Effect of current crowding on contact failure in heavily doped n + - and p + -silicon-on-insulator
- PDF / 851,414 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 92 Downloads / 176 Views
Chih Chen, C.C. Yeh, and K.N. Tu Department of Materials Science and Engineering, University of California—Los Angeles, Los Angeles, California 90095-1595
T.L. Shofner, J.L. Drown, R.B. Irwin, and C.B. Vartuli Cirent Semiconductor, 9333 South John Young Parkway, Orlando, Florida 32819 (Received 9 May 2000; accepted 4 August 2000)
Stability of submicron contacts under high current density has been an outstanding reliability issue in advanced Si devices. Polarity effect of failure was observed in Ni and Ni2Si contacts on n+-Si and p+-Si. In this report, we studied the failure due to high current density in contacts to n+- and p+-silicon-on-insulator (SOI). We found similar polarity effects below certain current: the p+-SOI failed preferentially at the cathode, while the n+-SOI failed preferentially at the anode. At higher current, damage occurred at both contacts. The effect of current crowding was evident in both cases.
I. INTRODUCTION
The demand of current density carrying capability of interconnects increased rapidly with technological advancement. The increased current density, however, may impact the failure of contacts and vias.1–3 Due to the high resistivity, current crowding and Joule heating are the key reasons for contact failure. The junction leakage due to Al spiking in the conventional Al contact systems has been extensively studied, and remedy solutions, such as alloying the Al with Si, have been employed.4–10 For W-plug technology, Al wear-out from the contact has been recognized as the predominant failure mode.2,3 Scientifically, the enhanced interfacial reactions between metal contact and Si under a high current density are of interest.11–15 Previous studies11,12,14,15 on contact pair structures have demonstrated the interplay of electrical and chemical forces in the contact reaction. Their combined action has led to polarity effect of contact failure, which was observed in Ni and Ni2Si contacts to n+- and p+-Si. Our previous study16 on heating behavior of n+and p+-Si suggested that the polarity effect may be related to junction leakage, which will lead to asymmetrical heating. For Ni/n+-Si, damage occurred at anode contacts due to wear-out and junction leakage mechanisms. For Ni/Ni2Si/n+-Si, damage occurred preferentially at cathode contacts due to enhanced silicide formation. For Ni/n+-Si and Ni/Ni2Si/n+-Si, it was proposed that electron-hole recombination and junction leakage were responsible for the damage at cathode contacts. J. Mater. Res., Vol. 15, No. 11, Nov 2000
http://journals.cambridge.org
Downloaded: 04 Apr 2015
In this work, we extended the polarity effect study to p+- and n+-silicon-on-insulator (SOI) systems. The SOI samples have the advantage that no junction leakage can occur, so junction leakage can be isolated from other parameters. Since polarity effect may be related to junction leakage, it was anticipated that polarity effect would not exist in SOI. However, we found that below a certain current, the Ni/p+-SOI failed preferentially at the cathode, while the Ni/n+-SOI fai
Data Loading...
