High density plasma etching of platinum films in BCl3/Ar and CF4/Ar inductively coupled plasmas

The etch characteristics of platinum films and the etch selectivities for platinum over the mask materials in BCl3/Ar and CF4/Ar ICP discharges have been investigated to establish a process window for the thick platinum structure formation in MEMS devices. Maximum etch rates of ≈1800 Å/minute and ≈1200 Å/minute were obtained at a moderate ICP source power (750 W) and a relatively high rf chuck power (400 W) condition for CF4/Ar and BCl3/Ar ICP discharges, respectively. Maximum etch selectivities of ≈2.6 for platinum over Al and of ≈2.1 for platinum over ZnO were obtained. CF4/Ar ICP etching with aluminum mask layer seems to be a very attractive tool for the fabrication of MEMS devices containing a thick platinum structure layer.