METHOD OF ETCHING COPPER FOR SEMICONDUCTOR DEVICES

摘要

Copper can be pattern etched in a manner which provides the desired feature dimension and integrity, at acceptable rates, and with selectivity over adjacent materials. To provide for feature integrity, the portion of the copper feature surface which has been etched to the desired dimensions and shape must be protected during the etching of adjacent feature surfaces. This is particularly important for feature sizes less than about 0.5 mu m, where presence of even a limited amount of a corrosive agent can eat away a large portion of the feature. The copper feature integrity is protected by several different mechanisms: 1) the reactive etchant species are designed to be only moderately aggressive, so that an acceptable etch rate is achieved without loss of control over the feature profile or the etch surface; 2) hydrogen is applied over the etch surface so that it is absorbed onto the etch surface, where it acts as a boundary which must be crossed by the reactive species and a chemical modulator for the reactive species; and 3) process variables are adjusted so that byproducts from the etch reaction are rendered more volatile and easily removable from the etch surface. In an inductively coupled plasma etch chamber, we have observed that the preferred chlorine reactive species are generated when the chlorine is dissociated from compounds rather than furnished as Cl2 gas.