JP2023066566A - Illumination optical system and laser processing device - Google Patents

Abstract

To prevent a high temperature of an optical element, and prevent elongation of an optical path length and an increase in a size of a device.SOLUTION: An illumination optical system guides a laser beam to an irradiation surface, and is provided with light quantity uniformizing parts for uniformizing the laser beam, and includes a first lens array 43a, second lens array 43b, and third lens array 43c in which the light quantity uniformizing parts are arrayed sequentially along an optical axis. The second lens array 43b is arranged in a position behind a focal point of the first lens array 43a. The illumination optical system is structured so that a light-condensing point does not exist on an optical path from the second lens array 43b to the irradiation surface. The first lens array 43a and third lens array 43c have positive power, and the second lens array 43b has negative power.SELECTED DRAWING: Figure 8

Description

The present invention relates to an illumination optical system used for irradiating a photomask with linear laser light, and a laser processing apparatus equipped with the illumination optical system.

A workpiece (workpiece, for example, a resin layer of a printed circuit board), which is a non-metallic material such as resin or silicon, is scanned with a laser beam that has passed through a photo-photomask, thereby scanning the workpiece with a pattern of the photo-photomask. It is known to ablate shapes (eg vias). When precision processing is required, processing is performed by ablation using an excimer laser (KrF laser, wavelength 248 nm).

Ablation processing using an excimer laser requires irradiating an object to be processed with extremely high-energy light, and a high-fluence beam passes through an illumination optical system. Therefore, there is a problem that glass materials, coating films, and the like of optical elements such as lenses are damaged by heat. In addition, if the optical element is arranged so that no focal point is formed on the optical element so that the temperature of the optical element does not become high, the optical element must be placed so as to avoid the focal point, which increases the optical path length, i.e., increases the size of the device. There was a problem of

For example, the illumination optical system described in Patent Document 1 has a configuration in which a hologram element 12, a cylindrical lens array 13a, and a cylindrical lens array 13b are arranged in order along the optical axis.

Patent Document 2 describes a beam homogenizer capable of lengthening and thinning the irradiation area. In the configuration of Patent Document 2, the cylinder arrays 1A, 2B, and 1B are arranged in order along the optical axis, and the condensing section is located behind the cylinder array 1B.

JP-A-2003-090959 JP-A-10-153746

In the illumination optical system of Patent Literature 1, the cylindrical lens array 13b has a problem of heat generation because the condensing portion exists in the vicinity of the lens surface of the cylindrical lens array 13b. In addition, in the configuration of Patent Document 2, although there is no condensing part on the optical element, the arrangement of the optical element is restricted, so the optical path becomes long and the size of the apparatus increases.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an illumination optical system and a laser processing apparatus that do not have a condensing portion in an optical element and that can prevent the optical path from becoming long.

The present invention provides an irradiation optical system for guiding a laser beam to an irradiation surface,
having a light intensity uniformizing unit for uniformizing the laser beam,
The light amount uniformizing unit has a first lens array, a second lens array, and a third lens array arranged in order along the optical axis,
A second lens array is installed at a position behind the focal point of the first lens array;
After the second lens array, there is no condensing point in the optical path to the irradiation surface,
An illumination optical system in which the first lens array and the third lens array have positive power, and the second lens array has negative power.
The present invention also provides an irradiation optical system for guiding a laser beam to an irradiation surface,
having a light intensity uniformizing unit for uniformizing the laser beam,
The z-axis is the optical axis direction, the direction perpendicular to the z-axis and the y-axis is the x-axis, the direction perpendicular to the z-axis and the x-axis is the y-axis,
The light amount equalizing section includes a first lens array section having a lens action in one of the x-axis direction and the y-axis direction, and a second lens array section having a lens action in the other of the x-axis direction and the y-axis direction. are arranged in order along the z-axis,
The first lens array section has a first cylindrical lens array, a second cylindrical lens array, and a third cylindrical lens array arranged in order along the optical axis,
A second cylindrical lens array is installed at a position behind the focal point of the first cylindrical lens array,
After the second cylindrical lens array, there is no condensing point in the optical path to the irradiation surface,
An illumination optical system in which the first cylindrical lens array and the third cylindrical lens array have positive power, and the second cylindrical lens array has negative power.
Furthermore, the present invention provides a light source that emits laser light,
an illumination optical system for irradiating a photomask with laser light having a linear cross section and scanning the photomask by a scanning mechanism;
a projection optical system that irradiates a workpiece with a laser beam passed through a photomask;
a workpiece placement table on which the workpiece is placed and which moves the workpiece in the xy direction;
This is a laser processing apparatus in which the light amount equalizing unit of the illumination optical system is configured as described above.

According to at least one embodiment, the present invention can prevent the optical element from becoming hot, and can prevent the optical path length from becoming long and the apparatus from becoming large. Note that the effects described herein are not necessarily limited, and may be any of the effects described herein or effects different from them.

FIG. 1 is a diagram showing a schematic configuration of a laser processing apparatus to which the present invention can be applied. FIG. 2 is a front view of one embodiment of the present invention. FIG. 3 is a plan view showing the relationship between a photomask and linear beams in one embodiment of the present invention. FIG. 4 is an enlarged plan view of an example substrate used in one embodiment of the present invention. FIG. 5 is a block diagram showing an optical system in one embodiment of the invention. FIG. 6A is a side view of the configuration of an example of the illumination optical system, and FIG. 6B is a top view of the configuration of the example of the illumination optical system. FIG. 7 is an enlarged side view of a configuration of a portion of one embodiment of the present invention; FIG. 8 is a side view of a variant of the invention.

Hereinafter, embodiments of the present invention and the like will be described with reference to the drawings. The embodiments and the like described below are preferred specific examples of the present invention, and the content of the present invention is not limited to these embodiments and the like.

FIG. 1 is a schematic configuration diagram of an example of a processing apparatus, such as a laser processing apparatus, to which the present invention can be applied. The laser processing device has a laser light source 11 . The laser light source 11 is, for example, an excimer laser light source that emits pulses of KrF excimer laser light with a wavelength of 248 nm. Laser light is supplied to the linear laser scanning mechanism 12 .

The linear laser scanning mechanism 12 has an illumination optical system that shapes the laser beam into a rectangular shape (line shape) and a scanning mechanism (linear motion mechanism) for scanning the photomask 13 with the laser beam LB.

The photomask 13 is formed with a mask pattern corresponding to a processing pattern formed by ablation on a workpiece (hereinafter, appropriately referred to as a substrate W). That is, a pattern of a light-shielding film (eg, Cr film) that blocks the KrF excimer laser is drawn on a substrate (eg, quartz glass) that transmits the KrF excimer laser. Processing patterns include through vias, non-through vias, trenches for wiring patterns, and the like. After the pattern is formed by ablation, it is filled with a conductor such as copper.

A laser beam LB that has passed through the photomask 13 is incident on the projection optical system 14 . The surface of the substrate W is irradiated with laser light emitted from the projection optical system 14 . The projection optical system 14 has focal planes at the photomask plane and the substrate W surface. The substrate W is a resin substrate in which a copper wiring layer is formed on a substrate such as epoxy resin, and an insulating layer is formed thereon.

The substrate W is provided with a plurality of pattern areas WA, and is fixed on a mounting table 15 for mounting a workpiece. The pattern area WA can be positioned with respect to the photomask 13 by displacing and rotating the mounting table 15 two-dimensionally. Further, in order to process the region to be processed over the entire substrate W, the mounting table 15 moves the substrate W stepwise in the scanning direction.

An embodiment of the laser processing apparatus will be described with reference to FIG. A laser processing device is attached to a base portion 21 and an upper frame 22 that constitute a support. The upper frame 22 is fixed on the base portion 21 . The base portion 21 and the upper frame 22 are made of a material with high rigidity and vibration damping properties.

A linear laser scanning mechanism consisting of a scanning mechanism 16 and an illumination optical system 17, a mask stage 18 (photomask support) on which the photomask 13 is placed, and a projection optical system 14 are fixed to the upper frame 22. be done. A mounting table 15 is fixed on the base portion 21 . That is, the scanning mechanism 16, the illumination optical system 17, the mask stage 18, the projection optical system 14, and the mounting table 15 satisfy a predetermined optical relationship (relationship in which laser light is correctly incident on the illumination optical system 17). After the positioning, when the base portion 21 and the upper frame 22 oscillate due to vibration caused by the scanning operation of the illumination optical system 17 and the displacement operation of the mounting table 15, they are displaced together. . The beam position corrector 27 corrects the incident position and incident angle of the laser beam with respect to the illumination optical system 17 .

The laser light source 11 is housed in a housing 24 provided separately from the base portion 21 and the upper frame 22 . A laser light source 11 emits pulses of a KrF excimer laser (called laser light) L1 having a wavelength of 248 nm. A laser beam L1 and a guide laser beam (not shown) are incident on a beam position corrector (called a beam steering mechanism) 27 .

The beam position corrector 27 is a mechanism for positioning (position and incident angle) of the laser beam L1 in real time. The beam position correction unit 27 adjusts the laser beam L1 so that it always enters the illumination optical system 17 at the correct position and angle regardless of the inclination of the base unit 21 and upper frame 22 of the laser processing apparatus. The wavelength of the guiding laser light is set to 400 nm to 700 nm, for example. The mirror included in the beam position correction unit 27 has two reflection films that reflect the wavelengths of the laser light L1 and the guide laser light, which have different wavelengths. The beam position correction unit 27 is provided with a beam shaping unit for making each laser beam incident on each reflection film.

A laser beam L1 emitted from the beam position correction unit 27 is reflected by the mirror 28 and enters the illumination optical system 17 . The illumination optical system 17 homogenizes the intensity distribution of the light emitted from the laser light source and shapes the light into a linear processing laser beam. The illumination optical system 17 has a lens array (also called a fly-eye lens array) for shaping linear laser light. The lens array is a lens array in which a plurality of convex lenses are arranged in a direction to magnify laser light. A linear laser beam LB from the illumination optical system 17 irradiates the mask 13 . A specific example of the illumination optical system 17 will be described later.

The scanning mechanism 16 is a part of the illumination optical system 17 and moves the entire illumination optical system 17 . The laser beam LB is moved with respect to the photomask 13 by the scanning mechanism 16, and the photomask 13 and the substrate W fixed to the mask stage 18 and the mounting table 15, respectively, are scanned with the laser beam.

FIG. 3 shows the relationship between the size of the laser beam LB and the photomask 13 . For example, the (length×width) of the laser beam LB is (100×0.1 (mm)), (35×0.3 (mm)), and the like. The width direction orthogonal to the length direction of the laser beam LB is the scanning direction.

In the photomask 13, a mask pattern is drawn by forming a blocking film (chromium film, aluminum film, etc.) for blocking KrF excimer laser light on a base material (for example, quartz glass) that transmits KrF excimer laser light. ing. On the photomask 13, a pattern that appears repeatedly on the substrate W may be drawn, or a pattern that covers the entire substrate W may be drawn.

The mask stage 18 holds the photomask 13 and has an xyθ stage capable of positioning the photomask. A camera (not shown) is provided for reading alignment marks provided on the photomask 13 and positioning the photomask 13 .

Laser light passing through the photomask 13 is incident on the projection optical system 14 . The projection optical system 14 is a projection optical system having focal points on the surface of the photomask 13 and the surface of the substrate W, and projects the light transmitted through the photomask 13 onto the substrate W. FIG. Here, the projection optical system 14 is configured as a reduction projection optical system (for example, 1/4 magnification).

The mounting table 15 fixes the substrate W by vacuum suction or the like, and positions the substrate W with respect to the photomask 13 by moving and rotating in the xy directions by a table moving mechanism. It is also step-movable along the scanning direction so that the entire substrate W can be ablated. An alignment camera (not shown) for capturing images of alignment marks provided on the substrate W is installed near the mounting table 15 . Furthermore, a z mechanism or the like for focus adjustment may be provided.

The substrate W (workpiece) is, for example, an organic substrate for a printed wiring board, and a layer to be processed by laser processing is formed on the surface thereof. The layer to be processed is, for example, a resin film or a metal foil, and is made of a material that can be subjected to processing such as via formation by laser light. A laser processing machine is used to form vias and wiring patterns, and in subsequent processes, the processed portions are filled with a conductor such as copper.

FIG. 4 shows an enlarged example of the substrate W. As shown in FIG. The substrate W is a multi-sided substrate, and pattern areas WA corresponding to the pattern of the photomask 13 are repeatedly provided in an (8×8) matrix on the substrate W. As shown in FIG. In FIG. 4, the horizontal direction is the secondary step direction, and the vertical direction is the main step direction. After one pattern area WA is scanned, the next pattern area is scanned. The illustrated scanning direction (arrow) is an example.

In one embodiment of the present invention, a transport mechanism (not shown) is provided, and the workpiece is placed on and removed from the placement table by the transport mechanism. For example, a SCARA robot or the like can be used. It also has an air-conditioning chamber (not shown) that covers the processing device and the housing of the laser light source.

In one embodiment of the invention described above, a vibration damping device (not shown) is provided for controlling the entire system. The control device controls the laser light source 11, controls each part of the driving section, aligns the photomask and the substrate W, manages production information, manages recipes, and the like.

FIG. 5 is a block diagram showing the optical system in the laser processing apparatus described above. Parts in FIG. 5 corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals. Laser light from the laser light source 11 is supplied to the beam shaping section 30 . A laser beam from the beam shaping section 30 is supplied to the beam position correcting section 27 . The beam position correction unit 27 adjusts the laser light so that the laser light always enters the illumination optical system 17 at the correct position and angle. As described above, the beam shaping section 30 shapes laser light so that the laser light from the laser light source 11 and the guide laser light are incident on a reflecting film different from the mirror.

The illumination optical system 17 has a configuration in which a beam shaping section 31, a lens array section 32 as a light amount homogenizing section, and a collimator lens section 33 are arranged in order along the optical axis. The beam shaping section 31 forms a rectangular laser beam having a predetermined length and width, and the lens array section 32 makes the distribution of the laser light uniform and linear laser light. The lens array section 32 includes three first cylindrical lens arrays (indicated as SLA in FIG. 5) 36a, a second cylindrical lens array 36b, and a third cylindrical lens array 36b arranged along the optical axis direction. It is composed of an x-direction lens array section 34 consisting of a cylindrical lens array 36c and a y-direction lens array section 35 consisting of two cylindrical lens arrays 37a and 37b arranged along the optical axis direction.

The laser light from the lens array section 32 is made into substantially parallel light by the collimator lens section 33 . The photomask 13 is irradiated with laser light from the collimating lens portion 33 of the illumination optical system 17 . Laser light passing through the photomask 13 is incident on the projection optical system 14 . The projection optical system 14 projects the light transmitted through the photomask 13 onto the substrate W. FIG.

An example of the illumination optical system 17 will be described with reference to FIG. The direction parallel to the optical axis of the illumination optical system 17 is the z-axis, the direction orthogonal to the z-axis and the y-axis is the x-axis, and the direction orthogonal to the z-axis and the x-axis is the y-axis. That is, the x-axis and the y-axis are perpendicular to the z-axis and perpendicular to each other. 6A is a side view of the illumination optical system 17, and FIG. 6B is a top view of the illumination optical system 17. FIG. Furthermore, the width direction of the line-shaped laser beam is the x-axis direction, and the length direction of the line-shaped laser beam is the y-axis direction. 17 is a side view showing an enlarged portion of the x-direction lens array section 34. As shown in FIG.

In the side view of FIG. 6A, a cylindrical lens 31a, cylindrical lens arrays 36a, 36b, and 36c, and a cylindrical lens 33a indicated by thick lines are elements having a lens action in the x-axis direction. In the side view of FIG. 6B, the cylindrical lens 31b, the cylindrical lens arrays 37a and 37b, and the cylindrical lens 33b indicated by thick lines are elements having a lens effect in the y-axis direction.

The beam shaping unit 31 includes a cylindrical lens 31a having a lens action in the x-axis direction (in other words, having power in the x-axis direction) and a lens in the y-axis direction (in other words, having power in the y-axis direction). It has a structure in which cylindrical lenses 31b having an action are arranged in order in the z-axis direction. When a laser beam from a light source is incident on the cylindrical lens 31a, a laser beam that spreads in the x-axis direction (width direction) is generated from the cylindrical lens 31a. Further, when the laser beam is incident on the cylindrical lens 31b, the laser beam is generated from the cylindrical lens 31b with a spread in the y-axis direction (longitudinal direction). A laser beam from the cylindrical lens 31 b is emitted from the beam shaping section 31 . The beam shaping section 31 expands the laser light according to the size of the incident surface of the cylindrical lens array of the lens array section 32 and makes the laser light incident on the lens array section 32 in parallel. . Note that the laser light incident on the fly-eye lens has an intensity bias such as a Gaussian curve.

Laser light emitted from the beam shaping section 31 is incident on the first cylindrical lens array 36a on the light source side of the x-direction lens array section 34 of the lens array section 32 (an enlarged side view is shown in FIG. 7). A second cylindrical lens array 36b and a third cylindrical lens array 36c are arranged parallel to the cylindrical lens array 36a along the z-axis direction. The cylindrical lens arrays 36a and 36c are formed by arranging a plurality of small-diameter cylindrical lenses (convex lenses) in the x-axis direction. Therefore, the cylindrical lens arrays 36a and 36c have positive lens power. The lens surface on the incident side of the cylindrical lens array 36a is convex, and the lens surface on the exit side is planar. The lens surface on the incident side of the cylindrical lens array 36c is flat, and the lens surface on the exit side is convex. The cylindrical lens array 36b has a plurality of small-diameter cylindrical lenses (concave lenses) arranged in the x-axis direction. Therefore, the cylindrical lens array 36b has negative lens power. Laser light is homogenized by cylindrical lens arrays 36a, 36b and 36c.

The laser light emitted from the x-direction lens array section 34 is incident on the cylindrical lens array 37 a on the light source side of the y-direction lens array section 35 of the lens array section 32 . A cylindrical lens array 37b is arranged parallel to the cylindrical lens array 37a along the z-axis direction. The cylindrical lens arrays 37a and 37b are formed by arranging a plurality of small-diameter cylindrical lenses (convex lenses) in the y-axis direction. The laser light is made uniform by the cylindrical lens arrays 37a and 37b.

Laser light emitted from the cylindrical lens array 37 b of the y-direction lens array section 35 of the lens array section 32 enters the first cylindrical lens 33 a of the collimator lens section 33 . The cylindrical lens 33a has a lens action in the x-axis direction. A second cylindrical lens 33b is arranged in parallel with the cylindrical lens 33a. The cylindrical lens 33b has a lens action in the y-axis direction. The collimator lens unit 33 converts the split laser beams into parallel beams and makes them uniform by superimposing them on the irradiation surface.

In one embodiment of the present invention, as shown in FIGS. 6A and 7, the second cylindrical lens array 36a of the x-direction lens array section 34 on the light source side is positioned after the focal point of the first cylindrical lens array 36a. A lens array 36b is installed so that no condensing point exists in the optical path from the second cylindrical lens array 36b to the irradiation surface.

In the above-described embodiment, the lens array section 32 is composed of the x-direction lens array section 33 and the y-direction lens array section 34, but it may be configured to have one of the lens array sections. Also, one lens array section may have a lens action in both the x-direction and the y-direction.

For example, as shown in FIG. 8, a beam shaping lens 41, a lens array section 42, and a collimating lens 43 are arranged in order from the light source to the irradiation surface, and the lens array section 42 includes a lens array 43a, a lens array 43b, and a lens array 43c. may be arranged in order. The lens arrays 43a and 43c are convex lens arrays, the lens array 43b is a concave lens array, and the lens array 43b is installed at a position behind the focal point of the lens array 43a. It is designed so that there is no focal point.

The above-described embodiment of the present invention can prevent the optical element from becoming hot due to the arrangement that does not create a focal point on the optical element, and also prevents the optical path length from becoming long and the apparatus from becoming large. can be prevented.

Although one embodiment of the present technology has been specifically described above, the present invention is not limited to the above-described one embodiment, and various modifications based on the technical idea of the present invention are possible. For example, the order of the x-direction lens array section 34 and the y-direction lens array section 35 may be reversed from the above-described embodiment. In addition, the configurations, methods, processes, shapes, materials, numerical values, etc., given in the above-described embodiments are merely examples, and if necessary, different configurations, methods, processes, shapes, materials, numerical values, etc. may be used. good too.

W Workpiece (substrate) 11 Laser light source 12 Linear laser scanning mechanism 13 Photomask 14 Projection optical system 15 Placement table , 16...scanning mechanism, 17...illumination optical system, 18...mask stage, 30, 31...beam shaping section, 32...lens array section, 33...collimating lens section, 36a , 36b, 36c... Cylindrical lens array

Claims (6)

An irradiation optical system for guiding a laser beam to an irradiation surface,
having a light intensity uniformizing unit for uniformizing the laser beam,
The light amount uniformizing unit has a first lens array, a second lens array, and a third lens array arranged in order along the optical axis,
The second lens array is installed at a position behind the focal point of the first lens array,
After the second lens array, there is no condensing point in the optical path to the irradiation surface,
An illumination optical system in which the first lens array and the third lens array have positive power, and the second lens array has negative power. 2. An illumination optical system according to claim 1, wherein said first and third lens arrays are sets of convex lenses, and said second lens array is a set of concave lenses. An irradiation optical system for guiding a laser beam to an irradiation surface,
having a light intensity uniformizing unit for uniformizing the laser beam,
The z-axis is the optical axis direction, the direction perpendicular to the z-axis and the y-axis is the x-axis, the direction perpendicular to the z-axis and the x-axis is the y-axis,
The light amount uniformizing section includes a first lens array section having a lens action in one of the x-axis direction and the y-axis direction, and a second lens array section having a lens action in the other of the x-axis direction and the y-axis direction. 2 lens array units are arranged in order along the z-axis,
The first lens array section has a first cylindrical lens array, a second cylindrical lens array, and a third cylindrical lens array arranged in order along the optical axis,
The second cylindrical lens array is installed at a position behind the focal point of the first cylindrical lens array,
After the second cylindrical lens array, there is no condensing point in the optical path to the irradiation surface,
An illumination optical system in which the first cylindrical lens array and the third cylindrical lens array have positive power, and the second cylindrical lens array has negative power. 4. An illumination optical system according to claim 3, wherein said first and third cylindrical lens arrays are sets of cylindrical convex lenses, and said third lens array is a set of cylindrical concave lenses. 5. The illumination optical system according to any one of claims 1 to 4, wherein the beam shaping section, the light amount homogenizing section, and the collimating lens section are arranged in order along the z-axis. a light source that emits laser light;
an illumination optical system that irradiates the photomask with the laser beam having a linear cross section and scans the photomask with a scanning mechanism;
a projection optical system for irradiating an object to be processed with laser light passed through the photomask;
a workpiece placement table on which the workpiece is placed and which moves the workpiece in xy directions;
4. A laser processing apparatus, wherein the light amount uniformizing section of the illumination optical system is configured as described in claim 3.

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