Methods for depositing an amorphous carbon layer onto a substrate, including over previously formed layers on the substrate, use a plasma-enhanced chemical vapor deposition (PECVD) process. In particular, the methods utilize a combination of RF AC power and pulsed DC power to create a plasma which deposits an amorphous carbon layer with a high ratio of sp3 (diamond-like) carbon to sp2 (graphite-like) carbon. The methods also provide for lower processing pressures, lower processing temperatures, and higher processing powers, each of which, alone or in combination, may further increase the relative fraction of sp3 carbon in the deposited amorphous carbon layer. As a result of the higher sp3 carbon fraction, the methods provide amorphous carbon layers having improved density, rigidity, etch selectivity, and film stress as compared to amorphous carbon layers deposited by conventional methods.