S2-4 Ext. Abs. the 5th International Workshop on Junction Technology 2005 Formation of S/D-Extension using Boron Gas Cluster Ion Beam Doping for Sub-50-nm PMOSFET T. Yamashita, T. Hayashi, Y. Nishida, Y Kawasaki, T. Kuroi, H. Oda, T. Eimori, and Y. Ohji Process Technology Development Div., Renesas Technology Corp. 4-1, Mizuhara, Itami, Hyogo, 664-0005, Japan Phone: +81-72-784-7322 E-mail: yamashita.tomohiro@renesas.com 1. Introduction Formation of ultra shallow junction (USJ) with sufficiently low resistance in source/drain extension (SDE) region is the key to realize high-performance MOSFET for 45-nm node and beyond. As for the doping technology, several techniques such as plasma doping [1] or cluster ion implantation [2-3] have been studied as replacement for conventional sub-keV ion implantation. Recently gas cluster ion beam (GCIB) doping is also reported to form boron USJ [4-5]. In this work we used boron GCIB doping to fabricate the SDE of pMOSFETs with gate lengths below 50nm for the first time. Advantage of GCIB doping to low-energy ion implantation is discussed from the view point of transistor performance. 2. Experimetal In this study, boron GCIB doping is simply replaced with boron implantation for SDE formation in conventional process flow. After the gate electrode formation, boron GCIB doping was implemented. The energy of boron gas cluster was 5 keV and the dosage was I 10 5 /cm2. As a reference, 0.2-keV-B+ implantation was also implemented using the deceleration-mode. Note that gate re-oxidation or offset spacer formation [6] is not performed in this experiment. After side-wall spacer formation and B+ implantation for deep source/drain (S/D) including gate electrode, spike annealing was accomplished at 1 050°C with a rapid ramp rate using lamp-based equipment. 3. Results and Discussions Profiles in Blank Wafers Fig. 1 shows 11B profiles for a 5-keV B GCIB doping and a 0.2-keV B+ implant before annealing. It is found that GCIB doping produces steep profile of 2.5 nm/decade without tail distribution which is observed for implantation due to channeling and/or energy contamination. It should be noted that GCIB doping includes 10B of natural isotropic ratio which is not shown in the figure. Profiles of GCIB doping with Ge incorporation and Ge and Ar incorporation are shown in Fig. 2. It is expected that they expedite amorphousization of Si-substrate and impede boron diffusion. Shallow and steep profiles are again obtained, and GCIB doping with Ge and Ar incorporation seems to be preferable by its box-like profile. Fig. 3 shows a profile after annealing. Conventional spike annealing considerably broadens the boron profile. It is considered that advanced annealing such as flash-lamp annealing [7] or laser annealing [8] would help to achieve full capability of GCIB doping. Transistor Characteristics Dependence of PMOS threshold voltage on the gate length is shown in Fig. 4. It is found that GCIB doping improves short-channel effect about 20 nm as compared with reference low-energy implantation, and superior roll-off characteristics are obtained for gate length < 50 nm. Fig. 5 shows Ion-loff characteristics at -L .OV. On-current as high as -400 EAm is obtained at 100-nA/im off-current both for GCIB doping and reference. Fig. 6 shows junction leakage current of pMOSFETs array. Deterioration of the distribution is not observed for GCIB doping as well as reference. Although the differences in the characteristics between GCIB doping and reference low-energy implantation of Figs. 4-6 is considered to be due in part to the difference in effective dosage, boron GCIB doping is shown to be successfully applied to short-channel PMOSFETs. Considering that these results are obtained with no offset spacer and conventional spike RTA, GCIB doping is promising technology for 45-nm node and beyond. 4. Conclusions Boron doping using gas cluster ion beam (GCIB) is .implemented for formation of S/D-extension of pMOSFETs with sub-50-nm gate length. As compared with low energy ion implantation, GCIB is confirmed to produce steep profile of -2.5 nm/decade without tail distribution. By simple replacement of low energy boron implantation with GCIB doping, about 20-nm improvement in short-channel effect and almost the same current drivability are obtained for pMOSFETs. Considering that conventional spike RTA and no offset space were used in the fabrication process, GCIB doping is considered to be promising technology for 45-nm node and beyond. Acknowledgements The authors would like to thank Dr. W. Skinner at Epion Corporation for GCIB doping. The authors would also like to thank Dr. J. 0. Borland at J. 0. B. Technologies for his helpful discussion. References [I] Y. Sasaki et al., Symp. VLSI Tech. Dig. (2004) p.1 80. [2] K. Goto et al., IEDM Tech Dig. (1996) p.435. [3] Y. Kawasaki et al. Proc. Intl. Conf on Ion Implantation Technology (2004) p.40. [4] J. Hautala et. al, Ext. Abstr. Intl. Workshop on Junction Technology (2004) p. 50. [5] J. Borland et. al, Solid State Technology, p. 53, May 2004. [6] H. Sayama et. al, IEDM Tech Dig. (2000) p.239. [7] T. Ito et al., Ext. Abstr. Solid State Devices and Materials, (2001) p. 182. [8] A. Shima et al., IEDM Tech Dig. (2003) p. 493