Collimated sputtering of TiN/Ti liners into sub-half-micrometer high aspect ratio contacts/lines

In situ sputtering of TiN/Ti liners into high aspect ratio (six to eight) sub-half-micrometer contacts with step coverages more than 40% on the side as well as on the bottom is demonstrated for the first time. The process utilizes a collimator, honeycomb-like structure through which atoms are directed into contact holes. A study of step coverages, deposition rates, contact resistances, and junction leakages for Ti and TiN layers as a function of the aspect ratio of the collimator is carried out. The extendibility of collimation beyond 0.25 μm contact geometries is demonstrated. The optimum deposition rate is achieved based on the aspect ratio of the collimator. The structures formed with chemical vapor deposition (CVD) of W on TiN/Ti liners exhibit an order of magnitude improvement in contact resistance over the structures formed without collimated liners, especially for geometries below a critical geometry. The reverse leakages using the shallow junctions (0.12-0.14 μm) remain unchanged.