Investigation of Platinum Silicide Schottky Barrier Height Modulation using a Dopant Segregation Approach
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1070-E02-10
Investigation of Platinum Silicide Schottky Barrier Height Modulation using a Dopant Segregation Approach Nicolas Breil1,2, Aomar Halimaoui1, Emmanuel Dubois2, Evelyne Lampin2, Guilhem Larrieu2, Ludovic Godet3, George Papasouliotis3, and Thomas Skotnicki1 1 STMicroelectronics, 850, rue Jean Monnet, Crolles, 38920, France 2 IEMN-ISEN, UMR CNRS 8520, Cité Scientifique, Avenue Poincaré, Villeneuve d'Ascq, 59652, France 3 Varian Semiconductor Equipment Associates, Inc., 35, Dory Rd., Gloucester, MA, 01930 ABSTRACT The role of the dopant activation on the segregation efficiency during the formation of platinum silicide (PtSi) is investigated in this paper. Using an implant before silicidation technique, we first demonstrate an important Schottky Barrier Height (SBH) modulation for As and B segregation. In the case of As, we highlight that an activation of the dopants before the silcidation does not impact the SBH modulation. On the contrary, an important impact of the dopant crystalline position is evidenced for Boron. Also, a comparison of conventional implant versus a PLAsma Doping (PLAD) highlights the suitability of the latter implantation tool for the SBH modulation. Those results are interpreted on the basis of SIMS depth profiling. INTRODUCTION As CMOS technology scaling continues, the contact resistance between the silicide and the doped junctions appears as a severe issue. This contact resistance shows an exponential dependence to the ratio between φb, the Schottky Barrier Height (SBH), and Nd1/2 the square root of the underlying silicon doping concentration [1]. As this latter parameter almost reached the dopant solubility limit, the modulation of φb appears as a promising performance booster. Using dopant segregation approaches, such SBH-engineered silicides can be integrated in a standard integration scheme, as well as in a more aggressive Schottky-Barrier transistor (SBMOS) approach [2]. Recently, severe issues appeared since the 65nm node concerning the stability of the conventional nickel silicide. Abnormal penetration under the gate and a poor thermal stability are two of the main drawbacks associated to this material. To leverage this issue, an increasing amount of platinum added during the nickel metal deposition is known to increase the process stability [3]. In this study, we investigate the potential of pure platinum as a successor to nickel. Furthermore, an original method for the selective etching of platinum versus platinum silicide was recently demonstrated from a morphological [4] and an electrical point of view [5], which makes this material a promising candidate for the future technology nodes. Recently, some authors have shown that dopant segregation techniques are an efficient way for the SBH engineering [6]. This study focuses on the impact of the dopant crystalline position in Si on the SBH modulation efficiency.
EXPERIMENT The test structures used in this study were patterned in a thermally grown 120nm thick SiO2 layer on p-type Si substrates. They are composed of two 100x1
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