Detection of both Insufficient Buried Contact (IBC) and cell-to-cell short defects is quite a challenging task for failure analysis in submicron Dynamic Random Access Memory (DRAM) devices. A combination of a well-controlled wet etch and high selectivity poly silicon etch is a key requirement in the deprocessing of DRAM for detection of these types of failures. High selectivity poly silicon etch methods have been reported using complicated system such as ECR (Electron Cyclotron Resonance) Plasma system. The fact that these systems use hazardous gases like Cl2, HBr, and SF6 motivates the search for safer alternative deprocessing chemistries. The present work describes high selectivity poly silicon etch using simple Reactive Ion Etch (RIE) plasma system using less hazardous gases such as CF4, O2 etc. A combination of controlled wet etch and high selectivity poly silicon etch have been used to detect both IBC and cell-to-cell shorts in submicron DRAMs.

Removal of polyimide layer after decapsulation of IC package is essential for many of the failure analysis techniques. An alternative method for polyimide removal is described in this paper. The method suggests appropriate modification of dual acid decapsulation system for this purpose. Device integrity is verified after removal of polyimide layer. This method becomes promising for devices which are sensitive / vulnerable for exposure to plasma.