Method of forming highly conformal amorphous carbon layer

A method of forming a conformal amorphous hydrogenated carbon layer on an irregular surface of a semiconductor substrate by plasma CVD, said irregular surface being constituted by a top surface and multiple recesses, each recess having a side wall and a bottom surface, said side wall being substantially or nearly perpendicular to the top surface, said bottom surface being substantially or nearly parallel to the top surface, said method comprising:

• vaporizing a hydrocarbon-containing precursor;
• introducing said vaporized precursor and an argon gas into a CVD reaction chamber inside which the semiconductor substrate is placed;
• depositing a conformal amorphous hydrogenated carbon layer on the irregular surface of the semiconductor substrate by plasma polymerization of the precursor;
• and
• controlling the deposition of the conformal ratio of the depositing conformal amorphous hydrogenated carbon layer, said controlling comprising (a) adjusting a step coverage of the conformal amorphous hydrogenated carbon layer to about 30% or higher as a function of substrate temperature, and (b) adjusting a conformal ratio of the conformal amorphous hydrogenated carbon layer to about 0.9 to about 1.1 as a function of RF power and/or argon gas flow rate,
• said step coverage being defined as a ratio of an average thickness of a portion of the conformal amorphous hydrogenated carbon layer deposited on the side wall of the recess to an average thickness of a portion of the conformal amorphous hydrogenated carbon layer deposited on the top surface, said conformal ratio being defined as a ratio of a thickness of a portion of the conformal amorphous hydrogenated carbon layer deposited at a top of the side wall of the recess to a thickness of a portion of the conformal amorphous hydrogenated carbon layer deposited at a midpoint of the side wall of the recess or at a lowest point along the side wall of the recess if the lowest point is higher than the midpoint.