JP7433715B2 - How to check the condition of laser processing equipment and condensing lens - Google Patents

Description

The present invention relates to a laser processing apparatus used when processing a workpiece, and a method for checking the state of a condenser lens used when checking the state of a condenser lens included in the laser processing apparatus.

When dividing a plate-shaped workpiece, such as a semiconductor wafer, into a plurality of chips, for example, a laser processing device including a laser oscillator and a condensing lens is used. By irradiating a laser beam generated by a laser oscillator through a condensing lens onto the street (to be processed line) of the workpiece, which is the boundary between chips, the workpiece is processed on the street and processed into multiple chips. (For example, see Patent Document 1).

JP2017-6930A

By the way, when processing a workpiece on the street by irradiating a laser beam, the focal length must be adjusted so that the laser beam can irradiate a narrow area inside the workpiece or a narrow area near the workpiece. A short condensing lens is often placed close to the workpiece.

However, if the condenser lens is placed close to the workpiece, small pieces of melted workpiece, vapor, etc. generated by the laser beam tend to adhere to the condenser lens. If the condensing lens becomes dirty with these particles or steam, part of the laser beam will be blocked, reducing the precision with which the workpiece is processed.

The present invention has been made in view of such problems, and its purpose is to provide a laser processing device and a method for checking the condition of the condenser lens that can easily check whether the condenser lens is dirty or not. That's true.

According to one aspect of the present invention, a chuck table has a holding surface for holding a workpiece, a laser oscillator generates a laser beam, and the laser beam generated by the laser oscillator is focused on the chuck table side. A detection unit that detects contamination on the condenser lens, a detector that detects the shape of the laser beam that has passed through the condenser lens, and a detection unit that detects the shape of the laser beam that has passed through the condenser lens; a determination unit that determines whether or not the condenser lens is dirty based on its shape; and a detection unit that moves the condenser lens in a direction perpendicular to the holding surface of the chuck table. a moving mechanism; while generating the laser beam with the laser oscillator, the moving mechanism moves the focusing lens to determine the shape of the laser beam and the light intensity of the laser beam detected by the detector; a detection result storage unit that stores the position of the laser beam together with the position of the optical lens; Provided is a laser processing device that determines whether the condenser lens is dirty based on the following .

In one aspect of the present invention, the detector is disposed on a side opposite to the chuck table with respect to the condenser lens, and after passing through the condenser lens and being reflected on the chuck table side, the detector The shape of the laser beam transmitted again may be detected.

Further, in one aspect of the present invention, the laser beam may be disposed on a side opposite to the chuck table with respect to the condenser lens, and reflect a part of the laser beam generated by the laser oscillator and guide the laser beam to the condenser lens. The detector further includes an optical element having a surface, and the detector is arranged on a side of the optical element opposite to the condensing lens, and detects the laser beam that has passed through the condensing lens again and then passed through the reflective surface. Shapes may be detected.

Further, in one aspect of the present invention, the detector may be disposed on the same side of the condenser lens as the chuck table. Further, in one aspect of the present invention, a central region of the light receiving surface of the detector may be covered with a mask .

Further, in one aspect of the present invention, the determination unit further includes a reference shape memory unit that stores a shape of the laser beam that can be detected by the detector when contamination of the condensing lens is within an allowable range. compares the shape of the laser beam stored in the reference shape memory with the shape of the laser beam detected by the detector to determine whether the condenser lens is dirty. Sometimes.

According to another aspect of the present invention, a chuck table has a holding surface that holds a workpiece, a laser oscillator that generates a laser beam, and the laser beam generated by the laser oscillator is focused on the chuck table side. Checking whether the condenser lens of a laser processing device including a condenser lens that emits light and a moving mechanism that moves the condenser lens in a direction perpendicular to the holding surface of the chuck table is dirty. A method for checking the state of a condenser lens, the method comprising: a laser beam generation step of generating the laser beam with the laser oscillator; a detection step of detecting the shape of the laser beam transmitted through the condenser lens; and the detection step. a determination step of determining whether or not the condenser lens is dirty based on the shape of the laser beam detected by the laser beam, and in the detection step, while generating the laser beam with the laser oscillator, The moving mechanism moves the condensing lens to detect the shape of the laser beam and the light intensity of the laser beam together with the position of the condensing lens, and in the determination step, the laser beam detected in the detection step is A method for checking the condition of a condenser lens is provided , which determines whether or not the condenser lens is dirty based on the shape of the laser beam at the position of the condenser lens where the light intensity is highest .

In another aspect of the present invention, in the detection step, the shape of the laser beam that has passed through the condenser lens, been reflected on the chuck table side, and then passed through the condenser lens again is detected by the condenser lens. On the other hand, it may be detected on the side opposite to the chuck table.

In another aspect of the present invention, the laser processing device is disposed on the opposite side of the chuck table with respect to the condenser lens, and reflects a part of the laser beam generated by the laser oscillator. The detection step further includes an optical element having a reflective surface that guides the laser beam to the condensing lens, and in the detection step, the shape of the laser beam that has passed through the condensing lens again and transmitted through the reflective surface is detected by the optical element. It may be detected on the opposite side of the condenser lens.

In another aspect of the present invention, in the detection step, the shape of the laser beam transmitted through the condenser lens may be detected on the same side of the condenser lens as the chuck table. In another aspect of the present invention, in the detection step, a region other than a central region of the shape of the laser beam may be detected .

In another aspect of the present invention, before the laser beam generation step, a reference shape acquisition step of acquiring a shape of the laser beam that can be detected while the condensing lens is within an allowable range. The determination step compares the shape of the laser beam acquired in the reference shape acquisition step and the shape of the laser beam detected in the detection step to determine whether the condenser lens is dirty. It may be determined whether the

A laser processing apparatus according to one embodiment of the present invention includes a detector that detects the shape of a laser beam that has passed through a condenser lens, and a detector that detects whether the condenser lens is dirty based on the shape of the laser beam detected by the detector. Since the detection unit includes a determination unit that determines whether the condenser lens is dirty or not, it is possible to easily check whether the condenser lens is dirty or not.

Further, a method for checking the state of a condensing lens according to another aspect of the present invention includes a detection step of detecting the shape of a laser beam transmitted through the condensing lens, and a detection step based on the shape of the laser beam detected in the detection step. , and a determination step of determining whether or not the condenser lens is dirty, so that it can be easily confirmed whether or not the condenser lens is dirty.

FIG. 1 is a perspective view showing an example of the configuration of a laser processing device. FIG. 2 is a schematic diagram showing how a laser beam progresses inside the laser processing device. FIG. 3 is a functional block diagram showing the functional structure of the control unit. FIG. 4 is a flowchart showing an overview of a method for checking the condition of the condenser lens. FIG. 5 is a diagram schematically showing an example of a reference profile. FIG. 6 is a diagram schematically showing an example of a detection profile. FIG. 7 is a diagram schematically showing another example of the detection profile. FIG. 8 is a schematic diagram showing a configuration example of a laser processing apparatus 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 according to the present embodiment. Note that in FIG. 1, some components of the laser processing device 2 are shown as functional blocks. Further, the X-axis direction (processing feed direction), Y-axis direction (indexing feed direction), and Z-axis direction (vertical direction) used in the following description are perpendicular to each other.

As shown in FIG. 1, the laser processing device 2 includes a base 4 that supports each component. A horizontal movement mechanism (processing feed mechanism, indexing 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 that are fixed to the upper surface of the base 4 and are generally parallel to the Y-axis direction. A Y-axis moving plate 10 is attached to the Y-axis guide rail 8 in such a manner that it can slide along the Y-axis direction.

A nut (not shown) constituting a ball screw is provided on the lower surface side of the Y-axis moving plate 10. A threaded shaft 12, which is generally parallel to the Y-axis guide rail 8, is rotatably screwed into this nut. A Y-axis pulse motor 14 is connected to one end of the screw shaft 12 . When the screw shaft 12 is rotated by the Y-axis pulse motor 14, the Y-axis moving plate 10 moves in the Y-axis direction along the Y-axis guide rail 8.

A pair of X-axis guide rails 16 that are generally parallel to the X-axis direction are provided on the upper surface of the Y-axis moving plate 10. An X-axis moving plate 18 is attached to the X-axis guide rail 16 in such a manner that it can slide along the X-axis direction. A nut (not shown) constituting a ball screw is provided on the lower surface side of the X-axis moving plate 18.

A threaded shaft 20, which is generally parallel to the X-axis guide rail 16, is rotatably screwed into this nut. An X-axis pulse motor 22 is connected to one end of the screw shaft 20. When the screw shaft 20 is rotated by the X-axis pulse motor 22, the X-axis moving plate 18 moves in the X-axis direction along the X-axis guide rail 16.

A cylindrical table base 24 is arranged on the upper surface side of the X-axis moving plate 18. Furthermore, a chuck table (holding table) 26 used for holding the workpiece 11 is arranged above the table base 24 . A rotational drive source (not shown) such as a motor is connected to the lower part of the table base 24 .

The force generated from this rotational drive source causes the chuck table 26 to rotate around a rotation axis that is generally parallel to the Z-axis direction. Further, 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.

The workpiece 11 is, for example, a disk-shaped wafer made of a semiconductor such as silicon. The surface (upper surface in FIG. 1) of the workpiece 11 is divided into a plurality of small areas by a plurality of streets (processing lines) that intersect with each other, and each small area includes an IC (Integrated Circuit), etc. devices have been formed.

For example, a tape (dicing tape) 13 having a larger diameter than the workpiece 11 is attached to the back surface (lower surface in FIG. 1) of the workpiece 11 . Further, the outer peripheral portion of the tape 13 is fixed to an annular frame 15. In this way, the workpiece 11 is processed while being supported by the frame 15 via the tape 13.

In this embodiment, the workpiece 11 is a disk-shaped wafer made of a semiconductor such as silicon, but there are no restrictions on the material, shape, structure, size, etc. of the workpiece 11. For example, a substrate made of other materials such as semiconductors, ceramics, resins, metals, etc. can also be used as the workpiece 11.

Similarly, there are no restrictions on the type, quantity, shape, structure, size, arrangement, etc. of devices formed on the workpiece 11. The workpiece 11 does not need to have a device formed thereon. Further, the workpiece 11 may be processed without the tape 13 attached or without being supported by the frame 15.

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 that contacts the tape 13 (or the workpiece 11 when the tape 13 is not attached) and holds the workpiece 11. 26a. This holding surface 26a is generally parallel to the X-axis direction and the Y-axis direction.

Further, the holding surface 26a is connected to a suction source (not shown) such as a vacuum pump via a flow path (not shown) provided inside the chuck table 26. Four clamps 28 are provided around the chuck table 26 to which the annular frame 15 that supports the workpiece 11 can be fixed.

A support structure 30 having a side surface generally 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 this support structure 30. The vertical movement mechanism 32 includes a pair of Z-axis guide rails 34 that are fixed to the side surface of the support structure 30 and are generally parallel to the Z-axis direction. A Z-axis moving plate 36 is attached to the Z-axis guide rail 34 in such a manner that it can slide along the Z-axis direction.

A nut (not shown) constituting a ball screw is provided on the back side of the Z-axis moving plate 36 (on the Z-axis guide rail 34 side). A threaded shaft (not shown) that is generally parallel to the Z-axis guide rail 34 is rotatably screwed into this nut. A Z-axis pulse motor 38 is connected to one end of the screw shaft. When the screw shaft is rotated by the Z-axis pulse motor 38, the Z-axis moving plate 36 moves in the Z-axis direction along the Z-axis guide rail 34.

A support 40 is fixed to the front side of the Z-axis moving plate 36, and a part of the laser beam irradiation unit 42 is supported by this support 40. FIG. 2 is a schematic diagram showing how the laser beam 21 progresses inside the laser processing device 2. As shown in FIG. As shown in FIGS. 1 and 2, the laser beam irradiation unit 42 includes, for example, a laser oscillator 44 fixed to the base 4, a cylindrical housing 46 supported by a support 40 and long in the Y-axis direction, and a housing 46 (the other end in the Y-axis direction).

The laser oscillator 44 includes, for example, a laser medium such as Nd:YAG suitable for laser oscillation, generates a laser beam 21 used for processing the workpiece 11, and emits it to the housing 46 side. In this embodiment, the laser oscillator 44 generates a laser beam 21 having a wavelength that passes through the workpiece 11 .

However, the laser oscillator 44 may be configured to be able to generate a laser beam with a wavelength that is absorbed by the workpiece 11. Note that a laser beam with a wavelength that passes through the workpiece 11 is suitable for modifying the workpiece 11 by multiphoton absorption, and a laser beam with a wavelength that is absorbed by the workpiece 11 is suitable for Suitable for ablation processing of the object 11, etc.

The housing 46 houses a part of the optical system constituting the laser beam irradiation unit 42 and guides the laser beam 21 emitted from the laser oscillator 44 to the irradiation head 48 . In this embodiment, as shown in FIG. 2, a mirror 46a and a mirror 46b are housed in a housing 46.

Another part of the optical system that constitutes the laser beam irradiation unit 42 is accommodated in the irradiation head 48 . For example, the irradiation head 48 changes the course of the laser beam 21 guided from the housing 46 downward using an optical element 48a such as a beam splitter (including a general mirror that transmits several percent of light or a half mirror). A condensing lens 48b disposed below condenses the light at a predetermined height position on the chuck table 26 side.

That is, the optical element 48a is arranged on the opposite side of the chuck table 26 with respect to the condensing lens 48b, and reflects a part of the laser beam 21 generated by the laser oscillator 44 on its reflecting surface, so that the condensing lens Leads to 48b. On the other hand, the reflective surface of this optical element 48a is configured to allow the other part of the laser beam 21 to pass therethrough. The condensing lens 48b is typically a convex lens.

Above the optical element 48a (on the opposite side of the optical element 48a from the condensing lens 48b, and on the opposite side of the condensing lens 48b from the chuck table 26) is a detector capable of detecting the beam profile of the laser beam 21. 50 are arranged. Note that the beam profile of the laser beam 21 includes the shape of the outline of the laser beam 21 when irradiating a plane perpendicular to the traveling direction, and the shape of the outline of the laser beam 21 when irradiating a plane perpendicular to the traveling direction. Contains information on two-dimensional intensity distribution.

The light-receiving surface of the detector 50 faces downward (on the optical element 48a side) so that the beam profile (contour shape and two-dimensional intensity distribution) of the laser beam 21 propagating from below (on the optical element 48a side) can be detected. It's suitable. Therefore, for example, by placing a reflecting member 23 with a flat reflecting surface capable of reflecting the laser beam 21 on the holding surface 26a of the chuck table 26, the laser beam 21 is reflected by the reflecting member 23 and transmitted through the condenser lens 48b and the optical element 48a. The beam profile of the laser beam 21 can be detected by the detector 50.

As the detector 50, for example, a beam profiler including a two-dimensional optical sensor such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor that is sensitive to the wavelength of the laser beam 21 is used. Further, as the detector 50, a light receiving element such as a split silicon photodiode may be used.

As shown in FIG. 1, a camera (imaging unit) 52 fixed to the housing 46 is arranged in an area on one side of the irradiation head 48 in the X-axis direction. The camera 52 includes, for example, a two-dimensional optical sensor such as a CMOS image sensor or a CCD image sensor that is sensitive to visible light, and is used to image the upper surface of the workpiece 11 held by the chuck table 26. be done.

The housing 46 and the irradiation head 48 of the laser beam irradiation unit 42 are moved in the Z-axis direction by the vertical movement mechanism 32 together with the camera 52 described above. That is, the vertical movement mechanism 32 moves components such as the optical element 48a and the condensing lens 48b provided on the irradiation head 48 in a direction generally perpendicular to the holding surface 26a of the chuck table 26. The detector 50 of this embodiment is fixed to the irradiation head 48 and moves in the Z-axis direction together with the irradiation head 48.

In this embodiment, an example is given in which the laser oscillator 44 is fixed to the base 4, but the laser oscillator 44 is configured to be movable in the Z-axis direction by the vertical movement mechanism 32 together with the housing 46 and the like. Sometimes it is done. Furthermore, the irradiation head 48 may be provided with an actuator or the like so that only the condenser lens 48b can be independently moved in the Z-axis direction.

The upper part of the base 4 is covered with a cover (not shown) that can accommodate each component. A touch screen (input/output device) 54 serving as a user interface is arranged on the side surface of this cover. For example, various conditions applied when processing the workpiece 11 are input to the touch screen 54. Note that instead of the touch screen 54 that combines a display device (output device) and an input device, a display device (output device) such as a liquid crystal display and an input device such as a keyboard or mouse may be provided. good.

Components such as the horizontal movement mechanism 6, the vertical movement mechanism 32, the laser beam irradiation unit 42, the detector 50, the camera 52, and the touch screen 54 are each connected to a control unit 56. The control unit 56 controls each of the above-described components in accordance with a series of steps necessary for processing the workpiece 11.

The control unit 56 is configured by a computer including, for example, a processing device such as a CPU (Central Processing Unit), a main storage device such as a DRAM (Dynamic Random Access Memory), and an auxiliary storage device such as a hard disk drive or flash memory. be done. The functions of the control unit 56 can be realized by operating the processing device and the like according to the software stored in the auxiliary storage device. However, the control unit 56 may be realized only by hardware.

FIG. 3 is a functional block diagram showing the functional structure of the control unit 56. As shown in FIG. 3, the control unit 56 includes a laser oscillation control section 56a that controls laser oscillation by the laser oscillator 44, and a movement control section 56b that controls the operations of the horizontal movement mechanism 6 and the vertical movement mechanism 32. .

When checking the state of the condenser lens 48b, for example, the laser oscillator 44 starts generating the laser beam 21 based on an instruction from the laser oscillation control section 56a. In this state, the movement control section 56b controls the operation of the vertical movement mechanism 32 to move the Z-axis movement plate 36 in the Z-axis direction. That is, while the laser oscillator 44 generates the laser beam 21, the vertical movement mechanism 32 moves the condenser lens 48b in a direction perpendicular to the holding surface 26a of the chuck table 26.

Information regarding the position of the Z-axis moving plate 36 in the Z-axis direction is sent from the movement control unit 56b to the detection result storage unit 56c as information regarding the position of the condensing lens 48b in the Z-axis direction (hereinafter referred to as "lens position"). It will be done. The detection result storage section 56c stores the lens position sent from the movement control section 56b together with the beam profile of the laser beam 21 detected by the detector 50 (hereinafter referred to as "detection profile").

Specifically, for example, the detection result storage unit 56c stores information regarding the detection profile and information regarding the lens position, which are acquired at the same timing, in a state where they are linked to each other. That is, the detection result storage unit 56c stores the relationship between the position of the condenser lens 48b in the Z-axis direction and the beam profile of the laser beam 21.

The detection profile stored in the detection result storage section 56c is used by the determination section 56d as needed. For example, the determination unit 56d compares the detection profile stored in the detection result storage unit 56c with the beam profile of the laser beam 21 serving as a reference (hereinafter referred to as “reference profile”), and determines whether the condenser lens 48b is dirty. Determine whether or not. Note that this reference profile is stored in advance in the reference profile storage section (reference shape storage section) 56e.

The result of the determination by the determination unit 56d is displayed on the touch screen 54, for example. By checking the determination result displayed on the touch screen 54, the operator can perform various processes corresponding to the determination result. In this way, the control unit 56 (determination section 56d) and the detector 50 constitute a detection unit for detecting dirt on the condenser lens 48b. More detailed functions and operations of the control unit 56 will be described later.

Next, a method of checking the condition of the condenser lens performed using the laser processing apparatus 2 described above will be described. FIG. 4 is a flowchart showing an overview of a method for checking the condition of the condenser lens. In the method for checking the condition of the condensing lens according to the present embodiment, first, a profile (reference profile) of the laser beam 21 that can be detected by the detector 50 is obtained while the condensing lens 48b is within an allowable range of dirt. (Reference profile acquisition step (reference shape acquisition step) ST1).

Specifically, for example, an operator places the reflective member 23 on the holding surface 26a of the chuck table 26 while the condensing lens 48b is clean, and then the laser oscillation controller 56a controls the laser beam 21 from the laser oscillator 44. Start generation. As shown in FIG. 2, a portion of the laser beam 21 emitted from the laser oscillator 44 is reflected by the reflective surface of the optical element 48a and guided to the condenser lens 48b. Note that as the reflecting member 23, for example, a wafer, a mirror, or the like having a flat reflecting surface is used.

The laser beam 21 that has passed through the condenser lens 48b is reflected by the reflection member 23 (that is, closer to the chuck table 26 than the condenser lens 48b), and then passes through the condenser lens 48b again. A portion of the laser beam 21 that has passed through the condenser lens 48b again passes through the reflective surface of the optical element 48a, and its beam profile is detected by the detector 50.

The beam profile of the laser beam 21 detected in this way is stored as a reference profile in the reference profile storage section 56e. FIG. 5 is a diagram schematically showing an example of a reference profile stored in the reference profile storage section 56e. When the condensing lens 48b is not dirty, as shown in FIG. 5, the outline of the laser beam 21 after passing through the condensing lens 48b becomes a circle, and the distribution of light intensity becomes a Gaussian distribution.

Note that in this embodiment, the beam profile of the laser beam 21 actually detected by the detector 50 is stored in the reference profile storage section 56e as a reference profile that serves as a reference for determination, but an ideal beam profile obtained by calculation etc. A typical beam profile can also be stored in the reference profile storage section 56e as a reference profile.

After acquiring the reference profile, the state of the condenser lens 48b can be checked at any timing. When checking the state of the condensing lens 48b, for example, the operator places the reflective member 23 on the holding surface 26a of the chuck table 26, and then the laser oscillation control unit 56a starts the generation of the laser beam 21 by the laser oscillator 44. (laser beam generation step ST2).

Then, the profile of the laser beam 21 is detected by the detector 50 (detection step ST3). As shown in FIG. 2, a portion of the laser beam 21 emitted from the laser oscillator 44 is reflected by the reflective surface of the optical element 48a and guided to the condenser lens 48b. The laser beam 21 that has passed through the condenser lens 48b is reflected by the reflection member 23 (that is, closer to the chuck table 26 than the condenser lens 48b), and then passes through the condenser lens 48b again.

A portion of the laser beam 21 that has passed through the condenser lens 48b again passes through the reflective surface of the optical element 48a, and its beam profile is detected by the detector 50. The beam profile of the laser beam 21 detected in this manner is stored in the detection result storage section 56c as a detection profile.

FIG. 6 is a diagram schematically showing an example of a detection profile stored in the detection result storage unit 56c, and FIG. 7 is a diagram schematically showing another example of a detection profile stored in the detection result storage unit 56c. It is a diagram. As shown in FIG. 6, when the condenser lens 48b is dirty, the outline of the laser beam 21 after passing through the condenser lens 48b becomes a deformed circle. The distribution of the light intensity of the laser beam 21 also deviates from the Gaussian distribution.

As shown in FIG. 7, when the condenser lens 48b is heavily contaminated (that is, when the degree of contamination is large), the outline shape of the laser beam 21 after passing through the condenser lens 48b is circular. It becomes a shape that is significantly deformed. Furthermore, the distribution of the light intensity of the laser beam 21 also deviates significantly from the Gaussian distribution.

Note that this beam profile detection is preferably performed while moving the Z-axis moving plate 36 using the vertical moving mechanism 32. Specifically, the beam profile is detected at each position while acquiring information regarding the position of the Z-axis moving plate 36 in the Z-axis direction. That is, while the laser oscillator 44 generates the laser beam 21, the vertical movement mechanism 32 moves the condenser lens 48b, and the beam profile of the laser beam 21 and the position of the condenser lens 48b are detected.

The information regarding the detection profile and the information regarding the lens position acquired at the same timing are stored in the detection result storage unit 56c in a mutually linked state. In this way, by obtaining the relationship between the position of the condenser lens 48b in the Z-axis direction and the beam profile of the laser beam 21, the state of the condenser lens 48b can be determined using a detection profile suitable for determining the state. It will be possible to increase accuracy.

When acquisition of the detection profile is completed, the determination unit 56d determines whether the condenser lens 48b is dirty based on the acquired detection profile (determination step ST4). Specifically, the determination unit 56d determines that the condenser lens 48b is not dirty when the detection profile is within the allowable range, and determines that the condenser lens 48b is not dirty when the detection profile is outside the allowable range. It is determined that the optical lens 48b is dirty.

Although there are no particular restrictions on the determination method, accurate determination can be made by determining and utilizing the strength of the correlation between the reference profile and the detection profile. Specifically, the methods include a method of comparing the shape of the outline of the laser beam 21, a method of comparing the two-dimensional light intensity distribution of the laser beam 21, a method of comparing the shape of the outline of the laser beam 21, a method of comparing the two-dimensional light intensity distribution of the laser beam 21, and a method of comparing the scattered light detected at a position away from the optical axis of the optical system. It is possible to adopt methods such as checking the strength of

In a method of comparing contour shapes, for example, the contour of the laser beam 21 in the reference profile and the contour of the laser beam 21 in the detection profile are extracted by image processing such as edge detection, and the strength of the correlation between these shapes is determined. seek. If the correlation is strong, the determining unit 56d determines that the condensing lens 48b is not dirty, and if the correlation is weak, the determining unit 56d determines that the condensing lens 48b is dirty. A position where the light intensity is equal between the reference profile and the detection profile may be extracted, and the determination may be made based on the strength of the correlation at that position.

In a method of comparing two-dimensional light intensity distributions, for example, the light-receiving surface of the detector 50 is divided into a plurality of (for example, four) regions having equal areas along a boundary passing through the center of the light-receiving surface. , detect the total light intensity in each region. By checking the symmetry of the laser beam 21 based on the light intensity of each region, it is possible to determine whether the condenser lens 48b is dirty.

For example, if the difference in light intensity between any two areas is less than or equal to the threshold value, it is determined that the condenser lens 48b is not dirty, and if the difference in light intensity between any two areas is greater than the threshold value, the condenser lens 48b is determined to be clean. 48b is determined to be dirty. Note that the determination can also be made based on the strength of the correlation between the distribution of the light intensity of the laser beam 21 in the reference profile and the distribution of the light intensity of the laser beam 21 in the detection profile.

In the method of checking the intensity of scattered light detected at a position far from the optical axis of the optical system, for example, if the light intensity at a position sufficiently far from the optical axis in the detection profile is below a threshold, It is determined that the lens 48b is not dirty. On the other hand, if the light intensity at a position sufficiently away from the optical axis in the detection profile is greater than the threshold value, it is determined that the condenser lens 48b is dirty. For example, when the light intensity at each position is expressed in 256 levels, it is easier to obtain good results by setting the 50th to 100th light intensities from the smallest to the lowest as the thresholds.

Note that when the beam profile of the laser beam 21 is acquired together with the position of the condensing lens 48b (Z-axis direction), the light intensity of the laser beam 21 detected by the detector 50 (for example, the total sum on the light receiving surface) It is preferable to determine whether or not the condenser lens 48b is dirty based on the beam profile of the laser beam 21 at the position of the condenser lens 48b where . Thereby, the state of the condenser lens 48b can be determined more appropriately.

If the difference between the reference profile and the detection profile is less than an arbitrary threshold, that is, if the detection profile is within the allowable range and it is determined that the condenser lens 48b is not dirty (determination step ST4: YES), the condenser lens 48b is determined to be clean. Processing is performed when the optical lens 48b is not dirty (first processing step ST5). For example, the determination unit 56d causes the touch screen 54 to display that the condenser lens 48b is not dirty. Further, the operator performs processing such as restarting processing of the workpiece 11.

On the other hand, if the difference between the reference profile and the detection profile is larger than an arbitrary threshold value, that is, if the detection profile is not within the allowable range and it is determined that the condenser lens 48b is dirty (determination step ST4: NO). ), processing is performed when the condenser lens 48b is dirty (second processing step ST6). For example, the determination unit 56d causes the touch screen 54 to display that the condenser lens 48b is dirty. The operator also performs maintenance work such as cleaning and replacing the condenser lens 48b.

As described above, the laser processing apparatus 2 according to the present embodiment includes the detector 50 that detects the shape of the laser beam 21 transmitted through the condensing lens 48b, and the profile (shape) of the laser beam 21 detected by the detector 50. ), it is possible to easily check whether or not the condenser lens 48b is dirty.

In addition, the method for checking the state of the condensing lens according to the present embodiment detects the profile (shape) of the laser beam 21 that has passed through the condensing lens 48b (detection step ST3), and based on the detected profile of the laser beam 21, Then, it is determined whether or not the condenser lens 48b is dirty (determination step ST4), so it can be easily confirmed whether or not the condenser lens 48b is dirty.

Note that the present invention is not limited to the description of the embodiments described above, and can be implemented with various modifications. For example, in the embodiment described above, the reflective member 23 is placed on the chuck table 26, but the reflective member 23 may be placed at a position adjacent to the chuck table 26. Further, a polarizing beam splitter is used as the optical element 48a, and a quarter wavelength plate is arranged between the optical element 48a and the condenser lens 48b, so that the amount of light of the laser beam 21 incident on the detector 50 can be adjusted. You can also do it.

Further, in the embodiment described above, the laser processing device 2 including the detection unit for detecting dirt on the condenser lens 48b and the method of checking the condition of the condenser lens using this laser processing device 2 have been described. The method for checking the condition of the optical lens can be carried out without using this laser processing device 2.

For example, by displaying the detection profile detected by the detector 50 on the touch screen 54 or the like, the operator may determine whether or not the condenser lens 48b is dirty. In this case, the laser processing apparatus does not need to include the determination section 56d, the reference profile storage section 56e, and the like.

In this case, it is preferable to determine whether the condenser lens 48b is dirty, for example, by checking the intensity of scattered light detected at a position away from the optical axis of the optical system. Specifically, when the light intensity at a position sufficiently distant from the optical axis in the detection profile is less than or equal to the threshold value, the operator determines that the condenser lens 48b is not dirty. On the other hand, if the light intensity at a position sufficiently distant from the optical axis in the detection profile is greater than the threshold value, the operator determines that the condenser lens 48b is dirty.

Note that if the condenser lens 48b is dirty, the laser beam 21 is more likely to be scattered, and the light intensity in the area on the outer circumferential side of the detection profile is likely to be increased. Therefore, the light intensity at each position may be weighted based on the distance from the center of the detection profile, so that the influence of the area on the outer circumferential side of the detection profile on the determination may be relatively increased. Further, the central area of the light receiving surface of the detector 50 (the area where the light intensity is high in the reference profile) may be covered in advance with a mask or the like.

Furthermore, in the above-described embodiment, the laser processing apparatus 2 is provided with the detector 50 disposed on the opposite side of the chuck table 26 with respect to the condenser lens 48b, but the detector 50 of the laser processing apparatus is It may be arranged on the same side as the chuck table 26 with respect to the optical lens 48b.

FIG. 8 is a schematic diagram showing a configuration example of a laser processing apparatus 102 according to a modification. Note that the basic structure of the laser processing device 102 according to the modification is the same as the basic structure of the laser processing device 2 of the embodiment described above. Therefore, the same reference numerals are given to the same components as those of the laser processing apparatus 2, and detailed explanation thereof will be omitted.

As shown in FIG. 8, the laser processing apparatus 102 according to the modified example includes a chuck table (holding table) 126 used to hold the workpiece 11. A part of the upper surface of this chuck table 126 is made of, for example, a material that can transmit the laser beam 21, and comes into contact with the tape 13 (or the workpiece 11 when the tape 13 is not attached), so that the workpiece 11 It functions as a holding surface 126a that holds. This holding surface 126a is generally parallel to the X-axis direction and the Y-axis direction.

A detector 50 that can detect the beam profile of the laser beam 21 is arranged below the holding surface 126a of the chuck table 126. The light-receiving surface of the detector 50 is located above (the holding surface 126a side of the chuck table 126) so as to be able to detect the beam profile (contour shape and two-dimensional intensity distribution) of the laser beam 21 propagating from above (the holding surface 126a side of the chuck table 126). 126a side).

Therefore, the beam profile of the laser beam 21 that passes through the condenser lens 48b and then passes through the holding surface 126a can be detected by the detector 50. Note that in this case, the optical element 48a does not need to be a beam splitter or the like having a reflective surface that partially transmits the laser beam 21. The optical element 48a may be, for example, a mirror that completely reflects the laser beam 21.

Further, the detector 50 may be placed adjacent to the chuck table 126. In this case, the beam profile of the laser beam 21 can be detected even when the workpiece 11 is placed on the chuck table 126. Note that in this case, the holding surface 126a of the chuck table 126 does not need to be made of a material that can transmit the laser beam 21.

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

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 plate 12: Screw shaft 14: Y-axis pulse motor 16: X-axis guide rail 18: X-axis moving plate 20: Screw shaft 22: X-axis pulse motor 24: Table 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 plate 38: Z-axis pulse motor 40: Support 42: Laser beam irradiation unit 44: Laser oscillator 46: Housing 46a: Mirror 46b: Mirror 48: Irradiation head 48a: Optical element 48b : Condensing lens 50 : Detector 52 : Camera (imaging unit)
54: Touch screen (input/output device)
56: Control unit 56a: Laser oscillation control section 56b: Movement control section 56c: Detection result storage section 56d: Judgment section 56e: Reference profile storage section (reference shape storage section)
102: Laser processing device 126: Chuck table (holding table)
126a: Holding surface 11: Workpiece 13: Tape (dicing tape)
15: Frame 21: Laser beam 23: Reflective member ST1: Reference profile acquisition step (reference shape acquisition step)
ST2: Laser beam generation step ST3: Detection step ST4: Judgment step ST5: First processing step ST6: Second processing step

Claims (12)

a chuck table having a holding surface for holding a workpiece;
a laser oscillator that generates a laser beam;
a condensing lens that condenses the laser beam generated by the laser oscillator onto the chuck table;
A detection unit that detects dirt on the condenser lens, a detector that detects the shape of the laser beam that has passed through the condenser lens, and a detector that detects the shape of the laser beam that is detected by the detector, The detection unit includes a determination unit that determines whether the condenser lens is dirty;
a moving mechanism that moves the condenser lens in a direction perpendicular to the holding surface of the chuck table;
While generating the laser beam with the laser oscillator, the moving mechanism moves the condensing lens to determine the shape of the laser beam and the light intensity of the laser beam detected by the detector, and the position of the condensing lens. a detection result storage unit that stores the detection result along with the detection result storage unit;
The determination unit determines whether or not the condenser lens is dirty based on the shape of the laser beam at a position of the condenser lens where the light intensity of the laser beam detected by the detector is highest. Laser processing equipment. The detector is arranged on a side opposite to the chuck table with respect to the condensing lens, and the laser beam passes through the condensing lens, is reflected on the chuck table side, and then passes through the condensing lens again. The laser processing device according to claim 1, which detects the shape of the laser beam. further comprising an optical element disposed on the side opposite to the chuck table with respect to the condenser lens, and having a reflective surface that reflects a portion of the laser beam generated by the laser oscillator and guides it to the condenser lens;
3. The detector is disposed on the opposite side of the optical element from the condenser lens, and detects the shape of the laser beam that has passed through the condenser lens again and then passed through the reflective surface. laser processing equipment. The laser processing apparatus according to claim 1, wherein the detector is arranged on the same side of the chuck table with respect to the condenser lens. further comprising a reference shape memory unit that stores a shape of the laser beam that can be detected by the detector when contamination of the condensing lens is within an allowable range;
The determining unit compares the shape of the laser beam stored in the reference shape memory unit with the shape of the laser beam detected by the detector to determine whether the condenser lens is dirty or not. The laser processing apparatus according to any one of claims 1 to 4, which determines. 6. The laser processing apparatus according to claim 1, wherein a central region of the light-receiving surface of the detector is covered with a mask. A chuck table having a holding surface for holding a workpiece, a laser oscillator that generates a laser beam, a condensing lens that focuses the laser beam generated by the laser oscillator on the chuck table side, and a A method for checking the condition of a condenser lens of a laser processing device , the method comprising: a moving mechanism for moving the condenser lens in a direction perpendicular to the holding surface; ,
a laser beam generation step of generating the laser beam with the laser oscillator;
a detection step of detecting the shape of the laser beam transmitted through the condensing lens;
a determination step of determining whether or not the condenser lens is dirty based on the shape of the laser beam detected in the detection step ;
In the detection step, while generating the laser beam with the laser oscillator, the moving mechanism moves the condensing lens to detect the shape of the laser beam and the light intensity of the laser beam together with the position of the condensing lens. ,
In the determination step, it is determined whether or not the condenser lens is dirty based on the shape of the laser beam at the position of the condenser lens where the light intensity of the laser beam detected in the detection step is highest. How to check the condition of the condenser lens. In the detection step, the shape of the laser beam that has passed through the condenser lens, been reflected on the chuck table side, and then passed through the condenser lens again is detected on the side opposite to the chuck table with respect to the condenser lens. 8. The method for checking the state of a condenser lens according to claim 7 , wherein the method detects the state of a condensing lens. The laser processing device is disposed on the opposite side of the chuck table with respect to the condenser lens, and has a reflective surface that reflects a portion of the laser beam generated by the laser oscillator and guides it to the condenser lens. further comprising an optical element;
9. The condenser according to claim 8 , wherein in the detection step, the shape of the laser beam that has passed through the condenser lens again and has passed through the reflective surface is detected on the opposite side of the optical element from the condenser lens. How to check the condition of the optical lens. 8. The method for checking the condition of a condenser lens according to claim 7, wherein in the detecting step, the shape of the laser beam transmitted through the condenser lens is detected on the same side of the condenser lens as the chuck table. Before the laser beam generation step, further comprising a reference shape acquisition step of acquiring a shape of the laser beam that can be detected while contamination of the condenser lens is within an allowable range;
In the determination step, the shape of the laser beam acquired in the reference shape acquisition step and the shape of the laser beam detected in the detection step are compared to determine whether or not the condenser lens is dirty. The method for checking the condition of a condensing lens according to any one of claims 7 to 10 , wherein the method determines the condition of a condenser lens. 12. The method for checking the state of a condensing lens according to claim 7, wherein in the detection step, an area other than a central area of the shape of the laser beam is detected.

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