JP2001158979A - Plasma cleaning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma cleaning device which facilitates the work to partially cover the surface of a work with a protective mask and the work to remove the mask and obviates the recontamination of the surface after cleaning when removing the mask from the work. SOLUTION: This plasma cleaning device has a process chamber 2 where the work 5 is disposed, an introducing pipe 7 which introduces inert gas and/or reactive gas into the process chamber 2 from a gas supply source and an exciting means 4 which forms inert ions and/or reaction active species by converting the introduced inert gas and/or reactive gas to a plasma. A protective mask 12 is mounted to the inside wall 2a of the process chamber 2 via the pressing means 14. The protective mask 12 is pressed to the work 5 to partially cover its surface by the pressing means 14. The surface 5b of the work 5 not covered with the protective mask 12 is cleaned by sputtering by the inert ions and/or the chemical reaction with the reaction active species.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma cleaning apparatus for cleaning a surface of an object to be processed by using sputtering of inert ions or a chemical reaction caused by reactive species.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional plasma cleaning apparatus 1. The plasma cleaning apparatus 1 includes a chamber 2b for shutting off outside air and maintaining an indoor atmosphere, and a supply source of an inert gas (for example, Ar gas). A gas cylinder 6, a gas introduction pipe 7 for introducing an Ar gas from the gas cylinder 6 into the processing chamber 2 in the chamber, and an excitation for applying a high-frequency voltage to the Ar gas introduced into the processing chamber 2 for ionization. High-frequency power supply 4 as a means,
Is connected to the electrode 3 connected thereto. The workpiece 5 is
It is disposed on the electrode 3 in the processing chamber 2 . The chamber 2b is grounded.

The surface of the processing object 5 is cleaned (sputter cleaning) by sputtering of Ar ions by the plasma cleaning apparatus 1 configured as described above. Next, this operation will be described.

First, the inside of the processing chamber 2 is evacuated to a predetermined pressure by a vacuum exhaust system (not shown).
Ar gas is introduced into the processing chamber 2 via And
A high frequency voltage is applied to the electrode 3 from the high frequency power supply 4 to cause a discharge of Ar gas.

As a result, as shown in FIG.
Ar gas molecules within 2 are electrons and argon ions (Ar ⁺ )
To ionize. Due to the difference in mobility between electrons and argon ions (the mass of electrons is much smaller than that of ions, the mobility is large), the surface of the electrode 3 has a high electron density, and a cathode voltage drop occurs on the surface of the electrode 3. Occurs (self-bias effect occurring on the high-frequency electrode surface). Thereby, the argon ions are accelerated toward the electrode 3 and collide with the surface of the workpiece 5. Then, contaminants such as organic substances on the surface of the processing object 5 are physically scraped (sputtered).

Here, since the distribution of the Ar gas in the processing chamber 2 cannot be controlled, the entire surface of the processing object 5 is sputtered, and spattering is performed at places other than necessary.

[0007] The target portion to be subjected to sputter cleaning is, for example, a BGA package of an IC chip.
(Ball Grid Array) There is a lead finger part of the package. The lead fingers (the underlying Ni is plated with Au) are contaminated with organic substances, or the underlying Ni precipitates depending on the plating method and plating thickness. In such a state, wire bonding with the chip is performed. In the process, the bonding strength with the Au wire becomes weak. Therefore, it is necessary to perform plasma cleaning before the wire bonding to clean the surface of the lead finger portion.

On the other hand, parts to be protected from sputtering include a carrier boat for transporting a chip and a BGA package substrate in each facility, a solder resist on a solder ball mounting surface, and the like. If you do not protect the chip, there is a problem of charge up due to Ar ^+, and as for the protection of the carrier boat, the carrier boat itself is controlled by static electricity countermeasures, so this may become an electrode and cause abnormal discharge. Regarding the protection of the solder resist, a flux (water-soluble) is used at the time of mounting the solder ball. However, if organic contaminants on the surface of the solder resist are removed, the spread of wetness becomes large and the mounting position of the solder ball is shifted. There is a problem.

Therefore, in order to perform partial sputtering, conventionally, as shown in FIG. 5, a protection mask 8 is applied to the object 5 to be processed, and the surface 5a not to be cleaned is covered, and only the surface 5b to be cleaned is covered. Is sputtered.

[0010]

However, the protection mask 8
Is applied by applying a resist, and after the application step and the sputter cleaning are completed, a step of removing an unnecessary resist film is required, and such an operation is troublesome and troublesome. Further, although the resist film is removed by using a resist stripping solution, there is a problem that the sputter-cleaned surface is again contaminated by the stripping solution.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and facilitates an operation of partially covering the surface of an object to be processed with a protective mask and an operation of removing the protective mask from the object to be processed. An object of the present invention is to provide a plasma cleaning apparatus in which a cleaned surface is not recontaminated when removed from a processing object.

[0012]

In order to solve the above problems, a plasma cleaning apparatus according to the present invention comprises a processing chamber in which an object to be processed is disposed, a supply source of an inert gas and / or a reactive gas, An introduction pipe for introducing an inert gas and / or a reactive gas from the supply source into the processing chamber, and converting the inert gas and / or the reactive gas introduced into the processing chamber into a plasma to generate an inert ion and / or a reaction gas Excitation means for generating active species, a protection mask is attached to the inner wall of the processing chamber via a pressing means, the protection means is pressed against the object to be processed by the pressing means to partially cover the surface thereof The surface of the object to be processed which is not covered with the protective mask is cleaned by sputtering with inert ions generated by the excitation means and / or chemical reaction with reactive species. That. That is, the protection mask is movably mounted in the processing chamber so that the distance to the processing object can be changed via the pressing means. When applying the protection mask to the processing object, the protection mask is pressed against the processing object by the pressing means. When covering the surface to be protected and removing the protective mask after cleaning, release the pressing force and separate from the workpiece.
Alternatively, the object is moved so as to be separated from the protective mask. Thus, the work of applying the protection mask to the object and the work of removing the protection mask can be easily performed. Also, when the protective mask is removed, the cleaned surface is not contaminated.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. The same components as those of the conventional example are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 shows a plasma cleaning apparatus 11 according to an embodiment of the present invention. The plasma cleaning device 11 includes a grounded chamber 2b as in the related art,
A gas cylinder as a supply source of an inert gas (Ar gas);
A gas introduction pipe 7 for introducing Ar gas from the gas cylinder into the processing chamber 2 in the chamber, which is introduced into the processing chamber 2 A
a high frequency power source 4 as an excitation means for ionizing by applying a high frequency voltage to the r gas, and an electrode 3 for the high-frequency power source 4 is connected, the object 5 is a cleaning object, the processing chamber 2 And on the electrode 3.

A protective mask 12 is mounted on the upper inner wall 2a of the processing chamber 2 via two coil springs 14 so as to be vertically movable. One end of the coil spring 14 is fixed to the upper inner wall 2 a, and the other end is fixed to an attachment member 13 integrally formed at both ends of the protection mask 12.
2 downward. Further, [2] in FIG.
-[2] Referring to FIG. 2 which is a cross-sectional view seen from the line direction,
The protective mask 12 has openings 12a (in the drawing, for example, two rectangular shapes) formed in accordance with the positions and shapes of the surface 5b of the object 5 to be subjected to sputter cleaning and the surface 5a of the object 5 to be protected. The opening 12a is formed on the surface 5b of the object 5 to be sputter-cleaned.
The protective mask 12 is pressed against the workpiece 5 by the urging force of the coil spring 14. Therefore, the portion other than the opening 12a of the protection mask 12 covers and protects the surface 5a of the workpiece 5 that is not desired to be sputter cleaned.

As a material of the protective mask 12, the temperature rise due to the sputter cleaning process is about 100 ° C., so that the heat resistance at that temperature and the insulating property because the conductive substance itself becomes an electrode and causes abnormal discharge, resulting in an insulating property. And rigidity that does not deform during processing are required. For example, ceramics and polyimide resin are suitable. Also, the sputtering resistance of the material is important, and the sputter yield (sputter rate) changes depending on the type of ions to be sputtered. However, the sputter yield is small according to the type of ions and the above three conditions are satisfied. It is made of material.

The plasma cleaning apparatus 11 according to the present embodiment is configured as described above. Next, this operation will be described.

As in the prior art, the inside of the processing chamber 2 is first reduced to a predetermined pressure by a vacuum exhaust system (not shown), and Ar gas is introduced into the processing chamber 2 through the introduction pipe 7. Then, a high-frequency voltage is applied to the electrode 3 from the high-frequency power supply 4 to cause the discharge of the Ar gas. As a result, the Ar gas molecules are ionized into electrons and argon ions (Ar ⁺ ), and the argon ions are attracted by the negative voltage on the surface of the high-frequency electrode 3 generated by the self-bias effect, and are disposed on the electrode 3. The object 5 is accelerated and collides. At this time, only the surface 5b that is not protected by the protective mask 12 is cleaned by physically removing (sputtering) organic contaminants and the like on the surface by argon ions.

Even when this protective mask 12 is used, in the protection of the surface 5a not to be cleaned and the cleaning of the surface 5b to be cleaned, the conventional processing object 5
The same effect as when the protective mask 8 is applied to itself can be obtained.

When the sputter cleaning is completed, the electrode 3 is lowered together with the object 5 to be processed by an elevating mechanism (not shown), and the protective mask 12 is removed from the object 5.
The workpiece 5 is taken out of the processing chamber 2 . The workpiece 5 before the sputter cleaning is carried into the processing chamber 2 by raising the electrode 3 on which the workpiece 5 is mounted by the elevating mechanism, and pressing the protection surface 5 a against the protection mask 12. Thereby, the work of protection by the protection mask 12 and the removal thereof can be easily performed, and further, there is no fear of contamination by the resist stripping solution as in the conventional case.

Also, by changing the shape and size of the protection mask 12 and the position and size of the opening 12a in accordance with the shape and size of the workpiece 5 and the position and area of the part to be cleaned and the part to be protected, respectively. It is possible to easily change the sputtering location, and it is possible to perform sputtering only at a necessary location according to the shape of the protective mask.

Although the embodiment of the present invention has been described above, the present invention is, of course, not limited to this, and various modifications can be made based on the technical idea of the present invention.

Excitation means for ionizing Ar gas is not limited to the high-frequency power supply 4. For example, two opposing electrodes are disposed in the processing chamber 2 , and the electrode side on which the object 5 is placed is connected to the cathode. A DC voltage may be applied so that

Further, in the above embodiment, and so as to remove contaminants on the object surface to be treated by sputtering using and Ar ⁺ is inactive ions, not limited thereto, the reaction in the processing chamber 2 A reactive gas (e.g., oxygen gas) is introduced and excited by application of a high-frequency voltage to generate reactive species (radical particles), and contaminants are removed by a chemical reaction between the reactive species and the contaminants. The surface of the processing object may be cleaned by removing or chemically modifying the surface. Further, an inert ion and a reactive species may be used in combination. In the case of removing the reactive species by a chemical reaction, the dimensional accuracy of the protective mask may be increased,
It is necessary to increase the pressing force or the like to improve the adhesion to the object to be processed, to eliminate the gap, and to prevent the gas from flowing to portions other than the cleaning surface.

In the above-described embodiment, the coil spring 14 is used as the pressing means. However, the present invention is not limited to this. For example, the protection mask may be pressed against the workpiece by a piston operated by air pressure or hydraulic pressure. Good. However, when the coil spring 14 is used, only the coil spring 14 is required, so that the configuration becomes simpler and the cost does not increase.

[0026]

As described above, according to the first aspect of the present invention, it is possible to easily clean the workpiece by partially covering the surface of the workpiece without the need for a troublesome operation such as a step of applying or removing a resist film. When the protective mask is removed from the object after cleaning, the surface subjected to the cleaning action is not contaminated.

According to the second aspect of the present invention, the object to be processed can be protected by improving the adhesion to the surface of the object to be protected with a simple structure utilizing the urging force of the coil spring.

According to the third aspect of the invention, the heat resistance, insulation and rigidity required for the protective mask can be sufficiently satisfied.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a plasma cleaning apparatus according to an embodiment of the present invention in a state where an object to be processed is partially masked by a protective mask attached to an inner wall of a processing chamber and undergoes sputter cleaning.

FIG. 2 is a cross-sectional view taken along the line [2]-[2] in FIG.

FIG. 3 is a schematic configuration diagram of a conventional plasma cleaning apparatus.

FIG. 4 is a schematic view for explaining the principle of sputter cleaning.

FIG. 5 shows a conventional plasma cleaning apparatus.
FIG. 4 is a cross-sectional view illustrating a state where a protection mask is partially applied to an object to be processed in a processing chamber and sputter cleaning is performed.

[Description of Signs] 2 ... processing chamber, 2a ... inner wall, 2b ... chamber, 3
...... Electrode, 4 ... High frequency power supply, 5 ... Workpiece, 6 ...
Gas cylinder, 7 introduction pipe, 11 plasma cleaning device, 12 protective mask, 12a opening, 14
…… Coil spring.

Claims (3)

[Claims] 1. A processing chamber in which an object is disposed, a supply source of an inert gas and / or a reactive gas, and the inert gas and / or the reactive gas from the supply source into the processing chamber. And an exciting means for converting the inert gas and / or the reactive gas introduced into the processing chamber into plasma to generate inert ions and / or reactive species. Applying a protective mask that partially covers the surface of the processed object, and performing sputtering by the inert ions and / or a chemical reaction with the reactive species to remove the surface of the processed object that is not covered with the protective mask. In the plasma cleaning apparatus configured to be cleaned, the protection mask is attached to an inner wall of the processing chamber via a pressing unit, and the protection mask is pressed against the workpiece by the pressing unit. A plasma cleaning apparatus characterized in that the surface is partially covered by applying a pressure. 2. The method according to claim 1, wherein the pressing unit is a coil spring disposed between an inner wall of the processing chamber and the protection mask, and for urging the protection mask toward the workpiece. The plasma cleaning apparatus according to claim 1. 3. The plasma cleaning apparatus according to claim 1, wherein the protection mask is made of a ceramic or a polyimide resin.