INFLUENCES OF DAMAGE AND CONTAMINATION FROM REACTIVE ION ETCHING ON SELECTIVE TUNGSTEN DEPOSITION IN A LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION REACTOR

Reactive ion etching (RIE) used in contact hole formation can result i n damage and contamination of the underlying silicon substrate. In thi s work, influences of these phenomena on selective tungsten deposition in a low-pressure chemical-vapor-deposition reactor have been studied . The damage was generated because of ion bombardment and radiation-in duced bonding changes in silicon lattices. It causes large Si consumpt ion, rough W/Si interface during tungsten deposition, and large leakag e current of W/Si Schottky structure. Simultaneously, contamination oc curred with two forms of residual layers and impurity permeation layer s in fluorocarbon-based RIE chemistries. The CF4/CHF3/O-2 RIE of oxide produces the SiFxCyOz complex layers deposited on the sidewall and on the Si surface as well as the embedding of impurities such as F and C in the Si substrate. The creep-up, selectivity loss, lateral encroach ment, high W film resistivity, and rough W/Si interface have been obse rved in the contaminated samples. Accordingly, a post-RTE etching tech nique used to remove the damage and contaminants before tungsten growt h has been developed. A CF4/O-2 plasma etching followed with an O-2 pl asma ashing step exhibits the capability of efficient surface cleaning . The excellent characteristics of W films such as elimination of encr oachment and creep-up, low selectivity loss (i.e., 0.25 pcs/cm(2)), lo w resistivity of W films, smooth W/Si interface, and very low leakage current of W/Si contacts are thus obtained. (C) 1996 American Institut e of Physics.