JP2024027845A - Laser processing equipment and laser processing method - Google Patents

Abstract

The present invention provides a laser processing device and a laser processing method that can evaluate whether or not a processing groove is normally formed during laser processing at low cost, in a short time, and in a space-saving manner. [Solution] Photographing to photograph the first processing points (processing points SP1, SP2) of the laser beams (first laser beam L1, second laser beam L2) irradiated onto the street C from the laser head 24 during laser processing. This is the shape of the plasma 68, 69 generated at the first processing point based on the means (cameras 45, 46A, 46B) and the first photographed image (photographed image D1, D2A, D2B) of the first processing point taken by the photographing means. It includes a plasma shape acquisition section 56 that acquires a plasma shape, and a plasma shape evaluation section 58 that evaluates the plasma shape acquired by the plasma shape acquisition section 56. [Selection diagram] Figure 7

Description

The present invention relates to a laser processing apparatus and a laser processing method for laser processing a wafer.

In recent years, in the field of semiconductor device manufacturing, multiple devices are manufactured using a laminate in which a low dielectric constant insulating film (Low-k film) made of a glassy material and a functional film forming a circuit are laminated on the surface of a substrate such as silicon. Wafers (semiconductor wafers) are known. In such a wafer, a plurality of devices are partitioned into a grid pattern by grid-like streets, and individual devices are manufactured by dividing the wafer along the streets.

Methods for dividing a wafer into multiple devices (chips) include using a blade that rotates at high speed, and forming a laser processing area along streets inside the wafer and applying external force along streets with reduced strength. Are known. However, in the case of a wafer to which a low-k film is applied, the material of the low-k film and the material of the wafer are different, so it is difficult to cut the low-k film and the substrate at the same time with the blade in the former method. be. Furthermore, in the latter method, when a low-k film is present on the street, it is difficult to divide into individual devices with good quality.

Therefore, Patent Document 1 and Patent Document 2 disclose that the wafer is processed along the street by irradiating laser light from the laser optical system onto the street while moving the laser optical system relative to the wafer in the processing feed direction along the street. A laser processing apparatus that performs laser processing to form grooves (ablation groove processing) is disclosed. According to this laser processing apparatus, by forming processing grooves along the streets, it is possible to remove the Low-k film and the like from above the streets.

In addition, the laser processing apparatus described in Patent Document 2 photographs the processing point of the laser beam during laser processing using a laser optical system, detects plasma generated at the processing point from the photographed image of this processing point, and detects the plasma generated at the processing point from the photographed image of this processing point. The positional relationship between the position and a predetermined processing planned position is measured. Thereby, the laser processing apparatus described in Patent Document 2 can correct the processing position of laser processing.

JP2021-093460A Japanese Patent Application Publication No. 2017-120820

When performing street laser processing using the laser processing apparatus described in each of the above patent documents, the beam pointing of the laser head may fluctuate, and the optical When a change in the position and orientation of the element occurs, the beam profile of the laser beam collapses. In this case, there is a risk that the shape of the processed groove formed by laser processing will deteriorate, but the laser processing apparatuses described in the above-mentioned patent documents do not have a function of detecting the collapse of the beam profile of the laser beam.

Therefore, it is conceivable to provide a beam profiler in the laser processing apparatus and measure the beam profile of the laser beam using this beam profiler. However, in this case, beam profile measurement cannot be performed during laser processing of the wafer. In addition, beam profilers are expensive, and if a beam profiler is provided for each of a plurality of laser processing devices, the cost increases and it becomes necessary to secure a new installation space for the beam profiler. Furthermore, when laser processing is performed simultaneously at a plurality of processing points using a laser head, it takes time to measure the beam profile for each processing point with one beam profile.

Another possible method is to provide a PSD (Position Sensitive Detector) in the optical path of the laser beam in the laser head, and use the PSD to measure the positional deviation of the laser beam with respect to the optical element in the laser head. However, this method does not directly evaluate the beam profile of the laser beam, and furthermore cannot measure the beam profile collapse that occurs in the optical path downstream of the PSD.

Furthermore, it is conceivable to provide a three-dimensional measuring device (microscope) to the laser processing device and measure the shape of the processed groove formed by laser processing using the three-dimensional measuring device. However, in this case, the shape of the processed groove cannot be measured during laser processing of the wafer. Furthermore, the three-dimensional measuring device is expensive, and it is also necessary to secure additional space for its installation. Furthermore, there is also the problem that it takes time to measure the shape of the machined groove using a three-dimensional measuring device.

The present invention has been made in view of these circumstances, and provides a laser processing device and laser processing that can evaluate whether or not a processed groove is normally formed during laser processing at low cost, in a short time, and in a space-saving manner. The purpose is to provide a method.

A laser processing apparatus for achieving the object of the present invention irradiates the street with laser light from the laser head while moving the laser head relative to the wafer in the processing feed direction along the street of the wafer. In a laser processing device that performs laser processing along a street, a photographing means for photographing a first processing point of the laser beam irradiated from a laser head onto a street during laser processing; The apparatus includes a plasma shape acquisition section that acquires the plasma shape of plasma generated at the first processing point from a photographed image, and a plasma shape evaluation section that evaluates the plasma shape acquired by the plasma shape acquisition section.

According to this laser processing apparatus, by evaluating the plasma shape at the first processing point, it is possible to evaluate whether the processing groove is normally formed during laser processing.

In the laser processing apparatus according to another aspect of the present invention, the laser head corrects the shape of the laser beam so that the plasma shape at the first processing point where the plasma shape has been evaluated as abnormal by the plasma shape evaluation section becomes normal. A shape correction section is provided. Thereby, a normal processed groove can be formed by laser processing.

A laser processing apparatus according to another aspect of the present invention includes: a brightness acquisition section that acquires the brightness of plasma from the first photographed image; and a brightness evaluation section that evaluates the brightness of the plasma acquired by the brightness acquisition section. , is provided. Thereby, it is possible to evaluate whether the machined shape (machined depth, etc.) of the machined groove is normal.

In the laser processing apparatus according to another aspect of the present invention, the laser head repeatedly performs laser processing on the same street, and the photographing means photographs the first processing point under different photographing conditions for each laser processing, and Photographing is performed under photographing conditions that provide a predetermined plasma brightness. This makes it possible to correct differences in plasma brightness caused by repeated laser processing on the same street.

In a laser processing apparatus according to another aspect of the present invention, the laser head repeatedly performs laser processing on the same street and includes an image processing section that performs image processing on the first captured image, the image processing section comprising: For each laser process, image processing is performed on the first captured image under image processing conditions that are different from each other and that allow a predetermined plasma brightness to be obtained. This makes it possible to correct differences in plasma brightness caused by repeated laser processing on the same street.

In the laser processing apparatus according to another aspect of the present invention, the laser head includes a first branching optical element that branches the laser beam into a plurality of beams, and the plurality of laser beams branched by the first branching optical element are focused on a street. The photographing means photographs the first processing point for each laser beam, the plasma shape acquisition unit acquires the plasma shape for each first processing point from the first photographed image, and the plasma shape evaluation unit photographs the first processing point for each laser beam. Evaluate the plasma shape point by point. Thereby, it is possible to evaluate whether the machining groove is normally formed at each first machining point.

In the laser processing apparatus according to another aspect of the present invention, the plasma shape evaluation section evaluates the plasma shape for each first processing point and the balance of the plasma size for each first processing point. Thereby, it is possible to evaluate whether the machining shape of the machining groove is uniform for each first machining point.

In a laser processing apparatus according to another aspect of the present invention, the laser head includes a shape correction section that corrects the plasma shape and size balance of the first processing point evaluated as abnormal by the plasma shape evaluation section. Thereby, a normal processed groove can be formed by laser processing.

A laser processing apparatus according to another aspect of the present invention includes a brightness acquisition unit that acquires plasma brightness for each first processing point from a first captured image; A brightness evaluation unit that evaluates the brightness of the plasma and the balance of the brightness of the plasma for each first processing point. Thereby, it is possible to evaluate whether the machining shape of the machining groove is uniform for each first machining point.

In the laser processing apparatus according to another aspect of the present invention, there is provided a position acquisition unit that acquires a plasma position for each first processing point from a first photographed image, and a plasma position for each first processing point acquired by the position acquisition unit. A positional relationship evaluation unit that evaluates the relationship. Thereby, it is possible to evaluate whether or not the forming position of the machining groove at each first machining point is appropriate.

A laser processing apparatus according to another aspect of the present invention includes a shape information acquisition unit that acquires in advance reference shape information indicating a plasma shape when a normal processed groove is formed on a street by laser processing, and a plasma shape evaluation unit However, the plasma shape is evaluated based on the degree of coincidence between the plasma shape acquired by the plasma shape acquisition section and the reference shape information acquired by the shape information acquisition section.

In the laser processing apparatus according to another aspect of the present invention, when the laser light is a Gaussian beam and the vertical direction is a direction perpendicular to both the processing feed direction and the optical axis of the laser head, the plasma shape is The evaluation unit evaluates the plasma shape based on the roundness of the plasma and the symmetry of the plasma in the vertical direction with respect to the line to be processed by laser processing. Thereby, it is possible to evaluate whether or not the machined groove is properly formed.

In the laser processing apparatus according to another aspect of the present invention, when the laser beam is a line beam and the vertical direction is a direction perpendicular to both the processing feed direction and the optical axis of the laser head, the plasma shape evaluation unit However, the plasma shape is evaluated based on the length of the plasma in the longitudinal direction and the lateral direction, and the length in the vertical direction from one end and the other end of the plasma in the longitudinal direction to the line to be processed by laser processing. Thereby, it is possible to evaluate whether or not the machined groove is properly formed.

In the laser processing apparatus according to another aspect of the present invention, the laser head includes a laser light source that emits a laser beam, and a condensing lens that condenses the laser beam onto the street, and the photographing means passes the laser beam through the condensing lens. The first processing point is photographed coaxially with the optical axis of the laser head.

In the laser processing apparatus according to another aspect of the present invention, there is provided a main optical path from the laser light source to the condensing lens, a branch optical path branching from the middle of the main optical path and reaching the photographing means, and a branch optical path provided in the middle of the branch optical path and the main optical path. and a second branching optical element that branches into a branched optical path, and a filter that is provided in the middle of the branched optical path and transmits only light in the plasma wavelength range. Thereby, the plasma shape can be more accurately acquired from the first photographed image.

In the laser processing apparatus according to another aspect of the present invention, the laser head performs laser processing on a workpiece that can be stably laser processed at a timing other than the timing when street laser processing is performed, and During laser processing, the photographing means photographs the second processing point of the laser beam irradiated from the laser head to the workpiece, and the plasma shape acquisition unit takes a second photograph of the second processing point photographed by the photographing means. The plasma shape of the plasma generated at the second processing point is acquired from the image, and the plasma shape evaluation section evaluates the plasma shape at the second processing point acquired by the plasma shape acquisition section. This makes it possible to determine whether there is a problem with the laser head, so if an abnormality occurs in the plasma shape during street laser processing, it is possible to identify the cause (problem with wafer processability). It is.

A laser processing apparatus according to another aspect of the present invention includes a shape estimation section that estimates the shape of a processed groove formed in a street by laser processing based on the plasma shape acquired by the plasma shape acquisition section. This eliminates the need to provide the laser processing apparatus with an expensive three-dimensional measuring device (microscope) for measuring the shape of the processed groove, so the cost of the laser processing apparatus can be reduced.

A laser processing method for achieving the object of the present invention is to irradiate the street with laser light from the laser head while moving the laser head relative to the wafer in the processing feed direction along the street of the wafer. In a laser processing method that performs laser processing along the street, there is a photographing step of photographing the first processing point of the laser beam irradiated from the laser head onto the street during laser processing; a shape acquisition step of acquiring a plasma shape that is a shape of plasma generated at a first processing point from one captured image; a shape evaluation step of evaluating whether or not the plasma shape acquired in the shape acquisition step is normal; has.

According to the present invention, it is possible to evaluate whether or not a processed groove is normally formed during laser processing at low cost, in a short time, and in a space-saving manner.

FIG. 1 is a schematic diagram of a laser processing apparatus according to a first embodiment. FIG. 2 is a plan view of a wafer. FIG. 3 is an explanatory diagram for explaining laser processing along odd-numbered streets. FIG. 3 is an explanatory diagram for explaining laser processing along even-numbered streets. FIG. 3 is an explanatory diagram for explaining edge cutting and hollowing by a laser head that is moved relative to the wafer in the outward direction, and photographing of each processing point. FIG. 6 is an explanatory diagram for explaining edge cutting and hollowing by a laser head that is moved relative to the wafer in the backward direction, and photographing of each processing point. FIG. 2 is a functional block diagram of a control device according to a first embodiment. It is a figure showing an example of the photographed image of a pair of processing points of edge cutting processing. It is a figure showing an example of the photographed image of each processing point of hollow processing. FIG. 6 is an explanatory diagram for explaining evaluation of the first plasma shape for each processing point by the second evaluation unit. FIG. 6 is an explanatory diagram for explaining evaluation of the second plasma shape for each processing point by the second evaluation unit. 2 is a flowchart showing the flow of laser processing of each street of a wafer by the laser processing apparatus of the first embodiment. 13 is a flowchart showing the flow of plasma shape evaluation processing in FIG. 12. FIG. It is a functional block diagram of a control device of a laser processing device of a 2nd embodiment. It is a block diagram showing the laser processing device of a 4th embodiment. It is a schematic diagram showing the main part of the laser head of the laser processing device of a 5th embodiment. It is a functional block diagram of a control device of a laser processing device of a 6th embodiment. 3 is a flowchart showing the flow of processing in the standard machining mode. It is a functional block diagram of a control device of a laser processing device of a 7th embodiment. It is a figure which showed the modification of the laser head which uses a common laser light source for edge cutting processing and hollow processing.

[Overall configuration of laser processing device of first embodiment]
FIG. 1 is a schematic diagram of a laser processing apparatus 10 according to the first embodiment. As shown in FIG. 1, the laser processing apparatus 10 performs laser processing (ablation groove processing) on the wafer 12 as a pre-process before dividing the wafer 12 into a plurality of chips 14 (see FIG. 2) by blade processing. give Note that the XYZ directions in the figure are orthogonal to each other, of which the X and Y directions are horizontal, and the Z direction is vertical. Here, the X direction corresponds to the processing feed direction of the present invention, and the Y direction corresponds to the vertical direction of the present invention.

FIG. 2 is a plan view of the wafer 12. As shown in FIG. 2, the wafer 12 is a laminate in which a low-k film and a functional film for forming a circuit are laminated on the surface of a substrate made of silicon or the like. The wafer 12 is divided into a plurality of regions by a plurality of streets C arranged in a grid pattern. A device 16 constituting the chip 14 is provided in each of the divided areas.

The laser processing apparatus 10 processes the substrate along each street C along one direction that intersects with each other, as shown by the numbers (1) to (4) in parentheses in the figure. Laser processing is performed to remove low-k films and the like. Further, when the laser processing of all streets C parallel to one direction is completed, the laser processing apparatus 10 rotates the wafer 12 by 90 degrees and performs low-k processing along each street C along the other direction. Perform laser processing to remove films, etc.

At this time, in order to reduce the takt time required for the laser processing of the wafer 12, the laser processing apparatus 10 uses a processing feed direction (relative movement direction) when moving a laser head 24, which will be described later, relative to the wafer 12 in the X direction. ) are switched alternately for each street C.

For example, when performing laser processing along odd-numbered streets C shown in parentheses (1), (3), etc. in the figure, the laser head 24 (described later) is moved in one direction in the X direction with respect to the wafer 12. side, which is the forward direction side XA (see FIG. 5). In addition, when laser processing is performed along even-numbered streets C shown in parentheses (2), (4), etc. in the figure, the laser head 24 is placed on the other side of the X direction with respect to the wafer 12. It is relatively moved to a certain return direction side XB (see FIG. 6).

FIG. 3 is an explanatory diagram for explaining laser processing along odd-numbered streets C. FIG. 4 is an explanatory diagram for explaining laser processing along even-numbered streets C.

As shown in FIGS. 3 and 4, the laser processing device 10 simultaneously (in parallel) performs edge cutting and hollow processing as laser processing. The edge cutting process is laser processing to form two edge cutting grooves 18 (corresponding to the processing grooves of the present invention) parallel to each other along the street C. This edge cutting process is performed using two lines of first laser light L1, which are split beams. Note that each of the two first laser beams L1 is a so-called Gaussian beam.

The hollowing process is laser processing that forms a hollow groove 19 (corresponding to the processing groove of the present invention) between the two edge cutting grooves 18 formed by the edge cutting process. This hollowing is performed using the second laser beam L2, which is a line beam that is branched into a plurality of lines in the processing feed direction (X direction). In addition, in order to prevent the drawing from becoming complicated, the number of branches of the second laser beam L2 is two, but it may be branched into three or more.

Note that the edge cutting process (two edge cutting grooves 18) and the hollowing process (hollowing grooves 19) are known techniques (see Patent Document 1), so a detailed explanation thereof will be omitted.

In this way, in the laser processing apparatus 10, when the laser head 24 is moved relative to the wafer 12 in the outward direction XA (see FIG. 5) or in the backward direction XB (see FIG. 6), In either case, edge cutting is performed prior to hollowing.

Returning to FIG. 1, in parallel with the laser processing on street C, the laser processing device 10 photographs the processing point SP1 of the two first laser beams L1 and the processing point SP2 of each second laser beam L2. and do. In addition, each processing point SP1, SP2 corresponds to the 1st processing point of this invention.

The laser processing device 10 includes a table 20, a laser head 24, a microscope 26, a relative movement mechanism 28, and a control device 30.

Table 20 holds wafer 12. This table 20 is moved by the relative movement mechanism 28 in the X direction, which is the processing feed direction parallel to the street C to be processed, and is also rotated about the central axis (rotation axis) of the table 20, which is parallel to the Z direction. Ru.

The laser head 24 (also referred to as a laser optical system or a laser unit) includes a first laser light source 22A, a second laser light source 22B, a first condensing lens 38, and two second condensing lenses 40A and 40B. Equipped with. The laser head 24 irradiates the street C with two lines of first laser light L1 from the first condenser lens 38. Further, the laser head 24 selectively irradiates each second laser beam L2 toward the street C from the two second condensing lenses 40A and 40B. Note that the laser head 24 is moved in the Y direction and the Z direction by a relative movement mechanism 28, which will be described later.

The microscope 26 is fixed to the laser head 24 and moves together with the laser head 24. The microscope 26 photographs the alignment reference formed on the wafer 12 before the wafer 12 is edge-cut and hollowed out. Note that various structures on the street C, the device 16, or known alignment marks are used as the alignment reference.

The relative movement mechanism 28 is composed of an XYZ actuator and a motor (not shown), and under the control of the control device 30, moves the table 20 in the X direction and rotates around the rotation axis, and moves the laser head 24 in the Y direction. movement in the direction and Z direction. Thereby, the relative movement mechanism 28 can move the laser head 24 and the microscope 26 relative to the table 20 and the wafer 12.

By driving the relative movement mechanism 28, the laser head 24 is aligned with the processing start position, which is one end of the street C to be processed, and the laser head 24 is aligned in the processing feed direction (X direction) along the street C. It is possible to perform a relative movement of . Further, by driving the relative movement mechanism 28 and rotating the table 20 by 90 degrees, the mutually intersecting streets C can be selectively made parallel to the processing feed direction (X direction).

The control device 30 centrally controls the operation of each part of the laser processing device 10 such as the laser head 24, the microscope 26, and the relative movement mechanism 28, and performs alignment of the laser head 24, laser processing for each street C, and each processing. The points SP1 and SP2 are photographed, and each plasma shape described below is evaluated for each of the processing points SP1 and SP2.

[Laser head]
FIG. 5 is an explanatory diagram for explaining edge cutting and hollowing by the laser head 24 that is moved relative to the wafer 12 in the outward direction XA, and photographing of each processing point SP1, SP2. FIG. 6 is an explanatory diagram for explaining the edge cutting and hollowing by the laser head 24 that is moved relative to the wafer 12 in the return direction side XB, and the photographing of each processing point SP1, SP2.

As shown in FIGS. 5 and 6, the laser head 24 includes a first laser light source 22A, a second laser light source 22B, a first light forming element 32, a beam splitter 33, a second light forming element 34, Beam splitter 35, branching optical element 35A, connection switching element 36, beam splitter 37, first condensing lens 38, second condensing lens 40A, 40B, illumination light source 41, beam splitter 42, 43A , 43B, cameras 45, 46A, 46B as photographing means, a first imaging lens 47, second imaging lenses 48A, 48B, and steering mirror mechanisms M1A, M1B.

The first laser light source 22A emits laser light LA under conditions (wavelength, pulse width, repetition frequency, etc.) suitable for edge cutting to the first light forming element 32 under the control of the control device 30. The second laser light source 22B emits laser light LB having conditions suitable for hollowing (wavelength, pulse width, repetition frequency, etc.) to the second light forming element 34. In this embodiment, the wavelength of the laser beams LA and LB is, for example, 355 nm.

The first light forming element 32 functions as a first branching optical element of the present invention, and for example, a diffractive optical element (DOE) is used. This first light forming element 32 branches (divides) the laser beam LA incident from the first laser light source 22A to form two first laser beams L1 corresponding to edge cutting processing, and The light L1 is emitted toward the beam splitter 33. As a result, a portion of the two first laser beams L1 is reflected by the beam splitter 33 toward the first condenser lens 38. As a result, two lines of the first laser beam L1 are focused by the first condensing lens 38 on the street C (outward path and return path), and a pair of processing points SP1 spaced apart in the Y direction are formed on the street C. .

As the second light forming element 34, for example, a diffractive optical element, a mask, etc. are used. The second light forming element 34 forms a second laser beam L2 corresponding to hollow processing from the laser beam LB incident from the second laser light source 22B. The second laser beam L2 forms a linear processing point SP2 on the wafer 12 between the two edge cutting grooves 18 (other shapes such as a circular shape are also possible). The width of this processing point SP2 in the Y direction is adjusted according to the interval between the two edge cutting grooves 18. A portion of the second laser beam L2 emitted from the second light forming element 34 is reflected by the beam splitter 35 toward the branching optical element 35A.

Note that by rotating the first light shaping element 32 around its optical axis, the interval in the Y direction between the pair of processing points SP1 can be adjusted, and by rotating the second light shaping element 34 around its optical axis. By rotating in the direction, the width of the processing point SP2 in the Y direction can be adjusted (see Patent Document 1 above).

The branching optical element 35A functions as a first branching optical element of the present invention like the first light forming element 32 described above, and directs the second laser beam L2 incident from the second light forming element 34 in the X direction. (processing feed direction) into multiple branches. As this branching optical element 35A, for example, a diffractive optical element, a refractive optical element, a prism, a combination thereof, etc. are used. Then, the branching optical element 35A emits each of the branched second laser beams L2 to the connection switching element 36.

The connection switching element 36 is, for example, a known optical switch. Note that the connection switching element 36 may be configured by appropriately combining a λ/2 plate, a polarizing beam splitter, a half mirror (beam splitter), a shutter, and the like. The connection switching element 36 selectively guides each second laser beam L2 emitted from the second light forming element 34 to either the second condenser lens 40A or the second condenser lens 40B.

The beam splitter 37 reflects a portion of each second laser beam L2 incident from the connection switching element 36 toward the second condenser lens 40B.

The first condenser lens 38 and the second condenser lenses 40A and 40B are arranged in a line along the X direction (processing feed direction). The first condenser lens 38 is arranged between the second condenser lens 40A and the second condenser lens 40B. The second condenser lens 40A is arranged on the return path side XB with respect to the first condenser lens 38. The second condensing lens 40B is arranged on the outgoing direction side XA with respect to the first condensing lens 38.

The first condensing lens 38 condenses the two lines of first laser light L1 incident from the first light forming element 32 onto the street C (outward path and return path). The second condensing lens 40A condenses each second laser beam L2 incident from the connection switching element 36 onto the street C (outgoing path). The second condensing lens 40B condenses each second laser beam L2 that has entered from the connection switching element 36 via the beam splitter 37 onto the street C (return path).

When the laser head 24 is moved relative to the wafer 12 in one of the forward direction side XA and the backward direction side The two laser beams L2 are guided to one of the second condensing lenses 40A and 40B, which is located on the other direction side of the forward direction side XA and the backward direction side XB with respect to the first condensing lens 38.

Specifically, when the laser head 24 is moved relative to the wafer 12 in the forward direction side XA, the connection switching element 36 switches each of the second laser beams L2 emitted from the second light forming element 34 to 2 to a condensing lens 40A (see FIG. 5). Thereby, each second laser beam L2 is focused onto the street C (outward path) by the second focusing lens 40A. As a result, edge cutting is performed in advance along street C (outgoing path) by the relative movement of the laser head 24 toward the forward direction side XA, thereby forming two edge cutting grooves 18, and then hollowing. By performing this, a hollow groove 19 is formed between the two edge cutting grooves 18.

Further, when the laser head 24 is moved relative to the wafer 12 in the return direction side The light is guided to the optical lens 40B (see FIG. 6). Thereby, each second laser beam L2 is focused onto the street C (return path) by the second focusing lens 40B. As a result, edge cutting is performed in advance along street C (return path) by the relative movement of the laser head 24 in the backward direction side XB, thereby forming two edge cutting grooves 18, and then hollowing. By performing this, a hollow groove 19 is formed between the two edge cutting grooves 18.

The illumination light source 41 emits illumination light L3 that illuminates the street C (the two edge cutting grooves 18 and the hollow groove 19) during laser processing. Note that the illumination light L3 is in a wavelength range (approximately 430 nm) is used.

Illumination light L3 emitted from the illumination light source 41 enters the first condenser lens 38 via the beam splitters 42 and 33, and is condensed onto the surface of the wafer 12 by the first condenser lens 38. Thereby, the surface of the wafer 12 is illuminated by the illumination light L3.

Further, the illumination light L3 emitted from the illumination light source 41 enters the second condenser lens 40A via the beam splitters 43A, 35 and the connection switching element 36, and is directed onto the surface of the wafer 12 by the second condenser lens 40A. The light is focused. Further, the illumination light L3 enters the second condenser lens 40B via the beam splitters 43B and 37, and is condensed onto the surface of the wafer 12 by the second condenser lens 40B. Thereby, the surface of the wafer 12 is illuminated by the illumination light L3.

Note that the illumination light source 41 stops emitting the illumination light L3 during laser processing of the street C (the two edge cutting grooves 18 and the hollow groove 19).

The optical path from the first laser light source 22A to the first condensing lens 38 and the optical path from the illumination light source 41 to the first condensing lens 38 constitute a main optical path OP1. The main optical path OP1 guides the first laser beam L1 to the first condenser lens 38 during the street C laser processing. Also, during the laser processing on street C (outward and return passes), the main optical path OP1 contains plasma that is the emission of plasma 68 (see FIG. 8) generated at each pair of processing points SP1 by the laser processing using the first laser beam L1. The light emission R1A and the first laser reflected light R1B, which is the reflected light of the first laser light L1, enter from the first condensing lens 38. The first laser reflected light R1B is the light that the first laser light L1 is reflected by the plume (steam) generated at the pair of processing points SP1 by the above-described laser processing. A portion of the plasma emission R1A and the first laser reflected light R1B that have entered the main optical path OP1 pass through the beam splitter 33 and enter the beam splitter 42.

A main optical path OP2 is constituted by the optical path from the second laser light source 22B to the second condensing lens 40A and the optical path from the illumination light source 41 to the second condensing lens 40A. The main optical path OP2 guides the second laser beam L2 to the second condenser lens 40A during street C (outward path) laser processing. In addition, during laser processing on street C (outward path), the main optical path OP2 includes plasma emission R2A, which is the emission of plasma 69 (see FIG. 9) generated at each processing point SP2 by laser processing using the second laser beam L2. Second laser reflected light R2B, which is reflected light of the second laser light L2, enters from the second condenser lens 40A. The second laser reflected light R2B is light obtained by reflecting the second laser light L2 from the plume generated at the processing point SP2 by the above-described laser processing. A part of the plasma emission R2A and the second laser reflected light R2B that have entered the main optical path OP2 pass through the connection switching element 36, the branching optical element 35A, and the beam splitter 35, and enter the beam splitter 43A.

The main optical path OP3 is constituted by the optical path from the second laser light source 22B to the second condensing lens 40B and the optical path from the illumination light source 41 to the second condensing lens 40B. The main optical path OP3 guides the second laser beam L2 to the second condenser lens 40B during street C (return path) laser processing. Further, during the laser processing on street C (return path), the above-mentioned plasma emission R2A and second laser reflected light R2B enter the main optical path OP3 from the second condenser lens 40B. A portion of the plasma emission R2A and the second laser reflected light R2B that have entered the main optical path OP3 pass through the beam splitter 37 and enter the beam splitter 43B.

Beam splitters 42, 43A, and 43B function as second branching optical elements of the present invention. The beam splitter 42 branches the branch optical path BP1 from the main optical path OP1. The beam splitter 42 reflects a portion of the plasma emission R1A and the first laser reflected light R1B that have entered from the beam splitter 33 toward the branched optical path BP1. Note that the first laser reflected light R1B reflected onto the branched optical path BP1 is blocked by, for example, a multi-band pass filter (filter 75 shown in FIG. 16, which will be described later).

The beam splitter 43A branches the branch optical path BP2 from the main optical path OP2. This beam splitter 43A reflects a part of the plasma emission R2A and the second laser reflected light R2B that have entered from the beam splitter 35 toward the branched optical path BP2. Note that the second laser reflected light R2B reflected onto the branched optical path BP2 is blocked by, for example, a multi-band pass filter (filter 76A shown in FIG. 16, which will be described later).

Beam splitter 43B branches branch optical path BP3 from main optical path OP3. This beam splitter 43B reflects a portion of the plasma emission R2A and the second laser reflected light R2B that have entered from the beam splitter 37 toward the branched optical path BP3. Note that the second laser reflected light R2B reflected onto the branched optical path BP3 is blocked by, for example, a multi-band pass filter (filter 76B shown in FIG. 16, which will be described later).

The first imaging lens 47 is arranged on the branched optical path BP1, and images the plasma emission R1A incident from the beam splitter 42 on the camera 45. The second imaging lens 48A is arranged on the branched optical path BP2, and images the plasma emission R2A incident from the beam splitter 43A on the camera 46A. The second imaging lens 48B is arranged on the branched optical path BP3, and images the plasma emission R2A incident from the beam splitter 43B on the camera 46B.

The cameras 45, 46A, and 46B are electronic cameras equipped with a photographing optical system and an image sensor (not shown). The cameras 45, 46A, and 46B photograph the processing points SP1 and SP2 coaxially with the laser head 24 (first condenser lens 38, second condenser lens 40A, 40B).

The camera 45 is arranged on the branch optical path BP1 and images the plasma emission R1A through the first imaging lens 47. As a result, the camera 45 captures the plasma 68 (see FIG. 8) generated at the pair of processing points SP1 through the first condenser lens 38 while edge cutting processing is being performed on the street C (outbound and return passes). Take a photo. Photographed images D1 (image data) of the pair of processing points SP1 (plasma 68) photographed by the camera 45 are output from the camera 45 to the control device 30.

The camera 46A is arranged on the branched optical path BP2, and images the plasma emission R2A through the second imaging lens 48A. As a result, the camera 46A photographs the plasma 69 (see FIG. 9) generated at each processing point SP2 through the second condenser lens 40A while the street C (outward path) hollowing process is being performed. Photographed images D2A (image data) of each processing point SP2 (plasma 69) photographed by the camera 46A are outputted from the camera 46A to the control device 30.

Camera 46B is arranged on branch optical path BP3, and images plasma emission R2A through second imaging lens 48B. Thereby, the camera 46B photographs the plasma 69 (see FIG. 9) generated at each processing point SP2 through the second condenser lens 40B while the street C (return path) hollowing process is being performed. A captured image D2B (image data) of each processing point SP2 (plasma 69) captured by the camera 46B is outputted from the camera 46B to the control device 30. Note that the photographed images D1, D2A, and D2B correspond to the first photographed images of the present invention.

The steering mirror mechanisms M1A and M1B correspond to the shape correction section of the present invention. The steering mirror mechanism M1A is provided between the first laser light source 22A and the first light forming element 32, and is composed of two or more steering mirrors 102. The steering mirror mechanism M1A adjusts the emission direction of the laser beam LA emitted from the first laser light source 22A (optical axis adjustment) by adjusting the angle of each steering mirror 102. Thereby, the positional deviation between the pair of processing points SP1 is corrected, or the deformation of the shape of plasma 68 (see FIG. 8), which will be described later, generated at each processing point SP1 is corrected.

The steering mirror mechanism M1B is provided between the second laser light source 22B and the second light forming element 34, and is composed of a plurality of steering mirrors 102 similarly to the steering mirror mechanism M1A. The steering mirror mechanism M1B adjusts the emission direction of the laser beam LB emitted from the second laser light source 22B (optical axis adjustment) by adjusting the angle of each steering mirror 102. Thereby, the positional deviation of each processing point SP2 is corrected, or the deformation of the shape of plasma 69 (see FIG. 9), which will be described later, generated at each processing point SP2 is corrected.

Note that a steering mirror mechanism M2A may be provided instead of the steering mirror mechanism M1A or together with the steering mirror mechanism M1A. The steering mirror mechanism M2A is provided between the first light forming element 32 and the beam splitter 33, and has the same configuration as the steering mirror mechanisms M1A and M1B. Thereby, it is possible to correct the positional deviation of each processing point SP1, or to correct the deformation of the plasma 68 (see FIG. 8).

Further, a steering mirror mechanism M2B may be provided instead of the steering mirror mechanism M1B or together with the steering mirror mechanism M1B. The steering mirror mechanism M2B is provided between the second light forming element 34 and the beam splitter 35, and has the same configuration as the steering mirror mechanisms M1A and M1B. Thereby, it is possible to correct the positional deviation of each processing point SP2, or to correct the deformation of the plasma 69 (see FIG. 9).

Furthermore, a steering mirror mechanism M3 may be provided between the connection switching element 36 and the beam splitter 37. The steering mirror mechanism M3 has the same configuration as the steering mirror mechanisms M1A and M1B, and corrects the positional deviation of each processing point SP2 (return direction side XB), and corrects the positional deviation of each processing point SP2 (return direction side XB). The deformation of the plasma 69 (see FIG. 9), which will be described later, which is generated during the process is corrected.

The steering mirror mechanisms M1A, M1B, M2A, M2B, and M3 may be provided in appropriate combinations. Furthermore, steering mirror mechanisms other than the steering mirror mechanisms M1A, M1B, M2A, M2B, and M3 may be provided. Furthermore, a steering mirror mechanism may be provided for each optical path of the plurality of laser beams L2 branched by the branching optical element 35A.

[Control device of first embodiment]
FIG. 7 is a functional block diagram of the control device 30 of the first embodiment. As shown in FIG. 7, the control device 30 is configured by an arithmetic device such as a personal computer, and includes an arithmetic circuit including various processors, memories, and the like. Various processors include CPU (Central Processing Unit), GPU (Graphics Processing Unit), ASIC (Application Specific Integrated Circuit), and programmable logic devices [for example, SPLD (Simple Programmable Logic Devices), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Arrays)]. Note that the various functions of the control device 30 may be realized by one processor, or may be realized by a plurality of processors of the same type or different types.

The control device 30 includes the above-described first laser light source 22A, second laser light source 22B, microscope 26, relative movement mechanism 28, illumination light source 41, cameras 45, 46A, 46B, and steering mirror mechanisms M1A, M1B (steering mirror In addition to the mechanisms M2A, M2B, M3), a storage section 31 and an operation section 49 are connected. The storage unit 31 stores reference shape information 70, which will be described later, in addition to a control program for the control device 30 (not shown). The operation unit 49 uses a keyboard, a mouse, an operation panel, operation buttons, etc., and receives inputs for various operations from an operator.

The control device 30 executes a control program (not shown) stored in the storage unit 31 to control the alignment detection unit 50, the laser processing control unit 52, the imaging control unit 54, the plasma shape acquisition unit 56, and the shape information acquisition unit. 58, functions as a plasma shape evaluation section 60, a correction section 62, a stop control section 64, and a notification section 66. It should be noted that what is described as "unit" of the control device 30 may also be "circuit", "apparatus", or "equipment". That is, what is described as "unit" may be composed of firmware, software, hardware, or a combination thereof.

The alignment detection unit 50 performs alignment detection to detect the position of each street C on the wafer 12 by controlling the microscope 26 and the relative movement mechanism 28 . For example, the alignment detection unit 50 first drives the relative movement mechanism 28 to adjust the position of the microscope 26 with respect to a predetermined alignment reference of the wafer 12. Next, the alignment detection unit 50 causes the microscope 26 to take a picture of a predetermined alignment reference, thereby acquiring a captured image of the alignment reference from the microscope 26 . The alignment detection unit 50 then detects the position of each street C, that is, performs alignment detection, using a known method based on the photographed image of the alignment reference.

The laser processing control unit 52 controls the first laser light source 22A, the second laser light source 22B, the relative movement mechanism 28, and the connection switching element 36 based on the alignment detection result by the alignment detection unit 50, and controls the laser processing for each street C. Execute processing (edge cutting, hollow processing).

Specifically, the laser processing control section 52 drives the relative movement mechanism 28 based on the detection result of the alignment detection section 50 to move the first condensing lens of the laser head 24 to the processing start position of street C (outward path and return path). 38 optical axes are aligned.

Next, the laser processing control unit 52 drives the connection switching element 36 to switch the lens that emits the second laser beam L2 to the second condensing lens 40A when performing street C (outward path) laser processing. Conversely, when performing street C (return path) laser processing, the lens that emits the second laser beam L2 is switched to the second condensing lens 40B.

Then, the laser processing control unit 52 causes the first laser light source 22A and the second laser light source 22B to emit laser beams LA and LB. Further, the laser processing control unit 52 drives the relative movement mechanism 28 to move the laser head 24 relative to the wafer 12 in the forward direction side XA when performing laser processing on street C (outward path). When performing C (return path) laser processing, the laser head 24 is moved relative to the wafer 12 in the return path direction side XB. As a result, the formation of the two edge cutting grooves 18 by the edge cutting process and the formation of the hollow groove 19 by the hollow cutting process are performed at the same time with an interval between them (see FIGS. 5 and 6). Thereafter, the laser processing control unit 52 repeatedly executes the above-described process for each street C.

The photographing control unit 54 controls the illumination light source 41 and cameras 45, 46A, and 46B to photograph the pair of processing points SP1 (plasma 68, see FIG. 8) and each processing point SP2 (plasma 69, see FIG. 9). Control. Specifically, the imaging control unit 54 repeatedly images the plasma emission R1A with the camera 45 and the plasma emission R2A with the camera 46A during laser processing on the street C (outward path). As a result, during laser processing on street C (outward path), the output of the photographed image D1 of the pair of processing points SP1 (plasma 68) by the camera 45 and the output of the photographed image D2A of each processing point SP2 (plasma 69) by the camera 46A are output. The output and are executed repeatedly.

Furthermore, the imaging control unit 54 continuously images the plasma emission R1A with the camera 45 and the plasma emission R2A with the camera 46B during the laser processing on street C (return trip). As a result, during the street C (return path) laser processing, the camera 45 outputs the photographed images D1 of the pair of processing points SP1 (plasma 68), and the camera 46B outputs the photographed images D2B of each processing point SP2 (plasma 69). The output and are executed repeatedly.

FIG. 8 is a diagram showing an example of a captured image D1 of a pair of processing points SP1 (plasma 68). FIG. 9 is a diagram showing an example of photographed images D2A and D2B of each processing point SP2 (plasma 69). As shown in FIG. 8, the photographed image D1 includes an image of plasma 68 generated at each processing point SP1. The plasma 68 is generated when a plume (steam) generated at each processing point SP1 by laser processing is heated by the first laser beam L1. Therefore, the first plasma shape, which is the shape of the plasma 68 at each processing point SP1, serves as an index indicating whether or not the beam profile of the two first laser beams L1 is normal.

As shown in FIG. 9, the photographed images D2A and D2B include a plurality of images of plasma 69 generated at each of a plurality of processing points SP2. Each plasma 69 is generated when a plume generated at each processing point SP2 by laser processing is heated by the second laser beam L2. Therefore, the second plasma shape, which is the shape of the plasma 69 at each processing point SP2, indicates whether or not the beam profile of each second laser beam L2 is normal.

Returning to FIG. 7, the plasma shape acquisition unit 56 acquires the first plasma shape of each processing point SP1 from the photographed image D1 every time the photographed image D1 is output from the camera 45 during the street C (outward path) laser processing. get. At the same time, the plasma shape acquisition unit 56 acquires the second plasma shape of each processing point SP2 from the photographed image D2A every time the photographed image D2A is output from the camera 46A.

Specifically, the plasma shape acquisition unit 56 compares the brightness values of each pixel in the photographed images D1 and D2A and selects pixels whose brightness values are equal to or higher than a predetermined threshold value, thereby obtaining the plasma 68, 69 areas are detected. Next, the plasma shape acquisition unit 56 determines the shape of each plasma based on the contours of the detected regions of the plasmas 68 and 69.

During street C (return path) laser processing, the plasma shape acquisition unit 56 acquires the first plasma shape of each processing point SP1 from the photographed image D1 every time the photographed image D1 is output from the camera 45. At the same time, the plasma shape acquisition unit 56 acquires the second plasma shape of each processing point SP2 from the photographed image D2B every time the photographed image D2B is output from the camera 46B.

The plasma shape acquisition unit 56 sequentially outputs information on each plasma shape to the plasma shape evaluation unit 60 every time each plasma shape is acquired from the photographed images D1, D2A or the photographed images D1, D2B.

The shape information acquisition unit 58 acquires reference shape information 70 from the storage unit 31 before the start of laser processing on street C (outward and backward passes) and when a first evaluation unit 60A described below evaluates each plasma shape. is obtained in advance and this reference shape information 70 is output to the first evaluation section 60A.

The reference shape information 70 includes a first plasma shape and a second plasma shape (hereinafter referred to as a reference shape) when two normal edge cutting grooves 18 and a hollow groove 19 are formed by laser processing (edge cutting processing, hollow processing). ). This reference shape information 70 is generated in advance and stored in the storage unit 31 before the laser processing of the wafer 12. When generating the reference shape information 70, for example, use a known beam profiler or the like to confirm that the beam profile of the laser head 24 is normal, and use the confirmed laser head 24 to determine whether the wafer 12 or processability is correct. Perform standard processing by laser processing a stable workpiece (silicon, etc.). Then, the reference shape information 70 is generated by observing each plasma shape generated at each processing point SP1, SP2 during this reference processing. Note that when there are multiple types (products) of wafers 12 to be laser processed, reference shape information 70 may be generated for each type of wafer 12.

The plasma shape evaluation unit 60 determines whether each plasma shape at each processing point SP1 and SP2 is normal (appropriate) or collapsed during laser processing on street C (outward and backward paths), that is, whether it is abnormal. Evaluate whether it is. This plasma shape evaluation section 60 includes a first evaluation section 60A that evaluates each plasma shape using the reference shape information 70, and a second evaluation section 60B that evaluates each plasma shape without using the reference shape information 70. , is provided. The first evaluation section 60A and the second evaluation section 60B selectively operate according to a selection operation on the operation section 49, for example.

First, evaluation of each plasma shape by the first evaluation section 60A will be described. The first evaluation section 60A acquires the reference shape information 70 from the shape information acquisition section 58 before starting the laser processing on street C (outbound and return trips). Then, each time the first plasma shape of each processing point SP1 is input from the plasma shape acquisition section 56 during laser processing, the first evaluation section 60A calculates the input first plasma shape and the reference shape information 70. The degree of agreement between the plasma 68 and the reference shape is calculated, and the first plasma shape is evaluated based on this degree of agreement. Specifically, the first evaluation unit 60A evaluates that the first plasma shape is normal when the degree of coincidence between the first plasma shape and the reference shape is greater than or equal to a predetermined threshold; If it is less than 1, the first plasma shape is evaluated to be abnormal.

In addition, each time the second plasma shape of each processing point SP2 is input from the plasma shape acquisition unit 56 during laser processing, the first evaluation unit 60A calculates the input second plasma shape and the reference shape information 70. The degree of coincidence of the plasma 69 with the reference shape is calculated, and it is evaluated whether the second plasma shape is normal or abnormal based on whether the degree of coincidence is greater than or equal to a predetermined threshold.

Next, evaluation of each plasma shape by the second evaluation section 60B will be explained using FIGS. 10 and 11.

FIG. 10 is an explanatory diagram for explaining the evaluation of the first plasma shape for each processing point SP1 by the second evaluation section 60B. Note that symbols A1 and A2 in the figure represent photographed images D1 (see symbol A1) when the first plasma shape at each processing point SP1 is normal, and when the first plasma shape at each processing point SP1 is abnormal. A photographed image D1 (see reference numeral A2) is shown. Further, reference numeral B1 in the figure is a cross-sectional view of two edge cutting grooves 18 formed at each processing point SP1 indicated by reference numeral A1, viewed from the X direction. Reference numeral B2 in the figure is a cross-sectional view of two edge cutting grooves 18 formed at each processing point SP1 indicated by reference numeral A2, viewed from the X direction.

Furthermore, the reference numeral J1 in the figure is a planned line for machining the two edge cutting grooves 18, and the reference numeral J2 is a planned line for machining the hollow groove 19.

As shown in FIG. 10, the second evaluation section 60B evaluates the input first plasma shape every time the first plasma shape for each processing point SP1 is input from the plasma shape acquisition section 56. Here, two first laser beams L1, which are split beams, are used for edge cutting, and each first laser beam L1 is a Gaussian beam. Therefore, the second evaluation unit 60B evaluates the first plasma shape corresponding to the Gaussian beam and the first plasma shape corresponding to the split beam.

Evaluation of the first plasma shape corresponding to the Gaussian beam is to evaluate whether the first plasma shape of each processing point SP1 is circular (including substantially circular). For example, the first evaluation unit 60A calculates evaluation items such as the circularity of each first plasma shape and the Y-direction symmetry of the plasma 68 with respect to the planned processing line J1 (see arrow E in the figure) using a known method. do. Then, the first evaluation unit 60A determines that each first plasma shape is normal based on whether the evaluation items (circularity and Y-direction symmetry) of each first plasma shape satisfy a predetermined threshold. Evaluate whether it is normal or abnormal.

Evaluation of the first plasma shape corresponding to the split beam means evaluating the balance of the size of the first plasma shape for each processing point SP1. For example, the second evaluation unit 60B compares the area of the first plasma shape for each processing point SP1, and determines whether the difference in area between the two is equal to or less than a predetermined threshold. Evaluate whether the shape size balance is normal or abnormal.

FIG. 11 is an explanatory diagram for explaining the evaluation of the second plasma shape for each processing point SP2 by the second evaluation section 60B. Note that the captured images D2A, D2B (see reference numeral A1) when the second plasma shape at each processing point SP2 is normal, and the captured images D2A, D2B (when the second plasma shape at each processing point SP2 is abnormal) (see reference numeral A2). Further, reference numeral B1 in the figure is a cross-sectional view of the hollow groove 19 formed at each processing point SP2 indicated by reference numeral A1, viewed from the FIG. 3 is a cross-sectional view of the hollow groove 19 formed at the processing point SP2 when viewed from the X direction.

As shown in FIG. 11, the second evaluation section 60B evaluates the input second plasma shape every time the second plasma shape for each processing point SP2 is input from the plasma shape acquisition section 56. Here, a plurality of second laser beams L2 that are split beams are used for the hollow processing, and each second laser beam L2 is a line beam. Therefore, the second evaluation unit 60B evaluates the second plasma shape corresponding to the line beam and the second plasma shape corresponding to the split beam.

Evaluation of the plasma shape corresponding to the line beam means evaluating whether the second plasma shape at each processing point SP2 satisfies a predetermined line shape. For example, the second evaluation unit 60B determines the length W1 (including its uniformity) in the longitudinal direction, the length W2 (including its uniformity) in the transverse direction, and the length W2 (including its uniformity) in the X direction for each second plasma shape. Various evaluation items including the angle θ in the longitudinal direction and the symmetry of the lengths d1 and d2 in the Y direction from one end and the other end in the longitudinal direction to the planned processing line J2 are calculated using known methods. Then, the second evaluation unit 60B evaluates each second plasma shape based on whether the evaluation items (uniformity of widths W1 and W2, angle θ, and symmetry) are within predetermined threshold ranges. It is evaluated whether the second plasma shape is normal or abnormal.

Evaluation of the second plasma shape corresponding to the split beam means evaluating the balance of the size of the second plasma shape for each processing point SP2. For example, the second evaluation unit 60B compares the area of the second plasma shape for each processing point SP2, and based on whether the difference in the individual areas is less than or equal to a predetermined threshold, the second evaluation unit 60B Evaluate whether the shape size balance is normal or abnormal.

Returning to FIG. 7, the correction section 62 corresponds to the shape correction section of the present invention. The correction unit 62 corrects the steering mirror mechanism M1A, when the first evaluation unit 60A or the second evaluation unit 60B evaluates that at least one of the plasma shapes at each processing point SP1, SP2 is abnormal. By driving M1B and the like to correct the optical axes of the respective laser beams L1 and L2, the plasma shape for which an abnormality evaluation has been made is corrected. That is, the correction unit 62 corrects the shape (position, balance) of the beam (first laser light L1, second laser light L2) so that the plasma shape evaluated as abnormal becomes normal.

For example, when the first plasma shape is abnormal, the correction unit 62 adjusts the difference between the first plasma shape and the reference shape of the plasma 68 indicated by the reference shape information 70 to be reduced (preferably minimized). ), the first plasma shape is corrected by driving the steering mirror mechanism M1A and the like to correct the optical axis of the two first laser beams L1. Alternatively, the correction unit 62 drives the steering mirror mechanism M1A etc. to adjust the first plasma shape so that the evaluation items (roundness, Y-direction symmetry, balance, etc.) of the first plasma shape satisfy predetermined threshold values. Make corrections.

Further, when the second plasma shape is abnormal, the correction unit 62 adjusts the difference between the second plasma shape and the reference shape of the plasma 69 indicated by the reference shape information 70 to be reduced (preferably minimized). ), the second plasma shape is corrected by driving the steering mirror mechanism M1B and the like to correct the optical axis of each second laser beam L2. Alternatively, the correction unit 62 drives the steering mirror mechanism M1B etc. so that the evaluation items of the second plasma shape (uniformity of widths W1 and W2, angle θ, symmetry, balance, etc.) satisfy predetermined threshold values. Correction of the second plasma shape is performed.

The stop control unit 64 performs laser processing control when either the first evaluation unit 60A or the second evaluation unit 60B determines that one of the plasma shapes is abnormal and the correction unit 62 cannot correct it. 52 to stop the laser processing on street C. Note that the case where correction by the correction unit 62 cannot be performed means, for example, when the difference between each plasma shape and the reference shape is larger than a predetermined upper limit value, or when the evaluation items for each plasma shape shown in FIGS. This may be the case if the value is not within the range, or if the correction by the correction unit 62 is not completed even after a certain period of time has elapsed.

When the stop control unit 64 stops the laser processing of street C, the notification unit 66 displays warning information on a monitor (not shown), outputs the warning information audibly from a speaker (not shown), or executes a combination thereof. This notifies the operator of warning information.

[Operation of the laser processing device of the first embodiment]
FIG. 12 is a flowchart showing the flow of laser processing of each street C of the wafer 12 by the laser processing apparatus 10 of the first embodiment. FIG. 13 is a flowchart showing the flow of the plasma shape evaluation process in FIG. 12 according to the laser processing method of the present invention. It is assumed that the reference shape information 70 is stored in the storage unit 31 by performing the reference processing described above in advance.

As shown in FIG. 12, when the wafer 12 to be processed is held on the table 20 after the laser processing apparatus 10 is powered on, the alignment detection unit 50 drives the relative movement mechanism 28 to move the microscope 2 After relatively moving the alignment reference (not shown) of the wafer 12 to a position where it can be photographed, the microscope 26 is caused to photograph the alignment reference. Then, the alignment detection unit 50 performs alignment detection to detect the position of each street C on the wafer 12 based on the image of the alignment reference taken by the microscope 26 (step S1).

When the alignment detection is completed, the laser processing control section 52 drives the relative movement mechanism 28 based on the detection result of the alignment detection section 50, and moves the first condensing lens of the laser head 24 to the processing start position of street C (outward path). 38 optical axes are aligned (step S2).

The laser processing control unit 52 also drives the connection switching element 36 to switch the lens that emits the second laser beam L2 to the second condenser lens 40A (step S3). Note that steps S2 and S3 may be performed in the reverse order or may be performed simultaneously.

When step S3 is completed, the laser processing control unit 52 starts laser processing on street C (outward path) (step S4). First, the laser processing control unit 52 causes the first laser light source 22A to emit the laser light LA. As a result, two lines of the first laser beam L1 are emitted from the first condensing lens 38 via the first light forming element 32, and the two lines of the first laser beam L1 reach the processing start position on the street C (outward path). The light is focused.

Next, the laser processing control unit 52 drives the relative movement mechanism 28 to move the laser head 24 relative to the wafer 12 in the forward direction side XA, and the optical axis of the second condensing lens 40A aligns with the above-mentioned processing start. Upon reaching the position, the second laser light source 22B emits the laser light LB. As a result, each second laser beam L2 is emitted from the second condensing lens 40A via the second light forming element 34, the branching optical element 35A, and the connection switching element 36, and each second laser beam L2 reaches the processing start position. The light is focused.

Subsequently, the laser processing control unit 52 drives the relative movement mechanism 28 to move the laser head 24 relative to the wafer 12 in the outward direction XA (step S5). As a result, as shown in FIGS. 3 and 5, along the street C (outgoing path), the formation of the two edge cutting grooves 18 by the edge cutting process and the formation of the hollow groove 19 by the hollow cutting process are spaced apart. are executed simultaneously.

Furthermore, plasma shape evaluation processing is started in conjunction with the start of laser processing (step S6).

As shown in FIG. 13, the imaging control unit 54 causes the camera 45 to start imaging the plasma emission R1A and the camera 46A to start imaging the plasma emission R2A. As a result, during laser processing, the camera 45 photographs the pair of processing points SP1 (plasma 68), and the camera 46A photographs each processing point SP2 (plasma 69) (step S6A, according to the present invention). (equivalent to the shooting step).

Next, the plasma shape acquisition unit 56 acquires the photographed image D1 from the camera 45 and the photographed image D2A from the camera 46A (step S6B). Then, the plasma shape acquisition unit 56 acquires a first plasma shape for each processing point SP1 from the photographed image D1, and acquires a second plasma shape for each processing point SP2 from the photographed image D2A, and converts each plasma shape into a plasma. It outputs to the shape evaluation section 60 (step S6C, corresponding to the shape acquisition step of the present invention).

The plasma shape evaluation section 60 (first evaluation section 60A, second evaluation section 60B) that receives the input of information on each plasma shape evaluates whether each plasma shape is normal or not (step S6D, according to the present invention). (equivalent to the shape evaluation step).

For example, when the first evaluation section 60A performs the evaluation, the shape information acquisition section 58 first acquires the reference shape information 70 from the storage section 31 and outputs this reference shape information 70 to the first evaluation section 60A. Then, the first evaluation unit 60A calculates the degree of coincidence between each plasma shape and the reference shape of the plasmas 68 and 69 indicated by the reference shape information 70, and determines whether or not each plasma shape matches the reference shape of the plasmas 68 and 69 indicated by the reference shape information 70. Evaluate whether each plasma shape is normal.

In addition, when the second evaluation section 60B performs the evaluation, the second evaluation section 60B calculates a plurality of evaluation items corresponding to each plasma shape as shown in FIGS. 10 and 11 described above, Based on whether each evaluation item satisfies a predetermined threshold value, it is evaluated whether each plasma shape is normal or not.

By evaluating each plasma shape at each processing point SP1, SP2 in this way, it is possible to utilize existing equipment without installing a beam profiler in the laser processing apparatus 10, and to perform laser processing at each processing point SP1, SP2 during laser processing. It is possible to determine whether the beam profiles of the laser beams L1 and L2 at SP2 are normal or not. Further, if each plasma shape during laser processing is normal (the beam profiles of the laser beams L1 and L2 are normal), there is a high possibility that the two edge grooves 18 and the hollow grooves 19 are formed normally. As a result, it was determined whether the two edge grooves 18 and the hollow grooves 19 were properly formed based on each plasma shape without installing a beam profiler, three-dimensional measuring device (microscope), etc. in the laser processing device 10. can be evaluated.

If all of the plasma shapes at each processing point SP1, SP2 are normal (YES in step S6E), the process moves to step S7 shown in FIG. 12 (step S6F).

On the other hand, if either of the plasma shapes at each processing point SP1, SP2 is abnormal (NO in step S6E), the correction unit 62 drives the steering mirror mechanisms M1A, M1B, etc. to correct the abnormal plasma shape. (YES in step S6G, step S6H). This prevents processing defects in laser processing from occurring. Then, the process moves to step S7 shown in FIG. 12 (step S6F).

If any of the plasma shapes is abnormal and correction by the correction unit 62 is impossible (NO in step S6E, NO in step S6G), the stop control unit 64 controls the laser processing control unit 52. The control is performed to stop the laser processing on street C (outward path) (step S6I). This prevents processing defects in laser processing from occurring.

Next, the notification unit 66 uses a monitor, a speaker, etc. (not shown) to notify the warning information (step S6J). This can prompt the operator to adjust the laser head 24 or review the processing conditions for laser processing, thereby making it possible to prevent processing defects on the entire wafer 12.

Returning to FIG. 12, when the process moves to step S7, the processes of step S6 and step S7 described above are repeatedly executed until the laser processing of street C (outbound path) is completed (NO in step S7). This allows the cameras 45 and 46A to photograph each processing point SP1 and SP2 (plasmas 68 and 69), the plasma shape acquisition unit 56 to acquire each plasma shape, and the plasma shape The evaluation of each plasma shape by the evaluation unit 60 is repeatedly performed. In addition, if any of the plasma shapes is evaluated as abnormal by the plasma shape evaluation unit 60, “correction by the correction unit 62” or “stopping of laser processing by the stop control unit 64 and warning by the notification unit 66” "Information notification" is executed.

The laser processing control unit 52 stops emitting the laser light LA from the first laser light source 22A in response to the pair of processing points SP1 reaching the processing end position of the street C (outward path), and then stops the emission of the laser beam LA from the first laser light source 22A, and then each processing point SP2 When the laser beam LB reaches the processing end position, the emission of the laser beam LB from the second laser light source 22B is stopped, and the driving of the relative movement mechanism 28 is also stopped. This completes the laser processing of street C (outward path) (YES in step S7).

When the laser processing of street C (outward path) is completed, the laser processing control unit 52 drives the relative movement mechanism 28 to align the optical axis of the first condensing lens 38 with the processing start position of the next street C (return path). (YES in step S8, step S2). The laser processing control unit 52 also drives the connection switching element 36 to switch the lens that emits the second laser beam L2 to the second condenser lens 40B (step S3).

Then, the processes from step S5 to step S7 described above are repeatedly executed. As a result, while the street C (return path) laser processing is being performed, the cameras 45 and 46B photograph each processing point SP1 and SP2 (plasmas 68 and 69), and the plasma shape acquisition unit 56 acquires each plasma shape. Evaluation of each plasma shape by the plasma shape evaluation section 60 is repeatedly performed. Furthermore, if the plasma shape evaluation unit 60 evaluates that any of the plasma shapes is abnormal, "correction" or "stopping laser processing and notification of warning information" is executed.

Similarly, the processes from step S2 to step S8 described above are repeatedly executed for every street C (outbound and return) parallel to the X direction. Next, the laser processing control unit 52 drives the relative movement mechanism 28 to rotate the table 20 by 90 degrees, thereby making each of the remaining streets C parallel to the Y direction on the wafer 12 parallel to the X direction. The series of processes described above are then repeatedly executed. As a result, laser processing is performed along each grid-like street C (NO in step S8).

As described above, in the first embodiment, each plasma shape at each processing point SP1, SP2 is acquired and evaluated from the photographed images D1, D2A, D2B of each processing point SP1, SP2 taken during laser processing. , it is possible to evaluate whether the two edge cutting grooves 18 and the hollow grooves 19 are formed normally. As a result, there is no need to use a beam profiler or three-dimensional measuring device (microscope), so it is possible to check whether the two edge grooves 18 and the hollow grooves 19 are properly formed during laser processing at low cost and in a short time. Moreover, evaluation can be performed in a space-saving manner.

In the first embodiment, the correction unit 62 drives the steering mirror mechanisms M1A, M1B, etc. to correct the abnormal plasma shape, but it corrects the plasma shape by other methods (each laser beam L1, L2 optical axis correction, etc.) may be performed. For example, a shift mirror mechanism may be arranged in place of the steering mirror mechanisms M1A and M1B.

In addition, instead of the steering mirror mechanisms M1A and M1B, a configuration including a plurality of mirrors arranged on the optical path of each laser beam L1 and L2 and an adjustment mechanism that adjusts at least one of the position and orientation of the plurality of mirrors is adopted. It is possible. In this case, two position detection sensors such as PSD are provided for each optical path of each laser beam L1 and L2, and adjustment is made for each optical path based on the position detection results of each laser beam L1 and L2 by each position detection sensor. The mechanism may be driven to correct the optical axis of each of the laser beams L1 and L2, that is, correct the plasma shape.

[Second embodiment]
FIG. 14 is a functional block diagram of the control device 30 of the laser processing apparatus 10 of the second embodiment. The laser processing apparatus 10 of the first embodiment evaluates whether each plasma shape at each processing point SP1, SP2 is normal, but the laser processing apparatus 10 of the second embodiment evaluates whether each plasma shape is normal or not. In addition to the evaluation, it is evaluated whether the brightness and positional relationship of the plasmas 68 and 69 at each processing point SP1 and SP2 are normal.

As shown in FIG. 14, the laser processing apparatus 10 of the second embodiment has the point that the control device 30 further functions as a brightness acquisition section 71, a position acquisition section 72, a brightness evaluation section 73, and a positional relationship evaluation section 74. Except for this, the configuration is basically the same as the laser processing apparatus 10 of the first embodiment. For this reason, the same reference numerals are given to the same elements in function or configuration as those in the first embodiment, and the explanation thereof will be omitted.

The brightness acquisition unit 71 calculates the brightness of the plasmas 68 and 69 from the captured images D1 and D2A each time the captured images D1 and D2A are output from the cameras 45 and 46A during laser processing on the street C (outward path). get. Specifically, the brightness acquisition unit 71 detects the areas of plasmas 68 and 69 from within the photographed images D1 and D2A in the same manner as the plasma shape acquisition unit 56 described above, and detects the areas of plasmas 68 and 69 within the detected areas of plasmas 68 and 69. The brightness of the plasmas 68 and 69 is obtained based on the brightness value of the pixel. In addition, during the street C (return trip) laser processing, the brightness acquisition unit 71 detects the brightness of the plasmas 68, 69 from the captured images D1, D2B every time the captured images D1, D2B are output from the cameras 45, 46B. Get the results.

Each time the brightness acquisition unit 71 acquires the brightness of the plasmas 68 and 69 from the photographed images D1 and D2A or the photographed images D1 and D2B, the brightness acquisition unit 71 transmits information indicating the brightness of the plasmas 68 and 69 to the brightness evaluation unit 73. Output sequentially to .

The position acquisition unit 72 acquires position information of the plasmas 68 and 69 from the photographed images D1 and D2A each time the photographed images D1 and D2A are output from the cameras 45 and 46A during the laser processing on the street C (outward path). do. Specifically, the position acquisition unit 72 detects the regions of plasma 68 and 69 from within the photographed images D1 and D2A in the same manner as the previously described plasma shape acquisition unit 56, and detects the plasma 68 and 69 regions within the photographed images D1 and D2A. , 69, the position information of the plasmas 68, 69 is acquired. In addition, during the street C (return trip) laser processing, the position acquisition unit 72 acquires position information of the plasmas 68 and 69 from the captured images D1 and D2B every time the captured images D1 and D2B are output from the cameras 45 and 46B. get.

Then, the position acquisition unit 72 sequentially outputs the position information of the plasmas 68 and 69 to the positional relationship evaluation unit 74 every time the position information of the plasmas 68 and 69 is acquired from the captured images D1 and D2A or the captured images D1 and D2B. .

The brightness evaluation unit 73 determines whether the brightness of the plasmas 68 and 69 (see FIGS. 10 and 11 described above) at each processing point SP1 and SP2 is normal during laser processing on street C (outbound and return passes). Evaluate whether or not.

Specifically, the brightness evaluation unit 73 evaluates each plasma 68 each time information indicating the brightness of the plasmas 68 and 69 at each processing point SP1 and SP2 is input from the brightness acquisition unit 71 during laser processing. , 69 is within a predetermined threshold range, it is evaluated whether the brightness of each plasma 68, 69 is normal. The brightness of the plasmas 68 and 69 affects the processing shape (processing depth, etc.) of the laser processing, so the processing shape of the laser processing is determined to be normal based on the evaluation results of the brightness of the individual plasmas 68 and 69. It is possible to evaluate whether or not

In addition, the brightness evaluation unit 73 determines whether the brightness balance of the plasma 68 at each processing point SP1 is normal each time information indicating the brightness of the plasma 68 at each processing point SP1 is input from the brightness acquisition unit 71. Evaluate whether or not. For example, the brightness evaluation unit 73 determines the brightness balance of the plasma 68 for each processing point SP1 (hereinafter referred to as the first Evaluate whether the brightness balance (brightness balance) is normal. Thereby, it is possible to evaluate whether the machined shape of the edge cutting groove 18 at each processing point SP1 is uniform.

Further, the brightness evaluation section 73 calculates a predetermined difference in the brightness of the plasma 69 at each processing point SP2 every time information indicating the brightness of the plasma 69 at each processing point SP2 is input from the brightness acquisition section 71. It is evaluated whether the brightness balance of the plasma 69 for each processing point SP2 (hereinafter referred to as second brightness balance) is normal or not based on whether or not the brightness is below the threshold value. Thereby, it is possible to evaluate whether the machined shape of the hollow groove 19 at each processing point SP2 is uniform.

Note that the machining shape (machining depth) of the hollow groove 19 at each machining point SP2 does not necessarily have to be uniform. In this case, the threshold values of the brightness of the plasma 69 for each processing point SP2 are different from each other, and furthermore, the evaluation of the second brightness balance is omitted.

The positional relationship evaluation unit 74 evaluates whether or not the positional relationship of the plasma 68 at each processing point SP1 (hereinafter referred to as the first positional relationship) is normal during laser processing on the street C (outward path and return path). , it is evaluated whether the positional relationship of the plasma 69 at each processing point SP2 (hereinafter referred to as a second positional relationship) is normal.

Specifically, the positional relationship evaluation unit 74 evaluates whether the first positional relationship is normal each time the positional information of the plasma 68 for each processing point SP1 is input from the position acquisition unit 72. For example, the positional relationship evaluation unit 74 calculates the distance in the Y direction from the planned machining line J2 to each plasma 68 based on the position of the plasma 68 for each pair of machining points SP1, as shown in FIG. The difference between these distances in the Y direction is calculated. Then, the positional relationship evaluation unit 74 evaluates whether the first positional relationship is normal based on whether the calculated difference is within a predetermined threshold. Thereby, it can be evaluated whether the position of each processing point SP1, that is, the formation position of the two edge cutting grooves 18 is appropriate.

Moreover, the positional relationship evaluation unit 74 evaluates whether the second positional relationship is normal or not every time the positional information of the plasma 69 for each processing point SP2 is input from the position acquisition unit 72. For example, the positional relationship evaluation unit 74 calculates the distance in the Y direction from the machining schedule line J2 to the plasma 69 for each machining point SP2 based on the position of the plasma 69 at each machining point SP2, as shown in FIG. do. Then, the positional relationship evaluation unit 74 calculates the difference in distance in the Y direction for each processing point SP2, that is, the amount of positional deviation in the Y direction of the plasma 69 at the following processing point SP2 with respect to the plasma 69 at the preceding processing point SP2. , based on whether the amount of positional deviation is within a predetermined threshold, it is evaluated whether the second positional relationship is normal. Thereby, it is possible to evaluate whether the position of each processing point SP2 during hollow processing is appropriate.

The correction unit 62 of the second embodiment corrects the brightness of the plasma 68 at each processing point SP1 when the brightness evaluation unit 73 makes an abnormal evaluation regarding the brightness or the first brightness balance of the plasma 68 at each processing point SP1. Correct the brightness. For example, the correction unit 62 adjusts the amount of laser light LA emitted from the first laser light source 22A so that the brightness or first brightness balance of each plasma 68 satisfies a predetermined reference value (predetermined reference range). The brightness of the plasma 68 at each processing point SP1 is corrected by driving the steering mirror mechanism M1A or the like.

Further, when the brightness evaluation unit 73 makes an abnormal evaluation regarding the brightness of the plasma 69 at each processing point SP2 or the second brightness balance, the correction unit 62 adjusts the brightness of the plasma 69 at each processing point SP2. to correct. For example, the correction unit 62 adjusts the amount of laser light LB emitted from the second laser light source 22B, or adjusts the steering mirror mechanism so that the brightness of each plasma 69 or the second brightness balance satisfies a predetermined reference value. By driving M1B etc., the brightness of the plasma 69 at each processing point SP2 is corrected.

Furthermore, when the positional relationship evaluation unit 74 evaluates the first positional relationship or the second positional relationship as abnormal, the correction unit 62 adjusts the steering so that the first positional relationship or the second positional relationship satisfies a predetermined reference value. The first positional relationship or the second positional relationship is corrected by driving the mirror mechanism M1A or the like or the steering mirror mechanism M1B.

As described above, in the laser processing apparatus 10 of the second embodiment, by evaluating whether the brightness and positional relationship of the plasmas 68 and 69 at each processing point SP1 and SP2 are normal, processing point SP1 , SP2, and whether the positional relationship between the machining points SP1 and SP2 is normal or not can also be evaluated.

[Third embodiment]
Next, the laser processing apparatus 10 of the third embodiment will be explained. In each of the above embodiments, the laser head 24 performs laser processing (edge cutting, hollow processing) only once on each street (outward and backward paths), but laser processing is repeatedly performed on the same street C. You can. Note that to repeatedly perform laser processing on the same street C, that is, to perform laser processing again on a street C that has already been laser processed, it is necessary to It also includes laser processing performed using the second laser beam L2 divided into a plurality of parts in a certain X direction.

When laser processing is repeatedly performed on the same street C in this way, there is a possibility that the brightness of the plasmas 68 and 69 generated at each processing point SP1 and SP2 will differ each time the laser processing is performed. Therefore, the difference in the number of times laser processing is performed on the same street C may affect the evaluation of the brightness of the plasmas 68 and 69.

Therefore, in the laser processing apparatus 10 of the third embodiment, the difference in brightness of the plasmas 68 and 69 at each processing point SP1 and SP2, which occurs due to repeated laser processing on the same street C, is corrected. The laser processing apparatus 10 of the third embodiment is basically the same as the laser processing apparatus 10 of the second embodiment, except that the functions of the photographing control section 54 (cameras 45, 46A, 46B) are partially different. It is the composition. For this reason, the same reference numerals are given to the same elements in function or configuration as those in the second embodiment, and the explanation thereof will be omitted.

The photographing control unit 54 of the third embodiment changes the photographing conditions (for example, exposure time) of the processing points SP1 and SP2 by the cameras 45, 46A, and 46B each time the same street C is repeatedly laser-processed. The photographing conditions for each laser processing are set by performing experiments or simulations in advance so that the brightness of the plasmas 68 and 69 becomes a predetermined brightness. This makes it possible to correct the difference in brightness between the plasmas 68 and 69 at the processing points SP1 and SP2, which is caused by repeated laser processing on the same street C.

In addition, when performing hollow processing using the second laser beam L2 divided into multiple parts in the processing feed direction (X direction), the preceding processing point in the imaging surface of the image sensor (COMS sensor) of the cameras 46A and 46B The exposure time of the imaging area corresponding to SP2 and the exposure time of the imaging area corresponding to the subsequent processing point SP2 are made different. Thereby, it is possible to correct the difference in brightness of the plasma 69 for each processing point SP2.

[Fourth embodiment]
FIG. 15 is a block diagram showing a laser processing apparatus 10 according to the fourth embodiment. In the third embodiment, when laser processing is repeatedly performed on the same street C, the photographing conditions of the cameras 45, 46A, and 46B are made different for each laser processing. On the other hand, in the fourth embodiment, when laser processing is repeatedly performed on the same street C, the image processing conditions of the photographed images D1, D2A, and D2B of the processing points SP1 and SP2 are made different for each laser processing.

Note that the laser processing apparatus 10 of the fourth embodiment has basically the same configuration as the laser processing apparatus 10 of the second embodiment, except that the control device 30 functions as the image processing section 55. Components that are the same in function or configuration as those in the second embodiment are given the same reference numerals, and the description thereof will be omitted.

The image processing unit 55 performs predetermined image processing on the captured images D1, D2A, and D2B each time the cameras 45, 46A, and 46B capture the captured images D1, D2A, and D2B at each processing point SP1 and SP2.

Further, when laser processing is repeatedly performed on the same street C, the image processing unit 55 performs image processing on the photographed images D1, D2A, and D2B under different image processing conditions for each laser processing. The image processing conditions for each laser processing are set so that the brightness of the plasma 68 in the photographed image D1 and the brightness of the plasma 69 in the photographed images D2A and D2B are respectively predetermined brightnesses. Thereby, as in the third embodiment, it is possible to correct the difference in brightness of the plasmas 68 and 69 at the processing points SP1 and SP2, which is caused by repeated laser processing on the same street C.

[Fifth embodiment]
FIG. 16 is a schematic diagram showing main parts of the laser head 24 of the laser processing apparatus 10 of the fifth embodiment. As explained in the first embodiment, the camera 45 images only the plasma emission R1A out of the plasma emission R1A and the first laser reflected light R1B, and the cameras 46A and 46B image the plasma emission R2A and the second laser reflected light R2B. It is preferable to image only the plasma emission R2A. Therefore, in the laser processing apparatus 10 of the fifth embodiment, the wavelength range of light incident on the cameras 45, 46A, and 46B is limited.

In addition, in the laser processing apparatus 10 of the fifth embodiment, a filter 75 is arranged in the middle of the branched optical path BP1 of the laser head 24, a filter 76A is arranged in the middle of the branched optical path BP2, and a filter 76B is further arranged in the middle of the branched optical path BP3. are arranged, and have basically the same configuration as the laser processing apparatus 10 of each of the embodiments described above. For this reason, the same reference numerals are given to the same elements in terms of function or configuration as in each of the above embodiments, and the explanation thereof will be omitted.

The filters 75, 76A, and 76B are bandpass filters that transmit only light in a wavelength range that is easy to observe (for example, a wavelength of 430 nm) among the light in the wavelength range that is generated when silicon, etc., which is the material of Street C, is turned into plasma. It's a filter. By providing a bandpass filter in each branch optical path BP1 to BP3, the cameras 45, 46A, 46B can capture the captured images D1, D2A, D2B without being affected by the chromatic aberration of each condensing lens 38, 39A, 39B. It can be carried out.

Note that when filters 75, 76A, and 76B, which are band-pass filters, are provided in each of the branch optical paths BP1 to BP3, the illumination light L3 emitted from the illumination light source 41 is in the same wavelength range as the transmission wavelength range of the band-pass filter ( For example, light with a wavelength of 430 nm is used.

By providing the filters 75, 76A, 76B in the middle of the branched optical paths BP1 to BP3 in this way, the noise light (first laser reflected light R1B and second laser reflected light R2B) is blocked by the filters 75, 76A, 76B. . Therefore, the cameras 45, 46A, 46B can selectively image only light in a specific wavelength range corresponding to the plasmas 68, 69. As a result, each plasma shape can be more accurately acquired from the photographed images D1, D2A, and D2B.

[Sixth embodiment]
FIG. 17 is a functional block diagram of the control device 30 of the laser processing apparatus 10 of the sixth embodiment. In each of the embodiments described above, it is evaluated whether each plasma shape at each processing point SP1, SP2 is normal or abnormal, but it is not possible to specify the cause of each plasma shape being abnormal. The causes of each plasma shape being abnormal include when there is a problem with the laser head 24 such as the beam profile of each laser beam L1 and L2 being collapsed, or when there is a problem with the processability of street C of the wafer 12, etc. is given as an example.

Therefore, the laser processing apparatus 10 of the sixth embodiment performs the reference processing at a timing other than the timing of the laser processing of the street C, for example, before the laser processing of the wafer 12. This reference processing is performed by performing laser processing on a known workpiece that can be stably laser processed (with stable machinability) by the laser processing device 10, such as a sub-table and a reference workpiece, as described above. It is.

Note that the laser processing apparatus 10 of the sixth embodiment has a reference processing mode in which reference processing is performed as an operation mode, and the control device 30 functions as the reference information generation section 80. It has basically the same configuration as the laser processing apparatus 10. For this reason, the same reference numerals are given to the same elements in terms of function or configuration as in each of the above embodiments, and the explanation thereof will be omitted.

In the reference processing mode, the laser processing control unit 52 controls the first laser light source 22A, the second laser light source 22B, the relative movement mechanism 28, the connection switching element 36, etc., and performs laser processing ( Execute edge cutting and hollow cutting). In the standard machining mode, similarly to the laser machining on street C, the photographing control section 54 (cameras 45, 46A, 46B) photographs the processing points SP1 and SP2, the plasma shape acquisition section 56 acquires each plasma shape, Then, the second evaluation unit 60B evaluates the plasma shape.

Note that the processing points SP1 and SP2 during the reference processing correspond to the second processing points of the present invention, and the photographed images D1, D2A, and D2B correspond to the second photographed images of the present invention.

The reference information generation section 80 generates the reference shape information 70 described in the first embodiment already described based on the plasma shape evaluated as normal by the second evaluation section 60B in the reference machining mode, and stores the generated reference shape information 70 in the storage section. 31 to be memorized.

FIG. 18 is a flowchart showing the flow of processing in the standard machining mode. As shown in FIG. 18, the control device 30 switches the operation mode of the laser processing apparatus 10 to the reference processing mode, for example, before laser processing the wafer 12.

First, the laser processing control unit 52 drives the relative movement mechanism 28 to align the optical axis of the first condensing lens 38 of the laser head 24 with respect to the workpiece for reference processing. The laser processing control unit 52 also drives the connection switching element 36 to switch the lens that emits the second laser beam L2 to the second condenser lens 40A.

Then, the laser processing control unit 52 causes the first laser light source 22A to emit the laser light LA and the second laser light source 22B to emit the laser light LB, thereby laser processing (edge cutting and hollowing) the workpiece. ) is started (step S11). Next, the laser processing control unit 52 drives the relative movement mechanism 28 to move the laser head 24 relative to the workpiece in the outward direction XA (step S12).

When the laser processing on the workpiece is started, the photographing control unit 54 controls the cameras 45 and 46A to photograph each processing point SP1 (plasma 68) with the camera 45 and each processing point SP2 (with the camera 46A). (step S13).

Hereinafter, similarly to each of the above embodiments, the plasma shape acquisition section 56 acquires the captured images D1 and D2A from the cameras 45 and 46A (step S14), and the plasma shape acquisition section 56 acquires each plasma shape (step S15). ), and evaluation of each plasma shape by the second evaluation unit 60B (step S16) are executed.

Since the workpiece for reference processing has stable workability, if the second evaluation unit 60B evaluates that an abnormality has occurred in each plasma shape (NO in step S17), each laser beam L1 There is a problem with the laser head 24, such as the beam profile of L2 being collapsed. In this case, the notification unit 66 uses a monitor, a speaker, etc. (not shown) to notify the warning information (step S18). Thereby, it is possible to notify the operator of an abnormality in the laser head 24.

On the other hand, if the second evaluation unit 60B evaluates that each plasma shape is normal (YES in step S17), the processes from step S12 to step S18 are continued (NO in step S19).

Then, when the reference processing is performed for a certain amount or a certain period of time, the laser processing control unit 52 drives the connection switching element 36 to switch the lens that emits the second laser beam L2 to the second condensing lens 40B, and The relative movement mechanism 28 is driven to move the laser head 24 relative to the workpiece in the return direction side XB. Thereafter, the processes from step S12 to step S18 are repeated again (NO at step S19).

When the reference machining is completed (YES in step S19), the reference information generation section 80 generates reference shape information 70 based on the plasma shape of each processing point SP1, SP2 evaluated as normal by the second evaluation section 60B. and is stored in the storage unit 31 (step S20). This allows the first evaluation section 60A to evaluate the plasma shape at each processing point SP1, SP2 during the street C laser processing.

As described above, in the sixth embodiment, the laser processing device 10 performs reference processing of a workpiece with stable workability, and during this reference processing, each plasma shape at each processing point SP1, SP2 is normal. By evaluating whether there is a problem, it is possible to determine whether there is a problem with the laser head 24, such as the beam profile of each laser beam L1, L2 being distorted. Thereby, after confirming that there is no problem with the laser head 24, it is possible to perform laser processing on street C and evaluate each plasma shape at each processing point SP1, SP2. Therefore, if each plasma shape is evaluated to be abnormal by the plasma shape evaluation section 60, the cause is on the wafer 12 side. As a result, it is possible to identify the cause of abnormal plasma shape at each processing point SP1, SP2.

Note that if the cause of each plasma shape being abnormal is on the wafer 12 (street C) side, the above-mentioned stop control section 64 may control the laser processing control section 52 to stop the laser processing. Alternatively, the above-mentioned correction unit 62 can stabilize each plasma shape at each processing point SP1, SP2 by changing the intensity, period (wavelength), etc. of each laser beam L1, L2, that is, stable laser processing can be performed. You can do it like this.

[Seventh embodiment]
FIG. 19 is a functional block diagram of the control device 30 of the laser processing apparatus 10 of the seventh embodiment. In each of the above embodiments, it is evaluated whether or not each plasma shape at each processing point SP1, SP2 acquired by the plasma shape acquisition unit 56 is normal, but in the seventh embodiment, the plasma shape is further evaluated based on each plasma shape. The shapes of the edge cutting grooves 18 and hollow grooves 19 of the strip are estimated.

As shown in FIG. 19, in the laser processing apparatus 10 of the seventh embodiment, first correspondence information 82A and second correspondence information 82B are stored in the storage section 31, and further, the control device 30 functions as the groove shape estimating section 84. The configuration is basically the same as the laser processing apparatus 10 of each of the embodiments described above except for this point. For this reason, the same reference numerals are given to the same elements in terms of function or configuration as in each of the above embodiments, and the explanation thereof will be omitted.

The first correspondence information 82A includes a plurality of types of first plasma shapes including a normal first plasma shape and an abnormal first plasma shape, and the processed shapes of two edge cutting grooves 18 for each of these first plasma shapes. It is a correspondence. The second correspondence information 82B associates a plurality of types of second plasma shapes, including a normal second plasma shape and an abnormal second plasma shape, and the processed shape of the hollow groove 19 for each of these second plasma shapes. It is something that Each piece of correspondence information 82A, 82B is generated by conducting an experiment or simulation in advance and then stored in the storage unit 31.

The groove shape estimation section 84 refers to the first correspondence information 82A in the storage section 31 based on the first plasma shape of each processing point SP1 acquired by the plasma shape acquisition section 56 during the laser processing of the street C. The machining shape of the two edge cutting grooves 18 formed at the machining point SP1 is estimated. At the same time, the groove shape estimation section 84 refers to the second correspondence information 82B in the storage section 31 based on the second plasma shape for each processing point SP2 acquired by the plasma shape acquisition section 56, and generates a groove shape for each processing point SP2. The shape of the hollow groove 19 to be machined is estimated.

As described above, in the seventh embodiment, the shapes of the two edge cutting grooves 18 and the hollow groove 19 can be estimated based on the plasma shapes of the respective processing points SP1 and SP2. There is no need to provide an expensive three-dimensional measuring device (microscope) in the laser processing device 10 to measure the shape of the punched groove 19.

[others]
FIG. 20 is a diagram showing a modification of the laser head 24 that uses a common laser light source 22 for edge cutting and hollowing. The laser head 24 of each of the above embodiments is provided with a first laser light source 22A for edge cutting and a second laser light source 22B for hollowing, but as shown in FIG. The laser head 24 may be provided with the laser light source 22 and the branching element 100 instead of the second laser light source 22B.

The laser light source 22 emits a laser beam L0 having conditions (wavelength, pulse width, repetition frequency, etc.) suitable for both edge cutting and hollow cutting toward the branching element 100.

For example, a beam splitter or the like is used as the branching element 100. The branching element 100 branches the laser beam L0 emitted from the laser light source 22 into two, emits one of the two branched laser beams L0 to the first light forming element 32, and forms the other laser beam L0 into a second light forming element. The light is emitted to the element 34. As a result, the first light shaping element 32 emits two first laser beams L1, and the second light shaping element 34 emits the second laser beam L2, as in each of the embodiments described above. Since it is sufficient to provide only one type of laser light source 22, the size and cost of the laser head 24 can be reduced.

In each of the above embodiments, only the second laser beam L2 is branched into multiple branches in the processing feed direction (X direction), but the two-striped first laser beam L1 may also be branched into multiple branches in the processing feed direction (X direction). good. In this case as well, similarly to each of the embodiments described above, photographing of each processing point SP1, acquisition of plasma shape, evaluation of plasma shape, correction, etc. are performed.

In each of the above embodiments, laser processing is performed while moving the laser head 24 relative to the street C (outward and backward) only once along the processing feed direction. Laser processing may be performed while relatively moving back and forth one or more times.

In each of the above embodiments, edge cutting and hollowing are performed as laser processing for the street C, but the present invention is also applicable to a laser processing device that performs one type of normal laser processing (see Patent Document 2 above). It is possible. Furthermore, the laser processing apparatus of the present invention is not limited to one that processes a wafer 12 on which a low-k film is formed on the surface of a substrate such as silicon, but may process various known wafers. Applicable.

10 Laser processing device 12 Wafer 14 Chip 16 Device 18 Edge cutting groove 19 Hollow groove 20 Table 22 Laser light source 22A First laser light source 22B Second laser light source 24 Laser head 26 Microscope 28 Relative movement mechanism 30 Control device 31 Storage section 32 First Light forming element 33 Beam splitter 34 Second light forming element 35 Beam splitter 35A Branching optical element 36 Connection switching element 37 Beam splitter 38 First condensing lens 40A, 40B Second condensing lens 41 Illumination light source 42, 43A, 43B Beam splitter 45, 46A, 46B camera (photography means)
47 First imaging lens 48A, 48B Second imaging lens 49 Operating section 50 Alignment detection section 52 Laser processing control section 54 Photographing control section 55 Image processing section 56 Plasma shape acquisition section 58 Shape information acquisition section 60 Plasma shape evaluation section 60A First evaluation section 60B Second evaluation section 62 Correction section 64 Stop control section 66 Notification section 68, 69 Plasma 70 Reference shape information 71 Brightness acquisition section 72 Position acquisition section 73 Brightness evaluation section 74 Positional relationship evaluation section 75, 76A, 76B Filter 80 Reference information generation section 82A First correspondence information 82B Second correspondence information 84 Groove shape estimation section 100 Branching element 102 Steering mirror BP1 Branching optical path BP2 Branching optical path BP3 Branching optical path C Street D1, D2A, D2B Photographed images J1, J2 Processing Scheduled line L0 Laser light L1 First laser light L2 Second laser light L3 Illumination light LA, LB Laser light M1A, M1B, M2A, M2B, M3 Steering mirror mechanism OP1, OP2, OP3 Main optical path R1A Plasma emission R1B First laser reflection Light R2A Plasma emission R2B Second laser reflected light SP1, SP2 Processing point XA Outward direction side XB Return direction side θ Angle

Claims (18)

In a laser processing apparatus that performs laser processing along the streets by irradiating the streets with laser light from the laser head while moving the laser head relative to the wafer in a processing feed direction along the streets of the wafer. ,
Photographing means for photographing a first processing point of the laser beam irradiated from the laser head onto the street during the laser processing;
a plasma shape acquisition unit that acquires a plasma shape of plasma generated at the first processing point from a first photographed image of the first processing point taken by the photographing means;
a plasma shape evaluation unit that evaluates the plasma shape acquired by the plasma shape acquisition unit;
A laser processing device equipped with. A claim in which the laser head includes a shape correction unit that corrects the shape of the laser beam so that the plasma shape at the first processing point where the plasma shape has been evaluated as abnormal by the plasma shape evaluation unit becomes normal. The laser processing device according to item 1. a brightness acquisition unit that acquires the brightness of the plasma from the first captured image;
a brightness evaluation unit that evaluates the brightness of the plasma acquired by the brightness acquisition unit;
The laser processing apparatus according to claim 1, comprising: The laser head repeatedly performs the laser processing on the same street,
The laser processing according to claim 3, wherein the photographing means photographs the first processing point for each laser processing under different photographing conditions and under photographing conditions that provide a predetermined brightness of the plasma. Device. The laser head repeatedly performs the laser processing on the same street,
comprising an image processing unit that performs image processing on the first captured image,
The image processing unit performs the image processing on the first photographed image under different image processing conditions for each laser processing and under which a predetermined brightness of the plasma is obtained. The laser processing device according to claim 3. The laser head includes a first branching optical element that branches the laser beam into a plurality of beams, and focuses the plurality of laser beams branched by the first branching optical element on the street,
The photographing means photographs the first processing point for each laser beam,
The plasma shape acquisition unit acquires the plasma shape for each of the first processing points from the first photographed image,
The laser processing apparatus according to claim 1, wherein the plasma shape evaluation section evaluates the plasma shape at each of the first processing points. The laser processing apparatus according to claim 6, wherein the plasma shape evaluation unit evaluates the plasma shape for each of the first processing points and the balance of the size of the plasma for each of the first processing points. The laser processing apparatus according to claim 7, wherein the laser head includes a shape correction section that corrects the balance between the plasma shape and the size of the first processing point that has been evaluated as abnormal by the plasma shape evaluation section. . a brightness acquisition unit that acquires the brightness of the plasma for each of the first processing points from the first captured image;
a brightness evaluation unit that evaluates the brightness of the plasma for each of the first processing points acquired by the brightness acquisition unit and the balance of the brightness of the plasma for each of the first processing points;
The laser processing apparatus according to claim 6, comprising: a position acquisition unit that acquires the position of the plasma for each of the first processing points from the first photographed image;
a positional relationship evaluation unit that evaluates the positional relationship of the plasma for each of the first processing points acquired by the position acquisition unit;
The laser processing apparatus according to claim 6, comprising: comprising a shape information acquisition unit that acquires in advance reference shape information indicating the plasma shape when a normal processed groove is formed on the street by the laser processing,
A claim in which the plasma shape evaluation section evaluates the plasma shape based on a degree of coincidence between the plasma shape acquired by the plasma shape acquisition section and the reference shape information acquired by the shape information acquisition section. The laser processing device according to any one of Items 1 to 10. When the laser beam is a Gaussian beam and the vertical direction is a direction perpendicular to both the processing feed direction and the optical axis of the laser head, the plasma shape evaluation section determines whether the plasma is perfectly circular. 11. The laser processing apparatus according to claim 1, wherein the plasma shape is evaluated based on the vertical symmetry of the plasma with respect to the planned processing line of the laser processing. When the laser beam is a line beam and the vertical direction is a direction perpendicular to both the processing feed direction and the optical axis of the laser head, the plasma shape evaluation section determines the length and width of the plasma. 11. The plasma shape is evaluated based on the length in the vertical direction and the length in the vertical direction from one end and the other end in the longitudinal direction of the plasma to a line to be processed by the laser processing. The laser processing device according to any one of the items. The laser head includes a laser light source that emits the laser light, and a condensing lens that focuses the laser light on the street,
11. The laser processing apparatus according to claim 1, wherein the photographing means photographs the first processing point coaxially with the optical axis of the laser head through the condenser lens. a main optical path from the laser light source to the condenser lens;
a branched optical path branching from the middle of the main optical path and reaching the photographing means;
a second branching optical element that is provided midway between the branch optical path and the main optical path and causes the branch optical path to branch;
a filter that is provided in the middle of the branched optical path and that transmits only light in the wavelength range of the plasma;
The laser processing apparatus according to claim 14, comprising: The laser head performs the laser processing on the workpiece that can be stably laser processed at a timing other than the timing when performing the laser processing on the street,
During the laser processing of the workpiece, the photographing means photographs a second processing point of the laser beam irradiated from the laser head to the workpiece,
The plasma shape acquisition unit acquires the plasma shape of the plasma generated at the second processing point from a second photographed image of the second processing point photographed by the photographing means,
The laser processing apparatus according to any one of claims 1 to 10, wherein the plasma shape evaluation section evaluates the plasma shape at the second processing point acquired by the plasma shape acquisition section. The laser according to any one of claims 1 to 10, further comprising a shape estimation section that estimates the shape of a processed groove formed in the street by the laser processing based on the plasma shape acquired by the plasma shape acquisition section. Processing equipment. In a laser processing method in which laser processing is performed along the streets by irradiating the streets with laser light from the laser head while moving the laser head relative to the wafer in a processing feed direction along the streets of the wafer. ,
a photographing step of photographing a first processing point of the laser beam irradiated onto the street from the laser head during the laser processing;
a plasma shape obtaining step of obtaining a plasma shape generated at the first processing point from a first photographed image of the first processing point taken in the photographing step;
a plasma shape evaluation step of evaluating whether the plasma shape acquired in the plasma shape acquisition step is normal;
A laser processing method having

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