Patent ID: 8051799

Claim:
An apparatus, comprising: a housing defining a chamber having a gas inlet and outlet in which an electric field is generated by upper and lower electrodes; and an internal ring-shaped member provided in said chamber, wherein at least one part of said internal ring-shaped member, every sidewall portion of the chamber, and said gas inlet and outlet are formed of a first dielectric material, wherein said electric field causes formation of a second dielectric deposit on the first dielectric material on the at least one part of said internal ring-shaped member including the sidewall portions, such that an m 1 (d∈ 1 /dm 1 ) value of said first dielectric material and an m 2 (d∈ 2 /dm 2 ) value of said second dielectric deposit are different from each other and are set so that production of particles from said second dielectric deposit is controlled, m 1 being a mass density of said first dielectric material, ∈ 1 being a permittivity of said first dielectric material, m 2 being a mass density of said second dielectric deposit, and ∈ 2 being a permittivity of said second dielectric deposit, wherein the internal ring-shaped member is provided to position a wafer on the lower electrode or is provided surrounding the upper electrode.