Abstract: A substrate holding apparatus is provided, which includes a top ring main body to which an elastic film having a surface that can suck a substrate can be attached, a first line communicating with a first area of the plurality of areas, a second line communicating with a second area different from the first area of the plurality of areas, a pressure adjuster that can pressurize the first area by feeding fluid into the first area through the first line and can generate negative pressure in the second area through the second line, and a determiner that performs determination of whether or not the substrate is sucked to the elastic film based on a volume of the fluid fed into the first area or a measurement value corresponding to pressure in the first area.

Abstract: A chemical mechanical polishing (CMP) apparatus is provided, including a polishing pad and a polishing head. The polishing pad has a polishing surface. The polishing head is configured to hold a wafer in contact with the polishing surface during the polishing process. The polishing head includes a retaining ring, at least one fluid channel, and a vacuum pump. The retaining ring is arranged along the periphery of the polishing head and configured to retain the wafer. The at least one fluid channel is provided inside the polishing head, wherein the retaining ring includes a bottom surface facing the polishing surface and a plurality of holes in fluid communication with the bottom surface and the at least one fluid channel. The vacuum pump is fluidly coupled to the at least one fluid channel.

Abstract: A polishing system includes a carriage arm having an actuator disposed on a lower surface thereof. The actuator includes a piston and a roller coupled to a distal end of the piston. The polishing system includes a polishing pad and a substrate carrier suspended from the carriage arm and configured to apply a pressure between a substrate and the polishing pad. The substrate carrier includes a housing, a retaining ring, and a membrane. The substrate carrier includes an upper load ring disposed in the housing. The roller of the actuator is configured to contact the upper load ring during relative rotation between the substrate carrier and the carriage arm. The actuator is configured to apply a load to a portion of the upper load ring thereby altering the pressure applied between the substrate and the polishing pad.

Abstract: A carrier head includes a housing, a support assembly having a support plate flexibly connected to the housing so as to be vertically movable, a plurality of fluid-impermeable barriers projecting from a bottom of the support plate to define a plurality of recesses that are open at bottom sides thereof, and pneumatic control lines. A volume between the support plate and the housing includes one or more independently pressurizable first chambers to apply pressure on a top surface of the support plate in one or more first zones. The barriers are positioned and configured such that when a planar substrate is loaded into the carrier head the barriers contact the substrate and divide a volume between the support plate and the substrate into a plurality of second chambers. The pneumatic control lines are coupled to the plurality of recesses to provide a plurality of independently pressurizable second zones.

Abstract: A retaining ring can be shaped by machining or lapping the bottom surface of the ring to form a shaped profile in the bottom surface. The bottom surface of the retaining ring can include flat, sloped and curved portions. The lapping can be performed using a machine that dedicated for use in lapping the bottom surface of retaining rings. During the lapping the ring can be permitted to rotate freely about an axis of the ring. The bottom surface of the retaining ring can have curved or flat portions.

Abstract: A pumping system for performing a hydraulic fracturing operation includes a first fluid conduit having a central axis, a fluid pump including an outlet configured to be inserted into the first fluid conduit, and a connector assembly including an engagement member having a first position configured to lock the outlet within the first fluid conduit and a second position configured to unlock the outlet from the first fluid conduit.

Abstract: A method of using a polishing system includes securing a wafer in a carrier head, the carrier head including a housing enclosing the wafer, in which the housing includes a retainer ring recess and a retainer ring positioned in the retainer ring recess, the retainer ring surrounding the wafer, in which the retainer ring includes a main body portion and a bottom portion connected to the main body portion, and a bottom surface of the bottom portion includes at least one first engraved region and a first non-engraved region adjacent to the first engraved region; pressing the wafer against a polishing pad; and moving the carrier head or the polishing pad relative to the other.

Abstract: An object of the present invention is to reduce an amount of use of the polishing liquid. There is provided an apparatus for polishing an object to be polished using a polishing pad having a polishing surface, the apparatus including: a polishing table for supporting the polishing pad, the polishing table being configured to be rotatable; a substrate holding unit configured to hold the object to be polished and press the object against the polishing pad; a supplying device for supplying polishing liquid to the polishing surface in a state in which the supplying device is pressed against the polishing pad; and a pressing mechanism configured to press the supplying device against the polishing pad, in which the pressing mechanism is capable of respectively adjusting pressing forces for pressing the sidewalls of on the upstream side and the downstream side of the supplying device against the polishing surface.

Abstract: A retaining ring can be shaped by machining or lapping the bottom surface of the ring to form a shaped profile in the bottom surface. The bottom surface of the retaining ring can include flat, sloped and curved portions. The lapping can be performed using a machine that dedicated for use in lapping the bottom surface of retaining rings. During the lapping the ring can be permitted to rotate freely about an axis of the ring. The bottom surface of the retaining ring can have curved or flat portions.

Abstract: A CMP tool for polishing a semiconductor wafer is disclosed. The CMP tool includes a polishing head with a wafer carrier unit on which a wafer is mounted for polishing. The wafer carrier unit includes a support plate with a seal disposed on its sidewall. The seal improves sealing of the flexible membrane to the support plate. This improves reliability by avoiding slippage during the dechucking stage as well as wafer slippage during wafer loading stage, thereby avoiding wafer damage as well as non-uniform polishing.

Abstract: Disclosed is a polishing head for a polishing apparatus for polishing a quadrangular substrate using a polishing pad attached to a polishing table, comprising a head body portion, a plurality of elastic bags disposed in a surface of the head body portion, which is to face the polishing table, and a substrate holding plate for holding the substrate, the substrate holding plate being pressed by the elastic bags in a direction away from the head body portion, the head body portion being provided with channels for bags, which are in communication with the respective elastic bags, the polishing head further including at least two support plates disposed between the elastic bags on one hand and the substrate holding plate on the other, the elastic bags being configured to press the substrate holding plate through the support plates.

Abstract: Provided is a substrate holding device used in a substrate polishing apparatus that polishes a substrate using a polishing pad. The substrate holding device includes: a retainer ring configured to hold a peripheral edge of the substrate; and a drive ring fixed to the retainer ring so as to rotate together with the retainer ring. The surface of the retainer ring at the polishing pad side has a convex portion at a position other than an innermost circumference following a shape of the drive ring.

Abstract: A method of processing a plate-shaped workpiece is provided. The method includes the steps of sticking a protective member to a face side of the workpiece, holding the face side of the workpiece on a holding surface of a chuck table with the protective member interposed therebetween, grinding a reverse side of the workpiece held on the chuck table to thin the workpiece by rotating a grinding wheel including grinding stones that contain abrasive grains, while a grinding fluid is being supplied from a grinding fluid supply nozzle to the reverse side of the workpiece, and after the step of grinding the reverse side of the workpiece, treating the workpiece or the grinding stones by rotating the grinding wheel and bringing the grinding stones into contact with the reverse side of the workpiece, while stopping supplying the grinding fluid from the grinding fluid supply nozzle.

Abstract: An elastic membrane capable of being easily secured to a head body of a substrate holding apparatus while inhibiting variation of a degree of deformation of the elastic membrane in a circumferential direction is disclosed. The elastic membrane according to the present invention is used in the substrate holding apparatus. The elastic membrane includes: a contact portion to be brought into contact with a substrate for pressing the substrate against a polishing pad; and an edge circumferential wall extending from a peripheral edge of the contact portion. The edge circumferential wall includes an edge-circumferential-wall lip portion sandwiched between a head body of the substrate holding apparatus and an edge mounting member for securing the edge circumferential wall to the head body. The edge-circumferential-wall lip portion has at least a part of a surface thereof roughened.

Abstract: A conditioner of a chemical mechanical polishing (CMP) apparatus includes a disk to polish a polishing pad of the CMP apparatus, a driver to rotate the disk, a lifter to lift the driver, an arm to rotate the lifter, and a connector to connect the driver to the lifter, the driver being tiltable with respect to the lifter.

Abstract: An object of the present invention is to reduce an amount of use of the polishing liquid. There is provided an apparatus for polishing an object to be polished using a polishing pad having a polishing surface, the apparatus including: a polishing table for supporting the polishing pad, the polishing table being configured to be rotatable; a substrate holding unit configured to hold the object to be polished and press the object against the polishing pad; a supplying device for supplying polishing liquid to the polishing surface in a state in which the supplying device is pressed against the polishing pad; and a pressing mechanism configured to press the supplying device against the polishing pad, in which the pressing mechanism is capable of respectively adjusting pressing forces for pressing the sidewalls of on the upstream side and the downstream side of the supplying device against the polishing surface.

Abstract: A platen for a metallographic grinder has an outer peripheral rim with an upper surface having a lower height. Also, fingers engaging a specimen are allowed to move laterally (i.e., wobble) to minimize the tipping forces on the specimen during the grinding process. Either one or both of these structures can be employed and results in a much flatter specimen surface for use in subsequent analysis.

Abstract: A reinforcement ring can be placed in a carrier head to abut an inner surface of a perimeter portion of a flexible membrane. The reinforcement ring has a substantially vertical cylindrical portion, a flange projecting outwardly from the bottom of the cylindrical portion, and a lip projecting outwardly from a top of the cylindrical portion. The flange projects outwardly farther than the lip.

Abstract: A cleaning apparatus for cleaning a cleaning tool that scrub-cleans a substrate includes a cleaning body. The cleaning body includes a contact portion configured to come into contact with the cleaning tool, and the contact portion includes a suction area configured to remove foreign matter from the cleaning tool.

Abstract: Present disclosure provides chemical mechanical polishing (CMP) apparatus, including a counterface configured to support a semiconductor wafer at a first surface, a first electromagnet array under the first surface, a polishing head over the counterface and configured to hold the semiconductor wafer at a second surface, and a controller connects to the first electromagnet array. The first electromagnet array comprises a plurality of electromagnets, a polarity of each of the plurality of electromagnets is capable of being individually controlled by the controller. Present disclosure also provides a CMP slurry and a method for using a chemical mechanical polishing apparatus.

Abstract: A wafer carrier assembly includes a wafer carrier and a fluid passage. The wafer carrier comprises a retainer ring confining a wafer accommodation space. The fluid passage is inside the wafer carrier. The fluid passage includes an inlet and at least an outlet to dispense fluid into the wafer accommodation space.

Abstract: A method includes attaching a substrate to a carrier, aligning external connectors on a first surface of a first semiconductor package to first conductive pads on a first surface of the substrate facing away from the carrier, and performing a reflow process, where a difference in coefficients of thermal expansion (CTEs) between the substrate and the carrier causes a first shape for the first surface of the substrate during the reflow process, where differences among CTEs of materials of the first semiconductor package causes a second shape for the first surface of the first semiconductor package during the reflow process, and wherein the first shape substantially matches the second shape. The method further includes removing the carrier from the substrate after the reflow process.

Abstract: A retaining ring can be shaped by machining or lapping the bottom surface of the ring to form a shaped profile in the bottom surface. The bottom surface of the retaining ring can include flat, sloped and curved portions. The lapping can be performed using a machine that dedicated for use in lapping the bottom surface of retaining rings. During the lapping the ring can be permitted to rotate freely about an axis of the ring. The bottom surface of the retaining ring can have curved or flat portions.

Abstract: Embodiments described herein relate to a substrate chucking apparatus having a plurality of cavities formed therein. The cavities are formed in a body of the chucking apparatus. In one embodiment, a first plurality of ports are formed in a chucking surface of the body and extend to a bottom surface of the body. In another embodiment, a second plurality of ports are formed in a bottom surface of the plurality of cavities and extend through the body to a bottom surface of the body.

Abstract: A method of fabricating a polishing pad using an additive manufacturing system includes receiving data indicative of a desired shape of the polishing pad to be fabricated by droplet ejection. The desired shape defines a profile including a polishing surface and one or more grooves on the polishing pad. Data indicative of a modified pattern of dispensing feed material is generated to at least partially compensate for distortions of the profile caused by the additive manufacturing system, and a plurality of layers of the feed material are dispensed by droplet ejection in accordance to the modified pattern.

Abstract: A polishing apparatus capable of preventing wear of rollers which are to transmit a load to a retainer ring and capable of preventing wear particles from escaping outside is disclosed. The polishing apparatus includes: a retainer ring disposed so as to surround the substrate and configured to press the polishing surface while rotating together with a head body; a rotary ring secured to the retainer ring and configured to rotate together with the retainer ring; a stationary ring disposed on the rotary ring; and a local-load exerting device configured to apply a local load to a part of the retainer ring through the rotary ring and the stationary ring. The rotary ring has rollers which are in contact with the stationary ring.

Abstract: Provided is a load cup including a cup having an internal space, a pedestal provided in the internal space, able to be lifted up and down, and loading a wafer onto or unloading a wafer from a polishing head, and a plurality of arrangement parts having a plurality of fastening portions disposed around the pedestal, and moved horizontally in a direction of a center of the pedestal, and arrangement part bodies coupled to the plurality of fastening portions, respectively, and rotated or reciprocated so as to contact a lateral surface of the polishing head, adjusting a center of the wafer to be aligned with a center of the polishing head. A polishing process may then be performed on a layer formed on the wafer.

Abstract: A SiC wafer is produced from a single crystal SiC ingot. Wafer producing apparatus includes a holding unit for holding the ingot, a flattening unit for grinding the upper surface of the ingot, thereby flattening the upper surface, a laser applying unit for setting the focal point of a laser beam having a transmission wavelength to the ingot inside the ingot at a predetermined depth from the upper surface of the ingot, the predetermined depth corresponding to the thickness of the wafer to be produced, and next applying the laser beam to the ingot to thereby form a separation layer for separating the wafer from the ingot, a wafer separating unit for holding the upper surface of the ingot to separate the wafer from the ingot along the separation layer, and a wafer storing unit for storing the wafer separated from the ingot.

Abstract: A method includes placing a polisher head on platen, the polisher head including a set of first magnets, and controlling a set of second magnets to rotate the polisher head on the platen, wherein controlling the set of second magnets includes reversing the polarity of at least one second magnet of the set of second magnets to produce a magnetic force on at least one first magnet of the set of first magnets, wherein the set of second magnets are external to the polisher head.

Abstract: A wafer producing apparatus for producing an SiC wafer from a single-crystal SiC ingot includes an ingot grinding unit, a laser applying unit that applies a pulsed laser beam having a wavelength that is transmittable through the single-crystal SiC ingot while positioning a focal point of the pulsed laser beam in the single-crystal SiC ingot at a depth corresponding to the thickness of the SiC wafer to be produced from an upper surface of the single-crystal SiC ingot, thereby forming a peel-off layer in the single-crystal SiC ingot, a wafer peeling unit that peels the SiC wafer off the peel-off layer in the single-crystal SiC ingot, and a delivery unit assembly that delivers the single-crystal SiC ingot between the ingot grinding unit, the laser applying unit, and the wafer peeling unit.

Abstract: The invention provides a method for polishing or planarizing a wafer of at least one of semiconductor, optical and magnetic substrates. The method includes rotating a polishing pad, the rotating polishing pad having radial feeder grooves in the polishing layer separating the polishing layer into polishing regions. The polishing regions are circular sectors defined by two adjacent radial feeder grooves. The radial feeder grooves extend from a location adjacent the center to a location adjacent the outer edge. Each polishing region includes a series of biased grooves connecting a pair of adjacent radial feeder grooves. Pressing and rotating the wafer against the rotating polishing pad for multiple rotations of the polishing pad adjusts polishing by either increasing or decreasing residence time of the polishing fluid under the wafer.

Abstract: The invention provides a method for polishing or planarizing a wafer of at least one of semiconductor, optical and magnetic substrates. The method includes rotating a polishing pad having radial feeder grooves in the polishing layer separating the polishing layer into polishing regions. The radial feeder grooves include a series of biased grooves connecting a pair of adjacent radial feeder grooves. A majority of the biased grooves have either an inward bias toward the center or an outward bias toward the outer edge of the polishing pad. Pressing and rotating the wafer against the rotating polishing pad for multiple rotations of the polishing pad at a fixed distance from the center of the polishing pad increases polishing or planarizing removal rate of the wafer.

Abstract: A wafer polishing method of polishing one surface of a wafer by rotating a rotating platen to which a polishing pad is affixed and a pressurizing head while supplying slurry onto the rotating platen and pressurizing/holding the wafer on the polishing pad with the pressurizing head, the method including: calculating an F/T value by monitoring a load current value F of a motor for rotating the rotating platen and a surface temperature T of the polishing pad during the wafer polishing; and controlling at least one of the rotation speed of the rotating platen and the polishing pressure of the pressurizing head based on the calculated F/T value.

Abstract: A wafer polishing apparatus is provided with a rotating platen to which a polishing pad is affixed and a polishing head that holds a wafer placed on the polishing pad while pressing the wafer. The polishing head has a membrane that contacts the upper surface of the wafer and applying a pressing force thereto and a support plate that supports the membrane. The membrane has a main surface part facing the bottom surface of the support plate and a side surface part facing the outer peripheral edge surface of the support plate. The vertical tension due to the side surface part of the membrane is larger than the lateral tension due to the main surface part of the membrane.

Abstract: A polishing method and a polishing apparatus which can increase a polishing rate and can control a polishing profile of a substrate being polished by adjusting a surface temperature of a polishing pad are disclosed. The polishing method for polishing a substrate by pressing the substrate against a polishing pad on a polishing table includes a pad temperature adjustment step of adjusting a surface temperature of the polishing pad, and a polishing step of polishing the substrate by pressing the substrate against the polishing pad having the adjusted surface temperature. In the pad temperature adjustment step, the surface temperature of a part of an area of the polishing pad, the area being to be brought in contact with the substrate, is adjusted during the polishing step so that the rate of temperature change of a temperature profile in a radial direction of the surface of the polishing pad becomes constant in the radial direction of the polishing pad.

Abstract: System including a rotary seal created by a dual-wiper gasket. In exemplary embodiments, the system may comprise a mounting portion and a gimbal assembly. The gimbal assembly may include a first gimbal pivotably connected to and supported by the mounting portion for rotation of the first gimbal about a first axis, and a second gimbal pivotably connected to and supported by the first gimbal for rotation of the second gimbal about a second axis transverse to the first axis. The system also may comprise a gasket encircling the first axis and creating a rotary seal between the mounting portion and the first gimbal. The gasket may have an inner wiper encircled by an outer wiper, with both wipers disposed in circumferentially sealed engagement with the mounting portion or the first gimbal.

Abstract: A polishing system includes a platen having a top surface, an annular polishing pad supported on the platen, a carrier head to hold a substrate in contact with the annular polishing pad, a support structure from which the carrier head is suspended and which is configured to move the hold the carrier head laterally across the polishing pad, and a controller. The platen is rotatable about an axis of rotation that passes through approximately the center of the platen, and the inner edge of the annular polishing pad is positioned around the axis of rotation. The controller is configured to cause the support structure to position the carrier head such that a portion of the substrate overhangs the inner edge of the annular polishing pad while the substrate is contacting the polishing pad.

Abstract: A polishing method including rubbing a wafer held by holding means against a polishing pad attached to a turntable while cooling the turntable by supplying a refrigerant to a refrigerant flow path provided in the turntable which is driven to rotate by a motor, thereby performing polishing, the polishing method being characterized in that, during standby after end of the polishing of the wafer and before performing the polishing of a next wafer, a flow volume of the refrigerant is controlled to be less than a flow volume of the refrigerant during the polishing where the wafer is polished, the turntable is rotated by the motor, and a water retaining liquid having a temperature adjusted to a room temperature or more is supplied to the polishing pad.

Abstract: In various embodiments, a method for processing a semiconductor wafer is provided. The semiconductor wafer includes a first main processing side and a second main processing side, which is arranged opposite the first main processing side, and at least one circuit region having at least one electronic circuit on the first main processing side. The method includes forming a stiffening structure, which at least partly surrounds the at least one circuit region and which stiffens the semiconductor wafer, wherein the stiffening structure has a cutout at least above part of the at least one circuit region, and thinning the semiconductor wafer, including the stiffening structure, from the second main processing side.

Abstract: A chemical-mechanical polishing system has a first polishing apparatus configured to perform a first chemical-mechanical polish on a workpiece and a second polishing apparatus configured to perform a second chemical-mechanical polish on the workpiece. A rework polishing apparatus comprising a rework platen and a rework CMP head is configured to perform an auxiliary chemical-mechanical polish on the workpiece when the workpiece is positioned on the rework platen. A measurement apparatus measures one or more parameters of the workpiece, and a transport apparatus transports the workpiece between the first polishing apparatus, second polishing apparatus, rework polishing apparatus, and measurement apparatus. A controller determines a selective transport of the workpiece to the rework polishing apparatus by the transport apparatus only when the one or more parameters are unsatisfactory.

Abstract: A substrate processing apparatus includes a polisher configured to polish a substrate using a polishing liquid, a first cleaner configured to clean the substrate polished by the polisher using sulfuric acid and hydrogen peroxide water, a second cleaner configured to clean the substrate cleaned by the first cleaner using a basic chemical liquid and hydrogen peroxide water, and a drier configured to dry the substrate cleaned by the second cleaner.

Abstract: A semiconductor manufacturing apparatus according to the present embodiment has a polisher polishing a substrate. A holder holds the substrate and rotates the substrate with respect to the polisher while pressing the substrate toward the polisher. A supplier supplies a polishing solution onto the polisher. A first annular part is attached to the holder. The first annular part is located around the substrate and between the holder and the polisher, when polishing the substrate. A second annular part is attached to the holder. The second annular part is located around the first annular part and between the holder and the polisher, when polishing the substrate. The first annular part is movable relative to the second annular part or the second annular part is movable relative to the first annular part, in a rotation direction of the substrate or the holder.

Abstract: Provided is a substrate holding device used in a substrate polishing apparatus that polishes a substrate using a polishing pad. The substrate holding device includes: a retainer ring configured to hold a peripheral edge of the substrate; and a drive ring fixed to the retainer ring so as to rotate together with the retainer ring. The surface of the retainer ring at the polishing pad side has a convex portion at a position other than an innermost circumference following a shape of the drive ring.

Abstract: According to one embodiment of the present disclosure, provided is a method of calibrating a relationship among a pressure command value, a pressure in an air-bag, and a pressure read value of the air-bag in a substrate polishing apparatus, the substrate polishing apparatus including: a polishing table; the air-bag configured to press a substrate against the polishing table, the pressure for pressing the substrate being variable; and a pressure control unit configured to control the pressure in the air-bag in accordance with the pressure command value inputted to the pressure control unit, and read the pressure in the air-bag.

Abstract: A retaining ring and a chemical mechanical planarization system (CMP) are disclosed. In one embodiment, a retaining ring for a polishing system includes a ring-shaped body having a polished inner diameter. The body has a bottom surface having grooves formed therein, an outer diameter wall, and an inner diameter wall, wherein the inner diameter wall is polished to a roughness average (Ra) of less than about 30 microinches (?in).

Abstract: During polishing of a substrate a first signal is received from a first in-situ monitoring system and a second signal is received from a second in-situ monitoring system. A clearance time at which a conductive layer is cleared and a top surface of an underlying dielectric layer of the substrate exposed and determine based on the first signal. An initial value of the second signal at the determined clearance time is determined. An offset is added to the initial value to generate a threshold value, and a polishing endpoint is triggered when the second signal crosses the threshold value.

Abstract: In some embodiments, the present disclosure relates to a method of performing a planarization process. The method may be performed by placing a wafer between a carrier head and an upper surface of a polishing pad. The carrier head has a retainer ring configured to surround the wafer, and the retainer ring has an abrasive structure configured to contact the upper surface of the polishing pad. Pressures within one or more chambers surrounded by the carrier head are independently regulated. The one or more chambers have one or more interior surfaces having a flexible membrane. The flexible membrane has a lower surface configured to contact the wafer. At least one of the carrier head or the polishing pad are moved relative to the other, and a roughness of the upper surface of the polishing pad is maintained within a predetermined range by using the abrasive structure of the retainer ring.

Abstract: A retaining ring for a polishing process is disclosed. The retaining ring includes a body comprising an upper portion and a lower portion, and a sacrificial surface disposed on the lower portion, the sacrificial surface comprising a negative tapered surface having a taper height that is about 0.0003 inches to about 0.00015 inches.

Abstract: A method and apparatus for conditioning a polishing pad is provided. In one embodiment, a pad conditioning device for a substrate polishing process is provided. The pad conditioning device includes an optical device coupled to a portion of a polishing station adjacent a polishing pad, the optical device comprising a laser emitter adapted to emit a beam toward a polishing surface of the polishing pad, the beam having a wavelength range that is substantially non-reactive with a polishing fluid utilized in the polishing process, but is reactive with the polishing pad.

Abstract: An elastic membrane capable of precisely controlling a polishing profile in a narrow area of a wafer edge portion is disclosed. The elastic membrane includes a contact portion to be brought into contact with a substrate; a first edge circumferential wall extending upwardly from a peripheral edge of the contact portion; and a second edge circumferential wall having a horizontal portion connected to an inner circumferential surface of the first edge circumferential wall. The inner circumferential surface of the first edge circumferential wall includes an upper inner circumferential surface and a lower inner circumferential surface, both of which are perpendicular to the contact portion. The upper inner circumferential surface extends upwardly from the horizontal portion of the second edge circumferential wall, and the lower inner circumferential surface extends downwardly from the horizontal portion.