JP5286039B2 - Laser processing equipment - Google Patents

Description

  The present invention relates to a laser processing apparatus that processes a workpiece such as an optical device wafer by irradiating a workpiece with a pulse laser beam.

  An optical device wafer in which a plurality of regions are partitioned by dividing lines called streets formed in a lattice shape on the surface of a sapphire substrate or the like, and an optical device such as a gallium nitride compound semiconductor is stacked on the partitioned regions, It is divided into optical devices such as individual light emitting diodes along the street, and is widely used in electronic equipment.

  Such cutting along the street of the optical device wafer is usually performed by a cutting apparatus that rotates a cutting blade at a high speed. However, since the sapphire substrate has a high Mohs hardness and is a difficult-to-cut material, there is a problem that it is necessary to slow the processing speed and productivity is poor.

  As a method of dividing along the streets of the above-mentioned optical device wafers, etc., a laser that uses a pulsed laser beam that is transparent to the wafer and irradiates the pulsed laser beam with the focusing point inside the region to be divided. Processing methods have also been attempted. In the dividing method using this laser processing method, a focused laser beam is irradiated from one side of the wafer to the inside, and a pulse laser beam having a wavelength that is transparent to the wafer is radiated, and the inside of the wafer follows the street. In this way, the deteriorated layer is continuously formed, and the workpiece is divided by applying an external force along the street whose strength is reduced by forming the deteriorated layer (see, for example, Patent Document 1). .

Japanese Patent No. 3408805

  However, since the objective lens (condensing lens) used to form the deteriorated layer inside the wafer has a large NA, the objective lens is arranged close to the wafer surface, so that it is irregular on the street unintentionally. There is a problem that if the laser beam is accidentally irradiated to the metal layer existing in (1), the objective lens is contaminated with scattered matter called debris.

  Further, in order to divide the wafer with high quality, it is necessary to form a deteriorated layer at a certain depth from the surface of the wafer, and it is also necessary to detect the surface height position of the wafer.

  The present invention has been made in view of the above, and provides a laser processing apparatus capable of simultaneously detecting the presence / absence of a foreign substance layer such as a metal layer on the workpiece surface and the surface height position of the workpiece. For the purpose.

In order to solve the above-described problems and achieve the object, a laser processing apparatus according to the present invention includes a holding unit that holds a workpiece , and a street that is a planned division line of the workpiece held by the holding unit. A laser processing apparatus including: a laser irradiation unit that irradiates a laser beam; and a state detection unit that detects a surface state of the workpiece on the street. The state detection unit includes a light source that emits detection light; and A condensing lens for condensing the detection light onto the work; a spectroscopic means for splitting the detection light reflected by the work into a first optical path and a second optical path; and a light guide to the first optical path. A restricting means for restricting a part of the emitted light, a first light receiving element for receiving the light restricted by the restricting means, and a second light receiving element for receiving all the light guided to the second optical path And the first light receiving The light received by the first light receiving element with reference to a control map in which the relationship between the detection ratio between the light received by the child and the light received by the second light receiving element and the surface height position of the workpiece is set in advance. A surface height detector for detecting the surface height position of the workpiece based on a detection ratio between the amount of light received by the second light receiving element and the amount of light received by the second light receiving element as a predetermined threshold. see containing and a foreign material layer detection unit for detecting a foreign material layer on the surface of the workpiece when it exceeds comparison threshold value, the state detection unit, before the irradiation of the laser beam by the laser irradiation means In addition, the surface height position of the workpiece and the foreign substance layer existing on the surface of the workpiece are detected at the same time .

  In the laser processing apparatus according to the present invention as set forth in the invention described above, the foreign material layer is a metal layer.

  In the laser processing apparatus according to the present invention, in the above invention, the restricting unit is positioned between the cylindrical lens installed in the first optical path, and between the cylindrical lens and the first light receiving element. And a slit disposed in the first optical path so that the longitudinal direction intersects the light collection direction of the cylindrical lens.

  According to the present invention, when a foreign substance layer such as a metal layer is present on the surface of the workpiece, the reflectance is higher than when it is not present, and the amount of detection light reflected by the workpiece changes. Paying attention to this, the amount of light received by the second light receiving element that receives all the light guided to the second optical path in the detection light reflected by the workpiece is compared with a predetermined threshold, and the threshold is exceeded. In this case, since the foreign substance layer is detected, it is possible to provide a laser processing apparatus capable of detecting the presence or absence of a foreign substance layer such as a metal layer on the workpiece surface together with the surface height position of the workpiece. There is an effect.

  Hereinafter, a laser processing apparatus which is the best mode for carrying out the present invention will be described with reference to the drawings. In the present embodiment, a laser that forms and cuts a modified layer by irradiating a pulse laser beam along a street (scheduled division line), which is a desired planned processing position of the workpiece, with focus on the inside of the workpiece. An example of application to a processing apparatus will be described.

  FIG. 1 is an external perspective view showing the main part of the laser processing apparatus of the present embodiment. The laser processing apparatus 20 according to the present embodiment includes a holding unit 21 that holds the workpiece W, a laser irradiation unit 22 that irradiates the workpiece W held on the holding unit 21 with a pulsed laser beam having a wavelength that is transmissive, An image pickup means 23 for picking up an image of the work W held on the holding means 21 is provided. The holding means 21 sucks and holds the workpiece W and is rotatably connected to the motor 24. The holding means 21 is provided so as to be movable in the X-axis direction, which is the horizontal direction, by a machining feed means 27 constituted by a ball screw 25, a nut (not shown), a pulse motor 26, and the like. Processing is relatively performed with respect to the pulse laser beam irradiated by the laser irradiation means 22.

  The laser irradiation means 22 includes a cylindrical casing 28 arranged substantially horizontally, and a ball screw (not shown), a nut (not shown), a pulse motor 29, and the like are passed through the casing 28. The Z-axis moving means 30 is configured to be movable in the Z-axis direction. Further, the laser irradiation means 22 is horizontally oriented by an indexing and feeding means 34 constituted by a casing 28, a base 31 on which the Z-axis moving means 30 is mounted, a ball screw 32, a nut (not shown), a pulse motor 33, and the like. It is provided so as to be movable in the Y-axis direction, and the laser irradiation means 22 is indexed and fed relative to the workpiece W on the holding means 21.

  Here, a pulse laser beam oscillation means 41 is provided in the casing 28 as shown in FIG. 2, and a machining pulse laser beam oscillated by the pulse laser beam oscillation means 41 is chucked at the tip of the casing 28. A condenser 42 for irradiating the work W held on the table 21 is attached. As the pulse laser beam oscillating means 41, a YVO4 pulse laser oscillator or a YAG laser oscillator which oscillates a processing pulse laser beam having a wavelength transmissive to the workpiece W, for example, 1064 nm, is used. Further, the condenser 42 has a well-known configuration such as a mirror 42a that reflects the machining pulse laser beam toward the workpiece W and a combined lens that collects the reflected machining pulse laser beam onto the workpiece W. Condensing lens 42b. In FIG. 2, the Z-axis moving means 30 is shown in a simplified manner.

  The imaging means 23 attached to the tip of the casing 28 images the surface of the workpiece W held on the holding means 21 and processes it with a pulsed laser beam emitted from the condenser 42 of the laser irradiation means 22. This is for detecting a region to be detected. The image pickup means 23 is composed of an image pickup device (CCD) or the like, and sends a picked up image signal to a control means described later.

  Further, the laser processing apparatus 20 of the present embodiment includes a state detection unit 50 for detecting the surface state of the workpiece W held by the holding unit 21 by using a part of the laser irradiation unit 22. . FIG. 2 is a schematic diagram showing a configuration example of the state detection unit 50 together with a part of the laser irradiation unit 22. The state detection means 50 includes a light source 51, a dichroic mirror 52, a half mirror 53, a condenser lens 54, a half mirror 55 which is a spectroscopic means, a regulation means 56, a first light receiving element 57, and a second light receiving element 57. Light receiving element 58 and control means 59.

  The light source 51 is for oscillating detection light LB having a frequency different from the frequency of the processing pulse laser beam oscillated from the pulse laser beam oscillation means 41 in the laser irradiation means 22. In the present embodiment, a CW laser light source that oscillates detection light LB having a wavelength of, for example, 635 nm is used.

  The dichroic mirror 52 is installed between the pulse laser beam oscillating means 41 and the mirror 42a, transmits the processing pulse laser beam emitted from the pulse laser beam oscillating means 41, and transmits the detection light LB emitted from the light source 51. It is for reflecting toward the mirror 42a (condensing lens 42b) side. The half mirror 53 transmits the detection light LB emitted from the light source 51 to the dichroic mirror 52 side, and reflects the detection light LB reflected by the work W and reflected by the dichroic mirror 52. is there.

  The condensing lens 54 is a lens for condensing the detection light LB transmitted through the half mirror 53 and reflected by the dichroic mirror 52 and the mirror 42 a and irradiating the work W held by the holding means 21. is there. Here, in the present embodiment, the condensing lens 54 is also used as the condensing lens 42 b in the laser irradiation means 22.

  The half mirror 55 is for splitting the detection light LB reflected by the workpiece W into the first optical path 60a and the second optical path 60b. The restricting means 56 is for restricting a part of the light guided to the first optical path 60a. In the present embodiment, the restricting means 56 includes a cylindrical lens 56a and a slit 56b. The cylindrical lens 56a is a lens that is installed in the first optical path 60a and has a condensing function that condenses the detection light LB reflected by the workpiece W in one dimension. In the present embodiment, the cylindrical lens 56a is arranged so as to have a light collecting property in the front and back direction of the paper surface in FIG. 2 and not to have a light collecting property in the vertical direction of the paper surface. The slit 56b is positioned between the cylindrical lens 56a and the first light receiving element 57, and the first optical path 60a is arranged such that the longitudinal direction of the opening having a predetermined width intersects, for example, is orthogonal to the condensing direction of the cylindrical lens 56a. Is installed.

  Further, the first light receiving element 57 is made of a photodetector that receives the light guided to the first optical path 60 a and regulated by the regulating means 56 in the detection light LB reflected by the workpiece W. The first light receiving element 57 outputs a voltage signal corresponding to the amount of received light to the control means 59. The second light receiving element 58 includes a photodetector that receives all the light guided to the second optical path 60b in the detection light LB reflected by the workpiece W. The second light receiving element 58 outputs a voltage signal corresponding to the amount of received light to the control means 59.

  Moreover, the control means 59 consists of a computer provided with CPU (not shown) and RAM (not shown) which perform arithmetic processing according to the control program stored in ROM (not shown). The control unit 59 controls the entire laser processing apparatus 20 and also controls the workpiece W held by the holding unit 21 based on the amount of reflected light detected by the first and second light receiving elements 57 and 58. A surface height detector 59a that executes a process for calculating the surface height position, and a difference detector that detects the presence or absence of a foreign substance layer on the workpiece W based on the amount of reflected light detected by the second light receiving element 58. A functional part with the material layer detection part 59b is provided.

  The surface height detection unit 59a presets the relationship between the detection ratio between the light reception amount of the first light receiving element 57 and the light reception amount of the second light receiving element 58 and the surface height position of the workpiece W in the memory. With reference to the stored control map 59c, the surface height position of the workpiece W is detected based on the detection ratio between the amount of light received by the first light receiving element 57 and the amount of light received by the second light receiving element 58. Is. Information on the detected surface height position is temporarily stored in a partial memory area 59d of the RAM. The foreign substance layer detection unit 59b detects a foreign substance layer such as a metal layer that is unintentionally irregularly placed on the workpiece W, and receives the light received by the second light receiving element 58. The amount is compared with a predetermined threshold TH, and when this threshold TH is exceeded, the foreign substance layer is detected. The detected position information of the different substance layer is temporarily stored in a memory area 59e of a part of the RAM. The control unit 59 refers to the surface height position information and the foreign material layer position information temporarily stored in the memory areas 59d and 59e, and controls the operations of the Z-axis moving unit 30 and the laser oscillator 41. A control unit 59f is provided.

  The operation of the state detection means 50 having such a configuration will be described. First, as shown in FIG. 2, the detection light LB oscillated from the light source 51 is guided to the mirror 42a side through the half mirror 53 and the dichroic mirror 52, and is placed on the workpiece W by the condenser lens 54 (42b). Focused. When irradiating such detection light LB on the surface of the work W held by the holding means 21, the Z-axis moving means 30 is operated so that the condensing point Pb is moved from the surface of the work W in the laser beam irradiation direction. Adjust so that it is located on the upstream side (upper side). As a result, the detection light LB is irradiated and reflected on the surface of the workpiece W held by the holding means 21.

  Thus, the detection light LB reflected by the surface of the workpiece W is reflected by the half mirror 53 via the condenser lens 52 (42b), the mirror 42a, and the dichroic mirror 52. The detection light LB reflected by the half mirror 53 is further split into a first optical path 60a and a second optical path 60b by the half mirror 55. The detection light LB dispersed in the first optical path 60a is condensed in a one-dimensional manner by the cylindrical lens 56a, and a part of the light restricted to a predetermined slit width by the slit 56b is received by the first light receiving element 57. Is done. The first light receiving element 57 sends a voltage signal corresponding to the amount of received light to the surface height detector 59 a in the control means 59. All of the detection light LB dispersed in the second optical path 60 b is received by the second light receiving element 58. The second light receiving element 58 sends out a voltage signal corresponding to the amount of received light to the surface height detector 59a and the foreign substance layer detector 59b in the control means 59.

  Here, the amount of light received by the first and second light receiving elements 57 and 58 and the detection light LB reflected by the surface of the workpiece W will be described. First, since the detection light LB received by the second light receiving element 58 is reflected by the half mirror 55 and received entirely, the amount of received light is substantially constant and is output from the second light receiving element 58. The voltage value (V2) corresponding to the amount of received light is constant (for example, 10V).

  On the other hand, the detection light LB received by the first light receiving element 57 is condensed one-dimensionally by the cylindrical lens 56a, and a part of the light restricted to a predetermined slit width by the slit 56b is the first light receiving element. Light is received at 57. Therefore, when the detection light LB is irradiated on the surface of the workpiece W, the amount of light received by the first light receiving element 57 depends on the distance from the condenser lens 54 to the surface of the workpiece W, that is, the height position of the surface of the workpiece W. Will change. Therefore, the voltage value (V1) corresponding to the amount of received light output from the first light receiving element 57 varies depending on the surface height position of the workpiece W irradiated with the detection light LB.

  For example, as shown in FIG. 3A, the detection is performed when the surface height position of the workpiece W is high (the thickness of the workpiece W is thick) and the distance H from the condenser lens 54 to the surface of the workpiece W is small. The working light LB is reflected by the spot Sa irradiated on the surface of the workpiece W. As described above, the reflected light is split into the first optical path 60a and the second optical path 60b by the half mirror 55, but all of the reflected light of the spot Sa split into the second optical path 60b is the first. Two light receiving elements 58 receive the light. On the other hand, the reflected light of the spot Sa dispersed in the first optical path 60a is condensed one-dimensionally by the cylindrical lens 56a, so that the cross section has a substantially elliptical shape. And since the reflected light whose cross section is narrowed to a substantially elliptical shape in this way is regulated to a predetermined slit width by the slit 56b, a part of the reflected light of the spot Sa dispersed in the first optical path 60a is Light is received by the first light receiving element 57. Accordingly, the amount of reflected light received by the first light receiving element 57 is smaller than the amount of light received by the second light receiving element 58 described above.

  Next, as shown in FIG. 3B, when the surface height position of the workpiece W is low (the thickness of the workpiece W is thin) and the distance H from the condenser lens 54 to the surface of the workpiece W is large, The detection light LB is reflected by the spot Sb irradiated on the surface of the workpiece W. As described above, the reflected light is split into the first optical path 60a and the second optical path 60b by the half mirror 55, but all of the reflected light of the spot Sb split into the second optical path 60b is the first. Two light receiving elements 58 receive the light. On the other hand, the reflected light of the spot Sb dispersed in the first optical path 60a is condensed one-dimensionally by the cylindrical lens 56a, so that the cross section has a substantially elliptical shape. And the length of the long side whose cross section is substantially elliptical is longer than that of the spot Sa. Since the reflected light whose cross section is narrowed to a substantially elliptical shape in this way is regulated to a predetermined slit width by the slit 56b, a part of the reflected light of the spot Sb dispersed in the first optical path 60a is the first. The light receiving element 57 receives the light. At this time, the amount of reflected light received by the first light receiving element 57 is smaller than the amount of light received in the case of FIG.

  Thus, the amount of reflected light received by the first light receiving element 57 is such that the smaller the distance H from the condenser lens 54 to the surface of the workpiece W (that is, the higher the surface height position of the workpiece W). On the other hand, as the distance H from the condensing lens 54 to the surface of the workpiece W increases (that is, as the surface height position of the workpiece W decreases), the number decreases.

  Here, the detection ratio between the voltage value V2 corresponding to the received light amount output from the second light receiving element 58 and the voltage value V1 corresponding to the received light amount output from the first light receiving element 57, and the work from the condenser lens 54 to the workpiece. The relationship with the distance H to the surface of W (that is, the surface height position of the workpiece W) will be described with reference to the control map shown in FIG. In FIG. 4, the horizontal axis represents the distance H from the condenser lens 54 to the surface of the workpiece W, and the vertical axis represents the voltage value V2 output from the second light receiving element 58 and the first light receiving element 57. The detection ratio (V2 / V1) with the voltage value V1 is shown. In the example shown in FIG. 4, when the distance H from the condenser lens 54 to the surface of the workpiece W is 30.0 mm, the voltage value detection ratio (V2 / V1) is “1”, and the condenser lens 54 to the workpiece When the distance H to the surface of W is 30.6 mm, the voltage value detection ratio (V2 / V1) is set to “10”. The control map 59c as shown in FIG. 4 is stored in advance in a RAM or the like in the control means 59 as shown in FIG.

  Note that the amount of reflected light received by the first light receiving element 57 is such that the surface of the workpiece W moves away from the condenser lens 54 (as the distance from the condensing point Pb increases), as shown in FIG. ) Not only decreases, but conversely decreases as the surface of the workpiece W approaches the condensing lens 54 beyond the condensing point Pb. Therefore, considering the degree of unevenness on the surface of the workpiece W, for example, as shown in FIG. 3A, the reflection position of the detection light LB does not approach the condensing lens 54 beyond the condensing point Pb. By setting the position shifted from the condensing point Pb toward the workpiece W as the reference position of the reflection position, the amount of light received when the reflection position is shifted up and down is changed linearly. As a result, the distance H can be detected in a linearly changing region as in the control map shown in FIG.

  Therefore, the surface height detection unit 59a detects the detection ratio between the voltage value V2 corresponding to the amount of received light output from the second light receiving element 58 and the voltage value V1 corresponding to the amount of received light output from the first light receiving element 57 ( V2 / V1) is obtained, and the detection ratio (V2 / V1) is referred to the control map 59c, whereby the distance H from the condenser lens 54 to the surface of the work W can be obtained, and the surface height of the work W is obtained. It can be converted into a position.

  Further, as described above, since the detection light LB received by the second light receiving element 58 is reflected by the half mirror 55 and received entirely, the amount of received light is substantially constant, and the second light receiving element The voltage value (V2) corresponding to the received light amount output from 58 is also substantially constant. However, in detail, when a foreign substance layer D (see FIG. 2) such as a metal layer irregularly placed on the surface of the workpiece W is present, the reflectance is higher than that on the surface of the workpiece W itself. The amount of reflected light increases when the foreign substance layer D is irradiated with the detection light LB. That is, the voltage value (V2) corresponding to the received light amount output from the second light receiving element 58 is normally substantially constant, but the voltage corresponding to the received light amount when the reflected light from the different material layer D is received. The value (V2) will be larger than usual.

  Therefore, the regular voltage value (V2) due to the reflected light reflected from the surface of the workpiece W itself and the irregular light due to the reflected light reflected when the foreign material layer D such as a metal layer exists on the surface of the workpiece W. The voltage value (V2) is measured in advance and an appropriate threshold value TH is set as a boundary value between the two, and the foreign substance layer detection unit 59b determines the voltage value V2 corresponding to the amount of light received by the second light receiving element 58 as the boundary value. By comparing with a predetermined threshold TH, it is possible to detect the presence of the foreign substance layer D when the threshold TH is exceeded.

  As described above, according to the state detection means 50 of the present embodiment, the light reception by the first light receiving element 57 that receives a part of the detection light LB reflected by the work W and dispersed in the first optical path 60a. Between the detection ratio of the amount of light received by the second light receiving element 58 that receives all of the detection light LB reflected by the workpiece W and split into the second optical path 60b, and the surface height position of the workpiece W , The surface height position of the workpiece W is detected based on the detection ratio between the amount of light received by the first light receiving element 57 and the amount of light received by the second light receiving element 58. Since the surface height detection unit 59a is provided, the surface height position of the workpiece W can be detected. Further, when the foreign substance layer D such as a metal layer is present on the surface of the workpiece W, the reflectance is higher than when it is not present, and the received light amount of the detection light LB reflected by the workpiece W changes. Paying attention to this, the amount of light received by the second light receiving element 58 that receives all of the detection light LB reflected by the work W and dispersed in the second optical path 60b is compared with a predetermined threshold TH, and this threshold TH Since the foreign substance layer detection part 59b which detects the foreign substance layer D when it exceeds is exceeded, whether the foreign substance layer D, such as a metal layer, exists on the surface of the workpiece | work W can be detected appropriately.

  Next, the operation of the laser processing apparatus 10 including the state detection unit 50 as described above will be described. FIG. 5 is a perspective view showing a configuration example of the workpiece W used in the laser processing apparatus 10. The workpiece W is not particularly limited, but in the present embodiment, a workpiece made of a material such as sapphire or quartz is used. For example, a sapphire work W is divided into a plurality of rectangular areas by a plurality of streets 61 arranged in a lattice pattern on the surface Wa, and an optical device 62 such as a light emitting diode or a laser diode is formed in the divided rectangular areas. Is formed.

  Therefore, a case will be described in which laser processing is performed using the laser processing apparatus 10 to irradiate a pulse laser beam along the street 61 of the work W and form a deteriorated layer along the street 61 inside the work W. When forming the deteriorated layer inside the workpiece W, if the thickness of the workpiece W varies, the deteriorated layer cannot be formed uniformly at a predetermined depth position. Further, when the foreign material layer D such as an irregular metal layer exists on the street 61, if the laser is mistakenly irradiated, the condensing lens 42b (54) is contaminated with the scattered matter called debris. For this reason, in the present embodiment, the surface height position of the street 61 portion of the workpiece W held by the holding unit 21 is detected by the surface height detection unit 59a of the state detection unit 50 described above, and the difference is detected. The presence or absence of the different material layer D on the street 61 of the workpiece W is detected by the material layer detection unit 59b, and the Z-axis position is adjusted by the Z-axis moving unit 30 by the operation control unit 59f according to the detection result, and The oscillation operation of the laser oscillator 41 is controlled so as not to irradiate the pulse laser beam in the portion where the different material layer D exists, and the laser irradiation means 22 performs laser processing.

  First, the work W is placed on the holding means 21 with the back surface Wb of the work W facing up, and the work W is sucked and held on the holding means 21. The holding means 21 that sucks and holds the workpiece W is positioned directly below the imaging means 23 by the processing feeding means 27.

  When the holding unit 21 is positioned directly below the image pickup unit 23, the image pickup unit 23 and the control unit 59 execute an alignment operation for detecting a machining area of the workpiece W to be laser processed. That is, the image pickup means 23 and the control means 59 are images such as pattern matching for aligning the street 61 formed in a predetermined direction of the workpiece W and the condenser lens 42b (54) along the street 61. Execute processing and perform alignment.

  When alignment is performed in this manner, the workpiece W on the holding means 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 W is held at a predetermined position of the holding means 21. FIG. 6B shows a state in which the holding means 21, that is, the workpiece W is rotated 90 degrees from the state shown in FIG.

  It should be noted that the feed start position coordinate values (A1, A2, A3,..., An) of each street 61 formed on the workpiece W in the state positioned at the coordinate positions shown in FIGS. End position coordinate values (B1, B2, B3,..., Bn), feed start position coordinate values (C1, C2, C3,..., Cn) and feed end position coordinate values (D1, D2, D3,. .., Dn) are stored in the RAM in the control means 59.

  Then, when the street 61 formed on the workpiece W held by the holding means 21 is detected and the laser processing position is aligned, the holding means 21 is moved to move the uppermost position in FIG. The street 61 is positioned directly below the condenser lens 54. FIG. 7 is an explanatory view showing a state detection step and a laser processing step for forming a deteriorated layer. Therefore, as shown in FIG. 7, the feed start position coordinate value A <b> 1 that is one end (the left end in FIG. 7) of the street 61 is positioned immediately below the condenser lens 54. Then, the state detecting means 50 is operated, and the holding means 21 is moved to the feed end position coordinate value B2 in the direction indicated by the arrow X1 in FIG.

  As a result, the surface height position (distance H from the condensing lens 54 to the surface (back surface Wb) of the workpiece W) of the workpiece W on the uppermost street 61 in FIG. 6A is determined by the surface height detection unit 59a. Sequentially detected. Information on the surface height position in the uppermost street 61 detected by the surface height detection unit 59a is temporarily stored in the memory area 59d. Further, the presence or absence of the foreign substance layer D in the uppermost street 61 in FIG. 6A of the workpiece W is detected by the foreign substance layer detection unit 59b, and when the foreign substance layer D exists, the foreign substance is detected. The position coordinate value of the layer D is temporarily stored in the memory area 59d as the different material layer information.

  After such state detection is performed on the uppermost street 61, the feed start position coordinate value A1 which is one end (the left end in FIG. 7) of the uppermost street 61 to be processed again is obtained from the condenser lens 42b. Position directly below. Then, the holding means 21 is moved in the direction indicated by the arrow X1 in FIG. 7 in accordance with a predetermined machining feed speed, and is moved to the feed end position coordinate value B2. At this time, with reference to the information on the surface height position and the different material layer information regarding the uppermost street 61 stored in the memory areas 59d and 59e, the pulse motor 29 of the Z-axis moving means 30 is operated by the operation control unit 59f. A laser oscillator that performs feedback control to adjust the height position of the condensing point of the pulse laser beam irradiated from the condensing lens 42b, and not to irradiate the pulse laser beam in the portion where the foreign substance layer D exists By controlling the oscillating operation 41, laser processing is performed in which a deteriorated layer is formed by the laser irradiation means 22 along the street 61 inside the work W.

  As a result, the condensing point of the processing pulse laser beam irradiated from the condensing lens 42b is adjusted to a predetermined depth position from the back surface Wb (front surface) of the work W, and the inside of the work W is shown in FIG. As shown, an altered layer 63 is formed in parallel to the back surface Wb (front surface) at a predetermined depth from the back surface Wb (front surface). In addition, since the pulse laser beam is not irradiated in the portion where the different substance layer D exists, there is no problem that the condensing lens 42b is contaminated with the scattered matter called debris.

  Then, as shown in FIG. 7, when the irradiation position of the condenser lens 42b reaches the other end of the street 61 (the right end in FIG. 7), the irradiation of the pulse laser beam is stopped and the movement of the holding means 21 is stopped. .

  As described above, when the state detection processing as described above and the laser processing processing are executed following the state detection processing along all the streets 61 extending in the predetermined direction of the workpiece W, the holding means 21 is moved to 90 degrees. Similarly, the state detection process and the laser processing process are executed following each state detection process along each street 61 extending in a direction orthogonal to the predetermined direction. When the state detection process and the laser processing process are executed along all the streets 61 formed in the workpiece W in this way, the holding means 21 that holds the workpiece W is in a position where the workpiece W is first sucked and held. Returned, the suction holding of the workpiece W is released here. And the workpiece | work W is conveyed by the division 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. In the present embodiment, the workpiece W is made of a material such as sapphire or quartz, but is not particularly limited. For example, the workpiece W is provided on a semiconductor wafer such as a silicon wafer or on the back surface of the wafer for chip mounting. Examples thereof include adhesive members such as DAF (Die Attach Film), semiconductor product packages, ceramic, glass, silicon-based substrates, various electronic components, and various processing materials that require micron-order accuracy.

It is an external appearance perspective view which shows the principal part of the laser processing apparatus of embodiment of this invention. It is the schematic which shows the structural example of a state detection means with a part of laser irradiation means. It is explanatory drawing which shows the state which irradiates the laser beam to the workpiece | work from which thickness differs. It is a characteristic view which shows an example of a control map. It is a perspective view which shows the structural example of the workpiece | work used with a laser processing apparatus. It is explanatory drawing which shows the relationship with the coordinate position in the state in which the workpiece | work was hold | maintained at the predetermined position of the holding means. It is explanatory drawing which shows collectively the laser processing process which forms a state detection process and a deteriorated layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Holding means 22 Laser irradiation means 50 State detection means 51 Light source 54 Condensing lens 55 Spectroscopic means 56 Control means 56a Cylindrical lens 56b Slit 57 1st light receiving element 58 2nd light receiving element 59a Surface height detection part 59b Different substance layer Detection unit 59c Control map 60a First optical path 60b Second optical path W Work D Foreign substance layer LB Detection light

Claims (3)

A holding means for holding a work, a laser irradiation means for irradiating a laser beam along a street that is a division line of the work held by the holding means, and a state detection for detecting a surface state of the work on the street A laser processing apparatus comprising:
The state detection means includes
A light source that emits detection light;
A condensing lens for condensing the detection light on the workpiece;
Spectroscopic means for splitting the detection light reflected by the workpiece into a first optical path and a second optical path;
A restricting means for restricting a part of the light guided to the first optical path;
A first light receiving element that receives light regulated by the regulating means;
A second light receiving element that receives all of the light guided to the second optical path;
With reference to a control map in which the relationship between the detection ratio between the light receiving amount of the first light receiving element and the light receiving amount of the second light receiving element and the surface height position of the workpiece is set in advance, the first light receiving A surface height detector for detecting a surface height position of the workpiece based on a detection ratio between a received light amount received by the element and a received light amount received by the second light receiving element;
A foreign substance layer detector that compares the amount of light received by the second light receiving element with a predetermined threshold and detects a foreign substance layer present on the surface of the workpiece when the threshold is exceeded;
Only including,
The state detection means simultaneously detects the surface height position of the workpiece and the foreign substance layer existing on the surface of the work before the laser irradiation by the laser irradiation means .   The laser processing apparatus according to claim 1, wherein the foreign substance layer is a metal layer. The regulating means is
A cylindrical lens installed in the first optical path;
A slit that is positioned between the cylindrical lens and the first light receiving element, and that is disposed in the first optical path so that a longitudinal direction thereof intersects a light collection direction of the cylindrical lens;
The laser processing apparatus according to claim 1, comprising:

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