Methods and apparatus for processing a substrate

An apparatus for processing a substrate, comprising:

• at least one of a high frequency RF power generator or a low frequency RF power generator;
• an upper electrode and a lower electrode operatively connected to the at least one of the high frequency RF power generator or the low frequency RF power generator;
• a controller programmed to:
• apply at least one of low frequency RF power or DC power to the upper electrode formed from a high secondary electron emission coefficient material disposed adjacent to a process volume;
• generate a plasma comprising ions in the process volume;
• control the at least one of low frequency RF power or DC power to the upper electrode such that the ions bombard the upper electrode to cause the upper electrode to emit secondary electrons and form an electron beam;
• control at least one of low frequency RF power or high frequency RF power to apply a bias power to the lower electrode disposed in the process volume to accelerate electrons of the electron beam toward the lower electrode to form an etch feature on a substrate with no charging effect;
• apply the at least one of low frequency RF power or DC power in a continuous mode to the upper electrode;
• and
• when the bias power comprises low frequency RF power, apply the low frequency RF power to the lower electrode in a pulsing mode, such that a given pulse of low frequency RF power provides a voltage to the lower electrode that is less than a voltage applied to the upper electrode during at least some portion of a sinusoidal cycle of the low frequency RF power.