Plasma etching techniques

A method for processing a semiconductor substrate, the method comprising:

• positioning a semiconductor substrate in a plasma chamber of a plasma tool, the semiconductor substrate comprising a film stack that comprises silicon layers and germanium-containing layers in an alternating stacked arrangement, with at least two silicon layers and at least two germanium-containing layers;
• generating, in the plasma chamber of the plasma tool, a plasma that comprises fluorine agents, nitrogen agents, and hydrogen agents, the plasma being generated from gases comprising a fluorine-containing gas, a nitrogen-containing gas, a hydrogen-containing gas, and a noble gas;
• and
• exposing, in the plasma chamber of the plasma tool, the film stack to the plasma, the plasma causing a nitride passivation layer to be formed on exposed surfaces of the silicon layers and selectively etching opposing exposed ends of the germanium-containing layers to form indents in the germanium-containing layers relative to opposing exposed ends of the silicon layers, the nitride passivation layer inhibiting etching of the silicon layers by the plasma.

A method for processing a semiconductor substrate, the method comprising:

• positioning a semiconductor substrate in a plasma chamber of a plasma tool, the semiconductor substrate comprising a film stack that comprises first layers of a first material and second layers of a second material in an alternating stacked arrangement, the first material being a germanium-containing material that includes germanium at a concentration of about ten to about fifty percent;
• generating a plasma for selectively etching the first layers of the first material, generating the plasma comprising introducing gases including fluorine, nitrogen, hydrogen, and a noble gas into the plasma chamber and maintaining a pressure in the plasma chamber of less than about 50 millitorr;
• and
• exposing, in the plasma chamber, the film stack to the plasma for a time period, the plasma causing a nitride passivation layer to be formed on exposed surfaces of the second layers of the second material and selectively etching opposing exposed ends of the first layers of the first material to form indents in the first layers of the first material relative to opposing exposed ends of the second layers of the second material.