The Effect of Impurities on Diffusion and Activation of ion Implanted Boron in Silicon
- PDF / 171,405 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 25 Downloads / 209 Views
The effect of impurities on diffusion and activation of ion implanted boron in silicon L. S. Robertson, R. Brindos, and K. S. Jones Dept. of Materials Science and Engineering, University of Florida M. E. Law Dept. of Electrical and Computer Engineering, University of Florida D. F. Downey, S. Falk, and J. Liu Varian Ion Implant Systems ABSTRACT The interaction between boron and silicon interstitials caused by ion implant damage is a physical process which hinders the formation of ultra-shallow, low resistivity junctions. The possibility of mitigating the effective interstitial point defect population via introduction of nonmetallic impurities in ion implanted silicon has been investigated. Amorphization of a n-type Czochralski wafer was achieved using a series of Si+ implants of 40 keV and 150 keV, each at a dose of 1x1015/cm2. The Si+ implants produced a 2800Å deep amorphous layer, which was then implanted with 8 keV 1x1014/cm2 B+. The samples were then implanted with high doses of either carbon, oxygen, sulfur, chlorine, selenium, or bromine. The implant energies of the impurities were chosen such that the damage and ion profiles of the impurity were contained within the amorphous layer. This allowed for the chemical species effect to be studied independent of the implant damage caused by the impurity implant. Post-implantation anneals were performed in a tube furnace at 750° C. Secondary ion mass spectrometry was used to monitor the dopant diffusion after annealing. Hall effect measurements were used to study the dopant activation. Transmission electron microscopy (TEM) was used to study the end-of-range defect evolution. The addition of carbon and chlorine appear to reduce the boron diffusion enhancement compared to the boron control. Carbon and chlorine also appear to prevent boron out-diffusion during annealing compared to the control, which exhibited 20% dose loss following annealing. INTRODUCTION In order to create a controlled, laterally uniform dopant profile, ion implantation is an integral part of modern integrated circuit (IC) processing. The impingement of energetic particles on the silicon substrate during ion implantation inherently produces a significant amount of damage to the silicon lattice. Following Frenkel pair recombination in the early stages of post-implantation annealing, a supersaturation of excess interstitials remains for both nonamorphizing1 and amorphizing2 implantations. The excess interstitials in the silicon wafer lead to enhancement of the diffusion rate of dopants such as B, P, and As which diffuse either principally or in part by an interstitialcy mechanism in silicon.3 Additionally, excess interstitials cluster with dopant atoms resulting in inactive dopant.4 The 1999 International Technology Roadmap for Semiconductors explicates the issues related to ultra-shallow junction formation. Unless resolved, these issues will prevent the current scaling trend known as Moore's Law from continuing through the end of the decade. Taking the 70 nm node from the aforementioned Roadmap as an
Data Loading...
