JP2018078249A - Wafer processing method - Google Patents

Abstract

An object of the present invention is to prevent contamination on a side surface of a chip divided from a wafer. After forming a modified layer (R) inside a wafer (W) along a division line (L), the wafer is divided along the division line with the modified layer as a starting point by a grinding operation. Next, after the expanded tape (ET) is attached to the back surface side of the ground wafer, the expanded tape is expanded in a direction to separate the adjacent chips (C), and a gap (S) is formed between the adjacent chips. I do. Thereafter, dry ice fine particles (DR) are sprayed at high speed into the gap between the chips along the plurality of chips to clean the space between the chips. [Selection diagram] FIG.

Description

  The present invention relates to a wafer processing method for dividing a wafer into a plurality of device chips.

  As a wafer processing method, a method using SDBG (Stealth Dicing Before Grinding) in which laser processing and grinding processing are combined has been proposed (for example, see Patent Document 1). In SDBG, after a protective member is attached to the front surface of the wafer, a pulsed laser beam having a wavelength that is transmissive to the wafer is condensed from the back side of the wafer along the planned dividing line of the wafer. Irradiate. As a result, a modified layer is formed along the planned dividing line inside the wafer. After forming the modified layer, the protective member side of the wafer is held by holding means of a grinding device. Then, by rotating the grinding wheel and pressing and grinding the back surface of the wafer, the wafer is thinned to a predetermined finish thickness, and the wafer is divided into individual device chips with the modified layer as a starting point by the grinding pressure. Divided.

Japanese Patent No. 3762409

  However, in the wafer processing method described above, chips are divided into chips during grinding, so that grinding waste enters between the chips in the state of being divided into pieces. For this reason, there is a problem that deposits such as grinding scraps adhere to the side surface of the chip and become contaminated, causing defective products.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a wafer processing method capable of preventing contamination of a chip side surface divided from a wafer.

  A wafer processing method according to one embodiment of the present invention is a wafer processing method in which devices are formed in a plurality of regions partitioned on a surface by dividing lines, and has transparency to the wafer from the back surface of the wafer. A laser beam with a wavelength is focused on the inside of the wafer and irradiated along the planned dividing line, and a modified layer forming step for forming a modified layer inside the wafer and a modified layer forming step are performed. Grinding from the back surface by grinding means to thin the finished thickness and dividing the wafer along the planned dividing line by the modified layer as a starting point by the grinding operation, and the back surface ground after performing the dividing step After performing the expand tape adhering step and the expand tape adhering step for adhering the expand tape to the side, After expanding the Pand tape and expanding in the direction that separates adjacent chips to form a gap between adjacent chips, and after performing the tape expansion step, dry ice fine particles are jetted into the gap between the chips at high speed And an inter-chip cleaning step for cleaning the space between the chips by spraying along a plurality of chips.

  According to this method, since the dry ice fine particles are sprayed into the gaps between the chips at high speed for cleaning, the deposits on the side surfaces of the chips can be efficiently removed. Thereby, it can avoid that the chip | tip side surface remains in the contaminated state, and can improve the product quality of the chip | tip after a process.

  According to the present invention, since cleaning is performed by spraying dry ice fine particles, it is possible to prevent contamination of the side surface of the chip divided from the wafer.

1 is a schematic perspective view of a wafer according to an embodiment. It is explanatory drawing of a modified layer formation step. It is explanatory drawing of a division | segmentation step. It is explanatory drawing of an expand tape sticking step. It is explanatory drawing of a tape expansion step. It is explanatory drawing of the chip | tip cleaning step. It is explanatory drawing of the chip | tip cleaning step.

  Hereinafter, the wafer processing method of the present embodiment will be described with reference to the accompanying drawings. First, a wafer processed by the wafer processing method of the present embodiment will be described with reference to FIG. FIG. 1 is a schematic perspective view of a wafer according to the present embodiment.

  As shown in FIG. 1, the wafer W is formed in a substantially disk shape. On the surface W1 of the wafer W, a plurality of division lines L are arranged in a lattice pattern, and a plurality of devices D partitioned by the division lines L are formed. A protective tape T for protecting the device D is attached to the surface W1 of the wafer W.

  The wafer W has a thickness of, for example, 300 [μm] or more, and is divided into individual device chips by SDBG that combines laser processing and grinding processing. In this case, after the modified layer is formed in the wafer W by laser processing, the wafer W is divided by the modified layer as a starting point while being ground to the finished thickness by grinding. The wafer W may be a semiconductor wafer in which a semiconductor device such as IC or LSI is formed on a semiconductor substrate such as silicon or gallium arsenide, or an optical device such as an LED is formed on an inorganic material substrate such as sapphire or silicon carbide. An optical device wafer may be used.

  Next, a wafer processing method according to the present embodiment will be described with reference to FIGS. 2 shows a modified layer forming step, FIG. 3 shows a dividing step, FIG. 4 shows an expanded tape attaching step, FIG. 5 shows a tape expanding step, and FIGS. In this embodiment, an example in which the wafer processing method is applied to SDBG will be described. However, the present invention can be applied to other methods in which a modified layer is divided from the inside of the wafer.

  As shown in FIG. 2, a modified layer forming step is first performed. In the modified layer forming step, first, the wafer W to which the protective tape T is adhered is sucked and held on the holding table 10 of the laser processing apparatus (not shown) via the protective tape T. Next, the exit port of the processing head 11 is positioned directly above the planned division line of the wafer W, and a laser beam is emitted from the processing head 11 toward the back surface W2 of the wafer W. The laser beam has a wavelength that is transmissive to the wafer W, and is adjusted so as to position a condensing point inside the wafer W. While the adjustment is made in this manner, the processing head 11 is relatively moved with respect to the wafer W, so that the modified layer R along the planned division line is formed inside the wafer W.

  After performing the modified layer forming step, the dividing step is performed as shown in FIG. In the dividing step, the wafer W is held on the chuck table 21 of the grinding apparatus 20 via the protective tape T. The grinding wheel (grinding means) 22 is brought close to the chuck table 21 while rotating, and the grinding wheel 22 and the back surface W1 of the wafer W are in rotational contact with each other while spraying a grinding liquid from a nozzle (not shown), so that the wafer W reaches the finished thickness. It is ground to be thinned. By this grinding operation, a grinding pressure is applied to the modified layer R from the grinding wheel 22, and cracks extend in the thickness direction of the wafer W starting from the modified layer R. As a result, the wafer W is divided along the division lines, and individual chips C (see FIG. 4) are formed according to the device.

  After performing the dividing step, as shown in FIG. 4, an expanding tape attaching step is performed. In the expanding tape attaching step, the wafer W is arranged inside the annular frame F, and then the expanded tape ET is integrally attached to the rear surface (lower surface) W2 side of the ground wafer W and the lower surface side of the frame F. Worn. Thus, the wafer W is mounted on the frame F via the expanded tape ET.

  After performing the expand tape sticking step, a tape expansion step is performed as shown in FIG. In the tape expansion step, the wafer W is placed on the expansion drum 31 of the expanding apparatus (not shown), and the frame F around the wafer W is held by the frame holding unit 32. At this time, the expansion drum 31 has a larger diameter than the wafer W, and the outer peripheral edge of the expansion drum 31 is in contact with the expanded tape ET between the wafer W and the frame F from below. The expansion drum 31 is relatively pushed up by moving the frame holding portion 32 in the downward direction.

  By expanding the expansion drum 31 and the frame holding part 32, the expanded tape ET is expanded in the radial direction. In other words, the expanded tape ET is expanded in a direction in which adjacent chips C are separated from each other, and a gap S is formed between the adjacent chips C on the wafer W.

  After performing the tape expansion step, an inter-chip cleaning step is performed as shown in FIGS. FIG. 7 is a cross-sectional view taken along line AA in FIG. In the inter-chip cleaning step, first, the tip of the injection nozzle 41 that injects the dry ice fine particles DR and the suction nozzle 42 (not shown in FIG. 6) while maintaining the state in which the gap S is formed between the adjacent chips C. Is positioned right above the gap S. At this time, the ejection nozzle 41 and the suction nozzle 42 are aligned in the extending direction of the gap S, and the suction nozzle 42 is disposed on the downstream side of the ejection nozzle 41 in the ejection direction. The air in the vicinity of the portion where the dry ice fine particles DR are ejected by the suction nozzle 42 is sucked while the dry ice fine particles DR are jetted at high speed from the jet nozzle 41 toward the gap S. While spraying and sucking are performed in this way, the spray nozzle 41 and the suction nozzle 42 are relatively moved with respect to the gap S, and the dry ice fine particles DR are sprayed along the plurality of chips C.

  Here, the dry ice fine particles DR ejected by the ejection nozzle 41 are, for example, produced from liquefied carbon dioxide gas and mixed with compressed air by a compressor and then ejected. The spray nozzle 41 may spray the dry ice fine particles DR in either a dot shape or a line shape, and the number of installation may be either singular or plural. The sprayed dry ice fine particles DR are sprayed and collide with the side surface of the chip C forming the gap S or the vicinity thereof. Due to this collision, the dry ice fine particles DR enter between the chip C and the adhering material such as the grinding dust adhering thereto. When the invaded dry ice fine particles DR are vaporized and expanded, the deposits are peeled off from the chips C and physically blown off, and the space between the chips C forming the gap S is cleaned. The deposit that has been blown off is sucked by the suction nozzle 42 and collected, and removed from the chip C.

  In this way, when cleaning with dry ice fine particles DR, since it is a dry cleaning that does not use a cleaning solution or a chemical solution, it can be cleaned even in an expanding apparatus that cannot cope with a wet environment, and the burden of recovery and processing of the cleaning solution etc. Thus, the process can be simplified. Further, by controlling the flow rate and particle size of the dry ice fine particles DR, the cleaning ability can be adjusted, and the cleaning effect can be stably exhibited.

  As described above, according to the processing method of the above-described embodiment, the sprayed dry ice fine particles DR enter the inside of the gap S, and the deposits on the side surfaces of the chip C are blown off by the dry ice fine particles DR to be removed. Can do. Therefore, even if grinding fluid or grinding debris from grinding enters the gap S and adheres to the side surface of the chip C in the dividing step in SDBG, the space between the chips C can be cleaned well, and the product quality of the chip C is improved. Can do. In addition, cleaning by spraying dry ice particulates DR can easily remove deposits that are difficult to remove by cleaning with a liquid such as pure water or high-pressure air. C side contamination can be prevented.

  Further, since the suction nozzle 42 is provided, the deposits blown off by the dry ice fine particles DR ejected by the ejection nozzle 41 can be sucked and removed from the chip C, and can be prevented from reattaching to the chip C. it can.

  The embodiments of the present invention are not limited to the above-described embodiments, and various changes, substitutions, and modifications may be made without departing from the spirit of the technical idea of the present invention. Furthermore, if the technical idea of the present invention can be realized in another way by technological advancement or another derived technique, the method may be used. Accordingly, the claims cover all embodiments that can be included within the scope of the technical idea of the present invention.

  After performing the inter-chip cleaning step of the above-described embodiment, the wafer W mounted on the frame F may be transferred to the spinner cleaning device via the expanded tape ET, and the surface of each chip C may be cleaned with the spinner. In this case, the installation of the suction nozzle 42 may be omitted as long as the deposits blown off by the dry ice fine particles DR by the spinner cleaning can be removed from the chip C.

  As described above, the present invention has an effect of preventing contamination of the side surface of a chip divided from a wafer, and is useful when a chip is formed by dividing a wafer with SDBG.

22 Grinding wheel (grinding means)
C Chip D Device DR Dry ice fine particle ET Expanding tape L Divided line R Modified layer S Gap W Wafer W1 Front W2 Back

Claims (1)

A method for processing a wafer in which devices are formed in a plurality of regions partitioned by division lines on the surface,
A modified layer forming step in which a condensing point of a laser beam having a wavelength transparent to the wafer from the back surface of the wafer is positioned inside the wafer and irradiated along the planned division line to form a modified layer inside the wafer; ,
After performing the modified layer forming step, the wafer is ground from the back surface of the wafer by a grinding means to reduce the thickness to a finished thickness, and the wafer is divided along the scheduled division line by the grinding operation as a starting point. Splitting step;
After performing the dividing step, an expanding tape attaching step for attaching an expanded tape to the ground back side;
After performing the expanding tape attaching step, a tape expanding step that expands the expanding tape and expands the adjacent chips in a direction to separate adjacent chips to form a gap between the adjacent chips;
After performing the tape expansion step, an inter-chip cleaning step for cleaning between the chips by spraying dry ice fine particles at a high speed in the gap between the chips and spraying between the plurality of chips;
A wafer processing method comprising:

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