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ngine versit omach plicati rate, a timize g high ricati 647 A eceive thin films limit aspect ratio and often contain residual stresses, bulk cally in Fig. 1. The titanium samples were mounted on a 6-in. sili-Socie.00 ©titanium may be a more suitable option for certain MEMS applica-tions. Dry etching of high aspect ratio structures in bulk titanium using a cyclic Cl2/Ar process has been demonstrated by the metal aniso-tropic reactive ion etching with oxidation MARIO process, but with relatively low etch rates due to the parallel plate system being used.2 This work reports the characterization of bulk titanium deep etching using Cl2/Ar chemistry with an inductively coupled plasma ICP source. Titanium etch rate, etch rate of a TiO2 masking layer, and roughness of the etched surface have been studied over a large parameter space on patterned samples. The ICP source power, sample rf power, process pressure, and gas flow rates were varied individually and plotted to determine first-order trends associated with each parameter. Based on the results of this etch characteriza-tion, parameters were optimized to develop the titanium ICP deep etch TIDE process for etching high aspect ratio microstructures in thick titanium substrates. Bulk titanium etch rates in excess of 2 m/min with high TiO2 mask selectivity 40:1, Ti:TiO2 were realized. The TIDE process can also be used to etch thin titanium con carrier wafer using diffusion pump fluid Santovac 5, polyphenyl ether pump fluid, Santovac Fluids, Inc., St. Charles, MO, which was used to create adequate thermal conductivity be-tween carrier wafer and sample. The lower electrode of the etching tool was held constant at 20°C, and helium backside cooling at 400 Pa was used to maintain constant carrier wafer temperature dur-ing all etches. The TiO2 etch mask was deposited using reactive sputtering En-deavor 3000 cluster sputter tool, Sputtered Films, Santa Barbara, CA with a titanium target in an O2/Ar environment using the fol