JP2018014451A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer processing method which can prevent a device failure owing to adhesive layer fragments and by which an adhesive layer can be divided without fault.SOLUTION: A wafer processing method comprises: a division-start point-forming step for applying a laser beam LB1 of a wavelength having permeability to a wafer W to the wafer from a backside Wb along each scheduled division line S to form a quality-modified layer 2 in the wafer W; a grinding step for grinding the backside Wb of the wafer W to divide the wafer W into device chips C along the quality-modified layers 2; an adhesive layer-forming step for forming an adhesive layer 3 on the backside Wb of the wafer W after the grinding step; and an adhesive layer-dividing step for applying a laser beam LB2 to the wafer W from the side of the adhesive layer 3 along division lines SL at which the wafer is divided, or dividing the adhesive layer 3 by cutting by a cutting blade 52 after the adhesive layer-forming step. According to this, a device failure can be prevented from being caused by fragments of the adhesive layer 3, and the adhesive layer 3 can be divided without fault.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a wafer processing method in which a device is formed in each region partitioned by a plurality of division lines that intersect.

  A device in which an adhesive layer such as an adhesive film called a die attach film (DAF) is formed to mount (die bonding) a device chip formed by dividing a wafer on a metal frame or substrate. Chips are widely adopted. Here, there is also a method of sticking an adhesive film on the back surface of the wafer in advance so that the device chips are not dispersed when the wafer is divided with a cutting blade (for example, see Patent Document 1 below).

  However, when the wafer and the adhesive layer are cut using a cutting blade, there is a problem in that chipping occurs on the back surface of the device chip, resulting in die bonding failure. Therefore, for example, a processing method has been proposed in which an adhesive layer is divided along a device chip using a tape expander by an expansion device (see, for example, Patent Document 2 below). In this processing method, the tape is radially expanded with the adhesive layer attached to the back surface of the wafer divided into individual device chips attached to the surface of the tape attached to the annular frame. Thus, it is possible to divide the adhesive layer along the planned dividing line.

JP 2000-182959 A JP 2006-49591 A

  However, when the chip size of the device chip is as small as 1 mm square or less, for example, there is a problem that even if the tape is expanded using the above processing method, an area where the adhesive layer is not broken along the device chip is generated. is there. Furthermore, in order to reliably divide the unbreakable region of the adhesive layer, if the tension applied to the adhesive layer is increased by increasing the tape expansion amount, the adhesive layer further breaks to generate debris. There is also a problem that it adheres on the chip and causes device failure.

  The present invention has been made in view of the above circumstances, and there is a problem to be solved by the present invention in a wafer processing method capable of preventing a device failure due to a fragment of the adhesive layer and reliably dividing the adhesive layer.

  The present invention relates to a method for processing a wafer in which devices are formed in each region divided by a plurality of intersecting scheduled lines, and a laser beam having a wavelength that is transmissive to the wafer is applied to the scheduled split lines. A split starting point forming step of forming a modified layer on the wafer by irradiating the wafer from the back surface of the wafer, and a surface protecting member arrangement for disposing the surface protecting member on the surface of the wafer before or after performing the split starting point forming step. After performing the setting step and the surface protection member disposing step, the back surface of the wafer is ground to be thinned to a predetermined thickness and the wafer is divided into a plurality of device chips along the modified layer. An adhesive layer forming step for forming an adhesive layer on the back surface of the wafer divided into a plurality of device chips after performing the grinding step, and the adhesive layer After performing the forming step, the dividing line on which the wafer is divided is detected, and a laser beam is irradiated along the detected dividing line from the side of the adhesive layer or cut with a cutting blade to divide the adhesive layer A layer dividing step.

  A wafer processing method according to the present invention includes a split starting point forming step of forming a modified layer on a wafer by irradiating a laser beam having a wavelength transparent to the wafer from the back surface along a planned split line; Grinding step for grinding the back surface to divide the wafer into a plurality of device chips along the modified layer, an adhesive layer forming step for forming an adhesive layer on the back surface of the wafer after performing the grinding step, and forming an adhesive layer After the step is performed, the wafer is provided with an adhesive layer dividing step of dividing the adhesive layer by irradiating the laser beam from the adhesive layer side along the dividing line into which the wafer is divided or by cutting with a cutting blade. No debris is generated on the layer, and it is possible to prevent debris from adhering to the device chip and causing device failure. It is possible to split.

It is a perspective view which shows the structure of an example of a wafer. It is a perspective view which shows a surface protection member arrangement | positioning step. It is sectional drawing which shows a division | segmentation starting point formation step. It is a perspective view which shows the wafer after division | segmentation starting point formation step implementation. It is sectional drawing which shows a grinding step. It is sectional drawing which shows a contact bonding layer formation step. It is sectional drawing which shows the state which detects the division line by which the wafer was divided | segmented among contact bonding layer division | segmentation steps. It is sectional drawing which shows the 1st example which divides | segments an contact bonding layer among contact bonding layer division | segmentation steps. It is sectional drawing which shows the 2nd example which divides | segments an contact bonding layer among contact bonding layer division | segmentation steps.

  A wafer W shown in FIG. 1 is an example of a workpiece having a circular plate-like substrate, and devices D are formed in each region partitioned by a plurality of division lines S that intersect the surface Wa. . On the other hand, the surface on the side opposite to the front surface Wa of the wafer W is a back surface Wb that is ground and thinned. Hereinafter, a wafer processing method for dividing the wafer W into a plurality of device chips will be described.

(1) Surface Protection Member Arrangement Step As shown in FIG. 2, the surface protection member 1 is disposed on the surface Wa of the wafer W. The surface protection member 1 has a size substantially the same as that of the wafer W. When the entire surface Wa of the wafer W is covered with the surface protection member 1, each device D is protected. The material of the surface protection member 1 is not particularly limited, and is made of, for example, polyolefin or polyvinyl chloride. The surface protection member disposing step is performed before or after performing the division starting point forming step described later.

(2) Division start point formation step As shown in FIG. 3, the wafer W is held by the holding table 10, and a laser beam is irradiated from the back surface Wb side of the wafer W using the laser beam irradiation means 20, as shown in FIG. The modified layer 2 serving as a division starting point is formed inside the wafer W along the division line S. The upper surface of the holding table 10 is a holding surface 10 a that holds the wafer W. The laser beam irradiation means 20 includes at least a condenser 21 for condensing the laser beam and an oscillator that oscillates a laser beam LB1 having a wavelength that is transmissive to the wafer W. The laser beam irradiation means 20 can be moved in the vertical direction, and the condensing position of the laser beam LB1 can be adjusted by moving the condenser 21 up and down.

  The wafer W held on the holding table 10 is moved below the laser beam irradiation means 20. Subsequently, the condensing point of the laser beam LB1 having a wavelength transmissive to the wafer W is collected by the condenser 21 while the holding table 10 is processed and fed in the horizontal direction (for example, the Y direction) at a predetermined processing feed rate. Is positioned inside the wafer W, and the laser beam LB1 is irradiated from the back surface Wb side of the wafer W along the planned division line S shown in FIG. Then, the modified layer 2 with reduced strength is formed inside the wafer W by repeatedly irradiating the laser beam LB1 along all the division lines S.

(3) Grinding Step Next, as shown in FIG. 5, the back surface Wb of the wafer W is ground by the grinding means 30 for grinding the wafer W to reduce the thickness to a predetermined thickness, and the wafer W is changed to the modified layer 2. A plurality of device chips C are divided. The grinding means 30 includes a spindle 31 having a vertical axis, a grinding wheel 33 attached to the lower part of the spindle 31 via a mount 32, and a grinding wheel 34 fixed to the lower part of the grinding wheel 33 in a ring shape. The whole can be moved up and down while rotating the grinding wheel 33. When the surface protection member disposing step is performed after the division start point forming step is performed, the grinding step is performed after the surface protecting member disposing step is performed.

  The front surface protection member 1 side is held by the holding table 10, the back surface Wb of the wafer W is exposed upward, and the holding table 10 is rotated in the direction of arrow A, for example. The grinding means 30 lowers the grinding wheel 33 at a predetermined feed speed while rotating it in the direction of arrow A, for example, and grinds the wafer W until it reaches a predetermined thickness while pressing the back surface Wb of the wafer W with the grinding wheel 34. Thin W. With this grinding operation, a dividing line SL extending from the modified layer 2 shown in FIG. 4 to the surface Wa of the wafer W is formed, and the wafer W is divided into a plurality of device chips C. The dividing line SL is a breaking groove in which the wafer W is broken. The chip size of the device chip C is, for example, 1 mm square or less.

(4) Adhesive Layer Formation Step After performing the grinding step, the adhesive layer 3 is formed on the back surface Wb of the wafer W divided into a plurality of device chips C as shown in FIG. The adhesive layer 3 is an adhesive film called a sheet-like die attach film (DAF) made of, for example, a polyimide resin, an epoxy resin, an acrylic resin, or the like. This adhesive film is adhered to the entire back surface Wb of the wafer W to form the adhesive layer 3. Alternatively, the adhesive layer 3 may be configured by applying a liquid die attach agent to the entire back surface Wb of the wafer W. When performing the adhesive layer forming step, the wafer W is divided into device chips C. At this time, since the interval between the adjacent device chips C is extremely small, the adhesive film is adhered to the back surface Wb. The device chip C does not move greatly. However, the device chip C is less likely to move when the liquid die attach agent is applied to the back surface Wb than when the adhesive film is attached to the back surface Wb.

  Here, the thinner the adhesive layer 3 is, the easier it is to detect the dividing line SL when performing the subsequent adhesive layer dividing step. However, if the adhesive layer 3 is too thin, the wafer W is divided. Then, the device chip C cannot be die bonded satisfactorily on a metal frame or substrate. The thickness of the adhesive layer 3 is preferably formed to a thickness sufficient to mount the device chip C (for example, 5 to 40 μm). In addition, although not shown in figure, it is preferable to implement the contact bonding layer formation step, without peeling the wafer W from said surface protection member 1. FIG.

(5) Adhesive layer dividing step After performing the adhesive layer forming step, as shown in FIG. 7, the dividing line SL into which the wafer W is divided is detected by the camera 40 arranged on the upper side of the holding table 10, The adhesive layer 3 is divided along the detected dividing line SL. The camera 40 is composed of, for example, an IR camera. In the camera 40, even if an opaque body exists in the direction in which the lens faces, it is possible to image the inside of the wafer W by transmitting the opaque body with infrared light. The camera 40 detects the division line SL formed inside the wafer W through the adhesive layer 3 by taking an image from the back surface Wb side of the wafer W.

  Next, the adhesive layer 3 is divided along the position of the dividing line SL detected by the camera 40 using the laser beam irradiation means 20a shown in FIG. First, the wafer W held on the holding table 10 is moved below the laser beam irradiation means 20a. Subsequently, while the holding table 10 is processed and fed in the horizontal direction at a predetermined processing feed rate, the condensing point of the laser beam LB2 having a wavelength having an absorptivity with respect to the adhesive layer 3 is set by the condenser 21. The laser beam LB2 is irradiated along the position of the dividing line SL. By repeatedly irradiating the laser beam LB2 along the positions of all the dividing lines SL, the adhesive layer 3 is divided. At this time, there is no possibility that fragments are generated in the divided adhesive layer 3.

  The adhesive layer dividing step is not limited to the case where it is performed using the laser beam irradiation means 20a. For example, as shown in FIG. 9, you may divide | segment by cutting the contact bonding layer 3 with the cutting means 50 which cuts a to-be-processed object. The cutting means 50 includes at least a rotatable spindle 51 and a cutting blade 52 attached to the end of the spindle 51. The thickness of the cutting blade 52 is, for example, 10 μm or less.

  While moving the holding table 10 holding the wafer W in the horizontal direction at a predetermined processing feed speed, the cutting means 50 rotates the spindle 51 to rotate the cutting blade 52 at a predetermined rotational speed, for example, in the direction of arrow B. However, the adhesive layer 3 is cut along the position of the dividing line SL detected by the camera 40. The cutting depth of the cutting blade 52 is set to a depth at which at least the adhesive layer 3 is completely cut. The adhesive layer 3 is divided by cutting with the cutting blade 52 along the positions of all the dividing lines SL. At this time, there is no possibility that fragments are generated in the divided adhesive layer 3. In this way, each device chip C singulated is picked up and then die-bonded on a metal frame or substrate.

  As described above, in the wafer processing method according to the present invention, the adhesive layer 3 is formed on the back surface Wb of the wafer W divided into the plurality of device chips C by performing the adhesive layer forming step after performing the grinding step. Then, the process proceeds to the adhesive layer dividing step and the adhesive layer 3 is divided along the dividing line SL by the laser beam LB2 or the cutting blade 52, so that there is no possibility that fragments are generated in the divided adhesive layer 3, It is possible to prevent debris from adhering to the device chip C and cause a device failure, and to reliably divide the adhesive layer 3.

1: Surface protective member 2: Modified layer 3: Adhesive layer 10: Holding table 10a: Holding surface 20, 20a: Laser beam irradiation means 21: Condenser 30: Grinding means 31: Spindle 32: Mount 33: Grinding wheel 34 : Grinding wheel 40: Camera 50: Cutting means 51: Spindle 52: Cutting blade

Claims (1)

A wafer processing method in which a device is formed in each region divided by a plurality of division lines intersecting each other,
A split starting point forming step of forming a modified layer on the wafer by irradiating a laser beam having a wavelength transparent to the wafer from the back surface of the wafer along the splitting line;
A surface protection member disposing step of disposing a surface protection member on the surface of the wafer before or after performing the division starting point forming step;
After performing the surface protection member disposing step, grinding the back surface of the wafer to reduce to a predetermined thickness and dividing the wafer into a plurality of device chips along the modified layer;
An adhesive layer forming step of forming an adhesive layer on the back surface of the wafer divided into a plurality of device chips after performing the grinding step;
After performing the adhesive layer forming step, a dividing line where the wafer is divided is detected, and a laser beam is irradiated from the adhesive layer side along the detected divided line, or cutting with a cutting blade is performed to form the adhesive layer. A wafer processing method comprising: an adhesive layer dividing step for dividing.

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