Analysis of Silicide / Diffusion Contact Resistance Making Use of Transmission Line Stuctures
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Analysis of Silicide / Diffusion Contact Resistance Making Use of Transmission Line Stuctures Amal Akheyar1, Anne Lauwers2, Richard Lindsay2, Muriel de Potter2, Georg Tempel1 and Karen Maex2 1 Infineon technologies AG, affiliated to IMEC vzw, Kapeldreef 75, B-3001 Leuven, Belgium 2 IMEC vzw, Kapeldreef 75, 3001 Leuven, BELGIUM Corresponding author: [email protected] ABSTRACT This work deals with the analysis of the resistances of Co-silicided As and B junctions. The influence of junction formation and salicide process on contact resistance was investigated. The contact resistance between the silicide and source/drain region was studied by making use of dedicated transmission line structures. The transmission line structures (TLM) consist of alternating silicided and unsilicided diffusion segments, obtained by making use of a salicide blocking mask. Our TLM results show that the contact resistance has a strong dependence on the doping profile of the diffused region and increases with decreasing surface doping, with increasing Co-silicide thickness, annealing temperatures and time of silicidation. INTRODUCTION The performance of MOS circuits depends strongly on transistor drive current. The drive current of the transistor is determined by the total device resistance, which consists of the channel resistance and the parasitic resistances associated with diffusions and contacts. As device dimensions shrink in each new technology generation, contact resistance scales as a power of the reciprocal dimensions [1]. It is expected that the contact resistance between silicide and source/drain region will dominate the total series resistance. This has serious consequences for current drive and device speed. The silicide must provide low contact resistance to the doped silicon regions. The reduction of this contact resistance, and the corresponding contact resistivity is a big issue in order to not compromise the device performance. Thus the ability to accurately measure the contact resistance is essential to contact development. For this purpose, a set of test structures were fabricated, including Van der Pauw structures for measuring sheet resistivity, standard Kelvin probe structures to measure metal-to-silicide contact resistivity and Transmission Line Structures with segments of varying length. DESCRIPTION AND ANALYSIS OF MEASUREMENT TECHNIQUE In this work we use a transmission line model proposed by Scott [2] which offers an attractive method to accurately measure the contact resistance Rc(Ω-µm) and extract both specific contact resistivity ρc (Ω-µm2) and sheet resistance ρds(Ω/sq) of the remaining doped region under the silicide contact. The transmission line structures consist of alternating silicided and unsilicided diffused segments, obtained by making use of a salicide blocking mask (Figure 1b).
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