Investigation of oxide layer removal mechanism using reactive gases

Etch rate of SiO2 and Si3N4 as a function of NH3/NF3 ratio.Display Omitted Etch rates were estimated as a function of various factors.NF3/NH3 dry etching is strongly related to NH4F concentration.As the temperature increases, the by-product removal time is reduced. In a CMOS technology, the removal of silicon oxide and nitride layer is one of the critical steps as it represents a possible source of high contact resistance and a decrease of gate oxide reliability. In high aspect ratio (HAR), it is very difficult to remove SiO2 with wet etching. In the present study, the effect of the gases such as plasma dry etching of ammonia (NH3) and nitrogen trifluoride (NF3) on the SiO2 and Si3N4 substrates were analyzed and the etch rate was measured. The measurement of the SiO2 and Si3N4 thickness was measured by Ellipsometer. Various factors such as chamber pressure, electrode power and NH3/NF3 gas ratio were affected by the combination and dissociation of NH4F molecules. The existence of the by-product was analyzed by using a contact angle analyzer and scanning electron microscope, respectively. In this study we have found that, the removal efficiency was mainly dependent on the reaction mechanism and the effect of the by-product.