JP2010118537A - Laser dicing method and laser dicing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser dicing method and a laser dicing device that expand and divide a laser-diced wafer without using any dedicated device, and improve the strength of a chip by reducing cracks. <P>SOLUTION: After a reformed area P is formed in the wafer W mounted on a frame F with a tape T interposed, the tape T is shrunk by exposing the wafer W to plasma to expand the wafer W, and the cut surface of a dicing street divided by the expanding is etched. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser dicing method and a laser dicing method in which a modified layer is formed with a laser beam inside a wafer on which a semiconductor device or an electronic component is formed to form a cutting line, and the chip is divided into individual chips along the cutting line. It relates to the device.

  Conventionally, when a wafer on which a semiconductor device or electronic component is formed is divided into individual chips, a blade-type dicing apparatus that cuts and cuts the wafer with a blade that is rotated at high speed by a spindle has been widely used. A blade-type dicing apparatus picks up images of a blade that is rotated at high speed by a spindle, a wafer table that holds a wafer, various movement axes that change the relative position between the blade and the wafer, and a wafer on the wafer table. An imaging unit such as a CCD camera or a microscope, a cleaning unit that cleans the wafer after dicing, and a control unit that controls each unit are provided.

  In recent years, instead of the conventional blade-type dicing device, the laser light emitted from the laser light source is condensed inside the wafer, and the modified region by multiphoton absorption is continuously formed inside the wafer to cleave the wafer. A dicing apparatus (hereinafter referred to as a laser dicing apparatus) is used (see, for example, Patent Document 1).

  The laser dicing apparatus includes a wafer table, moving means, imaging means, and control means as in the case of the blade dicing apparatus, and includes a laser head including a laser oscillator and a lens as processing means. In the laser dicing apparatus, the wafer on the wafer table is moved by the moving means while irradiating the laser beam, thereby forming one or more cutting lines by the modified region continuously along the planned cutting line of the wafer.

  The wafer on which the cutting line is formed is transferred to a device such as an expander having a fixing mechanism or a push-up mechanism, and is expanded or braked to be cut from the cutting line as a starting point and divided into individual chips.

As described above, in the laser dicing apparatus, the wafer is divided into chips by the laser beam instead of the blade formed of diamond or the like that rotates at high speed, so that a large force is not applied to the wafer and no chipping or cracking occurs. Further, since there is no portion that directly contacts the wafer and no heat or cutting waste is generated, no cutting water is required. Further, since the modified region is formed inside and the wafer is divided and divided into chips, the distance between the chips is much narrower than the cutting with the blade, and more chips can be obtained from one wafer.
JP 2002-192367 A

  However, in recent years, semiconductor devices and electronic components have been made thinner and smaller, and accordingly, the wafer has been thinned by polishing the back surface and diced in a state of being processed to an extremely thin thickness of 100 μm or less. Divided into chips. In such a thinned wafer, it is difficult to achieve both the strength and quality of the divided chips and the processing speed.

  In laser dicing, since minute cracks are formed inside the wafer, the cross section when divided is fragile, and it is difficult to improve the chip strength. Further, in laser dicing, another device such as an expander is required for division, and it is necessary to transport the wafer to the expander. In such conveyance, when the chips after dicing are almost in contact with each other as in laser dicing, there is a problem that the chips rub against each other and chipping occurs at the edge of the chip.

  To solve this problem, a plasma dicing method has been proposed in which dicing street is etched with plasma to form a wafer into chips. However, a photolithography process for exposing only dicing street is necessary, and the apparatus is very There was a problem of becoming expensive.

  The present invention has been made for such a problem, and a laser-diced wafer is expanded and divided without using a dedicated device, and is present on the back surface, side surface, side, corner, etc. of the chip. An object of the present invention is to provide a laser dicing method and a laser dicing apparatus that reduce the cracks and stress that occur and improve the strength of the chip.

  In order to achieve the above object, the present invention improves the inside of the wafer along the dicing street, which is a cutting line of the wafer, by condensing a laser beam inside the wafer mounted on the frame via a tape. A laser dicing process for forming a region, and exposing the wafer formed with a modified region mounted on the frame via the tape to a plasma atmosphere, thereby shrinking the tape and expanding the wafer. The wafer is cleaved into individual chips by a plasma cleaving stress relief process of cleaving into individual chips and etching a region exposed to the plasma atmosphere of the cleaved chips.

  Further, the present invention is characterized in that in the above invention, the plasma is a low temperature plasma irradiated at 40 ° C. or higher and 80 ° C. or lower.

  Furthermore, the present invention is characterized in that, in the above invention, the base material of the tape is formed of polyolefin, vinyl chloride, polyethylene, or polypropylene.

  According to the dicing method of the present invention, after the back surface is ground or the like, the device surface is attached to the frame via a dicing tape, and the laser beam is condensed into the mounted wafer to modify the inside of the wafer. A laser dicing machine equipped with a laser head for forming a region, a wafer table for holding a wafer, and a moving axis for moving the wafer table and the laser head relative to each other on a dicing street that is a planned cutting line of the wafer. A modified region is formed along the wafer.

  In laser dicing equipment, the tape is shrunk to expand the wafer and cleave it into individual chips. At the same time, the chip, cross-section, edges, corners, and grinding surface of the chip to which no tape is attached are exposed to a plasma atmosphere. A plasma irradiation unit for etching is provided, and the wafer after dicing is irradiated with low temperature plasma irradiated at 40 ° C. or more and 80 ° C. or less. As a result, the base material of the tape formed of polyolefin, vinyl chloride, polyethylene, or polypropylene contracts and advances from the modified region and the modified region, and the wafer is divided starting from the crack. At the same time, the portions of the individual chips exposed to the plasma atmosphere are etched by the plasma, so that micro cracks disappear, stress is removed, and the strength of the chips is improved.

  As described above, according to the laser dicing method and the laser dicing apparatus of the present invention, the laser dicing wafer mounted on the frame via the tape is placed in the plasma atmosphere by the laser dicing apparatus including the plasma irradiation unit. It is possible to improve the strength of the chip by being exposed and expanded into individual chips and etching the part exposed to the plasma atmosphere.

  Hereinafter, preferred embodiments of a laser dicing method and a laser dicing apparatus according to the present invention will be described in detail with reference to the accompanying drawings. First, the configuration of the laser dicing apparatus according to the present invention will be described. FIG. 1 is a perspective view showing an internal configuration of the laser dicing apparatus.

  As shown in FIG. 1, the laser dicing apparatus 1 includes a processing unit 3 having a laser head 2 arranged opposite to each other, a load port 4 on which a cassette containing a large number of wafers W is placed, and a transfer for transferring the wafers W. Means 5 is provided with control means 6 for storing the control procedure of each part necessary for control and machining of each part.

  In the processing section 3, a wafer table 8 provided on an X moving shaft 7 as a moving means is ground on the back surface as shown in FIG. W is placed. Above the wafer table 8, a Y moving shaft 9 as a moving means is provided so as to be orthogonal to the X moving shaft 7, and a Z moving shaft 10 as a moving means is provided on the Y moving shaft 9. The Z moving shaft 10 is provided with a laser head 2 facing it.

  The laser dicing apparatus 1 further includes a plasma irradiation unit 11 that exposes the workpiece W after laser dicing to a plasma atmosphere, an imaging unit (not shown) that images the surface of the wafer W, and the like.

  As shown in FIG. 3, the laser head 2 includes a laser oscillator 12, a collimating lens 13, a mirror 14, a condensation lens 15, and the like, and laser light L oscillated from the laser oscillator 12 is collimated in the horizontal direction by the collimating lens 13. And reflected by the mirror 14 in the vertical direction and condensed by the condensation lens 15.

  When the condensing point of the laser beam L is set inside the thickness direction of the wafer W placed on the wafer table 8, the laser beam L transmitted through the surface of the wafer W is collected as shown in FIG. Energy is concentrated at the light spot, and a modified region P such as a crack region, a melted region, a refractive index changing region or the like due to multiphoton absorption is formed in the vicinity of the condensing point inside the wafer.

  As shown in FIG. 4B, a plurality of modified regions P are formed in the wafer W by being moved in the horizontal direction by the X moving shaft 7 and along the dicing streets of the wafer W. A split line K is formed. A plurality of dividing lines K are formed along the dicing street, and the wafer W is divided starting from the dividing line K and divided into chips.

  The plasma irradiation unit 11 is provided with a chamber structure (not shown), an RF application electrode, and a gas introduction / exhaust system. The wafer W on which the cutting line K is formed by laser dicing is placed in the chamber and a gas is introduced. The wafer W is etched by exposing the wafer W to plasma by applying RF.

  The plasma to which the wafer W is exposed is a low-temperature plasma of 40 ° C. or more and 80 ° C. or less. For example, the plasma source ionizes fluorine gas such as CF 4 or SF 6 by high-frequency RF discharge. As the etching conditions, for example, the RF power of the high frequency RF discharge is about 1 to 10 kW, the etching rate is about 0.5 to 10 μm / min, and the etching time is about 0.5 to 10 min.

  As a result, the wafer T is thermally expanded and the tape T formed of polyolefin is shrunk by the plasma, and the wafer W is cracked from the cutting line K and is expanded along the dicing street to be cut into individual chips. . Each chip has a cracked surface, edges, corners, and ground surfaces where the tape T is not adhered, and a minute crack formed by etching with plasma is removed, and stress generated in the chip is removed.

  As a result, the wafer W is expanded in the laser dicing apparatus 1 and at the same time, the surface of each chip is etched by plasma, so that micro cracks disappear, stress is removed, and the chip strength is improved.

  Next, the laser dicing method according to the present invention will be described. FIG. 5 is a side view showing a laser dicing method according to the present invention, FIG. 6 is a perspective view showing a modified region formed wafer, FIG. 7 is an enlarged perspective view of an expanded wafer, and FIG. It is an expansion perspective view of the wafer after the expansion which was etched.

  In the laser dicing method of the present invention, as shown in FIG. 5A, the laser head is applied to the wafer W mounted on the frame F via the tape T after the back surface placed on the wafer table 8 is ground. The modified region P is formed by irradiating the laser beam L from 2. The wafer W is processed and fed by the X moving shaft 7 and index fed by the Y moving shaft 9 so that the modified region P is continuously formed, and a cutting line K is formed along the dicing street as shown in FIG. The

  Subsequently, as shown in FIG. 5B, the wafer W on which the cutting line K is formed is placed in the plasma irradiation unit 11 and plasma is generated to etch the wafer W. The plasma is a low temperature plasma of 40 ° C. or more and 80 ° C. or less, and the wafer T is thermally expanded, and the tape T formed of polyolefin, vinyl chloride, polyethylene, or polypropylene is contracted by the plasma. As a result, as shown in FIG. 7, the wafer W is cracked from the cutting line K and expanded along the dicing street to be cut into individual chips 16.

  As shown in FIG. 8, each chip 16 is irradiated with plasma, and as shown in FIG. 8, four side surfaces A 1, A 2, A 3, A 4 that are split sections, and sides B 1 to B 8 that are eight edges that connect each of them, The four corners C1 to C4 and the surface D which is a grinding surface are etched to remove minute cracks and stress.

  As a result, the wafer W is expanded in the laser dicing apparatus 1 and at the same time, the fractured surfaces, edges, corners, and ground surfaces of the individual chips are etched by the plasma, and the micro cracks disappear and the stress is removed. The strength of is improved.

  As described above, according to the laser dicing method and laser dicing apparatus according to the present invention, the wafer having the modified region formed therein is exposed to the plasma atmosphere, so that the thermal expansion of the wafer and the shrinkage of the tape are caused. As it occurs, cracks propagate from the modified region and the wafer is expanded into individual chips along the dicing street. The surface of each chip that is not attached to the tape is etched to remove minute cracks, and stress generated in the chip is removed. Thereby, the strength of the chip is improved at the same time as expanding in the laser dicing apparatus.

The perspective view which showed the structure inside the laser dicing apparatus concerning this invention. The perspective view which showed the wafer mounted through the tape on the flame | frame. Sectional drawing which showed the structure of the laser head. Sectional drawing which showed the mode of laser dicing. The side view which showed the laser dicing method concerning this invention. The perspective view which showed the wafer in which the modification | reformation area | region was formed. The expansion perspective view of the wafer expanded by plasma. The expanded perspective view of the wafer after the expansion by which the cut surface was etched.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser dicing apparatus, 2 ... Laser head, 3 ... Processing part, 4 ... Load port, 5 ... Conveyance means, 6 ... Control means, 7 ... X movement axis, 8 ... Wafer table, 9 ... Y movement axis, 10 ... Z movement axis, 11 ... plasma irradiation part, 12 ... laser head, 13 ... collimating lens, 14 ... mirror, 15 ... condensation lens, 16 ... chip, A1-A4 ... side, B1-B8 ... side, C1-C4 ... angle , F ... frame, K ... cleaving line, L ... laser beam, P ... modified region, T ... tape, W ... wafer

Claims (4)

A laser dicing step of forming a modified region inside the wafer along a dicing street that is a cutting planned line of the wafer by condensing a laser beam inside the wafer mounted on the frame via a tape;
Exposing the modified region mounted on the frame via the tape to a plasma atmosphere, shrinking the tape to expand the wafer and cleave it into individual chips; A laser dicing method, wherein the wafer is cleaved into individual chips by a plasma cleaving stress relief process for etching a region of the cleaved chip exposed to a plasma atmosphere.   The laser dicing method according to claim 1, wherein the plasma is low-temperature plasma irradiated at 40 ° C. or more and 80 ° C. or less.   The laser dicing method according to claim 1 or 2, wherein the base material of the tape is formed of polyolefin, vinyl chloride, polyethylene, or polypropylene. A laser head that forms a modified region within the wafer by condensing the laser light into the wafer mounted on the frame via a tape;
A wafer table for holding the wafer;
A movement axis for relatively moving the wafer table and the laser head;
A plasma irradiation unit that shrinks the tape exposed to a plasma atmosphere to expand the wafer and cleave it into individual chips, and etch a region of the cleaved chip that is exposed to the plasma atmosphere. A laser dicing apparatus characterized by that.

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