Etch back without a sacrificial layer

Despite the fact that a good etch back process is of prime importance for the success of a blanket plug process, not much has been 

Let us have a somewhat closer look at each of these constraints. 

Etch uniformity This has been highlighted under section 2.3.4. It is clear that for maximal process latitude the etch rate non-uniformity but also the tungsten thickness uniformity should be minimal. 

Selectivity Depending upon what adhesion layer is used different requirements will be needed in terms of etch rate selectivity of tungsten versus the oxide or the adhesion layer. Two cases can be distinguished  

Loading effects At the end of the etch back process two mechanisms (so called loading effects [van Laarhoven et al.61, Berthold et al.62]) can dramatically increase the etch rate of the plugs in the contacts  

---