Manufacturing method of device chip

Abstract

To provide a manufacturing method of a device chip, capable of suppressing damage to a pattern formed on the surface of a wafer when the wafer is divided along a planned division line.SOLUTION: A manufacturing method of a device chip includes: a shield tunnel forming step 1 of positioning a focal point of a laser beam having a wavelength that is transparent to the wafer inside the wafer and irradiating the wafer with a laser beam from the back side to form a shield tunnel including a pore and an amorphous region surrounding the pore along a planned division line; and a wafer dividing step 2 of applying an external force to the wafer to divide the wafer along the planned division line along which the shield tunnel is formed. In the shield tunnel forming step 1, the beam spot on the front side of the wafer of the laser beam that reaches the front side of the wafer is set to be equal to or smaller than the width of the planned division line.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a device chip. [Background technology]

[0002] In recent years, there has been an increasing demand for smaller chips in semiconductor wafers and optical device wafers, and as a result, importance has been placed on the straightness of the cross section of the device chip.

[0003] One method that has attracted attention as a processing technique that achieves high straightness in the cross section is to position the focal point of a pulsed laser beam with a wavelength that is transparent to the wafer inside the area to be divided and irradiate the beam to form a shielded tunnel consisting of a pore and the amorphous material surrounding the pore (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6062287 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is a possibility that some of the laser beams irradiated to form shield tunnels during processing may be transmitted through the front surface of the wafer, damaging the pattern and reducing the yield.

[0006] The present invention has been made in consideration of such problems, and its object is to provide a method for manufacturing device chips that can suppress damage to patterns formed on the surface of a wafer when the wafer is divided along the planned division lines. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the device chip manufacturing method of the present invention is a device chip manufacturing method in which a wafer having a plurality of planned division lines formed on its surface and a plurality of devices formed in areas partitioned by the planned division lines is divided into a plurality of chips along the planned division lines, the method including: a shield tunnel forming step in which a focal point of a laser beam having a wavelength that is transparent to the wafer is positioned inside the wafer and the laser beam is irradiated from the back side of the wafer to form a shield tunnel including a pore and an amorphous region surrounding the pore along the planned division lines; and a wafer dividing step in which an external force is applied to the wafer to divide the wafer along the planned division lines along which the shield tunnel is formed, the shield tunnel forming step being characterized in that a beam spot on the front side of the wafer of the laser beam that reaches the front side of the wafer is set to be equal to or smaller than the width of the planned division lines.

[0008] Also, in the method for manufacturing a device chip, in the shield tunnel formation step, the beam spot on the surface side of the wafer of the exit light of the laser beam that reaches the surface side of the wafer may be set to be rectangular having a longitudinal direction parallel to the extension direction of the planned division line.

[0009] Also, in the method for manufacturing a device chip, in the shield tunnel formation step, the beam spot on the surface side of the wafer of the exit light of the laser beam that reaches the surface side of the wafer may be set to have an elliptical shape having a major axis parallel to the extension direction of the planned division line. Effect of the Invention

[0010] The present invention can suppress damage to a pattern formed on the surface of a wafer when the wafer is divided along the planned division lines. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is a perspective view showing an example of a wafer to be processed in a method for manufacturing a device chip according to an embodiment. [Diagram 2] FIG. 2 is a flowchart showing the flow of the method for manufacturing the device chip according to the embodiment. [Diagram 3] FIG. 3 is a perspective view showing a configuration example of a laser processing apparatus for carrying out the shield tunnel forming step shown in FIG. [Figure 4] FIG. 4 is a schematic diagram of the laser beam irradiation unit of the laser processing apparatus shown in FIG. [Diagram 5] FIG. 5 is a side view, partially in section, showing one state of the shield tunnel forming step shown in FIG. [Figure 6] FIG. 6 is a side view, partly in section, showing a state subsequent to that shown in FIG. [Figure 7] FIG. 7 is a perspective view that illustrates a schematic structure of the shield tunnel. [Figure 8] FIG. 8 is a perspective view showing an example of a beam spot of the escape light. [Figure 9] FIG. 9 is a perspective view showing an example of a beam spot of the escape light. [Figure 10] FIG. 10 is a perspective view showing a beam spot of the escape light in the comparative example. [Figure 11] FIG. 11 is a side view, partly in section, showing one state of the wafer dividing step shown in FIG. [Figure 12] FIG. 12 is a side view, partly in section, showing a state subsequent to that shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0013] [Embodiment] A method for manufacturing a device chip 16 according to an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing an example of a wafer 10 to be processed in the method for manufacturing a device chip 16 according to an embodiment. The wafer 10 shown in Fig. 1 is a disk-shaped wafer such as a semiconductor device wafer or an optical device wafer, with a substrate 11 made of silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), silicon carbide (SiC), lithium tantalate (LiTaO3), or the like.

[0014] The wafer 10 has, on its surface 12, a plurality of planned dividing lines 13 set in a lattice pattern, and devices 14 formed in areas partitioned by the intersecting planned dividing lines 13. The devices 14 are, for example, integrated circuits such as ICs (Integrated Circuits) or LSIs (Large Scale Integrations), or image sensors such as CCDs (Charge Coupled Devices) or CMOSs ​​(Complementary Metal Oxide Semiconductors).

[0015] The wafer 10 is transported and processed while being supported by, for example, an annular frame 30 and a tape 31 as shown in Fig. 3 and other figures described below. The frame 30 is an annular plate member made of metal or resin and having an opening larger than the outer diameter of the wafer 10. The tape 31 is in the form of a sheet with an outer diameter larger than the opening of the frame 30, and is attached to the back side of the frame 30 so as to cover the opening of the frame 30.

[0016] The tape 31 may be configured to include, for example, a base layer made of an expandable synthetic resin and a glue layer laminated on the base layer and made of an expandable and adhesive synthetic resin, or may be configured of a thermoplastic resin without a glue layer. The wafer 10 is positioned at a predetermined position in the opening of the frame 30 and fixed to the frame 30 and the tape 31 by adhering the front surface 12 side or the back surface 15 side (in the embodiment, the front surface 12 side) to the tape 31.

[0017] The wafer 10 is divided along a plurality of planned division lines 13 into individual devices 14 to be manufactured into device chips 16. In the embodiment, the device chips 16 are square-shaped, but may be rectangular-shaped. In the embodiment, the wafer 10 is disk-shaped, but may not be disk-shaped in the present invention.

[0018] 2 is a flowchart showing a flow of a method for manufacturing the device chip 16 according to the embodiment. The method for manufacturing the device chip 16 is a method for manufacturing a plurality of device chips 16 from a wafer 10 to be processed. As shown in FIG. 2, the method for manufacturing the device chip 16 includes a shield tunnel forming step 1 and a wafer dividing step 2.

[0019] (Laser processing device 100) First, a configuration example of the laser processing apparatus 100 for performing the shield tunnel forming step 1 will be described. Fig. 3 is a perspective view showing a configuration example of the laser processing apparatus 100 for performing the shield tunnel forming step 1 shown in Fig. 2. Fig. 4 is a schematic configuration diagram of the laser beam irradiation unit 120 of the laser processing apparatus 100 shown in Fig. 3.

[0020] The laser processing apparatus 100 includes a chuck table 110, a laser beam irradiation unit 120, an imaging unit 140, and a moving unit (not shown) that moves the chuck table 110 and the laser beam irradiation unit 120 relatively. In the following description, the X-axis direction is one direction in a horizontal plane and is the processing feed direction. The Y-axis direction is a direction perpendicular to the X-axis in the horizontal plane and is the indexing feed direction. The Z-axis direction is a direction perpendicular to the X-axis and Y-axis directions and is the focus position adjustment direction.

[0021] The chuck table 110 is a support table that holds the wafer 10 on a holding surface 111. The chuck table 110 holds the front surface 12 side of the wafer 10 via, for example, a tape 31, and exposes the back surface 15 side. The holding surface 111 has a disk shape made of porous ceramics or the like, and is a flat surface parallel to the horizontal direction in the embodiment. The holding surface 111 is connected to a vacuum suction source via, for example, a vacuum suction path, and holds the wafer 10 placed on the holding surface 111 by suction.

[0022] The laser beam irradiation unit 120 is a unit that irradiates a pulsed laser beam 130 onto the wafer 10 held on the chuck table 110. As shown in FIG. 4, the laser beam irradiation unit 120 has an oscillator 121, a condenser 122, a mirror 123, and a beam shaping unit 124.

[0023] The oscillator 121 oscillates a laser beam 130 having a predetermined wavelength for processing the wafer 10. The condenser 122 is a condensing lens that condenses the laser beam 130 emitted from the oscillator 121 and irradiates the laser beam 130 toward the wafer 10 held on the holding surface 111 of the chuck table 110. The mirror 123 is provided on the optical path of the laser beam 130 between the oscillator 121 and the condenser 122, and reflects the laser beam 130 emitted from the oscillator 121 so as to guide it to the condenser 122.

[0024] The beam shaping unit 124 is provided on the optical path of the laser beam 130 between the oscillator 121 and the condenser 122, and shapes the beam shape of the laser beam 130 emitted from the oscillator 121 into a predetermined shape. The beam shaping unit 124 includes, for example, a well-known slit mask, a diffractive optical element (DOE), or a spatial light modulator (LCOS; Liquid Crystal On Silicon). The slit mask has a plate-shaped base material capable of blocking the laser beam 130, and a hole formed in the base material. The diffractive optical element adjusts the shape of the laser beam 130 by utilizing the diffraction phenomenon of light. The spatial light modulator has a display unit that displays a phase pattern for adjusting the optical characteristics when transmitting or reflecting (transmitting in the case of the arrangement shown in FIG. 4) the incident laser beam 130, and adjusts the shape of the emitted laser beam 130.

[0025] The imaging unit 140 shown in Fig. 3 captures an image of the wafer 10 held on the chuck table 110. The imaging unit 140 includes a CCD camera or an infrared camera. The imaging unit 140 is fixed, for example, adjacent to the collector 122 (see Fig. 4) of the laser beam irradiation unit 120. The imaging unit 140 captures an image of the wafer 10 to obtain an image for performing alignment between the wafer 10 and the laser beam irradiation unit 120, and outputs the obtained image.

[0026] (Shield tunnel formation step 1) Fig. 5 is a side view, partly in section, showing one state of the shield tunnel forming step 1 shown in Fig. 2. Fig. 6 is a side view, partly in section, showing one state after Fig. 5. Fig. 7 is a perspective view, partly in section, showing a schematic structure of the shield tunnel 20. The shield tunnel forming step 1 is a step of positioning a focal point 131 of a laser beam 130 having a wavelength that is transparent to the wafer 10 inside the wafer 10 and irradiating the wafer 10 from the back surface 15 side to form the shield tunnel 20 including the pores 21 and the amorphous regions 22 surrounding the pores 21 along the planned division line 13.

[0027] In the shield tunnel forming step 1, first, the front surface 12 side of the wafer 10 is sucked and held on the holding surface 111 of the chuck table 110 via the tape 31. Next, the planned dividing line 13 of the wafer 10 is aligned with the condenser 122 (see FIG. 4) of the laser beam irradiation unit 120. Specifically, the chuck table 110 is moved to the processing area below the laser beam irradiation unit 120 by a moving unit (not shown).

[0028] Next, the wafer 10 is photographed by the imaging unit 140 (see FIG. 3) to detect the planned dividing lines 13. Once the planned dividing lines 13 have been detected, alignment is performed to align the planned dividing lines 13 of the wafer 10 with the irradiation part of the laser beam irradiation unit 120. The irradiation part of the laser beam irradiation unit 120 is vertically opposed to the back surface 15 of the wafer 10 corresponding to the area where the planned dividing lines 13 are set, and then a focal point 131 of the laser beam 130 is set inside the wafer 10.

[0029] In the shield tunnel forming step 1, the chuck table 110 and the laser beam application unit 120 are then moved relatively in the processing feed direction to apply the laser beam 130 along the planned dividing line 13, while applying the pulsed laser beam 130 to the inside of the wafer 10. As a result, as shown in Fig. 6, shield tunnels 20 are formed along the planned dividing line 13 from near a focusing point 131 of the laser beam 130 positioned inside the wafer 10 toward the front surface 12 and the back surface 15 of the wafer 10. The shield tunnels 20 are formed at predetermined intervals along the planned dividing line 13 by application of the pulsed laser beam 130.

[0030] 7, the shield tunnel 20 has a pore 21 extending from the front surface 12 to the back surface 15 of the wafer 10, and a cylindrical amorphous region 22 surrounding the pore 21. The inner diameter 211 of the pore 21 is about 1 μm, the outer diameter 221 of the amorphous region 22 is about 5 μm, and the distance between adjacent amorphous regions 22 is about 10 μm.

[0031] At this time, a beam spot 133 on the surface 12 side of the through light 132 of the laser beam 130 that reaches the surface 12 side of the wafer 10 is set to be equal to or smaller than the width of the planned dividing lines 13. Figs. 8 and 9 are perspective views showing an example of the beam spot 133 of the through light 132. Fig. 10 is a perspective view showing the beam spot 133 of the through light 132 in a comparative example. Note that in Figs. 8 to 10, the entire wafer 10 is not shown, and only the planned dividing lines 13 formed on the surface 12 side are shown. Also, in Figs. 8 to 10, the light condensing point 131 is assumed to be positioned inside the wafer 10.

[0032] The beam spot 133 may be set to have a rectangular shape having a longitudinal direction parallel to the extension direction of the division line 13, as shown in FIG. 8, for example. Alternatively, the beam spot 133 may be set to have an elliptical shape having a major axis parallel to the extension direction of the division line 13, as shown in FIG. 9, for example. In other words, in the laser processing apparatus 100 performing the shield tunnel forming step 1, the beam shape of the laser beam 130 emitted from the oscillator 121 is adjusted by the beam shaping unit 124 so that the beam spot 133 has a desired shape. In this specification, the term "rectangular shape" is not limited to a strict rectangular shape, and includes a shape with rounded corners. In this specification, the term "elliptical shape" is not limited to a strict elliptical shape, and may be any shape consisting of a closed curved line that is convex overall, for example, an oval shape.

[0033] 10 shows a comparative example in which the beam shape of the laser beam 130 is not adjusted by the beam shaping unit 124. In such a case, the through light 132 that reaches the front surface 12 side of the wafer 10 exceeds the width of the planned division lines 13 and is irradiated onto the region in which the devices 14 are formed. In the embodiment, as shown in FIG. 8 and FIG. 9, the beam spot 133 is set to be equal to or smaller than the width of the planned division lines 13, thereby suppressing irradiation of the through light 132 onto the devices 14.

[0034] The processing conditions in the embodiment are as follows. The defocus is the distance from the back surface 15 of the wafer 10 to the focal point 131 as set in the device. The beam diameter before focusing is the beam diameter of the laser beam 130 before it is emitted from the oscillator 121 and enters the beam shaping unit 124 in the embodiment. The beam shape after focusing is the shape of the beam spot 133 on the front surface 12 side of the exit light 132 of the laser beam 130. ·Wavelength: 1064nm Output power: 1.6W Defocus: 0.015mm Frequency: 40kHz Feed speed: 700mm / s Beam diameter before focusing: 3.0mm -Beam shape after focusing: 60μm x 20μm rectangular

[0035] (Wafer division step 2) Fig. 11 is a side view, partially in section, showing one state of the wafer dividing step 2 shown in Fig. 2. Fig. 12 is a side view, partially in section, showing one state after Fig. 11. The wafer dividing step 2 is a step in which an external force is applied to the wafer 10 to divide the wafer 10 along the dividing lines 13 along which the shield tunnels 20 are formed.

[0036] 11 and 12, in wafer dividing step 2 of the embodiment, the expanding device 150 applies an external force in a radial direction to the tape 31, thereby dividing the wafer 10. The expanding device 150 includes a chuck table 151, a clamp member 152, a lifting unit 153, a push-up member 154, and a roller member 155. The push-up member 154 has a cylindrical shape and is provided on the outer periphery of and coaxial with the chuck table 151. The roller member 155 is provided on the same plane as or slightly above the holding surface of the chuck table 151, and at the upper end of the push-up member 154, so as to be freely rotatable.

[0037] 11, in wafer dividing step 2, first, the front surface 12 side of the wafer 10 is placed on the holding surface (upper surface) of a chuck table 151 via the tape 31, and the outer periphery of the frame 30 is fixed by clamp members 152. At this time, roller members 155 abut against the tape 31 between the inner edge of the frame 30 and the outer edge of the wafer 10.

[0038] 12, in wafer dividing step 2, next, the chuck table 151 and the push-up member 154 are raised together by the lifting unit 153. At this time, since the outer periphery of the tape 31 is fixed by the clamp member 152 via the frame 30, the portion between the inner edge of the frame 30 and the outer edge of the wafer 10 is expanded in the planar direction. Furthermore, the roller member 155 provided at the upper end of the push-up member 154 reduces friction with the tape 31.

[0039] In the wafer dividing step 2, as a result of the expansion of the tape 31, a radial tensile force acts on the tape 31. When the radial tensile force acts on the tape 31, the wafer 10 to which the tape 31 is attached is divided at the shield tunnels 20 along the planned dividing lines 13 as fracture starting points, and is divided into individual device chips 16, as shown in Fig. 12. After the wafer 10 is divided into the device chips 16, the device chips 16 are picked up from the tape 31 by, for example, a well-known picker in a pick-up process.

[0040] In addition, in the wafer dividing step 2, the method of applying an external force to the wafer 10 is not limited to the method of applying an external force by expanding the tape 31 shown in Figures 11 and 12, and may be, for example, a method in which a breaking device applies a pressing force in the thickness direction of the wafer 10 along the intended dividing line 13.

[0041] As described above, in the manufacturing method of the device chip 16 of the embodiment, of the laser beam 130 irradiated to form the shield tunnel 20, the beam spot 133 on the surface 12 side of the laser beam 130, which reaches the surface 12 side of the wafer 10, of the through light 132 is set to be equal to or smaller than the width of the planned division lines 13. This prevents the through light 132 from exceeding the width of the planned division lines 13 and being irradiated onto the region where the devices 14 are formed, thereby suppressing damage to the pattern formed on the surface 12 of the wafer 10 and improving the yield.

[0042] It should be noted that the present invention is not limited to the above-described embodiment, and can be practiced in various modified forms without departing from the gist of the present invention. [Explanation of symbols]

[0043] 10 wafers 11 Substrate 12 Surface 13 Division line 14 Devices 15 Back side 16 Device Chips 20 Shield Tunnel 21 Pore 22 Amorphous Region 30 frames 31 Tape 100 Laser processing equipment 110 Chuck table 120 Laser beam irradiation unit 121 Oscillator 122 Concentrator 123 Mirror 124 Beam Forming Unit 130 Laser Beam 131 Focus point 132 Light Through 133 Beam Spot 140 Imaging unit 150 Expansion Unit

Claims

1. A method for manufacturing device chips, comprising the steps of: dividing a wafer having a plurality of division lines formed on a surface thereof and a plurality of devices formed in areas partitioned by the division lines into a plurality of chips along the division lines, a shield tunnel forming step of positioning a focal point of a laser beam having a wavelength that is transparent to the wafer inside the wafer and irradiating the wafer from the back side of the wafer to form a shield tunnel including a pore and an amorphous region surrounding the pore along the intended division line; a wafer dividing step of dividing the wafer along the dividing lines along which the shield tunnels are formed by applying an external force to the wafer, In the shield tunnel forming step, The beam spot of the laser beam reaching the front surface side of the wafer is set to be equal to or smaller than the width of the intended dividing line. A method for manufacturing a device chip.

2. In the shield tunnel forming step, The beam spot on the surface side of the wafer of the laser beam that reaches the surface side of the wafer is set to have a rectangular shape having a longitudinal direction parallel to the extension direction of the dividing lines.

2. The method for manufacturing a device chip according to claim 1.

3. In the shield tunnel forming step, The beam spot on the surface side of the wafer of the laser beam that reaches the surface side of the wafer is set to have an elliptical shape having a major axis parallel to the extension direction of the dividing lines.

2. The method for manufacturing a device chip according to claim 1.

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