JP2015005558A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer processing method capable of dividing a wafer in which devices are formed in a plurality of regions partitioned by a plurality of division schedule lines formed in a lattice shape in a functional layer laminated on a surface of a substrate without adversely affecting the devices.SOLUTION: A wafer processing method includes the steps of: sticking a protective member to a surface of a functional layer 21 constituting a wafer (protective member sticking step); forming a cutting groove by holding a protective member side of the wafer on a chuck table and positioning a cutting blade at the region corresponding to a division schedule line from the rear surface side of the substrate, leaving a part not reaching the functional layer (cutting groove forming step); sticking a dicing tape 50 to the rear surface of the substrate constituting the wafer, supporting an outer peripheral part of the dicing tape by an annular frame, and peeling the protective member (wafer supporting step); and irradiating the wafer with a laser beam LB along the division schedule line 22 formed in the functional layer constituting the wafer and cutting the functional layer by ablation processing (functional layer cutting step).

Description

  The present invention relates to a wafer that divides a wafer in which devices are formed in a plurality of regions partitioned by a plurality of division lines formed in a lattice pattern on a functional layer laminated on the surface of the substrate along the division lines. It relates to the processing method.

  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. The semiconductor wafer formed in this way is partitioned by the planned division lines in which the above devices are formed in a lattice shape, and individual semiconductor devices are manufactured by dividing along the predetermined division lines.

  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 a division of the semiconductor wafer along the division line 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 peripheral portion of the side surface of the base. The cutting edge is fixed by electroforming diamond abrasive grains having a grain size of about 3 μm, for example, about 30 μm. It is formed in the thickness.

  However, the Low-k film described above is difficult to cut with a cutting blade. In other words, the low-k film is very brittle like mica, so when the cutting blade is cut along the planned dividing line, the low-k film is peeled off, and this peeling reaches the circuit, resulting in fatal damage to the device. There is a problem of giving.

  In order to solve the above problem, a laser beam is irradiated along the planned division line formed on the semiconductor wafer, a laser processing groove is formed along the planned division line, the functional layer is divided, and the laser processing groove is cut. Patent Document 1 below discloses a wafer dividing method in which a semiconductor wafer is cut along a predetermined division line by positioning the blade and relatively moving the cutting blade and the semiconductor wafer.

JP-A-2005-64231

Thus, as described in Patent Document 1, the laser beam is irradiated along the planned division line formed on the semiconductor wafer to form a laser processing groove along the planned division line to divide the functional layer. The wafer dividing method of positioning the cutting blade in the laser processing groove and cutting the semiconductor wafer along the planned dividing line has the following problems.
(1) Even if the width of the laser processing groove is sufficient, the cutting blade comes into contact with the melt adhering to the side surface of the laser processing groove, and the outer periphery of the device suddenly becomes chipped.
(2) If the functional layer is not sufficiently removed when forming the laser processed groove, the cutting blade will be displaced or fallen, resulting in peeling of the functional layer of the device.
(3) In order to form the laser processing groove in a range exceeding the width of the cutting blade, it is necessary to increase the width of the line to be divided, and the number of devices formed on the wafer is reduced.
(4) Since a passivation film containing SiO2, SiN, etc. 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, the energy of the laser beam that has reached the inside of the functional layer loses its escape, and a so-called undercut phenomenon occurs in which a circuit is formed and the processing spreads to the low density device side.

  The present invention has been made in view of the above facts, and the main technical problem thereof is that a plurality of regions defined by a plurality of division lines formed in a lattice pattern on a functional layer laminated on the surface of the substrate. An object of the present invention is to provide a wafer processing method capable of solving the above-described problems and dividing a wafer on which a device is formed into individual devices.

In order to solve the main technical problem, according to the present invention, a device is formed in a plurality of regions partitioned by a plurality of division lines formed in a lattice pattern on a functional layer stacked on the surface of a substrate. A wafer processing method for dividing a wafer along a division line,
A protective member attaching step for attaching a protective member to the surface of the functional layer constituting the wafer;
The protective member side of the wafer on which the protective member attaching step has been performed is held on the chuck table, and the cutting blade is positioned in the area corresponding to the planned division line from the back side of the substrate, leaving a part that does not reach the functional layer. Cutting groove forming step of forming cutting grooves,
A wafer support step of attaching a dicing tape to the back surface of the substrate constituting the wafer on which the cutting groove forming step has been performed, supporting the outer peripheral portion of the dicing tape with an annular frame, and peeling the protective member;
A functional layer cutting step of irradiating the functional layer with a laser beam along a division planned line formed on the functional layer constituting the wafer on which the wafer support step has been performed, and cutting the functional layer by cutting.
A method for processing a wafer is provided.

In the wafer support step, a dicing tape attached to an annular frame is attached to the back surface of the substrate constituting the wafer held on the chuck table and subjected to the cutting groove forming step.
In the wafer support step, the wafer is unloaded from the chuck table by a first suction holding pad that sucks and holds the entire back surface of the substrate constituting the wafer held by the chuck table and subjected to the cutting groove forming step. After transferring the wafer to the second suction holding pad that sucks and holds the entire surface of the protective member attached to the surface of the functional layer constituting the wafer, the wafer was mounted on the annular frame on the back surface of the substrate constituting the wafer. Apply dicing tape.

In the wafer processing method according to the present invention, the protective member attached to the surface of the functional layer constituting the wafer is held on the chuck table, and the cutting blade is positioned in the area corresponding to the division line from the back side of the substrate. A cutting groove forming step for forming a cutting groove leaving a part that does not reach the functional layer, and a dicing tape attached to the back surface of the substrate constituting the wafer on which the cutting groove forming step is performed, and the outer peripheral portion of the dicing tape Is supported by an annular frame, and a wafer supporting process for peeling off the protective member, and a function of irradiating a laser beam along a planned division line formed on a functional layer constituting the wafer on which the wafer supporting process is performed. Since the functional layer cutting step of cutting the layer by ablation processing is included, the following effects can be obtained.
(1) Even if a melt adheres to the side surface of the laser processing groove formed in the functional layer by the ablation processing by the laser processing step, the laser processing groove is not cut by the cutting blade, so the device is suddenly caused by contact with the cutting blade. This eliminates the problem of chipping on the outer periphery of the sheet.
(2) Even if the removal of the functional layer in the ablation processing by the laser processing step is insufficient, the wafer can be divided into individual devices if the laser processing groove reaches the cutting groove formed from the back side of the substrate. Since the laser processing groove is not cut with a cutting blade, the problem that peeling occurs in the functional layer is solved.
(3) Since it is not necessary to form a laser processing groove having a width exceeding the width of the cutting blade, the width of the line to be divided can be reduced, and the number of devices that can be formed on the wafer can be increased. .
(4) Even if a passivation film containing SiO2, SiN, etc. is formed on the surface of the functional layer, if the functional layer is irradiated with a laser beam along the division line in the laser processing step, the cutting formed from the back side of the substrate Since energy escapes to the groove, the so-called undercut problem is solved.

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. Explanatory drawing of the protection member sticking process in the processing method of the wafer by this invention. 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. Explanatory drawing which shows 1st Embodiment of the wafer support process in the processing method of the wafer by this invention. Explanatory drawing which shows 2nd Embodiment of the wafer support process in the processing method of the wafer by this invention. Explanatory drawing which shows 2nd Embodiment of the wafer support process in the processing method of the wafer by this invention. Explanatory drawing which shows 2nd Embodiment of the wafer support process in the processing method of the wafer by this invention. The principal part perspective view of the laser processing apparatus for implementing the functional layer cutting process in the processing method of the wafer by this invention. Explanatory drawing of the functional layer cutting 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 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. In addition, devices 23 such as ICs and LSIs are formed in a plurality of regions partitioned by a plurality of division lines 22 formed in a lattice pattern on the functional layer 21. 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, SiN, etc. formed on the surface.

A wafer processing method for dividing the semiconductor wafer 2 described above along the division line will be described.
First, in order to protect the device 23, the protective member 3 is stuck on the surface 21a of the functional layer 21 laminated on the substrate 20 constituting the semiconductor wafer 2 (protective member sticking step). The protective member 3 can be a rigid hard plate such as a resin sheet such as a polyethylene film or a glass substrate.

  If the above-described protective member attaching step is performed, the protective member 3 side of the semiconductor wafer 2 is held on the chuck table, and the cutting blade is positioned in a region corresponding to the division line 22 from the back surface side of the substrate 20. A cutting groove forming step is performed in which a cutting groove is formed while leaving a portion that does not reach the point. 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, as shown in FIG. 3, the protective member 3 side that is bonded to the semiconductor wafer 2 by performing the protective member bonding process on the chuck table 41. Is placed. Then, by operating a suction means (not shown), the semiconductor wafer 2 is held on the chuck table 41 via the protective member 3 (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 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 image pickup means 43 and the control means (not shown) perform image processing such as pattern matching for aligning the region corresponding to the division line 22 formed in a predetermined direction of the semiconductor wafer 2 and the cutting blade 423. And the cutting region is aligned by the cutting blade 423 (alignment process). In addition, the cutting position alignment by the cutting blade 423 is similarly performed on a region corresponding to the division line 22 formed on the semiconductor wafer 2 in a direction orthogonal to the predetermined direction. At this time, the surface 21a of the functional layer 21 on which the division line 22 of the semiconductor wafer 2 is formed is positioned on the lower side. However, as described above, the imaging unit 43 and the optical system that captures infrared rays and Since the image pickup device is provided with an image pickup device (infrared CCD) or the like that outputs an electric signal corresponding to infrared rays, the division planned line 22 can be picked up from the back surface 20b of the substrate 20 constituting the wafer. .

  When the region corresponding to the division line 22 of the semiconductor wafer 2 held on the chuck table 41 is detected and the cutting region is aligned as described above, the chuck table 41 holding the semiconductor wafer 2 is detected. Is moved to the cutting start position in the cutting area. At this time, as shown in FIG. 4A, the semiconductor wafer 2 has one end (the left end in FIG. 4A) of the region corresponding to the division line 22 to be cut at a right side by a predetermined amount from directly below the cutting blade 423. It is positioned to be located at.

  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 other end of the position corresponding to the division line 22 (the right end in FIG. 4B) is positioned to the left by a predetermined amount from directly below the cutting blade 423. When reaching the above, 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 in a direction perpendicular to the paper surface (index feed direction) by an amount corresponding to the interval between the scheduled division lines 22, and an area corresponding to the scheduled division line 22 to be cut next is defined as a cutting blade 423. Position it at the corresponding position. Thus, if the area | region corresponding to the division | segmentation scheduled line 22 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 regions corresponding to all the division lines 22 formed on the semiconductor wafer 2.

Next, a wafer in which a dicing tape is attached to the back surface 20b of the substrate 20 constituting the semiconductor wafer 2 on which the cutting groove forming step has been performed, and the outer peripheral portion of the dicing tape is supported by an annular frame, and the protective member 3 is peeled off. A support process is performed.
A first embodiment of the wafer support process will be described with reference to FIG. The first embodiment shown in FIG. 5 of the wafer support process is performed on the chuck table 41 on which the cutting groove forming process has been performed. That is, as shown in FIGS. 5 (a) and 5 (b), the outer peripheral portion is mounted on the back surface 5 of the annular frame 5 having the opening 51 having a size for accommodating the wafer so as to cover the opening 51. The surface 50a of the dicing tape 50 (adhesive layer is provided and an adhesive surface is formed) is pasted on the back surface 20b of the substrate 20 constituting the semiconductor wafer 2 held by the chuck table 41 on which the cutting groove forming step has been performed. To wear. Then, as shown in FIG. 5C, the protective member 3 adhered to the surface of the functional layer 21 constituting the semiconductor wafer 2 is peeled off.

  Next, a second embodiment of the wafer support process will be described with reference to FIGS. In the second embodiment of the wafer support step, the back surface of the substrate 20 constituting the semiconductor wafer 2 held by the chuck table 41 on which the cutting groove forming step shown in FIGS. 20 b is sucked and held using the first suction holding pad 6. The first suction holding pad 6 shown in FIGS. 6A and 6B includes a disk-shaped base 61 and a pad 62. The base 61 constituting the first suction holding pad 6 is provided with a circular recess 611 whose lower part is opened. A pad 62 formed in a disc shape by a porous ceramic member is fitted into the recess 611. Thus, the lower surface of the pad 62 fitted into the recess 611 of the base 61 functions as a suction surface for sucking and holding the workpiece. A circular recess 611 formed in the base 61 constituting the first suction holding pad 6 is connected to suction means (not shown). Therefore, when a suction means (not shown) is operated, negative pressure is applied to the lower surface (suction surface) of the pad 62 through the recess 611 of the base 61, and the workpiece is suctioned to the lower surface (suction surface) of the pad 62. Can be held. That is, as shown in FIG. 6A, the first suction holding pad 6 is formed on the back surface 20b (upper surface) of the substrate 20 constituting the semiconductor wafer 2 held by the chuck table 41 that has been subjected to the cutting groove forming step. The lower surface (suction surface) of the pad 62 is brought into contact with and a suction means (not shown) is operated to suck and hold the entire back surface 20b of the substrate 20 constituting the semiconductor wafer 2 on the lower surface (suction surface) of the pad 62. In this way, the first suction holding pad 6 that sucks and holds the substrate 20 constituting the semiconductor wafer 2 on the lower surface (suction surface) of the pad 62 is the substrate constituting the semiconductor wafer 2 as shown in FIG. 20 is moved upward from the upper surface of the chuck table 41 while being sucked and held, and then unloaded from the chuck table 41 (wafer unloading step).

  When the wafer unloading step described above is performed, the protective member 3 attached to the surface of the functional layer 21 constituting the semiconductor wafer 2 sucked and held by the first suction holding pad 6 is directed upward. Wafer transfer for sucking and holding the protective member 3 side adhered to the surface of the functional layer 21 constituting the semiconductor wafer 2 to the second suction holding pad to separate the first suction holding pad 6 from the semiconductor wafer 2. A replacement process is performed. In order to carry out this wafer transfer step, the second suction holding pad 7 shown in FIGS. 7A and 7B is used. The second suction / holding pad 7 shown in FIGS. 7A and 7B includes a disk-shaped base 71 and a pad 72. The base 71 constituting the second suction holding pad 7 is provided with a circular recess 711 whose lower part is opened. A pad 72 formed in a disk shape by a porous ceramic member is fitted into the recess 711. In this way, the lower surface of the pad 72 fitted in the recess 711 of the base 71 functions as a suction surface for sucking and holding the workpiece. A circular recess 711 formed in the base 71 constituting the second suction holding pad 7 is connected to suction means (not shown). Accordingly, when a suction means (not shown) is operated, a negative pressure is applied to the lower surface (suction surface) of the pad 72 via the recess 711 of the base 71, and the workpiece is suctioned to the lower surface (suction surface) of the pad 72. Can be held. In order to perform the wafer transfer process using the second suction holding pad 7, the first suction holding pad 6 that has performed the wafer unloading process is turned upside down as shown in FIG. The protective member 3 attached to the surface of the functional layer 21 constituting the semiconductor wafer 2 held by suction is directed upward. Next, the first suction holding pad 6 is positioned and raised below the second suction holding pad 7, and the second suction holding pad 7 is placed on the upper surface of the protective tape 3 attached to the surface of the semiconductor wafer 2. After the lower surface (suction surface) of the pad 72 is brought into contact, the suction holding of the semiconductor wafer 2 by the first suction holding pad 6 is released. Then, by operating a suction means (not shown), the protective member 3 adhered to the surface of the functional layer 21 constituting the semiconductor wafer 2 on the lower surface (suction surface) of the pad 72 of the second suction holding pad 7. Hold the entire surface by suction. Then, as shown in FIG. 7B, the first suction holding pad 6 is lowered and separated from the semiconductor wafer 2. In this way, the second suction holding pad 7 that sucks and holds the protective tape 3 attached to the surface of the semiconductor wafer 2 on the lower surface (suction surface) of the pad 72 is the next process in the state where the semiconductor wafer 2 is sucked and held. Transport to.

Next, a dicing tape attached to an annular frame is attached to the back surface 20b of the substrate 20 constituting the semiconductor wafer 2 in which the protective member 3 side is sucked and held on the second suction holding pad 7. Note that the dicing tape 50 attached to the annular frame 5 shown in FIG. 5 is used as the dicing tape attached to the annular frame.
That is, as shown in FIG. 8A, the dicing tape 50 mounted on the annular frame 5 is placed on the table 501 of the tape adhering device 500. With the dicing tape 50 placed on the table 501 as described above, the semiconductor wafer 2 in which the protective tape 3 side is sucked and held by the second suction holding pad 7 as shown in FIG. The back surface 20b of the substrate 20 is pressed against the adhesive surface which is the front surface (upper surface) of the dicing tape 50. In this way, the back surface 20b of the substrate 20 constituting the semiconductor wafer 2 in which the protective tape 3 side is sucked and held by the second suction holding pad 7 is adhered to the back surface 2b of the semiconductor wafer 2 as the front surface (upper surface) of the dicing tape 50. When the surface is attached, the protective member 3 attached to the surface of the functional layer 21 constituting the semiconductor wafer 2 is peeled off as shown in FIG.

  If the wafer supporting step is performed as described above, the functional layer cutting is performed by irradiating the functional layer 21 with the laser beam along the division lines formed on the functional layer 21 constituting the semiconductor wafer 2 and cutting the functional layer 21. Perform the process. This functional layer cutting step is performed using a laser processing apparatus 8 shown in FIG. A laser processing apparatus 8 shown in FIG. 9 has a chuck table 81 for holding a workpiece, a laser beam irradiation means 82 for irradiating a workpiece held on the chuck table 81 with a laser beam, and a chuck table 81. An image pickup means 83 for picking up an image of the processed workpiece is provided. The chuck table 81 is configured to suck and hold the workpiece. The chuck table 81 is moved in a processing feed direction indicated by an arrow X in FIG. 9 by a processing feed means (not shown), and in FIG. 9 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 82 includes a cylindrical casing 821 arranged substantially horizontally. In the casing 821, pulse laser beam oscillation means including a pulse laser beam oscillator and repetition frequency setting means (not shown) are arranged. A condenser 822 for condensing the pulse laser beam oscillated from the pulse laser beam oscillating means is attached to the tip of the casing 821. The laser beam irradiation unit 82 includes a condensing point position adjusting unit (not shown) for adjusting the condensing point position of the pulse laser beam collected by the condenser 822.

  The image pickup means 83 attached to the tip of the casing 821 constituting the laser beam irradiation means 82 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).

  Using the laser processing apparatus 8 described above, a functional layer cutting step is performed in which the functional layer 21 is ablated and cut by irradiating a laser beam along a planned division line formed on the functional layer 21 constituting the semiconductor wafer 2. First, the wafer support process described above is performed on the chuck table 81 of the laser processing apparatus 8 shown in FIG. 9 and the dicing tape 50 side attached to the back surface 20b of the substrate 20 constituting the semiconductor wafer 2 is mounted. Put. Then, by operating a suction means (not shown), the semiconductor wafer 2 is held on the chuck table 81 via the dicing tape 50 (wafer holding step). Accordingly, in the semiconductor wafer 2 held on the chuck table 81, the surface 21 a of the functional layer 21 stacked on the substrate 20 is on the upper side. In FIG. 9, the annular frame 5 to which the dicing tape 50 is attached is omitted, but the annular frame 5 is held by an appropriate frame holding means provided on the chuck table 81. In this way, the chuck table 81 that sucks and holds the semiconductor wafer 2 is positioned directly below the imaging unit 83 by a processing feed unit (not shown).

  When the chuck table 81 is positioned immediately below the image pickup means 83, an alignment operation for detecting a processing region to be laser processed of the semiconductor wafer 2 is executed by the image pickup means 83 and a control means (not shown). That is, the imaging unit 83 and the control unit (not shown) are configured to split the division line 22 formed on the surface 21 a of the functional layer 21 laminated on the substrate 20 constituting the semiconductor wafer 2, and emit the laser beam along the division line 22. Image processing such as pattern matching for performing alignment with the condenser 822 of the laser beam irradiation means 82 to be irradiated is executed, and alignment of the laser beam irradiation position is performed (alignment process). Similarly, the alignment of the laser beam irradiation position is also performed on the division lines 22 formed on the semiconductor wafer 2 in the direction orthogonal to the predetermined direction.

  When the alignment step described above is performed, the chuck table 81 is moved to the laser beam irradiation region where the condenser 822 of the laser beam irradiation means 82 for irradiating the laser beam as shown in FIG. It is positioned directly below the condenser 822. At this time, as shown in FIG. 10A, the semiconductor wafer 2 is positioned such that one end of the division planned line 22 (left end in FIG. 10A) is located directly below the condenser 822. Then, the condensing point P of the pulse laser beam LB irradiated from the condenser 822 is positioned near the surface 21 a of the functional layer 21 stacked on the substrate 20. Next, while irradiating the substrate 20 and the functional layer 21 with a pulsed laser beam having an absorptive wavelength from the condenser 822 of the laser beam irradiation means 82, the chuck table 81 is directed in the direction indicated by the arrow X1 in FIG. At a predetermined machining feed rate. Then, as shown in FIG. 10B, when the other end of the planned division line 22 (the right end in FIG. 10B) reaches a position directly below the condenser 822, the irradiation of the pulse laser beam is stopped and the chuck is performed. The movement of the table 81 is stopped (functional layer cutting step).

  Next, the chuck table 81 is moved in the direction perpendicular to the paper surface (index feed direction) by the interval of the division lines 22. Then, while irradiating a pulse laser beam from the condenser 822 of the laser beam irradiation means 82, the chuck table 81 is moved at a predetermined processing feed speed in the direction indicated by the arrow X2 in FIG. 10B, 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 81 is stopped.

  By performing the functional layer cutting step described above, as shown in FIG. 10C, the functional layer 21 remaining in the cutting groove forming step and the part 201 of the substrate 20 in the semiconductor wafer 2 are cut into the cutting grooves. A laser processing groove 220 reaching 210 is formed. As a result, the functional layer 21 and the part 201 of the substrate 20 remaining in the cutting groove forming step are broken by the laser processing groove 220. Then, the functional layer cutting step described above is performed along all the planned division lines 22 formed on the semiconductor wafer 2.

In addition, the said functional layer cutting process is performed on the following process conditions, for example.
Laser beam wavelength: 355 nm
Repetition frequency: 200 kHz
Output: 2W
Condensing spot diameter: φ6μm
Processing feed rate: 500 mm / sec

In the functional layer cutting step described above, the laser processing groove 220 formed in the functional layer 21 and part 201 of the substrate 20 is narrower than the width of the cutting groove 210 and forms a laser processing groove having a width exceeding the width of the cutting blade 423. Since it is not necessary, the width of the planned dividing line 22 can be reduced, and the number of devices that can be formed on the wafer can be increased.
Even if a passivation film containing SiO 2, SiN or the like is formed on the surface of the functional layer 21, it is formed from the back side of the substrate 20 when the functional layer 21 is irradiated with a laser beam along the division line 22 in the laser processing step. Since energy escapes to the cut grooves 210, the so-called undercut problem is solved.

  If the functional layer cutting step described above is performed, a device separation step is performed in which the dicing tape 50 to which the semiconductor wafer 2 is bonded is expanded to separate the wafer into individual devices along the planned division line 22. This device separation step is performed using a device separation apparatus 9 shown in FIG. The device separating apparatus 9 shown in FIG. 11 includes a frame holding means 91 for holding the annular frame 5 and a tape extending means for expanding the dicing tape 50 attached to the annular frame 5 held by the frame holding means 91. 92 and a pickup collet 93. The frame holding means 91 includes an annular frame holding member 911 and a plurality of clamps 912 as fixing means provided on the outer periphery of the frame holding member 911. An upper surface of the frame holding member 911 forms a mounting surface 911a on which the annular frame 5 is placed, and the annular frame 5 is placed on the mounting surface 911a. Then, the annular frame 5 placed on the placement surface 911 a is fixed to the frame holding member 911 by the clamp 912. The frame holding means 91 configured as described above is supported by the tape expanding means 92 so as to be movable back and forth in the vertical direction.

  The tape expansion means 92 includes an expansion drum 921 disposed inside the annular frame holding member 911. The expansion drum 921 has an inner diameter and an outer diameter that are smaller than the inner diameter of the annular frame 5 and larger than the outer diameter of the semiconductor wafer 2 attached to the dicing tape 50 attached to the annular frame 5. The expansion drum 921 includes a support flange 922 at the lower end. The tape expansion means 92 in the illustrated embodiment includes support means 923 that can advance and retract the annular frame holding member 911 in the vertical direction. The support means 923 includes a plurality of air cylinders 923 a disposed on the support flange 922, and the piston rod 923 b is connected to the lower surface of the annular frame holding member 911. As described above, the support means 923 including the plurality of air cylinders 923a is configured such that the annular frame holding member 911 has a reference position at which the mounting surface 911a is substantially flush with the upper end of the expansion drum 921 as shown in FIG. Then, as shown in FIG. 12 (b), it is moved in the vertical direction between the extended positions below the upper end of the expansion drum 921 by a predetermined amount.

  A device separation process performed using the device separation apparatus 9 configured as described above will be described with reference to FIG. That is, the annular frame 5 to which the dicing tape 50 to which the semiconductor wafer 2 is attached is attached to the mounting surface 911a of the frame holding member 911 constituting the frame holding means 91 as shown in FIG. It is placed on and fixed to the frame holding member 911 by the clamp 912 (frame holding step). At this time, the frame holding member 911 is positioned at the reference position shown in FIG. Next, the plurality of air cylinders 923a as the supporting means 923 constituting the tape extending means 92 are operated to lower the annular frame holding member 911 to the extended position shown in FIG. Accordingly, since the annular frame 5 fixed on the mounting surface 911a of the frame holding member 911 is also lowered, the dicing tape 50 attached to the annular frame 5 is an expansion drum as shown in FIG. It expands in contact with the upper edge of 921 (tape expansion process). As a result, since a tensile force acts radially on the semiconductor wafer 2 adhered to the dicing tape 50, the semiconductor wafer 2 is separated into individual devices 23 and a space S is formed between the devices.

  Next, as shown in FIG. 12 (c), the pickup collet 93 is operated to attract the device 23, peel off from the dicing tape 50, pick up, and transport to a tray or die bonding process (not shown). In the pickup process, the gap S between the individual devices 23 attached to the dicing tape 50 is widened as described above, so that the pickup can be easily performed without contacting the adjacent devices 23. it can.

2: Semiconductor wafer 20: Substrate 21: Functional layer 22: Planned division line 23: Device 210: Cutting groove 220: Laser processing groove 3: Protection member 4: Cutting device 41: Chuck table of cutting device 42: Cutting means 423: Cutting Blade 5: annular frame 50: dicing tape 6: first suction holding pad 7: second suction holding pad 8: laser processing device 81: chuck table of laser processing device 82: laser beam irradiation means 822: collector 9 : Device separation device 91: Frame holding means 92: Tape expansion means 93: Pickup collet

Claims (3)

A wafer processing method in which a wafer in which devices are formed in a plurality of regions partitioned by a plurality of planned division lines formed in a lattice pattern on a functional layer stacked on the surface of the substrate is divided along the planned division lines. There,
A protective member attaching step for attaching a protective member to the surface of the functional layer constituting the wafer;
The protective member side of the wafer on which the protective member attaching step has been performed is held on the chuck table, and the cutting blade is positioned in the area corresponding to the planned division line from the back side of the substrate, leaving a part that does not reach the functional layer. Cutting groove forming step of forming cutting grooves,
A wafer support step of attaching a dicing tape to the back surface of the substrate constituting the wafer on which the cutting groove forming step has been performed, supporting the outer peripheral portion of the dicing tape with an annular frame, and peeling the protective member;
A functional layer cutting step of irradiating the functional layer with a laser beam along a division planned line formed on the functional layer constituting the wafer on which the wafer support step has been performed, and cutting the functional layer by cutting.
A method for processing a wafer.   The wafer support step according to claim 1, wherein the wafer support step includes attaching a dicing tape attached to an annular frame to the back surface of the substrate constituting the wafer held on the chuck table and on which the cutting groove forming step has been performed. Processing method.   In the wafer support step, the wafer is unloaded from the chuck table by a first suction holding pad that sucks and holds the entire back surface of the substrate constituting the wafer held on the chuck table and on which the cutting groove forming step has been performed. After transferring the wafer to the second suction holding pad that sucks and holds the entire surface of the protective member attached to the surface of the functional layer constituting the wafer, the wafer was mounted on the annular frame on the back surface of the substrate constituting the wafer. The wafer processing method according to claim 1, wherein a dicing tape is attached.

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