Activated Pulsed Metalorganic Chemical Vapor Deposition of Ge 2 Sb 2 Te 5 Thin Films Using Alkyl Precursors
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1251-H03-23
Activated Pulsed Metalorganic Chemical Vapor Deposition of Ge2Sb2Te5 Thin Films Using Alkyl Precursors Denis Reso1, Mindaugas Silinskas1, Bodo Kalkofen1, Marco Lisker2 and Edmund P. Burte1 1
Institute of Micro and Sensor Systems, Otto-von-Guericke-University, Universitaetsplatz 2, D-39106 Magdeburg, Germany 2
Technology/Process Research Division, Innovations for High Performance Microelectronics (IHP), Im Technologiepark 25, D-15236 Frankfurt (Oder), Germany ABSTRACT Ge-Sb-Te (GST) thin films were deposited by chemical vapor deposition (CVD) and hotwire chemical vapor deposition (HW CVD). Several precursor sets (tetraethylgermanium trimethylantimony - dimethyltellurium (TEGe-TMSb-DMTe), tetraisopropylgermanium triisopropylantimony - di-tertiarybutyltellurium (TiPGe-TiPSb-DtBTe) and tetraallylgermanium triisopropylantimony - diisopropyltellurium (TAGe-TiPSb-DiPTe)) were tested for CVD. For the TEGe-TMSb-DMTe precursor set tellurium and germanium could be detected in the films for all deposition temperatures investigated, while Sb was found only in the films deposited at elevated temperature higher than 550 °C. The deposition temperature could be reduced by using two other precursor sets (TiPGe-TiPSb-DtBTe and TAGe-TiPSb-DiPTe). The Ge content, however, could not be sufficiently increased to obtain stoichiometric Ge2Sb2Te5 films. Therefore, the hot wire or catalytic method was applied to improve the decomposition of the precursors. In this case, the desired composition (e.g. Ge2Sb2Te5) was obtained at each investigated temperature by adjusting dosing and deposition parameters. Additionally, film roughness (as low as 2 nm) and deposition rates could be optimized by adjusting deposition temperature and pressure. INTRODUCTION Phase change memories are considered to belong to the most promising candidates for the next generation of non-volatile memories [1]. At the present time, the commonly used phase change materials are Ge-Sb-Te alloys or, particularly, Ge2Sb2Te5 compounds [2-3]. The critical challenges for these materials are the continued down-scaling of the devices and reduction of the reset/set currents [4]. One way to solve these problems is the transition to a three dimensional structure, where chalcogenide material is filled into a contact hole [5]. The conventional physical vapor deposition techniques are not suitable for such applications due to poor step coverage. Therefore, it is necessary to use deposition methods such CVD and/or ALD that offer better conformity and composition control [5-6]. Recently, CVD and atomic layer deposition (ALD) have been used for producing ternary Ge-Sb-Te films [3, 5-8]. Abrutis et al. [6] showed that a hot wire activation of the CVD process yields a lower surface roughness and a better lateral growth. Hydrogen as reactant gas has been used in CVD to promote the decomposition of precursors [7] and hydrogen plasma assisted ALD has been applied for the deposition of good quality GST films [5].
In a previous work [9], we have investigated GST film deposition using
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