JP2003285179A - Laser beam machining method and machining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining method which can form a hole with a large aperture ratio. <P>SOLUTION: The hole penetrating a metal layer is formed by converging a pulse laser beam on the surface of the metal layer of a work object in which the metal layer is arranged on the surface of an insulating layer made of an insulating material. The hole is formed on the insulating layer exposed on a bottom surface of the hole formed on the metal layer by enlarging a beam spot so that pulse energy density on the surface of the work object becomes less than the threshold for etching the metal layer. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing method and a processing apparatus, and more particularly, a laser beam is made incident on an object to be processed in which a metal layer which is difficult to be etched is arranged on the surface of a base member which is easily etched by the laser beam. TECHNICAL FIELD The present invention relates to a laser processing method and a processing apparatus for forming a hole.

[0002]

2. Description of the Related Art A conventional method for punching a laminated film for tape automatic bonding (TAB) in which copper layers are adhered to both sides of a resin base film will be described.

A resist pattern having openings corresponding to holes to be formed is formed on the surface of the copper layer. Using this resist pattern as a mask to chemically etch the copper layer,
Make holes in the copper layer. After removing the resist pattern,
Through the hole formed in the copper layer, the resin layer exposed on the bottom surface is irradiated with a carbon dioxide laser in the infrared region. A hole penetrating the resin layer is formed by the carbon dioxide laser. Since the carbon dioxide gas laser reflects on the copper surface, the copper layer in which the holes are formed acts as a mask. Therefore, holes matching the holes formed in the copper layer are formed in the resin layer. Further, the copper layer on the back surface remains on the bottom surface of the hole penetrating the resin layer.

When the hole diameter is 100 μm or more, a method of combining the above chemical etching and carbon dioxide laser irradiation is effective, but when the hole diameter becomes smaller, the chemical etching yield decreases. As a method of forming a small hole, a method is known in which a copper layer is irradiated with a laser beam in the ultraviolet region to form a hole in the copper layer by the energy of the laser beam.

[0005]

The beam profile of a laser beam is usually high at the center of the beam cross section and becomes lower toward the periphery. Therefore, the etching rate is high at the center of the beam spot, and the etching rate decreases as the distance from the center increases. As a result, the side surface of the formed hole becomes tapered, and the bottom surface of the hole becomes smaller than the opening. That is, the aperture ratio becomes small. Here, the aperture ratio is defined by B / T, where B is the diameter of the bottom of the hole and T is the diameter of the opening.

When the bottom surface of the hole becomes smaller, the contact area between the conductive material embedded in the hole and the copper layer exposed at the bottom surface of the hole becomes smaller and the contact resistance increases. An object of the present invention is to provide a laser processing method and a processing apparatus capable of forming a hole having a large aperture ratio.

[0007]

According to one aspect of the present invention, a pulsed laser beam is focused on the surface of a metal layer of an object having a metal layer disposed on the surface of an insulating layer made of an insulating material. Thereby, the step of forming a hole penetrating the metal layer, the pulse energy density on the surface of the workpiece is less than a threshold value for etching the metal layer, the beam spot is increased, and And a step of forming a hole in the insulating layer exposed on the bottom surface of the hole formed in the metal layer.

When the beam spot is enlarged, the intensity distribution in the beam spot becomes broad. Focusing on the bottom surface of the hole formed in the metal layer, the intensity distribution approaches flat.
Therefore, it is possible to form a hole having a large aperture ratio.

According to another aspect of the present invention, a laser light source for emitting a pulsed laser beam and a beam transmission hole through which the laser beam passes are provided, and the pulsed laser beam emitted from the laser light source passes through the beam transmission hole. A mask that shapes the beam cross section by passing the beam, a stage that holds the object to be processed, and a pulse laser beam that has passed through the beam transmission hole of the mask to be incident on the object to be processed held by the stage. A lens, a moving mechanism that moves the condenser lens in the direction of its central axis, and the moving mechanism that controls the moving mechanism so that the beam transmission hole forms an image on the surface of the workpiece held by the stage. The image forming state in which the pulsed laser beam is emitted from the laser light source, and the image forming surface of the beam transmission hole are shifted from the surface of the object to be processed. There is provided a laser processing apparatus including a control device that controls a moving mechanism and the laser light source by selecting one state from a non-imaging state in which a pulse laser beam is emitted from the laser light source by controlling the moving mechanism. .

In the imaged state, holes can be formed in the metal layer. In the non-imaging state, holes having a large aperture ratio can be formed in the insulating layer underlying the metal layer.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A shows a schematic view of a laser processing apparatus according to an embodiment of the present invention. The laser light source 1
A pulsed laser beam for processing is emitted.

FIG. 1B shows the structure of the laser light source 1. An optical resonator is defined by the total reflection mirror 10 and the partial reflection mirror 11. The laser medium 12 and the wavelength conversion element 13 are arranged in the optical resonator. For example, Nd: YAG is used as the laser medium 12. As the wavelength conversion element 13, BBO or KDP optical crystal can be used. From the partial reflecting mirror 11, for example, the second harmonic (wavelength 532 nm) and the third harmonic (wavelength 3) of an Nd: YAG laser are used.
55 nm) or the fourth harmonic (wavelength 266 nm) pulsed laser beam is emitted. The wavelength conversion element 13
May be out of the optical resonator.

As shown in FIG. 1A, the laser beam emitted from the laser light source 1 enters the mask 2. The laser beam that has passed through the beam transmission hole provided in the mask 2 enters the dichroic mirror 3. The dichroic mirror 3 reflects a laser beam having a wavelength of 532 nm and transmits visible light having other wavelengths.

The laser beam reflected by the dichroic mirror 3 enters the galvano scanner 4. The galvano scanner 4 includes a pair of swingable reflecting mirrors, and scans a laser beam in a two-dimensional direction. The laser beam scanned by the galvano scanner 4 is converged by the fθ lens 5 and is incident on the processing object 8 held on the XY stage 6.

The fθ lens 5 is supported by a moving mechanism 9 so as to be movable in the central axis (optical axis) direction. fθ
By adjusting the position of the lens 5, the beam transmission hole of the mask 2 can be imaged on the surface of the processing object 8. By moving the fθ lens 5 from this state, the image plane of the beam transmission hole of the mask 2 is moved to the object 8 to be processed.
Can be offset from the surface.

The laser light source 1, the XY stage 6, and the moving mechanism 9 are controlled by the controller 15. Control device 1
Reference numeral 5 denotes an image forming state in which the moving mechanism 9 is controlled so that the beam transmission hole of the mask 2 is imaged on the surface of the object to be processed 8 and the pulsed laser beam is emitted from the laser light source 1, and the connection of the beam transmission hole. The moving mechanism 9 is controlled so that the image plane deviates from the surface of the processing object 8, and one state is selected from the non-imaging state in which the pulsed laser beam is emitted from the laser light source 1, and the moving mechanism 9 and the laser light source 1 are connected. Control.

Next, a laser processing method according to the embodiment will be described with reference to FIG. In addition, if necessary, FIG.
Reference is made to (A). The object to be processed 8 is a copper film 2 on both sides of a base film 20 made of a resin such as polyimide.
Tape automatic bonding (TA
It is a tape for B). The base film 20 has a thickness of, for example, 25 to 50 μm, and the copper layers 21 and 22 have a thickness of, for example, 9 to 18 μm.

As shown in FIG. 2A, a second harmonic pulse laser beam 23 is incident on the copper layer 21. At this time, the position of the fθ lens 5 is adjusted so that the beam transmission hole of the mask 2 shown in FIG. 1 (A) forms an image on the surface of the copper layer 21. The wavelength of the pulse laser beam 23 is 5
32nm, pulse width 30ns, pulse frequency 10k
Hz, the output is 10 W, and the pulse energy density on the surface of the copper layer 21 is 10 J / cm ² . By irradiating 15 shots under this condition, a hole 21a penetrating a copper layer having a thickness of 12 μm is formed.

As shown in FIG. 2B, the fθ lens 5 is placed so that the image plane 27 of the beam transmission hole of the mask 2 is located above the surface of the copper layer 21 (in the defocused state). Then, it is moved by about 1 mm in a direction away from the object to be processed 8. In this state, the pulsed laser beam 26 is emitted from the laser light source 1. The pulse width, pulse frequency, and pulse energy of the pulsed laser beam 26 are determined by the copper layer 21.
The conditions are the same as when the holes 21a are formed in. Since the beam transmission hole of the mask 2 is imaged above the surface of the copper layer 21, the beam spot on the surface of the copper layer 21 is larger than the image of the beam transmission hole, that is, the hole 21a.

By increasing the beam spot,
The pulse energy density on the surface of the copper layer 21 decreases,
It is below the threshold value at which the copper layer 21 is etched. Therefore, the copper layer 21 around the hole 21a is not etched, and only the base film 20 exposed on the bottom surface of the hole 21a is etched. Thereby, the base film 20
A hole 20a aligned with the hole 21a is formed therein.

Since the beam spot on the surface of the copper layer 21 is large, the pulse energy density distribution becomes broader than that when the image is formed on the surface of the copper layer 21. That is, the difference between the pulse energy density at the center of the beam spot and the pulse energy density at the outer peripheral portion of the hole 21a becomes small. Therefore, the difference in etching rate between the central portion of the hole 21a and the vicinity of the outer periphery becomes small, and a hole having a large aperture ratio can be formed.

In the above embodiment, when the holes are formed in the base film 20, as shown in FIG.
Was placed above the copper layer 21, but the image plane 27 was
It may be arranged at a position deeper than the surface of (the in-focus state).

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0024]

As described above, according to the present invention,
After forming the holes in the metal layer, the holes having a high aperture ratio can be formed by forming the holes in the underlying insulating layer in the defocused state or the in-focus state.

[Brief description of drawings]

1A is a schematic diagram of a laser processing apparatus according to an embodiment of the present invention, and FIG. 1B is a schematic diagram of a laser light source.

FIG. 2 is a sectional view of an object to be processed for explaining the laser processing method according to the embodiment.

[Explanation of symbols]

1 laser light source 2 mask 3 dichroic mirror 4 galvano scanner 5 fθ lens 6 XY stage 8 Object to be processed 9 Moving mechanism 10 total reflection mirror 11 Partial reflector 12 Laser medium 13 Wavelength conversion element 15 Control device 20 base film 21, 22 Copper layer 25, 26 pulse laser beam 27 Image plane

Claims (3)

[Claims] 1. (a) A pulsed laser beam is focused on the surface of the metal layer of an object having a metal layer disposed on the surface of an insulating layer made of an insulating material to penetrate the metal layer. A step of forming a hole, and (b) a beam spot is enlarged so that the pulse energy density on the surface of the object to be processed is less than a threshold value for etching the metal layer, and the hole is formed on the metal layer. Forming a hole in the insulating layer exposed on the bottom surface of the hole. 2. The step (a) includes a step of condensing a pulse laser beam transmitted through a beam transmission hole formed in a mask on a surface of the metal layer by an objective lens, the objective lens comprising: The beam transmission hole is imaged on the surface of the metal layer, and the step (b) moves the objective lens in the optical axis direction so that the image formation position of the beam transmission hole is changed from the surface of the object to be processed. The laser processing method according to claim 1, further comprising a step of shifting. 3. A laser light source for emitting a pulsed laser beam and a beam transmission hole through which the laser beam passes are provided, and a pulsed laser beam emitted from the laser light source passes through the beam transmission hole to form a beam cross section. A mask for shaping, a stage for holding an object to be processed, a condenser lens for making a pulsed laser beam having passed through a beam transmission hole of the mask incident on the object to be processed held on the stage, the condenser lens A moving mechanism for moving the laser beam in the direction of its central axis, and controlling the moving mechanism so that the beam transmission hole forms an image on the surface of the processing object held on the stage, and a pulse laser beam is emitted from the laser light source. The moving mechanism is controlled so that the image forming state for emitting the light and the image forming surface of the beam transmitting hole are displaced from the surface of the object to be processed. Select the one state from the non-imaging state to emit a pulsed laser beam from a laser light source, a laser processing device and a control device for controlling the moving mechanism and the laser light source.