JP2018206890A - Wafer processing method - Google Patents

Abstract

A wafer processing method that enables grinding while measuring the thickness of the wafer without scattering the device. A method of processing a wafer is performed by irradiating a laser beam having a wavelength that has an absorptivity with respect to the wafer along a predetermined dividing line from the surface of the wafer excluding the outer peripheral region, and a depth reaching a finished thickness of the wafer. A groove forming step ST1 for forming the laser processed groove in the device region, a protective member attaching step ST2 for attaching a protective member to the surface of the wafer after the groove forming step, and the protective member side are held by a chuck table. A grinding step ST3 for grinding the back surface of the wafer to the finished thickness and exposing a laser-processed groove. In the grinding step ST3, the outer peripheral surplus remaining in a ring shape after the grinding step is performed on the contact measurement gauge Grinding while measuring the thickness of the wafer, contacting only the area. [Selection] Figure 2

Description

  The present invention relates to a wafer processing method.

  In a semiconductor device manufacturing process for manufacturing a semiconductor device widely used in electronic equipment, device chips tend to be small and thin for downsizing of electronic equipment. A technique called so-called dicing before grinding (DBG) is used to obtain a chip that is small and thin and has high bending strength (see, for example, Patent Document 1). In addition, in order to achieve further narrowing of the street and less chipping on the device surface side, the modified layer inside the wafer formed by the laser processing apparatus or the wafer formed by combining the groove formed by ablation on the wafer surface and grinding Processing methods have also been proposed (see, for example, Patent Document 2 and Patent Document 3).

  In DBG processing, grooves and modified layers are exposed at the end of grinding. During grinding, the wafer measurement is performed while measuring the thickness of the wafer, so it is common for a contact-type measurement gauge to contact the ground surface of the wafer. Problems are likely to occur. Further, there is a possibility that the device and the gauge come into contact with each other, and the devices come into contact with each other due to the contact with the gauge, or the device is scattered. Therefore, a non-contact optical measuring instrument has been proposed (see, for example, Patent Document 4).

JP-A-5-335411 JP 2013-254867 A JP 2007-090441 A JP 2009-050944 A

  However, the non-contact type optical measuring instrument shown in Patent Document 4 has a problem that accurate measurement is difficult in the case of a transparent substrate because it is adversely affected by a groove or a crack of the wafer.

  The present invention has been made in view of such problems, and an object thereof is to provide a wafer processing method that enables grinding while measuring the thickness of the wafer without scattering the device. With the goal.

  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 devices are formed in each region partitioned by a plurality of intersecting division lines, and the device region. A method of processing a wafer having an outer peripheral surplus area surrounding the surface, wherein a laser beam having a wavelength having an absorptivity with respect to the wafer is separated from the surface of the wafer along the planned division line excluding the outer peripheral surplus area. Irradiating and forming a laser-processed groove having a depth reaching the finished thickness of the wafer in the device region, and a protective member for attaching a protective member to the surface of the wafer after performing the groove forming step An affixing step and a grinding step for holding the protective member side with a chuck table, grinding the back surface of the wafer to the finished thickness, and exposing the laser processing groove. In the grinding step, a contact-type measurement gauge that contacts the back surface of the wafer and measures the thickness of the wafer remains in a ring shape after the grinding step is performed without the laser processing groove being formed. Grinding while contacting only the outer peripheral surplus area and measuring the thickness of the wafer.

  In the wafer processing method, the wafer may be a transparent body.

  Therefore, in the wafer processing method of the present invention, by limiting the laser processing groove formed by ablation processing to the device region, there is no groove on the back surface of the outer peripheral surplus region where the contact type measurement gauge contacts, and the device is scattered. It is possible to perform grinding while measuring the thickness of the wafer without making it.

FIG. 1 is a perspective view of a wafer to be processed in the wafer processing method according to the first embodiment. FIG. 2 is a flowchart illustrating the wafer processing method according to the first embodiment. FIG. 3 is a perspective view showing a groove forming step of the wafer processing method shown in FIG. FIG. 4 is a perspective view showing a protective member attaching step of the wafer processing method shown in FIG. FIG. 5 is a perspective view showing a grinding step of the wafer processing method shown in FIG. FIG. 6 is a side view of a grinding apparatus showing in cross section a wafer to be ground while its thickness is measured in the grinding step of the wafer processing method shown in FIG. FIG. 7 is a side view of the grinding apparatus showing in cross section the wafer divided into individual devices by the grinding step of the wafer processing method shown in FIG.

  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. In addition, various omissions, substitutions, or changes in the configuration can be made without departing from the scope of the present invention.

Embodiment 1
A wafer processing method according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a wafer to be processed in the wafer processing method according to the first embodiment.

  The wafer processing method according to the first embodiment is a method of processing the wafer 200 shown in FIG. 1, and is also a method of dividing the wafer 200 into individual devices 202. A wafer 200 to be processed by the wafer processing method according to the first embodiment is a disk-shaped semiconductor wafer having silicon as a substrate, an optical device wafer having sapphire, SiC (silicon carbide), or the like as a substrate. In the first embodiment, the wafer 200 is an optical device wafer that is a transparent body made of glass, sapphire, or quartz. However, the present invention is not limited to this.

  As shown in FIG. 1, the wafer 200 includes a device region 210 and an outer peripheral surplus region 211 on the surface 201. In the device area 210, the device 202 is formed in each area divided by a plurality of intersecting scheduled lines 203. The outer peripheral surplus region 211 surrounds the device region 210 and is a region where the device 202 is not formed. In the first embodiment, the wafer 200 is provided with the notch 204 that is a depression indicating the crystal orientation. However, in the present invention, an orientation flat that is a straight line portion may be provided instead of the notch 204. The wafer 200 is divided along the division line 203 and divided into individual devices 202.

  Next, a wafer processing method according to the first embodiment will be described. FIG. 2 is a flowchart illustrating the wafer processing method according to the first embodiment. FIG. 3 is a perspective view showing a groove forming step of the wafer processing method shown in FIG. FIG. 4 is a perspective view showing a protective member attaching step of the wafer processing method shown in FIG. FIG. 5 is a perspective view showing a grinding step of the wafer processing method shown in FIG. FIG. 6 is a side view of a grinding apparatus showing in cross section a wafer to be ground while its thickness is measured in the grinding step of the wafer processing method shown in FIG. FIG. 7 is a side view of the grinding apparatus showing in cross section the wafer divided into individual devices by the grinding step of the wafer processing method shown in FIG.

  The wafer processing method according to the first embodiment (hereinafter simply referred to as a processing method) is ground while measuring the thickness of the wafer 200 and thinned to a predetermined finished thickness 220 (shown in FIG. 7). This is a processing method of dividing into individual devices 202. As shown in FIG. 2, the processing method includes a groove forming step ST1, a protective member attaching step ST2, and a grinding step ST3.

(Groove forming step)
In the groove forming step ST1, a laser beam 300 having a wavelength (for example, 355 nm) having an absorptivity with respect to the wafer 200 is irradiated along the division line 203 excluding the outer peripheral surplus region 211 from the surface 201 of the wafer 200, This is a step of forming a laser processing groove 205 in the device region 210 having a depth up to the finished thickness 220. In the first embodiment, the groove forming step ST <b> 1 forms the laser processed groove 205 along the planned division line 203 except for the outer peripheral surplus region 211.

  The depth of the laser processed groove 205 formed in the groove forming step ST1 is equal to or greater than the finished thickness 220 of the wafer 200. In the first embodiment, in the groove forming step ST1, the laser processing apparatus 10 sucks and holds the back surface 206 of the wafer 200 on the holding surface 12 of the chuck table 11, and the laser beam irradiation unit 13 of the laser processing apparatus 10 and the wafer 200 are connected. The laser beam 300 is irradiated from the laser beam irradiation unit 13 by being relatively moved along the planned division line 203 in the device region 210. In the groove forming step ST <b> 1, the laser processing apparatus 10 performs ablation processing on each division planned line 203 in the device region 210 except for the outer peripheral surplus region 211 to form a laser processing groove 205. When the laser processing grooves 205 are formed in all the division lines 203 in the device region 210 except for the outer peripheral surplus region 211, the processing method proceeds to the protective member attaching step ST2.

(Protective member application step)
The protective member attaching step is a step of attaching the protective member 400 to the surface 201 of the wafer 200 as shown in FIG. 4 after performing the groove forming step ST1.

  The protection member 400 is, for example, an adhesive tape that is attached to the surface 201 of the wafer 200 and is a member for protecting the device 202. The protective member 400 may have the same diameter as that of the wafer 200 or may have a diameter larger than that of the wafer 200 and an outer peripheral edge attached to the opening peripheral edge of the annular frame. In that case, the wafer 200 is supported by the annular frame via the protection member 400. In the processing method, when the protective member 400 is attached to the front surface 201 side of the wafer 200, the processing proceeds to the grinding step ST3.

(Grinding step)
In the grinding step ST3, the protective member 400 side is held by the chuck table 21 of the grinding apparatus 20, the back surface 206 of the wafer 200 is ground until the finished thickness is 220, and the laser processing groove 205 is exposed on the back surface 206. This is a step of dividing the wafer 200 into individual devices 202. In the grinding step ST3, as shown in FIGS. 5, 6, and 7, the grinding apparatus 20 sucks and holds the surface 201 of the wafer 200 on the holding surface 22 of the chuck table 21 via the protective member 400, and the chuck table 21. Is rotated around the axis and the grinding wheel 24 of the grinding wheel 23 rotating around the axis is brought into contact with the back surface 206 of the wafer 200 while supplying the grinding water, so that the wafer 200 is thinned to the finished thickness 220. . In the grinding step ST3, the thickness of the wafer 200 is determined by bringing the contact measurement gauge 30 into contact with only the back surface 206 of the outer peripheral surplus region 211 that is not formed with the laser processing groove 205 and remains in a ring shape after the grinding step ST3. Grind while measuring.

  The contact-type measurement gauge 30 measures the thickness of the wafer 200 by contacting the back surface 206 of the wafer 200. As shown in FIGS. 6 and 7, the measurement for measuring the thickness of the wafer 200 is performed. A head 31 is provided. The measuring head 31 includes a measuring element 32 that comes into contact with the back surface 206 of the outer peripheral surplus region 211 of the wafer 200 where the laser processing groove 205 is not formed. The probe 32 contacts the back surface 206 of the outer peripheral surplus region 211 between the center side of the wafer 200 with respect to the notch 204 formed on the outer periphery of the wafer 200 and the outer peripheral side of the wafer 200 with respect to the device region 210. For this reason, for example, since the notch 204 is formed about 1.5 mm from the outer periphery to the inside, the measuring element 32 contacts the back surface 206 of the outer peripheral surplus region 211 in the range of about 3 to 10 mm from the outer periphery to the inner side of the wafer 200. To do.

  The contact-type measurement gauge 30 measures the thickness of the wafer 200 by measuring the height of the probe 32 that contacts the back surface 206 of the wafer 200. The contact measurement gauge 30 outputs the measurement result to a control device (not shown) which is a computer of the grinding device 20. The contact-type measurement gauge 30 is less susceptible to the grinding water supplied from the grinding wheel 23 when the wafer 200 is ground, so that the contact-type measurement gauge 30 is more suitable than the non-contact type measurement means during grinding of the wafer 200 by the grinding wheel 23. The thickness of the wafer 200 can be measured with high accuracy. Moreover, even if the contact-type measurement gauge 30 is a transparent body in which the thickness of the wafer 200 cannot be measured by the non-contact type measurement means, the thickness can be measured.

  In the grinding step ST3, the grinding device 20 ends the grinding when the thickness of the wafer 200 reaches the finished thickness 220 as shown in FIG. 7 based on the measurement result of the contact measurement gauge 30. Note that after the grinding step ST3, the device region 210 is divided into individual devices 202. However, since the outer peripheral surplus region 211 and the device 202 are supported by the protective member 400, the form of the wafer 200 is maintained. It is.

  The outer peripheral surplus region 211 remaining in the ring shape after the grinding step ST3 is removed by removal by a ring removal device (not shown) or by cutting by edge trimming.

  As described above, in the processing method according to the first embodiment, the laser processing groove 205 is formed in the contact measurement gauge 30 that measures the thickness of the wafer 200 by contacting the back surface 206 of the wafer 200 in the grinding step ST3. Grinding while measuring the thickness of the wafer 200 in contact with the back surface 206 of the outer peripheral surplus area 211 of the wafer 200 that is not. For this reason, the wafer 200 can be ground while measuring the thickness of the wafer 200.

  Further, the processing method is to limit the laser processing groove 205 formed by ablation processing to the device region 210, and there is no laser processing groove 205 on the back surface 206 of the outer peripheral surplus region 211 with which the contact measurement gauge 30 is brought into contact. Since the device 202 is formed in the device region 210, contact between the device 202 and the contact-type measurement gauge 30 can be avoided. As a result, since the processing method can avoid contact between the device 202 and the contact measurement gauge 30, contact between the devices 202 due to contact with the contact measurement gauge 30 and scattering of the device 202 can be suppressed. . Therefore, the processing method can enable grinding while measuring the thickness of the wafer 200 without scattering the device 202.

  In the processing method, since the laser processing groove 205 is formed on the wafer 200 by irradiation with the laser beam 300 in the groove forming step ST1, the start point and the end point of the laser processing groove 205 can be easily controlled. For this reason, the processing method can easily form the laser processing groove 205 in the device region 210 while leaving the outer peripheral surplus region 211. In the processing method, since the laser processing groove 205 is formed on the wafer 200 by irradiation with the laser beam 300 in the groove forming step ST1, the outer peripheral surplus region 211 starts from the laser processing groove 205 even if the back surface 206 is ground in the grinding step ST3. Is not split. As a result, the processing method can leave the outer peripheral surplus region 211 even after the grinding step ST3 is performed, and the scattering of the device 202 can be suppressed.

  Further, according to the wafer processing method according to the present embodiment, since the wafer 200 is a transparent body, it is difficult to measure with a non-contact type measuring means using reflected light, and particularly during grinding, such as grinding water. Although the thickness of the wafer 200 cannot be measured in the first place because of being affected, since the contact-type measurement gauge 30 is used, the thickness of the optical device wafer, which is a transparent body made of glass, sapphire, or quartz, is measured. The wafer 200 can be ground and thinned to a finished thickness of 220.

  Since the wafer 200 can be ground while measuring the thickness of the wafer 200 that is a transparent body, and the wafer 200 can be thinned to a finished thickness 220, the processing method can be performed when the wafer 200 is a transparent body. The wafer processing method according to the first embodiment is an indispensable technique.

  Next, the inventors of the present invention confirmed the effect of the processing method according to the first embodiment. The results are shown in Table 1 below.

  Table 1 evaluates the situation of the wafer 200 after being divided into devices 202. Comparative Example 1 in Table 1 attempted to perform the groove forming step ST1 using a cutting blade of a cutting device. Comparative Example 2 in Table 1 irradiates the laser beam with the condensing point of the laser beam having a wavelength transparent to the wafer 200 positioned within the division planned line 203 without performing the groove forming step ST1. After forming the modified layer along the planned division line 203 except for the outer peripheral surplus region 211, the protective member attaching step ST2 and the grinding step ST3 were performed. The product of the present invention was subjected to the processing method according to the first embodiment.

  According to Table 1, in Comparative Example 1, when the groove having the finishing thickness 220 is formed in the division line 203 of the device region 210 by the arc of the cutting blade, the device region is cut to the outer peripheral surplus region 211. A groove cannot be formed only in 210. In Comparative Example 2, when the wafer 200 is divided starting from the modified layer in the grinding step ST <b> 3, it is divided to the outer peripheral surplus area 211 starting from the modified layer, and the device 202 together with the divided outer peripheral surplus area 211. Has been scattered. Compared to Comparative Example 1 and Comparative Example 2 described above, the product of the present invention forms the laser processing groove 205 by ablation, so that the outer peripheral surplus region 211 is not divided in the grinding step ST3. It has been found that it is possible to perform grinding while measuring the thickness of the wafer 200 without scattering.

  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.

21 chuck table 30 contact measurement gauge 200 wafer 201 front surface 202 device 203 line to be divided 205 laser processing groove 206 back surface 210 device area 211 outer peripheral surplus area 220 finishing thickness 300 laser beam 400 protective member ST1 groove forming step ST2 protective member attaching step ST3 Grinding step

Claims (2)

A wafer processing method comprising, on a surface, a device region in which devices are formed in each region divided by a plurality of intersecting division lines, and an outer peripheral surplus region surrounding the device region,
A laser beam having a wavelength having an absorptivity with respect to the wafer is irradiated along the planned dividing line excluding the excess peripheral area from the surface of the wafer, and a laser processing groove having a depth reaching the finished thickness of the wafer is formed. Forming a groove in the device region;
After performing the groove forming step, a protective member attaching step for attaching a protective member to the surface of the wafer;
Holding the protection member side with a chuck table, grinding the back surface of the wafer to the finished thickness, and exposing the laser processing groove,
In the grinding step, a contact-type measurement gauge that contacts the back surface of the wafer and measures the thickness of the wafer is only formed in the outer peripheral surplus region that is not formed with the laser processing groove and remains in a ring shape after the grinding step is performed. A method of processing a wafer, wherein the wafer is ground while measuring the thickness of the wafer.   The wafer processing method according to claim 1, wherein the wafer is a transparent body.

Images