Characterization of sputter-induced temperature effect in fluorine doped SiO₂ film deposition by high-density plasma chemical vapor deposition

High-density plasma chemical vapor deposited fluorosilicate glass (FSG) has been successfully used for the inter-metal dielectric material in ultra-large semiconductor integration manufacturing due to its low-dielectric constant and stable gap-filling capability. However, temperatures rise and related effects due to sputter etch from the deposition process have become major concerns for film properties. In this paper, an independent helium-cooling system was employed to control a suitable temperature range from 410 °C to 460 °C during FSG deposition. Subsequently, film properties including fluorine concentration, distribution, refractive index, dielectric constant and gap-filling capability were thus examined as a function of He pressure used in the cooling system. The results show that both deposition rate and fluorine concentration increase with increasing helium pressure; however, more fluorine becomes inactive, which might be present as defects. We have shown that an FSG film with a dielectric constant down to 3.43 as well as good gap-filling capability can be achieved when employing this new cooling system with 9 mTorr helium pressure.