Dual Plasma Volume Processing Apparatus for Neutral/Ion Flux Control

A method for processing a semiconductor wafer, comprising:

• placing a semiconductor wafer on a top surface of an electrostatic chuck within a semiconductor wafer processing apparatus, wherein the semiconductor wafer process apparatus includes:
• a gas distribution unit positioned above and spaced apart from the electrostatic chuck, the gas distribution unit having a bottom surface oriented in a substantially parallel orientation with the top surface of the electrostatic chuck, a space between the top surface of the electrostatic chuck and the bottom surface of the gas distribution unit forming a lower plasma generation volume, the gas distribution unit configured to receive and distribute a process gas to the lower plasma generation volume, the gas distribution unit including an arrangement of through-holes extending from the bottom surface of the gas distribution unit to a top surface of the gas distribution unit, and
• an outer lower structural member configured to circumscribe the gas distribution unit and support the gas distribution unit in its position above and spaced apart from the electrostatic chuck, and
• a showerhead electrode positioned above and spaced apart from the gas distribution unit, the showerhead electrode having a bottom surface oriented in a substantially parallel orientation with the top surface of the gas distribution unit, a space between the bottom surface of the showerhead electrode and the top surface of the gas distribution unit forming an upper plasma generation volume, and
• an outer upper structural member configured to circumscribe the showerhead electrode and support the showerhead electrode in its position above and spaced apart from the gas distribution unit, and
• an exhaust channel configured to extend in a radial direction outward from a perimeter of the upper plasma generation volume, the exhaust channel configured to circumscribe the upper plasma generation volume and extend radially outward between the outer upper structural member and the outer lower structural member, and
• a throttle ring configured to move vertically within a conformally defined recessed region within the outer upper structural member so as to extend vertically into the exhaust channel by a controlled amount of distance;
• operating the electrostatic chuck to hold the substrate;
• flowing a first process gas through the showerhead electrode into the upper plasma generation volume;
• supplying radiofrequency power to the showerhead electrode to transform the first process gas into a plasma within the upper plasma generation volume, wherein reactive constituents of the plasma within the upper plasma generation volume travel through the arrangement of through-holes within the gas distribution unit and into the lower plasma generation volume;
• flowing a second process gas through the gas distribution unit into the lower plasma generation volume;
• and
• supplying radiofrequency power to the electrostatic chuck to transform the second process gas into a plasma within the lower plasma generation volume.