Semiconductor device manufacturing method and laser processing apparatus

Abstract

To provide a laser processing method capable of suppressing peeling of an organic film.SOLUTION: A laser processing method for performing laser processing on a wafer having a functional layer on a substrate includes: a blackening step 1003 of generating a pulsed laser beam of a wavelength that is transparent to the functional layer by an oscillator, and irradiating the functional layer with a pulsed laser beam having energy equal to or greater than a processing threshold value at which the functional layer is processed, such that the overlap rate of the pulsed laser beams successively radiated onto the functional layer is 90% or more and less than 100%, thereby blackening the functional layer; and a groove processing step 1004 of radiating a pulsed laser beam to the blackened functional layer to cause the blackened functional layer to absorb the pulsed laser beam after performing the blackening step 1003 to form a laser-processed groove.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a semiconductor device and a laser processing apparatus. [Background technology]

[0002] In recent years, in order to increase the processing speed of semiconductor devices, semiconductor devices have been formed by laminating an interlayer insulating film made of an organic low-dielectric constant material (so-called low-k material), which is a polymer film such as a polyimide or parylene, on a silicon wafer, and a circuit layer, and semiconductor wafers in which an organic film is laminated on the surface of a silicon substrate have been put to practical use (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-126054 A Summary of the Invention [Problem to be solved by the invention]

[0004] Low-k materials are brittle like mica and peel off when cut with a cutting blade. Therefore, as disclosed in the above-mentioned Patent Document 1, laser ablation technology is used to form laser-processed grooves in device layers containing low-k materials.

[0005] Laser beams with wavelengths of, for example, 355 nm or 532 nm are used for ablation processing of semiconductor wafers. However, the interlayer insulating film, which is made of low-k material, is transparent to these laser beams in the ultraviolet to visible light range and does not absorb the irradiated laser beam. Therefore, by focusing the laser beam on the silicon wafer, the device layer is processed along with the silicon wafer.

[0006] However, there were problems such as localized peeling of the organic film as the silicon wafer sublimated when the laser beam was focused on the silicon wafer, and improvements were eagerly sought.

[0007] An object of the present invention is to provide a semiconductor device manufacturing method and a laser processing apparatus that can suppress peeling of an organic film. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, the manufacturing method of a semiconductor device of the present invention is a manufacturing method of a semiconductor device, which comprises: a blackening step of irradiating a laser beam of a wavelength that is transparent to a functional layer of a semiconductor wafer having devices formed in each area partitioned by intersecting planned division lines along the planned division lines to blacken the functional layer; and a groove processing step of irradiating the laser beam along the planned division lines after the blackening step to cause the laser beam to be absorbed by the blackened functional layer to form laser processed grooves, and is characterized in that after the groove processing step, the wafer is divided along the planned division lines to form a plurality of devices.

[0009] In the method for manufacturing a semiconductor device, in the blackening step, the laser beam irradiated to the functional layer may be modified so that a Gaussian distribution has a vertical skirt.

[0010] In the method for manufacturing a semiconductor device, in the blackening step, the functional layer may be blackened by irradiating the laser beam with a higher overlap rate and lower energy than in the groove processing step, and in the groove processing step, the laser beam may be irradiated with a lower overlap rate and higher energy than in the blackening step to form the laser processed groove.

[0011] The laser processing apparatus of the present invention is characterized by comprising a chuck table that holds a semiconductor wafer having a functional layer including a low dielectric constant insulating coating and having devices formed in each area partitioned by intersecting planned division lines on the surface; a laser beam irradiation unit that performs the following steps: a blackening step in which a laser beam is irradiated onto the semiconductor wafer, the laser beam having a wavelength that is transparent to the functional layer being irradiated along the planned division lines to blacken the functional layer; and a groove processing step in which, after the blackening step, the laser beam is irradiated along the planned division lines to cause the blackened functional layer to absorb the laser beam, thereby forming laser processed grooves.

[0012] In the laser processing apparatus, the laser beam irradiation unit may include an energy distribution correction means for correcting a base portion of a Gaussian distribution of the laser beam irradiated to the functional layer in the blackening step into a vertical distribution.

[0013] In the laser processing apparatus, the laser beam irradiation unit may, in the blackening step, irradiate the laser beam with a higher overlap rate and lower energy than in the groove processing step to blacken the functional layer, and may, in the groove processing step, irradiate the laser beam with a lower overlap rate and higher energy than in the blackening step to form the laser processed groove. Effect of the Invention

[0014] The present invention has an effect of suppressing peeling of the organic film. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view of a wafer to be processed by the laser processing method according to the first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of a main part of the wafer shown in FIG. [Diagram 3] FIG. 3 is a perspective view showing an example of the configuration of a laser processing device for performing a part of the laser processing method according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating a schematic configuration of a laser beam irradiation unit of the laser processing apparatus shown in FIG. [Diagram 5] FIG. 5 is a diagram showing a schematic diagram of the energy distribution of the pulse laser beam before being shaped by the mask of the laser beam irradiation unit shown in FIG. [Figure 6] FIG. 6 is a diagram showing a schematic diagram of the energy distribution of the pulse laser beam shaped by the mask of the laser beam irradiation unit shown in FIG. [Figure 7] FIG. 7 is a flowchart showing the flow of the laser processing method according to the first embodiment. [Figure 8] FIG. 8 is a side view, partially in cross section, typically showing the protective film forming step of the laser processing method shown in FIG. [Figure 9] FIG. 9 is a diagram for explaining the overlap rate of the pulse laser beam in the laser processing method shown in FIG. [Figure 10] FIG. 10 is a side view, partially in section, typically showing the blackening step of the laser processing method shown in FIG. [Figure 11] FIG. 11 is a side view, partially in section, typically showing the groove machining step of the laser machining method shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 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.

[0017] [Embodiment 1] A laser processing method according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a wafer to be processed by the laser processing method according to the first embodiment. FIG. 2 is a cross-sectional view of a main part of the wafer shown in FIG. 1. FIG. 3 is a perspective view showing a configuration example of a laser processing device for carrying out a part of the laser processing method according to the first embodiment. FIG. 4 is a diagram showing a schematic configuration of a laser beam irradiation unit of the laser processing device shown in FIG. 3. FIG. 5 is a diagram showing a schematic energy distribution of a pulse laser beam before being shaped by a mask of the laser beam irradiation unit shown in FIG. 4. FIG. 6 is a diagram showing a schematic energy distribution of a pulse laser beam shaped by a mask of the laser beam irradiation unit shown in FIG. 4. FIG. 7 is a flowchart showing a flow of the laser processing method according to the first embodiment.

[0018] (Wafer) The laser processing method according to the first embodiment is a method of performing laser processing on a wafer 200 shown in Figures 1 and 2. The wafer 200 to be processed by the laser processing method according to the first embodiment is a disk-shaped semiconductor wafer having a silicon substrate 201. The wafer 200 has a surface 202 on which a plurality of mutually intersecting dividing lines 203 are set, and devices 204 are formed in areas defined by the dividing lines 203.

[0019] The device 204 is, for example, an integrated circuit such as an integrated circuit (IC) or a large scale integration (LSI), or an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS).

[0020] 1 and 2, the wafer 200 has a functional layer 205, which is an organic film, on a base material 201. The functional layer 205 includes a low dielectric constant insulator coating (hereinafter referred to as a low-k film) made of an inorganic film such as SiOF or BSG (SiOB), an organic film such as a polymer film of a polyimide or parylene, or carbon-containing silicon oxide (SiOCH), and a circuit layer made of a conductive metal.

[0021] The low-k film is laminated with a circuit layer to form a device 204. The circuit layer constitutes the circuit of the device 204. For this purpose, the device 204 is formed by the mutually laminated low-k films of the functional layer 205 laminated on the substrate 201 and the circuit layer laminated between the low-k films. The functional layer 205 of the planned division line 203 is formed of a low-k film and does not include a conductive film except for a TEG (Test Element Group). The TEG is an evaluation element for finding design and manufacturing problems that occur in the device 204.

[0022] 3, the wafer 200 is supported within an opening of the annular frame 210 by having a disc-shaped adhesive tape 209 having a diameter larger than the outer diameter of the wafer 200 and an annular frame 210 attached to its outer edge attached to a back surface 206 behind the front surface 202. The wafer 200 is cut along intended division lines 203 to be divided into individual devices 204.

[0023] (Laser processing equipment) A part of the laser processing method according to the first embodiment is performed by a laser processing apparatus 1 shown in Fig. 3. The laser processing apparatus 1 shown in Fig. 3 is an apparatus that irradiates a wafer 200 with a pulsed pulsed laser beam 21 and performs laser processing (corresponding to processing) on ​​the wafer 200. As shown in Fig. 3, the laser processing apparatus 1 includes a chuck table 10 having a holding surface 11 that holds the wafer 200, a laser beam irradiation unit 20, a moving unit 30, an imaging unit 40, and a control unit 100.

[0024] The chuck table 10 holds the wafer 200 on a holding surface 11 that is parallel to the horizontal direction. The holding surface 11 is disk-shaped and made of porous ceramics or the like, and is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown). The chuck table 10 holds the wafer 200 placed on the holding surface 11 by suction. A plurality of clamps 12 are arranged around the chuck table 10 to clamp an annular frame 210 that supports the wafer 200 in an opening.

[0025] Furthermore, the chuck table 10 is rotated by the rotary movement unit 34 of the moving unit 30 about an axis parallel to the Z-axis direction which is perpendicular to the holding surface 11 and parallel to the vertical direction. The chuck table 10, together with the rotary movement unit 34, is moved in the X-axis direction parallel to the horizontal direction by the X-axis movement unit 31 of the moving unit 30, and is moved in the Y-axis direction which is parallel to the horizontal direction and perpendicular to the X-axis direction by the Y-axis movement unit 32. The chuck table 10 is moved by the moving unit 30 between a processing area below the laser beam irradiation unit 20 and a carry-in / out area away from below the laser beam irradiation unit 20 where the wafer 200 is carried in and out.

[0026] The laser beam irradiation unit 20 is a unit that irradiates a pulsed pulsed laser beam 21 to the wafer 200 held on the chuck table 10. In the first embodiment, the laser beam irradiation unit 20 is a laser beam irradiation means that irradiates the wafer 200 with a pulsed pulsed laser beam 21 having a wavelength (514 nm in the first embodiment, but may be 355 nm or 266 nm in the present invention) that is absorbent for the base material 201 of the wafer 200 and transparent for the functional layer 205, thereby performing laser processing on the wafer 200.

[0027] In embodiment 1, a portion of the laser beam irradiation unit 20 is supported by a lifting member 4 that is moved in the Z-axis direction by a Z-axis moving unit 33 of a moving unit 30 provided on an erect wall 3 erected from the device main body 2, as shown in FIG.

[0028] Next, a description will be given of the configuration of the laser beam irradiation unit 20. As shown in Fig. 4, the laser beam irradiation unit 20 includes an oscillator 22 that oscillates a pulsed pulsed laser beam 21 for processing a wafer 200, a condenser lens 23 that condenses the pulsed laser beam 21 oscillated from the oscillator 22 onto the wafer 200 held on the holding surface 11 of the chuck table 10, at least one optical component 24 that is provided on the optical path of the pulsed laser beam 21 between the oscillator 22 and the condenser lens 23 and that guides the pulsed laser beam 21 generated by the oscillator 22 from the oscillator 22 to the condenser lens 23, and a mask unit 25.

[0029] In the first embodiment, the energy distribution 212 of the pulsed laser beam 21 generated by the oscillator 22 is a Gaussian distribution in which the energy is strongest on the optical axis 211 of the optical path of the pulsed laser beam 21 and gradually decreases with increasing distance from the optical axis 211, as shown in Fig. 5. The horizontal axis of Fig. 5 indicates the position in the Y-axis direction, and the center of the horizontal axis indicates the optical axis 211 of the optical path of the pulsed laser beam 21. The vertical axis of Fig. 5 indicates energy. Although Fig. 5 shows the energy distribution 212 of the pulsed laser beam 21 at a position parallel to the Y-axis direction, the energy distribution 212 of the pulsed laser beam 21 also has a Gaussian distribution at a position parallel to the X-axis direction.

[0030] The condenser lens 23 is disposed at a position facing the holding surface 11 of the chuck table 10 in the Z-axis direction. The condenser lens 23 transmits the pulsed laser beam 21 oscillated from the oscillator 22 and condenses the pulsed laser beam 21 at a condensing point 21-1. In the first embodiment, the laser beam irradiation unit 20 includes a mirror that reflects the pulsed laser beam 21 as the optical component 24, but in the present invention, the optical component 24 is not limited to a mirror.

[0031] The mask unit 25 corrects (changes) the energy distribution of the pulsed laser beam 21 generated by the oscillator 22. The mask unit 25 is provided on the optical path of the pulsed laser beam 21 between the oscillator 22 and the optical component 24. In the first embodiment, as shown in Fig. 4, the mask unit 25 includes a pair of Y-axis direction mask members 251, a pair of moving units 252, a pair of X-axis direction mask members 253, and a pair of X-axis direction moving units (not shown).

[0032] The pair of Y-axis direction mask members 251 are made of a material that blocks (i.e. does not transmit) the pulsed laser beam 21. The pair of Y-axis direction mask members 251 are arranged at a distance from each other in the Y-axis direction, and the optical axis 211 of the optical path of the pulsed laser beam 21 between the oscillator 22 and the optical component 24 is positioned between them. The pair of Y-axis direction mask members 251 are provided so as to be movable toward and away from each other in the Y-axis direction.

[0033] The moving unit 252 moves the pair of Y-axis direction mask members 251 in a direction in which they approach or move away from each other in the Y-axis direction. In the first embodiment, the moving units 252 are provided in one-to-one correspondence with the Y-axis direction mask members 251, and move the corresponding Y-axis direction mask members 251 in the Y-axis direction.

[0034] The pair of X-axis direction mask members 253 are made of a material that blocks (i.e. does not transmit) the pulsed laser beam 21. The pair of X-axis direction mask members 253 are arranged at a distance from each other in the X-axis direction, and position the optical axis 211 of the optical path of the pulsed laser beam 21 between the oscillator 22 and the optical component 24 between them. The pair of X-axis direction mask members 253 are provided so as to be movable toward and away from each other in the X-axis direction.

[0035] The X-axis direction moving unit moves the pair of X-axis direction mask members 253 in the X-axis direction in a direction toward or away from each other. In the first embodiment, the X-axis direction moving units are provided in one-to-one correspondence with the X-axis direction mask members 253, and move the corresponding X-axis direction mask member 253 in the X-axis direction. Note that the X-axis direction and Y-axis direction described in the explanation of the mask unit 25 refer to the X-axis direction and Y-axis direction of the pulse laser beam 21 when it is irradiated onto the wafer 200 held on the chuck table 10.

[0036] In the mask unit 25, a pair of Y-axis direction mask members 251 and a pair of X-axis direction mask members 253 block the portion of the pulsed laser beam 21 generated by the oscillator 22 away from the optical axis 211 (the base portion of the Gaussian distribution), and corrects the energy distribution 212 shown in FIG. 5 of the pulsed laser beam 21 generated by the oscillator 22 to an energy distribution 214 shown in FIG. 6 in which the energy rapidly decreases from value 213 on the energy distribution 212 shown in FIG. 5 to zero at a position away from the optical axis 211 by a distance 254 from the optical axis 211 of the mask members 251, 253.

[0037] Further, the mask unit 25 changes a distance 254 from the optical axis 211 of a pair of Y-axis direction mask members 251 by the moving unit 252, and changes a distance from the optical axis 211 of a pair of X-axis direction mask members 253 by the X-axis direction moving unit, thereby changing a position 215 of an energy distribution 214 shown in FIG. 6 where the energy distribution 214 rapidly decreases from a value 213 on the energy distribution 212 shown in FIG. 5 to zero. Note that, hereinafter, the value 213 on the energy distribution 214 at the position 215 where the energy distribution rapidly decreases to zero will be referred to as a boundary value. In this way, the mask unit 25 corrects the energy distribution 212 shown in FIG. 5, which is a Gaussian distribution of the pulsed laser beam 21, to an energy distribution 214 shown in FIG. 6, which is a distribution with a vertical base.

[0038] Thus, in the first embodiment, the mask unit 25 sets the distance in the X-axis direction between the pair of X-axis direction mask members 253 narrower than the distance in the Y-axis direction between the pair of Y-axis direction mask members 251, thereby forming the spot 216 of the pulsed laser beam 21 focused by the focusing lens 23 into a rectangular shape whose longitudinal direction is parallel to the Y-axis direction and whose lateral direction is parallel to the X-axis direction. The horizontal axis of FIG. 6 indicates the position in the Y-axis direction, and the center of the horizontal axis indicates the optical axis 211 of the optical path of the pulsed laser beam 21. The vertical axis of FIG. 6 indicates the energy. Although FIG. 6 shows the energy distribution 214 of the pulsed laser beam 21 at a position parallel to the Y-axis direction, the energy distribution 214 of the laser beam is similar to that of FIG. 6 even at a position parallel to the X-axis direction.

[0039] In addition, in embodiment 1, the laser beam irradiation unit 20 is equipped with a mask unit 25 as a means for correcting the energy distribution of the pulsed laser beam 21, but in the present invention, a DMD (Digital Micro-mirror Device) may be provided instead of the mask unit 25 as a means for correcting the energy distribution of the pulsed laser beam 21.

[0040] The moving unit 30 relatively moves the laser beam irradiation unit 20 and the chuck table 10 in the X-axis direction, the Y-axis direction, the Z-axis direction, and around an axis parallel to the Z-axis direction. The X-axis direction and the Y-axis direction are parallel to the holding surface 11. The X-axis direction is parallel to one of the planned dividing lines 203 of the wafer 200 held on the chuck table 10, and is a so-called processing feed direction in which the chuck table 10 is processed and fed when the laser processing apparatus 1 performs laser processing on the wafer 200. The Y-axis direction is perpendicular to the X-axis direction, and is a so-called indexing feed direction in which the chuck table 10 is indexed and fed when the laser processing apparatus 1 performs laser processing on the wafer 200.

[0041] The moving unit 30 includes an X-axis moving unit 31 which is a processing feed unit that moves the chuck table 10 in the X-axis direction, a Y-axis moving unit 32 which is an indexing feed unit that moves the chuck table 10 in the Y-axis direction, a Z-axis moving unit 33 which moves the focusing lens 23 included in the laser beam irradiation unit 20 in the Z-axis direction, and a rotational moving unit 34 which rotates the chuck table 10 around an axis parallel to the Z-axis direction.

[0042] The Y-axis moving unit 32 is a unit that relatively indexes and feeds the chuck table 10 and the laser beam irradiation unit 20. In the first embodiment, the Y-axis moving unit 32 is installed on the device body 2 of the laser processing device 1. The Y-axis moving unit 32 supports the moving plate 15 that supports the X-axis moving unit 31 so as to be freely movable in the Y-axis direction.

[0043] The X-axis moving unit 31 is a unit that relatively feeds the chuck table 10 and the laser beam irradiation unit 20 for processing. The X-axis moving unit 31 is installed on the moving plate 15. The X-axis moving unit 31 supports the second moving plate 16, which supports the rotation moving unit 34 that rotates the chuck table 10 around an axis parallel to the Z-axis direction, so as to be movable in the X-axis direction. The Z-axis moving unit 33 is installed on the standing wall 3, and supports the lifting member 4 so as to be movable in the Z-axis direction.

[0044] The X-axis moving unit 31, the Y-axis moving unit 32 and the Z-axis moving unit 33 each include a well-known ball screw that is rotatable about its axis, a well-known pulse motor that rotates the ball screw about its axis, and a well-known guide rail that supports the moving plates 15, 16 so as to be movable in the X-axis or Y-axis direction, and supports the lifting member 4 so as to be movable in the Z-axis direction.

[0045] The laser processing apparatus 1 also includes an X-axis position detection unit (not shown) for detecting the position of the chuck table 10 in the X-axis direction, a Y-axis position detection unit (not shown) for detecting the position of the chuck table 10 in the Y-axis direction, and a Z-axis position detection unit for detecting the position of the condenser lens 23 included in the laser beam irradiation unit 20 in the Z-axis direction. Each position detection unit outputs a detection result to the control unit 100.

[0046] The imaging unit 40 images the wafer 200 held on the chuck table 10. The imaging unit 40 includes an imaging element such as a CCD (Charge Coupled Device) imaging element or a CMOS (Complementary MOS) imaging element that images the wafer 200 held on the chuck table 10. In the first embodiment, the imaging unit 40 is attached to the tip of the tip of the lifting member and arranged at a position aligned with the condenser lens 23 of the laser beam irradiation unit 20 in the X-axis direction. The imaging unit 40 images the wafer 200 to obtain an image for performing alignment for aligning the wafer 200 with the laser beam irradiation unit 20, and outputs the obtained image to the control unit 100.

[0047] Moreover, in the first embodiment, the laser processing apparatus 1 includes a power meter 50. The power meter 50 measures the energy distribution of the pulsed laser beam 21 irradiated by the laser beam irradiating unit 20 when the pulsed laser beam 21 is irradiated from the laser beam irradiating unit 20. The power meter 50 outputs the measured energy distribution to the control unit 100. In the first embodiment, the power meter 50 is installed on the second moving plate 16, and can be opposed to the condenser lens 23 of the laser beam irradiating unit 20 in the Z-axis direction by the moving unit 252.

[0048] The control unit 100 controls each of the above-mentioned components of the laser processing apparatus 1 to cause the laser processing apparatus 1 to perform a laser processing operation on the wafer 200. The control unit 100 is a computer having an arithmetic processing device having a microprocessor such as a CPU (central processing unit), a storage device having a memory such as a ROM (read only memory) or a RAM (random access memory), and an input / output interface device. The arithmetic processing device of the control unit 100 performs arithmetic processing according to a computer program stored in the storage device, and outputs control signals for controlling the laser processing apparatus 1 to the above-mentioned components of the laser processing apparatus 1 via the input / output interface device, thereby realizing the functions of the control unit 100.

[0049] The control unit 100 is also connected to a display unit 110 configured with a liquid crystal display device or the like that displays the status and images of the machining operation, and an input unit (not shown) that an operator uses to register machining content information, etc. The input unit is configured with at least one of a touch panel provided on the display unit 110 and an external input device such as a keyboard.

[0050] The control unit 100 is also used to set the processing conditions of the laser processing device 1. The processing conditions include, for example, the energy of the pulsed laser beam 21, the repetition frequency of the pulsed pulsed laser beam 21, the overlap ratio described later, the processing threshold of the functional layer 205, the moving speed in the X-axis direction of the chuck table 10 during laser processing (hereinafter referred to as the processing feed speed), and the like. The energy of the pulsed laser beam 21 indicates the energy on the optical axis 211 of the energy distributions 212 and 214. The control unit 100 also has a function of calculating the relationship between the distance 254 of the mask members 251 and 253 from the optical axis 211 of the pulsed laser beam 21 and the boundary value 213 of the energy distribution 214 according to the energy of the pulsed laser beam 21, a function of calculating the width WX (shown in FIG. 9) of the spot 216 in the X-axis direction based on the processing threshold, and a function of calculating the processing feed speed based on the overlap ratio, the width WX, the repetition frequency, and the like, and inputting the calculated processing feed speed as the processing conditions. These functions are realized by the arithmetic processing device executing a program stored in the storage device. In addition, in the present invention, the above-mentioned functions may be realized by executing a program, or may be calculated by an operator.

[0051] The laser processing method according to the first embodiment is a method for performing laser processing on a wafer 200 having a functional layer 205, which is an organic film, on a substrate 201, and includes processing operations of a laser processing apparatus 1. As shown in Fig. 7, the laser processing method according to the first embodiment includes an energy distribution setting step 1001, a protective film forming step 1002, a blackening step 1003, and a groove processing step 1004.

[0052] (Energy distribution setting step) The energy distribution setting step 1001 is a step of adjusting the distances of the mask members 251, 253 from the optical axis 211 to set a boundary value 213 of the energy distribution 214. In the laser processing apparatus 1 configured as described above, the control unit 100 receives processing conditions input by an operator operating an input unit or the like. The processing conditions include a processing threshold value of the functional layer 205 of the wafer 200, the energy, repetition frequency, and overlap rate of the pulsed laser beam 21 in the blackening step 1003, and the energy, repetition frequency, and overlap rate of the pulsed laser beam 21 in the groove processing step 1004.

[0053] In embodiment 1, the laser processing apparatus 1 has a control unit 100 that calculates a distance 254 from the optical axis 211 of the mask members 251, 253 at which the boundary value 213 becomes the processing threshold based on the processing threshold of the functional layer 205 of the wafer 200, the energy of the pulsed laser beam 21 in the blackening step 1003, etc., and controls the moving unit 252 to set the distance 254 from the optical axis 211 of each mask member 251, 253 to the distance at which the boundary value 213 becomes the processing threshold.

[0054] In the first embodiment, the processing conditions include the processing threshold of the functional layer 205 of the wafer 200. In the case where the processing threshold of the functional layer 205 is unknown, the wafer 200 may be sucked and held on the chuck table 10, and the pulse laser beam 21 of various energies of the wafer 200 may be irradiated with the focal point 21-1 set on the functional layer 205, and the energy of the pulse laser beam 21 that carbonizes and blackens the functional layer 205 may be set as the processing threshold. Whether or not the functional layer 205 has been blackened may be confirmed by the operator of the laser processing device 1 by visual inspection, or by imaging the functional layer 205 with the imaging unit 40 and performing well-known image processing. When the functional layer 205 is blackened, the absorbency of the pulse laser beam 21 in the functional layer 205 is improved compared to before the blackening. In this way, the processing threshold in the present invention refers to the energy value of the pulsed laser beam 21 that can be used to carbonize the functional layer 205 and blacken it to the extent that it can absorb the pulsed laser beam 21 by irradiating the functional layer 205 with a pulsed laser beam 21 having energy equal to or greater than the processing threshold and setting the focal point 21-1 on the functional layer 205.

[0055] (Protective film formation step) Fig. 8 is a side view, partially in cross section, showing a schematic diagram of the protective film forming step of the laser processing method shown in Fig. 7. The protective film forming step 1002 is a step of coating the front surface 202 side of the wafer 200 with a water-soluble protective film.

[0056] In protective film forming step 1002, protective film coating device 60 suction-holds back surface 206 side of wafer 200 to holding surface 62 of spinner table 61 via adhesive tape 209, and clamps annular frame 210 with clamp parts 63 provided around spinner table 61. In protective film forming step 1002, protective film coating device 60 rotates spinner table 61 about its axis and drips water-soluble resin 65 from water-soluble resin supply nozzle 64 onto front surface 202 of wafer 200, as shown in FIG.

[0057] The dropped water-soluble resin 45 flows from the center to the outer periphery on the front surface 202 of the wafer 200 due to the centrifugal force generated by the rotation of the spinner table 61 , and is applied to the entire front surface 202 of the wafer 200 .

[0058] The water-soluble resin 65 is, for example, a water-soluble resin such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP). In the protective film forming step 1002, the water-soluble resin 65 applied to the entire surface of the front surface 202 of the wafer 200 is hardened to form a water-soluble protective film that covers the entire surface of the front surface 202 of the wafer 200.

[0059] (Blackening step) Fig. 9 is a diagram for explaining the overlapping ratio of the pulsed laser beam in the laser processing method shown in Fig. 7. Fig. 10 is a side view showing the blackening step in the laser processing method shown in Fig. 7, partially in cross section. Note that Fig. 10 omits the water-soluble protective film.

[0060] The blackening step 1003 is a step in which a pulsed laser beam 21 having a wavelength that is transparent to the functional layer 205 is generated by an oscillator 22, and the pulsed laser beam 21 having energy equal to or greater than the processing threshold at which the functional layer 205 is processed is irradiated onto the functional layer 205 so that the overlap rate of the pulsed laser beam 21 irradiated continuously onto the functional layer 205 is 90% or more and less than 100%, thereby blackening the functional layer 205.

[0061] The overlap rate refers to the percentage (%) of the area of ​​each of the spots 216-1, 216-2 of the region 216-3 (shown by parallel diagonal lines in FIG. 9) where the spot 216 of the earlier pulsed laser beam 21 (hereinafter referred to as 206-1) and the spot 216 of the later pulsed laser beam 21 (hereinafter referred to as 206-2) overlap among the spots 216 on the functional layer 205 of the wafer 200 of the pulsed laser beam 21 that are irradiated consecutively and successively as shown in FIG. 9.

[0062] Here, if the processing feed speed (mm / sec) is S, the width (mm) of the spots 216-1 and 216-2 in the X-axis direction is WX (shown in FIG. 9), and the repetition frequency (Hz) of the pulse laser beam 21 is F, then the overlap rate O (%) is defined by the following Equation 1.

[0063] O=[1-{S / (WX×F)}]×100...Equation 1

[0064] If the overlap rate O is less than 90%, the functional layer 205 cannot be blackened, and peeling of the functional layer 205 from the substrate 201 cannot be suppressed when the groove processing step 1004 is performed. If the overlap rate O is 100%, the pulsed laser beam 21 will continue to be irradiated to the same position all the time. In order to blacken the functional layer 205 and effectively suppress peeling of the functional layer 205 from the substrate 201 when the groove processing step 1004 is performed, the overlap rate O is desirably 95% or more.

[0065] In the blackening step 1003, in the laser processing apparatus 1, the wafer 200 having the surface 202 covered with a water-soluble protective film is placed on the holding surface 11 of the chuck table 10 positioned in the carry-in / out area via the adhesive tape 208. In the embodiment 1, when the control unit 100 receives an instruction to start the processing operation from the operator via the input unit, the laser processing apparatus 1 starts the processing operation, sucks and holds the wafer 200 on the holding surface 11 of the chuck table 10 via the adhesive tape 208, and clamps the annular frame 210 with the clamp unit 12.

[0066] In the blackening step 1003, the control unit 100 of the laser processing apparatus 1 calculates the width WX of the spots 216-1, 216-2 based on the processing threshold value and the calculated distance 254, and calculates the processing feed speed S that satisfies the formula 1 based on the overlap rate O and the repetition frequency F determined in the processing conditions. In the blackening step 1003, the moving unit 30 of the laser processing apparatus 1 moves the chuck table 10 toward the processing area, and the imaging unit 40 captures the wafer 200. The laser processing apparatus 1 performs alignment based on the image captured by the imaging unit 40.

[0067] In embodiment 1, the laser processing apparatus 1 sets the focal point 21-1 of the pulsed laser beam 21 on the functional layer 205 based on the processing conditions and the calculated processing feed speed S, etc., and as shown in Figure 10, the moving unit 30 moves the wafer 200 held on the chuck table 10 and the focal point 21-1 of the pulsed laser beam 21 irradiated by the laser beam irradiation unit 20 relatively along the planned division line 203 at the calculated processing feed speed S so that the overlap rate O is set by the processing conditions, while the laser beam irradiation unit 20 irradiates the pulsed pulsed laser beam 21 onto the planned division line 203, thereby performing laser processing on the wafer 200 and blackening the functional layer 205 on all of the planned division lines 203.

[0068] In the first embodiment, in the blackening step 1003, the wavelength of the pulsed laser beam 21 is set to 514 nm, and the energy of the pulsed laser beam 21 is set to 0.2 μJ or more and 2 μJ or less (preferably 0.2 μJ or more and 0.5 μJ or less).

[0069] In the first embodiment, in the blackening step 1003, for example, if the width WX (shown in FIG. 9) of each spot 216-1, 216-2 in the X-axis direction is 5 μm, the repetition frequency F of the pulsed laser beam 21 is 1 MHz, and the processing feed speed S is 50 mm / sec, the overlap rate O is 99%. When the overlap rate O is 99%, the width 216-4 (shown in FIG. 9) of the region 216-3 in the X-axis direction is 4.95 μm. In the first embodiment, in the blackening step 1003, for example, laser processing is performed with the overlap rate O being 99%.

[0070] Also, in the blackening step 1003, the pulsed laser beam 21 irradiated to the functional layer 205 is modified from the energy distribution 212 shown in Fig. 5 to the energy distribution 214 shown in Fig. 6. In this way, in the blackening step 1003, the pulsed laser beam 21 irradiated to the functional layer 205 is modified from the energy distribution 212 shown in Fig. 5 to the energy distribution 214 shown in Fig. 6 with a vertical base, thereby preventing the pulsed laser beam 21 with energy lower than the processing threshold from passing through the functional layer 205 and irradiating the substrate 201.

[0071] (Groove processing step) Fig. 11 is a side view showing a schematic partial cross section of the groove processing step of the laser processing method shown in Fig. 7. Note that the water-soluble protective film is omitted in Fig. 11. The groove processing step 1004 is a step in which, after the blackening step 1003, the blackened functional layer 205 is irradiated with the pulsed laser beam 21 to cause the blackened functional layer 205 to absorb the pulsed laser beam 21, thereby forming a laser processed groove 207.

[0072] In the first embodiment, in the groove processing step 1004, the laser processing apparatus 1 irradiates the pulsed laser beam 21 onto the blackened functional layer 205 so that the overlap rate O is greater than 0% and less than 80%, thereby removing the functional layer 205 and the surface layer of the base material 201 to form the laser processed groove 207. In the groove processing step 1004, the control unit 100 of the laser processing apparatus 1 calculates a processing feed speed S that satisfies Equation 1 based on the overlap rate O and repetition frequency F determined in the processing conditions.

[0073] In the groove processing step 1004, the laser processing device 1 sets the focal point 21-1 of the pulsed laser beam 21 on the blackened functional layer 205 based on the processing conditions and the calculated processing feed speed S, and while the moving unit 30 relatively moves the wafer 200 held on the chuck table 10 and the focal point 21-1 of the pulsed laser beam 21 irradiated by the laser beam irradiation unit 20 along the division planned line 203 at the calculated processing feed speed S so as to achieve the overlap rate O set by the processing conditions, as shown in Fig. 11, the laser beam irradiation unit 20 irradiates the pulsed pulsed laser beam 21 along the division planned line 203. In the groove processing step 1004, the laser processing device 1 performs laser processing, i.e., ablation processing, on the wafer 200 along the division planned line 203 by irradiating the pulsed laser beam 21 having a wavelength absorbed by the blackened functional layer 205 and the base material 201, thereby forming laser processed grooves 207 along all the division planned lines 203.

[0074] In the first embodiment, the wavelength of the pulsed laser beam 21 is set to 514 nm, and the energy of the pulsed laser beam 21 is set to 5 μJ or more and 10 μJ or less (preferably 8 μJ or more and 10 μJ or less) in the groove processing step 1004. In the first embodiment, the groove processing step 1004 performs laser processing with an overlap rate O of 75%, for example.

[0075] Also, in embodiment 1, in the groove processing step 1004, the laser processing apparatus 1 irradiates a pulse laser beam 21 having the energy distribution 214 shown in FIG. 6 and having rectangular spots 216-1, 216-2, as in the blackening step 1003, but in the present invention, a pulse laser beam 21 having a round (circular) spot shape may also be irradiated.

[0076] Thus, in the laser processing method of embodiment 1, in the blackening step 1003, a pulse laser beam 21 having a higher overlap rate O and lower energy than in the groove processing step 1004 is irradiated to blacken the functional layer 205, and in the groove processing step 1004, a pulse laser beam 21 having a lower overlap rate O and higher energy than in the blackening step 1003 is irradiated to form the laser processed groove 207.

[0077] In the first embodiment, the laser processing apparatus 1 stops irradiating the pulsed laser beam 21 when the laser grooves 207 are formed on all of the planned dividing lines 203 of the wafer 200. In the first embodiment, the laser processing apparatus 1 causes the moving unit 30 to move the chuck table 10 toward the carry-in / out area, stops the chuck table 10 at the carry-in / out area, the chuck table 10 stops suction-holding the wafer 200, the clamping unit 12 releases the clamp of the annular frame 210, the wafer 200 is carried out from the holding surface 11 of the chuck table 10, and the processing operation and the laser processing method are completed.

[0078] The wafer 200 that has been subjected to the laser processing method according to the first embodiment has the water-soluble protective film removed, is cut along intended division lines 203, and is divided into individual devices 204.

[0079] As described above, the laser processing method according to the first embodiment includes a blackening step 1003 and a groove processing step 1004. In the blackening step 1003, the laser processing method irradiates the pulsed laser beam 21 having lower energy than that in the groove processing step 1004, overlapping the pulsed laser beam 21 with an overlap rate O larger than that in the groove processing step 1004. In addition, in the groove processing step 1004, the laser processing method sets a focal point 21-1 on the blackened functional layer 205 and irradiates the pulsed laser beam 21.

[0080] For this reason, in the laser processing method, the pulsed laser beam 21 is irradiated to the functional layer 205 in a state in which it has been blackened and has improved absorbency of the pulsed laser beam 21 in the groove processing step 1004, so that the laser processed groove 207 can be formed by irradiating the pulsed laser beam 21 without setting a focal point 21-1 on the substrate 201, that is, in a state in which peeling of the functional layer 205 is suppressed. As a result, the laser processing method has the effect of being able to form the laser processed groove 207 in the wafer 200 while suppressing peeling of the functional layer 205.

[0081] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. [Explanation of symbols]

[0082] 21 Pulsed laser beam 22 Oscillators 200 wafers 201 Base material 205 Functional layer (organic film) 207 Laser-machined grooves

Claims

1. 1. A method for manufacturing a semiconductor device, comprising: a blackening step of blackening the functional layer by irradiating a laser beam having a wavelength that is transparent to the functional layer of a semiconductor wafer having a functional layer including a low dielectric constant insulating film and having devices formed in each of areas partitioned by intersecting planned dividing lines along the planned dividing lines; and a groove processing step of, after the blackening step, irradiating the laser beam along the planned division line to cause the blackened functional layer to absorb the laser beam and form a laser processed groove, After carrying out the groove processing step, the semiconductor device is divided along the intended dividing lines to form a plurality of devices.

2. The method for manufacturing a semiconductor device according to claim 1 , wherein in the blackening step, the laser beam irradiated to the functional layer has a Gaussian distribution whose tail is corrected to a vertical distribution.

3. 3. The method for manufacturing a semiconductor device according to claim 1, wherein in the blackening step, the functional layer is blackened by irradiating the laser beam with a higher overlap rate and lower energy than in the groove processing step, and in the groove processing step, the laser beam is irradiated with a lower overlap rate and higher energy than in the blackening step to form the laser processed groove.

4. a chuck table for holding a semiconductor wafer having a functional layer including a low dielectric constant insulating film and having devices formed in each of areas partitioned by intersecting division lines on a surface of the semiconductor wafer; a laser beam irradiation unit which performs a blackening step of irradiating the semiconductor wafer with a laser beam, the laser beam having a wavelength that is transparent to the functional layer, along the planned division lines to blacken the functional layer, and a groove processing step of irradiating the laser beam along the planned division lines after the blackening step, the laser beam being absorbed by the blackened functional layer to form laser processed grooves; A laser processing apparatus comprising:

5. 5. The laser processing apparatus according to claim 4, wherein the laser beam irradiation unit includes an energy distribution modifying means for modifying a skirt portion of a Gaussian distribution of the laser beam irradiated to the functional layer in the blackening step into a vertical distribution.

6. The laser processing apparatus of claim 4 or claim 5, wherein the laser beam irradiation unit irradiates the laser beam with a higher overlap rate and lower energy than the groove processing step to blacken the functional layer in the blackening step, and irradiates the laser beam with a lower overlap rate and higher energy than the blackening step to form the laser processed groove in the groove processing step.

Images