Low temperature plasma enhanced chemical vapor deposition of thin films combining mechanical stiffness, electrical insulation, and homogeneity in microcavities

Abstract

The deposition of hydrogenated amorphous carbon (a-C:H) as well as hydrogenated amorphous silicon carbonitride (SiCN:H) films was investigated in view of a simultaneous realization of a minimum Young’s modulus (>70 GPa), a high electrical insulation (≥1 MV/cm), a low permittivity and the uniform coverage of microcavities with submillimeter dimensions. For the a-C:H deposition the precursors methane (CH4) and acetylene (C2H2) were used, while SiCN:H films were deposited from mixtures of trimethylsilane [SiH(CH3)3] with nitrogen and argon. To realize the deposition of micrometer thick films with the aforementioned complex requirements at substrate temperatures ≤200 °C, several plasma enhanced chemical vapor deposition methods were investigated: the capacitively coupled rf discharge and the microwave electron cyclotron resonance (ECR) plasma, combined with two types of pulsed substrate bias. SiCN:H films deposited at about 1 Pa from ECR plasmas with pulsed high-voltage bias best met the requirements. Pulsed biasing with pulse periods of about 1 μs and amplitudes of about −2 kV was found to be most advantageous for the conformal low temperature coating of the microtrenches, thereby ensuring the required mechanical and insulating film properties.