Grinding device, program, non-transitory recording medium, and grinding device control method

Abstract

To provide a grinding device allowing an operator to easily confirm a sign of a failure of a non-contact thickness measurement unit.SOLUTION: A grinding apparatus includes a control unit configured to control a non-contact thickness measurement unit, etc. in accordance with a program stored in a storage device. The program causes the control unit to perform the steps of: positioning a light-projecting unit and a light-receiving unit of the non-contact thickness measurement unit at a reference plate measurement position; causing the light-receiving unit to receive light projected by the light-projecting unit at the reference plate measurement position and reflected by a reference plate, and causing an output unit to output received- light amount information; comparing the received-light amount information output from the output unit with reference received-light amount information stored in the storage device to determine whether or not an amount of light received by the light-receiving unit satisfies a reference; and, when determining that the amount of light received by the light-receiving unit does not satisfy the reference, outputting information on that determination to the notification device.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a grinding device used when grinding a workpiece such as a wafer, a program used to control the grinding device, a non-transitory recording medium on which the program is stored, and a method for controlling the grinding device. [Background technology]

[0002] In order to realize small and lightweight device chips, there are increasing opportunities to thin wafers having devices such as integrated circuits on their front side. For example, the front side of the wafer is held by the holding surface of a chuck table, and the chuck table and a grinding wheel with a grinding stone containing abrasive grains fixed thereto are rotated relative to each other, and the grinding stone is pressed against the back side of the wafer while a liquid such as pure water is supplied, thereby grinding the wafer to thin it.

[0003] When grinding a plate-shaped workpiece such as a wafer to reduce its thickness, it is important to properly control the workpiece's thickness during grinding. However, the surface of the workpiece has irregularities caused by the device, and to protect this device, a protective resin tape with large individual thickness variations is attached. Therefore, a contact-type thickness measurement unit that measures the height difference by contacting both the back surface (top surface) of the workpiece and the holding surface of the chuck table does not necessarily achieve high measurement accuracy.

[0004] Therefore, when it is necessary to grind a workpiece while measuring its thickness with high precision, a grinding device equipped with a non-contact thickness measurement unit (hereinafter referred to as the non-contact thickness measurement unit) is used, which measures the thickness of the workpiece without contact by utilizing the interference of light reflected from the back surface (top surface) and front surface (bottom surface) of the workpiece (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-209951 Summary of the Invention [Problem to be solved by the invention]

[0006] However, for non-contact thickness measurement units that require high-precision measurements, high requirements are also placed on the measurement conditions, and if the amount of light received by the sensor is insufficient due to, for example, the adhesion of dirt or deterioration of the light source, the non-contact thickness measurement unit will be unable to measure the thickness of the workpiece.If the non-contact thickness measurement unit is unable to measure the thickness of the workpiece, the grinding device will also be unable to proceed with grinding the workpiece.

[0007] When a malfunction occurs in the non-contact thickness measurement unit, maintenance (cleaning, repair, replacement, etc.) is performed. However, since the non-contact thickness measurement unit is precisely constructed and maintenance requires a long time, once a malfunction occurs in the non-contact thickness measurement unit, the productivity of the grinding machine drops significantly.

[0008] Therefore, an object of the present invention is to provide a grinding device etc. that allows an operator of the grinding device to easily check for signs of a malfunction in the non-contact thickness measurement unit before a malfunction that makes it impossible to measure the thickness of the workpiece occurs. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a non-contact thickness measurement unit having a holding surface for holding a plate-shaped workpiece, the non-contact thickness measurement unit including: a chuck table having a holding surface for holding a plate-shaped workpiece and rotatable about a rotation axis intersecting the holding surface; a grinding unit having a spindle that can rotate about an axis with a grinding wheel attached to its tip; a light-projecting unit that projects light directed downward; a light-receiving unit that receives light directed upward; and an output unit that outputs light-receiving amount information regarding the amount of light received by the light-receiving unit, the non-contact thickness measurement unit being used when measuring the thickness of the workpiece held on the holding surface of the chuck table in a non-contact manner; a reference plate that is used when determining the state of the non-contact thickness measurement unit; and a movement mechanism that moves the light-projecting unit and the light-receiving unit of the non-contact thickness measurement unit between a workpiece measurement position above the workpiece held on the holding surface of the chuck table and a reference plate measurement position above the reference plate. a storage chamber for storing the reference plate and having an opening through which the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit can enter and exit; and a lid for closing the opening; a control unit having a processing device and a storage device, and controlling the non-contact thickness measurement unit and the moving mechanism in accordance with a program stored in the storage device; and an alarm device for notifying information output by the control unit, wherein the program includes the steps of: positioning the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit to the reference plate measurement position by the moving mechanism based on a command to determine the state of the non-contact thickness measurement unit; causing the light-receiving unit to receive light that is emitted by the light-emitting unit at the reference plate measurement position and reflected by the reference plate, and outputting received light amount information to the output unit; comparing the received light amount information output from the output unit with reference received light amount information stored in the storage device to determine whether the amount of light received by the light-receiving unit satisfies a standard; and if it is determined that the amount of light received by the light-receiving unit does not satisfy the standard, outputting information to that effect to the alarm device. a step of switching the state of the lid to an open state in which the opening is exposed, before a step of positioning the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit at the reference plate measurement position, based on a command to determine the state of the non-contact thickness measurement unit; The grinding apparatus is provided such that the control unit executes the above.

[0010] According to another aspect of the present invention, there is provided a non-contact thickness measurement unit having a holding surface for holding a plate-shaped workpiece, the non-contact thickness measurement unit including: a chuck table having a holding surface for holding a plate-shaped workpiece and rotatable about a rotation axis intersecting the holding surface; a grinding unit having a spindle that can rotate about an axis with a grinding wheel attached to its tip; a light-projecting unit that projects light directed downward; a light-receiving unit that receives light directed upward; and an output unit that outputs light-receiving amount information regarding the amount of light received by the light-receiving unit, the non-contact thickness measurement unit being used when measuring the thickness of the workpiece held on the holding surface of the chuck table in a non-contact manner; a reference plate that is used when determining the state of the non-contact thickness measurement unit; and a movement mechanism that moves the light-projecting unit and the light-receiving unit of the non-contact thickness measurement unit between a workpiece measurement position above the workpiece held on the holding surface of the chuck table and a reference plate measurement position above the reference plate. a storage chamber for storing the reference plate and having an opening through which the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit can enter and exit; and a lid for closing the opening; a control unit having a processing device and a storage device, and controlling the non-contact thickness measurement unit and the moving mechanism according to a program; and an alarm device that notifies information output by the control unit, the program including the steps of: positioning the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit to the reference plate measurement position by the moving mechanism based on a command to determine the state of the non-contact thickness measurement unit; causing the light-receiving unit to receive light that is emitted by the light-emitting unit at the reference plate measurement position and reflected by the reference plate, and outputting information about the amount of received light from the output unit; comparing the information about the amount of received light output from the output unit with reference information about the amount of received light stored in the storage device to determine whether the amount of received light received by the light-receiving unit satisfies a standard; and, if it is determined that the amount of received light received by the light-receiving unit does not satisfy the standard, outputting information about that effect to the alarm device. a step of switching the state of the lid to an open state in which the opening is exposed, before a step of positioning the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit at the reference plate measurement position, based on a command to determine the state of the non-contact thickness measurement unit; A program is provided that causes the control unit to execute the following.

[0012] According to yet another aspect of the present invention, there is provided a non-transitory storage medium on which the program is stored.

[0013] According to yet another aspect of the present invention, there is provided a non-contact thickness measurement unit having a holding surface for holding a plate-shaped workpiece, the non-contact thickness measurement unit including: a chuck table having a holding surface for holding a plate-shaped workpiece and rotatable about a rotation axis intersecting the holding surface; a grinding unit having a spindle having a grinding wheel attached to its tip and rotatable about its axis; a light-projecting unit that projects light directed downward; a light-receiving unit that receives light directed upward; and an output unit that outputs received light amount information regarding the amount of light received by the light-receiving unit, the non-contact thickness measurement unit being used when measuring the thickness of the workpiece held on the holding surface of the chuck table in a non-contact manner; a reference plate that is used when determining the state of the non-contact thickness measurement unit; and a movement mechanism that moves the light-projecting unit and the light-receiving unit of the non-contact thickness measurement unit between a workpiece measurement position above the workpiece held on the holding surface of the chuck table and a reference plate measurement position above the reference plate. a storage chamber for storing the reference plate and having an opening through which the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit can enter and exit; and a lid for closing the opening; a control unit for controlling a grinding device, the control unit having a processing device and a storage device, and controlling the non-contact thickness measurement unit and the moving mechanism according to a program; and an alarm device for notifying information output by the control unit, the control method including the steps of: the control unit positioning the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit at the reference plate measurement position using the moving mechanism based on a command to determine the state of the non-contact thickness measurement unit; the control unit causing the light-receiving unit to receive light that is emitted by the light-emitting unit at the reference plate measurement position and reflected by the reference plate, and outputting information about the amount of received light from the output unit; the control unit comparing the information about the amount of received light output from the output unit with reference information about the amount of received light stored in the storage device to determine whether the amount of received light received by the light-receiving unit satisfies a standard; and the control unit outputting information about the amount of received light to the alarm device when it is determined that the amount of received light received by the light-receiving unit does not satisfy the standard. a step of the control unit switching the state of the lid to an open state in which the opening is exposed, before a step of positioning the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit at the reference plate measurement position, based on a command to determine the state of the non-contact thickness measurement unit; A method for controlling a grinding device is provided, comprising: [Effects of the Invention]

[0015] In the grinding device, program, and control method for a grinding device according to each aspect of the present invention, the control unit executes the following steps based on an instruction to determine the state of the non-contact thickness measurement unit: having the light emitted by the light-emitting unit and reflected by the reference plate received by the light-receiving unit and outputting received light amount information from the output unit; comparing the received light amount information output from the output unit with reference received light amount information stored in the memory device to determine whether the amount of light received by the light-receiving unit meets the standard; and if it is determined that the amount of light received by the light-receiving unit does not meet the standard, outputting information to that effect to an alarm device.

[0016] In other words, the operator of the grinding machine can easily check, at a predetermined timing or at any timing, whether the amount of light received by the light-receiving unit meets the standard, based on the information notified by the notification device. As described above, according to the grinding machine, the program, and the grinding machine control method according to each aspect of the present invention, the operator of the grinding machine can easily check for signs of a malfunction in the non-contact thickness measurement unit that makes it impossible to measure the thickness of the workpiece before this malfunction occurs. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view schematically showing a grinding device. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a part of the grinding device. [Figure 3] FIG. 3 is a diagram showing a schematic structure of the non-contact thickness measurement unit. [Figure 4] FIG. 4 is a functional block diagram that schematically shows the functional structure of the control unit. [Figure 5] FIG. 5 is a flowchart showing the flow of processing when determining the state of the non-contact thickness measurement unit. [Figure 6] FIG. 6 is a perspective view schematically showing a part of a grinding device according to a modified example. [Figure 7] FIG. 7 is a perspective view that schematically shows the state after the cover has been switched to the open state. [Figure 8]FIG. 8 is a flowchart showing the flow of processing according to the modified example. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view that schematically shows a grinding apparatus 2 of this embodiment, and Fig. 2 is a cross-sectional view that schematically shows a part of the grinding apparatus 2. In Fig. 1, some of the elements that make up the grinding apparatus 2 are expressed as functional blocks. In addition, the X-axis direction (front-rear direction), Y-axis direction (left-right direction), and Z-axis direction (vertical direction) used in the following description are perpendicular to one another.

[0019] As shown in Fig. 1, the grinding apparatus 2 includes a base 4 that supports various elements that make up the grinding apparatus 2. A recessed storage section 4a, whose upper end opens to the upper surface of the base 4, is provided at the front end of the upper surface of the base 4, and a first transport mechanism 6 used to transport a plate-shaped workpiece 11 is housed within this storage section 4a. The first transport mechanism 6 is typically a robot arm with multiple joints, and is capable of not only transporting the workpiece 11 but also turning the workpiece 11 upside down.

[0020] The workpiece 11 is, for example, a disk-shaped wafer made of a semiconductor material such as silicon. That is, the workpiece 11 has a circular front surface 11a and a circular back surface 11b opposite the front surface 11a. The front surface 11a side of the workpiece 11 is divided into a plurality of small regions by a plurality of intersecting streets (planned division lines), and a device such as an integrated circuit (IC) is formed in each small region.

[0021] The grinding device 2 of this embodiment is used, for example, when grinding the back surface 11b side of the workpiece 11. When grinding the back surface 11b side of the workpiece 11, it is desirable to attach a protective member, such as a protective tape made of a material such as resin, to the front surface 11a side of the workpiece 11. By attaching the protective member to the front surface 11a side of the workpiece 11, the impact applied to the front surface 11a side when the back surface 11b side is ground is alleviated, and devices and the like of the workpiece 11 are protected.

[0022] In addition, in this embodiment, a disk-shaped wafer made of a semiconductor material such as silicon is used as the workpiece 11, but the material, shape, structure, size, etc. of the workpiece 11 are not limited to this embodiment. For example, a substrate made of other semiconductors, ceramics, resin, metal, etc. may be used as the workpiece 11. Similarly, the type, number, shape, structure, size, arrangement, etc. of the devices are not limited to the above embodiment. The workpiece 11 does not necessarily have to have any devices formed thereon.

[0023] 1, cassette tables 10a and 10b are provided in front of the storage unit 4a, on which cassettes 8a and 8b, each capable of storing a plurality of workpieces 11, are placed. A position adjustment mechanism 12 for adjusting the position of the workpieces 11 is provided diagonally behind the storage unit 4a. The position adjustment mechanism 12 includes a disk-shaped position adjustment table and a plurality of pins arranged around the periphery of the position adjustment table.

[0024] By moving the pins in the radial direction of the position adjustment table, for example, the center of the workpiece 11 carried out from the cassette 8a by the first transport mechanism 6 and placed on the position adjustment table is aligned to a predetermined position in the X-axis direction and the Y-axis direction. The workpiece 11 is placed on the position adjustment table so that its surface to be ground (in this embodiment, the back surface 11b) is exposed upward.

[0025] A second transport mechanism 14 that holds and transports the workpiece 11 rearward is provided on the side of the position adjustment mechanism 12. The second transport mechanism 14 includes, for example, an arm and a holding pad that is connected to the tip of the arm and can hold the top surface (surface to be ground) of the workpiece 11 by suction, and transports the workpiece 11, whose position has been adjusted by the position adjustment mechanism 12, rearward by rotating the holding pad with the arm.

[0026] A turntable 16 is provided behind the second transport mechanism 14. The turntable 16 is connected to a motor (not shown) or the like, and rotates around a rotation axis that is roughly parallel to the Z-axis direction by the power of the motor or the like. Three sets of cylindrical (disk-shaped) table bases 18 are provided on the upper surface of the turntable 16 at roughly equal angular intervals along the circumferential direction of the turntable 16. However, the number of table bases 18 is not limited to this.

[0027] Each table base 18 is connected to a motor (not shown) or the like, and rotates around a rotation axis that is roughly parallel to the Z-axis direction or a rotation axis that is slightly tilted with respect to the Z-axis direction by the power of this motor, etc. Each table base 18 is supported on the turntable 16 via an angle adjustment mechanism (not shown), and the angle of the rotation axis of each table base 18 is adjusted by this angle adjustment mechanism.

[0028] A disk-shaped chuck table 20 used to hold the workpiece 11 is fixed to the upper end of each table base 18 with bolts or the like. As shown in FIG. 2, each chuck table 20 includes a disk-shaped frame 22 made of a material such as ceramics. A recess 22a is provided in the upper part of the frame 22, the upper end of which is circularly open to the upper surface of the frame 22. A porous disk-shaped holding plate 24 made of a material such as ceramics is fixed to this recess 22a.

[0029] The upper surface (holding surface) 24a of the holding plate 24 is configured in a shape corresponding to the side surface of a cone, for example, and functions as a holding surface that holds the workpiece 11. The difference in height (height difference) between the center of the upper surface 24a of the holding plate 24, which corresponds to the apex of the cone, and the outer periphery of the upper surface 24a of the holding plate 24 is approximately 10 μm to 30 μm.

[0030] The lower surface side of the holding plate 24 is connected to a suction source (not shown) such as an ejector via a flow path 22b provided inside the frame 22 and a valve (not shown) arranged outside the frame 22. Therefore, when the valve is opened and negative pressure from the suction source is applied while the workpiece 11 (protective member) or the like is in contact with the upper surface 24a of the holding plate 24, the workpiece 11 or the like is sucked by the chuck table 20. In other words, the workpiece 11 is held by the holding surface of the chuck table 20.

[0031] With the chuck table 20 fixed to the table base 18, the turntable 16 rotates, for example, in the direction of the arrow in Fig. 1 and in the direction opposite to the arrow. As the turntable 16 rotates, the table base 18 and the chuck table 20 move in the circumferential direction of the turntable 16.

[0032] The turntable 16 moves the table base 18 and the chuck table 20, for example, in the order of a load-in / load-out area adjacent to the second transport mechanism 14, a rough grinding area behind the load-in / load-out area, a finish grinding area to the side of the rough grinding area, and then the load-in / load-out area. The second transport mechanism 14 transports the workpiece 11 held by a holding pad from the position adjustment table of the position adjustment mechanism 12 to the chuck table 20 arranged in the load-in / load-out area.

[0033] 1, columnar support structures 30 are provided behind the rough grinding area and the finish grinding area (i.e., behind the turntable 16), respectively. A Z-axis movement mechanism 32 is provided on the front side of each support structure 30. Each Z-axis movement mechanism 32 has a pair of guide rails 34 that are generally parallel to the Z-axis direction, and a movement plate 36 is attached to the guide rails 34 in a slidable manner.

[0034] A nut portion (not shown) constituting a ball screw is provided on the rear surface side (back surface side) of each moving plate 36, and a screw shaft 38 that is generally parallel to the guide rail 34 is rotatably connected to this nut portion. A motor 40 or the like is connected to one end of the screw shaft 38. By rotating the screw shaft 38 by the motor 40 or the like, the moving plate 36 moves along the guide rail 34 (in the Z-axis direction).

[0035] A fixture 42 is provided on the front surface (surface) of each moving plate 36. Each fixture 42 supports a grinding unit 44 that can grind the workpiece 11. Each grinding unit 44 has a spindle housing 46 fixed to the fixture 42. Each spindle housing 46 accommodates a spindle 48 whose rotation axis is parallel to the Z-axis direction or slightly inclined with respect to the Z-axis direction, in a manner that the spindle 48 can rotate about its axis.

[0036] The lower end of each spindle 48 is exposed from the lower end surface of the spindle housing 46, and a disk-shaped mount 50 is fixed to this lower end. For example, the outer edge of each mount 50 is provided with a plurality of holes (not shown) that penetrate the mount 50 in the thickness direction, and a bolt 52 or the like is inserted into each hole.

[0037] A grinding wheel 54 for rough grinding is attached to the underside of the mount 50 of the grinding unit 44 on the rough grinding area side with bolts 52. In other words, the grinding wheel 54 for rough grinding is attached to the spindle 48 on the rough grinding area side. Furthermore, a motor (not shown) and the like connected to the upper end side of the spindle 48 are housed in the spindle housing 46 of the grinding unit 44 on the rough grinding area side. The grinding wheel 54 for rough grinding rotates together with the spindle 48 by the power of this motor and the like.

[0038] On the other hand, a grinding wheel 54 for finish grinding is attached with bolts 52 to the underside of the mount 50 of the grinding unit 44 on the finish grinding area side. In other words, the grinding wheel 54 for finish grinding is attached to the spindle 48 on the finish grinding area side. Furthermore, a motor (not shown) and the like connected to the upper end side of the spindle 48 are housed in the spindle housing 46 of the grinding unit 44 on the finish grinding area side. The grinding wheel 54 for finish grinding rotates together with the spindle 48 by the power of this motor and the like. Note that FIG. 2 mainly shows the structure around the grinding unit 44 on the finish grinding area side.

[0039] 2 and other figures, each grinding wheel 54 includes an annular wheel base 54a made of metal such as stainless steel or aluminum. A plurality of grinding stones 54b, each made of abrasive grains such as diamond dispersed in a binder such as vitrified or resinoid, are fixed to the underside of the wheel base 54a along the circumferential direction of the wheel base 54a.

[0040] For example, the average particle size of the abrasive grains contained in the grinding stone 54b of the grinding wheel 54 for finish grinding is smaller than the average particle size of the abrasive grains contained in the grinding stone 54b of the grinding wheel 54 for rough grinding. This allows for the realization of a grinding wheel 54 suitable for rough grinding and a grinding wheel 54 suitable for finish grinding. The specific size of the abrasive grains is appropriately set depending on the quality required of the workpiece 11 after grinding, etc.

[0041] A nozzle 56 capable of supplying a liquid (grinding fluid) such as pure water to the contact area between the workpiece 11 and the grinding wheel 54b is disposed near each grinding unit 44. Instead of or together with this nozzle 56, a liquid supply port used to supply a liquid may be provided in the grinding wheel 54 or the like.

[0042] Also, a part of a non-contact thickness measurement unit 58 used to measure the thickness of the workpiece 11 held by the chuck table 20 is disposed near the grinding unit 44 on the finish grinding area side. Fig. 3 is a diagram showing a schematic structure of the non-contact thickness measurement unit 58. Note that in Fig. 3, some of the elements constituting the non-contact thickness measurement unit 58 are expressed as functional blocks.

[0043] 3, the non-contact thickness measurement unit 58 includes a light source 60 that can emit light 60a having a broad spectrum in a wavelength range of, for example, 0.5 μm to 1500 μm. The light 60a emitted from the light source 60 is sent to a measurement head 62 via an optical fiber or the like. The light source 60 may be, for example, a super luminescent diode (SLD).

[0044] The measuring head 62 is provided with a window (light projecting unit, light receiving unit) 64 through which light 60a from the light source 60 can pass. The light 60a from the light source 60 that passes through the window 64 is reflected by a measurement object such as a workpiece 11 that is disposed below the measuring head 62. In this way, the window 64 functions as a light projecting unit that projects the light 60a toward the measurement object below. The distance between the bottom end of the measuring head 62 and the top end of the measurement object is, for example, about 1 mm to 4 mm.

[0045] A liquid supply port 66 capable of supplying a liquid such as pure water is provided near the window 64 of the measuring head 62, and when measuring the thickness of an object to be measured, the lower surface of the window 64 facing the object to be measured is covered with the liquid supplied from the liquid supply port 66. This prevents contamination from adhering to the lower surface of the window 64, for example, when measuring the thickness of the workpiece 11 during grinding. The flow rate of the liquid supplied from the liquid supply port 66 is typically about 0.5 L / min to 1.5 L / min.

[0046] Light reflected from the upper surface of the measurement object and light reflected from the lower surface of the measurement object interfere with each other constructively, for example, at a wavelength corresponding to the thickness of the measurement object. The interfering light 60b reflected from the measurement object passes through the upper window 64 and is sent to the spectroscopic element 68 via an optical fiber or the like. In other words, the window 64 also functions as a light receiving unit that receives the light 60b traveling upward. For example, a diffraction grating is used as the spectroscopic element 68.

[0047] The light 60c dispersed by the spectroscopic element 68 enters the photoelectric conversion element 70. For example, a line sensor having sensitivity to any wavelength range from 0.5 μm to 1500 μm is used as the photoelectric conversion element 70. In this case, the photoelectric conversion element 70 receives the light 60c that passes through the spectroscopic element 68 and is irradiated at a position according to the wavelength, and outputs an electrical signal according to the intensity of the light 60c of each wavelength. In other words, the electrical signal output from the photoelectric conversion element 70 contains information corresponding to the relationship between the amount of light 60b reflected by the object to be measured and incident on the window 64 (the amount of light 60b received by the light receiving unit) and the wavelength.

[0048] The electrical signal output from the photoelectric conversion element 70 is input to a calculation device (output section) 72 of the non-contact thickness measurement unit 58. The calculation device 72 includes, for example, a CPU (Central Processing Unit), and performs fast Fourier transform, filtering, etc. on information included in the electrical signal output from the photoelectric conversion element 70 (information corresponding to the relationship between the amount of light and the wavelength) to calculate the thickness of the object to be measured.

[0049] The arithmetic unit 72 also calculates the amount of light at any wavelength of the light 60b incident on the window 64 (the amount of light at any wavelength of the light 60b received by the light receiving unit) based on information included in the electrical signal output from the photoelectric conversion element 70. The arithmetic unit 72 also controls the light source 60 and the like.

[0050] The arithmetic device 72 outputs information relating to the calculated thickness of the measurement object as thickness information. The arithmetic device 72 also outputs information relating to the calculated amount of light (amount of received light) as received light amount information. The thickness information output from the arithmetic device 72 is used, for example, to control various parts when grinding the workpiece 11, and the received light amount information output from the arithmetic device 72 is used, for example, to determine the state of the non-contact thickness measurement unit 58.

[0051] 2, the measurement head 62 is disposed, for example, at the tip of an arm (movement mechanism) 74 whose base end is connected to a motor (not shown) or the like. The arm 74 rotates around a rotation axis roughly parallel to the Z-axis direction by the power of the motor or the like. When the arm 74 is rotated, the measurement head 62 disposed at the tip of the arm 74 moves (pivots) along an arc-shaped trajectory centered on the base end of the arm 74.

[0052] 2, when measuring the thickness of the workpiece 11 held on the upper surface 24a of the chuck table 20, the measuring head 62 is positioned at a workpiece measurement position A above the chuck table 20 (workpiece 11). On the other hand, when it is not necessary to measure the thickness of the workpiece 11, the measuring head 62 is positioned at a retracted position (reference plate measurement position) B away from the workpiece measurement position A. In other words, the arm 74 moves the measuring head 62, including the window 64, between the workpiece measurement position A and the retracted position B.

[0053] A holding table 76 is disposed below the retracted position B, and a reference plate 78 used to determine the state of the non-contact thickness measurement unit 58 is held on the upper surface of this holding table 76. The reference plate 78 is a substrate with known light reflectance and thickness, and is formed of, for example, the same material as the workpiece 11. A silicon substrate is typically used as this reference plate 78. However, the material of the reference plate 78 may be different from the material of the workpiece 11.

[0054] In the grinding device 2 of this embodiment, (a part of) the non-contact thickness measurement unit 58 is disposed only near the grinding unit 44 on the finish grinding region side, but a similar non-contact thickness measurement unit may also be disposed near the grinding unit 44 on the rough grinding region side. Also, a contact-type thickness measurement unit may be disposed near each grinding unit 44.

[0055] The workpiece 11 held on the chuck table 20 in the rough grinding area has its upper surface ground by the grinding unit 44 on the rough grinding area side. The workpiece 11 held on the chuck table 20 in the finish grinding area has its upper surface ground by the grinding unit 44 on the finish grinding area side.

[0056] That is, the chuck table 20 holding the workpiece 11 moves in the order of the carry-in / carry-out area, the rough grinding area, and the finish grinding area, thereby successively performing rough grinding and the finish grinding after the rough grinding of the workpiece 11. When the finish grinding of the workpiece 11 is completed, the chuck table 20 in the finish grinding area is again positioned in the carry-in / carry-out area.

[0057] A third transport mechanism 80 is provided in front of the loading / unloading area and to the side of the second transport mechanism 14, which holds and transports the ground workpiece 11 forward. The third transport mechanism 80 includes, for example, an arm and a holding pad connected to the tip of the arm and capable of holding the top surface of the workpiece 11 by suction, and transports the ground workpiece 11 forward from the chuck table 20 in the loading / unloading area by rotating the holding pad with the arm.

[0058] A cleaning unit 82 is provided on the side of the third transport mechanism 80 to clean the workpiece 11 carried out by the third transport mechanism 80. The cleaning unit 82 includes, for example, a spinner table that rotates while holding the lower surface of the workpiece 11, and a cleaning nozzle that sprays a cleaning fluid onto the upper surface of the workpiece 11 held by the spinner table.

[0059] The cleaning fluid used in the cleaning unit 82 is typically a mixed fluid (two-fluid) of water and air. Of course, water not mixed with air may also be used as the cleaning fluid. The workpiece 11 cleaned in the cleaning unit 82 is transported by the first transport mechanism 6 and stored in, for example, a cassette 8b.

[0060] A control unit 84 is connected to each element of the grinding device 2. This control unit 84 is configured by a computer including, for example, a processing device 84a and a storage device 84b, and controls the operation of each element of the grinding device 2 including the non-contact thickness measuring unit 58 and the arm 74 described above so that the workpiece 11 is properly ground.

[0061] The processing device 84a is typically a CPU (Central Processing Unit) and performs various processes required to control the above-mentioned elements. The storage device 84b includes, for example, a main storage device such as a DRAM (Dynamic Random Access Memory) and an auxiliary storage device such as a hard disk drive or flash memory. The functions of this control unit 84 are realized, for example, by the processing device 84a operating in accordance with software such as a program stored in the storage device 84b.

[0062] An input device 86 is connected to the control unit 84. The input device 86 is, for example, a touch panel, and inputs commands from an operator to the control unit 84. This touch panel also has a display function, and doubles as an alarm device 88 that notifies the operator of information output by the control unit 84. Note that a keyboard, a mouse, or the like may be used as the input device 86. Similarly, the alarm device 88 may be a speaker that notifies information by voice, or an indicator light that notifies information by light color or light emission state (light emitting, flashing, off, etc.).

[0063] In the grinding apparatus 2 configured in this manner, the state of the non-contact thickness measurement unit 58 is determined at a predetermined timing determined by a program or the like, or at any timing desired by the operator. For example, a program for causing the control unit 84 to execute the procedures necessary to determine the state of the non-contact thickness measurement unit 58 is recorded in part of the storage device 84b, which is also a non-transitory recording medium readable by a computer or the like, and the control unit 84 carries out the procedures necessary to determine the state of the non-contact thickness measurement unit 58 in accordance with this program.

[0064] 4 is a functional block diagram showing a functional structure of the control unit 84 implemented by the program of this embodiment. For ease of explanation, an input device 86, a notification device 88, and the arithmetic unit 72 of the non-contact thickness measurement unit 58, which are connected to the control unit 84, are also shown in FIG.

[0065] 4, the control unit 84 includes a position control unit 90 that controls the operation of the arm 74. For example, upon receiving a command to determine the state of the non-contact thickness measurement unit 58, the position control unit 90 positions the measuring head 62 at the retracted position B with the arm 74. The command to determine the state of the non-contact thickness measurement unit 58 may be input to the control unit 84 by an operator via the input device 86, or may be generated within the control unit 84 based on a program or the like.

[0066] The control unit 84 further includes a measurement control unit 92. For example, when the measurement head 62 is positioned at the retracted position B based on a command to determine the state of the non-contact thickness measurement unit 58, the measurement control unit 92 causes the light source 60 to emit light 60a and then causes the arithmetic device 72 to output information on the amount of received light. In other words, the measurement control unit 92 causes the arithmetic device 72 to calculate the amount of light 60b that is reflected by the reference plate 78 and enters the window 64 (the amount of light 60b received by the light receiving unit). More specifically, the measurement control unit 92 generates a command to perform such an operation and sends it to the arithmetic device 72.

[0067] The received light amount information output from the arithmetic unit 72 may consist of only information about the amount of light at a single wavelength, or may include information about the amount of light at multiple wavelengths. Furthermore, this received light amount information may be information obtained by statistically processing the amounts of light at multiple wavelengths. For example, the arithmetic unit 72 may output the average value of the amounts of light at multiple wavelengths as the received light amount information.

[0068] The received light amount information output from the arithmetic device 72 is input to the control unit 84 and used by the determination section 94. The determination section 94, for example, compares the received light amount information output from the arithmetic device 72 with reference received light amount information stored in advance in the storage device 84b of the control unit 84, and determines whether or not the amount of light 60b incident on the window 64 (the amount of light 60b received by the light receiving section) satisfies the reference standard.

[0069] The reference received light amount information used in the judgment of the judgment unit 94 is, for example, information about the light amount when signs of dirt adhesion, deterioration of the light source 60, etc. appear on the non-contact thickness measurement unit 58. The judgment result of this judgment by the judgment unit 94 is sent to the notification unit 96. The notification unit 96 notifies the notification device 88 of the judgment result of the judgment unit 94. For example, when the judgment unit 94 determines that the light amount (received light amount) does not satisfy the reference, the notification unit 96 displays a warning to that effect on the touch panel constituting the notification device 88.

[0070] 5 is a flowchart showing the process flow when determining the state of the non-contact thickness measurement unit 58, i.e., the control method for the grinding apparatus 2. First, when the position control unit 90 of the control unit 84 receives a command to determine the state of the non-contact thickness measurement unit 58, the position control unit 90 performs a procedure of positioning the measurement head 62 including the window 64 at the retracted position B by the arm 74 (step ST11).

[0071] For example, when the measuring head 62 is at the workpiece measurement position A, the position control unit 90 rotates the arm 74 to move the measuring head 62 to the retracted position B directly above the reference plate 78. On the other hand, when the measuring head 62 is already at the retracted position B, the position control unit 90 maintains the position of the measuring head 62 without rotating the arm 74.

[0072] When the measurement head 62 is positioned at the retracted position B, the measurement control unit 92 causes the light source 60 to emit light 60a. Because the measurement head 62 is positioned at the retracted position B directly above the reference plate 78, the light 60a emitted from the light source 60 passes through the window 64 and is reflected by the reference plate 78. The light 60b reflected by the reference plate 78 passes through the window 64 again and is dispersed by the spectroscopic element 68. When the light 60c dispersed by the spectroscopic element 68 enters the photoelectric conversion element 70, the photoelectric conversion element 70 sends an electrical signal including information corresponding to the relationship between the amount of light (amount of received light) and the wavelength to the calculation device 72.

[0073] The measurement control unit 92 causes the arithmetic unit 72 to calculate information regarding the amount of light (amount of received light) based on the information contained in this electrical signal, and also causes the arithmetic unit 72 to output this information as received light amount information. In this way, the measurement control unit 92 performs the procedure of causing the light source 60 to emit light 60a and causing the arithmetic unit 72 to output received light amount information (step ST12). The received light amount information output from the arithmetic unit 72 is sent to the determination unit 94.

[0074] The judgment unit 94 compares the received light amount information output from the calculation device 72 with the reference received light amount information previously stored in the memory device 84b of the control unit 84, and performs a procedure to judge whether the amount of light 60b incident on the window 64 (the amount of light 60b received by the light receiving unit) meets the standard (step ST13).

[0075] For example, if the amount of light (amount of received light) indicated by the received light amount information is lower than the amount of light (amount of received light) indicated by the reference received light amount information, the determination unit 94 determines that the amount of light (amount of received light) does not meet the standard. Also, if the amount of light (amount of received light) indicated by the received light amount information is not lower than the amount of light (amount of received light) indicated by the reference received light amount information, the determination unit 94 determines that the amount of light (amount of received light) meets the standard. The determination unit 94 sends the result of this determination to the notification unit 96.

[0076] The notification unit 96 notifies the notification device 88 of the result of the determination by the determination unit 94. For example, when the determination unit 94 determines that the amount of light (amount of received light) satisfies the criterion (YES in step ST13), the notification unit 96 executes a procedure of displaying information indicating that the criterion is met on the touch panel constituting the notification device 88 (step ST14).

[0077] On the other hand, for example, when the determination unit 94 determines that the amount of light (amount of received light) does not satisfy the standard (NO in step ST13), the notification unit 96 executes a procedure of displaying information indicating that the standard is not satisfied on the touch panel constituting the notification device 88 (step ST15). For example, when the information indicating that the standard is not satisfied is notified, the operator prepares for maintenance of the non-contact thickness measurement unit 58, such as arranging for parts required for repair. This reduces the time required for maintenance of the non-contact thickness measurement unit 58.

[0078] As described above, in the grinding device 2, program, and control method for the grinding device 2 according to this embodiment, based on a command to determine the state of the non-contact thickness measurement unit 58, the control unit 84 executes the following steps: a procedure of causing the light 60b that passes through the window 64 (projected by the light-projecting unit) and is reflected by the reference plate 78 to be incident on the window 64 again (received by the light-receiving unit) and outputting received light amount information to the calculation device (output unit) 72; a procedure of comparing the received light amount information output from the calculation device 72 with the reference received light amount information stored in the memory device 84b to determine whether the amount of light 60b that is incident on the window 64 again (the amount of light 60b received by the light-receiving unit) satisfies the standard; and a procedure of outputting information to that effect to the alarm device 88 if it is determined that the amount of light 60b that is incident on the window 64 does not satisfy the standard.

[0079] That is, the operator of the grinding apparatus 2 can easily check at a predetermined timing or at any timing whether the amount of light 60b incident on the window 64 meets the standard based on the information notified by the notification device 88. As described above, according to the grinding apparatus 2, program, and control method for the grinding apparatus 2 of this embodiment, the operator of the grinding apparatus 2 can easily check for signs of a malfunction that makes it impossible to measure the thickness of the workpiece 11 before such a malfunction occurs in the non-contact thickness measurement unit 58.

[0080] The present invention is not limited to the above-described embodiment and can be implemented with various modifications. For example, in the above-described embodiment, the state of the non-contact thickness measurement unit 58 is determined based on the amount of light 60b reflected by the reference plate 78 and re-entering the window 64 (the amount of light received by the light receiving unit). However, the state of the non-contact thickness measurement unit 58 may be determined based on other information. For example, the determination unit 94 may determine the state of the non-contact thickness measurement unit 58 based on thickness information of the reference plate 78 output from the calculation device 72.

[0081] Furthermore, in the above-described embodiment, even when the judgment unit 94 judges that the amount of light (amount of received light) meets the standard, the notification unit 96 notifies the notification device 88 of the result of the judgment, but when the judgment unit 94 judges that the amount of light (amount of received light) meets the standard, the notification unit 96 does not necessarily have to notify the notification device 88 of the result of the judgment.

[0082] Furthermore, in the above-described embodiment, the program for executing the control method for the grinding device 2 is recorded in the storage device 84b in the control unit 84, but this program may be recorded, for example, on any non-transitory recording medium that can be read by a computer, etc. For example, this program may be recorded on an optical disc such as a CD (Compact Disc) that can be distributed at low cost.

[0083] Furthermore, in the above-described embodiment, the holding table 76 holds the reference plate 78 so that the reference plate 78 is exposed, but the reference plate 78 may be covered, for example, by a cover or the like. FIG. 6 is a perspective view schematically showing a part of a grinding apparatus according to a modified example. Note that many of the elements of the grinding apparatus according to this modified example are common to the elements of the grinding apparatus 2 according to the above-described embodiment. Therefore, in the following, the common elements are given the same reference numerals and detailed description will be omitted, and elements (differences) that are different from the grinding apparatus 2 will mainly be described.

[0084] 6, the grinding apparatus according to the modified example includes a cover (accommodation chamber) 98 that covers the holding table 76 and the reference plate 78. That is, the holding table 76 and the reference plate 78 are accommodated in a space provided inside the cover 98. The cover 98 is provided with an opening 98a that connects the space inside the cover 98 with the outside, and the measuring head 62 including the window 64 of the non-contact thickness measuring unit 58 can enter and exit the space inside the cover 98 through this opening 98a.

[0085] In addition, a lid 100 capable of closing the opening 98a is attached to the cover 98. For example, an opening / closing mechanism (not shown) is connected to the lid 100, and this opening / closing mechanism switches the state of the lid 100 between a closed state in which the opening 98a is covered and an open state in which the opening 98a is exposed. Figure 7 is a perspective view that schematically shows the state of the lid 100 after it has been switched to the open state. For example, an actuator that moves the lid 100 up and down is used as the opening / closing mechanism that switches the state of the lid 100.

[0086] The control method for the grinding apparatus configured in this manner is basically the same as the control method for the grinding apparatus according to the above-described embodiment. However, before the procedure of positioning the measuring head 62 including the window 64 at the retracted position B, the state of the lid 100 is switched from the closed state (FIG. 6) to the open state (FIG. 7). Figure 8 is a flowchart showing the flow of processing according to the modified example, that is, the control method for the grinding apparatus according to the modified example.

[0087] As shown in FIG. 8, when the position control unit 90 of the control unit 84 receives an instruction to determine the state of the non-contact thickness measurement unit 58, the position control unit 90 first performs a procedure of moving the lid 100 downward using the opening / closing mechanism to switch the state of the lid 100 from a closed state to an open state (step ST21).

[0088] Thereafter, the control unit 84 performs the procedure of positioning the measurement head 62 including the window 64 at the retracted position B using the arm 74 (step ST22), as in the above-described embodiment, causes the light source 60 to emit light 60a and causes the calculation device 72 to output information on the amount of light received (step ST23), and performs the procedure of determining whether the amount of light 60b incident on the window 64 (the amount of light 60b received by the light receiving unit) meets the standard (step ST24).

[0089] Then, for example, when the control unit 84 determines that the amount of light (amount of received light) meets the standard (YES in step ST24), it performs a procedure of displaying information indicating that the standard is met on the touch panel constituting the notification device 88 (step ST25). Also, when the control unit 84 determines that the amount of light (amount of received light) does not meet the standard (NO in step ST24), it performs a procedure of displaying information indicating that the standard is not met on the touch panel constituting the notification device 88 (step ST26).

[0090] In this modification, it is desirable that the lid 100 be in the closed state except for a predetermined timing including the timing when the state of the non-contact thickness measurement unit 58 is determined. This prevents dirt from adhering to the reference plate 78. The measuring head 62 of the non-contact thickness measurement unit 58 is positioned at the workpiece measurement position A except for a predetermined timing including the timing when the state of the non-contact thickness measurement unit 58 is determined.

[0091] In addition, the structures, methods, etc. according to the above-described embodiments and modifications may be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0092] 2: Grinding equipment 4: Base 4a: Storage section 6: First transport mechanism 8a: Cassette 8b: Cassette 10a: Cassette table 10b: Cassette table 12:Position adjustment mechanism 14: Second transport mechanism 16: Turntable 18: Table base 20: Chuck table 22:Frame body 22a: recess 22b: Flow path 24: Holding plate 24a: Top surface (holding surface) 30:Support structure 32:Z-axis movement mechanism 34: Guide rail 36: Moving plate 38: Screw shaft 40: Motor 42: Fixture 44: Grinding unit 46: Spindle housing 48: Spindle 50: Mount 52: Bolt 54: Grinding wheel 54a: Wheel base 54b: Grinding wheel 56: Nozzle 58: Non-contact thickness measurement unit 60:Light source 60a: Light 60b: light 60c: light 62: Measuring head 64: Window (light-emitting part, light-receiving part) 66:Liquid supply port 68: Spectroscopic element 70: Photoelectric conversion element 72: Calculation unit (output unit) 74: Arm (movement mechanism) 76: Holding table 78: Reference plate 80: Third transport mechanism 82: Cleaning unit 84: Control unit 84a: Processing device 84b: Storage device 86: Input device 88: Alarm device 90: Position control section 92: Measurement control section 94: Judgment section 96: Information Department 98: Cover (containment room) 98a: Opening 100: Lid 11: Workpiece 11a: Surface 11b: Inside A: Measurement location of the workpiece B: Retreat position (baseline placement measurement position)

Claims

1. a chuck table having a holding surface for holding a plate-shaped workpiece and rotatable around a rotation axis intersecting the holding surface; a grinding unit having a spindle that can rotate around an axis with a grinding wheel attached to the tip thereof; a non-contact thickness measurement unit having a light-projecting section that projects light directed downward, a light-receiving section that receives light directed upward, and an output section that outputs received light amount information regarding the amount of light received by the light-receiving section, the non-contact thickness measurement unit being used when measuring the thickness of the workpiece held on the holding surface of the chuck table in a non-contact manner; a reference plate used to determine the state of the non-contact thickness measurement unit; a moving mechanism that moves the light projecting unit and the light receiving unit of the non-contact thickness measurement unit between a workpiece measurement position above the workpiece held on the holding surface of the chuck table and a reference plate measurement position above the reference plate; a storage chamber that stores the reference plate and has an opening through which the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit can enter and exit; a lid capable of closing the opening; a control unit having a processing device and a storage device, and controlling the non-contact thickness measurement unit and the movement mechanism in accordance with a program stored in the storage device; an alarm device that notifies the information output by the control unit, The program a step of positioning the light projecting unit and the light receiving unit of the non-contact thickness measurement unit at the reference plate measurement position by the movement mechanism based on a command to determine the state of the non-contact thickness measurement unit; a step of causing the light receiving unit to receive light that is projected by the light projecting unit at the reference plate measurement position and reflected by the reference plate, and causing the output unit to output information about the amount of light received; a step of comparing the received light amount information output from the output unit with reference received light amount information stored in the storage device to determine whether the amount of light received by the light receiving unit satisfies a reference; a step of outputting information indicating that the amount of light received by the light receiving unit does not satisfy a standard to the notification device when the amount of light received by the light receiving unit does not satisfy a standard; a step of switching the state of the lid to an open state in which the opening is exposed, before a step of positioning the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit at the reference plate measurement position, based on a command to determine the state of the non-contact thickness measurement unit.

2. a chuck table having a holding surface for holding a plate-shaped workpiece and rotatable around a rotation axis intersecting the holding surface; a grinding unit having a spindle that can rotate around an axis with a grinding wheel attached to the tip thereof; a non-contact thickness measurement unit having a light-projecting section that projects light directed downward, a light-receiving section that receives light directed upward, and an output section that outputs received light amount information regarding the amount of light received by the light-receiving section, the non-contact thickness measurement unit being used when measuring the thickness of the workpiece held on the holding surface of the chuck table in a non-contact manner; a reference plate used to determine the state of the non-contact thickness measurement unit; a moving mechanism that moves the light projecting unit and the light receiving unit of the non-contact thickness measurement unit between a workpiece measurement position above the workpiece held on the holding surface of the chuck table and a reference plate measurement position above the reference plate; a storage chamber that stores the reference plate and has an opening through which the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit can enter and exit; a lid capable of closing the opening; a control unit having a processing device and a storage device, and controlling the non-contact thickness measurement unit and the movement mechanism according to a program; and a notification device that notifies information output by the control unit, a step of positioning the light projecting unit and the light receiving unit of the non-contact thickness measurement unit at the reference plate measurement position by the movement mechanism based on a command to determine the state of the non-contact thickness measurement unit; a step of causing the light receiving unit to receive light that is projected by the light projecting unit at the reference plate measurement position and reflected by the reference plate, and causing the output unit to output information about the amount of light received; a step of comparing the received light amount information output from the output unit with reference received light amount information stored in the storage device to determine whether the amount of light received by the light receiving unit satisfies a reference; a step of outputting information indicating that the amount of light received by the light receiving unit does not satisfy a standard to the notification device when the amount of light received by the light receiving unit does not satisfy a standard; A program that causes the control unit to execute, based on an instruction to determine the state of the non-contact thickness measurement unit, a procedure of switching the state of the lid to an open state in which the opening is exposed, before a procedure of positioning the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit at the reference plate measurement position.

3. A non-transitory recording medium storing the program according to claim 2.

4. a chuck table having a holding surface for holding a plate-shaped workpiece and rotatable around a rotation axis intersecting the holding surface; a grinding unit having a spindle that can rotate around an axis with a grinding wheel attached to the tip thereof; a non-contact thickness measurement unit having a light-projecting section that projects light directed downward, a light-receiving section that receives light directed upward, and an output section that outputs received light amount information regarding the amount of light received by the light-receiving section, the non-contact thickness measurement unit being used when measuring the thickness of the workpiece held on the holding surface of the chuck table in a non-contact manner; a reference plate used to determine the state of the non-contact thickness measurement unit; a moving mechanism that moves the light projecting unit and the light receiving unit of the non-contact thickness measurement unit between a workpiece measurement position above the workpiece held on the holding surface of the chuck table and a reference plate measurement position above the reference plate; a storage chamber that stores the reference plate and has an opening through which the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit can enter and exit; a lid capable of closing the opening; a control unit having a processing device and a storage device, and controlling the non-contact thickness measurement unit and the movement mechanism according to a program; and a notification device that notifies information output by the control unit, a step of positioning the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit at the reference plate measurement position by the movement mechanism based on a command from the control unit to determine the state of the non-contact thickness measurement unit; a step in which the control unit causes the light receiving unit to receive light that is projected by the light projecting unit at the reference plate measurement position and reflected by the reference plate, and causes the output unit to output information about the amount of received light; a step in which the control unit compares the received light amount information output from the output unit with reference received light amount information stored in the storage device to determine whether the amount of light received by the light receiving unit satisfies a reference; When it is determined that the amount of light received by the light receiving unit does not satisfy a standard, the control unit outputs information to that effect to the notification device; a step in which the control unit switches the state of the lid to an open state in which the opening is exposed, before a step in which the light-emitting unit and the light-receiving unit of the non-contact thickness measurement unit are positioned at the reference plate measurement position, based on a command to determine the state of the non-contact thickness measurement unit.

Images