JP2015070267A - Scribe line-forming method of wafer laminate for image sensor, and scribe line-forming device of wafer laminate for image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scribe line-forming method of a wafer laminate for an image sensor and a scribe line-forming device of the wafer laminate for the image sensor, by and with which the wafer laminate for the image sensor can be parted effectively and finely according to a dry-system simple technique without using a dicing saw.SOLUTION: A wafer laminate W for an image sensor is structured by bonding a glass wafer 1 and a silicon wafer 2 by a resin layer 4 which is disposed so as to surround photodiode formation regions 3. A scribe line-forming method of the wafer laminate W for the image sensor and a scribe line-forming device are disclosed. The scribe line-forming method includes: forming a scribe line S1 by pressing/rolling a scribing wheel 10 along a predetermined parting line on a top face of the glass wafer 1; and next forming a scribe line S2 by pressing/rolling a diamond point cutter 25 including a protrusive blade point 25b on a tip of a blade body 25a along a predetermined parting line on an outer surface of the silicon wafer 2.

Description

The present invention relates to a scribe line forming method and a scribe line forming apparatus for separating a wafer laminate in which a wafer level package of a CMOS image sensor is patterned.

  In recent years, the use of CMOS image sensors has been rapidly increasing in various small electronic devices such as mobile phones, digital cameras, and optical mice where low power, high functionality, and high integration are important.

FIG. 8 is a sectional view schematically showing a configuration example of a wafer level package (chip size unit product) W1 of the CMOS image sensor. The wafer level package W1 has a laminated structure in which a (separated) glass wafer 1 and a (separated) silicon wafer 2 are bonded with a resin partition 4 interposed therebetween.
A photodiode region (sensing region) 3 is formed on the upper surface (joint surface side) of the silicon wafer 2, and the photodiode region 3 is provided by arranging the periphery so that the resin partition 4 surrounds in a lattice shape. The inner space is made airtight. Further, a metal pad 5 is formed on the upper surface of the silicon wafer 2 (outside the photodiode region 3), and a via (through hole) penetrating the silicon wafer 2 vertically below the portion where the metal pad 5 is formed. ) 6 is formed. The via 6 is filled with a conductive material 7 having excellent electrical conductivity, and a solder bump 8 is formed at the lower end of the via 6. The structure in which the via 6 is formed and the conductive material 7 is filled to make electrical connection is referred to as TSV (Through Silicon Via).
A PCB substrate or the like (not shown) on which a predetermined electric circuit is patterned is bonded to the lower surface of the solder bump 8 described above.

  As shown in FIGS. 8 to 10, the wafer level package W <b> 1, which is a chip-sized unit product, has a large-area glass wafer 1 and a large-area silicon wafer 2 bonded together via a resin partition 4. On the wafer stack W, a large number of patterns are formed by being divided into a lattice pattern by dividing lines L extending in the XY direction, and the wafer stack W is divided along the scheduled cutting lines L. Thus, the wafer level package W1 having a chip size (separated) is obtained.

  By the way, dicing saws as shown in Patent Documents 1 to 4 have been used in the past, including those for CMOS image sensors, in the process of dividing a silicon wafer into a product of a wafer level package. The dicing saw includes a rotating blade that rotates at a high speed, and is configured to perform cutting while spraying a cutting fluid that cools the rotating blade and cleans cutting waste generated during cutting onto the rotating blade.

JP-A-5-090403 JP-A-6-244279 JP 2002-224929 A JP 2003-051464 A

  Since the above-mentioned dicing saw is divided by cutting using a rotating blade, a large amount of cutting waste is generated, and even if the cutting fluid is cleaned with cutting fluid, a part of the cutting fluid remains or is scattered during cutting. As a result, cutting scraps may adhere to the package surface, which is a major cause of deterioration in quality and yield. Further, since a mechanism and piping for supplying the cutting fluid and collecting the waste fluid are required, the apparatus becomes large. In addition, since the glass wafer is cut by cutting, small chipping (chips) often occurs on the cut surface, and a clean cut section cannot be obtained. In addition, since the cutting edge of the rotating blade rotating at high speed is formed in a sawtooth shape or a continuous uneven shape, the cutting edge tends to be worn or damaged, and the service life is short. Furthermore, the thickness of the rotating blade cannot be made very thin from the viewpoint of strength, and even if it has a small diameter, it is formed with a thickness of 60 μm or more. There were problems such as being one of the limiting factors.

Accordingly, the present invention provides a method for forming a scribe line for an image sensor wafer package that can solve the above-described conventional problems, and can be effectively and cleanly divided by a simple dry method without using a dicing saw. An object of the present invention is to provide an apparatus for the same.

In order to achieve the above object, the present invention takes the following technical means. That is, in the scribe line forming method of the present invention, a glass wafer and a silicon wafer in which a plurality of photodiode formation regions are vertically and horizontally patterned are disposed through a resin layer arranged so as to surround each photodiode formation region. A method for forming a scribe line for a wafer laminate for an image sensor having a bonded structure, wherein a glass scribing wheel having a cutting edge having a predetermined cutting edge angle along a circumferential ridgeline is formed on the outside of the glass wafer. A glass scribing step for forming a scribe line on the outer surface of the glass wafer by rolling it while pressing along a planned cutting line on the surface, and a diamond point cutter having a protruding blade tip made of diamond at the tip, or Circumferential ridgeline than the glass scribing wheel A scribing line is formed on the outer surface of the silicon wafer by moving or rolling a silicon scrubbing wheel having a cutting edge with a small cutting edge angle along the planned cutting line on the outer surface of the silicon wafer. silicon scribing step of forming was set to be closed. Next to the glass scribe step and the silicon scribe step, the wafer laminated body is bent and pressed by pressing a pressing member along the scribe line from the outer surface side of the silicon wafer or the outer surface side of the glass wafer. You may make it have a cutting process which cuts a wafer and a silicon wafer along each scribe line.
Here, the pressing member may be pressed from the outer surface side of the silicon wafer or may be pressed from the outer surface side of the glass wafer. However, since the glass wafer generally tends to be less likely to be divided, It is preferable to press from the surface side.
In addition, either the glass scribe process or the silicon scribe process may be executed first, and the outer surface of the glass wafer and the outer surface of the silicon wafer may be scribed simultaneously. When the pressing member is pressed against the surface, it is preferable to perform the glass scribing step first from the viewpoint of inversion of the wafer stack.

Further, the scribe line forming apparatus of the present invention made from another point of view is arranged so that a glass wafer and a silicon wafer in which a plurality of photodiode forming regions are patterned vertically and horizontally surround each of the photodiode forming regions. A scribe line forming apparatus for a wafer laminated body for an image sensor having a structure bonded through a resin layer, the glass wafer comprising a ring body and having a predetermined edge angle along a circumferential ridgeline By rolling while pressing along the planned cutting line of the outer surface of the glass, a glass scribing wheel that forms a scribe line on the outer surface of the glass wafer, and a protruding blade edge made of diamond is formed at the tip, By moving while pressing along the dividing line on the outer surface of the silicon wafer, The diamond point cutter that forms a scribe line on the outer surface of the recon wafer, or the edge angle along the circumferential ridge line is smaller than the scribing wheel for glass, while pressing along the planned cutting line on the outer surface of the silicon wafer And a silicon scrubbing wheel that forms a scribe line on the outer surface of the silicon wafer by rolling . The wafer laminate is bent by pressing along the scribe line from the outer surface side of the silicon wafer or the outer surface side of the glass wafer, and the glass wafer and the silicon wafer are moved along the respective scribe lines. it may be provided with a pressing member for dividing Te.
In the present invention, the glass scribing wheel is a scribing wheel in which grooves or notches are formed along a circumferential ridge line, and the remaining ridge line (protrusion) serves as a cutting edge. The scribing wheel may have a good extension (penetration) in the thickness direction of the glass wafer along the vertical crack formed along the line, and the groove and notch are not formed along the circumferential ridge line. A scribing wheel may be used. The glass scribing wheel preferably has a blade tip angle (blade edge angle) in a cross section perpendicular to the circumferential ridgeline, for example, from 95 degrees to 155 degrees.
On the other hand, the silicon scribing wheel is a normal scribing wheel in which grooves and notches are not formed along the circumferential ridgeline, and the cutting edge angle is smaller than the cutting edge angle of the glass scribing wheel (for example, The blade edge angle is preferably 85 to 135 degrees.
In addition, although the preferable range of the scribing wheel for glass and the scribing wheel for silicon described above partially overlaps (95 degrees to 135 degrees), even if a wheel in this numerical range is used, it is for silicon. It is necessary to use a pair of wheels combined such that the cutting edge angle of the scribing wheel is relatively smaller than the cutting edge angle of the glass scribing wheel.

  According to the present invention, the pressing member is divided along the scribe line formed on each of the glass wafer and the silicon wafer, so that a large cutting width as in the case of cutting a conventional dicing saw is obtained. The material can be used effectively without the need. Moreover, generation | occurrence | production of chipping, a chip | tip, etc. like the case by cutting can be suppressed, and it can divide with a yield with a clean cut surface. In particular, when a diamond point cutter is used for scribing a silicon wafer, a scribe line can be formed on the silicon wafer with a low load coupled with the diamond point cutter being a fixed blade. There is also an advantage that unnecessary wrinkles such as chipping are hardly formed on the end face. In addition, when using a silicon scribing wheel for silicon wafer scribing, a silicon scribing wheel having a cutting edge angle smaller than that of the glass scribing wheel can be used to create a scribe line at a relatively low load. Since it can be formed, generation of unnecessary wrinkles such as chipping on the cut end surface of the silicon wafer can be suppressed.

  In particular, in the present invention, the cutting fluid such as a conventional dicing saw is not used, and the cutting is performed in a dry environment. Therefore, the mechanism and piping for supplying the cutting fluid and collecting the waste fluid can be omitted, and the cutting is performed. Subsequent washing and drying steps can be omitted, and the apparatus can be made compact. In addition, the scribing wheel formed with a ring body having a cutting edge along the circumferential ridgeline and the diamond point cutter with a blade edge made of diamond at the tip of the blade body are more difficult than conventional rotating blades that are prone to tooth spilling. Since the service life is long, the running cost can be reduced.

The figure which shows the 1st step (the scribe line formation step of a glass wafer) of the scribe line formation method of this invention. The figure which shows the 2nd stage (scribe line formation stage of a silicon wafer) of the scribe line formation method of this invention. The figure which shows the division | segmentation step along the scribe line by the scribe line formation method of this invention. The figure which shows another Example of FIG. The figure which shows the scribing wheel used for this invention, and its holder part. The figure which shows the diamond point cutter and its holder part used for this invention. The schematic front view of the scribe mechanism used for this invention. Sectional drawing which shows an example of the wafer level package for CMOS image sensors. Sectional drawing which shows a part of wafer laminated body for CMOS image sensors used as a base material. FIG. 9 is a schematic plan view showing the CMOS image sensor wafer laminate of FIG. 8.

Hereinafter, details of the method for dividing a wafer laminate for an image sensor according to the present invention will be described with reference to the drawings.
FIG. 1 shows a partial cross section of a wafer laminate W for a CMOS image sensor to be processed, which is the first stage of the cutting method of the present invention. The structure of the wafer stack W is basically the same as that shown in FIGS.
That is, a glass wafer 1 having a large area (for example, 8 inches in diameter) serving as a base and a silicon wafer 2 disposed on the lower surface side of the glass wafer 1 are bonded via a lattice-shaped resin partition 4.
A photodiode formation region (sensing region) 3 is provided on the upper surface (bonding surface side) of the silicon wafer 2. A photodiode array is formed in the photodiode region 3 and functions as a light receiving surface of the image sensor. In the vicinity of the photodiode region 3, a metal pad 5 is formed, and a via (through hole) 6 penetrating the silicon wafer 2 in the vertical direction is formed immediately below the portion where the metal pad 5 is formed. The via 6 is filled with a conductive material 7 having excellent electrical conductivity (TSV), and a solder bump 8 is formed at the lower end of the via 6. A PCB substrate or the like (not shown) on which a predetermined electric circuit is patterned is bonded to the lower surface of the solder bump 8 described above.
As shown in FIG. 10, the CMOS image sensor wafer stack W is divided into pieces by being cut along a grid-like cutting planned line L extending in the XY direction, and is a chip-sized unit product. A certain wafer level package W1 is taken out.

Next, a parting procedure will be described. When the wafer stack W is cut along the line L to be cut in FIG. 10, first, the scribe line S1 is processed on the surface of the glass wafer 1 using the scribing wheel 10 as shown in FIG.
The scribing wheel 10 is formed of a material having excellent tool characteristics such as cemented carbide or sintered diamond, and a cutting edge 10a is formed on a circumferential ridgeline (outer peripheral surface). Specifically, it is preferable to use one having a diameter of 1 to 6 mm, preferably 1.5 to 4 mm, and a cutting edge angle of 85 to 150 degrees, preferably 105 to 140 degrees. It is appropriately selected according to the type.
The scribing wheel 10 is for glass, is rotatably supported by the holder 11, and is attached to the scribe head 24 (see FIG. 7) of the scribe mechanism A via the elevating mechanism 12.

  The scribe mechanism A includes a table 15 on which the wafer stack W is placed and held. The table 15 can move in the Y direction (front-rear direction in FIG. 7) along the horizontal rail 17, and is driven by a screw shaft 18 that is rotated by a motor (not shown). Further, the table 15 can be rotated in a horizontal plane by a rotation drive unit 19 incorporating a motor.

  A bridge 22 including support columns 20 and 20 on both sides provided with the table 15 interposed therebetween and a beam (horizontal beam) 21 extending horizontally in the X direction is provided so as to straddle the table 15. The beam 21 is provided with a guide 23 extending horizontally in the X direction, and the scribe head 24 described above is attached to the guide 23 so that the motor M can move along the beam 21 in the X direction. The scribing head 24 is also attached with a scribing wheel 10 and a diamond point cutter 25 described later.

  As shown in FIG. 1, the wafer stack W is placed on the table 15 of the scribing mechanism A with the glass wafer 1 facing upward, and the scribing wheel 10 is divided on the outer surface of the glass wafer 1. A scribe line S <b> 1 is formed on the glass wafer 1 by rolling it while being pressed. The scribe line S1 is formed outside the resin partition 4 of the wafer level package W1.

Next, as a second stage, as shown in FIG. 2, the wafer stack W is reversed, and the diamond point cutter 25 is moved while being pressed along the planned cutting line on the outer surface of the silicon wafer 2. A scribe line S2 is formed on the outer surface of the substrate.
As shown in FIG. 6, the diamond point cutter 25 includes a projecting blade tip 25 b made of diamond on the lower surface of the tip of the blade body 25 a and is attached to the holder 26. Similar to the scribing wheel 10, the holder 26 is held by the scribing head 24 of the scribing mechanism A via the elevating mechanism 27 and is formed so as to be movable along the direction of the planned dividing line.

  Subsequently, as a third stage, as shown in FIG. 3, a pair of left and right cradles 13 and 13 extending along both sides of the outer surface of the glass wafer 1 on the lower side so as to sandwich the scribe line S1. The pressing member 14 is pressed from the outer surface of the silicon wafer 2 on the upper side toward the scribe line S2. In the present embodiment, a long and plate-like break bar is used as the pressing member 14, but it can be formed by a roller that rolls while pressing instead. The break bar as the pressing member 14 is formed so that it can be moved up and down via an elevating mechanism (not shown) such as a fluid cylinder.

By pressing the pressing member 14, the glass wafer 1 and the silicon wafer 2 are bent in the direction opposite to the pressing direction, and cracks are formed in the thickness direction along the scribe line S 1 of the glass wafer 1 and the scribe line S 2 of the silicon wafer 2. The wafer level package W1 that has been permeated and divided and thereby separated into pieces is completely divided along the line to be divided.
In this division by bending, both the glass wafer 1 and the silicon wafer 2 are divided by cracks penetrating in the thickness direction from the scribe lines S1 and S2, respectively. Therefore, as in the case of cutting with a conventional dicing saw, The cutting width is not required, the material can be used effectively, the generation of chipping and chips as in the case of cutting can be suppressed, and the cutting can be performed with a clean cut surface with a high yield.

  Further, in the present invention, the cutting fluid is not used as in the conventional dicing saw, and it is divided in a dry environment, so that the mechanism and piping for supplying the cutting fluid and collecting the waste fluid can be omitted, and the cutting is performed. Subsequent washing and drying steps can be omitted, and the apparatus can be made compact. Further, the scribing wheel 10 formed of a ring body having the cutting edge 10a along the circumferential ridge line used in the present invention and the diamond point cutter 25 having the cutting edge 25b made of diamond at the tip of the cutting body 25a are spilled. Since the service life is longer than that of conventional rotating blades that are prone to occur, the running cost can be reduced.

  In the present invention, at the time of the break processing by the pressing member 14, the pair of left and right cradles 13 and 13 for receiving the glass wafer 1 can be changed to be recessed so that the glass wafer 1 is bent as shown in FIG. 4. The cushion material 16 having a thickness may be disposed in contact with the scribe line S1 formation surface of the glass wafer 1.

While typical examples of the present invention have been described above, the present invention is not necessarily limited to the above embodiments. For example, in the above embodiment, the scribing wheel 10 and the diamond point cutter 25 are held by the common scribe head 24, but each may be configured to be held by different scribe heads.
Further, instead of the diamond point cutter 25, a silicon scribing wheel having a cutting edge angle smaller than that of the glass scribing wheel 10 may be used.
In addition, the present invention achieves its object and can be appropriately modified and changed without departing from the scope of the claims.

The scribe line forming method and apparatus of the present invention can be used for dividing a wafer laminate in which a glass wafer and a silicon wafer are bonded together.

A scribe mechanism S1 glass wafer scribe line S2 silicon wafer scribe line W wafer stack W1 wafer level package 1 glass wafer 2 silicon wafer 10 scribing wheel 10a blade edge 14 pressing member 15 table 25 diamond point cutter 25a blade body 25b blade edge

Claims (2)

For an image sensor having a structure in which a glass wafer and a silicon wafer in which a plurality of photodiode formation regions are patterned vertically and horizontally are bonded together via a resin layer disposed so as to surround each photodiode formation region. A method for forming a scribe line for a wafer laminate,
By rolling a glass scribing wheel on which a cutting edge having a predetermined cutting edge angle is formed along a circumferential ridge line while pressing along a planned cutting line of the outer surface of the glass wafer, the outer surface of the glass wafer A glass scribe process for forming a scribe line in
A diamond point cutter having a diamond-like cutting edge at the tip, or a silicon scrubbing wheel on which a cutting edge having a smaller cutting edge angle along a circumferential ridge line than the glass scribing wheel is formed. by moving or rolling while pressing along the cutting-scheduled line, the scribing line forming the wafer laminate for image sensor in so that the have a silicon scribing step of forming a scribe line on the outer surface of the silicon wafer Method. For an image sensor having a structure in which a glass wafer and a silicon wafer in which a plurality of photodiode formation regions are patterned vertically and horizontally are bonded together via a resin layer disposed so as to surround each photodiode formation region. A scribe line forming apparatus for a wafer stack,
A scribe line is formed on the outer surface of the glass wafer by rolling while pressing along a planned cutting line on the outer surface of the glass wafer, having a predetermined cutting edge angle along a circumferential ridge line made of a ring body. A glass scribing wheel to be formed;
A diamond point cutter that forms a scribe line on the outer surface of the silicon wafer by moving while pressing along a planned cutting line on the outer surface of the silicon wafer, wherein a protruding blade edge made of diamond is formed at the tip portion, or The edge angle along the circumferential ridge line is smaller than the scribing wheel for glass, and the scribe line is formed on the outer surface of the silicon wafer by rolling while pressing along the planned dividing line on the outer surface of the silicon wafer. forming scribe line forming apparatus of the wafer laminate for an image sensor, characterized in that it comprises a one, the silicon for scrubbing wheel which.

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