JP6800524B2 - How to maintain chip spacing - Google Patents

Description

The present invention relates to a chip spacing maintaining method for expanding and maintaining the spacing between a plurality of chips formed by dividing a workpiece such as a semiconductor wafer (hereinafter, may be simply abbreviated as a wafer).

Wafers in which devices such as ICs and LSIs are formed in each region divided into a plurality of planned division lines formed in a grid pattern on the front surface are scheduled to be divided after the back surface is ground and processed to a desired thickness. It is divided into individual chips along the line, and the divided chips are widely used in various electronic devices such as mobile phones and personal computers.

The wafer is supported by an annular frame via a dicing tape, which is an adhesive tape, and is mounted on a chuck table of a cutting device in this state. A cutting device called a dicer equipped with a cutting unit that rotatably supports a cutting blade is widely used for cutting a wafer.

In cutting with a cutting device, a cutting blade having an annular cutting edge with a thickness of about 20 to 40 μm is rotated at high speed to cut into a wafer, and a dividing groove is formed along the planned dividing line. Width is needed.

Therefore, in recent years, as a method of narrowing the width of the planned division line and increasing the share of device chips from one wafer, a modified layer is irradiated inside the wafer by irradiating the wafer with a laser beam having a wavelength having transparency. A method of applying an external force to a wafer to divide the wafer into individual chips using the modified layer as a division starting point is disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-129607.

Further, after the modified layer is formed at a position equal to or higher than the finished thickness of the device chip from the surface of the wafer by irradiation with a laser beam, the back surface of the wafer is ground and the modified layer is divided by grinding stress. A method is also known in which the wafer is divided into individual chips, and the wafer is ground to a predetermined thickness until the modified layer is removed to divide the wafer into individual chips. This method is also called SDBG (Stealth Dicking Before Grinding).

In these methods, since there is almost no space between the divided chips, there is a problem that adjacent chips come into contact with each other during handling after dividing the wafer into individual chips, resulting in chipping of the chips. is there.

In order to solve this problem, for example, Japanese Patent Application Laid-Open No. 2010-147317 states that after the tape is expanded and the wafer is divided into a plurality of chips, the tape is loosened between the outer peripheral edge of the wafer and the inner circumference of the annular frame. Described is a tape expansion method capable of accurately contracting only the slack region to be contracted without contracting the portion between the chips in the tape when the region is heated and contracted.

Japanese Unexamined Patent Publication No. 2005-129607 JP-A-2010-147317

However, even if the so-called heat shrink method described in Patent Document 2 is adopted, it is difficult to completely eliminate the slack of the expanding sheet (expanding tape), and an improvement method has been desired.

The present invention has been made in view of these points, and an object of the present invention is to maintain the distance between the chips in an expanded state, and the chips come into contact with each other due to loosening or contraction of the expanding sheet. It is an object of the present invention to provide a chip spacing maintenance method capable of preventing chip damage due to the above.

According to the present invention, a chip spacing that is attached to an expanding sheet and attached to an annular frame via the expanding sheet to maintain the distance between the chips of a work piece divided into a plurality of chips in an expanded state. a maintenance method, the outer and chip intervals forming step of forming a gap between the plurality of chips by expanding the expandable sheet, after performing the chip interval formation step, in a state of maintaining the spacing between the tip A resin that is cured by a target stimulus is applied in a ring shape only on the expanding sheet on the outer periphery of the workpiece , and then the resin on the expanding sheet is subjected to the external stimulus to cure the resin . Provided is a method for maintaining a chip spacing, which comprises a resin disposing step of disposing the resin ring formed by the above and fixing the spacing between the chips.

Preferably, the expanding sheet has a base material and a glue layer disposed on the base material, and the workpiece is disposed on the glue layer of the expanding sheet, and in the resin disposing step, the resin ring formed into a ring shape is adhered to該糊layer side or the substrate side of the expanded sheet.

According to the chip spacing maintaining method of the present invention, after forming the chip spacing, the ring-shaped resin is fixed on the expanding sheet on the outer periphery of the workpiece, so that the expanding sheet in the ring-shaped resin does not loosen. Therefore, the distance between the chips can be maintained in an expanded state, and damage to the chips due to contact between the chips due to slackening of the expanding sheet can be prevented.

It is a front side perspective view of the semiconductor wafer. It is a perspective view which shows the surface protection tape sticking step. It is sectional drawing which shows the laser processing step. It is a perspective view which shows the back surface grinding step of a wafer. FIG. 5 is a perspective view showing a transfer step in which the back surface of a wafer divided into chips is attached to an expanding sheet whose outer peripheral portion is mounted on an annular frame, and the protective tape is peeled off from the front surface of the wafer. It is a perspective view of the tape expansion device. It is an exploded perspective view of the tape expansion device in a state taken out from a casing. FIG. 8A is a cross-sectional view of the tape expansion device showing the frame arrangement step, and FIG. 8B is a cross-sectional view of the tape expansion device showing the frame fixing step. FIG. 9A is a cross-sectional view of the tape expansion device showing the chip spacing forming step by expanding the expand sheet, and FIG. 9B is a cross-sectional view of the tape expansion device showing the suction holding step. It is sectional drawing of the tape expansion apparatus which shows the heat shrink step. FIG. 11A is a cross-sectional view of the tape expansion device showing the liquid resin coating step, and FIG. 11B is a cross-sectional view of the tape expansion device showing the liquid resin curing step. FIG. 12A is a cross-sectional view of a tape expansion device showing a resin ring arrangement step for fixing the resin ring to the base material side of the expanding sheet, and FIG. 12B is fixing the resin ring to the glue layer side of the expanding sheet. It is sectional drawing of the tape expansion apparatus which shows the resin ring arrangement step.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. With reference to FIG. 1, a front side perspective view of a semiconductor wafer (hereinafter, may be simply abbreviated as a wafer) 11 is shown. A plurality of scheduled division lines 13 formed in a grid pattern are formed on the surface 11a of the wafer 11, and devices 15 such as ICs and LSIs are formed in each region partitioned by the intersecting scheduled division lines 13. There is. Reference numeral 11b is the back surface of the wafer 11.

In the chip spacing maintaining method of the embodiment of the present invention, first, as shown in FIG. 2, a surface protective tape 17 for protecting the device 15 is attached to the surface 11a of the wafer 11. Then, as shown in FIG. 3, the chuck table 10 of the laser processing apparatus sucks and holds the wafer 11 via the surface protective tape 17, and exposes the back surface 11b of the wafer 11.

Next, the infrared imaging element of the imaging unit equipped in the laser processing apparatus images the wafer 11 from the back surface 11b side thereof, and the region corresponding to the scheduled division line 13 is aligned with the condenser 12 in the processing feed direction. To carry out. For this alignment, well-known image processing such as pattern matching is used.

After the alignment of the scheduled division line 13 extending in the first direction is performed, the chuck table 10 is rotated by 90 °, and then the alignment of the scheduled division line 13 extending in the second direction orthogonal to the first direction is performed. ..

After the alignment is performed, the focusing point of the laser beam LB irradiated from the condenser 12 is positioned at a position shallower than the finished thickness of the device chip inside the wafer 11, and the light is transmitted from the back surface 11b side of the wafer 11 to the wafer 11. A laser beam LB having a wavelength of the above is irradiated along the scheduled division line 13, and a laser beam irradiation step of forming a modified layer 19 as a division starting point inside the wafer 11 is performed.

This laser beam irradiation step is carried out along all the planned division lines 13 extending in the first direction and the second direction, and a similar modified layer 19 is formed inside the wafer 11 along the planned division lines. Form.

The processing conditions in the laser beam irradiation step are set as follows, for example.

Light source: LD excitation Q-switch Nd: YVO4 pulsed laser Wavelength: 1064 nm
Repeat frequency: 100kHz
Pulse output: 10 μJ
Condensing spot diameter: φ1 μm
Machining feed rate: 100 mm / sec

After performing the laser beam irradiation step, the back surface 11b of the wafer 11 is ground to divide the wafer 11 into individual device chips 25, and the back surface grinding step of grinding the wafer 11 to a desired thickness is performed.

In this back surface grinding step, as shown in FIG. 4A, the surface 11a side of the wafer 11 is sucked and held by the chuck table 16 of the grinding device via the surface protection tape 17, and the back surface 11b side of the wafer 11 is exposed. ..

The grinding unit 18 of the grinding device includes a spindle 20 that is rotationally driven by a motor, a wheel mount 22 that is fixed to the tip of the spindle 20, and a grinding wheel 24 that is detachably fixed to the wheel mount 22 with a plurality of screws 23. Includes. The grinding wheel 24 is composed of an annular wheel base 26 and a plurality of grinding wheels 28 fixed in an annular shape to the outer peripheral portion of the lower end of the wheel base 26.

In the back surface grinding step, as shown in FIG. 4A, the chuck table 16 is rotated in the direction of arrow a at, for example, 300 rpm, and the grinding wheel 24 is rotated in the same direction as the chuck table 16, that is, in the direction of arrow b at, for example, 6000 rpm. While rotating, the grinding unit feed mechanism (not shown) is operated to bring the grinding wheel 28 into contact with the back surface 11b of the wafer 11.

Then, the grinding wheel 24 is grounded downward by a predetermined amount at a predetermined grinding feed rate to grind the wafer 11. When grinding is continued, as shown in FIG. 4B, the wafer 11 is divided into individual device chips 25 with the modified layer 19 as the starting point of division by the grinding pressure, and the wafer 11 can be ground to a desired finished thickness. it can. In this state, as shown in FIGS. 4 (B) and 5, the dividing lines 21 are almost in contact with each other.

After the wafer 11 is divided into individual device chips 25, as shown in FIG. 5, the back surface 11b of the wafer 11 divided into individual chips 25 is attached to an expanding sheet T whose outer peripheral portion is mounted on the annular frame F. Then, the transfer step of peeling the surface protective tape 17 from the surface 11a of the wafer 11 to form the frame unit 27 is performed.

When this transfer step is performed, the wafer 11 divided into the individual chips 25 is supported by the annular frame F via the expanding sheet T. Here, the expanding sheet T is composed of a base material formed of vinyl chloride or the like and a glue layer (adhesive layer) disposed on the base material.

In the above-described processing method for dividing the wafer 11 into individual device chips 25, after the modified layer 19 is formed inside the wafer 11, the back surface of the wafer 11 is ground to divide the wafer 11 into individual device chips 25. Therefore, it is sometimes referred to as SDBG (Stealth Dicking Wafer Grinding).

Instead of this embodiment, a cutting groove having a depth equal to or greater than the finished thickness of the device chip 25 is formed from the front surface 11a side of the wafer 11, and then the back surface 11b of the wafer 11 is ground to obtain the wafer 11 as an individual device. It may be divided into chips 25. This processing method is called DBG (Dicking Before Grinding).

Next, the chip spacing maintaining method according to the embodiment of the present invention will be described in detail with reference to FIGS. 6 to 12. With reference to FIG. 6, a perspective view of the tape expansion device 30 is shown. The tape expansion device 30 includes a casing 32, a holding plate 34, and a lid 36. The casing 32 has an insertion port for inserting and removing the frame unit 27 shown in FIG. 5, and is provided with a cover 33 for opening and closing the insertion port.

A holding unit 38 shown in FIG. 7 is arranged at the bottom of the casing 32. The holding unit 38 includes a frame holding table 40, a plurality of air cylinders 42 for raising and lowering the frame holding table 40, a wafer holding table 44, and an elevating mechanism 54 for raising and lowering the wafer holding table 44.

Holes 41 and 35 having a diameter substantially equal to the inner diameter of the annular frame F are formed concentrically with each other in the frame holding base 40 and the frame holding plate 34. An annular frame F of the frame unit 27 is concentrically placed on the upper surface around the hole 41 of the frame holding base 40. The air cylinder 42 is supported by the bottom of the casing 32, and the tip of the piston rod 42a that expands and contracts in the vertical direction is fixed to the lower surface of the frame holding base 40.

The frame holding base 40 is positioned at a frame unit receiving position below the frame holding plate 34, as shown in FIG. 8A, in a state where the piston rod 42a of the air cylinder 42 is reduced.

As shown in FIG. 8A, the wafer holding table 44 is composed of a frame body 46 formed of metal and a suction holding portion 48 formed of porous ceramics or the like, and the suction holding portion 48 is electromagnetically switched. It is selectively connected to a suction source 52 such as a vacuum pump via a valve 50.

The lower surface of the frame body 46 of the wafer holding table 44 is connected to the piston rods 60a of the plurality of air cylinders 60. As shown in FIG. 7, the plurality of air cylinders 60 of the elevating mechanism 54 are covered with a rectangular casing 56 and a cylindrical casing 58.

Above the frame holding plate 34, the heater unit 62 is arranged concentrically with the hole 35 of the frame holding plate 34. In the heater unit 62, a disk-shaped flange 66 is fixed to the lower end of a rod 64 extending in the vertical direction provided on the lower surface of the lid 36 so as to extend and contract, and as an external stimulus applying means to the outer peripheral portion of the lower surface of the flange 66. The working annular heater 68 is fixed.

Next, with reference to FIGS. 8 to 12, a chip spacing maintenance method using the tape expansion device 30 described above will be described. First, as shown in FIG. 8A, the cover 33 of the tape expansion device 30 is opened, the frame unit 27 shown in FIG. 5 is inserted into the tape expansion device 30, and the wafer 11 divided into individual chips is inserted. The annular frame F is placed on the frame holding table 40 while being placed on the holding table 44 via the expanding tape T.

Next, the air cylinder 42 is driven to extend the piston rod 42a, and as shown in FIG. 8B, the frame holding base 40 is raised to form the annular frame F with the frame holding plate 34 and the frame holding base 40. Hold and fix.

The frame holding plate 34 shown in FIG. 7 is shown in an abbreviated form for ease of understanding. Actually, as shown in FIG. 8A, the frame holding plate 34 is one of the box bodies 37. It is composed of parts and is fixedly arranged.

After the annular frame F is sandwiched and fixed between the frame holding plate 34 and the frame holding base 40, the air cylinder 60 of the elevating mechanism 54 is operated to extend the piston rod 60a, and as shown in FIG. 9A, The wafer holding table 44 is pushed up to expand (expand) the expanding sheet T in the radial direction, and the dividing line 21 shown in FIG. 5 is expanded to form a gap between adjacent chips 25 (chip spacing forming step). In this state, the electromagnetic switching valve 50 is positioned at the shutoff position.

After performing the chip spacing forming step, as shown in FIG. 9B, the electromagnetic switching valve 50 is switched to the communication position, the suction holding portion 48 of the holding table 44 is connected to the suction source 52, and the holding table 44 is connected. The suction holding portion 48 sucks and holds the wafer 11 in a state where a space is formed between the chips 25.

After performing the suction holding step, as shown in FIG. 10, when the piston rod 60a of the air cylinder 60 is reduced and the holding table 44 is lowered, the expansion between the outer circumference of the wafer 11 and the inner circumference of the annular frame F is expanded. Looseness occurs in the sheet T as indicated by the symbol Ts.

In order to remove this slack, it is preferable to remove the slack Ts by lowering the heater unit 62, heating the expanding sheet Ts of the slack portion with the heater 68, and performing heat shrink. If the degree of slack is not large, heat shrink may be omitted.

Next, as shown in FIG. 11A, a liquid resin 72 made of, for example, an ultraviolet (UV) curable epoxy resin is indicated by reference numeral 74 on the expanding sheet T on the outer peripheral side of the wafer 11 from the liquid resin supply nozzle 70. Apply (supply) in a ring shape. It is preferably supplied in a ring shape, but it may be supplied in a broken line shape.

After supplying the liquid resin, it is irradiated with ultraviolet rays to cure the ultraviolet (UV) curable liquid resin to form a resin ring. Then, as shown in FIG. 11B, the cured resin ring 74 is fixed to the expanding sheet T. That is, the UV irradiation device 78 is lowered, and ultraviolet rays 83 are irradiated from the UV lamp 82 arranged on the outer periphery of the lower end of the disk-shaped mounting plate 80 to the liquid resin 74 supplied in a ring shape to cure the liquid resin. , The resin ring 74 is fixed to the expanding sheet T.

Since the resin ring 74 is fixed to the expanded sheet T in the expanded state in this way, it is possible to prevent the expanding sheet T in the resin ring 74 from loosening or shrinking. Therefore, the distance between the chips can be maintained in an expanded state, and damage to the chips due to contact between the chips due to slackening of the expanding sheet T can be prevented.

Instead of the UV curable liquid resin, the thermosetting liquid resin may be supplied onto the expanding sheet T on the outer periphery of the wafer 11 and the liquid resin may be heated and cured by the heater 68 shown in FIG.

In another embodiment of the present invention, as shown in FIG. 12A, the resin ring 84 is arranged on the base material side of the expanding sheet T, and the expanding sheet of the portion where the resin ring 84 is arranged by the heater 68. The resin ring 84 may be thermocompression bonded to the expanding sheet T by heating T.

As a modified embodiment of the embodiment shown in FIG. 12 (A), as shown in FIG. 12 (B), the resin ring 84 is arranged on the glue layer side of the expanding sheet T, and the resin ring 84 is expanded by the heater 68. It may be thermocompression bonded to the sheet T.

Instead of thermocompression bonding of the resin ring 84, the resin ring 84 may be attached to the expanding sheet T by ultrasonic waves. Further, in FIGS. 12A and 12B, the heater 68 heats from the upper side of the expanding sheet T, but heating may be performed from the lower side of the expanding sheet T.

Also in the embodiment shown in FIGS. 12A and 12B, since the expanding sheet T is fixed in the expanded state by the thermocompression-bonded resin ring 84, the expanding sheet T does not loosen. Therefore, the distance between the chips can be maintained in an expanded state, and damage to the chips due to contact between the chips due to slackening of the expanding sheet T can be prevented.

In the above-described embodiment, the present invention is applied after the wafer 11 is divided into individual device chips 25 by the SDBG method or the DBG method, but the present invention is not limited to these embodiments, and the wafer is not limited to these embodiments. The present invention is carried out in which the modified layer 19 is formed inside the 11 and the wafer 11 is divided into individual device chips 25 with the modified layer 19 as the division starting point by the tape expansion device 30, and then the resin rings 74 and 84 are formed. You may try to do so.

11 Semiconductor wafer (wafer)
13 Scheduled division line 15 Device 17 Surface protection tape 18 Grinding unit 19 Modified layer 21 Division line 24 Grinding wheel 25 Device chip (chip)
27 Frame unit 28 Grinding wheel 30 Tape expansion device 32 Casing 34 Frame holding plate 36 Lid 38 Holding unit 40 Frame holding base 42,60 Air cylinder 54 Lifting mechanism 62 Heater unit 68 Heater 72 Liquid resin 74 Ring resin 82 Ultraviolet lamp 84 Resin ring

Claims (3)

It is a chip spacing maintaining method for maintaining a chip spacing of a work piece divided into a plurality of chips in an expanded state, which is attached to an expanding sheet and attached to an annular frame via the expanding sheet. ,
A chip spacing forming step that expands the expanding sheet to form a spacing between the plurality of chips.
After performing the chip spacing forming step, a resin that is cured by an external stimulus while maintaining the spacing between the chips is applied in a ring shape only on the expanding sheet on the outer periphery of the workpiece, and then the chip spacing is formed. A resin disposition step of disposing a resin ring formed by applying the external stimulus to the resin on the expanding sheet to cure the resin and fixing the distance between the chips.
A chip spacing maintenance method characterized by being equipped with. The expanding sheet has a base material and a glue layer disposed on the base material, and the workpiece is disposed on the glue layer of the expanding sheet.
The method for maintaining chip spacing according to claim 1, wherein in the resin disposing step, the resin ring formed in a ring shape is adhered to the glue layer side of the expanding sheet. The expanding sheet has a base material and a glue layer disposed on the base material, and the workpiece is disposed on the glue layer of the expanding sheet.
The method for maintaining chip spacing according to claim 1, wherein in the resin disposing step, the resin ring formed in a ring shape is adhered to the base material side of the expanding sheet.