Showerhead assembly for plasma processing chamber

A showerhead assembly for a plasma process apparatus for processing substrates, comprising:

• a showerhead body comprising a top plate and a bottom ionization plate, defining a cavity in between;
• a gas inlet formed in the top plate;
• a gas restriction plate positioned between the top plate and the ionization plate and dissecting the cavity into an upper gas compartment and a lower gas compartment and restricting flow such that the upper gas compartment supports a higher gas pressure than the lower gas compartment;
• and,
• wherein the bottom ionization plate comprises a single metallic plate having plurality of elongated ionization slots machined on its lower surface and a plurality of diffusion holes drilled on its upper surface, each of the diffusion holes making fluid connection from the lower gas compartment to more than one of the ionization slots.

A method for fabricating a gas ionization plate for use in a showerhead assembly of a plasma processing chamber, comprising:

• fabricating a plate;
• using gang cutter to form a plurality of gas ionization slots on the lower surface of the plate;
• and,
• drilling a plurality of gas distribution holes from the top surface of the plate such that each of the gas distribution holes reaches and opens to a plurality of the gas ionization slots.