JP2014207386A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer processing method capable of suppressing occurrence of chipping called a crack.SOLUTION: A wafer processing method comprises a grinding step, a metal film coating step, a groove forming step, and a dividing step. The grinding step forms a circular recess and an annular reinforcing part WS by grinding a rear surface corresponding to a device region of a wafer W. The metal film coating step coats the rear surface of the wafer W with a metal film after the grinding step. The groove forming step forms a plurality of grooves having a depth not reaching a rear surface of the device region by cutting the wafer W with a cutting blade along division schedule lines from the surface side of the wafer W to disperse internal stress after the metal film coating step. The dividing step forms a division groove DS having a depth reaching from a bottom of the groove to the rear surface of the device region with the cutting blade and divides the wafer W into a plurality of devices D after the groove forming step.

Description

  The present invention relates to a wafer processing method in which a wafer having a device region on the surface and an outer peripheral surplus region surrounding the device region is divided into individual devices.

  A wafer on which a plurality of devices such as ICs are formed is ground into a predetermined thickness by grinding the back surface, and then divided into individual devices by a dicing apparatus or the like and used for various electronic devices and the like. In recent years, in order to reduce the weight and size of electronic devices and the like, wafers have been formed to be extremely thin as 100 μm to 20 μm by grinding.

  However, such thinly formed wafers are difficult to handle due to their lack of elasticity like paper, hindering subsequent transport, and the thickness of gold, silver, titanium, etc. for the back electrode of the device. There is a problem that it becomes difficult to coat a ground surface of a metal film of several tens of nanometers. Accordingly, a grinding method has been proposed in which only the back surface corresponding to the device region of the wafer is ground, and a ring-shaped annular reinforcing portion is formed on the back surface of the wafer corresponding to the outer peripheral surplus region surrounding the device region (for example, Patent Documents). 1).

  Further, as a method of dividing the wafer having the ring-shaped annular reinforcing portion formed on the outer periphery of the back surface along the street (division planned line) in this way, after removing the ring-shaped annular reinforcing portion, the surface of the wafer A method of cutting with a cutting blade from the side has been proposed (see, for example, Patent Document 2).

JP 2007-019461 A JP 2007-019379 A

  In this way, after grinding very thinly, if the metal film is coated on the back surface of the wafer maintained without warping by the ring-shaped annular reinforcing part, the internal stress due to the difference in the thermal expansion coefficient due to the state that different materials are bonded together. Is included. Further, even if an annular reinforcing portion is provided, if warping occurs on a very thin ground surface, when the metal film is coated in order to keep the ground surface flat when the metal film is coated, Internal stress is contained inside. If normal dicing is performed with the internal stress contained, cracks called cracks are likely to occur on the back side (near the metal film) of the divided device, and the strength of the device is reduced. There was a fear.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a wafer processing method capable of suppressing generation of cracks called cracks.

  In order to solve the above-described problems and achieve the object, the wafer processing method of the present invention includes a device region in which a plurality of devices are partitioned by a plurality of division lines, and an outer peripheral surplus region surrounding the device region. Is a wafer processing method in which a wafer formed on the surface is divided into individual devices, the back surface of the wafer corresponding to the device region is ground to form a circular recess, and an annular outer periphery of the circular recess is formed. A grinding step for forming a reinforcing portion, a metal film coating step for coating a back surface of the wafer with a metal film after the grinding step, and a line to be divided from the front side of the wafer to the division line after the metal film coating step. A groove forming step in which the wafer is cut along with a cutting blade to form a plurality of grooves having a depth not reaching the back surface of the device region to disperse the stress; After the groove forming step, there is provided a dividing step of forming a dividing groove having a depth from the bottom of the groove to the back surface of the device region with the cutting blade, and dividing the wafer into a plurality of devices. And

  Further, the wafer processing method may include an annular reinforcing portion separation that cuts the wafer along the inner periphery of the annular reinforcing portion before or after the groove forming step to separate the annular reinforcing portion and the device region. It is preferred that the steps are performed.

  According to the wafer processing method of the present invention, after the metal film is coated on the ground surface leaving the outer peripheral surplus area of the wafer, a plurality of grooves having a depth not reaching the back surface are first formed, A dividing groove is formed from the bottom to divide each device. For this reason, when a groove with a depth that does not reach the back surface is formed, the internal stress of the wafer can be released to some extent, side cracks that are likely to occur when splitting can be suppressed, and the occurrence of cracks called cracks can be suppressed. Can do.

Fig.1 (a) is a perspective view which shows the wafer before sticking the protective tape of the wafer processing method which concerns on embodiment, FIG.1 (b) is sticking the protective tape of the wafer processing method which concerns on embodiment. It is a perspective view which shows the back wafer. FIG. 2 is a perspective view showing an outline of a grinding step of the wafer processing method according to the embodiment. FIG. 3A is a perspective view of the wafer after the grinding step of the wafer processing method according to the embodiment, and FIG. 3B is a cross-sectional view of the wafer after the grinding step of the wafer processing method according to the embodiment. FIG. FIG. 4 is a diagram showing an outline of the metal film coating step of the wafer processing method according to the embodiment. FIG. 5 is a cross-sectional view of the wafer after the metal film coating step of the wafer processing method according to the embodiment. FIG. 6A is a perspective view of the wafer supported by the annular frame after the metal film coating step of the wafer processing method according to the embodiment, and FIG. 6B is a wafer processing method according to the embodiment. It is sectional drawing of the wafer supported by the cyclic | annular flame | frame after the metal film coating step of this. FIG. 7 is a perspective view showing an outline of the protective tape peeling step of the wafer processing method according to the embodiment. FIG. 8 is a cross-sectional view illustrating an outline of the annular reinforcing portion separating step of the wafer processing method according to the embodiment. FIG. 9 is a cross-sectional view illustrating an outline of a groove forming step of the wafer processing method according to the embodiment. FIG. 10 is a cross-sectional view showing an outline of the division step of the wafer processing method according to the embodiment. FIG. 11 is a perspective view of the wafer after the dividing step of the wafer processing method according to the embodiment. FIG. 12 is a perspective view showing an outline of the annular reinforcing portion removing step of the wafer processing method according to the embodiment. FIG. 13 is a perspective view showing the annular reinforcing portion removing step of the wafer processing method according to the modification of the embodiment. FIG. 14 is a cross-sectional view illustrating an outline of a groove forming step of a wafer processing method according to a modification of the embodiment. FIG. 15 is a cross-sectional view illustrating an outline of the dividing step of the wafer processing method according to the modification of the embodiment. FIG. 16 is a perspective view of the wafer after the dividing step of the wafer processing method according to the embodiment.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the structures described below can be combined as appropriate. Various omissions, substitutions, or changes in the configuration can be made without departing from the scope of the present invention.

Embodiment
A wafer processing method according to the present embodiment will be described with reference to FIGS. FIG. 1A is a perspective view showing a wafer before sticking a protective tape of the wafer processing method according to the embodiment, and FIG. 1B is a diagram after sticking the protective tape of the wafer processing method according to the embodiment. FIG. 2 is a perspective view showing an outline of a grinding step of the wafer processing method according to the embodiment. FIG. 3A is a perspective view of the wafer after the grinding step of the wafer processing method according to the embodiment. FIG. 3B is a sectional view of the wafer after the grinding step of the wafer processing method according to the embodiment, and FIG. 4 is a diagram showing an outline of the metal film coating step of the wafer processing method according to the embodiment. FIG. 5 is a cross-sectional view of the wafer after the metal film coating step of the wafer processing method according to the embodiment, and FIG. 6 (a) is an annular frame after the metal film coating step of the wafer processing method according to the embodiment. Supported FIG. 6B is a sectional view of the wafer supported by the annular frame after the metal film coating step of the wafer processing method according to the embodiment, and FIG. 7 is a wafer processing method according to the embodiment. FIG. 8 is a cross-sectional view showing an outline of the annular reinforcing portion separating step of the wafer processing method according to the embodiment, and FIG. 9 is a view of the wafer processing method according to the embodiment. FIG. 10 is a cross-sectional view showing an outline of a groove forming step, FIG. 10 is a cross-sectional view showing an outline of a dividing step of the wafer processing method according to the embodiment, and FIG. 11 is a wafer after the dividing step of the wafer processing method according to the embodiment. FIG. 12 is a perspective view showing an outline of the annular reinforcing portion removing step of the wafer processing method according to the embodiment.

  A wafer processing method according to the present embodiment (hereinafter simply referred to as a processing method) is a processing method for processing the wafer W shown in FIG. 1, and includes a grinding step, a metal film coating step, a groove forming step, A dividing step, and grinding the back surface Wb side of the wafer W, and dividing the wafer W into individual devices D by cutting.

  In addition, the wafer W as a processing target divided into the individual devices D by the processing method according to the present embodiment is a disk-shaped semiconductor wafer or optical device whose base material is silicon, sapphire, gallium, or the like in the present embodiment. It is a wafer. As shown in FIG. 1, the wafer W has a device area W1 in which a plurality of devices D are partitioned by a plurality of division lines S1 and S2 and an outer peripheral surplus area W2 surrounding the device area W1 formed on the surface Wa. ing. As the planned division lines S1 and S2, a plurality of first division planned lines S1 that are parallel to each other and a plurality of second planned division lines S2 that are parallel to each other and orthogonal to the first planned division line S1 are provided. It has been.

  In the processing method according to the present embodiment, first, after the adhesive layer (not shown) of the protective tape T1 is opposed to the surface Wa of the wafer W, as shown in FIG. As shown in FIG. 1B, the adhesive layer of the protective tape T1 is attached to the surface Wa of the wafer W. The protective tape T1 is formed in an outer shape equivalent to the outer shape of the wafer W, and an adhesive layer is attached to the entire surface Wa of the wafer W to protect the entire surface Wa of the wafer W. Then, the process proceeds to the grinding step.

  In the grinding step, the surface Wa of the wafer W, that is, the protective tape T1 is held on the chuck table 11 of the grinding apparatus 10. After that, as shown in FIG. 2, the chuck table 11 is rotated around the axis, and the grinding unit 12 of the grinding apparatus 10 is pressed against the back surface Wb of the wafer W while rotating around the axis in the same direction as the chuck table 11. . Then, the back surface Wb of the wafer W corresponding to the device region W1 is ground. As shown in FIGS. 3A and 3B, a circular concave portion WR is formed on the back surface Wb side of the wafer W, and an annular reinforcing portion WS corresponding to the outer peripheral surplus region W2 is formed on the outer periphery of the circular concave portion WR. To do. That is, in the grinding step, a portion corresponding to the device region W1 of the back surface Wb of the wafer W is ground by the grinding unit 12 to form a circular recess WR, and a portion corresponding to the outer peripheral surplus region W2 of the back surface Wb of the wafer W is ground. The annular reinforcing portion WS is formed by leaving the outer peripheral surplus region W2 without grinding the unit 12. Then, the process proceeds to the metal film coating step.

  In the metal film coating step, after the grinding step, as shown in FIG. 4, the surface Wa of the wafer W, that is, the protective tape T <b> 1 is held by the holding unit 22 in the chamber 21 of the metal film coating apparatus 20. At this time, the bottom surface WRB of the wafer W, particularly the circular recess WR, is held by the holding unit 22 in a flat state without warping. For this reason, if warping or the like occurs on the bottom surface WRB of the circular recess WR of the wafer W after the grinding step, an internal stress is generated in the wafer W. Thereafter, a rare gas such as argon gas is introduced from the inlet 21a of the chamber 21, and the inside of the chamber 21 is decompressed by a decompression source (not shown) connected to the decompression port 21b. Then, the rare gas introduced and ionized from the introduction port 21a of the chamber 21 is collided with the sputtering source 25 applied by the high frequency power source 23 and supported by the exciting member 24, and the metal constituting the sputtering source 25 is removed from the wafer. The bottom surface WRB, the inner peripheral surface WRI, the remaining back surface Wb, and the entire outer peripheral surface WP of the circular recess WR of W are attached. Thus, as shown in FIG. 5, at least the entire back surface Wb of the wafer W is coated with the metal film MF. At this time, due to the difference in thermal expansion coefficient between the wafer W and the metal film MF, internal stress is generated on the bottom surface WRB of the circular recess WR of the wafer W.

  Thereafter, the back surface Wb of the wafer W is pressed against the adhesive surface of the dicing tape T2 (shown in FIG. 6 (a)) whose outer peripheral portion is mounted on the annular frame F (shown in FIG. 6 (a)). A slightly smaller convex member (not shown) is inserted into the circular concave portion WR via the dicing tape T2. Then, the adhesive surface of the dicing tape T2 is brought into close contact with the metal film MF coated on the wafer W, and the adhesive surface of the dicing tape T2 is coated on the entire back surface Wb of the wafer W as shown in FIG. Affixed to the metal film MF. Then, the process proceeds to the protective tape peeling step.

  In the protective tape peeling step, the protective tape T1 attached to the surface Wa of the wafer W is peeled from the surface Wa of the wafer W as shown in FIG. And it progresses to a cyclic | annular reinforcement part isolation | separation step.

  In the annular reinforcing portion separating step, the wafer W is held on the chuck table 31 of the cutting device 30 via the dicing tape T2 before the groove forming step. Then, as shown in FIG. 8, the device region W1 of the wafer W is rotated by the cutting blade 32-1 that rotates around the spindle axis of the cutting device 30 while rotating the wafer W around the axis through the chuck table 31. The boundary with the outer peripheral surplus area W2 is cut. Then, the wafer W is cut along the inner periphery of the annular reinforcing portion WS, and the annular reinforcing portion WS and the device region W1 are separated over the entire periphery of the wafer W. In the annular reinforcing portion separating step, the cutting blade 32-1 is used to cut to the center of the thickness of the dicing tape T2. Then, the process proceeds to the groove forming step.

  In the groove forming step, after the metal film coating step, while relatively moving the chuck table 31 and the cutting blade 32-2 rotating around the spindle axis of the cutting device 30 along the scheduled division lines S1, S2, As shown in FIG. 9, the wafer W is cut by the cutting blade 32-2 along the division lines S1 and S2 from the surface Wa side of the wafer W. Then, a plurality of grooves S having a depth not reaching the back surface Wb of the device region W1 are formed by the cutting blade 32-2, and the internal stress (corresponding to the stress) of the wafer W generated in the metal film coating step is dispersed (released). ) In the present embodiment, the grooves S are formed in all the planned division lines S1 and S2. Then, the process proceeds to the division step.

  In the dividing step, after the groove forming step, the chuck table 31 and the cutting blade 32-3 rotating around the axis of the cutting device 30 are relatively moved along the scheduled dividing lines S1 and S2, as shown in FIG. As shown, the wafer W is cut by the cutting blade 32-3 from the surface Wa side of the wafer W along the division lines S1 and S2. Then, a division groove DS having a depth from the bottom of the groove S to the back surface Wb of the device region W1 is formed by the cutting blade 32-3, and the wafer W is divided into a plurality of devices D as shown in FIG. Then, the process proceeds to the annular reinforcing portion removing step. In the annular reinforcing portion removing step, as shown in FIG. 12, after the annular reinforcing portion WS is removed from the dicing tape T2, the individually divided devices D are removed from the dicing tape T2.

  According to the processing method according to the embodiment, after the metal film MF is coated on the bottom surface WRB of the circular recess WR of the wafer W formed by grinding leaving the outer peripheral surplus region W2, the groove S has a depth that does not allow division. A plurality of are formed. Thereafter, the bottom of the groove S is cut again to form the divided groove DS, and the wafer W is divided into the devices D. For this reason, the internal stress of the wafer W generated when the metal film MF is coated can be released to some extent when the plurality of grooves S are formed. Therefore, side cracks that are likely to occur on the side surfaces of the device D when dividing each device D can be suppressed. Therefore, according to the processing method which concerns on embodiment, generation | occurrence | production of the crack called a crack can be suppressed.

[Modification]
A processing method according to a modification of the embodiment will be described with reference to FIGS. FIG. 13 is a perspective view showing the annular reinforcing portion removing step of the wafer processing method according to the modification of the embodiment, and FIG. 14 is a cross-sectional view showing an outline of the groove forming step of the wafer processing method according to the modification of the embodiment. FIG. 15 is a cross-sectional view showing an outline of a dividing step of a wafer processing method according to a modification of the embodiment, and FIG. 16 is a perspective view of the wafer after the dividing step of the wafer processing method according to the embodiment. .

  In the processing method according to the modification of the embodiment, the process proceeds to the annular reinforcing portion removing step after the annular reinforcing portion separating step. In the annular reinforcing portion removing step, as shown in FIG. 13, the annular reinforcing portion WS is removed from the dicing tape T2, and the process proceeds to the groove forming step.

  In the groove forming step, as in the above-described embodiment, the device region W1 is moved as shown in FIG. 14 while relatively moving the chuck table 31 and the cutting blade 32-2 along the scheduled division lines S1 and S2. A plurality of grooves S having a depth that does not reach the back surface Wb is formed by the cutting blade 32-2, and the internal stress (corresponding to the stress) of the wafer W generated in the metal film coating step is dispersed (released). In the modification, the grooves S are formed in all the planned division lines S1 and S2. Then, the process proceeds to the division step.

  In the dividing step, as shown in FIG. 15, the bottom of the groove S is moved while the chuck table 31 and the cutting blade 32-3 are relatively moved along the scheduled dividing lines S1 and S2, as in the above-described embodiment. A dividing groove DS having a depth extending from the device region W1 to the back surface of the device region W1 is formed by the cutting blade 32-3, and the wafer W is divided into a plurality of devices D as shown in FIG. Then, the individually divided device D is removed from the dicing tape T2.

  According to the processing method according to the modified example, the internal stress of the wafer W generated when the metal film MF is coated can be released to some extent when the plurality of grooves S are formed, as in the above-described embodiment. it can. Therefore, according to the processing method which concerns on a modification, when dividing for every device D, the side crack which is easy to generate | occur | produce on the side surface of the device D can be suppressed.

  In the embodiment and the modification described above, the grooves S are formed in all the planned division lines S1 and S2. However, in the present invention, for example, the grooves S are formed in all the planned division lines S1 or the division lines S2 are formed. The grooves S may be formed in all of them. In short, in the present invention, in the groove forming step, the grooves S may be formed in a plurality of all the planned division lines S1, S2.

  In the embodiment and the modification described above, the annular reinforcing portion separating step is performed before the groove forming step. However, in the present invention, the annular reinforcement separating step may be performed after the dividing step, that is, after the groove forming step. In short, in the present invention, the annular reinforcing portion separating step may be performed before or after the groove forming step. Furthermore, in this invention, what is necessary is just to implement an annular reinforcement part removal step at an appropriate timing.

  Furthermore, in the present invention, the cutting device 30 or the cutting blades 32-1, 32-2, and 32-3 used in the annular reinforcing portion separating step, the groove forming step, and the dividing step may be the same or different. . For example, the cutting blade 32-1 has a certain thickness to prevent breakage because the cutting line is circular, so a cutting blade having a certain thickness or more is suitable. The cutting blades 32-2 and 32- -3 is assumed to be a cutting blade that is thin enough to fit in the planned division lines S1 and S2 having a width of 100 μm or less.

  The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the scope of the present invention.

D device S1, S2 Scheduled division line W Wafer Wa Front surface Wb Back surface W1 Device region W2 Peripheral surplus region WR Circular concave portion WS Annular reinforcing portion MF Metal film S Groove DS Divided groove

Claims (2)

A wafer processing method for dividing a wafer in which a plurality of devices are partitioned by a plurality of scheduled division lines and a wafer formed on the surface with a peripheral excess region surrounding the device area into individual devices,
Grinding the back surface of the wafer corresponding to the device region to form a circular recess, and forming an annular reinforcing portion on the outer periphery of the circular recess;
After the grinding step, a metal film coating step for coating a metal film on the back surface of the wafer;
After the metal film coating step, the wafer is cut with a cutting blade from the front surface side of the wafer along the scheduled dividing line to form a plurality of grooves having a depth that does not reach the back surface of the device region. A groove forming step to be dispersed;
After the groove forming step, there is provided a dividing step of forming a dividing groove having a depth from the bottom of the groove to the back surface of the device region with the cutting blade, and dividing the wafer into a plurality of devices. Wafer processing method.   Before or after the groove forming step, an annular reinforcing portion separating step is performed in which the wafer is cut along the inner periphery of the annular reinforcing portion to separate the annular reinforcing portion and the device region. The wafer processing method according to claim 1.

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