JP2010271071A - Measuring device for workpiece held by chuck table, and laser beam machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machine having a measuring device capable of accurately measuring an upper face height of a workpiece, such as a semiconductor wafer, held by a chuck table. <P>SOLUTION: The measuring device includes: a white light source 61 for emitting light toward a workpiece held by the chuck table 36; a first color aberration lens 62 for irradiating the workpiece with white light; a beam splitter 63 for dispersing reflection light of the white light applied to the workpiece; a light separating means 65 for passing reflection light having a wavelength passing a light axis in reflection light dispersed by the beam splitter 63; a wavelength detection means 67 for detecting the wavelength of diffraction light diffracted by the diffraction grating 66; and a control means. The measuring device includes a second color aberration lens 64 that is disposed between the beam splitter 63 and the first color aberration lens 62 and forms an image of a virtual focus of white light entering from the white light source 61 through the beam splitter 63 on the light axis so that the focal point of each wavelength is proportional to a prescribed wavelength interval. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a measuring apparatus and a laser beam machine for measuring the upper surface height of a workpiece such as a semiconductor wafer held on a chuck table equipped in a machine such as a laser beam machine.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a substantially wafer-shaped semiconductor wafer, and devices such as ICs, LSIs, etc. are partitioned in the partitioned regions. Form. Then, the semiconductor wafer is cut along the streets to divide the region in which the device is formed to manufacture individual semiconductor devices.

  As a method of dividing along the street of the above-described semiconductor wafer or the like, there is a laser processing method in which a pulse laser beam having transparency to the wafer is used, and the pulse laser beam is irradiated with a focusing point inside the region to be divided. Has been tried. The dividing method using this laser processing method is to irradiate a pulse laser beam having a wavelength of 1064 nm, for example, having a light converging point from one surface side of the wafer and having the light converging point inside, so that a street is formed inside the wafer. The deteriorated layer is continuously formed along the surface, and the workpiece is divided by applying an external force along the street whose strength is reduced by the formation of the deteriorated layer. (For example, refer to Patent Document 1.) When the altered layer is formed inside along the street formed on the workpiece as described above, a laser beam condensing point is formed at a predetermined depth position from the upper surface of the workpiece. It is important to position.

  Further, as a method of dividing a plate-like workpiece such as a semiconductor wafer, a laser machining groove is formed by irradiating a pulse laser beam along a street formed on the workpiece, and along the laser machining groove. A method of cleaving with a mechanical braking device has been proposed. (For example, refer to Patent Document 2.) Even when the laser processing groove is formed along the street formed on the workpiece, the laser beam condensing point is positioned at a predetermined height position of the workpiece. is important.

  However, plate-like workpieces such as semiconductor wafers have undulations, and their thickness varies, making it difficult to perform uniform laser processing. That is, when forming an altered layer along the street inside the wafer, if the wafer thickness varies, the altered layer is uniformly formed at a predetermined depth position due to the refractive index when irradiating a laser beam. I can't. Further, even when the laser processing groove is formed along the street formed on the wafer, if the thickness varies, the laser processing groove having a uniform depth cannot be formed.

  In order to solve the above-mentioned problem, a measuring apparatus capable of reliably measuring the upper surface height of a workpiece such as a semiconductor wafer held on a chuck table is disclosed in Patent Document 3 below. The measuring device disclosed in Patent Document 3 below uses the fact that white light that has passed through a chromatic aberration lens has a focal length that differs depending on the wavelength, and determines the focal length by specifying the wavelength by the reflected light. The height position of the workpiece held on the table can be accurately measured.

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

  Thus, when white light is condensed by the chromatic aberration lens, a condensing point corresponding to each wavelength is positioned on the optical axis, but as the wavelength becomes longer, the interval between the condensing points with respect to the predetermined wavelength interval becomes smaller, and the wavelength becomes smaller. There is a problem that it becomes difficult to measure in a long region.

  The present invention has been made in view of the above-mentioned facts, and a main technical problem thereof is a measuring device and a measuring device capable of accurately measuring the upper surface height of a workpiece such as a semiconductor wafer held on a chuck table. It is to provide a laser processing machine equipped with the device.

In order to solve the main technical problem, according to the present invention, a white light source that emits white light toward a workpiece held on a chuck table provided in a processing machine, and a white light emitted by the white light source. The first chromatic aberration lens that collects the light and irradiates the workpiece held on the chuck table, and the white light that is disposed between the white light source and the first chromatic aberration lens and is irradiated to the workpiece. A beam splitter that splits the reflected light of the light, a light sorting unit that passes the reflected light having a wavelength passing through the optical axis in the reflected light split by the beam splitter, and the reflected light that has passed through the light sorting unit is converted into diffracted light A diffraction grating, a wavelength detection means for detecting the wavelength of the diffracted light diffracted by the diffraction grating, and a height position of the workpiece held on the chuck table based on a wavelength signal from the wavelength detection means. The measuring device of the workpiece held on the chuck table comprising a Mel control means,
A second chromatic aberration lens that is disposed between the beam splitter and the first chromatic aberration lens and forms an image of a virtual focal point of white light incident on the optical axis from the white light source through the beam splitter;
The distance between the first chromatic aberration lens and the second chromatic aberration lens is set such that the focal point of each wavelength collected on the optical axis by the first chromatic aberration lens is proportional to the predetermined wavelength interval. ing,
An apparatus for measuring a workpiece held on a chuck table is provided.

Further, according to the present invention, a chuck table having a holding surface for holding a workpiece, laser beam irradiation means for irradiating the workpiece held on the chuck table with a laser beam, and a workpiece held on the chuck table. In a laser processing machine comprising a measuring device for detecting the height position of a workpiece,
The measuring device includes a white light source that emits white light toward a workpiece held on the chuck table, and a white light emitted by the white light source that is collected and irradiated to the workpiece held on the chuck table. A first chromatic aberration lens, a beam splitter that is disposed between the white light source and the first chromatic aberration lens and divides the reflected light of the white light irradiated on the workpiece, the beam splitter and the first A second chromatic aberration lens disposed between the first chromatic aberration lens and forming an image of a virtual focal point of white light incident on the optical axis from the white light source through the beam splitter, and is split by the beam splitter A light separating unit that passes reflected light having a wavelength passing through the optical axis in the reflected light; a diffraction grating that converts the reflected light that has passed through the light separating unit into diffracted light; and a diffraction grating diffracted by the diffraction grating. Comprising a wavelength detector for detecting a length, and a control means for determining the height position of the workpiece held on the chuck table on the basis of the wavelength signal from the wavelength detection means, and
The laser beam irradiation unit is disposed between the laser beam oscillation unit that oscillates a laser beam, the first chromatic aberration lens, and the second chromatic aberration lens. The laser beam emitted from the laser beam oscillation unit is the first chromatic aberration. A dichroic mirror that changes direction toward the lens,
A laser beam machine characterized by the above is provided.

The workpiece measuring apparatus held on the chuck table according to the present invention is configured as described above, and utilizes the fact that the white light that has passed through the first chromatic aberration lens and the second chromatic aberration lens has a different focal length depending on the wavelength. Since the focal length is obtained by specifying the wavelength by the reflected light, the height position of the workpiece held on the chuck table can be accurately measured. Moreover, the distance between the first chromatic aberration lens and the second chromatic aberration lens is set so that the condensing point of each wavelength collected on the optical axis by the first chromatic aberration lens is proportional to the predetermined wavelength interval. Therefore, the height position of the workpiece held on the chuck table can be accurately measured even in a long wavelength region.
In addition, since the laser processing machine according to the present invention is equipped with the above-described measuring device, it is possible to accurately perform laser processing at a predetermined position based on the upper surface height position of the workpiece held by the chuck table. .

The perspective view of the laser processing machine comprised according to this invention. FIG. 2 is a block configuration diagram of a height position measuring device and laser beam irradiation means constituting a height measurement / laser irradiation unit equipped in the laser processing machine shown in FIG. The relationship between the wavelength of the white light collected by the first chromatic aberration lens and the focal length constituting the height position measuring device stored in the memory of the control means installed in the laser processing machine shown in FIG. 1 is set. The figure which shows a control map. FIG. 2 is a block configuration diagram of control means equipped in the laser beam machine shown in FIG. FIG. 2 is a perspective view of a semiconductor wafer as a workpiece to be processed by the laser processing machine shown in FIG. FIG. 6 is an explanatory diagram showing a relationship with coordinate positions in a state where the semiconductor wafer shown in FIG. 5 is held at a predetermined position of the chuck table of the laser beam machine shown in FIG. 1. Explanatory drawing of the height position detection process implemented by the measuring device of the workpiece hold | maintained at the chuck table with which the laser beam machine shown in FIG. 1 was equipped. FIG. 6 is an explanatory view of a processing step for forming a deteriorated layer on the semiconductor wafer shown in FIG. 5 by the laser processing machine shown in FIG. 1. Explanatory drawing which shows a process process in case the thickness of a to-be-processed object is thick.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Preferred embodiments of a workpiece measuring apparatus and a laser beam machine held on a chuck table configured according to the invention will be described in detail below with reference to the accompanying drawings.

  FIG. 1 shows a perspective view of a laser beam machine equipped with a measuring device for measuring the height of a workpiece held on a chuck table constructed according to the present invention. A laser beam machine 1 shown in FIG. 1 includes a stationary base 2 and a chuck table mechanism that is disposed on the stationary base 2 so as to be movable in a machining feed direction (X-axis direction) indicated by an arrow X and holds a workpiece. 3, a laser beam irradiation unit support mechanism 4 disposed on the stationary base 2 so as to be movable in the indexing feed direction (Y axis direction) indicated by the arrow Y orthogonal to the X axis direction, and the laser beam unit support mechanism 4 And a height measurement / laser irradiation unit 5 disposed so as to be movable in a condensing point position adjustment direction (Z-axis direction) indicated by an arrow Z.

  The chuck table mechanism 3 includes a pair of guide rails 31 and 31 disposed in parallel along the X-axis direction on the stationary base 2, and is arranged on the guide rails 31 and 31 so as to be movable in the X-axis direction. A first sliding block 32 provided, a second sliding block 33 movably disposed on the first sliding block 32 in the Y-axis direction, and a cylindrical member on the second sliding block 33 And a chuck table 36 as a workpiece holding means. The chuck table 36 includes a suction chuck 361 formed of a porous material, and holds, for example, a circular semiconductor wafer as a workpiece on a holding surface which is the upper surface of the suction chuck 361 by suction means (not shown). It is supposed to be. The chuck table 36 configured as described above is rotated by a pulse motor (not shown) disposed in the cylindrical member 34. The chuck table 36 is provided with a clamp 362 for fixing an annular frame described later.

  The first sliding block 32 has a pair of guided grooves 321 and 321 fitted to the pair of guide rails 31 and 31 on the lower surface thereof, and is parallel to the upper surface along the X-axis direction. A pair of formed guide rails 322 and 322 are provided. The first sliding block 32 configured in this manner moves in the X-axis direction along the pair of guide rails 31, 31 when the guided grooves 321, 321 are fitted into the pair of guide rails 31, 31. Configured to be possible. The chuck table mechanism 3 in the illustrated embodiment includes a processing feed means 37 for moving the first slide block 32 along the pair of guide rails 31, 31 in the X-axis direction. The processing feed means 37 includes a male screw rod 371 disposed in parallel between the pair of guide rails 31 and 31, and a drive source such as a pulse motor 372 for rotationally driving the male screw rod 371. One end of the male screw rod 371 is rotatably supported by a bearing block 373 fixed to the stationary base 2, and the other end is connected to the output shaft of the pulse motor 372 by transmission. The male screw rod 371 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the first sliding block 32. Therefore, the first sliding block 32 is moved along the guide rails 31 and 31 in the X-axis direction by driving the male screw rod 371 forward and backward by the pulse motor 372.

  The laser beam machine 1 in the illustrated embodiment includes a machining feed amount detection means 374 for detecting the machining feed amount of the chuck table 36. The processing feed amount detection means 374 includes a linear scale 374a disposed along the guide rail 31, and a read head disposed along the linear scale 374a along with the first sliding block 32 disposed along the first sliding block 32. 374b. In the illustrated embodiment, the reading head 374b of the feed amount detecting means 374 sends a pulse signal of one pulse every 1 μm to the control means described later. Then, the control means to be described later detects the machining feed amount of the chuck table 36 by counting the input pulse signals. When the pulse motor 372 is used as the drive source of the machining feed means 37, the machining feed amount of the chuck table 36 is counted by counting the drive pulses of the control means to be described later that outputs a drive signal to the pulse motor 372. Can also be detected. When a servo motor is used as a drive source for the machining feed means 37, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to a control means described later, and the pulse signal input by the control means. By counting, the machining feed amount of the chuck table 36 can also be detected.

  The second sliding block 33 is provided with a pair of guided grooves 331 and 331 which are fitted to a pair of guide rails 322 and 322 provided on the upper surface of the first sliding block 32 on the lower surface thereof. By fitting the guided grooves 331 and 331 to the pair of guide rails 322 and 322, the guided grooves 331 and 331 are configured to be movable in the Y-axis direction. The chuck table mechanism 3 in the illustrated embodiment has a first index for moving the second slide block 33 along the pair of guide rails 322 and 322 provided in the first slide block 32 in the Y-axis direction. A feeding means 38 is provided. The first index feed means 38 includes a male screw rod 381 disposed in parallel between the pair of guide rails 322 and 322, and a drive source such as a pulse motor 382 for rotationally driving the male screw rod 381. It is out. One end of the male screw rod 381 is rotatably supported by a bearing block 383 fixed to the upper surface of the first sliding block 32, and the other end is connected to the output shaft of the pulse motor 382. The male screw rod 381 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the second sliding block 33. Therefore, by driving the male screw rod 381 forward and backward by the pulse motor 382, the second slide block 33 is moved along the guide rails 322 and 322 in the Y-axis direction.

  The laser beam machine 1 in the illustrated embodiment includes index feed amount detection means 384 for detecting the index machining feed amount of the second sliding block 33. The index feed amount detecting means 384 includes a linear scale 384a disposed along the guide rail 322 and a read head disposed along the linear scale 384a along with the second sliding block 33 disposed along the second sliding block 33. 384b. In the illustrated embodiment, the reading head 384b of the feed amount detection means 384 sends a pulse signal of one pulse every 1 μm to the control means described later. Then, the control means described later detects the index feed amount of the chuck table 36 by counting the input pulse signals. When the pulse motor 382 is used as the drive source of the first indexing and feeding means 38, the drive table of the chuck table 36 is counted by counting the drive pulses of the control means to be described later that outputs a drive signal to the pulse motor 382. The index feed amount can also be detected. When a servo motor is used as a drive source for the machining feed means 37, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to a control means described later, and the pulse signal input by the control means. It is possible to detect the index feed amount of the chuck table 36 by counting.

  The laser beam irradiation unit support mechanism 4 includes a pair of guide rails 41 and 41 disposed in parallel along the Y-axis direction on the stationary base 2 and a direction indicated by an arrow Y on the guide rails 41 and 41. A movable support base 42 is provided so as to be movable. The movable support base 42 includes a movement support portion 421 that is movably disposed on the guide rails 41, 41, and a mounting portion 422 that is attached to the movement support portion 421. The mounting portion 422 is provided with a pair of guide rails 423 and 423 extending in the Z-axis direction on one side surface in parallel. The laser beam irradiation unit support mechanism 4 in the illustrated embodiment includes a second index feed means 43 for moving the movable support base 42 along the pair of guide rails 41 and 41 in the Y-axis direction. The second index feed means 43 includes a male screw rod 431 disposed in parallel between the pair of guide rails 41, 41, and a drive source such as a pulse motor 432 for rotationally driving the male screw rod 431. It is out. One end of the male screw rod 431 is rotatably supported by a bearing block (not shown) fixed to the stationary base 2, and the other end is connected to the output shaft of the pulse motor 432. The male screw rod 431 is screwed into a female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the moving support portion 421 constituting the movable support base 42. For this reason, when the male screw rod 431 is driven to rotate forward and reversely by the pulse motor 432, the movable support base 42 is moved along the guide rails 41, 41 in the Y-axis direction.

  The height measurement and laser irradiation unit 5 in the illustrated embodiment includes a unit holder 51 and a cylindrical unit housing 52 attached to the unit holder 51. The unit holder 51 is a movable support base. 42 is provided so as to be movable along a pair of guide rails 423 and 423. A unit housing 52 attached to the unit holder 51 irradiates a laser beam to the workpiece held on the chuck table 36 and a height measuring device for detecting the height position of the workpiece held on the chuck table 36. Laser beam irradiating means is provided. This height measuring device and laser beam irradiation means will be described with reference to FIG.

  The height measuring device 6 in the illustrated embodiment condenses the white light emitted by the white light source 61 and the white light emitted from the white light source 61 and irradiates the workpiece W held on the chuck table 36. A first chromatic aberration lens 62 and a beam splitter 63 disposed between the white light source 61 and the first chromatic aberration lens 62 for splitting the reflected light of the white light irradiated on the workpiece are provided. As the white light source 61, a white light, a light emitting diode (LED), or the like can be used. The first chromatic aberration lens 62 is a lens having chromatic aberration, such as a gradium lens, and has a refractive index different depending on the wavelength of light. Therefore, the white light entering the first chromatic aberration lens 62 has a different focal length (condensing position) depending on the wavelength. The beam splitter 63 transmits the white light emitted from the white light source 61 toward the first chromatic aberration lens 62 as indicated by a solid line, and reflects light reflected by the workpiece W at 90 degrees as indicated by a broken line. Reflect and angle spectroscopically.

  The height measuring device 6 in the illustrated embodiment includes a second chromatic aberration lens 64 disposed between the beam splitter 63 and the first chromatic aberration lens 62. The second chromatic aberration lens 64 is composed of a lens having a chromatic aberration, such as a gradient lens, like the first chromatic aberration lens 62, and has a different refractive index depending on the wavelength of light. The second chromatic aberration lens 64 forms an image of a virtual focal point for each wavelength of white light that enters from the white light source 61 through the beam splitter 63 on the optical axis.

  The first chromatic aberration lens 62 and the second chromatic aberration lens 64 position a condensing point corresponding to each wavelength on the optical axis, but the interval between the condensing points with respect to the predetermined wavelength interval decreases as the wavelength increases. However, in the present invention, the second chromatic aberration lens 64 and the first chromatic aberration lens 62 are arranged so that the condensing point of each wavelength collected on the optical axis by the first chromatic aberration lens 62 is proportional to the predetermined wavelength interval. The interval L is set. A method for setting the distance L between the second chromatic aberration lens 64 and the first chromatic aberration lens 62 will be described later in detail.

  The reflected light split by the beam splitter 63 reaches the wavelength detecting means 67 through the light separating means 65 and the diffraction grating 66 that allow the reflected light having the wavelength passing through the optical axis to pass. The light separating unit 65 includes a first condenser lens 651, a mask 652, and a second condenser lens 653. The first condenser lens 651 is made of a lens having no chromatic aberration, such as an achromatic lens, and condenses the reflected light dispersed by the beam splitter 63. The mask 652 includes a pinhole 652a that is disposed at the condensing point position of the first condenser lens 651 and through which the reflected light condensed by the first condenser lens 651 passes. The pinhole 652a may have a diameter of 10 to 100 μm. The second condenser lens 653 is a lens having no chromatic aberration, such as an achromatic lens, and condenses the reflected light that has passed through the pinhole 652a of the mask 652. The diffraction grating 66 converts the reflected light collected by the second condenser lens 653 into diffracted light. The wavelength detection means 67 is irradiated with the diffracted light converted by the diffraction grating 67. The wavelength detection means 67 is composed of CCD, CMOS, PSD, etc., detects the wavelength of the diffracted light irradiated, and sends the detected wavelength signal to the control means described later.

Here, a method for setting the distance L between the second chromatic aberration lens 64 and the first chromatic aberration lens 62 will be described. The first chromatic aberration lens 62 and the second chromatic aberration lens 64 are the same. A case will be described in which the variation in the height position of the workpiece W held on the chuck table 36 is detected with light having a wavelength of 300 nm to 900 nm.
Conditions for the first chromatic aberration lens 62 and the second chromatic aberration lens 64:
Focal length of light having a wavelength of 300 nm in the second chromatic aberration lens 64: f1 (known number)
Focal length of light having a wavelength of 600 nm in the second chromatic aberration lens 64: f2 (known number)
Focal length of light having a wavelength of 900 nm in the second chromatic aberration lens 64: f3 (known number)

Distance from the first chromatic aberration lens 62 having a wavelength of 300 nm to f1: a1 (unknown number)
Distance from the first chromatic aberration lens 62 having a wavelength of 600 nm to f2: a2 (unknown number)
Distance from the first chromatic aberration lens 62 having a wavelength of 900 nm to f3: a3 (unknown number)

Distance from the first chromatic aberration lens 62 to the focal point of the wavelength of 300 nm: b1 (unknown number)
Distance from the first chromatic aberration lens 62 to the focal point of the wavelength of 600 nm: b2 (unknown number)
Distance from the first chromatic aberration lens 62 to the focal point of the wavelength of 900 nm: b3 (unknown number)

From the above conditions, the following equation holds.
a1 ＝ L ・ f1 ・ ・ ・ ・ ・ ・ Formula 1
a2 ＝ L ・ f2 ・ ・ ・ ・ ・ ・ Formula 2
a3 ＝ L ・ f3 ・ ・ ・ ・ ・ ・ Formula 3

When the distance between the condensing point with a wavelength of 300 nm, the condensing point with a wavelength of 600 nm, and the condensing point with a wavelength of 900 nm is set as c, the following equation is established.
b1 = b + 0 Equation 4
b2 = b + c Equation 5
b3 = b + 2c Equation 6

From the above formulas 1 to 6, the following formula is established.
1 / a1 + 1 / b1 = 1 / f1 Equation 7
1 / a2 + 1 / b2 = 1 / f2 Equation 8
1 / a3 + 1 / b3 = 1 / f3 Equation 9

Substituting Formula 1 and Formula 4 into Formula 7, Substituting Formula 2 and Formula 5 into Formula 8, and Substituting Formula 3 and Formula 6 into Formula 9 yields the following formula.
1 / (L · f1) + 1 / b1 = 1 / f1 Equation 10
1 / (L · f2) + 1 / (b + c) = 1 / f2 Equation 11
1 / (L · f3) + 1 / (b + 2c) = 1 / f3 (12)

From the above-described unknowns L, b, c and Equations 10, 11, and 12, the equation can be solved, and the distance L between the second chromatic aberration lens 64 and the first chromatic aberration lens 62 can be obtained.
And
L ・ f1 ＝ a1
L ・ f2 ＝ a2
L ・ f3 ＝ a3
b = b1
b + c = b2
b + 2c = b3
It becomes.
For example, when c = 15 μm, the interval between the condensing points every 100 nm from 300 nm to 900 nm is 5 μm.

The operation of the above-described height measuring device 6 will be described.
The white light (R) emitted from the white light source 61 passes through the beam splitter 63 and enters the second chromatic aberration lens 64 as shown by a solid line in FIG. The second chromatic aberration lens 64 forms an image of a virtual focus corresponding to each wavelength of white light incident on the optical axis. Thus, the white light on which the image of the virtual focus corresponding to each wavelength is formed on the optical axis enters the first chromatic aberration lens 62, is condensed by the first chromatic aberration lens 62, and is collected on the chuck table 36. The held workpiece W is irradiated. At this time, since the white light (R) collected by the first chromatic aberration lens 62 has a different refractive index depending on the wavelength, the focal length differs depending on the wavelength. Accordingly, the white light (R) irradiated to the workpiece W is reflected on the upper surface of the workpiece W, and among these, the light with the wavelength whose focal point matches the upper surface of the workpiece W has the smallest diameter. reflect.

  The reflected light (R1) having a wavelength that matches the focal point reflected by the upper surface of the workpiece W passes through the second chromatic aberration lens 64 as shown by the broken line, is split by the beam splitter 63, and passes through the light separating means 65. The light enters the first condensing lens 651 to be configured. The reflected light (R 1) incident on the first condenser lens 651 is condensed and passes through the pinhole 652 a of the mask 652, and is collected again by the second condenser lens 653 to reach the diffraction grating 66. . The reflected light having a wavelength that does not match the focal point on the upper surface of the workpiece W has a large diameter. Therefore, even if the reflected light is condensed by the first condenser lens 651, it is blocked by the mask 652 and passes through the pinhole 652a. Is only a few. The reflected light that has reached the diffraction grating 66 is converted into diffracted light corresponding to the wavelength and irradiated to the wavelength detecting means 67. In the embodiment shown in FIG. 2, the wavelength of 600 nm is irradiated to the position of 600 nm in the wavelength detection means 67 as indicated by a broken line, and the wavelength of 300 nm is applied to the position of 300 nm in the wavelength detection means 67 as indicated by a one-dot chain line. The wavelength of 900 nm is irradiated to the position of 900 nm in the wavelength detecting means 67 as indicated by a two-dot chain line. The wavelength detection means 67 detects the wavelength of the reflected light based on the position where the diffracted light is irradiated, and sends the detected wavelength signal to the control means described later. Note that reflected light having a wavelength that does not coincide with the focal point of the upper surface of the workpiece W that has been blocked by the mask 652 and passed through the pinhole 652a is reflected at a predetermined angle by the diffraction grating 66 and reaches the wavelength detecting means 67. As described above, since the amount of light is extremely small, the wavelength detecting means 67 is not operated. The control means described later obtains the height position of the upper surface of the workpiece W held on the chuck table 36 by obtaining the focal length of the first chromatic aberration lens 62 with respect to the wavelength based on the input wavelength signal.

  The control means to be described later includes a control map in which the relationship between the wavelength of white light collected by the first chromatic aberration lens 62 and the focal length is set as shown in FIG. 3, and this control map is referred to. The focal length corresponding to the wavelength signal sent from the wavelength detecting means 67 is obtained. Accordingly, the position corresponding to the focal length from the first chromatic aberration lens 62 is the height position of the upper surface of the workpiece W held on the chuck table 36. For example, in the control map shown in FIG. 3, when the wavelength signal sent from the wavelength detecting means 67 is 600 nm, it is the focal length (for example, 29.4 mm) of the first chromatic aberration lens 62. The height position of the upper surface of the held workpiece W is 29.4 mm below the first chromatic aberration lens 62. In the illustrated embodiment, as described above, the interval between the condensing points for every 100 nm is 5 μm in the wavelength range from 300 nm to 900 nm of white light, so that the wavelength signal sent from the wavelength detecting means 67 is 500 nm. When the wavelength signal is 300 nm, the height position of the upper surface of the workpiece W held on the chuck table 36 is 29.395 mm below the first chromatic aberration lens 62. The height position of the upper surface of the workpiece W held is 29.385 mm below the first chromatic aberration lens 62. On the other hand, when the wavelength signal sent from the wavelength detecting means 67 is 700 nm, the height position of the upper surface of the workpiece W held on the chuck table 36 is 29.405 mm below the first chromatic aberration lens 62. When the wavelength signal is 900 nm, the height position of the upper surface of the workpiece W held on the chuck table 36 is 29.415 mm below the first chromatic aberration lens 62. As described above, in the height detection device 6 according to the present invention, since the condensing point of each wavelength of the white light condensed by the first chromatic aberration lens 62 changes linearly, the first chromatic aberration lens 62. Thus, the distance from the upper surface of the workpiece W held on the chuck table 36, that is, the height position of the upper surface of the workpiece W held on the chuck table 36 can be accurately measured.

  Referring back to FIG. 2, the laser beam application unit 7 includes a pulse laser beam oscillation unit 71 and a dichroic that changes the direction of the pulse laser beam oscillated from the pulse laser beam oscillation unit 71 toward the first chromatic aberration lens 62. A mirror 72 is provided. The pulse laser beam oscillation means 71 is composed of a pulse laser beam oscillator 711 composed of a YAG laser oscillator or a YVO4 laser oscillator, and a repetition frequency setting means 712 attached thereto, and oscillates a pulse laser beam having a wavelength of 1064 nm, for example. The dichroic mirror 72 is disposed between the second chromatic aberration lens 64 and the first chromatic aberration lens 62 and allows white light from the second chromatic aberration lens 64 to pass therethrough but is oscillated from the pulse laser beam oscillation means 71. The direction of the pulsed laser beam is changed toward the first chromatic aberration lens 62. Accordingly, the pulse laser beam (LB) oscillated from the pulse laser beam oscillating means 71 is changed in direction by 90 degrees by the dichroic mirror 72, enters the first chromatic aberration lens 62, and is collected by the first chromatic aberration lens 62. The workpiece W held on the chuck table 36 is irradiated. For this reason, the first chromatic aberration lens 62 has a function as a condensing lens constituting the laser beam irradiation means 7.

  Returning to FIG. 1, the explanation is continued. In the laser processing machine in the illustrated embodiment, the unit holder 51 is indicated by an arrow Z along a pair of guide rails 423 and 423 provided on the mounting portion 422 of the movable support base 42. Condensing point position adjusting means 53 is provided for moving in the condensing point position adjusting direction (Z-axis direction) shown, that is, in a direction perpendicular to the holding surface of the chuck table 36. The condensing point position adjusting means 53 includes a male screw rod (not shown) disposed between the pair of guide rails 423 and 423, and a drive source such as a pulse motor 532 for rotationally driving the male screw rod. The male screw rod (not shown) is driven to rotate forward and backward by the pulse motor 532, so that the height measuring / laser irradiation unit 5 is moved along the guide rails 423 and 423 in the Z-axis direction. In the illustrated embodiment, the height measurement / laser irradiation unit 5 is moved upward by driving the pulse motor 532 in the forward direction, and the height measurement / laser irradiation unit 5 is moved in the reverse direction by driving the pulse motor 532 in the reverse direction. It is designed to move downward.

  An imaging means 8 is disposed at the front end of the unit housing 52 that constitutes the height measurement / laser irradiation unit 5. The imaging unit 8 includes, in addition to a normal imaging device (CCD) that captures an image with visible light, an infrared illumination unit that irradiates a workpiece with infrared rays, an optical system that captures infrared rays emitted by the infrared illumination unit, An image sensor (infrared CCD) that outputs an electrical signal corresponding to the infrared rays captured by the optical system is used, and the captured image signal is sent to a control means to be described later.

  The laser processing apparatus 1 in the illustrated embodiment includes a control means 9 shown in FIG. The control means 9 is constituted by a computer, and a central processing unit (CPU) 91 that performs arithmetic processing according to a control program, a read-only memory (ROM) 92 that stores control programs and the like, and a readable and writable memory that stores arithmetic results and the like. A random access memory (RAM) 93, a counter 94, an input interface 95 and an output interface 96 are provided. Detection signals from the machining feed amount detection means 374, the index feed amount detection means 384, the wavelength detection means 67, the imaging means 8, and the like are input to the input interface 95 of the control means 8. A control signal is output from the output interface 96 of the control means 10 to the pulse motor 372, the pulse motor 382, the pulse motor 432, the pulse motor 532, the white light source 61 of the height measuring device 6, the pulse laser beam oscillation means 71, and the like. To do. The above-described control map shown in FIG. 3 is stored in a read only memory (ROM) 92 or a random access memory (RAM) 93.

The laser beam machine 1 in the illustrated embodiment is configured as described above, and the operation thereof will be described below.
FIG. 5 is a perspective view of a semiconductor wafer 10 as a workpiece to be laser processed. A semiconductor wafer 10 shown in FIG. 5 is made of a silicon wafer, and a plurality of areas are defined by a plurality of streets 101 arranged in a lattice pattern on the surface 10a, and devices such as IC and LSI are defined in the partitioned areas. 102 is formed.

An embodiment of laser processing in which the above-described laser processing machine 1 is used to irradiate a laser beam along the street 101 of the semiconductor wafer 10 to form a deteriorated layer along the street 101 inside the semiconductor wafer 10 will be described. In addition, when the altered layer is formed inside the semiconductor wafer 10, if the thickness of the semiconductor wafer varies, the altered layer can be uniformly formed at a predetermined depth due to the refractive index as described above. Can not. Therefore, before performing laser processing, the height position of the semiconductor wafer 10 held on the chuck table 36 is measured by the above-described height measuring device 6.
That is, first, the semiconductor wafer 10 is placed on the chuck table 36 of the laser processing machine 1 shown in FIG. 1 with the back surface 10b facing up, and the semiconductor wafer 10 is sucked and held on the chuck table 36. The chuck table 36 that sucks and holds the semiconductor wafer 10 is positioned immediately below the imaging unit 8 by the processing feeding unit 37.

  When the chuck table 36 is positioned immediately below the image pickup means 8, the image pickup means 8 and the control means 9 execute an alignment operation for detecting a processing region to be laser processed on the semiconductor wafer 10. That is, the image pickup means 8 and the control means 9 are the street 101 formed in the predetermined direction of the semiconductor wafer 10 and the height measurement that constitutes the height measurement / laser irradiation unit 5 of the semiconductor wafer 10 along the street 101. Image processing such as pattern matching for performing alignment with the first chromatic aberration lens 62 of the apparatus 6 is executed, and alignment of the height detection position is performed. Similarly, the alignment of the height detection position is performed on the street 101 formed in the direction orthogonal to the predetermined direction formed in the semiconductor wafer 10. At this time, the surface 10a on which the street 101 of the semiconductor wafer 10 is formed is located on the lower side. However, as described above, the imaging unit 7 is an infrared illumination unit, an optical system for capturing infrared rays, and an electrical signal corresponding to infrared rays. Since the image pickup means (infrared CCD) or the like is provided, the street 101 can be imaged through the back surface 10b.

  When alignment is performed as described above, the semiconductor wafer 10 on the chuck table 36 is positioned at the coordinate position shown in FIG. FIG. 6B shows a state in which the chuck table 36, that is, the semiconductor wafer 10, is rotated 90 degrees from the state shown in FIG.

  It should be noted that the feed start position coordinate values (A1, A2, A3... Of each street 101 formed on the semiconductor wafer 10 in the state positioned at the coordinate positions shown in FIGS. An), feed end position coordinate value (B1, B2, B3 ... Bn), feed start position coordinate value (C1, C2, C3 ... Cn) and feed end position coordinate value (D1, D2, D3 ... In Dn), the data of the design value is stored in the random access memory (RAM) 93.

  As described above, when the street 101 formed on the semiconductor wafer 10 held on the chuck table 36 is detected and the alignment of the height detection position is performed, the chuck table 36 is moved and the position shown in FIG. In a), the uppermost street 101 is positioned directly below the first chromatic aberration lens 62 of the height measuring device 6 constituting the height measuring / laser irradiation unit 5. Further, as shown in FIG. 7, the feed start position coordinate value (A1) (see FIG. 6A) which is one end (the left end in FIG. 7) of the street 101 is positioned immediately below the first chromatic aberration lens 62. Then, the height measuring device 6 is operated, and the chuck table 36 is moved in the direction indicated by the arrow X1 in FIG. 7 to move to the feed end position coordinate value (B1) (height position detecting step). As a result, the height position of the upper surface is measured along the uppermost street 101 in FIG. 6A of the semiconductor wafer 10 as described above. The measured height position is stored in the random access memory (RAM) 93. In this way, the height position detection process is performed along all the streets 101 formed in the semiconductor wafer 10, and the height position of the upper surface of each street 101 is stored in the random access memory (RAM) 93.

If the height position detection process is performed along all the streets 101 formed on the semiconductor wafer 10 as described above, laser processing for forming a deteriorated layer along the street 101 inside the semiconductor wafer 10 is performed. To do.
In order to carry out this laser processing, first, the chuck table 36 is moved and the uppermost street 101 in FIG. 6A is used as a condensing lens of the laser beam irradiation means 7 constituting the height measurement / laser irradiation unit 5. It is positioned directly below the functioning first chromatic aberration lens 62. Further, as shown in FIG. 8A, the feed start position coordinate value (A1) (see FIG. 6A) which is one end of the street 101 (the left end in FIG. 8A) is the first value. It is positioned directly below the chromatic aberration lens 62. Then, the condensing point P of the pulsed laser beam irradiated from the first chromatic aberration lens 62 constituting the laser beam irradiation means 7 is set to a predetermined depth position from the back surface 10b (upper surface) of the semiconductor wafer 10. Next, the laser beam irradiation means 7 is operated to move the chuck table 36 in the direction indicated by the arrow X1 at a predetermined processing feed rate while irradiating the first chromatic aberration lens 62 with a pulse laser beam (laser processing step). When the irradiation position of the first chromatic aberration lens 62 reaches the other end of the street 101 (the right end in FIG. 8B) as shown in FIG. 8B, the irradiation of the pulse laser beam is stopped, The movement of the chuck table 36 is stopped. In this laser processing step, the control means 9 controls the pulse motor 532 of the focusing point position adjusting means 53 based on the height position of the semiconductor wafer 10 stored in the random access memory (RAM) 93 on the street 101. Then, the height measurement / laser irradiation unit 5 is moved in the Z-axis direction, and the first chromatic aberration lens 62 constituting the laser beam irradiation means 7 is moved to a height on the street 101 of the semiconductor wafer 10 as shown in FIG. Move up and down according to the position. As a result, the altered layer 110 is formed in the semiconductor wafer 10 in parallel with the back surface 10b (upper surface) at a predetermined depth from the back surface 10b (upper surface) as shown in FIG. 8B.

In addition, the processing conditions in the said laser processing process are set as follows, for example.
Laser: YVO4 pulse laser Wavelength: 1064nm
Repetition frequency: 100 kHz
Pulse output: 2.5μJ
Condensing spot diameter: φ1μm
Processing feed rate: 100 mm / sec

  If the thickness of the semiconductor wafer 10 is thick, the plurality of altered layers 110a, 110b, It is desirable to form 110c. The altered layers 110a, 110b, and 110c are preferably formed by displacing the condensing point of the laser beam stepwise in the order of 110a, 110b, and 110c.

  As described above, when the laser processing step is executed along all the streets 101 extending in the predetermined direction of the semiconductor wafer 10, the chuck table 36 is rotated by 90 degrees to make the above-mentioned predetermined direction. The laser processing step is executed along each street 101 extending in the orthogonal direction. Thus, if the laser processing step is performed along all the streets 101 formed on the semiconductor wafer 10, the chuck table 36 holding the semiconductor wafer 10 first holds the semiconductor wafer 10 by suction. The semiconductor wafer 10 is released from the suction holding state. Then, the semiconductor wafer 10 is transferred to the dividing step by a transfer means (not shown).

  As mentioned above, although the example which applied the measuring device of the workpiece hold | maintained at the chuck table by this invention to the laser processing machine was shown, the measuring device by this invention is other processing machines, such as a cutting machine equipped with the cutting blade. You may apply to.

2: Stationary base 3: Chuck table mechanism 31: Guide rail 36: Chuck table 37: Work feed means 374: Work feed amount detection means 38: First index feed means 4: Laser beam irradiation unit support mechanism 41: Guide rail 42 : Movable support base 43: second indexing and feeding means 5: height measurement / laser irradiation unit 53: focusing point position adjusting means 6: height measuring device 61: white light source 62: first chromatic aberration lens 63: beam Splitter 64: Second chromatic aberration lens 65: Light separation means 66: Diffraction grating 67: Wavelength detection means 7: Laser beam irradiation means 71: Pulse laser beam oscillation means 72: Dichroic mirror 8: Imaging means 9: Control means 10: Semiconductor wafer

Claims (2)

A white light source that emits white light toward a work piece held on a chuck table equipped in a processing machine, and a white light emitted from the white light source is collected to the work piece held on the chuck table. A first chromatic aberration lens to be irradiated, a beam splitter that is disposed between the white light source and the first chromatic aberration lens and divides the reflected light of the white light irradiated to the workpiece, and is split by the beam splitter. Light separating means for passing reflected light having a wavelength passing through the optical axis in the reflected light, a diffraction grating for converting the reflected light that has passed through the light separating means into diffracted light, and diffraction light diffracted by the diffraction grating Wavelength detection means for detecting the wavelength, and a control means for determining the height position of the workpiece held on the chuck table based on the wavelength signal from the wavelength detection means. The measuring device of the workpiece was,
A second chromatic aberration lens that is disposed between the beam splitter and the first chromatic aberration lens and forms an image of a virtual focal point of white light incident on the optical axis from the white light source through the beam splitter;
The distance between the first chromatic aberration lens and the second chromatic aberration lens is set such that the focal point of each wavelength collected on the optical axis by the first chromatic aberration lens is proportional to the predetermined wavelength interval. ing,
An apparatus for measuring a workpiece held on a chuck table. A chuck table having a holding surface for holding a workpiece, laser beam irradiation means for irradiating the workpiece held on the chuck table with a laser beam, and detecting a height position of the workpiece held on the chuck table A laser processing machine comprising:
The measuring device includes a white light source that emits white light toward a workpiece held on the chuck table, and a white light emitted by the white light source that is collected and irradiated to the workpiece held on the chuck table. A first chromatic aberration lens, a beam splitter that is disposed between the white light source and the first chromatic aberration lens and divides the reflected light of the white light irradiated on the workpiece, the beam splitter and the first A second chromatic aberration lens disposed between the first chromatic aberration lens and forming an image of a virtual focal point of white light incident on the optical axis from the white light source through the beam splitter, and is split by the beam splitter A light separating unit that passes reflected light having a wavelength passing through the optical axis in the reflected light; a diffraction grating that converts the reflected light that has passed through the light separating unit into diffracted light; and a diffraction grating diffracted by the diffraction grating. Comprising a wavelength detector for detecting a length, and a control means for determining the height position of the workpiece held on the chuck table on the basis of the wavelength signal from the wavelength detection means, and
The laser beam irradiation unit is disposed between the laser beam oscillation unit that oscillates a laser beam, the first chromatic aberration lens, and the second chromatic aberration lens. The laser beam emitted from the laser beam oscillation unit is the first chromatic aberration. A dichroic mirror that changes direction toward the lens,
Laser processing machine characterized by that.

Images