Electromigration reliability of tungsten and aluminum vias and improvements under AC current stress

Author

Tao, Jiang ; Young, Konrad V. ; Cheung, Nathan W. ; Hu, Chenming

Author_Institution

Dept. of Electr. Eng. & Comput. Sci., California Univ., Berkeley, CA, USA

Volume

40

Issue

8

fYear

1993

fDate

8/1/1993 12:00:00 AM

Firstpage

1398

Lastpage

1405

Abstract

The reliability with respect to electromigration failure of tungsten and aluminum vias under DC, pulse-DC, and AC stressing has been studied using Kelvin test structures. The results indicate that although W-plug vias can eliminate the step coverage problem, this metallization system is not ideal because the intermetallic contact represents an undesirable flux divergence location for electromigration. Al vias are more reliable than W-plug vias with respect to electromigration failure. The unidirectional 50% duty factor pulse-DC lifetime is found to be twice the DC lifetime in the low-frequency region (<200 Hz) and four times the DC lifetime in the normal frequency region (> 10 kHz). The via lifetimes under bidirectional stressing current are found to be orders of magnitude longer than DC lifetimes under the same stressing current density for both W and Al vias. All the observations are in agreement with a vacancy relaxation model

Keywords

aluminium; circuit reliability; electromigration; metallisation; tungsten; AC current stress; Al vias; DC stressing; Kelvin test structures; W plug vias; bidirectional stressing current; duty factor pulse-DC lifetime; electromigration failure; flux divergence location; intermetallic contact; metallization system; pulse DC stressing; stressing current density; vacancy relaxation model; Aluminum; Artificial intelligence; Electromigration; Integrated circuit interconnections; Intermetallic; Kelvin; Metallization; Stress; Testing; Tungsten;

fLanguage

English

Journal_Title

Electron Devices, IEEE Transactions on

Publisher

ieee

ISSN

0018-9383

Type

jour

DOI

10.1109/16.223698

Filename

223698