Ultra-shallow Junction Formation via GeB- ion Implantation of Si
- PDF / 1,256,410 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 2 Downloads / 203 Views
Ultra-shallow junction formation via GeB- ion implantation of Si Xinming Lu, Lin Shao, Jianyue Jin, Qinmian Li, I. Rusakova, Q. Y. Chen, Jiarui Liu, WeiKan Chu Department of Physics and Texas Center for Superconductivity at University of Houston, Houston, TX 77204, U.S.A. Peiching Ling Advanced Materials Engineering Research, Inc., Sunnyvale, CA 94086, U.S.A. ABSTRACT GeB- Cluster ions have been used to effectively produce 0.65-2keV boron for low energy ion implantation. We have generated the GeB- cluster ions using the SNICS ion source (source of negative ion by cesium sputtering). Shallow junctions have been made by the GeB- cluster ions implanting into Si substrates at 15keV, 1x1015/cm2 and 5keV, 5x1014/cm2. The junction depth as small as 37nm has been achieved by rapid thermal annealing of the 5 keV sample at 1000oC for 1 second. A two-step annealing was also performed to study the diffusion of B in the GeB- ion cluster implanted Si by annealing the 15 keV implanted sample at 550oC/300sec+1000oC/10sec. We found that the junction depth of the two-step annealed sample was only half of the one-step annealed sample. TEM (transmission electron microscopy) showed clear recrystallization of the amorphized layer with no observable residual defects. We briefly discussed the role of Ge in regards to reduction of the junction depth. INTRODUCTION Low energy ion implantation is commonly used to fabricate ultra-shallow junction, which are required for scaling the Metal Oxide Semiconductor (MOS) devices down to sub 0.1µm range [1]. However, the quality of shallow junction is reduced by the channeling effect during low energy ion implantation. To overcome this problem, we used a GeB- cluster ion beam which is expected to combine Ge amorphization and B ion implantation into one process to reduce the channeling effect. This consideration was based on a TRIM (Transport and Range of Ions in Matter) simulation from which we found that the projected range of Ge was larger than that of B if the partial energies of Ge and B in GeB- cluster were taken to do simulation. The amorphization process is very fast due to the heavy damage by Ge, it closes a preamorphization for the whole implantation process. This suggests that heavy Ge preamorphization is immediately followed by the B ion implantation. Another advantage for GeB- cluster ion implantation is that Ge is a group-IV and thus does not cause unwanted chemical effect to the substrate as does F in BF2 ion implantation which could adversely affect material and device performance [2]. Further, using GeB- cluster ion implantation can reduce space charge effect because the fractional energy of B is only 13% of the total energy in GeB- ion cluster [3]. In order to reduce TED in the GeB- cluster ion implantation in Si, a two-step annealing was performed to study the diffusion of B. In this study, the two-step annealing process was introduced such that (i) the interstitial was restored back to the lattice positions with minimal defect in the first step of annealing, where solid phase epitaxia
Data Loading...
