Effect of Ti- capping on the formation of Co film deposited by metal organic chemical vapor deposition

Abstract

Metal silicides have been widely applied to the advanced semiconductor devices such as contacts, gate electrodes and interconnect. Among the metal silicides, Co-disilicide (CoSi2) is considered as a one of good choices due to its good thermal and chemical stability, low resistivity, and close lattice mismatch with the Si substrate. Because of these advantages, CoSi2 has been extensively investigated for the application in ultra-large-scale integration (ULSI) devices. However, the problem for the use of CoSi2 is the rough interface formation and the impurity incorporation such as oxygen. A possible solution for these problems is to use capping layer. Particularly, the use of Ti capping layer improves the interface roughness and oxygen incorporation in CoSi2. In this work, we studied Co films deposited by metal organic chemical vapor deposition (MOCVD) method using dicobalt (hexacarbony) tertbutylacetylene [C12H10O6(Co)2, CCTBA] as a Co precursor with H2 as a reactant gas. The impurity concentration in the as-deposited Co films decreased with increasing process pressure. At the process pressure of 10 Torr, the carbon and oxygen contents of as-deposited Co film were below 2 at.% and 1 at.%, respectively. And then Ti capping layer was deposited on these Co film by E-beam evaporation without vacuum breaking. For the comparison CoSi2 film formed without Ti capping layer and its formation temperature and surface and interface morphologies are examined with TEM, XRD, SEM and AFM. And the chemical and electrical characteristics of CoSi2 films were analyzed by AES, RBS and a four-point probe technique.