Stainless steel member for use in semiconductor production device and method of producing the same

Abstract

To provide a stainless-steel member coated with a chromium oxide film of low metallic impurities and excellent heat insulation.SOLUTION: The stainless-steel member coated with a chromium oxide film has a thickness of the chromium oxide film of 190 nm to 280 nm, and the maximum value of the surface-reflectance in the near infrared region (wavelengths of 750 nm to 2500 nm) of 60% or less, which is produced through a precision electrolytic polishing process and a chromium oxide film coating process. The precision electrolytic polishing process includes a pulse voltage application treatment, a micro-aeration treatment, and an electrolytic solution jet-stream treatment, and the polished stainless steel surface has a difference between a depression and a protrusion, measured by a scanning-type probe microscope of 30 nm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a stainless steel member for a semiconductor manufacturing apparatus and a method for manufacturing the same. In particular, the present invention relates to a stainless steel member for a semiconductor manufacturing apparatus coated with a metal oxide film formed by a wet process (wet process) on a stainless steel member whose surface has been smoothed by an electrolytic polishing method, and a method for manufacturing the same.

Background Art

[0002] The manufacturing of semiconductor devices involves repeating processes such as thin film formation, lithography, etching, and planarization. These processes are carried out in an ultra-high vacuum state or under reduced pressure conditions, and various semiconductor processing liquids are used. In recent years, with the miniaturization of semiconductor design rules, it has been required to manage metal impurities generated from members used in semiconductor manufacturing apparatuses and metal impurities contained in semiconductor processing liquids at the ppt level. In addition, since the semiconductor device manufacturing process needs to maintain a high temperature, members with high heat retention are required for semiconductor manufacturing apparatuses.

[0003] Patent Document 1 discloses a method for forming a stainless steel passive film in which the surface of stainless steel is subjected to electrolytic polishing treatment, then oxidized in an acidic atmosphere gas, and the iron oxide on the surface is reduced and removed by hydrogen gas, and a current-carrying component having a passive film with a surface roughness (Rmax) of 0.1 μm or less on the surface. Patent Document 2 discloses an austenitic stainless steel member in which a passive layer with a film thickness of 2 to 20 nm is formed on the surface of a base material made of austenitic stainless steel, and an apparatus in which a liquid contact portion with a semiconductor processing liquid is composed of the austenitic stainless steel member.

[0004] Patent Document 3 discloses an ingot manufacturing apparatus that is subjected to electrolytic polishing or chemical polishing treatment so that the heat absorption rate during blackening treatment is increased, and is blackened by the Inco method or the electrolytic coloring method.

[0005] Patent Document 4 discloses that by using an electrolytic polishing solution composed only of phosphoric acid and at least one organic sulfonic acid, the viscosity of the anolyte layer (Jacquet layer) formed near the metal to be polished in the electrolytic polishing process can be reduced, bubbles accompanying the anodic reaction are less likely to stay on the surface of the metal to be polished, as a result, the progress of electrolytic processing becomes uniform, the processing accuracy is improved, and the surface smoothness of stainless steel, which is the metal to be processed, is improved. An electrolytic polishing treatment solution for stainless steel, an electrolytic treatment method, and a manufacturing method of stainless steel in which a passive film is coated on the electrolytically treated stainless steel are disclosed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] The invention of the present application provides a chromium oxide film-coated stainless steel member capable of managing metal impurities generated from semiconductor manufacturing equipment and metal impurities contained in semiconductor processing liquids at the ppt level, having a low infrared reflectance and high heat retention, and a manufacturing method thereof.

Means for Solving the Problems

[0008] The problems of the invention of the present application can be solved by the following aspects. Specifically,

[0009] (Aspect 1) A chromium oxide film-coated stainless steel member in which a chromium oxide film is coated on the surface of an electrolytically polished stainless steel member, wherein the film thickness of the chromium oxide film is 190 nm to 280 nm, and the maximum value of the surface reflectance in the near-infrared region (wavelength 750 nm to 2500 nm) is 60% or less. This is because by setting the film thickness of the chromium oxide film to 190 nm to 280 nm, the maximum value of the surface reflectance in the near-infrared region (wavelength 750 nm to 2500 nm) can be made 60% or less.

[0010] (Aspect 2) The chromium oxide film-coated stainless steel member according to Aspect 1, wherein the surface of the electrolytically polished stainless steel member has an unevenness difference of 30 nm or less measured by a scanning probe microscope.

[0011] (Aspect 3) A method for manufacturing a chromium oxide film-coated stainless steel member in which the film thickness of the chromium oxide film is 190 nm to 280 nm, and the maximum value of the surface reflectance in the near-infrared region (wavelength 750 nm to 2500 nm) is 60% or less, comprising: an electrolytic polishing treatment step of electrolytically polishing the surface of a stainless steel member with an electrolytic polishing solution for stainless steel consisting only of phosphoric acid and at least one organic sulfonic acid; and a chromium oxide film coating step of immersing the electrolytically polished stainless steel member in a treatment solution composed of a mixed solution of 25 w / vol% chromic acid and 50 w / vol% sulfuric acid to form a chromium oxide film on the surface of the stainless steel member at a coloring potential of 17 mV to 28 mV, and immersing the member in a treatment solution composed of a mixed solution of chromic acid and phosphoric acid to cure the chromium oxide film.

[0012] (Aspect 4) The method for manufacturing a chromium oxide film-coated stainless steel member according to claim 3, wherein the electrolytic polishing treatment step includes pulse voltage application treatment, micro-aeration treatment, and electrolytic solution jet flow treatment, the thickness of the chromium oxide film is 190 nm to 280 nm, and the maximum value of the surface reflectance in the near-infrared region (wavelength 750 nm to 2500 nm) is 60% or less. By using any one or all of the pulse voltage application treatment, micro-aeration treatment, and electrolytic solution jet flow treatment in combination with the electrolytic polishing treatment, it is possible to eliminate the anode liquid layer (Jacquet layer) formed near the metal to be polished and the retention of bubbles associated with the anodic reaction in the electrolytic polishing treatment. As a result, the progress of the electrolytic processing becomes uniform, the processing accuracy is improved, and the surface smoothness of the stainless steel, which is the metal to be processed, is improved.

Effect of the Invention

[0013] According to the present invention, it is possible to provide a chromium oxide film-coated stainless steel member to be used in a semiconductor manufacturing apparatus with less generation of metal impurities equivalent to that of a stainless steel member subjected to precision electrolytic polishing treatment, and a method for manufacturing the same. In addition, by coating a chromium oxide film on a stainless steel member, it is possible to provide a chromium oxide film-coated stainless steel member to be used in a semiconductor manufacturing apparatus with low infrared reflectance and high heat retention, and a method for manufacturing the same.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0015] Hereinafter, the present invention will be described according to embodiments. However, the following description is for understanding the present invention and does not limit the present invention.

[0016] A. Chromium Oxide Film-Coated Stainless Steel Member The chromium oxide film-coated stainless steel member of the present invention is a stainless steel member in which a chromium oxide film is coated on the surface of an electrolytically polished stainless steel member. Further, the film thickness of the chromium oxide film is 190 nm to 280 nm, and the maximum value of the surface reflectance in the near-infrared region (wavelength 750 nm to 2500 nm) is 60% or less. The film thickness of the chromium oxide film is controlled to 190 nm to 280 nm by a chromium oxide film forming step described later. By setting the film thickness to 190 nm to 280 nm, the maximum value of the surface reflectance in the near-infrared region (wavelength 750 nm to 2500 nm) can be made 60% or less.

[0017] 1. Stainless Steel As the stainless steel used for the chromium oxide film-coated stainless steel member of the present invention, stainless steel used as piping and container members as main equipment materials in semiconductor manufacturing equipment can be preferably used. Specifically, there are ferritic stainless steel, martensitic stainless steel, and austenitic stainless steel. For high-pressure storage containers and high-pressure pipelines that require corrosion resistance and high strength, martensitic stainless steel (for example, 410C, 420, 430, 440C, 440B) and austenitic stainless steel (for example, 304, 304L, 321, 347, 316L) can be preferably used. The chromium oxide film-coated stainless steel members of the present invention include stainless steel subjected to welding for forming piping, container members, and structures for semiconductor manufacturing, which are the main equipment materials in semiconductor manufacturing apparatuses. For example, a pressure vessel for storage is manufactured by welding each member formed of a stainless steel plate to form the vessel and subjecting the inner surface to pickling treatment. A high-pressure pipe for transporting a chemical solution is manufactured by passing a stainless steel plate through a welded pipe production line in a strip state. To form a pipeline, a plurality of pipes are welded and manufactured.

[0018] B. Method for manufacturing chromium oxide film-coated stainless steel member As shown in FIG. 1, the chromium oxide film-coated stainless steel member of the present invention is subjected to a precision electrolytic polishing process of electrolytic polishing in an electrolytic cell equipped with a pulse voltage application process, a micro-aeration process, and an electrolytic solution jet flow process in an electrolytic solution composed of phosphoric acid and organic sulfonic acid on the surface of the stainless steel member, and a chromium oxide film forming process of forming a chromium oxide film on the surface of the electrolytically polished stainless steel member by a wet process and curing the chromium oxide film. In addition, a mechanical polishing process can be performed in advance to improve the accuracy and speed of electrolytic polishing. Hereinafter, the mechanical polishing process, the precision electrolytic polishing process, and the chromium oxide film forming process will be described in order.

[0019] 1. Mechanical polishing process In the mechanical polishing process for manufacturing the chromium oxide film-coated stainless steel member of the present invention, buff polishing can be preferably employed. By performing buff polishing before the electrolytic polishing process, the electrolytic polishing process can be accelerated, and the surface smoothness by electrolytic polishing is improved. Buff polishing is a method of polishing with an abrasive applied to the outer peripheral surface of a cloth or non-woven fabric. Those with a rough and uneven surface state can be polished from rough polishing to a state with gloss by polishing several times by changing the cloth, non-woven fabric, or abrasive. The types of buffs include, in the case of cloth buffs, sewn buffs, closed buffs, loose buffs, bias buffs, sisal buffs, etc. Other buffs include flap wheels, non-woven fabric wheels, wire wheels, etc. These buffs are used according to their applications. Those with raised nylon fibers are preferred. Also, as buff abrasives, there are abrasive materials mainly composed of relatively fine abrasive powder and uniformly mixed with a medium composed of this and oils and fats or other appropriate components. As the buff abrasive of the present invention, a finishing abrasive of 400 mesh or more can be preferably employed.

[0020] 2. Precision electrolytic polishing treatment process The precision electrolytic polishing treatment process for manufacturing the chromium oxide film-coated stainless steel member of the present invention serves as a pretreatment for removing or reducing surface defects such as oxide films, impurities (non-metallic inclusions), and work-affected layers on the surface of the stainless steel member, and forming a uniform and dense chromium oxide film on the surface of the stainless steel member. Electrolytic polishing treatment is a polishing method in which, by an external power source, in an electrolytic polishing solution, a direct current is passed with the metal to be polished as the anode (positive electrode), and the surface of the metal to be polished is smoothed and polished by dissolving the convex portions of the surface of the metal to be polished with fine irregularities. Different from physical polishing such as buff polishing, it has the advantage that it does not create work-affected layers or work-hardened layers, and there are few impurities and contaminants on the polished surface, so the polished surface becomes clean. In the anodic polarization curve (Jacquet curve) in the electrolytic polishing bath, there exists a range of constant current (limiting current) that does not depend on the electrode potential. In this limiting current range, a thick and highly viscous anolyte layer (Jacquet layer) is formed near the metal to be polished. It is considered that this anolyte layer (Jacquet layer) suppresses the diffusion of eluted cations, and thereby polishing is performed. That is, due to the irregularities on the surface of the metal to be polished, a difference is generated in the concentration gradient in the viscous liquid layer, and the diffusion current affects so that the current concentrates on the convex portions, and the irregularities on the surface disappear and polishing is performed.

[0021] (2-1) Electrolytic polishing solution In the electrolytic polishing treatment of the present invention, an electrolytic polishing solution for stainless steel composed only of phosphoric acid and methanesulfonic acid, in which the electrolytic solution composition is selected within the range of a phosphoric acid concentration of 25 to 50 vol% and a methanesulfonic acid concentration of 50 to 75 vol%, is preferable. That is, it is composed only of water as a solvent, phosphoric acid and methanesulfonic acid as solutes. By using methanesulfonic acid instead of highly viscous sulfuric acid as the solute of the electrolytic polishing solution, the viscosity of the electrolytic polishing solution can be lowered, and the retention of bubbles generated on the metal surface due to the anodic reaction during the electrolytic polishing treatment can be suppressed. Further, by setting the methanesulfonic acid concentration to be equal to or higher than the phosphoric acid concentration, the viscosity of the electrolytic polishing solution can be reduced. It also does not contain additives such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ester, or glycerin for stabilizing the electrolytic polishing solution because suppressing the generation of bubbles is effective for smoothing the metal surface rather than stabilizing the electrolytic solution. In addition, instead of methanesulfonic acid, organic sulfonic acids such as ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, p-phenolsulfonic acid, and vinylsulfonic acid can also be selected.

[0022] (2-2) Electrolytic polishing treatment The electrolytic polishing treatment of the present invention is performed by immersing a stainless steel member in an electrolytic polishing treatment tank filled with the above-described electrolytic polishing solution. Pulse voltage application treatment, micro-aeration treatment, and electrolytic solution jet flow treatment are employed. In addition, a swinging mechanism for swinging the anode vertically and horizontally is employed. By employing the pulse voltage application treatment, micro-aeration treatment, electrolytic solution jet flow treatment, and swinging mechanism, the smoothness of the surface of the electrolytically polished stainless steel member is improved, and the unevenness difference measured with a scanning probe microscope can be made 30 nm or less.

[0023] (2-2-1) Pulse voltage application treatment Figure 2 is a schematic diagram showing one embodiment of an electrolytic polishing apparatus 100 to be subjected to the electrolytic polishing treatment of the present invention. In this embodiment, a pulse voltage generator 20 that performs ON / OFF control with a switching element provided between a DC power source and a load as an external power source is installed in the electrolytic polishing treatment tank 10. The metal to be polished 21 is connected to the pulse voltage generator 20 by a conducting wire 22 with the metal to be polished 21 as an anode. Here, in the present invention, the metal to be polished 21 is stainless steel or a stainless steel member. The electrolytic polishing method of the present invention employs a pulse voltage application process in which a voltage with a pulse waveform (rectangular wave) is applied to the metal to be polished 21 during electrolysis in an electrolytic polishing solution 23 adjusted to a specific current density, thereby improving the smoothness of the surface of the metal to be polished 21.

[0024] Figure 2 schematically shows the pulse waveform (voltage waveform) in the pulse voltage application process of the present invention, which are the applied voltage (E + -E 0 ), the voltage application time (T on ), and the voltage pause time (T off ), respectively. The repetition period (T on ) of the voltage application time (T off ) and the voltage pause time (T cycle ) is 5 to 20 seconds. The ratio of the voltage application time (T on ) and the voltage pause time (T off ) can preferably adopt 7:3 to 8:2. For example, when the repetition period (T cycle ) is 10 seconds, the voltage application time (T on ) is 7 seconds and 8 seconds respectively, and the voltage pause time (T off ) is 2 seconds and 3 seconds respectively. By adopting the pulse voltage application process, during the voltage pause time (T off ), the applied voltage (E + -E 0 ) of the metal to be polished becomes zero (E 0 ), and the thick and highly viscous anolyte layer (Jacquet layer) near the metal to be polished diffuses. The current density is 10 to 30 A / dm 2 , preferably 10 to 30 A / dm 2 , and the electrolytic polishing time (Tall ) is 5 to 10 minutes. However, the applied voltage (E + -E 0 ), the voltage application time (T on ), the voltage pause time (T off ), and the electrolytic polishing time (T all ) can be appropriately changed according to the roughness of the surface of the metal to be polished and the material of the metal to be polished.

[0025] (2-2-2) Anode oscillation mechanism By providing an anode oscillation mechanism by an anode oscillation device (not shown), the bubbles staying on the electrolytic polishing surface can be peeled off from the surface.

[0026] (2-2-3) Micro-aeration treatment In the electrolytic polishing treatment tank 10 for performing the electrolytic polishing treatment of the present invention, an electrolytic polishing solution 23 composed only of phosphoric acid and at least one organic sulfonic acid is stored. A microbubble generator 11 is provided on the outer surface of the electrolytic polishing treatment tank 10, and a microbubble supply pipe 12 is provided on the inner surface. The microbubbles 13 are supplied from the bottom of the electrolytic polishing treatment tank 10 through the microbubble supply pipe 12. Further, a diffuser 14 is provided at the bottom of the electrolytic polishing treatment tank 10, and the gas supplied from a compressor 15 provided on the outer surface through a supply pipe 16 provided on the inner surface is supplied as bubbles from a diffusing surface (not shown) having a large number of small holes. The supplied microbubbles 13 and the fine bubbles supplied from the diffuser 14 are stirred and swirled in the electrolytic polishing treatment tank 10 as a swirling flow 17. Thereby, the bubbles staying on the surface of the metal 21 to be polished are peeled off from the surface of the metal 21 to be polished, and no longer reattach to the surface of the metal 21 to be polished. As a result, the bubbles staying on the surface of the metal 21 to be polished disappear, and the surface of the metal 21 to be polished is uniformly electrolytically polished, improving the surface smoothness of the metal 21 to be polished.

[0027] To obtain the effect of microbubbles, microbubbles with different average bubble diameters, namely, first microbubbles with an average bubble diameter of 10 to 40 μm and second microbubbles with an average bubble diameter of 80 to 150 μm, may be added to the smart removal tank. Here, the average bubble diameter refers to the diameter with the largest number of samples in the diameter distribution of 2,400 microbubbles. This is because the use of microbubbles with different average bubble diameters improves the smut removal performance. The average bubble diameter of the microbubbles added to the smart removal tank is controlled by the discharge amount. To add the first microbubbles with an average bubble diameter of 10 to 40 μm and the second microbubbles with an average bubble diameter of 80 to 150 μm according to the present invention, the discharge amount needs to be controlled to 105 to 150 L / min. The average bubble diameter of the microbubbles preferably ranges from 10 to 150 μm. This is because when it is less than 10 μm, the bubble generator becomes large and it is difficult to control the bubble diameter, and when it exceeds 150 μm, the bubble floating speed increases and the life of the bubbles in the electrolytic polishing treatment tank 10 becomes short.

[0028] The average bubble diameter of the microbubbles can be measured by a liquid particle counter or a bubble diameter distribution measuring device such as SALD-7100 (Shimadzu Corporation), Multisizer4 (Beckman Coulter), and an acoustic bubble diameter distribution measuring device (Nishinippon Fluid Technology Co., Ltd.). However, in the present invention, since it is important to control the generation of microbubbles with different average bubble diameters, a method of calculating the average diameter of 24,000 is adopted by actually measuring the bubble shape obtained from a still image based on the video of the bubbles generated in a certain period of time by image processing.

[0029] In the present invention, a diffuser device such as a diffuser including a gas supply pipe, a diffusing surface formed with a large number of small holes, and a diffusing member having an internal space to which gas is supplied can be used. The shape of the diffusing member is not particularly limited, and a cylindrical diffusing pipe having a diffusing surface on which a large number of uniform small holes are uniformly formed over the entire surface, or a diffusing plate in which one surface of a box-shaped object serves as the diffusing surface can be used. The small holes in the diffusing surface preferably have a diameter of about 0.3 to 2.0 mm in order to perform good agitation. By generating a swirling flow as the bubbles rise due to diffusion, the removal efficiency of the bubbles staying on the metal surface is increased. The swirling flow velocity is preferably 0.5 to 1.5 m / sec.

[0030] (2-2-4) Electrolyte jet treatment In addition to the pulse voltage application treatment and the micro-aeration treatment, an electrolyte jet treatment is performed in which a jet with a flow rate of 0.5 to 100 L / min is applied to the electrolytic polishing treatment surface. This is to peel off the bubbles staying on the electrolytic polishing surface from the surface in the same manner as in the micro-aeration treatment. The jet is applied from the jet nozzle 18 to the electrolytic polishing treatment surface.

[0031] 3. Chromium oxide film formation step The chromium oxide film formation step forms a chromium oxide film on the surface of the stainless steel member such that the maximum value of the surface reflectance in the near-infrared region (wavelength 750 nm to 2500 nm) is 60% or less, and plays a role of reducing the thermal emissivity of the stainless steel member in the near-infrared region. The chromium oxide film formation step includes a film formation treatment in which the stainless steel member surface is immersed in a treatment liquid composed of a mixed solution of chromic acid and sulfuric acid to form a chromium oxide film, and a curing treatment in which the chromium oxide film is immersed in a treatment liquid composed of a mixed solution of chromic acid and phosphoric acid to cure the chromium oxide film.

[0032] (3-1) Film formation treatment For the formation of the chromium oxide film, the so-called Inco method (see Japanese Patent Application Laid-Open No. Sho 48-011243) of forming the chromium oxide film in a mixed solution of chromic acid and sulfuric acid is adopted. The thickness of the formed chromium oxide film is controlled by the coloring potential (the potential difference between the anode and the reference electrode). The thickness of the chromium oxide film with a maximum surface reflectance of 60% or less in the near-infrared region (wavelength 750 nm to 2500 nm) is 190 nm to 280 nm, and the coloring potential is 17 mV to 27 mV.

[0033] By controlling the formation rate of the chromium oxide film (hereinafter referred to as "film formation rate"), the adhesion and uniformity of the film can be enhanced, and the occurrence of thin film portions and film defects (pinholes) that cause the retention of metal impurities generated from the members used in semiconductor manufacturing equipment and metal impurities contained in semiconductor processing liquids can be suppressed. The film formation rate can be controlled by the treatment liquid composition and temperature. As the treatment liquid composition, the mixing ratio of sulfuric acid and chromic acid (chromic acid / sulfuric acid) is preferably 40 to 50 wt / v% of sulfuric acid with respect to 15 to 30 wt / v% of chromic acid. This is because by reducing the chromic acid concentration, the formation rate of the chromium oxide film responsible for the hydrogen barrier function can be lowered, and the generated thickness of the chromium oxide film can be precisely controlled. The treatment liquid temperature is 60 to 90 °C. The film formation rate can be controlled by the potential rate (mV / sec). The potential rate is 0.002 to 0.08 mV / sec, preferably 0.005 to 0.065 mV / sec. This is because if the potential rate is less than 0.002 mV / sec, the formation of the chromium oxide film will be delayed and productivity will decrease. If the potential rate exceeds 0.08 mV / sec, the thickness of the formed chromium oxide film will be non-uniform, and thin film portions and film defects (pinholes) that cause a decrease in the hydrogen barrier property will occur. In order to compensate for the formation rate of the chromium oxide film accompanying the reduction of the chromic acid concentration in the treatment liquid, manganese ions (Mn 2+ ) can be added. As the manganese salt, manganese chloride (MnCl 2 ), manganese sulfate (MnSO 4 ), manganese nitrate (Mn(NO 3 ) 2) and the like, and one or more of these can be used. The concentration of manganese ions (Mn 2+ ) in the treatment liquid is preferably 0.5 to 300 mmol / L, more preferably 5 to 150 mmol / L. When the concentration of manganese ions (Mn 2+ ) is less than 0.5 mmol / L, there is no effect of promoting the formation of the chromium oxide film. When the concentration of manganese ions (Mn 2+ ) exceeds 300 mmol / L, insoluble portions remain, which affects the formation of the chromium oxide film.

[0034] (3-2) Hardening treatment The hardening treatment step plays a role in hardening and strengthening the chromium oxide film formed on the surface of the welded stainless steel. In the hardening treatment, the stainless steel member on which the chromium oxide film has been formed by the film formation step is used as the cathode, and the chromium oxide film is hardened by cathode electrolysis. The chromium oxide film formed by the film formation step has about 10 pores of 10 to 20 nm per 1 cm 2 hitting 10 11 distributed. These pores cause a decrease in the hydrogen barrier property, and the pores can be sealed by the hardening treatment. Also, a loose film can be strengthened. As the hardening treatment liquid, the mixing ratio of chromic acid and phosphoric acid (chromic acid / phosphoric acid) is preferably 0.2 to 0.3 wt / v% of phosphoric acid as a reaction accelerator with respect to 15 to 30 wt / v% of chromic acid. The current density is 0.2 to 1.0 A / dm 2 and carried out for 5 to 10 minutes.

[0035] 4. Property evaluation For the samples prepared in the examples and comparative examples, the following properties were evaluated.

[0036] (4-1) Surface roughness measurement The surface unevenness profile of the precision polished product was measured with a scanning probe microscope (SFT-4500 manufactured by Shimadzu Corporation), and the unevenness difference was determined.

[0037] (4-2) Chromium oxide film thickness The thickness of the chromium oxide film was measured by SEM observation of the fracture surface on which the film was formed. The conditions for SEM observation of the cross-sectional morphology were as follows: acceleration voltage: 10.0 kV, detection mode: secondary electron detection, magnification: 10,000 times. In addition, the color tone of the chromium oxide film was visually evaluated.

[0038] (4-3) Composition element analysis of the chromium oxide film layer The elements (Cr, O, C) constituting the chromium oxide film layer were measured by XPS (X-ray photoelectron spectroscopy). An X-ray photoelectron spectrometer (KRATOS AXIS-ultra manufactured by Shimadzu Corporation) was used. Monochromatic AlKα rays were used as the X-ray source, and the irradiation diameter was 30 μm. Wide scan (qualitative analysis) was performed at a pass energy of 160 eV and an energy step of 1 eV. Narrow scan (quantitative analysis, electron state analysis) was performed on the Cr 2p , O 2p , C 2p spectra at a pass energy of 80 eV and an energy step of 1 eV.

[0039] (4-4) Outgassing characteristics For the outgassing characteristics, after subjecting a stainless steel member coated with a chromium oxide film to ultrasonic treatment (120 seconds) in an acetone solution, it was introduced into a vacuum chamber, and the time required for the degree of vacuum to reach 4.9×10 -5 Pa was measured.

[0040] (4-5) Measurement of near-infrared region reflectance Using a spectrophotometer (V-670 manufactured by JASCO Corporation), the average reflectance in the near-infrared region (wavelength 750 - 2500 nm) was measured, and the maximum reflectance was obtained.

Examples

[0041] Next, embodiments demonstrating the effects of the present invention are shown as examples. The summary is shown in Table 1 (electropolishing treatment conditions and surface unevenness difference) and Table 2 (film formation treatment conditions and maximum reflectance / outgassing property). In addition, the relationship between the coloring potential and the thickness of the chromium oxide film, and the TEM cross-sectional photograph of green color tone are shown in Fig. 4, and the spectroscopic absorption data (250 nm to 2700 nm) of Examples 1-3 and Comparative Examples 1-3 are shown in Fig. 5, respectively.

[0042]

Table 1

[0043]

Table 2

[0044] <Summary> (1) As shown in Table 1 and Fig. 6, in the electrolytic polishing solution consisting only of phosphoric acid and at least one organic sulfonic acid of the present invention, the precision electrolytic polishing treatment (Examples 1 and 3) of the present invention using anodic oscillation, pulsed voltage application treatment, micro-aeration treatment, and electrolytic solution jet treatment in combination has unevenness differences measured by a scanning probe microscope (SFT-4500 manufactured by Shimadzu Corporation) of 21 nm and 27 nm, respectively, which are significantly smaller than 395 nm of the electrolytic polishing treatment (Comparative Example 4) performed in the electrolytic solution consisting of phosphoric acid and sulfuric acid. By smoothing the stainless steel surface forming the chromium oxide film on the nano-order, the chromium oxide film can be formed on the stainless steel surface uniformly and smoothly. (2) As shown in Table 2 and Fig. 4, the film thickness of the chromium oxide film is proportional to the coloring potential. Also, as shown in Table 2 and Fig. 5, the average reflectance in the near-infrared region (wavelength 750 to 2500 nm) decreases as the film thickness of the chromium oxide film increases, and by setting the film thickness to 190 nm to 280 nm, the maximum value of the surface reflectance in the near-infrared region (wavelength 750 nm to 2500 nm) can be made 60% or less. (3) As shown in Table 2, the degassing property of the chromium oxide film-coated stainless steel (Examples 1-3, Comparative Examples 1-2) is equivalent (58 min) to that of the precision electrolytic polished product (Comparative Example 3), and metal impurities can also be controlled at the ppt level in the chromium oxide film-coated products. (4) As shown in Fig. 7, in the surface element analysis by X-ray photoelectron spectroscopy, for the substrate (stainless steel), there is no distinct peak for the chromium element (Cr 2p ). By performing precision electrolytic polishing and chromium oxide film coating, the peaks of Cr 2p , O 2p , and C 2p become clearer. The sample with chromium oxide film coating is coated with chromium oxide only with the peaks of Cr 2p , O 2p , and C 2p .

[0045] Samples of Example 1-3 and Comparative Example 1-4 were prepared as follows.

[0046] <Example 1> Stainless steel (SUS304, 80×60×2 mm, 2B finish flat plate) polished with #400 abrasive by buffing was used as the workpiece to be polished. (1) Precision electrolytic polishing treatment An electrode (+) was attached to the workpiece to be polished, and the workpiece to be polished (stainless steel) was oscillated in the vertical or horizontal direction by an oscillation device, and precision electrolytic polishing was performed under the following treatment conditions to produce Precision Polishing Product 1. [Electrolytic polishing treatment conditions] · Composition of electrolytic polishing solution: 50 ml / L of phosphoric acid, 50 ml / L of methanesulfonic acid · Treatment temperature: 75°C · Treatment time: 5 min · Current density: 20 A / dm 2 · Electrolyte jet flow: 50 L / min [Pulse voltage treatment] A pulse voltage generator (NC-025025S20X manufactured by Chiyoda Electronics Co., Ltd.) was set to an applied voltage of 8 V, a repetition period of 10 sec, a voltage application time of 7 sec, and a voltage pause time of 3 sec, and pulse voltage treatment was applied to the electrolytic polishing treatment. [Micro-aeration treatment] Using a microbubble generator (manufactured by Kansai Automech Co., Ltd.; HBKA80-0.2S1-SDX model), microbubbles with an average bubble diameter of 30 μm and an average bubble diameter of 100 μm were generated at a discharge rate (120 L / min) per 2,400 counts. The average bubble diameter of the microbubbles was measured by an image processing method (actual measurement of the microbubble image). In addition, bubbles were generated from the bottom of the smart treatment tank at a gas supply rate (100 L / min) from a cylindrical diffuser (manufactured by Nishida Seisakusho Co., Ltd., size φ70 mm × 1,000 mm) to generate an up-and-down swirling flow in the electrolytic polishing tank. The treatment time was 180 seconds.

[0047] (2) Chromium Oxide Film Formation Treatment The polished product 1 was subjected to film formation treatment (color development treatment) and hardening treatment in sequence under the following conditions to produce a chromium oxide film formed product 1. 〔Film Formation Treatment Conditions〕 · Color developing solution composition: 250 g / L of chromium oxide, 500 g / L of sulfuric acid · Treatment temperature: 65 °C · Treatment time: 40 min · Color developing potential rate: 0.011 mV / sec · Color developing potential: 27 mV 〔Hardening Treatment Conditions〕 · Hardening solution composition: 250 g / L of chromium oxide, 2.5 g / L of phosphoric acid · Treatment temperature: 25 °C · Treatment time: 10 min · Current density: 0.5 A / dm 2

[0048] <Example 2> A precision polished product 2 and a chromium oxide film formed product 2 were produced in the same manner as in Example 1, except that the chromium oxide film formation treatment was performed under the following conditions.

[0049] (1) Chromium Oxide Film Formation Treatment 〔Film Formation Treatment Conditions〕 · Color developing solution composition: 250 g / L of chromium oxide, 500 g / L of sulfuric acid · Treatment temperature: 65 °C · Treatment time: 35 min · Color development potential rate: 0.011 mV / sec · Color development potential: 22 mV 〔Hardening treatment conditions〕 · Hardening solution composition: Chromium oxide 250 g / L, Phosphoric acid 2.5 g / L · Treatment temperature: 25 °C · Treatment time: 10 min · Current density: 0.5 A / dm 2

[0050] <Example 3> Precision polished product 3 and chromium oxide film formed product 3 were produced in the same manner as in Example 1, except that the chromium oxide film forming treatment was carried out under the following conditions.

[0051] (1) Chromium oxide film forming treatment 〔Film forming treatment conditions〕 · Color developing solution composition: Chromium oxide 250 g / L, Sulfuric acid 500 g / L · Treatment temperature: 65 °C · Treatment time: 26 min · Color development potential rate: 0.011 mV / sec · Color development potential: 17 mV 〔Hardening treatment conditions〕 · Hardening solution composition: Chromium oxide 250 g / L, Phosphoric acid 2.5 g / L · Treatment temperature: 25 °C · Treatment time: 10 min · Current density: 0.5 A / dm 2

[0052] <Comparative Example 1> Precision polished product 4 and chromium oxide film formed product 4 were produced in the same manner as in Example 1, except that the chromium oxide film forming treatment was carried out under the following conditions.

[0053] (1) Chromium oxide film forming treatment 〔Film forming treatment conditions〕 · Color developing solution composition: Chromium oxide 250 g / L, Sulfuric acid 500 g / L · Treatment temperature: 65 °C · Treatment time: 70 min · Color development potential rate: 0.0024 mV / sec · Color development potential: 10 mV 〔Hardening treatment conditions〕 · Composition of hardening solution: Chromium oxide 250 g / L, Phosphoric acid 2.5 g / L · Treatment temperature: 25 °C · Treatment time: 10 min · Current density: 0.5 A / dm 2

[0054] <Comparative Example 2> Five precision polished products and five chromium oxide film formed products were produced in the same manner as in Example 1, except that the chromium oxide film forming treatment was carried out under the following conditions.

[0055] (1) Chromium oxide film forming treatment 〔Film forming treatment conditions〕 · Composition of color developing solution: Chromium oxide 250 g / L, Sulfuric acid 500 g / L · Treatment temperature: 65 °C · Treatment time: 11 min · Color development potential speed: 0.011 mV / sec · Color development potential: 7 mV 〔Hardening treatment conditions〕 · Composition of hardening solution: Chromium oxide 250 g / L, Phosphoric acid 2.5 g / L · Treatment temperature: 25 °C · Treatment time: 10 min · Current density: 0.5 A / dm 2

[0056] <Comparative Example 3> Stainless steel (SUS304, 80 × 60 × 2 mm, 2B finish, flat plate) buffed with #400 abrasive was used as the workpiece to be polished. (1) Electropolishing treatment An electrode (+) was attached to the workpiece to be polished, and the workpiece to be polished was oscillated in the vertical or horizontal direction by an oscillation device, and precision electropolishing was carried out under the following treatment conditions to produce a precision polished product 6. [Electropolishing treatment conditions] · Composition of electropolishing solution: Phosphoric acid 50 ml / L, Methanesulfonic acid 50 ml / L · Treatment temperature: 75 °C · Treatment time: 5 min · Current density: 20 A / dm 2 · Electrolyte jet flow: 50 L / min [Pulse voltage treatment] A pulse voltage generator (NC-025025S20X manufactured by Chiyoda Electronics Co., Ltd.) was set to an applied voltage of 8 V, a repetition period of 10 s, a voltage application time of 7 s, and a voltage pause time of 3 s, and pulse voltage treatment was applied to the electrolytic polishing treatment. [Micro-aeration treatment] Using a microbubble generator (manufactured by Kansai Autome Machinery Co., Ltd.; HBKA80-0.2S1-SDX type), microbubbles with an average bubble diameter of 30 μm and an average bubble diameter of 100 μm were generated at a discharge rate (120 L / min) per 2400 counts. The average bubble diameter of the microbubbles was measured by an image processing method (actual measurement of the microbubble image). In addition, bubbles were generated from the bottom of the smart treatment tank at a gas supply rate (100 L / min) from a cylindrical diffuser (manufactured by Nishida Seisakusho Co., Ltd., size φ70 mm × 1000 mm) to generate an up-and-down swirling flow in the electrolytic polishing tank. The treatment time was 180 s.

[0057] [Comparative Example 4] Stainless steel (SUS304, 80 × 60 × 2 mm, 2B finish flat plate) polished with #400 abrasive was used as the workpiece to be polished. (1) Electrolytic polishing treatment An electrode (+) was attached to the workpiece to be polished, and precision electrolytic polishing was performed under the following treatment conditions to produce polished product 7. Note that pulse voltage treatment, micro-aeration treatment, and electrolyte jet flow were not performed. The workpiece to be polished was not oscillated in the vertical or horizontal direction by the oscillating device. [Electrolytic polishing treatment conditions] · Composition of electrolytic polishing solution: 25 ml / L of phosphoric acid, 75 ml / L of sulfuric acid · Treatment temperature: 75 °C · Treatment time: 5 min · Current density: 20 A / dm 2 [Industrial applicability]

[0058] The present invention can provide a stainless steel for use in a semiconductor manufacturing apparatus and a method for manufacturing the same.

Explanation of reference numerals

[0059] 100 Electropolishing apparatus 10 Electropolishing treatment tank 11 Microbubble generator 12 Microbubble supply pipe 13 Microbubble 14 Diffuser 15 Compressor 16 Air supply pipe 17 Swirling flow 18 Jet nozzle 20 Pulse voltage generator 21 Metal to be polished 22 Conductive wire 23 Electropolishing solution

Claims

1. A chromium oxide film-coated stainless steel member in which the surface of an electrolytically polished stainless steel member is coated with a chromium oxide film, wherein the film thickness of the chromium oxide film is 190 nm to 280 nm, and the maximum value of the surface reflectance in the near-infrared region (wavelength 750 nm to 2500 nm) is 60% or less. A chromium oxide film-coated stainless steel member characterized by the above.

2. The chromium oxide film-coated stainless steel member according to claim 1, wherein the surface of the electrolytically polished stainless steel member has an unevenness difference of 30 nm or less measured by a scanning probe microscope.

3. A method for manufacturing a chromium oxide film-coated stainless steel member, wherein the film thickness of the chromium oxide film is 190 nm to 280 nm, and the maximum value of the surface reflectance in the near-infrared region (wavelength 750 nm to 2500 nm) is 60% or less, an electrolytic polishing treatment step of electrolytically polishing the surface of the stainless steel member with an electrolytic polishing solution for stainless steel composed only of phosphoric acid and at least one organic sulfonic acid, a film formation treatment step of immersing the electrolytically polished stainless steel member in a treatment solution composed of a mixed solution of 25 w / vol% chromic acid and 50 w / vol% sulfuric acid to form a chromium oxide film on the surface of the stainless steel member at a coloring potential of 17 mV to 28 mV, and a hardening treatment step of immersing the member in a treatment solution composed of a mixed solution of chromic acid and phosphoric acid to harden the chromium oxide film, which together constitute a chromium oxidation film coating step, A method for manufacturing a chromium oxide film-coated stainless steel member, wherein the film thickness of the chromium oxide film formed thereby is 190 nm to 280 nm, and the maximum value of the surface reflectance in the near-infrared region (wavelength 750 nm to 2500 nm) is 60% or less.

4. The method for manufacturing a chromium oxide film-coated stainless steel member according to claim 3, wherein the electrolytic polishing treatment step includes a pulsed voltage application treatment, a micro-aeration treatment, and an electrolytic solution jet treatment, and the film thickness of the chromium oxide film is 190 nm to 280 nm, and the maximum value of the surface reflectance in the near-infrared region (wavelength 750 nm to 2500 nm) is 60% or less.

Images