TW201913776A - Method for processing wafer comprising a cutting groove forming step, a sealing step, a modifier layer forming step, a calibration step, a grinding step, and a cutting step - Google Patents

Abstract

The present invention is a wafer processing method, and its subject is to provide a wafer processing method that can perform a calibration process using a sealing material containing carbon black coated on the surface of the wafer. The solution means is a wafer processing method for forming a device having a plurality of protruding electrodes in each area of a surface divided by a plurality of predetermined dividing lines formed by crossing, including: from the surface side of the wafer, Along the planned dividing line, a cutting groove forming process for forming a cutting groove with a depth corresponding to the completed thickness of the device wafer is formed via a cutting blade, and after the cutting groove forming process is performed, the cutting groove is closed to close the groove containing the cutting groove The sealing process on the surface of the wafer, and after the sealing process is carried out, from the surface side of the wafer, through the sealing material through visible light photography means, the alignment mark is detected, and the thunder is detected based on the alignment mark After the calibration process of the predetermined dividing line of the laser processing and the implementation of the calibration process, for the sealing material, the collecting point of the laser beam with a transparent wavelength is positioned on the sealing material in the cutting groove Inside, from the surface side of the wafer, a laser beam is irradiated along the planned dividing line to form a reforming layer forming process of the reforming layer inside the sealing material in the cutting groove, and the reforming is carried out After the layer formation process, from the back side of the wafer to the completed thickness of the device wafer, the grinding process of grinding the wafer to expose the sealing material in the cutting trench, and after performing the grinding process, the cutting process The sealing material in the trench is given an external force, and the modified layer is used as a starting point for division, and is divided into the dividing process of the device wafer surrounding each of the surface and the four sides through the sealing material; in the calibration process, the The range of photography by means of visible light photography is implemented while obliquely irradiating light from oblique light.

Description

Wafer processing method

The invention relates to a method for processing a wafer to form a 5S molded package wafer.

As a structure for realizing miniaturization and high-density mounting of various devices such as LSI or NAND flash memory, for example, a chip size package (CSP) that packages device chips in a chip size is provided for practical use and is widely used in mobile Phone or smartphone etc. Moreover, in this CSP in recent years, not only the surface of the wafer but also the entire side of the CSP is closed with a sealing material, so-called 5S molded package is put into practical use.

The conventional 5S molded package was produced through the following process.　　 (1) On the surface of a semiconductor wafer (hereinafter, abbreviated as a wafer), external connection terminals called devices (circuits) and bump electrodes are formed.　　 (2) From the surface side of the wafer, the wafer is cut along the planned dividing line to form a cutting groove with a depth corresponding to the completed thickness of the device wafer.　　 (3) The surface of the wafer is sealed with a sealing material doped with carbon black.　　 (4) Grind the back side of the wafer to the finished thickness of the device wafer to expose the sealing material in the cutting groove. (5) The surface of the wafer is sealed with a sealing material doped with carbon black. The sealing material on the outer peripheral part of the wafer surface is removed to expose the alignment marks of the target pattern etc. According to the alignment marks Perform calibration to detect the planned dividing line.　　 (6) According to the calibration, the wafer is cut along the planned dividing line from the surface side of the wafer, and divided into 5S molded packages that close the surface and all sides with a sealing material.

As described above, the surface of the wafer is sealed with a sealing material containing carbon black, and devices formed on the surface of the wafer cannot be seen with the naked eye. In order to solve this problem, calibration can be performed, and as described in (5) above, the applicant developed the outer peripheral portion of the sealing material on the wafer surface to expose the alignment marks of the target pattern and the like, according to this pair A technique to detect the planned dividing line to be cut with reference marks and perform calibration (refer to Japanese Patent Laid-Open No. 2013-074021 and Japanese Patent Laid-Open No. 2016-015438). [Prior Technical Literature] [Patent Literature]

[Patent Literature 1] Japanese Patent Application Publication No. 2013-074021 　　 [Patent Literature 2] Japanese Patent Application Publication No. 2016-015438

[Problem to be solved by invention]

However, in the calibration method described in the above-mentioned publication, instead of cutting blades for cutting, a cutting blade with a wide width for edging and trimming is mounted on the mandrel, and the process of removing the sealing material on the outer peripheral portion of the wafer is necessary However, through the exchange of cutting inserts and edging and trimming, the man-hours for removing the closing material of the outer peripheral part are costly and have a problem of poor productivity.

The present invention is based on such a configuration, and its object is to provide a wafer processing method that can perform a calibration process using a sealing material including carbon black coated on the surface of the wafer. [Means to solve the problem]

According to the present invention, there is provided: a method of processing a wafer for forming a device having a plurality of protruding electrodes in each range of a surface divided by a plurality of planned dividing lines formed by crossing, characterized by comprising: On the surface side of the circle, a cutting groove forming process for forming a cutting groove with a depth corresponding to the completed thickness of the device wafer along the planned dividing line through the cutting blade, and after the cutting groove forming process is carried out, is enclosed with a sealing material The sealing process of the surface of the wafer of the cutting trench, and after the sealing process is carried out, from the surface side of the wafer, through the visible light photography means, through the sealing material, an alignment mark is detected, based on the alignment mark After finding out the calibration process of the predetermined dividing line to be processed by laser, and after implementing the calibration process, for the sealing material, the collecting point of the laser beam with a transparent wavelength is positioned in the cutting groove In the inside of the sealing material, a laser beam is irradiated from the surface side of the wafer along the planned dividing line to form a modified layer inside the sealing material in the cutting groove. And after performing the reforming layer forming process, from the back side of the wafer to the completed thickness of the device wafer, grinding the wafer to expose the sealing material in the cutting trench, and carrying out the grinding process After that, the sealing material in the cutting trench is given an external force, and the modified layer is used as a division starting point, and the device is divided into the device wafers with the surface and the 4 sides surrounded by the sealing material; Among them, a method of processing a wafer while irradiating light obliquely through oblique light means in a range photographed through the visible light photography means. [Effect of the invention]

According to the wafer processing method of the present invention, since the light is obliquely irradiated from the oblique light means, the alignment mark formed on the wafer is detected through the sealing material through visible light photography means, and then according to the Therefore, the calibration can be carried out without the need to remove the sealing material on the outer peripheral part of the wafer surface, and the calibration process can be carried out simply.

Therefore, for the sealing material, a laser beam having a transparent wavelength is positioned inside the sealing material in the cutting groove, and the laser beam is irradiated from the wafer surface side to form a modified layer on the sealing material Inside, from the back side of the wafer to the completed thickness of the device wafer, the wafer is ground to expose the sealing material in the cutting groove, and when the external material is applied to the sealing material, the modified layer is used as a division As a starting point, the wafer can be divided into device wafers surrounded by the sealing material and each of the surface and the four sides.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. When referring to FIG. 1, a surface side oblique view of a semiconductor wafer (hereinafter, abbreviated as a wafer) 11 suitable for processing by the processing method of the present invention is shown.

On the surface 11a of the semiconductor wafer 11, a plurality of planned dividing lines (dicing lines) 13 are formed in a lattice shape, and for each range divided by orthogonal dividing lines 13, IC, LSI, etc. are formed装置15。 Device 15.

The surface of each device 15 has a plurality of electrode bumps (hereinafter, abbreviated as a bump electrode) 17, and the wafer 11 has a plurality of bumps 17 formed with a plurality of bump electrodes 17 formed on its surface. The device range 19 of the device 15 and the remaining range 21 around the device range 19.

In the wafer processing method according to the embodiment of the present invention, first, as the first step, a depth equivalent to the completed thickness of the device wafer is formed from the surface side of the wafer 11 along the line to be divided 13 through a cutting blade via a cutting blade The cutting groove forming project of the cutting groove. The cutting groove forming process will be described with reference to FIG. 2.

The cutting unit 10 includes a cutting blade 14 that can be detachably attached to the front end of the mandrel 12, and a calibration unit 16 having a visible light photography means (visible light photography unit) 18. The photographing unit 18 is equipped with a microscope and a camera for photographing with visible light.

Before performing the cutting groove formation process, the photographing unit 18 photographs the surface of the wafer 11 with visible light, finds out the alignment marks of the target pattern formed in each device 15, and performs inspection based on the alignment marks The alignment of the planned dividing line 13 is cut out.

After the calibration is performed, the cutting blade 14 rotating at a high speed in the direction of 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 completed thickness of the device wafer, and the wafer is held by suction When the chuck processing (not shown in FIG. 11) is transferred to the direction of the arrow X1, a cutting groove forming process for forming a cutting groove 23 along the planned dividing line 13 is performed.

In this cutting groove forming process, the distance between each planned dividing line 13 is calculated and the conveying and cutting unit 10 is sequentially executed along the planned dividing line 13 extending in the first direction while being orthogonal to the processing conveying direction X1.

Next, after rotating a chuck (not shown) at 90°, the same cutting groove forming process is sequentially performed along the planned dividing line 13 extending in the second direction orthogonal to the first direction.

After the cutting groove forming process is performed, as shown in FIG. 3, the sealing material 20 is applied to the surface 11 a of the wafer 11, and the sealing process of closing the surface 11 a of the wafer 11 including the cutting groove 23 with the sealing material is performed. The sealing material 20 has fluidity. When the sealing process is performed, the cutting groove 23 is filled with the sealing material 20.

The sealing material 20 is made up by mass%, including epoxy resin or epoxy resin + phenol resin 10.3%, silica filler 85.3%, carbon black 0.1~0.2%, other components 4.2~4.3%. Examples of other component systems include metal hydroxides, antimony trioxide, and silicon dioxide.

The surface 11a of the wafer 11 is covered with the sealing material 20 composed in this way. When the surface 11a of the wafer 11 is closed, the sealing material 20 becomes black through a very small amount of carbon black contained in the sealing material 20. It is usually difficult to see the surface 11a of the wafer 11.

Here, the case where carbon black is mixed into the sealing material 20 is mainly to prevent the electrostatic destruction of the device 15, and currently there is no commercially available sealing material that does not contain carbon black.

The coating method of the sealing material 20 is not particularly limited, but it is preferable to apply the sealing material 20 to the height of the protruding electrode 17. Next, the sealing material 20 is etched by etching to expose the protruding electrode 17.

After the sealing process is carried out, from the surface 11a side of the wafer 11, the surface 11a of the wafer 11 is photographed through the sealing material 20 through visible light photography means, and at least two targets formed on the surface 11a of the wafer 11 are detected The alignment marks of the pattern and the like are used to perform the calibration process of detecting the predetermined dividing line 13 to be processed by laser based on the alignment marks.

This calibration process will be described in detail with reference to FIG. 4. Before performing the calibration process, on the back surface 11b side of the wafer 11, a dicing tape T attached with an outer peripheral portion to the ring-shaped frame F is attached.

In the calibration process, as shown in FIG. 4, by cutting the tape T, the wafer 11 is attracted and held by the chuck 40 of the laser processing apparatus, and the sealing material 20 closing the surface 11 a of the wafer 11 is exposed above. Then, the ring frame F is clamped and fixed by the clamp 42.

In the calibration process, the surface 11a of the wafer 11 is photographed with a photographic element such as a CCD of the visible light photographing unit 18A of the laser processing apparatus similar to the visible light photographing unit 18 of the cutting device. However, the sealing material 20 contains silicon dioxide filler, carbon black, etc., and the surface of the sealing material 20 has irregularities. In the vertical illumination of the visible light photography unit 18A, even through the sealing The material 20 and the surface 11a of the wafer 11 are photographed, and the photographic image is also out of focus, and it is difficult to detect alignment marks such as target patterns.

Therefore, in the calibration process of this embodiment, the vertical illumination of the visible light photography unit 18A is added from the oblique light means 31 to irradiate the light from the oblique angle to the photographic range to improve the defocus of the photographic image as a detectable alignment mark .

The light irradiated from the oblique light means 31 is preferably white light, and the incident angle to the surface 11a of the wafer 11 is preferably in the range of 30° to 60°. Ideally, the visible light photography unit 18A is provided with an exposure unit that can adjust the exposure time and the like.

Then, the straight line connecting these alignment marks is parallel to the processing conveying direction, θ rotates the chuck 40, and furthermore, by cutting only the distance between the alignment mark and the center of the planned dividing line 13, the cutting shown in FIG. 2 is cut. When the unit 10 moves in a direction orthogonal to the processing conveying direction X1, the planned dividing line 13 to be cut is found.

After the calibration process is performed, as shown in FIG. 5(A), from the surface 11a side of the wafer 11, along the planned dividing line 13, from the laser head (concentrator) 46 of the laser processing apparatus, the sealing material In terms of 20, a laser beam LB having a transmissive wavelength (for example, 1064 nm), locates its light collecting point inside the sealing material 20 in the cutting groove 23 and irradiates it, and transmits the chuck 40 in the direction of arrow X1 by processing At this time, a reforming layer forming process for forming the reforming layer 25 shown in FIG. 5(B) inside the sealing material 20 in the cutting groove 23 is performed.

After the modified layer forming process is carried out in sequence along the line 13 for dividing in the first direction, the chuck 40 is rotated 90° along the line for dividing in the second direction extending in the first direction Line 13 is implemented sequentially.

After the modified layer formation process is performed, the wafer 11 is ground from the back surface 11 b side of the wafer 11 to the completed thickness of the device wafer, and the grinding process of exposing the sealing material 20 in the cutting groove 23 is performed.

The grinding process will be described with reference to FIG. 6. The protection member 22 such as a surface protection tape is attached to the surface 11 a of the wafer 11, and the wafer 11 is attracted and held by the protection member 22 by the chuck 24 of the grinding device.

Grinding unit 26 includes: a mandrel 30 that is rotatably accommodated in a spindle sleeve 28 and not shown, a spindle 30 that is driven to rotate, and a disk holder 32 that is fixed to the front end of the spindle 30, and is detachable to the disk The grinding wheel 34 is installed on the base 32. The grinding wheel 34 is composed of a ring-shaped runner base 36 and a plurality of grinding stones 38 fixedly mounted on the outer periphery of the lower end of the runner base 36.

In the grinding process, the chuck 24 is rotated in the direction indicated by the arrow a, for example, at 300 rpm, and the grinding wheel 34 is rotated in the direction indicated by the arrow b, for example, at 6000 rpm, and the drive is not shown. The grinding unit transfer mechanism shown here makes the grinding stone 38 of the grinding wheel 34 contact the back surface 11b of the wafer 11.

Then, the grinding wheel 34 is ground and conveyed at a specific grinding transfer speed at a specific grinding transfer speed below, and the back surface 11b of the wafer 11 is ground. While measuring the thickness of the wafer 11 with a contact or non-contact thickness gauge, the wafer 11 is ground to a specific thickness, for example, 100 μm, to expose the sealing material 20 buried in the cutting groove 23.

After the grinding process is implemented, the dividing device 50 shown in FIG. 7 is used to apply an external force to the wafer 11, and a dividing step of dividing the wafer 11 into the device wafers 27 is performed. The dividing device 50 shown in FIG. 7 is provided with a frame holding means 52 for holding the ring-shaped frame F, and a tape expansion for expanding the cutting tape T mounted on the ring-shaped frame F held by the frame holding means 52 Means 54.

The frame holding means 52 is composed of an annular frame holding member 56 and a plurality of clamps 58 as fixing means arranged on the outer periphery of the frame holding member 56. The upper surface of the frame holding member 56 forms a mounting surface 56a on which the ring-shaped frame F is placed, and the ring-shaped frame F is placed on this mounting surface 56a.

In addition, the ring-shaped frame F placed on the mounting surface 56 a is fixed to the frame holding means 56 via the clamp 58. The frame holding means 52 thus constituted is supported by the tape expansion means 54 so as to be movable in the up-down direction.

The tape expansion means 54 includes an expansion cylinder 60 disposed inside the ring-shaped frame holding member 56. The upper end of the expansion cylinder 60 is closed by the cover 62. The expansion cylinder 60 has an inner diameter smaller than the inner diameter of the ring-shaped frame F, and a larger inner diameter than the outer diameter of the wafer 11 attached to the dicing tape T mounted on the ring-shaped frame F.

The expansion cylinder 60 has a support flange 64 integrally formed at the lower end thereof. The tape expansion means 54 is further provided with driving means 66 for moving the ring-shaped frame holding member 56 in the vertical direction. The driving means 66 is composed of a plurality of pneumatic cylinders 68 disposed on the supporting flange 64, and the piston load portion 70 is connected to the lower surface of the frame holding member 56.

The driving means 66 composed of a plurality of air cylinders 68 is a reference position where the ring-shaped frame holding member 56 is at the same height as the surface of the cover 62 whose mounting surface 56a is the upper end of the expansion cylinder 60 , And move to the up and down direction between the expansion positions where the upper end of the expansion cylinder 60 is below a certain amount.

The division process of the wafer 11 performed using the division device 50 configured as described above will be described with reference to FIG. 8. As shown in FIG. 8(A), the ring-shaped frame F supporting the wafer 11 by the dicing tape T is placed on the mounting surface 56a of the frame holding member 56 and then fixed to the clamp 58 Frame holding member 56. At this time, when the frame holding member 56 is positioned on its mounting surface 56a, it becomes a reference position at the same height as the upper end of the expansion cylinder 60.

Next, the pneumatic cylinder 68 is driven to lower the frame holding member 56 to the expanded position shown in FIG. 8(B). As a result, the ring frame F fixed on the mounting surface 56a of the frame holding member 56 is lowered, and the cutting tape T mounted on the ring frame F abuts against the upper edge of the expansion cylinder 60 It mainly expands in the radial direction.

As a result, a tensile force acts radially on the wafer 11 attached to the dicing tape T. In this way, when the tensile force is generated radially on the wafer 11, the modified layer 25 in the sealing material 20 formed in the cutting groove 23 along the planned dividing line 13 becomes the starting point for the division, while the wafer 11 The modified layer 25 is cut as shown in the enlarged view of FIG. 9, and then divided into device wafers 27 around the surface and the four sides via the sealing material 20.

10‧‧‧Cutting unit

11‧‧‧Semiconductor wafer

13‧‧‧schedule

14‧‧‧Cutting insert

15‧‧‧ Installation

16‧‧‧Calibration unit

17‧‧‧Electrode bump

18.18A‧‧‧Photography unit

20‧‧‧Enclosure

23‧‧‧Cutting groove

25‧‧‧ Modified layer

26‧‧‧ Grinding unit

27‧‧‧Device chip

31‧‧‧oblique light means

34‧‧‧ Grinding wheel

38‧‧‧Grinding stone

46‧‧‧Laser head (light collector)

50‧‧‧splitting device

FIG. 1 is a perspective view of a semiconductor wafer.　　 Figure 2 is a perspective view showing the cutting groove formation process.　　 Figure 3 is a perspective view showing a closed project.　　 Figure 4 is a cross-sectional view showing the calibration process. FIG. 5(A) is a cross-sectional view showing the reforming layer forming process, and FIG. 5(B) is an enlarged cross-sectional view of a part of the wafer after the reforming layer forming process is implemented.　　 Figure 6 is a cross-sectional view showing the grinding process.　　 Figure 7 is a perspective view of the dividing device.　　 Figure 8 is a cross-sectional view showing the division step. FIG. 9 is an enlarged cross-sectional view of a part of the wafer after the division step is performed.

Claims (1)

A wafer processing method is a wafer processing method for forming a device having a plurality of protruding electrodes in each range of a surface divided by a plurality of predetermined dividing lines formed by crossing, and is characterized by having: 　　From this On the surface side of the wafer, a cutting groove forming process for forming a cutting groove with a depth corresponding to the completed thickness of the device wafer along the planned dividing line is performed, and after performing the cutting groove forming process, it is closed with a sealing material After the sealing process of the surface of the wafer containing the cutting groove, after the sealing process is performed, from the surface side of the wafer, through the visible light photography means, an alignment mark is detected through the sealing material, and the alignment mark is determined according to the alignment Mark to find out the calibration process of the planned dividing line that should be processed by laser, and after implementing the calibration process, locate the collecting point of the laser beam of a wavelength that is transparent to the sealing material in the cutting groove In the inside of the sealing material, a laser beam is irradiated from the surface side of the wafer along the planned dividing line to form a modified layer inside the sealing material in the cutting groove. And after carrying out the modified layer forming process, grinding the wafer from the back side of the wafer to the completed thickness of the device wafer to expose the sealing material in the cutting trench, and after carrying out the grinding process , Giving the external force to the sealing material in the cutting trench, using the modified layer as a starting point for division, and dividing the device into a device wafer with a surface and four sides surrounded by the sealing material; 　　The calibration process is based on the The range of photography by visible light photography means is implemented while illuminating light obliquely through oblique light means.