JP5014964B2 - Workpiece holding mechanism in grinding machine - Google Patents

Description

  The present invention relates to a workpiece holding mechanism in a grinding apparatus.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a semiconductor wafer having a substantially disk shape, and devices such as ICs, LSIs, etc. are partitioned in the partitioned regions. Form. Then, the semiconductor wafer is cut into individual semiconductor chips by cutting the semiconductor wafer along the streets with a cutting device.

  The divided wafer is formed to have a predetermined thickness by grinding or etching the back surface before cutting along the street. In recent years, in order to achieve weight reduction and miniaturization of electrical equipment, the thickness of the wafer is required to be thinner, for example, about 50 μm.

  Grinding machines for thinly grinding the back surface of wafers have been developed in order to meet the demands and have developed equipment and processing conditions for finishing thin wafers with high bending strength. However, as the semiconductor wafer becomes thinner, a serious problem is that grinding waste (hereinafter referred to as contamination) generated by grinding remains on the chuck table.

In order to remove the contamination remaining on the chuck table, Japanese Patent Publication No. 5-55267 proposes a technique of rubbing the surface with a grindstone while jetting water from the lower side of the chuck table. Japanese Patent Application Laid-Open No. 11-226521 proposes a technique of removing contamination by cleaning the chuck table with a brush-like object.
Japanese Patent Publication No. 5-55267 JP-A-11-226521

  However, even if the conventional technique as disclosed in Patent Document 1 or Patent Document 2 is adopted, it is very difficult to completely remove fine contamination from the chuck table.

  If fine contamination remains on the chuck table for some reason as described above, the wafer to be ground next is fixed to the chuck table with the contamination interposed therebetween.

  And if the wafer is ground very thinly, the wafer is thin and not rigid, so the wafer is cracked due to contamination, or even if it is not broken, only that part becomes thin and it looks like a local dimple (dimple) Problem occurs.

  The present invention has been made in view of the above points, and the object of the present invention is grinding capable of preventing generation of cracks or local dimples in the workpiece even when the workpiece is thinly ground. It is to provide a workpiece holding mechanism in an apparatus.

  According to the present invention, there is provided a workpiece holding mechanism in a grinding apparatus, a chuck table having a porous suction chuck for sucking and holding a workpiece, a vacuum suction source, the vacuum suction source, and the chuck A suction on-off valve disposed in a suction path connecting the table, a mixed fluid source supplying a mixed fluid of compressed air and water, and a mixed fluid path connecting the mixed fluid source and the chuck table A mixed fluid on-off valve, a leak adjustment path branched from the suction path between the chuck table and the suction on-off valve and connected to the drain, and a leak adjustment arranged in the leak adjustment path And a leak opening / closing valve disposed in the leak adjustment path upstream of the leak adjustment valve, and is generated in the suction chuck by adjusting the leak adjustment valve to adjust a leak amount. negative Holding mechanism of a workpiece is provided in the grinding apparatus, characterized by adjusting the pressure of the.

  Preferably, the grinding apparatus includes a conveying means for conveying the workpiece in the apparatus, and when the workpiece sucked and held by the suction chuck is transferred to the conveying means, the suction opening / closing valve is closed. After the suction force of the suction chuck is shut off, the mixed fluid on-off valve is opened to eject the mixed fluid from the suction chuck at the same time or after the leak on-off valve is closed.

  According to the present invention, since the leak adjustment valve is disposed in the leak adjustment path branched from the suction path, the suction force generated in the suction chuck can be adjusted by adjusting the leak adjustment valve, The workpiece can be fixed so weak that it does not peel off the chuck. As a result, since it becomes less susceptible to contamination during grinding, it is possible to suppress the occurrence of cracks in the workpiece or local dimples in the workpiece.

  When the mixed fluid is ejected from the suction chuck with the vacuum turned off (air blow), the mixed fluid is closed at the same time or after the suction on-off valve is closed to shut off the suction force of the suction chuck and then the leak on-off valve is closed. Because the mixed fluid is ejected from the suction chuck by opening the on-off valve, it is possible to prevent the strong mixed fluid from being blown up, which can damage the workpiece, and to prevent water leakage from the leak adjustment valve. .

  Hereinafter, a grinding apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a perspective view of a grinding apparatus according to an embodiment of the present invention is shown. The grinding apparatus includes a device housing 2 having a substantially rectangular parallelepiped shape. A vertical support plate 4 is adjacent to the upper right end of the device housing 2.

  Two pairs of guide rails 6 and 8 extending in the vertical direction are provided on the inner surface of the vertical support plate 4. A rough grinding unit 10 is mounted on one guide rail 6 so as to be movable in the vertical direction, and a finish grinding unit 12 is mounted on the other guide rail 8 so as to be movable in the vertical direction.

  The rough grinding unit 10 includes a unit housing 14, a grinding wheel 18 attached to a wheel mount 16 rotatably attached to the lower end of the unit housing 14, and a wheel mount 16 attached to the lower end of the unit housing 14 counterclockwise. An electric motor 20 that rotates in the rotating direction and a moving base 22 on which the unit housing 14 is mounted are configured.

  The grinding wheel 18 includes an annular grinding wheel base 18a and a grinding wheel 18b for rough grinding mounted on the lower surface of the grinding wheel base 18a. A pair of guided rails 24 are formed on the moving base 22, and these guided rails 24 are movably fitted to guide rails 6 provided on the vertical support plate 4, so that the rough grinding unit 10 can be moved. Is supported so as to be movable in the vertical direction.

  A grinding feed mechanism 26 moves the moving base 22 of the rough grinding unit 10 along the guide rail 6 and feeds the grinding wheel 18 by grinding. The grinding feed mechanism 26 is arranged on the vertical support plate 4 in a vertical direction parallel to the guide rail 6 and rotatably supported, a pulse motor 30 that rotationally drives the ball screw 28, and a moving base 22. It comprises a nut (not shown) that is mounted and screwed onto the ball screw 28.

  By rotating the ball screw 28 forward or backward by the pulse motor 30, the rough grinding unit 10 is moved in the vertical direction (perpendicular to the holding surface of the chuck table described later).

  The finish grinding unit 12 is configured in the same manner as the rough grinding unit 10, and includes a unit housing 32, a grinding wheel 36 attached to a wheel mount 34 rotatably attached to the lower end of the unit housing 32, and a unit housing 32. An electric motor 38 that is mounted on the upper end and drives the wheel mount 34 in a counterclockwise direction, and a moving base 40 on which the unit housing 32 is mounted. The grinding wheel 36 includes an annular grindstone base 36a and a grinding wheel 36b for finish grinding mounted on the lower surface of the grindstone base 36a.

  A pair of guided rails 42 is formed on the movable base 40, and these guided rails 42 are movably fitted to guide rails 8 provided on the vertical support plate 4, so that the finish grinding unit 12 can be moved. Is supported so as to be movable in the vertical direction.

  Reference numeral 44 denotes a grinding feed mechanism that moves the moving base 40 of the finish grinding unit 12 along the guide rail 8 and feeds the grinding wheel 36 by grinding. The grinding feed mechanism 44 includes a ball screw 46 that is vertically supported on the vertical support plate 4 in parallel with the guide rail 8, a pulse motor 48 that rotationally drives the ball screw 46, and a moving base 40. And a nut (not shown) that engages with the ball screw 46.

  By driving the ball screw 46 forward or backward by the pulse motor 48, the finish grinding unit 12 is moved in the vertical direction (perpendicular to the holding surface of the chuck table described later).

  The grinding apparatus includes a turntable 50 disposed so as to be substantially flush with the upper surface of the apparatus housing 2 on the front side of the vertical support plate 4. The turntable 50 is formed in a relatively large-diameter disk shape, and is rotated in a direction indicated by an arrow 51 by a rotation driving mechanism (not shown).

  On the turntable 50, three chuck tables 52 are arranged so as to be rotatable in a horizontal plane, spaced from each other by 120 degrees in the circumferential direction. The chuck table 52 includes a disk-shaped base 54 and a suction chuck 56 formed in a disk shape from a porous ceramic material. The chuck table 52 includes suction means (not shown) for a wafer placed on the holding surface of the suction chuck 56. Holds by suction when activated.

  The chuck table 52 configured as described above is rotated in a direction indicated by an arrow 53 by a rotation driving mechanism (not shown). The three chuck tables 52 arranged on the turntable 50 are rotated in accordance with the rotation of the turntable 50, so that the wafer loading / unloading area A, rough grinding area B, finish grinding area C, and wafer loading / unloading are performed. The region A is sequentially moved.

  The grinding device is disposed on one side with respect to the wafer carry-in / out region A, and is disposed on the other side with respect to the first cassette 58 for stocking the wafer before grinding, and the wafer carry-in / out region A, A second cassette 60 for stocking the wafer after grinding is provided.

  Between the first cassette 58 and the wafer loading / unloading area A, a temporary placing table 62 for placing the wafer unloaded from the first cassette 58 is disposed. A spinner cleaning means 68 is disposed between the wafer loading / unloading area A and the second cassette 60.

  The wafer transfer means 70 is composed of a holding arm 72 and a multi-joint link mechanism 74 that moves the holding arm 72. The wafer transport means 70 carries out the wafer stored in the first cassette 58 to the temporary placement table 60 and spinner cleaning means. The wafer cleaned at 68 is transported to the second cassette 60.

  The wafer carry-in means 76 carries the wafer that has been placed on the temporary placement table 62 and before grinding to the chuck table 52 that is positioned in the wafer carry-in / out area A. The wafer carry-out means 78 carries the wafer after grinding mounted on the chuck table 52 positioned in the wafer carry-in / out area A to the spinner cleaning means 68.

  A semiconductor wafer 11 shown in FIG. 2 is accommodated in the first cassette 58. The semiconductor wafer 11 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of streets 13 are formed in a lattice shape on the surface 11a, and an IC, a plurality of areas partitioned by the plurality of streets 13, A device 15 such as an LSI is formed.

  The semiconductor wafer 11 configured as described above includes a device region 17 in which the device 15 is formed, and an outer peripheral surplus region 19 that surrounds the device region 17. In addition, the width | variety of the outer periphery surplus area | region 19 is set to about 2-3 mm. A notch 21 is formed on the outer periphery of the semiconductor wafer 11 as a mark indicating the crystal orientation of the silicon wafer.

  A protective tape 23 is attached to the surface 11a of the semiconductor wafer 11 by a protective tape attaching process. Therefore, the front surface 11a of the semiconductor wafer 11 is protected by the protective tape 23, and as shown in FIG. 3, the back surface 11b is exposed, and the plurality of semiconductor wafers 11 are placed in the first cassette 58 with the back surface 11b facing upward. It is stored.

  Next, the semiconductor wafer holding mechanism according to the first embodiment of the present invention will be described with reference to FIG. In the description of the wafer holding mechanism, the chuck tables 52a, 52b, and 52c are used in FIG. 4 to distinguish the three chuck tables 52 from each other. Each chuck table 52 a to 52 c has a fitting recess 55 formed in a disk-shaped base 54, and a suction chuck 56 is mounted on a step portion of the fitting recess 55.

  The fitting recess 55 of each chuck table 52 a to 52 c is connected to the vacuum suction source 80 via the suction path 88 and is connected to the mixed fluid source 86 via the mixed fluid path 92. The mixed fluid source 86 includes a water source 84 and a compressed air source 82, and supplies a mixed fluid of compressed air and water to the mixed fluid path 92.

  Suction on / off valves 90 a to 90 c are disposed in a suction path 88 that connects the chuck tables 52 a to 52 c to the vacuum suction source 80. In addition, mixed fluid on-off valves 94 a to 94 c are disposed in the mixed fluid path 92 that connects the chuck tables 52 a to 52 c to the mixed fluid source 86.

  Leakage adjustment paths 96 branch from suction paths 88 between the respective chuck tables 52a to 52c and the respective suction opening / closing valves 90a to 90c. Leakage opening / closing valves 98a to 98c are connected to these leakage adjustment paths 96 from the upstream side. In addition, leak adjustment valves 100a to 100c are provided. Reference numeral 102 denotes a drain.

  The suction on / off valves 90 a to 90 c, the mixed fluid on / off valves 94 a to 94 c, the leak on / off valves 98 a to 98 c, and the leak adjustment valves 100 a to 100 c are connected to the controller 104 and controlled by the controller 104. In FIG. 4, connection lines between the leak adjustment valves 100 a to 100 c and the controller 104 are omitted.

  In the present embodiment, throttle valves are used as the leak control valves 100a to 100c. However, the present invention is not limited to this, and a speed control valve or a slow start valve may be used as the leak control valves 100a to 100c. good.

  The operation of the wafer holding mechanism of the present embodiment configured as described above will be described below. When the wafer 11 is sucked and held by the chuck table 52a, the mixed fluid on-off valve 94a is closed and the suction on-off valve 90a is opened.

  Accordingly, the suction chuck 56 is connected to the vacuum suction source 80 via the suction opening / closing valve 90a and the suction path 88, and the suction chuck 56 is vacuum-sucked, so that the wafer 11 can be sucked and held by the suction chuck 56.

  In order to adjust the suction force of the suction chuck 56, the leak opening / closing valve 98 a is opened and the suction chuck 56 is connected to the leak adjustment valve 100 a via the leak adjustment path 96. By adjusting the degree of throttling of the leak adjustment valve 100a by the controller 104, the degree of negative pressure for sucking the suction chuck 56 can be adjusted.

  For example, when a throttle valve is employed as the leak adjustment valve 100a, the relationship between the rotation speed of the throttle valve 100a and the pressure in the leak adjustment path 96 is shown in Table 1.

  With reference to FIG. 5 (A) and FIG. 5 (B), the effect | action at the time of pinching the grinding waste (contamination) 106 between the adsorption | suction chuck 56 of the chuck table 52 and the wafer 11 is demonstrated.

  As indicated by the arrow 108 in FIG. 5A, when the suction force of the suction chuck 56 is strong, when the wafer 11 is ground very thinly, the wafer 11 is sandwiched between the grinding scraps 106. Therefore, the wafer 11 may be damaged as indicated by 107.

  When there is such a fear, the controller 104 opens (turns on) the leak on-off valve 98a and adjusts the opening of the leak adjustment valve 100a, thereby reducing the suction negative pressure of the suction chuck 56 as shown in FIG. ), As shown by the arrow 110 of FIG.

  As a result, since the suction force of the suction chuck 56 becomes weak, even when the grinding waste 106 is interposed between the wafer 11 and the suction chuck 56, the wafer 11 is damaged due to the sandwiched grinding waste 106. Can be prevented.

  Next, an operation when the wafer 11 sucked and held by the chuck table 52a is transferred to the wafer carry-out means 78 will be described. In this case, first, the suction on / off valve 90a is closed (turned off) to shut off the suction force of the suction chuck 56 of the chuck table 52a.

  Thereafter, almost simultaneously with closing (turning off) the leak on-off valve 98a, the mixed fluid on-off valve 94a is opened (turned on), and the mixed fluid of compressed air and water is ejected from the adsorption chuck 56 of the chuck table 52a.

  As a result, the surface of the suction chuck 56 is cleaned with the mixed fluid, and the wafer 11 is easily peeled off from the chuck table 52a. Therefore, the wafer unloading device 78 sucks the wafer 11 and easily carries the wafer out of the chuck table 52a. be able to.

  Note that turning on (opening) the mixed fluid on-off valve 94a is not simultaneously with closing the leak on-off valve 98a, and the mixed fluid on-off valve 90a may be turned on with a predetermined time delay.

  Since the suction force adjustment and air blow operation of the chuck table 52b or the chuck table 52c are the same as the suction force adjustment and air blow operation described in relation to the chuck table 52a, description thereof will be omitted.

  In the present embodiment, the suction force of the chuck tables 52a to 52c is adjusted by adjusting the leak adjusting valves 100a to 100c, and the vacuum suction source 80 is not adjusted at all. Therefore, the suction force of one chuck table 52a is adjusted. Alternatively, the action at the time of air blowing does not affect the actions of the other chuck tables 52b and 52c.

  Referring to FIG. 6, a wafer holding mechanism according to a second embodiment of the present invention is shown. In the present embodiment, a release path 112 for connecting the mixed fluid path 92 to the drain 102 and a release opening / closing valve 114 disposed in the release path 112 are added to the wafer holding mechanism shown in FIG. Other configurations of the present embodiment are the same as those of the first embodiment shown in FIG.

  In the present embodiment, by opening the release opening / closing valve 114 and releasing a part of the mixed fluid to the drain 102, the pressure of the mixed fluid can be reduced and the momentum of the mixed fluid ejected from the adsorption chuck 56 can be suppressed.

  Therefore, the wafer 11 can be removed from the chuck tables 52a to 52c by controlled air blowing without causing defects such as cracks in the thinly ground wafer 11.

  According to each of the embodiments described above, the suction force generated on the chuck tables 52a to 52c can be individually adjusted, and the wafer 11 can be fixed so weak that it does not peel off the chuck table. It is possible to suppress the influence of grinding debris sandwiched between the two during the grinding and to perform thin grinding without damaging the wafer.

  Further, when the mixed fluid is ejected from the chuck table with the vacuum turned off, the opening / closing timing of each open / close valve is controlled to prevent the strong mixed fluid from being blown up so as to damage the wafer, and the leak adjusting valves 100a to 100c. Water leakage from the water can also be prevented.

  In the above description, an example in which a semiconductor wafer is ground as a workpiece has been described. However, the present invention is not limited to this, and can be similarly applied to other workpieces that need to be thinly ground. is there.

1 is an external perspective view of a grinding apparatus to which the present invention is applicable. It is a front side perspective view of a semiconductor wafer. It is a back surface side perspective view of the semiconductor wafer where the protective tape was stuck. It is a circuit diagram of the holding mechanism of the wafer concerning a 1st embodiment of the present invention. 5A is a cross-sectional view of the chuck table for explaining the operation when the suction force is strong, and FIG. 5B is a cross-sectional view of the chuck table for explaining the operation when the suction force is weak. It is a circuit diagram of the holding mechanism of the wafer concerning a 2nd embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Coarse grinding unit 12 Finish grinding unit 18a Coarse grinding wheel 18b Coarse grinding wheel 36 Finish grinding wheel 36b Finish grinding wheel 50 Turntable 52, 52a-52c Chuck table 54 Adsorption chuck 80 Vacuum suction source 82 Compressed air source 84 Water source 86 Mixed fluid Source 88 Suction path 90a to 90c Suction on / off valve 92 Mixed fluid path 94a to 94c Mixed fluid on / off valve 96 Leak adjustment path 98a to 98c Leak on / off valve 100a to 100c Leak adjustment valve 102 Drain 104 Controller

Claims (2)

A workpiece holding mechanism in a grinding apparatus,
A chuck table having a porous suction chuck for sucking and holding a workpiece;
A vacuum suction source;
A suction on-off valve disposed in a suction path connecting the vacuum suction source and the chuck table;
A mixed fluid source for supplying a mixed fluid of compressed air and water;
A mixed fluid on-off valve disposed in a mixed fluid path connecting the mixed fluid source and the chuck table;
A leakage adjustment path branched from the suction path between the chuck table and the suction opening / closing valve and connected to a drain;
A leak adjustment valve disposed in the leak adjustment path;
A leak on-off valve disposed in the leak adjustment path upstream of the leak adjustment valve;
A workpiece holding mechanism in a grinding apparatus, wherein a negative pressure generated in the suction chuck is adjusted by adjusting the leak adjusting valve to adjust a leak amount. The grinding apparatus has a conveying means for conveying the workpiece in the apparatus,
When transferring the workpiece sucked and held by the suction chuck to the conveying means,
After closing the suction on-off valve and shutting off the suction force of the adsorption chuck, simultaneously with or after closing the leak on-off valve, the mixed fluid on-off valve is opened to eject the mixed fluid from the adsorption chuck. The workpiece holding mechanism in the grinding apparatus according to claim 1.

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