JP2010003817A - Laser dicing method, and laser dicing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser dicing method improving the deflection strength of a chip by controlling a formation situation of a modifying region, and to provide a laser dicing device. <P>SOLUTION: Irradiation and irradiation stoppage of a laser light L emitted from a laser head 4 is controlled by a control means, and forming regions 11 with modifying regions continuously formed therein, and continuous non-forming regions 12 without forming the modifying regions are formed around a chip, whereby efficient laser dicing having a high yield, without deflection strength becoming deteriorated. <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 move the blade and the relative position of the wafer, and a wafer on the wafer table. An imaging means such as a CCD camera or a microscope, a cleaning means for cleaning the work after dicing, a control means for controlling each part, and the like 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 cleaving line is formed is cleaved naturally starting from the cleaving line, or the wafer is transferred to an expander or the like equipped with a fixing mechanism or a push-up mechanism and expanded or braked to start the cleaving line. Cleaved 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 cleaved 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, when picking up a chip after dicing with a laser in recent years, there has been a problem that the chip breaks. This is because the thinning of the wafer and the shrinking of the chip have progressed and the bending strength has decreased, and the modified region formed continuously by the laser at the chip periphery has made the chip periphery brittle, further increasing the chip bending strength. It is thought that it has decreased.

  The present invention has been made for such a problem, and a laser dicing method and a laser dicing apparatus which improve the bending strength of a chip by controlling the formation of a modified region by controlling the irradiation of laser light. The purpose is to provide.

  In order to achieve the above object, the dicing method of the present invention forms a cutting line by forming a modified region with a laser beam inside a wafer placed on a wafer table and moved by a moving means, and the cutting line is formed. Forming a modified region by irradiating the laser beam in a laser dicing method in which the wafer is divided along the planned cutting line by forming one or more along the planned cutting line of the wafer The cleaving line is formed by a process and an unformed process in which the modified region is not formed.

  According to the dicing method of the present invention, a wafer table, a processing means for forming a modified region inside the wafer by laser light, an imaging means for imaging the wafer, a plurality of moving means, and a control for controlling the operation of each part. The wafer is divided along the planned cutting line by forming one or more cutting lines formed by the continuous modified region along the planned cutting line of the wafer.

  At this time, each cutting line is formed by a continuous non-formed region that does not form a modified region by stopping the irradiation of laser light, and a formation region that is formed by continuously irradiating a laser beam to form a modified region. Yes.

  As a result, on the peripheral edge of each of the divided chips, a portion where the trace of the formed modified region remains and a portion of the material that forms the wafer having no trace of the modified region are formed. The peripheral edge of the film does not become brittle, the bending strength is not lowered, and efficient laser dicing with a high yield becomes possible.

  The dicing method of the present invention is the dicing method according to the present invention, wherein the non-formed regions formed by the non-formed step and the formed regions formed by the forming step are alternately formed along the planned cutting line, A plurality of unformed regions and formed regions are arranged vertically in the depth direction of the wafer and perpendicular to the surface of the wafer.

  According to the present invention, the non-formed regions and the formed regions are alternately formed with a predetermined length when forming one breaking line. The unformed region and the formed region formed in the second and subsequent cutting lines are formed at the same position and length as the first so as to be aligned in the depth direction of the wafer perpendicularly to the surface of the wafer. .

  As a result, a portion having a trace of a parallel striped modified region remaining on the periphery of the chip and a portion having no trace of the modified region are formed, and the entire periphery of the chip does not become brittle, and the bending strength is reduced. Is reduced, and efficient laser dicing with a high yield becomes possible.

  As described above, according to the dicing method and the laser dicing apparatus of the present invention, the unformed region and the formed region are formed in the cleaving line by controlling the irradiation of the laser beam, and the peripheral edge of the chip is not made brittle. High-yield and efficient laser dicing without lowering the bending strength becomes possible.

  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 front view showing a processing portion of a laser dicing apparatus.

  The laser dicing apparatus includes a processing unit equipped with a laser head, a load port for mounting a cassette containing a number of wafers W mounted on a frame, a transport means for transporting the wafer W, and each unit necessary for control and processing of each unit. A control means for storing device data in which the control procedure and numerical values are input.

  In the processing unit 10 of the laser dicing apparatus, as shown in FIG. 1, a wafer W is placed on a wafer table 2 provided on an X moving shaft 1 as a moving means, and the X moving shaft 1 is placed on the wafer table 2. A laser head 4 is provided to face a Y moving shaft 3 as a moving means provided so as to be orthogonal to each other. In addition to this, the processing unit 10 includes a Z movement axis for moving the laser head 4 in the vertical direction, an imaging means for imaging the surface of the wafer W, and the like.

  The laser head 4 includes a laser oscillator 5, a collimating lens 6, a mirror 7, a condensation lens 8, and the like. The laser light L oscillated from the laser oscillator 5 is converted into parallel rays in the horizontal direction by the collimating lens 6. The light is reflected in the vertical direction and collected by the condensation lens 8.

  When the condensing point of the laser beam L is set inside the thickness direction of the wafer W placed on the wafer table 2, 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 workpiece.

  As shown in FIG. 2B, the modified region P is formed side by side inside the wafer W when the wafer W is moved in the horizontal direction by the X movement axis 1, and follows the planned cutting line of the wafer W. Thus, the cutting line K is formed. A plurality of cleaving lines K are formed along the planned cleaving lines, and in this state, the wafer W is naturally cleaved starting from the cleaving line K, or is transferred to an expander or the like equipped with a fixing mechanism or a push-up mechanism. And breaking is performed with the breaking line K as a starting point. The cleaved wafer W is easily divided into chips without causing chipping on the front and back surfaces.

  Next, the laser dicing method according to the present invention will be described. FIG. 3 is a sectional view of a wafer diced by the laser dicing method according to the present invention.

  In the laser dicing method of the present invention, the laser light L is irradiated from the laser head 4 to the wafer W placed on the wafer table 2 shown in FIG. The reforming region P is continuously formed, and the cutting line K is formed along the planned cutting line.

  At this time, irradiation of the laser light L irradiated from the laser head 4 and irradiation stop are controlled based on device data stored in the control means. As a result, as shown in FIG. 3A, the laser beam L is irradiated as shown by L1, and the modified region is continuously formed, and the laser beam L is irradiated as indicated by L2. The continuous unformed regions 12, 12... That stop and do not form the modified region are alternately formed to form the cutting line K.

  After the first breaking line K is formed in this way, the second breaking line K1 is formed. As shown in FIG. 3B, the cleavage line K1 is formed with the formation region 11 and the non-formation region 12 at the same position as the cleavage line K and with the same length. Subsequently, as shown in FIG. 3 (c), the cutting lines K2, K3,... Are formed at the same position and the same length as the cutting line K so as to be aligned perpendicular to the surface of the wafer W in the depth direction of the wafer W. Region 11 and unformed region 12 are formed.

  The ratio of forming the formation region 11 and the non-formation region 12 is adapted to a ratio that can be divided by using Expand + Bracing, and is optimal depending on the doping amount of the wafer substrate and the surface device structure (mainly the film structure on the street and the TEG situation). Conditions are different.

  After the cleaving line is formed in the planned cleaving line in this way, the wafer W is naturally cleaved, or is transferred to an expander or the like equipped with a fixing mechanism or a push-up mechanism, and expanded or braked. Is divided into individual chips by cleaving from the cleaving line as a starting point.

  As a result, a formed region 11 in which the trace of the formed modified region remains and an unformed region 12 made of a material having no trace of the modified region are formed at the periphery of the chips divided individually. Since the unformed region 12 made of a material having no trace of the modified region is formed on the periphery of the chip, the periphery of the chip does not become brittle and the bending strength does not decrease.

  As described above, according to the laser dicing method and the laser dicing apparatus according to the present invention, the unformed region and the formed region are formed in the cleaving line by controlling the irradiation of the laser light and the irradiation stop, and the peripheral edge of the chip. The entire circumference is not made brittle. As a result, the bending strength does not decrease in a thinned wafer, a reduced chip, or a relatively fragile MEMS (Micro Electro Mechanical Systems) device, and high yield and efficient laser dicing becomes possible. . Moreover, the dust at the time of cleaving is also reduced, and it becomes possible to provide a high-quality product.

  In the present embodiment, the unformed region and the formed region are formed in the same length as the first one so as to be aligned in the depth direction of the wafer perpendicularly to the surface of the wafer, and the peripheral edge of the chip. However, the present invention is not limited to this, and other regions may be used as long as the non-formed region and the formed region are formed so as to satisfy a predetermined relationship. Even if it forms so that it may become a shape, it can implement suitably.

  As an example of forming the non-formed region and the formed region other than the present embodiment, for example, when the non-formed region and the formed region are formed in parallel stripes as shown in FIG. When the non-formed region and the formed region are formed in a triangular shape as shown in FIG. 4B, the formed region is formed in a triangular shape facing each other as shown in FIG. The case where it forms so that a rhombus shape may be comprised is feasible.

The side view which showed the structure of the laser dicing apparatus. The side view which showed the state of the dicing by a laser. Sectional drawing of the wafer diced by the laser dicing method concerning this invention. Sectional drawing of the wafer by another embodiment of the laser dicing method concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... X movement axis, 2 ... Wafer table, 3 ... Y movement axis, 4 ... Laser head, 5 ... Laser oscillator, 6 ... Collimating lens, 7 ... Mirror, 8 ... Condensation lens, 10 ... Laser dicing apparatus, 11 ... Formation Area, 12 ... Unformed area, K, K2, K3 ... Cleaving line, L ... Laser light, P ... Modified area, W ... Wafer

Claims (3)

A modified region is formed by laser light inside the wafer placed on the wafer table and moved by the moving means to form a cleaving line, and one or more cleaving lines are formed along the cleaving line of the wafer. Thus, in the laser dicing method of dividing the wafer along the planned cutting line,
Forming the modified region by irradiating the laser beam; and
The laser dicing method, wherein the cleaving line is formed by an unformed step in which the modified region is not formed.   The non-formed regions formed by the non-formed step and the formed regions formed by the formed step are alternately formed along the planned cutting line, and the non-formed regions and the formed regions are respectively formed on the wafer. The laser dicing method according to claim 1, wherein a plurality of lines are arranged vertically in the depth direction with respect to the surface of the wafer. A wafer table on which the wafer is placed;
Processing means for forming a modified region inside the wafer by laser light;
Moving means for relatively moving the wafer table and the processing means;
By control means for controlling the operation of the processing means and the moving means,
Performing a forming step of forming the modified region by irradiating the laser beam and a non-forming step of not forming the modified region to form one or more cutting lines along a planned cutting line of the wafer; A laser dicing apparatus that divides a wafer along the cleaving line.

Images