JP7486902B2 - Measurement equipment - Google Patents

Description

The present invention relates to a measuring device that irradiates light onto an object to be measured and measures the height position and thickness of the object from the reflected light.

In the manufacturing process of device chips used in electronic devices such as mobile phones and personal computers, first, multiple planned division lines (streets) that intersect with each other are set on the surface of a wafer made of a material such as a semiconductor. Then, devices such as ICs (Integrated Circuits) and LSIs (Large-scale Integration) are formed in each area partitioned by the planned division lines. The wafer is then ground from the back side to thin it, and divided along the planned division lines to form individual device chips.

The grinding device for thinning the wafer includes a holding table capable of holding the wafer, and a grinding unit equipped with a grinding wheel capable of grinding the wafer. The grinding device further includes a measuring device capable of monitoring the height position of the top surface of the wafer held on the holding table and the thickness of the wafer. The grinding device uses this measuring device to measure the thickness of the wafer while grinding the wafer, thinning the wafer to a predetermined thickness (see Patent Document 1).

The division of the wafer is carried out, for example, by a laser processing device capable of irradiating a wafer with a laser beam to laser-process the wafer. The laser processing device includes a holding table for holding a workpiece such as a wafer, and a laser beam irradiation unit for irradiating the workpiece held on the holding table with a laser beam to laser-process the workpiece. In addition, the laser processing device includes a measuring device for measuring the height position of the top surface of the workpiece held on the holding table and the thickness of the workpiece.

The laser beam irradiation unit focuses a laser beam with a wavelength that is transparent to the workpiece (a wavelength that can pass through the workpiece) at a specified depth position within the workpiece, forming a modified layer inside the workpiece that serves as the starting point for division.

In a laser processing device, when a laser beam is irradiated onto a workpiece, the height position of the top surface of the workpiece held on a holding table is measured by a measuring device. Then, based on the measured height position of the top surface of the workpiece, the focal point of the laser beam is positioned at a predetermined height position (see, for example, Patent Document 2 and Patent Document 3).

The measuring device focuses the light emitted by the light source and inputs it into one end of an optical fiber. The other end of the optical fiber is directed toward the top surface of the workpiece held on the holding table, and the light emitted from this other end is irradiated onto the workpiece. The height of the top surface of the workpiece and the thickness of the workpiece are then determined by detecting the reflected light.

JP 2011-143488 A JP 2011-122894 A JP 2008-170366 A

Conventional measurement devices have used white LEDs (Light Emitting Diodes) as light sources. The spot diameter of the light emitted from a white LED is large, making it difficult to focus the light on one end of an optical fiber. This makes it difficult to pass a sufficient amount of light through the optical fiber, and it is not possible to irradiate the object being measured with a sufficient amount of light, resulting in insufficient measurement accuracy and resolution.

One possible solution is to use an excitation light source such as a blue LD (Laser Diode) as the light source, irradiate the phosphor with the blue light emitted from the excitation light source as excitation light, and generate white-like light by combining the generated fluorescence with the blue light. The light obtained by this method has a high intensity.

In order to improve the measurement accuracy of a measuring device, it is possible to increase the intensity of the light used for measurement. Therefore, it is possible to use a multimode LD as the light source of the excitation light that is irradiated onto the phosphor. When a multimode LD is used as the light source of the excitation light, it is possible to use excitation light with high intensity.

However, in a multimode LD, the size of the light-emitting point (emitter size) is large, and the cross-sectional shape of the excitation light is elliptical. The cross-sectional shape of the fluorescence generated from the phosphor reflects the cross-sectional shape of the excitation light. Therefore, it is difficult to focus the fluorescence generated by irradiation with excitation light having a large emitter size and an elliptical cross-sectional shape efficiently at one end of the optical fiber.

The present invention was made in consideration of these problems, and its purpose is to provide a measuring device that can perform highly accurate measurements by focusing the fluorescent light irradiated on the workpiece at one end of an optical fiber with high efficiency.

According to one aspect of the present invention, there is provided a measurement device including a holding table for holding an object to be measured and a measurement unit for measuring the height or thickness of the upper surface of the object to be measured held on the holding table, the measurement unit including a light source unit, an optical fiber for guiding light emitted by the light source unit, and a condenser for condensing the light guided by the optical fiber onto the object to be measured, the light source unit including an excitation light source, a phosphor that emits fluorescence having a different wavelength from the excitation light when receiving the excitation light emitted by the excitation light source, a beam shaping unit that changes the cross-sectional shape of the excitation light emitted by the excitation light source and condenses the excitation light onto the phosphor, and a first condensing lens that condenses probe light including the fluorescence emitted by the phosphor onto the end face of the optical fiber, and the beam shaping unit changes the cross-sectional shape of the excitation light by different magnifications in a first direction perpendicular to the direction of travel of the excitation light emitted by the excitation light source and a second direction perpendicular to the direction of travel and the first direction.

Preferably, the beam shaping unit includes a collimating lens that converts the excitation light emitted by the excitation light source, which has an elliptical cross-sectional shape, into parallel light, an anamorphic prism pair that expands the short side direction of the cross-sectional shape of the excitation light that has been collimated by the collimating lens, and a second focusing lens that focuses the excitation light, the short side direction of the cross-sectional shape of which has been expanded by the anamorphic prism pair, onto the phosphor.

Alternatively, the beam shaping unit preferably includes a collimating lens that converts the excitation light emitted by the excitation light source, which has an elliptical cross-sectional shape, into parallel light, one or more cylindrical lenses that expand the short side direction of the cross-sectional shape of the excitation light that has been collimated by the collimating lens, and a second focusing lens that focuses the excitation light, the short side direction of the cross-sectional shape of which has been expanded by the cylindrical lens, onto the phosphor.

Alternatively, the beam shaping unit preferably includes one or more toric lenses that expand the short side of the excitation light emitted by the excitation light source and having an elliptical cross-sectional shape, and then focus the excitation light on the phosphor.

A measurement device according to one aspect of the present invention includes a light source unit having an excitation light source, a phosphor, a beam shaping unit, and a first focusing lens. Here, the beam shaping unit changes the cross-sectional shape of the excitation light emitted by the excitation light source and focuses the excitation light on the phosphor. In particular, the beam shaping unit changes the cross-sectional shape of the excitation light by different magnifications in a first direction perpendicular to the propagation direction of the excitation light emitted by the excitation light source and in a second direction perpendicular to the propagation direction and the first direction.

For example, the beam shaping unit can deform the cross-sectional shape of the excitation light before it is focused on the phosphor so that the cross-sectional shape of the excitation light with a large emitter size approaches a circle. In this case, the cross-sectional shape of the fluorescence generated by the phosphor can also be made to approach a circle, so that this fluorescence can be focused with high efficiency on one end of the optical fiber, allowing high-intensity light to be used to measure the object to be measured, improving the accuracy of the measurement of the object to be measured.

Therefore, according to one aspect of the present invention, a measuring device is provided that can perform highly accurate measurements by focusing the fluorescent light irradiated on the workpiece at one end of an optical fiber with high efficiency.

FIG. 2 is a perspective view showing a grinding apparatus incorporating a measuring device; FIG. 1 is a perspective view showing a schematic diagram of a laser processing apparatus incorporating a measuring device. FIG. 2 is a side view showing a schematic diagram of a basic structure of the measurement device. 4A and 4B are side views that diagrammatically show the optical system of a measurement apparatus that uses an anamorphic prism pair in a beam shaping unit. 5A and 5B are side views that diagrammatically show an optical system of a measurement device that uses a cylindrical lens in the beam shaping unit. 6A and 6B are side views that diagrammatically show an optical system of a measurement apparatus that uses a toric lens in a beam shaping unit. FIG. 13 is a side view illustrating a modified example of the optical system of the measurement apparatus.

A measuring device according to one aspect of the present invention will be described with reference to the attached drawings. The measuring device according to this embodiment is used by being incorporated into a processing device that processes a workpiece such as a semiconductor wafer. First, the workpiece processed by the processing device will be described. The workpiece is, for example, a disk-shaped wafer made of Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductor material.

Alternatively, the workpiece may be a substantially disk-shaped substrate made of a material such as sapphire, glass, or quartz. The glass may be, for example, alkali glass, non-alkali glass, soda-lime glass, lead glass, borosilicate glass, or quartz glass. The workpiece may also be a package substrate or a ceramic substrate. Below, an example will be described in which the workpiece is a disk-shaped wafer.

The surface of the wafer is divided by a number of planned division lines arranged in a grid pattern. Devices such as ICs and LSIs are formed in each area divided by the planned division lines on the surface of the wafer. The wafer is then ground from the backside to thin it, and divided along the planned division lines to obtain individual device chips.

Grinding of the wafer is performed by a grinding machine equipped with a grinding wheel. Furthermore, division of the wafer is performed by a laser processing machine that irradiates the wafer with a laser beam to laser-process the wafer. The measurement device according to this embodiment is used by being incorporated into a processing device such as a grinding machine or a laser processing machine.

Here, a grinding device will be described as an example of a processing device in which a measuring device is incorporated. FIG. 1 is a perspective view showing a grinding device 2. The grinding device 2 has a rectangular base 4 that supports each component. An opening 4a is provided on the top surface of the base 4 along the X-axis direction, and an X-axis moving table 8 is provided within the opening 4a.

The grinding device 2 is equipped with an X-axis direction movement mechanism that moves the X-axis direction movement table 8 along the X-axis direction. The X-axis direction movement table 8 moves between a loading/unloading area 10 where the workpiece is loaded and unloaded by the X-axis direction movement mechanism, and a processing area 12 where the workpiece is ground. A chuck table 6 that holds the workpiece by suction is provided on the upper surface of the X-axis direction movement table 8.

The chuck table 6 comprises a porous member exposed above and a frame that houses the porous member in a recess. A suction passage is formed inside the frame that connects the porous member to a suction source. When a workpiece is placed on the porous member and the suction source is activated, negative pressure acts on the workpiece, and the workpiece is sucked and held on the chuck table 6. In other words, the upper surface of the porous member becomes the holding surface 6a.

A grinding unit 14 that grinds the workpiece is disposed above the processing area 12. A support 18 that supports the grinding unit 14 so that it can be raised and lowered via a Z-axis movement mechanism 16 is erected on the rear side of the base 4. The Z-axis movement mechanism 16 that raises and lowers the grinding unit 14 includes a pair of Z-axis guide rails 20 that extend in the Z-axis direction and are provided on the front surface of the support 18, and a Z-axis movement plate 22 that is slidably attached to each of the Z-axis guide rails 20.

A nut portion (not shown) is provided on the back side (rear side) of the Z-axis moving plate 22, and a Z-axis ball screw 24 parallel to the Z-axis guide rail 20 is screwed into this nut portion. A Z-axis pulse motor 26 is connected to one end of the Z-axis ball screw 24. A grinding unit 14 is fixed to the lower front side of the Z-axis moving plate 22. When the Z-axis ball screw 24 is rotated by the Z-axis pulse motor 26, the Z-axis moving plate 22 to which the grinding unit 14 is fixed moves in the Z-axis direction along the Z-axis guide rail 20.

The grinding unit 14 has a spindle 30 that rotates around the Z-axis direction, and a spindle housing 28 that houses the upper part of the spindle 30. A motor that rotates the spindle 30 is housed inside the spindle housing 28. A disk-shaped wheel mount 32 is fixed to the lower end of the spindle 30, and a grinding wheel 34 that rotates in accordance with the rotation of the spindle 30 is attached to the underside of the wheel mount 32. Grinding stones 36 arranged in a ring shape are fixed to the underside of the grinding wheel 34.

The workpiece is held on the chuck table 6, the chuck table 6 is moved to the processing area 12, the spindle 30 is rotated, the grinding wheel 34 is lowered, and the grinding stone 36 moving on a circular orbit is brought into contact with the workpiece, and the workpiece is ground.

The grinding device 2 is provided with a measuring device 38 according to this embodiment on the X-axis moving table 8, which measures the height of the top surface of the workpiece held by the chuck table 6 as the object to be measured and measures the thickness of the object to be measured. In other words, the measuring device 38 according to this embodiment is incorporated into the grinding device 2 for use. The chuck table 6 functions as a holding table for the measuring device 38 and holds the object to be measured.

The grinding device 2 uses the workpiece as a measurement object, measures the height or thickness of the upper surface with the measuring device 38, and grinds the workpiece with the grinding unit 14. The workpiece is then ground until it reaches a predetermined thickness.

Next, a laser processing machine will be described as another example of a processing machine in which the measuring device according to this embodiment is incorporated. FIG. 2 is a perspective view showing a laser processing machine 42. The laser processing machine 42 includes a base 44 that supports each component.

A pair of X-axis guide rails 50 parallel to the X-axis direction are provided on the front of the upper surface of the base 44, and an X-axis moving plate 52 is slidably attached to the X-axis guide rails 50. A nut portion (not shown) is provided on the underside of the X-axis moving plate 52, and an X-axis ball screw 54 parallel to the X-axis guide rails 50 is screwed into this nut portion. An X-axis pulse motor 56 is connected to one end of the X-axis ball screw 54.

A support stand 58 that supports the chuck table 46 is disposed on the X-axis moving plate 52, and the chuck table 46 is disposed on the support stand 58. The chuck table 46 is configured in the same manner as the chuck table 6 of the grinding device 2 described above, and its upper surface serves as the holding surface 46a.

The workpiece brought into the laser processing device 42 is attached to tape that has already been applied to the annular frame so as to cover the opening. In other words, the workpiece, tape, and annular frame are integrated in advance to form a frame unit. Clamps 46b are provided around the chuck table 46 to secure the annular frame that holds the workpiece via the tape.

When the X-axis ball screw 54 is rotated by the X-axis pulse motor 56, the X-axis moving plate 52 moves in the X-axis direction along the X-axis guide rail 50. The pair of X-axis guide rails 50, the X-axis moving plate 52, the X-axis ball screw 54, and the X-axis pulse motor 56 function as an X-axis moving mechanism that moves the workpiece held on the chuck table 46 in the X-axis direction.

A pair of Y-axis guide rails 60 are provided along the Y-axis direction perpendicular to the X-axis direction at the rear of the upper surface of the base 44 of the laser processing device 42. A support 62 is slidably attached to the Y-axis guide rails 60. The support 62 includes a base 62a attached to the Y-axis guide rails 60 and a wall 62b erected on the base 62a.

A nut portion (not shown) is provided on the underside of the base 62a of the support 62, and a Y-axis ball screw 64 parallel to the Y-axis guide rail 60 is screwed into this nut portion. A Y-axis pulse motor 66 is connected to one end of the Y-axis ball screw 64.

When the Y-axis ball screw 64 is rotated by the Y-axis pulse motor 66, the support 62 moves in the Y-axis direction along the Y-axis guide rails 60. The pair of Y-axis guide rails 60, the Y-axis ball screw 64, and the Y-axis pulse motor 66 function as a Y-axis movement mechanism that moves the laser processing unit 48 (described below) in the Y-axis direction.

A pair of Z-axis guide rails 68 are arranged along the Z-axis direction perpendicular to the X-axis and Y-axis directions on the rear side of the wall 62b of the support 62. A unit holder 70 is slidably attached to the Z-axis guide rails 68. A nut portion (not shown) is provided on the surface of the unit holder 70 facing the wall 62b, and a Z-axis ball screw (not shown) parallel to the Z-axis guide rails 68 is screwed into this nut portion. A Z-axis pulse motor 72 is connected to one end of the Z-axis ball screw.

When the Z-axis ball screw is rotated by the Z-axis pulse motor 72, the unit holder 70 moves in the Z-axis direction along the Z-axis guide rails 68. The pair of Z-axis guide rails 68, the Z-axis ball screw, and the Z-axis pulse motor 72 function as a lifting unit that raises and lowers the laser processing unit 48 in the Z-axis direction.

Some of the components of the laser processing unit 48 are fixed to the unit holder 70. The laser processing unit 48 has the function of irradiating a laser beam onto a workpiece held on the holding surface 46a of the chuck table 46, and laser processing the workpiece.

The laser processing unit 48 includes a medium such as Nd:YAG or Nd: _YVO4 , and includes a laser oscillator that emits a laser beam. The laser processing unit 48 can irradiate the workpiece with a laser beam having a wavelength that transmits the workpiece (a wavelength that is transparent to the workpiece).

The laser processing unit 48 includes a processing head 74 located above the chuck table 46, and an imaging unit 76 adjacent to the processing head 74. The imaging unit 76 can capture an image of the surface of the workpiece held on the chuck table 46, and is used when performing alignment so that a laser beam can be irradiated onto the workpiece along the planned division line. In addition, the laser processing unit 48 incorporates a measuring device according to this embodiment, and the measuring device shares a portion of its optical system with the laser processing unit 48.

The laser processing device 42 further includes a control unit (not shown) that controls each component of the laser processing device 42. The control unit is composed of a computer including a processing device such as a CPU (Central Processing Unit), a main storage device such as a DRAM (Dynamic Random Access Memory), and an auxiliary storage device such as a flash memory. By operating the processing device etc. according to the software stored in the auxiliary storage device, the control unit functions as a concrete means of cooperation between the software and the processing device (hardware resources).

The laser processing unit 48 focuses a laser beam at a predetermined height position inside the workpiece held by the chuck table 46. In order to position the focusing point of the laser beam at a predetermined height position, the laser processing device 42 measures the height position or thickness of the top surface of the workpiece held by the chuck table 46 with a measuring device.

A focal point is positioned inside the workpiece at a position that overlaps with the planned division line, and the laser beam is focused at the focal point while the chuck table 46 and the laser processing unit 48 are moved relatively in a direction parallel to the holding surface 46a (X-axis direction or Y-axis direction). The laser beam is then irradiated onto the workpiece along the planned division line, and the workpiece is laser-processed along the planned division line.

In this way, a measuring device is used in processing devices such as the grinding device 2 and the laser processing device 42. Next, the measuring device according to this embodiment will be described. The measuring device includes a measurement unit that measures the height or thickness of the upper surface of the object to be measured held on the holding table. The measurement unit includes an optical fiber that guides the light emitted by the light source unit, and a collector that focuses the light guided by the optical fiber on the object to be measured.

In the measurement device, the light emitted by the light source unit is focused and incident on one end of an optical fiber. The other end of the optical fiber is directed toward the top surface of the object to be measured, which is held on a holding table, and the light emitted from the other end is irradiated onto the object to be measured by a condenser. The measurement device determines the height of the top surface of the object to be measured, etc., by dispersing the reflected light with a spectroscope.

To improve the measurement accuracy of a measuring device, it is advisable to use a high-power probe light for the measurement. For example, a high-power excitation light source such as a blue or purple LD can be used as the light source, and the light emitted from the excitation light source can be irradiated onto a phosphor as excitation light. The generated fluorescence can then be combined with the excitation light to produce light of a color similar to white.

In addition, it is possible to use a multi-mode LD, which has a higher output than a single-mode LD, as the light source. More specifically, the output of a single-mode LD is about 0.5 W or less, while the output of a multi-mode LD can be increased to about 5 W or less. However, the emitter size of a single-mode LD is several μm x several μm, while the emitter size of a multi-mode LD is several μm x several tens of μm, and the emitter size of the emitted light is large, and the cross-sectional shape tends to be elliptical.

The fluorescence generated by focusing excitation light with a large emitter size and an elliptical cross-sectional shape on a phosphor is difficult to focus efficiently on one end of an optical fiber. Therefore, the measurement device according to this embodiment changes the cross-sectional shape of the excitation light emitted from the excitation light source. The measurement device according to this embodiment is described below.

Figure 3 is a side view showing a schematic diagram of the basic configuration of the measuring device 78 according to this embodiment. The configuration and arrangement of each optical component can be changed as appropriate. The measuring device 78 has a holding table 80 that holds the object 1 to be measured. When the measuring device 78 is incorporated into the grinding device 2 shown in Figure 1 and used, the chuck table 6 becomes the holding table 80 of the measuring device 78. When the measuring device 78 is incorporated into the laser processing device 42 shown in Figure 2 and used, the chuck table 46 becomes the holding table 80 of the measuring device 78.

The measuring device 78 includes a measuring unit 82 that measures the height or thickness of the upper surface of the object 1 held on the holding table 80. The measuring unit 82 includes a light source unit 84, an optical fiber 86 that guides the light emitted by the light source unit 84, and a concentrator 88 that focuses the light guided by the optical fiber 86 on the object 1.

The light source unit 84 includes an excitation light source 90, a phosphor 94 that emits fluorescence when it receives excitation light 92 emitted by the excitation light source 90, and a beam shaping unit 100 that changes the cross-sectional shape of the excitation light 92 emitted by the excitation light source 90 and focuses the excitation light 92 on the phosphor 94. The excitation light source 90 uses a multimode LD that generates short-wavelength light such as blue or purple.

The excitation light 92 emitted from the excitation light source 90 using a multimode LD tends to have an elliptical cross-sectional shape in a plane perpendicular to the direction of propagation. The beam shaping unit 100 changes the cross-sectional shape of the excitation light 92 so that it approaches a circle. A detailed configuration example, function, and action of the beam shaping unit 100 will be described later.

The phosphor 94 on which the excitation light 92 is focused is provided on one side of a support plate 96 that is capable of transmitting light in the wavelength band of the visible light region. The phosphor 94 is made of a material that receives the excitation light 92 emitted by the excitation light source 90 and can emit fluorescence in a wavelength band that is different from and longer than the wavelength of the excitation light 92. More specifically, a material that generates fluorescence of a long wavelength, such as green, yellow, or red, upon receiving short-wavelength excitation light 92, such as blue or purple, can be used.

More specifically _, materials such as _yttrium aluminum oxide: cerium ( _{Y3Al5O12 :} Ce) and yttrium gadolinium aluminum oxide: cerium ((Y,Gd) _{3Al5O12 :} Ce) can be used for the phosphor 94. However, the material of the phosphor 94 is not limited to these.

The light source unit 84 has a first focusing lens 102 that focuses the light emitted by the phosphor 94 toward the end face of the optical fiber 86. When the excitation light 92 is irradiated onto the phosphor 94, fluorescence is generated. Then, the probe light 98 containing this fluorescence passes through the support plate 96. The first focusing lens 102 has the function of focusing this probe light 98 toward the end face of the optical fiber 86. A condenser 88 is connected to the end face of the optical fiber 86 opposite to the end face.

The following describes an example in which the measurement of the thickness of the object 1 using the probe light 98 is performed by confocal thickness measurement. However, the measurement of the thickness of the object 1 using the probe light 98 may be performed by other methods. For example, the probe light 98 may be used for spectral interference thickness measurement.

The condenser 88 has a chromatic aberration lens (not shown). A chromatic aberration lens is a lens whose refractive index varies depending on the color (wavelength), and the focusing position in the forward and backward directions of the light propagation direction varies depending on the color (wavelength).

The probe light 98 that reaches the condenser 88 through the optical fiber 86 has an intensity at the wavelength of the fluorescence emitted by the phosphor 94. In other words, the probe light 98 is non-monochromatic light and has multiple wavelength components. The probe light 98 may contain some of the excitation light 92 in addition to the fluorescence. The probe light 98 emitted from the condenser 88 is then irradiated onto the object to be measured 1.

Of the multiple wavelength components contained in the probe light 98, those whose focal point of the chromatic aberration lens of the collector 88 coincides with the top surface of the object to be measured 1 are reflected by the top surface of the object to be measured 1 and reach the chromatic aberration lens of the collector 88 again, and are focused on the end surface of the optical fiber 86. On the other hand, those whose focal point of the chromatic aberration lens of the collector 88 does not coincide with the top surface of the object to be measured 1 are not focused on the end surface of the optical fiber 86, even if they are reflected by the top surface of the object to be measured 1 and reach the chromatic aberration lens of the collector 88 again.

The optical fiber 86 has a branch, and the measurement device 78 includes a spectrometer 106 to which the reflected light 104 focused on the end face of the optical fiber 86 reaches through the optical fiber 86. The spectrometer 106 splits the reflected light 104 that reaches the spectrometer 106 and measures the intensity of the reflected light 104 at each wavelength. In other words, the spectrometer 106 identifies the color (wavelength) of the reflected light 104.

The chromatic aberration lens of the condenser 88 has a unique focal point position for each color (wavelength). Therefore, the distance from the condenser 88 to the top surface of the object to be measured 1 can be determined from the color (wavelength) of the reflected light 104 identified by the spectroscope 106. In other words, the measurement device 78 can derive the height of the top surface of the object to be measured 1, and can determine the thickness of the object to be measured 1 from the difference in height between the top surface of the holding table 80 and the top surface of the object to be measured 1.

As can be understood from the measurement principle of the measuring device 78 described above, in order for the measuring device 78 to determine the height position, etc. of the top surface of the object to be measured 1 with high accuracy, it is desirable for the probe light 98 to be light such as white light with a wide wavelength band. However, the probe light 98 does not need to be white light in strict accordance with the definition, and the probe light 98 does not need to contain light of all wavelengths with an equal intensity distribution or a specific intensity distribution.

In other words, the probe light 98 must be non-monochromatic light that is not monochromatic light consisting of at least a specific wavelength component, and is preferably light having multiple wavelength components regardless of intensity distribution. Here, light having multiple wavelength components regardless of intensity distribution can also be called light having a wavelength band. The phosphor 94 emits light having a wavelength band when it receives the excitation light 92 emitted by the excitation light source 90. The probe light 98 is light that includes light having this wavelength band, and is light that is different from the excitation light 92.

Next, the beam shaping unit 100 will be described. The beam shaping unit 100 has a function of deforming the cross-sectional shape of the excitation light 92 having a large emitter size emitted by the excitation light source 90 and concentrating the light on the phosphor 94. Here, the excitation light 92 emitted by the excitation light source 90 has an elliptical shape whose size differs in a first direction perpendicular to the traveling direction and a second direction perpendicular to the traveling direction and the first direction. Here, the traveling direction of the excitation light 92 is _Z1 , the longitudinal direction of this elliptical shape is the first direction _X1 , and the transverse direction is the second direction _Y1 .

The beam shaping unit 100 changes the cross-sectional shape of the excitation light 92 at different magnifications in a first direction _X1 perpendicular to the traveling direction _Z1 of the excitation light 92 emitted by the excitation light source 90 and in a second direction _Y1 perpendicular to the traveling direction _Z1 and the first direction _X1 , and focuses the excitation light 92 on a phosphor 94.

A first configuration example of the beam shaping unit 100 will be described. Figures 4(A) and 4(B) are side views that diagrammatically show the light source unit 84 including the beam shaping unit 100a according to the first configuration example. Figure 4(A) is a side view of the light source unit 84 seen from a second direction _Y1 perpendicular to the traveling direction _Z1 of the excitation light 92, and Figure 4(B) is a side view of the light source unit 84 seen from a first direction _X1 perpendicular to the traveling direction _Z1 and the second direction _Y1 .

4A and 4B, the beam shaping unit 100a according to the first configuration example includes a collimator lens 108, an anamorphic prism pair 110, and a second condenser lens 114. The cross-sectional shape of the excitation light 92 emitted by the excitation light source 90 is an elliptical shape having a longitudinal direction in the first direction _X1 and a transverse direction in the second direction _Y1 .

The collimating lens 108 converts the excitation light 92 emitted by the excitation light source 90 into parallel light. When the excitation light source 90 is a multimode LD, the emitted light tends to diffuse. Therefore, the collimating lens 108 is used to convert the excitation light 92 into parallel light. In other words, the excitation light 92 converted into parallel light travels to the anamorphic prism pair 110.

The anamorphic prism pair 110 includes two prisms 112a and 112b, and mainly expands the cross-sectional shape of the excitation light 92 in the short direction (second direction _Y1 ) to approximate the size in the long direction (first direction _X1 ). The two prisms 112a and 112b are arranged so as to achieve this.

For example, the incident and exit surfaces of the two prisms 112a and 112b are parallel to the first direction _X1 . Furthermore, two or more of the four incident and exit surfaces of the two prisms 112a and 112b are inclined with respect to the second direction _Y1 and the traveling direction _Z1 of the excitation light 92.

In the anamorphic prism pair 110, the magnification ratio in the short direction of the cross-sectional shape of the excitation light 92 can be changed by adjusting the angle of the two prisms 112a, 112b. The arrangement of the two prisms 112a, 112b is determined so that the cross-sectional shape of the excitation light 92 emerging from the anamorphic prism pair 110 becomes closer to a circle compared to when the excitation light 92 traveled to the anamorphic prism pair 110.

The second focusing lens 114 focuses the excitation light 92, the cross-sectional shape of which has been expanded in the short direction by the anamorphic prism pair 110, onto the phosphor 94. Here, the cross-sectional shape of the excitation light 92 traveling to the second focusing lens 114 is closer to a circle as a result of the cross-sectional shape being expanded in the short direction.

Next, a second configuration example of the beam shaping unit 100 will be described. Figures 5(A) and 5(B) are side views that diagrammatically show a light source unit 84 including a beam shaping unit 100b according to the second configuration example. Figure 5(A) is a side view of the light source unit 84 seen from a second direction _Y1 perpendicular to the traveling direction _Z1 of the excitation light 92, and Figure 5(B) is a side view of the light source unit 84 seen from a first direction _X1 perpendicular to the traveling direction _Z1 and the second direction _Y1 .

5(A) and 5(B), the beam shaping unit 100b according to the second configuration example includes a collimator lens 108, one or more cylindrical lenses 116 and 118, and a second condenser lens 114. The cross-sectional shape of the excitation light 92 emitted by the excitation light source 90 is an elliptical shape having a longitudinal direction in the first direction _X1 and a transverse direction in the second direction _Y1 . The collimator lens 108 and the second condenser lens 114 are similar to those of the beam shaping unit 100a according to the first configuration example, and therefore will not be described.

In FIG. 5(A) and FIG. 5(B), the beam shaping unit 100b includes two cylindrical lenses 116, 118, but the number of cylindrical lenses 116, 118 is not limited to this. A single cylindrical lens, or multiple cylindrical lenses working together, expands the short side of the cross-sectional shape of the excitation light 92 that has been collimated by the collimator lens 108. Below, an example will be described in which the beam shaping unit 100b includes two cylindrical lenses 116, 118.

The incident surface and the exit surface of the two cylindrical lenses 116 and 118 are parallel to the first direction _X1 . The incident surface of the first cylindrical lens 116 for the excitation light 92 and the exit surface of the second cylindrical lens 118 for the excitation light 92 are curved along the second direction _Y1 and are arc-shaped with a center on the near side of the traveling direction _Z1 . This mainly expands the short side direction (second direction _Y1 ) of the cross-sectional shape of the excitation light 92, and brings it closer to the size in the long side direction (first direction _X1 ).

In the beam shaping unit 100b, for example, the magnification ratio in the short direction of the cross-sectional shape of the excitation light 92 can be changed by using another cylindrical lens with a different curvature of the curved surface. The arrangement of each cylindrical lens 116, 118 is then determined so that the cross-sectional shape of the excitation light 92 emerging from the cylindrical lens 118 becomes closer to a circle compared to when the excitation light 92 advances to the cylindrical lens 116.

Further, a third configuration example of the beam shaping unit 100 will be described. Figures 6(A) and 6(B) are side views that diagrammatically show a light source unit 84 including a beam shaping unit 100c according to the third configuration example. Figure 6(A) is a side view of the light source unit 84 seen from a second direction _Y1 perpendicular to the traveling direction _Z1 of the excitation light 92, and Figure 6(B) is a side view of the light source unit 84 seen from a first direction _X1 perpendicular to the traveling direction _Z1 and the second direction _Y1 .

6A and 6B, the beam shaping unit 100c according to the third configuration example includes one or more toric lenses 120. The cross-sectional shape of the excitation light 92 emitted by the excitation light source 90 is an elliptical shape having a longitudinal direction in the first direction _X1 and a transverse direction in the second direction _Y1 .

In Fig. 6(A) and Fig. 6(B), the beam shaping unit 100c includes one toric lens 120, but the number of toric lenses 120 is not limited to this. A single toric lens, or multiple toric lenses working together, expands the short side of the cross-sectional shape of the excitation light 92. Below, an example will be described in which the beam shaping unit 100c includes one toric lens 120.

The entrance surface 120a of the toric lens 120 on which the excitation light 92 is incident is a toric surface. That is, the entrance surface 120a is a curved surface having a different radius of curvature along the first direction _X1 and along the second direction _Y1 . As a result, when the excitation light 92 is incident on the toric lens 120, the excitation light 92 is refracted at different refraction angles in the first direction _X1 and the second direction _Y1 on the entrance surface 120a. More specifically, the cross-sectional shape of the excitation light 92 is mainly expanded in the short direction (second direction _Y1 ) to approach the size in the long direction (first direction _X1 ).

Then, the excitation light 92 that travels through the toric lens 120 and exits from the exit surface 120b is focused on the phosphor 94. For example, the exit surface 120b has a radius of curvature along the first direction _X1 that coincides with a radius of curvature along the second direction _Y1 . However, the exit surface 120b is not limited to this, and the two radii of curvature may be different. In any case, the cross-sectional shape of the excitation light 92 when it reaches the phosphor 94 is made closer to a circle than the cross-sectional shape when it is emitted from the excitation light source 90.

As described above, in the measurement device 78 according to this embodiment, the beam shaping unit 100 of the light source unit 84 deforms the cross-sectional shape of the excitation light 92 emitted by the excitation light source 90 to focus the light on the phosphor 94. In particular, when the cross-sectional shape of the excitation light 92 emitted from the excitation light source 90 is elliptical, the beam shaping unit 100 deforms the excitation light 92 so that the cross-sectional shape becomes closer to a circle.

In this case, the cross-sectional shape of the fluorescence generated by the phosphor 94 also reflects the cross-sectional shape of the excitation light 92 and is made closer to a circle, so that the probe light 98 is easily focused onto one end of the optical fiber 86 by the first focusing lens 102 (see FIG. 3, etc.). In the measuring device 78 according to this embodiment, the probe light 98 focused onto the optical fiber 86 with high efficiency is irradiated onto the object to be measured 1 through the optical fiber 86, so that the height position of the top surface of the object to be measured 1 and the thickness of the object to be measured 1 can be detected with high accuracy.

The present invention is not limited to the above embodiment, and can be modified in various ways. For example, in the above embodiment, the phosphor 94 of the light source unit 84 is supported by a support plate 96 that transmits the probe light 98, but one aspect of the present invention is not limited to this.

Figure 7 is a side view showing a schematic configuration of a measurement device 78a according to a modified example. In Figure 7, a part of the optical fiber 86 of the measurement device 78a, the holding table 80, the condenser 88, and the spectrometer 106 are omitted. Also, Figure 7 shows a case where the measurement device 78a includes a light source unit 84a including two cylindrical lenses 116, 118, but the light source unit 84a is not limited to this.

The light source unit 84a includes an excitation light source 90, a collimator lens 108, two cylindrical lenses 116 and 118, a second condenser lens 114a, a first condenser lens 102a, and a phosphor 94. Here, the phosphor 94 is supported by a support plate 96a that reflects light.

In the measurement device 78a, the excitation light 92 generated by operating the excitation light source 90 is converted into parallel light by the collimator lens 108, and the cross-sectional shape is changed by the two cylindrical lenses 116 and 118. The light source unit 84a further includes a dichroic mirror 122. The excitation light 92, whose cross-sectional shape has been changed, is reflected by the dichroic mirror 122 toward the second focusing lens 114a and the phosphor 94.

The excitation light 92 is then focused on the phosphor 94 by the second focusing lens 114a. When the excitation light 92 is focused on the phosphor 94, fluorescence is generated. Then, the probe light 98 containing this fluorescence is finally irradiated onto the object to be measured 1. The probe light 98 is collimated by the second focusing lens 114a and proceeds to the dichroic mirror 122. The probe light 98 passes through the dichroic mirror 122 and is focused on the end face of the optical fiber 86 by the first focusing lens 102a.

In this way, even in the measurement device 78a according to the modified example, the cross-sectional shape of the excitation light 92 is deformed and focused on the phosphor 94. Therefore, the fluorescence generated in the phosphor 94 is made closer to a circle, and can be efficiently focused on the end face of the optical fiber 86 by the first focusing lens 102a. Then, the probe light 98 is irradiated onto the object 1 through the optical fiber 86, so that the height position of the top surface of the object 1 can be detected with high accuracy.

In addition, in the above embodiment, the measurement device 78 is described as being incorporated into a processing device such as the grinding device 2 or the laser processing device 42 for use, but this aspect of the present invention is not limited to this. In other words, the measurement device 78 according to one aspect of the present invention may be used independently of a processing device or the like.

In addition, the structures, methods, etc. relating to the above embodiments can be modified as appropriate without departing from the scope of the purpose of the present invention.

REFERENCE SIGNS LIST 1 Object to be measured 2 Grinding device 4, 44 Base 4a Opening 6, 46 Chuck table 6a, 46a Holding surface 8 X-axis moving table 10 Loading/unloading area 12 Processing area 14 Grinding unit 16 Z-axis direction moving mechanism 18 Support section 20 Z-axis guide rail 22 Z-axis moving plate 24 Z-axis ball screw 26 Z-axis pulse motor 28 Spindle housing 30 Spindle 32 Wheel mount 34 Grinding wheel 36 Grinding stone 38 Measuring device 42 Laser processing device 46b Clamp 48 Laser processing unit 50, 60, 68 Guide rail 52 Moving plate 54, 64 Ball screw 56, 66, 72 Pulse motor 58 Support table 62 Support 62a Base 62b Wall 70 Unit holder 74 Processing head 76 Imaging unit 78, 78a Measuring device 80 Holding table 82 Measuring unit 84, 84a Light source unit 86 Optical fiber 88 Condenser 90 Excitation light source 92 Excitation light 94 Fluorescent material 96, 96a Support plate 98 Probe light 100, 100a, 100b, 100c
102, 102a, 114, 114a Condenser lens 104 Reflected light 106 Spectrometer 108 Collimator lens 110 Anamorphic prism pair 112a, 112b Prism 116, 118 Cylindrical lens 120 Toric lens 120a Incident surface 120b Exit surface 122 Dichroic mirror

Claims (4)

A holding table for holding the object to be measured;
a measurement unit that measures the height or thickness of an upper surface of the object to be measured held on the holding table,
the measurement unit includes a light source unit, an optical fiber that guides the light emitted by the light source unit, and a collector that focuses the light guided by the optical fiber on the object to be measured;
The light source unit comprises:
An excitation light source;
a phosphor that emits fluorescence having a wavelength different from that of the excitation light when it receives the excitation light emitted by the excitation light source;
a beam shaping unit that changes a cross-sectional shape of the excitation light emitted by the excitation light source and focuses the excitation light on the phosphor;
a first focusing lens that focuses the probe light, including the fluorescence emitted by the fluorescent material, toward an end face of the optical fiber;
The beam shaping unit changes the cross-sectional shape of the excitation light emitted by the excitation light source at different magnifications in a first direction perpendicular to the propagation direction of the excitation light and a second direction perpendicular to the propagation direction and the first direction. The beam shaping unit comprises:
a collimator lens that converts the excitation light having an elliptical cross-sectional shape emitted from the excitation light source into parallel light;
an anamorphic prism pair that expands the cross-sectional shape of the excitation light that has been converted into parallel light by the collimator lens in a short-side direction;
a second condenser lens that condenses the excitation light, the cross-sectional shape of which has been expanded in the short-side direction by the anamorphic prism pair, onto the phosphor;
The measurement device according to claim 1 , further comprising: The beam shaping unit comprises:
a collimator lens that converts the excitation light having an elliptical cross-sectional shape emitted from the excitation light source into parallel light;
one or more cylindrical lenses that expand the cross-sectional shape of the excitation light that has been collimated by the collimator lens in a short-side direction;
a second condenser lens that condenses the excitation light, the cross-sectional shape of which has been expanded in the short-side direction by the cylindrical lens, onto the phosphor;
The measurement device according to claim 1 , further comprising: The measurement device according to claim 1, characterized in that the beam shaping unit includes one or more toric lenses that expand the short side direction of the excitation light emitted by the excitation light source and having an elliptical cross-sectional shape, and then focus the excitation light on the phosphor.

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