Coupling Between Precipitation and Plastic Deformation During Electromigration in a Passivated Al (0.5wt%Cu) Interconnec
- PDF / 314,362 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 56 Downloads / 166 Views
F7.4.1
Coupling Between Precipitation and Plastic Deformation During Electromigration in a Passivated Al (0.5wt%Cu) Interconnect R.I. Barabash1∗, G.E. Ice1, N. Tamura2, B.C. Valek3, R. Spolenak4, J.C. Bravman3 and J.R. Patel2 1
Metals & Ceramics Divisions, Oak Ridge National Laboratory, Oak Ridge TN 37831 Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley CA 94720 3 Dept. Materials Science & Engineering, Stanford University, Stanford CA 94305 4 Max Planck Institut für Metallforschung, Heisenbergstrasse 3, D-7056 Stuttgart, Germany 2
ABSTRACT In the present paper the evolution of the dislocation structure during electromigration in different regions along the Al(Cu) interconnect line is considered. It is shown that plastic deformation increases in the regions close to cathode end of the interconnect line. A coupling between the dissolution, growth and re-precipitation of Al2Cu precipitates and the electromigration-induced plastic deformation of grains in interconnects is observed. Possible mechanism of the Cu doping effect on the improved electromigration resistance of the Al(Cu) interconnects is discussed. INTRODUCTION The scaling of device dimensions with a simultaneous increase in functional density imposes a challenge to materials technology and reliability of interconnects1, 2. Although the general mechanism of electromigration is understood3 - 5, the effect of the atomic flow on the local metallic line microstructure is largely unknown. Recently white beam X-ray microdiffraction6 - 17 was used to probe microstructure in interconnects. The first quantitative analysis of the dislocation structure in individual grains of a polycrystalline interconnect line was performed in15 - 17 and it was shown that dislocations with their lines almost parallel to the current flow direction are formed first. Electromigration in Al(Cu) interconnects and the effects of Cu were studied extensively since 70’s3, 4. Recent measurements of precipitate evolution during electromigration in Al (Cu) interconnects17 – 21 , in agreement with earlier results of Rosenberg3 and Hu et al4 indicates that Cu is preferentially depleted from the cathode end of the line and accumulates at the anode. However it is still not completely understood why doping with small amount of Cu greatly improves the electromigration resistance of Al-based interconnect lines. In the present paper we consider a model describing the possible correlation between Cu drift, precipitation and formation of dislocations in an Al(Cu) interconnect line. EXPERIMENTAL Data collection has been carried out at the X-ray microdiffraction end-station on beamline 7.3.3 at the Advanced Light Source. The sample is a patterned Al (0.5% wt. ∗
Corresponding author Dr. Rosa Barabash
F7.4.2
Cu) line (length:30 µm, width: 4.1 µm, thickness: 0.75 µm) sputter deposited on a Si wafer and buried under a glass passivation layer (0.7 µm thick). Electrical connections to the line are made through unpassivated Al (Cu) pads connected to the sample by W vias. Details on the experi
Data Loading...
