Measuring and processing equipment

Abstract

To measure a height of an upper surface of a measured object and the like without narrowing a measurement wavelength band region per single head part and at multi-points more than two points.SOLUTION: A measurement device 2 is provided that comprises a measurement unit 10 having: a light source unit 8; a first optical fiber 12 transmitting light 13 the light source unit emits; a branch part 14 branching the light transmitted by the first optical fiber; a head unit 18 with a plurality of head parts 18a and 18b including condensers 20a and 20b converging the branched light on the measured object 11 respectively; a second optical fiber being branched in the branch part, and transmitting return light 15; and a spectroscopic unit 24 having a spectrometer dispersing the return light and a light reception unit receiving light dispersed by the spectrometer. The measurement device is provided that further comprises an evaluation unit 36 evaluating variations of a height or thickness of the measured object at a converging point of the light with which the measured object is irradiated from each condenser on the basis of a difference between wavelengths of the return lights received by the light reception unit and from each head part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a measuring device capable of measuring the height or thickness of a workpiece, and a processing device equipped with the measuring device. [Background technology]

[0002] A semiconductor wafer having devices formed on its front surface is ground on its back surface by a grinding device to thin it to a predetermined thickness before being divided into individual device chips by a processing device such as a cutting device or a laser processing device.

[0003] The thickness of the thinned semiconductor wafer is measured, for example, by a spectral interference measuring device (see, for example, Patent Document 1). Another measuring device for measuring the thickness of a semiconductor wafer is one that uses a 1×2 type optical fiber coupler to focus light from a light source onto the top surface of the object to be measured and separates the light reflected from the top surface (see, for example, Patent Document 2).

[0004] However, when a 1×2 type optical fiber coupler is used, approximately half of the return light is lost at the end of the optical fiber. Therefore, in order to reduce the loss of return light, a measuring device that uses a 2×2 type optical fiber coupler to measure the thickness of an object to be measured has been proposed (for example, see Patent Document 3).

[0005] In the measurement device described in Patent Document 3, a 2x2 optical fiber coupler is used to split the light from a light source into two head units, and the returning light from each head unit is dispersed by a single spectroscope and then received by a single image sensor.

[0006] However, in order to identify the correspondence between the return light and the head portion, a first optical filter that transmits light of a predetermined wavelength band is arranged in the first head portion, and a second optical filter that transmits light of a wavelength band different from the predetermined wavelength band is arranged in the second head portion. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2011-122894 A [Patent Document 2] International Publication No. 2015 / 199054 [Patent Document 3] JP 2014-178287 A Summary of the Invention [Problem to be solved by the invention]

[0008] In this way, when optical filters with different transmission wavelength bands are arranged for each head, there is a problem that as the number of heads increases, the wavelength measurement range for each head becomes narrower.

[0009] The present invention has been made in consideration of these problems, and aims to measure the height of the top surface of an object to be measured at two or more points using two or more heads without narrowing the measurement wavelength band per head. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided a measurement device having a holding unit for holding an object to be measured, and a measurement unit capable of measuring the height or thickness of the object to be measured held by the holding unit, the measurement unit having a light source unit that emits light in a predetermined wavelength band, a first optical fiber that transmits the light emitted by the light source unit, a branching unit that branches the light transmitted by the first optical fiber into at least two measurement optical fibers, a head unit having a plurality of head units each including a light collector that focuses the light branched at the branching unit on the object to be measured, a spectroscopic unit having a second optical fiber that is branched at the branching unit with respect to the first optical fiber and transmits return light from each of the measurement optical fibers reflected by the object to be measured, a spectrometer that splits the return light from each measurement optical fiber transmitted by the second optical fiber, and a light receiving unit that receives the light split by the spectrometer, and the measurement device is capable of detecting a difference in wavelength of the return light from each head unit received by the light receiving unit. The degree of overlap of the returned light in the graph of wavelength and received signal intensity, as reflected by Based on this, there is provided a measurement apparatus further comprising an evaluation unit that evaluates the variation in height or thickness of the object to be measured at the focusing points of the light irradiated from each collector to the object to be measured.

[0011] According to another aspect of the present invention, there is provided a measuring device having a holding unit for holding a measurement object and a measuring unit capable of measuring a height or thickness of the measurement object held by the holding unit, a processing unit having a spindle and a processing tool attached to a lower end of the spindle for processing the measurement object, and a control unit having a processor and controlling the operation of the measuring device and the processing unit, the measuring unit including a light source unit for emitting light in a predetermined wavelength band, a first optical fiber for transmitting the light emitted by the light source unit, and at least two measurement light beams for transmitting the light transmitted by the first optical fiber. a head unit having a plurality of head portions each including a branching portion branching into optical fibers and a light collector for collecting the light branched at the branching portion on the object to be measured; a spectroscopic unit having a second optical fiber branched at the branching portion with respect to the first optical fiber and transmitting return light from each of the measurement optical fibers reflected by the object to be measured, a spectrometer for spectroscopically separating the return light from each of the measurement optical fibers transmitted by the second optical fiber, and a light receiving portion for receiving the light dispersed by the spectrometer, and the control portion is configured to determine a difference in wavelength of the return light from each of the head portions received by the light receiving portion. The degree of overlap of the returned light in the graph of wavelength and received signal intensity, as reflected by Based on this, a processing device is provided which has an evaluation unit which evaluates the variation in height or thickness of the object to be measured at the focal point of light irradiated from each collector to the object to be measured, and the control unit evaluates the variation in height or thickness of the object to be measured while processing the object with the processing tool. Effect of the Invention

[0012] In a measurement device according to one aspect of the present invention, the return light from each measurement optical fiber is split by a splitting unit. When the peak wavelengths of the return lights are far from each other, multiple peaks are formed in the received light signal, but as the peak wavelengths approach each other, the peak of the received light signal becomes one.

[0013] The evaluation unit of the measurement device evaluates the variation in height or thickness of the object from the received light signal formed based on the difference in the wavelength (peak wavelength) of the return light from each head unit. Therefore, the variation in height or thickness of the object can be evaluated at multiple points (two or more) without providing optical filters with different transmission wavelength bands to each head unit. [Brief description of the drawings]

[0014] [Figure 1] FIG. [Diagram 2] FIG. 2 is a schematic diagram of a spectroscopic unit. [Diagram 3] FIG. 3A is a diagram showing an example of a light receiving signal, and FIG. 3B is a diagram showing another example of a light receiving signal. [Figure 4] FIG. 4 is a diagram showing a plurality of signal waveforms pre-stored in an auxiliary storage device. [Diagram 5] FIG. [Figure 6] FIG. 6A is a partial cross-sectional side view of the chuck table and the polishing pad, and FIG. 6B is a diagram showing an example of the positional relationship between the light focusing point and the polishing pad. [Figure 7] FIG. 7(A) is a diagram showing an example of a light receiving signal before polishing, and FIG. 7(B) is a diagram showing an example of a light receiving signal after polishing. [Figure 8] 11A and 11B are diagrams showing the positions of the object to be measured and the light focusing point before and after adjustment of the polishing area; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a schematic diagram of a measurement device 2 according to a first embodiment. In Fig. 1, some of the components of the measurement device 2 are shown in functional blocks. Note that the Z-axis direction shown in Fig. 1 is a vertical direction, and the X-axis direction and the Y-axis direction, each perpendicular to the Z-axis direction, constitute horizontal directions.

[0016] The measuring device 2 measures the height of the upper surface 11a of the object 11 and the thickness 11c of the object 11. The measuring device 2 is mounted on, for example, a processing device (polishing device, grinding device, etc.). However, the measuring device 2 in this embodiment is not an accessory of the processing device, but is a device separate and independent from the processing device.

[0017] The measuring device 2 has a chuck table (holding unit) 4. A rotation drive source (not shown) such as a motor that rotates the chuck table 4 in a predetermined direction is connected to the lower part of the chuck table 4. The chuck table 4 has a disk-shaped frame.

[0018] A flow path (not shown) is formed in the lower part of the frame for applying negative pressure generated by a suction source (not shown) such as an ejector to the porous plate. A disk-shaped recess is formed in the upper part of the frame, and a disk-shaped porous plate (not shown) is fixed in this recess.

[0019] The upper surface of the porous plate and the upper surface of the frame are substantially flush with each other, forming a substantially flat holding surface 4a. The holding surface 4a suction-holds the lower surface 11b of the object to be measured 11. The object to be measured 11 is, for example, a silicon wafer.

[0020] When the lower surface 11b of the object to be measured 11 is sucked and held by the holding surface 4a, the upper surface 11a located opposite to the lower surface 11b is exposed upward. The measuring light 13 is irradiated onto the upper surface 11a from each of the heads 18a and 18b (described in detail later) of the measuring unit 6.

[0021] The measurement unit 6 has a light source section 8. The light source section 8 of this embodiment includes an excitation light source (not shown). The excitation light source has, for example, a laser diode (LD) that emits blue light (for example, wavelength λ=450 nm).

[0022] The excitation light is irradiated onto the phosphor through a predetermined optical system such as a lens and a prism. The phosphor is, for example, a YAG:Ce phosphor (in one example, ((Y,Gd)3Al5O 12:Ce), which absorbs excitation light and emits light in a predetermined wavelength band (for example, 500 nm to 700 nm) including light of green, yellow, red, etc.

[0023] The light generated from the phosphor passes through a focusing lens (not shown) of the light source unit 8, is focused onto one end of a first optical fiber 12 corresponding to the first port of a 2x2 type optical fiber coupler 10, and is transmitted as measurement light 13 by the first optical fiber 12 to a branching unit 14.

[0024] The optical fiber coupler 10 is formed, for example, by fusing and extending parts of two optical fibers. Two measurement optical fibers 16a and 16b that constitute a third port and a fourth port of the optical fiber coupler 10 are provided on the opposite side of the first optical fiber 12 with respect to the branching portion 14.

[0025] Light in a predetermined wavelength band from the light source unit 8 is branched into two measurement optical fibers 16a and 16b at a ratio of, for example, 50:50 from the branch unit 14. The measurement optical fiber 16a is connected to the head unit 18a.

[0026] The head unit 18a has a condenser 20a therein. The condenser 20a of the present embodiment has a chromatic aberration lens. Due to the axial chromatic aberration of the condenser 20a, the height position of the condensing point 13a of the light that has passed through the condenser 20a changes depending on the wavelength of the light.

[0027] Specifically, the longer the wavelength component, the farther the light is collected from the collector 20a, and the shorter the wavelength component, the closer the light is to the collector 20a. The collector 20a may have a diffractive optical element and a collecting lens instead of a chromatic aberration lens. In this case, the longer the wavelength component, the closer the light is to the collector 20a, and the shorter the wavelength component, the farther the light is to the collector 20a.

[0028] A part of the measurement light 13 irradiated from the condenser 20a to the object 11 is reflected by the upper surface 11a and then returns to the measurement optical fiber 16a via the condenser 20a again as return light 15. The wavelength of the return light 15 corresponds to the distance from the condenser 20a to the upper surface 11a of the object 11.

[0029] In addition, the wavelength components focused on the upper surface 11a mainly pass through the measurement optical fiber 16a, and the wavelength components not focused on the upper surface 11a are almost entirely blocked by the measurement optical fiber 16a. In this way, a confocal optical system is configured in the head unit 18a.

[0030] However, as long as a confocal optical system is configured, the configuration of the head unit 18a is not limited to the form shown in Fig. 1. For example, an additional condenser lens may be provided between the condenser 20a and the measurement optical fiber 16a.

[0031] The measurement optical fiber 16b is connected to the head unit 18b. In this specification, the head units 18a and 18b are collectively referred to as the head unit 18. The head unit 18b also has a condenser 20b including a chromatic aberration lens, and constitutes a confocal optical system together with the measurement optical fiber 16b.

[0032] Due to the axial chromatic aberration of the condenser 20b, the height position of the condensing point 13b of the light that has passed through the condenser 20b changes depending on the wavelength. Similarly, a part of the measurement light 13 irradiated from the condenser 20b to the object 11 is reflected by the upper surface 11a and returns as return light 15 to the measurement optical fiber 16b via the condenser 20b.

[0033] The wavelength of the return light 15 corresponds to the distance from the collector 20b to the upper surface 11a of the object 11. The collector 20b is disposed at approximately the same height as the collector 20a, and its optical axis is disposed approximately parallel to the Z-axis direction, similar to the collector 20a.

[0034] The return light 15 passing through the measurement optical fiber 16a or 16b is transmitted through the branching section 14 to the second optical fiber 22 constituting the second port of the optical fiber coupler 10. The second optical fiber 22 is branched off from the first optical fiber 12 at the branching section 14.

[0035] A spectroscopic unit 24 is connected to one end of the second optical fiber 22. Fig. 2 is a schematic diagram of the spectroscopic unit 24. The spectroscopic unit 24 has a collimator lens 26 that converts the return light 15 into approximately parallel light.

[0036] The return light 15 that passes through the collimator lens 26 is reflected by the diffraction grating 28, passes through the condenser lens 30, and is received by the light receiving region 32a of the light receiving unit 32. The light receiving unit 32 has an image sensor such as a CMOS (Complementary Metal-Oxide-Semiconductor) or a CCD (Charge-Coupled Device) having a plurality of photoelectric conversion elements.

[0037] 2, the light receiving unit 32 of this embodiment has a two-dimensional image sensor, but the light receiving unit 32 may have a one-dimensional image sensor (also called a linear image sensor, a line sensor, etc.). Also, instead of the diffraction grating 28, a dispersive spectrometer such as a prism may be used.

[0038] The light receiving signal generated by the light receiving unit 32 is input to a control unit 34 that controls the measuring device 2. The control unit 34 is configured by a computer including, for example, a processor (processing device) represented by 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.

[0039] The functions of the control unit 34 are realized by operating the processing device and the like in accordance with the software stored in the auxiliary storage device. The control unit 34 has an evaluation unit 36 ​​that performs a predetermined evaluation on the light reception signal output from the spectroscopic unit 24.

[0040] The function of the evaluation unit 36 ​​is realized, for example, by a program stored in an auxiliary storage device. However, the function of the evaluation unit 36 ​​may be realized by an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0041] Here, the light receiving signal and its evaluation method will be described. Fig. 3(A) is a diagram showing an example of the light receiving signal from each head part 18a, 18b, and Fig. 3(B) is a diagram showing another example of the light receiving signal from each head part 18a, 18b. In Fig. 3(A) and Fig. 3(B), the horizontal axis indicates the size of the wavelength λ (nm) of light, and the vertical axis indicates the intensity of the light receiving signal.

[0042] As shown in FIG. 3A, when the wavelength difference d1 between the peak wavelength λ1 of return light 15A1 from head portion 18a and the peak wavelength λ2 of return light 15A2 from head portion 18b is sufficiently large, each return light 15A1, 15A2 is measured almost individually.

[0043] In this case, the wavelength of the measurement light 13 focused on the upper surface 11a is different between the heads 18a and 18b. This means that the difference in height between the upper surface 11a directly below the head 18a and the upper surface 11a directly below the head 18b is relatively large.

[0044] In contrast, as shown in FIG. 3(B), when the wavelength difference d2 between the peak wavelength λ3 of return light 15A3 (dashed line) from head portion 18a and the peak wavelength λ4 of return light 15A4 (dashed line) from head portion 18b is smaller than the difference d1, each return light 15A3, 15A4 is measured as superimposed return light 15A5 (peak wavelength λ5).

[0045] The return light 15A5 indicates that the height of the upper surface 11a directly below the head portion 18a is slightly different from the height of the upper surface 11a directly below the head portion 18b, but the difference in height at the upper surface 11a is smaller than that in FIG. 3(A).

[0046] In this way, in the received light signal measured by the spectroscopic unit 24, the height variation of the upper surface 11a at each of the focusing points 13a, 13b is measured as the degree of overlap of each of the return lights 15, which reflects the difference in the peak wavelength of each of the return lights 15.

[0047] The evaluation unit 36 ​​evaluates the received light signal by comparing it with a plurality of signal waveforms pre-stored in the auxiliary storage device. Fig. 4 is a diagram showing five signal waveforms B1 to B5 pre-stored in the auxiliary storage device. In Fig. 4, the horizontal axis indicates the relative wavelength based on the peak wavelength of the signal waveform B1, and the vertical axis indicates the signal intensity.

[0048] The signal waveform B1 is formed by superposing two return lights 15 having the same peak wavelength. The signal waveform B1 has a predetermined peak intensity C and a predetermined full width at half maximum (FWHM) α.

[0049] The signal waveform B2 is formed by superposing two return lights 15 whose peak wavelengths differ by 0.25α, and has a smaller peak intensity than the signal waveform B1.

[0050] The signal waveform B3 is composed of two overlapping return lights 15 whose peak wavelengths differ by 0.5α, and has a smaller peak intensity than the signal waveform B2.

[0051] Signal waveform B4 is composed of two overlapping return lights 15 with a peak wavelength difference of α, and has a smaller peak intensity than signal waveform B3. The top of the peak of signal waveform B4 is generally flat over a wider range than signal waveforms B1 to B3.

[0052] Signal waveform B5 is composed of two overlapping return lights 15 with a peak wavelength difference of 1.5α, and has a smaller peak intensity than signal waveform B4. Note that, since the difference in peak wavelength is relatively large, signal waveform B5 has two peaks and a valley between them.

[0053] The evaluation unit 36 ​​evaluates the difference in wavelength (i.e., the degree of overlap) of the return light 15 from each head unit 18a, 18b by comparing the shape and intensity of the five signal waveforms B1 to B5 with the received light signal, thereby evaluating the height variation of the upper surface 11a at each of the light-collecting points 13a, 13b.

[0054] For example, when the received light signal has a peak interval equal to or greater than the peak interval between the two mountains shown in the signal waveform B5, the difference in the peak wavelengths of the return light 15 from each head unit 18a, 18b is relatively large (i.e., the overlap of the return light 15 is relatively small). In this case, the evaluation unit 36 ​​evaluates the height variation of the upper surface 11a as Level 6, which is relatively large.

[0055] In addition, if the received light signal is smaller than the peak distance between the two mountains shown in signal waveform B5 but does not have a substantially flat peak intensity as shown in signal waveform B4, the evaluation unit 36 ​​evaluates the height variation of the upper surface 11a as level 5, which is smaller than level 6.

[0056] When the received light signal has a substantially flat peak intensity as shown by signal waveform B4, the evaluation unit 36 ​​evaluates the height variation of the upper surface 11a as level 4, which is smaller than level 5.

[0057] If the received light signal does not have a substantially flat peak intensity as shown in signal waveform B4, but has one hill but has a peak intensity greater than signal waveform B4 and less than signal waveform B3, the evaluation unit 36 ​​evaluates the height variation of the upper surface 11a to level 3, which is smaller than level 4.

[0058] When the received light signal has a peak intensity equal to or greater than the signal waveform B3 and smaller than the signal waveform B2, the evaluation unit 36 ​​evaluates the height variation of the upper surface 11a as Level 2, which is smaller than Level 3.

[0059] When the received light signal has a peak intensity equal to or greater than the signal waveform B2 and smaller than the signal waveform B1, the evaluation unit 36 ​​evaluates the height variation of the upper surface 11a as Level 1, which is smaller than Level 2.

[0060] When the received light signal coincides with the peak intensity shown in the signal waveform B1, the evaluation unit 36 ​​evaluates the height variation of the upper surface 11a as level 0, which is the smallest variation. The above-mentioned evaluation method is shown in Table 1.

[0061] [Table 1]

[0062] In this manner, in this embodiment, the evaluation unit 36 ​​can evaluate the variation in height of the object 11 from the light receiving signal formed based on the difference in the peak wavelength of the return light 15 from each of the heads 18a, 18b. Therefore, the variation in height of the upper surface 11a of the object 11 can be evaluated at multiple points (two or more points) without providing optical filters with different transmission wavelength bands to each of the heads 18a, 18b.

[0063] When evaluating the variation in height of the upper surface 11a using the measurement device 2, the focusing points 13a and 13b of the heads 18a and 18b are arranged on the radius of the holding surface 4a when viewed from above. Then, the chuck table 4 holding the lower surface 11b side of the object 11 to be measured is rotated around a predetermined rotation axis at a predetermined speed (e.g., 300 rpm).

[0064] The control unit 34 receives a light reception signal from the spectroscopic unit 24 at a predetermined time interval, and stores the received data in an auxiliary storage device. The evaluation unit 36 ​​evaluates the variation in height of the upper surface 11a based on the data stored in the auxiliary storage device.

[0065] In this embodiment, the distance from the head portions 18a, 18b to the upper surface 11a is defined as the height of the upper surface 11a based on the holding surface 4a, but the thickness 11c of the object to be measured 11 can be measured by calculating the difference between the height of the upper surface 11a and the height of the holding surface 4a (i.e., the lower surface 11b).

[0066] In the first embodiment, an example having two heads 18a and 18b has been described, but the measurement unit 6 may have three or more heads. In this case, a plurality of signal waveforms each of which is obtained by superimposing three return beams 15 is stored in advance in the auxiliary storage device.

[0067] In the above description, an example has been described in which a plurality of signal waveforms are pre-stored in the auxiliary storage device. However, instead of a plurality of signal waveforms, numerical values ​​of predetermined parameters such as a peak wavelength, a full width at half maximum α, etc., determined based on predicted values ​​calculated by simulation or actual measured values ​​may be pre-stored in the auxiliary storage device.

[0068] In this case, the evaluation unit 36 ​​evaluates the difference (i.e., the degree of overlap) in the wavelengths of the return light 15 from each head unit 18a, 18b by comparing predetermined parameters such as the peak wavelength and full width at half maximum α of the received light signal with the numerical values ​​of the parameters stored in advance, thereby evaluating the height variation of the upper surface 11a at each of the focusing points 13a, 13b.

[0069] A display device (not shown) such as a monitor may be connected to the control unit 34. For example, the monitor displays an outline of the upper surface 11a and information indicating the height of each measurement point on the upper surface 11a. If the information indicating the height of each measurement point is displayed in a different color, the unevenness of the upper surface 11a can be visually grasped.

[0070] Next, a second embodiment will be described. In the second embodiment, a polishing apparatus (processing apparatus) 40 equipped with a measuring device 2 having a measuring unit 6 polishes (processes) a measured object 11. FIG. 5 is a perspective view of the polishing apparatus 40.

[0071] The polishing apparatus 40 includes a base 42 that supports each of the components. A cassette 44 that accommodates a measurement object (workpiece) 11 is disposed on the upper front portion (one side in the X-axis direction) of the base 42. A transfer robot 46 disposed on the upper front portion of the base 42 takes out the measurement object 11 from the cassette 44 and transfers it to a positioning unit 48 disposed behind the cassette 44.

[0072] An opening 42a having a longitudinal portion in the X-axis direction is formed behind the positioning unit 48. A moving table 50 that is movable along the X-axis direction is disposed in the opening 42a. A chuck table (holding unit) 52 is provided on the moving table 50.

[0073] The structure of the chuck table 52 is approximately the same as that of the above-mentioned chuck table 4, but the holding surface 52a of the chuck table 52 has a conical shape with the center portion slightly protruding from the outer periphery (see FIG. 6(A)).

[0074] The rotation axis of the chuck table 52 is inclined at a predetermined angle with respect to the Z-axis direction so that a part of the holding surface 52a is approximately parallel to the XY plane. A rotation drive source (not shown) such as a motor is connected to the lower part of the chuck table 52.

[0075] A ball screw type X-axis moving mechanism (not shown) that moves the chuck table 52, the rotary drive source, the moving table 50, etc. along the X-axis direction is provided below the rotary drive source. The X-axis moving mechanism moves the chuck table 52 between a load / unload position 54a on the front side and a processing position 54b on the rear side.

[0076] A first transfer arm 56 is disposed on one side in the Y-axis direction of the positioning unit 48. The object 11, the position of which has been adjusted by the positioning unit 48, is transferred from the positioning unit 48 to the chuck table 52 by the first transfer arm 56.

[0077] A device such as an IC (Integrated Circuit) is formed on one surface (lower surface 11b) of the object to be measured 11. A resin protective tape (not shown) is attached to the surface. When the one surface is sucked and held by the holding surface 4a via the protective tape, the object to be measured 11 deforms to follow the shape of the holding surface 52a.

[0078] The chuck table 52, which holds the workpiece 11 by suction, is moved to the processing position 54b by the X-axis movement mechanism. A rectangular pillar-shaped support part 60 is provided at the rear end of the base 42 so as to extend in the Z-axis direction. A pair of guide rails 62, which are arranged approximately parallel to the Z-axis direction, are fixed to the front side surface of the support part 60.

[0079] A movable plate 64 is fixed to the pair of guide rails 62 so as to be slidable in the Z-axis direction. A nut portion (not shown) is provided on the rear side surface of the movable plate 64, and a ball screw 66 arranged substantially parallel to the Z-axis direction is rotatably connected to the nut portion.

[0080] A driving source 68 such as a pulse motor is connected to the upper end of the ball screw 66. When the driving source 68 is operated, the moving plate 64 moves along a polishing feed direction that is approximately parallel to the Z-axis direction. A polishing unit (processing unit) 70 is fixed to the front side surface of the moving plate 64.

[0081] The polishing unit 70 has a cylindrical spindle housing 72 whose height direction is arranged substantially parallel to the Z-axis direction. A columnar spindle 74 is rotatably housed in the spindle housing 72. A motor (not shown) that rotates the spindle 74 is provided on the upper side of the spindle 74.

[0082] The center of the upper surface side of a disk-shaped mount 76 is fixed to the lower end of the spindle 74. A polishing pad (machining tool) 78 is attached to the lower surface side of the mount 76. The polishing pad 78 has a disk-shaped base 78a made of metal.

[0083] A pad portion 78b having approximately the same diameter as the base portion 78a is fixed to the lower surface side of the base portion 78a. The pad portion 78b has a diameter smaller than that of the holding surface 52a (for example, a diameter of about 1 / 10 to 1 / 2 of the diameter of the holding surface 4a). Fig. 6(A) is a partial cross-sectional side view of the chuck table 52 and the polishing pad 78.

[0084] The pad portion 78b is, for example, a fixed abrasive polishing pad in which abrasive grains are fixed in the pad. The pad portion 78b can be manufactured, for example, by impregnating a urethane solution in which abrasive grains of a size on the order of μm are dispersed into a polyester nonwoven fabric, and then drying the same.

[0085] The abrasive grains are formed from materials such as silicon oxide, silicon carbide, cBN (cubic boron nitride), diamond, metal oxide fine particles, etc. Examples of metal oxide fine particles used in the abrasive grains include cerium oxide, zirconium oxide, aluminum oxide, etc.

[0086] Returning to FIG. 5, for example, alkaline slurry (polishing liquid) not containing free abrasive grains is supplied to the polishing pad 78 from a slurry supply unit 80 through a predetermined flow path formed in the spindle 74.

[0087] The above-mentioned measuring unit 6 is disposed on one side in the Y-axis direction of the chuck table 52 disposed at the processing position 54b. The measuring unit 6 has an arm 82 disposed above the opening 42a in a manner substantially parallel to the Y-axis direction.

[0088] The heads 18a, 18b are fixed to the lower portion of the arm 82 so as to be independently slidable in the Y-axis direction. Each of the heads 18a, 18b is moved along the Y-axis direction by a driving source (not shown) such as an actuator.

[0089] 6(B) is a diagram showing an example of the positional relationship between the light condensing points 13a and 13b and the polishing pad 78. As shown in FIG. 6(B), the light condensing points 13a and 13b are disposed at positions that are outside the rotation center 52b of the holding surface 52a and do not overlap with the polishing pad 78.

[0090] After polishing the object 11 while measuring the height of the upper surface 11a with the heads 18a, 18b, the chuck table 52 is returned to the carry-in / carry-out position 54a. Then, the second transport arm 84 disposed on one side of the first transport arm 56 in the Y-axis direction transports the object 11 from the chuck table 52 to the spinner cleaning unit 86 (see FIG. 5).

[0091] 5, the object 11 cleaned in the spinner cleaning unit 86 is transferred by the transfer robot 46 to a cassette 88 disposed in front of the base 42. The polishing apparatus 40 has a control unit 90 that controls the operation of each of the components such as the measuring device (the chuck table 52 and the measuring unit 6), the polishing unit 70, etc.

[0092] The control unit 90 is configured, for example, by a computer including a processor (processing device) represented by 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.

[0093] The functions of the control unit 90 are realized by operating a processing device or the like in accordance with software stored in the auxiliary storage device. The control unit 90 has the above-mentioned evaluation unit 36. The functions of the evaluation unit 36 ​​are realized, for example, by a program stored in the auxiliary storage device, but may also be realized by an ASIC or an FPGA.

[0094] The control unit 90 evaluates the variation in height of the upper surface 11a (i.e., the unevenness of the upper surface 11a) using the evaluation unit 36 ​​while polishing the object 11 with the polishing pad 78. Fig. 7(A) is a diagram showing an example of the light receiving signal before polishing, and Fig. 7(B) is a diagram showing an example of the light receiving signal after polishing.

[0095] In Figures 7(A) and 7(B), the horizontal axis indicates the wavelength λ (nm) of light, and the vertical axis indicates the intensity of the received light signal. In Figures 7(A) and 7(B), the scales of the horizontal axis are the same, and the scales of the vertical axes are the same.

[0096] Before polishing, when the difference between the height of upper surface 11a at focal point 13a and the height of upper surface 11a at focal point 13b is relatively large, the difference d3 between the peak wavelength λ6 of return light 15A6 at focal point 13a and the peak wavelength λ7 of return light 15A7 at focal point 13b is sufficiently large. Therefore, each of return lights 15A6 and 15A7 is measured approximately individually (see FIG. 7(A)).

[0097] During polishing, with the workpiece 11 held by suction on the holding surface 52a, the chuck table 52 and the polishing pad 78 are rotated, and the polishing pad 78 is fed downward at a predetermined feed speed for polishing while slurry is being supplied.

[0098] When the pad portion 78b comes into contact with the upper surface 11a, the upper surface 11a is polished by the pad portion 78b. When the upper surface 11a side is polished for a predetermined time, the object 11 becomes thinner, and the distance from the condensers 20a, 20b to the upper surface 11a becomes longer.

[0099] As described above, the collectors 20a, 20b of this embodiment have chromatic aberration lenses, so as the distance from the collectors 20a, 20b to the upper surface 11a increases, the peak wavelength of the return light 15 increases (see the arrows in Figures 7(A) and 7(B)).

[0100] In addition, when the unevenness of the upper surface 11a is reduced by polishing, the difference in the peak wavelengths of the received light signals is reduced. Therefore, the return light 15A8 (peak wavelength λ8) at the light-converging point 13a and the return light 15A9 (peak wavelength λ9) at the light-converging point 13b overlap each other to form a return light 15A. 10 (Peak wavelength λ 10 ) is measured (see FIG. 7(B)). 10is, for example, a received light signal that is equal to or lower than level 3 (that is, any one of levels 3, 2, 1, and 0).

[0101] In the polishing apparatus 40 of this embodiment, the evaluation unit 36 ​​evaluates the variation in height of the object 11 from a received light signal formed based on the difference in peak wavelength of the return light 15 from each of the heads 18a, 18b. Therefore, the variation in height of the object 11 can be evaluated at multiple points (two or more points) without providing optical filters with different transmission wavelength bands to each of the heads 18a, 18b.

[0102] Incidentally, the polishing apparatus 40 can also reduce unevenness on the upper surface 11a (i.e., reduce the difference in peak wavelengths) by changing the polishing area of ​​the object 11 to be measured in accordance with the received light signal (i.e., the difference in peak wavelengths of the return light 15 from each head portion 18a, 18b).

[0103] For example, when the upper surface 11a at the light-focus point 13a is higher than the upper surface 11a at the light-focus point 13b, a difference in peak wavelength occurs as shown in Fig. 7(A). Therefore, the control unit 90 adjusts the polishing area so that the upper surface 11a corresponding to the light-focus point 13b is not polished, but the upper surface 11a corresponding to the light-focus point 13a is polished.

[0104] Specifically, first, the polishing unit 70 is temporarily raised and moved away from the object 11. Next, the chuck table 52 is moved toward the load / unload position 54a, thereby moving the object 11 by the length L (see FIG. 8).

[0105] Fig. 8 is a diagram showing the object 11 and the positions of the light-focusing points 13a and 13b before and after the adjustment of the polishing area. In Fig. 8, the object 11 before movement is indicated by a dashed line, and the object 11 after movement is indicated by a solid line.

[0106] Due to the movement of the chuck table 52, the region of the upper surface 11a where the light condensing point 13b hits (circle 90-1) moves to a circle 90-2. Similarly, the region of the upper surface 11a where the light condensing point 13a hits (circle 90-3) moves to a circle 90-4.

[0107] Furthermore, the control unit 90 operates a driving source such as an actuator to place the light-focusing point 13a on the circle 90-4, as shown by an arrow 92. At this time, the relative position of the light-focusing point 13b with respect to the upper surface 11a changes, but in this embodiment, the light-focusing point 13b is not moved so as to offset the change.

[0108] Thereafter, the polishing unit 70 is lowered again to polish the object 11 while measuring the return light 15 to evaluate the height variation at the focal points 13a and 13b. Note that the peak wavelength of the return light 15 at the focal point 13b of the object 11 before the movement is recorded, and the height variation may be evaluated by comparing this peak wavelength with the peak wavelength of the return light 15 at the focal point 13a of the object 11 after the movement.

[0109] In the case where the polishing rate differs between the central portion and the peripheral portion of upper surface 11a, by appropriately polishing the areas that need to be flattened based on the difference in peak wavelength in this manner, it is possible to achieve a higher flatness of upper surface 11a than if the entire upper surface 11a was polished uniformly.

[0110] Of course, in the second embodiment, the evaluation unit 36 ​​may also evaluate the difference in wavelength (i.e., the degree of overlap) of the return light 15 from each head unit 18a, 18b by comparing predetermined parameters such as the peak wavelength and full width at half maximum α of the received light signal with the numerical values ​​of parameters stored in advance.

[0111] Furthermore, when adjusting the polishing area by moving the chuck table 52, both of the light condensing points 13a, 13b may be fixed without being moved. This causes the relative positions of the light condensing points 13a, 13b with respect to the upper surface 11a to change before and after the movement of the chuck table 52, but it is possible to eliminate the deviation in the height positions of the light condensing points 13a, 13b that accompanies the movement of the head parts 18a, 18b.

[0112] In addition, the structures, methods, etc. according to the above-mentioned embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention. In the first and second embodiments, the thickness 11c of the object 11 may be evaluated instead of or in addition to the height variation of the upper surface 11a.

[0113] Also, instead of the polishing unit 70, a grinding wheel (not shown) may be attached to the underside of the mount 76. The grinding wheel has an annular wheel base made of metal. On the bottom side of the wheel base, a plurality of grinding stones are arranged at predetermined intervals along the circumferential direction of the wheel base.

[0114] Each grinding wheel has abrasive grains such as diamond, cBN (cubic boron nitride), etc., and a binder such as metal, ceramics, resin, etc., for fixing the abrasive grains. A grinding water supply port for supplying grinding water such as pure water is formed in the wheel base. Therefore, a grinding water supply unit (not shown) is arranged instead of the slurry supply unit 80.

[0115] During grinding, the grinding unit is fed downward for grinding while rotating the grinding wheel around the spindle 74. The lower surface 11b side of the workpiece 11 is suction-held by the holding surface 52a, and the chuck table 52 is rotated (see FIG. 6(A)).

[0116] When the upper surface 11a of the workpiece 11 held by the holding surface 52a comes into contact with the lower surface of the grinding wheel, the upper surface 11a is ground. The height of the upper surface 11a can be measured using the measurement unit 6 before and after grinding, and even during grinding. [Explanation of symbols]

[0117] 2: measuring device, 4: chuck table, 4a: holding surface 6: Measurement unit, 8: Light source, 10: Optical fiber coupler 11: Object to be measured, 11a: Top surface, 11b: Bottom surface, 11c: Thickness 12: first optical fiber, 14: branching portion, 16a, 16b: measurement optical fibers 13: Measurement light, 13a, 13b: Focus point 15,15A1,15A2,15A3,15A4,15A5,15A6,15A7,15A8,15A9,15A 10 : Return light 18: head unit, 18a, 18b: head section, 20a, 20b: light collector 22: Second optical fiber 24: Spectroscopic unit, 26: Collimating lens, 28: Diffraction grating, 30: Condenser lens 32: light receiving section, 32a: light receiving area, 34: control section, 36: evaluation section 40: Polishing device, 42: Base, 42a: Opening 44: cassette, 46: transport robot, 48: positioning unit 50: moving table, 52: chuck table, 52a: holding surface, 52b: center of rotation 54a: Loading / unloading position, 54b: Processing position, 56: First transfer arm 60: Support portion, 62: Guide rail, 64: Moving plate, 66: Ball screw, 68: Driving source 70: polishing unit, 72: spindle housing, 74: spindle, 76: mount 78: polishing pad, 78a: base, 78b: pad portion, 80: slurry supply unit 82: Arm, 84: Second transport arm 86: spinner cleaning unit, 88: cassette, 90: control unit 90-1, 90-2, 90-3, 90-4: Circles, 92: Arrows B1, B2, B3, B4, B5: Signal waveform, C: Peak intensity d1, d2, d3: difference, L: length λ1,λ2,λ3,λ4,λ5,λ6,λ7,λ8,λ9,λ 10 : Peak wavelength, α: Full width at half maximum

Claims

1. A measuring device having a holding unit that holds an object to be measured and a measuring unit that can measure a height or a thickness of the object to be measured held by the holding unit, The measurement unit includes: A light source unit that emits light in a predetermined wavelength band; a first optical fiber that transmits light emitted by the light source unit; a branching unit that branches the light transmitted by the first optical fiber into at least two measurement optical fibers; a head unit having a plurality of head parts each including a condenser for condensing the light branched by the branching part onto the object to be measured; a second optical fiber that is branched from the first optical fiber at the branching portion and transmits return light from each of the measurement optical fibers that is reflected by the object to be measured; a spectroscopic unit including a spectrometer that separates return light from each measurement optical fiber transmitted through the second optical fiber, and a light receiving unit that receives the light separated by the spectrometer; having The measuring device comprises: A measuring device characterized by further comprising an evaluation unit that evaluates the variation in height or thickness of the object to be measured at the focusing point of light irradiated from each collector to the object to be measured, based on the degree of overlap of the returned light in a graph of wavelength and intensity of the received signal, which reflects the difference in wavelength of the returned light from each head unit received by the light receiving unit.

2. A measuring device including a holding unit for holding an object to be measured and a measuring unit capable of measuring a height or thickness of the object to be measured held by the holding unit; a processing unit having a spindle and a processing tool attached to a lower end of the spindle for processing the workpiece; A control unit having a processor and controlling operations of the measuring device and the processing unit; Equipped with The measurement unit includes: A light source unit that emits light in a predetermined wavelength band; a first optical fiber that transmits light emitted by the light source unit; a branching unit that branches the light transmitted by the first optical fiber into at least two measurement optical fibers; a head unit having a plurality of head parts each including a condenser for condensing the light branched by the branching part onto the object to be measured; a second optical fiber that is branched from the first optical fiber at the branching portion and transmits return light from each of the measurement optical fibers that is reflected by the object to be measured; a spectroscopic unit including a spectrometer that separates return light from each measurement optical fiber transmitted through the second optical fiber, and a light receiving unit that receives the light separated by the spectrometer; having The control unit has an evaluation unit that evaluates the variation in height or thickness of the object at the focusing point of the light irradiated from each collector to the object based on the degree of overlap of the return light in a graph of wavelength and intensity of the received light signal, which reflects the difference in wavelength of the return light from each head unit received by the light receiving unit, The control unit evaluates a variation in height or thickness of the workpiece while machining the workpiece with the machining tool.

Images