Multi-state pulsing for achieving a balance between bow control and mask selectivity

A method for etching a stack below a mask in a plasma processing chamber, comprising:

• flowing an etch gas comprising a metal fluoride or a tungsten-containing passivant and an etch component into the plasma processing chamber;
• and
• transforming the etch gas into a plasma, comprising:
• generating a primary radio frequency (RF) signal at a first frequency range, wherein the primary RF signal pulses among at least three states including a first state, a second state, and a third state;
• and
• generating a secondary RF signal at a second frequency range, wherein the secondary RF signal pulses among the at least three states and wherein the first frequency range is less than the second frequency range;
• wherein during the second state, the primary RF signal has a power level that is less than 80% of a power level of the primary RF signal during the first state;
• wherein during the third state, the primary RF signal has a power level that is less than 20% of the power level of the primary RF signal during the second state;
• and
• wherein during the third state, a power level of the secondary RF signal is less than 20% of a power level of the secondary RF signal during the second state.