Charge-free layer by layer etching of dielectrics

A method for etching a substrate, comprising:

• providing a plasma chamber equipped with a first gas supply;
• providing a neutralization chamber, equipped with a second gas supply, which is in communication with the plasma chamber by way of an acceleration grid;
• oscillating the gas flow into the plasma chamber and neutralization chamber between a first state in which the gas flow into the plasma chamber has the composition ƒ11 and the gas flow into the neutralization chamber has the composition ƒ21, and a second state in which the gas flow into the plasma chamber has the composition ƒ12 and the gas flow into the neutralization chamber has the composition ƒ22;
• and
• oscillating the potential applied to the acceleration grid such that the voltage applied to the grid is V1 when the gas flow into the plasma chamber is in the first state, and the voltage applied to the grid is V2 when the gas flow into the plasma chamber is in the second state.

An apparatus for etching a dielectric film, comprising:

• an acceleration grid having a variable potential;
• a first chamber equipped with a first gas supply and being adapted to generate a plasma;
• a second chamber equipped with a second gas supply, wherein the second chamber is in communication with the first chamber by way of said acceleration grid;
• a first oscillator adapted to oscillate the gas flow into the plasma chamber between a first state in which the gas flow into the first chamber has the composition ƒ11 and the gas flow into the second chamber has the composition ƒ21, and a second state in which the gas flow into the first chamber has the composition ƒ12 and the gas flow into the second chamber has the composition ƒ22;
• and
• a second oscillator adapted to oscillate the potential applied to the acceleration grid such that the voltage applied to the grid is V1 when the gas flow into the plasma chamber is in the first state, and the voltage applied to the grid is V2 when the gas flow into the plasma chamber is in the second state.