JP2008277610A - Method for dicing wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To satisfactorily dice a wafer which is thick in the peripheral section, and which is thin in the central section. <P>SOLUTION: This method for dicing a wafer 10 which is thick in the peripheral section and which is thin in the central section formed with a plurality of circuit patterns as semiconductor elements to manufacture the pieces of the semiconductor elements includes a process (a) for cutting the peripheral section by a first blade 31 by leaving thickness which can be cut by a second blade 32 whose blade width is smaller than that of the first blade 31 and a process for cutting the remaining section in the process (a) and the central part by the second blade 32. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of dicing a wafer having a thick peripheral portion and a thin central portion on which circuit patterns to be a plurality of semiconductor elements are formed.

  In recent years, as electronic devices such as mobile phones have become smaller and more advanced, SIP (System in Package) technology that integrates multiple semiconductor chips into one package has become widespread, and as a result, products with a chip thickness of 100 μm or less Has been put into practical use.

  For manufacturing such a thin product, a processing technique called wafer thinning is indispensable, and various methods have been proposed. Among them, a wafer thinning technology has been developed in which the central portion where the semiconductor element is formed is thin and the peripheral portion is thick, and warpage, cracking, chipping, etc. of the wafer accompanying thinning can be prevented. It has attracted attention because it can improve the handleability (see, for example, Patent Document 1).

However, in such a wafer having a thick peripheral edge, cutting resistance changes greatly at the portion where the thickness changes during dicing, which may cause blade breakage, wafer chipping, dicing street meandering, and the like. It was. In addition, the blade width and blade height (blade tip protrusion amount) of the blade are usually limited (usually, the blade height is 20 times or less of the blade width), which is suitable for cutting the peripheral edge. When a blade with a large blade width is used, the dicing width is increased and the number of chips taken per wafer is reduced, and when a blade with a small blade width suitable for cutting a thin central portion is used, the edge is insufficient due to insufficient blade height. There was a possibility that the part could not be cut.
JP 2004-153193 A

  An object of the present invention is to provide a wafer dicing method that can satisfactorily dice a wafer having a thick peripheral portion and a thin central portion on which a circuit pattern to be a plurality of semiconductor elements is formed.

  According to an aspect of the present invention, there is provided a method of dicing a wafer having a thick peripheral portion and a thin central portion on which a circuit pattern to be a plurality of semiconductor elements is formed into individual pieces of the semiconductor element, A step (a) of cutting the peripheral portion with a first blade leaving a thickness that can be cut by a second blade having a blade width smaller than that of the first blade, and a portion left in the step (a); And a step of cutting the central portion with the second blade. A wafer dicing method is provided.

  According to the wafer dicing method of one embodiment of the present invention, a wafer having a thick peripheral portion and a thin central portion on which a circuit pattern to be a plurality of semiconductor elements is formed can be diced satisfactorily.

  Embodiments according to the present invention will be described below. Although the description will be made based on the drawings, the drawings are provided for illustration only, and the present invention is not limited to the drawings.

(First embodiment)
First, a wafer to which the wafer dicing method according to the first embodiment of the present invention is applied will be described. 1A is a top view of the wafer, and FIG. 1B is a cross-sectional view.

  As shown in FIGS. 1A and 1B, this wafer 10 includes a disk-shaped wafer body 11 having a thickness of 60 μm, for example, and a wafer body 11 having a width of 2 mm and a thickness of 625 μm provided on the outer periphery thereof. And a reinforcing ring 12 made of the same material. A circuit pattern 14 to be a plurality of semiconductor elements 13 is formed at the center of the surface of the wafer body 11, that is, the inner surface of the reinforcing ring 12, and the circuit pattern 14 is further protected by a surface protection film 15 made of polyimide resin or the like. ing. The reinforcing ring 12 is thermocompression bonded to the wafer body 11 via the surface protective film 15.

  For example, as shown in FIG. 2 (A), the wafer 10 has a reinforcing ring 12 on the outer periphery of a silicon wafer 11a having a thickness of, for example, 625 μm, on which a circuit pattern 14 and a surface protective film 15 are formed. After thermocompression bonding, as shown in FIG. 2B, the silicon wafer 11a is formed by thinning the back surface by back grinding, wet etching, dry etching or the like. Note that the silicon wafer 11a is in-feed ground to a thickness that does not easily warp or crack, for example, to a thickness of about 150 μm, and then thinned by thermocompression bonding of the reinforcing ring 12 or back grinding. You may do it.

  Next, a wafer dicing method according to the present embodiment, in which the semiconductor element 13 is separated from the wafer 10 thus configured, will be described. FIG. 3 is a schematic diagram for explaining a wafer dicing method according to the present embodiment.

  In the present embodiment, two kinds of blades having different blade widths as cutting blades, for example, a first blade 31 having a blade width of 700 μm and a blade width smaller than that of the first blade 31, for example, having a blade width of 25 μm. A second blade 32 is used. As the dicing apparatus, it is preferable to use a twin dicer or the like to which the first and second blades 31 and 32 can be attached.

  First, as shown in FIG. 3A, the first blade 31 causes the reinforcing ring 12 on the wafer body 11 to be 10 μm thick from the bottom of the reinforcing ring 12, for example, along the dicing line from one end of the dicing line. Cut leaving. That is, by this cutting, a groove 33 having a rectangular cross section having a width of 700 μm and a depth of 615 μm, for example, is formed in the reinforcing ring 12. The cutting depth may be a depth that allows the second blade 32 to be cut with the wafer main body 11 so that the cutting force can be cut with the second blade 32. As a result, the blade may be damaged, the wafer may be chipped, and the dicing street may be meandered. On the other hand, if the depth is too deep, the cutting edge of the second blade 32 may come into contact with the wafer body 11 and be damaged. From this point of view, although it depends on the blade width of the second blade 32 and the thickness of the wafer body 11, it is usually preferable to perform cutting while leaving a thickness of about 10 to 30 μm.

  Next, as shown in FIG. 3B, the second blade 32 is used to cut from the groove 33 of the reinforcing ring 12 across the center of the surface of the wafer body 11 along the dicing line. The reinforcing ring 12 also exists on the other end side of the dicing line. However, as shown in FIG. Then, leave the required thickness and cut. FIG. 3C is a cross-sectional view showing the portion of the reinforcing ring 12 after being cut by the first blade 31 and the second blade 32 in this way. In FIG. 3, reference numeral 34 denotes a flange for fixing the blade.

  The wafer 10 is diced into pieces of a plurality of semiconductor elements 13 by repeating the above-described process for dicing lines that exist in a plurality of lengthwise and widthwise directions.

  In such a method, two types of cutting blades having different blade widths are used, and first, a peripheral portion having a large thickness is cut with a blade having a large blade width, and thereafter, a central portion having a small thickness is further cut from the cutting portion. Since cutting is performed with a cutting portion and a blade having a small blade width along the dicing line, the change in the cutting resistance of the blade in the portion where the thickness changes can be reduced, and the blade resistance caused by the change in the cutting resistance of the blade can be reduced. The occurrence of breakage, wafer chipping, dicing street meandering, etc. can be suppressed. In addition, since the central part that becomes a semiconductor element is cut with a blade having a small blade width, the number of semiconductor elements that can be taken per wafer is not reduced. Therefore, cutting failure due to insufficient blade height does not occur.

  In order to confirm the effect of the present embodiment, a wafer 10 (625 μm-thick disk-shaped wafer) in which a reinforcing ring 12 made of silicon having a width of 2 mm and a thickness of 625 μm is provided on the outer periphery of a disk-shaped wafer body 11 having a thickness of 60 μm (The silicon wafer 11a is in-feed ground to a thickness of 150 μm, and then the reinforcing ring 12 is thermocompression bonded, and then thinned by single-wafer spin wet etching, and the processed surface is further subjected to metal treatment.) On the other hand, a cutting blade with a blade width of 700 μm is used as the first blade 31, a cutting blade with a blade width of 25 μm and a blade height of 500 μm is used as the second blade 32, and the cutting depth by the first blade 31 is 615 μm. Then, after dicing according to the above procedure, blade breakage, wafer chipping, dicing street Dancing was possible without causing meandering.

  In the example shown in FIG. 3, the center of the cutting width of the first blade 31 and the center of the dicing line are made to coincide with each other, but for example, the second blade 32 is offset as shown in FIG. You may make it cut. Compared to the above method, it is possible to use a blade having a small blade width as the first blade 31, and it is possible to reduce the cutting resistance when cutting the reinforcing ring 12, thereby improving the blade life. For example, as shown in FIG. 5, a chamfering V-shaped blade may be used as the first blade 31 instead of the cutting blade. As in the case of FIG. 4, the cutting resistance when cutting the reinforcing ring 12 can be reduced, so that the life of the blade can be extended. However, in the former, it is difficult to adjust the dicing apparatus, and in the latter, there is a problem that the cutting shape is not stable.

  Further, although not shown, a blade having a blade width exceeding the width of the reinforcing ring 12, for example, when the reinforcing ring has a width of 2 mm, a blade width exceeding that, for example, a blade having a width of 2.5 mm, is used. The entire reinforcing ring may be cut and then cut by the second blade 32.

(Second Embodiment)
6A and 6B are views showing a wafer to which the wafer dicing method according to the second embodiment of the present invention is applied. FIG. 6A is a top view and FIG. 6B is a cross-sectional view. FIG. 7 is a cross-sectional view for explaining an example of the wafer manufacturing method shown in FIG. 6, and FIG. 8 is a schematic diagram for explaining the wafer dicing method according to the present embodiment. In the present embodiment, in order to avoid redundant description, description of points that are the same as those in the first embodiment will be omitted, and differences will be mainly described.

  As shown in FIG. 6, the wafer 20 in the present embodiment is a disk-shaped silicon wafer 11 a having a thickness of, for example, 725 μm, on which a circuit pattern 14 and a surface protective film 15 to be a plurality of semiconductor elements 13 are formed. It has a structure that is ground from the back surface leaving its outer periphery. In one example, the peripheral portion 21 has a thickness and a width of about 725 μm and 2 mm, respectively, and the central portion 22 has a thickness of, for example, 50 μm. The back surface is covered with a metal layer (not shown) over the entire surface.

  In the present embodiment, as in the case of the first embodiment, two types of blades having different blade widths as cutting blades, for example, a first blade having a blade width of 700 μm, are formed on the wafer 20 configured as described above. The blade 31 and the second blade 32 having a blade width smaller than the first blade 31, for example, a blade width of 25 μm, are used for cutting, but the peripheral edge portion 21 protrudes from the back surface of the wafer 20. As shown in FIG. 8, cutting is performed from the back side. In the first blade 31, the peripheral portion 21 is cut to a depth where the thickness that can be cut by the second blade 32 remains (FIG. 8A), and then the peripheral portion is cut by the second blade 32. The wafer 33 is cut from the groove 33 formed in 21 along the dicing line. FIG. 8C is a cross-sectional view showing the peripheral edge portion 21 after being cut by the first blade 31 and the second blade 32 as described above.

  Normally, when cutting the workpiece from the back side, the alignment mark on the front side is monitored from the back side with an infrared camera to check the cutting line. In this embodiment, the wafer on which the metal layer is formed Since the cutting is performed from the back surface of 20, the alignment mark attached to the front surface cannot be confirmed. Therefore, in the present embodiment, after performing the step shown in FIG. 8A in the pre-alignment, the alignment mark on the dicing line is recognized by the infrared camera from the bottom surface of the cut groove 33, and the alignment is performed. To do. In the process of FIG. 8 (A), since a blade having a large blade width is used, alignment with no practical problem is possible even with pre-alignment. Confirmation enables highly accurate alignment.

  Also in the second embodiment, similarly to the first embodiment, two types of cutting blades having different blade widths are used, first, a thick peripheral edge is cut with a blade having a large blade width, and then Cutting from the cutting part to the central part with a small thickness and further to the cutting part on the other side with a blade with a small blade width along the dicing line reduces the change in the cutting resistance of the blade at the part where the thickness changes. It is possible to suppress the occurrence of blade breakage, wafer chipping, dicing street meandering, and the like due to changes in the cutting resistance of the blade. In addition, since the central part that becomes a semiconductor element is cut with a blade having a small blade width, the number of semiconductor elements that can be taken per wafer is not reduced. Therefore, cutting failure due to insufficient blade height does not occur.

  In order to confirm the effect of the present embodiment, a blade having a blade width of 700 μm as a first blade with respect to the wafer 20 having a peripheral portion thickness and width of 725 μm and 2 mm and a central portion thickness of 60 μm, When a blade having a blade width of 25 μm and a blade height of 500 μm was used as the second blade, and dicing was performed according to the procedure shown in FIG. 8 under the condition that the cutting depth by the first blade was 615 μm, damage to the blade, Dancing was successfully performed without causing chipping or meandering of the dicing street.

  Also in this embodiment, the second blade 32 may be offset and cut as in the case of the first embodiment described above. As a result, a blade having a small blade width can be used as the first blade 31, cutting resistance when cutting the peripheral edge portion 21 can be reduced, and blade life can be improved. Further, as the first blade 31, a chamfering V-shaped blade as shown in FIG. Since the cutting resistance at the time of cutting the peripheral portion can be reduced, the life of the blade can be extended. Further, a blade having a blade width exceeding the width of the peripheral portion 21 may be used to cut the entire peripheral portion 21 and then the second blade 32 may be used for cutting. In this case, the above-described pre-alignment is not necessary.

  The present invention is not limited to the description of the embodiment described above, and it goes without saying that the structure, material, arrangement of each member, and the like can be appropriately changed without departing from the gist of the present invention. Nor.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the wafer to which the dicing method of the wafer which concerns on 1st Embodiment is applied, (A) is a top view, (b) is sectional drawing. It is sectional drawing which shows an example of the manufacturing method of the wafer shown in FIG. It is a schematic diagram explaining the dicing method of the wafer which concerns on 1st Embodiment. It is a schematic diagram explaining the modification of 1st Embodiment. It is a schematic diagram explaining the other modification of 1st Embodiment. It is a figure which shows the wafer to which the dicing method of the wafer which concerns on 2nd Embodiment is applied, (A) is a top view, (b) is sectional drawing. It is sectional drawing which shows an example of the manufacturing method of the wafer shown in FIG. It is a schematic diagram explaining the dicing method of the wafer which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10, 20 ... Wafer, 11 ... Wafer main body, 12 ... Reinforcement ring, 13 ... Semiconductor element, 14 ... Circuit pattern, 21 ... Peripheral part, 22 ... Center part, 31 ... First blade, 32 ... Second blade, 33 ... groove.

Claims (5)

A method of dicing a wafer having a thick peripheral portion and a thin central portion on which a circuit pattern to be a plurality of semiconductor elements is formed into individual pieces of the semiconductor elements,
A step (a) of cutting the peripheral portion with a first blade leaving a thickness that can be cut by a second blade having a blade width smaller than that of the first blade, and a portion left in the step (a) And (b) cutting the central portion with the second blade,
A wafer dicing method comprising:   2. The wafer positioning in the step (b) is performed by recognizing an alignment mark provided in advance on a dicing line with an infrared camera from a portion cut in the step (a). Wafer dicing method.   The peripheral edge protrudes to either the front surface or the back surface of the wafer, and in the step (a), the thickness of the central portion of the wafer on which the circuit pattern is formed is the same as the thickness of the first blade from the protruding side. 3. The wafer dicing method according to claim 1, wherein the wafer is cut while leaving a slightly large thickness.   4. The wafer dicing method according to claim 1, wherein the wafer is formed by adhering a reinforcing ring to an outer peripheral portion of a surface of a flat wafer.   The wafer dicing method according to any one of claims 1 to 3, wherein the wafer is formed by grinding a flat wafer from the back surface while leaving an outer peripheral portion thereof.

Images