Method for etching an Al metallization by a C12/HC1 based plasma

摘要

RIE of metallization is achieved at low power and low pressure using Cl2 and HCl as reactant species by creating a transformer coupled plasma with power applied to electrodes positioned both above and below a substrate with metallization thereon to be etched. Three layer metallizations which include bulk aluminum or aluminum alloy sandwiched between barrier layers made from, for example, Ti/TiN, are etched in a three step process wherein relatively lower quantities of Cl2 are used in the plasma during etching of the barrier layers and relatively higher quantities of Cl2 are used during etching of the bulk aluminum or aluminum alloy layer. The ratio of etchants Cl2 and HCl and an inert gas, such as N2 are controlled in a manner such that a very thin side wall layer (10-100 ANGSTROM ) of reaction byproducts created during RIE are deposited on the side walls of trenches formed in the metallization during etching. The side wall layer improves the isotropic nature of the etch such that submicron metallization lines with defect free side walls are formed. Hydrogen (H2) can be added to the plasma and will act to reduce corrosion. <IMAGE>