TW201816358A - Thickness measuring device capable of efficiently measuring the thickness of a plate-like object in a short period of time - Google Patents

Abstract

The object of the present invention is to provide a thickness measuring device capable of efficiently measuring the thickness of a plate-like object in a short period of time. The thickness measuring device according to the present invention is at least composed of a broadband light source configured to emit light with a wavelength range penetrative to a plate-like object; a light splitter configured to split the light emitted from the broadband light source in the wavelength range; a distribution device configured to change the distribution direction of the light of each wavelength split by the light splitter over time; a condensing lens configured to condense the light of each wavelength distributed by the distribution device; an optical transmission device opposite to the condensing lens and configured to transmitting the light of each wavelength condensed by the condensing lens by arranging the end surface of one end of a plurality of optical fibers in a row; a measuring terminal configured to arrange the end surface of the other end of the optical fibers in a row opposite to the plate-like object, and having a plurality of objective lenses corresponding to each end surface and arranged between the plate-like object; a light branching device configured to arrange a light reflected from the upper surface of the plate-like object, and a return light penetrating through the plate-like object, reflected from the lower surface, and reversely traveling in each optical fiber, on a light transmission path of the optical transmission device in order to branch light from each optical fiber; a spectral interference waveform generation device configured to obtain each wavelength of the return light branched by the light branching device and corresponding to each optical fiber during the distribution device performs distribution to each optical fiber, and detects the intensity of light of each wavelength, in order to generate a spectral interference waveform corresponding to each optical fiber; and a calculation device configured to calculate the thickness of the plate-like object corresponding to each optical fiber by performing waveform analysis on the spectral interference waveform corresponding to each optical fiber and generated by the spectral interference waveform generation device.

Description

Thickness measuring device

FIELD OF THE INVENTION The present invention relates to a thickness measuring device for measuring the thickness of a plate.

BACKGROUND OF THE INVENTION A wafer on which a plurality of devices such as ICs and LSIs are formed on a front surface divided by a predetermined division line. After the back surface is ground to a predetermined thickness, it is divided by a cutting device and a laser processing device Each device is used in electrical devices such as mobile phones and personal computers.

The conventional grinding device has been proposed as follows: at least, a work chuck for holding a wafer in a plate shape, and a grinding method for grinding the back surface of the wafer that is held on the work chuck for grinding. Grinding wheels for grinding stones are rotatably installed grinding equipment, and inspection equipment that detects the thickness of the wafer in a non-contact manner by using a spectroscopic interference waveform, thereby grinding the wafer to a desired thickness (For example, refer to Patent Document 1). Prior Art Literature Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2011-143488

SUMMARY OF THE INVENTION Problems to be Solved by the Invention However, in the technique described in the above Patent Document 1, a structure is formed in which a terminal for detecting the thickness of a wafer held in a holding device is swung horizontally to detect the entire wafer. In the case where it is necessary to appropriately measure the horizontal swing and the movement of the wafer, it takes a considerable amount of time to detect the thickness of the entire wafer using such equipment, and there is a problem of poor productivity.

This invention is made in view of the said fact, The main technical subject is to provide the thickness measuring device which can measure the thickness of a plate-shaped object efficiently in a short time. Means to solve the problem

In order to solve the above-mentioned main technical problems, a thickness measuring device can be provided according to the present invention, which is a thickness measuring device for measuring the thickness of a plate, and at least consists of the following: a broadband light source that emits light through the plate. Light in a transparent wavelength range; a beam splitter that splits the light emitted by the broadband light source in the wavelength range; a distribution device that changes the distribution direction of the light of each wavelength split by the beam splitter over time; The optical lens condenses light of each wavelength allocated by the distribution device; the optical transmission device is opposite to the condenser lens, and an end surface of one end of a plurality of optical fibers is arranged in a row to transmit the light through the condenser Light of each wavelength condensed by an optical lens; a measurement terminal, the end faces of the other ends of the plurality of optical fibers constituting the optical transmission device are opposed to the plate to form a row, and are provided corresponding to each end face and aligned with the plate. A plurality of object-receiving lenses arranged between the objects; the light branching device interferes with the light reflected on the upper surface of the plate and the light reflected on the lower surface through the plate and interferes with each light The retrograde return light of the optical fiber is arranged on the light transmission path of the optical transmission device to diverge from each optical fiber; the spectral interference waveform generation device will divide the return optical light corresponding to each optical fiber that is diverged by the optical divergence device. The wavelength is obtained from the time for which the optical fiber is distributed by the distribution device, and the light intensity of each wavelength is detected to generate a spectral interference waveform corresponding to each optical fiber; and the thickness calculation device generates the spectral interference waveform from the spectral interference waveform generating device. Waveform analysis is performed corresponding to the spectral interference waveform of each optical fiber to calculate the thickness of the plate-shaped object corresponding to each optical fiber.

In addition, it is preferable that the measuring terminal and the holding device are configured to be relatively movable in the X-axis direction, and the measuring terminal and the holding device are configured to be relatively movable in the X-axis direction. The column of objective lenses arranged on the end face is positioned in the Y-axis direction orthogonal to the X-axis direction, and is provided with a recording device in the X-axis direction with the measurement terminal and the holding device opposite to each other. The X-coordinate and Y-coordinate specified by the moving and positioning lens positioned in the Y-axis direction store the thickness of the plate-shaped object calculated by the thickness calculation device. Invention effect

The thickness measuring device of the present invention is at least composed of a broadband light source, a beam splitter, a distribution device, a condenser lens, a light transmission device, a measurement terminal, a light divergence device, a spectral interference waveform generation device, and a thickness calculation device, wherein the broadband light source It emits light in a wavelength range that is transmissive to the plate. The beam splitter splits the light emitted by the broadband light source in the wavelength range. The distribution device divides the wavelength of the light split by the beam splitter. The light changes its distribution direction based on the elapsed time. The condenser lens focuses light of each wavelength allocated by the distribution device. The light transmission device faces the condenser lens and focuses one end of a plurality of optical fibers. The end faces are arranged in a row to transmit light of each wavelength condensed by the condenser lens, and the measurement terminal is formed by aligning the end faces of the other ends of the plurality of optical fibers constituting the optical transmission device with the plate. And is provided with a plurality of object-receiving lenses arranged between the plate and the plate corresponding to each end surface, and the light divergence device is light reflected on the upper surface of the plate and penetrates The light reflected on the lower surface interferes with the return light retrograde on each optical fiber, and is arranged on the light transmission path of the optical transmission device to diverge from each optical fiber. The optical interference waveform generating device will The wavelength of the return light corresponding to each fiber branched by the optical branching device is obtained from the time allocated to each fiber by the distribution device, and the light intensity of each wavelength is detected to generate a spectral interference waveform corresponding to each fiber. The thickness calculation device analyzes the waveform of the spectral interference waveform corresponding to each optical fiber generated by the spectral interference waveform generating device to calculate the thickness of the plate-shaped object corresponding to each optical fiber. Therefore, the thickness calculation device can be arranged in a plurality of columns. The plurality of objective lenses and the plurality of optical fibers obtain the plurality of thickness information at the same time, and it becomes possible to perform the necessary measurement in a short time.

Forms for Implementing the Invention Hereinafter, referring to the drawings, preferred embodiments of a thickness measuring device constructed in accordance with the present invention will be described in detail. Shown in FIG. 1 is an overall perspective view of a grinding device 1 provided with a thickness measuring device of the present invention, and a wafer 10 as a plate-shaped object whose thickness is measured by the thickness measuring device of the present invention.

The grinding device 1 shown in FIG. 1 has a device housing, which is generally designated by reference numeral 2. The device housing 2 has a main portion 21 having a substantially rectangular parallelepiped shape, and an upright wall 22 provided at a rear end portion (upper right end in FIG. 1) of the main portion 21 and extending upward. A grinding unit 3 as a grinding device is mounted on the front surface of the upright wall 22 so as to be movable in the vertical direction.

The grinding unit 3 includes a moving base 31 and a spindle unit 4 mounted on the moving base 31. The moving base 31 is configured to be slidably engaged with a pair of guide rails arranged on one of the upright walls 22. In this manner, the main unit 4 as a grinding device is mounted on the front surface of the moving base 31 slidably mounted on one of the guide rails provided on the guide rail 22 through the support portion protruding forward.

The spindle unit 4 includes a spindle housing 41, a rotary spindle 42 rotatably disposed in the spindle housing 41, and a servo motor 43 as a drive source for rotationally driving the rotary spindle 42. The rotating main shaft 42 rotatably supported by the main shaft housing 41 is provided with one end portion (lower end portion in FIG. 1) protruding from the lower end of the main shaft housing 41, and a wheel seat 44 is provided at the lower end portion. The grinding wheel 5 is mounted on the lower surface of the wheel base 44. A grinding stone 51 composed of a plurality of grinding wheel segments is arranged on the lower surface of the grinding wheel 5.

The illustrated grinding device 1 includes a grinding unit feeding mechanism 6 that moves the grinding unit 3 along the pair of guide rails in a vertical direction (a direction perpendicular to a holding surface of a work clamp table described later). The grinding unit feed mechanism 6 includes a male screw 61 that is disposed on the front side of the upright wall 22 and extends substantially vertically, and a pulse motor 62 as a driving source for rotationally driving the male screw 61. A bearing member and the like of a male screw 61 (not shown) provided on the rear surface of the moving base 31 are configured. When the pulse motor 62 rotates forward, it will cause the moving base 31 (that is, the grinding unit 3) to fall (even if it is advanced), and when the pulse motor 62 reverses, it will cause the moving base 31 (that is, the grinding unit) 3) Up (even if it goes back).

The main part 21 of the housing 2 is provided with a work clamp mechanism 7 as a holding device that holds a plate-like object (wafer 10) as a workpiece. The work clamp mechanism 7 includes a work clamp 71, a cover member 72 covering the periphery of the work clamp 71, and telescopic cover devices 73 and 74 disposed before and after the cover member 72. The work chuck 71 is configured to suck and hold the wafer 10 on the upper surface (holding surface) by using a suction device (not shown). In addition, the work clamp table 71 is rotatably constituted by a rotation driving device (not shown), and it can be placed in the workpiece placement area shown in FIG. 1 by a work clamp table moving device (not shown). 70a and the grinding area 70b which faces the grinding wheel 5 (in the X-axis direction shown by arrow X) are moved.

In addition, the above-mentioned servo motor 43, pulse motor 62, and work clamp moving device (not shown) are controlled by the control device 20 described below. In addition, in the illustrated embodiment, a wafer 10 is formed with a notch indicating a crystal orientation on the outer peripheral portion, and a protective tape 12 as a protective member is affixed on the front surface thereof, and the protective tape 12 is held on the side. On the upper surface (holding surface) of the work clamp table 71.

The grinding device 1 shown in the figure is provided with a thickness measuring device 8 that measures the thickness of the wafer 10 held on the work table 71. This thickness measuring device 8 is built in a measuring case 80, and the measuring case 80 is provided on the upper surface of the main body 21 of the rectangular parallelepiped shape constituting the device case 2 as shown in the figure, and is arranged on the work clamp 71 When moving from the workpiece placement area 70a to the side in the path between the grinding areas 70b, and when the work table 71 is moved between the workpiece placement area 70a and the grinding area 70b, The whole is arranged so as to measure the entire wafer 10 held on the work table 71. The thickness measuring device 8 will be further described with reference to FIG. 2.

The thickness measuring device 8 in the illustrated embodiment is provided with a light emitting source 81 as a broadband light source and a beam splitter 82. The light emitting source 81 as a broadband light source emits light that is transparent to the wafer 10 as a workpiece. Containing light in a predetermined wavelength range (for example, a wavelength of 1000 nm to 1100 nm), the beam splitter 82 reflects the light 8a from the light emitting source 81 and splits the light in a predetermined wavelength range. The light emitting source 81 can be selected from LED, SLD (Superluminescent diode), ASE (Amplified Spontaneous Emission), SC (Supercontinuum), halogen light source, and the like. The beam splitter 82 is constituted by a diffraction grating, and by the action of the diffraction grating, the light 8a composed of a wavelength of 1000 nm to 1100 nm is split to form a light 8b having a predetermined widening. The light 8b can be split into light having a shorter wavelength (1000 nm) on the lower side and a longer wavelength (1100 nm) on the upper side in the figure.

The light 8b split and reflected by the spectroscope 82 is reflected by a distribution device having a function of changing the distribution direction of light of each wavelength over time. The distribution device is constituted by a polygon mirror 83 formed of, for example, a regular octahedron formed on each side by a reflecting surface (mirror), and the polygon mirror 83 is configured to be clockwise in the figure. Rotate at a predetermined rotation speed. The light 8 b incident on the reflecting surface of the polygon mirror 83 is reflected with a predetermined width and becomes light 8 c. The light 8 b is incident on a condenser lens 84 which is arranged to face the reflecting surface of the polygon mirror 83. Then, the light 8c condensed by the condenser lens 84 is incident on, for example, 18 optical fibers (1) to (18) constituting an optical transmission device that are sequentially arranged at a predetermined interval and hold the ends with the holding members 85. Of the end face. Furthermore, the diameter of the optical fiber relative to the diameter of the wafer can be reduced, and the number of optical fibers (for example, 100) can be increased to improve the resolution of the measurement described below. In this embodiment, when the polygon mirror 83 is located at a predetermined angular position as shown in FIG. 2, all the light reflected on one of the reflection surfaces of the polygon mirror 83 is incident on the condenser lens 84. The setting positions and angles of the beam splitter 82, the polygon mirror 83, the condenser lens 84, and the holding member 85 can be set to the optical fibers (1) to (18) held by the holding member 85 at each wavelength of the separated light Incident. The function of the polygon mirror 83 will be described in detail later.

This thickness measuring device 8 is provided with a light branching device 86 which is the first one for passing light incident on the optical fibers (1) to (18) through the light formed by the optical fibers (1) to (18). The path 8d is guided to the side of the second path 8e facing the wafer 10 held on the stage 71, and the reflected light reflected on the wafer 10 and retrograde in the second path 8e is diverged and guided to the third path 8f. The first to third paths 8d to 8f are composed of optical fibers (1) to (18), and the optical branching device 86 may be, for example, a polarization maintaining fiber coupler, a polarization maintaining fiber circulator, or a single-mode fiber coupler. Either choose appropriately.

The light guided to the second path 8 e through the light branching device 86 is guided to the measurement terminal 87 facing the wafer 10 held on the work clamp 71. The measurement terminal 87 is formed in a shape elongated in the Y-axis direction, and is formed in a size covering the diameter of the wafer 10 as a measurement target. In addition, the measurement terminal 87 is provided with a plurality of object-receiving lenses 88, and the object-receiving lenses 88 will hold the ends of the other ends of the plurality of optical fibers (1) to (18) constituting the optical transmission device, and will be guided to The light at the end is guided from the end surface to the wafer 10 held on the work clamp 71, and the objective lens 88 is arranged in a direction (Y orthogonal to the direction (X direction) in which the work clamp 71 moves) Axis direction).

The third path 8f is light that will go backwards on the second path 8e, and is formed by the optical fibers (1) to (18) that are transmitted by being diverged in the optical branching device 86, and is located at a position facing the end surface. A line image sensor 90 is provided as a device for detecting the intensity of light. The light intensity measured by the linear image sensor 90 is transmitted to the control device 20 constituting the thickness measurement device 8 and stored in the control device 20 together with the detected time (t).

The control device 20 is composed of a computer, and includes a central processing unit (CPU) that performs calculation processing according to a control program, a unique memory (ROM) that stores a control program, and the like, temporarily stores detected values, Read and write random access memory (RAM), input interface, and output interface (such as the details shown). The control device 20 in the present embodiment is a device that controls each driving part of the grinding device 1 and constitutes the thickness measuring device 8. As described above, the control device 20 can be configured to have the following functions: the linear image sensor 90 The detection value is stored in a random access memory (RAM), and the thickness of the wafer 10 is calculated by driving the polygon mirror 83 and the light emitting device 81. The grinding device 1 and the thickness measuring device 8 of the present embodiment are configured substantially as described above, and their effects will be described below.

The measurement of the thickness of the wafer 10 by the thickness measuring device 8 of the present invention is performed by, for example, grinding the wafer 10 that has been placed on the work clamp table 71 with the grinding device 1 and moving it from the grinding area. 70b moves to the to-be-processed object mounting area 70a so that it may pass directly under the measuring terminal 87. At this time, the control device 20 obtains the spectral interference waveform shown in FIG. 5 from the detection signal indicating the intensity of light of the linear image sensor 90, and performs waveform analysis based on the spectral interference waveform, and can be obtained from the on-board The thickness (T) of the wafer 10 is calculated from the difference between the return light reflected by the upper surface of the wafer 10 placed on the work table 71 and retrograde light and the length of the optical path traveled by the return light reflected on the lower surface and retrograde. The specific calculation method will be described later.

The procedure for calculating the thickness of the wafer 10 in this embodiment will be described with reference to FIGS. 2 to 4. As described above, the polygon mirror 83 is configured by forming a regular octagonal side with a reflecting surface (mirror), and by using a driving device such as a pulse motor (not shown), the rotation position and time (t) The association is established and stored in a random access memory (RAM) of the control device 20, and is rotated in a clockwise direction in the figure.

When the light is irradiated from the light emitting source 81 and the polygon mirror 83 is rotated in the direction of the arrow in the figure, a part of the light 8 b having the broadening by the beam splitter 82 is reflected on the reflection surface 83 a of the polygon mirror 83 and formed. The reflected light 8c starts to enter the condenser lens 84. When the reflecting surface 83a of the polygon mirror 83 is in the state shown in FIG. 3 (a), a range of a wavelength of 1000 nm constituting a part of the light 8c condensed by the condenser lens 84 is made incident to hold one end portion Optical fiber (1) of member 85 (time t1). Light having a wavelength of 1000 nm incident on the optical fiber (1) travels through the first and second paths 8d and 8e constituting the optical transmission device described above, and reaches the measurement terminal 87. The light having a wavelength of 1000 nm that has reached the objective lens 88 of the measurement terminal 87 is reflected on the upper and lower surfaces of the wafer 10 moving in the X-axis direction directly below the measurement terminal 87, and is formed in the second path. The return light of 8e goes retrograde, and reaches the position of the optical fiber (1) in the line-type image sensor 90 that is diverged in the optical divergence device 86. As a result, it is possible to detect the light intensity of the reflected light formed by the return light reflected on the upper and lower surfaces of the wafer 10 during the time t1 when the light is incident on the optical fiber (1). This light intensity is associated with the position of the X coordinate in the X-axis direction and the Y coordinate in the Y-axis direction at time t1 and the irradiated wafer 10 and is stored in any random access memory (RAM) of the control device 20 Storage area.

In addition, FIG. 4 shows whether the time (t) is indicated on the horizontal axis and the arrangement position of the ends of the optical fibers (1) to (18) is indicated on the vertical axis, and whether the time (t) elapses. In contrast, when the arbitrary wavelength range of light having a wavelength of 1000 nm to 1100 nm reflected by the polygon mirror 83 is incident on an arbitrary optical fiber (1) to (18), it can be understood that, for example, at time t1, the wavelength of 1000 nm Light starts to enter the fiber (1). By storing the relationship between the time (t) shown in FIG. 4 and whether or not an arbitrary wavelength range is incident on an arbitrary optical fiber (1) to (18) in the control device 20, the linear image sensing can be performed. The light intensity detected by the detector 90 is related to whether the light intensity detected when the light enters an arbitrary optical fiber (1) to (18) in an arbitrary wavelength range.

Returning to FIG. 3 to continue the description, it can be known that, due to the time t1, the light split by the spectroscope 82 is incident on the optical fiber (1), and then the polygon mirror 83 continues to rotate so that the reflection surface 83a of the polygon mirror 83 is relative to the light 8b. The direction of the beam is changed, so that the wavelength range of 1000 nm to 1100 nm of the separated light 8b moves downward in the figure, and is sequentially irradiated to the holding device 85 that holds the ends of the optical fibers (1) to (18). Next, at time t2, as shown in FIG. 3 (b), with respect to the optical fibers (1) to (18), all the wavelength ranges of the light 8c split by the spectroscope 82 are made incident (also Refer to FIG. 4 together. In this state, a wavelength range of 1100 nm is made incident on the optical fiber (1), and a wavelength range of 1000 nm is made incident on the optical fiber (18). In other words, with respect to the optical fiber (1), from time t1 to time t2, all of the wavelengths in the wavelength range of 1000 nm to 1100 nm that are split by the spectroscope 82 are incident.

As can be seen from the state shown in FIG. 3 (b), when the polygon mirror 83 is further rotated and reaches time t3, as shown in FIG. 3 (c), it will be in the wavelength range of the light split by the spectroscope 82 In the state where the wavelength range of 1100 nm is incident on the optical fiber (18), and in the time t1 to t3, the light of the wavelength of 1000 nm to 1100 nm separated by the beam splitter 82 can be irradiated to all of the optical fibers (1) to (18). . In addition, as can be understood from FIGS. 3 and 4, when time further elapses to become t4, the reflected surface 83 b adjacent to the reflective surface 83 a of the polygon mirror 83 can be irradiated with the light 8 b to be split and the wavelength can be 1000 nm. The irradiation of the optical fiber (1) in the range is started again, and the state is the same as that in FIG. 3 (a), and the same operation is repeated thereafter.

As described above, the control device 20 stores the relationship between the time (t) and the light intensity to be detected by the linear image sensor 90 and each of the time (t) as shown in FIG. 4. The optical fibers (1) to (18) use the wavelengths assigned by the polygon mirror 83, and can refer to both to generate a spectral interference waveform as shown in FIG. 5 for each optical fiber (1) to (18). Figure 5 shows, for example, the spectral interference waveform (F (1)) detected by the optical fiber (1), and the horizontal axis represents the wavelength (λ) of the reflected light incident on the optical fiber, and the vertical axis represents The intensity of the light detected by the detector 90. Hereinafter, an example of calculating the thickness and height of the wafer 10 will be described based on the waveform analysis performed by the control device 20 based on the above-mentioned spectral interference waveform.

The length of the optical path from the ends of the optical fibers (1) to (18) positioned in the second path 8e of the measurement terminal 87 to the lower surface of the wafer 10 held on the work clamp 71 is (L1), and The length of the optical path from the ends of the optical fibers (1) to (18) in the second path 8e to the upper surface of the wafer 10 held on the work clamp table 71 is (L2), and the optical path length (L1) and The difference between the optical path lengths (L2) is the first optical path length difference (d1 = L1-L2).

Next, the control device 20 performs waveform analysis based on the spectral interference waveforms (F (1) to F (18)) generated for each of the optical fibers (1) to (18) as shown in FIG. 5 described above. This waveform analysis can be performed based on, for example, the Fourier transform theory or the wavelet transform theory, but in the embodiment described below, the Fourier transform shown in the following mathematical formula 1, mathematical formula 2, and mathematical formula 3 is used An example of the formula is used for illustration.

[Mathematical formula 1]

[Mathematical formula 2]

[Mathematical formula 3]

In the above mathematical formula, λ is a wavelength, d is the first optical path length difference (d1 = L1-L2), and W (λ _n ) is a window function. The above mathematical formula 1 is to find the optical path length difference (d) with the closest wave period (high correlation) in the comparison between the theoretical waveform of cos and the above-mentioned spectral interference waveform (I (λ _n )), that is, to obtain The difference in optical path length (d) between the spectral interference waveform and the theoretical waveform function is high. In addition, the above-mentioned mathematical formula 2 is to find the first optical path length difference (d1 = L1) in which the wave periods are most similar (high correlation) in the comparison between the theoretical waveform of sin and the spectral interference waveform (I (λ _n )). -L2), that is, the correlation coefficient between the spectral interference waveform and the theoretical waveform function is calculated as the first optical path length difference (d1 = L1-L2). In addition, the above-mentioned mathematical formula 3 is an average value of the results of the mathematical formula 1 and the results of the mathematical formula 2.

The control device 20 can perform calculations according to the above-mentioned mathematical formula 1, mathematical formula 2, and mathematical formula 3, and can obtain interference as shown in FIG. 6 based on the spectral interference caused by the difference in the optical path lengths of the return light included in the reflected light. The waveform of the signal strength shown. In FIG. 6, the horizontal axis represents the optical path length difference (d), and the vertical axis represents the signal intensity. In the example shown in FIG. 6, the signal intensity is displayed higher at a position where the optical path length difference (d) is 150 μm. That is, the signal strength at the position where the optical path length difference (d) is 150 μm is the optical path length difference (d1 = L1-L2), and the thickness (T) of the wafer 10 is displayed. Then, the coordinates (X coordinate, Y coordinate) of the measurement position specified at the position of the X-axis direction of the measurement terminal 87 and the work clamp 71 and the position of the objective lens 88 positioned at the Y-axis direction are set. The thickness (T) of the wafer 10 in) is stored. This measurement is performed on the whole while moving the wafer 10 in the X-axis direction.

As described above, according to the thickness measurement device 8 in the illustrated embodiment, the thickness of the wafer 10 can be easily obtained, and the spectral interference waveform obtained based on the difference in optical path length caused by the reflected reflected light. Since the thickness (T) of the wafer 10 during the processing of the wafer 10 is detected, the wafer 11 can be accurately measured without being affected by changes in the thickness of the protective tape 12 attached to the front surface of the wafer 10 Of thickness (T).

The thickness measuring device 8 is configured as described above, and a procedure for grinding the wafer 10 to a predetermined thickness using the grinding device 1 provided with the thickness measuring device 8 will be described below.

The wafer 10 to which the protective tape 12 is attached on the front side is a work chuck 71 by placing the protective tape 12 side on the workpiece placement area 70a which has been positioned in the grinding device 1 shown in FIG. 1. The suction device (not shown in the figure) is actuated and held on the work clamp 71. Therefore, the wafer 11 attracted and held on the work table 71 becomes the back surface 10b on the upper side.

Next, the control device 20 activates a moving device (not shown) of the work clamp table 71 that has held the wafer 10, moves the work clamp table 71 to position to the grinding area 70b, and grinds a plurality of grinding wheels 5. The outer periphery of the grindstone 51 is positioned to pass through the rotation center of the work clamp 71.

In this manner, the grinding wheel 5 and the wafer 10 held on the work clamp table 71 are set in a predetermined positional relationship, and the control device 20 drives a rotation drive device (not shown) to rotate the work clamp table at a rotation speed of, for example, 300 rpm. 71, and drives the above-mentioned servo motor 43 to rotate the grinding wheel 5 at a rotation speed of, for example, 6000 rpm. Then, the wafer 10 is supplied with grinding water, and the pulse motor 62 of the grinding unit feeding mechanism 6 is driven in a forward direction to lower the grinding wheel 5 (grinding feed), and a plurality of grindings are performed at a predetermined pressure. The grinding stone 51 is pressed against the surface to be ground which is the upper surface (back surface 10b) of the wafer 10. As a result, the ground surface of the wafer 10 can be ground (grinding step).

After the grinding step is completed, the work clamp stage 71 holding the ground wafer 10 is moved to the workpiece placement area 70a side in front of the X-axis direction to position the wafer 10 at Directly below the measurement terminal 87 of the thickness measurement device 8, the thickness measurement device 8 is operated as described above to obtain a spectral interference waveform corresponding to each part of the entire wafer 10 and analyze the waveform to measure the thickness of the wafer 10. The table shown in FIG. 7 shows an example of measuring the thickness (T) of the wafer 10 when the measurement terminal 87 passes through the center of the wafer 10 and at a predetermined position along the Y-axis direction. By performing such measurement at every predetermined interval in the X-axis direction of the wafer 10, and storing the thickness (T) of the front surface of the wafer 10, and confirming the thickness of the entire wafer 10 after grinding, the grinding can be judged Good quality of the cutting steps, and re-grinding if necessary.

Furthermore, in this embodiment, although the polygon mirror 83 is used as a distribution device that changes the distribution direction of light of each wavelength separated by a beam splitter over time, the present invention is not limited to this, and may be adopted It is possible to control the direction of the reflecting surface together with the elapsed time, such as a galvo scanner. In addition, in this embodiment, although the linear image sensor 90 is used as a light receiving element for detecting the intensity of reflected light, the linear image sensor 90 is not limited to this, and may be corresponding to each optical fiber (1). ~ (18) and a photodetector.

Moreover, in the above-mentioned embodiment, although the whole wafer was measured by the thickness measuring device 8 after the grinding process was described, it is not limited to this. For example, the thickness may be The installation position of the measurement housing 80 of the measurement device 8 is set near the grinding area 70b shown in FIG. 1, and the installation position of the measurement housing 80 is movably set. With such a structure, when the wafer 10 held by the work chuck mechanism 7 of the grinding apparatus 1 is subjected to the action of the grinding wheel 5 to be ground, it can face the exposed wafer 10 The measuring terminal 87 is submerged in the grinding water supplied during grinding and positioned to measure the thickness of the wafer 10 during grinding, and the thickness of the wafer 10 during grinding can be fed back to the control device 20 to grind to the desired thickness. In addition, the thickness measuring device 8 constructed according to the present invention does not need to be arranged in the grinding device 1 as in the present embodiment, and can also be configured as a single device independent of the grinding device 1 or provided in parallel with the grinding device 1. The grinding device 1 is different from other processing devices.

1‧‧‧Grinding device

10‧‧‧ wafer

10b‧‧‧ back

12‧‧‧ protective tape

20‧‧‧Control equipment

2‧‧‧device housing

21‧‧‧Main Department

22‧‧‧ upright wall

3‧‧‧Grinding unit

31‧‧‧ Mobile Abutment

4‧‧‧ Spindle Unit

41‧‧‧ Spindle housing

42‧‧‧rotating spindle

43‧‧‧Servo motor

44‧‧‧ wheel seat

5‧‧‧Grinding wheel

51‧‧‧grinding stone

6‧‧‧Grinding unit feed mechanism

61‧‧‧Male Screw

62‧‧‧Pulse motor

7‧‧‧Work clamp mechanism

70a‧‧‧processed object placement area

70b‧‧‧grinding area

71‧‧‧Working clamp

72‧‧‧ cover member

73, 74‧‧‧ Telescopic hood equipment

8a, 8b, 8c‧‧‧‧light

8‧‧‧ thickness measuring device

8d‧‧‧First Path

8e‧‧‧2nd path

8f‧‧‧3rd path

80‧‧‧ measuring housing

81‧‧‧light source

82‧‧‧ Beamsplitter

83‧‧‧ Polygonal mirror (dispensing equipment)

83a, 83b‧‧‧ Reflective surface

84‧‧‧ condenser lens

85‧‧‧ holding member

86‧‧‧Optical divergence equipment

87‧‧‧Measurement terminal

88‧‧‧Object lens

90‧‧‧ Linear Image Sensor

F (1) ~ F (18) ‧‧‧Spectral interference waveform

X, Y‧‧‧ directions

FIG. 1 is a perspective view of a grinding device to which a thickness measuring device constructed according to the present invention can be applied. FIG. 2 is an explanatory diagram for explaining a configuration of a thickness measuring device constructed according to the present invention. 3 (a) to (c) are explanatory diagrams for explaining the operation of the thickness measuring device shown in FIG. 2. FIG. 4 is an explanatory diagram for explaining an operation of a polygon mirror constituting the thickness measuring device shown in FIG. 3. FIG. 5 is a diagram showing an example of a spectral interference waveform generated by the thickness measuring device shown in FIG. 2. FIG. 6 is a diagram showing an example of a difference in optical path length and a signal intensity obtained by analyzing the spectral interference waveform by the thickness measuring device shown in FIG. 2. FIG. 7 is a diagram showing an example of the thickness of a wafer obtained for each optical fiber by the thickness measuring device of the present invention.

Claims (2)

A thickness measuring device capable of measuring the thickness of a plate. The thickness measuring device is composed of at least the following: a broadband light source that emits light in a wavelength range that is transparent to the plate; a beam splitter that converts the broadband light source The emitted light is split in a wavelength range; the distribution device will change the distribution direction of the light of each wavelength separated by the beam splitter over time; the condenser lens will use the wavelength of each wavelength allocated by the distribution device Concentrating light; an optical transmission device facing the condensing lens and arranging end faces of one end of a plurality of optical fibers in a row to transmit light of each wavelength condensed by the condensing lens; The end faces of the other ends of the plurality of optical fibers of the optical transmission device are aligned in a row facing the plate, and are provided with a plurality of object-receiving lenses corresponding to the respective end faces and disposed between the plate and the plate; Equipment that interferes with the light reflected on the upper surface of the plate and the light reflected on the lower surface that penetrates the plate and returns to the retrograde light of each optical fiber, and is arranged in the light transmission path of the light transmission device The splitting is performed from each optical fiber; the spectroscopic interference waveform generation device obtains the wavelength of the return light corresponding to each optical fiber that is diverged by the optical divergence device from the time allocated to each optical fiber by the distribution device, And detecting the light intensity of each wavelength to generate a spectral interference waveform corresponding to each optical fiber; and a thickness calculation device that performs waveform analysis on the spectral interference waveform corresponding to each optical fiber generated by the spectral interference waveform generating device to calculate a waveform corresponding to each optical fiber; The thickness of the plate of the optical fiber. For example, the thickness measuring device of claim 1 includes a holding device for holding the plate, and the measurement terminal and the holding device are configured to be relatively movable in the X-axis direction. The column of objective lenses arranged at the end faces of each optical fiber is positioned in the Y-axis direction orthogonal to the X-axis direction, and is provided with a recording device on the X-axis with the measurement terminal and the holding device facing each other. The thickness of the plate-shaped object calculated by the thickness calculation device is stored in the X coordinate and the Y coordinate specified by the movement in the direction and the objective lens positioned in the Y axis direction.