Standard Chemistries such as dilute hydrofluoric acid (dHF) and Buffered Oxide Etch (BOE) are not the complete solution for advanced surface preparations.

Application: High Aspect Ratio Contact Clean
Critical Performance Measures: 
               Selective removal of Thermal Oxide (ThOx) without damage to Spin On Dielectrics (SOD) and
                    Doped Oxides(BPSG) 
               Selectivity of TEOS:ThOx and BPSG:ThOx should be less than or equal to 1.0

While removing the etch-generated ThOx from the bottom of the contact, excessive etch of TEOS and BPSG negatively affects the contact critical dimensions (CD).  In every case, the HF solution etches ThOx far slower than other oxide films.  Use of dHF is high aspect ratio contact cleans results in overetching the oxides and poor CDs.  

Application: Sacrificial FEOL Oxide Etching
Critical Performance Measures:
            Fast removal of thermal and doped oxides
            Protection of SiN and TiN films 

When removing sacrificial oxide films in Hardmask and Cylindrical Capacitor applications, fast oxide removal is required, but with excellent protection of exposed SiN structures.  The more dilute HF solutions etch the critical SiN layers far less, but the desired BPSG and TEOS etch rates are too low.

Selectivity is the key to the future of FEOL success.  Let SACHEM help you get there.