Polarity control for remote plasma

A method of etching a substrate, the method comprising:

• transferring the substrate into a substrate processing region of a substrate processing chamber;
• applying a unipolar oscillating voltage between an electrode and a perforated plate, wherein the unipolar oscillating voltage negatively biases the electrode relative to the perforated plate;
• flowing a halogen-containing precursor into a remote plasma between the electrode and the perforated plate while forming a remote plasma to form plasma effluents;
• flowing the plasma effluents into the substrate processing region housing the substrate, wherein the plasma effluents flow into the substrate processing region through perforations in the perforated plate;
• and
• etching the substrate with the plasma effluents.

A method of etching a patterned substrate, the method comprising:

• transferring the patterned substrate into a substrate processing region of a substrate processing chamber;
• sending a DC voltage through a full bridge of four switching devices to form a unipolar oscillating voltage;
• applying the unipolar oscillating voltage between a concave electrode and a flat nickel-plated perforated plate, wherein the unipolar oscillating voltage biases the concave electrode at a negative voltage relative to the flat nickel-plated perforated plate;
• flowing a fluorine-containing precursor into a remote plasma between the concave electrode and the flat nickel-plated perforated plate while forming a remote plasma to form plasma effluents;
• flowing the plasma effluents into the substrate processing region housing the patterned substrate, wherein the plasma effluents flow into the substrate processing region through perforations in the flat nickel-plated perforated plate;
• and
• selectively etching the patterned substrate with the plasma effluents.