JP6978237B2 - Wafer division method - Google Patents

Description

The present invention relates to a method of dividing a wafer into a device.

By condensing and irradiating the inside of the wafer with a laser beam, a modified layer is formed inside the wafer along the planned division line, and then an expand tape is attached to the back surface of the wafer to expand the expand tape. A method of dividing a wafer into devices is known. In this case, since the modified layer remains on the side surface of the device after the division, a technique for removing the remaining modified layer by plasma etching has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2009-11147

However, when the expanded tape is expanded to divide the wafer into devices, the device may float from the expanded tape. If plasma etching is performed while the device is floating from the expanding tape, the bottom surface of the device and the corners on the bottom surface side are etched, resulting in deterioration of the quality of the device.

The present invention has been considered to have such a problem, and it is an object of the present invention to prevent the bottom surface and the corners on the bottom surface side of the device from being etched by plasma etching after expanding the expand tape and dividing the wafer into devices. And.

It is a method of dividing a wafer in which a device is formed in each region divided by a plurality of planned division lines formed on the surface along the planned division line, and the wafer is divided along the planned division line. By irradiating the wafer by positioning the condensing point of the laser beam having a wavelength that is transparent to the wafer from the back surface side inside the wafer, the modified layer is inside the wafer and the modified layer is applied to the front surface and the back surface of the wafer. After performing the modified layer forming step of forming the cracks toward the wafer, the expanding tape attaching step of attaching the expanded tape to the back surface of the wafer, the expanding step of expanding the expanded tape to widen the distance between the devices, and the expansion step. A heating step for heating the expanded tape and the device in order to enhance the adhesiveness between the expanded tape and the device, and a modification in which plasma etching gas is supplied from the surface side of the wafer and remains on the side surface of the device. It has a plasma etching step of removing a layer, and the heating step is characterized in that the surface side of the wafer is sucked and held on a heated holding table and heated from the surface side.

In the present invention, the expanded tape attached to the back surface of the wafer is expanded in the expansion process to divide the wafer into devices, and then the expanded tape and the device are heated in the heating process, so that the expanded tape becomes soft and easy to imitate the device. Therefore, the adhesiveness between the expanded tape and the device can be improved. Therefore, it is possible to prevent the bottom surface of the device and the corners on the bottom surface side from being etched in the plasma etching process.
By performing the heating process while sucking and holding the wafer on the heated holding table, heat can be reliably transferred between the expanded tape and the device, and the adhesiveness between the expanded tape and the bottom surface of the device D can be reliably improved. can.
When performing the heating process while sucking and holding the surface side of the wafer on the holding table, if a heated holding table is used, warm air rises and easily enters between the expanding tape and the bottom surface of the device, so it is expanded. The adhesiveness between the tape and the bottom surface of the device D can be improved more reliably.

It is a perspective view which shows the example of a wafer. It is sectional drawing which shows the wafer which coated the protective film on the surface. It is sectional drawing which shows the modified layer formation process. It is sectional drawing which shows the wafer after the modification layer formation process. It is sectional drawing which shows the expanding tape sticking process. It is sectional drawing which shows the expansion process. It is sectional drawing which shows the wafer after carrying out the expansion process. It is sectional drawing which shows the heating process. It is sectional drawing which shows the wafer after carrying out a heating process. It is sectional drawing which shows the plasma etching process.

As shown in FIG. 1, the wafer W to be machined has a plurality of scheduled division lines L intersecting on its surface Wa, and a device D is formed in each region partitioned by the scheduled division lines L. ..

As shown in FIG. 2, the surface Wa of the wafer W is coated with the protective film P. The protective film P is made of, for example, a water-soluble resin, and has a role of protecting the device D in a plasma etching step to be performed later. As the water-soluble resin, for example, Hogomax provided by DISCO Corporation can be used. The protective film P is in a state of being cured by irradiation with ultraviolet rays.

(1) Modified layer forming step As shown in FIG. 3A, the protective tape T1 is attached to the protective film P on the surface Wa side of the wafer W. Then, the protective tape T1 side is held by the chuck table 11 of the laser processing apparatus 1. The chuck table 11 is movable in the X-axis direction and in the Y-axis direction orthogonal to the plane direction with respect to the X-axis.

The laser processing apparatus 1 includes an irradiation head 12 that irradiates the wafer W with a laser beam. The irradiation head 12 is positioned above one end of the scheduled division line L shown in FIG. 1, and a laser beam having a wavelength that is transparent to the wafer W from the irradiation head 12 while moving the chuck table 2 in the + X direction, for example. The LB is irradiated on the back surface Wb side of the wafer W. The condensing point of the laser beam LB at this time is positioned inside the wafer W. As shown in FIG. 3B, when the laser beam LB is irradiated from one end to the other end of the scheduled division line L, the modified layer R is formed inside the wafer W along the scheduled division line L. To.

While index-feeding the chuck table 11 in the Y-axis direction, irradiation of the same laser beam LB is performed for all scheduled division lines L in the same direction, and after the chuck table 11 is further rotated by 90 degrees, irradiation of the laser beam LB is performed in the same manner. By performing the above, the modified layer R is formed vertically and horizontally along all the planned division lines L. When the modified layer R is formed inside the wafer W, cracks Ca and Cb from the modified layer R toward the front surface Wa and the back surface Wb are formed, respectively, as shown in FIG. The cracks Ca and Cb may extend from the modified layer S of the wafer W toward the front surface Wa and the back surface Wb, and may not reach the front surface Wa and the back surface Wb.

note that. Prior to the modified layer forming step, a back surface grinding step of grinding the back surface Wb of the wafer W to a predetermined thickness is performed. Since the protective tape is attached to the front surface Wa of the wafer W in the back surface grinding step, this protective tape can be used as it is in the modified layer forming step.

(2) Expanded Tape Attaching Step After the modified layer forming step, the expanded tape T2 is attached to the back surface Wb of the wafer W and the protective tape T1 is peeled off from the front surface Wa as shown in FIG. The expanded tape T2 is formed to have a larger diameter than the wafer W. Further, a ring-shaped frame may be attached to the outer peripheral portion of the expanding tape T2.

(3) Expansion Step After the expanding tape attaching step, as shown in FIG. 6, the expanding tape T2 is radially expanded in the A direction, which is the direction toward the outside in the plane direction thereof, so that the distance between adjacent devices D is spaced. Spread out. Since the reformed layer R and the cracks Ca and Cb are formed inside the wafer W along the planned division line L, the expanded tape T2 can be expanded to easily transfer the wafer W to each device D. Can be split. Further, since the protective film P is cured, the protective film P is also divided together with the device D.
Even if the cracks Ca and Cb do not reach the front surface Wa and the back surface Wb of the wafer W, respectively, the expansion of the expanded tape T2 applies a force in the same direction as the expansion tape T2 to the cracks Ca and Cb. The wafer W can be divided into individual devices D.

When this step is performed, as shown in FIG. 7, the expanding tape T2 is peeled off from a part of the bottom surface Db of the device D, and the bottom surface Db of the device D and the corner portion Dc on the bottom surface Db side are lifted from the expanding tape T2. Sometimes. If the subsequent plasma etching step is performed in this state, the bottom surface Db and the corner Dc will be etched. Therefore, after the expansion step and before the plasma etching step, the heating step shown below is carried out to ensure the adhesive state between the expanded tape T2 and the bottom surface Db of the device D.

(4) Heating step In this step, as shown in FIG. 8, the divided wafer W is sucked and held on the holding table 21. In this example, the surface Wa side of the wafer W is suction-held. The holding table 21 has a built-in heater 22 for heating the suction-held wafer W and the expanded tape T2.

When the wafer W and the expanding tape T2 are heated by the heater 22 in a state where the wafer W divided in the holding table 21 is sucked and held from the surface Wa side, as shown in FIG. 9, the wafer W floats from the expanding tape T2 in the expansion step. The expanded tape T2 softened by heating can be imitated and adhered to the bottom surface Db of the device D. Further, by adhering the expand tape T2 to the bottom surface Db of the device D, the state in which the corner portion Dc of the device D is floated is also eliminated.

The holding table 21 used in this step may be dedicated for the heating step or may be provided in the expanding device used in the expansion step.

In this step, the expanding tape T2 side may be held and heated in the holding table 21, but the wafer W and the expanding by the heater 22 built in the holding table 21 while holding the surface Wa side of the wafer W in the holding table 21. When the tape T2 is heated, the warm air 22a rises and easily enters between the expanded tape T2 and the bottom surface Db of the device D, so that the adhesiveness between the expanded tape T2 and the bottom surface Db of the device D can be improved more reliably. can. For example, it was confirmed that when the holding table 21 was heated at 80 ° C. for 3 minutes, the floating of the device D from the expanded tape T2 was eliminated.
Further, in this step, the expanding tape T2 may be heated by blowing warm air from above without using the holding table 21 having a built-in heater.

(5) Plasma etching step After the heating step, as shown in FIG. 10, the expanded tape T2 is held in the chamber of the plasma etching apparatus to expose the protective film P side. Then, the plasma 3 is supplied to the protective film P side. The plasma 3 may be a plasma in which the etching gas introduced into the chamber is converted into plasma, or a remote plasma in which the plasma generated outside the chamber is introduced into the chamber.

When plasma is supplied to the protective film P side in this way, the protective film P is coated on the upper surface Da of each device D, and the expanding tape T2 is attached to the bottom surface Db of the device D, so that the device D is attached. Only the side surface Dd of the above is etched, and the remaining modified layer R is removed. Further, since the expanding tape T2 is adhered to the bottom surface Db of the device D in the heating step and plasma does not penetrate between the expanding tape T2 and the bottom surface Db of the device D, the corners on the bottom surface Db and the bottom surface Db side of the device D. Part Dc is not etched.

(6) Cleaning step After the plasma etching step, wash water is sprinkled on the device D. Since the protective film P is water-soluble, the protective film P is removed by spraying with washing water. When the protective film P is a resist film or the like that is not water-soluble, the protective film P is removed by using an ashing device or the like.

As described above, after the expanded tape T2 is expanded in the expansion step to divide the wafer W into the device D, the expanded tape T2 and the device D are heated in the heating step, so that the expanded tape T2 becomes soft and the device D becomes soft. Since it is easy to imitate the garden Db, the adhesiveness between the expanded tape T2 and the bottom surface Db of the device D is improved, and the bottom surface Db of the device D and the corner Dc on the bottom surface Db side are prevented from being etched in the plasma etching process. Can be done.

In the above embodiment, the expanding tape T2 is attached to the back surface Wb of the wafer W and the protective tape T1 is peeled off from the front surface Wa before the expansion step, but the protective tape T1 can be expanded in the surface direction. If so, it is not necessary to replace the wafer W with the expanding tape T2.

W: Wafer Wa: Front surface L: Scheduled division line Wb: Back surface D: Device Da: Top surface Db: Bottom surface Dc: Corner portion R: Modified layer Ca, Cb: Crack P: Protective film T1: Protective tape T2: Expanded tape 1 : Laser processing device 11: Chuck table 12: Irradiation head 21: Holding table 22: Heater 3: Plasma

Claims (1)

It is a wafer division method for dividing a wafer in which a device is formed in each region partitioned by a plurality of planned division lines formed on the surface along the planned division line.
By irradiating the inside of the wafer with a condensing point of a laser beam having a wavelength that is transparent to the wafer from the back surface side of the wafer along the planned division line, the modified layer and the modification are formed inside the wafer. A modified layer forming step of forming cracks from the quality layer to the front and back surfaces of the wafer,
The process of attaching the expanded tape to the back of the wafer, and the process of attaching the expanded tape,
An expansion process that expands the expanding tape to widen the spacing between the devices, and
After performing the expansion step, a heating step of warming the expand tape and the device in order to enhance the adhesiveness between the expand tape and the device, and a heating step.
A plasma etching process in which plasma etching gas is supplied from the surface side of the wafer and the modified layer remaining on the side surface of the device is removed.
Have a,
In the heating step, a method for dividing a wafer is characterized in that the surface side of the wafer is sucked and held on a heated holding table and heated from the surface side.

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