CN106992150A - The processing method of chip - Google Patents

Abstract

Provided is a method of processing a wafer having devices formed in each region of the front side divided by a plurality of crossing predetermined dividing lines, each device having a plurality of bumps protruding from the front side, the method of processing the wafer having the following Steps: a groove forming step, forming a groove from the front surface of the wafer along the planned dividing line with a depth deeper than the specified thickness and not completely cutting the wafer; a resin covering step, using 1.5 to 5 times the height of the bump. times the thickness of the liquid resin to cover the front surface of the wafer where the groove is formed; a resin hardening step, after performing the resin covering step, hardening the liquid resin; and a grinding step, after implementing the resin hardening step Grinding the back surface of the wafer to thin the wafer to the predetermined thickness, and exposing the groove on the back surface, thereby dividing the wafer along the planned dividing line to form a plurality of device chips of a predetermined thickness .

Description

Wafer processing method

technical field

The present invention relates to a method of processing a wafer in which devices are formed in each region of the front side divided by a plurality of crossing planned dividing lines, and each device has a plurality of bumps protruding from the front side.

Background technique

In the manufacturing process of semiconductor device chips, a plurality of dividing lines called streets are formed in a grid on the front surface of a wafer made of silicon or compound semiconductors, and LSIs are formed in each area divided by the dividing lines. and other devices. After the back surface of these wafers is ground and thinned to a predetermined thickness, they are divided along the streets by a cutting device or the like to manufacture individual semiconductor device chips.

In recent years, a mounting technique called flip-chip bonding has been put into practical use as a technology for reducing the weight, weight and size of semiconductor device modules, in which a large number of metal protrusions called bumps are formed on the front surface of the device. These bumps are directly bonded to electrodes formed on a wiring board (for example, refer to Japanese Patent Application Laid-Open No. 2001-237278).

Also, as a technique for dividing a wafer into thinner device chips, a dividing technique called a so-called dicing method (Dicing Before Grinding) has been developed and put into practical use (for example, refer to Japanese Patent Application Laid-Open No. 11-40520). .

This dicing-in-first method is a technique that can process the device chip to a thickness of 50 μm or less by forming a predetermined depth (equivalent to After that, the back surface of the wafer with the division grooves formed on the front surface is ground to expose the division grooves to the back surface to divide the wafer into individual device chips.

In recent years, among wafers on which bumps are formed on the front surface, there are also wafers mounted with high bumps called high bumps. When performing back grinding on such a wafer, a protective tape having a considerable thickness is bonded to the front surface of the wafer and the back grinding is performed. However, since the height of the bumps is high, even if the bumps are planarized by absorbing the unevenness of the bumps with the protective tape, it is difficult to completely planarize them.

As a result, when the back surface of the wafer is ground by attaching a protective tape to the front surface of the wafer with bumps, the unevenness of the bumps will be transferred to the grinding surface, or the thickness of the wafer after grinding will vary. Bigger problem. In addition, when the wafer is sucked and held by the chuck table through the protective tape, there is a problem that the suction and holding of the wafer becomes incomplete due to negative pressure leakage due to the inability of the protective tape to completely follow.

Patent Document 1: Japanese Patent Laid-Open No. 2001-237278

Patent Document 2: Japanese Patent Application Laid-Open No. 11-40520

Patent Document 3: Japanese Patent Laid-Open No. 2012-160515

Patent Document 4: Japanese Patent Laid-Open No. 2012-119594

However, in addition to the problem of high cost, the protection tape having a thickness that absorbs bumps also has the following problem: since the adhesive layer of the protection tape is relatively soft, the chip will be stuck on the protection tape during grinding. When the chips are shaken, the chips collide with each other to cause peripheral defects of the chips or cracks of the wafers.

Contents of the invention

The present invention has been made in view of such points, and an object of the present invention is to provide a method of processing a wafer that does not transfer unevenness of the bumps to the grinding surface even if the height of the bumps is high while suppressing costs. , The thickness deviation of the wafer after grinding is also controlled very small, preventing the chips from colliding with each other during grinding, and no leakage of negative pressure will occur when the wafer is held on the chuck table.

According to the present invention, there is provided a method of processing a wafer having devices formed in each area of the front side divided by a plurality of crossing planned dividing lines, each device having a plurality of bumps protruding from the front side, the wafer having The processing method is to divide the wafer along the dividing line to form a plurality of device chips having a predetermined thickness. The predetermined line forming depth is deeper than the prescribed thickness and does not completely cut off the groove of the wafer; the resin covering step uses a liquid resin having a thickness of 1.5 times to 5 times the height of the bump to cover the wafer where the groove is formed the front side; a resin hardening step of hardening the liquid resin after the resin coating step; and a grinding step of grinding the backside of the wafer to thin the wafer to the backside of the wafer after the resin hardening step. A predetermined thickness is obtained and the groove is exposed on the back surface, thereby dividing the wafer along the planned dividing line to form a plurality of device chips having a predetermined thickness.

Preferably, the wafer processing method further includes a step of arranging a protective sheet on the resin simultaneously with the resin covering step or after the resin covering step.

In the processing method of the present invention, since the liquid resin is cured by external stimuli such as ultraviolet irradiation or heating after the resin covering step is carried out, the resin with a thickness of 1.5 times to 5 times the height of the bump is bonded. The backside grinding of the wafer is carried out on the front side of the wafer, so the chip can be prevented from shaking during grinding, and the unevenness of the bumps can be eliminated by the hardened resin, and the transfer of the bumps to the grinding surface and the thickness of the wafer can be prevented. Deviation can prevent leakage of negative pressure during suction and holding.

Description of drawings

FIG. 1 is a perspective view of a semiconductor wafer having a plurality of bumps for each device.

2(A) is a cross-sectional view showing a groove forming step, and FIG. 2(B) is a cross-sectional view of a wafer after the groove forming step is completed.

(A) and (B) of FIG. 3 are sectional views explaining the resin covering step.

(A) and (B) of FIG. 4 are sectional views explaining the resin covering step.

Fig. 5 is a sectional view showing a resin hardening step.

(A) of FIG. 6 is a partial cross-sectional side view showing a grinding step, and FIG. 6(B) is a cross-sectional view after the grinding step is completed.

Fig. 7 is a sectional view showing a transferring step.

Fig. 8 is a cross-sectional view after the peeling step is performed.

Fig. 9 is a cross-sectional view illustrating a pick-up step.

Label description

11: semiconductor wafer; 12: cutting unit; 13: dividing line; 14: spindle; 15: device; 16: cutting tool; 17: bump; 18: supporting table; 20: protective sheet; 22: providing nozzle; 23: tank; 24: resin supply source; 25: device chip; 26: liquid resin; 28: holding table; 37: pressing mechanism; 40: ultraviolet lamp; 42: chuck table; 44: grinding unit; 40 : grinding wheel.

detailed description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1 , there is shown a perspective view of a semiconductor wafer (hereinafter, sometimes simply referred to as a wafer) 11 having a plurality of bumps for each device formed on the front surface.

The semiconductor wafer 11 is formed of silicon or a compound semiconductor, has a front surface 11a and a back surface 11b, and on the front surface 11a, a plurality of dividing lines (separation lanes) 13 are vertically formed, and are formed in respective regions divided by the dividing lines 13. There are devices 15 such as LSI.

As shown in the enlarged view of FIG. 1 , a plurality of protruding bumps 17 are formed on four sides of each device 15 . Since bumps 17 are formed on four sides of each device 15, the semiconductor wafer 11 has a device region (bump forming region) 19 in which bumps 17 are formed and a peripheral remaining region around device region 19 (bump not formed). area) 21.

The processing method of the wafer of the present invention is based on the processing method of dicing before Grinding (Dicing Before Grinding), so at first implement the groove forming step, on the front surface 11a of the wafer 11, form the predetermined depth along the planned dividing line 13 (completion of the chip) depth above the thickness) of the groove.

In the embodiment of the present invention, as shown in FIG. 2(A) , the groove forming step is performed by the cutting unit 12 of the cutting device. The cutting unit 12 includes: a main shaft 14 that is rotationally driven at high speed; and a cutting tool 16 that is fixed to the front end of the main shaft 14 .

In the groove forming step, the cutting tool 16 rotating at high speed is cut into a predetermined depth (a depth equal to or greater than the finished chip thickness) from the front surface 11a of the wafer 11 along the planned dividing line 13, and the wafer 11 is processed and fed, thereby, Grooves 23 having a predetermined depth are formed. The predetermined depth needs to be a depth at which the wafer 11 is not completely cut.

By index-feeding the cutting blade 16 , grooves 23 of a predetermined depth are formed along the planned dividing lines 13 extending in the first direction. Next, after the chuck table holding the wafer 11 is rotated by 90°, grooves 23 of a predetermined depth are formed along planned dividing lines 23 extending in a second direction perpendicular to the first direction. (B) of FIG. 2 shows a cross-sectional view of the wafer 11 after the groove forming step is completed.

In this embodiment, although the groove forming step is performed by a cutting device, it is also possible to irradiate the front surface 11a of the wafer 11 along the planned division line 13 with a laser beam having an absorbing wavelength (for example, 355 nm) to the wafer 11, and pass Grooves 23 of a predetermined depth are formed by ablation processing with a laser beam.

After the groove forming step is completed, a resin coating step is performed to cover the front surface 11 a of the wafer 11 on which the groove 23 is formed with a resin having a thickness of 1.5 times to 5 times the height of the bump 17 . This resin covering step will be described with reference to FIG. 3(A) to FIG. 4(B) .

First, as shown in FIG. 3(A) , a protective sheet 20 is disposed on a support table 18 , and a liquid resin 26 is supplied onto the protective sheet 20 from a supply nozzle 22 connected to a resin supply source 24 . The resin 26 is a resin that is cured by application of external stimuli. For example, an ultraviolet curable resin that is cured by irradiation of ultraviolet rays or a thermosetting resin that is cured by heating can be used. In this embodiment, ultraviolet curable resin is used as the liquid resin 26 .

After the liquid resin 26 is supplied to the protective sheet 20 supported on the supporting table 18, as shown in FIG. , and push the front 11 a side of the wafer 11 against the liquid resin 26 .

In (B) of FIG. 3 , the holding table 28 is composed of a housing 30 formed with a circular concave portion 30 a and a suction holding portion 32 , wherein the suction holding portion 32 is formed by fitting the circular concave portion 30 a of the housing 30 . Porous ceramics in the formation.

The suction holding unit 32 is selectively connected to a suction source 36 via a suction path 34 . The holding table 28 is connected to the supporting member 38 of the pressing mechanism 37 and is configured to be movable in the vertical direction by the pressing mechanism 37 .

In the pressing step, as shown in (B) of FIG. 3 and (A) of FIG. The front surface 11 a is pushed against the liquid resin 26 supplied onto the protective sheet 20 .

By this pushing, the liquid resin 26 spreads between the protective sheet 20 and the wafer 11, and as shown in FIG. The liquid resin 26 preferably has a thickness of 1.5 times to 5 times the height of the bump 17 .

By covering the front surface 11 a of the wafer 11 with the liquid resin having such a thickness, the unevenness of the bumps 17 is completely eliminated on the protection sheet 20 . In addition, the above-mentioned pressing step constitutes a part of the resin covering step.

In addition, in the above-mentioned embodiment, although the protective sheet 20 is arranged on the support table 18, and the liquid resin 26 is dropped on the protective sheet 20 to cover the front surface 11a of the wafer 11 with the resin 26, the protective sheet 26 does not It is not essential, and the protective sheet 20 may be omitted, and the liquid resin 26 may be directly supplied on the support table 18 to cover the front surface 11 a of the wafer 11 with the resin 26 . In this case, the upper surface of the support table 18 needs to be sufficiently flat, and the cured resin 26 needs to be easily peelable from the upper surface of the support table 18 .

After performing the resin coating step, a resin hardening step of hardening the liquid resin 26 is carried out. Since ultraviolet curable resin is used as resin 26 in this embodiment, as shown in FIG.

In addition, the supporting table 18 and the protective sheet 20 need to have a property of transmitting ultraviolet rays irradiated from the ultraviolet lamp 40 . When a thermosetting resin is used as the liquid resin 26 , the liquid resin 26 is heated to be cured.

After the resin hardening step has been performed, a grinding step is performed to thin the wafer 11 to a predetermined thickness by grinding the back surface 11b of the wafer 11, and the grooves 23 are exposed along the back surface 11b to form a pair of wafers along the planned dividing line 13. The wafer 11 is divided to form a plurality of device chips 25 having a predetermined thickness.

In the grinding step, after the resin hardening step shown in FIG. 5 is performed, as shown in FIG. 6(A), the protective sheet 20 peeled off from the support table 18 is placed on the chuck of the grinding device. On the stage 42, the wafer 11 is sucked and held by the chuck stage 42 through the protective sheet 20, and the back surface 11b of the wafer 11 is exposed.

In FIG. 6(A), the grinding unit 44 includes: the main shaft 16; the wheel mount 48, which is fixed on the front end of the main shaft 16; Installed on the wheel mount 48. The grinding wheel 50 is composed of an annular grinding wheel base 52 and a plurality of grinding stones 54 fixedly attached to the outer periphery of the lower end portion of the grinding wheel base 52 .

In the grinding step, while the chuck table 42 is rotated in the direction of the arrow a at, for example, 300 rpm, the grinding wheel 50 is rotated in the direction of the arrow b at, for example, 6000 rpm, and a grinding feed mechanism (not shown) is driven. The grinding stone 54 is pressed against the back surface 11 b of the wafer 11 to grind the back surface 11 b of the wafer 11 .

When the back surface 11b of the wafer 11 is ground and the wafer 11 is thinned to a predetermined thickness, the grooves 23 are exposed on the back surface 11b of the wafer 11 as shown in FIG. Chip 25. A cross-sectional view of the wafer 11 after the grinding step is shown in (B) of FIG. 6 .

In the grinding step of the present embodiment, since the plurality of bumps 17 formed on the front surface 11a of the wafer 11 are embedded in the resin 26 and the irregularities of the bumps 17 are completely absorbed by the resin 26, the back surface 11b of the wafer 11 can be processed. Grinding is performed to process the wafer 11 to a uniform thickness.

After the grinding step is performed, as shown in FIG. 7 , a transfer step is performed to bond the rear surface 11b of the wafer 11 to the adhesive tape T whose outer peripheral portion is attached to the ring frame F. Next, as shown in FIG. 8 , a peeling step is performed to peel the resin 26 and the protective sheet 20 from the front surface 11 a of the wafer 11 . Since the resin 26 is hardened by irradiation of ultraviolet rays, the resin 26 and the protective sheet 20 can be easily peeled off from the front surface 11 a of the wafer 11 .

After the peeling step is performed, as shown in FIG. 9 , a pick-up step is performed to pick up the device chip 25 from the adhesive tape T by a pick-up device not shown, and store the picked-up device chip 25 in a tray or the like.

Claims (2)

1. a kind of processing method of chip, positive each region that the chip is divided in a plurality of segmentation preset lines by intersecting to form Inside it is formed with device, and each device has prominent multiple salient points on front, the processing method of the chip is along this point Cut multiple device chips that preset lines are split to the chip and form defined thickness, the feature of the processing method of the chip It is, with the steps：

Groove forming step, from the front of chip along segmentation preset lines formation depth ratio defined thickness depth and not by chip The groove completely cut through；

Resin covering step, the groove will be formed with using the fluid resin of 1.5 times~5 times of thickness of the height with the salient point Chip the front covering；

Resin-hardening phase, after the resin covering step is implemented, hardens the fluid resin；And

Step is ground, after the resin-hardening phase is implemented, the back side of chip is ground and extremely should wafer thinning Defined thickness and the groove is exposed to the back side, thus chip is split along the segmentation preset lines and regulation is formed Thickness multiple device chips.

2. the processing method of chip according to claim 1, it is characterised in that

The processing method of the chip also there is following screening glass to arrange step：With the resin covering step while or implementing After the resin covering step, screening glass is arranged over the resin.