JP4476866B2 - Wafer holding method - Google Patents

Description

  The present invention relates to a wafer holding method for holding a wafer such as a semiconductor wafer so as not to move on a chuck table when performing predetermined processing on the wafer.

  A semiconductor chip having an electronic circuit such as an IC or LSI formed on its surface is now indispensable for downsizing various electric / electronic devices. A semiconductor chip is a process in which a rectangular region of a lattice shape is defined by cutting lines called streets on the surface of a disk-shaped semiconductor wafer, an electronic circuit is formed in these rectangular regions, and then the semiconductor wafer is divided along the streets. Manufactured by.

  By the way, in recent years, in order to enable further miniaturization of electric and electronic equipment, bumps having a height of about 15 to 100 μm are formed as electrodes on the surface of the device, and the bumps are formed on the mounting substrate. A device called a flip chip, which is directly bonded to the formed electrode, has been developed and put into practical use. In addition, a technology for reducing the size by mounting or stacking a plurality of devices on a substrate called an interposer has been developed and put into practical use.

  In any of the above technologies, the substrates are bonded together by bonding via a plurality of bumps formed on the surface of the device. Must be uniform. In view of this, the present applicant has proposed a processing apparatus for cutting the tips of bumps protruding from the surface of a semiconductor wafer with a cutting tool such as a cutting tool so as to align the height (Patent Document 1).

JP 2004-319697 A

  When the bumps on the surface of the semiconductor wafer are removed with a cutting tool as in the device described in Patent Document 1, there is an advantage that the height can be easily adjusted without causing a short circuit.

  In this apparatus, a semiconductor wafer is adsorbed and held on a vacuum chuck type chuck table, and the tips of the bumps are shaved with a cutting tool arranged above the semiconductor wafer so that the bumps have a uniform height. When cutting a bump with a cutting tool, cutting scraps are generated, but especially fine cutting scraps of a few microns fall on the chuck table when the semiconductor wafer is attached to or detached from the chuck table. There is a case.

  Therefore, every time a semiconductor wafer is placed on the chuck table, the chuck table is cleaned. However, the next semiconductor wafer may be placed on the chuck table in a state where fine cutting waste cannot be removed, and if it is adsorbed as it is, the cutting waste is sandwiched between the chuck table and the semiconductor wafer, There has been a phenomenon that the surface of the semiconductor wafer is slightly convexly curved.

  If the bump is cut while the semiconductor wafer is curved in a convex manner in this way, the bump at the curved portion is eventually cut lower than the other portion, resulting in a non-uniform bump height. . Therefore, an attempt has been made to adopt a so-called pin chuck type chuck table in which a plurality of pins protrude and have a holding surface (see Patent Documents 2 and 3).

  This pin chuck type chuck table supports the semiconductor wafer with the tips of a plurality of pins, and since the contact area with the semiconductor wafer is relatively small, it is difficult for cutting waste to be caught. However, it has occurred that the cutting waste is interposed between the semiconductor wafer and the holding surface, that is, the tip of the pin. Therefore, the above-mentioned problems are not completely solved and are problems to be improved. is the current situation.

JP 2003-68835 A JP 2003-86664 A

  Therefore, the present invention can effectively remove the cutting waste that has fallen on the chuck table, hold the wafer so that the processing can be performed normally without deformation of the wafer due to the cutting waste. It aims to provide a method.

  The present invention relates to a chuck table for holding a wafer having a device with a plurality of bumps protruding on the surface, a cutting means for cutting the bumps of the wafer held on the chuck table, and a carry-in for carrying the wafer to the chuck table. A wafer holding method on a chuck table, wherein the holding surface of the chuck table has a plurality of pins projecting, and the wafer is carried into the holding surface of the chuck table. In the process, water is supplied to the holding surface so that the pin is buried under the water surface, and the water is interposed between the wafer and the tip of the pin, and between the wafer and the tip of the pin, By reducing the interval, water intervening between the two is pushed out and drained while increasing the flow velocity, and the wafer is applied to the tip of the pin. It is characterized by comprising a step of holding the is allowed by the chuck table.

  According to the present invention, after interposing water between the wafer and the tip of the pin of the chuck table, the wafer is brought close to the chuck table by pushing down the wafer from above or raising the chuck table. When the distance between the pin and the tip of the pin is reduced, the water interposed between the two is drained while increasing the flow velocity, and the wafer is held in contact with the tip of the pin.

  Here, when the cutting waste generated when the bump is cut adheres to the tip of the pin, the cutting waste is flushed and removed by water drained from between the wafer and the tip of the pin. . When the water intervening between the wafer and the tip of the pin is drained with the gap between the wafer and the tip of the pin being reduced, the flow velocity increases as the gap decreases, so that the cutting waste tends to flow away. Effectively removed. Moreover, since it is a pin, the cutting waste adhering to the tip thereof is immediately removed from the tip even if it flows in any direction of 360 °, so that it is reliably removed. Therefore, when the wafer is held on the chuck table, it prevents the occurrence of problems such as the wafer being deformed due to the chip being sandwiched between the wafer and the tip of the pin, which hinders subsequent processing. Can do.

  In the present invention, as a means for stably holding the wafer on the holding surface of the chuck table so as not to move, a suction port is formed between the pins of the holding surface of the chuck table, and the wafer is brought into contact with the tip of the pin. After that, by sucking water and air on the holding surface side from the suction port, a means for adsorbing the wafer to the tip of the pin can be employed.

  According to the present invention, the water interposed between the wafer and the tip of the pin constituting the holding surface of the chuck table is drained while increasing the flow velocity by reducing the distance between the wafer and the tip of the pin. Therefore, the cutting waste adhering to the tip of the pin is effectively removed by this drainage. Since the tip of the pin is cleaned in this manner, the wafer is held on the chuck table without being deformed, and the processing can be performed normally.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[1] Apparatus Configuration FIG. 1 shows the entire bump processing apparatus to which the wafer holding method of the present invention is applied, and FIG. 2 shows a semiconductor wafer processed by the apparatus.

  As shown in FIG. 2A, the semiconductor wafer 1 has a thin disk shape, and a plurality of semiconductor chips 2 are formed in a lattice shape on the surface thereof. Each semiconductor chip 2 is formed with a plurality of bumps 3 as shown in FIG. The bumps 3 are bonded to the electrodes of the electronic circuit formed on the semiconductor chip 2 and protrude from the surface of the semiconductor wafer 1. These bumps 3 are formed by, for example, a well-known stud bump forming method, and the heights are often uneven. The bump processing apparatus performs processing on the semiconductor wafer 1 to cut the tips of all the bumps 3 so as to make the heights uniform.

  As shown in FIG. 1, the bump processing apparatus includes a base 10 on which various mechanisms are mounted. The base 10 is installed in a horizontally long state and is a rectangular parallelepiped table 11 which is the main body of the base 10, and a longitudinal end of the table 11 (end on the back side in FIG. 1) And a wall portion 12 extending in the width direction and vertically upward. In FIG. 1, the longitudinal direction, the width direction, and the vertical direction of the base 10 are shown as a Y direction, an X direction, and a Z direction, respectively.

On the table 11 of the base 10, the wall 12 side from the substantially middle portion in the longitudinal direction is a processing area 11A, and the opposite side supplies the unprocessed semiconductor wafer 1 to the processing area 11A and the processed semiconductor. A supply / recovery area 11 </ b> B for collecting the wafer 1 is used.
Hereinafter, various mechanisms provided in the bump processing apparatus will be described separately for those provided in the processing area 11A and those provided in the supply / recovery area 11B.

(A) Mechanism of processing area As shown in FIG. 1, a rectangular recess 13 is formed in the processing area 11 </ b> A, and a disc-shaped chuck is placed in the recess 13 via a movable table 14. A table 70 is provided so as to be movable in the Y direction. The movable table 14 is slidably attached to a guide rail disposed in the table 11 and extending in the Y direction, and is reciprocated in the same direction by an appropriate drive mechanism (none of which is shown).

  One end of the bellows 15, 16 is attached to both ends of the moving table 14 in the moving direction, and the other end of the bellows 15, 16 is the recess facing the inner surface of the wall portion 12 and the wall portion 12. Each is attached to the inner wall surface of 13. These bellows 15, 16 cover the moving path of the moving table 14 and prevent cutting chips and the like from falling on the moving path, and expand and contract as the moving table 14 moves.

  The chuck table 70 is fixed on the moving table 14 so that the upper surface, which is the holding surface of the semiconductor wafer 1, is horizontal. The semiconductor wafer 1 is held on the chuck table 70 in a vacuum chuck manner with the surface on which the bumps 3 are formed facing upward.

  The vacuum chuck structure of the chuck table 70 will be described. As shown in FIG. 3A, an edge 71 protrudes from the outer peripheral edge of the upper surface of the chuck table 70, and a bottom surface 72 surrounded by the edge 71. In addition, a large number of pins 73 formed in a thin columnar shape at the same height as the edge portion 71 are projected at substantially equal intervals. For example, the pins 73 have a diameter of 0.5 mm and a height of 0.5 mm, and the distance between the pins 73 is about 1.5 mm. In addition, as shown in FIG. 3B, a plurality of suction ports 74 are formed on the bottom surface 72. As shown in FIG. 3C, these suction ports 74 are formed at a plurality of locations (four locations in this case) equally divided between the center of the bottom surface 72 and the circumference from the center to the edge portion 71. In addition, illustration of many pins 73 is abbreviate | omitted in FIG.3 (c).

  As shown in FIG. 3B, a post portion 76 having a duct 75 extends downward from the center of the lower surface of the chuck table 70. In the chuck table 70, suction branch passages 77 communicating from the duct 75 to the suction ports 74 are formed in a radial pattern. A vacuum device (not shown) is connected to the duct 75. When the vacuum device is operated, the semiconductor wafer 1 placed on a large number of pins 73 is held in contact with the tips of the pins 73. It is like that.

  As shown in FIG. 1, the chuck table 70 moves to the wall 12 side and is positioned at a predetermined processing position. A cutting unit (cutting means) 20 is disposed above the processing position. The cutting unit 20 is attached to the wall portion 12 of the base 10 through a moving plate 32 and a guide rail 31 so as to be movable up and down, and is moved up and down by a feed mechanism 30.

  The cutting unit 20 includes a cylindrical housing 22 whose axial direction extends in the Z direction, a rotary shaft 23 that is coaxially and rotatably supported by the housing 22, and a servo motor 24 that rotationally drives the rotary shaft 23. The disk-shaped wheel mount 25 is coaxially fixed to the lower end of the rotating shaft 23, and the bite 26 is detachably attached to the wheel mount 25. A block 34 is attached to the moving plate 32. The housing 22 is fixed via the via. The wheel mount 25 is rotated in the direction of the arrow (described on the upper surface of the wheel mount 25) in FIG. The cutting tool 26 has a blade portion made of diamond or the like, and the workpiece is cut by the blade portion.

(B) Mechanism of Supply / Recovery Area As shown in FIG. 1, a rectangular recess 18 is formed in the supply / recovery area 11 </ b> B. A transfer mechanism 60 in which a fork 60b is mounted is installed at the tip of a node link type horizontal turning arm 60a.

  A supply arm 63 having a suction plate 63b attached to the front end of the cassette 61, the alignment table 62, and the horizontal turning arm 63a of the first node is disposed around the recess 18 counterclockwise as viewed from above. The recovery arm 64 having the same structure as the supply arm 63, the horizontal turning arm 64a and the suction plate 64b, the spinner type cleaning device 65, and the cassette 66 are arranged.

  The cassette 61, the alignment table 62, and the supply arm 63 are means for supplying the semiconductor wafer 1 to the chuck table 70. The recovery arm 64, the cleaning device 65, and the cassette 66 allow the processed semiconductor wafer 1 from the chuck table 70. It is a means to collect. Although the two cassettes 61 and 66 have the same structure, they will be referred to as a supply cassette 61 and a recovery cassette 66 depending on the application. These cassettes 61 and 66 are for accommodating and carrying a plurality of semiconductor wafers 1 and are set at predetermined positions on the table 11.

  A plurality of unprocessed semiconductor wafers 1 are accommodated in the supply cassette 61 in a stacked state. The transfer mechanism 60 takes out one semiconductor wafer 1 from the supply cassette 61 by raising / lowering and turning the arm 60a and gripping the fork 60b, and further, the semiconductor wafer 1 is placed on the surface on which the bumps 3 are formed. It has a function of being placed on the alignment table 62 in a state of facing upward.

  On the alignment table 62, the semiconductor wafer 1 is placed in a state determined at a certain position. The supply arm 63 sucks the semiconductor wafer 1 on the alignment table 62 to the suction plate 63b, turns the arm 63a, places the semiconductor wafer 1 on the chuck table 70, and lowers the horizontal turning arm 63a. The semiconductor wafer 1 is placed on the chuck table 70 by stopping the suction operation.

  The recovery arm 64 has a function of sucking the processed semiconductor wafer 1 from the chuck table 70 onto the suction plate 64b and rotating the arm 64a to transfer the semiconductor wafer 1 into the cleaning device 65. The cleaning device 65 has a function of rotating the semiconductor wafer 1 and shaking off the moisture after the semiconductor wafer 1 is washed with water. Then, the semiconductor wafer 1 cleaned by the cleaning device 65 is transferred and accommodated in the collection cassette 66 by the transfer mechanism 60.

  When the semiconductor wafer 1 is attached to or detached from the chuck table 70 by the supply arm 63 and the recovery arm 64, the moving base 14 is moved to the supply / recovery area 11B side and stopped at a predetermined supply / recovery position.

  Between the supply arm 63 and the recovery arm 64, a high pressure air is sprayed onto the chuck table 70 to clean the chuck table 70, and thereafter, a nozzle 67 for supplying water onto the chuck table 70 is disposed as will be described later. ing.

  The processing position of the semiconductor wafer 1 by the cutting unit 20 is a range moved by a predetermined distance from the supply / recovery position to the wall 12 side. You can go back and forth between locations. The cleaning of the chuck table 70 by the nozzle 67 and the supply of water are performed at the supply / recovery position.

[2] Operation of the apparatus Next, the usage method and operation of the bump processing apparatus having the above configuration will be described below. In the operation described here, the operation of holding the semiconductor wafer 1 on the chuck table 70 is a specific example of the holding method of the present invention.

  The operator sets a supply cassette 61 containing a plurality of semiconductor wafers 1 and an empty collection cassette 66 at predetermined positions in the supply / collection area 11B to prepare for processing.

  Subsequently, a single semiconductor wafer 1 is taken out from the supply cassette 61 by the transfer mechanism 60, and the semiconductor wafer 1 is further placed on the alignment table 62 with the back surface facing upward by the transfer mechanism 60. Is done.

  Further, the chuck table 70 is positioned at the supply / recovery position. Then, as shown in FIG. 4A, water is jetted from the nozzle 67 toward the upper surface of the chuck table 70, and water W is supplied until the pin 73 is buried under the water surface. The water W supplied onto the chuck table 70 accumulates on the chuck table 70 in a state where the water surface is curved in a convex shape due to surface tension.

  Next, the semiconductor wafer 1 placed on the alignment table 62 is brought up to the surface of the water W supplied on the chuck table 70 by the supply arm 63 as shown in FIG. Touched towards. Further, from this state, the horizontal turning arm 63a of the supply arm 63 is gradually lowered to bring the semiconductor wafer 1 closer to the chuck table 70 as shown in FIG. 4 (c), and eventually FIG. 4 (d). As shown in FIG.

  Next, the vacuum device of the chuck table 70 is operated, whereby the semiconductor wafer 1 is sucked and held on the chuck table 70. The water remaining on the chuck table 70 is sucked from the suction port 74. Note that the vacuum device may be operated before the semiconductor wafer 1 contacts the tip of the pin 73 of the chuck table 70, and in this case, the flow rate of the drained water is further increased.

  In the series of operations for holding the semiconductor wafer 1 on the chuck table 70 as described above, in the process in which the semiconductor wafer 1 is lowered so as to approach the chuck table 70, the distance between the semiconductor wafer 1 and the tip of the pin 73 is increased. The water W which decreases and intervenes between them is drained while increasing the flow velocity. Most of the drainage flows out from between the semiconductor wafer 1 and the chuck table 70, but a part of the drainage enters the suction port 74 of the chuck table 70.

  Here, when cutting waste (indicated by reference numeral 4 in the enlarged view of FIG. 4C) generated when the bump 2 is cut is attached to the tip of the pin 73, the cutting waste is the semiconductor wafer 1. And the water W drained as described above from between the tip of the pin 73 and the pin 73 and removed. When the water W interposed between the semiconductor wafer 1 and the tip of the pin 73 is drained when the distance between the two is reduced, the flow velocity increases as the distance decreases, so that the cutting waste easily flows. 73 is effectively removed from the tip of 73. Since the tip of the pin 73 has, for example, a minute circular shape, the cutting waste adhering to the tip is immediately removed from the tip regardless of the direction of 360.degree. Is done. Thus, when removing the cutting waste from the tip of the pin 73, it is preferable to apply ultrasonic vibration to the water because the cutting waste is easily detached from the pin 73.

  For this reason, when the semiconductor wafer 1 is held on the upper surface of the chuck table 70 by the vacuum chuck, it is possible to prevent cutting waste from being sandwiched between the semiconductor wafer 1 and the tip of the pin 73. As a result, the semiconductor wafer 1 is not deformed so as to be convexly curved, and there is no problem that the bumps 2 are uneven in height when a subsequent bump cutting process is performed.

The bump cutting process is performed as follows.
The vertical position of the cutting unit 20 is adjusted by the feed mechanism 30 so that the cutting tool 26 can cut the bump 3 to a predetermined height, and the wheel mount 25 is rotated by the servo motor 24. From this state, the moving table 14 is moved to the cutting unit 20 side, and the semiconductor wafer 1 held on the chuck table 70 is fed to a processing position below the cutting unit 20 at a predetermined speed. Thereby, the tip of the bump 3 is cut by the blade portion of the cutting tool 26, and when the cutting process on the entire surface of the semiconductor wafer 1 is finished, the bump cutting process is finished.

Next, the operation of recovering the processed semiconductor wafer 1 with the tips of the bumps 3 aligned will be described. First, the chuck table 70 is moved to the supply / recovery position, and the operation of the vacuum device is stopped. The holding state of the semiconductor wafer 1 on 70 is released. Next, the semiconductor wafer 1 is transferred into the cleaning device 65 by the recovery arm 64 and washed with water, and then the water is removed. Then, the semiconductor wafer 1 is transferred and accommodated in the recovery cassette 66 by the transfer mechanism 60. Further, high pressure air is jetted from the nozzle 67 toward the chuck table 70 stopped at the supply / recovery position, and the chuck table 70 is cleaned. Thereafter, water is jetted from the nozzle 67 onto the chuck table 70, and water W is supplied until the pin 73 is buried under the water surface.
The above is a cycle in which the tips of the bumps 3 are cut on one semiconductor wafer 1 and then washed and collected. This cycle is repeated.

[3] Effect According to the method of holding the semiconductor wafer 1 on the chuck table 70 as described above, the semiconductor wafer 1 is brought into contact with the water surface of the water W supplied to the upper surface of the chuck table 70, and the semiconductor wafer 1 is chucked. By approaching the table 70, the water W interposed between the semiconductor wafer 1 and the tip of the pin 73 is drained while increasing the flow velocity, and the cutting waste adhering to the tip of the pin 73 flows mixed with the drainage. And removed.

  In this embodiment, the chuck table 70 is first cleaned by jetting high-pressure air from the nozzle 67. At this time, the cutting waste is not completely removed, and the cutting waste is attached to the tip of the pin 73. However, the cutting waste can be completely removed from the tip of the pin 73 by the holding method. Since the tips of the pins 73 are cleaned in this way, the semiconductor wafer 1 is held on the chuck table 70 without being deformed, and the bump cutting process can be performed normally.

1 is an overall perspective view of a bump processing apparatus to which the method of the present invention is applied. FIG. 2A is an overall perspective view of a semiconductor wafer on which bumps are processed by the bump processing apparatus shown in FIG. 1, and FIG. 2B is a plan view of a semiconductor chip formed on the semiconductor wafer. 2A is a perspective view, FIG. 2B is a partial cross-sectional view, and FIG. 2C is a plan view of the chuck table included in the bump processing apparatus shown in FIG. 1. It is sectional drawing which shows the process in which a semiconductor wafer is hold | maintained on a chuck table in order of (a)-(d).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor wafer 20 ... Cutting unit (cutting means)
70 ... Chuck table 73 ... Pin 74 ... Suction port W ... Water

Claims (2)

A chuck table for holding a wafer having a device with a plurality of bumps protruding on the surface;
Cutting means for cutting the bumps of the wafer held by the chuck table;
A method of holding the wafer to the chuck table in a bump processing apparatus comprising a loading means for loading the wafer into the chuck table,
The holding surface of the chuck table is configured by projecting a plurality of pins,
When carrying the wafer into the holding surface of the chuck table,
Supplying water to the holding surface so that the pin is buried under the water surface, and interposing the water between the wafer and the tip of the pin;
By reducing the distance between the wafer and the tip of the pin, the water interposed between the two is pushed out and drained while increasing the flow velocity, and the wafer is held on the chuck table by contacting the tip of the pin. And a wafer holding method. A suction port is formed between the pins on the holding surface of the chuck table, and after the wafer is brought into contact with the tip of the pin, water and air on the holding surface side are sucked from the suction port. The wafer holding method according to claim 1, wherein the wafer is attracted to a tip of the pin.

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