Wafer suction chuck mechanism cleaning equipment

Abstract

To provide a cleaning device for a wafer suction chuck mechanism capable of automatically and easily performing cleaning processing of a chuck surface for sucking and holding a wafer and cleaning processing of a frame suction holding portion.SOLUTION: Frame suction holding portion cleaning means 10B that removes sludge on a frame suction holding portion 11B includes a scraper 17 and a brush 18 pressed against the frame suction holding portion 11B, and a water nozzle 19 that discharges and supplies water onto the frame suction holding portion 11B.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cleaning device for a wafer suction chuck mechanism, and more particularly to a cleaning device for a wafer suction chuck mechanism that suction-holds a wafer integrated with a ring frame by an adhesive film. [Background technology]

[0002] In the field of semiconductor manufacturing, wafers are becoming larger every year. Furthermore, wafers are becoming thinner to increase packaging density. To thin wafers, a process known as back grinding is performed, in which the back surface of a semiconductor wafer (hereinafter referred to as "wafer") is ground to thin the wafer (see, for example, Patent Document 1).

[0003] Currently, grinding machines for thinning wafers are configured to releasably hold a wafer attached to a ring frame by suction on a chuck table, and to releasably hold the ring frame by suction on an annular frame suction holder surrounding the suction chuck. In these grinding machines, cutting sludge adheres to the chuck surface of the chuck table that suction-holds the wafer and to the frame suction holder that suction-holds the ring frame. Therefore, this type of grinding machine requires a mechanism for removing grinding sludge.

[0004] A conventional chuck table is divided into a chuck surface that holds the wafer by suction and a frame suction holder that holds the ring frame by suction. The chuck surface that holds the wafer by suction is cleaned by bringing a rotating dressing grinding wheel into contact with the rotating chuck table. Meanwhile, if sludge is not removed from the frame suction holder, it will interfere with the ring frame's suction. Therefore, to clean the frame suction holder, after wafer grinding, the operator rotates the frame suction holder together with the chuck table, supplies pure water to the frame suction holder with a water gun, and removes sludge by contacting it with Bencotton or similar. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-137349 Summary of the Invention [Problem to be solved by the invention]

[0006] In a cleaning device for a wafer suction chuck mechanism, the chuck surface that suction-holds the wafer is cleaned by pressing a rotating dressing grindstone against a rotating chuck table, and the frame suction holder is cleaned by an operator who, after grinding the wafer, supplies pure water to the frame suction holder with a water gun while rotating the frame suction holder and the chuck table, and removes sludge by contacting it with Bencotton or the like. Therefore, the frame suction holder is cleaned manually by an operator, which poses the problem of poor workability.

[0007] Therefore, a technical problem has arisen that must be solved in order to provide a cleaning device for a wafer suction chuck mechanism that can automatically and easily perform cleaning of the chuck surface that suction-holds the wafer and cleaning of the frame suction-holding portion, and an object of the present invention is to solve this problem. [Means for solving the problem]

[0008] The present invention has been proposed to achieve the above object, and the invention described in claim 1 is a cleaning device for a rotating wafer suction chuck mechanism having a wafer suction chuck portion for suction-holding a wafer attached to a ring frame via an adhesive film, and an annular frame suction holding portion for suction-holding the ring frame outside the wafer suction chuck portion, the cleaning device comprising frame suction holding portion cleaning means that is movable onto the frame suction holding portion and cleans the frame suction holding portion, the frame suction holding portion cleaning means comprising a scraper and brush that can come into contact with the frame suction holding portion. Shitoand a water nozzle for discharging water onto the frame suction holding portion. The water nozzle, brush, and scraper are arranged in this order from the upstream side to the downstream side in the rotation direction of the frame suction holding part. A cleaning device for a wafer suction chuck mechanism is provided.

[0009] According to this configuration, when removing sludge from the frame suction holder, while the wafer chuck mechanism is rotated, the frame suction holder cleaning means is positioned above the frame suction holder, and water is sprayed onto the frame suction holder from the water nozzle while either a brush or a scraper is applied to the frame suction holder. The water causes the sludge to float, and the sludge is then scraped off by either the brush or the scraper. Furthermore, the sludge scraped off by either the brush or the scraper, or both, can be washed away and discharged from the frame suction holder using water sprayed from the water nozzle. Therefore, by linking this operation with the cleaning operation using the suction chuck cleaning grindstone to remove sludge from the frame suction holder cleaning means, sludge removal from the wafer suction chuck and the frame suction holder can be performed simultaneously.

[0010] The invention as set forth in claim 2 provides a wafer suction chuck mechanism cleaning device as set forth in claim 1, further comprising an suction chuck cleaning grindstone unit configured to be movable above the wafer suction chuck unit and to clean the wafer suction chuck unit, and the frame suction holding unit cleaning means is configured to be movable integrally with the suction chuck cleaning grindstone unit.

[0011] With this configuration, when the dressing grindstone of the suction chuck cleaning grindstone unit is brought into contact with the wafer suction chuck unit while the frame suction holder cleaning means is positioned on the frame suction holder, while the wafer chucking mechanism is rotated, the sludge on the wafer suction chuck unit is scraped off by the dressing grindstone, and the sludge on the frame suction holder is scraped off by the frame suction holder cleaning means, thereby enabling sludge removal from the wafer suction chuck unit and the frame suction holder to be performed simultaneously.

[0012] The invention of claim 3 provides a cleaning device for a wafer suction chuck mechanism, in the configuration of claim 1 or 2, wherein the frame suction holding portion has a water discharge hole that discharges water onto the frame suction holding portion.

[0013] According to this configuration, when cleaning the frame suction holding section, water is ejected from the multiple water ejection holes provided in the frame suction holding section to wet the entire frame suction holding section, and water is ejected from the water nozzle to bring the brush into contact with it, making it easier for sludge to float up and then scraped off with the scraper, improving the cleaning process effectiveness.

[0014] The invention described in claim 4 provides a cleaning device for a wafer suction chuck mechanism, in the configuration described in any one of claims 1 to 3, wherein the frame suction holding portion cleaning means is equipped with a spring mechanism that elastically absorbs the pressing force of the scraper or the brush against the frame suction holding portion.

[0015] With this configuration, when the scraper or brush is pressed excessively against the frame suction holding portion, the force with which the scraper and brush abut against the frame suction holding portion can be cushioned and kept approximately constant by the spring action of the spring mechanism.

[0016] The invention described in claim 5 provides a cleaning device for a wafer suction chuck mechanism, in the configuration described in any one of claims 1 to 4, further having a keep-wet nozzle that intermittently supplies water onto the frame suction holding portion.

[0017] According to this configuration, when the cleaning device is on standby, water is intermittently supplied onto the frame suction holding portion from the keep-wet nozzle, so that adhesion of sludge to the frame suction holding portion due to drying can be prevented. [Effects of the Invention]

[0018] According to the present invention, cleaning of the wafer suction chuck and the frame suction holding portion can be performed simultaneously, which makes it possible to automate the cleaning process of the chuck surface that suction-holds the wafer and the cleaning process of the frame suction holding portion. To remove sludge from the frame suction holder, a frame suction holder cleaning means is placed on the frame suction holder while the wafer chuck mechanism is rotated, and water is sprayed onto the frame suction holder from a water nozzle while either a brush or a scraper is applied. The sludge floats in the water and is then scraped off by either the brush or the scraper, or both. The scraped sludge is then washed away outside the frame suction holder with water sprayed from the water nozzle, allowing the sludge on the frame suction holder to be easily and cleanly removed. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a perspective view showing a wafer chuck mechanism and a cleaning device shown as an example according to an embodiment of the present invention. FIG. [Figure 2] 2 is a perspective view of the wafer chuck mechanism and the cleaning device as seen from the front right side of FIG. 1. [Figure 3] 1A and 1B are diagrams showing the suction chuck cleaning grindstone unit and the frame suction holding unit cleaning means with the arm positioned at the cleaning position and with some of the components omitted, where (a) is a side view and (b) is a plan view with some of the components of (a) omitted. [Figure 4] 1A and 1B are diagrams showing the suction chuck cleaning grindstone unit and the frame suction holding unit cleaning means with the arm positioned at the standby position and with some of the components omitted, where (a) is a side view and (b) is a plan view with some of the components of (a) omitted. [Figure 5] 2 is an enlarged view of the main configuration of the frame suction holding unit cleaning means in the cleaning device, as viewed from the direction AA in FIG. 1. [Figure 6] 3 is a perspective view showing a main configuration of a frame suction holding portion cleaning means in the cleaning device. FIG. [Figure 7]FIG. 10 is a plan view showing an example of a wafer held by a ring frame via an adhesive film. DETAILED DESCRIPTION OF THE INVENTION

[0020] In order to achieve the object of the present invention to provide a cleaning device for a wafer suction chuck mechanism that can automatically and easily perform cleaning of the chuck surface that suction-holds a wafer and cleaning of the frame suction holding part, the cleaning device for a rotating wafer suction chuck mechanism has a wafer suction chuck part that suction-holds a wafer attached to a ring frame via an adhesive film, and an annular frame suction holding part that suction-holds the ring frame outside the wafer suction chuck part, and is realized by providing a frame suction holding part cleaning means that is movable above the frame suction holding part and cleans the frame suction holding part, and the frame suction holding part cleaning means is equipped with at least one of a scraper and a brush that can come into contact with the frame suction holding part, and a water nozzle that sprays water onto the frame suction holding part. [Example]

[0021] An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In the following embodiment, when the number, value, amount, range, etc. of components is mentioned, the number is not limited to the specific number, and may be more or less than the specific number, unless otherwise specified or when it is clearly limited to a specific number in principle.

[0022] Furthermore, when referring to the shape or positional relationship of components, etc., it includes things that are substantially similar or approximate to those shapes, etc., unless otherwise specified or when it is clearly considered otherwise in principle.

[0023] In addition, the drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional proportions of the components may not be the same as in reality. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

[0024] In the following description, expressions indicating directions such as up, down, left, and right are not absolute and are appropriate when each part of the cleaning device for a wafer suction chuck mechanism of the present invention is in the position shown in the drawing, but if the position changes, the expressions should be interpreted accordingly. Furthermore, the same elements are denoted by the same reference numerals throughout the description of the embodiments.

[0025] 1 to 6 show a cleaning apparatus 10 according to the present invention. The cleaning apparatus 10 removes sludge adhering to a chuck mechanism 11 and includes a suction chuck cleaning grindstone unit 10A, a frame suction holding unit cleaning means 10B, and a position moving means 10C. The chuck mechanism 11 includes a wafer suction chuck unit 11A and a frame suction holding unit 11B that surrounds the outside of the wafer suction chuck unit 11A. The wafer suction chuck unit 11A and the frame suction holding unit 11B rotate integrally in the direction of arrow D in FIG. 2. A wafer W is attached to the chuck mechanism 11 during grinding.

[0026] The wafer W used here is, for example, a wafer W held by a ring frame 102 via an adhesive film 101, as shown in FIG. 7. During grinding, the wafer W is adsorbed and held together with the adhesive film 101 on the chuck surface 11a of the wafer suction chuck unit 11A, and the ring frame 102 is adsorbed and held by the frame suction holding unit 11B. The wafer suction chuck unit 11A and the frame suction holding unit 11B are independent of each other, and can move vertically relative to each other. When the wafer suction chuck unit 11A moves upward while the frame suction holding unit 11B adsorbs and holds the ring frame 102, the entire adhesive film 101 is stretched, making it easier to remove the wafer W from the adhesive film 101.

[0027] The chuck surface 11a of the wafer suction chuck portion 11A is formed of a porous material, and can suction and hold a wafer W attached to an adhesive film 101 and placed on the chuck surface 11a by vacuuming. When cleaning the chuck surface 11a, cleaning water (pure water) can be ejected from the entire chuck surface 11a.

[0028] The frame suction holder 11B has a plurality of suction holes 12a that vacuum the ring frame 102 placed on the frame suction holder 11B and vacuum the ring frame 102 onto the frame suction holder 11B, and a plurality of water discharge holes 12b that discharge cleaning water (pure water) from the upper surface of the frame suction holder 11B when cleaning the frame suction holder 11B. These holes are arranged in a circumferential row at approximately equal intervals. In this embodiment, the suction holes 12a and the water discharge holes 12b are shared as the same hole, but they may also be provided separately. Note that the piping system for vacuuming the frame suction holder 11B and the piping system for vacuuming the chuck surface 11a of the wafer suction chuck 11A are separate systems. Therefore, vacuuming can be controlled separately for each system.

[0029] The position moving means 10C of the cleaning apparatus 10 moves the suction chuck cleaning stone unit 10A and the frame suction holder cleaning means 10B together between the cleaning position and the standby position. The position moving means 10C includes a rail member 13 that horizontally guides the suction chuck cleaning stone unit 10A and the frame suction holder cleaning means 10B between the cleaning position and the standby position along one side of the wafer suction chuck unit 11A, and an arm 14 that holds the suction chuck cleaning stone unit 10A. That is, the suction chuck cleaning stone unit 10A and the frame suction holder cleaning means 10B move between the cleaning position and the standby position using the guide of the arm 14 and the rail member 13. The rail member 13 is attached to a base member 21. A drying prevention nozzle 22 is attached to the base member 21 to supply water to the frame suction holder 11B to prevent it from drying out during standby.

[0030] The suction chuck cleaning grindstone unit 10A has a dressing grindstone 15 attached to the lower end of an arm 14 so as to be horizontally rotatable. The dressing grindstone 15 rotates in the direction of arrow E in FIG. 2 by the driving force of a motor (not shown). As the arm 14 moves up and down while rotating, the dressing grindstone 15 is pressed against, i.e., comes into contact with, the chuck surface 11a of the wafer suction chuck unit 11A, which is also rotating, and scrapes off sludge adhering to the chuck surface 11a. During contact, water is ejected from the underside of the dressing grindstone 15, causing the sludge on the chuck surface 11a to float up and be scraped off.

[0031] The frame suction-holding portion cleaning means 10B is attached as a unit to a flange-shaped member 14a that is fixed to the lower end of the arm 14, adjacent to the upper surface of the dressing grindstone 15. That is, the frame suction-holding portion cleaning means 10B has a unit base 16 that is detachably attached to the flange-shaped member 14a, and a scraper 17, a brush 18, and a water nozzle 19 are attached to the underside of the unit base 16 in this order, opposite the rotation direction of the frame suction-holding portion 11B, thereby forming a unit. Furthermore, the frame suction-holding portion cleaning means 10B that is unitized by the unit base 16 is detachably attached to the flange-shaped member 14a as a unit with bolts, nuts, etc.

[0032] 1, 2, and 3, when the frame suction-holding unit cleaning means 10B is moved to the cleaning position by the position moving means 10C, a water nozzle 19, a brush 18, and a scraper 17 are arranged on the frame suction-holding unit 11B in this order from upstream to downstream in the rotation direction of the frame suction-holding unit 11B. Also, as shown in FIG. 5, a spring mechanism 20 is provided between the unit base 16 and the brush 18 and scraper 17 to buffer the contact force (pressing force) of the brush 18 and scraper 17 on the frame suction-holding unit 11B so that it remains substantially constant. The brush 18 is attached at an angle to the frame suction-holding unit 11B so that it can remove sludge adhering to corners 23a of a base 23 of the frame suction-holding unit 11B.

[0033] The operation of the cleaning apparatus 10 is controlled by a control means (not shown). The control means controls each of the components constituting the cleaning apparatus 10. The control means is, for example, a computer, and is composed of a CPU, memory, etc. The functions of the control means may be realized by control using software, or may be realized by operating using hardware.

[0034] Next, we will explain an example of the operation of the cleaning device 10. When the grinding device is grinding the wafer W, the suction chuck cleaning grindstone unit 10A and the frame suction holding unit cleaning means 10B are moved to the standby positions shown in Figure 4 by the position moving means 10C.

[0035] When the grinding process by the grinding device is completed and sludge cleaning of the chuck surface 11a of the wafer suction chuck portion 11A and the frame suction holding portion 11B is to be performed, the position moving means 10C moves the arm 14 to the cleaning position while the wafer suction chuck portion 11A and the frame suction holding portion 11B are rotating. As a result, the suction chuck cleaning grindstone portion 10A and the frame suction holding portion cleaning means 10B move together with the arm 14 to above the cleaning position.

[0036] Before the sludge cleaning process actually starts, i.e., during standby, the wafer suction chuck portion 11A and the frame suction holding portion 11B are rotated at a predetermined speed. Furthermore, to prevent the sludge adhering to the chuck surface 11a of the wafer suction chuck portion 11A and the frame suction holding portion 11B from drying out, the wafer suction chuck portion 11A sprays water from the chuck surface 11a, while the frame suction holding portion 11B receives water from the water discharge holes 12b and the drying prevention nozzle 22.

[0037] Next, the dressing grindstone 15 of the suction chuck cleaning grindstone unit 10A is rotated, and the arm 14 is lowered. Figures 1, 2, and 3 show the arm 14 in this cleaning position and then lowered.

[0038] In the suction chuck cleaning grindstone section 10A, the rotating dressing grindstone 15 is pressed against (contacts) the chuck surface 11a of the wafer suction chuck section 11A to clean the sludge adhering to the chuck surface 11a. In this sludge cleaning process, cleaning water is discharged from the grindstone surface of the dressing grindstone 15 and from the entire surface of the chuck surface 11a to clean the sludge, and the cleaning water is then discharged outside the chuck surface 11a.

[0039] Meanwhile, in the frame suction-holding portion cleaning means 10B, cleaning water is discharged from the water nozzle 19 onto the frame suction-holding portion 11B, and the scraper 17 and brush 18 are brought into contact with the rotating frame suction-holding portion 11B to clean the sludge adhering to the frame suction-holding portion 11B. In this cleaning process of the sludge from the frame suction-holding portion 11B, water is discharged from the multiple water discharge holes 12b provided in the frame suction-holding portion 11B to wet the entire frame suction-holding portion 11B, and then water is discharged from the water nozzle 19 and the brush 18 is brought into contact with the frame suction-holding portion 11B, which makes it easy for the sludge to float up and be scraped off by the scraper 17, thereby smoothly scraping it off. This allows the cleaning process of the chuck surface 11a of the wafer suction chuck portion 11A and the cleaning process of the frame suction-holding portion 11B to be performed simultaneously.

[0040] Furthermore, when the cleaning process of the chuck surface 11a of the wafer suction chuck unit 11A and the cleaning process of the frame suction holding unit 11B are completed, the water nozzle 19 stops supplying cleaning water, and the dressing grindstone 15 and the chuck surface 11a stop supplying cleaning water. Then, the rotation of the dressing grindstone 15 also stops, and the arm 14 rises, moving the dressing grindstone 15 away from the chuck surface 11a. The suction chuck cleaning grindstone unit 10A and the frame suction holding unit cleaning means 10B are then moved to the standby position shown in FIG. 4 by the position moving means 10C. This completes one cycle of the cleaning process of the chuck surface 11a of the wafer suction chuck unit 11A and the cleaning process of the frame suction holding unit 11B. Then, the system waits for an instruction to perform the cleaning process of the chuck surface 11a of the wafer suction chuck unit 11A and the cleaning process of the frame suction holding unit 11B again.

[0041] Therefore, in the cleaning apparatus 10 of this embodiment, cleaning of the wafer suction chuck portion 11A and cleaning of the frame suction holding portion 11B can be performed simultaneously, making it possible to automatically perform the cleaning process of the chuck surface 11a that suction-holds the wafer W and the cleaning process of the frame suction holding portion 11B.

[0042] Furthermore, frame suction holding portion 11B is provided with a plurality of water discharge holes 12b for discharging water in the circumferential direction of frame suction holding portion 11B, and therefore when cleaning frame suction holding portion 11B, water is discharged from water discharge holes 12b provided in frame suction holding portion 11B to wet the entire frame suction holding portion 11B, and then water is discharged from water nozzle 19 and brush 18 is applied to it, which makes it easier for sludge to float up and then scrape it off with scraper 17, improving the effectiveness of the cleaning process.

[0043] Furthermore, the wafer suction chuck portion 11A is provided with water discharge holes that discharge water from the entire chuck surface 11a when cleaning the wafer suction chuck portion 11A. Therefore, when cleaning the wafer suction chuck portion 11A, water can be discharged from the entire chuck surface 11a of the wafer suction chuck portion 11A, and the dressing grindstone 15 can be brought into contact with the wafer suction chuck portion while keeping the entire wafer suction chuck portion wet. This suppresses heat generation when the dressing grindstone 15 comes into contact, and also makes it possible to easily discharge sludge scraped off by the dressing grindstone 15 outside the wafer suction chuck portion 11A.

[0044] Furthermore, the frame suction-holding portion cleaning means 10B is provided with a spring mechanism 20 for cushioning the scraper 17 and brush 18 against the frame suction-holding portion 11B, so that the force (pressing force) with which the scraper 17 and brush 18 contact the frame suction-holding portion 11B is cushioned by the spring action of the spring mechanism 20 and made substantially constant, allowing the scraper 17 and brush 18 to contact the frame suction-holding portion 11B with a constant force. The spring mechanism 20 may be a single mechanism shared by both the scraper 17 and the brush 18, or a separate spring mechanism 20 for the scraper 17 and a separate spring mechanism 20 for the brush 18. In the case of separate mechanisms, more precise cushioning adjustments can be made.

[0045] In addition, a drying prevention nozzle (keep wet nozzle) 22 is provided to intermittently supply water onto the frame suction holding portion 11B when the cleaning device 10 is on standby, and water is intermittently supplied onto the frame suction holding portion 11B from the drying prevention nozzle 22 when the cleaning device 10 is on standby, thereby preventing sludge from drying and adhering to the frame suction holding portion 11B.

[0046] In the above embodiment, when removing sludge from the frame suction holding portion 11B, a configuration has been disclosed in which, while the wafer suction chuck portion 11A is rotated, water is sprayed onto the frame suction holding portion 11B from the water nozzle 19 while the brush 18 is applied thereto, and furthermore, the scraper 17 is brought into contact with the frame suction holding portion 11B to scrape off the sludge. However, the sludge may be removed by applying either the brush 18 or the scraper 17. Furthermore, the present invention can be modified in various ways without departing from the spirit of the present invention, and it is natural that the present invention also covers such modifications. [Explanation of symbols]

[0047] 10: Cleaning equipment 10A: Adsorption chuck cleaning grindstone part 10B: Frame suction holding part cleaning means 10C: Position movement means 11: Chuck mechanism 11A: Wafer suction chuck part 11B: Frame suction holding part 11a: Chuck surface 12a: Adsorption hole 12b: Water discharge hole 13: Rail member 14: Arm 14a: flange-shaped member 15: Dressing stone 16: Unit Base 17: Scraper 18: Brush 19: Water nozzle 20: Spring mechanism 21: Base material 22: Nozzle to prevent drying 23: Pedestal 23a: Location 101: Adhesive film 102: Ring frame W: Wafer

Claims

1. A cleaning device for a rotating wafer suction chuck mechanism, the cleaning device having a wafer suction chuck portion that suction-holds a wafer attached to a ring frame via an adhesive film, and an annular frame suction-holding portion that suction-holds the ring frame outside the wafer suction chuck portion, a frame suction-holding part cleaning means that is movable onto the frame suction-holding part and that cleans the frame suction-holding part; the frame suction-holding portion cleaning means includes a scraper and a brush that can come into contact with the frame suction-holding portion, and a water nozzle that discharges water onto the frame suction-holding portion; The cleaning device for a wafer suction chuck mechanism is characterized in that the water nozzle, brush, and scraper are arranged in this order from the upstream side to the downstream side in the rotation direction of the frame suction holding part.

2. a suction chuck cleaning grindstone unit configured to be movable onto the wafer suction chuck unit and to clean the wafer suction chuck unit; 2. The apparatus for cleaning a wafer suction chuck mechanism according to claim 1, wherein said frame suction holding portion cleaning means is configured to be movable integrally with said suction chuck cleaning stone portion.

3. 3. The cleaning device for a wafer suction chuck mechanism according to claim 1, wherein the frame suction holding portion has a water discharge hole for discharging water onto the frame suction holding portion.

4. 4. The cleaning device for a wafer suction chuck mechanism according to claim 1, wherein the frame suction holding portion cleaning means includes a spring mechanism that elastically absorbs the pressing force of the scraper or the brush against the frame suction holding portion.

5. 5. The cleaning device for a wafer suction chuck mechanism according to claim 1, further comprising a keep-wet nozzle for intermittently supplying water onto the frame suction holding portion.

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