JP2005088045A - Method and apparatus for laser drilling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a highly accurate and high speed machining compared with a galvano optical system for a high density buildup substrate. <P>SOLUTION: When drilling numerous holes on the substrate, a high output laser 30 is irradiated over a mask 32 on which a large number of holes are formed corresponding to the hole positions on the substrate so that the hole positions on the mask are transferred to a workpiece 10 and the numerous holes are drilled simultaneously. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laser drilling method and apparatus for drilling a large number of holes in a substrate, and in particular, can quickly and accurately form a high-density hole suitable for use in forming a via in a build-up substrate. The present invention relates to a laser drilling method and apparatus capable of performing the same.

As illustrated in FIG. 1, the wiring pattern 14 is formed on both surfaces of the core substrate 12, and a film-like or liquid insulating resin 16 is laminated or spin-coated thereon, and a hole is formed in the insulating resin 16 with a laser. The build-up substrate 10 in which the pattern 18 is formed by plating or the like is widely used in small electronic devices including cellular phones. When forming vias (drilling) in this build-up substrate, conventionally, as shown in FIG. 2, a carbon dioxide (CO ₂ ) laser or a harmonic solid (UV) laser is used as the light source 20 to realize high-speed processing. A galvano optical system including a galvano scanner 22 that scans in the X and Y directions and an fθ lens 24 is used. In the figure, 26 is a mirror.

  However, the method using the galvano optical system has the following problems.

  (1) Since the galvano optical system is positioned for each hole and the laser oscillates after the movement is completed, the processing speed is proportional to the number of holes. Therefore, as the number of holes per unit area increases and the hole density increases, the processing time increases. In particular, the hole density tends to increase in the future.

  (2) As the density increases, the hole diameter φl of the via 16A shown in FIG. 3 is changed from the conventional 75-100 μm to 30-50 μm, and the diameter φL of the pad 14A below the via 16A is changed from the conventional 150-200 μm. Although it is necessary to reduce it to 100 to 130 μm, in order to reduce the pad diameter, it is necessary to improve the laser irradiation position accuracy. In the case of a galvano optical system, there is a limit in improving the accuracy of the galvano scanner itself.

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to realize high-precision and high-speed processing on a high-density substrate.

  In the present invention, when a large number of holes are made in a substrate, a high-power laser is irradiated to a mask in which a large number of holes corresponding to the hole positions are formed, and a pattern on the mask is collectively transferred to a workpiece. The above-mentioned problem is solved by simultaneously opening the holes.

  The high power laser is an excimer laser.

  Further, a chrome mask is used as the mask.

  Furthermore, an alignment mark is provided on the mask.

  Further, when drilling, the workpiece and the mask are driven synchronously.

  Alternatively, when drilling, the workpiece and the mask are first positioned, and the workpiece is drilled in a stopped state.

  The present invention is also a laser drilling device for drilling a large number of holes in a substrate, comprising a high-power laser and a mask in which a large number of holes corresponding to the hole positions are formed. The laser drilling apparatus is characterized in that a large number of holes are simultaneously drilled by collectively transferring the pattern on the mask onto the work.

  In the case of an apparatus using a conventional galvano scanner, the positioning accuracy of the galvano scanner itself is about ± 15 μm in the case of a carbon dioxide laser, and an error about half that occurs in the case of a UV laser. On the other hand, in the case of the apparatus according to the present invention, the error of the galvano scanner is eliminated, and an error occurs between the stage (for example, XY stage) on which the substrate is mounted and the stage (for example, XY stage) on which the mask is mounted. Since the rotation error when setting the mask can be corrected by, for example, the θ stage, the laser processing position accuracy is determined by the accuracy of both XY stages. The XY stage can be highly accurate, and the total position accuracy can be suppressed to 5 μm or less.

The processing speed is determined by the hole density on the substrate. In general, a galvano type apparatus uses a biaxial machine and has a productivity of about 1000 holes per second. In contrast, according to the present invention, since the mask pattern batch transfer method is used, the processing surface takes about 1 ^second per 1 cm ² . Therefore, if there is a hole density of 1000 holes or more in this range, productivity is improved over the conventional method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In the present embodiment, as shown in FIG. 4, an excimer laser 30 as a high-power laser, a mask 32 in which a large number of holes corresponding to hole positions of a substrate (also referred to as a workpiece) 10 are formed, and the workpiece 10 are mounted. For example, a work stage 24 that is an XY stage having a vacuum chuck plate 26, a mask stage 34 that can be moved / rotated in the X, Y, and θ directions for mounting the mask 32, and the work 10 And a CCD camera 36 for detecting the projected alignment mark. In the figure, reference numeral 40 denotes mirrors provided at various places to change the optical path of the laser beam 31, reference numeral 42 denotes a homogenizer for making the laser beam uniform, and reference numeral 44 denotes a mask 32 which is reduced and projected onto the workpiece 10. Projection lens.

As the excimer laser 30, for example, a KrF excimer laser having 1 pulse energy of 1 J, an oscillation frequency of 300 Hz, and a wavelength of 248 nm can be used. In this case, the processed surface energy density of the resin material (16) is about 0.5 J / cm ² . Since the utilization efficiency of the beam transmission system is approximately 50%, the beam size on the processed surface is approximately 1 cm ² .

As the mask 32, for example, a chrome mask that is inexpensive and can be manufactured in a short delivery time can be used. Usually, since the chrome mask needs to have an energy density of 50 mJ / cm ² or less, the reduction ratio of the projection lens 44 is, for example, about 4 or more (about 2 in the conventional example using the dielectric mask). As shown in FIG. 5, the mask 32 is provided with four alignment marks 32 </ b> B <b> 1 to 32 </ b> B <b> 4 in addition to the processing pattern 32 </ b> A that is M times the actual pattern (here, M = 4). Therefore, when the mask is replaced, a plurality of alignment mark portions are irradiated onto the processing surface, and the irradiation position is recognized by the CCD camera 36, thereby detecting the mask position and fixing the mask according to the detection result. X, Y, θ Direction correction can be performed.

Specifically, as shown in FIG. 6, after setting the mask 32 on the mask stage 34, for example, setting the polyimide film mask position confirmation sheet 50 on the vacuum chuck plate 26 of the XY stage 24, (1) First The mark 32B1 is moved to the mask surface beam irradiation position. Then, (2) First, it is processed into a polyimide film (50) set on the vacuum chuck plate 26 (at this time, the resin processing energy density is set to the same condition as 0.5 to 1.0 J / cm ² ). (3) Next, the second mark 32B2 is moved to the mask surface beam irradiation position. (4) The work stage 24 (polyimide film 50) is moved by 1 / M of the mask movement amount and processed.

  Similar to the above, the process is performed up to the fourth mark 32B4.

  Thus, four points are processed on the mask position confirmation sheet 50 at 1 / M of the mask pattern.

  After processing, (1) Offset points (X and Y directions) are set at the processing point and CCD camera recognition point at the beginning, and the offset amount is moved so that the processing position on the polyimide film (50) (4 points) Measure. (2) The shift amount in the θ direction shown in FIG. 7 can be calculated from the measurement result. (3) Using the θ stage on the mask stage 34, Δθ rotation correction is performed.

  After performing the rotation correction, in order to correct ΔX and ΔY of the mask 32, the first to fourth marks 32B1 to 32B1 are processed again, and the processing points are measured. From the measurement results, correction amounts ΔX and ΔY are calculated as shown in FIG. 8, and ΔX and ΔY amounts are corrected using the mask stage 34.

  In this way, the amount of deviation in the X, Y, and θ directions at the time of mask setting is detected, and automatic correction is performed.

  The processing is performed as shown in FIG. Specifically, as shown in FIG. 10, a rectangular beam is formed, the mask stage 34 is driven in the short side direction, and the work stage 24 is driven in synchronism with the mask stage drive. As shown in FIG. 4, any one of the method of processing by the step-and-repeat method in which the mask 32 and the workpiece 10 are first positioned and processed in a stopped state can be used.

  In the embodiment, the KrF excimer laser is used. However, the type of laser is not limited to this, and other excimer lasers such as ArCl, ArF, KrCl, XeCl, and XeF, and other high-power lasers. It is also possible to use. The processing target is not limited to the build-up board.

Sectional view showing the configuration of the build-up board to be processed The figure which shows the basic composition of the conventional galvano type drilling device Section III enlarged sectional view of FIG. 1 for explaining one of the problems of the prior art The perspective view which shows the whole structure of embodiment of the laser drilling apparatus which concerns on this invention The top view which shows the example of the mask used by the said embodiment The perspective view which similarly shows the alignment method Similarly, a plan view showing the deviation in the θ direction Similarly, a plan view showing a deviation in the X and Y directions Similarly perspective view showing the processing state The perspective view which shows an example of the drive method of the mask stage and work stage at the time of a process A perspective view showing another example

Explanation of symbols

10 ... Substrate (workpiece)
16A ... via 24 ... work stage 30 ... excimer laser 31 ... laser beam 32 ... mask 32A ... processing pattern 32B1-4 ... alignment mark 34 ... mask stage 36 ... CCD camera 44 ... projection lens

Claims (7)

When making a lot of holes in the board,
Irradiate the mask with a large number of holes corresponding to the hole position with high power laser,
A laser drilling method characterized in that a large number of holes are simultaneously drilled by collectively transferring a pattern on a mask onto a workpiece.   The laser drilling method according to claim 1, wherein the high-power laser is an excimer laser.   The laser drilling method according to claim 1, wherein a chrome mask is used as the mask.   4. The laser drilling method according to claim 2, wherein an alignment mark is provided on the mask.   5. The laser drilling method according to claim 1, wherein the workpiece and the mask are driven in synchronism when drilling.   5. The laser drilling method according to claim 1, wherein when drilling, the workpiece and the mask are first positioned and the workpiece is drilled in a stopped state. A laser drilling device for drilling a large number of holes in a substrate,
A high power laser,
A mask having a large number of holes corresponding to the positions of the holes, and irradiating the mask with a high-power laser to collectively transfer the pattern on the mask to the workpiece, thereby simultaneously opening a large number of holes. Laser drilling device.

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