• PDF / 151,633 Bytes
• 6 Pages / 612 x 792 pts (letter) Page_size
• 42 Downloads / 259 Views

DOWNLOAD

REPORT

---

TRANSIENT ENHANCED DIFFUSION OF ARSENIC BY SELF-IMPLANTATION 6JGTQNGQH#U+ENWUVGTU  Ryangsu Kim, Takenori Aoki, Yoshikazu Furuta, Hiroyuki Kobyashi, Jianxin Xia, Tomoya Saito, Yoshinari Kamakura and Kenji Taniguchi Dept. of Electronics and Information Systems, Osaka University, Osaka, 565-0871 JAPAN, [email protected] ABSTRACT Transient enhanced diffusion of implanted arsenic in silicon with/without additional self-implantation has been investigated. The experimental results show the suppression of As diffusion with Si self-implantation during initial stage of annealing in contrast to the prediction of conventional models. The results suggest that the arsenic and self-interstitial atoms might form immobile clusters during Si implantation or initial stage of annealing. After the clusters dissolve for further annealing, the transient enhanced diffusion of As increases with silicon implantation dose as expected from the "+1" model. These results clarify that interstitials/ As I clusters play a major role in transient arsenic diffusion. INTRODUCTION Ion implantation is an essential process technology to form the ultra-shallow junction for deep sub-micron MOSFETs. However, large amount of point defects generated in the Si wafer during the implantation process gives rise to the transient enhanced diffusion (TED) of dopant atoms [1,2]. In the case of high dose implantation which forms amorphous layer, the end-of-range (EOR) defects such as dislocation loop and/or {311} defect would be formed at the region just beyond the amorphous/crystalline interface on post-implantation annealing. Since the {311} defect is energetically unstable compared to the dislocation loop, self-interstitials released from the EOR {311} defects might cause TED of dopant atoms [3]. Arsenic atom which diffuses both interstitial(cy)- and vacancy-mechanism [4] is widely used as n-type dopant in Si devices because of its high solubility and low diffusivity. The TED of arsenic during post-implantation annealing at low temperature has been observed [5] in the same manner as the diffusion of boron and phosphorus. The experimental results using boron and antimony doped super-lattice wafers showed that TED of As is predominantly controlled by interstitials [6]. To the contrary, it have been also shown that self-implantation causes excess TED of B, and P [7,8] but not for As although the implantation of silicon generates the self-interstitials in the lattice in proportion to implanted dose. There are also contradictory reports [9-12] on the suppression of TED of As in low temperature preannealing before rapid thermal annealing (RTA). Still controversial issues on the TED of arsenic exist. For accurate simulation of arsenic diffusion during post-implantation annealing, the detailed understanding and correct modeling of arsenic TED are indispensable. The aim of this paper is to clarify the physical origin of TED of As by the use of self-implantation in addition to normal As implantation. EXPERIMENT Figure 1 shows the flowchart of the experimental