There has been widely practiced anodic oxidation treatment in which an anodic oxide film is formed on a surface of a member including, as a substrate, aluminum, aluminum alloy, or the like to improve plasma resistance and gaseous corrosion resistance of the substrate. For example, a vacuum chamber used in a plasma treatment apparatus in a semiconductor manufacturing facility or each of various components provided in the inside of the vacuum chamber typically comprises aluminum alloy. However, if the aluminum alloy member is used for such an application while being not treated (while being solid, or as it is formed into a component), the component cannot maintain its plasma resistance, gaseous corrosion resistance, and the like. Consequently, an anodic oxide film is formed on a surface of the member comprising aluminum alloy to improve the plasma resistance, the gaseous corrosion resistance, and the like.
In recent years, power to be applied for plasma generation increases with increase in plasma density due to narrowed interconnection width. In existing anodic oxide films, therefore, dielectric breakdown may be induced by high temperature and high voltage occurring at high power application. Etching uniformity or film formation uniformity is degraded due to varied electric properties at a portion where such dielectric breakdown has occurred; hence, a member to be used is desired to have excellent withstand voltage properties and excellent hot cracking resistance (heat resistance). The insulating member for semiconductor is recently used in a higher temperature environment associated with higher density, smaller size, and higher power of semiconductor, and is recently subjected to higher temperature during a manufacturing process of semiconductor; hence the insulating member is also necessary to have excellent withstand voltage properties and excellent hot cracking resistance (heat resistance). In addition, it is also an important requirement to achieve such demand characteristics at low cost.
There have been proposed various techniques for improving properties of the aluminum alloy member having the anodic oxide film thereon. For example, PTL 1 proposes a technique for improving withstand voltage properties by using an aluminum alloy having higher purity as a substrate to decrease the number of intermetallic compound particles. However, film cracking may occur under high temperature in such an anodic-oxidation-treated aluminum alloy member that is therefore not improved in hot cracking resistance.
PTL 2 proposes an aluminum-alloy metal substrate with an insulating layer for a solar cell, which is improved in withstand voltage properties by minimizing metallic silicon in the aluminum alloy. This technique also does not consider the hot cracking resistance; hence, film cracking may occur under high temperature in the metal substrate.