Silicon mandrel etch after native oxide punch-through

A method for removing a silicon structure disposed on a workpiece, the workpiece disposed in a second chamber that is separated from a first chamber by a separation grid, the separation grid comprising a first grid plate disposed adjacent to the first chamber, a second grid plate disposed between the first grid plate and the third grid plate, and a third grid plate disposed adjacent to the second chamber, wherein the first grid plate, the second grid plate, and the third grid plate spaced in parallel relationship to one another, the method comprising:

• generating a capacitively coupled plasma using a capacitively coupled plasma source in a second chamber, wherein the capacitively coupled plasma is generated at a power of about 1 W up to about 150 W;
• exposing the silicon structure of the workpiece to the capacitively coupled plasma to remove at least a portion of a native oxide layer on top of the silicon structure;
• subsequent to exposing the silicon structure of the workpiece to the capacitively coupled plasma, generating species from a process gas using an inductive coupling element in the first chamber;
• introducing a fluorine containing gas with the species to create a mixture, wherein the fluorine containing gas is introduced by a gas injection source disposed between the second grid plate and the third grid plate;
• and
• exposing the silicon structure of the workpiece to the mixture to remove at east a portion of the silicon structure.