JP2920605B2 - Surface treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object to be processed made of metal, in particular, a vacuum chamber, a component of a vacuum system such as a connecting part of a vacuum chamber and a vacuum pump, and a vacuum such as a mask used in a film forming process. The present invention relates to a method for treating a surface of a jig or the like used in a system device.

[0002]

2. Description of the Related Art In a film forming process in the manufacture of a liquid crystal panel or an LSI, masking of a region not to be formed using an austenitic stainless steel mask or the like is performed. Is going. Since this mask is expensive, the mask is reused by periodically performing a regeneration process for removing a film attached to the mask.

[0003] One method of this regeneration treatment is a chemical treatment of cleaning the mask with a chemical. However, there is a problem that the corrosion resistance of the mask to the chemical is low, a problem with the treatment of the used chemical, and a low efficiency of the chemical treatment. There was a problem. Due to these problems, a physical treatment of mechanically polishing or blasting the mask surface has been performed. However, when such a physical treatment is performed, the austenitic stainless steel has a problem that a mechanically deteriorated layer in which the surface portion is martensitized is formed, work hardening occurs, and corrosion resistance is reduced.

On the other hand, when a regenerated mask is reused in a film forming apparatus, the mask is placed in a vacuum chamber provided in the film forming apparatus, so that the rising speed when depressurizing the vacuum chamber is increased. Therefore, it is necessary to remove moisture adhering to the mask surface. In order to remove the moisture adhering to the mask surface, usually, a heat treatment of carrying the mask into a baking furnace and heating it at several hundred degrees Celsius has been performed. However, there is a problem that the size of the mask that can be subjected to the heat treatment is limited by the size of the baking furnace. On the other hand, if the size of the baking furnace is increased to cope with the heat treatment of a mask having a large size, there is a problem that the cost required for the furnace is high.

Further, as a method of removing a trace amount of organic substances remaining on the mask surface, ozone is supplied at a predetermined flow rate under reduced pressure, and the ozone is decomposed by irradiating ultraviolet rays (UV) to chemically decompose the ozone. UV-ozone treatment for decomposing organic substances by active decomposition products is known. However, since this method is performed under reduced pressure, there is a problem that the size of a mask that can be processed is limited by the size of the vacuum chamber.

[0006] Further, the martensite layer, which is a mechanically deteriorated layer formed on the mask surface, maintains its state by the heat treatment for removing moisture by the above-described baking furnace and the UV-ozone treatment. These processes inevitably reduce the quality of the mask.

The present invention has been made in view of the above circumstances, and an object of the present invention is to physically treat an object to be treated and then perform a plasma treatment so that organic matter and water on the surface of the object are treated. It is an object of the present invention to provide a surface treatment method capable of maintaining the quality of an object to be processed by removing the material and transforming the mechanically damaged layer into the original structure.

[0008]

A surface treatment method according to the present invention is a method for treating a surface of a metal object to be processed, wherein the surface of the object is mechanically polished and / or blasted. > Processing process and sealing on the surface of the workpiece
While forming a gas curtain with degas,
Irradiating a plasma jet controlled at 0 ° C to 2000 ° C.

[0009]

In the surface treatment method of the present invention, the surface of the metallic article to be treated, depending on the physical treatment such as mechanical polishing and / or blasting, used in contaminant, or depressurization system device Most of the dirt attached in the part manufacturing process is removed. Then, 1800 ° C. to 2000 ° C.
By radiating the plasma jet, the organic matter remaining on the surface of the object to be treated is decomposed and gasified to volatilize and remove, and the water is evaporated, and the mechanical processing generated on the surface of the object by the physical treatment the affected layer can brought transformation to the original tissue by softening annealing effect of heating of the plasma.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a side sectional view showing an embodiment of a surface treatment method according to the present invention, in which S is a metal workpiece. The surface of the workpiece S has been subjected to mechanical polishing such as buffing and / or blasting such as glass bead blasting (GBB) or alumina blasting. Most of them have been removed.

An object S is placed on a stage 20. The stage 20 moves the object S in the horizontal and orthogonal x-axis and y-axis directions. A plasma irradiation head 1 is disposed above the workpiece S so as to face the workpiece S, and the head 1 has a double structure including an outer nozzle 2 and an inner nozzle 6. The outer nozzle 2 has a substantially cylindrical shape, and a thick portion 3 whose inner diameter gradually decreases toward the opening 5 is formed at the tip portion. An annular water passage 4 is provided inside the thick portion 3, and cooling water flows through the water passage 4.

Inside the outer nozzle 2, a cylindrical inner conductive nozzle 6 having the same shape as the inner surface of the outer nozzle 2 is provided with a predetermined distance between its outer peripheral surface and the inner peripheral surface of the outer nozzle 2. The tip of the opening 7 of the inner nozzle 6 is aligned with the tip of the opening 5 of the outer nozzle 2 in the vertical direction. The gap between the outer nozzle 2 and the inner nozzle 6 is N ₂ ,
A gas passage 8 through which a shielding gas such as Ar flows is provided, and an inside of the inner nozzle 6 is a working gas passage 9 through which a gas for plasma generation such as N ₂ or He—O ₂ is passed. ing.

A sharp rod-shaped electrode 10 is arranged inside the inner nozzle 6 on the center axis of the inner nozzle 6, and the tip of the electrode 10 is arranged at a predetermined distance from the opening 7 of the inner nozzle 6. It is. The electrode 10 is connected to the cathode of a DC power supply 15, and the anode of the DC power supply 15 is connected to the inner nozzle 6.

In such a head 1, the water passage 4
Cooling water flows through the inside to cool the tip of the head 1, and also supplies a shielding gas to the gas passage 8 and blows the gas from the opening 5 of the outer nozzle 2 to the surface of the workpiece S to blow the gas curtain. To form Then, a required output from the DC power supply 15 is applied to the electrode 10 and the inner nozzle 6 to cause arc discharge, for example, nitrogen gas is introduced into the working gas passage 9 at a required flow rate, and plasma is generated by the arc discharge. The plasma is emitted from the opening 7 of the inner nozzle 6 to the surface of the workpiece S as a plasma jet.

The head 1 is movable in the vertical direction. The height of the head 1 is adjusted so that the distance between the head 1 and the processing object S is determined in advance by a test, so that the plasma jet can be performed. Temperature of about 1800 ° C to 20
Control within the range of 00 ° C.

The surface of the object S is treated by the plasma jet to evaporate the moisture attached to the surface and decompose and remove the organic matter. On the other hand, the object to which the plasma jet is emitted by the shielding gas covering the plasma jet Oxidation of the surface of S is prevented. In the above-described temperature range of the plasma jet, the surface of the workpiece S undergoes a crystal structure change due to the softening annealing effect, and the mechanically damaged layer generated by the physical treatment is transformed into the original structure.

Next, the results of implementing the surface treatment method according to the present invention will be described. Using a SUS304 film-forming masking jig as an object to be processed, the film adhered to the surface was removed by buff polishing and GBB processing. The workpiece is set in the apparatus shown in FIG. 1, nitrogen gas is supplied as a working gas at a rate of 25 L / min, and a plasma jet generated at an output of 20 A is applied at a distance between the head and the workpiece of 4 to 4.
It was adjusted to 5 cm and emitted from the head to the surface of the object to be processed, and plasma processing was performed at a processing speed of 1 to 2 cm / sec. The surface of the object before and after the plasma treatment was evaluated by metal crystal structure inspection, gas release characteristics, and contact angle measurement.

FIG. 2 is a cross-sectional view of the processing target before the plasma processing, and FIG. 3 is a cross-sectional view of the processing target after the plasma processing. As is clear from FIG. 2, the metal structure of the object to be treated after the physical treatment and before the plasma treatment has a needle-like martensite structure near the surface thereof, but as is clear from FIG. The metal structure of the workpiece
No martensite structure was observed, and the structure was transformed to austenite structure.

Table 1 shows the measurement results of the gas release characteristics. The gas release characteristics are such that an object to be processed before or after plasma processing is heated in a chamber provided with a heating device, nitrogen gas having a dew point of -120 ° C flows into the chamber, and the dew point of the nitrogen gas discharged from the chamber. Was measured and evaluated by converting to water content.

[0020]

[Table 1]

As is evident from Table 1, the water content is significantly reduced after the plasma treatment as compared to before the treatment.

Table 2 shows the results obtained by dropping water droplets on the object before and after the plasma treatment, and measuring the contact angle of the water droplets. As is evident from Table 2, the contact angle of the water droplet is significantly reduced after the plasma treatment compared to before the treatment, and it is considered that the organic matter on the surface of the object to be treated is removed to a monomolecular film level by the plasma treatment. Can be

[0023]

[Table 2]

In this embodiment, the mask used in the process of forming a semiconductor as an object to be processed is described. However, the present invention is not limited to this. It is needless to say that it is particularly suitable for the surface treatment of metal parts and the like used in the above, and also suitable for the surface treatment of metal parts and the like used under normal pressure.

[0025]

As described above in detail, in the surface treatment method according to the present invention , the temperature is set to 18 in a shielding gas atmosphere.
Release plasma jet controlled at 00 ° C to 2000 ° C
By morphism, to remove organic matter and moisture remaining on the surface of the object to be treated, also machine by softening annealing effect
Because the mechanically damaged layer generated on the surface of the workpiece by the mechanical processing such as mechanical polishing and / or blasting is transformed into the original structure, the quality of the workpiece can be reduced without deteriorating the quality of the workpiece. The surface is cleaned and regenerated, and when the object to be processed is used under reduced pressure, the rise of the reduced pressure is fast. In addition, by using the gas curtain of the shielding gas, the plasma processing can be performed at normal pressure, so that the surface processing can be performed regardless of the size of the processing object, and the processing object having a large size can be performed. Even in this case, the present invention has excellent effects such as surface treatment can be performed at low cost.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an embodiment of a surface treatment method according to the present invention.

FIG. 2 is a cross-sectional view of an object to be processed before plasma processing.

FIG. 3 is a cross-sectional view of an object to be processed after plasma processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Head 2 Outer nozzle 6 Inner nozzle 10 Electrode 15 DC power supply S Workpiece

Claims (1)

(57) [Claims] 1. A method for treating a surface of a metal object to be processed, comprising: mechanically polishing and / or blasting the surface of the object ;
Temperature of 1800 ° C while forming a gas curtain
Irradiating a plasma jet controlled to ２０００2000 ° C.