Leakage current mechanisms for damascene process of Cu/methylsilane-doped low-k chemical vapor deposited oxides

This work investigates the leakage current mechanisms in the Cu damascene structure with a methylsilane-doped low-k chemical vapor deposited (CVD) organosilicate glass (OSG) as the intermetal dielectric (IMD). The leakage between Cu lines was dominated by the Frenkel-Poole emission at higher temperatures and at voltages above 5 V. In the structure using a SiN etching stop layer (ESL), the leakage component through SiN also contributed a substantial amount to the total leakage in addition to the bulk leakage from the field-assisted thermal injection of the trapped electrons in OSG. With SiC replacing SiN, the total leakage was greatly reduced due to the negligible leakage contribution through the SiC layer. Moreover, drastically increased leakage was observed in the structure without any passivation.