Processing apparatus

A wafer held on a delivery pad is lifted from a holding surface, and when a lower surface of the wafer has been spaced in its entirety from the holding surface, an air flow rate regulating valve is opened to eject air from the holding surface. As the distance between the holding surface and the wafer spaced from the holding surface increases by lifting of a delivery unit, the degree of opening of the air flow rate regulating valve is adjusted to increase a flow rate of air from the holding surface, thereby spacing the wafer from the holding surface in a short period of time without rupturing the wafer.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a processing apparatus.

Description of the Related Art

As disclosed in Japanese Patent Laid-open No. 2007-294588, a processing apparatus for processing a wafer held on a holding surface operates to eject a mixed fluid including a mixture of water and air from the holding surface for separating the processed wafer from the holding surface with use of a delivery pad that holds the wafer.

SUMMARY OF THE INVENTION

However, the disclosed processing apparatus is problematic in that the wafer tends to be ruptured by the pressure of the mixed fluid ejected from the holding surface. To solve the above problem, there has been proposed an invention regarding a processing apparatus that gradually increases the amount of a mixed fluid ejected from a holding surface, as disclosed in Japanese Patent Laid-open No. 2009-076720. However, the proposed invention is disadvantageous in that it takes time to separate a processed wafer from the holding surface.

It is therefore an object of the present invention to provide a processing apparatus that is capable of separating a wafer from a holding surface in a short period of time without rupturing the wafer.

In accordance with an aspect of the present invention, there is provided a processing apparatus including a chuck table for holding a lower surface of a wafer on a holding surface thereof, a processing unit for processing an upper surface of the wafer whose lower surface is held on the holding surface, a delivery unit for unloading, from the holding surface, the wafer held on the holding surface, and a control unit. In the processing apparatus, the chuck table includes a fluid communication passage providing fluid communication between the holding surface and a water supply source, a branching portion included in the fluid communication passage, an air fluid communication passage providing air fluid communication between the branching portion and an air supply source, a water flow rate regulating valve disposed in the fluid communication passage between the holding surface and the water supply source, for regulating a flow rate of water from the water supply source, and an air flow rate regulating valve disposed in the air fluid communication passage, for regulating a flow rate of air from the air supply source. The control unit controls the delivery unit to hold the wafer held on the holding surface, opens the water flow rate regulating valve to eject water from the holding surface, spaces the wafer from the holding surface and lifts the delivery unit holding the wafer, from the holding surface, with the water ejected from the holding surface, opens the air flow rate regulating valve to eject air from the holding surface when the lower surface of the wafer has been spaced in its entirety from the holding surface, and increases the flow rate of air as a distance between the holding surface and the wafer spaced from the holding surface increases by lifting of the delivery unit.

According to the present invention, it is possible to space a wafer quickly from a holding surface without rupturing the wafer, with use of a delivery unit, resulting in an increase in productivity.

The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and an appended claim with reference to the attached drawings showing a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As illustrated inFIG.1, a processing apparatus1according to an embodiment of the present invention is illustrated as a grinding apparatus including a processing unit3for processing an upper surface140of a wafer14held on a holding surface200. The wafer14is made of silicon carbide (SiC), for example, and has a thickness of approximately 2 cm before it is processed. Structural details of the processing apparatus1will be described hereinbelow. The processing apparatus1will be described in relation to a three-dimensional coordinate system including X, Y, and Z axes extending respectively along X-axis, Y-axis, and Z-axis directions. The X-axis directions extend horizontally and include +X and −X directions, and the Y-axis directions extend horizontally perpendicularly to the X-axis directions and include +Y and −Y directions. The Z-axis directions extend vertically perpendicularly to the X-axis directions and the Y-axis directions and include +Z and −Z directions.

As illustrated inFIG.1, the processing apparatus1includes a base10extending in the Y-axis directions and a column11erected in the +Z direction on an end portion of the base10in the +Y direction. The processing apparatus1also includes a processing feed mechanism4mounted on a side face of the column11that faces in the −Y direction. The processing unit3is vertically movably supported on the processing feed mechanism4. The processing unit3includes a grinding unit including, for example, a spindle30having a central axis extending vertically in the Z-axis directions, a housing31on which the spindle30is rotatably supported, a spindle motor32coupled to the spindle30for rotating the spindle30about the central axis thereof, a mount33connected to a lower end of the spindle30, and a grinding wheel34detachably mounted on a lower surface of the mount33.

The grinding wheel34includes a wheel base341and an annular array of grindstones340, each in the shape of a substantially rectangular parallelepiped, disposed on a lower surface of the wheel base341. The grindstones340have respective lower surfaces that jointly make up a grinding surface342for contacting the wafer14.

When the spindle motor32is energized, it rotates the spindle30about its central axis, rotating the mount33connected to the spindle30and the grinding wheel34mounted on the lower surface of the mount33in unison with each other.

The processing feed mechanism4includes a ball screw40having a rotational axis45extending vertically in the Z-axis directions, a pair of guide rails41being disposed on both sides of the ball screw40and extending parallel thereto, a Z-axis motor42coupled to the ball screw40for rotating the ball screw40about the rotational axis45, a lifting and lowering plate43having therein an unillustrated nut operatively threaded over the ball screw40and side portions held in sliding contact with the guide rails41, and a holder44being coupled to the lifting and lowering plate43and supporting the processing unit3.

When the Z-axis motor42is energized, it rotates the ball screw40about the rotational axis45, causing the lifting and lowering plate43to move vertically in the Z-axis directions while being guided by the guide rails41and moving the grinding wheel34of the processing unit3held by the holder44, vertically in the Z-axis directions.

A holding unit2is disposed on the base10. The holding unit2includes a chuck table for holding the wafer14thereon, for example. The holding unit2includes a suction member20shaped as a circular plate and a frame21supporting the suction member20. The suction member20includes a porous member, for example, having a number of pores therein. The suction member20has an upper surface acting as a holding surface200for holding a lower surface141of the wafer14thereon. The frame21has an upper surface210lying flush with the holding surface200.

The base10has an inner base12disposed therein. A horizontal moving mechanism5for moving the holding unit2horizontally is disposed on the inner base12.

The horizontal moving mechanism5includes a ball screw50having a rotational axis extending in the Y-axis directions, a pair of guide rails51being disposed on both sides of the ball screw50and extending parallel thereto, a Y-axis electric motor52coupled to the ball screw50for rotating the ball screw50about the rotational axis, and a movable plate53having a nut disposed on a bottom surface thereof and operatively threaded over the ball screw50, the movable plate53being movable along the guide rails51in the Y-axis directions. When the Y-axis electric motor52is energized, it rotates the ball screw50about the rotational axis, causing the movable plate53to move horizontally in the Y-axis directions while being guided by the guide rails51.

A plurality of (two inFIG.1) support posts291are erected on the movable plate53and support an annular joint member29thereon. A base table23is rotatably supported on the annular joint member29. As illustrated inFIG.2, the holding unit2is mounted on the base table23with the frame21supported on the base table23. In other words, the holding unit2is disposed on the movable plate53with the support posts291, the joint member29, and the base table23interposed therebetween.

A rotary unit26for rotating the base table23about its vertical central axis is disposed below the holding unit2. The rotary unit26includes a pulley mechanism, for example, and includes a drive shaft262rotatable about a vertical central axis along the Z-axis directions by an electric motor260, a drive pulley263coupled to an upper end of the drive shaft262, an endless transmission belt264trained around the drive pulley263and a driven pulley265, for transmitting drive power from the drive pulley263to the driven pulley265, a driven shaft266to which the driven pulley265is connected, and a rotary joint267coupled to a lower end of the driven shaft266. The driven shaft266is coupled to the base table23.

When the electric motor260is energized to rotate the drive shaft262about its vertical central axis, the drive pulley263is rotated in unison with the drive shaft262, causing the transmission belt264to transmit drive power from the drive pulley263to the driven pulley265and rotating the driven pulley265. The driven shaft266connected to the driven pulley265is thus rotated about a vertical rotational axis25extending in the Z-axis directions, rotating the base table23coupled to the driven shaft266about the vertical rotational axis25.

A suction source240, an air supply source241, and a water supply source242are disposed below the holding unit2. The holding unit2includes a fluid communication passage243that provides fluid communication between the holding surface200and the water supply source242. The fluid communication passage243extends through the frame21, the base table23, the driven shaft266, and the rotary joint267, for example, and protrudes out of the rotary joint267from a side surface thereof.

The fluid communication passage243has a first branching portion248and a second branching portion249and is branched from the first branching portion248and the second branching portion249into a suction fluid communication passage2430, an air fluid communication passage2431, and a water fluid communication passage2432. The suction fluid communication passage2430provides fluid communication between the first branching portion248and the suction source240. The air fluid communication passage2431provides fluid communication between the second branching portion249and the air supply source241. The water fluid communication passage2432provides fluid communication between the second branching portion249and the water supply source242.

A suction valve2400and a suction force regulating valve2440are connected between the first branching portion248and the suction source240. When the suction source240is actuated while the suction valve2400is open, a suction force generated by the suction source240is transmitted through the fluid communication passage243to the holding surface200of the suction member20.

For example, when the suction valve2400is opened and the suction source240is actuated while the wafer14is placed on the holding surface200, the wafer14is held under suction on the holding surface200by the suction force from the suction source240. The intensity of the suction force transmitted to the holding surface200can be regulated by adjusting the restriction provided by the suction force regulating valve2440.

An air valve2410and an air flow rate regulating valve2441are connected between the second branching portion249and the air supply source241. When the air supply source241is actuated to supply air while the air valve2410is open, the supplied air is transmitted through the fluid communication passage243to the suction member20and ejected through the pores in the holding surface200into a space above the holding surface200. The flow rate of the air ejected from the holding surface200can be regulated by adjusting the restriction provided by the air flow rate regulating valve2441.

A water valve2420and a water flow rate regulating valve2442are connected between the second branching portion249and the water supply source242. When the water supply source242supplies water while the water valve2420is open, the supplied water is transmitted through the fluid communication passage243to the suction member20and ejected from the pores in the holding surface200. The flow rate of the water ejected from the holding surface200can be regulated by adjusting the restriction provided by the water flow rate regulating valve2442.

As illustrated inFIG.1, for example, a cover27and a bellows28that is stretchably and contractibly coupled to the cover27are disposed in the base10and coupled to the holding unit2. When the holding unit2is moved in the Y-axis directions, the cover27is also moved in the Y-axis directions in unison with the holding unit2, stretching and contracting the bellows28.

A cassette stage700is attached to an end surface of the base10that faces in the −Y direction. A cassette70is placed on the cassette stage700. The cassette70houses a plurality of wafers14to be ground, for example, and also houses wafers14that have been ground.

A robot71is mounted on the base10at a position close to but spaced from the cassette70on the cassette stage700in the +X direction and the +Y direction. The robot71has a robot hand710and a rotatable shaft712on which the robot hand710is swiveled. The robot hand710has a holding surface711as an upper surface connected to a suction source, not shown. When the suction source is actuated, the holding surface711can hold a wafer14under suction thereon.

When the robot71is in operation, it removes a wafer14to be ground from the cassette70and holds the wafer14under suction on the holding surface711of the robot hand710. The shaft712is rotated to turn the robot hand710, take out the wafer14from the cassette70, and deliver the wafer14to a temporary rest area720on the base10adjacent to the robot71.

The temporary rest area720where the wafer14to be ground is temporarily held at rest is positioned within a movable range of the robot71near an end area of the movable range in the +X direction. A cleaning area742for cleaning a wafer14that has been ground is positioned on the base10within the movable range of the robot71near an opposite end area of the movable range in the −X direction.

A positioning mechanism72is disposed in the temporary rest area720. The positioning mechanism72is connected to a rotary unit73including a rotational shaft730, an encoder731, and an electric motor732that are disposed in the base10. The positioning mechanism72is rotatable about a central axis extending vertically in the Z-axis directions by the rotary unit73. The wafer14taken out of the cassette70and placed on the temporary rest area720is aligned with a predetermined position by the positioning mechanism72.

Spinner cleaning means74is disposed in the cleaning area742. The spinner cleaning means74includes a spinner table740for holding a wafer14thereon and a cleaning fluid supply nozzle741for ejecting a cleaning fluid to the wafer14held on the spinner table740. The spinner table740is rotatable about a central axis extending vertically in the Z-axis directions by an unillustrated rotary unit connected to the spinner table740.

When the spinner cleaning means74is in operation, a wafer14that has been ground is held on the upper surface of the spinner table740, and then the spinner table740is rotated about its vertical central axis while at the same time the cleaning fluid supply nozzle741supplies the cleaning fluid to the wafer14to clean the wafer14.

A first delivery unit61for loading the wafer14positioned in the temporary rest area720onto the holding surface200of the holding unit2is disposed on the base10at a position adjacent to the temporary rest area720. The first delivery unit61includes a circular delivery pad60for holding the upper surface140of the wafer14under suction thereon. The delivery pad60has an air flow channel601(seeFIG.2) defined therein. The air flow channel601is defined in an annular shape within the delivery pad60and has ends open at a lower surface600of the delivery pad60into a space outside of the delivery pad60.

The air flow channel601leads to an air flow passage extending upwardly out of the delivery pad60and being branched into an air supply passage6910and a suction passage6810. The air supply passage6910is connected to an air supply source690whereas the suction passage6810is connected to a suction source680. The air supply passage6910has an air valve691connected thereto, and the suction passage6810has a suction valve681connected thereto.

Two O-rings609having different diameters are disposed on the lower surface600of the delivery pad60near an outer circumferential edge thereof in respective positions that are spaced radially inwardly and outwardly from the openings of the air flow channel601in the lower surface600. The O-rings609function as sealing members that are held in intimate contact with the upper surface140of the wafer14to keep the wafer14firmly on the delivery pad60when the wafer14is held under suction on the delivery pad60.

When the air valve691is open, the air supply source690is operated to supply air through the air flow channel601to the openings thereof in the lower surface600, from which the air is ejected downwardly. When the air valve691is closed and the suction valve681is open, the suction source680is operated to produce a suction force that is transmitted through the air flow channel601to the openings thereof in the lower surface600of the delivery pad60.

While the upper surface140of the wafer14is being held in contact with the lower surface600of the delivery pad60, the suction force produced by the suction source680and transmitted through the air flow channel601to the openings thereof in the lower surface600of the delivery pad60acts on the wafer14, attracting the wafer14under suction to the lower surface600of the delivery pad60.

Three (two illustrated inFIG.2) support rods602are fixed to an upper surface603of the delivery pad60. The support rods602extend vertically in the Z-axis directions and have respective flanges6020on their upper ends. The support rods602extend through respective through holes630defined in a joint member63, so that the flanges6020are supported on the joint member63.

The joint member63is coupled to an end of an arm65whose other end is coupled to an upper end of a shaft66erected vertically in the Z-axis directions. The shaft66is connected to an unillustrated rotary unit and can be rotated about a central axis extending vertically in the Z-axis directions by the rotary unit. When the rotary unit rotates the shaft66about its vertical central axis, the arm65is turned to angularly move the delivery pad60between the temporary rest area720and the holding surface200of the suction member20.

The shaft66is supported on a lifting and lowering mechanism64. The lifting and lowering mechanism64includes a ball screw642extending vertically in the Z-axis directions, an electric motor640connected to an upper end of the ball screw642for rotating the ball screw642about a vertical central axis extending in the Z-axis directions, an encoder641for controlling the angular displacement of the electric motor640, and a movable member643that is vertically movable in the Z-axis directions by an unillustrated nut that is disposed therein and that is operatively threaded over the ball screw642. The movable member643is coupled to the shaft66.

When the electric motor640is energized to rotate the ball screw642about its vertical central axis, the movable member643is vertically moved in one of the Z-axis directions by the nut operatively threaded over the ball screw642, thereby moving the shaft66coupled to the movable member643, the arm65coupled to the shaft66, and the delivery pad60supported on the arm65in unison with each other vertically in the same Z-axis direction.

As illustrated inFIG.1, a second delivery unit62for unloading a wafer14that has been ground from the holding surface200into the cleaning area742is disposed on the base10at a position that is close to but spaced from the first delivery unit61in the −X direction. Since the second delivery unit62is structurally similar to the first delivery unit61, some components of the second delivery unit62are denoted by reference characters identical to those of the first delivery unit61and will not be described in detail below.

A thickness measuring unit16is disposed on the base10in the vicinity of the holding unit2. The thickness measuring unit16has a contact-type height gauge or the like, for example, and is capable of measuring the thickness of a wafer14on the holding unit2by bringing the height gauge into contact with the upper surface140of the wafer14and the upper surface210of the frame21and measuring the difference between the heights of the upper surface140and the upper surface210with the height gauge.

The processing apparatus1includes a control unit9that controls operation of the various components of the processing apparatus1, as follows: For grinding a wafer14on the processing apparatus1, the robot71illustrated inFIG.1takes the wafer14out of the cassette70on the cassette stage700and temporarily places the wafer14in the temporary rest area720, after which the positioning mechanism72positions the wafer14into alignment with a predetermined position.

After the wafer14has been positioned by the positioning mechanism72, the first delivery unit61loads the wafer14temporarily placed in the temporary rest area720onto the holding surface200of the holding unit2. Specifically, the shaft66illustrated inFIG.2is rotated about its vertical central axis to turn the arm65until the delivery pad60is positioned above the wafer14temporarily placed in the temporary rest area720.

Then, the lifting and lowering mechanism64lowers the delivery pad60in the −Z direction to bring the lower surface600of the delivery pad60into contact with the upper surface140of the wafer14. While the upper surface140of the wafer14is in contact with the lower surface600of the delivery pad60, the suction source680is actuated to generate and transmit a suction force to the lower surface600of the delivery pad60, attracting and holding the wafer14under suction on the lower surface600of the delivery pad60.

With the wafer14being held under suction on the lower surface600of the delivery pad60, the arm65is turned to position the wafer14held under suction on the lower surface600of the delivery pad60into a position above the holding surface200of the holding unit2. The delivery pad60is then lowered to place the wafer14onto the holding surface200. While the wafer14is being placed on the holding surface200, the suction valve2400is opened and the suction source240held in fluid communication with the holding surface200is actuated to generate and transmit a suction force to the holding surface200, attracting and holding the wafer14under suction on the holding surface200. Thereafter, the suction force applied from the suction source680and acting on the lower surface600of the delivery pad60is canceled, releasing the wafer14from the lower surface600of the delivery pad60.

Next, the horizontal moving mechanism5illustrated inFIG.1is actuated to move the wafer14held on the holding surface200in the +Y direction and position the wafer14below the processing unit3. Then, the rotary unit26illustrated inFIG.2is actuated to rotate the holding unit2about the rotational axis25. The wafer14held on the holding surface200is now rotated about the rotational axis25. In addition, the spindle motor32illustrated inFIG.1is actuated to rotate the grindstones340.

While the wafer14held on the holding surface200is rotating and also the grindstones340are rotating, the processing feed mechanism4is actuated to lower the grindstones340in the −Z direction. The grinding surface342of the grindstones340is now brought into contact with the upper surface140of the wafer14held on the holding surface200. While the grinding surface342of the grindstones340is in contact with the upper surface140of the wafer14, the grindstones340are further lowered in the −Z direction, grinding the wafer14. The thickness measuring unit16measures the thickness of the wafer14as it is being ground. When the wafer14has been ground to a predetermined thickness as measured by the thickness measuring unit16, the process of grinding the wafer14comes to an end.

After the process of grinding the wafer14has ended, the processing feed mechanism4is actuated to lift the grindstones340in the +Z direction, spacing the grindstones340in the +Z direction away from the upper surface140of the wafer14. Then, the horizontal moving mechanism5is actuated to move the wafer14held on the holding surface200in the −Y direction.

Thereafter, the second delivery unit62is actuated to unload the wafer14from the holding surface200. Specifically, the control unit9controls the processing apparatus1to unload, from the holding surface200, the wafer14held on the holding surface200with the second delivery unit62, as follows: First, as illustrated inFIG.2, the delivery pad60of the second delivery unit62is positioned above the wafer14, and then lowered in the −Z direction by the lifting and lowering mechanism64until the lower surface600of the delivery pad60comes into contact with the upper surface140of the wafer14. While the upper surface140of the wafer14is being held in contact with the lower surface600of the delivery pad60, the suction source680is actuated to generate and transmit a suction force to the lower surface600of the delivery pad60, attracting and holding the wafer14under suction on the lower surface600of the delivery pad60.

The suction valve2400is closed to prevent the suction force generated by the suction source240from being transmitted to holding surface200. Then, the water valve2420and the water flow rate regulating valve2442are opened to supply water from the water supply source242through the water fluid communication passage2432and the fluid communication passage243to the porous suction member20, through which the water is ejected upwardly in the +Z direction from the holding surface200.

When the water is ejected from the holding surface200, the water forms a water film between the holding surface200and the lower surface141of the wafer14, raising the delivery pad60that is holding the wafer14and hence spacing the wafer14from the holding surface200. In other words, the holding surface200supports the delivery pad60that is holding the wafer14with the water film interposed therebetween. The flanges6020of support rods602are thus lifted off the joint member63. At this stage, the water has spread fully over the holding surface200, forming a water film entirely between the holding surface200and the lower surface141of the wafer14.

In this state, the lifting and lowering mechanism64lifts the arm65in the +Z direction to cause the joint member63to bear the flanges6020and lift the delivery pad60that is holding the wafer14in the +Z direction from the holding surface200.

When the joint member63has borne the flanges6020, the air valve2410and the air flow rate regulating valve2441are opened to supply air from the air supply source241through the air fluid communication passage2431into the fluid communication passage243where the air is mixed with the water from the water supply source242. The air and the water that are mixed together is supplied as a mixed fluid through the fluid communication passage243to the porous suction member20, through which the mixed fluid is ejected upwardly in the +Z direction from the holding surface200.

Even after the lower surface141of the wafer14has been spaced in its entirety from the holding surface200, the lifting and lowering mechanism64lifts the wafer14held on the delivery pad60in the +Z direction. As the distance between the holding surface200and the wafer14spaced from the holding surface200increases, the opening of the air flow rate regulating valve2441is progressively increased in a manner commensurate with the increasing distance, thereby increasing the amount of air ejected from the holding surface200. By thus introducing the air into the water film formed in the clearance between the holding surface200and the lower surface141of the wafer14, the surface tension of the water film is broken, allowing the wafer14to be separated easily from the water film.

FIG.3is a graph illustrating by way of example the relation between the distance between the holding surface200and the wafer14spaced from the holding surface200and the flow rates of water and air ejected from the holding surface200. As illustrated inFIG.3, when the distance between the holding surface200and the wafer14spaced from the holding surface200is in the range of 0 to 2 mm, the flow rate of air is controlled to be 6.5 liters/min and the flow rate of water is controlled to be 1.4 liters/min. When the distance between the holding surface200and the wafer14spaced from the holding surface200is in excess of 2 mm, the flow rate of air is controlled to be 39 liters/min and the flow rate of water is controlled to be 1.0 liters/min.

When the wafer14is spaced from the holding surface200by a predetermined distance, the shaft66is rotated to turn the arm65and position the wafer14held on the delivery pad60in the cleaning area742, and the lifting and lowering mechanism64is actuated to lower the wafer14held on the delivery pad60. The wafer14is now held on the upper surface of the spinner table740. While the spinner table740is rotating, the cleaning fluid supply nozzle741ejects the cleaning fluid to the upper surface140of the wafer14, cleaning away swarf and debris deposited on the upper surface140of the wafer14. After the upper surface140of the wafer14has been cleaned, the robot71is actuated to store the wafer14back into the cassette70.

With the processing apparatus1, when the second delivery unit62is actuated to unload the wafer14that has been ground, from the holding surface200, only water is ejected from the holding surface200to the lower surface141of the wafer14as it is spaced from the holding surface200, forming a water film on the holding surface200, and the water film raises the delivery pad60that is holding the wafer14, to space the wafer14from the holding surface200. The holding surface200supports the delivery pad60that is holding the wafer14with the water film interposed therebetween. Thereafter, the lifting and lowering mechanism64is actuated to lift the wafer14and space the wafer14away from the holding surface200. Consequently, the wafer14can be spaced from the holding surface200safely without being ruptured.

Furthermore, after the wafer14is completely spaced from the holding surface200, the lifting and lowering mechanism64lifts the wafer14while air is ejected to the water film from the holding surface200. Since the larger the distance between the holding surface200and the lower surface141of the wafer14is, the larger the amount of air ejected from the holding surface200becomes, the wafer14can be lifted quickly from the holding surface200.

The processing apparatus1is able to unload a wafer14being ground, safely and quickly from the holding surface200, when a need arises to unload the wafer14being ground, from the holding surface200, due to some trouble occurring during the process of grinding the wafer14, for example. Particularly, a wafer having modified layers formed therein is more likely to be ruptured before it is ground to remove the modified layers. In a case where there is a need for the unloading of a wafer with modified layers formed therein from the holding surface200for some reason while the wafer is being ground on the processing apparatus1to remove the modified layers, the processing apparatus1can unload the wafer safely and quickly from the holding surface200.

The present invention is not limited to the details of the above described preferred embodiment. The scope of the invention is defined by the appended claim and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention.