JP7193956B2 - Wafer processing method - Google Patents

Description

The present invention relates to a wafer processing method for grinding the backside of a wafer to thin it to a finished thickness.

When the back surface of the wafer is ground and thinned, a so-called sharp edge is formed at the chamfered portion of the outer peripheral edge of the wafer. So-called edge trimming (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100000) is widely used to remove the chamfered portion.

JP-A-2000-173961

However, edge trimming uses a thicker blade with a width of about 1 mm compared to a cutting blade with a width of about 20 μm that is used in normal dicing. It is more likely to cause chipping or cracks at the edge of the cutting groove, which is called chipping. If the generated crack reaches the device, it will damage the device, which is a problem.

Therefore, in the processing method of grinding the back surface of the wafer to thin it, there is a problem of preventing the device from being damaged by the cracks generated when trimming the chamfered portion of the outer peripheral edge of the wafer.

In order to solve the above problems, the present invention has a device region in which a plurality of devices are formed on the surface and an outer peripheral surplus region surrounding the device region, and grinds the back surface of a wafer having a chamfered portion on the outer periphery. A wafer processing method for thinning to a finished thickness by cutting a cutting blade from the surface of the wafer to the chamfered portion to a depth that reaches the finished thickness and cutting along the outer peripheral edge to the chamfered portion. a trimming step of removing the chamfered portion; and a grinding step of grinding the backside of the wafer after performing the trimming step to thin it to the finished thickness; A laser beam having a wavelength that is transmissive to the wafer is irradiated along the outer peripheral edge in the outer peripheral surplus area and inside the wafer from the position where the cutting blade is cut in the trimming step to remove the laser beam from the surface of the wafer. a laser processing step of forming an annular modified region extending to the depth of cut of the cutting blade, wherein the annular modified region prevents cracks generated in the trimming step from extending into the device region. , a wafer processing method.

In the wafer processing method according to the present invention, before the trimming step is performed, a laser beam having a wavelength that is transparent to the wafer is located in the outer peripheral surplus region and inside the wafer from the position where the cutting blade is cut in the trimming step. A laser processing step that irradiates the beam along the outer periphery to form an annular modified region from the surface of the wafer to the cutting depth of the cutting blade, thereby extending the cracks generated in the trimming step to the device region. It becomes possible to dam up the change in the annular modified region. That is, it is possible to prevent the device from being damaged by cracks generated when trimming the chamfered portion.

It is a perspective view which shows an example of a wafer. It is a cross-sectional view showing an example of a wafer. It is an explanatory view explaining an example of a laser processing step. FIG. 4 is an enlarged cross-sectional view showing a state in which an annular modified region is formed on a wafer; FIG. 4 is a plan view showing an example of a wafer on which an annular modified region is formed; FIG. 4 is a cross-sectional view for explaining a state in which an annular modified region is formed by irradiating a wafer with a laser beam a plurality of times while changing the focal point position in the thickness direction of the wafer; FIG. 4 is a plan view showing an example of a wafer in which an annular modified region including pores and modified regions is formed; FIG. 4 is a cross-sectional view for explaining a state in which a chamfered portion of a wafer is trimmed; FIG. 4 is a cross-sectional view illustrating a state in which the back surface of a wafer is ground and thinned to a finished thickness; It is a perspective view which shows an example of a bonded wafer. It is a sectional view showing an example of a bonded wafer. It is an explanatory view explaining an example of a laser processing step performed on a bonded wafer. FIG. 4 is an enlarged cross-sectional view showing a state in which a modified layer and cracks are formed on the wafer of the bonded wafer; FIG. 4 is an enlarged cross-sectional view showing a state in which an annular modified region is formed on a wafer; FIG. 4 is a cross-sectional view illustrating a state in which the chamfered portion of the bonded wafer is trimmed; FIG. 4 is a cross-sectional view illustrating a state in which the back surface of the bonded wafer is ground and thinned to a finished thickness;

(Embodiment 1)
Each step of the wafer processing method according to the present invention (hereinafter referred to as the wafer processing method of Embodiment 1) will be described below.

(1-1) An example of laser processing step The wafer W shown in FIGS. A surplus peripheral area Wa2 surrounding Wa1 is provided. The device area Wa1 is partitioned into a grid pattern by a plurality of dividing lines S that intersect each other at right angles, and a device D such as an IC is formed in each partitioned region of the grid pattern. The back surface Wb of the wafer W facing downward in FIG. 1 is a surface to be ground later. The outer periphery of the wafer W is, for example, chamfered to form a chamfered portion Wd having a substantially arcuate cross section.
The wafer W may be made of gallium arsenide, sapphire, gallium nitride, silicon carbide, or the like other than silicon.

The wafer W is transported, for example, to the laser processing apparatus 1 shown in FIG. The laser processing apparatus 1 includes at least a holding table 10 for sucking and holding a wafer W, and a laser beam irradiation means 11 capable of irradiating a laser beam having a wavelength having transparency to the wafer W held on the holding table 10 . ing.

The holding table 10 is rotatable about an axis in the Z-axis direction, and is reciprocally movable in the X-axis direction, which is the machining feed direction, and the Y-axis direction, which is the indexing feed direction, by a moving means (not shown). The holding table 10 has, for example, a circular outer shape and a flat holding surface 10a that holds the wafer W and is made of a porous member. A suction force generated by a suction source (not shown) communicating with the holding surface 10a is transmitted to the holding surface 10a, so that the holding table 10 can suction-hold the wafer W on the holding surface 10a.

The laser beam irradiation means 11 causes the laser beam oscillated from the laser beam oscillator 119 to enter the condenser lens 111a inside the condenser 111 via the transmission optical system, so that the laser beam is held by the holding table 10. The wafer W can be irradiated with a focused laser beam. The height position of the focal point of the laser beam can be adjusted in the Z-axis direction by focal point position adjusting means (not shown).

The laser processing apparatus 1 includes alignment means 14 for recognizing the coordinate position of the chamfered portion Wd of the wafer W and the coordinate position of the center of the wafer W. As shown in FIG. The alignment means 14 is a camera composed of a light irradiation means (not shown), an optical system for capturing reflected light from the wafer W, and an imaging device for photoelectrically converting a subject image formed by the optical system and outputting image information. 140.

In the laser processing step, first, as shown in FIG. 3, the wafer W is placed on the holding surface 10a of the holding table 10 with the surface Wa facing upward, and the holding table 10 holds the wafer W by suction. The center of rotation of the holding table 10 and the center of the wafer W are substantially aligned.

For example, moving means (not shown) moves the holding table 10 below the alignment means 14 to perform edge alignment. That is, the holding table 10 rotates, and the camera 140 captures images of the outer peripheral edge of the wafer W held by the holding table 10 at a plurality of locations. Then, for example, the coordinates of three points spaced apart on the outer peripheral edge are detected, and the more accurate center coordinates of the wafer W on the holding table 10 are obtained by geometric calculation processing based on the coordinates of the three points.

Then, based on the information on the center coordinates of the wafer W and the information on the pre-recognized size of the wafer W, the holding table 10 is moved in the horizontal direction so that the outer peripheral surplus area Wa2 is shown in the trimming step to be described later. The holding table 10 is positioned at a predetermined position so that a predetermined position Y1 on the inner side of the wafer W is positioned directly below the collector 111 from the position Y2 where the cutting blade 613 shown in FIG.

Next, the position of the focal point of the laser beam condensed by the condenser lens 111a is set to a predetermined height position inside the wafer W, that is, to a depth that reaches the finished thickness L1 of the wafer W shown in FIG. 3, for example. It is positioned at a height position Z3 (cutting depth position of the cutting blade 613) slightly below the height position Z2. The finished thickness L1 is the thickness of the upper surface of the device D from the height position Z1 to the height position Z2. A laser beam having a wavelength that is transmissive to the wafer W is pulse-oscillated from the laser beam oscillator 119 at a predetermined repetition frequency, and the laser beam is condensed and irradiated to the inside of the wafer W held by the holding table 10 . .
The output of the laser beam is set, for example, under the condition that cracks are generated vertically from the modified layer formed on the wafer W, but the output is reduced to set the condition so that cracks are not generated vertically from the modified layer. may be Also, the setting of the focal point position is not limited to the above example.

The laser beam before reaching the focal point position is transparent to the wafer W, but the laser beam having reached the focal point position locally has extremely high absorption characteristics with respect to the wafer W. indicate. Therefore, as shown in FIG. 4, the wafer W near the focal point position is modified by absorbing the laser beam, and the modified layer extends vertically (mainly upward) from the focal point position. It is formed. In addition, fine cracks are simultaneously formed in the vertical direction from the modified layer. That is, a modified region M including a modified layer and cracks is formed on the wafer W. As shown in FIG. The upper end of the formed modified region M reaches the front surface Wa of the wafer W. As shown in FIG.

While irradiating the laser beam along the outer peripheral edge of the wafer W, the holding table 10 is rotated 360 degrees around the axis in the Z-axis direction at a predetermined rotational speed. An annular modified region M is formed extending from the outer peripheral surplus region Wa2 of the surface Wa to the cutting depth of the cutting blade 613 . Note that the area outside the two-dot chain line in the outer peripheral surplus area Wa2 of the wafer W shown in FIG.

Formation of the annular modified region M is not limited to the above example. For example, when the finished thickness of the wafer W is thick (when the depth of cut of the cutting blade 613 is increased), the holding table 10 is rotated at a predetermined rotational speed while irradiating the laser beam along the outer peripheral edge of the wafer W. Each time the laser beam is rotated 360 degrees around the axis in the Z-axis direction, the laser beam is irradiated to the wafer W in multiple passes while shifting the focal point position upward by a predetermined distance in the thickness direction (Z-axis direction) of the wafer W. good too.

6 formed by rotating the holding table 10 holding the wafer W by 360 degrees, the annular modified region M (the first modified layer from the −Z direction) including the modified layer Ma and the crack C shown in FIG. Above the modified region M), a second-stage annular modified region M including the modified layer Ma and the cracks C may be further formed. Further, a third modified layer and cracks and a fourth modified layer and cracks (not shown in FIG. 6) are formed up to the surface Wa. In this case, for example, the crack C extending upward from the first modified layer Ma and the crack C extending downward from the second modified layer Ma are connected. Cracks C in other stages are also connected in the same manner. Then, an annular modified region M is formed inside the wafer W from the peripheral surplus region Wa2 of the surface Wa to the height position Z3 corresponding to the cutting depth of the cutting blade 613 .
Although the modified layer Ma itself may be connected in the thickness direction of the wafer W instead of the cracks C in each stage to form the modified region M, it is better to connect the cracks C in each stage in fewer paths. laser beam irradiation can form an annular modified region M extending from the outer peripheral surplus region Wa2 of the surface Wa to the cutting depth of the cutting blade 613 inside the wafer W, which is efficient.

In addition, in forming the annular modified region M, each time the holding table 10 is rotated 360 degrees around the axis in the Z-axis direction, the focal point position is shifted upward by a predetermined distance in the thickness direction (Z-axis direction). Instead of irradiating the laser beam in multiple paths, the laser beam oscillated from the laser beam oscillator 119 shown in FIG. The light spots are positioned at different positions of the wafer W in the thickness direction. Then, by rotating the holding table 10 at a predetermined rotation speed by 360 degrees around the axis in the Z-axis direction, the inside of the wafer W is simultaneously reformed at a plurality of condensing points, and the inside of the wafer W is changed to the surface. An annular modified region M may be formed extending from the outer peripheral surplus region Wa2 of Wa to the depth of cut of the cutting blade 613 .

(1-2) Another Example of Laser Processing Step Another example of the laser processing step will be described below.
Edge alignment is performed in the same manner as in the example of the (1-1) laser processing step described above, and in the outer peripheral surplus region Wa2 and in the trimming step described later, the cutting blade 613 shown in FIG. The holding table 10 shown in FIG. 3 is positioned so that the predetermined position Y1 inside the wafer W is positioned directly below the light collector 111. As shown in FIG.

For example, additional lenses may be provided above or below the condenser lens 111a shown in FIG. 3, or the condenser lens 111a shown in FIG. The focal point of the beam can be positioned so as to extend in the thickness direction of the wafer W.
Then, with the focal point linearly extending in the thickness direction of the wafer W, the laser beam oscillator 119 pulse-oscillates a laser beam having a wavelength that is transmissive to the wafer W at a predetermined repetition frequency. The beam is condensed and irradiated inside the wafer W. As shown in FIG.
It is only necessary to irradiate the wafer W with the laser beam in a state in which aberration occurs in the optical axis direction. Therefore, a pulsed laser beam having a predetermined divergence angle is oscillated from the laser beam oscillator 119 and condensed by the condensing lens 111a. You may make it shine.

By the irradiation of the laser beam, inside the wafer W, a pore Mc or a crack (not shown) extending in the thickness direction (Z-axis direction) of the wafer W shown in FIG. A denatured region Md extending in the thickness direction is formed. That is, a modified region Mg (a so-called shield tunnel) is formed in the wafer W from the surface Wa of the wafer W to the cutting depth of the cutting blade 613, which is composed of the pores Mc or cracks and the modified region Md.
Then, while irradiating the laser beam along the outer peripheral edge of the wafer W, the holding table 10 is rotated 360 degrees around the axis in the Z-axis direction at a predetermined rotational speed, so that the wafer W is positioned as shown in FIG. The modified region Mg is annularly formed inside. In this example, the denatured regions Md adjacent to each other are formed so as to partially overlap each other. good.
Note that the area outside the two-dot chain line in the outer peripheral surplus area Wa2 of the wafer W shown in FIG.

(2) Trimming Step The trimming step for the wafer W formed with the modified regions M shown in FIGS. 5 and 8 will be described below. Note that even if the wafer W is the wafer W on which the modified region Mg shown in FIG. 7 is formed, the trimming step is performed in the same procedure as described below.
The wafer W on which the modified region M is formed is conveyed to the holding table 65 of the cutting device 6 shown in FIG. The holding table 65 is rotatable about an axis in the Z-axis direction and reciprocally movable in the X-axis direction.
The cutting means 61 for trimming the wafer W provided in the cutting device 6 includes a spindle 610 whose axial direction is the Y-axis direction, a motor (not shown) for rotating the spindle 610, and a cutting blade 613 attached to the tip of the spindle 610. The cutting blade 613 rotates as the motor rotates the spindle 610 .
The cutting blade 613 is a cutting blade for edge trimming that is thicker than a normal cutting blade for dicing (for example, a blade thickness of 1 mm).

In the trimming step, for example, alignment means (not shown) recognizes information on the coordinate position of the center of the wafer W on the holding table 65 and the coordinate position of the outer peripheral edge of the wafer W (edge alignment is performed). Then, the cutting means 61 is moved in the Y-axis direction based on the information, and the cutting blade 613 is positioned at a position Y2 radially inward by a predetermined distance from the outer peripheral edge in the outer peripheral surplus area Wa2. That is, for example, the cutting blade 613 is positioned so that about two-thirds of the lower end surface of the cutting blade 613 contacts the outer peripheral surplus region Wa2 of the wafer W including the chamfered portion Wd of the wafer W.

Next, a motor (not shown) rotates the spindle 610 counterclockwise at high speed when viewed from the +Y direction side, thereby rotating the cutting blade 613 fixed to the spindle 610 at high speed in the same direction. Furthermore, the cutting means is positioned so that the lowest end of the cutting blade 613 is positioned at the height position Z3 (the height position slightly lower than the height position Z2), which is the depth from the surface Wa of the wafer W to the finished thickness L1. 61 is sent in the -Z direction. The cutting means 61 may be lowered until the lowest end of the cutting blade 613 reaches the height position Z2.

Then, after the rotating cutting blade 613 is cut into the chamfered portion Wd from the surface Wa of the wafer W to the depth of the finished thickness L1, the holding table 65 is moved to the +Z direction side while the cutting blade 613 is kept rotating at high speed. By rotating the wafer W 360 degrees counterclockwise as viewed from the top, cutting (down-cut trimming) is performed along the outer peripheral edge of the wafer W, and the chamfered portion Wd of the entire circumference of the wafer W is removed.

A crack generated on the outer peripheral edge of the wafer W by trimming the chamfered portion Wd with the cutting blade 613 is blocked by the annular modified region M extending from the outer peripheral surplus region Wa2 of the surface Wa to the cutting depth of the cutting blade 613. Device D is prevented from being damaged.

(3) Grinding step Next, a surface protection tape T shown in FIG. 9 having approximately the same diameter as the wafer W is adhered to the surface Wa of the wafer W by a rolling roller or the like in a tape mounter (not shown) to protect the surface Wa. state.

The wafer W to which the surface protection tape T is adhered is transported to the chuck table 75 of the grinding device 7 shown in FIG.
Grinding means 71 for grinding the wafer W of the grinding device 7 shown in FIG. and a grinding wheel 714 removably connected to the underside of the. The grinding wheel 714 includes a wheel base 714b and a plurality of substantially rectangular parallelepiped grinding wheels 714a annularly arranged on the bottom surface of the wheel base 714b.

First, the chuck table 75 moves in the +Y direction, the center of rotation of the grinding wheel 714a is horizontally displaced from the center of rotation of the wafer W by a predetermined distance, and the trajectory of rotation of the grinding wheel 714a passes through the center of rotation of the wafer W. , the chuck table 75 is positioned. Then, as the rotary shaft 710 rotates, the grinding wheel 714 rotates about the Z-axis direction. Further, the grinding means 71 is sent in the -Z direction, and the grinding wheel 714a is brought into contact with the back surface Wb of the wafer W, whereby the grinding process is performed. During grinding, the wafer W rotates as the chuck table 75 rotates, so the grinding wheel 714a grinds the entire back surface Wb of the wafer W. FIG. Grinding water is supplied to the contact point between the grinding wheel 714a and the back surface Wb of the wafer W, and the contact point is cooled by the grinding water and the grinding dust is washed away.
Then, after grinding the wafer W to the finished thickness L1, the grinding means 71 is moved in the +Z direction to separate from the wafer W. As shown in FIG. Note that even if the modified region M remains on the wafer W after grinding, no problem occurs because the position where the modified region M is formed is the peripheral surplus region Wa2.

(Embodiment 2)
Each step of the wafer processing method according to the present invention (hereinafter referred to as the wafer processing method of Embodiment 2) will be described below.

(1) Laser Processing Step A wafer W shown in FIGS. 10 and 11 is the same as the wafer described in the first embodiment. As shown in FIGS. 10 and 11, the wafer W is placed on a carrier plate WP with an adhesive member J (not shown in FIG. 10) such as resin so that it can be easily transported and held in each step of the wafer processing method of the second embodiment. , that is, the bonded wafer WT. The centers of the wafer W and the carrier plate WP are substantially aligned.

The carrier plate WP shown in FIGS. 10 and 11 is made of, for example, silicon as a base material, and has a highly rigid and flat circular outer shape. In the illustrated example, the circular carrier plate WP has approximately the same diameter as the wafer W, but it may have a larger diameter than the wafer W. It may be
In FIG. 10, the constituent material of the bonding member J that bonds the downward facing surface Wa of the wafer W and the upward facing surface WPa of the carrier plate WP is, for example, a UV A curable resin or a heat-curable resin that is cured when heated is used.

The bonded wafer WT is transported, for example, to the laser processing apparatus 1 shown in FIG. 12 described in the first embodiment. Then, the bonded wafer WT is placed on the holding surface 10a of the holding table 10 with the rear surface Wb of the wafer W facing upward, and is held by the holding table 10 by suction. The center of rotation of the holding table 10 and the center of the bonded wafer WT are substantially aligned.

Edge alignment is performed by the alignment means 14, and accurate center coordinates of the wafer W on the holding table 10 are obtained. Then, based on the information on the center coordinates of the wafer W and the information on the pre-recognized size of the wafer W, the holding table 10 is moved in the horizontal direction so that the outer peripheral surplus area Wa2 is shown in the trimming step to be described later. The holding table 10 is positioned at a predetermined position so that a predetermined position Y4 on the inner side of the wafer W than the position Y5 where the cutting blade 613 shown in FIG.

Next, the focal point position of the laser beam condensed by the condenser lens 111a is, for example, a height position slightly below the height position Z4, which is the depth up to the finished thickness L4 of the wafer W shown in FIG. positioned in The finished thickness L4 is the thickness of the upper surface of the device D from the height position Z5 to the height position Z4. A laser beam having a wavelength that is transparent to the inside of the wafer W is pulse-oscillated from the laser beam oscillator 119 at a predetermined repetition frequency, and the inside of the wafer W is condensed and irradiated with the laser beam.
Note that the setting of the focal point position is not limited to the above example.

As shown in FIG. 13, the modified layer Ma is formed so as to extend vertically (mainly upward) from the focal position. In addition, fine cracks C are simultaneously formed in the vertical direction from the modified layer Ma. While irradiating the laser beam along the outer peripheral edge of the wafer W, the holding table 10 is rotated 360 degrees around the axis in the Z-axis direction at a predetermined rotation speed, thereby forming a plurality of modified layers Ma inside the wafer W. and a crack C extending vertically from the modified layer Ma are formed annularly along the outer peripheral edge of the wafer W. As shown in FIG. An annular modified region M composed of the modified layer Ma and the crack C is defined as a modified region M of the first stage.

Furthermore, every time the holding table 10 is rotated 360 degrees around the axis in the Z-axis direction at a predetermined rotational speed, the laser beam is shifted upward by a predetermined distance in the thickness direction (Z-axis direction) of the wafer W. By irradiating the wafer W with the beam in multiple passes, an annular modified region M composed of the second modified layer Ma and the crack C shown in FIG. and an annular modified region M composed of the fourth-stage modified layer Ma and the crack C are formed. As a result, an annular modified region M is formed along the outer peripheral edge of the wafer W from the rear surface Wb to the front surface Wa by the annular modified region M made up of the four stages of the modified layers Ma and the cracks C. Note that the annular modified region M extending from the back surface Wb to the front surface Wa may be connected to each step of the modified layer Ma instead of the crack C, or the modified layer Ma may be connected to the front surface Wa or the back surface Wb of the wafer W. May be exposed. Alternatively, the modified layer Ma and the crack C may be formed step by step downward from the back surface Wb side of the wafer W to form the annular modified region M from the back surface Wb to the front surface Wa.

The laser processing step is not limited to the above examples. For example, the laser beam oscillated from the laser beam oscillator 119 shown in FIG. Then, by rotating the holding table 10 at a predetermined rotation speed by 360 degrees around the axis in the Z-axis direction, the inside of the wafer W is simultaneously reformed at a plurality of condensing points, and the back surface of the wafer W is formed inside the wafer W. An annular modified region M extending from Wb to the surface Wa may be formed.
Alternatively, an annular modified region Mg called a shield tunnel consisting of pores Mc or cracks and modified region Md described in another example of (1-2) laser processing step in Embodiment 1 is formed inside the wafer W on the back surface. It may be formed so as to extend from Wb to the surface Wa.

(2) Trimming Step The bonded wafer WT in which the modified region M is formed on the wafer W is transferred to the holding table 65 of the cutting device 6 shown in FIG. is held by suction on the holding surface 65a. In the trimming step, for example, alignment means (not shown) recognizes information on the coordinate position of the center of the wafer W on the holding table 65 and the coordinate position of the outer peripheral edge thereof. Then, the cutting means 61 is moved in the Y-axis direction based on the information, and the cutting blade 613 is positioned at a position Y5 radially inward by a predetermined distance from the outer peripheral edge of the wafer W in the outer peripheral surplus area Wa2. That is, for example, the cutting blade 613 is positioned so that approximately two-thirds of the end surface of the cutting blade 613 contacts the back surface Wb of the wafer W including the chamfered portion Wd.

Next, the cutting blade 613 is rotated, for example, clockwise when viewed from the +Y direction side. Furthermore, cutting is performed so that the lowermost end of the cutting blade 613 is positioned at a height position (a position slightly lower than the height position of the outer peripheral surplus region Wa2) where the depth reaches the finished thickness L4 from the back surface Wb of the wafer W. A means 61 is sent in the -Z direction. Then, after the rotating cutting blade 613 is cut into the chamfered portion Wd from the back surface Wb of the wafer W to the depth of the finished thickness L4, the holding table 65 is moved to the +Z direction side while the cutting blade 613 is kept rotating at high speed. By rotating the wafer W 360 degrees counterclockwise as viewed from above, cutting (up-cut trimming) is performed along the outer peripheral edge of the wafer W, and the chamfered portion Wd of the entire circumference of the wafer W is removed. The reason for trimming by up-cutting is that trimming by down-cutting may scatter generated chips on the carrier plate WP and damage the carrier plate WP.

The cracks generated on the outer peripheral edge of the wafer W due to the trimming of the chamfered portion Wd by the cutting blade 613 are blocked by the annular modified region M extending from the back surface Wb of the wafer W to the front surface Wa of the wafer W, so that the device D is damaged. You can prevent it from falling off.

(3) Grinding Step The edge-trimmed bonded wafer WT is conveyed to the chuck table 75 of the grinding device 7 shown in FIG. be done.

The chuck table 75 is positioned so that the rotation locus of the grinding wheel 714a passes through the rotation center of the wafer W when the chuck table 75 moves in the +Y direction. Grinding wheel 714 is then rotated about its Z axis. Further, the grinding means 71 is sent in the -Z direction, and the grinding wheel 714a is brought into contact with the back surface Wb of the wafer W, whereby the grinding process is performed. Since the chuck table 75 rotates and the bonded wafer WT also rotates during grinding, the grinding wheel 714a grinds the entire back surface Wb of the wafer W. FIG. Further, grinding water is supplied to the contact portion between the grinding wheel 714a and the back surface Wb of the wafer W, and cooling and cleaning and removal of grinding dust are performed.
Then, after grinding the wafer W to the finished thickness L4, the grinding means 71 is moved in the +Z direction to separate from the wafer W. As shown in FIG. Note that even if the modified region M remains on the wafer W after grinding, no problem occurs because the position where the modified region M is formed is the peripheral surplus region Wa2.

It goes without saying that the wafer processing method according to the present invention is not limited to the first and second embodiments described above, and may be implemented in various forms within the scope of the technical idea. Also, the configurations of the laser processing apparatus 1, the cutting apparatus 6, and the grinding apparatus 7 illustrated in the accompanying drawings are not limited to this, and can be changed as appropriate within the range in which the effects of the present invention can be exhibited.

W: Wafer Wa: Front surface of wafer Wa1: Device area Wa2: Surplus peripheral area Wb: Back surface of wafer Wd: Chamfered portion 1: Laser processing apparatus 10: Holding table 10a: Holding surface 11: Laser beam irradiation means 111: Concentrator 111a: condenser lens 119: laser beam oscillator 14: alignment means 140: camera M: modified region Ma: modified layer C: crack Mg: modified region Mc: pore Md: modified region 6: cutting device 65: holding Table 65a: Holding surface 61: Cutting means 610: Spindle 613: Cutting blade T: Surface protection tape 7: Grinding device 75: Chuck table 75a: Holding surface 71: Grinding means 710: Rotating shaft 713: Mount 714: Grinding wheel WP: Carrier plate J: Adhesive member WT: Bonded wafer

Claims (1)

Processing of a wafer having a device region with a plurality of devices formed on the surface and an outer peripheral surplus region surrounding the device region, and having a chamfered portion on the outer periphery by grinding the back surface of the wafer to thin it to the finished thickness. a method,
a trimming step of cutting the chamfered portion from the surface of the wafer with a cutting blade to a depth that reaches the finished thickness and cutting along the outer peripheral edge to remove the chamfered portion;
after performing the trimming step, grinding the backside of the wafer to thin it to the finished thickness;
before performing the trimming step, a laser beam having a wavelength that is transparent to the wafer in the outer peripheral surplus region and inside the wafer from a position where the cutting blade cuts in the trimming step is applied to the outer peripheral edge; forming an annular modified region from the surface of the wafer to the depth of cut of the cutting blade, wherein cracks generated in the trimming step extend into the device region. A method of processing a wafer, wherein the ring-shaped modified region dams.

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