PECVD trench bottom profile control with pulsed dual RF plasma

A non-transitory computer readable medium including instructions, that, when executed by a controller of a processing chamber, cause the processing chamber to perform operations comprising:

• positioning a substrate in a processing chamber, the substrate having a surface and a feature extending a depth into the surface;
• introducing at least one precursor gas into the processing chamber;
• generating a dual radiofrequency (RF) plasma with the at least one precursor gas by pulsing a first RF power source and a second RF power source, the first RF power source and the second RF power source having different frequencies and being electrically connected to a gas distributor;
• depositing a layer on the substrate with the dual RF plasma to change a bottom profile of the feature from a first shape to a concave shape;
• introducing at least one additional precursor gas into the processing chamber;
• generating an etching plasma by applying the first RF power source to the at least one additional precursor gas;
• and
• etching the layer with the etching plasma.