Device Characteristics of Ultra-shallow Junctions Formed by fRTP Annealing
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Device Characteristics of Ultra-shallow Junctions Formed by fRTP Annealing A. Satta , R . Lindsay, S. Severi, K. Henson, K. Maex IMEC, Kapeldreef 75, B-3001 Heverlee, Belgium S. McCoy, J. Gelpey, K. Elliott Vortek Industries Ltd., 605 West Kent Ave., Vancouver, BC, V6P 6T7 Canada ABSTRACT The creation of ultra-shallow junction for CMOS devices at the sub-100 nm node is driving significant efforts in developing thermal processing to give rise to high dopant activation in combination with limited diffusion. Flash-assist Rapid Thermal Annealing™ (fRTP™)∗ is a promising new annealing technique, which involves the heating of the bulk of the wafer to an intermediate temperature using rather conventional spike RTP, followed by a short and intense pulse of light localized on the implanted wafer surface. In this work, we have systematically investigated the junction formation of different implants under fRTP anneals in terms of profile and devices. Co-implanted Ge and F species provide more box-like profiles with improved activation. Although leakage currents are higher for fRTP-annealed junctions than for spike-annealed junctions, appropriate fRTP process parameters and correct process conditions provide a critical tool to control and reduce the leakage current of co-implanted fRTP junctions to acceptable levels. Proper implant and anneal are requested for minimizing pattern effect and improving device performance. INTRODUCTION The scaling of device dimensions demands ultra-shallow junctions for metal-oxidesemiconductor (CMOS) drain extensions, with high level of activation and abruptness. While this forces implantation of dopants towards low energy and high dose conditions, the thermal processing required to activate the dopant to the level of the solid solubility at the anneal temperatures must be, simultaneously, a diffusionless annealing. Flash-assist Rapid Thermal Annealing is an advanced annealing technique, using a high power Ar arc lamp system capable of producing a short time discharge, due to its essentially zero thermal mass. The lamp produces continuous optical radiation in an electric arc operating in high pressure argon gas, in a spectral region where can be absorbed in Si more efficiently than that produced by the W-halogen lamp, traditionally used in spike annealing [1,2]. fRTP is therefore able to operate in the time gap between laser thermal processing (LTA, which has an effective time in the order of 10-9 s) and the spike RTP process which shows a characteristic time on the order of 1 s. The short pulse of intense light in the order of 1-10 ms of fRTP is responsible for very high dopant activation level and diffusionless profiles [1,2,3]. The high temperature-anneal with quenching may lead to instability in activation and diffusion of dopants. Such phenomena have been indeed reported for laser annealing of implanted layers [4]. Clearly, instability of junction active profiles would affect the reverse currents of fRTP diodes, as well as the transistor performance and would lead to a number of integ
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