffractive optical element 122 and the diffraction condensing lens 131 is used. , 800, 900, and 1000 nm are branched and condensed so as to spread to positions corresponding to wavelengths in the same plane (YZ plane) as shown in FIG. At this time, as high-order diffracted light, for example, a part of the spectrum of second-order diffracted light that is adjacent order light overlaps with the long-wavelength side spectrum of the first-order diffracted light. Specifically, the wavelength light 400 and 500 nm in the second-order diffracted light that has passed through the diffractive optical element 122 and the diffractive condenser lens 131 are substantially overlapped with the 800 and 1000 nm in the first-order diffracted light in the same plane (YZ plane). Focused. As a result, the wavelength detection sensor 133 cannot distinguish between the first-order diffracted light 800 nm and the second-order diffracted light 400 nm, the first-order diffracted light 1000 nm and the second-order diffracted light 500 nm, and is restricted in use in the free spectral region of the first-order diffracted light having a wavelength of 700 nm or less. It will be.

  Therefore, in this embodiment, the wavelength dispersion filter 132 is added, and the first-order diffracted light and the second-order diffracted light are angled differently for each wavelength in the direction outside the YZ plane (same plane) branched by the diffractive optical element 122. As shown in FIG. 4, the first-order diffracted light and the second-order diffracted light can be discriminated by giving a two-dimensional spread in the X-axis direction as shown in FIG. The detection unit 133a of the wavelength detection sensor 133 collects the first-order diffracted light out of the first-order diffracted light and the second-order diffracted light (high-order diffracted light) collected by the wavelength dispersion filter 132 at different positions for each wavelength. It arrange | positions so that it may have a sensitivity only in a location. Accordingly, there is no overlapping region between the first-order diffracted light and the second-order diffracted light in the detection unit 133a, and the entire wavelength region of 400 to 1000 nm can be used as the desired first-order diffracted light.

  Further, the surface height position calculation unit 135 sets the relationship between the focal length of each wavelength light included in the white light collected by the chromatic aberration lens 102 and the surface height position of the workpiece 1 in advance and stores it in the memory 134. The height position information is obtained by calculating the surface height position of the workpiece W based on the detection result of the wavelength detection sensor 133 with reference to the control map. The control map in which the focal length of each wavelength is set and stored in the memory 134 includes the Z-axis height (the height position of the surface 1a of the workpiece 1) and the detection wavelength of the peak detected by the wavelength detection sensor 133. This relationship is obtained by measuring in advance.

  Next, the detection principle of the height position of the surface 1a of the workpiece 1 in the present embodiment will be described. White light emitted from the white light source 101 is output from the end of the fiber through optical fibers 107 and 111, converted into a parallel beam by the collimator lens 108, and then condensed on the surface 1 a of the workpiece 1 through the chromatic aberration lens 102. The The white light reflected by the surface 1a reverses the optical path. At this time, the light focused on the surface 1a of the workpiece 1 is only light of a specific wavelength. Therefore, among the white light, light having a wavelength focused on the surface 1a is most strongly recombined with the small-diameter core of the common optical fiber 111 (optical fiber 121), and light having other wavelengths is recombined with the common optical fiber 111 ( The optical fiber 121) is cut off with little recombination with the core.

  As a result, the focused wavelength light recombined with the core of the common optical fiber 111 (optical fiber 121) is efficiently guided to the diffractive optical element 122 side in the detection means 120 by the optical fiber 121. Then, the light is branched by the diffractive optical element 122 into diffracted light spreading in a predetermined YZ plane. The branched diffracted light is condensed by the wavelength detection sensor 133 at an angle corresponding to the wavelength by the diffraction condensing lens 131. At this time, the diffracted light collected by the diffraction condensing lens 131 may include second-order diffracted light in addition to the first-order diffracted light. With folding light, the light is refracted at different angles in accordance with the wavelength in the X-axis direction outside the YZ plane with respect to a predetermined YZ plane. Only the first-order diffracted light is received by the detection unit 133 a of the wavelength detection sensor 133. The wavelength detection sensor 133 can detect the wavelength of light focused on the surface 1a of the workpiece 1 by measuring the wavelength of the received light (first-order diffracted light) and calculating the peak of the measured wavelength. it can.

  Therefore, the surface height position calculation unit 135 acquires the peak wavelength information as the detection result from the wavelength detection sensor 133 and refers to the control map stored in the memory 134, so that the height of the surface 1 a of the current workpiece 1 is high. The height position information is obtained by calculating the height position. Here, since the wavelength detection sensor 133 using a spectroscope can sequentially acquire peak wavelength information at a high speed of a sampling rate of 1 kHz or higher, for example, when the workpiece 1 moves at a speed of 600 mm / s, each of the streets S1 and S2 The height of the surface 1a of the workpiece 1 can be measured at intervals of 0.6 mm.

  In the present embodiment, since the white light is condensed by the chromatic aberration lens 102 and irradiated toward the holding surface 21a, the surface 1a of the workpiece 1 is compared with the case where single wavelength light is used. Even if there are variations in the height position, there is a point where the peak power of the focal point always returns, so that the height position of the surface 1a can be detected with high accuracy.

  This point will be described in more detail with reference to FIG. As described above, the white light emitted from the white light source 101 is irradiated toward the work 1 held on the holding surface 21 a of the holding means 21 through the chromatic aberration lens 102. At this time, the chromatic aberration lens 102 has a focal length in which the white light that has passed differs depending on the wavelength. That is, the chromatic aberration lens 102 forms a plurality of focal points on the optical axis toward the work 1 for each wavelength included in white light. Therefore, as shown in FIG. 5, an infinite number of focal points exist for each wavelength included in the white light in the range L immediately below the optical axis center of the chromatic aberration lens 102. Therefore, if the white light is irradiated so that the surface 1a of the work 1 exists in this range L where the myriad focal points exist, the focus is achieved regardless of the variation in the height position of the surface 1a of the work 1. The reflected light always exists, and the height position of the surface 1a of the workpiece 1 can be reliably detected.

  Note that the range L indicating the variation in focus can be freely designed from several μm to several mm depending on the numerical aperture NA and material of the chromatic aberration lens 102, the use of a diffractive lens as the chromatic aberration lens 102, or the like.

  Moreover, the light reflected by the surface 1a of the workpiece 1 travels back along the optical path and enters the common optical fiber 111 (optical fiber 121). At this time, for example, the light reflected by the holding surface 21a that is out of focus is difficult to recombine with the common optical fiber 111, and the amount of incident light is small. Therefore, the light intensity detected by the wavelength detection sensor 133 is small. On the other hand, among the white light, regardless of the height position variation of the surface 1a of the work 1, light having a wavelength irradiated in the focused state near the surface 1a is, as shown in FIG. The core 111a surrounded by the clad 111b is most strongly recombined. As a result, the light intensity that is guided to the second optical path 109b by the common optical fiber 111 (optical fiber 121) and detected by the wavelength detection sensor 133 increases.

  As described above, according to the present embodiment, the white light reflected by the surface 1a of the workpiece 1 is guided and incident on the wavelength detection sensor 133 side by the common optical fiber 111 (optical fiber 121) having a core diameter of 50 μm, for example. Therefore, the accuracy as a spatial filter is high, and the degree of freedom in arrangement is high.

  It continues and demonstrates the effect | action of the laser processing apparatus 20 provided with the above height detection apparatuses 100. FIG. First, the work 1 is placed on the holding surface 21a of the holding means 21 and sucked and held. Then, the holding means 21 that sucks and holds the workpiece 1 is positioned immediately below an imaging means (not shown), and an alignment operation for detecting a machining area of the workpiece 1 to be laser processed is executed. That is, a pattern for aligning the first street 4a formed in a predetermined direction of the workpiece 1 and a processing condenser lens (not shown) in the condenser 39 along the first street 4a. Image processing such as matching is executed to perform alignment. The same applies to the second street 4b.

  When alignment is performed in this manner, the workpiece 1 on the holding means 21 is positioned at the coordinate position as shown in FIG. FIG. 7 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 holding means 21. FIG. 7B shows a state in which the holding means 21, that is, the work 1 is rotated 90 degrees from the state shown in FIG.

  And if the 1st street 4a currently formed in the workpiece | work 1 currently hold | maintained at the holding means 21 is detected and alignment of a laser processing position is performed, a control means will be formed in the workpiece | work 1 in this way. A workpiece surface height detection process is executed along the first street 4a to be processed. That is, the holding means 21 is moved to position the lowest first street 4a in FIG. 7A directly below the chromatic aberration lens 102. Therefore, the height detection device 100 is operated and the holding means 21 is moved in the machining feed direction in accordance with a predetermined machining feed speed. By this process, the height position of the surface 1a of each part on the lowest first street 4a is sequentially detected with respect to the lowest first street 4a. Information on the detected surface height is temporarily stored in a memory (not shown) in association with the X and Y coordinates at the time of detection.

  The height position of the surface 1a is sequentially acquired according to the sampling rate of the wavelength detection sensor 133. As described above, the sampling rate is 1 kHz and the workpiece 1 moves at a speed of 600 mm / s. For example, the height of the surface 1a of the workpiece 1 is sequentially detected at intervals of 0.6 mm on the street 4a.

  When the detection process relating to the lowest first street 4a is completed, the control means moves the holding means 21 so that the lowest first street 4a in FIG. Position directly below. At this time, the chromatic aberration lens 102 is set to be positioned immediately below the preceding first street 4a. And a control means performs in parallel the laser processing process with respect to the lowest 1st street 4a, and the detection process of the workpiece | work surface height with respect to the following 1st street 4a preceding.

  That is, the holding means 21 is moved in the machining feed direction according to a predetermined machining feed speed. In this processing, the control means 20 controls the laser processing operation with reference to the surface height information relating to the lowest first street 4a stored in the memory.

  First, by driving the processing laser beam irradiation means 3 so that the processing laser beam is irradiated when the processing condensing lens reaches the beam irradiation start position A1, the processing laser beam on the workpiece 1 is driven. Start irradiation. Then, by controlling a Z-axis lens actuator (not shown) based on the surface height information of the workpiece 1, the focusing point of the processing laser beam emitted from the processing focusing lens coincides with the surface 1 a of the workpiece 1. While adjusting the height position, laser processing for forming a laser processing groove on the surface 1a of the workpiece 1 along the lowest first street 4a is performed. As a result, the converging point of the processing laser beam emitted from the processing condensing lens is aligned with the surface 1a of the work 1, and a laser processing groove is reliably formed on the surface 1a regardless of the unevenness of the surface 1a of the work 1. Is done.

  The driving of the processing laser beam irradiation means 3 is stopped so that the irradiation of the processing laser beam stops when the first condenser lens 4 reaches the beam irradiation end position B1, so that The irradiation of the processing laser beam is stopped.

  On the other hand, by operating the height detection device 100 in parallel with such a processing operation, the height position of the surface 1a of each part on the first street 4a is determined with respect to the next preceding first street 4a. Detect sequentially. Information on the detected surface height is temporarily stored in the memory in association with the X and Y coordinates at the time of detection.

  Thereafter, such laser processing and detection processing by the height detection apparatus 100 are repeatedly performed as parallel processing in the same manner for the subsequent first street 4a. And if the laser processing process with respect to all the 1st streets 4a and the detection process by the height detection apparatus 100 are performed, the holding means 21 will be rotated 90 degree | times, and it will be positioned in a state as shown in FIG.7 (b), Similarly, laser processing and detection processing by the height detection device 100 are executed for all of the second streets 4b. When all the processes are completed, the holding means 21 holding the workpiece 1 is first returned to the position where the workpiece 1 is sucked and held, and the suction holding of the workpiece 1 is released here. And the workpiece | work 1 is conveyed to a division | segmentation process by the conveyance means which is not shown in figure.

  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 above-described embodiment, the first-order diffracted light detection unit 130 that uses the first-order diffracted light included in the diffracted light as a target to be detected is the n-th order diffracted light detection unit. The order of diffracted light is not limited to the first order diffracted light. The point is that the n-order diffracted light detecting means detects only the n-order diffracted light among the predetermined n-order diffracted light (n is an integer) included in the diffracted light and the different-order diffracted light having a different order from the n-th order. Alternatively, other orders of diffracted light may be predetermined diffracted light, and furthermore, the diffracted light to be detected may be on the higher order side instead of the lower order side.

  Further, for example, in the above-described embodiment, the laser processing example in which the laser processing groove is formed by irradiating the processing laser beam having the wavelength absorbed by the workpiece 1 has been described. Even in the case of laser processing in which a modified layer is formed by irradiating a laser beam, the modified layer is formed at a certain depth position from the surface 1a by applying the same in the same manner regardless of the fluctuation of the surface 1a. Can be made.

  In the above embodiment, the example of the work 1 using the dicing tape 3 has been described. However, the work 1 is directly held on the holding surface 21 a of the holding means 21 without using the dicing tape 3. Even if it is a thing, it is applicable similarly.

DESCRIPTION OF SYMBOLS 1 Work 20 Laser processing apparatus 21 Holding means 21a Holding surface 100 Height detection apparatus 101 White light source 102 Chromatic aberration lens 120 Height detection means 121 Optical fiber 122 Diffractive optical element 130 First order diffracted light detection means 131 Diffracted light condensing lens 132 Wavelength dispersion Filter 133 Wavelength detection sensor 133a Detection unit 134 Memory

Claims (1)

A height detection device that is mounted on a processing machine and detects the height of a work held by a holding means,
A white light source that emits white light;
A chromatic aberration lens that condenses each wavelength contained in the white light and forms a plurality of condensing points on the optical axis toward the workpiece;
Height detection means for detecting reflected light that is collected by the chromatic aberration lens and reflected by the workpiece;
With
The height detecting means includes
Light regulating means for regulating the passage of light other than the light focused near the workpiece surface out of the light reflected by the workpiece surface;
A diffractive optical element that branches the reflected light that has passed through the light restricting means into diffracted light that spreads in the same plane;
N-order diffracted light detecting means for detecting only the n-th order diffracted light among predetermined n-order diffracted light (n is an integer) included in the diffracted light and different-order diffracted light having a different order from the n-th order;
Have
The n-order diffracted light detecting means is
A diffracted light condensing lens that condenses the diffracted light including the nth order diffracted light and the different order diffracted light;
A chromatic dispersion filter that refracts the diffracted light including the nth-order diffracted light and the different-order diffracted light collected by the diffracted light condensing lens at different angles for each wavelength in a direction outside the same plane;
A detector is provided only at a location where the n-th order diffracted light is condensed among the n-th order diffracted light and the different-order diffracted light collected at different locations for each wavelength by the wavelength dispersion filter, and the n next time A wavelength detection sensor that detects the light intensity for each wavelength of the folded light only;
A memory for storing a control map storing focal lengths of the respective wavelengths included in the white light collected by the chromatic aberration lens;
Including
A height detection apparatus characterized in that a height position of the work held by the holding means is obtained based on a signal from the wavelength detection sensor and the control map.

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