JP7242140B2 - Aberration confirmation method - Google Patents

Description

The present invention relates to an aberration confirmation method used when confirming aberration due to an optical system of a laser beam irradiation unit.

Device chips to be incorporated into various types of electronic equipment are manufactured by dividing the surface of a wafer, which is the base material, into multiple areas by division lines called streets. It is obtained by dividing along the planned division line. When dividing a plate-shaped workpiece such as a wafer, for example, a laser processing apparatus equipped with a laser beam irradiation unit that can irradiate a laser beam with a wavelength that is absorbed by the workpiece is used (for example, patent Reference 1).

A laser beam irradiation unit generally includes a laser oscillator and an optical system made up of a plurality of optical components, and the laser beam generated by the laser oscillator is guided to a workpiece by the optical system. By using this laser beam irradiation unit to irradiate a laser beam so as to converge on the surface or inside of a work piece, a groove or the like can be formed in the work piece by so-called ablation processing.

By the way, if the laser beam used for ablation processing cannot be sufficiently focused, the processing of the workpiece is likely to be adversely affected. Therefore, it is important to appropriately manage astigmatism due to the optical system of the laser beam irradiation unit so that the laser beam can be sufficiently focused.

JP 2007-275912 A

As a method of confirming astigmatism as described above, for example, a laser beam is irradiated to a workpiece under a plurality of conditions in which the height of the optical system (position in the Z-axis direction) is different to form a machining mark, There is a method of confirming the width of this processing mark in two mutually perpendicular directions (X-axis direction and Y-axis direction). However, in this method, a plurality of machining marks are formed on the workpiece, and then the relationship between the width of the machining marks and the height of the optical system is graphed, which requires a great deal of time and labor. there were.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and an object of the present invention is to provide an aberration confirmation method that enables easy confirmation of aberration due to an optical system of a laser beam irradiation unit.

According to one aspect of the present invention, there is provided an aberration confirmation method for confirming aberration due to an optical system of a laser beam irradiation unit that irradiates a laser beam having a wavelength that can be absorbed by a workpiece, the upper surface being inclined with respect to the lower surface. A part of the optical system is positioned at a position of a predetermined height with respect to the lower surface of the first workpiece including the By relatively moving the first workpiece and the part of the optical system along the lower surface in the first direction, a first groove having a region narrower than both ends and opening to the upper surface is formed. forming the part of the optical system on the first workpiece; and move the second workpiece and the portion of the optical system along the bottom surface in the first direction while focusing the laser beam at a position flush with a portion of the top surface. a second processing step of forming, in the second workpiece, a second groove having regions narrower than both ends and opening in the upper surface by relatively moving the groove in a second direction perpendicular to the second workpiece; a first identifying step of identifying a first region where the laser beam is most focused on the top surface of the first workpiece based on the width of one groove; Aberration by the optical system is confirmed from a second identification step of identifying a second region where the light is most focused on the upper surface of the second workpiece, and the position of the first region and the position of the second region. Aberration confirmation method is provided, comprising: an aberration confirmation step;

According to another aspect of the present invention, there is provided an aberration confirmation method for confirming an aberration due to an optical system of a laser beam irradiation unit that irradiates a laser beam having a wavelength that can be absorbed by a workpiece, the aberration confirmation method comprising: While continuously changing the height of a part of the optical system with reference to the lower surface of the first workpiece including the upper surface, and the first workpiece and the part of the optical system By irradiating the first workpiece with the laser beam while relatively moving along the lower surface in the first direction, the first groove having regions narrower than both ends and opening to the upper surface is formed. a first processing step of forming a first workpiece; and continuously varying the height of the portion of the optical system with reference to the lower surface of the second workpiece including the upper surface parallel to the lower surface while relatively moving the second workpiece and the part of the optical system along the lower surface in a second direction perpendicular to the first direction, a second processing step of irradiating an object with the laser beam to form, in the second workpiece, a second groove having regions narrower than both ends and opening in the upper surface; and a width of the first groove. a first identifying step of identifying a first region where the laser beam is most focused on the top surface of the first workpiece based on a width of the second groove; a second identification step of identifying a second region where the light is most focused on the upper surface of the object; and an aberration confirmation step of confirming aberration due to the optical system from the position of the first region and the position of the second region. Aberration checking methods are provided, including:

In the above-described aberration confirmation method, if the aberration confirmed in the aberration confirmation step is within an allowable range, it is determined that there is no need to adjust the optical system, and the aberration confirmed in the aberration confirmation step is outside the allowable range, the step of determining that the optical system needs to be adjusted may be further included. Moreover, in the aberration confirmation method described above, the first workpiece may be used as the second workpiece.

In an aberration confirmation method according to an aspect of the present invention, while condensing a laser beam at a position of a predetermined height, a first workpiece including an inclined upper surface and a part of an optical system are placed relative to each other in a first direction. By moving the substrate symmetrically, a first groove having an area narrower than both ends and having an open upper surface is formed. Also, while focusing the laser beam at a predetermined height position, the second workpiece including the inclined upper surface and the part of the optical system are moved relatively in a second direction perpendicular to the first direction. By moving, a second groove having an area narrower than both ends and having an open upper surface is formed.

The width of the first groove thus formed represents the size of the laser beam in the second direction, and is the smallest in the first region where the laser beam is most focused on the top surface of the first workpiece. Also, the width of the second groove represents the size of the laser beam in the first direction, and is the smallest in the second region where the laser beam is most focused on the upper surface of the second workpiece. Therefore, by specifying the first region and the second region, it is possible to easily check how the laser beam is focused in the first direction and how the laser beam is focused in the second direction from the positional relationship between the regions. can. That is, the aberration due to the optical system of the laser beam irradiation unit can be easily confirmed.

Similarly, in an aberration confirmation method according to another aspect of the present invention, while continuously changing the height of a part of the optical system, the first workpiece including the upper surface parallel to the lower surface and the optical system by relatively moving in the first direction, a first groove having an area narrower than both ends and having an open upper surface is formed. Further, while continuously changing the height of the part of the optical system, the second workpiece including the upper surface parallel to the lower surface and the part of the optical system are moved in the second direction perpendicular to the first direction. By relatively moving, a second groove having a narrower width than both ends and an open upper surface is formed.

The width of the first groove thus formed represents the size of the laser beam in the second direction, and is the smallest in the first region where the laser beam is most focused on the top surface of the first workpiece. Also, the width of the second groove represents the size of the laser beam in the first direction, and is the smallest in the second region where the laser beam is most focused on the upper surface of the second workpiece. Therefore, by specifying the first region and the second region, it is possible to easily check how the laser beam is focused in the first direction and how the laser beam is focused in the second direction from the positional relationship between the regions. can. That is, the aberration due to the optical system of the laser beam irradiation unit can be easily confirmed.

It is a perspective view which shows the structural example of a laser processing apparatus. It is a perspective view which shows the structural example of a to-be-processed object. FIG. 3A is a side view schematically showing how a workpiece is irradiated with a laser beam, and FIG. 3B is a diagram showing how a groove (first groove) is formed in the workpiece. It is a perspective view showing typically. It is a top view which shows typically the whole image of a groove|channel (1st groove|channel). FIG. 5(A) is a side view schematically showing how a laser beam is irradiated onto a workpiece, and FIG. 5(B) shows how a groove (second groove) is formed on the workpiece. It is a perspective view showing typically. It is a top view which shows typically the whole image of a groove|channel (2nd groove|channel). FIG. 4 is a plan view schematically showing two grooves arranged so that their longitudinal directions are parallel to each other; FIG. 11 is a side view schematically showing how a laser beam is applied to a workpiece according to a modification;

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view showing a configuration example of a laser processing apparatus 2 in which the aberration checking method according to this embodiment is used. In addition, in FIG. 1, some components of the laser processing apparatus 2 are shown as functional blocks. Also, the X-axis direction (processing feed direction), the Y-axis direction (indexing feed direction), and the Z-axis direction (height direction) used in the following description are perpendicular to each other.

As shown in FIG. 1, the laser processing apparatus 2 includes a base 4 that supports each component. A horizontal movement mechanism (processing feed mechanism, index feed mechanism) 6 is arranged on the upper surface of the base 4 . The horizontal movement mechanism 6 includes a pair of Y-axis guide rails 8 fixed to the upper surface of the base 4 and substantially parallel to the Y-axis direction. A Y-axis moving table 10 is slidably attached to the Y-axis guide rail 8 .

A nut portion (not shown) is provided on the lower surface side of the Y-axis moving table 10 . A Y-axis ball screw 12 substantially parallel to the Y-axis guide rail 8 is screwed into the nut portion of the Y-axis moving table 10 . A Y-axis pulse motor 14 is connected to one end of the Y-axis ball screw 12 . When the Y-axis ball screw 12 is rotated by the Y-axis pulse motor 14, the Y-axis moving table 10 moves along the Y-axis guide rail 8 in the Y-axis direction.

A pair of X-axis guide rails 16 that are substantially parallel to the X-axis direction are provided on the upper surface of the Y-axis moving table 10 . An X-axis moving table 18 is slidably attached to the X-axis guide rail 16 . A nut portion (not shown) is provided on the lower surface side of the X-axis moving table 18 .

An X-axis ball screw 20 substantially parallel to the X-axis guide rail 16 is screwed into the nut portion of the X-axis moving table 18 . An X-axis pulse motor 22 is connected to one end of the X-axis ball screw 20 . When the X-axis ball screw 20 is rotated by the X-axis pulse motor 22, the X-axis moving table 18 moves along the X-axis guide rail 16 in the X-axis direction.

A columnar table base 24 is arranged on the upper surface side of the X-axis moving table 18 . A chuck table (holding table) 26 used to hold the workpiece 11 (see FIG. 2) is arranged above the table base 24 . A rotary drive source (not shown) such as a motor is connected to the lower portion of the table base 24 .

The chuck table 26 rotates around a rotation axis substantially parallel to the Z-axis direction by the force generated from this rotational drive source. The table base 24 and the chuck table 26 are moved in the X-axis direction and the Y-axis direction (processing feed, indexing feed) by the horizontal movement mechanism 6 described above.

FIG. 2 is a perspective view showing a configuration example of the workpiece 11. As shown in FIG. As shown in FIG. 2, the workpiece 11 used in this embodiment is formed in a plate shape having a substantially flat lower surface 11b and an upper surface 11a inclined with respect to the lower surface 11b. That is, the workpiece 11 includes a plurality of regions having different thicknesses (distances from the lower surface 11b to the upper surface 11a).

The workpiece 11 is obtained, for example, by tilting a flat substrate made of a semiconductor material such as silicon and then grinding the upper surface side (or the lower surface side) of this substrate. Alternatively, for example, the workpiece 11 may be obtained by coating the upper surface (or the lower surface) of a flat substrate made of a semiconductor material such as silicon with a film made of polyimide or the like.

When processing the workpiece 11 with the laser processing apparatus 2, an adhesive tape (dicing tape) 13 (see FIG. 3A) having a diameter larger than that of the workpiece 11 is applied to the lower surface 11b of the workpiece 11. ) is attached. Further, an annular frame 15 (see FIG. 3B, etc.) is fixed to the outer peripheral portion of the adhesive tape 13 . That is, the workpiece 11 is supported by the frame 15 via the adhesive tape 13 .

The material, shape, structure, size, etc. of the workpiece 11 are not limited. For example, the workpiece 11 obtained from a substrate made of a material other than silicon, such as semiconductors, ceramics, resins, and metals, may be used. Further, if the workpiece 11 can be properly held by the chuck table 26 , the adhesive tape 13 does not necessarily have to be attached to the lower surface 11 b of the workpiece 11 .

A part of the upper surface of the chuck table 26 is made of, for example, a porous material, and serves as a holding surface 26a for holding the workpiece 11 . The holding surface 26 a is formed substantially parallel to the X-axis direction and the Y-axis direction, and is connected to a suction source (not shown) through a suction path (not shown) provided inside the chuck table 26 . It is connected. Also, four clamps 28 are provided around the chuck table 26 to fix the annular frame 15 that supports the workpiece 11 .

A columnar support structure 30 having side surfaces substantially perpendicular to the X-axis direction is provided in a region on one side of the horizontal movement mechanism 6 in the Y-axis direction. A vertical movement mechanism (height adjustment mechanism) 32 is arranged on the side surface of the support structure 30 . The vertical movement mechanism 32 includes a pair of Z-axis guide rails 34 fixed to the side surfaces of the support structure 30 and substantially parallel to the Z-axis direction. A Z-axis moving table 36 is slidably attached to the Z-axis guide rail 34 .

A nut portion (not shown) is provided on the back side of the Z-axis moving table 36 (on the Z-axis guide rail 34 side). A Z-axis ball screw (not shown) substantially parallel to the Z-axis guide rail 34 is screwed into the nut portion of the Z-axis moving table 36 . A Z-axis pulse motor 38 is connected to one end of the Z-axis ball screw. When the Z-axis pulse motor 38 rotates the Z-axis ball screw, the Z-axis moving table 36 moves along the Z-axis guide rail 34 in the Z-axis direction.

A support 40 is fixed to the surface side of the Z-axis moving table 36 , and a part of the laser beam irradiation unit 42 is supported by the support 40 . The laser beam irradiation unit 42 includes, for example, a laser oscillator (not shown) fixed to the base 4, a tubular housing 44 supported by the support 40, and an end portion of the housing 44 in the Y-axis direction. and an irradiation head 46 .

The laser oscillator includes, for example, a laser medium such as Nd:YAG suitable for laser oscillation, generates a laser beam having a wavelength that can be absorbed by the workpiece 11, and emits the laser beam toward the housing 44 side. The housing 44 accommodates a part of the optical system that constitutes the laser beam irradiation unit 42 and guides the laser beam emitted from the laser oscillator to the irradiation head 46 . This optical system is mainly composed of optical parts such as mirrors and lenses.

Another part of the optical system that constitutes the laser beam irradiation unit 42 is provided in the irradiation head 46 . For example, the irradiation head 46 changes the course of the laser beam guided from the housing 44 downward by a mirror (not shown) or the like, and the laser beam is directed to a predetermined height by a condensing lens 46a (see FIG. 3A, etc.). converge on

An imaging unit 48 fixed to the housing 44 of the laser beam irradiation unit 42 is arranged in a region on one side of the irradiation head 46 in the X-axis direction. The imaging unit 48 includes, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, a CCD (Charge Coupled Device) image sensor, or the like, and is used when imaging the upper surface 11a side of the workpiece 11 held by the chuck table 26. be done.

The top of the base 4 is covered with a cover (not shown) that can accommodate each component. A touch panel type display (input/output unit) 50 serving as a user interface is arranged on the side surface of the cover. For example, various conditions applied when processing the workpiece 11 are input to the laser processing apparatus 2 via this display 50 . Also, the image generated by the imaging unit 48 is displayed on the display 50 .

Components such as the horizontal movement mechanism 6 , the vertical movement mechanism 32 , the laser beam irradiation unit 42 , the imaging unit 48 , the display 50 and the like are each connected to a control section (control unit) 52 . The control unit 52 controls each component described above in accordance with a series of steps required for machining the workpiece 11 .

The control unit 52 is typically configured by a computer including a processing device such as a CPU (Central Processing Unit) and a storage device such as a flash memory. The functions of the control unit 52 are realized by operating the processing device and the like according to the software stored in the storage device.

When processing the workpiece 11 using the laser processing apparatus 2, first, the workpiece 11 is placed on the chuck table 26 via the adhesive tape 13 attached to the lower surface 11b, and the negative pressure of the suction source is maintained. Act on surface 26a. As a result, the workpiece 11 is held on the chuck table 26 and its upper surface 11a is exposed. Note that the frame 15 is fixed by four clamps 28 .

After the workpiece 11 is held by the chuck table 26, for example, while the chuck table 26 is moved in the X-axis direction by the horizontal movement mechanism 6, the laser beam 21 is emitted downward from the irradiation head 46 of the laser beam irradiation unit 42. do. The position (height) of the irradiation head 46 in the Z-axis direction is adjusted, for example, so that the laser beam 21 is condensed at a predetermined height from the lower surface 11b of the workpiece 11 .

As a result, the workpiece 11 is irradiated with the laser beam 21 along the movement path of the chuck table 26, and the upper surface 11a side of the workpiece 11 can be processed by the laser beam 21 (ablation processing). Here, since the workpiece 11 and the irradiation head 46 move relatively along the X-axis direction, a groove along the X-axis direction is formed on the upper surface 11a side of the workpiece 11 .

As described above, the imaging unit 48 is fixed to the housing 44 of the laser beam irradiation unit 42 and arranged on one side of the irradiation head 46 in the X-axis direction. Therefore, for example, after forming a groove along the X-axis direction in the workpiece 11 , the groove can be imaged by the imaging unit 48 by moving the chuck table 26 in the X-axis direction.

In the aberration confirmation method of this embodiment, first, while irradiating the laser beam 21 from the irradiation head (a part of the optical system) 46 positioned at a predetermined height, the workpiece 11 (first workpiece) and the irradiation head 46 are relatively moved along the X-axis direction (first direction) to form a groove (first groove) in the workpiece 11 (first processing step).

FIG. 3A is a side view schematically showing how a laser beam 21 is applied to a workpiece 11, and FIG. 3B shows a groove (first groove) 11c in the workpiece 11. It is a perspective view which shows a mode that it is formed typically. Specifically, first, the workpiece 11 is held by the chuck table 26 so that a plurality of regions having different thicknesses (distances from the lower surface 11b to the upper surface 11a) are arranged along the X-axis direction. In other words, the workpiece 11 is held by the chuck table 26 so that the thickness of the workpiece 11 varies along the X-axis direction.

Further, as shown in FIG. 3A, the height of the irradiation head 46 is adjusted by the vertical movement mechanism 32 so that the laser beam 21 is condensed at the position of the height H1 with the lower surface 11b of the workpiece 11 as a reference. to adjust. In this embodiment, the height H1 is set to a value smaller than the maximum thickness of the workpiece 11 and larger than the minimum thickness of the workpiece 11 . More specifically, the value of the height H1 is set so that the laser beam 21 is condensed at the same height position as part of the upper surface 11a of the workpiece 11 .

In this state, the horizontal movement mechanism 6 moves the chuck table 26 holding the workpiece 11 in the X-axis direction while irradiating the laser beam 21 downward from the irradiation head 46 . That is, the irradiation head 46 is positioned at a predetermined height position with respect to the lower surface 11b of the workpiece 11, and the laser beam 21 is condensed at the same height position as a part of the upper surface 11a. 11 and the irradiation head 46 are relatively moved in the X-axis direction along the lower surface 11b.

As a result, the laser beam 21 irradiated to the workpiece 11 forms a groove 11c in the workpiece 11 that opens in the upper surface 11a and extends in the X-axis direction, as shown in FIG. 3B. In this embodiment, as shown in FIG. 3A, as the chuck table 26 moves, there are two states: a state a in which the focal point 23 is positioned below the upper surface 11a, and a state a in which the focal point 23 is positioned on the upper surface 11a. b and a state c in which the condensing point 23 is located above the upper surface 11a are realized in order.

State a in which the condensing point 23 is positioned below the upper surface 11a and state c in which the condensing point 23 is positioned above the upper surface 11a are different from state b in which the condensing point 23 is positioned on the upper surface 11a. A wide area of the upper surface 11a is irradiated with a laser beam 21. As shown in FIG. Therefore, the width (the length in the Y-axis direction) of the groove 11c formed in the states a and c is wider than the width of the groove 11c formed in the state b.

FIG. 4 is a plan view schematically showing an overall image of the groove 11c. As shown in FIG. 4, the workpiece 11 has a width narrower than the width (length in the Y-axis direction) at one end A in the length direction (X-axis direction) and the width at the other end B in the length direction. Thus, a groove 11c having a region of is formed. The groove 11c (the groove 11c of the first region 11d in FIG. 4) formed in the state b in which the condensing point 23 is positioned on the upper surface 11a has the narrowest width of the entire groove 11c.

After forming the groove 11c in the workpiece 11, for example, the groove 11c is imaged from above to obtain an image (first image acquisition step). Specifically, for example, after forming the groove 11 c in the workpiece 11 , the chuck table 26 is moved in the X-axis direction to position the groove 11 c below the imaging unit 48 .

Then, the image pickup unit 48 picks up an image of the lower groove 11c. In this case, it is preferable to move the imaging unit 48 in the Z-axis direction and focus the imaging unit 48 on the groove 11c. Thereby, an image in which the groove 11c is reflected can be acquired. The image acquired by the imaging unit 48 is stored, for example, in the control section 52 and displayed on the display 50 as necessary.

When only part of the groove 11c is imaged by the imaging unit 48, another part of the groove 11c is imaged in the same procedure. This procedure is repeated, for example, to the extent that the entire image of the groove 11c shown in FIG. 4 can be grasped. That is, the above procedure is repeated to acquire a plurality of images showing different portions of the groove 11c.

Of course, if the entire groove 11c can be imaged at once, there is no need to acquire a plurality of images. Moreover, even when acquiring a plurality of images, it is not necessary to repeat the above procedure under the condition that the entire groove 11c can be completely grasped. That is, the grooves 11c may be imaged at a certain wide interval along the X-axis direction.

After obtaining the image showing the groove 11c, a groove (second groove) is formed in the same procedure on another workpiece 11 (second workpiece) (second processing step). However, this groove is formed by relatively moving the workpiece 11 and the irradiation head 46 along the Y-axis direction (second direction) perpendicular to the X-axis direction.

FIG. 5A is a side view schematically showing how a laser beam 21 is applied to a workpiece 11, and FIG. 5B shows a groove (second groove) 11e in the workpiece 11. It is a perspective view which shows a mode that it is formed typically. Specifically, first, the workpiece 11 is held by the chuck table 26 so that a plurality of regions having different thicknesses (distances from the lower surface 11b to the upper surface 11a) are arranged along the Y-axis direction.

In other words, the workpiece 11 is held by the chuck table 26 so that the thickness of the workpiece 11 varies along the Y-axis direction. In addition, in this embodiment, as the workpiece 11, a workpiece equivalent to the workpiece 11 in which the grooves 11c are formed is used. As a result, conditions such as the inclination of the upper surface 11a with respect to the lower surface 11b are approximately the same for the two workpieces 11, so the amount of calculation required to confirm aberrations caused by the optical system of the laser beam irradiation unit 42 is reduced. .

More specifically, the inclination of the upper surface 11a of the workpiece 11 (second workpiece) in the YZ cross section is the same as the inclination of the upper surface of the workpiece 11 (first workpiece) in the XZ cross section when forming the groove 11c. It is preferable to hold the workpiece 11 by the chuck table 26 so that the inclination is approximately the same as the inclination of the workpiece 11a.

Further, as shown in FIG. 5A, the height of the irradiation head 46 is adjusted by the vertical movement mechanism 32 so that the laser beam 21 is condensed at the position of the height H2 with the lower surface 11b of the workpiece 11 as a reference. to adjust. In this embodiment, the height H2 is set to a value smaller than the maximum thickness of the workpiece 11 and larger than the minimum thickness of the workpiece 11 .

More specifically, the value of the height H2 is set so that the laser beam 21 is condensed at the same height position as a part of the upper surface 11a of the workpiece 11 . In this embodiment, since the groove 11e is formed in the workpiece 11 equivalent to the workpiece 11 in which the groove 11c is formed, the value of the height H2 should be equal to the value of the height H1.

In this state, the horizontal movement mechanism 6 moves the chuck table 26 holding the workpiece 11 in the Y-axis direction while irradiating the laser beam 21 downward from the irradiation head 46 . That is, the irradiation head 46 is positioned at a predetermined height position with respect to the lower surface 11b of the workpiece 11, and the laser beam 21 is condensed at the same height position as a part of the upper surface 11a. 11 and the irradiation head 46 are relatively moved in the Y-axis direction along the lower surface 11b.

As a result, a groove 11e that opens in the upper surface 11a and extends in the Y-axis direction is formed in the workpiece 11 by the laser beam 21 irradiated to the workpiece 11, as shown in FIG. 5B. In this embodiment, as shown in FIG. 5(A), as the chuck table 26 moves, there is a state a in which the condensing point 23 is positioned below the upper surface 11a, and a state a in which the condensing point 23 is positioned on the upper surface 11a. b and a state c in which the condensing point 23 is located above the upper surface 11a are realized in order.

State a in which the condensing point 23 is positioned below the upper surface 11a and state c in which the condensing point 23 is positioned above the upper surface 11a are different from state b in which the condensing point 23 is positioned on the upper surface 11a. A wide area of the upper surface 11a is irradiated with a laser beam 21. As shown in FIG. Therefore, the width (the length in the X-axis direction) of the groove 11e formed in the states a and c is wider than the width of the groove 11e formed in the state b.

FIG. 6 is a plan view schematically showing the overall image of the groove 11e. As shown in FIG. 6, the workpiece 11 has a width narrower than the width (length in the X-axis direction) at one end A in the length direction (Y-axis direction) and the width at the other end B in the length direction. Thus, a groove 11e having a region of is formed. The width of the groove 11e (the groove 11e of the second region 11f in FIG. 6) formed in the state b in which the condensing point 23 is positioned on the upper surface 11a is the narrowest among all the grooves 11e.

As described above, in this embodiment, the groove 11e is formed in the workpiece 11 equivalent to the workpiece 11 having the groove 11c formed therein. In this case, the relative movement distance between the workpiece 11 and the irradiation head 46 when forming the groove 11e is the relative distance between the workpiece 11 and the irradiation head 46 when forming the groove 11c. It is better to make it the same as the distance of movement.

That is, in this embodiment, the grooves 11c and 11e having approximately the same length are formed. In addition, since the inclination of the upper surface 11a with respect to the lower surface 11b of the two workpieces 11 is approximately the same, the inclination of the grooves 11c and the inclination of the grooves 11e are also approximately the same. In other words, the height difference between one end A and the other end B of the groove 11c (difference in position in the thickness direction of the workpiece 11) is approximately the same as the height difference between the one end A and the other end B of the groove 11e. . This reduces the amount of computation required to confirm aberrations caused by the optical system, compared to the case of forming two grooves with different inclinations.

After forming the groove 11e in the workpiece 11, for example, the groove 11e is imaged from above to obtain an image (second image acquisition step). Specifically, for example, after forming the groove 11 e in the workpiece 11 , the chuck table 26 is moved in the Y-axis direction to position the groove 11 e below the imaging unit 48 .

Then, the image pickup unit 48 picks up an image of the lower groove 11e. In this case, it is preferable to move the imaging unit 48 in the Z-axis direction and focus the imaging unit 48 on the groove 11e. As a result, an image showing the groove 11e can be acquired. The image acquired by the imaging unit 48 is stored, for example, in the control section 52 and displayed on the display 50 as necessary.

When only part of the groove 11e is imaged by the imaging unit 48, another part of the groove 11e is imaged in the same procedure. This procedure is repeated, for example, to the extent that the entire image of the groove 11e shown in FIG. 6 can be grasped. That is, the above procedure is repeated to obtain a plurality of images showing different portions of the groove 11e.

Of course, if the entire groove 11e can be imaged at once, there is no need to acquire a plurality of images. Moreover, even when acquiring a plurality of images, it is not necessary to repeat the above procedure under the condition that the entire groove 11e can be completely grasped. That is, the grooves 11e may be imaged at a certain wide interval along the Y-axis direction.

After acquiring the image of the groove 11c, the first region 11d where the laser beam 21 is most focused on the upper surface 11a of the workpiece 11 is specified based on the width of the groove 11c (first specifying step). As described above, the groove 11c has the narrowest width in the first region 11d. Therefore, the first region 11d can be specified by extracting the narrowest position of the groove 11c from the obtained image of the groove 11c along the length direction of the groove 11c.

Specifically, for example, the control unit 52 performs processing such as edge detection on the acquired image of the groove 11c, and a pair of edges forming the contour of the groove 11c at an arbitrary position in the length direction of the groove 11c. Calculate the coordinates of the edge of . Then, the width of the groove 11c at the target position is calculated from the coordinates of these two edges. This procedure is repeated until the position where the groove 11c has the narrowest width can be appropriately extracted.

That is, the width of the groove 11c is calculated at a plurality of positions along the length of the groove 11c. After calculating the width of the groove 11c at a plurality of positions, the controller 52 extracts the position where the width of the groove 11c is the narrowest. Then, this extracted position is stored in the controller 52 as the first region 11d.

Similarly, after acquiring an image showing the groove 11e, the second area 11f where the laser beam 21 is most focused on the upper surface 11a of the workpiece 11 is specified based on the width of the groove 11e (second specifying area 11f). step). As described above, the groove 11e has the narrowest width in the second region 11f. Therefore, the second region 11f can be identified by extracting the narrowest position of the groove 11e from the acquired image of the groove 11e along the length direction of the groove 11e.

Specifically, for example, the control unit 52 performs processing such as edge detection on the acquired image of the groove 11e, and a pair of edges forming the contour of the groove 11e at arbitrary positions in the length direction of the groove 11e. Calculate the coordinates of the edge of . Then, the width of the groove 11e at the target position is calculated from the coordinates of these two edges. This procedure is repeated to the extent that the narrowest position of the groove 11e can be properly extracted.

That is, the width of the groove 11e is calculated at a plurality of positions along the length direction of the groove 11e. After calculating the width of the groove 11e at a plurality of positions, the controller 52 extracts the position where the width of the groove 11e is the narrowest. Then, this extracted position is stored in the control unit 52 as the second area 11f.

After specifying the first region 11d and the second region 11f, the aberration due to the optical system of the laser beam irradiation unit 42 is confirmed based on the positions of the first region 11d and the second region 11f (aberration confirmation step). FIG. 7 is a plan view schematically showing grooves 11c and 11e arranged so that their longitudinal directions are parallel to each other.

As described above, in this embodiment, the grooves 11c and 11e having approximately the same length are formed. Further, the inclination of the groove 11c with respect to the lower surface 11b and the inclination of the groove 11e with respect to the lower surface 11b are approximately the same. Therefore, the aberration caused by the optical system of the laser beam irradiation unit 42 can be easily confirmed by simply comparing the grooves 11c and 11e.

Specifically, for example, as shown in FIG. 7, the position of one end A of the groove 11c and the position of one end A of the groove 11e correspond in the length direction, and the position of the other end B of the groove 11c and the position of the groove 11e The groove 11c and the groove 11e are compared side by side so that the position of the other end B corresponds in the length direction. Since the grooves 11c and 11e are formed along the inclined upper surface 11a of the workpiece 11, the widths of the grooves 11c and 11e at predetermined positions in the length direction are corresponds to the cross-sectional size of the laser beam 21 at a predetermined position in the height direction (Z-axis direction) corresponding to .

That is, the width (length in the Y-axis direction) of the groove 11c at a predetermined position in the length direction corresponds to the width in the Y-axis direction of the cross section of the laser beam 21 at a predetermined position in the height direction. Become. Further, the width (length in the X-axis direction) of the groove 11e at a predetermined position in the length direction corresponds to the width in the X-axis direction of the cross section of the laser beam 21 at a predetermined position in the height direction. Become.

The position of the first region 11d and the position of the second region 11f are shifted by .DELTA. It takes a value corresponding to the position in the height direction where the width in the X-axis direction of the cross section of is minimized and the deviation (that is, astigmatism). Therefore, the aberration caused by the optical system of the laser beam irradiation unit 42 can be easily confirmed from the deviation between the position of the first region 11d and the position of the second region 11f.

Confirmation of this aberration is performed, for example, by an operator. Of course, the aberration may be confirmed by arithmetic processing of the control unit 52 or the like. Moreover, there is no particular limitation on the specific confirmation method. For example, the degree of aberration may be specifically calculated based on the amount of deviation Δ between the position of the first region 11d and the position of the second region 11f.

As described above, in the aberration confirmation method according to the present embodiment, while condensing the laser beam 21 at the position of the predetermined height H1, the workpiece 11 (first workpiece) including the inclined upper surface 11a and By relatively moving the irradiation head (a part of the optical system) 46 in the X-axis direction (first direction), an area narrower than both ends (one end A and the other end B) is formed and an opening is formed on the upper surface 11a. Then, a groove (first groove) 11c is formed.

In addition, while condensing the laser beam 21 at a position of a predetermined height H2, the workpiece 11 (second workpiece) including the inclined upper surface 11a and the irradiation head 46 are perpendicular to the X-axis direction. By relatively moving in the Y-axis direction (second direction), a groove (second groove) 11e having a region narrower than both ends (one end A and the other end B) and opening to the upper surface 11a is formed.

The width of the groove 11c thus formed represents the width (size) of the laser beam 21 in the Y-axis direction. is the minimum at The width of the groove 11e represents the width (size) of the laser beam 21 in the X-axis direction, and is the smallest in the second region 11f where the laser beam 21 is most focused on the upper surface 11a of the workpiece 11. .

Therefore, by specifying the first region 11d and the second region 11f, it is possible to determine how the laser beam 21 is focused in the X-axis direction and how it is focused in the Y-axis direction from the positional relationship between these regions. Easy to check. That is, the aberration caused by the optical system of the laser beam irradiation unit 42 can be easily confirmed.

It should be noted that the present invention is not limited to the description of the above-described embodiment and can be implemented with various modifications. For example, after confirming the aberration due to the optical system of the laser beam irradiation unit 42 according to the procedure of the embodiment described above, it may be further determined whether or not this optical system needs to be adjusted (determination step).

In this case, for example, if the amount of deviation Δ between the position of the first region 11d and the position of the second region 11f is within an allowable range, it is determined that there is no need to adjust the optical system. Further, if the amount of deviation Δ between the position of the first region 11d and the position of the second region 11f is out of the allowable range, it is determined that the optical system needs to be adjusted. The permissible range is, for example, 100 μm or less, preferably 50 μm or less, when the deviation amount Δ is converted to a deviation in the height direction.

That is, if the confirmed aberration due to the optical system is within the allowable range, it is determined that there is no need to adjust the optical system, and if the confirmed aberration due to the optical system is outside the allowable range, the optical system is determined to need to be adjusted. This determination may be made by the control unit 52 or by an operator.

In the above-described embodiment, after the workpiece 11 and the irradiation head 46 are relatively moved along the X-axis direction to form the groove 11c, the workpiece 11 and the irradiation head 46 are moved in the Y-axis direction. Although the groove 11e is formed by relatively moving along the .theta., the groove 11c may be formed after the groove 11e is formed. Similarly, the procedures of the above-described embodiments can be interchanged without causing conflict.

Furthermore, in the above-described embodiment, the workpiece 11 in which the grooves 11c are formed and the workpiece 11 in which the grooves 11e are formed are equivalent, but they are not necessarily equivalent. It doesn't have to be. That is, conditions such as the inclination of the upper surface 11a with respect to the lower surface 11b may differ between the workpiece 11 in which the groove 11c is formed and the workpiece 11 in which the groove 11e is formed. In this case, it is desirable that the controller 52 performs various arithmetic processing so that the grooves 11c and 11e can be easily compared.

In the above-described embodiment, one of the two workpieces 11 is formed with the groove 11c and the other of the two workpieces 11 is formed with the groove 11e. and grooves 11e may be formed. That is, the workpiece 11 in which the groove 11c is formed can also be used as the workpiece 11 in which the groove 11e is formed.

In the above-described embodiment, the state a in which the condensing point 23 is positioned below the upper surface 11a, the state b in which the condensing point 23 is positioned on the upper surface 11a, and the state b in which the condensing point 23 is positioned above the upper surface 11a. The workpiece 11 and the irradiation head 46 are moved relative to each other so that the state c, and , are realized in this order, and the state c, state b, and state a are realized in this order. As shown, the workpiece 11 and the irradiation head 46 may be moved relatively.

Further, in the above-described embodiment, the workpiece 11 including the upper surface 11a inclined with respect to the lower surface 11b is used to check the aberration due to the optical system of the laser beam irradiation unit 42. Aberrations due to the optical system of the laser beam irradiation unit 42 can also be checked using a workpiece that includes a parallel top surface.

FIG. 8 is a side view schematically showing how the laser beam 21 is applied to the workpiece 31 according to the modification. The workpiece 31 has generally flat and parallel upper and lower surfaces 31a and 31b. When checking the aberration due to the optical system of the laser beam irradiation unit 42 , an adhesive tape (dicing tape) 33 having a diameter larger than that of the workpiece 31 is attached to the lower surface 31 b of the workpiece 31 . Also, an annular frame (not shown) is fixed to the outer peripheral portion of the adhesive tape 33 .

In this method of confirming aberration using the workpiece 31, first, the height of the irradiation head (part of the optical system) 46 is continuously changed with the lower surface 31b of the workpiece 31 (first workpiece) as a reference. and while moving the workpiece 31 and the irradiation head 46 relatively along the lower surface 31b in the X-axis direction (first direction), the workpiece 31 is irradiated with the laser beam 21. A groove (first groove) having a narrower width and opening to the upper surface 31a is formed in the workpiece 11 (first processing step).

Specifically, first, the workpiece 31 is held by the chuck table 26 . Then, the horizontal movement mechanism 6 moves the chuck table 26 holding the workpiece 31 in the X-axis direction while irradiating the laser beam 21 downward from the irradiation head 46 . At the same time, the height of the irradiation head 46 is continuously raised. In this case, if the height of the irradiation head 46 is changed at a constant speed, the amount of calculation required for confirming the aberration can be reduced.

As a result, the laser beam 21 irradiated to the workpiece 31 forms a groove in the workpiece 31 that opens in the upper surface 31a and extends in the X-axis direction. In this embodiment, as shown in FIG. 8, as the chuck table 26 and the irradiation head 46 move, the condensing point 23 is positioned below the upper surface 31a, and the condensing point 23 is positioned above the upper surface 31a. A state b and a state c in which the condensing point 23 is located above the upper surface 31a are realized in order.

State a in which the condensing point 23 is located below the upper surface 31a and state c in which the condensing point 23 is located above the upper surface 31a are different from state b in which the condensing point 23 is located on the upper surface 31a. A wide area of the upper surface 31a is irradiated with the laser beam 21 . Therefore, the width (the length in the Y-axis direction) of the grooves formed in states a and c is wider than the width of the grooves formed in state b.

Although the height of the irradiation head 46 is continuously raised here, the height of the irradiation head 46 may be lowered continuously. After forming the groove in the workpiece 31, for example, the groove is imaged from above to obtain an image (first image acquisition step). A specific procedure may be the same as the procedure of the embodiment described above.

After obtaining the image showing the grooves, grooves (second grooves) are formed in the same procedure on another workpiece 31 (second workpiece) (second processing step). However, this groove is formed by relatively moving the workpiece 31 and the irradiation head 46 along the Y-axis direction (second direction) perpendicular to the X-axis direction.

That is, while continuously changing the height of the irradiation head 46 with the lower surface 31b of the workpiece 31 as a reference, the workpiece 31 and the irradiation head 46 are moved relative to each other along the lower surface 31b in the Y-axis direction. By irradiating the workpiece 31 with the laser beam 21 while moving, a groove having an area narrower than both ends and opening to the upper surface 31 a is formed in the workpiece 31 . After forming the groove in the workpiece 31, for example, the groove is imaged from above to obtain an image (second image acquisition step). A specific procedure may be the same as the procedure of the embodiment described above.

After obtaining an image of each groove, the first and second regions where the laser beam 21 is most focused on the upper surface 31a of the workpiece 31 are identified based on the width of each groove (first identification step and a second identification step). Then, based on the position of the first area and the position of the second area, the aberration due to the optical system of the laser beam irradiation unit 42 is confirmed (aberration confirmation step). A specific procedure may be the same as the procedure of the embodiment described above.

As described above, in the aberration confirmation method using the workpiece 31 according to the modification, while continuously changing the height of the irradiation head (a part of the optical system) 46, the upper surface 31a parallel to the lower surface 31b By relatively moving the workpiece 31 (first workpiece) and the irradiation head 46 in the X-axis direction (first direction), the upper surface 31a has an area narrower than both ends. A groove (first groove) is formed.

In addition, while continuously changing the height of the irradiation head 46, the workpiece 31 (second workpiece) including the upper surface 31a parallel to the lower surface 31b and the irradiation head 46 are arranged perpendicular to the X-axis direction. By relatively moving in the Y-axis direction (second direction), a groove (second groove) having regions narrower than both ends and opening to the upper surface 31a is formed.

Therefore, in this case as well, by specifying the first region and the second region, it is possible to determine how the laser beam 21 is focused in the X-axis direction and how the laser beam 21 is focused in the Y-axis direction from the relationship between these positions. You can easily check the situation. That is, the aberration caused by the optical system of the laser beam irradiation unit 42 can be easily confirmed.

It should be noted that in this aberration checking method using the workpiece 31, instead of continuously changing the height of the irradiation head 46 (instead of continuously raising or lowering the irradiation head 46), the holding surface of the chuck table 26 is 26a may be tilted with respect to the X-axis direction and the Y-axis direction. In this case, only by relatively moving the workpiece 31 and the irradiation head 46 along the X-axis direction or the Y-axis direction, the workpiece 31 can be projected without changing the position of the irradiation head 46 . The height of the irradiation head 46 with respect to the lower surface 31b can be changed.

In addition, the structures, methods, and the like according to the above-described embodiments and modifications can be modified without departing from the scope of the present invention.

Reference Signs List 11: workpiece 11a: upper surface 11b: lower surface 11c: groove (first groove)
11d: first region 11e: groove (second groove)
11f: Second region 13: Adhesive tape (dicing tape)
15: Frame 21: Laser beam 23: Focusing point 31: Workpiece 31a: Upper surface 31b: Lower surface 33: Adhesive tape (dicing tape)
2: laser processing device 4: base 6: horizontal movement mechanism (processing feed mechanism, indexing feed mechanism)
8: Y-axis guide rail 10: Y-axis moving table 12: Y-axis ball screw 14: Y-axis pulse motor 16: X-axis guide rail 18: X-axis moving table 20: X-axis ball screw 22: X-axis pulse motor 24: Table base Base 26: Chuck table (holding table)
26a: holding surface 28: clamp 30: support structure 32: vertical movement mechanism (height adjustment mechanism)
34: Z-axis guide rail 36: Z-axis moving table 38: Z-axis pulse motor 40: Support 42: Laser beam irradiation unit 44: Housing 46: Irradiation head (part of optical system)
46a: lens 48: imaging unit 50: display (input/output unit)
52: control unit (control unit)

Claims (4)

An aberration confirmation method for confirming aberration due to an optical system of a laser beam irradiation unit that irradiates a laser beam having a wavelength that can be absorbed by a workpiece,
A part of the optical system is positioned at a predetermined height position with respect to the lower surface of the first workpiece including the upper surface inclined with respect to the lower surface, and the optical system is positioned at the same height as the part of the upper surface. By relatively moving the first workpiece and the part of the optical system along the lower surface in the first direction while condensing the laser beam, the first workpiece and the part of the optical system have regions narrower than both ends. a first processing step of forming, in the first workpiece, a first groove that is open to the upper surface;
positioning the part of the optical system at a position at a predetermined height with respect to the lower surface of the second workpiece including the upper surface inclined with respect to the lower surface, and at the same height position as the part of the upper surface; By relatively moving the second workpiece and the part of the optical system along the lower surface in a second direction perpendicular to the first direction while condensing the laser beam, a second processing step of forming in the second workpiece a second groove having regions narrower than both ends and opening to the upper surface;
a first identifying step of identifying a first region where the laser beam is most focused on the top surface of the first workpiece based on the width of the first groove;
a second identifying step of identifying a second region where the laser beam is most focused on the upper surface of the second workpiece based on the width of the second groove;
and an aberration confirmation step of confirming aberration due to the optical system from the position of the first area and the position of the second area. An aberration confirmation method for confirming aberration due to an optical system of a laser beam irradiation unit that irradiates a laser beam having a wavelength that can be absorbed by a workpiece,
While continuously changing the height of a part of the optical system with reference to the lower surface of the first workpiece including the upper surface parallel to the lower surface, and the first workpiece and the optical system By irradiating the first workpiece with the laser beam while relatively moving the part along the bottom surface in the first direction, the first workpiece has a narrower width than both ends and an opening on the top surface. a first processing step of forming a first groove in the first workpiece;
While continuously changing the height of the part of the optical system with reference to the lower surface of the second workpiece including the upper surface parallel to the lower surface, and the second workpiece and the optical system by irradiating the second workpiece with the laser beam while relatively moving the part of and along the lower surface in a second direction perpendicular to the first direction, thereby increasing the width from both ends a second processing step of forming in the second workpiece a second groove that has a narrow region of and is open to the top surface;
a first identifying step of identifying a first region where the laser beam is most focused on the top surface of the first workpiece based on the width of the first groove;
a second identifying step of identifying a second region where the laser beam is most focused on the upper surface of the second workpiece based on the width of the second groove;
and an aberration confirmation step of confirming aberration due to the optical system from the position of the first area and the position of the second area. If the aberration confirmed in the aberration confirmation step is within the allowable range, it is determined that there is no need to adjust the optical system, and if the aberration confirmed in the aberration confirmation step is outside the allowable range 3. The aberration confirmation method according to claim 1, further comprising a step of determining that said optical system needs to be adjusted if there is any. 4. The aberration confirmation method according to claim 1, wherein the first workpiece is used as the second workpiece.

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