Selective wet etching of high-k gate dielectrics

The expected process sequence for high-k gate dielectrics requires etching of the high-k film using the polysilicon gate electrode as a mask. The leading high-k material candidates, the oxides and silicates of hafnium and zirconium, are very difficult to etch with good selectivity to other exposed SiO2 features. We have developed a series of high-k etch chemistries that provide good etch rates of metal silicate films and good selectivity to SiO2.