JP2013115283A - Method of correcting position of wafer and method of processing wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer position correction method capable of easily matching the center of a wafer carried on a chuck table with the rotation center of the chuck table by a simple method.
A wafer position correcting method for aligning the center position of a wafer placed on a chuck table with the center of rotation of the chuck table, wherein the wafer is transported to a holding surface of the chuck table by a transport means. A wafer placing step, and before or after performing the wafer placing step, liquid is supplied between the holding surface of the chuck table and the wafer by a liquid supply means, and a liquid is provided between the holding surface and the wafer. And a position correction step for autonomously matching the center position of the wafer with the rotation center position of the chuck table by the surface tension of the liquid, and after performing the position correction step, the liquid is discharged from the holding surface of the chuck table. A suction holding step for sucking and holding the wafer by the chuck table while discharging.
[Selection] Figure 4

Description

  The present invention relates to a wafer position correction method for matching a wafer center position with a rotation center of a chuck table that holds the wafer, and a wafer processing method using the position correction method.

  Semiconductor wafers defined by dividing lines (streets) in which a number of devices such as ICs and LSIs are formed on the surface and each device is formed in a lattice shape are ground to a predetermined thickness by a grinding machine. After being processed, the cutting device (dicing device) cuts it into division lines and divides it into individual devices. The divided devices are used in various electric devices such as mobile phones and personal computers.

  However, when the semiconductor wafer is transported between the respective manufacturing steps of the semiconductor device manufacturing process, there is a possibility that the outer peripheral portion of the semiconductor wafer is cracked due to contact with other members. For this reason, an arc-shaped chamfering process from the front surface to the back surface is performed on the outer peripheral portion of the semiconductor wafer. By this chamfering process, the outer peripheral portion of the semiconductor wafer is formed in an R shape.

  If the wafer is thinned by grinding the back surface of the semiconductor wafer having the arc-shaped chamfered portion on the outer periphery in this way, the knife edge (庇) formed by the arc surface and the ground surface remains in the chamfered portion, which is dangerous. There is a problem.

  Further, when the semiconductor wafer is thinned, the bending strength of the wafer is extremely lowered. For this reason, there is a problem that chipping easily occurs when a slight stress is applied to the outer edge of the knife edge during back-grinding or an impact in the post-processing process, and the semiconductor wafer is liable to be cracked.

  In order to solve this problem, Japanese Patent Application Laid-Open No. 2003-273053 discloses that the outer periphery of a semiconductor wafer is preliminarily inclined with a cutting blade in a vertical cut or from the back side to the front side before performing the back surface grinding. It proposes a method of cutting at an angle.

  By this method, even if the semiconductor wafer is thinned by backside grinding, the edge angle of the backside can be set to at least 90 degrees to prevent the outer peripheral portion from becoming a knife edge. Further, chipping or the like does not occur on the outer peripheral portion on the back surface side due to a load during grinding.

  By the way, when the outer peripheral portion of the semiconductor wafer is cut into a circular shape by a cutting blade, the width of the portion to be cut in the outer peripheral portion is constant unless the center of the semiconductor wafer and the center of rotation of the chuck table coincide with each other. Don't be.

  However, when the semiconductor wafer is placed on the chuck table by the transfer device, it is very difficult to completely match the center of the semiconductor wafer with the center of rotation of the chuck table. An error in position accuracy is inevitably generated.

  Accordingly, when the outer peripheral portion of the semiconductor wafer is cut, the semiconductor wafer is eccentrically rotated with respect to the chuck table, so that the width of the portion to be cut in the outer peripheral portion is not constant (that is, the same distance from the center of the semiconductor wafer). There was a problem that a certain circle could not be cut).

  Therefore, in order to cut a circle on the same distance from the center of the semiconductor wafer, a method has been developed in which the cutting blade is moved and adjusted in the Y-axis direction, which is the indexing feed direction, during cutting (Japanese Patent Laid-Open No. 2006-2006). No. 93333).

JP 2003-273053 A JP 2006-93333 A

  However, this method is a process in which a high load is applied to the cutting blade, semiconductor wafer, and each axis of the cutting machine in a direction that is not normally applied. Therefore, the side surface of the cutting blade may be scraped and eventually damaged. There is a problem that the edge of the semiconductor wafer is cracked.

  Furthermore, there is also a problem that a high load is excessively applied to the θ-axis motor of the chuck table. This problem was significant because the moving speed in the Y-axis direction had to be maximized in order to shorten the processing time.

  The present invention has been made in view of the above points, and an object of the present invention is to easily match the center of the wafer carried on the chuck table with the center of rotation of the chuck table by a simple method. It is an object to provide a wafer position correction method that can be used.

  According to the first aspect of the present invention, there is provided a chuck table having a vertical rotating shaft and sucking and holding a disk-shaped wafer having a diameter substantially equal to the holding surface with a circular holding surface around the rotating shaft. A cutting means for rotatably supporting a cutting blade for cutting the wafer held on the chuck table; a conveying means for conveying the wafer to the chuck table; and a liquid supply for supplying a liquid to the holding surface of the chuck table A wafer position correcting method for aligning the center position of the wafer placed on the chuck table with the center of rotation of the chuck table, wherein the wafer is moved by the conveying means. Wafer mounting step for transporting and mounting on the holding surface, and before or after performing the wafer mounting step, the liquid supply hand The liquid is supplied between the holding surface of the chuck table and the wafer to fill the space between the holding surface and the wafer with the liquid, and the center position of the wafer is autonomously adjusted by the surface tension of the liquid. A position correcting step for matching the position, and a suction holding step for sucking and holding the wafer with the chuck table while discharging the liquid from the holding surface of the chuck table after the position correcting step is performed. A feature wafer position correction method is provided.

  According to a second aspect of the present invention, there is provided a wafer processing method, wherein after the wafer position correcting method according to the first aspect is performed, the cutting is performed on the outer peripheral edge of the wafer held on the holding surface of the chuck table. There is provided a wafer processing method comprising a cutting step in which the chuck table is rotated while cutting a blade to cut the outer peripheral edge of the wafer.

  According to the wafer position correction method of the present invention, the wafer moves autonomously in the center direction of the chuck table by utilizing the surface tension of the liquid supplied between the chuck table surface and the wafer placed on the chuck table. Then, correction is performed so that the center of the wafer coincides with the center of rotation of the chuck table. Therefore, in the process of concentrically cutting the outer peripheral edge of the wafer, which is performed in the next process, an effect is obtained that the load applied to each axis of the cutting blade and the apparatus can be reduced.

  In addition, when correcting the position of a wafer that is easily damaged, there is no need for a process such as bringing a hard member into contact with the wafer and moving it, so the possibility of damaging the wafer is low, and it is necessary to prepare new drive means There is also an effect that there is no.

  Further, the back surface of the wafer is cleaned with the liquid, and there is also an effect that the dust such as fine processing scraps on the holding surface of the chuck table is also cleaned with the liquid.

1 is a perspective view of a cutting apparatus suitable for carrying out the wafer position correcting method of the present invention. It is a surface side perspective view of a semiconductor wafer. It is a partial cross section side view which shows a wafer mounting step. It is a partial cross section side view which shows a position correction step. It is a partial cross section side view which shows a suction holding step. It is a partial cross section side view which shows the position correction step of 2nd Embodiment. It is a top view which shows a cutting step. FIG. 8 is a front view of FIG. 7.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a perspective view of a cutting device 2 suitable for applying the wafer position correcting method of the present invention. On the front side of the cutting apparatus 2, an operation panel 4 is provided for an operator to input instructions to the apparatus such as machining conditions. In the upper part of the apparatus, a display monitor 6 such as a CRT on which a guidance screen for an operator and an image captured by an imaging unit described later are displayed is provided.

  As shown in FIG. 2, the semiconductor wafer 11 to be cut by the cutting apparatus 2 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of streets (division lines) are formed in a lattice shape on the surface 11a. In addition, devices 15 such as ICs and LSIs are formed in each region partitioned by a plurality of streets 13.

  The thus configured semiconductor wafer 11 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 a flat portion on the surface thereof. An arc-shaped chamfered portion 11 e is formed on the outer peripheral portion of the semiconductor wafer 11. Reference numeral 21 denotes a notch as a mark indicating the crystal orientation of the silicon wafer.

  A plurality of semiconductor wafers 11 (hereinafter sometimes simply referred to as wafers) 11 shown in FIG. 2 are accommodated in the wafer cassette 8 shown in FIG. The wafer cassette 8 is placed on a cassette elevator 9 that can move up and down.

  Behind the wafer cassette 8, a loading / unloading unit 10 is provided for unloading the wafer 11 from the wafer cassette 8 and loading the wafer after cutting into the wafer cassette 8.

  Between the wafer cassette 8 and the carry-in / out unit 10, a temporary placement area 12, which is an area on which the wafer 11 to be carried in / out, is temporarily placed, is provided. An alignment mechanism 14 is provided for aligning the position at a certain position.

  A transport unit 16 having a swivel arm that sucks and transports the wafer 11 is disposed in the vicinity of the temporary placement area 12, and the wafer 11 that has been transported to the temporary placement area 12 and aligned is transported by the transport unit 16. Is sucked and conveyed onto the chuck table 18 and sucked and held by the chuck table 18.

  The chuck table 18 is configured to be rotatable and reciprocally movable in the X-axis direction by a machining feed mechanism (not shown). An area to be cut of the wafer 11 is formed above the movement path of the chuck table 18 in the X-axis direction. An alignment unit 20 for detection is provided.

  The alignment unit 20 includes an imaging unit 22 that images the surface of the wafer 11, and can detect a region to be cut by processing such as pattern matching based on an image acquired by imaging. The image acquired by the imaging unit 22 is displayed on the display monitor 6.

  On the left side of the alignment unit 20, a cutting unit 24 for cutting the wafer 11 held on the chuck table 18 is disposed. The cutting unit 24 is configured integrally with the alignment unit 20, and both move together in the Y-axis direction and the Z-axis direction.

  The cutting unit 24 is configured by mounting a cutting blade 28 having a cutting edge on the outer periphery at the tip of a rotatable spindle 26 and is movable in the Y-axis direction and the Z-axis direction. The cutting blade 28 is located on the extended line of the imaging unit 22 in the X-axis direction. The movement of the cutting unit 24 in the Y-axis direction is achieved by an index feed mechanism (not shown).

  Reference numeral 27 denotes a spinner cleaning unit that cleans the wafer 11 that has been subjected to the cutting process. The wafer 11 that has been subjected to the cutting process is transported to the spinner cleaning unit 27 by the transport unit 25, and is subjected to spin cleaning and spin drying by the spinner cleaning unit 27. .

  Hereinafter, the wafer position correcting method according to the embodiment of the present invention will be described mainly with reference to FIGS. The wafer 11 accommodated in the wafer cassette 8 is pulled out from the wafer cassette 8 to the temporary placement area 12 by the carry-in / out unit 10.

  After the center alignment is performed by the alignment mechanism 14 in the temporary placement region 12, the wafer 11 is sucked by the transport unit 16 and placed on the chuck table 18 as shown in FIG.

  The transport unit 16 is designed to place the wafer 11 on the chuck table 18 with the center of the wafer 11 aligned with the center of rotation of the chuck table 18, but an error in positional accuracy of about ± 1 mm usually occurs. End up.

  In FIG. 3, the chuck table 18 has a suction holding unit 30 made of porous ceramics or the like, and the wafer 11 is placed on a holding surface 30 a of the suction holding unit 30. In the present embodiment, the wafer 11 has a diameter approximately equal to the diameter of the circular holding surface 30a.

  The suction holding unit 30 is selectively connected to a negative pressure suction source 36 via a suction path 32 and an electromagnetic switching valve 34. The suction holding unit 30 is further selectively connected to the liquid supply source 42 via the liquid supply path 38 and the electromagnetic switching valve 40. In the present embodiment, the liquid supply path 38, the electromagnetic switching valve 40, and the liquid supply source 42 constitute a liquid supply means. Pure water is used as a preferred liquid.

  In the wafer mounting step shown in FIG. 3, the electromagnetic switching valves 34 and 40 are respectively switched to the OFF position, and the communication between the negative pressure suction source 36 and the liquid supply source 42 of the suction holding unit 30 is blocked. .

  After performing the wafer mounting step, as shown in FIG. 4, the electromagnetic switching valve 40 is switched to the ON position, the suction holding unit 30 is connected to the liquid supply source 42, and the liquid is supplied between the holding surface 30 a and the wafer 11. Supply.

  As shown in FIG. 4, when the space between the holding surface 30 a and the wafer 11 is filled with the liquid 44, the center position of the wafer 11 autonomously matches the rotation center of the chuck table 18 due to the surface tension of the liquid 44. The wafer 11 moves in the direction of arrow A (position correction step). In addition, it is preferable to hold the liquid 44 only on the holding surface 30a by performing a water repellent treatment on the upper surface of the metal frame of the chuck table 18 surrounding the suction holding unit 30.

  In the embodiment described above, after the wafer placement step shown in FIG. 3 is performed, the liquid 44 is supplied between the holding surface 30a and the wafer 11 and the position correction step is performed. Before performing the step, the electromagnetic switching valve 40 may be switched to the ON position to form a liquid layer on the holding surface 30a, and then the wafer mounting step may be performed. In this case, when the wafer placement step is performed, the position correction step based on the surface tension of the liquid is immediately executed.

  After performing the position correction step, as shown in FIG. 5, the electromagnetic switching valve 40 is switched to the OFF position to cut off the supply of the liquid onto the holding surface 30 a, and the electromagnetic switching valve 34 is switched to the ON position to suck the holding unit 30. Is connected to the negative pressure suction source 36, the wafer 11 is sucked and held on the holding surface 30a of the suction holding unit 30 while the liquid on the holding surface 30a is sucked.

  Referring to FIG. 6, there is shown a partial cross-sectional side view showing the position correction step of the second embodiment of the present invention. In the present embodiment, a chuck table 18A having a diameter approximately equal to the diameter of the wafer 11 is used.

  In the position correction step, the electromagnetic switching valve 40 is switched to the ON position so that the liquid is continuously supplied between the holding surface 30a and the wafer 11 so as to maintain the surface tension. In order to continue the supply of the liquid, the liquid 44 on the outer peripheral portion of the chuck table 18A is pushed by the supplied liquid and falls from the upper surface of the chuck table 18A.

  Thus, since the surface tension of the liquid 44 is continuously maintained, the wafer 11 is moved by the surface tension so that the center of the wafer 11 coincides with the rotation center of the chuck table 18A.

  After the position correction step, the suction holding step shown in FIG. 5 is performed as in the first embodiment. That is, the electromagnetic switching valve 40 is switched to the OFF position, and the electromagnetic switching valve 34 is switched to the ON position, and the wafer 11 is sucked and held by the holding surface of the chuck table 18A while discharging the liquid 44.

  If the wafer 11 is sucked and held by the chuck table 18 with the center of the wafer 11 aligned with the center of rotation of the chuck table 18, the processing feed mechanism is driven to position the wafer 11 directly below the imaging unit 22 and image the wafer 11. Then, alignment is performed to detect a processing region in which the outer peripheral portion of the wafer 18 is cut into a circular shape.

  After the alignment is performed, the machining feed mechanism is operated to position the cutting start point of the wafer 11 directly below the cutting blade 28, and as shown in FIGS. 7 and 8, a predetermined amount is cut into the wafer 11 with the cutting blade 28 rotating at high speed. By rotating the chuck table 18 at a low speed, the chamfered portion 11 e of the wafer 11 is cut into a circular shape to form the cutting groove 23.

  According to the wafer position correction method of the embodiment described above, the wafer 11 is autonomously moved by using the surface tension of the liquid 44 supplied between the chuck table surface and the wafer 11 placed on the chuck table 18. The center of the wafer 11 can be aligned with the center of rotation of the chuck table 18 by moving in the direction of the center position of the chuck table 18.

  Therefore, in the cutting process in which the chamfered portion 11e of the wafer 11 is cut into a circle, which is performed in the next step, the load applied to the cutting blade 28 and each axis of the apparatus can be reduced. Further, it is not necessary to move the cutting blade 28 in the Y-axis direction while cutting the outer peripheral portion of the wafer 11 in a circular shape, and uneven wear and breakage of the cutting blade 28 can be prevented. Further, it is possible to solve the problem that an excessive load is applied to the motor that rotates the chuck table 18 and the other mechanical portions of the cutting device 2.

2 Cutting device 11 Semiconductor wafer 11e Chamfer 17 Device area 18 Chuck table 19 Outer peripheral area 22 Imaging unit 24 Cutting unit 28 Cutting blade 30 Suction holding part 30a Holding surface 34, 40 Electromagnetic switching valve 36 Negative pressure suction source 42 Liquid supply source 44 liquid

Claims (2)

A chuck table having a vertical rotating shaft and sucking and holding a disk-shaped wafer having a diameter substantially equal to the holding surface with a circular holding surface centered on the rotating shaft, and a wafer held on the chuck table A cutting apparatus comprising: a cutting means that rotatably supports a cutting blade that cuts the wafer; a conveying means that conveys the wafer to the chuck table; and a liquid supply means that supplies liquid to the holding surface of the chuck table. A wafer position correction method for matching the center position of a wafer placed on the chuck table with the center of rotation of the chuck table,
A wafer mounting step of transporting and placing the wafer on the holding surface of the chuck table by the transport means;
Before or after performing the wafer mounting step, liquid is supplied between the holding surface of the chuck table and the wafer by the liquid supply means so that the space between the holding surface and the wafer is filled with liquid. A position correction step for automatically matching the center position of the wafer with the rotation center position of the chuck table by tension;
A suction holding step for sucking and holding the wafer by the chuck table while discharging the liquid from the holding surface of the chuck table after performing the position correction step;
A method for correcting the position of a wafer. Wafer processing method,
2. After the wafer position correction method according to claim 1, the chuck table is rotated while cutting the cutting blade into the outer peripheral edge of the wafer held on the holding surface of the chuck table, and the outer peripheral edge of the wafer A method for processing a wafer comprising a cutting step for performing a cutting process on a wafer.

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