Pulsed plasma deposition etch step coverage improvement

A method for processing a substrate, comprising:

• forming a dielectric layer on exposed surfaces of one or more trenches in the substrate by a plasma deposition process, wherein a first plasma is formed by a first pulsed RF power in a process chamber;
• densifying the dielectric layer by a plasma treatment to form a treated dielectric layer;
• forming a passivation layer on the treated dielectric layer and within the one or more trenches;
• and
• etching a portion of the treated dielectric layer and the passivation layer by a plasma etch process, wherein a second plasma formed from a gas mixture of a fluorine-containing gas and a carrier gas, wherein the second plasma is formed in the process chamber by a second pulsed RF power, a top portion of the one or more trenches etched at a faster rate than at a bottom surface of the one or more trenches.

A method for processing a substrate, comprising:

• forming a dielectric layer on patterned features of the substrate by a plasma deposition process, wherein a first plasma is formed by a first pulsed RF power in a process chamber;
• densifying the dielectric layer by a plasma treatment using a gas mixture of nitrogen and helium in the process chamber to form a treated dielectric layer;
• forming a first passivation layer on the treated dielectric layer;
• etching the first passivation layer and a portion of the dielectric layer by a plasma etch process to form an etched dielectric layer, wherein a second plasma is formed in the process chamber by a second pulsed RF power at a frequency of about 5 kHz to about 30 kHz to etch a top surface of the patterned features at a faster etch rate than at a bottom sidewall of the patterned features;
• and
• forming a second passivation layer on the etched dielectric layer.