CN107464762B - Inspection method and inspection device for workpiece, laser processing device, and expansion device - Google Patents

Abstract

The present invention provides a method for inspecting a workpiece, an inspection apparatus, a laser processing apparatus, and an expansion apparatus, which can appropriately and easily determine the state of a modified layer. This method for inspecting a workpiece includes a step of forming a modified layer, by irradiating a laser beam (L2) having a wavelength that is transparent to the workpiece (11) to form a modified layer inside the workpiece (11). The modified layer (17) at the starting point when the workpiece is broken, and unevenness corresponding to the modified layer is generated on the exposed surface of the workpiece; in the photographing step, the light (L1) emitted from the light source (6) is The exposed surface of the workpiece is reflected and irradiated on the projection surface (8) to form a projection image (31) that emphasizes unevenness, and the projection image is photographed to form an image; The state of the stratum.

Description

Inspection method, inspection device, laser processing device, and extension device for workpiece

technical field

The present invention relates to a method for inspecting a workpiece, an inspection apparatus, a laser processing apparatus, and an expansion apparatus, which can confirm the state of a modified layer as a starting point when the workpiece is broken.

Background technique

When a wafer made of a material such as silicon, SiC, or sapphire is divided into a plurality of chips, for example, a transparent laser beam is converged to generate multiphoton absorption, thereby locally modifying the inside of the wafer to form a modified A modified layer (modified region) (for example, refer to Patent Document 1). Since the modified layer is brittle compared with other regions, the wafer can be broken and divided into a plurality of chips by applying a small force afterward.

However, when a workpiece such as a wafer is divided by the above-described method, it is necessary to reliably form the modified layer along the line to be divided (spacer) set on the workpiece. Therefore, a confirmation method or the like has been proposed in which the inside of the workpiece is photographed using a camera or the like having sensitivity in the infrared region, and the position of the modified layer is confirmed (for example, see Patent Document 2).

Patent Document 1: Japanese Patent Laid-Open No. 2005-223284

Patent Document 2: Japanese Patent Laid-Open No. 2005-169407

However, the width of the modified layer formed inside the workpiece is narrow, and the state of the modified layer cannot be easily grasped even by the above-mentioned confirmation method. Therefore, in reality, it is not possible to properly determine whether or not a desired reforming layer is formed before actually trying to break the workpiece.

SUMMARY OF THE INVENTION

The present invention has been made in view of this problem, and an object thereof is to provide an inspection method, an inspection apparatus, a laser processing apparatus, and an expansion apparatus of a workpiece which can appropriately and easily determine the state of the modified layer.

According to a first aspect of the present invention, there is provided a method for inspecting a workpiece, the method for inspecting a workpiece including a step of forming a modified layer by irradiating a laser beam having a wavelength that is transparent to the workpiece. beam, a modified layer is formed inside the workpiece as a starting point when the workpiece is broken, and unevenness corresponding to the modified layer is generated on the exposed surface of the workpiece; The emitted light is reflected on the exposed surface of the workpiece and irradiated on the projection surface to form a projection image with an emphasis on the unevenness, and the projection image is photographed to form an image; and a step of determining, based on the image to determine the state of the modified layer.

In the first aspect of the present invention, the workpiece may be a wafer in which devices are formed in a region on the front side divided by a plurality of planned dividing lines, and the modified layer may be formed along the planned dividing lines of.

Furthermore, in the first aspect of the present invention, the inspection method of the workpiece may include a step of: a dicing tape bonding step, and prior to the modified layer forming step, bonding the workpiece to the workpiece a dicing tape; and a step of expanding and dividing, after the step of forming the modified layer, expanding the dicing tape to apply a force to the workpiece, and dividing the workpiece into a plurality of pieces with the modified layer as a starting point of fracture For each chip, the extended dividing step is performed in parallel with the photographing step.

According to a second aspect of the present invention, there is provided an inspection apparatus for inspecting a modified layer of a workpiece formed inside by being irradiated with a laser beam having a transmissive wavelength There is the modified layer as a starting point of fracture, and irregularities corresponding to the modified layer are generated on the exposed surface of the workpiece, wherein the inspection device includes a holding table for the workpiece to be processed. The object is held; the light source irradiates light to the exposed surface of the workpiece held on the holding table; the projection surface is irradiated with light from the light source reflected by the workpiece to form the unevenness. a projected image with emphasis; a photographing means for photographing the projected image formed on the projection surface to form an image; and a determination means for comparing the formed image with a preset condition to determine the change The state of the stratum.

According to a third aspect of the present invention, there is provided a laser processing apparatus including: a chuck table that holds a workpiece; and a laser beam irradiation member that is held on the chuck table by the pair The workpiece is irradiated with a laser beam to form a modified layer inside the workpiece as a starting point when the workpiece is broken, and irregularities corresponding to the modified layer are generated on the exposed surface of the workpiece; keep a table for holding the workpiece after being irradiated with the laser beam; a light source for irradiating light to the exposed surface of the workpiece held on the holding table; and a projection surface for being irradiated with light The light from the light source reflected by the processed object forms a projection image in which the unevenness is emphasized; the imaging means captures the projection image formed on the projection surface to form an image; the determination means The image is compared with preset conditions to determine the state of the modified layer; and a control member controls each structural element.

In the third aspect of the present invention, the holding table may be the chuck table, that is, the chuck table can be used as the holding table.

According to a fourth aspect of the present invention, there is provided an expansion device including a support base that supports the object to be processed by a dicing tape adhered to the object to be processed by being irradiated A laser beam having a transparent wavelength to form a modified layer as a starting point for fracture inside, and to generate irregularities corresponding to the modified layer on the exposed surface of the workpiece; an expansion member for the A dicing belt is extended; a holding table holds the workpiece; a light source irradiates light to the exposed surface of the workpiece held on the holding table; a projection surface is irradiated The light from the light source reflected by the processed object forms a projection image in which the unevenness is emphasized; the imaging means captures the projection image formed on the projection surface to form an image; the determination means The image is compared with preset conditions to determine the state of the modified layer; and a control member controls each structural element.

In the fourth aspect of the present invention, the holding table may be the support base. That is, the support base can be used as a holding table.

In the inspection method of the workpiece according to the first aspect of the present invention, the light emitted from the light source is reflected on the surface of the workpiece on which the fine irregularities corresponding to the modified layer are formed, and is irradiated to the projection surface. Since a projected image in which the unevenness in the plane is emphasized is formed, and the state of the modified layer is determined from an image formed by photographing the projected image, it is possible to include the emphasized unevenness corresponding to the modified layer. The image of the modified layer can be appropriately and easily determined.

Further, the inspection apparatus of the second aspect, the laser processing apparatus of the third aspect, and the expansion apparatus of the fourth aspect of the present invention all include a light source that irradiates light to the exposed surface of the workpiece, and a projection surface that is irradiated by The light from the light source reflected by the object to be processed forms a projection image that emphasizes the unevenness; and the judgment means compares the formed image with preset conditions to judge the state of the modified layer, so that it is possible to The state of the modified layer can be appropriately and easily determined by implementing the above-mentioned inspection method of the workpiece.

Description of drawings

FIG. 1 is a diagram schematically showing a configuration example and the like of an inspection apparatus.

FIG. 2 is a perspective view schematically showing a tape bonding step.

FIG. 3 is a perspective view schematically showing a back grinding step.

FIG. 4 is a side view schematically showing a back grinding step.

FIG. 5 is a perspective view schematically showing a step of forming a modified layer.

FIG. 6 is a partial cross-sectional side view schematically showing a step of forming a reforming layer.

FIG. 7 is a diagram showing an example of a projected image when an appropriate modified layer is formed on the workpiece.

FIG. 8 is a diagram showing an example of a projected image when an appropriate modified layer is not formed on the workpiece.

FIG. 9 is a perspective view schematically showing a configuration example of a laser processing apparatus.

FIGS. 10(A) and 10(B) are partial cross-sectional side views schematically showing a configuration example of an expansion device and an expansion division step.

FIG. 11 is a diagram showing an example of a projected image after the expansion division step.

Label description

11: workpiece; 11a: front surface; 11b: back surface; 13: planned dividing line (spacer lane); 15: device; 17: modified layer (modified region); 21: tape (dicing tape); 21a: 1st side; 21b: 2nd side; 31: projected image; 33: shadow; 35a, 35b, 35c, 35d: defective area; 41: tape (dicing tape); 43: frame; L1: light; L2: laser beam; 2: inspection device; 4: holding table; 4a: holding surface; 6: light source; 8: projection surface; 10: imaging unit (photographing member); 12: determination unit (determination member); ;24: Chuck table; 24a: Holding surface; 26: Grinding unit; 28: Spindle; 30: Mounting seat; 32: Grinding wheel; 34: Grinding wheel base; 36: Grinding tool; 42: Laser 44: chuck table; 44a: holding surface; 46: laser irradiation unit; 48: imaging unit; 52: extension device; 54: support structure (holding table); 56: extension drum (support base, Holding table); 58: Frame supporting table; 60: Clamp; 62: Elevating mechanism (expansion member); 64: Cylinder barrel; 66: Piston rod; 68: Control unit (control member); 102: Laser processing device; 104: base; 104a: protrusion; 106: support structure; 106a: support arm; 108: cassette lifter; 110: cassette; , indexing feed mechanism); 118: Y-axis guide rail; 120: Y-axis moving table; 122: Y-axis ball screw; 124: Y-axis pulse motor; 126: X-axis guide rail; 128: X-axis moving table ;130: X-axis ball screw; 132: Table base; 134: Chuck table (holding table); 134a: Holding surface; 136: Fixture; 138: Laser irradiation unit; 140: Shooting unit; 142: Control unit (control member).

Detailed ways

An embodiment of one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing a configuration example and the like of an inspection apparatus. As shown in FIG. 1 , the inspection apparatus 2 of the present embodiment includes a holding table 4 for holding a plate-shaped workpiece 11 having a modified layer (modified region) formed therein. A part of the upper surface of the holding table 4 becomes the holding surface 4a for holding the workpiece 11 (or the tape (dicing tape) 21 attached to the workpiece 11).

A light source 6 for emitting light L1 to the entire workpiece 11 held by the holding table 4 is arranged above the holding table 4 . As the light source 6, an incandescent lamp, an LED, or the like is used, for example. However, there is no limitation on the type, position, and the like of the light source 6 . In addition, the light L1 may be parallel light or non-parallel light. In the case where the light L1 is parallel light, for example, an optical element such as a lens may be combined with the light source 6 . On the other hand, when the light L1 is made non-parallel light, it is preferable to use the light source 6 which has a small light emission area and can be regarded as a point light source.

As shown in FIG. 1 , a projection surface 8 on which a projected image is formed by irradiating the reflected light L1 is provided on the path (optical path) of the light L1 reflected by the workpiece 11 . Typically, the projection surface 8 is a flat screen, and is formed to be approximately the same size as the workpiece 11 . In addition, this projection surface 8 should just be provided in the form (position, size, shape, etc.) which can project at least the whole to-be-processed object 11.

In the present embodiment, the light source 6 is arranged obliquely above the holding table 4 , and the projection surface 8 substantially perpendicular to the back surface 11 b of the workpiece 11 is arranged on the path of the light L1 reflected by the workpiece 11 . Therefore, when light L1 traveling obliquely downward is emitted from the light source 6 to the workpiece 11 , the light L1 is reflected by the exposed surface (here, the back surface 11 b ) of the workpiece 11 and irradiated on the projection surface 8 . As a result, a projected image reflecting the state of the exposed surface (ie, the back surface 11 b ) of the workpiece 11 is formed on the projection surface 8 .

At a position facing the projection surface 8 , an imaging unit (imaging member) 10 for capturing a projected image formed on the projection surface 8 to form an image is disposed. The imaging unit 10 is, for example, a digital camera in which an optical element such as a lens is combined with an imaging element such as a CCD or a CMOS, and outputs an image (video) formed by capturing a projected image to the outside. In addition, as the imaging unit 10, either a digital still camera that forms still images or a digital still camera that forms moving images can be used.

The imaging unit 10 is connected to a determination unit (determination means) 12 for comparing the image output from the imaging unit 10 with preset conditions to determine the modification formed in the workpiece 11 the state of the layer. Details such as the processing performed by the determination unit 12 will be described later.

Next, an example of the inspection method of the workpiece 11 using the above-mentioned inspection apparatus 2 will be described. In the inspection method of the workpiece 11 according to the present embodiment, first, a tape bonding step (dicing tape bonding step) is performed to bond the tape (dicing tape) 21 to the workpiece 11 . FIG. 2 is a perspective view schematically showing a tape bonding step.

As shown in FIG. 2 , the workpiece 11 is, for example, a disk-shaped wafer formed of materials such as silicon, SiC, glass, and sapphire, and the front surface 11a side is divided into a central device region and a peripheral remaining region surrounding the device region. The device region is further divided into a plurality of regions by a plurality of planned division lines (spacers) 13 set in a grid shape, and devices 15 such as ICs (LSIs) and LEDs are formed in each region.

In this embodiment, a wafer made of materials such as silicon, SiC, glass, and sapphire is used as the workpiece 11 , but the material, shape, structure, and the like of the workpiece 11 are not limited. For example, the workpiece 11 formed of any material such as semiconductor, ceramic, resin, and metal may be used. Likewise, there are no restrictions on the arrangement of the lines to be divided 13, the types of the devices 15, and the like.

In the tape bonding step, the tape 21 having a function as, for example, a protective member or the like is bonded to the front surface 11a side of the above-described workpiece 11 . The tape 21 is, for example, a resin film formed to be not smaller than the size (for example, diameter) of the workpiece 11, and an adhesive layer (paste layer) formed of a resin having an adhesive force or the like is provided on the first surface 21a side thereof. ).

Thereby, as shown in FIG. 2 , the tape 21 can be attached to the workpiece 11 by bringing the first surface 21a side of the tape 21 into contact with the front surface 11a side of the workpiece 11 . By affixing such a tape 21 to the workpiece 11 , it is possible to prevent, for example, breakage of the device 15 due to a load or the like applied during subsequent grinding.

In this embodiment, the tape 21 having the same size as the workpiece 11 is attached to the front surface 11 a of the workpiece 11 , but a larger tape 21 may be attached to the workpiece 11 . In this case, an annular frame can be fixed to the outer peripheral portion of the belt 21 so that the workpiece 11 can be indirectly supported by the annular frame.

After the tape bonding step, a back surface grinding step is performed to grind the back surface 11b of the workpiece 11 so that the workpiece 11 has a predetermined thickness. FIG. 3 is a perspective view schematically showing the back grinding step, and FIG. 4 is a side view schematically showing the back grinding step. The back surface grinding step is performed by, for example, the grinding device 22 shown in FIGS. 3 and 4 .

The grinding device 22 has a chuck table 24 for sucking and holding the workpiece 11 . The chuck table 24 is connected to a rotational drive source (not shown) such as a motor, and rotates about a rotational axis substantially parallel to the vertical direction. Further, a table moving mechanism (not shown) is provided below the chuck table 24, and the chuck table 24 is moved in the horizontal direction by the table moving mechanism.

A part of the upper surface of the chuck table 24 becomes a holding surface 24a for attracting and holding the second surface 21b side of the tape 21 attached to the workpiece 11 . A suction force for sucking the belt 21 is generated by applying a negative pressure of a suction source (not shown) to the holding surface 24a by a flow path (not shown) formed in the chuck table 24 and the like.

A grinding unit 26 is arranged above the chuck table 24 . The grinding unit 26 has a spindle housing (not shown) supported by a grinding unit lift mechanism (not shown). The main shaft 28 is accommodated in the main shaft housing, and a disk-shaped mount 30 is fixed to the lower end of the main shaft 28 . A grinding wheel 32 having substantially the same diameter as the mounting seat 30 is mounted on the lower surface of the mounting seat 30 .

The grinding wheel 32 has a grinding wheel base 34 formed of a metal material such as stainless steel and aluminum. On the lower surface of the grinding wheel base 34, a plurality of grinding tools 36 are arranged in a ring shape. A rotary drive source (not shown) such as a motor is connected to the upper end side (base end side) of the main shaft 28 , and the grinding wheel 32 is rotated about a rotation axis substantially parallel to the vertical direction by the rotational force transmitted from the rotary drive source. rotate.

In the back grinding step, first, the second surface 21b of the tape 21 attached to the workpiece 11 is brought into contact with the holding surface 24a of the chuck table 24, and a negative pressure of the suction source is applied. Thereby, the workpiece 11 is sucked and held by the chuck table 24 in a state in which the back surface 11b side is exposed upward.

Next, the chuck table 24 is moved below the grinding wheel 32 . Then, as shown in FIGS. 3 and 4 , the chuck table 24 and the grinding wheel 32 are rotated, respectively, and the spindle housing (spindle 28 ) is lowered while supplying grinding fluid such as pure water. The amount of descending of the spindle housing is adjusted so that the lower surface of the grinding wheel 36 comes into contact with the back surface 11 b of the workpiece 11 .

Thereby, the workpiece 11 can be thinned by grinding the back surface 11b side. This back surface grinding step is performed, for example, while measuring the thickness of the workpiece 11 . When the workpiece 11 is thinned to a predetermined thickness (representatively, the finishing thickness of the device chip), the back surface grinding step is terminated.

After the backside grinding step, a modified layer forming step is performed, and a laser beam having a wavelength having transmittance to the workpiece 11 is irradiated and condensed to the workpiece 11 to form the inside of the workpiece 11 as a laser beam for the workpiece 11 . The modified layer at the starting point when the workpiece 11 is fractured. FIG. 5 is a perspective view schematically showing a modification layer forming step, and FIG. 6 is a partial cross-sectional side view schematically showing a modification layer forming step. The modified layer forming step is performed by, for example, the laser processing apparatus 42 shown in FIGS. 5 and 6 .

The laser processing apparatus 42 has a chuck table 44 for sucking and holding the workpiece 11 . The chuck table 44 is connected to a rotational drive source (not shown) such as a motor, and rotates about a rotational axis substantially parallel to the vertical direction. Further, a table moving mechanism (not shown) is provided below the chuck table 44, and the chuck table 44 is moved in the horizontal direction by the table moving mechanism.

A part of the upper surface of the chuck table 44 becomes a holding surface 44a for attracting and holding the second surface 21b side of the tape 21 attached to the workpiece 11 . A negative pressure of a suction source (not shown) acts on the holding surface 44a through a flow path (not shown) formed in the chuck table 44 and the like, and a suction force for sucking the tape 21 is generated.

A laser irradiation unit 46 is arranged above the chuck table 44 . An imaging unit 48 for imaging the workpiece 11 is provided at a position adjacent to the laser irradiation unit 46 . The laser irradiation unit 46 irradiates and converges the laser beam L2 pulsed by a laser oscillator (not shown) to a predetermined position. The laser oscillator is configured to be able to pulse-oscillate a laser beam L2 having a wavelength (wavelength that is difficult to absorb) that is transparent to the workpiece 11 .

In the modified layer forming step, first, the second surface 21b of the tape 21 attached to the workpiece 11 is brought into contact with the holding surface 44a of the chuck table 44, and a negative pressure of the suction source is applied. Thereby, the workpiece 11 is sucked and held by the chuck table 44 in a state in which the back surface 11b side is exposed upward.

Next, the chuck table 44 holding the workpiece 11 is moved and rotated, and the laser irradiation unit 46 is aligned with the end of the planned dividing line 13 to be processed. Then, while irradiating the laser beam L2 from the laser irradiation unit 46 toward the back surface 11 b of the workpiece 11 , the chuck table 44 is moved in a direction parallel to the planned dividing line 13 of the workpiece. That is, the laser beam L2 is irradiated along the planned dividing line 13 from the back surface 11b side of the workpiece 11 .

At this time, the position of the condensing point of the laser beam L2 is aligned with the inside of the workpiece 11 . As a result, the vicinity of the condensing point of the laser beam L2 can be modified by multiphoton absorption, and the modified layer (modified region) 17 can be formed along the line to be divided 13 to be processed. The movement and rotation of the chuck table 44 and the irradiation and convergence of the laser beam L2 are repeated. For example, when the modified layer 17 is formed along all the planned dividing lines 13 , the modified layer forming step is completed.

In addition, when the laser beam L2 is irradiated and converged on the object to be processed 11 in this modified layer forming step, the object to be processed 11 expands in the vicinity of the converging point of the laser beam L2, and the surface 11a and the rear surface 11b are modified with the laser beam L2. At positions corresponding to the layer 17 , fine convex portions (representatively, in units of submicron order) that cannot be visually recognized are formed. That is, the protrusions are formed at substantially the same timing as when the modified layer 17 is formed inside the workpiece 11 , and the front surface 11 a and the back surface 11 b of the workpiece 11 are present in a state where the modified layer forming step is completed. The fine irregularities corresponding to the modified layer 17 .

In the inspection method of the workpiece of the present embodiment, the state of the modified layer 17 is determined using the irregularities. Specifically, after the step of forming the modified layer, an imaging step is performed to reflect the light L1 on the workpiece 11 to form a projection image in which the unevenness is emphasized, and the projection image is captured by the imaging unit 12 to form an image. .

The imaging step is carried out by the above-described inspection device 2 . First, the workpiece 11 is placed on the holding table 4 . Specifically, as shown in FIG. 1 , the second surface 21 b of the tape 21 attached to the workpiece 11 is brought into contact with the holding surface 4 a of the holding table 4 . Thereby, the workpiece 11 is held by the holding table 4 in a state where the back surface 11b side is exposed upward.

Next, as shown in FIG. 1 , light L1 is emitted from the light source 6 . The light source 6 is installed in a form (position, orientation, etc.) capable of irradiating the light L1 to the entire workpiece 11 held by the holding table 4 . Thereby, the light L1 emitted from the light source 6 is reflected by the back surface 11 b of the workpiece 11 .

Moreover, the projection surface 8 is arrange|positioned on the path|route of the light L1 reflected by the to-be-processed object 11. Thereby, the light L1 reflected by the back surface 11b of the to-be-processed object 11 is irradiated to the projection surface 8, and the projection image corresponding to the state of the back surface 11b of the to-be-processed object 11 is formed. FIG. 7 is a diagram showing an example of a projected image when an appropriate modified layer 17 is formed on the workpiece 11 .

The back surface 11 b of the workpiece 11 is substantially flat except for the fine convex portions by the modified layer 17 . That is, the light L1 irradiated to the region other than the convex portion of the back surface 11b is hardly diffused even after being reflected by the back surface 11b. On the other hand, the light L1 irradiated to the convex portion of the back surface 11b is diffused by the function of a convex mirror of the convex portion.

Thereby, when the light L1 reflected by the back surface 11b of the to-be-processed object 11 is irradiated to the projection surface 8, the projection image 31 shown in FIG. 7 is obtained. In this projected image 31 , the unevenness corresponding to the modified layer 17 is emphasized to form a shadow 33 . Then, the projection image 31 is captured by the capturing unit 10 to form an image including the information of the projection image 31 . When the image formed by the photographing unit 10 is sent to the determination unit 12, the photographing step is ended.

After the imaging step, a determination step is performed, and the state of the modified layer 17 is determined by comparing the image formed by the imaging unit 10 with predetermined conditions. As shown in FIG. 7 , when the modified layer 17 suitable for breaking the workpiece 11 is formed, for example, the width of the shadow 33 formed corresponding to the modified layer 17 also increases.

Thereby, by detecting the width of the shadow 33 by image processing or the like, and comparing it with a predetermined reference width (reference value, condition), it can be determined whether or not an appropriate modified layer 17 is formed. Specifically, for example, when the width of the shadow 33 is equal to or larger than the reference value, the determination unit 12 determines that an appropriate modified layer 17 is formed. On the other hand, when the width of the shadow 33 is narrower than the reference value, the determination unit 12 determines that an appropriate modified layer 17 is not formed.

In addition, the area in the image formed by the imaging unit 10 is divided into a plurality of minute areas (micro areas), and the width of the shadow 33 detected in each minute area is compared with a reference value, whereby it can be determined that the area in each minute area is whether an appropriate reforming layer 17 is formed in it. Furthermore, by using this method, the position of the defective region where the appropriate reforming layer 17 is not formed can also be identified.

FIG. 8 is a diagram showing an example of a projected image 31 in a case where an appropriate modified layer 17 is not formed in the workpiece 11 . As shown in FIG. 8 , when the appropriate modified layer 17 is not formed, defective regions 35 a , 35 b , 35 c , and 35 d in which the width of the shadow 33 is narrower than the reference value are present in the projected image 31 . The positions of the defective regions 35a, 35b, 35c, and 35d can be specified by the above-described method of determining whether or not the appropriate modified layer 17 is formed in each minute region.

When the defective regions 35a, 35b, 35c, and 35d are found in the workpiece 11, for example, the modified layer forming step may be performed again to form the modified layer 17 in the defective regions 35a, 35b, 35c, and 35d. Also, the processing conditions of the modification layer forming step may be changed in order to prevent subsequent processing failures.

As described above, in the inspection method of the workpiece according to the present embodiment, the light L1 emitted from the light source 6 is reflected on the back surface 11b of the workpiece 11 in which the fine irregularities corresponding to the modified layer 17 have been formed, and is irradiated onto the workpiece 11 . The projection surface 8 forms a projected image 31 in which the unevenness in the surface is emphasized, and the state of the modified layer 17 is determined based on the image formed by photographing the projected image 31. The state of the modified layer 17 can be appropriately and easily determined according to the image including the highlighted concavities and convexities.

Further, the inspection apparatus 2 of the present embodiment includes a light source 6 that irradiates the back surface (exposed surface) 11b of the workpiece 11 with the light L1 , and a projection surface 8 that is projected from the light source 6 and reflected by the workpiece 11 . the light L1 to form a projection image 31 in which unevenness in the plane is emphasized; an imaging unit (imaging means) 10 that captures the projected image 31 projected on the projection surface 8 to form an image; and a determination unit (determination means) 12. The state of the modified layer 17 is determined by comparing the formed image with preset conditions. Therefore, the state of the modified layer 17 can be appropriately and easily determined by implementing the above-mentioned inspection method of the workpiece.

In addition, the present invention is not limited to the description of the above-described embodiment, and can be implemented with various modifications. For example, the inspection apparatus 2 of the above-described embodiment may be incorporated in a laser processing apparatus. FIG. 9 is a perspective view schematically showing a configuration example of a laser processing apparatus in which the inspection apparatus 2 is incorporated. As shown in FIG. 9, the laser processing apparatus 102 has the base 104 which supports each structure. A support structure 106 extending in the Z-axis direction (vertical direction, height direction) is provided at the end of the base 104 .

Protruding portions 104 a protruding upward are provided at corners of the base 104 away from the support structure 106 . A space is formed inside the protruding portion 104a, and the cassette lifter 108 which can be raised and lowered is provided in the space. A cassette 110 capable of accommodating a plurality of workpieces 11 is placed on the upper surface of the cassette lifter 108 .

A temporary placing mechanism 112 for temporarily placing the above-described workpiece 11 is provided at a position close to the protruding portion 104a. The escrow mechanism 112 includes, for example, a pair of guide rails 112a and 112b that approach or separate from each other while maintaining a state parallel to the Y-axis direction (index feed direction).

Each of the guide rails 112a and 112b has a support surface for supporting the workpiece 11 (an annular frame) and a side surface substantially perpendicular to the support surface, and the workpiece 11 pulled out from the cassette 110 by a conveying mechanism (not shown) is provided. The (annular frame) is clamped in the X-axis direction (processing feed direction) and aligned at a predetermined position.

In the center of the base 104, a moving mechanism (processing feed mechanism, index feed mechanism) 116 is provided. The moving mechanism 116 has a pair of Y-axis guide rails 118 parallel to the Y-axis direction, and the pair of Y-axis guide rails 118 are arranged on the upper surface of the base 104 . The Y-axis moving table 120 is slidably mounted on the Y-axis guide rail 118 .

A nut portion (not shown) is provided on the back side (lower surface side) of the Y-axis moving table 120 , and the Y-axis ball screw 122 parallel to the Y-axis guide rail 118 is screwed to the nut portion. The Y-axis pulse motor 124 is connected to one end of the Y-axis ball screw 122 . When the Y-axis ball screw 122 is rotated by the Y-axis pulse motor 124 , the Y-axis moving table 120 moves in the Y-axis direction along the Y-axis guide rail 118 .

A pair of X-axis guide rails 126 parallel to the X-axis direction are provided on the front surface (upper surface) of the Y-axis moving table 120 . The X-axis moving table 128 is slidably mounted on the X-axis guide rail 126 .

A nut portion (not shown) is provided on the back side (lower surface side) of the X-axis moving table 128 , and the X-axis ball screw 130 parallel to the X-axis guide rail 126 is screwed to the nut portion. An X-axis pulse motor (not shown) is connected to one end of the X-axis ball screw 130 . When the X-axis ball screw 130 is rotated by the X-axis pulse motor, the X-axis moving table 128 moves in the X-axis direction along the X-axis guide rail 126 .

A table base 132 is provided on the front side (upper surface side) of the X-axis moving table 128 . A chuck table (holding table) 134 for sucking and holding the workpiece 11 is arranged on the upper part of the table base 132 . Four jigs 136 are provided around the chuck table 134 to fix an annular frame that supports the workpiece 11 from four directions.

The chuck table 134 is connected to a rotational drive source (not shown) such as a motor, and rotates about a rotation axis substantially parallel to the Z-axis direction (vertical direction, height direction). When the X-axis moving table 128 is moved in the X-axis direction by the above-described moving mechanism 116, the chuck table 134 is processed and fed in the X-axis direction. Then, when the Y-axis moving table 120 is moved in the Y-axis direction by the moving mechanism 116, the chuck table 134 is indexed and fed in the Y-axis direction.

The upper surface of the chuck table 134 serves as a holding surface 134 a for holding the workpiece 11 . The holding surface 134a is formed so as to be substantially parallel to the X-axis direction and the Y-axis direction, and is connected to a suction source (not shown) through a flow path (not shown) formed inside the chuck table 134 or the table base 132 and the like. connect.

The support structure 106 is provided with a support arm 106a that protrudes toward the center side of the base 104, and a laser irradiation unit 138 that irradiates a laser beam downward is disposed at the front end of the support arm 106a. In addition, an imaging unit 140 for imaging the workpiece 11 is provided at a position adjacent to the laser irradiation unit 138 .

The laser irradiation unit 138 has a laser oscillator (not shown) that pulse-oscillates a laser beam having a wavelength that is transparent to the workpiece 11 . For example, when it is desired to form the modified layer 17 on the workpiece 11 made of a semiconductor material such as silicon, a laser oscillator having a laser medium such as Nd:YAG that pulse-oscillates a laser beam with a wavelength of 1064 nm can be used.

In addition, the laser irradiation unit 138 includes a condenser (not shown) for condensing the laser beam pulsed from the laser oscillator, and irradiates and condenses the laser beam to the workpiece 11 and the like held on the chuck table 134 bundle. The workpiece 11 can be laser-processed (modified) along the X-axis direction by feeding the chuck table 134 in the X-axis direction while irradiating the laser beam with the laser beam irradiating unit 138 .

The processed to-be-processed object 11 is conveyed, for example, to the holding table 4 of the inspection apparatus 2 adjacent to the temporary storage mechanism 112 . The projection surface 8 is formed on the holding table 4 side of the support structure 106 . In addition, in FIG. 9, a part of the structure of the inspection apparatus 2 is abbreviate|omitted. The workpiece 11 inspected by the inspection apparatus 2 is placed on the temporary placing mechanism 112 by, for example, a conveying mechanism, and is accommodated in the cassette 110 .

Components such as the conveying mechanism, the moving mechanism 116 , the chuck table 134 , the laser irradiation unit 138 , and the imaging unit 140 are connected to the control unit (control means) 142 , respectively. The control unit 142 controls each of the above-described components in accordance with a series of steps required for processing the workpiece 11 .

In addition, the chuck table 134 of the laser processing apparatus 102 may have a function as the holding table 4 of the inspection apparatus 2 . In this way, by using the chuck table 134 as the holding table 4, the holding table 4 can be omitted. In this case, the light source 6 , the projection surface 8 , the imaging unit (imaging member) 10 , and the like are arranged on the chuck table 134 . Likewise, the control unit 142 may function as the determination unit 12 of the inspection apparatus 2 . In this case, the determination unit 12 can be omitted.

Furthermore, the inspection apparatus 2 of the above-described embodiment may be incorporated into an expansion device for expanding a tape (dicing tape). FIGS. 10(A) and 10(B) are partial cross-sectional side views schematically showing a configuration example of an expansion device incorporating the inspection device 2 and an expansion and division step using the expansion device. In addition, in the case of using this expansion device, in the above-mentioned tape bonding step (dicing tape bonding step), etc., the tape 41 having a larger diameter than the workpiece 11 is bonded to the workpiece 11, and is An annular frame 43 is fixed to the outer peripheral portion of the belt 41 .

As shown in FIGS. 10(A) and 10(B) , the expansion device 52 includes a support structure (holding table) 54 that supports the workpiece 11 from the side via the belt 41 and the frame 43 , and a cylinder A shaped expansion drum (support base, holding table) 56 supports the workpiece 11 from below with the belt 41 interposed therebetween. For example, the inner diameter of the expansion drum 56 is larger than the diameter of the workpiece 11 , and the outer diameter of the expansion drum 56 is smaller than the inner diameter of the frame 43 fixed to the belt 41 .

The support structure 54 includes a frame support table 58 that supports the frame 41 . The upper surface of the frame support table 58 serves as a support surface for supporting the frame 43 fixed to the outer peripheral portion of the belt 41 . A plurality of jigs 60 for fixing the frame 41 are provided on the outer peripheral portion of the frame support table 58 .

A lift mechanism (expansion member) 62 is provided below the support structure 54 . The elevating mechanism 62 includes a cylinder tube 64 fixed to a base (not shown) below, and a piston rod 66 inserted into the cylinder tube 64 . A frame support table 58 is fixed to the upper end of the piston rod 66 .

The elevating mechanism 62 elevates the support structure 54 so that the upper surface (support surface) of the frame support table 58 is between a reference position having a height equal to the upper end of the expansion drum 56 and an expansion position lower than the upper end of the expansion drum 56 move. The operation of the elevating mechanism 62 is controlled by, for example, a control unit (control member) 68 connected to the elevating mechanism 62 .

Above the support structure 54 and the expansion drum 56 , the light source 6 , the projection surface 8 , the imaging unit (imaging means) 10 and the like that constitute the inspection device 2 are arranged. In addition, the support structure 54 of the expansion device 52 or the expansion drum 56 functions as the holding table 4 of the inspection device 2 . Of course, the holding table 4 may also be provided separately from the support structure 54 or the expansion drum 56 .

When performing the expansion and division step of expanding the belt 41 to divide the workpiece 11, first, as shown in FIG. 10(A) , the frame 43 is placed on the frame support table 58 moved to the reference position. surface, and the frame 43 is fixed with the clamp 60 . Thereby, the upper end of the expansion drum 56 is brought into contact with the belt 41 between the workpiece 11 and the frame 43 .

Next, the support structure 54 is lowered by the elevating mechanism 62, and as shown in FIG. As a result, the expansion drum 56 rises with respect to the frame support table 58, and the belt 41 is pushed up by the expansion drum 56 to expand radially.

When the belt 41 is expanded, a force (radial force) in a direction in which the belt 41 is expanded is applied to the workpiece 11 . Thereby, the workpiece 11 is divided into a plurality of chips with the modified layer 17 as the starting point of fracture, and the interval between the adjacent chips is expanded. Before and after the extended division step, for example, the above-described imaging step may be performed to inspect the workpiece 11 .

FIG. 11 is a diagram showing an example of a projected image after the expansion division step. In the expansion and division step, the workpiece 11 is divided into a plurality of chips, and the width of the shadow 33 is also widened when the interval between the adjacent chips is expanded. In addition, since the stress (internal stress) generated during grinding of the workpiece 11 remains in the chips divided from the modified layer 17 as a starting point, the chips are slightly bent due to the stress. As a result, the light L1 emitted to the chips is slightly condensed, and a projected image including the shadow 33 that further emphasizes the distance between the chips is obtained.

Thereby, by detecting the width of the shadow 33 by image processing or the like, and comparing it with a predetermined reference width (reference value, condition), it is possible to reliably determine whether or not the workpiece 11 is appropriately divided and the chip Whether the distance between them is appropriate, etc. In addition, when the grinding step of grinding the back surface 11b of the workpiece 11 is not performed, the stress (internal stress) generated when the device 15 or the like is patterned remains in the workpiece 11 . The same effect of emphasizing the shadow 33 is obtained by the warping of the chip caused by this stress.

In addition, the photographing step may be performed in parallel (simultaneously) with the extended division step. For example, by using a camera capable of high-speed imaging as the imaging unit 6 and imaging the projection image 31 in the expansion and division step, it is possible to check the progress of the fracture. Then, the speed at the time of expanding the belt 41 , the direction of expansion, the type of the belt 41 , and the like are set based on the result of the confirmation, whereby the workpiece 11 can be divided more reliably.

Furthermore, the control unit 68 may function as the determination unit 12 of the inspection apparatus 2 . In this case, the determination unit 12 can be omitted.

In addition, in the above-described embodiment, the back surface grinding step is performed before the reforming layer forming step, but the back surface grinding process and the like may be omitted. In addition, the back surface grinding step may be performed after the reforming layer forming step. Moreover, although the back surface 11b of the to-be-processed object 11 is exposed in the said embodiment, when exposing the front surface 11a of the to-be-processed object 11, the to-be-processed object 11 can be inspected by the same method.

In addition to this, the structure, method, and the like of the above-described embodiments can be appropriately changed and implemented without departing from the scope of the present invention.

Claims (8)

1. A method for inspecting a workpiece, comprising the steps of:

a modified layer forming step of forming a modified layer serving as a starting point for breaking a workpiece in the workpiece by irradiating the workpiece with a laser beam having a wavelength that is transparent to the workpiece, and forming irregularities corresponding to the modified layer on an exposed surface of the workpiece;

an imaging step of forming a projected image in which the irregularities are emphasized by reflecting light emitted from the light source on the exposed surface of the workpiece and irradiating the reflected light onto a projection surface, and imaging the projected image to form an image; and

a determination step of determining a state of the modified layer based on the image.

2. The method of inspecting a workpiece according to claim 1,

the object to be processed is a wafer having devices formed in regions on the front surface side divided by the plurality of lines to divide,

the modified layer is formed along the line to divide.

3. The method of inspecting a workpiece according to claim 1 or 2,

the method for inspecting the workpiece includes the following steps:

a dicing tape bonding step of bonding a dicing tape to the workpiece before the modified layer forming step; and

a spreading and dividing step of spreading the dicing tape to apply a force to the object to be processed after the modified layer forming step, and dividing the object to be processed into a plurality of chips with the modified layer as a starting point of breaking,

the expanding and dividing step is performed in parallel with the photographing step.

4. An inspection apparatus for inspecting a modified layer of a workpiece, the workpiece being irradiated with a laser beam having a transmissive wavelength to form the modified layer therein as a starting point of fracture, and an exposed surface of the workpiece having irregularities corresponding to the modified layer, the inspection apparatus comprising:

a holding table for holding a workpiece;

a light source that irradiates the exposed surface of the workpiece held on the holding table with light;

a projection surface that forms a projection image in which the irregularities are emphasized by light from the light source reflected by the irradiated object;

an imaging means for imaging the projection image formed on the projection surface to form an image; and

and a determination means for comparing the formed image with a predetermined condition to determine the state of the modified layer.

5. A laser processing apparatus is characterized by comprising:

a chuck table for holding a workpiece;

a laser beam irradiation means for irradiating the workpiece held on the chuck table with a laser beam to form a modified layer serving as a starting point for breaking the workpiece inside the workpiece and to form irregularities corresponding to the modified layer on an exposed surface of the workpiece;

a holding table that holds the workpiece irradiated with the laser beam;

a light source that irradiates the exposed surface of the workpiece held on the holding table with light;

a projection surface that forms a projection image in which the irregularities are emphasized by light from the light source reflected by the irradiated object;

an imaging means for imaging the projection image formed on the projection surface to form an image;

a determination means for comparing the formed image with a predetermined condition to determine the state of the modified layer; and

and a control means for controlling each component.

6. Laser processing apparatus according to claim 5,

the holding table is the chuck table.

7. An expansion device, characterized in that the expansion device has:

a support base for supporting a workpiece by a dicing tape adhered to the workpiece, the workpiece being irradiated with a laser beam having a wavelength which is transparent to the laser beam to form a modified layer therein as a starting point of fracture, and the workpiece having an exposed surface on which irregularities corresponding to the modified layer are formed;

an expanding member that expands the dicing tape;

a holding table for holding the workpiece;

a light source that irradiates the exposed surface of the workpiece held on the holding table with light;

a projection surface that forms a projection image in which the irregularities are emphasized by light from the light source reflected by the irradiated object;

an imaging means for imaging the projection image formed on the projection surface to form an image;

a determination means for comparing the formed image with a predetermined condition to determine the state of the modified layer; and

and a control means for controlling each component.

8. The extension device of claim 7,

the holding table is the supporting base.

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