TWI881961B - Laser processing equipment - Google Patents

Abstract

[Topic] Since the accuracy can be maintained even when the device is swung, laser processing can be performed even in the swung state, thereby improving productivity. [Solution] A laser processing device includes: an illumination optical system that irradiates a linear processing laser light onto a mask and scans the mask by a scanning mechanism; a projection optical system that irradiates the processing laser light through the mask onto a workpiece; a workpiece mounting table that mounts the workpiece and moves the workpiece in the x-y direction; a support that fixes the illumination optical system, the mask support, the projection optical system, and the workpiece mounting table to move as a whole; and a vibration damping device that suppresses vibration of the support.

Description

Laser processing equipment

The present invention relates to a laser processing device, which scans a mask with linear laser light and processes a substrate with the light that has passed through the mask, and is particularly designed to prevent the optical position relationship from shifting due to vibration.

It is known that a non-metallic material to be processed (workpiece, such as the resin layer of a printed circuit board) such as resin or silicon is scanned by a linear laser light that has passed through a mask, and the processed object is processed into the shape of the mask pattern (such as a through hole) by ablation (ablation: removal processing by melting and evaporation) (for example, refer to Patent Document 1). In addition, linear laser light means laser light whose cross-sectional shape in a plane orthogonal to the optical axis is linear. In a packaging substrate, which is a type of printed wiring board, through holes (VIA) are used to connect the wiring layers. In addition, the diameter coefficient of the through hole is tens of μm to several μm. In the case where the through hole diameter is small and precision processing is required, ablation processing using an excimer laser (KrF laser, wavelength 248nm) is performed.

In the laser processing device of patent document 1, the irradiation position of the laser light is fixed, and the mask is moved. In addition, the printed substrate 1 is fixed on a workbench 13 that can move freely in a direction parallel to the moving direction of the mask. During processing, the laser light source 11 and the printed substrate 1 move in opposite directions to the fixed laser beam, so that the conductor pattern formed on the mask 11 is transferred to the printed substrate 1 in a reduced manner.

Furthermore, the laser processing device described in Patent Document 2 scans the processing area of the printed wiring substrate 20 by scanning a linear beam having a length direction dimension equal to or greater than the width of the contact mask 14-2 in a one-axis direction. For example, this is achieved by making the reflector 13 movable in the L-axis direction. The processing area of the printed wiring substrate 20 is moved using the xy worktable mechanism 30.

[Prior patent literature]

[Patent Literature]

[Patent Document 1] Patent Publication No. 2001-079678

[Patent Document 2] Patent Publication No. 2008-147242

Patent document 1 is configured to fix the laser irradiation position, but vibration occurs due to the movement of the mask and the action of the workbench 13. In the case of patent document 2, vibration occurs in the scanning mechanism of the reflector 13, the xy workbench mechanism 30, etc. However, since neither patent document 1 nor patent document 2 takes measures to deal with vibration, the processing accuracy may be reduced. That is, vibration occurs or the center of gravity of the device changes with the movement of the scanning mechanism or the processing workbench. Therefore, since the illumination optical system, mask, projection optical system, and substrate vibrate with different movement amounts, errors occur in the projection position of the mask pattern. Therefore, it is necessary to wait for the vibration to converge before starting processing, but productivity is reduced by the amount of this waiting time. In particular, when the vibration damping mechanism is a passive vibration damping device, the vibration is charged. When an active vibration damping device is used, the vibration is reduced, but the device is expensive.

Therefore, the purpose of the present invention is to provide a laser processing device that is designed to prevent a decrease in processing accuracy or a decrease in productivity caused by swinging.

The present invention is a laser processing device, which includes: an illumination optical system, which irradiates a linear processing laser light onto a mask and scans the mask by a scanning mechanism; a projection optical system, which irradiates a processing laser light through the mask onto a workpiece; a workpiece loading table, which loads the workpiece and moves the workpiece in the x-y direction; a support body, which fixes the illumination optical system, the mask support part, the projection optical system and the workpiece loading table into a unitary displacement; and a vibration damping device, which suppresses the vibration of the support body.

According to at least one embodiment, the present invention can maintain accuracy even when the laser processing device is swung (vibrated), and laser processing can be performed in a swung state, so productivity can be improved. In addition, the effects described here are not necessarily limited, and can also be any effect described in this patent specification or effects that are different from those.

W: workpiece (substrate)

11: Laser light source

12: Laser scanning mechanism

13: Mask

14: Projection optical system

15: Place the workbench

16: Scanning agency

17: Illumination optical system

18: Masking workbench

21: Base

22: Upper rack

23: Vibration damping device

24: Frame

25:Guide beam light source

27: Beam position correction unit

28: 1st adjustment of the reflector

29: Tube

30: xy workbench mechanism

31: Spectroscope

32: Sensor

41,42: Reflective film

43,44: Light Spot

B:Boundary

L1: Laser light for processing

L2: guided by laser light

LB: Linear laser light

WA: Pattern area

[Figure 1] is a diagram showing the schematic structure of a laser processing device to which the present invention can be applied.

[Figure 2] is a front view of one embodiment of the present invention.

[Figure 3] is a three-dimensional diagram of one embodiment of the present invention.

[Figure 4] is a schematic diagram used to explain the beam position correction unit of one embodiment of the present invention.

[Figure 5] is an enlarged stereoscopic diagram used to illustrate the reflector used in one embodiment of the present invention.

[Figure 6] is an enlarged plan view of an example of a substrate used in one embodiment of the present invention.

Below, the embodiments of the present invention are described with reference to the drawings. In addition, the embodiments described below are suitable specific examples of the present invention, and the content of the present invention is not limited to these embodiments.

FIG1 is a schematic diagram showing an example of a processing device, such as a laser processing device, 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 pulses KrF excimer laser light with a wavelength of 248 nm. The laser light is supplied to a linear laser scanning mechanism 12.

The linear laser scanning mechanism 12 has: an illumination optical system that shapes the laser beam into a rectangle (linear, for example, 100×0.1 (mm)); and a scanning mechanism (linear motion mechanism) that allows the linear laser light LB to scan the mask 13. The linear laser scanning mechanism 12 is displaced in the x direction.

On the mask 13, a mask pattern is formed, which corresponds to the processing pattern formed on the workpiece (hereinafter appropriately referred to as the substrate W) by ablation. That is, on the substrate (such as quartz glass) that allows the KrF excimer laser to pass through, a pattern of a light-shielding film (such as a Cr film) that blocks the KrF excimer laser is drawn. The processing pattern includes through-holes, non-through-holes, trenches for wiring patterns, etc. After the processing pattern is formed by ablation, a conductor such as copper is filled.

The linear laser light LB that has passed through the mask 13 is injected into the projection optical system 14. The linear laser light emitted from the projection optical system 14 is irradiated onto the surface of the substrate W. The projection optical system 14 has a focal plane between the mask surface and the surface of the substrate W. 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 loading table 15 for loading the workpiece. By displacing and rotating the loading table 15 in the x-y direction, the pattern areas WA can be positioned separately with respect to the mask 13. In addition, in order to make it possible to process the processing area on the entire substrate W, the loading table 15 moves the substrate W in a stepwise manner in a scanning direction such as the x direction.

In the above-mentioned laser processing device, during the scanning action of the linear laser scanning mechanism 12 and the displacement action of the loading table 15 in the x-y direction, the laser processing device vibrates. Due to the vibration, the linear laser light LB does not correctly scan the mask 13 or the substrate W, resulting in pattern shape errors or uneven irradiation energy. In the embodiment of the present invention, a vibration control device is provided to suppress the vibration of the laser processing device caused by the vibration.

Referring to Fig. 2 and Fig. 3, one embodiment of the present invention is described. A laser processing device is mounted on a base 21 and an upper frame 22 constituting a support body. The upper frame 22 is fixed to the base 21. The base 21 and the upper frame 22 are made of a material having high rigidity and a vibration attenuation property. A vibration damping device 23 is provided between the base 21 and the floor surface. As the vibration damping device 23, for example, a passive vibration damping device is used. With the vibration damping device 23 as a starting point, the base 21 and the upper frame 22 can be swung.

The upper frame 22 is fixed with a linear laser scanning mechanism composed of a scanning mechanism 16 and an illumination optical system 17, a mask table 18 (a support portion for the mask) on which the mask 13 is placed, and a projection optical system 14. The placement table 15 is fixed to the base 21. That is, these scanning mechanism 16, illumination optical system 17, mask table 18, projection optical system 14, and placement table 15 are positioned to satisfy a predetermined optical relationship (a relationship in which the processing laser light is correctly incident on the illumination optical system 17), and after positioning, when the base 21 and the upper frame 22 are swung due to vibration caused by the scanning action of the illumination optical system 17 and the displacement action of the placement table 15, they are displaced integrally. This oscillation is suppressed by the vibration control device 23, but because it cannot be completely eliminated, the incident position and incident angle of the processing laser light to the illumination optical system 17 are corrected by the beam position correction unit 27.

The laser light source 11 is housed in a frame 24 that is separately provided with the base 21 and the upper frame 22. The laser light source 11 pulses KrF excimer laser light (referred to as processing laser light) L1 with a wavelength of 248nm. In addition, it has a guide beam light source 25 that generates a guide laser light L2 for adjusting the laser position. The processing laser light L1 and the guide laser light L2 are formed to have parallel optical paths at a predetermined interval.

The processing laser light L1 and the guiding laser light L2 are incident on the beam position correction unit (referred to as the beam control mechanism) 27. The beam position correction unit 27 is a mechanism for real-time positioning (position and incident angle) of the processing laser light L1.

FIG4 shows an example of a beam position correction unit 27. A first adjustment reflector 28 is provided on the side of the laser light source 11. The processing laser light L1 and the guide laser light L2 reflected by the first adjustment reflector 28 pass through the tube 29 and are then incident on the second adjustment reflector 30 mounted on the base 21 or the upper frame 22. The processing laser light L1 reflected by the second adjustment reflector 30 is reflected by the reflector 33 and incident on the illumination optical system 17.

The guided laser light L2 reflected by the second adjustment reflector 30 is branched into two optical paths by the spectroscope 31 and is incident on the sensor 32. The sensor 32 is mounted on the base 21 or the upper frame 22, and has a position sensor that detects the position from the two branched guided laser lights and an angle sensor that detects the angle. As the position sensor and angle sensor, for example, PSD (Position Sensitive Detector) is used. The first adjustment reflector 28 and the second adjustment reflector 30 are made so that the angle of the reflector can be adjusted in the two-axis direction by two actuators. The actuator is feedback-controlled according to the detection signal of the sensor 32.

That is, a processing device that processes the signal from the sensor 32 (position sensor, angle sensor) performs feedback control on the actuator that drives the first adjustment reflector and the second adjustment reflector, and adjusts the processing laser light so that the processing laser light always enters the illumination optical system 17 at the correct position and angle regardless of the inclination of the base 21 and the upper frame 22 of the laser processing device.

The first adjustment reflector 28 and the second adjustment reflector 30 are both injected with processing laser light L1 with a wavelength of, for example, 248nm and guiding laser light L2 with a wavelength of, for example, 400nm to 700nm. In order to reflect two types of laser light with greatly different wavelengths, the first adjustment reflector 28 and the second adjustment reflector 30 form two different reflective films.

As shown in FIG5 , the first adjustment reflector 28 and the second adjustment reflector 30 are formed by separating the reflective film 41 corresponding to the processing laser light and the reflective film 42 corresponding to the guiding laser light at the boundary B. FIG5 shows the light spot 43 of the processing laser light and the light spot 44 of the guiding laser light incident on each area. The interval between the processing laser light and the guiding laser light is set so that the light spots 43 and 44 do not enter the area of the different reflective films.

The processing laser light L1 reflected by the second adjustment reflector 30 is incident on the illumination optical system 17. The illumination optical system 17 has an optical unit that makes the intensity distribution of the light emitted by the laser light source uniform and deforms it into a linear processing laser light. The illumination optical system 17 has an optical unit 17a, which has: a lens array 17b (first optical element) that expands the light in one direction (Y direction); and a second optical element that shrinks the light in a direction orthogonal to the expansion direction of the first optical element and makes it linear. The first optical element is a lens array in which a plurality of lenses are arranged in the light expansion direction. That is, the optical unit 17a has: a lens system (not shown) that converts the expanded light into parallel light; and a lens system 17c (second optical element) that reduces the parallel light in a direction orthogonal to the expansion direction of the lens array (X direction when observed on the mask). The optical unit 17a shapes the beam of laser light into a linear beam and guides the linear laser light LB to the mask 13. For example, the linear laser light LB is shaped into a linear direction of 100 mm and a longitudinal direction of 0.1 mm.

The scanning mechanism 16 is a part of the illumination optical system 17, and moves the entire illumination optical system including the optical unit 17a. The optical unit 17a slides on the stage along the scanning direction (x direction), so that the optical unit 17a moves back and forth. As the optical unit 17a moves, the linear laser light LB moves to the mask 13, and the mask 13 and the substrate W fixed on the mask workbench 18 and the loading workbench 15 are scanned by the processing laser light.

In the case of the previous structure using a displacement reflector, the shape of the processing laser light is deformed as the reflector moves. As a result, it is impossible to obtain a uniform intensity distribution in the entire processing range, and uneven processing results occur depending on the position. In this way, when scanning the linear processing laser light, there is a problem that the linear shape cannot be scanned with high precision (the shape will not be deformed during scanning). According to one embodiment of the present invention, since the linear laser light does not deform during scanning, the processing accuracy can be improved.

The mask 13 is formed by forming a shielding film (chromium film, aluminum film, etc.) that blocks the KrF excimer laser light on a substrate (such as quartz glass) that allows the KrF excimer laser light to pass through, and a mask pattern is drawn. The mask 13 can also draw a pattern that appears repeatedly on the substrate W, or a pattern that is drawn on the entire substrate W.

The mask workbench 18 is an xyθ workbench that holds the mask 13 and can position the mask. It has a camera (not shown) that is used to read the alignment mark set on the mask 13 and position the mask 13.

The processing laser light passing through the mask 13 is injected into the projection optical system 14. The projection optical system 14 is a projection optical system having focal points on the surface of the mask 13 and the surface of the substrate W, and projects the light passing through the mask 13 onto the substrate W. Here, the projection optical system 14 is configured as a reduced projection optical system (for example, 1/4 times).

The loading table 15 fixes the substrate W by vacuum adsorption, etc., and positions the substrate W relative to the mask 13 by moving and rotating the table moving mechanism in the x-y direction. In addition, in order to perform melting and grinding processing on the entire substrate W, stepping movement can be performed along the scanning direction (here, the x direction). Next to the loading table 15, an alignment camera (not shown) is set, which takes pictures of the alignment marks set on the substrate W. Furthermore, a z mechanism for focus adjustment can also be set.

The substrate W (workpiece) is, for example, an organic substrate for a printed wiring board, and a processed layer for laser processing is formed on the surface. The processed layer is, for example, a resin film or a metal foil, and is formed of a material that can be processed by laser light, such as forming through holes. Through holes or wiring patterns are formed by a laser processing machine, and conductors such as copper are filled in the processed parts in subsequent steps.

FIG6 is an enlarged view of an example of a substrate W. The substrate W is a multiple board, and on the substrate W, a pattern area WA corresponding to the pattern of the mask 13 is repeatedly arranged in an array of (8×8). In FIG6, the x direction is the sub-stepping direction, and the y direction is the main stepping direction. When a certain pattern area WA is scanned, the next pattern area is scanned. In addition, the scanning direction (arrow) shown in the figure is an example.

In addition, in one embodiment of the present invention, a transport mechanism not shown in the figure is provided, and the workpiece is placed on or taken out of the loading table by the transport mechanism. For example, a selectively compliant assembly robot arm can be used. In addition, there is an air-conditioned room not shown in the figure that has a frame covering the processing device and the laser light source.

In one embodiment of the present invention described above, there is a control device (not shown) for controlling the entire device. The control device controls the laser light source 11, controls each part of the drive unit, aligns the mask and substrate W, manages production information or recipes, etc.

The above specifically describes one embodiment of the present technology, but the present invention is not limited to the above embodiment, and various modifications can be made according to the technical concept of the present invention. In addition, the structures, methods, steps, shapes, materials, and values listed in the above embodiment are purely examples, and different structures, methods, steps, shapes, materials, and values can also be used according to needs.

W: workpiece (substrate)

11: Laser light source

13: Mask

14: Projection optical system

15: Place the workbench

16: Scanning agency

17: Illumination optical system

17a: Optical unit

17b: Lens array

17c: Lens system

18: Masking workbench

21: Base

22: Upper rack

23: Vibration damping device

24: Frame

25:Guide beam light source

27: Beam position correction unit

33: Reflector

L1: Laser light for processing

L2: guided by laser light

LB: Linear laser light

Claims (5)

A laser processing device includes: an illumination optical system, which irradiates a linear processing laser light onto a mask and scans the mask by a scanning mechanism; a projection optical system, which irradiates the processing laser light through the mask onto a workpiece; a workpiece loading table, which loads the workpiece and moves the workpiece in the x-y direction; a support body, which fixes the illumination optical system, the mask support, the projection optical system and the workpiece loading table into a unitary displacement; and a vibration damping device, which dampens the vibration of the support body, wherein the illumination optical system emits a linear processing laser light, and the scanning mechanism causes the processing laser light to linearly displace in a direction orthogonal to the linear direction. For example, in the laser processing device of item 1 of the patent application, a laser light source for generating the processing laser light is provided separately from the support body; and a beam position correction unit is used to control the incident position and incident angle of the processing laser light to the illumination optical system to a predetermined value. For example, in the laser processing device of item 2 of the patent application, a laser light source for generating the processing laser light and the guiding laser light is provided separately from the supporting body; the processing laser light is incident on the illumination optical system; the processing laser light and the guiding laser light are supplied to the beam position correction unit; and the incident position and incident angle of the processing laser light on the illumination optical system are corrected to a predetermined value based on the guiding laser light by the beam position correction unit. For example, in the laser processing device of item 3 of the patent application, the beam position correction unit has at least one optical element; the optical element performs surface processing corresponding to the processing laser light and surface processing corresponding to the guiding laser light on a surface. For example, in the laser processing device of item 1 of the patent application, the worktable carrying the workpiece is intermittently moved in the line direction to process multiple areas of the workpiece one by one.