Volume 91, Issue 9, 01 May 2002
Index of content:
- DEVICE PHYSICS (PACS 85)
91(2002); http://dx.doi.org/10.1063/1.1459756View Description Hide Description
We use modeling and simulation tools to determine the beneficial additives or dopants to Cuinterconnect. We have designed a virtual simulation procedure to cover several important aspects in screening a potential dopant to Cu with the assumption that grain-boundary (GB) diffusion is dominant for Cuelectromigration performance. The procedure investigates dopant segregation to GB, bulk diffusion,dopant and Cuself-diffusion at the GB, and the effect of the dopant’s presence on Cudiffusion at the GB. Defect formation and migration energies as well as activation energies were calculated using the state of the art ab initio method. Two primary mechanisms for a dopant to be effective were identified, namely, dopant blocking and dopant dragging mechanisms. For dopant blocking mechanism the desired dopants occupy the GB interstitial sites and block the fast diffusion pathway for Cu. In the case where Cu atoms occupy the GB interstitial sites, the desired dopants segregate to the nearby substitutional sites and drag the fast diffusing Cu. Early experimental results have confirmed model prediction for several dopants identified so far. The mean time to failure has increased more than 60% with a dopant concentration as low as 0.01 at. % in Cu and the resistivity increase can be controlled below 15% compared to undoped Cu. We demonstrate that modeling and simulation have become valuable alternatives to experiment for design of advanced materials systems for technology research and development.
91(2002); http://dx.doi.org/10.1063/1.1467630View Description Hide Description
Metal–semiconductor–metal detectors have been fabricated based on AlGaN grown on Si by molecular beam epitaxy. Field distribution and collection efficiency were studied with the ion beam induced charge collection method. The results were explained by numerical two-dimensional calculations of the electric field distribution. The calculated field map and charge buildup at the electrodes are used to explain the bias and position dependence of the ion beam induced charge collection. The similarities and differences with the case of optical detection are discussed.
91(2002); http://dx.doi.org/10.1063/1.1468904View Description Hide Description
Amorphousfilms were obtained by magnetron cosputtering and conditions for obtaining good diffusion barrierproperties against penetration by Cu were evaluated by Auger electron spectroscopy. Controlling the B/Ti ratio is of major importance. It was found that the best diffusion barrierproperties were obtained in stoichiometric or overly stoichiometric titaniumboride. Almost no penetration of Cu occurred at 953 K for 30 min. Films of where are of inferior barrier quality. At complete deterioration of the barrier property occurs. The effect of composition is explained in terms of the packing density of the amorphousfilm. Preliminary diffusion studies by secondary ion mass spectroscopy in the amorphoustitaniumboride of near-stoichiometric composition (B/Ti≈2.07) indicate that two mechanisms seem to operate in the film. The low temperature mechanism occurs in the amorphous disordered structure, whereas at higher temperature diffusion occurs in an amorphousfilm in which short-range order exists. An activation energy of ≈2.0 eV was derived from the steep slope of the Arrhenius curve that represents diffusion in the short-range ordered region.