Microstructural development in asymmetric processing of tantalum plate

Abstract

Sputtered tantalum (Ta) and TaN are employed as barrier layers in modern integrated circuits to enable reliable use of Cu as an interconnect material. The directional properties of sputtering Ta can result in nonuniform film thicknesses (from heavily textured plate) and unpredictable sputtering rates (from plates with through thickness texture gradients). This results in film thicknesses larger than necessary because of the sputtering being unpredictable. This presentation reports on an effort to increase textural and grain size uniformity in Ta by deforming the plate under conditions that simulate asymmetric rolling. This is accomplished by using a channel die configuration with uneven friction on the top and bottom plates so that a strong shear component is added to the plane strain condition enforced by the channel dies. Results indicate a trend towards less severe texture banding and more uniform structure in the plate processed by asymmetric friction conditions.