JP6623035B2 - Imaging method, imaging apparatus, and processing method of workpiece - Google Patents

Description

  The present invention relates to a wafer imaging method, an imaging apparatus, and a processing method for processing a workpiece, for example, a thin plate-like wafer partitioned by a plurality of scheduled division lines and having a plurality of devices formed along the scheduled division lines. About.

  A wafer in which a plurality of devices such as IC, LSI, etc. are defined by a division line and formed on the front surface is attached to the front surface, a back surface is ground by a grinding machine to a predetermined thickness, and then the wafer is Electrical equipment such as mobile phones and personal computers that are attached to a protective tape and separated into individual devices by a dicing machine after the protective tape attached to the front surface is peeled off and supported by a frame having an opening that accommodates the wafer. Used for

  In addition, in order to suppress the decrease in productivity caused by the replacement of the protective tape as described above and the high cost associated with the use of the consumable tape, it is possible to reduce the number of wafers without changing the tape after grinding the back surface of the wafer. A technique for detecting a pattern formed on the front surface of the wafer by infrared rays from the back surface and dividing the wafer into individual devices based on the pattern has been proposed by the present applicant (see Patent Document 1).

  However, grinding marks that form uneven shapes remain on the back surface of the ground wafer like a striped pattern, and the infrared rays irradiated to detect the pattern are irregularly reflected on the striped pattern and watermarked from the back side of the wafer. There was a problem that the pattern formed on the surface could not be recognized.

  Also, in the technology of forming a modified layer along the planned dividing line by irradiating a laser beam condensing point from the rear surface of the wafer to the inside of the planned dividing line, depending on the state of the rear surface of the wafer, the wafer may be irradiated by infrared rays. It has been found that there may be a problem that a pattern formed on the surface of the film cannot be recognized (see, for example, Patent Document 2).

JP-A-10-284449 JP 2005-2222988 A

  The problems as described above are not limited to the case where a pattern formed on the surface of the silicon wafer substrate is detected by infrared rays from the back surface of the wafer, and processing is performed based on the pattern. Even in the technology where the pattern formed on the front side of the wafer is detected by visible light and processed based on the pattern, and the wafer is divided into individual devices, unevenness is formed on the back side by grinding etc. May cause the same problem as described above.

  Therefore, there is a problem to be solved in an imaging method, an imaging apparatus, and a processing method for processing a wafer by imaging a pattern formed on the front surface through the back side of the wafer as a workpiece.

In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a wafer imaging method for imaging the inside of a wafer partitioned by a plurality of division lines and formed with a plurality of devices , the chuck table of a laser processing apparatus. The liquid is dropped onto the back surface of the wafer by the placing step of placing the front side of the wafer on the substrate and the cover glass arranging means arranged in the laser processing apparatus, and the cover glass is arranged on the dropped liquid. and a cover glass disposed step, an imaging step for imaging the inside of the wafer through the cover glass with imaging means for imaging wafers positioned on top of the cover glass, is at least composed of, after the imaging process is completed, the laser beam Before moving the wafer to the laser beam irradiation area, move the cover glass away from the back of the wafer. That the imaging method of a wafer is provided.

  The image pickup means may pick up an image of the inside of the wafer with infrared rays that pass through the wafer. The liquid is preferably water. Further, by executing the imaging method, the position of the planned division line is detected by imaging the planned division line or the device, and then the region corresponding to the planned division line is processed from the back surface of the wafer. A processing method for performing the process is provided.

Furthermore, in order to solve the main technical problem described above, according to the present invention, there is provided an imaging apparatus for imaging the inside of a workpiece to be mounted on a laser processing apparatus, the surface side being held by a chuck table of the laser processing apparatus. And a cover glass disposing means for dropping a liquid onto the imaging surface on the back surface of the workpiece by a liquid dripping means and disposing a cover glass on the liquid , the cover glass disposing means comprising: workpiece, prior to being moved to the laser beam irradiation region for irradiating a laser beam to the workpiece, is kept away the cover glass from the back of the workpiece imaging device is provided. Furthermore, it is preferable to use water as the liquid used in the imaging apparatus.

A wafer imaging method according to the present invention is a wafer imaging method for imaging an interior of a wafer partitioned by a plurality of scheduled division lines and having a plurality of devices formed on a chuck table of a laser processing apparatus. And a cover glass disposing step of dropping a liquid on the back surface of the wafer by a cover glass disposing means disposed in the laser processing apparatus and disposing the cover glass on the dripped liquid. And an imaging step for imaging the inside of the wafer through the cover glass by positioning an imaging means for imaging the wafer on the upper part of the cover glass, so that grinding marks remain on the back surface of the wafer. , The back surface of the wafer is restrained from being diffusely reflected on the back surface of the wafer. Imaging a pattern of the device or dividing lines watermark al, it can be detected. An imaging apparatus according to the present invention is an imaging apparatus that images the inside of a workpiece to be mounted on a laser processing apparatus, and is provided on the back surface of the workpiece that is held on the front side by a chuck table of the laser processing apparatus . And a cover glass disposing means for dripping a liquid onto the imaging surface by a liquid dripping means and disposing a cover glass on the liquid , the cover glass disposing means comprising: a workpiece to be processed; before being moved to the laser beam irradiation region for irradiating a laser beam to the object, Runode away the cover glass from the back of the workpiece, the light beam for grinding traces on the imaging surface of the workpiece to image be left It is possible to suppress and detect irregular reflection on the imaging surface, and to capture and detect a pattern that serves as a reference for processing on the workpiece through the inside from the imaging surface of the workpiece.

The perspective view of the laser processing apparatus provided with the imaging device for enforcing the imaging method of the to-be-processed object by this invention. The perspective view of the imaging means of the imaging device with which the laser processing apparatus shown in FIG. 1 is equipped, and a cover glass arrangement | positioning means. The perspective view showing the state which stuck the semiconductor wafer as a to-be-processed object, and this semiconductor wafer to the protective tape with which the cyclic | annular flame | frame was mounted | worn. Explanatory drawing which shows the cover glass arrangement | positioning process implemented by the imaging means shown in FIG. 2, and a cover glass arrangement | positioning means, and an imaging process.

  Hereinafter, a preferred embodiment of a laser processing apparatus including an imaging apparatus using an imaging method according to the present invention will be described in more detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a laser processing apparatus provided with an imaging apparatus according to the present invention. A laser processing apparatus 1 shown in FIG. 1 includes a stationary base 2, a chuck table mechanism 3 that is disposed on the stationary base 2 so as to be movable in the X-axis direction indicated by an arrow X, and holds a workpiece. And a laser beam irradiation unit 4 disposed on the table 2.

  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 arranged 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 disposed on the first sliding block 32 so as to be movable in the Y-axis direction indicated by an arrow Y orthogonal to the X-axis direction, A cover table 35 supported by a cylindrical member 34 on the second sliding block 33 and a chuck table 36 as holding means for holding a workpiece are provided. The chuck table 36 includes a suction chuck 361 formed of a porous material having air permeability, and holds a workpiece by operating suction means (not shown) on a holding surface which is the upper surface of the suction chuck 361. It is supposed to be. The chuck table 36 configured as described above is rotated by a pulse motor (not shown) disposed in the cylindrical member 34. The chuck table 36 is provided with a clamp 362 for fixing an annular frame that supports a workpiece via a protective tape.

  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, and is formed on the upper surface in parallel along the Y-axis direction. A pair of guide rails 322 and 322 are provided. The first sliding block 32 configured in this manner moves in the X-axis direction along the pair of guide rails 31 and 31 by the guided grooves 321 and 321 fitting into the pair of guide rails 31 and 31. Configured to be possible. The illustrated chuck table mechanism 3 includes X-axis direction moving means 37 for moving the first sliding block 32 along the pair of guide rails 31, 31 in the X-axis direction. The X-axis direction moving means 37 is transmission-coupled to a male screw rod 371 arranged in parallel between the pair of guide rails 31 and 31 and an output shaft of a pulse motor 372 for rotationally driving the male screw rod 371. Has been. The male screw rod 371 is screwed into a penetrating female screw hole formed in a male screw block (not shown) provided on the lower surface of the center portion of the first sliding block 32. Therefore, the first sliding block 32 is moved in the X-axis direction along the guide rails 31 and 31 by driving the male screw rod 371 forward and backward by the pulse motor 372.

  The illustrated laser processing apparatus 1 includes X-axis direction position detection means (not shown) for detecting the position of the chuck table 36 in the X-axis direction. The X-axis direction position detecting means moves along the linear scale along with the linear scale (not shown) arranged along the guide rail 31 and the first sliding block 32 arranged along the linear scale. The reading head is not shown. The reading head of the X-axis direction position detecting means sends a pulse signal of 1 pulse to the control means described later, for example, every 1 μm. And the control means mentioned later detects the X-axis direction position of the chuck table 36 by counting the input pulse signal. When the pulse motor 372 is used as the drive source for the X-axis direction moving means 37, the drive pulse of the control means, which will be described later, that outputs a drive signal to the pulse motor 372 is counted. The position in the axial direction can also be detected. When a servo motor is used as the drive source for the X-axis direction moving means 37, 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, and is input by the control means. By counting the pulse signal, the position of the chuck table 36 in the X-axis direction can also be detected. In the present invention, the type of means for detecting the position in the X-axis direction is not particularly limited.

  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. By fitting the guided grooves 331 and 331 to the pair of guide rails 322 and 322, the guide grooves 331 and 331 are configured to be movable in the Y-axis direction. The illustrated chuck table mechanism 3 includes Y-axis direction moving means 38 for moving the second slide block 33 in the Y-axis direction along a pair of guide rails 322 and 322 provided on the first slide block 32. It has. The Y-axis direction moving 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. Yes. 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 male screw block (not shown) provided on the lower surface of the center portion of the second sliding block 33. Accordingly, the second slide block 33 is moved along the guide rails 322 and 322 in the Y-axis direction by driving the male screw rod 381 forward and backward by the pulse motor 382.

  The illustrated laser processing apparatus 1 includes Y-axis direction position detection means (not shown) for detecting the Y-axis direction position of the second sliding block 33. The Y-axis direction position detecting means is arranged on the linear scale (not shown) arranged along the guide rail 322 and the second sliding block 33, as in the above-described X-axis direction position detecting means. It comprises a reading head (not shown) that moves along the linear scale together with the sliding block 33. The reading head of the Y-axis direction position detecting means sends a pulse signal of 1 pulse to the control means described later, for example, every 1 μm. And the control means mentioned later detects the Y-axis direction position of the 2nd sliding block 33 by counting the input pulse signal. When the pulse motor 382 is used as the drive source of the Y-axis direction moving means 38, the second sliding block 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. It is also possible to detect the position of 33 in the Y-axis direction. When a servo motor is used as a drive source for the Y-axis direction moving 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 described later, and the control means inputs it. By counting the pulse signal, the position of the second sliding block 33 in the Y-axis direction can also be detected.

  The laser beam irradiation unit 4 includes a support member 41 disposed on the stationary base 2, a casing 42 supported by the support member 41 and extending substantially horizontally, and a laser beam irradiation disposed in the casing 42. Means 5, an imaging means 6 that is disposed at the front end of the casing 42 and detects a processing region to be laser processed, and a cover glass arrangement that is adjacent to the imaging means 6 and is disposed along the Y-axis direction. The installation means 7 is provided. The imaging unit 6 includes an illuminating unit that illuminates the workpiece, an optical system that captures an area illuminated by the illuminating unit, an imaging device (CCD) that captures an image captured by the optical system, Infrared illumination means for irradiating a workpiece with infrared light, an optical system for capturing the infrared light irradiated by the infrared illumination means, an image sensor (infrared CCD) for outputting an electrical signal corresponding to the infrared light captured by the optical system, etc. The captured image signal is sent to the control means described later.

  The cover glass disposing means 7 will be further described with reference to FIG. The cover glass disposing means 7 includes at least a liquid dropping means 73 and a cover glass holding means 74, and further includes an air cylinder 71 and a piston rod 72. A liquid dripping means 73 and a cover glass holding means 74 are connected to the lower end of a piston rod 72 supported by the air cylinder 71 and extending downward. The liquid dripping means 73 and the cover glass holding means 74 supported by the piston rod 72 can be moved up and down (Z-axis direction) by the action of the air cylinder 71 and rotate around the axis of the piston rod 72. It is configured to be possible.

  The liquid dripping unit 73 includes a nozzle holding arm 73 a and a dripping nozzle 73 b, and the nozzle holding arm 73 a is disposed so as to extend in the horizontal direction from the lower end portion of the piston rod 72. In addition, a dropping nozzle 73b for dropping water droplets downward is provided at the tip of the nozzle holding arm 73a, and a flexible tube disposed inside the nozzle holding arm 73a is provided from a water tank (not shown). Then, water is supplied to the dripping nozzle 73a.

  The cover glass holding means 74 is composed of a cover glass holding arm 74a and a cover glass holding plate 74b. A thin cover glass 74c (for example, 18 mm × 18 mm, thickness 0) is provided on the front end side of the cover glass holding plate 74b. .13 to 0.17 mm). The cover glass holding arm 74a extends in the horizontal direction from the lower end of the piston rod 72, and is configured to form an angle of approximately 90 degrees with the nozzle holding arm 73a in a horizontal plane including the nozzle holding arm 73a. Yes. Further, as is apparent from FIG. 2, a step is provided on the front end portion side of the cover glass holding arm 74a so as to be lowered one step downward, and the cover glass holding plate 74b is located with respect to the cover glass holding arm 74a. The cover glass 74c is formed so that the lower surface of the cover glass 74c is flush with the lower surface of the cover glass holding plate 74b, or the lower surface of the cover glass 74c slightly protrudes downward.

  The imaging means 6 is disposed above the cover glass 74c held by the cover glass holding plate 74b. The imaging means 6 of the present embodiment is composed of an infrared imaging element 61 (infrared CCD) provided with infrared irradiation means and a microscope unit 62 constituting an optical system, irradiates the cover glass 74c with infrared rays, and covers the cover. Through the glass 74c, it is possible to image through the inside of the workpiece.

  The illustrated laser processing apparatus 1 includes control means (not shown). The control means is constituted by a computer, a central processing unit (CPU) that performs arithmetic processing according to a control program, a read-only memory (ROM) that stores a control program, and a random read / write that stores arithmetic results and the like. In addition to the image signal input from the imaging unit 6, detection signals from the X-axis direction position detection unit, the Y-axis direction position detection unit, and the like are input to the access memory (RAM) and the input interface. From the output interface of the control means, the X-axis direction moving means 37, the Y-axis direction moving means 38, the laser beam irradiation means 5, the cover glass arranging means 7, the monitor M, a pulse laser beam oscillation means (not shown), and an output A control signal or the like is output to the adjusting means or the like.

  The operation of the laser processing apparatus 1 configured as described above will be described below. FIG. 3A is a perspective view of a semiconductor wafer 20 as a wafer to be imaged and processed by a laser processing apparatus to which the wafer imaging method and processing method according to the present invention are applied. The semiconductor wafer 20 is made of, for example, a silicon wafer having a diameter of 200 mm and a thickness of 600 μm. A plurality of division lines 21 are formed in a lattice shape on the surface 20 a and are partitioned by the plurality of division lines 21. In addition, devices 22 such as IC and LSI are formed in a plurality of regions.

  In order to divide the above-described semiconductor wafer along the planned division line, a wafer support process is performed in which the semiconductor wafer is attached to the surface of a protective tape attached to an annular frame. That is, as shown in FIG. 3B, the surface 20a of the semiconductor wafer 20 is adhered to the surface of the protective tape T with the outer peripheral portion mounted so as to cover the inner opening of the annular frame F. Accordingly, the back surface 20b of the semiconductor wafer 20 attached to the surface of the protective tape T is on the upper side.

  When the wafer support process described above is performed, a back surface grinding process is performed in which the back surface 20b of the semiconductor wafer 20 is ground to form the semiconductor wafer 2 with a predetermined finished thickness of the device. This back grinding process is carried out using a grinding device (not shown), but does not have a special feature in the present invention, and a known grinding device can be used, and the details thereof are omitted. The back surface 20b of the semiconductor wafer 20 is ground by the back surface grinding step, and the semiconductor wafer 20 is formed to a predetermined thickness (for example, 200 to 300 μm). Before the semiconductor wafer 20 is attached to the protective tape T, a back surface grinding process for grinding the back surface of the semiconductor wafer 20 may be performed.

  When the back surface grinding process is performed as described above, the condensing point of the laser beam having a wavelength that is transmissive to the semiconductor wafer 20 is positioned from the back surface side of the semiconductor wafer 20 to the inside and irradiated along the planned dividing line 21. Then, a modified layer forming step is performed in which a modified layer that propagates cracks toward the surface of the semiconductor wafer 20 is formed along the division line. This modified layer forming step is performed using the laser processing apparatus shown in FIG. The laser processing apparatus 1 shown in FIG. 1 has a chuck table 36 that holds a workpiece, laser beam irradiation means 5 that irradiates a workpiece held on the chuck table 36 with a laser beam, and a chuck table 36 that holds the workpiece. An imaging means 6 for imaging the processed workpiece is provided. The chuck table 36 is configured to suck and hold the workpiece. The chuck table 36 is moved by the X-axis direction moving unit 37 in the processing feed direction indicated by the arrow X in FIG. 1 is moved in the index feed direction indicated by the arrow Y.

  The laser beam irradiation means 5 is constituted by a pulse laser beam oscillation means provided with a pulse laser beam oscillator and a repetition frequency setting means (not shown). A condenser 51 for condensing the pulse laser beam oscillated from the pulse laser beam oscillating means is attached to the tip of the casing 42. The laser beam irradiating unit 5 includes a condensing point position adjusting unit (not shown) for adjusting the condensing point position of the pulse laser beam condensed by the condenser 51.

  In the illustrated embodiment, the imaging means 6 attached to the tip of the casing 42 in which the laser beam irradiation means 5 is disposed is outside a normal imaging device (CCD) that images a workpiece with visible light. Infrared illuminating means for irradiating a workpiece with infrared rays, an optical system for capturing the infrared rays irradiated by the infrared illuminating means, and an image sensor (infrared CCD) for outputting an electrical signal corresponding to the infrared rays captured by the optical system The captured image signal is sent to a control means (not shown).

  Using the above-described laser processing apparatus 1, the semiconductor wafer 20 on which the above-described wafer support process and back surface grinding process have been performed is provided with a condensing point of a pulsed laser beam having a wavelength transmissive to the semiconductor wafer 20. A modified layer forming step is performed in which a modified layer that is irradiated from the back surface side of the semiconductor wafer 20 along the planned dividing line 21 and propagates cracks toward the surface of the semiconductor wafer 20 is formed along the planned dividing line. First, the protective tape T side on which the semiconductor wafer 20 is adhered is placed on the suction chuck 361 of the chuck table 36. Then, by operating a suction means (not shown), the semiconductor wafer 20 is held on the chuck table 36 via the protective tape T (wafer holding step). Therefore, the semiconductor wafer 20 held on the chuck table 36 has the back surface 20b on the upper side, and the annular frame F on which the protective tape T is mounted is fixed by the clamp 362 provided on the chuck table 36. In this way, the chuck table 36 that sucks and holds the semiconductor wafer 20 is positioned directly below the imaging unit 6 by the X-axis direction moving unit 37 and the Y-axis direction moving unit 38.

  When the chuck table 36 is positioned immediately below the image pickup means 6, the image pickup means 6 and a control means (not shown) emit the laser beam along the planned division line 21 formed in a predetermined direction of the semiconductor wafer 20 and the planned division line 21. Alignment for performing alignment with the condenser 51 of the laser beam irradiation means 5 to be irradiated is performed (alignment process).

  Here, when performing the alignment step, if the imaging means 6 attempts to image the division line 21 as it is, as described above, the ground surface of the ground surface 20b of the semiconductor wafer 20 is striped with concavo-convex shapes. The infrared rays irradiated to detect the planned division line 21 are irregularly reflected in the striped pattern, and the planned division line 21 formed on the front surface 20a side through the back surface 20b side of the semiconductor wafer 20 is recognized. The problem that it is not possible arises.

  Therefore, in the present embodiment based on the present invention, a liquid is dropped on the back surface 20b of the semiconductor wafer 20, and a cover glass arranging step of arranging a cover glass on the dropped liquid, and imaging for imaging the semiconductor wafer 20 are performed. An imaging method is performed including positioning the means 6 on the top of the cover glass and imaging the inside of the semiconductor wafer 20 through the cover glass. The cover glass arrangement step and the imaging step will be described with reference to FIG.

(Cover glass placement process)
4A to 4D show the semiconductor wafer 20 held on the chuck table (not shown) via the protective tape T and the cover glass disposing means 7. First, as shown in FIG. 4 (a), the piston rod 72 supported by the air cylinder 71 is rotated about the longitudinal axis, and the dropping nozzle 73b disposed at the tip of the nozzle holding arm 73a is While being positioned at a substantially central portion of the back surface 20 b of the semiconductor wafer 20, the piston rod 72 is lowered to bring the dropping nozzle 73 b close to the semiconductor wafer 20. Further, water supplied from a water supply source (not shown) is dropped from the dropping nozzle 73b, and the water droplet W is supplied to the center. The water droplet W supplied to the back surface 20b of the semiconductor wafer 20 is held in a hemispherical shape in the central portion by the surface tension.

  After the water droplet W is supplied to the back surface 20b of the semiconductor wafer 20, the cover glass 74c is rotated 90 degrees around the axis of the piston rod 72 and held on the glass holding plate 74b above the previously supplied water droplet W. Is positioned (see FIG. 4B). Then, the piston rod 72 is lowered to approach the back surface 20b of the semiconductor wafer 20 to a distance of about 1 mm (see FIG. 4C). Then, the water droplets W held on the back surface 20b of the semiconductor wafer 20 fill a region sandwiched between the back surface 20b and the cover glass 74c, and the water droplets W are formed on the concavo-convex portions forming the striped pattern on the back surface 20b. It enters, and it will be in a state as shown in FIG.4 (d), and a cover glass arrangement | positioning process is completed.

(Imaging process)
Returning to FIG. 2, the imaging process performed subsequent to the cover glass arranging process will be described. In the present embodiment, the image capturing means 6 is in the state where the cover glass 74c is positioned on the semiconductor wafer 20 and the region sandwiched between the back surface 20b and the cover glass 74c is filled with the water droplets W. Is positioned above. As described above, the imaging means 6 includes the infrared imaging element 61 (infrared CCD) and the microscope unit 62. In the imaging process, infrared rays are transmitted from the infrared imaging element 61 (infrared CCD) onto the cover glass 74c. Irradiate. Here, the back surface 20b of the semiconductor wafer 20 is formed with striped uneven portions formed during grinding, but the space formed by the cover glass 74c and the back surface 20b is filled with the water droplets W. Accordingly, the irregular reflection of the infrared rays on the uneven surface is suppressed, and the irradiated infrared rays are transmitted through the semiconductor wafer 20.

  The infrared rays emitted from the imaging means 6 pass through the cover glass 74c, the water droplets W, and the semiconductor wafer 20, and the planned dividing line 21 and the device 22 on the surface side 20a are captured by the infrared imaging element 61 (infrared CCD). The obtained image data is input to a control means (not shown) and output to a monitor M used by an operator who operates the processing apparatus, and an imaging process is executed.

  Through the above imaging step, the operator can confirm an image as displayed on the monitor M in FIG. 2, and the laser beam irradiation is performed in parallel with the planned dividing line 21 and the X-axis moving direction displayed on the monitor M. Compared with the reference line L indicating the position through which the means passes, the angle of the planned dividing line 21 with respect to the X-axis direction is driven and a pulse motor (not shown) housed in the cylindrical member 34 is driven and moved in the Y-axis direction. The means 38 is driven and finely adjusted so that the reference line L is adjusted to be in the center of the planned division line 21 and parallel to the planned division line 21, and the control means (not shown) corresponds to the planned division line 21. Alignment information is stored (alignment process). Note that the cover glass holding plate 74b is not physically connected to the semiconductor wafer 20, and when the angle of the suction chuck 361 is finely adjusted, its relative position is shifted in a close state. In any of the cover glass arrangement process, the imaging process, and the alignment process, there is no direct contact.

  As described above, when the division line 21 formed on the semiconductor wafer 20 held on the chuck table 36 is detected and the alignment process of the position where the laser beam is irradiated is performed, the cover glass arranging means The piston rod 72 is raised to the position shown in FIG. 4B, and the piston rod 72 is rotated by about 90 degrees in the direction in which the dropping arm 73a is disposed when viewed from the cover glass holding plate 74b. 73a and the cover glass holding plate 74b are driven away from the chuck table 36, and high pressure air is blown onto the back surface 20b from an air nozzle (not shown), and water droplets dropped on the back surface of the semiconductor wafer 20 Is removed.

  After the alignment is completed and the water droplets dropped on the back surface of the semiconductor wafer 20 are removed, the chuck table 36 is moved to the laser beam irradiation region where the condenser 51 of the laser beam irradiation means 5 for irradiating the laser beam is located. One end of the predetermined division line 21 is positioned immediately below the condenser 51 of the laser beam irradiation means 5, and the focusing point of the pulse laser beam is positioned at a predetermined position inside the semiconductor wafer 20. The chuck table 36 is moved at a predetermined feed rate in the X-axis direction while irradiating the semiconductor wafer 20 with a pulse laser beam having a wavelength that is transmissive from the collector 51, and the laser beam from the collector 51 is moved. When the irradiation position reaches the position of the other end of the division planned line 21, the irradiation of the pulse laser beam is stopped and the movement of the chuck table 36, that is, the semiconductor wafer 20, is stopped. As a result, a modified layer by a laser beam is formed inside the semiconductor wafer 20 along the planned division line 21 (modified layer forming step).

In addition, the conditions of the laser processing used in the said modified layer formation process are set as follows, for example.
Wavelength: 1064 nm pulse laser Repeat frequency: 100 kHz
Average output: 0.3W
Focusing spot: φ1μm
Processing feed rate: 100 mm / sec

  When the modified layer forming step is performed along the predetermined division line 21 as described above, the chuck table 51 is moved by the interval of the division line 21 formed on the semiconductor wafer 20 in the direction indicated by the arrow Y in FIG. Indexing movement (indexing process) is performed, and the modified layer forming step is performed. If the modified layer forming step is performed along all the division lines 21 formed in the predetermined direction in this way, the chuck table 36 is rotated by 90 degrees, and the division division formed in the predetermined direction is performed. The modified layer forming step is executed along all the planned division lines 21 extending in a direction orthogonal to the line 21.

  When the modified layer forming step described above is executed, an external force is applied to the semiconductor wafer 20, and the semiconductor wafer 20 is divided into individual devices along the division line 21 on which the modified layer is formed. A dividing step of dividing into 22 is performed. In addition, since the said division | segmentation process can apply a well-known technique suitably and does not comprise the principal part of this invention, the detail is abbreviate | omitted. And if this division | segmentation process is implemented, the device 22 divided | segmented using the pick-up means which is not shown in figure can be peeled off from the protective tape T and picked up, and the device 22 divided | segmented separately can be obtained. it can.

  As mentioned above, although this invention was demonstrated based on embodiment of illustration, this invention is not limited only to above-described embodiment, A various deformation | transformation is possible in the range of the meaning of this invention. For example, in the above-described embodiment, the image pickup means used in the image pickup process irradiates the semiconductor wafer with infrared rays and picks up an image of the planned division line from the back side to the front side by the infrared imaging element (infrared CCD). However, the present invention is not limited to this, and can be applied to any case in which a pattern on the front surface side is imaged through the front surface side from the back surface using a light beam having transparency to the workpiece. The present invention can also be applied to an apparatus that irradiates visible light from the back side of a sapphire substrate used for manufacturing a device and images a division planned line on the front side. In the above-described embodiment, the liquid dripping means 73 and the cover glass holding means 74 of the cover glass disposing means 7 are connected and integrated with one piston rod 72 driven by the air cylinder 71. However, the present invention is not necessarily limited thereto, and may be connected to different air cylinders and piston rods and operated respectively.

1: Laser processing device 2: Stationary base 3: Chuck table mechanism 36: Chuck table 4: Laser beam irradiation unit 5: Laser beam irradiation means 6: Imaging means 7: Cover glass arrangement means 73: Liquid dropping means 74: Cover glass holding Means 74a: Cover glass holding arm 74b: Cover glass holding plate 74c: Cover glass 74c
20: Semiconductor wafer 21: Planned division line 22: Device

Claims (6)

A wafer imaging method for imaging an interior of a wafer partitioned by a plurality of division lines and having a plurality of devices formed thereon,
A mounting step of mounting the front side of the wafer on the chuck table of the laser processing apparatus;
A cover glass disposing step of dropping a liquid on the back surface of the wafer by a cover glass disposing means disposed in the laser processing apparatus, and disposing a cover glass on the dripped liquid;
An imaging step of imaging an image of a wafer is positioned at the top of the cover glass and images the inside of the wafer through the cover glass, and is configured at least .
A wafer imaging method in which the cover glass is moved away from the back surface of the wafer after the imaging step is completed and before the laser beam is moved to a laser beam irradiation region that irradiates the wafer with the laser beam .   The wafer imaging method according to claim 1, wherein the imaging means images the inside of the wafer with infrared rays that pass through the wafer.   The wafer imaging method according to claim 1, wherein the liquid is water. By performing the imaging method according to any one of claims 1 to 3, the position of the planned division line is detected by imaging the planned division line or the device,
Thereafter, a wafer processing method for performing a processing step of processing a region corresponding to the division planned line from the back surface of the wafer. An imaging device for imaging the inside of a workpiece to be mounted on a laser processing device ,
Cover glass disposing means for dripping liquid by liquid dripping means on the imaging surface of the back surface of the workpiece held on the chuck table of the laser processing apparatus , and disposing a cover glass on the liquid;
Imaging means for imaging the inside of the workpiece through the cover glass with light transmitted through the workpiece;
At least it consists of,
The cover glass disposed means, the workpiece, prior to being moved to the laser beam irradiation region for irradiating a laser beam to the workpiece, the imaging is kept away the cover glass from the back of the workpiece apparatus.   The imaging apparatus according to claim 5, wherein the liquid is water.