JP7246260B2 - Reflectance measuring device and laser processing device - Google Patents

Description

The present invention relates to a reflectance measuring device and a laser processing device.

In order to divide a workpiece such as a semiconductor wafer into chip sizes, a laser beam with a wavelength that is transparent to the workpiece is condensed and irradiated to form a reformed layer that serves as a splitting starting point inside the workpiece. A processing method for forming is disclosed (see, for example, Patent Document 1).

However, in some cases, the back surface of the workpiece is coated with a film such as an oxide film or a nitride film that makes it difficult for the laser beam to pass through. be.

Therefore, the back surface of the workpiece is irradiated with light, the reflectance is calculated from the amount of reflected light, and the appropriate pulse energy is determined based on the correlation between the reflectance and pulse energy for each type of film stored in advance in the memory of the controller. A laser processing apparatus that determines and processes a workpiece has been proposed (see Patent Document 2, for example).

Japanese Patent No. 3408805 JP 2013-230477 A

However, the laser processing apparatus disclosed in Patent Document 2 has a problem that the laser beam irradiated to the workpiece for measuring the reflectance damages the workpiece.

In addition, since the light incident on the detection unit that detects the reflected light is designed to be in the same state as the processing point, if the chuck table expands due to heat, the workpiece placed on the chuck table is irradiated with the laser in a non-focused state. As a result, the reflected light is incident on the detection unit in a non-focused state, and the intensity of the reflected light changes compared to when it is incident in a focused state, making it impossible to accurately measure the reflectance. There was also the issue of no

The present invention has been made in view of the above facts, and its object is to provide a reflectance measuring apparatus and a laser processing apparatus that can accurately measure reflectance while suppressing damage to a workpiece. That is.

In order to solve the above-described problems and achieve the object, the reflectance measuring apparatus of the present invention includes a chuck table for holding a workpiece and a reflector for measuring the reflectance of the workpiece held on the chuck table. A reflectance measurement apparatus comprising a reflectance measurement unit and a control unit for controlling the reflectance measurement unit, the reflectance measurement unit being a laser beam of a wavelength transmissive to the workpiece. a laser oscillator that oscillates, a first condenser lens that condenses the laser beam oscillated from the laser oscillator and irradiates it on the workpiece, and the first condenser lens that passes through the workpiece to the workpiece a detection unit for detecting reflected light of the irradiated laser beam; A phase delay unit for delaying the phase of the outer peripheral part of the laser beam so that the laser beam is irradiated in a non-focused state and enters the detection unit in a focused state, and a focus area of the laser beam is extended. a spherical aberration imparting unit imparting spherical aberration to the laser beam so that the laser beam is incident on the detection unit in a state in which it is present.

In the reflectometry device, the phase retardation unit may comprise a DOE and the spherical aberration imparting unit may comprise a concave lens.

In the reflectometry device, the functions of the phase retardation unit and the spherical aberration imparting unit may be realized by a spatial light phase modulator (LCOS).

A laser processing apparatus of the present invention is a laser processing apparatus comprising the reflectance measuring device, wherein a laser beam oscillated from a laser oscillator of the reflectance measuring unit is transferred to the first laser beam without passing through the phase delay unit. The modified layer is formed by condensing light using a condensing lens and irradiating the workpiece held on the chuck table with the condensing point positioned therein.

ADVANTAGE OF THE INVENTION This invention is effective in the ability to measure a correct reflectance, suppressing the damage inflicted on a to-be-processed object.

FIG. 1 is a perspective view showing a configuration example of a laser processing apparatus according to Embodiment 1. FIG. FIG. 2 is a diagram schematically showing the configuration of a laser beam irradiation unit of the laser processing apparatus shown in FIG. 1. As shown in FIG. 3 is a plan view of the laser beam on the workpiece when the laser beam irradiation unit shown in FIG. 2 measures the reflectance of the workpiece; FIG. 4 is a plan view of a laser beam on the light receiving surface of the detection unit when the reflectance measurement unit shown in FIG. 2 measures the reflectance of the workpiece; FIG. FIG. 5 is a diagram schematically showing a state in which the laser beam irradiation unit shown in FIG. 2 forms a modified layer on the workpiece. FIG. 6 is a diagram schematically showing the configuration of a laser beam irradiation unit of a laser processing apparatus according to Embodiment 2. FIG.

A form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. In addition, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. In addition, various omissions, substitutions, or changes in configuration can be made without departing from the gist of the present invention.

[Embodiment 1]
A reflectance measuring unit and a laser processing apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a configuration example of a laser processing apparatus according to Embodiment 1. FIG. FIG. 2 is a diagram schematically showing the configuration of a laser beam irradiation unit of the laser processing apparatus shown in FIG. 1. As shown in FIG. 3 is a plan view of the laser beam on the workpiece when the laser beam irradiation unit shown in FIG. 2 measures the reflectance of the workpiece; FIG. 4 is a plan view of a laser beam on the light receiving surface of the detection unit when the reflectance measurement unit shown in FIG. 2 measures the reflectance of the workpiece; FIG. FIG. 5 is a diagram schematically showing a state in which the laser beam irradiation unit shown in FIG. 2 forms a modified layer on the workpiece.

A laser processing apparatus 1 according to Embodiment 1 is an apparatus for performing laser processing by irradiating a laser beam 21 to a workpiece 200 shown in FIG. A workpiece 200 to be processed by the laser processing apparatus 1 shown in FIG. 1 is a wafer such as a disk-shaped semiconductor wafer or an optical device wafer having a substrate 201 made of silicon, sapphire, gallium arsenide, or the like.

The workpiece 200 has dividing lines (not shown) set in a grid pattern on the surface of the substrate 201 and devices formed in regions partitioned by the dividing lines. The device is, for example, an integrated circuit such as an IC (Integrated Circuit) or LSI (Large Scale Integration), a CCD (Charge Coupled Device), or an image sensor such as a CMOS (Complementary Metal Oxide Semiconductor).

A workpiece 200 has a substrate 201 whose back surface is covered with a film 202 such as an oxide film or a nitride film. In the first embodiment, the workpiece 200 has an annular frame 210 attached to its outer edge, and a tape 211 having a larger diameter than the outer diameter of the workpiece 200 is attached to the front surface of the workpiece 200 to cover the film 202 on the back side. It is supported in an opening in annular frame 210 in an exposed state.

In the first embodiment, the workpiece 200 is irradiated with a laser beam 21 having a wavelength that is transmissive to the substrate 201 of the workpiece 200 along the planned division line, so that the modified layer is formed along the planned division line. It is then formed into individual devices. The reflectance of the film 202 for the laser beam 21 changes depending on the material forming the film 202 or the thickness of the film 202 . The modified layer means a region whose density, refractive index, mechanical strength and other physical properties are different from those of the surrounding area. Examples include a refractive index change region and a region in which these regions are mixed. In addition, the modified layer has lower mechanical strength and the like than other portions of the workpiece 200 .

The laser processing apparatus 1 includes a chuck table 10, a laser beam irradiation unit 20 which is a reflectance measurement unit, a moving unit 30, an imaging unit 90, and a control unit 100, as shown in FIG.

The chuck table 10 holds the workpiece 200 on the holding surface 11 . The holding surface 11 is disk-shaped and made of porous ceramic or the like, and is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown). The chuck table 10 sucks and holds the workpiece 200 placed on the holding surface 11 . In Embodiment 1, the holding surface 11 is a plane parallel to the horizontal direction. A plurality of clamping units 12 are arranged around the chuck table 10 to clamp an annular frame 210 that supports the workpiece 200 in the opening. Also, the chuck table 10 is rotated around an axis parallel to the Z-axis direction parallel to the vertical direction by the rotary movement unit 33 of the movement unit 30 . The rotary movement unit 33 and the chuck table 10 are moved in the X-axis direction parallel to the horizontal direction by the X-axis movement unit 31 of the movement unit 30 .

The laser beam irradiation unit 20 is a unit that irradiates a pulsed laser beam 21 onto the workpiece 200 held on the chuck table 10 . The laser beam irradiation unit 20 also measures the reflectance of the laser beam 21 on the film 202 of the workpiece 200 held on the chuck table 10 .

As shown in FIG. 2, the laser beam irradiation unit 20 has a laser oscillator 22 that oscillates a laser beam 21 having a wavelength that is transparent to a workpiece 200, and chucks the laser beam 21 emitted from the laser oscillator 22. A dichroic mirror 23 that reflects toward a workpiece 200 held on a holding surface 11 of a table 10, and a laser beam 21 that is reflected by the dichroic mirror 23 and oscillated from a laser oscillator 22 is condensed to the workpiece 200. The reflected light 25 of the laser beam 21 irradiated to the workpiece 200 through the first condenser lens 24 for irradiation, the not-shown focal point position adjusting means, and the first condenser lens 24 is detected. It has a detection unit 26 and a second condenser lens 27 that collects the reflected light 25 incident on the detection unit 26 .

A laser oscillator 22 emits a laser beam 21 toward a dichroic mirror 23 . The dichroic mirror 23 reflects the laser beam 21 oscillated by the laser oscillator 22 toward the first condenser lens 24 and transmits the reflected light 25 of the laser beam 21 irradiated to the workpiece 200 . The first condensing lens 24 transmits the laser beam 21 reflected by the dichroic mirror 23, converges the laser beam 21 on the workpiece 200, and reflects the laser beam 21 irradiated on the workpiece 200. It transmits light 25 . The focal point position adjusting means displaces the position of the focal point 21-1 of the laser beam 21 in the Z-axis direction parallel to the vertical direction.

The detection unit 26 has a light receiving surface 261 that receives the reflected light 25 . In Embodiment 1, the detection unit 26 is a CMOS (Complementary MOS) camera capable of detecting the output of the reflected light 25 condensed on the light receiving surface 261, but the present invention is not limited to a CMOS camera. The detection unit 26 outputs to the control unit 100 information indicating the power of the laser beam 21 condensed on the light receiving surface 261 . The second condenser lens 27 transmits the reflected light 25 that has passed through the dichroic mirror 23 and converges the reflected light 25 on the light receiving surface 261 .

In addition, as shown in FIG. 2, the laser beam irradiation unit 20 further includes a phase delay lens 28 as a phase delay unit and a spherical aberration applying lens 29 as a spherical aberration applying unit.

The phase delay lens 28 irradiates the laser beam 21 emitted from the laser oscillator 22 to the workpiece 200 held on the chuck table 10 in a non-focused state as shown in FIG. In 261, as shown in FIG. 4, the phase of the outer peripheral portion of the laser beam 21 is retarded from that of the central portion so that the reflected light 25 of the laser beam 21 is incident in a focused state. In Embodiment 1, the phase retardation lens 28 is arranged between the laser oscillator 22 and the dichroic mirror 23 and can transmit the laser beam 21 emitted by the laser oscillator 22 .

The phase delay lens 28 has a reflectance measurement position shown in FIG. It is movably provided by a driving mechanism (not shown) to a retracted position (not shown) where the beam 21 does not pass. In Embodiment 1, the phase delay lens 28 includes a DOE (Diffractive Optical Element) 281 that delays the phase of the transmitted laser beam 21 in the outer peripheral portion from that in the central portion.

The spherical aberration imparting lens 29 is arranged on the light receiving surface 261 of the detection unit 26 in a state in which the light condensing area 25-1 of the reflected light 25 of the laser beam 21 transmitted through the dichroic mirror 23 extends in the optical axis direction of the laser beam 21. It imparts spherical aberration to the reflected light 25 of the laser beam 21 so that it is incident. In Embodiment 1, the spherical aberration imparting lens 29 is arranged between the second condenser lens 27 and the light receiving surface 261 of the detection unit 26, and can transmit the reflected light 25 of the laser beam 21 transmitted through the dichroic mirror 23. and imparts spherical aberration to the reflected light 25 . In Embodiment 1, the spherical aberration imparting lens 29 is a concave lens. That is, the spherical aberration applying unit of the present invention includes a concave lens.

In Embodiment 1, a part of the optical system included in the laser beam irradiation unit 20 is attached to the tip of the support column 4 whose base end is attached to the standing plate 3 erected from the device main body 2 of the laser processing device 1. installed.

The moving unit 30 relatively moves the laser beam irradiation unit 20 and the chuck table 10 . The moving unit 30 includes an X-axis moving unit 31 that moves the chuck table 10 in the X-axis direction, and a Y-axis moving unit 32 that moves the chuck table 10 in a Y-axis direction parallel to the horizontal direction and orthogonal to the X-axis direction. , and a rotary movement unit 33 for rotating the chuck table 10 about an axis parallel to the Z-axis direction orthogonal to the X-axis direction and the Y-axis direction.

In Embodiment 1, the Y-axis moving unit 32 is installed on the apparatus main body 2 of the laser processing apparatus 1, and moves the moving plate 34 supporting the X-axis moving unit 31 in the Y-axis direction. The X-axis movement unit 31 is installed on the movement plate 34 and supports the chuck table 10 and the rotation movement unit 33 so as to be movable in the X-axis direction.

The X-axis moving unit 31 and the Y-axis moving unit 32 include well-known ball screws 311 and 321 which are rotatably provided around the axis, and known pulse motors 312 and 322 which rotate the ball screws 311 and 321 around the axis. and well-known guide rails 313 and 323 which support the moving plate 14, the chuck table 10 and the rotary moving unit 33 so as to be movable in the X-axis direction or the Y-axis direction.

The laser processing apparatus 1 also includes an X-axis position detection unit (not shown) for detecting the position of the chuck table 10 in the X-axis direction, and a Y-axis direction detection unit (not shown) for detecting the position of the chuck table 10 in the Y-axis direction. and a position detection unit. Each position detection unit outputs a detection result to the control unit 100 .

The imaging unit 90 is for imaging the workpiece 200 held on the chuck table 10 . The imaging unit 90 is composed of an infrared camera that detects a planned division line by imaging the workpiece 200 held on the chuck table 10 from the back surface film 202 side. In Embodiment 1, the imaging unit 90 is attached to the tip of the support column 4 and arranged in a position aligned with a part of the optical system included in the laser beam irradiation unit 20 in the X-axis direction. The imaging unit 90 captures an image of the workpiece 200 to obtain an image for performing alignment for aligning the workpiece 200 and the laser beam irradiation unit 20, and outputs the obtained image to the control unit 100. do.

The control unit 100 controls the above-described components of the laser processing apparatus 1 to cause the laser processing apparatus 1 to perform processing operations on the workpiece 200 . Note that the control unit 100 includes an arithmetic processing unit having a microprocessor such as a CPU (central processing unit), a storage device having a memory such as ROM (read only memory) or RAM (random access memory), and an input/output unit. A computer having an interface device. The arithmetic processing unit of the control unit 100 performs arithmetic processing according to a computer program stored in the storage device, and outputs a control signal for controlling the laser processing apparatus 1 to the laser processing apparatus 1 via the input/output interface device. The functions of the control unit 100 are implemented by outputting to the components described above.

The control unit 100 includes a display unit 101 configured by a liquid crystal display device or the like for displaying the state of machining operation and images, an input unit (not shown) used by the operator to register machining content information and the like, and an input unit (not shown). A notification unit is connected. The input unit is composed of at least one of a touch panel provided on the display unit 101 and an external input device such as a keyboard. The notification unit emits at least one of sound and light to notify the operator. Moreover, the chuck table 10, the laser beam irradiation unit 20, and the control unit 100 constitute the reflectance measuring apparatus 40 according to the first embodiment. That is, the laser processing device 1 includes a reflectance measuring device 40 .

In the laser processing apparatus 1 having the above-described configuration, the control unit 100 receives processing content information input by the operator via the input unit 102, stores it in the storage device of the control unit 100, and places it on the chuck table 10 via the tape 211. A workpiece 200 is placed. The processing content information includes information indicating the output of the laser beam 21 of the laser oscillator 22, information indicating the upper limit value and information indicating the lower limit value of the reflectance of the laser beam 21 of the film 202 of the workpiece 200. In the first embodiment, the upper limit value and the lower limit value of the reflectance are equal to or more than the upper limit value and equal to or less than the lower limit value. If the reflectance exceeds the upper limit value or is less than the lower limit value, it is a value indicating that an inappropriate film 202 is formed on the workpiece 200 to be processed.

When the laser processing apparatus 1 receives a processing start instruction input by the operator via the input unit 102 , the laser processing apparatus 1 suction-holds the workpiece 200 on the chuck table 10 and clamps the annular frame 210 with the clamp section 12 . to clamp. The control unit 100 of the laser processing apparatus 1 controls a drive unit (not shown) to position the phase retardation lens 28 at the reflectance measurement position shown in FIG. By controlling the means, the laser oscillator 22 is controlled, and the laser beam 21 is oscillated from the laser oscillator 22 .

Then, the laser beam 21 emitted from the laser oscillator 22 passes through the phase delay lens 28, is reflected by the dichroic mirror 23, and is condensed by the first condensing lens 24. FIG. When the laser beam 21 is transmitted through the phase delay lens 28, the DOE 281 delays the phase of the outer peripheral portion from the phase of the central portion. , the film 202 on the back side of the workpiece 200 is illuminated in a non-focused state, as shown in FIG. In the first embodiment, the condensing point 21-1 is formed above the film 202 of the workpiece 200 (on the side away from the chuck table 10).

The reflected light 25 of the laser beam 21 from the film 202 of the workpiece 200 passes through the first condenser lens 24, the dichroic mirror 23, the second condenser lens 27 and the spherical aberration giving lens 29 in order, and is detected. Incident on the light receiving surface 261 of the unit 26 . Since the reflected light 25 is given spherical aberration by the spherical aberration applying lens 29, as shown in FIG. A condensing area 25-1 composed of a plurality of condensing points 25-2 is formed in the optical axis direction. For this reason, the reflected light 25 is incident on the light-receiving surface 261 of the detection unit 26 in a focused state, as shown in FIG.

The detection unit 26 detects the output of the reflected light 25 incident on the light receiving surface 261 in a focused state, and outputs the detection result to the control unit 100 . The control unit 100 calculates the reflectance of the film 202 from the detection result of the detection unit 26 and information indicating the output of the laser beam 21 of the laser oscillator 22, and the calculated reflectance is equal to or higher than the upper limit value of the processing content information. And it is determined whether or not it is equal to or less than the lower limit. In this way, the laser beam irradiation unit 20, which is a reflectance measurement unit of the reflectance measurement device 40, measures the reflectance of the film 202 of the workpiece 200 held on the chuck table 10 in cooperation with the control unit 100 and the like. .

When the control unit 100 determines that the reflectance of the film 202 is not less than the upper limit value and not less than the lower limit value, the control unit 100 operates the notification unit to notify the operator by at least one of sound and light. When the control unit 100 determines that the reflectance of the film 202 is equal to or higher than the upper limit value and equal to or lower than the lower limit value, the processing operation is started. In the processing operation, the control unit 100 of the laser processing apparatus 1 causes the X-axis movement unit 31 to move the chuck table 10 and causes the imaging unit 90 to image the workpiece 200 on the chuck table 10 . The laser processing apparatus 1 detects a line to be divided from an image obtained by imaging the workpiece 200 and performs alignment for aligning the workpiece 200 and the laser beam irradiation unit 20 .

The laser processing apparatus 1 irradiates the workpiece 200 with the laser beam 21 while relatively moving the chuck table 10 and the laser beam irradiation unit 20 along the dividing line. As shown in FIG. 5, the laser processing apparatus 1 focuses a laser beam 21 oscillated from a laser oscillator 22 of a laser beam irradiation unit 20 using a first condenser lens 24 without a phase delay lens 28. A modified layer is formed by irradiating the laser beam 21 with the focal point 21-1 positioned inside the workpiece 200 held on the chuck table 10. FIG.

In this way, the laser processing apparatus 1 forms a modified layer inside the workpiece 200 along the dividing line. When the modified layer is formed inside the workpiece 200 along all the planned division lines, the laser processing apparatus 1 ends the processing operation. In Embodiment 1, the output of the laser beam 21 when measuring the reflectance of the film 202 of the workpiece 200 is made weaker than the output of the laser beam 21 when forming the modified layer. However, it is not limited to this.

As described above, the reflectance measuring apparatus 40 and the laser processing apparatus 1 according to Embodiment 1, when measuring the reflectance of the film 202, the laser beam 21 to the workpiece 200 by the DOE 281 of the phase retardation lens 28. is irradiated in a non-condensed state, and the reflected light 25 is incident on the light-receiving surface 261 of the detection unit 26 by the spherical aberration imparting lens 29 in a condensed state, so damage to the workpiece 200 can be suppressed. It becomes possible.

In addition, the reflectance measurement device 40 and the laser processing device 1 form a condensing area 25-1 with the spherical aberration imparting lens 29, and the reflected light 25 incident on the light receiving surface 261 of the detection unit 26 is condensed at a condensing point 25-1. -2 extends in the optical axis direction. Even if the position of the light-condensing point 25-2 relative to the light-receiving surface 261 of the unit 26 changes in the optical axis direction, the reflected light 25 can be incident on the light-receiving surface 261 of the detection unit 26 in a condensed state. Therefore, the reflectance measurement device 40 and the laser processing device 1 can accurately measure the reflectance of the film 202 of the workpiece 200 .

As a result, the reflectance measurement device 40 and the laser processing device 1 can improve the stability of the reflectance measurement, prevent the processing of the workpiece 200 that deviates from the specifications, and set appropriate processing conditions according to the reflectance. can be set, and the reflectance can be accurately measured while suppressing damage to the workpiece 200 .

[Embodiment 2]
A reflectance measurement unit and a laser processing apparatus according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 6 is a diagram schematically showing the configuration of a laser beam irradiation unit of a laser processing apparatus according to Embodiment 2. FIG. In addition, FIG. 6 attaches|subjects the same code|symbol to the same part as Embodiment 1, and abbreviate|omits description.

As shown in FIG. 6, the laser beam irradiation unit 20, which is the reflectance measurement unit of the laser processing apparatus according to the second embodiment, includes a spatial optical phase modulator (Liquid The configuration is the same as that of the first embodiment except that a Crystal on Silicon-Spatial Light Modulator (LCOS-SLM) 50 is provided.

When the spatial light phase modulator 50 measures the reflectance of the film 202 of the workpiece 200 , the workpiece 200 held on the chuck table 10 reflects the laser beam 21 emitted from the laser oscillator 22 . A phase delay unit that delays the phase of the outer peripheral portion of the laser beam 21 from that of the central portion so that the light 25 is irradiated in a non-focused state and the laser beam 21 is incident on the light receiving surface 261 of the detection unit 26 in a focused state. Then, the reflected light 25 of the laser beam 21 transmitted through the dichroic mirror 23 is incident on the light-receiving surface 261 of the detection unit 26 in a state in which the condensing region 25-1 extends in the optical axis direction of the laser beam 21. It realizes the function of a spherical aberration imparting unit that imparts spherical aberration to the laser beam 21 emitted by the laser oscillator 22 .

In Embodiment 2, the spatial light phase modulator 50 is arranged between the laser oscillator 22 and the dichroic mirror 23 . When measuring the reflectance of the film 202 of the workpiece 200, the spatial light phase modulator 50 adjusts the phase of the outer peripheral portion of the laser beam 21 emitted by the laser oscillator 22 by the control unit 100 to be lower than the phase of the central portion. The driving conditions are set so as to delay the laser beam 21 and impart spherical aberration to the laser beam 21 emitted by the laser oscillator 22 . Further, when forming the modified layer, the spatial light phase modulator 50 is set to drive conditions for forming the modified layer at a predetermined position in the thickness direction of the workpiece 200 . These drive conditions are included in the processing content information of the laser processing apparatus 1 .

In the reflectance measurement device 40 and the laser processing device 1 according to the second embodiment, when measuring the reflectance of the film 202, the phase of the outer peripheral portion of the laser beam 21 emitted from the laser oscillator 22 by the spatial light phase modulator 50 is The phase of the laser beam 21 delayed from the central portion and emitted by the laser oscillator 22 is imparted with spherical aberration. The reflected light 25 is incident on the light receiving surface 261 in a focused state. As a result, the reflectance measuring apparatus 40 and the laser processing apparatus 1 according to the second embodiment have the effect of enabling accurate reflectance measurement while suppressing damage to the workpiece 200 . In the second embodiment, since the spatial light phase modulator 50 is arranged between the laser oscillator 22 and the dichroic mirror 23, when measuring the reflectance of the film 202 of the workpiece 200, An object 200 is irradiated with a laser beam 21 imparted with spherical aberration.

Next, the inventors of the present invention confirmed the effects of the reflectance measuring device 40 of the present invention. The results are shown in Table 1 below.

Table 1 shows the range in the optical axis direction of the reflected light 25 in which the output of the reflected light 25 can be measured without being affected by changes in the intensity of the reflected light 25 by the detection units 26 of the products of the present invention and the comparative example. . The comparative example has the same configuration as the reflectance measurement device 40 according to the first embodiment except that the phase delay lens 28 and the spherical aberration imparting lens 29 shown in the first embodiment are not provided. The product of the present invention is the reflectance measuring device 40 according to the first embodiment.

According to Table 1, the range in which the detection unit 26 can measure the output of the reflected light 25 in the comparative example is ±0.2 μm, whereas in the product of the present invention, the detection unit 26 measures the output of the reflected light 25. The measurable range was ±1.5 μm. Therefore, according to Table 1, by providing the phase delay unit and the spherical aberration imparting unit, the stability of reflectance measurement is improved, and accurate reflectance measurement is performed while suppressing damage to the workpiece 200. It became clear that it is possible to

It should be noted that the present invention is not limited to the above embodiments. That is, various modifications can be made without departing from the gist of the present invention.

1 laser processing device 10 chuck table 20 laser beam irradiation unit (reflectance measurement unit)
21 laser beam 21-1 focal point 22 laser oscillator 24 first condenser lens 25 reflected light 26 detection unit 27 second condenser lens 28 phase delay lens (phase delay unit)
29 spherical aberration imparting lens (spherical aberration imparting unit, concave lens)
30 mobile unit 40 reflectometry device 50 spatial light phase modulator (LCOS)
100 control unit 200 workpiece 281 DOE

Claims (4)

a chuck table for holding a workpiece;
a reflectance measurement unit that measures the reflectance of the workpiece held on the chuck table;
a control unit for controlling the reflectance measurement unit;
A reflectance measurement device comprising
The reflectance measurement unit comprises:
a laser oscillator that oscillates a laser beam having a wavelength that is transparent to the workpiece;
a first condenser lens for condensing a laser beam emitted from the laser oscillator and irradiating the workpiece;
a detection unit that detects the reflected light of the laser beam that has passed through the first condenser lens and is applied to the workpiece;
a second condenser lens for condensing the reflected light incident on the detection unit;
a phase delay unit for delaying the phase of the outer peripheral portion of the laser beam so that the laser beam is irradiated to the workpiece in a non-focused state and the laser beam is incident on the detection unit in a focused state; ,
a spherical aberration imparting unit that imparts spherical aberration to the laser beam so that the laser beam is incident on the detection unit with the focused area of the laser beam extended;
A reflectance measurement device, further comprising: the phase delay unit includes a DOE;
2. The reflectance measurement device of claim 1, wherein the spherical aberration imparting unit comprises a concave lens. Reflectometry apparatus according to claim 1, characterized in that the functions of the phase retardation unit and the spherical aberration imparting unit are realized by a spatial light phase modulator (LCOS). A laser processing apparatus comprising the reflectance measuring device according to any one of claims 1 to 3,
condensing a laser beam oscillated from a laser oscillator of the reflectance measurement unit using the first condenser lens without passing through the phase delay unit;
A laser processing apparatus characterized in that a modified layer is formed by irradiating a work piece held on a chuck table with a focal point positioned inside the work piece.

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