DOUBLE-SIDED POLISHING TOOL

Abstract

A double-sided polishing device (10) comprises: a lower (13) and an upper (14) surface plate (13) and a carrier (20) arranged between these plates (13; 14), which holds a disc-shaped workpiece (W) such that the carrier (20) is rotatable about a center of both the lower (13) and the upper (14) plate (13) as well as a center of the carrier (20), wherein the polishing device includes a thickness measuring sensor (34) at a fixed position above the upper (14) or below the lower (13) plate or at a movable position in an upper section of the upper plate (14) or a lower section of the lower plate (13), wherein the carrier (20) includes through holes (22) which each hold the workpiece (W) in a position eccentric to the center of the carrier (20), wherein a distance between a center of the upper (14) or the lower (13) plate and a center of one of the holes (22) on the shortest or longest, and where a position,The second reference position (F) is defined as a first reference position (E) located half a first distance (G) towards the center of the carrier, wherein a first distance (G) is a predetermined length within 30% of a radius of the through-hole (22), the sensor (34) is arranged in a region in a top view of the first distance (G) around the second reference position (F), and the sensor (34) is designed to measure a thickness of the workpiece (W) in a state in which the workpiece (W) is held in the through-hole (22), through a measuring aperture (35) located in the upper plate (14) or the lower plate (13) closer to a side where the sensor (34) is arranged.

Description

DOUBLE-SIDED POLISHING MACHINE

[0001] The present invention relates to a double-sided polishing apparatus that polishes a top and a bottom surface of a workpiece such as a wafer.

[0002] A double-sided polishing machine that includes a wafer (often referred to as a "workpiece" in this application) in a carrier between an upper and a lower platen and polishes the wafer is known. According to PTL 1 (JP 2008-227393 A), such a double-sided polishing machine includes a thickness measuring sensor provided on a support frame located above the upper surface platen. Furthermore, a window (corresponding to a "measuring aperture") is provided on the upper surface platen. A laser beam of the thickness measuring sensor passes through the window of the rotating upper surface platen, allowing the thickness measuring sensor to detect a thickness of the workpiece immediately below the window.According to PTL 2 (JP 2017 - 207455 A), a thickness is detected on a trajectory on which a workpiece thickness measuring hole provided at a position radially outward from a center of the upper surface plate by a predetermined distance passes through the workpiece (hereinafter often simply referred to as "passing trajectory") in order to detect a thickness distribution of the workpiece during machining.

[0003] For a better understanding of the present invention, reference is further made to DE 11 2009 001 875 T5, which relates to a wafer polishing method and a double-side polishing apparatus with which a wafer for a semiconductor with a high degree of flatness can be produced economically, and DE 10 2014 112 190 A1, which relates to an apparatus and a method for double-sided polishing of a workpiece, which enable the polishing to be stopped in a timely manner by accurately determining the thickness of the workpiece when polishing a round workpiece such as a semiconductor wafer, which must have a high degree of flatness. Brief description of the invention

[0004] In the double-sided polishing machines disclosed in PLT 1 and PTL 2, the carrier holding the workpiece is rotated around a center of the lower surface plate and the upper surface plate (orbits in a direction C) and also rotated around a center of the carrier (rotates around an axis of the carrier in a direction D), as shown in, for example, Fig. 1. Furthermore, in the double-sided polishing apparatus disclosed in PTL 2, the upper or lower surface plate provided with the measuring hole or the thickness measuring sensor is rotated in a direction opposite to a rotation direction of the carrier. Furthermore, the workpiece is held in a position eccentric to the center of the carrier. With these configurations, a trajectory of a center of the workpiece is complex, such as a trochoid curve. As disclosed in PTL 2, when the upper or lower surface plate provided with the measuring hole or the thickness measuring sensor is rotated, the trajectory of the center of the workpiece with respect to the measuring hole and the thickness measuring sensor is more complicated.

[0005] On the other hand, even if the thickness gauge sensor is placed anywhere in the height direction of the double-sided polisher, it is desirable to detect the thickness of the workpiece when the measuring port and the thickness gauge sensor pass near the center of the workpiece. However, it is difficult to find an area where the measuring port or the thickness gauge sensor passing through a vicinity of the workpiece is located more frequently with respect to the complex passing trajectory. More specifically, if a user sets a data acquisition area near the center of the workpiece, it is difficult to locate the area of ​​the measuring port or the thickness gauge sensor that passes through this data acquisition area more frequently.

[0006] The present invention has been made to solve the problems, and it is an object of the present invention to provide a double-sided polishing apparatus comprising a measuring aperture and a thickness measuring sensor arranged in an area where the measuring aperture and the thickness measuring sensor pass through a predetermined data acquisition area at a higher frequency.

[0007] A double-sided polishing apparatus according to the present invention comprises: (1) a lower surface plate; (2) an upper surface plate; and (3) a carrier arranged between the lower surface plate and the upper surface plate and holding at least one disc-shaped workpiece, wherein (a) the carrier is configured to rotate about a center of the lower surface plate, a center of the upper surface plate, and a center of the carrier; (b) the double-sided polishing apparatus includes a thickness measuring sensor at a fixed position above the upper surface plate or below the lower surface plate, or at a movable position in an upper portion of the upper surface plate or a lower portion of the lower surface plate; (c) the carrier includes circular through-holes each for holding the workpiece at a position eccentric to the center of the carrier;(d) when a central position of one of the through-holes preset by a user is defined as a first reference position, wherein a distance between a center of the upper surface plate or the lower surface plate and a center of one of the through-holes preset by the user is the shortest or the longest, (e) a position that is half a first distance away from the first reference position toward the center of the carrier is defined as a second reference position, the first distance being a predetermined length within 30% of a radius of the through-hole, (f) the thickness measuring sensor is arranged in a range in a plan view of the first distance around the second reference position, and (g) the thickness measuring sensor is configured to measure a thickness of the workpiece in a state where the workpiece is held in the through-hole through a measuring aperture,which is located in the upper surface plate or the lower surface plate closer to a side where the thickness measuring sensor is located.

[0008] A double-sided polishing apparatus according to the present invention comprises: (1) a lower surface plate; (2) an upper surface plate; and (3) a carrier disposed between the lower surface plate and the upper surface plate and holding at least one of a triangular, a rectangular, a square, and a polygonal flat plate workpiece, wherein (a) the carrier is configured to rotate about a center of the lower surface plate, a center of the upper surface plate, and a center of the carrier, (b) the double-sided polishing apparatus includes a thickness measuring sensor (34) at a fixed position above the upper surface plate or below the lower surface plate, or at a movable position in an upper portion of the upper surface plate or a lower portion of the lower surface plate, (c) the carrier includes through holes,which each hold the workpiece at a position eccentric to the center of the carrier and each have an identical shape to the workpiece, (d) when a user-preset center position of one of the through-holes is defined as a first reference position, wherein a distance between a center of the upper surface plate or the lower surface plate and a center of a circumcircle of all user-preset vertices of the through-holes is the shortest or the longest, (e) a position that is half a first distance away from the first reference position toward the center of the carrier is defined as a second reference position, wherein the first distance is a predetermined length within 30% of a radius of the circumscribed circle, (f) the thickness measuring sensor is arranged in a range of the first distance around the second reference position in a plan view, and (g) the thickness measuring sensor is designed,to measure a thickness of the workpiece in a state where the workpiece is held in the through hole through a measuring hole located on the upper surface plate or the lower surface plate closer to a side on which the thickness measuring sensor is arranged.,

[0009] According to these configurations, it is possible to increase the frequency with which the measuring port and the thickness measuring sensor pass through the data acquisition range preset by the user.

[0010] Preferably, the center position of the measuring hole or the center position of the circumference of the measuring hole, at which a distance between the center of the upper surface plate or the lower surface plate and the center of the measuring hole or the center of the circumference is the smallest, is set as the first reference position. According to this configuration, the thickness gauge sensor can be arranged on an inner peripheral side of the surface plate, whereby a passing speed (circumferential speed) of the measuring hole and the thickness gauge sensor when passing through the measuring hole and the thickness gauge sensor on the workpiece is lower than in a case where the measuring hole and the thickness gauge sensor are arranged on an outer peripheral side of the surface plate. Thus, the thickness of the workpiece can be correctly and precisely detected. Furthermore, a measuring interval for measuring the thickness of the workpiece becomes smaller, enabling the detection of the high-precision thickness distribution. Advantageous effects of the invention

[0011] According to the present invention, it is possible to realize a double-sided polishing apparatus with high detection frequency of a thickness and a thickness distribution according to a passing trajectory when a measuring aperture and a thickness measuring sensor pass through a predetermined data detection range. Short description of the drawings Fig. 1 is an explanatory diagram showing an example of a relationship between a rotation about a self-axis and a revolution of a carrier according to embodiments of the present invention. Fig. 2 is an explanatory diagram illustrating a state of change in the vicinity of a center of a workpiece (data acquisition area) with a horizontal axis defined as time and a vertical axis defined as distance from a center of a lower surface plate and an upper surface plate. Fig. 3 is a front view of a double-sided polishing apparatus according to a first embodiment of the present invention. Fig. 4 is a block diagram of a thickness measuring section in the Fig. 3 shown double-sided polishing device. Fig. 5 is a block diagram of a control unit in the Fig. 3 shown double-sided polishing device. Fig. 6 is a front view of a double-sided polishing apparatus according to a second embodiment of the present invention. Fig. 7 is a block diagram of the thickness measuring section in the Fig. 6 shown double-sided polishing device. Fig. 8 is a graph illustrating the frequency with which a scanning trajectory passes in the vicinity of the center of the workpiece (data acquisition area) according to Example 1. Fig. 9 is a graph illustrating the frequency with which a scanning trajectory passes in the vicinity of the center of the workpiece (data acquisition area) according to Example 2. Fig. 10 is a graph illustrating the frequency with which a scanning trajectory passes in the vicinity of the center of the workpiece (data acquisition area) according to Example 3. Fig. 11 is a graph showing the frequency with which a sweep trajectory passes through the vicinity of the center of the workpiece (data acquisition area) according to Example 4. Description of the Embodiments (First Embodiment)

[0012] Embodiments of the present invention will now be described in detail with reference to the drawings. Fig. 1 is an explanatory diagram showing a relationship between a rotation about its own axis and a revolution of a carrier 20 according to the first and second embodiments. Fig. 2 is an explanatory diagram illustrating a state of change in the vicinity of a center of a workpiece W (data acquisition area) with a horizontal axis defined as time and a vertical axis defined as distance from a center of a lower surface plate 13 and an upper surface plate 14. Fig. 3 is a front view of a double-sided polishing apparatus 10 according to the first embodiment of the present invention. Fig. 4 is a block diagram of a thickness measuring section 30 in the Fig. 3 shown double-sided polishing device 10. Fig. 5 is a block diagram of a control unit 40 in the Fig. 3. It should be noted that elements having the same function are designated by the same reference numeral and are not repeatedly described in all the drawings for describing the present embodiment.

[0013] In the present embodiment, an arrangement range of a thickness measuring sensor 34 will first be described with respect to a center position of a circular through-hole 22 provided in each carrier 20. When a workpiece W is disk-shaped and held in the through-hole 22 without a gap, the arrangement range may be set with respect to a center position of each workpiece W. Further, when the through-hole 22 is triangular, rectangular, square, or polygonal in shape, the arrangement range may be set with respect to a center position of a circumscribed circle of all the vertices of the through-holes 22. When a workpiece W is held in the through-hole 22 without a gap, the arrangement range may be set with respect to a center position of a circumscribed circle of all the vertices of the workpiece W.

[0014] In the present embodiment, when the workpiece W is disc-shaped, the "surroundings of the center of the workpiece W" are defined as "a region within 30% of a radius of the through-hole 22 (workpiece W)" from the center of the through-hole 22 (workpiece W). Further, in the present embodiment, when the workpiece W is triangular, rectangular, square, or polygonal, the "surroundings of the center of the workpiece W" are defined as "a region within 30% of a radius of the circumcircle of the through-hole 22 (workpiece W) from the center of the circumcircle of all vertices of the through-hole 22 (workpiece W)." Even if the workpiece W is not disc-shaped, the surroundings of the center of the workpiece W are a circular region.

[0015] Furthermore, the "data acquisition range" is a range in which thickness data should be acquired on a passing trajectory passing through this range, and is set within an arbitrary distance from the center of the workpiece W or the center of the circumscribed circle of the workpiece W depending on the purpose (hereinafter often simply referred to as "distance indicating the data acquisition range"). In the present embodiment, for example, the "data acquisition range" is defined as "a range that is within 30% of either the radius of the through hole 22 (workpiece W) or the radius of the circumscribed circle of all vertices of the through hole 22 (workpiece W) from either the center of the through hole 22 (workpiece W) or the center of the circumscribed circle of the through hole 22 (workpiece W), and in which the thickness data should be acquired via the passing trajectory of passing through this range."That is, the data acquisition range is a value preset by a user. This enables the acquisition of thickness data on the scanning trajectory of the scan through the user-preset range "near the center of the workpiece W." Furthermore, a "first distance G" to be described later is a distance that forms the basis for determining the arrangement range of a measuring port 35 and the thickness measuring sensor 34, and is preferably configured to be set in conjunction with the data acquisition range. That is, when the user specifies the data acquisition range, the first distance G is also set as a predetermined length within 30% of either the radius of the through-hole 22 (workpiece W) or the radius of the circumscribed circle of all the vertices of the through-hole 22 (workpiece W).Note that the first distance G, for example, is treated as the same distance as the distance indicating the data acquisition range according to the present embodiment. The double-sided polishing apparatus 10 according to each embodiment indicates an arrangement range in which the measuring aperture 35 and the thickness measurement sensor 34 traverse the user-preset data acquisition range at a higher frequency. More specifically, the double-sided polishing apparatus 10 according to each embodiment identifies the arrangement range in which the measuring aperture 35 and the thickness measurement sensor 34 traverse the user-preset range of "the vicinity of the center of the workpiece W" at a higher frequency.

[0016] Furthermore, in the first embodiment, the phrase "measuring port 35 and thickness measuring sensor 34 pass through the workpiece W" indicates a state in which the upper surface plate 14 or the lower surface plate 13 is rotated to pass the measuring port 35 through the workpiece W and allow the thickness measuring sensor 34 to measure the thickness or thickness distribution of the workpiece W through the measuring port 35. In a second embodiment described later, "measuring port 35 and thickness measuring sensor 34 pass through the workpiece W" indicates a state in which the upper surface plate 14 or the lower surface plate 13 is rotated to pass the measuring port 35 through the workpiece W.In the second embodiment, the measuring port 35 and the thickness measuring sensor 34 are provided at the same location in a plan view; therefore, once the measuring port 35 passes through the workpiece W, the thickness measuring sensor 34 can measure the thickness or thickness distribution of the workpiece W through the measuring port 35. (Double-sided polishing machine)

[0017] As in the Fig. 3, Fig. 4 and Fig. 5, the double-sided polishing apparatus 10 according to the present embodiment includes a main body 12 that polishes both surfaces of the workpiece W, the thickness measuring section 30 that measures time series data on the thickness of the workpiece W during polishing, and the control unit 40 that controls the cross-sectional shape measurement and a rotational speed of the carrier 20.

[0018] On the other hand, the workpiece W to be polished is a flat, plate-shaped (especially disc-shaped) workpiece W such as a wafer (e.g., a silicon wafer), and the outer diameter and thickness of the workpiece W are not limited to specific values ​​(e.g., the outer diameter may be about several cm to several tens of cm, and the thickness may be about several μm to several mm). Alternatively, the workpiece W may be a flat workpiece W (especially a triangular, rectangular, square, or polygonal workpiece W), and the dimensions and thickness of the workpiece W are not limited to specific dimensions (e.g., the diameter of the circumscribed circle of all vertices of the rectangle may be about several cm to several tens of cm, and the thickness may be about several μm to several mm).It should be noted that the circumscribed circle of the workpiece W can be regarded as a region of the workpiece W in each control by the control unit 40 to be described later and each embodiment to be described later.

[0019] The main body 12 of the double-sided polishing apparatus 10 according to the present embodiment includes, for example, the lower surface plate 13, the upper surface plate 14, an internal gear 15 disposed on the outer peripheral sides of the lower surface plate 13 and the upper surface plate 14, a sun gear 16 disposed to be rotatable between the central portions of the lower surface plate 13 and the upper surface plate 14, and the supports 20 disposed between the lower surface plate 13 and the upper surface plate 14. Furthermore, polishing pads 17, 18 are attached to the upper surface of the lower surface plate 13 and the lower surface of the upper surface plate 14, respectively.

[0020] Next, the lower surface plate 13 according to the present embodiment is formed into a circular shape in a plan view using a metallic material (e.g., a stainless alloy) and placed on a surface plate holder 26 so that the lower surface plate 13 is positioned as shown in Fig. 3. The plate holder 26 is supported on a base 52 via bearings 51. Furthermore, the surface holder 26 is designed such that it can be rotated by means of a rotary drive (e.g., an electric motor drive) 55, wherein a driving force of the rotary drive 55 is transmitted to the surface holder 26 via a power transmission gear 53 and a cylindrical shaft 54. The rotary drive of the plate holder 26 also causes the lower surface plate 13 to rotate.

[0021] Next, the upper surface plate 14 according to the present embodiment is formed into a circular shape in a plan view using a metallic material (e.g., a stainless alloy) and suspended from a disk 24 via rods 25 so that the upper surface plate 14 is formed as shown in Fig. 3. The disc 24 is supported above a suspension column 23 by a support frame 28 so that it is vertically movable and can rotate freely. The suspension column 23 is configured to be driven into vertical movement and rotation by a rotary drive (e.g., an electric motor drive) 62 and a vertical movement drive 63. The rotational drive of the suspension column 23 and the disc 24 also drives the upper surface plate 14 into rotation. It should be noted that the upper surface plate 14 and the lower surface plate 13 are rotated in opposite directions.

[0022] Furthermore, Fig. 3, the upper surface plate 14 has the measuring aperture 35 at the same position in a plan view as the thickness measuring sensor 34 described below. That is, in a plan view, a distance from the center of the upper surface plate 14 to the thickness measuring sensor 34 is equal to a distance from the center of the upper surface plate 14 to the measuring aperture 35. Since the upper surface plate 14 rotates, the thickness measuring sensor 34 and the measuring aperture 35 are designed to overlap in a preset rotation phase in a plan view. On the side of the measuring aperture 35 facing the workpiece W, a window (not shown) is provided, which is made of glass, for example.

[0023] Next, the internal gear 15 according to the present embodiment is formed on the outer peripheral side of the lower surface plate 13 using a metallic material (e.g., a stainless alloy) with an axial center of the internal gear 15 coinciding with those of the lower surface plate 13 and the upper surface plate 14, as shown in Fig. 3. The internal gear 15 is rotated by a rotary drive (e.g., an electric motor drive) 58, e.g., in a direction A, and a driving force of the rotary drive 58 is transmitted to the internal gear 15 via a power transmission gear 56 and a cylindrical shaft 57.

[0024] Subsequently, the sun gear 16 according to the present embodiment is formed by using a metallic material (e.g., a stainless alloy) at a center-side upper portion of the lower surface plate 13 and a center-side lower portion of the upper surface plate 14, wherein an axial center of the sun gear 16 coincides with those of the lower surface plate 13 and the upper surface plate 14, as shown in Fig. 3. The sun gear 16, like the inner gear 15, is rotated by a rotary drive (e.g., an electric motor drive) 61, e.g., in a direction B, wherein a driving force of the rotary drive 61 is transmitted to the sun gear 16 via a power transmission gear 59 and a cylindrical shaft 60. The number of teeth of each carrier 20, the number of teeth of the sun gear 16, the number of teeth of the ring gear 15, a speed and a rotation direction of the sun gear 16, and a speed and a rotation direction of the ring gear 15 determine a speed and a rotation direction of the carrier 20 about its own axis, and a speed and a rotation direction of the carrier 20. When the rotation speed of the internal gear 15 in direction A is set to a predetermined rotation speed that is lower than the rotation speed of the sun gear 16 in direction B, the carrier 20 revolves in a direction C and rotates around its own axis in a direction D, as shown in FIG. Fig. 1 is shown.

[0025] The carriers 20 according to the present embodiment, as shown in Fig. 1, formed from a metallic material (e.g., a stainless alloy), meshing with both the internal gear 15 and the sun gear 16, and arranged between the internal gear 15 and the sun gear 16 at certain intervals in the circumferential direction. Furthermore, each carrier 20 is provided internally with through holes 22 for receiving the workpiece W. As shown in Fig. 1, the carriers 20, together with the internal gear 15 and the sun gear 16, form a planetary gear assembly. The internal gear 15 and the sun gear 16 rotate in the same direction at different preset speeds, so that the carriers 20 rotate (orbit) around the sun gear 16 and rotate about their own axes. Furthermore, the lower surface plate 13 and the upper surface plate 14 rotate in opposite directions, whereby the polishing wheels 17, 18 slide on the surfaces of the individual workpieces W. While, in the present embodiment, five carriers 20, each with three through holes 22, are arranged between the internal gear 15 and the sun gear 16, the configuration is not limited to this. Furthermore, the through holes 22 are provided at positions eccentric to the center of each carrier 20.Furthermore, the structure of the carrier 20 is not limited to that in which the carriers 20 are engaged with the internal gear 15 and the sun gear 16.

[0026] Next, the control unit 40 according to the present embodiment is equipped with a CPU and a memory, and operates based on a preset operation program and setting signals input from an operating section. The following describes the control for setting the rotational speeds of the carrier 20 and the lower and upper surface plates 13, 14, respectively. A rotation control unit 43 corresponds to the CPU. Further, a storage section 41 corresponds to the memory. In the storage section 41, coordinates of the passing trajectory of the measuring aperture 35 and a distance of the measuring aperture 35 from a center of each through-hole 22 (workpiece W) during polishing (hereinafter often simply referred to as "pre-data") are stored.The rotation control unit 43 is configured to control the rotation speeds (number of revolutions) of the rotary actuators 58, 61 via an output section 44 so that the rotation speed (number of revolutions) of the carrier 20 decreases when the measuring aperture 35 passes through the vicinity of the center of the workpiece W (data acquisition area) and the thickness measurement sensor 34 can detect the thickness or thickness distribution of the workpiece W through the measuring aperture 35. That is, the control unit 40 is configured to adjust the internal gear 15 and / or the sun gear 16 (including decreasing, maintaining, and increasing the speed) to reduce the rotation speed (number of revolutions) of the carrier 20.Furthermore, the rotation control unit 43 can be configured to control the rotation speeds (number of revolutions) of the rotary actuators 55, 62 via the output section 44 so as to decelerate the upper surface plate 14 or the lower surface plate 13 on which the measuring opening 35 is located in the above case. That is, the control unit 40 is configured to reduce the rotation speed (number of revolutions) of the upper surface plate 14 or the lower surface plate 13 on which the measuring opening 35 is provided. By decelerating the carrier 20 or the upper and / or lower surface plates 13, 14, the thickness or thickness distribution can be correctly and precisely detected. In addition, the measurement interval for measuring the pass trajectory of the pass in the vicinity of the center of the workpiece W (data acquisition area) can be reduced, enabling the detection of the high-precision thickness distribution.When the workpiece W is a triangular, rectangular, square, or polygonal flat workpiece W, the storage section 41 may be configured to store the coordinates of the passing trajectory of the measuring hole 35 and the distance of the measuring hole 35 from the center of the circumference of all the vertices of the through hole 22 (workpiece W). That is, the control unit 40 may be configured to reduce the rotation speeds (number of revolutions) of the carrier 20 and the surface plate 13, 14 when the measuring hole 35 passes through the vicinity of the center of the workpiece W (data acquisition area) and the measuring hole 35 or the thickness gauge 34 passes through the area of ​​the circumscribed circle.

[0027] Furthermore, according to the present embodiment, the main body 12 is equipped with a slurry supply device (not shown) that supplies slurry. With this configuration, the supply (including non-supply) of the slurry during machining processes can be appropriately adjusted depending on a material and machining conditions of the workpiece W.

[0028] Furthermore, the base body 12 may be configured, for example, with a known carrier detection sensor (not shown) in the measuring port 35. With this configuration, it is possible to detect the carriers 20 during polishing and to detect a time at which the thickness measuring sensor 34 passes an actual measurement boundary portion between each carrier 20 and the workpiece W. Furthermore, even if a slurry film has formed on the carrier 20, the carrier 20 is detected, and it can be determined that the thickness is a thickness of the slurry on the carrier 20.

[0029] As it is in Fig. 4, the thickness measuring section 30 according to the present embodiment is equipped with, for example, a laser light source 31, a circulator 32, a laser sensor (e.g., a probe) 34 serving as a thickness measuring sensor 34, a photodiode 36, and a data collector 37. Note that the thickness measuring sensor (probe) 34 is arranged at a position opposite to the upper surface plate 14 (i.e., a fixed position) on the support frame 28. That is, in the present embodiment, the thickness measuring sensor (probe) 34 is fixedly connected to the support frame 28 and therefore does not rotate together with the upper surface plate 14 or the lower surface plate 13. The thickness measuring sensor 34 fixed to the support frame 28 can detect the thickness of the workpiece W unaffected by rotations and vibrations of the upper and lower surface plates 13, 14, respectively.During polishing, laser light is emitted from the laser light source 31 through the measurement aperture 35 onto the workpiece W, and is reflected by a front surface of the window, a back surface of the window, the front surface of the workpiece W, and the back surface of the workpiece W. Interference light from the front and back surfaces of the workpiece W is observed as electrical signals (hereinafter referred to as "interference light signals") under this reflected light, enabling the acquisition of time-series data on the thickness of the workpiece W. The time-series thickness data is output to a thickness calculation section 42 described below. Arrangement positions of the measurement aperture 35 and the thickness measuring sensor 34 are described in detail in (Arrangement Range of Thickness Measuring Sensor).

[0030] Note that the measuring port 35 may be disposed on the lower surface plate 13 (not shown). In this case, the thickness measuring sensor 34 is disposed at a position opposite to the lower surface plate 13 on the support frame (not shown) closer to the lower surface plate 13. Furthermore, the thickness measuring sensor 34 and the measuring port 35 overlap in a predetermined rotation phase in a plan view because the lower surface plate 13 rotates.

[0031] Furthermore, the thickness measuring section 30 is not limited to a laser light version. As another example, a scattered light source or an ultrasonic source can be used as an alternative to the laser light source, and the thickness measuring sensor 34 can be a photoelectric sensor or an ultrasonic sensor. When the ultrasonic sensor is used, the thickness of the workpiece W can be measured without being affected by the material and color of the workpiece W, compared to cases where the laser sensor and the photoelectric sensor are used.

[0032] Next, the control for detecting the thickness of the workpiece W will be described. The thickness calculation section 42 corresponds to the CPU of the control unit 40. By linking the preliminary data read from the storage section 41 with the thickness time series data, the thickness calculation section 42 can detect the thickness distribution of the workpiece W per pass trajectory. (Arrangement area of ​​the thickness measuring sensor)

[0033] The main body 12, the thickness measuring section 30, and the control unit 40 of the double-sided polishing machine 10 described above can polish the two surfaces of the workpiece W and detect the thickness of the workpiece W. The arrangement range of the measuring port 35 and the thickness measuring sensor 34 according to the present embodiment will be described below. The center of the workpiece W and the vicinity of the center of the workpiece W (data detection range) are actually like a complicated trajectory such as a trochoid curve. In the present embodiment, the residence time in the center of the workpiece W and the vicinity of the center of the workpiece W (data detection range) can be observed at each position. A horizontal axis is defined as time, and a vertical axis is defined as the distance from the center of the lower surface plate 13 or the upper surface plate 14.In this case, if the carrier 20 rotates around its own axis at a constant speed, a trajectory of the center of the workpiece W is one in . Fig. 2. In addition, a trajectory of the vicinity of the center of the workpiece W (data acquisition area) is a Fig. 2. As a result of a special study by the inventors, it was found that the residence time of the center of the workpiece W was the longest when the center of the workpiece W arrived at an innermost circumference and an outermost circumference (ie, vertices of a sine wave) of the lower surface plate 13 and the upper surface plate 14, as shown in Fig. 2. In contrast, it was found that the residence time in the vicinity of the center of the workpiece W (data acquisition area) was the longest when the center of the workpiece W arrived in the vicinity of the inside of each vertex of the sine curve.

[0034] Taking advantage of the characteristics of the trajectory of the vicinity of the center of the workpiece W (data acquisition area), the inventors investigated the following areas as the arrangement positions of the measuring port 35 and the thickness measuring sensor 34.

[0035] The inventors have provided the following configurations as the arrangement range of the measuring port 35 and the thickness gauge sensor 34 according to the present embodiment (hereinafter often simply referred to as the "first range"). First, there are the shortest and longest distances between the center of the lower surface plate 13 and the upper surface plate 14 and the center of one of the user-preset through holes 22 (i.e., the workpiece W) and the center of the circumscribed circle of all the vertices of one of the user-preset through holes 22 (workpiece W), respectively. The center position of the through hole 22 (workpiece W) or the center position of the circumscribed circle of all the vertices of the through hole 22 (workpiece W) at the position (hereinafter often simply referred to as the "first reference position E") is set as the reference.Note that the user sets the first distance G, which is a predetermined length within 30% of the radius of the through-hole 22 (workpiece W) or the radius of the circumscribed circle of all the vertices of the through-hole 22 (workpiece W), to correspond to the data acquisition range. Furthermore, a position away from the first reference position E by half the first distance G toward the center of the carrier 20 (rotation center) (hereinafter often simply referred to as the "second reference position F") is set as a reference. With the second reference position F as the center, the measuring port 35 and the thickness gauge sensor 34 are arranged within a range of the first distance G. More specifically, the measuring port 35 is provided on the upper surface plate 14 or the lower surface plate 13 so as to fall within the first range in a plan view.Furthermore, the thickness measuring sensor 34 is arranged on the support frame 28 to fall into the first area in a plan view.

[0036] This can increase the frequency with which the measuring port 35 and the thickness measuring sensor 34 pass through the data acquisition range set by the user.

[0037] Further, the center position of the through hole 22 (workpiece W) or the center position of the circumference of all the vertices of the through hole 22 (workpiece W) at which the distance between the center of the upper surface plate 14 or the lower surface plate 13 and the center of the through hole 22 (workpiece W) or the center of the circumference of the through hole 22 is the smallest is preferably set as the first reference position E. The measuring port 35 and the thickness measuring sensor 34 may be arranged on the inner peripheral side of the upper surface plate 14 or the lower surface plate 13, whereby the passing speed (circumferential speed) of the measuring port 35 when passing through the measuring port 35 on the workpiece W is lower than in the case where the measuring port 35 and the thickness measuring sensor 34 are arranged on an outer peripheral side of the upper surface plate 14 or the lower surface plate 13.Thus, the thickness of the workpiece W can be measured correctly and precisely. Furthermore, the measuring interval for measuring the thickness of the workpiece W becomes smaller, enabling the detection of the highly accurate thickness distribution. (Second embodiment)

[0038] A second embodiment of the present invention will be described below, focusing mainly on the differences from the first embodiment. The double-sided polishing apparatus 10 according to the second embodiment has the features shown in Fig. 6 and Fig. 7, which differ from the configurations of the double-sided polishing apparatus 10 according to the first embodiment. That is, the thickness measuring sensor (probe) 34 is provided at the measuring opening 35 of the upper surface plate 14 or the lower surface plate 13. It should be noted that in the Fig. 6 and Fig. 7 illustrates a case where the thickness measuring sensor (probe) 34 is provided at the measuring opening 35 of the upper surface plate 14. In the first embodiment, the thickness measuring sensor (probe) 34 is arranged on the support frame 28 and thus fixed. In contrast, in the present embodiment, the thickness measuring sensor (probe) 34 is designed to rotate together with the upper surface plate 14 or the lower surface plate 13 (i.e., the thickness measuring sensor (probe) 34 is arranged at a movable position). Furthermore, the control unit 40 is also connected to the rotary drive 62, even if the rotary drive 62 and the vertical movement drive 63 are in Fig. 6 are not shown.

[0039] The measuring hole 35 and the thickness measuring sensor 34 according to the present embodiment can be provided in a similar area in a plan view as the area according to the first embodiment. More specifically, the measuring hole 35 and the thickness measuring sensor 34 are provided on the upper surface plate 14 or the lower surface plate 13 to be located in the first area in a plan view. Further, the center position of the through hole 22 (workpiece W) at which the distance between the center of the upper surface plate 14 or the lower surface plate 13 and the center of the through hole 22 (workpiece W) is the smallest is preferably set as the first reference position E.

[0040] It should be noted that the thickness measuring section 30 according to the present embodiment is provided with a rotary joint 33 as shown in Fig. 7, since the thickness measuring sensor 34 rotates together with the upper surface plate 14 or the lower surface plate 13, in contrast to the first embodiment.

[0041] The control unit 40 is configured to reduce the rotational speed of the carrier 20 when the measuring aperture 35 or the thickness measurement sensor 34 passes through the vicinity of the center of the workpiece W (data acquisition area) during actual polishing. That is, the control unit 40 is configured to adjust the rotational speed (number of revolutions) of the internal gear 15 and / or the sun gear 16 to reduce the rotational speed of the carrier 20. Furthermore, the control unit 40 may be configured to decelerate the upper surface plate 14 or the lower surface plate 13 on which the measuring aperture 35 is disposed. By decelerating the carrier 20 or the surface plates 13 and / or the surface plates 14, the thickness or thickness distribution can be accurately and precisely detected.Furthermore, the measurement interval for measuring the pass trajectory of the pass in the vicinity of the center of the workpiece W (data acquisition area) can be reduced, enabling the detection of the high-precision thickness distribution. In the second embodiment, unlike the first embodiment, the thickness measurement sensor 34 rotates together with the upper surface plate 14 or the lower surface plate 13. Therefore, every time the measurement port 35 or the thickness measurement sensor 34 passes the vicinity of the center of the workpiece W (data acquisition area), the thickness or thickness distribution of the workpiece W can be detected.When the workpiece W is a triangular, rectangular, square, or polygonal flat workpiece W, the storage section 41 may be configured to store the coordinates of the passing trajectory of the measuring hole 35 and the distance of the measuring hole 35 from the center of the circumference of all the vertices of the through hole 22 (workpiece W) during polishing in the second embodiment, as in the first embodiment. That is, the control unit 40 may be configured to reduce the rotation speeds (number of revolutions) of the carrier 20 and the upper and lower surface plates 13, 14, respectively, when the measuring hole 35 or the thickness measuring sensor 34 passes around the center of the workpiece W (data acquisition area) and the measuring hole 35 or the thickness measuring sensor 34 passes through the area of ​​the circumscribed circle. [Examples](Simulation methods)

[0042] Based on the configurations of the double-sided polishing machine 10 according to the second embodiment, a simulation was performed to calculate the sweep frequency at which the measuring port 35 and the thickness measuring sensor 34 sweep around the vicinity of the center of the workpiece W (data acquisition area) at each arrangement position of the measuring port 35 and the thickness measuring sensor 34. The first reference position E, at which the distance between the center of the through-hole 22 (workpiece W) and the center of the lower surface plate 13 and the upper surface plate 14 was the smallest, was set to the zero point at the arrangement position of the measuring port 35 and the thickness measuring sensor 34. Based on the arrangement positions of the measuring port 35 and the thickness measuring sensor 34 at preset intervals, the number of times the measuring port 35 and the thickness measuring sensor 34 sweep around the vicinity of the center of the workpiece W (data acquisition area) was counted. Fig. In the results shown, the vertical axis indicates the pass frequency of the thickness gauge sensor 34, with a value set to one for the maximum number of passes. Universal numerical calculation software was used for the simulation. Furthermore, the simulation conditions were set as described later. (Example 1)

[0043] The outer diameter of the workpiece W was φ = 200 mm, and the three through holes 22 provided in a support 20 were symmetrically arranged in the center of the support 20. The center of the workpiece W was offset by 140 mm from the center of the support 20. The distance between the center of the support 20 and the center of the lower surface plate 13 and the upper surface plate 14 was set to 460 mm. That is, the distance between the center of the workpiece W and the center of the lower surface plate 13 and the upper surface plate 14 was 320 mm when the workpiece W was located on the innermost circumference, while the distance between the center of the workpiece W and the center of the lower surface plate 13 and the upper surface plate 14 was 600 mm when the workpiece W was located on the outermost circumference.

[0044] It was determined that, while the internal gear 15 rotates at 5.5 rpm in direction A and the sun gear 16 rotates at 17 rpm in direction B, the carrier 20 orbits the center of the lower surface plate 13 and the upper surface plate 14 at a rotational speed of approximately 8 rpm in direction C and rotates around its own axis at a rotational speed of approximately 1 rpm in direction D. Furthermore, it was determined that the surface plate 13, 14 on which the sensor was mounted rotated at 12 rpm (at a relative speed of 20 rpm to the speed of the carrier 20) in the direction opposite to the rotational direction of the carrier 20. This simulation assumed that the rotations were transmitted without the influence of backlash or the like.

[0045] In addition, the rotational speeds of the internal gear 15, the sun gear 16, and the upper and lower surface plates 13, 14 vary depending on the polishing stage during actual polishing. However, Example 1 refers to the simulation, and the rotational speeds are all constant. That is, the simulation according to the present example was performed under the assumption that the carrier 20 orbits or rotates at constant speeds and the upper and lower surface plates 13, 14 rotate at the constant speed.

[0046] In the simulation, each carrier 20 was rotated at a constant speed from an arbitrary initial state (any initial state of any phase of each carrier 20 can be used), and the number of times the measuring port 35 and the thickness gauge 34 passed through the vicinity of the center of the workpiece W (data acquisition area) within five minutes was counted. The vicinity of the center of the workpiece W (data acquisition area) in this example was set to 10 mm from the center of the through hole 22 (workpiece W) (correspondingly, within 10% of the radius of the through hole 22 (workpiece W)). The first distance G was also set to 10 mm. (Simulation result 1)

[0047] Fig. Figure 8 shows a result. The first reference position E is located where the arrangement position x of the thickness measuring sensor is between 0 mm and 280 mm. The second reference position F is located where the arrangement position x of the thickness measuring sensor is between 5 mm and 275 mm. The first range is -5 mm ≤ x ≤ 15 mm and 265 mm ≤ x ≤ 285 mm (corresponding to the shaded areas in Fig. 8). As it is in Fig. 8, it was confirmed that in each first region, the sweep frequency had its peak value in the vicinity of a position which is the first distance G from the first reference position E to the center of the carrier 20. As shown in Fig. 8, it was also confirmed that the sweep frequency decreased from each peak toward the center of the beam 20 and converged to a constant value (hereinafter often referred to simply as the "convergence value"). That is, the sweep frequency varied in the shape of a bathtub curve between the peaks. It was further confirmed that the sweep frequency of the thickness gauge sensor 34 monotonically decreased from each peak to the outside of the beam 20. The first regions each included the peak value, and the sweep frequency was higher than the convergence value in the bathtub curve. Therefore, when the thickness gauge sensor 34 was arranged in the first region, a sweep frequency higher than the convergence value can be obtained.In order to make the sweep frequency highest in the vicinity of the center of the workpiece W (data acquisition area) when the distance indicating the data acquisition area was equal to the first distance G, it was confirmed that the thickness measuring sensor 34 could be arranged in the vicinity of the position separated by the first distance G from the first reference position E to the center of the carrier 20. (Example 2)

[0048] Subsequently, a simulation was performed in which the data acquisition range was set to 30 mm from the center of the through hole 22 (workpiece W) (corresponding to within 30% of the radius of the through hole 22 (workpiece W)) under similar conditions as in Example 1. The first distance G was also set to 30 mm. (Simulation result 2)

[0049] Fig. Figure 9 illustrates a result. The first reference position E is located where the arrangement position x of the thickness measuring sensor is 0 mm and 280 mm. The second reference position F is located where the arrangement position x of the thickness measuring sensor is 15 mm and 265 mm. The first range is -15 mm ≤ x ≤ 45 mm and 235 mm ≤ x ≤ 295 mm (which corresponds to the shaded areas in Fig. 9). As in Example 1, it was confirmed that in each first region, the sweep frequency peaks in the vicinity of a position which is the first distance G from the first reference position E to the center of the carrier 20. As shown in Fig. 9, it was also confirmed that the sweep frequency decreases from each peak toward the center of the beam 20 and converges to the convergence value, and that the sweep frequency varies in the bathtub curve region between the peaks. It was further confirmed that the sweep frequency of the thickness gauge sensor 34 monotonically decreases from each peak toward the outside of the beam 20. The first regions each included the peak, and the sweep frequency was higher than the convergence value in the bathtub curve. Therefore, by disposing the thickness gauge sensor 34 in the first region, a higher sweep frequency than the convergence value can be achieved.Furthermore, in Example 2, as in Example 1, it was confirmed that the thickness measuring sensor 34 can be arranged in the vicinity of the position separated by the first distance G from the first reference position E to the center of the carrier 20 to make the sweep frequency highest in the vicinity of the center of the workpiece W (data acquisition range) when the distance indicating the data acquisition range is equal to the first distance G. From the simulation results of Examples 1 and 2, it is estimated that for the workpiece W at φ 200mm, a conspicuous effect can be achieved in a range from the second reference position F to the first distance G, regardless of the vicinity of the center of the workpiece W (data acquisition range). (Example 3)

[0050] Subsequently, the outer diameter of the workpiece W was set to φ = 75 mm. The center of the workpiece W was set at a distance of 53 mm from the center of the carrier 20. The distance between the center of the carrier and the center of the lower surface plate 13 and the upper surface plate 14 was set to 220 mm. That is, the distance between the center of the workpiece W and the center of the lower surface plate 13 and the upper surface plate 14 was 167 mm when the workpiece W was located on the innermost circumference, while the distance between the center of the workpiece W and the center of the lower surface plate 13 and the upper surface plate 14 was 273 mm when the workpiece W was located on the outermost circumference.

[0051] It was also determined that the carrier 20 rotates around its own axis at a rotational speed of approximately 8 revolutions per minute and at a rotational speed of approximately 1 revolution per minute when the internal gear 15 rotates at 5.4 revolutions per minute and the sun gear 16 rotates at 15 revolutions per minute.

[0052] The vicinity of the center of the workpiece W (data acquisition area) was set to 5 mm from the center of the through hole 22 (workpiece W) (corresponding to within 14% of the radius of the through hole 22 (workpiece W)). The first distance G was also set to 5 mm.

[0053] The other simulation conditions are also similar to those in Examples 1 and 2. (Simulation result 3)

[0054] Fig. Figure 10 illustrates a result. The first reference position E is located where the arrangement position x of the thickness measuring sensor is 0 mm and 106 mm. The second reference position F is located where the arrangement position x of the thickness measuring sensor is 2.5 mm and 103.5 mm. The first range is -2.5 mm ≤ x ≤ 7.5 mm and 98.5 mm ≤ x ≤ 108.5 mm (which corresponds to the shaded areas in Fig. 10). As in Examples 1 and 2, it was confirmed that in each first region, the sweep frequency reached its peak in the vicinity of a position spaced by the first distance G from the first reference position E to the center of the beam 20. It was also confirmed that the sweep frequency decreased from each peak toward the center of the beam 20 and converged to the convergence value, and that the sweep frequency varied in the bathtub curve region between the peaks. It was further confirmed that the sweep frequency of the thickness gauge sensor 34 decreased monotonically from each peak toward the outside of the beam 20. The first regions each included the peak, and the sweep frequency was higher than the convergence value in the bathtub curve. Therefore, by disposing the thickness gauge sensor 34 in the first region, a sweep frequency higher than the convergence value can be achieved.Moreover, in Example 3, as in Examples 1 and 2, it was confirmed that the thickness measuring sensor 34 can be arranged in the vicinity of the position separated by the first distance G from the first reference position E to the center of the carrier 20 to make the sweep frequency highest in the vicinity of the center of the workpiece W (data acquisition area) when the distance indicating the data acquisition area was equal to the first distance G. (Example 4)

[0055] Subsequently, a simulation was performed in a case where the first distance G was set to 10 mm when the data acquisition range was set to 10 mm from the center of the through hole 22 (workpiece W) (corresponding to within 27% of the radius of the through hole 22 (workpiece W)) under similar conditions as in Example 3. (Simulation result 4)

[0056] Fig. Figure 11 illustrates a result. The first reference position E is located where the arrangement position x of the thickness measuring sensor is 0 mm and 106 mm. The second reference position F is located where the arrangement position of the thickness measuring sensor is 5 mm and 101 mm. The first range is -5 mm ≤ x ≤ 15 mm and 91 mm ≤ x ≤ 111 mm (corresponds to the shaded areas in Fig.11). As in Examples 1 to 3, it was confirmed that in each first region, the sweep frequency peaks in the vicinity of a position spaced by the first distance G from the first reference position E to the center of the beam 20. It was also confirmed that the sweep frequency decreases from each peak toward the center of the beam 20 and converges to the convergence value, and that the sweep frequency varies in the bathtub curve region between the peaks. It was further confirmed that the sweep frequency of the thickness gauge sensor 34 monotonically decreases from each peak toward the outside of the beam 20. The first regions each included the peak, and the sweep frequency was higher than the convergence value in the bathtub curve. Therefore, by disposing the thickness gauge sensor 34 in the first region, a sweep frequency higher than the convergence value can be achieved.Furthermore, in Example 4, as in Examples 1 to 3, it was confirmed that the thickness measuring sensor 34 can be arranged in the vicinity of the position separated by the first distance G from the first reference position E to the center of the carrier 20 to make the sweep frequency highest in the vicinity of the center of the workpiece W (data acquisition area) when the distance indicating the data acquisition area is equal to the first distance G. From the simulation results of Examples 1 and 4, it is estimated that a similar effect can be achieved if the first distance G is set within 30% of the radius of the workpiece W (e.g., equal to the distance indicating the data acquisition area), regardless of the diameter of the through hole 22 (workpiece W). It is assumed that for the workpiece W with a diameter of, for example,φ 300 and φ 400, a similar effect can be achieved when the thickness measuring sensor 34 is arranged in the first region. It is also preferable to set the first distance G to satisfy (2 / 3 of the distance indicating the data acquisition range)≤(First distance G)≤(Distance indicating the data acquisition range). This is because the first region always includes the peak of the sweep frequency of the thickness measuring sensor 34, and the measuring port 35 or the thickness measuring sensor 34 can be arranged in the region where the sweep frequency falling within the first region is higher.

[0057] The simulation results have already been described. It is assumed that actual polishing (the rotational speed of the carrier 20 is not constant) has a similar effect (the passing frequency of each position can be achieved within five minutes, despite the different passing frequency, in a similar trend to Examples 1 to 4). To make the passing frequency highest in the vicinity of the center of the workpiece W (data acquisition area), when the distance indicating the data acquisition area is equal to the first distance G, the thickness measuring sensor 34 can be arranged in the vicinity of the position separated by the first distance G from the first reference position E to the center of the carrier 20. Furthermore, in the present simulations, it was assumed that the thickness measuring sensor 34 is provided on the upper surface plate 14.A similar effect can be achieved even when the thickness measuring sensor 34 is arranged on the support frame 28 (that is, the thickness measuring sensor 34 is located at the fixed position). Furthermore, even when the workpiece W is a triangular, rectangular, square, or polygonal flat workpiece W, the circumference of all vertices of the workpiece W can be regarded as the range of the workpiece W, and the first distance G and the first range can be set based on the radius and the central position of the circumference. In this case, it is estimated that a similar effect to that of the disk-shaped workpiece W (Examples 1 to 4) can be achieved.Furthermore, when the workpiece W is a triangular, rectangular, square, or polygonal flat workpiece W, an inscribed circle of the shape (a predetermined inscribed circle for the rectangle) can be regarded as the area of ​​the workpiece W, and the first distance G and the first area can be set based on a radius and a center position of the inscribed circle. In this case, a similar effect to that of the disc-shaped workpiece W (Examples 1 to 4) can be achieved.

[0058] The present invention is not limited to the embodiments described so far and can be changed and modified in various ways without departing from the present invention. For example, the thickness measuring sensor 34 may be arranged at a fixed position at a location other than the support frame 28, the upper surface plate 14, and the lower surface plate 13. Specifically, the thickness measuring sensor 34 may be designed to be arranged at the fixed position in a predetermined space between the upper surface plate 14 or the lower surface plate 13 and the support frame 28. Alternatively, the thickness measuring sensor 34 may be designed to be rotatably arranged in a predetermined space between the upper surface plate 14 or the lower surface plate 13 and the support frame 28.More specifically, the thickness measuring sensor 34 may be configured to be provided in a predetermined space between the upper surface plate 14 or the lower surface plate 13 and the support frame 28 and provided on a rotating member (not shown) that rotates synchronously with the upper surface plate 14 or the lower surface plate 13.

Claims

[1] Double-sided polishing device (10), comprising: a lower surface plate (13); an upper surface plate (14); and a carrier (20) arranged between the lower surface plate (13) and the upper surface plate (14) and holding at least one disc-shaped workpiece (W), wherein the carrier (20) is designed to rotate about a center of the lower surface plate (13), a center of the upper surface plate (14) and a center of the carrier (20), the double-sided polishing device comprises a thickness measuring sensor (34) at a fixed position above the upper surface plate (14) or below the lower surface plate (13) or at a movable position in an upper portion of the upper surface plate (14) or a lower portion of the lower surface plate (13), the support (20) comprises circular through holes (22) each holding the workpiece (W) at a position eccentric to the center of the support (20), when a central position of one of the through holes (22) preset by a user is defined as a first reference position (E), wherein a distance between a center of the upper surface plate (14) or the lower surface plate (13) and a center of one of the through holes (22) preset by the user is the shortest or the longest, a position which is away from the first reference position (E) by half a first distance (G) towards the center of the carrier is defined as a second reference position (F), wherein the first distance (G) is a predetermined length within 30% of a radius of the through hole (22), the thickness measuring sensor (34) is arranged in a region in a plan view of the first distance (G) around the second reference position (F), and the thickness measuring sensor (34) is designed to measure a thickness of the workpiece (W) in a state in which the workpiece (W) is held in the through hole (22) through a measuring hole (35) located in the upper surface plate (14) or the lower surface plate (13) closer to a side on which the thickness measuring sensor (34) is arranged. [2] The double-sided polishing apparatus (10) according to claim 1, wherein the center position of the through-hole (22) at which a distance between the center of the upper surface plate (14) or the lower surface plate (13) and the center of the through-hole (22) is the smallest is set as the first reference position (E). [3] A double-sided polishing device (10) according to claim 1, further comprising: a control unit (40), wherein the control unit (40) is designed such that when a passage trajectory of the measuring opening (35) or the thickness measuring sensor (34) of the passage through the workpiece (W) lies within a predetermined range from the center of the through hole (22) and traverses a data acquisition range preset by the user, the control unit (40) reduces a rotational speed of the carrier (20) corresponding to the passage trajectory so that it is lower than a rotational speed of the carrier (20) corresponding to the other passage trajectory. [4] Double-sided polishing device (10) according to one of claims 1 to 3, wherein the thickness measuring sensor (34) is designed so that at the fixed position, the thickness measuring sensor (34) is arranged on a support frame (28) located above the upper surface plate (14) or below the lower surface plate (13), and measures a thickness of the workpiece (W) in a state in which it is held by the measuring opening (35) in the through hole (22), or is designed so that at the movable position the thickness measuring sensor (34) is arranged on the upper surface plate (14) or the lower surface plate (13) to rotate together with the upper surface plate (14) or the lower surface plate (13), and measures the thickness of the workpiece (W) in the state in which it is held in the through hole (22) through the measuring opening (35). [5] Double-sided polishing device (10), comprising: a lower surface plate (13); an upper surface plate (14); and a carrier (20) arranged between the lower surface plate (13) and the upper surface plate (14) and holding at least one of a triangular, a rectangular, a square, and a polygonal flat plate workpiece (W), wherein the carrier (20) is designed to rotate about a center of the lower surface plate (13), a center of the upper surface plate (14) and a center of the carrier (20), the double-sided polishing device comprises a thickness measuring sensor (34) at a fixed position above the upper surface plate (14) or below the lower surface plate (13) or at a movable position in an upper portion of the upper surface plate (14) or a lower portion of the lower surface plate (13), the support (20) comprises through holes (22) each holding the workpiece (W) at a position eccentric to the center of the support (20) and each having an identical shape to the workpiece (W), when a user-preset central position of one of the through-holes (22) is defined as a first reference position (E), wherein a distance between a center of the upper surface plate (14) or the lower surface plate (13) and a center of a circumcircle of all user-preset vertices of the through-holes (22) is the shortest or the longest, a position which is away from the first reference position (E) by half a first distance (G) towards the center of the carrier (20) is defined as a second reference position (F), the first distance (G) being a predetermined length within 30% of a radius of the circumscribed circle, the thickness measuring sensor (34) is arranged in a plan view in a region of the first distance (G) around the second reference position (F), and the thickness measuring sensor (34) is designed to measure a thickness of the workpiece (W) in a state in which the workpiece (W) is held in the through hole (22) through a measuring hole (35) located on the upper surface plate (14) or the lower surface plate (13) closer to a side on which the thickness measuring sensor (34) is arranged. [6] Double-sided polishing apparatus (10) according to claim 5, wherein the first reference position (E) is set to the central position of the circumscribed circle at which the distance between the center of the upper surface plate (14) or the lower surface plate (13) and the center of the circumscribed circle is the smallest. [7] A double-sided polishing device (10) according to claim 5, further comprising: a control unit (40), wherein the control unit (40) is designed so that when a passage trajectory of the measuring opening (35) or the thickness measuring sensor (34) when passing through the workpiece (W) lies within a predetermined range from the center of the circumscribed circle and passes through a data acquisition range preset by the user, the control unit (40) reduces a rotational speed of the carrier (20) corresponding to the passage trajectory so that it is lower than a rotational speed of the carrier (20) corresponding to the other passage trajectory. [8] Double-sided polishing device (10) according to one of claims 5 to 7, wherein the thickness measuring sensor (34) is designed so that at the fixed position, the thickness measuring sensor (34) is arranged on a support frame (28) located above the upper surface plate (14) or below the lower surface plate (13), and measures a thickness of the workpiece (W) in a state in which it is held by the measuring opening (35) in the through hole (22), or designed so that at the movable position the thickness measuring sensor (34) is arranged on the upper surface plate (14) or the lower surface plate (13) to rotate together with the upper surface plate (14) or the lower surface plate (13), and measures the thickness of the workpiece (W) in the state of being held in the through hole (22) through the measuring opening (35).

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