Roles of N-2 gas in etching of platinum by inductively coupled Ar/Cl-2/N-2plasmas

Recently, much effort has been expended on etching platinum film, which is the candidate electrode material for the capacitor structure of future dyna mic random access memory and ferroelectric random access memory. One of the most critical problems in the etching of platinum was generally considered to be the gradual character of the etch slope. Therefore, the addition of N-2 gas into the Ar/Cl-2 gas mixture, which had been proposed as the optimi zed platinum etching gas combination in our previous article, was performed . The selectivity of platinum to oxide as an etch mask increased with the a ddition or N-2 gas, and a steeper etch slope, over 75 degrees, could be obt ained. These phenomena were interpreted as the result of a blocking layer, such as Si-N or Si-O-N, on the oxide mask. Compositional analysis was carri ed out by x-ray photoelectron spectroscopy and secondary ion mass spectrome try. Moreover, the higher etch rate of the Pt film and a steeper profile wi thout residues (such as Pt-Cl and Pt-Pt) could be obtained by the addition of 20% N-2 gas in the Ar(90)/Cl-2(10) plasma. The plasma characteristics we re extracted from optical emission spectroscopy. (C) American Vacuum Societ y. [S0734-2101(00)09404-5].