Methods and systems for dry etching

A dry etching method, comprising:

• generating a plasma in a plasma generating chamber;
• and
• flowing the plasma through a showerhead to dry etch a substrate in a plasma treatment chamber;
• wherein the showerhead comprises a perforated plate that comprises in sequence from a center of the perforated plate radially outward:
• a primary solid zone having no holes;
• a first annular zone having a first hole percentage of from about 7% to about 11%;
• a secondary solid zone having no holes;
• a second annular zone having a second hole percentage of from about 15% to about 24%;
• a third annular zone having a third hole percentage of from about 9% to about 14%;
• and
• a fourth annular zone having a fourth hole percentage of from about 49% to about 69%.

A dry etching method, comprising:

• generating a plasma in a plasma generating chamber;
• and
• flowing the plasma through a showerhead to dry etch a substrate in a plasma treatment chamber;
• wherein the showerhead comprises a perforated plate that comprises in sequence from a center of the perforated plate radially outward:
• a primary solid zone having an outer radius of about 3 mm to about 38 mm and having no holes;
• a first annular zone having an outer radius of 35 mm to about 53 mm and having a first total hole area;
• a secondary solid zone having an outer radius of about 45 mm to about 68 mm and having no holes;
• a second annular zone having an outer radius of about 65 mm to about 98 mm and havinga second total hole area;
• a third annular zone having an outer radius of about 80 mm to about 120 mm and having a third total hole area;
• a fourth annular zone having an outer radius of about 110 mm to about 150 mm and having a fourth total hole area;
• wherein the third total hole area is greater than the first total hole area and less than the second total hole area, and the fourth total hole area is greater than the second total hole area.