JP2014165246A - Processing method of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method of a wafer capable of efficiently dividing a wafer, in which devices are formed by functional layers laminated on the surface of a substrate, into individual devices.SOLUTION: Provided is a processing method of a wafer for dividing the wafer, in which devices are formed by functional layers laminated on the surface of a substrate, along a plurality of streets for sectioning the devices. The method includes a cutting groove formation step for forming cutting grooves while leaving a part not reaching a functional layer, by positioning a cutting blade in an area corresponding to the street from the rear side of the substrate, and a laser processing step for breaking the residual part of the substrate and the functional layer, by irradiation with a laser beam from the rear side of the substrate, subjected to the cutting groove formation step, along the bottom of the cutting groove.

Description

  The present invention relates to a wafer processing method in which a wafer in which a device is formed by a functional layer laminated on a surface of a substrate is divided along a plurality of streets that partition the device.

  As is well known to those skilled in the art, in a semiconductor device manufacturing process, a semiconductor wafer in which a plurality of devices such as ICs and LSIs are formed in a matrix by a functional layer in which an insulating film and a functional film are laminated on the surface of a substrate such as silicon. Is formed. In the semiconductor wafer formed in this way, the above devices are partitioned by dividing lines called streets, and individual semiconductor devices are manufactured by dividing along the streets.

  Recently, in order to improve the processing capability of semiconductor chips such as IC and LSI, inorganic films such as SiOF and BSG (SiOB) and polymer films such as polyimide and parylene are formed on the surface of a substrate such as silicon. A semiconductor wafer having a form in which a semiconductor device is formed by a functional layer in which a low dielectric constant insulator film (Low-k film) made of an organic film is laminated has been put into practical use.

  Such division of the semiconductor wafer along the street is usually performed by a cutting device called a dicer. This cutting apparatus includes a chuck table for holding a semiconductor wafer as a workpiece, a cutting means for cutting the semiconductor wafer held on the chuck table, and a movement for relatively moving the chuck table and the cutting means. Means. The cutting means includes a rotating spindle that is rotated at a high speed and a cutting blade attached to the spindle. The cutting blade is composed of a disk-shaped base and an annular cutting edge mounted on the outer periphery of the side surface of the base. The cutting edge is formed by fixing diamond abrasive grains having a grain size of about 3 μm, for example, by electroforming. ing.

  However, since the Low-k film described above is different from the material of the wafer, it is difficult to cut simultaneously with a cutting blade. That is, the low-k film is very fragile like mica, so when the cutting blade cuts along the street, the low-k film peels off, and this peeling reaches the circuit, causing fatal damage to the device. There is a problem.

  In order to solve the above problem, a laser beam is irradiated along the street on both sides of the street formed on the semiconductor wafer, and two laser processing grooves are formed along the street to divide the functional layer. Patent Document 1 discloses a wafer dividing method for cutting a semiconductor wafer along a street by positioning a cutting blade between the outer sides of the laser processing groove and relatively moving the cutting blade and the semiconductor wafer.

JP 2005-142398 A

Thus, as described in Patent Document 1, two laser processing grooves are formed along the street by irradiating the laser beam along the street on both sides of the street formed on the semiconductor wafer. The wafer dividing method for cutting the semiconductor wafer along the street by positioning the cutting blade between the two laser processing grooves outside the two sections has the following problems.
(1) In order to divide the functional layer, it is necessary to form at least two laser-processed grooves along the street, and productivity is poor.
(2) If the functional layer is not sufficiently divided when forming the laser processing groove, the cutting blade may be displaced or fall down, or the cutting blade may be unevenly worn.
(3) Since a debris scatters when a laser processing groove is formed from the surface of the wafer, it is necessary to cover the surface of the wafer with a protective film.
(4) By irradiating the laser beam at least twice to form two laser-processed grooves, thermal strain remains on the wafer and the bending strength of the device decreases.
(5) In order to form the two laser processing grooves in a range exceeding the width of the cutting blade, it is necessary to increase the width of the street, and the number of devices formed on the wafer is reduced.
(6) Since a passivation film containing SiO2, SiO, SiN, and SiNO is formed on the surface of the functional layer, when irradiated with a laser beam, it passes through the passivation film and reaches the inside of the functional layer. As a result, heat generated by the irradiation of the laser beam reaching the inside of the functional layer is temporarily confined by the passivation film, so that a circuit is formed and peeling occurs on the device side having a low density.

  The present invention has been made in view of the above-mentioned facts, and its main technical problem is to divide a wafer in which a device is formed by a functional layer laminated on the surface of a substrate into individual devices by solving the above problems. It is to provide a method for processing a wafer that can be performed.

In order to solve the above-mentioned main technical problem, according to the present invention, a wafer processing method for dividing a wafer in which a device is formed by a functional layer laminated on the surface of a substrate along a plurality of streets partitioning the device. Because
A cutting groove forming step of positioning a cutting blade in a region corresponding to the street from the back side of the substrate and forming a cutting groove leaving a part not reaching the functional layer;
A laser processing step of irradiating a laser beam along the bottom of the cutting groove from the back surface side of the substrate on which the cutting groove forming step has been performed, and breaking a part of the remaining substrate and the functional layer.
A method for processing a wafer is provided.

The laser processing step irradiates a part of the remaining substrate and the functional layer with a laser beam having a wavelength that absorbs the substrate and the functional layer along the bottom of the cutting groove from the back side of the substrate. Grooves are formed.
In the laser processing step, a laser beam having a wavelength that is transmissive to the substrate and the functional layer is irradiated with a condensing point positioned at a part of the remaining substrate and an intermediate portion of the functional layer. A modified layer is formed on a part of the substrate and the functional layer.
Further, the wafer processing method includes an opening having a size for adhering an adhesive tape to the surface of the functional layer laminated on the substrate constituting the wafer and accommodating the wafer before the cutting groove forming step is performed. The wafer support process for supporting the wafer via an adhesive tape with an annular frame, and the adhesive tape to which the wafer is adhered after the laser processing process is expanded to expand the wafer to individual devices along the street. And a device separation step of separating.

In the wafer processing method according to the present invention, a cutting groove forming step of forming a cutting groove by positioning a cutting blade in a region corresponding to the street from the back surface side of the substrate and leaving a part not reaching the functional layer, and the cutting groove A laser processing step of irradiating a laser beam along the bottom of the cutting groove from the back side of the substrate on which the forming step has been performed, and breaking a part of the remaining substrate and the functional layer. The effect is obtained.
(1) Since it is not necessary to form a plurality of laser processing grooves along the street in order to divide the functional layer, productivity is improved.
(2) Since the laser processing groove is not formed in the functional layer, the cutting blade is not displaced or falls, and the cutting blade does not have uneven wear.
(3) Since the laser beam is not irradiated from the surface of the wafer, it is not necessary to cover the surface of the wafer with a protective film.
(4) Since the bottom of the cutting groove is irradiated with a laser beam, the energy is small and thermal strain does not remain on the wafer, and the bending strength of the device is not reduced.
(5) Since the cutting grooves are formed from the back surface side of the substrate, a wide street is unnecessary, and the number of devices that can be formed on the wafer can be increased.
(6) Since the laser beam is not irradiated from the surface of the wafer, the functional layer is processed through the passivation film and the heat escape is temporarily lost, so that no peeling occurs on the device side.

The perspective view and principal part expanded sectional view which show the semiconductor wafer divided | segmented by the processing method of the wafer by this invention. The perspective view which shows the state by which the semiconductor wafer in which the wafer support process was implemented in the processing method of the wafer by this invention was affixed on the surface of the adhesive tape with which the cyclic | annular flame | frame was mounted | worn. The principal part perspective view of the cutting device for implementing the cutting groove formation process in the processing method of the wafer by this invention. Explanatory drawing of the cutting groove formation process in the processing method of the wafer by this invention. The principal part perspective view of the laser processing apparatus for implementing the laser processing process in the processing method of the wafer by this invention. Explanatory drawing which implements 1st Embodiment of the laser processing process in the processing method of the wafer by this invention. Explanatory drawing which implements 2nd Embodiment of the laser processing process in the processing method of the wafer by this invention. The perspective view of the device separation apparatus for implementing the device separation process in the processing method of the wafer by this invention. Explanatory drawing of the device isolation | separation process in the processing method of the wafer by this invention.

  Hereinafter, a wafer processing method according to the present invention will be described in more detail with reference to the accompanying drawings.

  1A and 1B show a perspective view and an enlarged cross-sectional view of a main part of a semiconductor wafer divided into individual devices by the wafer processing method according to the present invention. A semiconductor wafer 2 shown in FIGS. 1A and 1B has a plurality of ICs by a functional layer 21 in which an insulating film and a functional film for forming a circuit are laminated on a surface 20a of a substrate 20 such as silicon having a thickness of 140 μm. A device 22 such as an LSI is formed in a matrix. Each device 22 is partitioned by streets 23 formed in a lattice shape. In the illustrated embodiment, the insulating film forming the functional layer 21 is an SiO 2 film, an inorganic film such as SiOF or BSG (SiOB), or an organic film such as a polymer film such as polyimide or parylene. It consists of a low dielectric constant insulator film (Low-k film) made of a film, and the thickness is set to 10 μm. The functional layer 21 thus configured has a passivation film containing SiO2, SiO, SiN, and SiNO formed on the surface.

A wafer processing method for dividing the semiconductor wafer 2 described above along the street will be described.
First, an adhesive tape is attached to the surface 21a of the functional layer 21 laminated on the substrate 20 constituting the semiconductor wafer 2, and an annular frame having an opening size to accommodate the semiconductor wafer 2 is interposed through the adhesive tape. A wafer support process for supporting the wafer is performed. For example, as shown in FIG. 2, the surface 21 a of the functional layer 21 constituting the semiconductor wafer 2 is attached to the surface of the adhesive tape 30 with the outer peripheral portion mounted so as to cover the inner opening of the annular frame 3. Accordingly, in the semiconductor wafer 2 adhered to the surface of the adhesive tape 30, the back surface 20b of the substrate 20 is on the upper side. The pressure-sensitive adhesive tape 30 has a pressure-sensitive adhesive applied to the surface of a polyethylene film having a thickness of 100 μm, for example. In the embodiment shown in FIG. 2, the example in which the surface 21 a of the functional layer 21 constituting the semiconductor wafer 2 is attached to the surface of the adhesive tape 30 having the outer peripheral portion attached to the annular frame 3 is shown. The adhesive tape 30 may be attached to the surface 21a of the functional layer 21 laminated on the substrate 20 constituting the semiconductor wafer 2 and the outer peripheral portion of the adhesive tape 30 may be simultaneously attached to the annular frame 3.

  When the wafer support process described above is performed, a cutting groove forming process is performed in which the cutting blade is positioned in a region corresponding to the street from the back surface side of the substrate to leave a part that does not reach the functional layer to form a cutting groove. This cutting groove forming step is performed using a cutting device 4 shown in FIG. The cutting apparatus 4 shown in FIG. 3 includes a chuck table 41 that holds a workpiece, a cutting means 42 that cuts the workpiece held on the chuck table 41, and a workpiece held on the chuck table 41. An image pickup means 43 for picking up images is provided. The chuck table 41 is configured to suck and hold a workpiece. The chuck table 41 is moved in a processing feed direction indicated by an arrow X in FIG. 3 by a processing feed means (not shown) and is indicated by an arrow Y by an index feed means (not shown). It can be moved in the index feed direction shown.

  The cutting means 42 includes a spindle housing 421 arranged substantially horizontally, a rotating spindle 422 rotatably supported by the spindle housing 421, and a cutting blade 423 attached to the tip of the rotating spindle 422. The rotating spindle 422 is rotated in the direction indicated by the arrow 423a by a servo motor (not shown) disposed in the spindle housing 421. The cutting blade 423 includes a disk-shaped base 424 made of aluminum and an annular cutting edge 425 attached to the outer peripheral portion of the side surface of the base 424. The annular cutting edge 425 is composed of an electroformed blade in which diamond abrasive grains having a particle diameter of 3 to 4 μm are hardened by nickel plating on the outer peripheral portion of the side surface of the base 424. In the illustrated embodiment, the annular cutting edge 425 has an outer thickness of 40 μm. The diameter is 52 mm.

  The imaging means 43 is mounted at the tip of the spindle housing 421. In the illustrated embodiment, the illumination means irradiates a workpiece with infrared rays in addition to a normal imaging device (CCD) that captures an image with visible light. And an image pickup device (infrared CCD) that outputs an electric signal corresponding to the infrared rays captured by the optical system, and the like. A signal is sent to control means (not shown).

  In order to perform the cutting groove forming process using the cutting device 4 described above, the adhesive tape 30 side on which the wafer supporting process is performed and the semiconductor wafer 2 is adhered is mounted on the chuck table 41 as shown in FIG. Put. Then, by operating a suction means (not shown), the semiconductor wafer 2 is held on the chuck table 41 via the adhesive tape 30 (wafer holding step). Accordingly, in the semiconductor wafer 2 held on the chuck table 41, the back surface 20b of the substrate 20 is on the upper side. In FIG. 3, the annular frame 3 to which the adhesive tape 30 is attached is omitted. However, the annular frame 3 is held by an appropriate frame holding unit disposed on the chuck table 41. In this way, the chuck table 41 that sucks and holds the semiconductor wafer 2 is positioned directly below the imaging unit 43 by a processing feed unit (not shown).

  When the chuck table 41 is positioned immediately below the image pickup means 43, an alignment process for detecting an area to be cut of the semiconductor wafer 2 is executed by the image pickup means 43 and a control means (not shown). That is, the imaging unit 43 and a control unit (not shown) execute image processing such as pattern matching for aligning the region corresponding to the street 23 formed in a predetermined direction of the semiconductor wafer 2 and the cutting blade 423. Then, alignment of the cutting area by the cutting blade 423 is performed (alignment process). In addition, the alignment of the cutting position by the cutting blade 423 is similarly performed on the region corresponding to the street 23 formed in the direction orthogonal to the predetermined direction on the semiconductor wafer 2. At this time, the surface 21a of the functional layer 21 on which the streets 23 of the semiconductor wafer 2 are formed is positioned on the lower side. However, as described above, the imaging unit 43 has an infrared illumination unit and an optical system that captures infrared rays, and infrared rays. Since the imaging means configured by an imaging device (infrared CCD) that outputs a corresponding electrical signal is provided, the street 23 can be imaged through the back surface 20b of the substrate 20 constituting the wafer.

  When the area corresponding to the street 23 of the semiconductor wafer 2 held on the chuck table 41 is detected as described above and the cutting area is aligned, the chuck table 41 holding the semiconductor wafer 2 is cut. Move to the cutting start position of the area. At this time, as shown in FIG. 4A, the semiconductor wafer 2 has one end of the region corresponding to the street 23 to be cut (the left end in FIG. 4A) positioned to the right by a predetermined amount from just below the cutting blade 423. Positioned to do.

  When the chuck table 41, that is, the semiconductor wafer 2 is thus positioned at the cutting start position in the cutting region, the cutting blade 423 is moved from the standby position indicated by the two-dot chain line in FIG. It cuts and feeds downward, and is positioned at a predetermined cutting feed position as shown by the solid line in FIG. This cutting feed position is a position where the lower end of the cutting blade 423 does not reach the functional layer 21 constituting the semiconductor wafer 2 as shown in FIGS. 4A and 4C (for example, the functional layer 21 is laminated). The position is set to 5 to 10 μm from the front surface 20a of the substrate 20 to the back surface 20b side.

  Next, the cutting blade 423 is rotated at a predetermined rotational speed in the direction indicated by an arrow 423a in FIG. 4A, and the chuck table 41 is rotated at a predetermined cutting feed speed in the direction indicated by an arrow X1 in FIG. Move with. Then, as shown in FIG. 4B, the chuck table 41 reaches the other end of the position corresponding to the street 23 (the right end in FIG. 4B) until it is positioned to the left by a predetermined amount from just below the cutting blade 423. Then, the movement of the chuck table 41 is stopped. By cutting and feeding the chuck table 41 in this way, as shown in FIG. 4D, the substrate 20 of the semiconductor wafer 2 is formed with a cutting groove 210 leaving a part 201 from the back surface 20b to the front surface 20a side. (Cutting groove forming process).

  Next, the cutting blade 423 is raised as shown by an arrow Z2 in FIG. 4B and positioned at a standby position shown by a two-dot chain line, and the chuck table 41 is moved in the direction shown by an arrow X2 in FIG. Move to return to the position shown in FIG. Then, the chuck table 41 is indexed and fed by an amount corresponding to the interval between the streets 23 in a direction perpendicular to the paper surface (index feeding direction), and an area corresponding to the street 23 to be cut next is set to a position corresponding to the cutting blade 423. Position. Thus, if the area | region corresponding to the street 23 which should be cut next is located in the position corresponding to the cutting blade 423, the cutting groove formation process mentioned above will be implemented.

In addition, the said division | segmentation groove | channel formation process is performed on the following process conditions, for example.
Cutting blade: outer diameter 52mm, thickness 40μm
Cutting blade rotation speed: 30000 rpm
Cutting feed rate: 50 mm / sec

  The above-described cutting groove forming process is performed on the areas corresponding to all the streets 23 formed on the semiconductor wafer 2.

  When the cutting groove forming step is performed as described above, a laser beam is irradiated from the back surface 20b side of the substrate 20 along the bottom of the cutting groove 210, and the remaining part 201 of the substrate 20 and the functional layer 21 are broken. Implement the laser processing process. This laser processing step is performed using a laser processing apparatus 5 shown in FIG. A laser processing apparatus 5 shown in FIG. 5 has a chuck table 51 that holds a workpiece, a laser beam irradiation means 52 that irradiates a workpiece held on the chuck table 51 with a laser beam, and a chuck table 51 that holds the workpiece. An image pickup means 53 for picking up the processed workpiece is provided. The chuck table 51 is configured to suck and hold a workpiece. The chuck table 51 is moved in a processing feed direction indicated by an arrow X in FIG. 5 by a processing feed means (not shown) and is also shown in FIG. 5 by an index feed means (not shown). It can be moved in the index feed direction indicated by the arrow Y.

  The laser beam irradiation means 52 includes a cylindrical casing 521 disposed substantially horizontally. In the casing 521, a pulse laser beam oscillation means having a pulse laser beam oscillator and a repetition frequency setting means (not shown) are arranged. A condenser 522 for condensing the pulse laser beam oscillated from the pulse laser beam oscillating means is attached to the tip of the casing 521. The laser beam irradiation unit 52 includes a condensing point position adjusting unit (not shown) for adjusting the condensing point position of the pulse laser beam collected by the condenser 522.

  The imaging means 53 attached to the tip of the casing 521 constituting the laser beam irradiation means 52 includes an illumination means for illuminating the workpiece, an optical system for capturing an area illuminated by the illumination means, and the optical system. An image sensor (CCD) or the like that captures the captured image is provided, and the captured image signal is sent to a control unit (not shown).

Using the laser processing apparatus 5 described above, a laser processing step of irradiating a laser beam along the bottom of the cutting groove 210 from the back surface 20b side of the substrate 20 to break the remaining part 201 of the substrate 20 and the functional layer 21. The first embodiment will be described with reference to FIGS. 5 and 6. FIG.
First, the pressure-sensitive adhesive tape 30 side on which the semiconductor wafer 2 on which the above-described cutting groove forming step has been performed is mounted on the chuck table 51 of the laser processing apparatus 5 shown in FIG. 5 described above. Then, by operating a suction means (not shown), the semiconductor wafer 2 is held on the chuck table 51 via the adhesive tape 30 (wafer holding step). Accordingly, in the semiconductor wafer 2 held on the chuck table 51, the back surface 20b of the substrate 20 is on the upper side. In FIG. 5, the annular frame 3 to which the adhesive tape 30 is attached is omitted, but the annular frame 3 is held by an appropriate frame holding means provided on the chuck table 51. In this manner, the chuck table 51 that sucks and holds the semiconductor wafer 2 is positioned directly below the imaging unit 53 by a processing feed unit (not shown).

  When the chuck table 51 is positioned immediately below the image pickup means 53, an alignment operation for detecting a processing region to be laser processed of the semiconductor wafer 2 is executed by the image pickup means 53 and a control means (not shown). That is, the image pickup unit 53 and a control unit (not shown) include a cutting groove 210 formed in a predetermined direction from the back surface 20b side of the substrate 20 constituting the semiconductor wafer 2, and a laser beam irradiation unit that irradiates a laser beam along the cutting groove 210. Image processing such as pattern matching for performing alignment with the 52 condensers 522 is executed, and alignment of the laser beam irradiation position is performed (alignment process). In addition, alignment of the laser beam irradiation position is similarly performed on the cutting groove 210 formed in the semiconductor wafer 2 in a direction orthogonal to the predetermined direction.

  When the alignment step described above is performed, the chuck table 51 is moved to the laser beam irradiation region where the condenser 522 of the laser beam irradiation means 52 for irradiating the laser beam is located as shown in FIG. It is positioned directly below the optical device 522. At this time, as shown in FIG. 6A, the semiconductor wafer 2 is positioned such that one end of the cutting groove 210 (the left end in FIG. 6A) is located directly below the light collector 522. Then, as shown in FIG. 6C, the condensing point P of the pulse laser beam LB irradiated from the condenser 522 is matched with the vicinity of the bottom surface of the cutting groove 210. Next, while irradiating the substrate 20 and the functional layer 21 with a pulsed laser beam having an absorptive wavelength from the condenser 522 of the laser beam irradiation means 52, the chuck table 51 is in the direction indicated by the arrow X1 in FIG. At a predetermined machining feed rate. Then, as shown in FIG. 6B, when the other end of the cutting groove 210 (the right end in FIG. 6B) reaches a position directly below the condenser 522, the irradiation of the pulse laser beam is stopped and the chuck table is stopped. The movement of 51 is stopped (laser machining groove forming step).

  Next, the chuck table 51 is moved in the direction perpendicular to the paper surface (index feed direction) by the interval of the cutting grooves 210 (corresponding to the interval of the streets 23). Then, while irradiating a pulse laser beam from the condenser 522 of the laser beam irradiation means 52, the chuck table 51 is moved at a predetermined processing feed speed in the direction indicated by the arrow X2 in FIG. 6B, and FIG. When the position shown in FIG. 2 is reached, the irradiation of the pulse laser beam is stopped and the movement of the chuck table 51 is stopped.

  By performing the laser processing groove forming step described above, the laser beam is applied to the part 201 of the substrate 20 and the functional layer 21 remaining in the semiconductor wafer 2 in the cutting groove forming step as shown in FIG. A machining groove 220 is formed. As a result, the part 201 of the substrate 20 and the functional layer 21 remaining in the cutting groove forming step are broken by the laser processing groove 220. Then, the laser processing groove forming process described above is performed along all the streets 23 formed in the semiconductor wafer 2.

In addition, the said laser processing groove | channel formation process is performed on the following processing conditions, for example.
Laser beam wavelength: 355 nm
Repetition frequency: 200 kHz
Output: 1.5W
Condensing spot diameter: φ10μm
Processing feed rate: 300 mm / sec

Next, a second embodiment of a laser processing step of irradiating a laser beam along the bottom of the cutting groove 210 from the back surface 20b side of the substrate 20 to break the remaining part 201 of the substrate 20 and the functional layer 21 will be described. This will be described with reference to FIG. In addition, 2nd Embodiment of a laser processing process can be implemented using the laser processing apparatus substantially the same as the said laser processing apparatus 5. FIG. Accordingly, in the second embodiment shown in FIG. 7, the same members as those of the laser processing apparatus 5 are described with the same reference numerals.
Also in the second embodiment shown in FIG. 7, the wafer holding step and the alignment step are performed in the same manner as in the first embodiment shown in FIGS.

  When the alignment step described above is performed, the chuck table 51 is moved to the laser beam irradiation region where the condenser 522 of the laser beam irradiation means 52 for irradiating the laser beam is positioned as shown in FIG. It is positioned directly below the optical device 522. At this time, as shown in FIG. 7A, the semiconductor wafer 2 is positioned so that one end of the cutting groove 210 (the left end in FIG. 7A) is located directly below the light collector 522. Then, as shown in FIG. 7C, the condensing point P of the pulsed laser beam irradiated from the condenser 522 is positioned in the middle part of the remaining part 201 of the substrate 20 and the functional layer 21. Next, while irradiating a pulsed laser beam having a wavelength that is transmissive to the substrate 20 and the functional layer 21 from the condenser 522 of the laser beam irradiation means 52, the chuck table 51 is directed in the direction indicated by the arrow X1 in FIG. At a predetermined machining feed rate. Then, as shown in FIG. 7B, when the other end of the cutting groove 210 (the right end in FIG. 7B) reaches a position directly below the condenser 522, the irradiation of the pulse laser beam is stopped and the chuck table is stopped. The movement of 51 is stopped (modified layer forming step).

  Next, the chuck table 51 is moved in the direction perpendicular to the paper surface (index feed direction) by the interval of the cutting grooves 210 (corresponding to the interval of the streets 23). Then, while irradiating a pulse laser beam from the condenser 522 of the laser beam irradiation means 52, the chuck table 51 is moved at a predetermined processing feed speed in the direction indicated by the arrow X2 in FIG. 7B, and FIG. When the position shown in FIG. 2 is reached, the irradiation of the pulse laser beam is stopped and the movement of the chuck table 51 is stopped.

  By performing the above-described modified layer forming step, as shown in FIG. 7D, the semiconductor wafer 2 is cut into the part 201 of the substrate 20 and the functional layer 21 remaining in the cutting groove forming step. A modified layer 230 is formed along the groove 210. The modified layer 230 is easily broken in a melted and resolidified state. Then, the modified layer forming step described above is performed along all the streets 23 formed on the semiconductor wafer 2.

In addition, the said modified layer formation process is performed on the following process conditions, for example.
Laser beam wavelength: 1064 nm
Repetition frequency: 80 kHz
Output: 0.2W
Condensing spot diameter: φ1μm
Processing feed rate: 180 mm / sec

  When the laser processing step (laser processing groove forming step or modified layer forming step) described above is carried out, the adhesive tape 30 to which the semiconductor wafer 2 is adhered is expanded, and the wafer is moved along the streets 23 to individual devices. A device separation step is performed to separate the device. This device separation step is performed using a device separation apparatus 6 shown in FIG. The device separating apparatus 6 shown in FIG. 8 includes a frame holding means 61 for holding the annular frame 3 and a tape expanding means for expanding the adhesive tape 30 attached to the annular frame 3 held by the frame holding means 61. 62 and a pickup collet 63. The frame holding means 61 includes an annular frame holding member 611 and a plurality of clamps 612 as fixing means provided on the outer periphery of the frame holding member 611. An upper surface of the frame holding member 611 forms a mounting surface 611a on which the annular frame 3 is placed, and the annular frame 3 is placed on the mounting surface 611a. The annular frame 3 placed on the placement surface 611 a is fixed to the frame holding member 611 by the clamp 612. The frame holding means 61 configured in this manner is supported by the tape expanding means 62 so as to be able to advance and retract in the vertical direction.

  The tape expansion means 62 includes an expansion drum 621 disposed inside the annular frame holding member 611. The expansion drum 621 has an inner diameter and an outer diameter smaller than the inner diameter of the annular frame 3 and larger than the outer diameter of the semiconductor wafer 2 attached to the adhesive tape 30 attached to the annular frame 3. Further, the expansion drum 621 includes a support flange 622 at the lower end. The tape expansion means 62 in the illustrated embodiment includes support means 623 that can advance and retract the annular frame holding member 611 in the vertical direction. The support means 623 includes a plurality of air cylinders 623 a disposed on the support flange 622, and the piston rod 623 b is connected to the lower surface of the annular frame holding member 611. As described above, the support means 623 including the plurality of air cylinders 623a is configured such that the annular frame holding member 611 has a reference position where the mounting surface 611a is substantially flush with the upper end of the expansion drum 621 as shown in FIG. Then, as shown in FIG. 9 (b), it is moved in the vertical direction between the extended positions below the upper end of the expansion drum 621 by a predetermined amount.

  A device separation step performed using the device separation apparatus 6 configured as described above will be described with reference to FIG. That is, the annular frame 3 to which the adhesive tape 30 to which the semiconductor wafer 2 is attached is attached to the mounting surface 611a of the frame holding member 611 constituting the frame holding means 61 as shown in FIG. It is placed on and fixed to the frame holding member 611 by the clamp 612 (frame holding step). At this time, the frame holding member 611 is positioned at the reference position shown in FIG. Next, the plurality of air cylinders 623a as the supporting means 623 constituting the tape extending means 62 are operated to lower the annular frame holding member 611 to the extended position shown in FIG. 9B. Accordingly, since the annular frame 3 fixed on the mounting surface 611a of the frame holding member 611 is also lowered, the adhesive tape 30 attached to the annular frame 3 is an expansion drum as shown in FIG. 9B. Expansion is performed in contact with the upper edge of 621 (tape expansion process). As a result, since a tensile force acts radially on the semiconductor wafer 2 adhered to the adhesive tape 30, the semiconductor wafer 2 is separated into individual devices 22 and a space S is formed between the devices. Further, when a radial tensile force acts on the semiconductor wafer 2 adhered to the adhesive tape 30, the modification formed on the part 201 of the substrate 20 and the functional layer 21 along the cutting groove 210 (and therefore the street 23). The layer 230 is broken, and the semiconductor wafer 2 is separated into individual devices 22 and a space S is formed between the devices.

  Next, as shown in FIG. 9 (c), the pickup collet 63 is operated to adsorb the device 22, peeled off from the adhesive tape 30, picked up, and conveyed to a tray or die bonding process (not shown). In the pickup process, as described above, the gap S between the individual devices 22 adhered to the adhesive tape 30 is widened, so that the pickup can be easily performed without contacting the adjacent devices 22. it can.

2: Semiconductor wafer 20: Substrate 21: Functional layer 22: Device 23: Street 210: Cutting groove 220: Laser processing groove 230: Modified layer 3: Annular frame 30: Adhesive tape 4: Cutting device 41: Chuck of cutting device Table 42: Cutting means 423: Cutting blade 5: Laser processing apparatus 51: Chuck table of laser processing apparatus 52: Laser beam irradiation means 522: Light collector 6: Device separation device 61: Frame holding means 62: Tape expansion means 63: Pickup Collet

Claims (4)

A wafer processing method for dividing a wafer in which a device is formed by a functional layer laminated on a surface of a substrate, along a plurality of streets partitioning the device,
A cutting groove forming step of positioning a cutting blade in a region corresponding to the street from the back side of the substrate and forming a cutting groove leaving a part not reaching the functional layer;
A laser processing step of irradiating a laser beam along the bottom of the cutting groove from the back surface side of the substrate on which the cutting groove forming step has been performed, and breaking a part of the remaining substrate and the functional layer.
A method for processing a wafer.   The laser processing step irradiates a part of the remaining substrate and the functional layer with a laser beam having a wavelength that absorbs the substrate and the functional layer along the bottom of the cutting groove from the back side of the substrate. The wafer processing method according to claim 1, wherein a processing groove is formed.   In the laser processing step, a laser beam having a wavelength that is transmissive to the substrate and the functional layer is irradiated with a focusing point positioned at a part of the remaining substrate and an intermediate portion of the functional layer, and the remaining substrate The wafer processing method according to claim 1, wherein a modified layer is formed on a part of the substrate and the functional layer. Before carrying out the cutting groove forming step, the adhesive tape is adhered to the surface of the functional layer laminated on the substrate constituting the wafer, and the adhesive tape is an annular frame having an opening having a size for accommodating the wafer. A wafer support process for supporting the wafer via
A device separation step of expanding the adhesive tape to which the wafer is attached and separating the wafer into individual devices along the street after performing the laser processing step. The wafer processing method according to any one of the above.

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