Methods and apparatus for the optimization of highly selective process gases

In a capacitively-coupled plasma processing system, a method for etching a barrier material of a semiconductor substrate, said barrier material selected from the group consisting of SiCN, SiON, and Si3N4, the method comprising:

• placing said semiconductor substrate in a plasma processing chamber of said plasma processing system, wherein said semiconductor substrate includes said barrier material and a low-k material, said low-k material representing one of Orthosilicate glass (OSG) and a Spin-On Dielectric (SOD);
• flowing an etchant gas mixture into said plasma processing chamber, wherein said etchant gas mixture comprises CH3F, Ar, CF4, O2, and CO;
• and
• striking a plasma from said etchant gas mixture, said plasma etching said barrier material and said low-k material at a chamber pressure between 40 m Torr and 200 m Torr, wherein said plasma is configured to etch said barrier material at a first etch rate, said plasma is configured to etch said low-k material at a second etch rate, and said first etch rate is greater than said second etch rate.