Rare earth fluoride spray powder and rare earth fluoride-sprayed article

Abstract

A powder comprising rare earth element fluoride particles having an aspect ratio of up to 2, an average particle size of 10-100 m, a bulk density of 0.8-1.5 g/cm³, and a carbon content of 0.1-0.5 wt % is amenable to atmospheric plasma spraying. An article obtained by spraying the rare earth fluoride spray powder to a substrate undergoes few partial color changes and performs well even when used in a halogen gas plasma.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2011-246164 filed in Japan on Nov. 10, 2011, the entire contents of which are hereby incorporated by reference.TECHNICAL FIELD[0002]This invention relates to a rare earth element fluoride thermal spray powder, especially suited for use to form a sprayed coating having corrosion resistance in a halogen-based corrosive gas plasma atmosphere as encountered in the semiconductor device fabrication process, and a rare earth element fluoride-sprayed article.BACKGROUND ART[0003]In the prior art, sprayed coatings having corrosion resistance are used for protecting substrates in a variety of service environments. While aluminum, chromium and similar metal oxides are often used as the thermal spray material, these spray materials are inadequate for use in the semiconductor fabrication process which may include exposure to hot plasma, corrosive attacks, ...

AI Technical Summary

Benefits of technology

[0016]The rare earth element fluoride spray powder defined herein is amenable to atmospheric plasma spraying. An article obtained by spraying the rare earth element fluoride spray powder to a substrate undergoes few partial color changes and performs well until its own long life even when used in a halogen gas plasma.

[0017]One embodiment of the invention is a rare earth element fluoride thermal spray powder comprising rare earth element fluoride particles having an aspect ratio of up to 2 as shape index, an average particle size of 10 m to 100 m, a bulk density of 0.8 g/cm3 to 1.5 g/cm3, and a carbon content of 0.1% to 0.5% by weight. This thermal spray powder is effective for plasma spraying a rare earth element fluoride in air. In general, the thermal spray powder should desirably meet the requirements including (1) smooth flow and (2) that the material is not decomposed by plasma spraying. The rare earth element fluoride spray powder defined herein has these advantages.

[0018]The thermal spray powder should preferably comprise particles of spherical shape. When a spray powder is fed into a flame for thermal spraying, a poor fluidity may make the powder inconvenient to feed such as by clogging a feed tube. To ensure smooth flow, the spray powder should preferably consist of spherical particles. The particles have an aspect ratio of up to 2, preferably up to 1.5. The “aspect ratio” is used herein as one shape index of the three dimensions and refers to a ratio of length to breadth of a particle.

[0019]The rare earth element used in the rare earth element fluoride spray powder may be selected from among yttri

Problems solved by technology

While aluminum, chromium and similar metal oxides are often used as the thermal spray material, these spray materials are inadequate for use in the semiconductor fabrication process which may include exposure to hot plasma, corrosive attacks, and in particular, treatment in a halogen-based corrosive gas plasma atmosphere.

On the other hand, the rare earth fluoride