JP2011054715A - Laser beam machining apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining apparatus wherein a wafer being stuck to a dicing tape applied to an annular frame can be mounted while matching the center of the wafer with the center of a chuck table. <P>SOLUTION: The laser beam machining apparatus including the chuck table having a wafer holding area equal to or slightly smaller than the size of the wafer and a laser beam buffer groove formed around the outside of the wafer holding area, and a laser beam irradiation means further includes a displacement detection mechanism which detects a displacement of the centers of the wafer stuck to the dicing tape applied to the annular frame and the annular frame, and a control means for controlling a machining feed means and an indexing feed means and a wafer transfer means based on the gap between the centers of the wafer and the annular frame, wherein the control means displaces the chuck table positioned at the removal position of the wafer and the transfer position of a wafer which is transferred by the wafer transfer means relatively so that the center of the wafer to be transferred matches the center position of the chuck table. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus that performs predetermined laser processing by irradiating a predetermined region of a workpiece with a laser beam.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a substantially wafer-shaped semiconductor wafer, and devices such as ICs, LSIs, etc. are partitioned in the partitioned regions. Form. Then, the semiconductor wafer is cut along the streets to divide the region where the circuit is formed to manufacture individual devices. In addition, optical device wafers with gallium nitride compound semiconductors laminated on the surface of a sapphire substrate are also divided into individual optical devices such as light emitting diodes and laser diodes by cutting along the streets, and are widely used in electrical equipment. ing.

  As a method for dividing a wafer such as a semiconductor wafer or an optical device wafer, a pulsed laser beam having a wavelength (for example, 1064 nm) having transparency to the wafer is applied along the street by aligning the focal point inside the wafer. There has also been proposed a method of dividing a wafer by continuously forming an altered layer along the street inside the wafer and applying an external force along the street whose strength has been reduced by the formation of the altered layer. . (For example, refer to Patent Document 1.)

  Further, as the wafer dividing method described above, a laser processing groove is formed by irradiating a pulse laser beam having a wavelength (for example, 355 nm) having an absorptivity with respect to the wafer along the street formed on the wafer. A method of cleaving along a groove with a mechanical braking device has been proposed. (For example, see Patent Document 2.)

  In recent years, inorganic films such as SiOF and BSG (SiOB), polyimide films, parylene films and the like are formed on the surface of a semiconductor substrate such as a silicon wafer in order to improve the processing capability of circuits such as IC and LSI. A semiconductor wafer having a form in which a low dielectric constant insulator film (Low-k film) made of an organic film, which is a polymer film, is laminated has been put into practical use. However, the Low-k film is laminated in multiple layers (5 to 15 layers) like mica and is very fragile. Therefore, when cutting along the street with a cutting blade, the Low-k film peels off. There is a problem that the peeling reaches the circuit and causes fatal damage to the semiconductor chip.

  In order to solve the above-described problem, the Low-k film formed on the street of the semiconductor wafer is irradiated with a laser beam to remove the Low-k film, and the street from which the Low-k film has been removed is cut with a cutting blade. A processing apparatus has been proposed. (For example, refer to Patent Document 3.)

  In order to perform laser processing on the semiconductor wafer, the chuck table and the laser beam irradiation means are relatively moved in the processing feed direction while irradiating the laser beam from the laser beam irradiation means while holding the semiconductor wafer on the chuck table. However, when the laser beam is irradiated beyond the outer peripheral edge of the semiconductor wafer, the laser beam is irradiated to the chuck table holding the semiconductor wafer, and the wafer holding area of the chuck table is damaged and the surface accuracy is lowered. . Further, when the semiconductor wafer is divided along the street, a laser beam is irradiated along the street in a state where the semiconductor wafer is attached to a dicing tape attached to an annular frame. However, as described above, when the laser beam is irradiated beyond the outer peripheral edge of the semiconductor wafer, the dicing tape is heated and melted to adhere to the wafer holding region of the chuck table. There is a problem that the suction hole for applying a negative pressure formed in the wafer holding area by the adhering dicing tape is clogged, or the surface accuracy of the wafer holding area is lowered. For this reason, it is necessary to scrape off the dicing tape adhering to the wafer holding region with a grindstone, and in some cases, the chuck table must be replaced.

  In order to solve the above-mentioned problems, a chuck table for a laser processing apparatus is proposed in which a wafer holding area for holding a wafer is formed to be slightly smaller and similar to the wafer, and a laser beam buffering groove is formed around the outside of the wafer holding area. Has been. (For example, see Patent Document 4)

Japanese Patent No. 3408805 JP 2004-9139 A JP 2003-320466 A JP 2005-262249 A

  Thus, since the wafer attached to the dicing tape attached to the annular frame is attached to the center region of the annular frame with a tolerance, the center of the annular frame and the center of the wafer are not necessarily located. It does not match. On the other hand, the conveyance means for conveying the wafer attached to the dicing tape attached to the annular frame to the chuck table positioned at the wafer attachment / detachment position conveys the center of the annular frame so as to coincide with the center of the chuck table. To do. Therefore, if the center of the wafer attached to the dicing tape attached to the annular frame does not coincide with the center of the annular frame, the center of the chuck table does not coincide with the center of the wafer, and the wafer is chucked. It is placed at a position shifted from the wafer holding area of the table. As a result, the problem that the wafer holding area where the wafer is not placed is irradiated with the laser beam and the dicing tape is heated and melted and adheres to the wafer holding area of the chuck table cannot be solved.

  The present invention has been made in view of the above-mentioned fact, and the main technical problem thereof is to place the center of the wafer attached to the dicing tape mounted on the annular frame so as to coincide with the center of the chuck table. It is providing the laser processing apparatus which can be performed.

In order to solve the above main technical problem, according to the present invention, a wafer holding region that is the same as or slightly smaller than the size of the wafer, a chuck table in which a laser beam buffering groove is formed around the outside of the wafer holding region, and the chuck Laser beam irradiating means for irradiating a wafer held on a table with a laser beam; and processing feed means for moving the chuck table between a wafer attaching / detaching position and a processing region by the laser beam irradiating means in a processing feed direction (X-axis direction); , An index feed means that moves in an index feed direction (Y-axis direction) orthogonal to the X-axis direction, and a cassette that accommodates a wafer attached to a dicing tape mounted on an annular frame and is placed on a cassette table And a dicing tape mounted on an annular frame housed in the cassette A wafer unloading means for unloading the adhered wafer; an alignment means for performing center alignment of the annular frame unloaded by the wafer unloading means; and an annular frame unloaded to the alignment means. In a laser processing apparatus comprising: a wafer transfer means for transferring a wafer attached to a mounted dicing tape to a chuck table positioned at a wafer attachment / detachment position;
A displacement amount detecting mechanism for detecting a displacement amount between the center of the wafer and the center of the annular frame attached to the dicing tape attached to the annular frame centered in the alignment means;
Control means for controlling the processing feed means, the index feed means, and the wafer transport means based on the amount of displacement between the center of the wafer and the center of the annular frame detected by the displacement amount detection mechanism. ,
The control means is positioned at the wafer attaching / detaching position so that the center of the wafer attached to the dicing tape attached to the annular frame conveyed by the wafer conveying means coincides with the center position of the chuck table. The wafer table attached to a dicing tape mounted on an annular frame conveyed by the wafer conveying means and the chuck table being relatively displaced.
A laser processing apparatus is provided.

The control means performs the processing so that the center position of the chuck table positioned at the wafer attaching / detaching position coincides with the center of the wafer attached to the dicing tape attached to the annular frame conveyed by the wafer conveying means. The feeding means and the index feeding means are controlled.
Further, the displacement detection mechanism includes an imaging unit that images the entire wafer attached to a dicing tape attached to an annular frame that is center-aligned by the positioning unit, and an image that is captured by the imaging unit. Control means for determining the amount of displacement in the X-axis direction and Y-axis direction between the center of the wafer and the center of the annular frame based on image information.

  The laser processing apparatus according to the present invention detects the amount of displacement between the center of the wafer and the center of the annular frame attached to the dicing tape mounted on the annular frame centered by the alignment means. And a control means for controlling the processing feed means, the index feed means and the wafer transport means based on the deviation between the center of the wafer detected by the displacement detection mechanism and the center of the annular frame. The chuck table and the wafer transport means are positioned at the wafer attachment / detachment position so that the center of the wafer attached to the dicing tape mounted on the annular frame transported by the wafer transport means coincides with the center position of the chuck table. Adhered to dicing tape mounted on an annular frame conveyed by Therefore, even if the center of the wafer affixed to the dicing tape mounted on the annular frame is misaligned with the center of the annular frame, the center of the wafer is not aligned with the chuck table. Can be centered. Accordingly, when the laser beam is overrun when the laser beam is irradiated by the laser beam irradiation means and the laser beam is irradiated, the dicing tape is irradiated to the outside of the outer peripheral edge of the wafer, but the chuck table is not applied to the region where the laser beam is irradiated to the dicing tape. Therefore, even if the dicing tape is melted by irradiation with a laser beam, the wafer holding area does not adhere to the wafer holding area. The laser beam applied to the dicing tape passes through the dicing tape and is applied to the bottom surface of the laser beam buffering groove, but the bottom surface of the laser beam buffering groove is sufficiently away from the focal point and the laser is diffused. There is no energy density that can be processed, and the chuck table is not damaged.

The perspective view of the laser processing apparatus comprised according to this invention. The principal part perspective view of the laser processing apparatus shown in FIG. The principal part perspective view of the chuck table with which the laser processing apparatus shown in FIG. 1 is equipped. FIG. 4 is a cross-sectional view of the chuck table shown in FIG. The block diagram which shows simply the structure of the laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped. FIG. 6 is a simplified diagram for explaining a condensing spot diameter of a laser beam irradiated from the laser beam irradiation means shown in FIG. 5. The perspective view of the semiconductor wafer as a wafer. The expanded sectional view of the semiconductor wafer shown in FIG. The perspective view which shows the state which affixed the semiconductor wafer shown in FIG. 7 on the dicing tape with which the cyclic | annular flame | frame was mounted | worn. The block block diagram of the control means with which the laser processing apparatus shown in FIG. 1 is equipped. Explanatory drawing of the displacement amount detection process implemented by the displacement amount detection mechanism with which the laser processing apparatus shown in FIG. 1 is equipped. Explanatory drawing of the chuck table position correction process implemented by the laser processing apparatus shown in FIG. Explanatory drawing of the laser beam irradiation process implemented by the laser processing apparatus shown in FIG. Explanatory drawing which shows one Embodiment at the time of the laser beam irradiation process shown in FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a preferred embodiment of a laser processing apparatus configured according to the present invention will be described in detail with reference to the accompanying drawings.

  The laser processing apparatus shown in FIG. 1 includes an apparatus housing 1 having a substantially rectangular parallelepiped shape. In the apparatus housing 1, a stationary base 2 shown in FIG. 2 and a wafer as a workpiece, which is disposed on the stationary base 2 so as to be movable in a machining feed direction (X-axis direction) indicated by an arrow X, are provided. A chuck table mechanism 3 having a chuck table to be held, and a laser beam irradiation unit support mechanism 4 disposed on the stationary base 2 so as to be movable in an indexing feed direction (Y-axis direction) indicated by an arrow Y orthogonal to the X-axis direction. The laser beam irradiation unit support mechanism 4 includes a laser beam irradiation unit 5 disposed so as to be movable in a condensing point position adjustment direction (Z-axis direction) indicated by an arrow Z which is the vertical direction in the drawing.

  The chuck table mechanism 3 includes a pair of guide rails 31 and 31 disposed in parallel along the X-axis direction on the stationary base 2 and is disposed on the guide rails 31 and 31 so as to be movable in the X-axis direction. A first sliding block 32 provided, a second sliding block 33 movably disposed on the first sliding block 32 in the Y-axis direction, and a cylindrical member on the second sliding block 33 And a chuck table 36 for holding a wafer as a workpiece. The chuck table 36 is made of a metal material such as stainless steel, and includes a wafer holding region 360 for holding a workpiece as shown in FIGS. A fitting hole 361 having an open top is formed in the wafer holding region 360, and an adsorption chuck 362 made of a porous material such as porous ceramics is fitted into the fitting hole 361. A circular suction groove 363 is formed at the center of the bottom surface of the fitting hole 361, and an annular suction groove 364 is formed outside the suction groove 363. The suction grooves 363 and 364 communicate with suction means (not shown) through the suction passage 365. The wafer holding region 360 is formed to be the same as the wafer size described later or slightly smaller (2 to 3 mm) than the outer diameter of the wafer. As described above, the chuck table 36 having the wafer holding region 360 is formed with an annular buffer groove 366 around the outside of the wafer holding region 360. The annular laser beam buffer groove 366 may have a depth of 5 to 10 mm and a width of 20 to 30 mm. A laser beam absorbing member 367 such as alumite that absorbs the laser beam is disposed on the bottom surface of the laser beam buffering groove 366. The chuck table 36 configured in this manner is configured to place, for example, a disk-shaped semiconductor wafer, which is a workpiece, on the wafer holding region 360, and to suck and hold the workpiece by operating suction means (not shown). . Further, the chuck table 36 is rotated by a pulse motor (not shown) disposed in the cylindrical member 34 shown in FIG. The chuck table 36 in the illustrated embodiment includes a clamp 368 for fixing a dicing frame on which a dicing tape to which a wafer, which will be described later, which is a workpiece, is attached, is mounted.

  When the description is continued with reference to FIG. 2, the first sliding block 32 is provided with a pair of guided grooves 321 and 321 fitted to the pair of guide rails 31 and 31 on the lower surface thereof, A pair of guide rails 322 and 322 formed in parallel along the Y-axis direction are provided on the upper surface. The first sliding block 32 configured in this way moves in the X-axis direction along the pair of guide rails 31, 31 when the guided grooves 321, 321 are fitted into the pair of guide rails 31, 31. Configured to be possible. The chuck table mechanism 3 in the illustrated embodiment includes a processing feed means 37 for moving the first sliding block 32 along the pair of guide rails 31, 31 in the X-axis direction. The processing feed means 37 includes a male screw rod 371 disposed in parallel between the pair of guide rails 31 and 31, and a drive source such as a pulse motor 372 for rotationally driving the male screw rod 371. One end of the male screw rod 371 is rotatably supported by a bearing block 373 fixed to the stationary base 2, and the other end is connected to the output shaft of the pulse motor 372 by transmission. The male screw rod 371 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the first sliding block 32. Therefore, the first sliding block 32 is moved along the guide rails 31 and 31 in the X-axis direction by driving the male screw rod 371 forward and backward by the pulse motor 372. In this way, the first slide block 32 is moved in the X-axis direction along the guide rails 31, 31, and the processing feed means 37 is used to move the chuck table 36 to the wafer attachment / detachment position shown in FIGS. 1 and 2 and the laser beam irradiation unit 5. Move to the machining area in the X-axis direction.

  The laser processing apparatus in the illustrated embodiment includes a processing feed amount detecting means 374 for detecting the processing feed amount of the chuck table 36. The processing feed amount detection means 374 includes a linear scale 374a disposed along the guide rail 31, and a read head disposed along the linear scale 374a along with the first sliding block 32 disposed along the first sliding block 32. 374b. In the illustrated embodiment, the reading head 374b of the processing feed amount detection means 374 sends a pulse signal of 1 pulse to the control means to be described later every 1 μm. Then, the control means to be described later detects the machining feed amount of the chuck table 36 by counting the input pulse signals. When the pulse motor 372 is used as the drive source of the machining feed means 37, the machining feed amount of the chuck table 36 is counted by counting the drive pulses of the control means to be described later that outputs a drive signal to the pulse motor 372. Can be detected. When a servo motor is used as a drive source for the machining feed means 37, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to a control means described later, and the pulse signal input by the control means. Is counted, the machining feed amount of the chuck table 36 can be detected.

  The second sliding block 33 is provided with a pair of guided grooves 331 and 331 which are fitted to a pair of guide rails 322 and 322 provided on the upper surface of the first sliding block 32 on the lower surface thereof. By fitting the guided grooves 331 and 331 to the pair of guide rails 322 and 322, the guided grooves 331 and 331 are configured to be movable in the Y-axis direction. The chuck table mechanism 3 in the illustrated embodiment has a first index for moving the second slide block 33 along the pair of guide rails 322 and 322 provided in the first slide block 32 in the Y-axis direction. A feeding means 38 is provided. The first index feed means 38 includes a male screw rod 381 disposed in parallel between the pair of guide rails 322 and 322, and a drive source such as a pulse motor 382 for rotationally driving the male screw rod 381. It is out. One end of the male screw rod 381 is rotatably supported by a bearing block 383 fixed to the upper surface of the first sliding block 32, and the other end is connected to the output shaft of the pulse motor 382. The male screw rod 381 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the second sliding block 33. Therefore, by driving the male screw rod 381 forward and backward by the pulse motor 382, the second slide block 33 is moved along the guide rails 322 and 322 in the Y-axis direction.

  The laser processing apparatus in the illustrated embodiment includes index feed amount detection means 384 for detecting the index feed amount of the second sliding block 33. The index feed amount detection means 384 includes a linear scale 384a disposed along the guide rail 322, and a reading head 384b disposed on the second sliding block 33 and moving along the linear scale 384a. In the illustrated embodiment, the reading head 384b of the index feed amount detection means 384 sends a pulse signal of 1 pulse to the control means described later for every 1 μm. And the control means mentioned later detects the index feed amount of the laser beam irradiation unit 5 by counting the input pulse signal. When the pulse motor 382 is used as the drive source of the first indexing and feeding means 38, the laser beam irradiation unit 5 is counted by counting the drive pulses of the control means to be described later that outputs a drive signal to the pulse motor 382. The index feed amount can be detected. When a servo motor is used as the drive source for the second indexing and feeding means 38, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to the control means, which will be described later. By counting the pulse signals, the index feed amount of the second sliding block 33, that is, the chuck table 36 can be detected.

  The laser beam irradiation unit support mechanism 4 includes a pair of guide rails 41 and 41 arranged on the stationary base 2 in parallel along the indexing feed direction indicated by an arrow Y, and a Y-axis on the guide rails 41 and 41. A movable support base 42 is provided so as to be movable in the direction. The movable support base 42 includes a movement support portion 421 that is movably disposed on the guide rails 41, 41, and a mounting portion 422 that is attached to the movement support portion 421. The mounting portion 422 is provided with a pair of guide rails 423 and 423 extending in the Z-axis direction on one side surface in parallel. The laser beam irradiation unit support mechanism 4 in the illustrated embodiment includes a second index feed means 43 for moving the movable support base 42 along the pair of guide rails 41 and 41 in the Y-axis direction. The second index feed means 43 includes a male screw rod 431 disposed in parallel between the pair of guide rails 41, 41, and a drive source such as a pulse motor 432 for rotationally driving the male screw rod 431. It is out. One end of the male screw rod 431 is rotatably supported by a bearing block (not shown) fixed to the stationary base 2, and the other end is connected to the output shaft of the pulse motor 432. The male screw rod 431 is screwed into a female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the moving support portion 421 constituting the movable support base 42. For this reason, when the male screw rod 431 is driven to rotate forward and reversely by the pulse motor 432, the movable support base 42 is moved along the guide rails 41, 41 in the Y-axis direction.

  The laser beam irradiation unit 5 in the illustrated embodiment includes a unit holder 51 and laser beam irradiation means 52 attached to the unit holder 51. The unit holder 51 is provided with a pair of guided grooves 511 and 511 that are slidably fitted to a pair of guide rails 423 and 423 provided in the mounting portion 422. By being fitted to the guide rails 423 and 423, the guide rails 423 and 423 are supported so as to be movable in the Z-axis direction.

  The illustrated laser beam application means 52 includes a cylindrical casing 521 that is fixed to the unit holder 51 and extends substantially horizontally. In the casing 521, as shown in FIG. 5, a pulse laser beam oscillation means 522 and a transmission optical system 523 are arranged. The pulse laser beam oscillation means 522 is composed of a pulse laser beam oscillator 522a composed of a YAG laser oscillator or a YVO4 laser oscillator, and a repetition frequency setting means 522b attached thereto. The transmission optical system 523 includes an appropriate optical element such as a beam splitter. A condenser 524 containing a condenser lens (not shown) composed of a combination lens that may be in a known form is attached to the tip of the casing 521.

  The laser beam oscillated from the pulse laser beam oscillating means 522 reaches the condenser 524 through the transmission optical system 523, and a predetermined focused spot diameter is applied to the workpiece held on the chuck table 36 from the condenser 524. Irradiated with D. As shown in FIG. 6, the focused spot diameter D is D (μm) = 4 × λ × f / (π ×) when a pulsed laser beam having a Gaussian distribution is irradiated through the condenser lens 524 a of the condenser 524. W), where λ is defined by the wavelength (μm) of the pulse laser beam, W is the diameter (mm) of the pulse laser beam incident on the objective lens 524a, and f is the focal length (mm) of the condenser lens 524a.

  Returning to FIG. 2, the description is continued. At the front end portion of the casing 521 constituting the laser beam irradiation means 52, an imaging means 6 for detecting a processing region to be laser processed by the laser beam irradiation means 52 is disposed. . In the illustrated embodiment, the imaging unit 6 includes, in addition to a normal imaging device (CCD) that captures an image with visible light, an infrared illumination unit that irradiates a workpiece with infrared rays, and an infrared ray that is irradiated by the infrared illumination unit. The optical system includes a capturing optical system and an image sensor (infrared CCD) that outputs an electrical signal corresponding to the infrared light captured by the optical system. The captured image signal is sent to a control unit described later.

  The laser beam irradiation unit 5 in the illustrated embodiment includes a moving means 53 for moving the unit holder 51 along the pair of guide rails 423 and 423 in the Z-axis direction. The moving means 53 includes a male screw rod (not shown) disposed between the pair of guide rails 423 and 423, and a drive source such as a pulse motor 532 for rotationally driving the male screw rod. By driving the male screw rod (not shown) by the motor 532 in the normal and reverse directions, the unit holder 51 and the laser beam irradiation means 52 are moved along the guide rails 423 and 423 in the Z-axis direction. In the illustrated embodiment, the laser beam irradiation means 52 is moved upward by driving the pulse motor 532 forward, and the laser beam irradiation means 52 is moved downward by driving the pulse motor 532 in reverse. It has become.

  Returning to FIG. 1, the description will continue. The illustrated laser processing apparatus includes a cassette mounting portion 8a on which a cassette for storing a wafer as a workpiece is mounted. A cassette table 8 is disposed on the cassette mounting portion 8a so as to be movable up and down by lifting means (not shown). A cassette 9 is mounted on the cassette table 8. In the illustrated embodiment, the wafer accommodated in the cassette 9 is composed of a semiconductor wafer 10 as shown in FIGS. The semiconductor wafer 10 is divided into a plurality of areas by a plurality of streets 111 arranged in a lattice pattern on a surface 11a of a semiconductor substrate 11 made of a silicon wafer, and devices 112 such as ICs and LSIs are formed in the divided areas. ing. The semiconductor wafer 10 is formed by laminating a low dielectric constant insulator film 113 on the surface of the semiconductor substrate 11.

  As shown in FIG. 9, the semiconductor wafer 10 configured as described above is bonded to a dicing tape T made of a synthetic resin sheet such as vinyl chloride mounted on an annular frame F with the front surface 11a facing upward. (Frame support process). The semiconductor wafer 10 subjected to the frame supporting process in this manner is accommodated in the cassette 9 while being supported on the annular frame F via the dicing tape T.

  A temporary placement region 13a is set in the apparatus housing 1, and the semiconductor wafer 10 attached to the dicing tape T attached to the annular frame F is temporarily placed in the temporary placement region 13a and the annular shape is temporarily set. Alignment means 13 for performing center alignment of the frame F is provided. The positioning means 13 is configured to be positioned in parallel with the position restricting plate 131 so as to be able to advance and retreat with respect to the position restricting plate 131 extending in the direction of carrying out the semiconductor wafer 10 from the cassette 9. It consists of a sliding plate 132. Accordingly, the semiconductor wafer 10 supported on the annular frame F via the dicing tape T is placed between the position regulating plate 131 and the sliding plate 132, and the sliding plate 132 is moved toward the position regulating plate 131. Thus, the annular frame F that supports the semiconductor wafer 10 via the dicing tape T is positioned between the position regulating plate 131 and the sliding plate 132.

  In the laser processing apparatus in the illustrated embodiment, the semiconductor wafer 10 supported on the annular frame F accommodated in the cassette 9 placed on the cassette table 8 via the dicing tape T is used as the alignment means 13. Wafer unloading means 14 for unloading and first wafer transfer means 15 for transferring the semiconductor wafer 10 unloaded to the alignment means 13 onto the chuck table 36 positioned at the wafer attaching / detaching position shown in FIGS. Cleaning means 16 for cleaning the semiconductor wafer 10 laser-processed on the chuck table 36, and second wafer transfer means 17 for transferring the semiconductor wafer 10 laser-processed on the chuck table 36 to the cleaning means 16. is doing. In addition, the laser processing apparatus in the illustrated embodiment includes a display unit 18 that displays an image captured by the imaging unit 6.

  Continuing the description with reference to FIG. 1, the laser processing apparatus in the illustrated embodiment is a semiconductor wafer 10 attached to a dicing tape T attached to an annular frame F carried out to the positioning means 13. A displacement amount detection mechanism 20 for detecting a displacement amount between the center of the ring frame F and the center of the annular frame F is provided. This displacement amount detection mechanism 20 has an image pickup means 201 for picking up an image of the semiconductor wafer 10 attached to a dicing tape T attached to an annular frame F carried out to the alignment means 13, and an image pickup by the image pickup means 201. It comprises control means (to be described later) for determining the amount of displacement between the center of the semiconductor wafer 10 and the center of the annular frame F based on the image information. The image pickup means 201 includes an image pickup device (CCD) that picks up an image with visible light, is disposed on the center axis of the annular frame F that is placed on the alignment means 13 and is center-positioned, and is attached to the annular frame F. The entire semiconductor wafer 10 attached to the dicing tape T can be imaged. The imaging unit 201 sends the captured image signal to a control unit described later.

  The laser processing apparatus in the illustrated embodiment includes a control means 30 shown in FIG. 10 includes a central processing unit (CPU) 301 that executes arithmetic processing according to a control program, a read-only memory (ROM) 302 that stores a control program and the like, and a central processing unit. A readable / writable random access memory (RAM) 303 that stores a calculation result by the device (CPU) 301, a counter 304, an input interface 305, and an output interface 306 are provided. In the read only memory (ROM) 302, a processing program for controlling the laser beam irradiation means 52, coordinate values of the annular frame F in a state where the annular frame F is placed on the positioning means 13, and a wafer The coordinate value of the chuck table 36 positioned at the attachment / detachment position is stored. The input interface 306 of the control means 30 configured as described above includes the reading head 374b of the machining feed amount detection means 374, the reading head 384b of the index feed amount detection means 384, the imaging means 6, and the displacement amount detection mechanism 20. A detection signal is input from the imaging unit 201 and the like. From the output interface 307 of the control means 30, the pulse motor 372, the pulse motor 382, the pulse motor 432, the pulse motor 532, the laser beam irradiation means 52, the alignment means 13, the wafer carry-out means 14, the first wafer conveyance means. 15, a control signal is output to the cleaning means 16, the second wafer transport means 17, the display means 18, and the like.

Next, a procedure for laser processing a workpiece using the laser processing apparatus described above will be described.
The control means 30 operates a raising / lowering means (not shown) of the cassette table 8 to move the semiconductor wafer 10 (dicing tape attached to the annular frame F) accommodated in a predetermined position of the cassette 9 placed on the cassette table 8. Position the item (attached to T) at the unloading position. Then, the control means 30 operates the unloading means 14 to unload the semiconductor wafer 10 positioned at the unloading position onto the alignment means 13. When the semiconductor wafer 10 is transported to the alignment means 13, the control means 30 operates the sliding plate 132 of the alignment means 13 to support the semiconductor wafer 10 via the dicing tape T. Perform positioning. The annular frame F thus positioned is positioned at the coordinate values shown in FIG. The coordinate value of the center P of the annular frame F positioned in this way is defined as (x0, y0).

  As described above, the annular frame F that supports the semiconductor wafer 10 carried to the alignment means 13 via the dicing tape T is positioned, and its center P is positioned at the coordinate value of (x0, y0). If so, the control means 30 operates the imaging means 201 to image the entire semiconductor wafer 10 attached to the dicing tape T attached to the annular frame F. The control means 30 selects any three points (A, B, C) on the outer peripheral edge of the semiconductor wafer 10 based on the image signal from the imaging means 201, and the perpendicular line and the straight line B from the center position of the straight line AB. The intersection (P1) with the perpendicular from the center position of −C is obtained as the center of the semiconductor wafer 10. Then, the control means 30 obtains a displacement amount (dx, dy) in the X-axis direction and the Y-axis direction from the center P of the annular frame F of the center P1 of the semiconductor wafer 10, and calculates the displacement amount (dx, dy). It is stored in a random access memory (RAM) 303 (displacement detection step). Therefore, the imaging means 201 for imaging the entire semiconductor wafer 10 and the control means 30 for obtaining the center P1 of the semiconductor wafer 10 based on the image signal from the imaging means 201 are applied to the dicing tape T mounted on the annular frame F. It functions as a displacement amount detection mechanism 20 that detects a deviation between the center of the semiconductor wafer 10 and the center of the annular frame 11.

  On the other hand, the chuck table 36 positioned at the wafer attachment / detachment position shown in FIGS. 1 and 2 is set such that the center P0 thereof is positioned at coordinate values of, for example, x100 and y100 as shown in FIG. This coordinate value (x100, y100) is obtained by the annular wafer F in which the annular frame F supporting the semiconductor wafer 10 positioned by the alignment means 13 via the dicing tape T is conveyed by the first wafer conveying means 15. Is set to coincide with the center P of the frame F. However, as described above, the center P1 of the semiconductor wafer 10 attached to the dicing tape T attached to the annular frame F is displaced from the center P of the annular frame F in the X-axis direction and the Y-axis direction. In the state where the annular frame F supporting the semiconductor wafer 10 positioned by the alignment means 13 via the dicing tape T is conveyed to the chuck table 36 by the first wafer conveying means 15, the chuck table 36 and the center P1 of the semiconductor wafer 10 attached to the dicing tape T attached to the annular frame F do not coincide with each other. That is, the center P1 of the semiconductor wafer 10 is displaced from the center P0 (x100, y100) of the chuck table 36 by dx and dy in the X-axis direction and the Y-axis direction.

  Therefore, in the present invention, the displacement amount (dx) in the X-axis direction between the center P1 of the semiconductor wafer 10 attached to the dicing tape T attached to the annular frame F and the center P of the annular frame F, and Corresponding to the displacement amount (dy) in the Y-axis direction, the position of the chuck table 36 positioned at the wafer attaching / detaching position is corrected as shown by a two-dot chain line as shown in FIG. The first wafer transport means 15 for transporting the semiconductor wafer 10 attached to the dicing tape T attached to the annular frame F has converted the semiconductor wafer 10 positioned in the alignment means 13 by 180 degrees. It is conveyed to the chuck table 36 in a state. Therefore, the control means 30 operates the machining feed means 37 and the first index feed means 38 so that the center P0 of the chuck table 36 has a coordinate value of (x: 100−dx, y: 100−dy). (Chuck table position correction process). By performing the chuck table position correcting step in this way, the wafer is adhered to the dicing tape T mounted on the annular frame F which is positioned by the positioning means 13 and is transported to the chuck table 36 by the first wafer transport means 15. The center P1 of the semiconductor wafer 10 is positioned at the center P0 of the chuck table 36.

  When the chuck table position correcting step is performed as described above, the control unit 30 operates the first wafer transport unit 15 to be positioned in the alignment unit 13 and the displacement amount detecting step is performed. The semiconductor wafer 10 attached to the dicing tape T attached to the frame F is conveyed to the chuck table 36 on which the chuck table position correcting step has been performed. The semiconductor wafer 10 attached to the dicing tape T attached to the annular frame F transported to the chuck table 36 that has been subjected to the chuck table position correction process in this way has its center P1 at the center of the chuck table 36. Located at center P0. Next, the control unit 30 operates a suction unit (not shown) to hold the semiconductor wafer 20 on the wafer holding region 360 of the chuck table 36 via the dicing tape T. At this time, since the wafer holding region 360 is formed to be the same as the size of the semiconductor wafer 10 or slightly smaller (2 to 3 mm) than the outer diameter of the wafer as described above, the semiconductor wafer 10 matches the wafer holding region 360. Alternatively, the outer peripheral portion slightly protrudes outward from the outer peripheral edge of the wafer holding region 360 and is positioned above the annular buffer groove 366. The dicing frame F is fixed by a clamp 368 disposed on the chuck table 36. The clamp 368 is configured to be fixed to the dicing frame F with an allowance of several millimeters in the X-axis direction and the Y-axis direction. When the semiconductor wafer 10 adhered to the dicing tape T mounted on the annular frame F is sucked and held on the chuck table 36 in this way, the control means 30 operates the processing feed means 37 to operate the chuck table. 36 is positioned directly below the imaging means 6 disposed in the laser beam irradiation unit 5.

  If the chuck table 36 is positioned immediately below the image pickup means 6, the control means 30 operates the image pickup means 6 to pick up an image of the semiconductor wafer 10, and performs an alignment operation for detecting a processing region to be laser processed on the semiconductor wafer 10. Execute. That is, the control means 30 performs pattern matching for aligning the street 111 formed in a predetermined direction of the semiconductor wafer 10 with the condenser 524 of the laser beam irradiation unit 5 that irradiates the laser beam along the street 111. The image processing such as the above is executed to align the laser beam irradiation position. Further, the control means 30 similarly performs alignment of the laser beam irradiation position with respect to the street 111 formed in the semiconductor wafer 10 and extending in a direction perpendicular to the predetermined direction.

  As described above, when the street 111 formed on the semiconductor wafer 10 held on the chuck table 36 is detected and alignment of the laser beam irradiation position is performed, the control means 30 performs the processing feeding means 37 and the first feeding means 37. The index feed means 38 is actuated to move the chuck table 36, and a predetermined street 111 extending in a predetermined direction (left-right direction in FIG. 13A) is positioned immediately below the condenser 524 of the laser beam irradiation means 52. Further, as shown in FIG. 13A, one end of the street 111 (the left end in FIG. 13A) is positioned immediately below the condenser 524. Next, the control unit 30 operates the laser beam irradiation unit 52 to operate the processing feed unit 37 while irradiating the low dielectric constant insulator film 113 formed on the street 111 from the condenser 524 with the laser beam LB. The chuck table 36 is moved at a predetermined processing feed speed in the processing feed direction indicated by the arrow X1. At this time, the condensing point P of the laser beam LB irradiated from the condenser 524 is matched with the surface of the low dielectric constant insulating film 113. Then, as shown in FIG. 13B, after moving to the other end of the street 111 (the right end in FIG. 13B), the control unit 30 controls the laser beam irradiation unit 52 to stop the irradiation of the laser beam LB. . As a result, the low dielectric constant insulator film 113 formed on the street 111 is removed (laser beam irradiation step).

  In the laser beam irradiation process described above, when the laser beam LB irradiated from the condenser 524 of the laser beam irradiation means 52 is irradiated over the semiconductor wafer 10 as shown in FIG. There is. At this time, the semiconductor wafer 10 attached to the dicing tape T mounted on the annular frame F held by the chuck table 36 has the center P1 positioned at the center P0 of the chuck table 36 as described above. Therefore, the wafer holding area 361 of the chuck table 36 is entirely covered. Accordingly, the laser beam LB irradiated by overrunning the semiconductor wafer 10 is irradiated to the dicing tape T outside the outer peripheral edge of the semiconductor wafer 10 as shown in FIG. 14, but the laser beam LB is irradiated to the dicing tape T. Since the wafer holding area 361 of the chuck table 36 does not exist in the area where the dicing tape T is melted by irradiation with the laser beam LB, the wafer holding area 360 does not adhere to the wafer holding area 360. The laser beam LB applied to the dicing tape T passes through the dicing tape T and is applied to the bottom surface of the laser beam buffering groove 366. However, the bottom surface of the laser beam buffering groove 366 is sufficiently away from the condensing point P, and the laser beam is irradiated. Is diffused, the energy density is not high enough to be processed, and the chuck table 36 is not damaged. In the illustrated embodiment, since the laser beam absorbing member 367 is disposed on the bottom surface of the laser beam buffering groove 366, the chuck table 36 can be reliably prevented from being damaged.

In the illustrated embodiment, the processing conditions in the laser beam irradiation step are set as follows.
Light source: YAG laser or YVO4 laser Wavelength: 355 nm
Output: 0.5W
Repeat frequency: 50 kHz
Pulse width: 10nsec
Condensing spot diameter: φ9.2 μm
Processing feed rate: 100 mm / sec

  As described above, when the laser beam irradiation process is performed on the predetermined street 111 as shown in FIG. 13A, the control unit 30 operates the first indexing and feeding unit 38 to move the chuck table 36 to the street. Indexing and feeding are performed in the direction perpendicular to 111 by the street interval, and the laser beam irradiation step is performed. By repeatedly executing this indexing and laser beam irradiation process, the low dielectric constant insulator film 113 formed on all the streets 111 extending in a predetermined direction of the semiconductor wafer 20 is removed. As described above, when the laser beam irradiation process is performed on the street 111 extending in a predetermined direction of the semiconductor wafer 10, the control means 30 operates the pulse motor (not shown) to move the chuck table 36 and thus the semiconductor wafer 10 to 90 degrees. The laser beam irradiation process described above is performed on the street 111 that rotates and extends in the direction orthogonal to the street 111 that extends in the predetermined direction. As a result, the low dielectric constant insulator film 113 formed on all the streets 111 of the semiconductor wafer 20 is removed.

  When the low dielectric constant insulator film 113 formed on all the streets 111 of the semiconductor wafer 10 is removed as described above, the control means 30 operates the processing feed means 37 to hold the semiconductor wafer 10. The chuck table 36 is first returned to the position where the semiconductor wafer 10 is sucked and held, and the suction and holding of the semiconductor wafer 20 by the suction means (not shown) is released. Next, the control unit 30 operates the second wafer transfer unit 17 to transfer the laser-processed semiconductor wafer 10 on the chuck table 36 to the cleaning unit 16. Next, the control means 10 operates the cleaning means 16 to clean and dry the laser-processed semiconductor wafer 10.

  If the cleaning and drying operations of the laser-processed semiconductor wafer 10 are performed as described above, the control unit 30 operates the first transfer unit 15 to transfer the cleaned semiconductor wafer 10 to the alignment unit 13. . Next, the control unit 30 operates the unloading unit 14 to store the semiconductor wafer 10 conveyed to the alignment unit 13 in a predetermined position of the cassette 19.

  As described above, in the above-described embodiment, an example in which laser processing for removing the low dielectric constant insulator film formed on the street of the semiconductor wafer has been shown, but the laser processing apparatus according to the present invention is applied to the street of the semiconductor wafer. For example, the present invention can be applied to laser processing or the like that irradiates a semiconductor laser with a pulse laser beam having a wavelength of, for example, 1064 nm to form a continuous deteriorated layer inside the semiconductor wafer. In addition, the laser processing apparatus according to the present invention is suitable for laser processing for forming a laser processing groove on a semiconductor wafer by irradiating the semiconductor wafer with a pulsed laser beam having a wavelength of 355 nm, for example, having absorptivity to the semiconductor wafer along the street of the semiconductor wafer. Can be applied.

  Although the present invention has been described based on the illustrated embodiment, the present invention is not limited to the embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, in the embodiment described above, the center position of the chuck table positioned at the wafer attachment / detachment position based on the displacement amount between the center of the wafer and the center of the annular frame detected by the displacement amount detection mechanism is determined by the wafer transport means. Although an example in which the processing feeding means and the index feeding means are controlled so as to coincide with the center of the wafer attached to the dicing tape attached to the annular frame to be conveyed is shown, it is detected by the displacement detection mechanism. The transfer position of the wafer attached to the dicing tape mounted on the annular frame conveyed by the wafer conveyance means based on the amount of displacement between the center of the wafer and the center of the annular frame is determined in the X-axis direction and the Y-axis direction. You may control to.

2: stationary base 3: chuck table mechanism 31, 31: pair of guide rails 32: first sliding block 33: second sliding block 36: chuck table 360: wafer holding region 366: annular buffer groove 37: processing Feed means 38: First index feed means 4: Laser beam irradiation unit support mechanism 41, 41: A pair of guide rails 42: Movable support base 43: Second index feed means 5: Laser beam irradiation unit 51: Unit holder 52: Laser beam irradiation means 524: Condenser 6: Imaging means 8: Cassette table 9: Cassette 10: Semiconductor wafer 13: Positioning means 14: Wafer unloading means 15: First wafer conveying means 16: Cleaning means 17: Wafer conveying means 18: Display means 20: Displacement amount detection mechanism 201: Imaging means 30: Control means
F: Ring frame
T: Dicing tape

Claims (3)

A wafer holding area that is the same as or slightly smaller than the wafer size, a chuck table in which a laser beam buffering groove is formed around the outside of the wafer holding area, and a laser beam irradiation means for irradiating the wafer held by the chuck table with a laser beam A machining feed means for moving the chuck table between a wafer attachment / detachment position and a machining area by the laser beam irradiation means in a machining feed direction (X-axis direction), and an index feed direction (Y-axis direction) orthogonal to the X-axis direction. An index feeding means for moving the wafer, a cassette for storing a wafer attached to a dicing tape mounted on an annular frame, and being placed on a cassette table; and an annular frame accommodated in the cassette. Wafer unloading means for unloading the wafer attached to the dicing tape; Wafer attachment / detachment is performed by positioning means for aligning the center of the annular frame unloaded by the wafer unloading means and a wafer attached to the dicing tape mounted on the annular frame unloaded by the alignment means. In a laser processing apparatus comprising a wafer transfer means for transferring to a chuck table positioned at a position,
A displacement amount detecting mechanism for detecting a displacement amount between the center of the wafer and the center of the annular frame attached to the dicing tape attached to the annular frame centered in the alignment means;
Control means for controlling the processing feed means, the index feed means, and the wafer transport means based on the amount of displacement between the center of the wafer and the center of the annular frame detected by the displacement amount detection mechanism. ,
The control means is positioned at the wafer attaching / detaching position so that the center of the wafer attached to the dicing tape attached to the annular frame conveyed by the wafer conveying means coincides with the center position of the chuck table. The wafer table attached to a dicing tape mounted on an annular frame conveyed by the wafer conveying means and the chuck table being relatively displaced.
Laser processing equipment characterized by that.   The control means is configured such that the center position of the chuck table positioned at the wafer attaching / detaching position coincides with the center of the wafer attached to a dicing tape attached to an annular frame conveyed by the wafer conveying means. The laser processing apparatus according to claim 1, wherein the processing feeding means and the indexing feeding means are controlled.   The displacement amount detection mechanism includes an image pickup means for picking up an image of the entire wafer attached to a dicing tape attached to an annular frame centered in the position adjustment means, and image information picked up by the image pickup means. 3. The laser processing apparatus according to claim 1, further comprising a control unit that obtains displacement amounts in the X-axis direction and the Y-axis direction between the center of the wafer and the center of the annular frame based on the above.

Images