JP2018021760A - Thickness measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thickness measurement device with which it is possible to measure the thickness of a tabular object efficiently in a short time.SOLUTION: The thickness measurement device comprises: a broadband light source 81 for emitting light of a wavelength region having permeability to a tabular object; a spectroscope 82 for spectrally separating the light emitted by the broadband light source; distribution means 83 for changing the distribution direction of light of each wavelength spectrally separated by the spectroscope with the passage of time; light transmission means for transmitting the light of each wavelength condensed by a condenser lens; spectral interference waveform generation means for finding return light retrogressing each optical fiber due to interference between the light reflected on the top face of the tabular object and the light reflected at the underside after transmitting the tabular object, using time which the wavelength of the return light is distributed to each optical fiber by the distribution means, and detecting the optical intensity of each wavelength, then generating a spectral interference waveform in correspondence to each optical fiber; and means for analyzing the spectral interference waveform and calculating the thickness of the tabular object that corresponds to each optical fiber.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a thickness measuring device that measures the thickness of a plate-like object.

  A wafer in which a plurality of devices such as IC, LSI, etc. are defined by dividing lines and formed on the front surface is ground into a predetermined thickness by grinding the back surface, and then divided into individual devices by a dicing apparatus and a laser processing apparatus. Used in electrical equipment such as mobile phones and personal computers.

  Grinding means comprising a chuck wheel for holding a plate-like wafer and a grinding wheel in which a grinding wheel for grinding a back surface of the wafer held on the chuck table is arranged in an annular manner relative to a conventional grinding apparatus. It is proposed to grind the wafer to a desired thickness by including at least a detecting means for detecting the thickness of the wafer in a non-contact manner using a spectral interference waveform (see, for example, Patent Document 1).

JP 2011-143488 A

  However, in the technique described in the above-mentioned Patent Document 1, the entire surface of the wafer is detected by swinging a terminal for detecting the thickness of the wafer held by the holding means in the horizontal direction. In addition, it is necessary to perform measurement while appropriately repeating the movement of the wafer, and it takes a considerable amount of time to detect the thickness of the entire surface of the wafer using such means, and there is a problem that productivity is poor. .

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

  In order to solve the main technical problem, according to the present invention, a thickness measuring device for measuring the thickness of a plate-like object, a broadband light source that emits light in a wavelength region having transparency to the plate-like object, A spectroscope that splits the light emitted from the broadband light source into a wavelength region, a distribution unit that changes the distribution direction of light of each wavelength dispersed by the spectrograph over time, and each wavelength distributed by the distribution unit A condensing lens that condenses the light of the light, and faces the condensing lens. One end face of a plurality of optical fibers is arranged in a row and transmits light of each wavelength collected by the condensing lens. A plurality of light transmitting means and a plurality of optical fibers constituting the light transmitting means are arranged between the other end faces of the light receiving means so as to face the plate-like object and form a row corresponding to each end face. A measuring terminal equipped with an objective lens and a plate-like object The light reflected by the light and the light transmitted through the plate and reflected by the lower surface interfere with each other and return light that travels backward through each optical fiber is arranged on the light transmission path of the light transmission means and branches from each optical fiber. Corresponding to each optical fiber by detecting the light intensity of each wavelength from the optical branching means and the wavelength of the return light corresponding to each optical fiber branched by the optical branching means from the time distributed to each optical fiber by the distributing means The spectral interference waveform generating means for generating the spectral interference waveform and the spectral interference waveform corresponding to each optical fiber generated by the spectral interference waveform generating means are subjected to waveform analysis, and the thickness of the plate corresponding to each optical fiber is calculated. And a thickness measuring device comprising at least a thickness calculating means.

  In addition, a holding means for holding the plate-like object is provided, the measurement terminal and the holding means are configured to be relatively movable in the X-axis direction, and correspond to the end face of each optical fiber constituting the measurement terminal. The arranged rows of objective lenses are positioned in the Y-axis direction orthogonal to the X-axis direction, the relative movement of the measurement terminal and the holding means in the X-axis direction, and the objective positioned in the Y-axis direction. It is preferable to provide recording means for storing the thickness of the plate-like object calculated by the thickness calculating means at the X coordinate and Y coordinate specified by the lens.

  The thickness measuring device of the present invention includes a broadband light source that emits light in a wavelength range that is transparent to a plate-like object, a spectroscope that splits the light emitted from the broadband light source into the wavelength range, and spectrally separated by the spectroscope. A distribution unit that changes a distribution direction of the light of each wavelength with time, a condensing lens that condenses the light of each wavelength distributed by the distribution unit, and a plurality of optical fibers facing the condensing lens One end face of the optical fiber is arranged in a row and transmits light of each wavelength collected by the condenser lens, and the other end face of the plurality of optical fibers constituting the light transfer means is the plate. A measuring terminal having a plurality of objective lenses arranged between the plate-like objects corresponding to each end face, and a light and a plate reflected by the upper surface of the plate-like object Each optical fiber interferes with the light transmitted through the object and reflected from the lower surface. The light branching means is arranged on the light transmission path of the light transmission means and branches from each optical fiber, and the wavelength of the return light corresponding to each optical fiber branched by the light branching means. Spectral interference waveform generation means for generating a spectral interference waveform corresponding to each optical fiber by detecting the light intensity of each wavelength obtained from the time distributed to each optical fiber by the distribution means, and generated by the spectral interference waveform generation means And at least a thickness calculating means for calculating the thickness of the plate-like material corresponding to each optical fiber, and arranged in a plurality of rows. A plurality of thickness information can be obtained simultaneously by a plurality of objective lenses and a plurality of optical fibers, and a necessary measurement can be performed in a short time.

1 is a perspective view of a grinding device to which a thickness measuring device configured according to the present invention is applied. It is explanatory drawing for demonstrating the structure of the thickness measuring apparatus comprised based on this invention. It is explanatory drawing for demonstrating the effect | action of the thickness measuring apparatus shown in FIG. It is explanatory drawing for demonstrating the effect | action of the polygon mirror which comprises the thickness measuring apparatus shown in FIG. It is a figure which shows an example of the spectral interference waveform produced | generated by the thickness measuring apparatus shown in FIG. It is a figure which shows an example of the optical path length difference and signal strength which are obtained by carrying out waveform analysis of the spectral interference waveform with the thickness measuring apparatus shown in FIG. It is a figure which shows an example of the thickness of the wafer acquired for every optical fiber with the thickness measuring apparatus of this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of a thickness measuring device configured according to the invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an overall perspective view of a grinding apparatus 1 equipped with a thickness measuring device of the present invention and a wafer 10 as a plate-like object whose thickness is measured by the thickness measuring device of the present invention.

  The grinding apparatus 1 shown in FIG. 1 is provided with an apparatus housing generally indicated by numeral 2. The device housing 2 has a substantially rectangular parallelepiped main portion 21 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 grinding means 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 movable base 31 is configured to slidably engage with a pair of guide rails disposed on the upright wall 22. Thus, the spindle unit 4 as a grinding means is attached to the front surface of the movable base 31 slidably mounted on the pair of guide rails provided on the upright wall 22 via a support portion protruding forward. It is done.

  The spindle unit 4 includes a spindle housing 41, a rotary spindle 42 rotatably disposed on the spindle housing 41, and a servo motor 43 as a drive source for rotationally driving the rotary spindle 42. . The rotary spindle 42 rotatably supported by the spindle housing 41 has one end portion (lower end portion in FIG. 1) protruding from the lower end of the spindle housing 41, and a wheel mount 44 is provided at the lower end portion. Yes. Then, the grinding wheel 5 is attached to the lower surface of the wheel mount 44. A grinding wheel 51 composed of a plurality of segments is disposed on the lower surface of the grinding wheel 5.

  The illustrated grinding apparatus 1 includes a grinding unit feed mechanism 6 that moves the grinding unit 3 in the vertical direction (direction perpendicular to the holding surface of the chuck table described later) along the pair of guide rails. The grinding unit feed mechanism 6 includes a male screw rod 61 disposed on the front side of the upright wall 22 and extending substantially vertically, and a pulse motor 62 as a drive source for rotationally driving the male screw rod 61. It is comprised from the bearing member etc. of the male screw rod 61 (not shown) with which the back surface of 31 was equipped. When the pulse motor 62 is rotated forward, the moving base 31, that is, the polishing unit 3 is lowered or advanced, and when the pulse motor 62 is reversed, the moving base 31, that is, the grinding unit 3 is raised or moved backward.

  A chuck table mechanism 7 as a holding means for holding a plate-like object (wafer 10) as a workpiece is disposed on the main portion 21 of the housing 2. The chuck table mechanism 7 includes a chuck table 71, a cover member 72 that covers the periphery of the chuck table 71, and bellows means 73 and 74 disposed before and after the cover member 72. The chuck table 71 is configured to suck and hold the wafer 10 on its upper surface (holding surface) by operating suction means (not shown). Further, the chuck table 71 is configured to be rotatable by a rotation driving means (not shown), and a workpiece placement area 70a and a grinding area 70b facing the grinding wheel 5 shown in FIG. (In the X-axis direction indicated by arrow X).

  The servo motor 43, the pulse motor 62, the chuck table moving means (not shown), and the like described above are controlled by the control means 20 described later. Further, in the illustrated embodiment, the wafer 10 has a notch representing a crystal orientation on the outer peripheral portion, and a protective tape 12 as a protective member is attached to the surface of the wafer 10, and the protective tape 12 side is the chuck table 71 side. It is held on the upper surface (holding surface).

  The illustrated grinding apparatus 1 includes a thickness measuring device 8 that measures the thickness of the wafer 10 held on the chuck table 71. The thickness measuring device 8 is built in a measuring housing 80. The measuring housing 80 has a chuck table 71 mounted on a workpiece on the upper surface of a rectangular parallelepiped main portion 21 constituting the device housing 2 as shown in the figure. The chuck table 71 is disposed on the side of the path that is moved from the placement area 70a to the grinding area 70b, and is held on the chuck table 71 when the chuck table 71 moves between the workpiece placement area 70a and the grinding area 70b. The entire wafer 10 is arranged so that it can be measured from above. The thickness measuring device 8 will be further described with reference to FIG.

  A thickness measuring device 8 in the illustrated embodiment includes a light emitting source 81 as a broadband light source that emits light including a predetermined wavelength region (for example, a wavelength of 1000 nm to 1100 nm) that is transparent to a wafer 10 as a workpiece. A spectroscope 82 is provided for spectroscopically separating the light 8a from the light source 81 into a predetermined wavelength region while reflecting the light 8a. The light emitting source 81 can be selected from an LED, an SLD (Superluminous Diode), an ASE (Amplified Spontaneous Emission), an SC (Supercontinuum), a halogen light source, and the like. The spectroscope 82 is constituted by a diffraction grating, and by the action of the diffraction grating, the light 8a having a wavelength of 1000 nm to 1100 nm is split to form light 8b having a predetermined spread. The light 8b is split so as to be composed of light having a short wavelength (1000 nm) on the lower side and a long wavelength (1100 nm) on the upper side.

  The light 8b split and reflected by the spectroscope 82 is reflected by a distribution means having a function of changing the distribution direction of light of each wavelength over time. The distributing means is constituted by a polygon mirror 83 having a regular octahedron, for example, each side comprising a reflecting surface (mirror), and the polygon mirror 83 is configured to rotate clockwise at a predetermined rotational speed in the drawing. Has been. The light 8b incident on the reflection surface of the polygon mirror 83 is reflected with a predetermined spread and becomes light 8c, which is incident on the condenser lens 84 disposed opposite to the reflection surface of the polygon mirror 83. The light 8c collected by the condensing lens 84 is arranged in order at predetermined intervals, and has, for example, 18 optical fibers (1) to (18) constituting a light transmission means whose end is held by the holding member 85. Incident on the end face of Note that the measurement resolution described later can be increased by reducing the diameter of the optical fiber relative to the diameter of the wafer and increasing the number of optical fibers (for example, 100). In the present embodiment, when the polygon mirror 83 is at a predetermined angular position as shown in FIG. 2, all the light reflected by one reflecting surface of the polygon mirror 83 is incident on the condenser lens 84. Installation positions of the spectroscope 82, the polygon mirror 83, the condensing lens 84, and the holding member 85 so as to be incident on the optical fibers (1) to (18) held by the holding member 85 for each wavelength separated. , Angle, etc. are set. The operation of the polygon mirror 83 will be described in detail later.

  The thickness measuring device 8 held the light incident on the optical fibers (1) to (18) on the chuck table 71 through the first path 8d of the light formed by the optical fibers (1) to (18). A light branching means 86 is provided for guiding the second path 8e toward the wafer 10 to the side of the second path 8e and branching the reflected light reflected by the wafer 10 and going back through the second path 8e to the third path 8f. Yes. The first to third paths 8d to 8f are configured by optical fibers (1) to (18), and the optical branching means 86 is, for example, a polarization maintaining fiber coupler, a polarization maintaining fiber circulator, a single A mode fiber coupler or the like is selected as appropriate.

  The light guided to the second path 8 e via the light branching means 86 is guided to the measurement terminal 87 facing the wafer 10 held on the chuck table 71. The measurement terminal 87 has an elongated shape in the Y-axis direction, and is formed with a dimension that covers the diameter of the wafer 10 to be measured. The measurement terminal 87 holds the other end of the plurality of optical fibers (1) to (18) constituting the light transmission means, and holds the light guided to the end on the chuck table 71 from the end surface. A plurality of objective lenses 88 guided on the wafer 10 are provided, and the objective lenses 88 form a line in a direction (Y axis direction) orthogonal to a direction (X axis direction) in which the chuck table 71 moves. It is arranged.

  The third path 8f is formed by the optical fibers (1) to (18) in which the light traveling backward through the second path 8e is branched and transmitted by the light branching means 86, and is located at a position facing the end face. A line image sensor 90 is provided as means for detecting the intensity of light. The light intensity measured by the line image sensor 90 is sent to the control device 20 constituting the thickness measuring device 8, and is stored in the control device 20 together with the detected time (t).

  The control means 20 is constituted by a computer, and a central processing unit (CPU) that performs arithmetic processing in accordance with a control program, a read-only memory (ROM) that stores a control program and the like, and temporarily detects detected values and arithmetic results. A random access memory (RAM) that can be read and written, an input interface, and an output interface (details are not shown). The control means 20 in this embodiment controls each drive part of the grinding device 1 and constitutes the thickness measuring device 8. As described above, the control means 20 stores the detection value of the line image sensor 90 in a random access memory ( RAM) and driving the polygon mirror 83 and the light emitting means 81 so as to have a function of calculating the thickness of the wafer 10. The grinding device 1 and the thickness measuring device 8 of the present embodiment are configured as described above, and their operation will be described below.

  Measurement of the thickness of the wafer 10 by the thickness measuring device 8 of the present invention is performed, for example, after the wafer 10 placed on the chuck table 71 is ground by the grinding device 1 and then transferred from the grinding area 70b to the workpiece placement area 70a. By moving it, it passes under the measuring terminal 87. At that time, the control means 20 obtains a spectral interference waveform as shown in FIG. 5 from the detection signal indicating the light intensity by the line image sensor 90, executes waveform analysis based on the spectral interference waveform, It is possible to calculate the thickness (T) of the wafer 10 from the difference in the optical path lengths of the return light reflected back from the upper surface of the wafer 10 placed on the back and the return light reflected back from the lower surface. A specific calculation method will be described later.

  A procedure for calculating the thickness of the wafer 10 in the present embodiment will be described with reference to FIGS. As described above, each side of the polygon mirror 83 is formed of a reflecting surface (mirror) with a regular octagon, and its rotational position is associated with time (t) by a driving means such as a pulse motor (not shown). While being stored in the random access memory (RAM) of the means 20, it is rotated in the clockwise direction in the figure.

  When light is emitted from the light source 81 and the polygon mirror 83 is rotated in the direction of the arrow in the figure, a part of the light 8b that is spread and spread by the spectroscope 82 is reflected by the reflecting surface 83a of the polygon mirror 83. The reflected light 8c is formed and enters the condenser lens 84. When the reflecting surface 83a of the polygon mirror 83 is in the state shown in FIG. 3A, the 1000 nm wavelength region constituting a part of the light 8c condensed by the condenser lens 84 is formed on the holding member 85. The light enters the optical fiber (1) having one end held (time t1). The 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 light transmission means 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 by the upper and lower surfaces of the wafer 10 that is moved in the X-axis direction immediately below the measurement terminal 87, and returns in the reverse direction along the second path 8e. Light is formed, branched by the light branching means 86, and reaches a position assigned to the optical fiber (1) in the line image sensor 90. As a result, the light intensity of the reflected light composed of the return light reflected from the upper surface and the lower surface of the wafer 10 at the time t1 when the light is incident on the optical fiber (1) is detected. This light intensity is related to the time t1 and the position of the X coordinate in the X axis direction and the Y coordinate in the Y axis direction of the irradiated wafer 10 in an arbitrary storage area of the random access memory (RAM) of the control means 20. Remembered.

  In FIG. 4, the horizontal axis indicates time (t), and the vertical axis indicates the arrangement positions of the end portions of the optical fibers (1) to (18), which are reflected by the polygon mirror 83 as time (t) elapses. It indicates which wavelength region of light having a wavelength of 1000 nm to 1100 nm is incident on which optical fiber (1) to (18). For example, at time t1, light having a wavelength of 1000 nm is applied to the optical fiber (1). Will begin to enter. The time (t) shown in FIG. 4 and the relationship indicating which wavelength region is incident on which optical fiber (1) to (18) are stored in the control means 20, so that a line image is obtained. The light intensity detected by the sensor 90 can be correlated with which wavelength region is detected when entering which optical fiber (1) to (18).

  Returning to FIG. 3, the description is continued. After the light split by the spectroscope 82 enters the optical fiber (1) at time t1, the polygon mirror 83 continues to rotate, so that the reflecting surface 83a of the polygon mirror 83 with respect to the light 8b. , And the holding unit 85 that sequentially holds the ends of the optical fibers (1) to (18) is irradiated while the region of the wavelength of 1000 nm to 1100 nm of the dispersed light 8b moves downward in the figure. At time t2, as shown in FIG. 3B, all the wavelength regions of the light 8c dispersed by the spectroscope 82 are incident on the optical fibers (1) to (18). (See also FIG. 4). In this state, a 1100 nm wavelength region is incident on the optical fiber (1), and a 1000 nm wavelength region is incident on the optical fiber (18). In other words, from the time t1 to the time t2, all of the wavelength region of 1000 nm to 1100 nm spectrally separated by the spectroscope 82 is incident on the optical fiber (1).

  When the polygon mirror 83 further rotates and reaches time t3 from the state shown in FIG. 3B, the wavelength region of 1100 nm in the wavelength region of the light dispersed by the spectroscope 82 as shown in FIG. The region enters the optical fiber (18), and light having a wavelength of 1000 nm to 1100 nm dispersed by the spectroscope 82 is applied to all the optical fibers (1) to (18) over time t1 to t3. As will be understood from FIGS. 3 and 4, when time elapses and t4 is reached, the light 8b that has been split is applied to the reflection surface 83b adjacent to the reflection surface 83a of the polygon mirror 83, resulting in a wavelength of 1000 nm. The region of (1) begins to be irradiated again to the optical fiber (1), the same state as in FIG. 3 (a) is obtained, and thereafter the same operation is repeated.

As described above, the control means 20 includes the light intensity detected by the line image sensor 90 in association with the time (t), and the optical fibers (1) to (1) at the time (t) as shown in FIG. 18), the wavelength distributed by the polygon mirror 83 is stored, and a spectral interference waveform as shown in FIG. 5 is generated for each of the optical fibers (1) to (18) by referring to both. Can do. FIG. 5 shows, for example, the spectral interference waveform (F (1)) detected for the optical fiber (1). The horizontal axis indicates the reflected light wavelength (λ) incident on the optical fiber, and the vertical axis indicates the line sensor 90. Shows the light intensity.
Hereinafter, an example in which the thickness and height of the wafer 10 are calculated based on the waveform analysis performed by the control unit 20 based on the above-described spectral interference waveform will be described.

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

  Next, the control means 20 analyzes the waveform 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. Execute. This waveform analysis can be executed based on, for example, Fourier transformation theory or wavelet transformation theory. In the embodiment described below, examples using the Fourier transformation formulas shown in the following formulas 1, 2, and 3 are used. explain.

  In the above formula, λ is a wavelength, d is the first optical path length difference (d1 = L1−L2), and W (λn) is a window function. Equation (1) is the closest wave period (high correlation) in comparison between the theoretical waveform of cos and the spectral interference waveform (I (λn)), that is, the phase between the spectral interference waveform and the theoretical waveform function. An optical path length difference (d) having a high relation number is obtained. Also, the above formula 2 is the closest wave period (highly correlated) in comparison between the theoretical waveform of sin and the spectral interference waveform (I (λn)), that is, the spectral interference waveform and the theoretical waveform function The first optical path length difference (d1 = L1-L2) is obtained. Then, the above Equation 3 obtains the average value of the result of Equation 1 and the result of Equation 2.

  The control means 20 performs the calculation based on the above-described Equation 1, Equation 2, and Equation 3, thereby performing the signal intensity shown in FIG. 6 based on the spectral interference caused by each optical path length difference of the return light included in the reflected light. Waveform can be obtained. 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 high when the optical path length difference (d) is 150 μm. That is, the signal intensity at the position where the optical path length difference (d) is 150 μm is the optical path length difference (d1 = L1−L2), and represents the thickness (T) of the wafer 10. Then, the coordinates (X coordinate, Y coordinate) of the measurement position specified by the relative position of the measurement terminal 87 and the chuck table 71 in the X axis direction and the position of the objective lens 88 positioned in the Y axis direction. The thickness (T) of the wafer 10 is stored. Such measurement is performed on the entire surface while moving the wafer 10 in the X-axis direction.

  As described above, according to the thickness measuring apparatus 8 in the illustrated embodiment, the thickness of the wafer 10 can be easily obtained, and the wafer is based on the spectral interference waveform obtained due to the optical path length difference of the reflected light to be reflected. Since the thickness (T) of the wafer 10 at the time of processing 10 is detected, the thickness (T) of the wafer 11 is accurately measured without being affected by the change in the thickness of the protective tape 12 attached to the surface of the wafer 10. can do.

  The thickness measuring device 8 is configured as described above. Hereinafter, 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.

  The wafer 10 with the protective tape 12 attached to the surface is placed on the chuck table 71 positioned in the workpiece placement area 70a in the grinding apparatus 1 shown in FIG. By operating the means, the chuck table 71 is sucked and held. Therefore, the back surface 10b of the wafer 11 sucked and held on the chuck table 71 is on the upper side.

  Next, the control means 20 operates a moving means (not shown) of the chuck table 71 that holds the wafer 10 to move the chuck table 71 to be positioned in the grinding area 70 b, and the outer peripheral edges of the plurality of grinding wheels 51 of the grinding wheel 5. Is positioned so as to pass through the center of rotation of the chuck table 71.

  In this way, the wafer 10 held on the grinding wheel 5 and the chuck table 71 is set in a predetermined positional relationship, and the control means 20 drives a rotation driving means (not shown) to rotate the chuck table 71 at a rotational speed of, for example, 300 rpm. At the same time, the above-described servo motor 43 is driven to rotate the grinding wheel 5 at a rotational speed of, for example, 6000 rpm. Then, while supplying the grinding water to the wafer 10, the pulse motor 62 of the grinding unit feed mechanism 6 is driven to rotate in the forward direction to lower the grinding wheel 5 (grind feed) so that a plurality of grinding wheels 51 are placed on the upper surface of the wafer 10 ( The surface to be ground which is the back surface 10b) is pressed with a predetermined pressure. As a result, the surface to be ground which is the wafer 10 is ground (grinding step).

  When the grinding process is completed, the chuck 10 holding the ground wafer 10 is moved to the workpiece placement area 70a located forward in the X-axis direction, so that the wafer 10 is moved to the thickness measuring device 8. The thickness measuring device 8 is operated as described above to obtain a spectral interference waveform corresponding to each part of the entire surface of the wafer 10 and analyze the waveform to measure the thickness of the wafer 10. The table shown in FIG. 7 shows an example in which the thickness (T) of the wafer 10 is measured at a predetermined position along the Y-axis direction where the measurement terminal 87 passes through the center of the wafer 10. Such measurement is performed at predetermined intervals in the X-axis direction of the wafer 10, the thickness (T) of the surface of the wafer 10 is stored, and the thickness of the entire surface of the wafer 10 after grinding is confirmed, so that the quality of the grinding process is good. And regrinding can be performed as necessary.

  In this embodiment, the polygon mirror 83 is used as a distribution unit that changes the distribution direction of light of each wavelength separated by the spectroscope with time. However, the present invention is not limited to this, and the light is reflected with time. For example, a galvano scanner that can control the direction of the surface can be employed. Furthermore, in this embodiment, the line image sensor 90 is used as the light receiving element for detecting the intensity of the reflected light. However, the present invention is not limited to this, and it is made to correspond to each of the optical fibers (1) to (18). The photo detector to arrange | position may be sufficient.

  In the above-described embodiment, the measurement by the thickness measuring device 8 has been described as being performed on the entire surface of the wafer after the grinding process. However, the present invention is not limited to this, and for example, the thickness measuring device. The installation position of the eight measurement housings 80 can be set in the vicinity of the grinding area 70b shown in FIG. With such a configuration, when the wafer 10 held by the chuck table mechanism 7 of the grinding apparatus 1 is ground by the action of the grinding wheel 5, the measurement terminal 87 faces the exposed wafer 10. It is also possible to measure the thickness of the wafer 10 being ground by immersing it in the grinding water supplied during grinding, and to feed back the thickness of the wafer 10 being ground to the control means 20 to achieve a desired thickness. Is possible. Further, the thickness measuring device 8 configured based on the present invention does not need to be disposed in the grinding device 1 as in the present embodiment, and may be configured as one device independent of the grinding device 1 or may be ground. It may be provided in another processing apparatus different from the apparatus 1.

1: Grinding device 2: Device housing 3: Grinding unit 4: Spindle unit 5: Grinding wheel 7: Chuck table mechanism 8: Thickness measuring device 8d: First route 8e: Second route 8f: Third route 80: Measuring housing 81: Light emission source 82: Spectrometer 83: Polygon mirror (distribution means)
86: Optical branching means 87: Measurement terminal 88: Objective lens 89: Mirror 90: Line image sensor

Claims (2)

A thickness measuring device for measuring the thickness of a plate-like object,
A broadband light source that emits light in a wavelength region that is transparent to the plate-like object;
A spectroscope that splits the light emitted by the broadband light source into a wavelength region;
Distribution means for changing the distribution direction of the light of each wavelength dispersed by the spectrometer over time;
A condensing lens that condenses light of each wavelength distributed by the distribution means;
A light transmission means that faces the condenser lens, one end face of a plurality of optical fibers is arranged in a row, and transmits light of each wavelength collected by the condenser lens;
The other end surfaces of the plurality of optical fibers constituting the light transmission means face the plate-like object, form a row, and include a plurality of objective lenses disposed between the plate-like objects corresponding to the end surfaces. Measuring terminals,
The light reflected on the upper surface of the plate-like object and the light transmitted through the plate-like object and reflected on the lower surface interfere with each other, and return light that travels backward through each optical fiber is disposed on the light transmission path of the light transmission means. Optical branching means branching from each optical fiber,
The wavelength of the return light corresponding to each optical fiber branched by the optical branching means is obtained from the time when the distributing means is distributed to each optical fiber, the light intensity of each wavelength is detected, and the spectral interference waveform corresponding to each optical fiber. Spectral interference waveform generating means for generating
Waveform analysis of the spectral interference waveform corresponding to each optical fiber generated by the spectral interference waveform generating means, and a thickness calculating means for calculating the thickness of the plate corresponding to each optical fiber;
A thickness measuring device composed of at least. A holding means for holding the plate-like object;
The measurement terminal and the holding means are configured to be relatively movable in the X-axis direction,
A row of objective lenses arranged corresponding to the end face of each optical fiber constituting the measurement terminal is positioned in the Y-axis direction orthogonal to the X-axis direction,
A plate shape calculated by the thickness calculation means at the X and Y coordinates specified by the relative movement of the measurement terminal and the holding means in the X-axis direction and the objective lens positioned in the Y-axis direction. The thickness measuring apparatus according to claim 1, further comprising recording means for storing the thickness of the object.