Physical and Electrical Characteristics of Methylsilane- and Trimethylsilane-Doped Low Dielectric Constant Chemical Vapor Deposited Oxides

This work investigates the physical and electrical properties of two species of inorganic C-doped low dielectric constant (low- k ) chemical vapor deposited (CVD) organosilicate glasses (OSGs, α-SiCO:H). They are both deposited by plasma-enhanced CVD (PECVD) processes using methylsilane 1 MS]- and trimethylsilane 3 MS]-based gases as the reagents, and are designated as OSG1 and OSG2, respectively. Experimental results indicate that the thermal stability temperature of OSG1 is 500°C, while that of OSG2 is 600°C, based on the results of thermal annealing for 30 min in an ambient. The deterioration of the low- k property in OSG1 is predominately due to the thermal decomposition at temperatures above 500°C of methyl groups, which are introduced to lower the density and polarizability of OSGs. For the Cu-gated oxide-sandwiched low- k dielectric metal-insulator-semiconductor (MIS) capacitors, Cu permeation was observed in both OSG1 and OSG2 after the MIS capacitors were bias-temperature stressed at 150°C with an effective applied field of 0.8 MV/cm. Moreover, Cu appeared to drift more readily in OSG1 than in OSG2, presumably because OSG1 has a more porous and less cross-linked structure than OSG2. The Cu penetration can be mitigated by a thin nitride dielectric barrier.