JP2014135348A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer processing method which can remove a functional layer stacked on a surface of a substrate between two arrays of laser processed grooves which are formed along each street provided in the functional layer and remove fused materials adhering to the two arrays of laser processes grooves.SOLUTION: A wafer processing method of dividing a wafer on which devices are formed by a functional layer stacked on a surface of a substrate along a plurality of streets for partitioning the devices comprises: a laser processed groove formation process of radiating laser beams along both sides of each street and forming two arrays of laser processed grooves which reach the substrate to segmentalize the functional layer; and a fused material removal process of forming a liquid column for introducing laser beams to a central part of each two arrays of laser processed grooves formed along each street and radiating laser beams to remove the functional layer between the two arrays of laser processes grooves and remove fused materials adhering to the two arrays of laser processed grooves.

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.

  In addition, a metal pattern in which a metal film called a test element group (TEG) is partially placed on the street of a semiconductor wafer, and the device functions are tested through the metal pattern before dividing the semiconductor wafer. Such semiconductor wafers have 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-mentioned problem, a laser beam is irradiated along the street on both sides of the street formed on the semiconductor wafer, two laser processing grooves are formed along the street, and the laminate is divided. 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, two laser-processed grooves are formed along the street by irradiating a laser beam along the street on both sides of the street formed on the semiconductor wafer as in the wafer dividing method described in Patent Document 1 above. When formed, there is a problem that the melt adheres to the laser-processed groove and the bending strength of the device is lowered. In particular, when the metal pattern referred to as TEG described above is disposed on the street, when the metal melt adheres to the laser processing groove and the center portion of the two laser processing grooves is cut with a cutting blade, There is a problem that chipping occurs and the quality of the device is lowered.

  The present invention has been made in view of the above-mentioned facts, and the main technical problem thereof is the function between the two laser processing grooves formed along the street provided in the functional layer laminated on the surface of the substrate. An object of the present invention is to provide a wafer processing method capable of removing a layer and removing a melt adhering to two laser processing grooves.

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 laser processing groove forming step of irradiating laser beams along both sides of the street to form two laser processing grooves reaching the substrate and dividing the functional layer;
A liquid column that guides the laser beam is formed at the center of the two laser processing grooves formed along the street, and the laser beam is irradiated to remove the functional layer between the two laser processing grooves and to perform two laser processing. A melt removal step for removing the melt adhering to the groove,
A method for processing a wafer is provided.

After performing the melt removal step, a substrate cutting step is performed in which the cutting blade is positioned between the two laser processing grooves on the substrate from which the functional layer has been removed along the street, and the substrate is cut along the street.
Further, the melt removing step forms a liquid column that guides a laser beam between the two laser processing grooves formed along the street and irradiates the laser beam to form a functional layer between the two laser processing grooves. A dividing groove is formed in the substrate along the street while removing.

  In the wafer processing method according to the present invention, a laser processing groove forming step of dividing the functional layer by irradiating a laser beam along both sides of the street formed on the wafer to form two laser processing grooves reaching the substrate; Then, a liquid column for guiding the laser beam is formed at the center of the two laser processing grooves formed along the street formed on the wafer, and the functional layer between the two laser processing grooves is removed by irradiating the laser beam. And a melt removal step for removing the melt adhering to the two laser processing grooves, so that the two strips formed in the functional layer in the laser processing groove forming step by performing the melt removal step. The melt adhering to the laser processing groove is destroyed and removed. Therefore, the problem that the bending strength of the device is reduced due to the melt adhering to the laser processing groove is solved. In addition, even when a metal pattern called TEG is arranged on the street, melting of the metal adhering to the two laser-processed grooves formed in the functional layer by performing the melt removal process as described above. Since the object is destroyed and removed, when the cutting blade is positioned at the center of the two laser processing grooves in the substrate where the functional layer has been removed along the street, the substrate is cut along the street. The problem of chipping and degrading device quality is eliminated.

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 wafer support process in the processing method of the wafer by this invention was implemented, and the semiconductor wafer was affixed on the surface of the dicing tape with which the cyclic | annular flame | frame was mounted | worn. The principal part perspective view of the laser processing apparatus for implementing the laser processing groove | channel formation process in the processing method of the wafer by this invention. Explanatory drawing of the laser processing groove | channel 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 melt removal process in the processing method of the wafer by this invention. Sectional drawing of the process head which comprises the laser processing apparatus shown in FIG. Explanatory drawing of the melt removal process in the processing method of the wafer by this invention. The principal part perspective view of the cutting device for implementing the board | substrate cutting process in the processing method of the wafer by this invention. Explanatory drawing of the board | substrate cutting process in the processing method of the wafer by this invention. Explanatory drawing of the board | substrate cutting process in the processing method of the wafer by this invention. Sectional drawing which expands and shows the principal part of the semiconductor wafer in which other embodiment of the melt removal process in the processing method of the wafer by this invention was implemented.

  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 2a 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.

  A method of removing the functional layer 21 constituting the semiconductor wafer 2 described above along the street 23 will be described with reference to FIGS.

  First, a wafer support process is performed in which the back surface 2b of the substrate 20 constituting the semiconductor wafer 2 is adhered to the surface of a dicing tape mounted on an annular frame. That is, as shown in FIG. 2, the back surface 2 b of the substrate 20 constituting the semiconductor wafer 2 is attached to the surface of the dicing tape 30 with the outer peripheral portion mounted so as to cover the inner opening of the annular frame 3.

  If the wafer supporting process described above is performed, the laser processing groove that divides the functional layer 21 by irradiating the laser beam along both sides of the street 23 of the semiconductor wafer 2 to form two laser processing grooves reaching the substrate 20. A forming step is performed. This laser processing groove forming step is performed using a laser processing apparatus 4 shown in FIG. A laser processing apparatus 4 shown in FIG. 3 includes a chuck table 41 that holds a workpiece, laser beam irradiation means 42 that irradiates a workpiece held on the chuck table 41 with a laser beam, and a chuck table 41 that holds the workpiece. An image pickup means 43 for picking up an image of the processed workpiece is provided. The chuck table 41 is configured to suck and hold the 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 also shown in FIG. It can be moved in the index feed direction indicated by the arrow Y.

  The laser beam application means 42 includes a cylindrical casing 421 arranged substantially horizontally. In the casing 421, pulse laser beam oscillation means including a pulse laser beam oscillator and repetition frequency setting means (not shown) are arranged. A condenser 422 for condensing the pulse laser beam oscillated from the pulse laser beam oscillating means is attached to the tip of the casing 421. The laser beam irradiating unit 42 includes a condensing point position adjusting unit (not shown) for adjusting the condensing point position of the pulsed laser beam condensed by the condenser 422.

  The image pickup means 43 attached to the tip of the casing 421 constituting the laser beam irradiation means 42 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 pickup device (CCD) or the like for picking up the captured image is provided, and the picked-up image signal is sent to a control means (not shown).

Laser processing groove formation that divides the functional layer 21 by irradiating a laser beam along both sides of the street 23 of the semiconductor wafer 2 to form two laser processing grooves reaching the substrate 20 using the laser processing apparatus 4 described above. A process is demonstrated with reference to FIG. 3 and FIG.
First, the dicing tape 30 side on which the semiconductor wafer 2 is adhered is placed on the chuck table 41 of the laser processing apparatus 4 shown in FIG. 3 described above. Then, the semiconductor wafer 2 is held on the chuck table 41 via the dicing tape 30 by operating a suction means (not shown) (wafer holding step). Therefore, the surface 2a of the semiconductor wafer 2 held on the chuck table 41 is on the upper side. In FIG. 3, the annular frame 3 to which the dicing tape 30 is attached is omitted, but the annular frame 3 is held by an appropriate frame holding means provided 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 operation for detecting a processing region to be laser processed of the semiconductor wafer 2 is executed by the image pickup means 43 and a control means (not shown). That is, the image pickup means 43 and the control means (not shown) align the streets 23 formed in a predetermined direction of the semiconductor wafer 2 with the condenser 422 of the laser beam irradiation means 42 that irradiates the laser beams along the streets 23. Image processing such as pattern matching is performed to perform the laser beam irradiation position alignment (alignment process). Similarly, alignment of the laser beam irradiation position is performed on the street 23 formed on the semiconductor wafer 2 in a direction orthogonal to the predetermined direction.

  When the alignment process described above is performed, the chuck table 41 is moved to the laser beam irradiation region where the condenser 422 of the laser beam irradiation means 42 for irradiating the laser beam as shown in FIG. It is positioned directly below the vessel 422. At this time, as shown in FIG. 4A, the semiconductor wafer 2 is positioned so that one end of the street 23 (the left end in FIG. 4A) is located directly below the condenser 422. Next, the chuck table 41 is moved at a predetermined processing feed speed in the direction indicated by the arrow X1 in FIG. 4A while irradiating a pulse laser beam from the condenser 422 of the laser beam irradiation means 42. Then, as shown in FIG. 4B, when the other end of the street 23 (the right end in FIG. 4B) reaches a position directly below the condenser 422, the irradiation of the pulse laser beam is stopped and the chuck table 41 is stopped. Stop moving. In this laser processing groove forming step, the condensing point P of the pulse laser beam is matched with the vicinity of the surface of the street 23.

  Next, the chuck table 41 is moved in the direction perpendicular to the paper surface (index feed direction) by 40 μm in the illustrated embodiment. Then, while irradiating a pulse laser beam from the condenser 422 of the laser beam irradiation means 42, the chuck table 41 is moved at a predetermined processing feed speed in the direction indicated by the arrow X2 in FIG. 4B, 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 41 is stopped.

  By performing the above-described laser processing groove forming step, two streets of the laser processing groove reaching the substrate 20 in the street 23 of the semiconductor wafer 2 are deeper than the thickness of the functional layer 21 as shown in FIG. 24, 24 are formed. As a result, the functional layer 21 is divided by the two laser processing grooves 24 and 24. The melts 24a and 24a adhere to the two laser-processed grooves 24 and 24 formed by performing the laser-processed groove forming step in this way. Note that the distance (B) between the two outer sides of the two laser processing grooves 24, 24 formed on the street 23 is a radius of the focused spot diameter of 5 μm + a moving amount of the chuck table 41 of 40 μm + condensing in the illustrated embodiment. The spot diameter is set to 50 μm with a radius of 5 μm. 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
Average output: 1.5W
Repetition frequency: 200 kHz
Condensing spot diameter: φ10μm
Processing feed rate: 400 mm / sec

  Next, a liquid column for guiding a laser beam is formed at the center of the two laser processing grooves 24 and 24 formed along the streets 23 formed on the semiconductor wafer 2 to irradiate the laser beam. The functional layer 21 between the grooves 24 and 24 is removed, and a melt removing process for removing the melts 24a and 24a attached to the two laser-processed grooves 24 and 24 is performed. This melt removal step is performed using a laser processing apparatus 5 shown in FIG. The laser processing apparatus 5 shown in FIG. 5 irradiates a laser beam to the chuck table 51 that holds the workpiece and the workpiece that is held on the chuck table 51 in the same manner as the laser processing apparatus 4 shown in FIG. Laser beam irradiation means 52 and imaging means 53 for imaging a workpiece held on the chuck table 51 are 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.

  As shown in FIG. 6, the laser beam irradiation means 52 includes a cylindrical casing 521 (see FIG. 5) that extends substantially horizontally, a pulse laser beam oscillation means 54 disposed in the casing 551, and a casing 521. And a processing head 55 for condensing the laser beam emitted from the pulsed laser beam oscillation means 54. The pulse laser beam oscillating means 54 includes a pulse laser beam oscillator 541 composed of a YAG laser oscillator or a YVO4 laser oscillator, and a repetition frequency setting means 542 attached thereto.

  As shown in FIG. 6, the processing head 55 includes a head housing 551, a direction changing mirror 552 that is disposed in the head housing 551 and changes the direction of the laser beam emitted from the pulse laser beam oscillation means 54 downward. A condensing lens 553 for condensing the laser beam whose direction has been changed by the direction changing mirror 552 is provided. A liquid chamber 551a is formed in the lower portion of the head housing 551, and an injection nozzle 551b is formed on the lower wall forming the liquid chamber 551a. The injection port of the injection nozzle 551b is formed on the optical axis of the laser beam while the condensing point collected by the condensing lens 553 is positioned. A transparent plate 554 is disposed on the upper wall that forms the liquid chamber 551a. The liquid is supplied by the liquid supply means 56 to the liquid chamber 551a of the processing head 55 configured as described above. The liquid supply means 56 configured as described above supplies, for example, a liquid having a pressure of 15 MPa to the liquid chamber 551a. The liquid supplied to the liquid chamber 551a by the liquid supply means 56 is ejected as a liquid column 57 from the ejection port of the ejection nozzle 551b. The diameter of the liquid column 57 is set to 40 μm in the illustrated embodiment.

  A gas flow cylinder 58 that forms a passage 58a through which the liquid column 57 ejected from the ejection port of the ejection nozzle 551b passes is disposed below the ejection nozzle 551b provided in the lower portion of the head housing 551. . The gas flow cylinder 58 is attached to the lower surface of the lower wall forming the liquid chamber 551a so as to surround the injection port of the injection nozzle 551b. A gas introduction port 581 communicating with the passage 58a is formed on the side surface of the gas flow tube 58, and a jet port 582 is provided at the lower end. Gas is supplied from the gas supply means 59 to the gas inlet 581 of the gas flow cylinder 58 configured as described above. The gas supply means 59 configured as described above supplies, for example, 5 liters of gas to the gas distribution cylinder 58 per minute.

Using the laser processing apparatus 5 described above, a thread-like water column that guides the laser beam is formed between the two laser processing grooves 24 and 24 formed along the streets 23 formed in the semiconductor wafer 2 to emit the laser beam. FIG. 5 to FIG. 5 show the melt removal step of irradiating and removing the functional layer 21 between the two laser processed grooves 24 and 24 and removing the melts 24a and 24a adhering to the two laser processed grooves 24 and 24. This will be described with reference to FIG.
First, the dicing tape 30 side on which the semiconductor wafer 2 on which the laser processing groove forming step described above is 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 dicing tape 30 (wafer holding step). Therefore, the surface 2a of the semiconductor wafer 2 held on the chuck table 51 is on the upper side. In FIG. 5, the annular frame 3 to which the dicing tape 30 is mounted 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 means 53 and the control means (not shown) include two laser processing grooves 24 and 24 formed along the street 23 formed in a predetermined direction of the semiconductor wafer 2, and the two laser processing grooves 24. , 24, performs image processing such as pattern matching for aligning with the processing head 55 of the laser beam irradiation means 52 that irradiates the laser beam, and performs alignment of the laser beam irradiation position (alignment process). In addition, the alignment of the laser beam irradiation position is similarly performed on the two laser processing grooves 24 and 24 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 processing head 55 of the laser beam irradiation means 52 for irradiating the laser beam is positioned as shown in FIG. The central portions of the two laser processing grooves 24 and 24 are positioned immediately below the processing head 55. At this time, as shown in FIG. 7A, the semiconductor wafer 2 is arranged such that one end (the left end in FIG. 7A) of the two laser processing grooves 24, 24 is located immediately below the processing head 55. Positioned. Next, the liquid supply means 56 is operated to supply the high-pressure liquid to the liquid chamber 551 a of the processing head 55. The high-pressure liquid supplied to the liquid chamber 551 a is ejected from the ejection port of the ejection nozzle 551 b toward the surface (upper surface) of the semiconductor wafer 2 held on the chuck table 51 as a liquid column 57. On the other hand, the pulsed laser beam oscillated from the pulsed laser beam oscillating means 54 is condensed by the condenser lens 553 via the direction conversion mirror 552 and guided to the liquid column 57 through the transparent plate 554 and irradiated. Therefore, the spot of the pulse laser beam is the diameter D of the liquid column 57 (40 μm in the illustrated embodiment). Therefore, in the illustrated embodiment, the relationship between the two laser processing grooves 24, 24 and the diameter of the liquid column 57 is the center of the two laser processing grooves 24, 24 as shown in FIG. The diameter of the liquid column 57 is positioned between the positions, that is, in the central portion. At the time of this laser beam irradiation, the gas supply means 59 is operated, and the gas is ejected from the ejection port 582 toward the semiconductor wafer 2 held by the chuck table 51 through the passage 58a of the gas flow tube 58.

  As described above, the chuck table 51 is processed in a predetermined direction in the direction indicated by the arrow X1 in FIG. 7A while irradiating the pulse laser beam LB guided from the processing head 55 of the laser beam irradiation means 52 to the liquid column 57. Move at feed rate. Then, as shown in FIG. 7B, when the other ends (the right end in FIG. 7B) of the two laser processing grooves 24, 24 formed on the street 23 reach a position directly below the processing head 55. Then, the irradiation of the pulsed laser beam guided to the liquid column 57 is stopped and the movement of the chuck table 51 is stopped. In this melt removal step, the functional layer 21 between the two laser processing grooves 24 and 24 is removed by irradiation with a pulsed laser beam guided to the liquid column 57 as shown in FIG. In the melt removal step, high-pressure liquid for forming the liquid column 57 for guiding the pulsed laser beam is ejected from the ejection port of the ejection nozzle 551b. , 24 are destroyed and removed. This melt removal step is carried out along the two laser processing grooves 24 and 24 formed on all the streets 23 formed on the semiconductor wafer 2.

In addition, the said melt removal process is performed on the following process conditions, for example.
Laser beam wavelength: 532 nm
Average output: 17W
Repetition frequency: 200 kHz
Liquid column diameter: 40 μm
Pressure of high pressure liquid: 15MPa
Processing feed rate: 150 mm / sec

  By performing the melt removal step under the above processing conditions, the functional layer 21 between the two laser processing grooves 24 and 24 is removed, and from the surface of the functional layer 21 as shown in FIG. The processed groove 25 is formed by processing about 50 μm.

  Next, a substrate cutting step is performed in which a cutting blade is positioned at the center of the two laser processing grooves 24 and 24 in the substrate 20 from which the functional layer 21 has been removed along the street 23 to cut the substrate along the street. . In the illustrated embodiment, this substrate cutting step is performed using a cutting device 6 shown in FIG. 8 includes a chuck table 61 that holds a workpiece, a cutting means 62 that cuts the workpiece held on the chuck table 61, and a workpiece that is held on the chuck table 61. An image pickup means 63 for picking up images is provided. The chuck table 61 is configured to suck and hold a workpiece. The chuck table 61 is moved in a processing feed direction indicated by an arrow X in FIG. 8 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 62 includes a spindle housing 621 arranged substantially horizontally, a rotating spindle 622 rotatably supported by the spindle housing 621, and a cutting blade 623 attached to the tip of the rotating spindle 622. The rotary spindle 622 is rotated in the direction indicated by the arrow 623a by a servo motor (not shown) disposed in the spindle housing 621. The cutting blade 623 includes a disk-shaped base 624 made of aluminum, and an annular cutting edge 625 attached to the outer periphery of the side surface of the base 624. The annular cutting edge 625 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 624. The diameter is 52 mm.

  The imaging means 63 is mounted at the tip of the spindle housing 621, and illuminates the work piece, an optical system that captures the area illuminated by the illumination means, and an image captured by the optical system. An image pickup device (CCD) or the like for picking up images is provided, and the picked up image signal is sent to a control means (not shown).

  In order to perform the substrate cutting process using the cutting device 6 described above, as shown in FIG. 8, the dicing tape 30 side on which the semiconductor wafer 2 on which the melt removal process has been performed is attached on the chuck table 61 is disposed. Place. Then, by operating a suction means (not shown), the semiconductor wafer 2 is held on the chuck table 61 via the dicing tape 30 (wafer holding step). Therefore, the surface 2a of the semiconductor wafer 2 held on the chuck table 61 is on the upper side. In FIG. 8, the annular frame 3 to which the dicing tape 30 is mounted is omitted, but the annular frame 3 is held by an appropriate frame holding means provided on the chuck table 61. In this manner, the chuck table 61 that sucks and holds the semiconductor wafer 2 is positioned directly below the imaging unit 63 by a processing feed unit (not shown).

  When the chuck table 61 is positioned immediately below the image pickup means 63, an alignment process for detecting an area to be cut of the semiconductor wafer 2 is executed by the image pickup means 63 and a control means (not shown). In this alignment process, the two laser-processed grooves 24 and 24 formed along the streets 23 of the semiconductor wafer 2 in the laser-processed groove forming process are imaged and executed by the imaging means 63. The imaging unit 63 and a control unit (not shown) are for aligning the two laser processing grooves 24 and 24 formed along the streets 23 formed in a predetermined direction of the semiconductor wafer 2 and the cutting blade 623. The image processing such as pattern matching is executed, and the cutting region is aligned by the cutting blade 623 (alignment process). In addition, the cutting position alignment by the cutting blade 623 is similarly performed on the two laser processing grooves 24 and 24 formed in the semiconductor wafer 2 in a direction orthogonal to the predetermined direction.

  If the two laser processing grooves 24, 24 formed along the street 23 of the semiconductor wafer 2 held on the chuck table 61 as described above are detected and the cutting area is aligned, The chuck table 61 holding the semiconductor wafer 2 is moved to the cutting start position in the cutting area. At this time, as shown in FIG. 9A, the semiconductor wafer 2 is positioned so that one end of the street 23 to be cut (the left end in FIG. 9A) is positioned to the right by a predetermined amount from just below the cutting blade 623. It is done. At this time, in the illustrated embodiment, since the two laser processing grooves 24, 24 formed on the street 23 in the alignment step described above are directly imaged and the cutting area is detected, FIG. As shown in FIG. 4, the center position between the two laser processing grooves 24, 24 formed on the street 23, that is, the central portion is surely positioned at a position facing the cutting blade 623. In the illustrated embodiment, as shown in FIG. 7 (d), the substrate 20 has a processing groove 25 formed in the center between the two laser processing grooves 24, 24 formed on the street 23. Therefore, as shown in FIG. 10A, the machining groove 25 is positioned at a position facing the cutting blade 623.

  When the chuck table 61, that is, the semiconductor wafer 2 is thus positioned at the cutting start position in the cutting region, the cutting blade 623 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 and feeding position as shown by a solid line in FIG. This cutting feed position is set to a position where the lower end of the cutting blade 623 reaches the dicing tape 30 adhered to the back surface of the semiconductor wafer 2 as shown in FIGS. 10 (a) and 10 (c). .

  Next, the cutting blade 623 is rotated at a predetermined rotational speed in the direction indicated by an arrow 623a in FIG. 9A, and the chuck table 61 is rotated at a predetermined cutting feed speed in the direction indicated by an arrow X1 in FIG. Move with. Then, when the chuck table 61 reaches the other end of the street 23 (the right end in FIG. 9B) to the left of a predetermined amount from just below the cutting blade 623 as shown in FIG. 61, that is, the movement of the semiconductor wafer 2 is stopped. By cutting and feeding the chuck table 61 in this way, the substrate 20 of the semiconductor wafer 2 is cut to reach the back surface between both sides of the laser processing grooves 24 and 24 formed in the street 23 as shown in FIG. The groove 26 is formed and cut (cutting process).

  Next, the cutting blade 623 is raised as shown by the arrow Z2 in FIG. 9B and positioned at the standby position shown by the two-dot chain line, and the chuck table 61 is moved in the direction shown by the arrow X2 in FIG. 9B. It moves and returns to the position shown in FIG. Then, the chuck table 61 is indexed and fed by an amount corresponding to the interval between the streets 23 in the direction perpendicular to the paper surface (index feeding direction), and the street 23 to be cut next is positioned at a position corresponding to the cutting blade 623. In this way, when the street 23 to be cut next is positioned at a position corresponding to the cutting blade 623, the above-described cutting process is performed.

In addition, the said cutting process is performed on the following processing conditions, for example.
Cutting blade: outer diameter 52mm, thickness 40μm
Cutting blade rotation speed: 40000 rpm
Cutting feed rate: 50 mm / sec

  The cutting process described above is performed on all the streets 23 formed on the semiconductor wafer 2. As a result, the semiconductor wafer 2 is cut along the streets 23 and divided into individual devices 22.

  The device 22 divided as described above is attached to the two laser processed grooves 24 and 24 formed in the functional layer 21 in the laser processed groove forming process by performing the melt removing process as described above. Since the melted materials 24a and 24a are destroyed and removed, the problem that the bending strength of the device is reduced due to the melt adhering to the laser processing grooves 24 and 24 is solved. Further, even when a metal pattern called TEG is arranged on the street, it adheres to the two laser processing grooves 24 and 24 formed in the functional layer 21 by performing the melt removal step as described above. Since the molten metal is destroyed and removed, chipping occurs when the metal melt adheres to the laser processing groove and the center of the two laser processing grooves is cut with a cutting blade. The problem of lowering the quality of the product is solved.

Next, in the melt removal step, two laser beams are formed by irradiating the laser beam by forming a liquid column that guides the laser beam at the center of the two laser processing grooves 24 and 24 formed along the street 23. An embodiment in which the functional layer 21 of the processed grooves 24 and 24 is removed and the divided grooves are formed in the substrate 20 along the streets 23 will be described.
In this embodiment, the machining feed rate under the above-described machining conditions is changed from 150 mm / second to 50 mm / second. Other processing conditions are set to be the same as the above-described processing conditions. By performing the melt removal step under such processing conditions, the functional layer 21 between the two laser processing grooves 24 and 24 is removed as shown in FIG. 11 and the thickness along the street 23 is 10 μm. The division grooves 27 are formed in the functional layer 21 and the substrate 20 having a thickness of 140 μm. Also in this melt removal step, since the high-pressure liquid for forming the liquid column 57 for guiding the pulsed laser beam is ejected from the ejection port of the ejection nozzle 551b, the two laser processing grooves 24 in the laser processing groove forming step, The melts 24 a and 24 a adhering to 24 are destroyed and removed, and a newly generated melt does not adhere to the substrate 20 and the functional layer 21.

2: Semiconductor wafer 20: Substrate 21: Functional layer 22: Device 23: Street 24, 24: Laser processing groove 3: Annular frame 30: Dicing tape 4: Laser processing device 41: Chuck table of laser processing device 42: Laser beam irradiation Means 422: Condenser 5: Laser processing device 51: Chuck table of laser processing device 52: Laser beam irradiation means 55: Processing head 56: Liquid supply means 6: Cutting device 61: Chuck table of cutting device 62: Cutting means 623: Cutting blade

Claims (3)

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 laser processing groove forming step of irradiating laser beams along both sides of the street to form two laser processing grooves reaching the substrate and dividing the functional layer;
A liquid column that guides the laser beam is formed at the center of the two laser processing grooves formed along the street, and the laser beam is irradiated to remove the functional layer between the two laser processing grooves and to perform two laser processing. A melt removal step for removing the melt adhering to the groove,
A method for processing a wafer.   After performing the melt removal step, a substrate cutting step is performed in which the cutting blade is positioned at the center of the two laser processing grooves on the substrate from which the functional layer has been removed along the street, and the substrate is cut along the street. The method for processing a wafer according to claim 1.   The melt removal step forms a liquid column that guides the laser beam at the center of the two laser processing grooves formed along the street and irradiates the laser beam to form a functional layer between the two laser processing grooves. The wafer processing method according to claim 1, wherein the dividing grooves are formed in the substrate along the streets while being removed.

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