JP2007009256A - Rare earth metal member, and making method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rare earth metal member having a high surface purity, a large grain size, minimized grain boundaries, and improved halogen resistance or corrosion resistance by using a rare earth metal containing not more than 100 ppm of at least one metal element other than the rare earth metal, machining the same into a member and cleaning the rare earth metal member after the machining with an organic acid-base capping agent. <P>SOLUTION: The rare earth metal member is composed entirely of a rare earth metal, and contains not more than 100 ppm of at least one metal element other than the rare earth metal in a zone extending from the outermost surface to a depth of 2 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a member made of a high-purity rare earth metal element, particularly a rare earth metal member having an extremely high surface purity. More specifically, a semiconductor manufacturing apparatus, a liquid crystal manufacturing apparatus, an organic EL manufacturing apparatus, an inorganic EL manufacturing apparatus, etc. The present invention relates to a rare earth metal member which is suitably used for a flat panel display manufacturing apparatus and the like and has corrosion resistance to a halogen-based corrosive gas or plasma thereof and is formed entirely of rare earth metal, and a method for manufacturing the same.

  Flat panel display manufacturing equipment such as semiconductor manufacturing equipment, liquid crystal manufacturing equipment, organic and inorganic EL manufacturing equipment used in a halogen-based corrosive gas atmosphere uses high-purity materials to prevent impurities from being contaminated. In particular, the purity of the surface is important.

  In a semiconductor manufacturing process, a gate etching apparatus, an insulating film etching apparatus, a resist film ashing apparatus, a sputtering apparatus, a CVD apparatus, and the like are used. On the other hand, in a liquid crystal manufacturing process, an etching apparatus or the like for forming a thin film transistor is used. These manufacturing apparatuses are configured to have a plasma generation mechanism for the purpose of high integration by microfabrication.

In these manufacturing processes, halogen-based corrosive gases such as fluorine-based and chlorine-based gases are used in the above-described apparatuses because of their high reactivity. Examples of the fluorine-based gas include SF ₆ , CF ₄ , CHF ₃ , ClF ₃ , HF, and NF ₃ , and examples of the chlorine-based gas include Cl ₂ , BCl ₃ , HCl, CCl ₄ , and SiCl ₄ . When microwaves or high frequencies are introduced into the atmosphere into which these gases are introduced, these gases are turned into plasma. The apparatus members exposed to these halogen-based gases or their plasmas are required to have very little metal other than material components on the surface and high corrosion resistance.

  Conventionally, as a material for imparting corrosion resistance to halogen-based gas or plasma thereof, ceramics such as quartz, alumina, silicon nitride, aluminum nitride, alumite-treated film, or these as a base material What sprayed on the surface and formed the sprayed coating is used. Japanese Patent Laid-Open No. 2002-241971 (Patent Document 1) proposes a plasma-resistant member in which a surface region exposed to plasma under corrosive gas is formed of a metal layer of Group IIIA of the periodic table. It is described that the layer thickness is about 50 to 200 μm.

  However, the ceramic member has a problem that the processing cost is high and particles remain on the surface. When such a member is exposed to plasma in a corrosive gas atmosphere, although there is a difference in degree, corrosion proceeds gradually and crystal particles constituting the surface region are detached, so-called particle contamination occurs. That is, the detached particles adhere to the vicinity of the semiconductor wafer, the lower electrode, etc., adversely affect the etching accuracy, and the semiconductor performance and reliability are likely to be impaired.

Further, the ceramic member has a characteristic that it is not electrically conductive, and cannot be used for a high-frequency grounding material or the like that requires electrical conductivity. In parts where such characteristics are required, aluminum anodized parts have been used, but there are problems in that the lifetime is short and a large amount of AlF particles are generated. In recent years, a member sprayed with Y ₂ O ₃ having higher halogen plasma resistance has been used for such a part.

  However, the plasma environment in recent years has a tendency to become higher energy, and a problem has arisen that the balance of plasma is lost and sparks are partially generated. One of the causes of the spark is that the insulator is sprayed on the surface of the conductive material, and it is considered that fine pores generated by spraying and open pores connected to the ground are the cause. Therefore, it has been studied to make the surface irregularities as small as possible and to reduce the pores, but the countermeasures have not been sufficient.

  As a means to solve this problem, there was an idea to set an electrically conductive part in the plasma environment and let the DC component escape to the ground so as not to generate sparks, but I could not find a member that could withstand that idea. Is the current situation.

  Japanese Patent Laid-Open No. 2002-241971 proposes a plasma-resistant member in which a surface film region exposed to plasma under a corrosive gas is formed of a metal layer of Group IIIA of the periodic table as described above. However, the layer thickness is 50 to 200 μm, and the resistance value is not described. In a semiconductor manufacturing apparatus, periodic cleaning is necessary to remove reaction products adhering to the in-chamber manufacturing apparatus member due to the reaction between the process gas and the object to be processed. However, when the corrosion-resistant member has a layer shape of about 200 μm, the corrosion-resistant layer is scraped during handling during polishing and cleaning to remove the reaction product, the substrate is easily exposed, and the corrosion resistance cannot be maintained over repeated use. The problem also arises.

  In recent years, semiconductor devices and the like have been made larger in size with miniaturization, and low-pressure and high-density plasma is being used in so-called dry processes, particularly in etching processes. When this low-pressure high-density plasma is used, it has a large effect on the plasma-resistant member compared to conventional etching conditions, and it causes erosion due to plasma, contamination of member components resulting from this erosion, and reaction products due to surface impurities. Problems such as contamination caused by the problem have become prominent.

  Furthermore, the surface of the member is contaminated by metal processing jigs such as cutting and grinding used when processing these members. When such a member is used in a halogen plasma atmosphere, it causes particle contamination and erosion. .

JP 2002-241971 A

  The present invention has been made in view of the above circumstances, and the entire member is formed of a rare earth metal, sufficiently withstands exposure to a halogen-based gas or plasma thereof, and does not deteriorate the corrosion resistance in regular cleaning. And it aims at providing the rare earth metal member excellent in corrosion resistance (plasma resistance) without surface contamination, and its manufacturing method.

As a result of intensive studies to achieve the above object, the present inventors have found that the whole is a rare earth metal member formed of a rare earth metal, and a metal other than the rare earth metal element in a portion within a depth of 2 μm from the outermost surface. A rare earth metal member having a content of at least one element of 100 ppm or less is dense and exhibits corrosion resistance itself, so there is no need to form a corrosion resistant layer on the surface, and a halogen resistant gas or halogen resistant plasma. It has been found that it is useful for semiconductor manufacturing equipment, flat panel display manufacturing equipment, etc., and that this member itself exhibits corrosion resistance, so that corrosion resistance performance is not deteriorated by repeated cleaning damage. It was. Moreover, after manufacturing and processing ingots using rare earth metals each containing at least 100 ppm of one or more metal elements other than rare earth metal elements, washing with an organic acid sequestering agent solution such as citric acid or tartaric acid By removing the processing contamination from the surface of the processed rare earth metal member, it is possible to prevent contamination of the object to be processed by the reaction product with the halogen-based gas, having a bulk equivalent surface purity, The rare earth metal having a surface resistivity of 1 × 10 ⁻⁵ to 1 × 10 ² Ω / □ and being useful as a member for semiconductor manufacturing equipment, a member for flat panel display manufacturing equipment, etc. The present inventors have found that a member can be provided and have made the present invention.

That is, the present invention
(1) A rare earth metal member formed entirely of a rare earth metal, wherein the content of one or more metal elements other than the rare earth metal element in a portion within 2 μm in depth from the outermost surface is 100 ppm or less, respectively. Rare earth metal member,
(2) The rare earth metal according to (1), wherein the rare earth metal element is one or more selected from Y, Sc, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. Element,
(3) The metal element other than the rare earth metal element is an element selected from Na, K, Ca, Mg, Fe, Cr, Cu, Ni, Zn and Al (1) or (2) Rare earth metal members,
(4) The rare earth according to (1), (2) or (3), wherein the content of metal elements other than the rare earth metal element in the portion from the outermost surface to a depth of 300 μm is 100 ppm or less, respectively. Metal parts,
(5) A rare earth metal member formed entirely of rare earth metal, wherein the content of at least one metal element other than the rare earth metal element is 100 ppm or less,
(6) Any one of (1) to (5), wherein an ingot obtained from a rare earth metal having a content of one or more metal elements other than the rare earth metal element is 100 ppm or less, respectively. The rare earth metal member according to the description,
(7) The member according to any one of (1) to (6), wherein the member is a polycrystal of a rare earth metal element, and the crystal diameter of crystal grains constituting the polycrystal is 3 mm or more. Rare earth metal components,
(8) The rare earth metal member according to any one of (1) to (7), which is for a semiconductor manufacturing apparatus or a flat panel display manufacturing apparatus,
(9) The rare earth metal member according to (8), which is used in a halogen-based gas or a halogen-based plasma atmosphere,
(10) An ingot obtained from a rare earth metal having a content of at least one metal element other than the rare earth metal element of 100 ppm or less is processed and then washed with an organic acid sequestering agent solution (1 ) To (9), a method for producing a rare earth metal member according to any one of
(11) Organic acid sequestering agent is citric acid, monoammonium citrate, gluconic acid, glycolic acid, ditric triacetate, ethylenediaminetetraacetic acid, diethylenetriaminopentaacetic acid, dihydroxyethylene glycine, triethanolamine, hydroxyethylenediamine 4 The method for producing a rare earth metal member according to (10), characterized in that it is selected from acetic acid, L-ascorbic acid, malic acid, tartaric acid, oxalic acid, gallic acid, glyceric acid, hydroxybutyric acid, glyoxylic acid, and salts thereof. provide.

  By creating a member using a rare earth metal in which the content of one or more metal elements other than the rare earth metal element is 100 ppm or less, and washing the processed rare earth metal member with an organic acid sequestering agent, the surface becomes It is possible to provide a rare earth metal member having high purity, a large crystal diameter and few grain boundaries, and excellent halogen resistance (corrosion resistance).

  The member of the present invention is a rare earth metal member formed entirely of rare earth metal, and the content of one or more metal elements other than the rare earth metal element in the portion within 2 μm depth from the outermost surface is 100 ppm or less, respectively. It is a certain rare earth metal member.

  The rare earth metal element used in the member of the present invention is a rare earth metal element selected from Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. And more preferably a rare earth metal element selected from Y, Sc, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. These rare earth metal elements can be used alone or in combination of two or more.

  Here, in the semiconductor manufacturing process and the like, examples of metal elements that cause product defects include Na, K, Ca, Mg, Fe, Cr, Cu, Ni, Zn, and Al, and in particular, Fe, Cu, Ni, and Zn. Cr is a problem. The content of metal elements other than these rare earth metal elements contained in the rare earth metal member of the present invention is 100 ppm or less, preferably 60 ppm or less, in a portion within a depth of 2 μm from the outermost surface of the member. Further, Na, K, Ca, Mg, Cr, and Zn are each preferably 10 ppm or less. If the content of metal elements other than rare earth metal elements exceeds 100 ppm, metal contamination in the semiconductor product will exceed the allowable amount.

  In the member of the present invention, the content of a metal element other than the rare earth metal element in the portion within a depth of 300 μm from the outermost surface of the member, particularly the entire member is preferably within the above range. Even if the content of the metal element on the surface of the member is small, if the content inside the member is too large, the metal element may be diffused and contaminated. preferable.

Moreover, since the member of the present invention uses a rare earth metal element, it has excellent electrical conductivity, and the surface resistivity is preferably 1 × 10 ⁻⁵ to 1 × 10 ² Ω / □, more preferably 1 × 10. ^-5 to 1 × 10 ¹ Ω / □. If the surface resistivity is too large, the function of the electrically conductive member may not be fulfilled, such as insufficient grounding.

Next, the manufacturing method of the rare earth metal member of this invention is demonstrated.
In the production method of the present invention, first, an ingot is produced by a conventional method by dissolving rare earth metals each containing 100 ppm or less of the above metal elements other than the rare earth metal elements. Examples of the rare earth metal melting method include electron beam melting, arc melting, induction melting and the like. At that time, the oxygen content in the rare earth metal ingot obtained by melting is preferably 0.03 to 2.0 mass%. If the oxygen content is less than 0.03% by mass, the hardness of the ingot will be too low, and machining of the member of the present invention may be difficult. Moreover, when it exceeds 2.0 mass%, the electrical conductivity of a rare earth metal may fall.

  Next, the ingot is processed into a desired shape. Examples of the processing method include lathe processing, milling, wire cut electric discharge processing, laser cutting, fine blanking, dicing, planar, water jet and the like.

  Since the surface contamination by the processing jig remains on the processed surface of the processed member, it is necessary to remove such contamination. For example, Fe, Ni, Cr contamination by a milling tool, Cu, Zn contamination by wire cut electric discharge machining, and the like can be mentioned.

  As a method for removing surface contamination, polishing, ultrasonic cleaning, mineral acid cleaning, and alkali cleaning can be mentioned. However, polishing cannot diffuse the surface contamination and completely remove the contamination. The ultrasonic cleaning can remove contamination that adheres to the surface, but it cannot remove contamination that sticks to the surface of the material due to the anchor effect, or contamination that dissolves in the main material. In the mineral acid cleaning, metal elements are taken into the oxide film formed on the surface of the rare earth metal during the cleaning, and these metal elements cannot be completely removed. In alkali cleaning, for example, Cu and Zn that are not dissolved in the main material with a mixed aqueous solution of ammonia and hydrogen peroxide can be removed, but Fe and the like cannot be removed. As a result of intensive studies by the present inventors on the cleaning method, it has been found that cleaning with an organic acid-based blocking agent is preferable as a method for removing surface contamination.

  Examples of organic acid blocking agents include citric acid, monoammonium citrate, gluconic acid, glycolic acid, ditric triacetate, ethylenediaminetetraacetic acid, diethylenetriaminopentaacetic acid, dihydroxyethyleneglycine, triethanolamine, hydroxyethylenediaminetetraacetic acid, Examples include L-ascorbic acid, malic acid, tartaric acid, oxalic acid, gallic acid, glyceric acid, hydroxybutyric acid, glyoxylic acid and salts thereof. Among these, citric acid and tartaric acid are particularly preferable.

  The organic acid-based blocking agent is preferably diluted with pure water so as to be 0.001 to 1 mol / L, particularly 0.05 to 0.5 mol / L. If the concentration is too low, the cleaning effect is insufficient, and if it is too high, the member may be eroded too much, and it may be difficult to adjust the cleaning time. The processed member is immersed in this solution to dissolve and remove surface contaminants. At this time, cleaning is further promoted by immersion cleaning in an ultrasonic water bath. The immersion time is preferably 30 seconds to 30 minutes depending on the degree of contamination.

  The member after immersion is washed with pure water in order to sufficiently remove adhered components (contaminants). In order to sufficiently remove the adhering component (contaminant) that has entered the concave portion of the member surface, it is preferable to wash in an ultrasonic water bath.

  By the way, when manufacturing ingots by melting rare earth metals, impurity elements are aggregated at crystal grain boundaries. For this reason, when a member made of a crystal having many grain boundaries is used in a halogen gas atmosphere, the grain boundary is selectively etched by the halogen gas. preferable. According to the production method of the present invention, when the major axis diameter of 30 crystals is measured and the average value is taken as the crystal diameter, the crystal diameter is 3 mm or more by setting the metal element other than the rare earth metal to 100 ppm or less. A rare earth metal polycrystalline member having a size can be obtained. Thereby, the corrosion which arises from a grain boundary can be prevented, and the corrosion resistance of a member can be improved. As shown in FIG. 1, the crystal diameter was measured by setting the interval when the outline of the crystal grain was sandwiched between two parallel lines in contact with X as Xmax = major axis diameter. When measuring the crystal diameter, the washed rare earth metal member is immersed in a nital solution (nitric acid 3 VOL% + ethanol 97 VOL%) for about 5 minutes, and then the nital solution is washed with pure water. Rinse thoroughly.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to the following Example.

[Example 1]
Electron beam melting of granular metal yttrium containing 100ppm or less each of metallic elements other than rare earths Na, K, Ca, Mg, Fe, Cr, Cu, Ni, Zn, and Al to produce an ingot of 50 mm x 50 mm x 200 mm did. It was 1.0 mass% when the oxygen content of the obtained ingot was measured by IR combustion method using EMGA-650 by Horiba Ltd. The ingot was sliced by wire-cut electric discharge machining to produce a plate of 5 mm × 20 mm × 20 mm, 5 mm × 40 mm × 100 mm. The machined surface was brass due to brass contamination. This plate was immersed in a 0.25 mol / L citric acid aqueous solution for 10 minutes with stirring. The plate after acid cleaning was washed with pure water and then immersed in pure water for 5 minutes in an ultrasonic bath, and further washed with pure water.

The depth of the surface-washed metal yttrium plate was analyzed by glow discharge mass spectrometry (measuring device: glow discharge mass spectrometer model VG9000 manufactured by Thermo Electron). The analysis results are shown in Table 1. The surface resistivity was 2.178 × 10 ⁻⁴ Ω / □ as measured with a resistivity meter Loresta HP manufactured by Mitsubishi Chemical Corporation.

Subsequently, the cleaned metal yttrium plate was subjected to an exposure test in CF ₄ plasma for 10 hours using an RIE (reactive ion etching) apparatus to measure the etching rate. The etching rate was determined by masking a part of the metal yttrium plate with a polyimide tape and measuring the difference in height with a laser microscope (manufactured by Keyence Corporation, VK-8500). The analysis results are shown in Table 2. For comparison, the quartz etching rate was measured at the same time.
The washed metal yttrium plate was immersed in a nital solution for 5 minutes, then washed with water, and the crystal diameter was measured with a metal microscope BX60M manufactured by Olympus Corporation.

[Example 2]
A plate similar to that in Example 1 was prepared using granular metal dysprosium containing 100 ppm or less of metallic elements other than rare earth elements Na, K, Ca, Mg, Fe, Cr, Cu, Ni, Zn and Al, and citric acid. The surface was washed with an aqueous solution. The results of glow discharge mass spectrometry performed in the same manner as in Example 1 are shown in Table 1. Table 2 shows the results of the plasma etching test. The crystal diameter was 5.7 mm. When the surface resistivity was measured in the same manner as in Example 1, it was 2.056 × 10 ⁻⁴ Ω / □.

[Comparative Example 1]
A plate is prepared in the same manner as in Example 1 using granular metal yttrium containing 100 ppm or less of each of the metal elements Na, K, Ca, Mg, Fe, Cr, Cu, Ni, Zn and Al other than rare earth, The processed surface was polished with silicon carbide polishing paper to remove processing contamination, and the metal yttrium plate was washed with running pure water, then immersed in pure water for 5 minutes in an ultrasonic bath, and further washed with running pure water. The washed metal yttrium plate was analyzed for depth by glow discharge mass spectrometry in the same manner as in Example 1. The analysis results are shown in Table 1.

It is the figure which showed the measuring method of a crystal diameter.

Claims (11)

  A rare earth metal member formed entirely of rare earth metal, wherein the content of one or more metal elements other than the rare earth metal element in a portion within 2 μm in depth from the outermost surface is 100 ppm or less, respectively. Rare earth metal member.   2. The rare earth metal member according to claim 1, wherein the rare earth metal element is one or more selected from Y, Sc, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.   3. The rare earth metal member according to claim 1, wherein the metal element other than the rare earth metal element is an element selected from Na, K, Ca, Mg, Fe, Cr, Cu, Ni, Zn and Al.   4. The rare earth metal member according to claim 1, wherein the content of a metal element other than the rare earth metal element in a portion from the outermost surface to a depth of 300 μm is 100 ppm or less.   A rare earth metal member formed entirely of rare earth metal, wherein the content of one or more metal elements other than the rare earth metal element is 100 ppm or less.   The rare earth metal according to any one of claims 1 to 5, wherein an ingot obtained from a rare earth metal having a content of at least one metal element other than the rare earth metal element is 100 ppm or less. Element.   The rare earth metal member according to any one of claims 1 to 6, wherein the member is a polycrystal of a rare earth metal element, and a crystal diameter of crystal grains constituting the polycrystal is 3 mm or more.   The rare earth metal member according to claim 1, wherein the rare earth metal member is used for a semiconductor manufacturing apparatus or a flat panel display manufacturing apparatus.   The rare earth metal member according to claim 8, which is used in a halogen-based gas or a halogen-based plasma atmosphere.   10. An ingot obtained from a rare earth metal having a content of at least one metal element other than the rare earth metal element of 100 ppm or less is processed, and then washed with an organic acid sequestering agent solution. The manufacturing method of the rare earth metal member of any one of these.   Organic acid sequestering agents are citric acid, monoammonium citrate, gluconic acid, glycolic acid, ditric triacetate, ethylenediaminetetraacetic acid, diethylenetriaminopentaacetic acid, dihydroxyethyleneglycine, triethanolamine, hydroxyethylenediaminetetraacetic acid, L 11. The method for producing a rare earth metal member according to claim 10, wherein the method is selected from ascorbic acid, malic acid, tartaric acid, oxalic acid, gallic acid, glyceric acid, hydroxybutyric acid, glyoxylic acid, and salts thereof.

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