Deposition properties of selective tungsten chemical vapor deposition

Abstract

This work investigates the basic deposition properties of selective tungsten chemical vapor deposition (W-CVD) using the process of silane reduction of WF6 with the SiH4/WF6 flow rate ratio less than 0.6 over the temperature range 280–350 °C. Selective W-CVD was performed on a contact hole patterned silicon substrate with in situ NF3 plasma etching of the silicon substrate prior to the selective tungsten deposition. The W deposition rate, deposition selectivity and W film resistivity were investigated with respect to the SiH4 partial pressure, WF6 partial pressure, total (SiH4 + WF6) deposition pressure, as well as the flow rate of the hydrogen carrier gas. It was found that the deposition rate is proportional to the SiH4 partial pressure. With a constant SiH4/WF6 flow rate ratio, the deposition rate increases with total pressure. At given flow rates of SiH4 and WF6, the deposition rate and film resistivity are dependent on the flow rate of the carrier gas. The experimental results show that the reverse bias junction leakage for the wet etching pretreated W/p+-n junction diode is smaller than that of the plasma pretreated diode. On the other hand, the contact resistance of the Al/W/n+p diode is smaller than that of the Al/W/p+n diode.