KR20190028301A - Processing method of wafer - Google Patents

Abstract

The present invention is to provide a method for processing a wafer, which is capable of performing an alignment process through a sealing material containing carbon black coated on a surface of a wafer. A method for processing a wafer, in which devices each having a plurality of bumps are formed on each region of a surface partitioned by a plurality of division-intended lines formed to cross each other, comprises: a cutting groove forming process for forming a cutting groove having the depth corresponding to the finishing depth of a device chip by means of a cutting blade along the division-intended line from a surface side of the wafer; a sealing process for, after performing the cutting groove forming process, sealing the surface of the wafer including the cutting groove by using a sealing material; a grinding process for, after performing the sealing process, exposing the sealing material in the cutting groove by grinding the wafer from the rear side of the wafer to the finishing thickness of the device chip; an alignment process for, after performing the grinding process, detecting an alignment mark by penetrating the sealing material through an infrared photographing means from the surface side of the wafer to photograph the surface side of the wafer, and detecting the division-intended line to be processed by a laser beam on the basis of the alignment mark; and a division process for, after performing the alignment process, irradiating the laser beam of a wavelength having absorption with respect to the sealing material along the division-intended line from the surface side of the wafer, and dividing the wafer into individual device chip having a surface and four sides surrounded by the sealing material by abrasion processing.

Description

[0001] PROCESSING METHOD OF WAFER [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of processing a wafer by processing a wafer to form a 5S mold package.

As a structure for realizing miniaturization and high-density mounting of various devices such as LSI and NAND type flash memory, for example, a chip size package (CSP) in which device chips are packaged in a chip size is provided for practical use, . In recent years, CSP, a so-called 5S mold package, in which not only the surface of the chip but also the entire side surface of the chip is sealed with a sealing material has been developed and put to practical use.

The conventional 5S mold package is manufactured by the following process.

(1) An external connection terminal called a device (circuit) and a bump is formed on the surface of a semiconductor wafer (hereinafter sometimes abbreviated as a wafer).

(2) The wafer is cut along the line to be divided from the front side of the wafer to form a cutting groove having a depth corresponding to the finish thickness of the device chip.

(3) The surface of the wafer is sealed with a sealing material containing carbon black.

(4) The back side of the wafer is ground to the finish thickness of the device chip to expose the sealing material in the cutting groove.

(5) Since the surface of the wafer is sealed with a sealing material containing carbon black, the sealing material at the outer peripheral portion of the wafer surface is removed to expose the alignment marks such as the target pattern, and based on this alignment mark, An alignment for detecting a line is performed.

(6) Based on the alignment, the wafer is cut along the line to be divided from the front side of the wafer, and the wafer is divided into a 5S mold package in which the front surface and the entire side surface are sealed with a sealing material.

As described above, since the surface of the wafer is sealed with the sealing material containing carbon black, devices formed on the wafer surface can not be seen by the naked eye at all. In order to solve this problem and enable alignment, as described in (5) above, the peripheral portion of the sealing material on the surface of the wafer is removed to expose an alignment mark such as a target pattern, (See Japanese Patent Application Laid-Open Nos. 2013-074021 and 2016-015438). [0004] The present invention has been made in view of the above circumstances.

[Patent Document 1] Japanese Patent Application Laid-Open No. 2013-074021 [Patent Document 2] JP-A-2016-015438

However, in the alignment method described in the above publication, a step of removing a sealing material on the outer peripheral portion of the wafer by mounting a cutting blade having a wide width for edge trimming on the spindle is required in place of the cutting blade for dicing, It takes time to remove the sealing material of the outer circumferential portion by the edge trimming, resulting in a problem of poor productivity.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of processing a wafer capable of performing an alignment process through a sealing material containing carbon black coated on a wafer surface.

According to the present invention, there is provided a method of processing a wafer in which a device having a plurality of bumps is formed in each region of a surface partitioned by a plurality of lines to be divided formed so as to cross each other, A cutting groove forming step of forming a cutting groove with a depth corresponding to the finishing thickness of the device chip by the blade; and a sealing step of sealing the surface of the wafer including the cutting groove with a sealing material after the cutting groove forming step is performed A grinding step of grinding the wafer from the back side of the wafer to the finishing thickness of the device chip to expose the sealing material in the cutting groove after the sealing step is performed; And the infrared rays are transmitted through the sealing material from the front surface side by the infrared ray imaging means, An alignment step of detecting an alignment mark and detecting the line to be divided to be laser-machined based on the alignment mark; and an alignment step of aligning the line to be divided And a dividing step of dividing the surface and the four side surfaces into individual device chips surrounded by the sealing material by ablation processing by irradiating the sealing material with a laser beam of a wavelength having absorbency, In the sealing step, the surface of the wafer is sealed by a sealing material having permeability through which infrared rays received by the infrared imaging means are transmitted.

Preferably, the infrared imaging means used in the alignment step includes an InGaAs imaging element.

According to the wafer processing method of the present invention, the surface of the wafer is sealed with a sealing material through which infrared rays received by the infrared ray imaging means are transmitted, the alignment mark formed on the wafer is transmitted through the sealing material by the infrared ray imaging means, Therefore, the alignment process can be carried out simply without removing the sealing material at the outer peripheral portion of the wafer surface as in the prior art. Therefore, the wafer can be divided into individual device chips by ablation processing by irradiating the sealing material with a laser beam having a water absorbing property from the surface side of the wafer along the line to be divided.

1 is a perspective view of a semiconductor wafer.
2 is a perspective view showing a first cutting groove forming process.
3 is a perspective view showing the sealing process.
4 is a partial cross-sectional side view showing the grinding process.
5 is a cross-sectional view showing the alignment process.
FIG. 6A is a cross-sectional view showing a dividing step, and FIG. 6B is an enlarged sectional view showing a dividing step.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1, there is shown a front side perspective view of a semiconductor wafer 11 (hereinafter simply referred to as a wafer) suitable for processing by the processing method of the present invention.

On the surface 11a of the semiconductor wafer 11, a plurality of lines 13 to be divided (streets) 13 are formed in a lattice shape, and IC, LSI And the like are formed.

Each of the devices 15 has a plurality of electrode bumps 17 (hereinafter may be simply referred to as bumps) 17 on the surface thereof. The wafers 11 are each provided with a plurality of bumps 17 A device region 19 formed with the device region 19 and an outer peripheral region 21 surrounding the device region 19 are provided on the surface thereof.

In the method of processing a wafer according to the embodiment of the present invention, firstly, as a first step, a cutting groove is formed along the line to be divided 13 from the front side of the wafer 11, A cutting groove forming step is performed. The cutting groove forming process will be described with reference to FIG.

The cutting unit 10 is provided with a cutting blade 14 detachably mounted on the distal end portion of the spindle 12 and an alignment unit 16 having an image pickup means (image pickup unit) The imaging unit 18 includes a microscope and a camera for imaging with visible light, and an infrared imaging device for imaging an infrared image. In this embodiment, an InGaAs imaging element is employed as an infrared imaging element.

The surface of the wafer 11 is picked up with visible light by the image pickup unit 18 to detect an alignment mark such as a target pattern formed on each device 15, Alignment to detect the line to be divided 13 to be cut is performed.

The cutting blade 14 rotating at a high speed in the direction of the arrow R1 is cut from the surface 11a side of the wafer 11 along the line to be divided 13 to a depth corresponding to the finish thickness of the device chip, A cutting groove forming step of forming the cutting grooves 23 along the line to be divided 13 is performed by transferring the chuck table (not shown) sucked and held by the chuck table 11 in the direction of the arrow X1.

This cutting groove forming step is carried out along the line to be divided 13 extending in the first direction while the cutting unit 10 is being indexed and transferred in the direction orthogonal to the machining feed direction X1 by the pitch of the dividing line 13 Conduct.

Subsequently, after the chuck table (not shown) is rotated by 90 degrees, the same cutting groove forming step is performed in order along the line to be divided 13 extending in the second direction orthogonal to the first direction.

The sealing material 20 is applied to the front surface 11a of the wafer 11 to form the surface 11a of the wafer 11 including the cutting groove 23 ) Is sealed with a sealing material. Since the sealing material 20 has fluidity, when the sealing step is performed, the sealing material 20 is filled in the cutting groove 23. [

As the sealing material 20, a composition including 10.3% by weight of epoxy resin or epoxy resin + phenol resin, 85.3% by silica filler, 0.1-0.2% by carbon black, and 4.2-4.3% by other components was used as the mass%. Other components include, for example, metal hydroxides, antimony trioxide, silicon dioxide and the like.

When the surface 11a of the wafer 11 is covered with the sealing material 20 having such a composition and the surface 11a of the wafer 11 is sealed with the sealing material 20, It is usually difficult to see the surface 11a of the wafer 11 through the sealing material 20. [

Here, the incorporation of carbon black in the sealing material 20 is mainly intended to prevent electrostatic breakdown of the device 15, and a sealing material not containing carbon black at present is not commercially available.

The method of applying the sealing material 20 is not particularly limited but it is preferable to apply the sealing material 20 to the height of the bumps 17 and then the sealing material 20 is etched by the etching, .

A grinding process is performed to expose the sealing material 20 in the first cut groove 23 by grinding the wafer 11 from the backside 11b side of the wafer 11 to the finished thickness of the device chip do.

This grinding process will be described with reference to Fig. The surface protection tape 22 is adhered to the surface 11a of the wafer 11 and the wafer 11 is sucked and held on the chuck table 24 of the grinding apparatus through the surface protective tape 22. [

The grinding unit 26 includes a spindle 30 rotatably received in a spindle housing 28 and rotationally driven by a motor not shown, a wheel mount 32 fixed to the tip of the spindle 30, And a grinding wheel 34 detachably mounted on the mount 32. The grinding wheel 34 is composed of an annular wheel base 36 and a plurality of grinding wheels 38 fixed to the outer periphery of the lower end of the wheel base 36.

In the grinding process, the chuck table 24 is rotated at, for example, 6000 rpm in the direction indicated by the arrow b while rotating the chuck table 24 at 300 rpm in the direction indicated by the arrow a, The grinding wheel 38 of the grinding wheel 34 is brought into contact with the rear face 11b of the wafer 11 by driving the mechanism.

Then, the back surface 11b of the wafer 11 is ground while the grinding wheel 34 is fed with a predetermined grinding downward at a predetermined grinding feed rate. The wafer 11 is ground to a predetermined thickness, for example, 100 占 퐉, while the thickness of the wafer 11 is measured by a contact or non-contact thickness gauge to expose the sealing material 20 buried in the cut groove 23.

The surface 11a of the wafer 11 is picked up by the infrared image pickup means from the surface 11a side of the wafer 11 through the sealing material 20 after the grinding process and is formed on the surface of the wafer 11 And an alignment step of detecting a line to be divided 13 to be laser-processed based on these alignment marks is performed.

This alignment process will be described in detail with reference to FIG. The outer peripheral portion of the back surface 11b side of the wafer 11 is bonded to the dicing tape T mounted on the annular frame F before the alignment process.

5, the wafer 11 is sucked and held in the chuck table 40 of the cutting apparatus through the dicing tape T, the surface 11a of the wafer 11 is sealed The sealing member 20 is exposed upward. Then, the annular frame (F) is clamped and fixed by the clamp (42).

In the alignment step, the surface 11a of the wafer 11 is imaged by the infrared imaging element of the imaging unit 18 of the same laser machining apparatus as the imaging unit 18 of the cutting apparatus shown in Fig. The sealing material 20 is formed of a sealing material through which the infrared rays received by the infrared ray imaging element of the image pickup unit 18 are transmitted so that at least two target patterns formed on the surface 11a of the wafer 11 by the infrared ray imaging element And the like can be detected.

Preferably, an InGaAs imaging element having high sensitivity is used as the infrared imaging element. Preferably, the image pickup units 18 and 18A are provided with exposures capable of adjusting the exposure time and the like.

Subsequently, the chuck table 40 is rotated in the &thetas; so that the straight line connecting these alignment marks is parallel to the processing transfer direction, and the chuck table 40 is machined by the distance between the alignment mark and the center of the line to be divided 13 (See Fig. 6 (A)) in the transfer direction X1 (see Fig. 6 (A)), thereby detecting the line to be divided 13 to be subjected to laser processing.

6 (A), the laser beam is focused from the surface 11a side of the wafer 11 along the line to be divided 13 to the laser head (light condenser) 46 of the laser processing apparatus A laser beam LB having an absorbing wavelength (e.g., 355 nm) is irradiated onto the sealing material 20 to form a laser machining groove 25 as shown in Fig. 6B by ablation processing And the wafer 11 is subjected to a dividing step in which the surface 11a and the four side surfaces of the wafer 11 are divided into individual device chips 27 straddled by the sealing material 20. [

This dividing step is sequentially performed along the dividing line 13 extending in the first direction and then the chuck table 40 is rotated by 90 degrees and the dividing line extending in the second direction orthogonal to the first direction 13, the wafer 11 is transferred to the surface 11a and the individual device chips 27 whose four sides are sealed by the sealing material 20, as shown in Fig. 6 (B) Can be divided.

Since the beam diameter of the laser beam LB used in the dividing step is smaller than the width of the cutting blade 14 used in the cutting groove forming step, the laser machining groove 25 shown in Fig. 6B is formed The side surface of the device chip 27 is sealed with the sealing material 20.

The device chip 27 thus manufactured can be mounted on the motherboard by flip chip bonding in which the front and back of the device chip 27 are inverted and the bumps 17 are connected to the conductive pads of the motherboard.

10: cutting unit 11: semiconductor wafer
13: Line to be divided 14: Cutting blade
15: Device 16: Alignment unit
17: electrode bumps 18, 18A: image pickup unit
20: sealing material 23: cutting groove
25: laser machining groove 26: grinding unit
27: device chip 34: grinding wheel
38: grinding stone 46: laser head (condenser)

Claims (2)

There is provided a method of processing a wafer in which devices each having a plurality of bumps are formed in respective regions of a surface partitioned by a plurality of lines to be divided,
A cutting groove forming step of forming a cutting groove having a depth corresponding to the finishing thickness of the device chip from the front side of the wafer by the cutting blade along the line to be divided,
A sealing step of sealing the surface of the wafer including the cut groove with a sealing material after performing the cutting groove forming step,
A grinding step of grinding the wafer from the back side of the wafer to the finishing thickness of the device chip after the sealing step to expose the sealing material in the cutting groove;
After the grinding process is performed, the sealing material is transmitted from the front side of the wafer by the infrared image pickup means to pick up the front side of the wafer to detect the alignment mark, and based on the alignment mark, An alignment step of detecting an alignment mark,
After the alignment step is performed, a laser beam of a wavelength having an absorbing property is applied to the sealing material from the surface side of the wafer along the line to be divided along the dividing line, and the surface and four sides of the sealing material are abraded And dividing the device chip into individual device chips,
Wherein in the sealing step, the surface of the wafer is sealed by a sealing material having permeability through which infrared rays received by the infrared imaging unit are transmitted. The method of processing a wafer according to claim 1, wherein the infrared imaging unit used in the alignment process includes an InGaAs imaging device.

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