Dual-frequency plasma deposition of high quality insulating thin films

Dual-mode microwave/radiofrequency PECVD processes have been used for the fabrication of four types of amorphous dielectric films: SiN_1.3, SiO₂, a-C:H, and plasma-polymerized hexamethyldisiloxane (PP-HMDSO). For each of these materials, we have determined values of the critical average ion energy E¯_i (between about 70 and 170 eV) and of the critical ion flux, which characterize the transition from a porous to a densely packed microstructure, at low (~25°C) substrate temperature T_s and high deposition rates (between 20 and 120 Å/s). When E¯ _i values are optimized, the d.c. resistivity and the dielectric loss tangent values for all of these dielectrics are found to be about 10¹⁶ Ω cm and 10^-3, respectively. We present evidence which shows that E¯_i and T_s can be considered as interchangeable process parameters. Large area scale-up and continuous deposition onto flexible substrate materials are also discussed