Apparatus and method for gas delivery in semiconductor process chambers

A process chamber, comprising:

• a chamber body has a substrate support disposed within an inner processing volume of the chamber body;
• and
• a showerhead disposed within the inner processing volume the chamber body opposite the substrate support, the showerhead comprising:
• at least one gas distribution plate formed of an electroformed, monolithic nickel structure;
• a plurality of gas passageways that extend through an uppermost surface of the gas distribution plate to a lowermost surface of the gas distribution plate, wherein at least one of the plurality of gas passageways has uncoated and non-machined nickel surfaces throughout and wherein the at least one of the plurality of gas passageways has a nonconstant diameter with a curved inner sidewall throughout the gas distribution plate;
• at least one cavity that surrounds one of the plurality of gas passageways internally to the gas distribution plate, wherein the at least one cavity is fluidly separated from any of the plurality of gas passageways;
• an electroformed heatsink material only partially filling the at east one cavity;
• and
• a flange which engages with a periphery of at least one of the at least one gas distribution plate to provide support for mounting to a component of the process chamber.