JPH05208288A - Laser beam machining method and device therefor - Google Patents

Abstract

PURPOSE:To enable machining of a high-aspect-ratio hole and groove by elevating a machining face corresponding to an increment of the depth of a machined hole at the time of laser beam machining. CONSTITUTION:Considering the depth of the hole determined by the energy density of a laser beam 2, the diameter of the hole and the focal distance of a condensing lens 5, the face of a material to be machined 6 is controlled to be elevated using a Z axis stage 7, a motor 9, a drive 10 and a pulse generator 11 at every specified number of shot. Thus the required machining for the high-aspect-ratio hole and groove is carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam processing method, and more particularly, to a method for accurately processing a hole or groove having a high aspect ratio.

[0002]

2. Description of the Related Art Conventionally, a deep hole drilling method has mainly been a mechanical hole drilling method using a drill. However, with this method, for example, it is difficult to form a hole having a diameter smaller than 100 μm. In addition, recently, as the performance of electronic devices has been improved, high density wiring has been required. For this reason, there is an increasing need for processing fine holes at a small pitch even in a circuit board or the like, which is a typical example requiring a large number of holes. As one of the processing methods satisfying this requirement, there is a method of irradiating a workpiece with a laser beam through a mask partially having an opening to partially process a sample. For example, as disclosed in JP-A-60-13449,
When processing through-holes in a wiring board in which a metal layer is attached to the surface of an organic substrate such as polyimide, polyester, or glass epoxy, first, the surface metal layer is selectively etched into a pattern to be processed, and then this metal layer There is a method of irradiating the substrate with an ultraviolet laser beam using the as a mask to process the through holes. Also, Japanese Patent Laid-Open No. 61-4858
In the microfabrication method that uses both etching and laser light irradiation as disclosed in No. 2, a photoresist film is set in the same position on both surfaces of the work material with the same pattern, and before the holes penetrate the etching work. There is a processing method of interrupting and removing all or a predetermined number of formed bridges with a laser beam that travels along the same trajectory as the photoresist pattern after removing the resist film.

[0003]

The above-mentioned prior art has the following problems. In the case of processing an organic substance or the like using an ultraviolet laser beam, a method of simply focusing the laser beam and irradiating the work piece, for example, a hole of about 20 μm, depending on the focal length of the condenser lens and the size of the opening hole. In this case, there is a problem that only a hole having a depth of about 20 μm can be processed. This is mainly because the focused laser beam is out of focus as the machining progresses, and the energy density (threshold value) becomes lower than the limit for machining the workpiece, and the hole depth is saturated. it is conceivable that.

An object of the present invention is to provide a method for drilling a hole having a high aspect ratio with an ultraviolet laser beam.

[0005]

In order to achieve the above object, in the laser processing method according to the present invention, in the Z direction during processing, the sample stage itself is processed at an appropriate speed according to the depth of the hole in the workpiece. By ascending, defocusing is prevented and holes and grooves with a high aspect ratio are processed.

[0006]

In the present invention, the Z stage is used to move the sample surface in the beam irradiation direction. Further, the Z-stage control device has a function of controlling the Z-stage to move up in response to a decrease in the material removal rate in the depth direction.

[0007]

EXAMPLES Examples of the present invention will be described below with reference to FIGS.
Will be explained.

FIG. 1 shows a perspective view of the apparatus of the first embodiment according to the laser processing method of the present invention.

In FIG. 1, 1 is an ultraviolet laser oscillator, 2
Is an ultraviolet laser beam, 3 is a reflection mirror, 4 is a transfer mask, 5
Is a condenser lens, 6 is a workpiece, 7 is a Z-axis stage, 8 is an XY stage, 9 is a motor, 10 is a drive, and 11 is a pulse generator. As shown in FIG. 1, the ultraviolet laser light 2 emitted from the ultraviolet laser oscillator 1 reaches the transfer mask by the reflection mirror 3. As the reflection mirror 3, a dielectric thin film having a high reflectance for ultraviolet laser light is deposited on a quartz substrate, and the loss of the laser light due to reflection is suppressed. After that, the laser beam 2
It is irradiated onto the transfer mask 4 and is reduced and projected on the material to be processed by the condenser lens. Hole depth l _{0 that} can be machined in the workpiece
Is determined by the energy density and hole diameter of the laser beam and the focal length of the condensing lens. Therefore, the sample surface is Z-sized while considering the number of shots required to process the depth of l _0.
The shaft stage 8, the motor 9, the drive 10, and the pulse generator 11 are used to raise a fixed number of shots for drilling with a high aspect ratio.

FIG. 2 shows the outline of the first embodiment of the laser processing method according to the present invention.

FIG. 2A shows an ultraviolet laser beam (wavelength 208).
is a graph showing the relationship between the hole depth and the number of shots when a polyimide film (Kapton) is processed to have a hole diameter of 20 μm. From this figure, it is understood that the processed hole depth becomes saturated when the number of shots exceeds 50 at any energy density. FIG. 2B shows an example of the control method of the Z-axis stage when the position of the Z-axis stage is raised by 20 μm every 50 shots. For example, in FIG.
From (a), when the energy density is 0.5 J / cm ² , 2
With a hole depth of 0 μm, it is possible to process with 50 shots without saturating the hole depth. As shown in FIG. 2B, the position of the Z-axis stage is set to 20 every 50 shots, as shown in FIG.
The result of processing by increasing μm is shown. As shown in FIG. 2C, by controlling the number of shots, a hole having a desired depth can be obtained without saturating the hole depth.

[0012]

According to the present invention, since a hole having a high aspect ratio can be formed on a material to be processed by using laser light, the applicable range of laser processing is greatly expanded. By applying this method to the processing by the ultraviolet laser, it becomes possible to form minute through holes and improve the quality of the processed holes.

[Brief description of drawings]

FIG. 1 is a perspective view of an apparatus of a first embodiment of a laser processing method according to the present invention.

FIG. 2 is a schematic view of a first embodiment of a laser processing method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser oscillator, 2 ... Laser beam, 3 ... Reflection mirror, 4 ... Transfer mask, 5 ... Condensing lens, 6 ... Workpiece material, 7 ... Z-axis stage, 8 ... XY stage, 9 ... Motor, 10 ... Driver , 11 ... Pulse generator.

Claims (4)

[Claims] 1. A laser processing method in which a laser beam is focused on a specific place on a sample surface to remove a local portion of a material, and the sample surface is raised in accordance with an increase in a hole depth during processing to increase a high aspect ratio. Laser processing method characterized by performing hole and groove processing of the above. 2. A laser processing method, wherein ultraviolet laser light is used as a light source for processing. 3. The sample surface is controlled by raising it every fixed number of shots, taking into consideration the hole density that can be processed, which is determined by the energy density and hole diameter of the laser beam and the focal length of the condenser lens. 2. The laser processing method according to claim 1, wherein a hole having a desired high aspect ratio is processed by the method described above. 4. The method according to claim 1, further comprising a stage capable of changing the height of the sample table according to the removal rate in the depth direction of the material during processing, and capable of processing holes and grooves having a high aspect ratio. A laser processing device characterized by the above.