JP2015167197A - Processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method that allows a die attach film (DAF) to be surely divided corresponding to individual devices.SOLUTION: The processing method that divides a DAF adhered to a backside of a wafer, on a surface of which a plurality of devices are formed by being partitioned by scheduled division lines formed in a lattice shape, corresponding to the individual devices, performs: a wafer preparing step of preparing a wafer having a modified layer formed inside the wafer along the scheduled division lines or a wafer divided into the individual devices along the scheduled division lines; a wafer arranging step of positioning the wafer prepared in the wafer preparing step at an annular frame having an opening portion for storing the wafer and arranging a backside of the wafer at an expand tape while interposing the DAF therebetween; and a DAF dividing step of expanding the expand tape and applying tensile force to the wafer through the DAF after the wafer arranging step so as to widen an interval between adjacent devices and divide the DAF corresponding to the devices, where the DAF is softened by heating the DAF up to a predetermined temperature in the DAF dividing step.

Description

  The present invention relates to a processing method, and more particularly, to a processing method for dividing a DAF attached to the back surface of a wafer corresponding to a device.

  In a semiconductor device manufacturing process, a semiconductor device is formed by dividing a semiconductor wafer (hereinafter abbreviated as a wafer) on which a plurality of devices such as ICs and LSIs are formed into individual devices. Is done.

  The divided semiconductor devices are die-bonded (adhered) to a metal substrate (lead frame), a tape substrate, and the like, and individual semiconductor chips are manufactured by dividing these metallic substrates and tape substrates. The semiconductor chip thus manufactured is widely used in electronic devices such as mobile phones and personal computers.

  In order to die-bond a semiconductor device on a substrate, an adhesive such as solder, Au-Si eutectic, resin paste or the like is supplied to the semiconductor device mounting position on the substrate, and the semiconductor device is mounted thereon and bonded. The method is used.

  In recent years, for example, as disclosed in Japanese Patent Application Laid-Open No. 11-219962, a method in which an adhesive film called DAF (die attach film) is bonded in advance to the back surface of a semiconductor wafer has been widely adopted.

  That is, the semiconductor wafer with the die attach film bonded to the back surface is divided into individual devices, thereby forming a semiconductor device with the adhesive film attached to the back surface. Thereafter, die bonding is performed on the substrate via the DAF on the back surface of the semiconductor device, so that there is an advantage that the adhesive to be used can be minimized and the mounting area of the semiconductor device can be minimized.

  On the other hand, in recent years, electric devices such as mobile phones and personal computers are required to be lighter and smaller, and thinner devices are required. As a technique for dividing a wafer into thinner devices, a dividing technique called a so-called first dicing method has been developed and put into practical use (for example, see Japanese Patent Application Laid-Open No. 11-40520).

  This tip dicing method is a semiconductor in which a dividing groove having a predetermined depth (a depth corresponding to the finished thickness of the device) is formed along the line to be divided from the surface of the semiconductor wafer, and then the dividing groove is formed on the surface. In this technique, the back surface of the wafer is ground and a dividing groove is exposed on the back surface to divide the wafer into individual devices. The thickness of the device can be processed to 100 μm or less.

  Further, in the wafer laser processing method, a condensing point of a laser beam having a wavelength (for example, 1064 nm) that is transmissive to the wafer is positioned inside the wafer corresponding to the planned division line, and the laser beam is formed on the planned division line. A method is known in which a modified layer is formed inside the wafer by irradiation along the surface, and then an external force is applied to divide the wafer into individual devices (see, for example, Japanese Patent No. 3408805).

  However, in this method, a modified layer is formed inside the wafer, DAF is attached to the back surface of the wafer, and then the wafer is divided into individual devices by applying an external force. There is a problem that it is difficult to cut.

  As a method for solving this problem, Japanese Patent Application Laid-Open No. 2007-27250 discloses a wafer divided into individual devices by a pre-dicing method, or a modified layer formed inside the wafer along the planned dividing line. A technique is described in which an expanded tape is attached to the back surface of a wafer via a DAF, and the expanded tape is expanded to widen the gap between the devices and at the same time divide the DAF corresponding to the device.

Japanese Patent Laid-Open No. 11-219962 JP 11-40520 A JP 2007-272505 A

  However, in the DAF dividing method disclosed in Patent Document 3, the DAF is cooled to reduce the proof stress, or the expansion force is increased during expansion of the expanded tape to improve the dividing force. There remains a problem that it is difficult to reliably divide correspondingly.

  The present invention has been made in view of these points, and an object of the present invention is to provide a processing method capable of reliably dividing a DAF in correspondence with each device.

  According to the present invention, in a processing method of dividing a DAF attached to the back surface of a wafer formed on a front surface by dividing a plurality of devices by a predetermined division line formed in a lattice shape, corresponding to each device. And a wafer preparation step for preparing a wafer in which a modified layer is formed inside the wafer along the planned division line, or a wafer divided into individual devices along the planned division line, and the wafer. Position the wafer prepared in the wafer preparation step on an annular frame having an opening, and arrange the wafer rear surface on the expanded tape via the DAF. After the wafer arrangement step, the expanded tape is Expand and apply a pulling force to the wafer via the DAF to widen the space between adjacent devices and Includes a DAF dividing step of dividing in correspondence to the scan, and the DAF dividing step, the processing method characterized by softening by heating the DAF to a predetermined temperature is provided.

  Preferably, the predetermined temperature is in the range of 50 ° C to 150 ° C.

  According to the present invention, since the DAF is heated and then the expanded tape is expanded, the DAF located between the devices is expanded following the expansion of the expanded tape, and the DAF is surely corresponding to each device. Can be divided into

It is a surface side perspective view of a semiconductor wafer. It is a perspective view which shows the cutting process in the tip dicing method. It is an expanded sectional view showing a cutting process. It is a perspective view which shows a division | segmentation process. It is a perspective view which shows a modified layer formation process. It is sectional drawing which shows a modified layer formation process. It is a perspective view explaining the wafer arrangement | positioning process which arrange | positions a wafer to an expanded tape via DAF. It is a perspective view of a dividing device. It is a partial cross section side view which shows a DAF division | segmentation process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a front side perspective view of a semiconductor wafer (hereinafter sometimes simply referred to as a wafer) 11.

  A plurality of planned division lines (streets) 13 are formed in a lattice shape on the surface 11 a of the wafer 11, and devices 15 such as ICs and LSIs are formed in each region partitioned by the planned division lines 13. Reference numeral 11 b denotes the back surface of the wafer 11. The wafer 11 is, for example, a silicon wafer and has a thickness of about 700 μm.

  In the processing method of the present invention, first, a wafer preparation step for preparing a wafer to be processed is performed. The first embodiment of the wafer preparation step is an embodiment in which a wafer is divided into individual devices by a pre-dicing method, and a wafer is prepared in which the wafer is divided into individual devices. Refer to FIGS. 2 to 4. I will explain.

  In this tip dicing method, the back surface 11b side of the wafer 11 is sucked and held by a chuck table of a cutting device (not shown), and a cutting blade 6 attached to the tip of the spindle 4 of the cutting unit 2 is used as shown in FIGS. A cutting process is performed in which the surface 11a of the wafer 11 is cut along the planned dividing line 13 to form a cutting groove 8 (groove depth of about 100 μm) reaching the finished thickness of the wafer 11.

  In the cutting process, the dividing line to which the cutting blade 6 that rotates at a high speed (for example, 30000 rpm) in the direction of the arrow A is extended in the first direction while the chuck table that sucks and holds the wafer 11 is fed in the direction of the arrow X1 in FIG. 13 is cut into the surface 11 a of the wafer 11 to form a cutting groove 8 that reaches the finished thickness of the wafer 11.

  While the cutting blade 6 is indexed and fed by the pitch of the division line 13, all the division lines 13 extending in the first direction are cut to form similar cutting grooves 8. Next, after rotating a chuck table (not shown) holding the wafer 11 by 90 °, the same cutting groove 8 is formed along the planned dividing line 13 extending in the second direction orthogonal to the first direction.

  After performing the cutting process, the back surface 11b of the wafer 11 is ground to thin the wafer 11 to a finished thickness, and the cutting grooves 8 are exposed on the back surface 11b of the wafer 11 so that the wafer 11 is transferred to the individual device chips 15. The division step of dividing is performed.

  This division step will be described with reference to FIG. In the dividing step, as shown in FIG. 4A, a protective tape 17 is attached to the surface of the wafer 11, and the surface 11a side of the wafer 11 is sucked and held through the protective tape 17 by the chuck table 10 of the grinding apparatus. Then, the back surface 11b side of the wafer 11 is exposed.

  The grinding unit 12 of the grinding apparatus includes a spindle 14 that is rotationally driven by a motor, a wheel mount 16 that is fixed to the tip of the spindle 14, and a grinding wheel 18 that is detachably fixed to the wheel mount 16 with a plurality of screws 20. Is included. The grinding wheel 18 includes an annular wheel base 22 and a plurality of grinding wheels 24 that are annularly fixed to the outer periphery of the lower end of the wheel base 22.

  In the dividing step, while rotating the chuck table 10 in the direction of arrow a at 300 rpm, for example, the grinding wheel 18 is rotated in the same direction as the chuck table 10, that is, in the direction of arrow b at 6000 rpm, for example. In operation, the grinding wheel 24 is brought into contact with the back surface 11 b of the wafer 11.

  Then, the grinding wheel 18 is ground and fed by a predetermined amount at a predetermined grinding feed speed, and the wafer 11 is ground. When grinding is continued and the wafer 11 is thinned to a finished thickness (for example, 90 μm), as shown in FIG. 4B, the cutting grooves 8 are exposed on the back surface 11b of the wafer 11, and the wafer 11 is an individual device. Divided into chips 15.

  Next, with reference to FIG.5 and FIG.6, 2nd Embodiment of a wafer preparation process is described. In the second embodiment, a modified layer is formed inside the wafer along the division line 13 of the wafer 11. FIG. 5 is a perspective view showing a modified layer forming step, and FIG. 6 is a sectional view thereof.

  In the modified layer forming step, a condensing point of a laser beam having a wavelength (for example, 1064 nm) that is transmissive to the wafer 11 is positioned inside the wafer 11 corresponding to the division line 13 and the chuck table 26 is moved to the arrow X1. The modified layer 19 is formed inside the wafer 11 by irradiating the laser beam along the division line 13 while moving in the direction.

  As shown in FIG. 6B, when the laser beam irradiated from the condenser 28 reaches the end of the wafer 11, the irradiation of the laser beam is stopped and the processing feed of the chuck table 26 is stopped.

  A modified layer 19 is formed inside the wafer along the planned division line 13 extending in the first direction while indexing and feeding the wafer 11 by the pitch of the planned division line 13. Next, after the chuck table 26 is rotated by 90 °, the same modified layer 19 is formed inside the wafer along all the planned dividing lines 13 extending in the second direction orthogonal to the first direction.

  As described above, in the wafer preparation process of the second embodiment, the wafer 11 having the modified layer 19 formed inside the wafer is prepared along the division line 13.

  After the wafer preparation process, as shown in FIG. 7, the wafer 11 is positioned on an annular frame F having an opening for accommodating the wafer 11, and the wafer 11 is expanded with a DAF 21 attached to the back surface of the wafer 11. A wafer disposing step for disposing at T1 is performed. The expanded tape T1 is an expanded tape with DAF in which the DAF 21 is formed in advance, and the outer peripheral portion thereof is attached to the annular frame F to form the wafer unit 23.

  In the wafer unit 23, the wafer 11 with the DAF 21 attached to the back surface is supported by the annular frame F via the expanded tape T1. The wafer 11 shown in FIG. 7 is a wafer 11 divided into individual devices 15 by the tip dicing method, and the protective tape 17 attached to the surface 11a of the wafer 11 during the dividing process is in the state shown in FIG. It is peeled off.

  The wafer 11 of the wafer unit 23 shown in FIG. 7 is a wafer divided into individual devices 15 by the tip dicing method, but the modified layer 19 is formed along the planned division line 13 inside the wafer described in the wafer preparation process. The wafer according to the second embodiment in which is formed may be used.

  After performing the wafer disposing step, the expand tape T1 is expanded to apply a pulling force to the wafer 11 to widen the interval between the adjacent devices 15, and the DAF dividing step of dividing the DAF 21 corresponding to the device 15 is performed. In this dividing step, for example, a dividing device 30 as shown in FIG. 8 is used.

  8 includes a frame holding means 32 for holding the annular frame F and a tape extending means 34 for expanding the expanded tape T1 attached to the annular frame F held by the frame holding means 32. Yes.

  The frame holding means 32 includes an annular frame holding member 36 and a plurality of clamps 38 as fixing means arranged on the outer periphery of the frame holding member 36. An upper surface of the frame holding member 36 forms a mounting surface 36a on which the annular frame F is placed, and the annular frame F is placed on the mounting surface 36a.

  The annular frame F placed on the placement surface 36 a is fixed to the frame holding member 36 by a clamp 38. The frame holding means 32 configured in this manner is supported by the tape expanding means 34 so as to be movable in the vertical direction.

  The tape expansion means 34 includes an expansion drum 40 disposed inside an annular frame holding member 36. The expansion drum 40 has an inner diameter that is smaller than the inner diameter of the annular frame F and larger than the outer diameter of the semiconductor wafer 11 attached to the expanded tape T1 attached to the annular frame F.

  The expansion drum 40 has a support flange 42 integrally formed at the lower end thereof. The tape expanding means 34 further includes a driving means 44 that moves the annular frame holding member 36 in the vertical direction. The drive means 44 is composed of a plurality of air cylinders 46 disposed on the support flange 42, and the piston rod 48 is connected to the lower surface of the frame holding member 36.

  The driving means 44 composed of a plurality of air cylinders 46 has a predetermined amount from the reference position where the mounting surface 36a of the annular frame holding member 36 is substantially the same height as the upper end of the expansion drum 40 and a predetermined amount from the upper end of the expansion drum 40 Move vertically between lower expansion positions.

  The dividing means 30 further includes a heating table 50 disposed inside the expansion drum 40. The heating table 50 incorporates a Peltier element or the like inside, and the surface temperature of the heating table 50 can be controlled by controlling the applied current. The heating table 50 can be moved in the vertical direction by a driving means (not shown).

  The dividing process performed using the dividing apparatus 30 configured as described above will be described with reference to FIGS. 9A and 9B. As shown in FIG. 9 (A), the annular frame F, which supports the wafer 11 with the DAF 21 attached to the back surface via the expanded tape T1, is placed on the placement surface 36a of the frame holding member 36 and clamped. The frame holding member 36 is fixed by 38. At this time, the frame holding member 36 is positioned at a reference position where the mounting surface 36 a is substantially the same height as the upper end of the expansion drum 40.

  In this state, the heating table 50 is raised and brought into contact with the expanded tape T1, and the DAF 21 attached to the back surface of the wafer 11 is heated via the expanded tape T1. Preferably, the DAF 21 is heated by the heating table 50 to a temperature within the range of 50 ° C to 150 ° C. By this heating, the DAF 21 is softened and easily broken.

  When the DAF 21 is sufficiently heated to a predetermined temperature, the heating table 50 is lowered. Then, the air cylinder 46 is driven to lower the frame holding member 36 to the extended position shown in FIG. As a result, the annular frame F fixed on the mounting surface 36a of the frame holding member 36 is also lowered, so that the expanded tape T1 attached to the annular frame F mainly contacts the upper end edge of the expansion drum 40. Expanded radially.

  As a result, a tensile force acts radially on the DAF 21 and the wafer 11 attached to the expanded tape T1. Thus, when a radial pulling force acts on the wafer 11 and the DAF 21, the wafer 11 follows the expansion of the expanded tape T <b> 1 and the distance between the adjacent devices 15 is widened, and the DAF 21 positioned between the adjacent devices 15. Since it is heated to a predetermined temperature and is easily expanded, it is expanded in the radial direction, and the DAF 21 is surely divided corresponding to each device 15.

  In the wafer 11 prepared in the wafer preparation process of the second embodiment described above, the modified layer 19 is formed along the division line 13 inside the wafer. Therefore, when the expand tape T1 is expanded, the wafer 11 is modified. The material layer 19 is formed and divided into the individual devices 15 along the planned dividing line 13 whose strength is reduced, and the DAF 21 is heated to a predetermined temperature to be easily expanded, so that it is expanded in the radial direction. The DAF 21 is reliably divided corresponding to each device 15.

6 Cutting blade 8 Cutting groove 11 Semiconductor wafer 13 Scheduled division line 15 Device 17 Protective tape 18 Grinding wheel 19 Modified layer 21 DAF
24 Grinding wheel 28 Concentrator 30 Dividing device 32 Frame holding means 34 Tape expansion means 40 Expansion drum 50 Heating table

Claims (2)

A processing method of dividing a DAF attached to the back surface of a wafer formed on a surface by dividing a plurality of devices by a division line formed in a lattice shape, corresponding to each device,
A wafer preparation step of preparing a wafer in which a modified layer is formed inside the wafer along the division line, or a wafer divided into individual devices along the division line;
A wafer disposing step of positioning the wafer prepared in the wafer preparatory step on an annular frame having an opening for accommodating a wafer, and disposing the back surface of the wafer on an expanded tape via a DAF;
A DAF dividing step of expanding the expanded tape and applying a pulling force to the wafer via the DAF to widen the interval between adjacent devices and dividing the DAF corresponding to the device after the wafer arranging step is performed,
In the DAF dividing step, the DAF is heated to a predetermined temperature and softened.   The processing method according to claim 1, wherein the predetermined temperature is in a range of 50 ° C. to 150 ° C.

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