Cleaning method

Abstract

To clean a thickness measuring device with the thickness measuring device attached to a grinding device.SOLUTION: A cleaning method, which cleans a thickness measuring device in a grinding device having a chuck table for holding a work-piece by a holding surface and the thickness measuring device for measuring a thickness of the work-piece held by the holding surface, comprises: a liquid discharge process in which a liquid, which passes an interior of a circular wheel base and is supplied to a grindstone part, is discharged from a grinding wheel which has the circular wheel base and a grindstone part annularly located on one surface of the wheel base, and is attached to a lower end of a spindle; and a cleaning process in which the thickness measuring device is cleaned by bringing the liquid into contact with each upper part of an arm and a sensor head in the thickness measuring device including the arm and the sensor head fixed to a tip of the arm.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a cleaning method for cleaning a thickness gauge in a grinding machine having a chuck table that holds a workpiece on a holding surface and a thickness gauge that measures the thickness of the workpiece held on the holding surface. [Background technology]

[0002] In the manufacturing process of semiconductor device chips, in order to thin the semiconductor device chips, after forming a plurality of devices on the surface of a semiconductor wafer, the back surface of the semiconductor wafer is ground with a grinding device to thin the semiconductor wafer before dividing the semiconductor wafer into device units.

[0003] The grinding device is equipped with a grinding unit that grinds the semiconductor wafers, as well as a thickness gauge that measures the thickness of the semiconductor wafers. While measuring the thickness of the semiconductor wafer with the thickness gauge, the grinding unit grinds the semiconductor wafers until they reach the target thickness.

[0004] Known thickness gauges include non-contact thickness gauges that project measurement light in a wavelength band that passes through a semiconductor wafer from a sensor head, receive reflected light from the front and back surfaces of the semiconductor wafer in response to the measurement light, and use the interference of these reflected lights to measure the thickness of a semiconductor wafer using an optical method without contacting the semiconductor wafer (see, for example, Patent Document 1).

[0005] Another known thickness gauge is a contact type that measures the thickness of a semiconductor wafer by using a first stylus that contacts the semiconductor wafer and a second stylus that contacts the holding surface of a chuck table that holds the semiconductor wafer by suction.

[0006] The grinding unit has a spindle, and a circular grinding wheel is attached to the lower end of the spindle. The grinding wheel has a circular wheel base and a plurality of grinding stones arranged at approximately equal intervals around the circumferential direction of the wheel base on the underside of the wheel base.

[0007] When a semiconductor wafer is ground using a grinding device, the semiconductor wafer is ground while grinding water such as pure water is supplied to the contact area between the grinding wheel and the semiconductor wafer. When the semiconductor wafer is ground, a mist of grinding water mixed with grinding debris is scattered around.

[0008] The mist-like grinding water containing grinding debris may adhere to the thickness gauge and then fall from the gauge onto the holding surface of the chuck table. If the fallen grinding debris adheres to the holding surface, the semiconductor wafer may be ground with the grinding debris trapped between the holding surface and the semiconductor wafer, which may lead to cracking of the semiconductor wafer or poor adhesion of the semiconductor wafer to the holding surface.

[0009] Of course, grinding debris can be removed by cleaning the thickness gauge, but the thickness gauge is located inside the processing chamber cover that defines the grinding chamber, and this processing chamber cover is located inside the housing of the grinding device.

[0010] Therefore, in order to clean the thickness gauge, a series of steps are required: the operation of the grinding machine must be stopped, the thickness gauge placed inside the grinding chamber must be removed from the grinding machine, the gauge must be cleaned, and then the gauge must be returned to its original position.

[0011] Of course, the thickness gauge can be cleaned by removing it from the grinding machine, but the above-mentioned series of steps requires a worker with sufficient work experience to perform the steps, and the grinding machine cannot be used during the steps. Therefore, there is a demand for a way to clean the thickness gauge while it is attached to the grinding machine. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-119123 Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention has been made in view of the above problems, and has as its object to clean a thickness gauge while the thickness gauge remains attached to a grinding machine. [Means for solving the problem]

[0014] According to one aspect of the present invention, there is provided a cleaning method for cleaning a thickness gauge in a grinding apparatus having a chuck table that holds a workpiece on a holding surface and a thickness gauge that measures the thickness of the workpiece held on the holding surface, the cleaning method comprising: a liquid discharging step of discharging liquid from a grinding wheel that has a circular wheel base and a grinding stone portion arranged in a ring shape on one surface of the wheel base, the liquid passing through the inside of the wheel base and being supplied to the grinding stone portion from a grinding wheel attached to the lower end of a spindle; and a cleaning step of cleaning the thickness gauge by bringing the liquid into contact with the upper parts of the arm and the sensor head, the thickness gauge including an arm and a sensor head fixed to the tip of the arm.

[0015] Preferably, in the cleaning step, the thickness gauge is cleaned while a fluid is jetted outward from the holding surface on which the workpiece is not held.

[0016] Preferably, in the cleaning step, the thickness measuring device is cleaned in a state where the sensor head is placed in a retracted position where the sensor head does not overlap the holding surface in the vertical direction.

[0017] Preferably, in the cleaning process, the upper parts of the arm and the sensor head are cleaned with the liquid supplied from the grinding wheel, and the lower part of the sensor head is cleaned with fluid ejected from the holding surface by moving the sensor head horizontally. [Effects of the Invention]

[0018] In a cleaning method according to one aspect of the present invention, the upper portions of the arm and the sensor head of the thickness gauge are cleaned with the liquid discharged from the grinding wheel, which passes through the inside of the wheel base and is supplied to the grinding wheel portion. Therefore, the thickness gauge can be cleaned while it is attached to the grinding machine. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a flow diagram of a cleaning method. [Figure 2] FIG. [Figure 3] FIG. 2 is a partial cross-sectional side view showing how the thickness of a workpiece is measured by a thickness gauge. [Figure 4] FIG. 4(A) is a partially sectional side view showing the liquid discharging step and the cleaning step according to the first embodiment, and FIG. 4(B) is a plan view showing the liquid discharging step and the cleaning step according to the first embodiment. [Figure 5] FIG. 5(A) is a partially cross-sectional side view of the liquid discharging step and the cleaning step according to the first modified example, and FIG. 5(B) is a plan view of the liquid discharging step and the cleaning step according to the first modified example. [Figure 6] FIG. 6(A) is a partially cross-sectional side view of the liquid discharging step and the cleaning step according to the second modified example, and FIG. 6(B) is a plan view of the liquid discharging step and the cleaning step according to the second modified example. [Figure 7] FIG. 7(A) is a partially cross-sectional side view of the liquid discharging step and the cleaning step according to the third modified example, and FIG. 7(B) is a plan view of the liquid discharging step and the cleaning step according to the third modified example. [Figure 8] FIG. 10 is a partial cross-sectional side view showing how the thickness of a workpiece is measured by a thickness measuring device according to a second embodiment. [Figure 9] FIG. 9(A) is a partial cross-sectional side view showing the liquid discharging step and the cleaning step according to the second embodiment, and FIG. 9(B) is a plan view showing the liquid discharging step and the cleaning step according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] (First embodiment) An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a flow diagram of a cleaning method. The cleaning method of this embodiment includes a liquid releasing step S10 and a cleaning step S20.

[0021] The liquid discharging step S10 includes discharging grinding water (liquid) 44a (see FIG. 4(A) etc.) from the rough grinding wheel 48a to a thickness measuring device 20 (see FIG. 2) described later. The cleaning step S20 includes cleaning the thickness measuring device 20 with the discharged grinding water 44a.

[0022] The cleaning step S20 is not started after the liquid discharging step S10 is completed, but is started after the liquid discharging step S10 is started and while the grinding water 44a is being continuously discharged. Therefore, the time when the liquid discharging step S10 is performed and the time when the cleaning step S20 is performed partially overlap.

[0023] The liquid discharging step S10 is usually completed before the timing when the cleaning step S20 is completed. However, the amount of the grinding water 44a discharged per unit time may be significantly reduced, so that the cleaning of the thickness gauge 20 with the grinding water 44a is substantially completed while the discharge of the grinding water 44a continues.

[0024] In this case, the liquid discharging process S10 will still be ongoing when the cleaning process S20 ends, resulting in the waste of grinding water 44a that is not used for grinding or cleaning, but this may be acceptable if the amount of grinding water 44a discharged per unit time is very small.

[0025] The above contents are included in the flow diagram shown in Fig. 1. That is, the flow diagram shown in Fig. 1 at least means that the liquid releasing step S10 is started first, and then the cleaning step S20 is started.

[0026] Here, a grinding apparatus 2 in which the above-mentioned cleaning method is performed will be described with reference to Fig. 2. Fig. 2 is a perspective view of the grinding apparatus 2. Note that the X-axis, Y-axis, and Z-axis shown in Fig. 2 are perpendicular to one another. The Z-axis is parallel to the up-down direction.

[0027] In this embodiment, one direction along the Z axis is referred to as the upward direction, and the other direction along the Z axis is referred to as the downward direction. Also, one direction along the Y axis is referred to as the forward direction (or front), and the other direction along the Y axis is referred to as the backward direction (or rear).

[0028] The grinding device 2 includes a substantially rectangular parallelepiped base 4. A recess 4a is formed in the front region of the base 4. A horizontal articulated robot (hereinafter referred to as a transfer robot 6) for transferring a workpiece 11 (see FIG. 3) is provided in this recess 4a.

[0029] Cassette placement areas 8a and 8b are provided near the recess 4a. A cassette 10a containing one or more workpieces 11 before grinding is placed in the cassette placement area 8a, and similarly, a cassette 10b containing one or more workpieces 11 before grinding is placed in the cassette placement area 8b.

[0030] A positioning table 12 is provided near the recess 4a and behind the cassette placement areas 8a and 8b to determine the position of the workpiece 11 carried out by the transfer robot 6. Near the positioning table 12, a base end of a loading arm 14 is provided to carry the workpiece 11 out of the positioning table 12.

[0031] The loading arm 14 has a disk-shaped pad at its tip for suction-holding the workpiece 11. A disk-shaped turntable 16 that can rotate within the XY plane is provided behind the base end of the loading arm 14.

[0032] A plurality of partition plates 16a are provided radially on the upper surface of the turntable 16. The plurality of partition plates 16a divide the upper surface of the turntable 16 into a plurality of fan-shaped regions each having approximately the same central angle.

[0033] In this embodiment, the upper surface of the turntable 16 is divided into three sector-shaped areas, and one disk-shaped chuck table 18 is provided in the center of each sector-shaped area. Each sector-shaped area corresponds to one of a carry-in / carry-out area A, a rough grinding area B, and a finish grinding area C.

[0034] The sector-shaped area closest to the base end of the loading arm 14 is the loading / unloading area A. The loading arm 14 transports the workpiece 11 from the positioning table 12 to the chuck table 18 in the loading / unloading area A.

[0035] A fan-shaped area approximately 120 degrees clockwise from the carry-in / carry-out area A in a top view is the rough grinding area B. The workpiece 11 placed in the rough grinding area B is ground by a rough grinding unit 36a, which will be described later.

[0036] A fan-shaped area approximately 120 degrees counterclockwise from the carry-in / carry-out area A in a top view is the finish grinding area C. The workpiece 11 placed in the finish grinding area C is ground by the finish grinding unit 36b, which will be described later.

[0037] A rotary drive source (not shown), such as a motor, is provided below the turntable 16. When the rotary drive source is operated, the turntable 16 rotates. The turntable 16 can rotate both clockwise and counterclockwise.

[0038] As the turntable 16 rotates, the chuck tables 18 of the sector-shaped areas move, but the positions of the loading / unloading area A, rough grinding area B, and finish grinding area C in the grinding device 2 remain fixed and do not move.

[0039] Here, the chuck table 18 will be described with reference to Fig. 3. The chuck table 18 has a disk-shaped frame body 18b made of dense ceramics that is not porous. A disk-shaped recess is formed on the top surface of the frame body 18b.

[0040] A disk-shaped porous plate 18c made of porous ceramics is fixed to the recess of the frame body 18b using an adhesive, etc. A negative pressure is transmitted to the porous plate 18c from a suction source (not shown) such as a vacuum pump through a flow path (not shown) formed in the frame body 18b.

[0041] The upper surface of the frame body 18b and the upper surface of the porous plate 18c are substantially flush with each other, forming a holding surface 18a for suction-holding the workpiece 11. The holding surface 18a has a conical shape with the center slightly protruding compared to the outer periphery.

[0042] When the workpiece 11 is held by suction on the holding surface 18a, the workpiece 11 is held by suction on the holding surface 18a in a deformed state following the shape of the holding surface 18a. However, since the amount of protrusion at the center of the holding surface 18a is extremely small (for example, about 20 μm), the holding surface 18a is shown as being approximately flat in FIG.

[0043] The outer diameter of the holding surface 18a (i.e., the outer diameter of the frame body 18b) is, for example, 230 mm, and the outer diameter of the porous plate 18c is a predetermined value, for example, between 185 mm and 205 mm. The outer diameter of the holding surface 18a is appropriately selected depending on the diameter of the workpiece 11 to be ground. The workpiece 11 to be ground by the grinding device 2 has, for example, a diameter of approximately 200 mm (8 inches) and a thickness of 725 μm.

[0044] A rotary drive source (not shown), such as a motor, is provided below each chuck table 18. When the rotary drive source is operated, the chuck table 18 rotates around the rotation axis 18d without any restriction on the rotation angle.

[0045] A thickness measuring device 20 is provided outside the turntable 16, to the side of the rough grinding area B (see FIG. 2). The thickness measuring device 20 of this embodiment is a spectral interference type thickness measuring device, and can measure the thickness of the workpiece 11 held by suction on the holding surface 18a without directly contacting the workpiece 11 (i.e., non-contact).

[0046] 3 is a partial cross-sectional side view showing how the thickness of the workpiece 11 is measured by the thickness gauge 20. The thickness gauge 20 has a cylindrical base 20a. The longitudinal direction of the base 20a is aligned along the Z-axis direction.

[0047] The base end of a rod-shaped arm 20b is fixed to the top of the base 20a in a manner that it protrudes from the side of the top. The arm 20b has a shape such as a polygonal pillar or a cylinder. The longitudinal direction of the arm 20b is arranged along the XY plane.

[0048] For example, if arm 20b has a rectangular prism shape, upper surface 20b1 and lower surface 20b2 of arm 20b are each approximately flat surfaces, and if arm 20b is cylindrical, upper surface 20b1 and lower surface 20b2 are each curved surfaces corresponding to the side surfaces of a semi-cylinder.

[0049] A rotary drive source (not shown), such as a motor, is provided at the bottom of the base 20a. The rotary drive source enables the arm 20b to rotate around a rotation axis 20a1 of the base 20a. A cylindrical sensor head 20c is fixed to the tip of the arm 20b.

[0050] The sensor head 20c has a shape such as a polygonal pillar or a cylinder. The longitudinal direction of the sensor head 20c is arranged along the Z-axis direction. Fig. 3 shows the case where the sensor head 20c has a cylindrical shape. The sensor head 20c has a circular upper surface 20c1 and a circular lower surface 20c2.

[0051] The sensor head 20c may have a cylindrical lower and middle section and a truncated cone-shaped upper section. In this case, the lower, middle, and upper sections are arranged concentrically. In either configuration, the sensor head 20c includes an upper section that protrudes above the arm 20b and a lower section that protrudes below the arm 20b.

[0052] The thickness measuring device 20 of this embodiment includes an optical fiber, a spectroscopic element, a photoelectric conversion element, and a computing device (none of which are shown) in addition to a base 20 a, an arm 20 b, and a sensor head 20 c. The light source is, for example, a super luminescent diode (SLD).

[0053] The light emitted from the light source has a relatively wide spectral width (for example, 0.5 μm to 1500 μm) and can be transmitted through single crystal substrates such as silicon (Si), GaAs (gallium arsenide), and SiC (silicon carbide).

[0054] Light emitted from the light source is transmitted to the sensor head 20c through an optical fiber or the like. A part of the measurement light emitted from the sensor head 20c is reflected by the back surface 11b (corresponding to the top surface in FIG. 3) of the workpiece 11, and another part of the measurement light emitted from the sensor head 20c is reflected by the front surface 11a (corresponding to the bottom surface in FIG. 3) of the workpiece 11.

[0055] The interference light between the light reflected from the rear surface 11b and the light reflected from the front surface 11a returns to the sensor head 20c and enters a spectroscopic element such as a diffraction grating through an optical fiber, etc. The interference light separated according to wavelength by the spectroscopic element is converted into an electrical signal according to the intensity of each wavelength by a photoelectric conversion element such as a line sensor.

[0056] The electrical signal output from the photoelectric conversion element is input to a calculation device, which is, for example, a computer including a CPU (Central Processing Unit), and performs processing such as fast Fourier transform and filtering on the information contained in the electrical signal from the photoelectric conversion element to calculate the thickness of the workpiece 11.

[0057] The arithmetic unit may be housed in an independent housing and electrically connected to the grinding apparatus 2, or may be housed together in a housing that houses a controller (described later). The arithmetic unit may be connected to the grinding apparatus 2 via wireless communication.

[0058] A thickness gauge 22 is provided outside the turntable 16, to the side of the finish grinding area C. The thickness gauge 22 is a spectral interference type thickness gauge like the thickness gauge 20, so a detailed description thereof will be omitted. The description of the thickness gauge 20 also applies to the thickness gauge 22.

[0059] Returning now to Figure 2, a square pillar-shaped support structure 24a is provided behind the turntable 16 in a manner that protrudes from the upper surface of the base 4. A grinding feed unit 26 is provided on the front side of the support structure 24a.

[0060] The grinding feed unit 26 has a pair of Z-axis guide rails 28 that are fixed to the front surface of the support structure 24a and are generally parallel to the Z-axis direction. A moving plate 30 is slidably attached to the pair of Z-axis guide rails 28.

[0061] A nut portion (not shown) is provided on the back surface of the moving plate 30. A screw shaft 32 is rotatably coupled to the nut portion via a plurality of balls (not shown). The screw shaft 32 is provided between the pair of Z-axis guide rails 28, with its longitudinal direction aligned along the Z-axis direction.

[0062] A motor 34 such as a pulse motor or a stepping motor is connected to the upper end of the screw shaft 32. When the motor 34 rotates the screw shaft 32, the moving plate 30 moves along the Z-axis direction. A rough grinding unit 36a is fixed to the front surface of the moving plate 30.

[0063] The rough grinding unit 36a has a cylindrical holding member 38. The rough grinding unit 36a will now be described with reference to Fig. 4(A). As shown in Fig. 4(A), a cylindrical spindle housing 40 is provided inside the holding member 38.

[0064] A cylindrical spindle 42, whose longitudinal direction is arranged substantially parallel to the Z-axis direction, is partially rotatably housed within the spindle housing 40. The spindle 42 can be rotated by a motor (not shown) provided within the spindle housing 40 without any restriction on the rotation angle.

[0065] A first flow path 42a for supplying grinding water 44a such as pure water is formed inside the spindle 42. A grinding water supply source 44 is connected to the first flow path 42a. The grinding water supply source 44 may be provided inside the base 4, or may be arranged outside the base 4 and connected to the grinding device 2 via a pipe (not shown).

[0066] The grinding water supply source 44 includes a storage tank (not shown) in which pure water or the like is stored, a pump (not shown) for supplying pure water from the storage tank to the first flow path 42a, etc. The lower end of the spindle 42 protrudes downward beyond the lower ends of the spindle housing 40 and the holding member 38.

[0067] A disk-shaped wheel mount 46 is fixed to the lower end of the spindle 42. A central flow path for the grinding water 44a is formed from the center of the upper surface of the wheel mount 46 to a predetermined depth along the thickness direction of the wheel mount 46.

[0068] The central passage of the wheel mount 46 is connected to the first passage 42a of the spindle 42 on the upper surface of the wheel mount 46. The lower end of the central passage of the wheel mount 46 is connected to a plurality of second passages 46a, each extending radially from the center of the wheel mount 46 along the radial direction at a predetermined depth within the wheel mount 46.

[0069] The outer peripheral end of the second flow passage 46a terminates at a predetermined position in the radial direction of the wheel mount 46 that does not reach the outer peripheral side surface of the wheel mount 46. An outer flow passage 46b that extends along the thickness direction of the wheel mount 46 and reaches the underside of the wheel mount 46 is connected to each outer peripheral end of the multiple second flow passages 46a.

[0070] The multiple outer flow passages 46b in the wheel mount 46 are connected and arranged at approximately equal intervals along the radial direction of the wheel mount 46. The central flow passage, the multiple second flow passages 46a, and the multiple outer flow passages 46b form a flow passage for the grinding water 44a within the wheel mount 46.

[0071] An annular rough grinding wheel 48a is attached by a fixing member (not shown) such as a bolt to the lower surface of the wheel mount 46. In other words, the rough grinding wheel 48a is attached to the lower end of the spindle 42 via the wheel mount 46.

[0072] The rough grinding wheel 48a includes an annular wheel base 50a made of a metal material such as stainless steel, and a plurality of rough grinding stones (grinding stone portions) 54a fixed to a lower surface (one surface) 52a of the wheel base 50a. The outer diameter of the wheel base 50a is approximately the same as the outer diameter of the holding surface 18a.

[0073] The upper surface of the wheel base 50a is generally flat, but the lower surface of the wheel base 50a has an annular stepped shape, with the thickness of the lower surface of the wheel base 50a gradually decreasing from the outer side to the inner side in the radial direction.

[0074] The annular stepped shape includes a relatively thick first annular region and a relatively thin second annular region located more inward than the first annular region. The inner peripheral edge of the lower surface of the first annular region and the outer peripheral edge of the lower surface of the second annular region are connected by an annular inner peripheral side surface having a shape corresponding to the side surface of a truncated cone.

[0075] A plurality of rough grinding wheels 54a are fixed to the lower surface of the first annular region, and are arranged at approximately equal intervals along the circumferential direction of the lower surface 52a of the wheel base 50a.

[0076] The rough grinding wheel 54a is formed by mixing abrasive grains such as diamond or cBN (cubic boron nitride) with a binder such as metal, ceramics, or resin, and then molding and firing the mixture.

[0077] The second annular region is provided with a plurality of wheel passages. Each wheel passage extends from the upper surface to the lower surface of the second annular region so as to penetrate the wheel base 50a. The upper end of each wheel passage is connected to a corresponding outer passage 46b.

[0078] The lower end of each wheel flow path is an opening exposed on the underside of the wheel base 50a. A plurality of openings are arranged at approximately equal intervals on the underside of the wheel base 50a along the circumferential direction of the wheel base 50a.

[0079] The grinding water 44a supplied from the grinding water supply source 44 passes through the first flow path 42a of the spindle 42, the central flow path, the second flow path 46a and the outer flow path 46b of the wheel mount 46, and the wheel flow path of the wheel base 50a, and is discharged from the opening of the second annular region.

[0080] The grinding water 44a discharged from the opening in the second annular region flows along the inner peripheral side surface of the wheel base 50a to the rough grinding wheel 54a and then falls downward from the rough grinding wheel 54a. When the spindle 42 is rotated with the grinding water 44a being discharged from the opening in the second annular region, the grinding water 44a that has reached the rough grinding wheel 54a is scattered to the outside of the rough grinding wheel 48a by centrifugal force.

[0081] Returning now to Figure 2, a square pillar-shaped support structure 24b is provided at a position adjacent to the support structure 24a in the X-axis direction behind the turntable 16. The grinding feed unit 26 described above is also provided on the front side of the support structure 24b.

[0082] The grinding feed unit 26 can move the finish grinding unit 36b along the Z-axis direction. The finish grinding unit 36b has a cylindrical holding member 38. The above-mentioned spindle housing 40 is provided inside the holding member 38. A portion of the above-mentioned spindle 42 is rotatably housed in the spindle housing 40.

[0083] The above-mentioned wheel mount 46 is provided at the lower end of the spindle 42. An annular finish grinding wheel 48b is attached to the lower surface of the wheel mount 46. In other words, the finish grinding wheel 48b is attached to the lower end of the spindle 42 via the wheel mount 46.

[0084] The finish grinding unit 36b has substantially the same shape and structure as the rough grinding unit 36a, except that a finish grinding wheel 48b is mounted on the wheel mount 46. The finish grinding wheel 48b includes a wheel base having the same shape and structure as the wheel base 50a.

[0085] A plurality of finish grinding wheels (grinding wheel portions) are arranged at approximately equal intervals along the circumferential direction of the underside of the wheel base. The average grain size of the abrasive grains of the finish grinding wheels is smaller than the average grain size of the abrasive grains of the rough grinding wheels 54a.

[0086] Grinding water 44a supplied from the grinding water supply source 44 passes through the spindle 42 and the wheel mount 46 in that order, and is discharged from an opening in the second annular region located radially inside the finish grinding stone of the finish grinding wheel 48b.

[0087] Incidentally, a machining chamber cover (not shown) is provided above and to the side of the turntable 16 so as to cover the rough grinding area B and the finish grinding area C excluding the carry-in / carry-out area A. The machining chamber cover has a plurality of side plates, and a notch large enough to allow the partition plate 16a to pass through when the turntable 16 rotates is formed in the lower end of one of the side plates.

[0088] An exhaust opening is formed in the center of the other side plate, which is different from the side plate in which the notch is formed. One end of an exhaust duct (not shown) is connected to the exhaust opening, and the other end of the exhaust duct is connected to a suction source (not shown), such as a vacuum pump or an ejector.

[0089] The mist-like grinding water 44a that fills the machining chamber when the workpiece 11 is ground is exhausted from the machining chamber through an exhaust duct. However, it is not possible to exhaust all of the mist-like grinding water 44a, and some of the mist-like grinding water 44a adheres to the thickness gauges 20 and 22, causing grinding chips to adhere to the thickness gauges 20 and 22.

[0090] The top plate of the processing chamber cover is formed with a first opening for the rough grinding wheel 48a to pass through and a second opening for the finish grinding wheel 48b to pass through. The processing chamber cover also covers the thickness gauges 20 and 22 described above.

[0091] The base end of an unloading arm 60 is provided in front of the turntable 16. The unloading arm 60 has a disk-shaped pad at its tip that suction-holds the workpiece 11. The unloading arm 60 carries the workpiece 11 out of the chuck table 18 in the carry-in / carry-out area A to a spinner cleaning unit 62.

[0092] The spinner cleaning unit 62 cleans and dries the ground workpiece 11. The workpiece 11 cleaned and dried in the spinner cleaning unit 62 is returned by the transfer robot 6 to the cassettes 10a, 10b from which it was taken out.

[0093] The operation of the grinding device 2 is controlled by a controller (not shown). The controller is configured by a computer including, for example, a processing device such as a CPU (Central Processing Unit), a main storage device such as a DRAM (Dynamic Random Access Memory), and an auxiliary storage device such as a flash memory.

[0094] The functions of the controller are realized by operating the processing device etc. in accordance with the software stored in the auxiliary storage device. Next, a cleaning method for cleaning the thickness measuring device 20 in the grinding device 2 will be described with reference to Figures 4(A) and 4(B).

[0095] FIG. 4(A) is a partially cross-sectional side view of the liquid discharging step S10 and the cleaning step S20 according to the first embodiment, and FIG. 4(B) is a plan view of the liquid discharging step S10 and the cleaning step S20 according to the first embodiment.

[0096] Before grinding the workpiece 11, the rough grinding unit 36a and the finish grinding unit 36b are warmed up (i.e., idling or warm-up operation) for a predetermined time (e.g., 30 minutes) while the workpiece 11 is not held on the holding surface 18a. The thickness gauges 20 and 22 are cleaned, for example, during this warm-up period.

[0097] Incidentally, if the spindle 42 is rotated when cleaning the thickness gauges 20 and 22, there is an advantage in that cleaning of the thickness gauges 20 and 22 and warming up of the rough grinding unit 36a and the finish grinding unit 36b can be performed at the same time.

[0098] 4(A) and 4(B) show the liquid discharging step S10 and the cleaning step S20 in the rough grinding unit 36a, but the liquid discharging step S10 and the cleaning step S20 in the finish grinding unit 36b are similar.

[0099] During warm-up, the sensor head 20c is made stationary at a measurement position P1 (see FIG. 4B) that does not overlap with the rough grinding unit 36a in the Z-axis direction and is located above the holding surface 18a.

[0100] First, the height position of the rough grinding wheel 48a is adjusted using the grinding feed unit 26, and the lower surface of the rough grinding stone 54a is positioned higher than the upper surface 20c1 of the sensor head 20c and the upper surface 20b1 of the arm 20b. At this time, the lower surface of the rough grinding stone 54a is spaced apart from the holding surface 18a by a predetermined distance, for example, between 5 cm and 10 cm.

[0101] Of course, the height position of the lower surface of the rough grinding stone 54a (i.e., the rough grinding wheel 48a) is adjusted appropriately depending on the rotational speed (rpm) of the spindle 42 and the flow rate (l / min) of the grinding water 44a supplied to the rough grinding wheel 48a.

[0102] Next, rotation of the spindle 42 and supply of grinding water 44a to the rough grinding wheel 48a are started from the grinding water supply source 44. At this time, the spindle 42 is rotated at the same rotation speed as that used when grinding the workpiece 11 (for example, a predetermined value between 2500 rpm and 5000 rpm when the diameter of the rough grinding wheel 48a is 200 mm).

[0103] Furthermore, the grinding water 44a is supplied to the rough grinding wheel 48a from the grinding water supply source 44 at a predetermined flow rate of, for example, 2 (L / min) to 5 (L / min). In this manner, the rough grinding wheel 48a is rotated, and the grinding water 44a that passes through the inside of the wheel base 50a and is supplied to the rough grinding stone 54a is discharged from the rough grinding wheel 48a (liquid discharging step S10).

[0104] Then, the thickness measuring device 20 is cleaned by bringing grinding water 44a into contact with the upper surface (upper portion) 20c1 of the sensor head 20c and the upper surface (upper portion) 20b1 of the arm 20b, and grinding debris adhering to the thickness measuring device 20 and water containing the grinding debris are removed with the grinding water 44a (cleaning process S20).

[0105] In the cleaning step S20 of this embodiment, in particular, the entire upper surface 20c1 of the sensor head 20c is cleaned, and the tip of the upper surface 20b1 of the arm 20b near the sensor head 20c is cleaned.

[0106] In this embodiment, the thickness gauge 20 can be washed without removing it from the grinding apparatus 2, while the thickness gauge 20 remains attached to the grinding apparatus 2.

[0107] Furthermore, by rotating the rough grinding wheel 48a, the grinding water 44a can be sprayed with more force than when the grinding water 44a is allowed to drop, which improves the cleaning effect compared to when the rough grinding wheel 48a is not rotated.

[0108] In the cleaning step S20, it is sufficient to clean the upper portions of the arm 20b and the sensor head 20c that overlap with the holding surface 18a in the Z-axis direction, and it is not necessary to clean the base 20a. Since the base 20a is always located outside the holding surface 18a in the XY plane view, it does not matter whether the base 20a is cleaned or not.

[0109] Incidentally, in the liquid discharging step S10 and the cleaning step S20, it is not essential to rotate the spindle 42, and the spindle 42 does not have to be rotated. That is, the rotation speed of the spindle 42 may be set to zero rpm. In this case, the height of the rough grinding wheel 48a and the flow rate of the grinding water 44a are appropriately adjusted so that the thickness gauge 20 is covered with water.

[0110] Furthermore, the warm-up of the rough grinding unit 36a and the finish grinding unit 36b may be performed separately from the cleaning of the thickness gauges 20 and 22. For example, after the rough grinding unit 36a and the finish grinding unit 36b are warmed up by rotating the spindle 42, the thickness gauges 20 and 22 may be cleaned without rotating the spindle 42.

[0111] Conversely, after cleaning the thickness gauges 20, 22 without rotating the spindle 42, the spindle 42 can be rotated to warm up the rough grinding unit 36a and the finish grinding unit 36b.

[0112] In the cleaning step S20, the grinding water 44a containing grinding chips and the like falls onto the holding surface 18a during cleaning, but the fallen grinding water 44a generally falls outside the holding surface 18a. However, some of the grinding water 44a may remain on the holding surface 18a.

[0113] In order to prevent the grinding water 44a containing grinding chips and the like from remaining on the holding surface 18a and causing the grinding chips to adhere to the holding surface 18a, pure water or the like may be sprayed from a nozzle (not shown) onto the holding surface 18a after the cleaning step S20 to clean the holding surface 18a.

[0114] (First Modification) Next, a first modification of the first embodiment will be described with reference to Figures 5(A) and 5(B). Figure 5(A) is a partially cross-sectional side view of the liquid discharging step S10 and the cleaning step S20 according to the first modification, and Figure 5(B) is a plan view of the liquid discharging step S10 and the cleaning step S20 according to the first modification.

[0115] In addition to a suction source (not shown), the flow path of the frame body 18b of the first modified example is connected to an air supply source 64 that supplies air (i.e., a gaseous fluid) to the chuck table 18 and a pure water supply source 66 that supplies pure water (i.e., a liquid fluid) 68 to the chuck table 18.

[0116] The air supply source 64 includes a compressor (not shown) that compresses and sends out air taken in from the atmosphere, a tank (not shown) that stores the compressed air, etc. An on-off valve 64a such as a solenoid valve is provided between the flow path of the frame 18b and the air supply source 64.

[0117] The pure water supply source 66 includes a storage tank (not shown) in which pure water 68 and the like are stored, and a pump (not shown) for supplying the pure water 68 from the storage tank to the flow path in the frame body 18b. An opening / closing valve 66a such as an electromagnetic valve is provided between the flow path in the frame body 18b and the pure water supply source 66.

[0118] The air supply source 64 and the pure water supply source 66 are generally arranged outside the base 4 and connected to the grinding device 2 via pipes (not shown), but may also be provided inside the base 4.

[0119] When air is to be ejected from the holding surface 18a, first, the suction source is disconnected from the flow path of the frame body 18b, and then the on-off valve 64a is opened to supply air from the air supply source 64 to the chuck table 18.

[0120] Similarly, when the pure water 68 is to be sprayed from the holding surface 18a, first, the suction source is disconnected from the flow path of the frame body 18b. Next, the on-off valve 66a is opened, and the pure water 68 is supplied from the pure water supply source 66 to the chuck table 18.

[0121] Instead of only the pure water 68, a gas-liquid mixed fluid (i.e., two-fluid) of air and pure water 68 may be sprayed from the holding surface 18a. In this case, the connection between the suction source and the flow path of the frame body 18b is cut off, and the on-off valves 64a and 66a are opened to supply air from the air supply source 64 and pure water 68 from the pure water supply source 66 to the chuck table 18, respectively.

[0122] In the first modified example, the thickness measuring device 20 is also cleaned when the grinding device 2 is warmed up, with the workpiece 11 not being held by the holding surface 18a. In the liquid discharging step S10 shown in Figures 4(A) and 4(B), the height position of the rough grinding wheel 48a is adjusted, and pure water 68 is sprayed from the holding surface 18a.

[0123] Next, rotation of the spindle 42 and supply of grinding water 44a to the rough grinding wheel 48a are started from the grinding water supply source 44. Then, in the cleaning process S20, the upper surface (upper portion) 20c1 of the sensor head 20c and the upper surface (upper portion) 20b1 of the arm 20b are cleaned while pure water 68 is sprayed from the holding surface 18a.

[0124] Of course, instead of only the pure water 68, only air may be ejected from the holding surface 18a, or the above-mentioned gas-liquid mixed fluid may be ejected from the holding surface 18a. In the first modified example, since the fluid is ejected from the holding surface 18a, the amount of grinding chips that fall from the thickness measuring device 20 onto the holding surface 18a and remain on the holding surface 18a can be reduced.

[0125] Therefore, the holding surface 18a can be made cleaner after the cleaning step S20 compared to when no fluid is sprayed from the holding surface 18a in the cleaning step S20. Of course, the various alternative aspects described in the first embodiment, such as whether or not the spindle 42 rotates, can also be applied to the first modified example.

[0126] (Second Modification) Next, a second modification of the first embodiment will be described with reference to Figures 6(A) and 6(B). Figure 6(A) is a partially cross-sectional side view of the liquid discharging step S10 and the cleaning step S20 according to the second modification, and Figure 6(B) is a plan view of the liquid discharging step S10 and the cleaning step S20 according to the second modification.

[0127] The second variant is a further variant of the first variant, in which, before the liquid release step S10, the arm 20b is rotated and moved to position the sensor head 20c at a retracted position P2 where the sensor head 20c does not overlap with the holding surface 18a in the downward direction (i.e., vertical direction).

[0128] At this time, the arm 20b and the sensor head 20c as a whole move outside the holding surface 18a in the XY plane view. With the sensor head 20c stationary at the retracted position P2, the liquid discharging step S10 and the cleaning step S20 are performed to clean the thickness measuring device 20.

[0129] Of course, instead of only the pure water 68, only air may be sprayed from the holding surface 18a, or a gas-liquid mixed fluid may be sprayed from the holding surface 18a. In the second modified example, the amount of grinding chips that drop from the thickness gauge 20 onto the holding surface 18a and come into contact with the holding surface 18a can be further reduced compared to the first modified example. In the second modified example, the various alternative aspects described in the first embodiment, such as whether or not the spindle 42 rotates, can also be applied.

[0130] (Third Modification) Next, a third modification of the first embodiment will be described with reference to Figures 7(A) and 7(B). Figure 7(A) is a partially cross-sectional side view of the liquid discharging step S10 and the cleaning step S20 according to the third modification, and Figure 7(B) is a plan view of the liquid discharging step S10 and the cleaning step S20 according to the third modification. The third modification is a further modification of the first and second modifications.

[0131] In the cleaning process S20 of the third modified example, the arm 20b is rotated around the rotation axis 20a1 to oscillate (i.e., move) the sensor head 20c in the horizontal direction (a direction parallel to the XY plane) between the measurement position P1 and the retracted position P2, and pure water 68 is sprayed from the holding surface 18a to clean the thickness gauge 20.

[0132] The upper surface 20b1 of the arm 20b and the upper surface 20c1 of the sensor head 20c are cleaned with grinding water 44a supplied from the rough grinding wheel 48a, and by moving the sensor head 20c horizontally, the lower surface (lower part) 20b2 of the arm 20b and the lower surface (lower part) 20c2 of the sensor head 20c are cleaned with pure water 68 sprayed from the holding surface 18a.

[0133] Of course, instead of only the pure water 68, only air may be ejected from the holding surface 18a, or a gas-liquid mixed fluid may be ejected from the holding surface 18a. In the third modified example, the arm 20b and the sensor head 20c are swung above the holding surface 18a and a fluid is ejected from the holding surface 18a, so that the lower parts of the arm 20b and the sensor head 20c can be cleaned with the fluid from the holding surface 18a.

[0134] Of course, the grinding water 44a can be used to clean the upper parts of the arm 20b and the sensor head 20c, and the fluid ejected from the holding surface 18a can reduce the amount of grinding debris remaining on the holding surface 18a. Of course, the various alternative aspects described in the first embodiment, such as whether or not the spindle 42 rotates, can also be applied to the third modified example.

[0135] (Second embodiment) Next, a second embodiment will be described with reference to Fig. 8, Fig. 9(A) and Fig. 9(B). In the second embodiment, a contact-type thickness gauge 80 is provided near the rough grinding region B. In this respect, it differs from the non-contact-type thickness gauge 20 in the first embodiment.

[0136] 8 is a partial cross-sectional side view showing how the thickness of the workpiece 11 is measured by a thickness measuring device 80 according to the second embodiment. The thickness measuring device 80 comes into direct contact with the workpiece 11, thereby being able to measure the thickness of the workpiece 11 held by suction on the holding surface 18a.

[0137] The thickness measuring device 80 has a rectangular pillar-shaped base 82a. The base end of a rod-shaped first arm 82b and the base end of a rod-shaped second arm 84b are fixed to the top of the base 82a. The base 82a can be moved along the Z-axis direction by an actuator (not shown).

[0138] A cylindrical first sensor head 82c is fixed to the tip of the first arm 82b, and a cylindrical second sensor head 84c is fixed to the tip of the second arm 84b.

[0139] An upper surface 82c1 of the first sensor head 82c protrudes upward beyond an upper surface 82b1 of the first arm 82b, and an upper surface 84c1 of the second sensor head 84c protrudes upward beyond an upper surface 84b1 of the second arm 84b.

[0140] The lower portions of the first sensor head 82c and the second sensor head 84c are tapered. A lower end 82c2 of the first sensor head 82c protrudes downward beyond the lower surface 82b2 of the first arm 82b. A lower end 84c2 of the second sensor head 84c protrudes downward beyond the lower surface 84b2 of the second arm 84b.

[0141] When measuring the thickness of the workpiece 11, the lower end 82c2 of the first sensor head 82c is brought into contact with the back surface 11b of the workpiece 11, and the lower end 84c2 of the second sensor head 84c is brought into contact with the upper surface of the frame 18b of the chuck table 18.

[0142] The thickness measuring device 80 has a calculation device with a CPU, and this calculation device calculates the thickness of the workpiece 11 by calculating the difference between the height position measured using the first sensor head 82c and the height position measured using the second sensor head 84c.

[0143] The thickness measuring device 80 of the second embodiment includes a base 82a, a first arm 82b, a first sensor head 82c, a second arm 84b, a second sensor head 84c, and a computing device. However, the computing device may be configured integrally with the above-mentioned controller.

[0144] Although not shown, a contact-type thickness gauge similar to thickness gauge 80 is provided outside turntable 16 and to the side of finish grinding area C. Next, a cleaning method for cleaning thickness gauge 80 will be described.

[0145] FIG. 9(A) is a partially cross-sectional side view of the liquid discharging step S10 and the cleaning step S20 according to the second embodiment, and FIG. 9(B) is a plan view of the liquid discharging step S10 and the cleaning step S20 according to the second embodiment.

[0146] In the second embodiment, cleaning is also performed during warm-up of the thickness measuring device 80. During warm-up, first, the height position of the rough grinding wheel 48a is adjusted by the grinding feed unit 26 so that the rough grinding stone 54a is positioned above the upper surface 80c1 of the sensor head 80c and the upper surface 80b1 of the arm 80b.

[0147] Next, rotation of the spindle 42 and supply of grinding water 44a to the rough grinding wheel 48a are started from the grinding water supply source 44. In this way, while the rough grinding wheel 48a is rotated, the grinding water 44a that passes through the inside of the wheel base 50a and is supplied to the rough grinding stone 54a is discharged from the rough grinding wheel 48a (liquid discharge step S10).

[0148] Then, the thickness measuring device 80 is cleaned by bringing grinding water 44a into contact with the upper surface (upper part) 82c1 of the first sensor head 82c, the upper surface (upper part) 84c1 of the second sensor head 84c, the upper surface (upper part) 82b1 of the first arm 82b, and the upper surface (upper part) 84b1 of the second arm 84b, thereby removing grinding chips adhering to the thickness measuring device 80 and water containing the grinding chips with the grinding water 44a (cleaning process S20).

[0149] In the second embodiment, the thickness gauge 80 can also be cleaned while it is attached to the grinding apparatus 2, without having to be removed from the grinding apparatus 2. Furthermore, by rotating the rough grinding wheel 48a, the grinding water 44a can be sprayed more forcefully than when the grinding water 44a is allowed to fall. In other words, the cleaning effect can be improved compared to when the rough grinding wheel 48a is not rotated.

[0150] Incidentally, in the liquid discharging step S10 and the cleaning step S20 of the second embodiment, it is not essential to rotate the spindle 42, and it is also possible not to rotate the spindle 42. In other words, the rotation speed of the spindle 42 may be set to zero rpm.

[0151] In addition, in the cleaning process S20, the upper surface 82c1 of the first sensor head 82c, the upper surface 84c1 of the second sensor head 84c, the upper surface 82b1 of the first arm 82b, and the upper surface 84b1 of the second arm 84b may be cleaned while pure water 68 is sprayed from the holding surface 18a.

[0152] Of course, instead of only the pure water 68, only air may be sprayed from the holding surface 18a, or a gas-liquid mixed fluid may be sprayed from the holding surface 18a. By spraying a fluid from the holding surface 18a, the amount of grinding chips that fall from the thickness measuring device 80 onto the holding surface 18a and remain on the holding surface 18a can be reduced.

[0153] A contact-type thickness gauge (not shown) provided near the finish grinding area C can also be cleaned in the same manner as the thickness gauge 80. In addition, the structures, methods, etc. according to the above-described embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention.

[0154] In the cleaning step S20 in the above-described embodiment and various modified examples, the chuck table 18 may be rotated. By rotating the chuck table 18, the grinding water 44a, pure water 68, etc. overflowing from the holding surface 18a can be quickly removed by centrifugal force, thereby further reducing the amount of grinding debris remaining on the holding surface 18a. [Explanation of symbols]

[0155] 2: Grinding equipment 4: base, 4a: recess 6: Transport robot 8a, 8b: cassette placement area 10a, 10b: cassette 11: Workpiece, 11a: Front surface, 11b: Back surface 12: Positioning table 14: Loading arm 16: Turntable, 16a: Partition 18: Chuck table 18a: holding surface, 18b: frame, 18c: porous plate, 18d: rotating shaft 20: Thickness measuring instrument 20a: base, 20a1: rotation axis 20b: Arm, 20b1: Top surface (top), 20b2: Bottom surface (bottom) 20c: Sensor head, 20c1: Top surface (upper part), 20c2: Bottom surface (lower part) 22: Thickness measuring instrument 24a, 24b: Support structure 26: Grinding feed unit 28: Z-axis guide rail, 30: moving plate, 32: screw shaft, 34: motor 36a: Rough grinding unit 36b: Finish grinding unit 38: Holding member 40: Spindle housing 42: spindle, 42a: first flow path 44: grinding water supply source, 44a: grinding water (liquid) 46: Wheel mount, 46a: Second flow path, 46b: Outer flow path 48a: Rough grinding wheel, 48b: Finish grinding wheel 50a: Wheel base, 52a: Lower surface, 54a: Rough grinding wheel (grinding wheel part) 60: Unloading arm 62: Spinner cleaning unit 64: Air supply source, 64a: Opening and closing valve 66: pure water supply source, 66a: on-off valve 68: Pure water (fluid) 80: Thickness measuring instrument 82a: Base 82b: First arm, 82b1: Upper surface (upper part), 82b2: Lower surface (lower part) 82c: first sensor head, 82c1: upper surface (upper part), 82c2: lower end (lower part) 84b: 2nd arm, 84b1: Top surface (top), 84b2: Bottom surface (bottom) 84c: second sensor head, 84c1: upper surface (upper part), 84c2: lower end (lower part) A: Loading / unloading area, B: Rough grinding area, C: Finish grinding area P1: Measurement position, P2: Evacuation position S10: Liquid discharge process, S20: Cleaning process

Claims

1. 1. A cleaning method for cleaning a thickness gauge in a grinding machine having a chuck table that holds a workpiece with a holding surface and a thickness gauge that measures the thickness of the workpiece held on the holding surface, comprising: a liquid discharging step of discharging liquid from a grinding wheel having an annular wheel base and a grinding stone portion annularly arranged on one surface of the wheel base, the liquid passing through the inside of the wheel base and being supplied to the grinding stone portion from the grinding wheel attached to the lower end of the spindle; a cleaning step of cleaning the thickness gauge by bringing the liquid into contact with upper portions of the arm and the sensor head of the thickness gauge, the thickness gauge including the arm and the sensor head fixed to the tip of the arm; A cleaning method comprising:

2. 2. The cleaning method according to claim 1, wherein in the cleaning step, the thickness gauge is cleaned while a fluid is jetted outward from the holding surface on which the workpiece is not held.

3. 3. The cleaning method according to claim 1, wherein in the cleaning step, the thickness measuring device is cleaned with the sensor head positioned at a retracted position where the sensor head does not overlap the holding surface in the vertical direction.

4. 3. The cleaning method according to claim 1, wherein in the cleaning step, the upper parts of the arm and the sensor head are cleaned with the liquid supplied from the grinding wheel, and the lower part of the sensor head is cleaned with fluid ejected from the holding surface by moving the sensor head along a horizontal direction.

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