Process for etching dielectric films with improved resist and/or etch profile characteristics

A method of etching openings in a dielectric layer, comprising:

• supporting a semiconductor substrate on a substrate support in a dual frequency medium density capacitively coupled plasma etch reactor, the substrate having a dielectric layer that comprises a stack of layers of low-k materials with or without etch stop layers therebetween, and a patterned photoresist layer and/or hardmask above the dielectric layer;
• supplying to the plasma etch reactor an etchant gas comprising (i) a fluorocarbon gas (CxFyHz, where x≧1, y≧1, and z≧0), comprising at least C4F8, (ii) silane-containing gas, (iii) an optional oxygen-containing gas, and (iv) an optional inert gas;
• wherein the flow rate ratio of silane-containing gas to fluorocarbon gas is less than or equal to 0.1;
• energizing the etchant gas into a plasma state, wherein C4F8 undergoes dissociation according to the stages C4F8→C2F8→CF2→CF +F;
• and
• etching openings in the dielectric layer to depths of at least 2 μm with increased photoresist and/or hardmask to dielectric layer selectivity and decreased photoresist distortion or striation,
• wherein the dielectric layer comprises an inorganic low-k material or an organic low-k material.

A method of etching openings in a dielectric layer, comprising:

• supporting a semiconductor substrate on a substrate support in a plasma etch reactor, the substrate having a dielectric layer and a patterned photoresist layer and/or hardmask above the dielectric layer;
• supplying to the plasma etch reactor an etchant gas comprising (i) a fluorocarbon gas comprising C4F6, (ii) silane-containing gas, (iii) O2 and (iv) an optional inert gas;
• wherein the flow rate ratio of silane-containing gas to fluorocarbon gas is less than or equal to 0.1 and wherein the C4F6 and O2 are supplied to the plasma etch reactor at flow rates having a flow rate ratio of C4F6:O2 of 0.5:1 to 3:1;
• energizing the etchant gas into a plasma state, and
• etching openings in the dielectric layer with increased photoresist andlor hardmask to dielectric layer selectivity and decreased photoresist distortion or striation,
• wherein the dielectric layer comprises an inorganic low-k material or an organic low-k material.