JPH08197277A - Laser processing device and method therefor - Google Patents

Abstract

PURPOSE: To clean both of an optical window and an object to be irradiated without degrading material characteristics. CONSTITUTION: This laser processing device for irradiating a circuit board 6 with laser beam is provided with a vacuum chamber 1, a fixing pallet 5, a laser irradiation part 3, an optical window 4 and a high frequency electrode 7. The vacuum chamber 1 is kept in a prescribed degree of vacuum. The fixing pallet 5 is arranged inside the vacuum chamber 1, and holds the circuit board 6. The laser irradiation part 3 is arranged outside the vacuum chamber 1 to irradiate the circuit board 6 held by the fixing pallet 5 with the laser beam. The optical window 4 is provided on the wall face of the vacuum chamber 1 to introduce the laser beam emitted from the laser irradiation part 3. The high frequency electrode 7 generates the plasma between the optical window 4 and the fixing pallet 5 to clean the circuit board 6 and the optical window 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus and a laser processing method, and more particularly to a laser processing apparatus and a laser processing method for irradiating an object to be irradiated with a laser beam in a vacuum for processing.

[0002]

2. Description of the Related Art Conventionally, when laser processing is performed in a vacuum, scattered particles generated by ablation adhere to an optical window for passing a laser beam and an object to be irradiated, thereby causing a laser beam transmittance of the optical window and an object to be irradiated. There is a problem that the product reliability of the irradiated object is reduced. As a conventional method of cleaning an optical window that solves this problem, there is a wet cleaning method (chemical method) of cleaning the surface of the optical window with a chemical such as alcohol to remove contaminants. In this method, the surface of the optical window is washed with alcohol and then the alcohol is dried.

There is also known a laser processing apparatus which employs a dry cleaning method (physical method) in which contaminants are removed by the ion sputtering effect by generating high-frequency plasma around the optical window (special feature). Kaihei 4-66290
Issue). This laser processing apparatus obliquely irradiates an object to be irradiated with laser light, and vapor of the object to be irradiated is vapor-deposited on a substrate arranged above. In this device, a gas introduction differential pressure chamber is separately provided in the laser light introduction part of the vacuum container in which the object to be irradiated and the substrate are arranged, and plasma is generated in the gas introduction differential pressure chamber by high frequency, and the sputtering effect of gas and ions is generated. The optical window is designed to prevent contamination.

[0004]

In the case of the former wet cleaning method using chemicals, there is a problem that not only a drying step is required but also a risk of ignition is involved. In contrast,
In the case of the latter dry cleaning method using high-frequency plasma, plasma is generated in the gas introduction differential pressure chamber, so the effect that contaminants adhering to the optical window surface can be removed has already been confirmed. There is a problem that it only works on the optical window.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laser processing apparatus and a laser processing method capable of cleaning both an optical window and an object to be irradiated without deteriorating the material characteristics. To do.

[0006]

In order to solve the above-mentioned problems, a laser processing apparatus according to the invention of claim 1 is a laser processing apparatus for irradiating an object to be irradiated with a laser beam for processing, and a vacuum chamber A holding means, a laser irradiation means, an optical window, and a plasma generation means are provided. The vacuum chamber can be maintained at a predetermined degree of vacuum. The holding means is arranged in the vacuum chamber and holds the irradiation target. The laser irradiation means is arranged outside the vacuum chamber,
The irradiation target held by the holding means is irradiated with laser light.
The optical window is provided on the wall surface of the vacuum chamber in order to guide the laser light emitted from the laser irradiation means into the vacuum chamber.
The plasma generating means has a plasma electrode for generating plasma between the optical window and the holding means, and a high frequency power source for applying a high frequency voltage to the plasma electrode.

A laser processing apparatus according to the invention of claim 2 is
The apparatus according to claim 1, further comprising moving means for moving the plasma electrode between the holding means and the optical window. A laser processing apparatus according to a third aspect of the present invention is the second aspect.
In the apparatus described above, the moving means arranges the plasma electrode at a first position near the holding means during laser irradiation by the laser irradiation means, and moves the second electrode near the optical window after the laser irradiation is completed.
Place in position.

A laser processing apparatus according to the invention of claim 4 is
The apparatus according to claim 1, wherein the plasma electrode has a coil shape and has a divergent shape toward the holding means. A laser processing apparatus according to a fifth aspect of the present invention is the apparatus according to the first aspect, further comprising a first voltage applying unit that applies a first voltage between the object to be irradiated and the plasma electrode.

A laser processing apparatus according to the invention of claim 6 is
The apparatus according to claim 1, further comprising second voltage applying means for applying a second voltage between the plasma electrode and the optical window. A laser processing apparatus according to a seventh aspect of the present invention is the apparatus according to the first aspect, wherein a first voltage is applied between the object to be irradiated and the plasma electrode, and a second voltage is applied between the plasma electrode and the optical window. It further comprises a third voltage applying means for applying.

A laser processing apparatus according to the invention of claim 8 is
The apparatus according to claim 1, further comprising timing control means for controlling the plasma generation timing of the plasma generation means. A laser processing apparatus according to a ninth aspect of the present invention is the laser processing apparatus according to the first aspect, further comprising: an air inflow means for inflowing air around the optical window; and an assist gas inflow means for injecting an assist gas around the irradiation object. Is further equipped.

According to a tenth aspect of the present invention, in the laser processing apparatus according to the first aspect, the non-reactive gas inflow means for injecting the non-reactive gas into the periphery of the optical window and the assist to the periphery of the object to be irradiated. It further comprises assist gas inflow means for inflowing gas. According to an eleventh aspect of the present invention, there is provided a laser processing apparatus according to the first aspect, further comprising a gas inflow means for selectively injecting a reactive gas and a non-reactive gas into the periphery of the optical window according to timing, It further comprises an assist gas inflow means for injecting the assist gas around the irradiation object.

According to a twelfth aspect of the present invention, there is provided a laser processing apparatus according to the first aspect, further comprising a shield plate provided inside the plasma electrode and allowing only high frequencies to pass therethrough. A laser processing apparatus according to the invention of claim 13 is
In the device according to claim 12, the material of the shielding plate is the same as the material of the optical window.

A laser processing apparatus according to a fourteenth aspect of the present invention is the apparatus according to the first aspect, further comprising cooling means for cooling the plasma electrode. A laser processing apparatus according to the invention of claim 15 is the apparatus according to claim 1,
The plasma generating means is arranged outside the vacuum chamber. A laser processing apparatus according to a sixteenth aspect of the present invention is the laser processing apparatus according to the first aspect, further including operating means for operating the plasma generating means when the holding means does not hold an irradiation target.

A laser processing method according to a seventeenth aspect of the present invention is a method for irradiating an object to be irradiated, which is held in a vacuum chamber, with a laser beam through an optical window to perform processing, wherein the optical window and the object to be irradiated are processed. It is characterized in that high-frequency plasma is generated in the vacuum chamber so as to exert a purifying effect on and.

[0015]

In the laser processing apparatus according to the first aspect, the irradiation object held by the holding means in the vacuum chamber is irradiated with the laser light through the optical window by the laser irradiation means. As a result, the irradiation object is processed. During this process, a high frequency voltage is applied to the plasma electrode to generate plasma between the optical window and the holding means. The generated plasma diffuses the ionized particles and collides with the optical window and the irradiation target, whereby contaminants on the surfaces of the optical window and the irradiation target are removed. In addition, when the scattered particles generated from the irradiated object are reactive substances, the scattered particles are vaporized by a chemical reaction with the particles in the plasma atmosphere, and as a result, the scattered light particles are emitted to the optical window and the irradiated object. The scattered particles that adhere are reduced.

In the laser processing apparatus according to the second aspect, the moving means moves the plasma electrode between the holding means and the optical window. Here, even if the action exerted by the plasma discharge differs depending on the substance, the optimum cleaning action can always be exerted on the optical window and the irradiation target by changing the position of the plasma electrode. In the laser processing apparatus according to the third aspect, the moving means arranges the plasma electrode at the first position near the holding means during laser irradiation, and disposes at the second position near the optical window after the laser irradiation is completed. Here, since plasma is generated in the vicinity of the object to be irradiated during laser irradiation, the scattered particles at the time of irradiation can be vaporized and the scattered particles redeposited on the object to be irradiated can be removed by etching. In addition, after the end of irradiation,
Since plasma is generated in the vicinity of the optical window, scattered particles attached to the optical window can be removed by etching.

In the laser processing apparatus according to the fourth aspect, since the plasma electrode has a shape which spreads toward the holding means,
The scattered particles from the irradiated object that diffuse as the distance from the processing point increases can be effectively vaporized according to the diffusion shape, the number of scattered particles can be reduced, and the scattered particles adhere to the optical window and the irradiated object. The amount can be reduced. In the laser processing apparatus according to the fifth aspect, the power of the generated positive ions to the holding means is controlled by the first voltage applied between the object to be irradiated and the plasma electrode by the first voltage applying means. . Here, since the power of the positive ions to the holding means can be arbitrarily controlled by the first voltage, it is possible to exert an optimum cleaning action on the optical window and the irradiation target.

In the laser processing apparatus according to claim 6, the second
The power of the generated positive ions to the optical window is controlled by the second voltage applied between the plasma electrode and the optical window by the voltage applying means. Here, since the power of the positive ions to the optical window can be arbitrarily controlled by the second voltage, it is possible to exert an optimum cleaning action on the optical window and the irradiation target.

According to a seventh aspect of the laser processing apparatus of the present invention,
The first ion voltage applied between the object to be irradiated and the plasma electrode by the voltage application means and the second voltage applied between the plasma electrode and the optical window, the object to be irradiated and the optical of the positive ion plasma. Power to the window is controlled. Here, the power of positive ions to the irradiation target and the optical window is
Also, since it can be controlled arbitrarily by the second voltage, it is possible to exert an optimum cleaning action on the optical window and the irradiation target even if plasma discharge is performed with constant power.

In the laser processing apparatus according to the eighth aspect, the plasma generation timing of the plasma generation means is controlled by the timing control means. For example, plasma is not generated during laser irradiation, but plasma is generated after irradiation.
As a result, it is possible to suppress the laser power from being attenuated by plasma and to purify the optical window and the irradiation target. In the laser processing apparatus according to the ninth aspect, air flows into the periphery of the optical window and assist gas flows into the periphery of the object to be irradiated. Here, since air flows into the periphery of the optical window, an air layer is formed around the optical window, and scattered particles do not easily reach the optical window. Also,
Since the assist gas flows into the periphery of the object to be irradiated, scattered particles are less likely to reattach to the object to be irradiated.

In the laser processing apparatus according to the tenth aspect, the non-reactive gas flows into the periphery of the optical window and the assist gas flows into the periphery of the object to be irradiated. Here, since the non-reactive gas having a high etching effect flows into the periphery of the optical window, the etching effect in the optical window is improved and the cleaning effect of the optical window by the plasma becomes more effective. Moreover, since the assist gas flows into the periphery of the object to be irradiated, scattered particles are less likely to reattach to the object to be irradiated.

According to the eleventh aspect of the laser processing apparatus, the reactive gas and the non-reactive gas selectively flow into the periphery of the optical window according to the timing, and the assist gas flows into the periphery of the object to be irradiated. Here, for example, immediately after laser irradiation, the reactive gas can be caused to flow around the optical window to effectively vaporize the scattered particles, and then the non-reactive gas can be caused to flow in to effectively etch the optical window. Moreover, since the assist gas flows into the periphery of the object to be irradiated, scattered particles are less likely to reattach to the object to be irradiated.

In the laser processing apparatus according to the twelfth aspect, the shield plate provided inside the plasma electrode can prevent the electrode component that is ejected by the sputtering of the plasma electrode itself from adhering to the optical window. In the laser processing apparatus according to claim 13, since the material of the shielding plate is the same as the material of the optical window, even if the shielding plate is sputtered and the scattered particles adhere to the optical window, the transmittance of the optical window is reduced. Less likely to affect.

In the laser processing apparatus according to the fourteenth aspect, the plasma electrode is cooled by the cooling means. here,
Since the plasma electrode is cooled, the amount of sputtering of the electrode itself can be reduced. In the laser processing apparatus according to the fifteenth aspect, since the plasma generating means is arranged outside the vacuum chamber, it is possible to prevent the electrode component that is ejected due to the sputtering of the plasma electrode itself from adhering to the optical window.

In the laser processing apparatus according to the sixteenth aspect, the plasma generating means operates when the holding means does not hold the object to be irradiated. As a result, contaminants adhering to the vacuum chamber and the holding means can be removed, and the inside of the vacuum chamber can always be maintained in a clean atmosphere. In the laser processing method according to the seventeenth aspect of the present invention, the high frequency plasma is generated in the vacuum chamber so as to exert a cleaning action on the optical window and the irradiation target. The generated plasma diffuses the ionized particles,
The contaminants on the surfaces of the optical window and the irradiation target are removed by colliding with the optical window and the irradiation target. Also, when the scattered particles generated from the irradiated object are reactive substances,
The scattered particles are vaporized by a chemical reaction with the particles in the plasma atmosphere, and as a result, the scattered particles attached to the optical window and the irradiation target are reduced.

[0026]

Embodiments of the present invention will be described below. In the embodiment, the surface of the optical window for passing the laser beam and the surface of the circuit board are mainly cleaned. 1 to 3 are sectional views of the laser processing apparatus according to the first embodiment. The laser processing apparatus is provided with a box-shaped vacuum chamber 1 in which an optical window 4 is arranged on the upper outer wall. In the vacuum chamber 1,
A vacuum pump 2 is connected, and the inside thereof is maintained at a vacuum degree of about 5 × 10 ^-2 Torr by the vacuum pump 2. The laser irradiation unit 3 is arranged above the optical window 4. Inside the vacuum chamber 1, a fixing pallet 5 for holding a circuit board 6 which is an irradiation target is arranged so as to face the optical window 4. A high frequency electrode 7 for generating plasma is arranged between the optical window 4 and the fixing pallet 5. The high frequency electrode 7 is a coiled metal electrode. To the high frequency electrode 7, a high frequency generation source 9 including a matching section 9a and a high frequency power source 9b arranged outside the vacuum chamber 1 is connected.

Next, the operation of the first embodiment will be described. The laser beam 3a is emitted from the laser irradiation unit 3 to the circuit board 6 held by the fixing pallet 5 through the optical window 4, and the conductor portion of the circuit board 6 is laser-processed. At that time, a high-frequency voltage is applied to the high-frequency electrode 7 by a high-frequency generation source 9 to energize it to generate plasma. Then, even if scattered particles generated from the circuit board 6 due to ablation by laser processing adhere to the optical window 4 or are re-adhered to the circuit board 6 and are temporarily contaminated, the discharge-diffused ions are dispersed in the optical window 4 and the circuit board. The contaminants can be removed by etching 6. Further, the amount of the scattered particles attached to the optical window 4 and the circuit board 6 can be reduced by vaporizing the scattered particles by the chemical reaction between the scattered particles and the particles in the plasma atmosphere.

At this time, it is desirable that the optical window 4 is made of a substance that transmits the laser beam 3a, such as synthetic quartz. Further, as for plasma power, it is necessary to have a power that exerts the effect of ion etching and vaporization of scattered particles, and that does not adversely affect the laser light, such as fluctuation and position shift.
About 200 W is desirable. Further, regarding the plasma discharge time, it is desirable to discharge for at least 10 seconds after the laser treatment in order to exert the etching effect.

By using the above-mentioned processing apparatus, the life of the optical window 4 is about 5 times as long as that when plasma discharge is not performed.
Also, regarding the circuit board 6, the bonding strength of the wire bonding in the subsequent conductor portion is 1 at the average value of 100 points.
It increased from 0.25 g to 10.93 g. FIG. 4 shows a sectional view of the laser processing apparatus according to the second embodiment. It should be noted that in the following description of the embodiments, the description of the common parts with the first embodiment will be omitted. In Example 2, the high frequency electrode 7
By making the position of the optical disk movable, it is possible to exert an optimum cleaning action on both the optical window 4 and the circuit board 6. That is, since the optical window 4 and the circuit board 6 are made of different substances, the way they are affected by plasma discharge is different. Therefore, a moving mechanism 7a for moving the high-frequency electrode 7 up and down is provided, and the position of the high-frequency electrode 7 is controlled so that an optimum cleaning action is exerted on both the optical window 4 and the circuit board 6. As the moving mechanism 7a for the high frequency electrode 7, a driving mechanism such as a motor may be used.

FIG. 5 shows a sectional view of the laser processing apparatus according to the third embodiment. In the third embodiment, the position of the high-frequency electrode 7 that exerts the optimum cleaning action on the optical window 4 and the circuit board 6 is obtained separately, and the electrode moves during each cleaning, so that the optimum cleaning action can be exerted. I am trying. That is, a moving mechanism 7a for moving the high frequency electrode 7 up and down is provided, and when the laser irradiation is performed, the
As shown in (a), the high-frequency electrode 7 is provided around the circuit board 6.
By disposing, the scattered particles that fly out at the time of irradiation are vaporized, and the scattered particles that have partially reattached to the circuit board 6 are removed by etching. On the other hand, at the end of laser irradiation, as shown in FIG. 5B, the high frequency electrode 7 is arranged around the optical window 4 in order to remove the scattered particles adhering to the optical window 4 by etching. A more effective cleaning action can be exerted on the optical window 4 and the circuit board 6 by this method.

FIG. 6 is a sectional view of the laser processing apparatus according to the fourth embodiment. In the fourth embodiment, the shape of the high-frequency electrode 7 is controlled so that an optimum purifying action can be exerted. In other words, the scattered particles that fly out during laser irradiation diffuse as the distance from the processing point increases, so that the shape of the high-frequency electrode 7 is expanded to match the diffused shape, and the scattered particles are more effectively vaporized. By this method, the number of scattered particles is reduced, and the amount attached to the optical window 4 and the circuit board 6 is reduced.

7 to 9 show three Examples 5 to 7 showing the effect of the purifying action by the voltage control. In Example 5 shown in FIG. 7, by applying a voltage between the circuit board 6 and the high frequency electrode 7, it is possible to exert an optimum purifying action. That is, when high-power plasma is generated for cleaning the optical window 4, the cleaning of the circuit board 6 may be adversely affected. Therefore, a grid electrode 8c is provided between the circuit board 6 and the high frequency electrode 7, and the grid electrode 8a is connected to the fixing pallet 5 via the first voltmeter 8a. Then, by controlling the voltage with the first voltmeter 8a, adjustment is performed so that appropriate power can reach the circuit board 6. At this time, it is desirable that the plasma power exerted on the circuit board 6 is about 20 to 100 W, so when purifying the optical window 4 with a lower power,
The circuit board 5 is cleaned by generating a negative voltage around the circuit board 6 and attracting the positive ions generated by the high frequency plasma to etch the surface of the circuit board 6. On the contrary, when the optical window 4 is cleaned with a power higher than the plasma power exerted on the circuit board 6, a positive voltage is generated around the circuit board 6 so that positive ions generated by the high frequency plasma are not attracted.

In the sixth embodiment shown in FIG. 8, contrary to the fifth embodiment, an optimum purifying action can be exerted by applying a voltage between the optical window 4 and the high frequency electrode 7. In the sixth embodiment, the grid electrode 8c is connected to the second voltmeter 8b.
It is connected to the optical window 4 via. Here, the plasma power around the circuit board 6 is always kept constant, a voltage is applied between the optical window 4 and the high frequency electrode 7, and the second voltmeter 8 is used.
The optical power is adjusted to reach the optical window 4 by controlling with b. Also at this time, as in the case of FIG. 5, when the optical window 4 is cleaned with a plasma power lower than the power for cleaning the circuit board 6, a positive voltage is generated around the optical window, and conversely. When purifying the optical window 4 with plasma power higher than that for purifying
Generate a negative voltage around the optical window.

In the seventh embodiment shown in FIG. 9, an optimum purifying action can be exerted by combining the fifth and sixth embodiments. That is, in this method, a voltage is applied between the circuit board 6 and the high frequency electrode 7 and between the optical window 4 and the high frequency electrode 7, and the voltage is controlled by the first voltmeter 8a and the second voltmeter 8b. Thus, even when plasma discharge is performed with a constant power, an appropriate purifying action can be exerted individually.

FIG. 10 shows a sectional view of the laser processing apparatus according to the eighth embodiment. In the eighth embodiment, the timing of plasma discharge is controlled. When laser irradiation is performed in a plasma atmosphere, there is a problem that laser power is attenuated due to emission of laser light. In addition, the purpose of discharging plasma is to react the vaporized particles ejected by ablation with the gas in the atmosphere to vaporize them and to remove the vaporized particles once attached to the optical window 4 or the circuit board 6 by plasma etching. is there. Therefore, efficient plasma discharge becomes possible by making plasma discharge only when it meets the purpose,
Also, the laser power is not attenuated. Regarding the timing of plasma discharge, when laser oscillation is being performed, the timing of FIG.
As shown in FIG. 10A, the plasma atmosphere may not be set, but plasma discharge may be performed at the end of the laser treatment so that the plasma atmosphere 10 is obtained as shown in FIG. 10B.

11 to 13 show three Examples 9 to 11 which exert a purifying action by controlling the atmospheric gas in the vacuum chamber 1. Example 9 shown in FIG.
Then, the nozzle 13 is installed around the optical window 4, and an external air source (not shown) is connected thereto via the flow rate adjusting valve 12. Then, air having a flow rate adjusted by the flow rate adjusting valve 12 is ejected from the outside from the nozzle 13 to the periphery of the optical window 4. On the other hand, the nozzles 16 are also provided around the circuit board 6.
Gas cylinder 1 filled with an inert gas
4 is connected via a flow control valve. Then, by flowing an assist gas for preventing re-adhesion to the circuit board 6 with respect to scattered particles that have jumped out from the circuit board 6 during ablation, it is possible to more efficiently exert a cleaning action when plasma discharge is performed. .

Specifically, the gas flowing from the external atmosphere through the flow rate adjusting valve 12 flows through the nozzle 13 around the optical window 4. As a result, a gas layer is formed around the optical window 4, so that the particles scattered during ablation collide with the gas layer and do not reach the optical window 4. At this time, the flow rate of the gas may be such that the degree of vacuum in the vacuum chamber 1 does not change. Specifically, about 1 liter / minute is desirable. On the other hand, around the circuit board 6, the gas cylinder 14 is used to control the flow rate control valve 1
The gas flowing through 5 is allowed to flow through the nozzle 16. Regarding the gas to be flown, He having a small molecular weight is desirable in order to prevent re-adhesion to the circuit board 6 due to collision with molecules in the atmosphere.

In the tenth embodiment shown in FIG. 12, a nozzle 13 is installed around the optical window 4, and a gas cylinder 11 filled with a gas having a high etching effect is provided in the nozzle 13 to adjust the flow rate.
Connect through. Then, a gas having a high etching effect is ejected around the optical window 4. On the other hand, a nozzle 16 is also installed around the circuit board 6, and a gas cylinder 14 filled with an inert gas is connected to the nozzle 16 via a flow rate adjusting valve 15. Then, the assisting gas for preventing reattachment of the particles scattered during the ablation onto the circuit board 6 is caused to flow from the nozzle 16, so that the cleaning effect can be more efficiently exerted when the plasma discharge is performed.

Specifically, the gas flowing from the gas cylinder 11 via the flow rate adjusting valve 12 passes through the nozzle 13 to the periphery of the optical window 4. Similarly, the gas flowing from the gas cylinder 14 via the flow rate adjusting valve 15 passes through the nozzle 16 and flows around the circuit board 6. With respect to the gas to be flown, it is theoretically desirable that the periphery of the optical window 4 has a large molecular weight, but Ar or the like is generally used in terms of cost. Regarding the assist gas flowing around the circuit board 6,
In order to prevent redeposition on the circuit board 6 due to collision with molecules in the atmosphere, He having a small molecular weight is desirable.

In the eleventh embodiment shown in FIG. 13, two nozzles 13 and 19 are installed in the periphery of the optical window 4, and the gas to be flown is changed according to the timing of the laser processing, so that the purifying action can be performed more efficiently. I am able to influence.
Specifically, when ablation occurs immediately after laser irradiation, the gas flowing from the gas cylinder 17 containing the reactive gas through the flow rate adjusting valve 18 flows through the nozzle 19 to the periphery of the optical window 4. To As a result, the scattered particles that have jumped out are effectively vaporized. After that, with respect to the scattered particles attached to the optical window 4 without being vaporized, the gas flowing from the gas cylinder 11 containing the gas having a high etching effect through the flow rate adjusting valve 12
Through to the periphery of the optical window 14. As a result, scattered particles attached to the optical window 4 without being vaporized are removed by etching. At this time, O ₂ or the like is desirable for the reactive gas. In addition, He or the like may be flown around the circuit board 6 as an assist gas.

FIGS. 14 to 19 show fourteenth embodiments having means for preventing the components that are ejected by the sputtering of the high frequency electrode 7 itself from adhering to the optical window.
~ 15 are shown. Example 12 shown in FIGS. 14 to 16
In order to prevent the components of the sputtered high-frequency electrode 7 from adhering to the optical window, a shield plate 20 that allows only high-frequency waves to pass through is provided inside the high-frequency electrode 7, that is, on the surface side irradiated with laser light. ing. When the plasma discharge power is increased, the electron density and the ion density are increased accordingly, so that the number of times the high frequency electrode 7 is sputtered increases. Therefore, when discharge is performed with high plasma power, the amount of components of the high frequency electrode 7 attached to the optical window 4 increases, and the transmittance of the optical window 4 is likely to decrease. As described above, the shield plate 20 may be made of any material as long as it allows electromagnetic waves to pass therethrough, but a glass tube or the like is generally used.

In the thirteenth embodiment shown in FIG. 17, the twelfth embodiment is described.
By making the material of the shield plate 20 the same as the material of the optical window 4 in the above, even if the shield plate 20 is sputtered and adheres to the optical window 4, it does not affect the reduction of the transmittance of the optical window 4. I am trying. As a material of the optical window 4 and the shielding plate 20, synthetic quartz or the like that allows the laser beam 3a to pass through is desirable.

In the fourteenth embodiment shown in FIG. 18, the high frequency electrode 7 is cooled to suppress the sputtering of the high frequency electrode 7 itself. When the plasma discharge is performed, the high frequency electrode 7 is heated and is easily sputtered. Therefore, a cooling liquid is caused to flow from the liquid flow pipe 21 to the high-frequency electrode 7 to cool the high-frequency electrode 7, thereby suppressing heating of the high-frequency electrode 7. The liquid to be cooled at this time may be any liquid as long as it is an insulator.

In Example 15 shown in FIG. 19, the high frequency electrode 7 is installed outside the vacuum chamber 1. Thereby, the sputtering of the high frequency electrode 7 itself does not occur, and the sticking out component can be prevented from adhering to the optical window 4.
At this time, at least the high-frequency electrode 7 of the vacuum chamber 1
The material around the is preferably a material that allows electromagnetic waves to pass, such as Pyrex glass (trademark).

FIG. 20 is a sectional view of the laser processing apparatus according to the sixteenth embodiment. In the sixteenth embodiment, the vacuum chamber 1 and the circuit board fixing pallet 5 are cleaned by plasma discharge. When a large amount of laser processing is performed, the vacuum chamber 1 and the fixing pallet 5 are gradually contaminated. Therefore, plasma is discharged from the high frequency electrode 7 and these contaminants attached to the vacuum chamber 1 and the fixing pallet 5 are removed by etching.
At this time, if the removed contaminants are exhausted by the vacuum pump 2, more effective cleaning can be performed. The high frequency electrode 7 can be moved freely by driving a motor.

As described above, by generating the high frequency plasma in the vacuum chamber 1, the frequency of exchanging the optical window for passing the laser beam is reduced, and the product reliability of the irradiated object is further improved.

[0047]

In the laser processing apparatus according to the first aspect of the present invention, ionized particles are diffused by the generated plasma and collide with the optical window and the object to be irradiated, whereby contaminants on the surface of the optical window and the object to be irradiated are removed. To be removed. In addition, when the scattered particles generated from the irradiated object are reactive substances, the scattered particles are vaporized by a chemical reaction with the particles in the plasma atmosphere, and as a result, the scattered light particles are emitted to the optical window and the irradiated object. The scattered particles that adhere are reduced.

In the laser processing apparatus according to the second aspect of the present invention, the optimum cleaning action can always be exerted on the optical window and the object to be irradiated by changing the position of the plasma electrode even if the action given by the plasma discharge differs depending on the substance. . In the laser processing apparatus according to claim 3, since plasma is generated in the vicinity of the object to be irradiated during laser irradiation, the scattered particles at the time of irradiation are vaporized, and the scattered particles redeposited on the object to be irradiated are removed by etching. it can. In addition, after the end of irradiation,
Since plasma is generated in the vicinity of the optical window, scattered particles attached to the optical window can be removed by etching.

In the laser processing apparatus according to the fourth aspect, since the plasma electrode has a shape which spreads toward the holding means,
The scattered particles from the irradiated object that diffuse as the distance from the processing point increases can be effectively vaporized according to the diffusion shape, the number of scattered particles can be reduced, and the scattered particles adhere to the optical window and the irradiated object. The amount can be reduced. In the laser processing apparatus according to the fifth aspect, the power of the positive ions to the holding means can be arbitrarily controlled by the first voltage, so that the optical window and the irradiation object can be optimally purified.

In the laser processing apparatus according to the sixth aspect, since the power of the positive ions to the optical window can be arbitrarily controlled by the second voltage, the optical window and the irradiation object can be optimally purified. In the laser processing apparatus according to claim 7,
Since the power of the positive ions to the object to be irradiated and the optical window can be arbitrarily controlled by the first and second voltages, even if plasma discharge is performed at a constant power, the optical window and the object to be irradiated can be optimally purified. it can.

In the laser processing apparatus according to the eighth aspect, the plasma is not generated during the laser irradiation but is generated after the irradiation, so that the attenuation of the laser power due to the plasma can be suppressed and the optical window and the object to be irradiated can be purified. . In the laser processing apparatus according to the ninth aspect, since air flows into the periphery of the optical window, a layer of air is formed around the optical window, and scattered particles do not easily reach the optical window. Moreover, since the assist gas flows into the periphery of the object to be irradiated, scattered particles are less likely to reattach to the object to be irradiated.

In the laser processing apparatus according to the tenth aspect, since the non-reactive gas having a high etching effect flows into the periphery of the optical window, the etching effect in the optical window is improved and the cleaning action of the optical window by the plasma is further improved. Become effective. Also,
Since the assist gas flows into the periphery of the object to be irradiated, scattered particles are less likely to reattach to the object to be irradiated. In the laser processing apparatus according to claim 11, the reactive gas can be caused to flow into the periphery of the optical window immediately after laser irradiation to effectively vaporize the scattered particles, and then the non-reactive gas can be caused to flow in the optical window. Can be effectively etched. Moreover, since the assist gas flows into the periphery of the object to be irradiated, scattered particles are less likely to reattach to the object to be irradiated.

In the laser processing apparatus according to the twelfth aspect, the shield plate provided inside the plasma electrode can prevent the electrode component that is ejected by the sputtering of the plasma electrode itself from adhering to the optical window. In the laser processing apparatus according to claim 13, since the material of the shielding plate is the same as the material of the optical window, even if the shielding plate is sputtered and the scattered particles adhere to the optical window, the transmittance of the optical window is reduced. Less likely to affect.

In the laser processing apparatus according to the fourteenth aspect, since the plasma electrode is cooled, the amount of sputtering of the electrode itself can be reduced. In the laser processing apparatus according to the fifteenth aspect, since the plasma generating means is arranged outside the vacuum chamber, it is possible to prevent the electrode component that is ejected due to the sputtering of the plasma electrode itself from adhering to the optical window.

According to the sixteenth aspect of the laser processing apparatus, the contaminants attached to the vacuum chamber and the holding means can be removed, and the inside of the vacuum chamber can always be maintained in a clean atmosphere. Claim 17
In the laser processing method according to the invention described above, ionized particles are diffused by the generated plasma and collide with the optical window and the irradiation target to remove contaminants on the surface of the optical window and the irradiation target. Further, when the scattered particles generated from the irradiation object is a reactive substance, the scattered particles are vaporized by a chemical reaction with the particles in the plasma atmosphere,
As a result, scattered particles attached to the optical window and the object to be irradiated are reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a laser processing apparatus provided with high frequency plasma.

FIG. 2 is a II-II plan view of FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG. 1;

FIG. 4 is a cross-sectional view of a laser processing device in which a high frequency electrode is movable.

FIG. 5 is a cross-sectional view of a laser processing apparatus in which a high frequency electrode moves during laser irradiation and after laser irradiation ends.

FIG. 6 is a cross-sectional view of a laser processing apparatus in which the shape of a high frequency electrode is controlled.

FIG. 7 is a cross-sectional view of a laser processing apparatus in which a voltage is applied between an irradiation object and a high frequency electrode.

FIG. 8 is a cross-sectional view of a laser processing apparatus in which a voltage is applied between the optical window and the high frequency electrode.

FIG. 9 is a cross-sectional view of a laser processing apparatus in which a voltage is applied between an object to be irradiated and a high frequency electrode and between an optical window and the high frequency electrode.

FIG. 10 is a cross-sectional view of a laser processing apparatus in which the timing of plasma discharge is controlled.

FIG. 11 is a cross-sectional view of a laser processing apparatus in which air is flown around an optical window and an assist gas is set around an object to be irradiated.

FIG. 12 is a cross-sectional view of a laser processing apparatus in which a non-reactive gas is installed around an optical window and an assist gas is installed around an object to be irradiated.

FIG. 13 is a cross-sectional view of a laser processing apparatus in which a reactive gas and a non-reactive gas are installed around an optical window and an assist gas is installed around an object to be irradiated.

FIG. 14 is a cross-sectional view of a laser processing apparatus in which a shielding plate that allows only high frequencies to pass is installed inside a high frequency electrode.

FIG. 15 is a plan view of XV-XV in FIG.

16 is a sectional view taken along line XVI-XVI of FIG.

FIG. 17 is a cross-sectional view of a laser processing apparatus in which the material of the shielding plate is the same as the material of the optical window.

FIG. 18 is a sectional view of a laser processing apparatus that cools a high frequency electrode with an insulated liquid.

FIG. 19 is a cross-sectional view of a laser processing apparatus in which a high frequency electrode is installed outside a vacuum chamber.

FIG. 20 is a cross-sectional view of a laser processing apparatus that cleans a vacuum chamber and a fixing pallet by plasma discharge.

[Explanation of symbols]

 1 vacuum chamber 3 laser irradiation part 3a laser light 4 optical window 5 fixing pallet 6 circuit board 7 high frequency electrode 8a first voltmeter 8b second voltmeter 8c grid electrode 9 high frequency generation source 11, 14, 17 gas cylinder 13, 16, 19 nozzle 20 shield plate 21 liquid flow pipe

Claims (17)

[Claims] 1. A laser processing apparatus for irradiating an object to be irradiated with a laser beam in a vacuum for processing, comprising: a vacuum chamber which can be maintained at a predetermined degree of vacuum; Holding means for holding an object, laser irradiation means arranged outside the vacuum chamber for irradiating the object to be irradiated held by the holding means with laser light, and laser light irradiated from the laser irradiation means for the vacuum chamber An optical window provided on the wall surface of the vacuum chamber, a plasma electrode for generating plasma between the optical window and the holding means, and a high-frequency power source for applying a high-frequency voltage to the plasma electrode. And a plasma processing unit having the same. 2. A moving means for moving the plasma electrode between the holding means and the optical window is further provided.
The laser processing apparatus according to claim 1. 3. The moving means arranges the plasma electrode at a first position near the holding means during laser irradiation by the laser irradiation means, and at a second position near the optical window after the laser irradiation is completed. The laser processing apparatus according to claim 2, wherein 4. The laser processing apparatus according to claim 1, wherein the plasma electrode has a coil shape, and has a divergent shape toward the holding means. 5. The laser processing apparatus according to claim 1, further comprising first voltage applying means for applying a first voltage between the object to be irradiated and the plasma electrode. 6. The laser processing apparatus according to claim 1, further comprising second voltage applying means for applying a second voltage between the plasma electrode and the optical window. 7. A third voltage applying means for applying a first voltage between the object to be irradiated and the plasma electrode and a second voltage between the plasma electrode and the optical window. The laser processing apparatus according to claim 1, wherein 8. The laser processing apparatus according to claim 1, further comprising timing control means for controlling a plasma generation timing of said plasma generation means. 9. The laser processing according to claim 1, further comprising an air inflow means for inflowing air around the optical window and an assist gas inflow means for injecting assist gas around the irradiation object. apparatus. 10. A non-reactive gas inflow means for inflowing a non-reactive gas into the periphery of the optical window, and an assist gas inflow means for injecting an assist gas into the periphery of the object to be irradiated. Item 2. A laser processing apparatus according to item 1. 11. A gas inflow means for selectively injecting a reactive gas and a non-reactive gas into the periphery of the optical window according to timing, and an assist gas inflow to inject the assist gas into the periphery of the object to be irradiated. The laser processing apparatus according to claim 1, further comprising: 12. The laser processing apparatus according to claim 1, further comprising a shield plate which is provided inside the plasma electrode and allows only high frequencies to pass therethrough. 13. The laser processing apparatus according to claim 12, wherein the material of the shielding plate is the same as the material of the optical window. 14. The laser processing apparatus according to claim 1, further comprising cooling means for cooling the plasma electrode. 15. The laser processing apparatus according to claim 1, wherein the plasma generating means is arranged outside the vacuum chamber. 16. The laser processing apparatus according to claim 1, further comprising an operating means for operating the plasma generating means when the holding means does not hold the irradiation object. 17. A laser processing method for irradiating an object to be irradiated, which is held in a vacuum chamber, through an optical window to perform processing, wherein a cleaning action is exerted on the optical window and the object to be irradiated. A high frequency plasma is generated in the vacuum chamber as described above.