JPH0699291A - Abrasion machining method - Google Patents

Abstract

PURPOSE:To easily remove a reaction product by making a reactive gas to blow to the abrasion producing material scattered with an excimer laser beam. CONSTITUTION:An excimer laser beam emitted from an excimer laser head 11 is shaped by regulating the optical path thereof with mirrors 13, 14 and making it incident on a mask 15, passes through an imaging lens 17 and an image is formed on a work piece 18. Plural gas blowing holes are provided on a nozzle 10, a reactive gas, for example, such as O2 gas or H2 gas is made to blow. The gas is made to blow toward the crossing point of the excimer laser beam 4 on the front surface of material 18 to be machined, or toward slightly lower than the point. In such a way, an ascending current is generated on the irradiating part and the abrasion reaction product hardly reaches on the front surface of the material to be machined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to laser processing, and more particularly to ablation processing using an excimer laser.

[0002]

2. Description of the Related Art For laser processing, YAG laser or C
A thermal processing process using an infrared laser such as an O ₂ laser is known, but in recent years, an ablation process in which a high-intensity ultraviolet laser such as an excimer laser is used to instantaneously decompose and scatter an irradiated portion of a workpiece. Is proposed.

It is said that the ablation process using ultraviolet rays is a phenomenon in which a workpiece is decomposed and scattered by a photochemical phenomenon, not by evaporation and scattering of the workpiece by heating.

When the polymer is ablated using an excimer laser, the polymer of the work piece is not carbonized or otherwise affected. It is possible to realize a fineness of processing of about several μm and a reproduction accuracy of a processed shape of 1 μm or less.

Further, since the processing proceeds at a submicron depth for each excimer laser pulse, the processing speed is proportional to the thickness of the workpiece, and the depth can be controlled. For example,
It can be suitably used for removing polyimide from the inner lead portion and outer lead portion of tape automated bonding (TAB).

[0006]

When the work piece is irradiated with excimer laser light to cause ablation, the work piece is instantaneously decomposed and scattered. However, the ablation product, which is once decomposed and scattered, may be deposited again on the surface of the workpiece due to the collision with the ambient atmosphere gas.

For example, when polymer ablation is performed, black soot-like substances adhere to the periphery of the processed region. It is believed that this is mainly due to carbon generated by decomposition of the polymer.

Such reattachment of the ablation-generating substance is not limited to the polymer, but the workpiece is a ceramic material,
The same occurs in the case of metal materials and the like. The redeposition of the ablation product material reduces the processing accuracy. In addition, the appearance of the work piece after the working process is impaired. In addition, if the ablation generating substance is conductive, the insulating property of the work piece is deteriorated.

In the ablation process using such excimer laser light, in order to prevent soot-like deposits, He gas has conventionally been sprayed around the processed part from a specific direction. Since He gas has a small mass number, the He gas and He
It is considered that the frequency of collision with the gas is reduced, and the drop adhesion onto the surface of the workpiece is reduced.

However, according to this method, expensive H
A large amount of e-gas is required, resulting in high processing cost. Moreover, it is difficult to set conditions such as the hole diameter, height, and spray angle of the He gas spray nozzle, and soot remaining in the downstream direction of the spray gas is likely to adhere.

Japanese Unexamined Patent Publication No. 1-273687 discloses an ablation processing apparatus for supplying oxygen radicals or hydrogen radicals to an excimer laser irradiation section in a reduced pressure atmosphere.
In this case, an exhaust device for forming a decompressed atmosphere, an airtight container, an excitation source for radical generation, etc. are required, resulting in an increase in cost.

In addition, various methods have been proposed for preventing soot adhesion in ablation processing.
A satisfactory product has not been proposed yet in terms of both cost and effect.

An object of the present invention is to provide an ablation processing method capable of preventing adverse effects of an ablation substance on the surface of a workpiece in the ablation processing using excimer laser light.

[0014]

The ablation processing method of the present invention is an ablation processing method of irradiating an object to be processed with excimer laser light in the atmosphere to cause ablation, and an excimer laser light is applied to a region to be processed. While irradiating, from a direction almost symmetrical with respect to the irradiation position,
It is characterized in that a gas reactive with the ablation product is blown.

Here, the reactive gas is preferably a gas capable of chemically reacting with the ablation generating substance to form a compound that is a gas at room temperature.

[0016]

[Function] When the excimer laser light is irradiated onto the region to be processed,
The surface of the work piece is instantly decomposed and scattered. This decomposition,
When the scattered ablation product is blown with a reactive gas, the ablation product reacts with the gas to form a compound.

When the compound is a gas at room temperature, the ablation-producing substance is gasified and can be easily removed. Further, if the reaction product of the ablation generation substance and the reactive gas becomes an insulating substance, the deterioration of the electrical insulation characteristic can be suppressed even if the deposition occurs.

Even if the ablation-producing substance remains, the gas is blown from a substantially symmetrical direction,
It is rarely deposited on the surface of the work piece.

[0019]

FIG. 1 shows the system configuration of an ablation processing system using excimer laser light.

In FIG. 1A, an excimer laser head 11 includes, for example, a KrF laser tube, and is driven by a laser driving section 12. The excimer laser beam emitted from the excimer laser head 11 is reflected by the mirror 1
The optical path is adjusted by 3, 14 and the light is incident on the mask 15.

The excimer laser beam shaped by the mask 15 having the opening is bent downward by the mirror 16 and passes through the imaging lens 17 to form an image on the workpiece 18. The nozzle 10 has a plurality of gas spray ports and sprays a reactive gas such as O ₂ gas or H ₂ gas onto the workpiece 18.

The nozzle may have an inner diameter of 50, for example.
mmφ, outer diameter 80 mmφ, three gas outlets 3 are provided at 120 ° intervals toward the center of the ring, the inner diameter r of the gas outlets is 1 mmφ, 3 mmφ, and the gas outlet angle θ is 25 ° with respect to the horizontal line, 45 Those having an angle of degrees can be used. The nozzle height h is, for example, 5
It can be selected within a range of up to 20 mm.

The positions of the mask 15 and the imaging lens 17 are adjusted by a control signal from the controller 21 so that an image can be formed on the work piece at a desired magnification. The mirror 16 is transparent to visible light, and the workpiece 18 is observed by the imaging monitor 19 from above. The monitor signal is supplied to the controller 21. Further, the height monitor 22 monitors the height of the workpiece 18 and uses the measurement result as a height detection signal in the controller 21.
Supply to.

The controller 21 generates a signal for controlling each control part based on the monitor signals supplied from the image pickup monitor 19 and the height monitor 22. The controller 21 sends an alignment signal to the processing stage 25 including the X stage 23 and the Y stage 24, and the workpiece 18
Adjust the position of. The processing stage 25 can perform Z adjustment and θ adjustment as well as X and Y adjustments.

In the case of a KrF laser, the excimer laser head 11 uses, for example, a laser beam of 8 mm × 25 mm, a pulse repetition rate of 200 pps, an output energy of 250 mJ,
It occurs with an average output of 50 W and a pulse width of 16 ns. In addition,
The wavelength of the KrF laser is about 248 nm.

When the excimer laser is ArF,
The oscillation wavelength is about 193 nm, and in the case of the XeCl laser, the oscillation wavelength is about 308 nm. For the processing of the metal film, the wavelength of the excimer laser light is about 10 J / c.
An energy density of about m ² or more is preferable.

The excimer laser uses pulse oscillation, and the etching depth can be controlled with high precision by controlling the number of pulses. Further, the excimer laser can be shaped into a desired shape by using a mask and an optical system.

FIG. 1B schematically shows a method of shaping an excimer laser beam. The mask 15 is formed of a metal such as copper alloy or molybdenum, and has openings 28 having a desired pattern. The excimer laser beam incident on the mask 15 is imaged on the workpiece 18 by the imaging lens 17 using the mask 15 as a new light source.

If the distance between the mask 15 and the imaging lens 17 is a, and the distance between the imaging lens 17 and the workpiece 18 is b , then 1 / a + 1 / b = 1 /
The relationship of f is established. Here, f is the focal length of the imaging lens 17. When changing the focus position and magnification of the optical system, the Z adjustment mechanism 26 provided in the imaging lens 17 and the drive mechanism of the mask 15 are used to adjust these positions.

FIG. 2 shows the structure of the nozzle 10 shown in FIG. 1 in more detail. FIG. 2A shows a plan configuration of the nozzle 10, and FIG. 2B shows a sectional configuration thereof. Figure 2 (A)
2, the nozzle 10 has a ring shape, and its cross section is a hollow rectangle as shown in FIG. 2 (B). The nozzle 10 has a nozzle fixing arm 1 fixed around the ring-shaped member, and a gas introduction pipe 2 that is electrically connected to the hollow ring-shaped member.

Further, in the illustrated case, the ring-shaped member is provided with three gas blow-out holes 3 at intervals of approximately 120 degrees.
As shown in FIG. 2 (B), the gas blowout holes 3 are open obliquely downward.

FIG. 2C is an enlarged view of the gas blowing hole 3. The ring-shaped member is composed of a ring-shaped groove member having a U-shaped cross section and a ring-shaped lid member covering the upper surface thereof. A gas blowout hole 3 is obliquely formed in the inner bent portion of the ring-shaped groove member having a U-shaped cross section. The gas blowing hole 3 has a hole diameter r and an angle θ with respect to the horizontal direction.

In addition to the nozzle shape shown in FIG. 2,
Various forms can be adopted. For example, the number of gas outlets is arbitrary as long as they are in a plurality of directions that are substantially symmetrical with respect to the expected excimer laser irradiation position. The nozzle shape is not limited to the circular shape, and may be an elliptical shape, a rectangular shape, or the like.
Further, the cross-sectional shape of the nozzle is not limited to the rectangular shape, and various shapes can be used. However, in order to stably arrange the nozzles with high accuracy, it is preferable that the nozzle bottom surface be flat, for example.

FIG. 3 shows an example of nozzle arrangement. In the figure, the nozzle 10 is held horizontally on the surface of the workpiece 18 at a height h. The excimer laser light 4 is applied vertically to the center of the nozzle 10.

Further, the gas blowout holes provided in the nozzle 10 are in a direction substantially symmetrical with respect to the center of the nozzle, and at the point where the excimer laser beam 4 intersects the surface of the workpiece 18.
Or preferably slightly below it. According to such a configuration, it is considered that an ascending airflow is generated in the irradiated portion, and the ablation-producing substance rarely reaches the surface of the workpiece.

With such an arrangement, a sufficient amount of gas can be supplied to the ablation-producing substance decomposed and scattered from the surface of the workpiece 18 by the irradiation of the excimer laser beam 4.

FIG. 4 shows another form of the nozzle. The illustrated nozzle 10a has a racetrack type shape, and two gas introduction pipes 2 are connected to both ends thereof. Further, a large number of gas outlets 3 are formed in the racetrack type gas pipe.

By using such a nozzle,
It is possible to apply a large number of holes at the same time in a region inside the racetrack mold while keeping the nozzle position fixed.

FIG. 5 shows that when the workpiece is polyimide, no gas is blown, O ₂ gas is blown, and He gas is blown by the conventional technique. The result of having observed the adhering carbon is shown.

The gas spraying angle θ of the nozzle is 45.
The degree and height h were 5 mm, and the hole diameter r was 3 mmφ. As the excimer laser, a KrF excimer laser (oscillation wavelength 248 nm) manufactured by Lumonix was used. The output was 50 W, the repetitive frequency was 200 Hz, the processing time was 1 second, and the object to be processed was a 500 H polyimide film having a thickness of 125 μm, and a hole having a diameter of about 300 μm was opened by excimer laser light.

When the gas was not blown, as shown in the left side of FIG. 5A, carbon was widely attached to the periphery of the ablation processed portion. When He gas is sprayed, when the spraying gas flow rate is 10 l / min,
As shown in the diagram on the right side of FIG. 5 (A), the amount of attached carbon was considerably reduced.

When the gas spray nozzle of the embodiment described above is used and the O ₂ gas is sprayed at a flow rate of 1 l / min,
As shown in the middle diagram of FIG. 5 (A), the amount of attached carbon was significantly reduced. As can be seen here, the flow rate of the blown O ₂ gas is 1/10 of the flow rate of He gas.

It is considered that the effectiveness of the present example is shown that the amount of carbon adhering was remarkably reduced although the flow rate of the sprayed gas was remarkably smaller than that of He gas.

FIG. 5B is a graph showing changes in the diameter of the adhered carbon when the flow rate of the gas to be sprayed is changed variously. Note that N ₂ gas was further sprayed as compared with the case of FIG. By spraying N ₂ gas, although the diameter of the adhered carbon is somewhat reduced,
It turns out that most of it does not change.

On the other hand, when He gas is sprayed, it is found that the diameter of the adhered carbon is remarkably reduced at the gas flow rate gas of 10 l / min. It should be noted that the gas flow rate is not necessarily high, and if the flow rate of He gas is further increased, the diameter of the adhered carbon will increase again.

When the O ₂ gas was sprayed, the diameter of the adhering carbon was remarkably reduced at a gas flow rate of about 1/10 as compared with the He gas. In this case as well, when the gas flow rate is further increased, the diameter of the adhered carbon is slightly expanded.

From these results, it is understood that in the case of ablation processing of polyimide by an excimer laser, if the required amount of O ₂ gas is supplied to the excimer laser light irradiation portion, the amount of carbon adhered around the processing portion can be significantly reduced.

It is considered that the reduction of the deposits around the processing region in the ablation process is caused by spraying the reactive gas to the ablation substance and forming the volatile gas compound. This action is not limited to polymers, but can be applied to ablation processing of other materials such as ceramic materials and metal materials.

In the case where the deposit around the ablation processed region poses a problem in terms of insulation characteristics, it is possible to improve the insulation characteristics by reducing the adhesion of the conductive substance even if the adhesion cannot be completely prevented. . In the case of ablation of a metal material, if a metal substance that decomposes or scatters is oxidized to form an insulator, the insulating property is improved even if adhesion occurs.

Although the case where the oxidation reaction is used to remove the ablation-producing substance has been described, a volatile gas can be generated by the reduction reaction. For example, when C is generated by ablation, hydrogen gas is supplied and C
If the reaction of + 2H ₂ → CH ₄ is caused, CH ₄ becomes a gas, and it can be removed without adhering to the surface of the workpiece.

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 changes, improvements, combinations and the like can be made.

[0052]

In the ablation process using the excimer laser light, it is possible to reduce the influence of deposits in the periphery of the ablation process region.

If the ablation-producing substance is reacted with a gas to make it a volatile substance, it is possible to significantly reduce the adhesion in the ablation processing region.

[Brief description of drawings]

FIG. 1 is a perspective view of an ablation processing system using excimer laser light according to an embodiment of the present invention.

2A and 2B are a plan view and a cross-sectional view showing the shape of a nozzle used in the system of FIG.

FIG. 3 is a schematic side view for explaining a nozzle arrangement.

FIG. 4 is a schematic plan view showing the shape of a racetrack nozzle.

FIG. 5 is a sketch and a graph showing changes in adhered carbon due to gas blowing.

[Explanation of symbols]

 1 Nozzle Fixing Arm 2 Gas Introducing Tube 3 Gas Blowing Hole 4 Laser Light 10 Nozzle 11 Excimer Laser Head 12 Laser Driving Unit 13, 14, 16 Mirror 15 Mask 17 Imaging Lens 18 Workpiece 19 Imaging Monitor 21 Controller 22 Height Monitor 23 X Stage 24 Y Stage 25 Processing Stage 26 Z Adjustment Mechanism 28 Opening

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Yamanaka Sumitomo Heavy Industries, Ltd. Laser Business Center

Claims (2)

[Claims] 1. A method of ablation for irradiating an object to be processed with excimer laser light in the atmosphere to cause ablation, wherein the area to be processed is irradiated with excimer laser light and is substantially symmetrical with respect to an irradiation position. An ablation processing method characterized in that a gas reactive with an ablation substance is blown from a direction. 2. The ablation processing method according to claim 1, wherein the reactive gas is a gas capable of chemically reacting with an ablation generating substance to form a compound that is a gas at room temperature.