JP5739297B2 - Stainless steel - Google Patents

Description

  The present invention relates to a stainless steel applicable to a member of a processing apparatus such as a semiconductor wafer cutting apparatus or a grinding apparatus.

  Damping materials having a function of reducing vibration and noise are used in fields such as automobiles and precision equipment. Various damping materials are known. For example, Patent Document 1 describes damping stainless steel.

JP 2010-090472 A

  By the way, a cutting device or polishing device or the like (hereinafter referred to as a processing device if necessary) that performs processing such as cutting or polishing on a semiconductor wafer is referred to as cutting water or grinding water (hereinafter referred to as cutting water or the like if necessary). ) To cut or polish the semiconductor material. For this reason, a chuck table that supports a semiconductor wafer, a spindle that holds and rotates a blade, and the like are also used in an environment where cutting water or the like adheres. In order to ensure the processing accuracy of the semiconductor wafer, the chuck table and the spindle are manufactured from a damping material having a high ability to absorb vibration (hereinafter referred to as damping ability).

  Currently known damping materials include, for example, manganese damping alloys (M2052), iron-aluminum alloys (ALFE or interior), and all of these have low corrosion resistance. For this reason, these damping materials cannot often be used in an environment where cutting water or the like adheres because rust and elution may occur.

  SUS430 or SUS431 is often used for the chuck table and spindle of the processing apparatus, but rusting may occur when these are used in an environment where cutting water or the like adheres. Further, a higher damping capacity is required for the chuck table and spindle of the processing apparatus.

  An object of this invention is to provide the stainless steel which improved the damping ability and corrosion resistance.

  In order to solve the above-described problems and achieve the object, the present invention provides silicon of 1.5 to 3% by weight, manganese of 0.2 to 0.5% by weight, chromium of 21 to 23% by weight, molybdenum of 0.5 to It is a stainless steel containing 1.5% by weight, aluminum 1.5 to 3% by weight, niobium 0.2 to 0.8% by weight, consisting of the remaining amount of iron and inevitable impurities, and being a ferrite single phase. .

  The present invention is preferably used as a material for a member used in an environment to which cutting water or grinding water of an apparatus for processing a semiconductor wafer adheres.

  The present invention can provide stainless steel with improved vibration damping ability and corrosion resistance. For this reason, if the stainless steel according to the present invention is applied instead of the stainless steel applied to the conventional processing apparatus, it is possible to improve the processing accuracy by improving the vibration damping capability of the chuck table and the spindle of the processing apparatus. It is possible to suppress the occurrence of rust.

FIG. 1 is an explanatory diagram of a vibration damping performance evaluation method. FIG. 2 is a diagram illustrating evaluation results of vibration damping characteristics. FIG. 3 is a diagram showing the results of a rusting experiment. FIG. 4 is a diagram showing the results of a rusting experiment. FIG. 5 is a diagram showing the results of a rusting experiment.

  Hereinafter, modes for carrying out the invention (embodiments) will be described. The present invention is not limited to the contents of the embodiments described below, and various modifications can be made without departing from the spirit of the present invention.

  Stainless steel is alloy steel containing chromium or chromium and nickel for the purpose of improving corrosion resistance. In general, steels with a chromium content of about 11% or more are called stainless steels, and are classified into five types according to their structures: martensite, ferrite, austenite, austenite / ferrite, and precipitation hardening (JIS). G 0203).

  The stainless steel according to the present embodiment includes 1.5 to 3% by weight of silicon (Si), 0.2 to 0.5% by weight of manganese (Mn), 21 to 23% by weight of chromium (Cr), and molybdenum. (Mo) 0.5 to 1.5 wt%, aluminum (Al) 1.5 to 3 wt%, niobium (Nb) 0.2 to 0.8 wt%, and the remaining amount is iron In addition, it consists of inevitable impurities, and the structure is a single phase of ferrite.

  As described above, the stainless steel according to the present embodiment has a larger content ratio of Si and Al than a general stainless steel such as SUS304. Al improves the vibration damping ability of stainless steel by improving the vibration damping ability. When stainless steel contains Al, the corrosion resistance decreases, so the inclusion of Si suppresses the decrease in corrosion resistance caused by Al. Cr, Mo and Nb improve the corrosion resistance. In particular, Mo and Nb improve resistance to crevice corrosion and intergranular corrosion.

  By adopting such a composition, the stainless steel according to the present embodiment has a high vibration damping capability due to Al, and has corrosion resistance due to Si, Cr, Mo, Nb, in particular, high resistance against rusting (high resistance to rusting). Rust). For this reason, when the stainless steel according to the present embodiment is used for the spindle and chuck table of the processing apparatus, rust due to adhesion of cutting water or the like hardly occurs. Further, since the vibration damping capability is high, vibrations generated during cutting or polishing are efficiently absorbed by the spindle and table chuck, so that vibrations of tools such as blades and wafers are efficiently suppressed. As a result, the processing accuracy of the wafer can be ensured.

  The composition of the stainless steel according to the present embodiment will be described. When the silicon content decreases, the corrosion resistance of stainless steel decreases, and when the silicon content increases, embrittlement, that is, brittleness tends to occur. For this reason, the silicon content is preferably 1.5% by weight or more and 3% by weight or less. If it is this range, while being able to ensure corrosion resistance, moderate ductility can be ensured.

  When the aluminum content decreases, the hardness of the stainless steel decreases, and when it increases, the ductility decreases. For this reason, the aluminum content is preferably 1.5% by weight or more and 3% by weight or less. If it is this range, moderate hardness and ductility are securable. As a result, at the time of manufacturing stainless steel, rolling is facilitated, so that productivity is improved and quality is improved. Moreover, the performance as a member of the processing apparatus can be ensured.

  The content of Cr is preferably 21% by weight or more and 23% by weight or less. By setting the Cr content within this range, the structure of the stainless steel becomes ferrite. And the corrosion resistance of stainless steel can be ensured even if almost no Ni is added. The content of Nb is preferably 0.2% by weight or more and 0.8% by weight or less. The content of Mo is preferably 0.5% by weight to 1.5% by weight. Thus, by adding Nb and Mo, the intergranular corrosion which the carbide | carbonized_material which Cr and carbon couple | bonded precipitates on a crystal grain boundary can be suppressed, and the corrosion resistance of stainless steel can be improved. In addition, by setting the Mo content in the above-described range, the stainless steel according to the present embodiment can effectively exhibit the effect of improving the local repair ability of the passive film. The Mn content is preferably 0.2% by weight or more and 0.5% by weight or less.

  The stainless steel according to the present embodiment may contain 0.5% by weight or less of at least one of titanium (Ti) and nickel (Ni) in addition to the above composition. These elements improve the corrosion resistance of stainless steel. Ni has the effect of enhancing the corrosion resistance against non-oxidizing acids such as sulfuric acid or hydrochloric acid, and has the effect of fixing the austenite phase. Since the structure of the stainless steel according to the present embodiment is a ferrite single phase, the Ni content is preferably within the above range in order to obtain this structure. Ti has an effect of improving corrosion resistance by suppressing intergranular corrosion in which carbides in which Cr and C are combined are precipitated at the grain boundaries of stainless steel.

  In the stainless steel according to the present embodiment, the time from when vibration is applied until it is attenuated to a predetermined amplitude is about 1/5 to 1/4 of SUS303 and SUS430. From this result, it can be said that the damping capacity of the stainless steel according to the present embodiment is 4 to 5 times that of SUS303 and SUS430. Further, the stainless steel according to the present embodiment has extremely high corrosion resistance as compared with SUS303 and SUS430.

(Production method)
The stainless steel according to the present embodiment can be manufactured by a manufacturing method similar to general stainless steel, and can be manufactured by, for example, a manufacturing method having the following steps. In addition, it is not limited to the following manufacturing method.
Step 1: A steel material adjusted to the components of stainless steel according to the present embodiment is melted in a vacuum high-frequency melting furnace.
Step 2: Casting the molten steel material to obtain a steel ingot.
Process 3: The scale and casting sand of the obtained steel ingot are removed by sandblasting or the like.
Step 4: The steel ingot from which scales and the like have been removed is roughly formed by hot forging.
Step 5: Rolling the roughly formed steel ingot to obtain a rolled material.
Process 6: Annealing a rolling material.
The stainless steel which concerns on this Embodiment is obtained by the process 1-6 mentioned above.

  Thus, since the stainless steel which concerns on this Embodiment can be manufactured with the manufacturing method similar to general stainless steel, a special installation, a special process, and a special process are unnecessary. As a result, since it can be manufactured using the existing manufacturing equipment, there is an advantage that a new capital investment becomes unnecessary and an increase in manufacturing cost can be suppressed.

  As described above, the stainless steel according to the present embodiment can achieve both high vibration damping performance and high corrosion resistance. For this reason, the stainless steel according to the present embodiment is attached to cutting water or grinding water such as a chuck table, a spindle and a wheel cover of a cutting apparatus or a polishing apparatus that performs processing such as cutting or polishing on a semiconductor wafer. It is suitable as a material for members used in an environment. Moreover, since the stainless steel which concerns on this Embodiment is a ferrite type, the usage-amount of Ni can be reduced and the raise of cost can be suppressed.

  The stainless steel which concerns on embodiment mentioned above was manufactured by the process 1-6 mentioned above, and the performance was evaluated. The melting temperature of the steel material in the vacuum high-frequency melting furnace in step 1 was 1800 ° C., and the hot forging temperature in step 4 was 1200 ° C. The composition of the manufactured stainless steel is as follows: Si is 2.0% by weight, Mn is 0.3% by weight, Ni is 0.3% by weight, Cr is 22% by weight, Mo is 1.0% by weight, and Al is 2.% by weight. 0% by weight, Ti is 0.3% by weight, Nb is 0.5% by weight, and the remaining amount is Fe. This stainless steel was taken as an example. SUS303 was evaluated as Comparative Example 1, and SUS430 was evaluated as Comparative Example 2.

(Evaluation of mechanical properties)
The mechanical properties of Examples, Comparative Example 1 and Comparative Example 2 were evaluated. Table 1 shows the evaluation items and the evaluation results. The yield strength (0.2% yield strength), tensile strength, elongation and drawing were determined from the results of tensile tests on Examples, Comparative Examples 1 and 2. The hardness was determined by the Rockwell hardness test for Examples, Comparative Examples 1 and 2. Specific gravity calculated | required the mass per unit volume of an Example, the comparative example 1, and the comparative example 2 in a 20 degreeC environment. The thermal conductivity was determined by a laser flash method. The coefficient of thermal expansion is the coefficient of thermal expansion when the samples of Example, Comparative Example 1 and Comparative Example 2 were heated at a constant rate from 0 ° C. to 100 ° C. When the sample length at 0 ° C. is L0 and the sample length at 100 ° C. is L100, the coefficient of thermal expansion is (L100−L0) / (100 × L0). The pitting corrosion potential is a dynamic potential method pitting corrosion potential V ′ _{C, PIT} measured by a stainless steel pitting corrosion potential measuring method specified in JIS G 0577.

  As can be understood from the results in Table 1, the examples have greater yield strength, tensile strength, and hardness (Rockwell hardness) than Comparative Examples 1 and 2. For example, SUS430 (Comparative Example 2) is often used for the chuck table, spindle, wheel cover, and the like of the processing apparatus. As can be understood from the above evaluation results, the example is more mechanical than the comparative example 2. Since the mechanical strength is high, it can be suitably used as a material for a chuck table or the like.

(Evaluation of vibration control performance)
FIG. 1 is an explanatory diagram of a vibration damping performance evaluation method. The damping performance was evaluated by a characteristic (vibration damping characteristic) in which vibration generated in the specimen is attenuated by exciting the specimen. The vibration damping characteristic is high, that is, the vibration damping performance is higher as the vibration is attenuated faster.

  A specimen 2 of a round bar having a diameter D of 20 mm and a length L of 500 mm was prepared using the stainless steel of Examples, Comparative Examples 1 and 2 as a raw material. As shown in FIG. 1, the acceleration sensor 3 is attached to one end of the specimen 2. A signal detected by the acceleration sensor 3 is input to the measuring device 4. When the specimen 2 is vibrated, a 50 g iron ball 5 is dropped from a position where the height H from the specimen 2 is 100 mm to a predetermined position in the longitudinal direction of the specimen 2 and collides with the specimen 2. The predetermined position of the specimen 2 on which the iron ball 5 collides is, for example, a position of 4 × L / 5 (400 mm in this example) from one end of the specimen 2 to which the acceleration sensor 3 is attached. In this way, the specimen 2 is vibrated. The acceleration sensor 3 detects the acceleration of the specimen 2. The measuring device 4 obtains the acceleration detected by the acceleration sensor 3 and obtains the time change of the vibration of the specimen 2.

  FIG. 2 is a diagram illustrating evaluation results of vibration damping characteristics. C1 in FIG. 2 is the vibration attenuation characteristic of Comparative Example 1, C2 is the vibration attenuation characteristic of Comparative Example 2, and E is the vibration attenuation characteristic of the Example. The vertical axis in FIG. 2 is the amplitude of vibration (magnitude of acceleration), and the horizontal axis is time (seconds). As shown in FIG. 2, it takes 0.2 seconds for SUS303 and 0.27 seconds for SUS430 to reach the same amplitude (vibration value) A as in comparative example 1 (SUS303) and comparative example 2 (SUS430). In contrast, the example is 0.05 seconds. Thus, it can be said that the Example has a vibration damping capability 4 to 5 times that of Comparative Example 1 and Comparative Example 2, and has high damping performance.

(Evaluation of corrosion resistance)
In order to evaluate corrosion resistance, the rusting experiment of the Example, the comparative example 1, and the comparative example 2 was done. In the rusting experiment, specimens of a round bar having a diameter of 20 mm and a length of 20 mm were prepared for each of Example, Comparative Example 1 and Comparative Example 2, and the time when rust was generated by spraying salt water on them was investigated. The rusting test was conducted according to the salt spray test method defined in JIS Z 2371 (revised on February 20, 2000, confirmed in 2005).

  3-5 is a figure which shows the result of a rusting experiment. 3 shows the evaluation result of Comparative Example 1, FIG. 4 shows the evaluation result of Comparative Example 2, and FIG. 5 shows the evaluation result of the Example. Table 1 described above shows the time (rust spray rusting time) when rust was generated on the specimen. In Comparative Example 1, generation of rust was observed in 50 hours after the start of spraying of salt water, and in Comparative Example 2, generation of rust was observed in 20 hours. As shown in FIGS. 3 and 4, in Comparative Examples 1 and 2, a considerable amount of rust is generated in 240 hours. Rust is a black spot-like part appearing in FIGS. 3 and 4.

  On the other hand, in FIG. 5 showing the evaluation results of the examples, the black spot-like portions as seen in FIGS. 3 and 4 do not appear. From this, it can be understood that in the examples, the generation of rust is not observed at the point of 1000 hours. Thus, it can be understood that the Examples have high corrosion resistance with respect to Comparative Example 1 (SUS304) and Comparative Example 2 (SUS430).

(Influence of added elements)
The contents of Si and Al were varied between 1.0 wt% and 3.5 wt%, and the influence of the contents of these elements on the properties of stainless steel was investigated. When the content of Si is less than 1.0% by weight, the corrosion resistance of stainless steel is lowered. More specifically, generation of rust was observed in 1000 hours in the rusting experiment described above. On the other hand, when the Si content exceeds 3.5% by weight, the ductility of the stainless steel is lowered and brittleness is exhibited. For this reason, there exists a possibility that the performance as a material of the member of a processing apparatus, especially the material of the member used in the environment where cutting water etc. adhere may not be ensured. Note that ductility or brittleness was evaluated by a tensile fracture test.

  When the Al content is less than 1.0% by weight, the hardness of the stainless steel is lowered, and there is a possibility that performance as a material for a processing apparatus, particularly a material such as a chuck table and a spindle cannot be secured. Moreover, when Al content exceeds 3.5 weight%, the ductility of stainless steel will fall. More specifically, the elongation and aperture values are reduced. As a result, rolling may be difficult during the production of stainless steel.

  From the above results, the content of Si and Al is preferably 1.5% by weight or more and 3.0% by weight or less, respectively. If it is such a range, while being able to ensure the performance as a material of the member of the processing apparatus used in the environment where cutting water etc. adhere, productivity of stainless steel also improves.

2 Specimen 3 Acceleration sensor 4 Measuring device 5 Iron ball

Claims (2)

  1.5 to 3% by weight of silicon, 0.2 to 0.5% by weight of manganese, 21 to 23% by weight of chromium, 0.5 to 1.5% by weight of molybdenum, 1.5 to 3% by weight of aluminum, 0. Stainless steel containing 2 to 0.8% by weight, the remaining amount of iron and inevitable impurities, and being a ferrite single phase.   The stainless steel according to claim 1, which is used as a material for a member used in an environment where cutting water or grinding water adheres in an apparatus for processing a semiconductor wafer.

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