Performance Characteristics of 65nm PFETs Using Molecular Implant Species for Source and Drain Extensions
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1070-E03-02
Performance Characteristics of 65nm PFETs Using Molecular Implant Species for Source and Drain Extensions C. F. Tan1, L. W. Teo1, C-S. Yin1, J. G. Lee1, J. Liu1, A. See1, M. S. Zhou1, E. Quek1, S. Chu1, C. Hatem2, N. Variam2, E. Arevalo2, A. Gupta2, and S. Mehta2 1 Technology Development, Chartered Semiconductor Manufacturing, 60 Woodlands Industrial Park D, Singapore, Singapore 2 Varian Semiconductor Equipment Associates, Gloucester, MA, 01930 ABSTRACT We investigated the performance of 65nm pFETs whereby the source and drain extensions (SDE) were implanted with Carborane, (C2B10H12) a novel form of molecular species. The high atomic mass of this molecule (146 a.m.u.) and the number of boron atoms transported per ion enables the productivity at low energy required for manufacturing of ultra shallow junctions for advanced scaling. In this investigation, Carborane was implanted at 13 keV to produce a Boron profile near equivalent to that produced by the reference BF2 implant. Results of electrical measurements did not exhibit any compromise in the I-V characteristics in terms of Id-Vg and Id-Vd and Ion-Ioff. External resistance and Vt roll-off shifted slightly with respect to the reference devices. This is attributed to a deeper junction with Carborane due to slight offset in the profile matching. It will be shown that with fully matched profiles, a perfect match of the device characteristics can be achieved. B
I. INTRODUCTION Suppression of short channel effects in advanced MOSFET devices is driving the SDE junction depths shallower, leading to significant drop in associated implant energies. These energies are now reaching the sub keV scale for Boron [1,2]. The consequential drop in productivity of the implant process is resulting in a high level of interest in molecular forms of implantation to extend the energy range below 500 eV for devices beyond the 45 nm node [3].
Figure 1. Molecular structure of Carborane. [1] Carborane, a form of molecular species (referred to as CBH in the text of this paper), shown in Figure (1) has been recently [4] demonstrated as a means to form junctions as shallow as 10 nm at 5E18 to meet the 32nm node requirements. Nevertheless, for the successful integration of CBH into the fabrication process, a better understanding of the performance characteristics of devices fabricated with this molecular species is necessary. This work is the first investigation of electrical characteristics of pFETs, whereby implantation of CBH was employed to dope the SDE regions for a 65 nm process.
II. DEVICE FABRICATION The fabrication of the pFET transistor follows a typical flow as shown in the flowchart in Figure 2. SDE splits between the reference BF2 and CBH were performed on device wafers from the same lot. In both cases a standard Ge pre-amorphization implant was done before the SDE implant. SIMS analysis was used to match the as-implanted B profiles from CBH to that of the reference BF2 implant. Implant energy of 13 keV was used for CBH to achieve a close match as depicted in Figur
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