JP2015097223A - Segmentation method of wafer laminate, and segmentation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a segmentation method of a wafer laminate for an image sensor capable of segmenting the wafer laminate effectively and clean in accordance with a dry-type simple method without using a dicing saw, and a segmentation device.SOLUTION: A segmentation method of a wafer laminate W for an image sensor that is structured by bonding a glass wafer 1 and a silicon wafer 2 via a resin layer 4 that is disposed to surround photodiode formation areas 3, includes the steps of: pressing/rolling a scribing wheel 10 along a predetermined segmentation line on a top face of the glass wafer 1 or relatively moving a diamond point to form a scribe line S1; next irradiating an outer surface of the silicon wafer 2 with laser light along the predetermined segmentation line to form a groove S2 by means of ablation on the outer surface of the silicon wafer 2; further pressing a pressing member 14 from the outer surface side of the glass wafer 1 or the silicon wafer 2 along the scribe line, for example; and bending the wafer laminate W to segment the glass wafer 1 and the silicon wafer 2.

Description

  The present invention relates to a wafer stacking method and a cutting apparatus, and more particularly to a cutting method and a cutting apparatus for separating a wafer stack 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 formation region (sensing region) 3 is formed on the upper surface (bonding surface side) of the silicon wafer 2, and the photodiode formation 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 forming region 3), and a via (through-hole) penetrating the silicon wafer 2 vertically below the portion where the metal pad 5 is formed. Hole) 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 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 blade tip portion of the rotating blade rotating at high speed is formed in a sawtooth shape or a continuous uneven shape, the blade tip portion is likely 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 has been made to solve the above-described conventional problems, and to divide an image sensor wafer package that can be effectively and cleanly divided by a simple dry method without using a dicing saw, and its An object is to provide an apparatus.

In order to achieve the above object, the present invention takes the following technical means. That is, the cutting method of the present invention is a method for cutting a wafer laminate having a structure in which a glass wafer and a silicon wafer are bonded together via a resin layer, and the cutting surface of the glass wafer is scheduled to be cut by a cutting edge. A glass scribe process for forming a scribe line along the line, and a silicon groove for forming a groove by ablation on the outer surface of the silicon wafer by irradiating a laser beam along the planned cutting line on the outer surface of the silicon wafer A forming step, and subsequent to the glass scribe step and the silicon groove forming step, the glass wafer and the silicon wafer are divided along respective scribe lines or grooves.
Here, the wafer laminated body may be a wafer laminated body for an image sensor, the silicon wafer may be a silicon wafer in which a plurality of photodiode forming regions are vertically and horizontally patterned, and the resin layer may be It may be a wafer laminate disposed so as to surround each photodiode formation region. Further, the wafer stack for the image sensor may be a wafer stack for a CMOS image sensor, and a TSV may be formed on the wafer stack.
Further, the cutting edge may be a scribing wheel having a cutting edge portion along a circumferential ridge line, or may be a diamond point (also referred to as a diamond point cutter).
By rolling the scribing wheel along the planned cutting line while pressing the cutting edge of the scribing wheel against the outer surface of the glass wafer, or the cutting edge (projection (vertex) or ridgeline) of the diamond point is made of glass. A scribe line can be formed along the planned cutting line on the outer surface of the glass wafer by relatively moving the diamond point and the glass wafer along the planned cutting line while pressing against the outer surface of the wafer.

In the dividing step, the glass wafer is pressed by pressing a pressing member along the scribe line from the outer surface side of the glass wafer or by pressing the pressing member along the groove from the outer surface side of the silicon wafer. In addition, the silicon wafer can be divided along each scribe line or groove.
Here, the pressing member may be pressed from the outer surface side of the glass wafer, or may be pressed from the outer surface side of the silicon wafer, but generally the glass wafer tends to be more difficult to break, and the silicon wafer Since the grooves formed on the outer surface of the steel have a certain width, when pressed from the outer surface side, they tend to be relatively well divided compared to cracks caused by scribe lines. Therefore, it is preferable to press from the outer surface side of the silicon wafer.
In addition, either the glass scribe process or the silicon groove process may be performed first, but in particular, when pressing the pressing member against the outer surface of the silicon wafer in the dividing process, from the viewpoint of reversal of the wafer laminate, etc. It is preferable to perform the glass scribing step first.

In another aspect of the present invention, there is provided a cutting apparatus for a wafer laminate, which irradiates a laser beam along a cutting line for forming a scribe line on the outer surface of the glass wafer and a cutting line on the outer surface of the silicon wafer. Thus, a laser irradiation unit for forming a groove by ablation on the outer surface of the silicon wafer and a dividing means for dividing the glass wafer and the silicon wafer along respective scribe lines or grooves are provided.
Here, the cutting edge may be a scribing wheel or a diamond point having a cutting edge portion along a circumferential ridgeline, and the cutting means is the scribe from the outer surface side of the glass wafer or the outer surface side of the silicon wafer. It may be a pressing member that presses along a line or groove.

In the present invention, a scribing wheel used as a cutting edge is a scribing wheel in which grooves or notches are formed along a circumferential ridge line, and the remaining ridge line (projection) serves as a cutting edge part. Or, it may be a scribing wheel having good penetration of the crack formed along the scribe line (vertical crack) in the thickness direction of the glass wafer, and grooves and notches are not formed along the circumferential ridgeline. A normal scribing wheel may be used. In this scribing wheel, it is preferable that the angle (blade edge angle) of the edge of the blade edge in the cross section perpendicular to the circumferential ridge line is, for example, 95 degrees to 155 degrees.
On the other hand, when diamond points are used in the present invention, single crystal diamond or polycrystalline diamond formed with protrusions or ridge lines serving as blade edges can be used.
The laser light emitted from the laser irradiation unit is preferably a UV laser with a wavelength of 1064 nm or a Green laser with a wavelength of 532 nm. By irradiating such laser light, it is possible to satisfactorily form grooves by ablation on the outer surface of the silicon wafer.
In the present invention, the groove formed by ablation formed on the outer surface of the silicon wafer by irradiating the laser beam usually has a width of, for example, 20 μm or less, preferably about 1 to 10 μm, and a depth of, for example, 20 μm or less. Preferably, it may be about 1 to 10 μm. Since the groove due to ablation has a predetermined width, there is little influence due to the crystal direction of the silicon wafer, and in the cutting step where the pressing member presses, the influence due to the pressing direction (pressing from the outer surface side or pressing from the back surface side) Therefore, the silicon wafer can be satisfactorily divided.

  According to the present invention, for example, by pressing the pressing member, a crack that extends along a scribe line formed on the outer surface of the glass wafer and a crack that extends from a groove formed on the outer surface of the silicon wafer are thickened. Since it is divided by penetrating (extending) in the direction, it does not require a large cutting width as in the case of cutting a conventional thick dicing saw, and the material can be used effectively and by cutting Such as chipping and chips can be suppressed, and it can be divided with a clean cut surface with a high yield.

  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 used in the present invention (scribing wheel or diamond point), particularly the scribing wheel that has a cutting edge portion along the circumferential ridgeline and rolls during use, is more difficult than conventional rotating blades that are prone to tooth spilling and the like. Since the service life is long, the running cost can be reduced.

The figure which shows the 1st step of the cutting method of this invention. The figure which shows the 2nd step of the cutting method of this invention. The figure which shows the 3rd step of the dividing method of this invention. The figure which shows another Example of FIG. The figure which shows the scribing wheel used in one Embodiment of this invention. The figure which shows the state which attached the scribing wheel of FIG. 5 to the holder. 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 of the wafer stack for the CMOS image sensor in FIG. 8.

Hereinafter, a method for dividing a wafer laminate for an image sensor according to an embodiment of the present invention will be described in detail 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 formation region 3 and functions as a light receiving surface of the image sensor. A metal pad 5 is formed in the vicinity of the photodiode forming region 3, and a via (through hole) 6 penetrating the silicon wafer 2 vertically 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 excellent in tool characteristics such as cemented carbide or sintered diamond, and a blade edge portion 10a is formed on a circumferential ridge line (outer peripheral surface). Specifically, it is preferable to use a glass wafer 1 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 thickness and type.
The scribing wheel 10 is rotatably supported by a holder 11 and is attached to a scribe head 24 (see FIG. 7) of the scribe mechanism A via an elevating mechanism 12.
In the present invention, instead of the scribing wheel 10 that rolls (passively rotates) at the time of use, a diamond point that is a fixed blade can be used as the cutting edge.

  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. The scribe head 24 having the scribing wheel 10 can be moved in the X direction along the beam 21 by the motor M. It is attached to.
The scribe head 24 is also provided with a laser irradiation unit 25 that irradiates laser light.

  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 inverted, the laser light from the laser irradiation unit 25 is condensed, and irradiated along the planned cutting line on the outer surface of the silicon wafer 2. By this ablation by laser irradiation, a thin groove S2 having a width and depth of about several μm (1 to 10 μm) is formed on the outer surface of the silicon wafer 2.
The laser light emitted from the laser irradiation unit 25 is preferably a UV laser with a wavelength of 1062 nm, a Green laser with a wavelength of 532 nm, or the like.

  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 groove 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 the glass wafer 1 is cracked along the scribe line S 1 of the glass wafer 1 and the groove S 2 of the silicon wafer 2. The crack extending from the groove of the silicon wafer 2 penetrates and is divided in the thickness direction, and thereby the separated wafer level package W1 is completely divided along the division line.
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 respective scribe lines S1 and grooves S2, so that the case of cutting with a conventional dicing saw is performed. Therefore, the material can be used effectively without any need for a cutting width, and 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 cutting edge (scribing wheel or diamond point) used in the present invention, particularly the scribing wheel 10 that has a cutting edge portion 10a along the circumferential ridgeline and rolls during use, is a conventional rotating blade that is prone to tooth spilling and the like. The service life is longer than that, so running costs can be reduced.

  In the present invention, at the time of the break processing by the pressing member 14, instead of the pair of left and right receiving bases 13 and 13 that receive the glass wafer 1, as shown in FIG. 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-described embodiment, the scribing wheel 10 and the laser irradiation unit 25 are held by the common scribe head 24, but each may be configured to be held by different scribe heads.
In addition, the present invention achieves its object and can be appropriately modified and changed without departing from the scope of the claims.

  The dividing method 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 groove W wafer stack W1 wafer level package 1 glass wafer 2 silicon wafer 10 scribing wheel 10a cutting edge 14 pressing member 15 table 25 laser irradiation unit

Claims (8)

A method for dividing a wafer laminate having a structure in which a glass wafer and a silicon wafer are bonded via a resin layer,
A glass scribing step for forming a scribe line along a cutting line on the outer surface of the glass wafer by a blade edge; and
A silicon groove forming step of forming a groove by ablation on the outer surface of the silicon wafer by irradiating a laser beam along a predetermined division line of the outer surface of the silicon wafer;
Subsequent to the glass scribe step and the silicon groove forming step, the method for dividing a wafer laminate, comprising a dividing step of dividing the glass wafer and the silicon wafer along respective scribe lines or grooves.   The wafer laminate is a wafer laminate for an image sensor, the silicon wafer is a silicon wafer in which a plurality of photodiode formation regions are patterned vertically and horizontally, and the resin layer surrounds each photodiode formation region. The method for dividing a wafer laminate according to claim 1, wherein the wafer laminate is disposed on the substrate.   3. The method for dividing a wafer laminate according to claim 2, wherein the wafer laminate for the image sensor is a wafer laminate for a CMOS image sensor, and TSV is formed on the wafer laminate.   The method for dividing a wafer laminate according to claim 1, wherein the cutting edge is a scribing wheel or a diamond point having a cutting edge portion along a circumferential ridge line.   The glass wafer is pressed by pressing the pressing member along the scribe line from the outer surface side of the glass wafer, or pressing the pressing member along the groove from the outer surface side of the silicon wafer. The method for dividing a wafer laminate according to any one of claims 1 to 4, which is a step of dividing the silicon wafer along each scribe line or groove. A wafer laminate separating apparatus having a structure in which a glass wafer and a silicon wafer are bonded together via a resin layer,
A cutting edge that forms a scribe line on the outer surface of the glass wafer;
A laser irradiation unit that forms a groove by ablation on the outer surface of the silicon wafer by irradiating a laser beam along a division planned line on the outer surface of the silicon wafer;
A wafer lamination body cutting device comprising: a cutting means for cutting the glass wafer and the silicon wafer along respective scribe lines or grooves.   The wafer cutting body cutting apparatus according to claim 6, wherein the cutting edge is a scribing wheel or a diamond point having a cutting edge portion along a circumferential ridge line.   The cutting device according to claim 6 or 7, wherein the cutting means is a pressing member that presses along the scribe line or groove from the outer surface side of the glass wafer or the outer surface side of the silicon wafer.

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