Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
  • C22C21/08—Alloys based on aluminium with magnesium as the next major constituent with silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/047—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with magnesium as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/05—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys of the Al-Si-Mg type, i.e. containing silicon and magnesium in approximately equal proportions
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
  • C25D11/08—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/16—Pretreatment, e.g. desmutting

Definitions

• the invention relates to a method of manufacturing an aluminium alloy plate of an Al-Mg-Si alloy (also known as a 6XXX-series aluminium alloy) for forming elements of the vacuum chambers of apparatuses for manufacturing semiconductor devices and liquid crystal devices, such as CVD systems, PVD systems, ion-implanting systems, sputtering systems and dry etching systems, and those placed in the vacuum chambers.
• the invention relates also to a method of manufacturing vacuum chamber elements from the Al-Mg-Si alloy plate.
• Reactive gases, etching gases, and corrosive gases containing halogen as a cleaning gas are supplied into the vacuum chambers of apparatuses for manufacturing semiconductor devices and liquid crystal devices, such as CVD systems, PVD systems, ion-implanting systems, sputtering systems and dry etching systems. Therefore, the vacuum chambers are required to have corrosion resistance to corrosive gases (hereinafter, referred to as "corrosive gas resistance"). Since a halogen plasma is often produced in the vacuum chamber, resistance to plasmas (hereinafter, referred to as "plasma resistance”) is also important. Recently, aluminium and aluminium alloy materials have been used for forming elements of the vacuum chamber because aluminium and aluminium alloy materials are light and excellent in thermal conductivity.
• US patent document US-2012/0325381-A1 discloses a manufacturing process for a block of aluminium at least 250 mm thick designed for manufacture of an element for a vacuum chamber, the method comprises casting a block of a given 6XXX-series aluminium alloy, optionally homogenizing said cast block, performing a solution heat treatment directly on the cast and optionally homogenized block, quenching the block, stress relieving of the quenched block by means of cold compression, followed by artificial ageing to a T652 condition.
• a key element of the disclosed process is that prior to the solution heat treatment the block has not been hot or cold worked to reduce its thickness.
• the resultant plate product is a so-called "cast plate".
• a disadvantage of cast plate is that the unavoidable phases resulting from the combination and precipitation at grain boundaries of elements like iron, manganese, magnesium, and silicon, often in an eutectic form after solidification, cannot be fully dissolved in the subsequent processing steps like homogenization and solution heat treatment and remain as sites for crack initiation, thus significantly lowering the mechanical properties (e.g., ultimate tensile strength, elongation, toughness, and others), or as initiators of local corrosion (e.g. pitting corrosion) and are harmful also for final treatments like anodization which is of particular relevance for vacuum chamber elements. Any oxide layer present within the cast alloy will also remain in its original shape therefore also lowering the mechanical properties.
• cast plate products might be produced more cost effective, because substantially the as-cast microstructure is maintained, and strongly depends on the local cooling speed during the casting operation, there is much more variation in mechanical properties as function of the testing location as compared to rolled plate products, rendering cast plates less suitable for many critical applications.
• aluminium alloy designations and temper designations refer to the Aluminium Association designations in Aluminium Standards and Data and the Registration Records, as published by the Aluminium Association in 2019 and are well known to the person skilled in the art.
• the temper designations are laid down also in European standard EN515.
• up to 0.08% Zn may include an aluminium alloy having no Zn.
• an aluminium alloy plate for vacuum chamber elements comprising the steps of, in this order: (a) providing a rolling feedstock material of an Al-Mg-Si aluminium alloy having a composition comprising of, in wt.%, Mg 0.80% to 1.05%; Si 0.70% to 1.0%; Mn 0.70% to 0.90%; Fe up to 0.20%; Zn up to 0.08%, preferably up to 0.05%; Cu up to 0.05%, preferably up to 0.03%; Cr up to 0.03%, preferably up to 0.02%; Ti up to 0.06%, preferably 0.01% to 0.06%; unavoidable impurities each ⁇ 0.03%, total ⁇ 0.10%, balance aluminium; (b) homogenizing of the rolling feedstock at a temperature in a range of 550°C to 595°C; (c) hot-rolling of the homogenized rolling feedstock in one or more rolling steps to a
• the resultant aluminium alloy plate is ideally suitable for manufacturing vacuum chamber elements. It is available in a wide range of thicknesses and is very good anodisable with a hard anodic coating.
• the aluminium plate material has high mechanical properties providing good shape stability of the vacuum chamber element. Several properties of an anodised element depend on the plate material's microstructure and composition.
• the plate product has a microstructure having a uniform distribution of phases within the plate leading to a less affected anodic layer concerning e.g. plate thickness and uniformity at the surface after anodisation.
• the resultant plate product according to this invention provides a high corrosive gas resistance, e.g. as tested in a bubble test using 5% HCI; and has a high breakdown voltage (AC, DC) measured according to ISO-2376(2010).
• the Al-Mg-Si alloy plate at thickness 55 mm in T651 condition has a tensile yield strength (YS) of at least 250 MPa, and even of at least 265 MPa, in the LT-direction in accordance with the applicable norm ISO 6892-1 B.
• YS tensile yield strength
• the Al-Mg-Si alloy plate at thickness 55 mm in T651 condition has a tensile strength (UTS) of at least 300 MPa, and even of at least 310 MPa, in the LT-direction in accordance with the applicable norm ISO 6892-1 B.
• UTS tensile strength
• the Al-Mg-Si alloy plate at thickness 55 mm in T651 condition has an elongation (A 50mm ) at least 8%, and even of at least 10%, in the LT-direction in accordance with the applicable norm ISO 6892-1 B.
• Mg in combination with Si are the main alloying elements in the aluminium alloy to provide strength by the formation of Mg 2 Si phases.
• the Mg should be in a range of 0.80% to 1.05%, and preferably in a range of 0.85% to 1.05%.
• a preferred upper-limit for the Mg content is 1.0%.
• a too high Mg content may lead to lead to the formation of coarse Mg 2 Si phases having an adverse effect of the quality of a subsequently applied anodisation coating.
• a too low Mg content has an adverse effect on the tensile properties of the aluminium plate.
• the Si should be in a range of 0.70% to 1.0%.
• the Si content is at least 0.75%, preferably at least 0.80%, and most preferably at least 0.84%.
• the upper-limit for the Si-content is 0.95%.
• the ratio of Mg/Si, in wt.% is more than 0.9, and preferably more than 1.0, and most preferably more than 1.05. Reducing the amount of free Si in the aluminium alloy favours an increased elongation in the aluminium plate after SHT at relative high temperatures as done in accordance with the invention.
• Mn Another important alloying element is Mn and should be in a range of 0.70% to 0.90% to increase the strength in the aluminium plate and to control the grain structure and leads recrystallisation after solution heat treatment and quenching.
• a preferred lower limit is 0.75%.
• a preferred upper-limit is 0.85%.
• Fe is an impurity element which should not exceed 0.20%.
• the Fe level is preferably up to 0.12%. However, it is preferred that at least 0.03% is present, and more preferably at least 0.04%.
• a too low Fe content may lead to undesirable recrystallized grain coarsening and makes the aluminium alloy too expensive.
• a too high Fe content results in reduced tensile properties and has an adverse effect on for example the breakdown voltage after anodisation due to the formation of amongst others AlFeSi phases and has also an adverse effect on the corrosive gas resistance.
• Zn up to about 0.08%, Cu up to about 0.05%, and Cr up to about 0.03% are tolerable impurities and have an adverse effect on the quality of a subsequently applied anodisation coating, e.g. reduced corrosive gas resistance.
• the Zn is up to about 0.05%, and preferably up to about 0.03%.
• the Cu is up to about 0.03%, and preferably up to about 0.02%.
• the Cr is up to about 0.02%.
• Ti up to 0.06% is added as a grain refiner of the as-cast microstructure. In an embodiment it is present in a range of about 0.01% to 0.06%, and preferably in a range of about 0.01% to 0.04%.
• Impurities are present up to 0.03% each and up to 0.10% total.
• the Al-Mg-Si aluminium alloy has a composition consisting of, in wt.%, Mg 0.80% to 1.05%, Si 0.70% to 1.0%, Mn 0.70% to 0.90%, Fe up to 0.20%, Zn up to 0.08%, Cu up to 0.05%, Cr up to 0.03%, Ti up to 0.06%, unavoidable impurities each up to 0.03%, total up to 0.10%, balance aluminium, and with preferred narrower ranges as herein described and claimed.
• the Al-Mg-Si-Mn aluminium alloy is provided as an ingot or slab for fabrication into a hot rolled plate product by casting techniques regular in the art for cast products, e.g. Direct-Chill (DC)-casting, Electro-Magnetic-Casting (EMC)-casting, Electro-Magnetic-Stirring (EMS)-casting, and preferably having an ingot thickness in a range of about 220 mm or more, e.g. 400 mm, 500 mm or 600 mm.
• the as-cast ingot is commonly scalped to remove segregation zones near the cast surface of the ingot.
• Grain refiners such as those containing titanium and boron, or titanium and carbon, are used as is well-known in the art to obtain a fine as-cast grain structure.
• the purpose of a homogenisation heat treatment has at least the following objectives: (i) to dissolve as much as possible coarse soluble phases formed during solidification, and (ii) to reduce concentration gradients to facilitate the dissolution step.
• a preheat treatment achieves also some of these objectives.
• the homogenisation process is done a temperature range of 550°C to 595°C.
• the homogenization temperature is at least 555°C, and more preferably at least 565°C.
• the soaking time at the homogenisation temperature is in the range of about 1 to 20 hours, and preferably does not exceed about 15 hours, and is more preferably in a range of about 5 to 15 hours.
• the heat-up rates that can be applied are those which are regular in the art.
• the hot rolling is performed to a hot rolling plate thickness of 10 mm or more.
• the upper-limit is about 230 mm, preferably about 200 mm and more preferably about 180 mm.
• a next important process step is solution heat treating ("SHT") of the hot rolled plate material.
• the plate product should be heated to bring as much as possible all or substantially all portions of the soluble alloying elements into solution.
• the SHT is preferably carried out at a temperature in the temperature range of about 540°C to 590°C.
• a higher SHT temperature provides more favourable mechanical properties, e.g. an increased R m .
• the lower-limit for the SHT temperature is 545°C, preferably it is 550°C.
• the upper-limit for the SHT temperature is about 580°C, and more preferably about 575°C.
• a low SHT temperature reduces the strength of the aluminium plate and some large Mg 2 Si phases main remain undissolved and may create so called "hot spots" and reducing the corrosion resistance after anodization and reduce the breakdown voltage. It is believed that shorter soaking times are very useful, for example in the range of about 10 to 180 minutes, preferably in a range of 10 to 40 minutes, and more preferably in a range of 10 to 35 minutes, for example for plate thicknesses up to 50 mm.
• a too long soaking time at a relative high SHT temperature results in the growth of several phases adversely affecting the ductility of the aluminium plate.
• the SHT is typically carried out in a batch or a continuous furnace.
• the plate material be cooled with a high cooling rate to a temperature of 100°C or lower, preferably to below 40°C, to prevent or minimise the uncontrolled precipitation of secondary phases.
• cooling rates should preferably not be too high to allow for a sufficient flatness and low level of residual stresses in the plate product. Suitable cooling rates can be achieved with the use of water, e.g. water immersion or water jets.
• the SHT and quenched plate material is further cold worked, preferably by means of stretching in the range of about 1% to 5% of its original length to relieve residual stresses therein and to improve the flatness of the plate product.
• the stretching is in the range of about 1.5% to 4%, more preferably of about 2% to 3.5%.
• the stretched plate material is aged, preferably artificially aged, more preferably to provide a T6 condition, more preferably a T651 condition.
• the artificial ageing is performed at a temperature in the range of 150°C to 190°C, and preferably for a time of 5 to 60 hours.
• the stretch plate material is aged to an over-aged T7 condition, preferably to a T74 or T76 condition, and more preferably to an T7651 condition.
• a vacuum chamber element in a further aspect of the invention it relates to a method of manufacturing a vacuum chamber element, the method comprising the steps of manufacturing the Al-Mg-Si alloy plate having a thickness of at least 10 mm as herein set forth and claimed, and further comprising the subsequent steps of:
• the anodization is performed using an electrolytic solution comprising at least sulfuric acid at a temperature about 15°C to 30°C and a current density from about 1.0 A/dm 2 to about 2 A/dm 2 .
• the acid concentration in the anodizing bath is typically in a range of about 5 to 20 vol.%.
• the process takes from about 0.5 to 60 minutes, depending on the desired oxide layer thickness.
• the sulfuric anodizing generally yields an oxide layer with a thickness from about 8 microns to about 40 microns.
• the anodization is performed in an electrolytic solution comprising at least sulfuric acid at a temperature from about 0°C to about 10°C and a current density from about 3 A/dm 2 to about 4.5 A/dm 2 .
• the process generally takes from about 20 minutes to about 120 minutes.
• This hardcoat anodizing generally yields an oxide layer with a thickness from about 30 microns to about 80 microns, or even thicker.
• the invention relates to a method of manufacturing an aluminium alloy plate for vacuum chamber elements, the method comprising the steps of: (a) providing a rolling feedstock material of an Al-Mg-Si aluminium alloy having a composition comprising of, in wt.%, Mg 0.80%-1.05%, Si 0.70%-1.0%, Mn 0.70%-0.90%, Fe up to 0.20%, Zn up to 0.08%, Cu up to 0.05%, Cr up to 0.03%, Ti up to 0.06%, unavoidable impurities and balance aluminium; (b)homogenizing of the rolling feedstock at a temperature in a range of 550-595°C; (c) hot-rolling of the homogenized rolling feedstock in one or more rolling steps to a hot-rolled plate having a thickness of at least 10 mm; (d) solution heat-treatment (SHT”) of the hot rolled plate at a temperature in a range of 540-590°C; (e) rapid cooling the SHT plate; (f) stretching of the

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• 2020
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