| CPC C23C 16/26 (2013.01) [C23C 16/042 (2013.01); C23C 16/402 (2013.01)] | 27 Claims |

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1. A method comprising:
exposing a semiconductor substrate in a chamber to a process gas comprising a hydrocarbon precursor gas and helium gas, substantially without any other inert gas;
depositing on the substrate an interfacial layer by a first plasma enhanced chemical vapor deposition (PECVD) process, wherein depositing the interfacial layer comprises igniting a plasma generated by a dual radio frequency (RF) plasma source including a high frequency (HF) component and a low frequency (LF) component, wherein the interfacial layer is a carbon-containing layer; and
depositing on the interfacial layer an ashable hard mask (AHM) film by a second PECVD process, wherein the second PECVD process comprises:
maintaining the chamber pressure between about 3 and 30 mTorr;
igniting a plasma generated by the dual RF plasma source including a high frequency (HF) component and a low frequency (LF) component, wherein the HF component and the LF component of the second PECVD process are at a higher power than during deposition of the interfacial layer.
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