Precise chrome etching in downstream chlorine plasmas with electron depletion through negative ion production

In micropatterning down to 0.1 mum class devices, photolithography requires highly accurate microfabrication of chrome (Cr) reticle masks. In this pap er we report the vertical chrome etching using electron beam (EB) resist ma sks in downstream chlorine plasmas, where the resist damage during etching can be suppressed because of the reduced electron density through negative ion production. Though the Cr etch rare in pure Cl-2 downstream plasmas was only 15 Angstrom /min, slight oxygen addition of 1% resulted in a great in crease of Cr etch rates as large as 20 times, while resist etch rates incre ased only twice. Though isotropic Cr etching reactions with chlorine and ox ygen radicals caused undercut features, appropriate substrate biasing allow s vertical patterning of 0.2 mum wide lines and spaces due to sidewall prot ection by redeposition of by-products from etched Cr and resists. (C) 2000 The Electrochemical Society. S0013-4651(00)02-080-2. All rights reserved.