The influence of Ar addition to a Cl-2/CF4 dry etch gas mix on the etch character of patterned Pt films is evaluated. The incremental substitution of Ar for Cl-2 is shown to be detrimental to the Pt etch process by enhancing the severity of redeposits that form on the sidewalls of the fully etched structures. In addition, the water solubility of this redeposited layer diminishes with increasing Ar concentration. Ultimately, the residue becomes insoluble when Cl-2 is eliminated from the gas mix. This residue dependence on Ar concentration is accompanied by a decrease in the etch rate of the Pt film layer. In order to clarify that the Ar concentration directly contributed to this decrease, additional etch rate measurements were made on blanket Pt films. First, the etch conditions used for the patterned samples were repeated. Then, a second set of measurements were made with CF4 excluded from the gas mix. In both instances, the etch rate of Pt decreased as the percentage of Ar rose. Since the blanket film results were similar to those obtained from the patterned samples, we conclude that neither redeposition of photoresist from the mask or plasma deposition of CF4 cracking fragments strongly influence the observed Pt etch behavior.