JP2010093005A - Processing method of wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a processing method of a wafer in which no degradation in yield occurs when cutting a semiconductor wafer from a front surface side to split it into devices, wherein the semiconductor wafer has been ground only on the rear surface corresponding to a device region while an annular reinforcing part has been formed on the rear surface corresponding to an outer peripheral marginal region surrounding the device region. <P>SOLUTION: The wafer includes on its surface a device region where a device is formed in a section partitioned by a plurality of cutting planned lines formed in lattice and an outer peripheral marginal region which surrounds the device region. A circular recess is formed on a rear surface corresponding to the device region, and an annular reinforcing part including the marginal region is formed on the outer peripheral side of the circular recess. A processing method for the wafer includes an adhesive tape pasting step for pasting an adhesive tape on the rear surface of the wafer, a cutting groove formation step for forming a cutting groove along the cutting planned line from the front surface side of the wafer to which the adhesive tape is pasted, and an expand step which, after the cutting groove formation step, expands the adhesive tape under the condition that the front surface of the wafer faces down. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wafer processing method in which a circular recess is formed on the back surface.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a semiconductor wafer having a substantially disk shape, and devices such as ICs and LSIs are placed in the partitioned regions. Form. Then, the semiconductor wafer is cut into individual semiconductor chips (devices) by cutting the semiconductor wafer along a street with a cutting device.

  The wafer to be divided is formed to a predetermined thickness by grinding or polishing the back surface before cutting along the street. In recent years, in order to achieve a reduction in weight and size of electrical equipment, it has been required to make the wafer thinner, for example, about 50 μm.

  Such thin wafers are difficult to handle and may be damaged during transportation. Therefore, Japanese Patent Laid-Open No. 2007-19461 proposes a grinding method in which only the back surface corresponding to the device region of the wafer is ground, and an annular reinforcing portion is formed on the back surface of the wafer corresponding to the outer peripheral surplus region surrounding the device region. Yes.

  As a method of dividing the wafer having the annular reinforcing portion formed on the outer periphery of the back surface along the street (scheduled cutting line), after removing the annular reinforcing portion, a method of cutting with a cutting blade from the front side of the wafer. It has been proposed (see JP 2007-19379 A).

  However, the wafer from which the annular reinforcing portion has been removed has a problem that it is easily damaged by handling during cutting. A method of cutting from the back side without removing the annular reinforcing portion is also conceivable, but since the street is formed on the surface of the wafer, in order to cut along the street from the back side, the street of the wafer is cut from the back side. It needs to be detected.

Therefore, for example, an infrared camera using a wavelength that transmits the wafer is required, and if the wafer is thick or the street pattern is not clear, it is difficult to detect the street from the back side.
JP 2007-19461 A JP 2007-19379 A

  On the other hand, when a semiconductor wafer having an annular reinforcing portion formed on the outer periphery of the back surface is cut and divided from the front surface side, an uncut region is formed in a portion in the thickness direction on the back surface side of the semiconductor wafer in the annular reinforcing portion.

  This uncut area is divided along with the expansion in the later expanding process, but the fragments and debris generated when the uncut area is divided may damage the surface of the device or adhere to the surface of the device. There is a risk that bonding failure will occur in the subsequent bonding process, and there is a concern that the yield will decrease.

  The present invention has been made in view of such a point, and the object of the present invention is to grind only the back surface corresponding to the device region, and to form the annular reinforcing portion on the back surface corresponding to the outer peripheral surplus region surrounding the device region. It is an object of the present invention to provide a method for processing a wafer that does not cause a decrease in yield when the semiconductor wafer formed with is cut from the surface side and divided into each device.

  According to the present invention, a device region in which a device is formed in a region partitioned by a plurality of scheduled cutting lines formed in a lattice shape, and an outer peripheral surplus region surrounding the device region are provided on the surface, and the device region Is a processing method of a wafer in which a circular recess is formed on the back surface corresponding to, and an annular reinforcing portion including the outer peripheral surplus region is formed on the outer peripheral side of the circular recess, and the pressure-sensitive adhesive sticks an adhesive tape to the back surface of the wafer. A tape attaching step, a cutting groove forming step for forming a cutting groove along the planned cutting line from the surface side of the wafer to which the adhesive tape is attached, and a surface of the wafer facing downward after the cutting groove forming step. And an expanding step of expanding the adhesive tape while being held in a wafer.

  Preferably, in the cutting groove forming step, at least the device region of the wafer is completely cut by the cutting groove in the thickness direction of the wafer, and the annular reinforcing portion is cut so that a cutting groove is not formed on a part of the wafer back side in the thickness direction of the wafer. A non-groove region is formed. And in an expanding process, the cutting groove non-formation area | region is divided | segmented.

  According to the present invention, only the back surface corresponding to the device region is ground, and the semiconductor wafer having the annular reinforcing portion formed on the back surface corresponding to the outer peripheral surplus region surrounding the device region is cut from the front surface side and divided into each device. In this case, a wafer processing method that does not cause a decrease in yield is provided.

  By expanding the wafer surface downward when expanding, the chips and debris generated when the cutting groove non-formed area is divided will not fall on the wafer surface, so the wafer surface will not be damaged or soiled. There is no risk of problems in the process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a semiconductor wafer before being processed to a predetermined thickness. The semiconductor wafer 11 shown in FIG. 1 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of streets 13 are formed in a lattice shape on the surface 11a, and a plurality of streets partitioned by the plurality of streets 13 are formed. A device 15 such as an IC or LSI is formed in the region.

  The semiconductor wafer 11 configured as described above includes a device region 17 in which the device 15 is formed, and an outer peripheral surplus region 19 that surrounds the device region 17. A notch 21 is formed on the outer periphery of the semiconductor wafer 11 as a mark indicating the crystal orientation of the silicon wafer.

  A protective tape 23 is attached to the surface 11a of the semiconductor wafer 11 by a protective tape attaching process. Therefore, the front surface 11a of the semiconductor wafer 11 is protected by the protective tape 23, and the back surface 11b is exposed as shown in FIG.

  A grinding method for forming a circular concave portion on the back surface corresponding to the device region 17 of the semiconductor wafer 11 and forming an annular reinforcing portion including an outer peripheral surplus region 19 on the outer peripheral side of the circular concave portion is described with reference to FIGS. To explain. First, referring to FIG. 3, a perspective view of a main part of the grinding device 2 is shown.

  The grinding apparatus 2 includes a chuck table 4 that can rotate while holding a wafer, and a grinding unit 6 that performs grinding on the wafer. The grinding unit 6 includes a rotatable spindle 8 that can be raised and lowered, a grinding wheel 10 that is attached to the tip of the spindle 8, and a grinding wheel 12 that is fixed to the lower surface of the grinding wheel 10.

  The wafer 11 is sucked and held on the side of the protective tape 23 by the chuck table 4, and the back surface 11 b of the wafer 11 is set to face the grinding wheel 12. Here, the relationship between the wafer 11 held on the chuck table 4 and the grinding wheel 12 mounted on the grinding wheel 10 will be described with reference to FIG.

  The rotation center P1 of the chuck table 4 and the rotation center P2 of the grinding wheel 12 are eccentric, and the outer diameter of the grinding wheel 12 is smaller than the diameter of the boundary line 28 between the device region 17 and the outer peripheral surplus region 19 of the wafer 11. The size of the grinding wheel 12 is set so as to pass through the rotation center P 1 of the chuck table 4.

  While rotating the chuck table 4 in the direction indicated by an arrow 30 at, for example, 300 rpm, the grinding wheel 12 is rotated in the direction indicated by an arrow 32, for example, at 6000 rpm, and a grinding feed mechanism (not shown) is operated to operate the grinding wheel 12 of the grinding wheel 10. Is brought into contact with the back surface of the wafer 11. Then, the cutting wheel 10 is ground and fed downward by a predetermined amount at a predetermined grinding feed speed.

  As a result, on the back surface of the semiconductor wafer 11, as shown in FIG. 5, a region corresponding to the device region 17 is ground and removed to form a recess 24 having a predetermined thickness (for example, 50 μm), and an outer peripheral surplus region 19. The region corresponding to is left and an annular reinforcing portion 26 including the outer peripheral surplus region 19 is formed.

  Next, a chuck table suitable for use in cutting the wafer 11 by holding the semiconductor wafer 11 that has been ground as shown in FIG. 5 with reference to FIGS. 6 and 7 will be described. .

  Referring to FIG. 6, prior to cutting the wafer 11, the wafer 11 is attached to a dicing tape (adhesive tape) 34 having an outer peripheral portion attached to an annular frame 36. The dicing tape 34 is attached so as to go around not only the annular reinforcing portion 26 but also the circular recess 24.

  Referring to FIG. 7, there is shown a longitudinal sectional view of a chuck table 40 suitable for sucking and holding the wafer 11 to which the dicing tape 34 is adhered as shown in FIG. The chuck table 40 includes a rotating shaft 42 on which a vacuum suction path 44 is formed, and a base 46 mounted and fixed on the rotating shaft 42.

  The base 46 is made of a metal such as SUS and has a mounting circular recess 48 and a vacuum suction path 50 communicated with the vacuum suction path 44 of the rotating shaft 42. The vacuum suction path 50 opens in the recess 48. The vacuum suction path 44 of the rotating shaft 42 is connected to a vacuum suction source (not shown). In the circular recess 48 of the base 46, a disc-shaped porous adsorbing portion 52 made of porous ceramic or the like is disposed.

  In the chuck table 40 having such a structure, the chuck table 40 is configured by the base 46 having the circular recess 48 and the disc-shaped porous suction portion 52 having a predetermined height disposed in the circular recess 48. The porous suction portion 52 can be fitted into the circular recess 24 of the wafer 11 to hold the wafer flat.

  When the chuck table 40 is employed as a chuck table of a cutting apparatus and the wafer 11 is cut along the street with a cutting blade of a well-known cutting apparatus, the state shown in FIG. 8 is obtained. Reference numeral 38 denotes a cutting groove. Therefore, when the chuck table 40 is employed in the chuck table of the cutting apparatus, chips (devices) that are not completely cut are not generated at the wafer outer peripheral portion, and a defective device is not formed.

  When the wafer 11 is cut by sucking and holding the wafer 11 with the chuck table 40, a cutting groove non-formation region 39 is formed in a part in the thickness direction on the back surface side of the annular reinforcing portion 26 as shown in FIG.

  After the cutting process is completed, the dicing tape 34 is expanded in the radial direction, and an expanding process is performed in which the distance between the devices 15 and 15 is expanded. The expanding process is performed with the semiconductor wafer 11 facing downward as shown in FIG.

  For example, the dicing tape 34 is expanded in the radial direction by holding the annular frame 36 and pressing the dicing tape 34 uniformly downward in the state shown in FIG. Accordingly, the distance between the devices 15 and 15 is also expanded.

  When the expanding process is performed with the semiconductor wafer 11 facing downward in this manner, the chips and debris generated when the cutting groove non-formed region 39 is divided do not fall on the surface of the wafer 11, thereby damaging the wafer surface. There is no possibility that the cutting scraps adhere to the surface of the device 15 and cause a bonding failure or the like in the subsequent bonding process.

  After completion of the expanding process, the wafer 11 is held again with the front side facing up, and the individual devices 15 are picked up by a well-known pickup device.

It is a surface side perspective view of a wafer. It is a back surface side perspective view of a wafer in the state where a protective tape was stuck on the back surface. It is a perspective view which shows the principal part of a grinding device. It is explanatory drawing of the circular recessed part grinding process implemented by the grinding device. It is sectional drawing of the semiconductor wafer in which the circular recessed part grinding process was implemented. It is sectional drawing of the wafer of the state with which the cyclic | annular flame | frame was mounted | worn through the dicing tape. It is a longitudinal cross-sectional view of a chuck table suitable for holding a wafer having a circular recess. It is a longitudinal cross-sectional view of the wafer after a cutting process. It is a longitudinal cross-sectional view of the wafer after an expanding process implementation.

Explanation of symbols

2 Grinding device 4 Chuck table 6 Grinding unit 10 Grinding wheel 11 Semiconductor wafer 12 Grinding wheel 13 Street 15 Device 24 Circular recess 26 Annular reinforcement 34 Dicing tape 36 Annular frame 38 Cutting groove 39 Cutting groove non-formation area 40 Chuck table 52 Porous adsorption Part

Claims (3)

A device region in which a device is formed in a region partitioned by a plurality of cutting lines formed in a lattice shape, and an outer peripheral surplus region surrounding the device region are provided on the surface, and a back surface corresponding to the device region A wafer processing method in which a circular recess is formed, and an annular reinforcing portion including the outer peripheral surplus region is formed on the outer peripheral side of the circular recess,
An adhesive tape attaching process for attaching an adhesive tape to the back surface of the wafer;
A cutting groove forming step of forming a cutting groove along the planned cutting line from the surface side of the wafer to which the adhesive tape is attached;
An expanding step of expanding the adhesive tape in a state where the surface of the wafer is held downward after the cutting groove forming step;
A wafer processing method characterized by comprising: In the cutting groove forming step, at least the device region of the wafer is completely cut in the thickness direction of the wafer by the cutting groove,
A cutting groove non-formation region where a cutting groove is not formed in a part of the wafer back surface side in the thickness direction of the wafer is formed in the annular reinforcing portion,
The wafer processing method according to claim 1, wherein the cutting groove non-formed region is divided in the expanding step.   The wafer processing method according to claim 1 or 2, wherein an annular frame is adhered to the outer periphery of the adhesive surface of the adhesive tape.

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