Thermal properties of In–Sb–Te films and interfaces for phase change memory devices Roberto Fallica a,⇑ , Claudia Wiemer a , Toni Stoycheva a , Elena Cianci a , Massimo Longo a , Huu Tan Nguyen a,b , Andrzej Kusiak b , Jean-Luc Battaglia b a Laboratorio MDM, IMM-CNR, via C. Olivetti 2, 20864 Agrate Brianza (MB), Italy b Laboratoire Inter établissement ‘‘TRansferts Ecoulements Fluides Energétique’’, UMR 8508, Université de Bordeaux, 351 Cours de la Libération, 33405 Talence Cedex, France article info Article history: Available online 9 November 2013 Keywords: Phase change materials Chalcogenides 3 x Thermal conductivity Thermal boundary resistance abstract The thermal properties of two different compositions (Te 12 and 17 at.%) of In–Sb–Te, obtained by met- alorganic chemical vapour deposition, were investigated by the 3 x method. The thermal conductivity of these chalcogenides, of interest for phase change memory applications, was found to decrease with increasing tellurium content. Thermal treatment at 480 °C of these materials caused an increase of their crystallinity and improved the thermal conductivity. However, this effect was more marked in the Te-poor composition than in the Te-rich one. In addition, the thermal boundary resistance between In–Sb–Te and various capping dielectrics (SiO 2 , Si 3 N 4 and Al 2 O 3 ) was measured and it was found to be closely correlated to the interlayer roughness, as indicated by X-ray reflectivity. In this regard, silicon oxide and alumina yielded a smoother and less resistive interface with In–Sb–Te than silicon nitride. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Phase change memories (PCM) exploit the fast, reversible tran- sition between the amorphous and crystalline phase of a material to encode a binary data (RESET or SET, respectively). These devices implement a non-volatile memory because data are stored as long as the structural phase of the material is retained. Chalcogenide al- loys of tellurium are materials of choice for this application and Ge 2 Sb 2 Te 5 is the most technologically important of these, due to its broad resistivity contrast, fast switching in the nanosecond timescale and good stability of the amorphous phase. This latter characteristic, which is roughly proportional to the crystallization temperature of the material, affects the retention of the RESET state of the memory cell. In this regard, the crystallization temper- ature of Ge 2 Sb 2 Te 5 (150 °C) guarantees data retention up to 10 years at 110 °C [1], which is not enough to meet automotive or military-grade requirements (125 °C continuous operation). To overcome this limitation, several studies have shown that the replacement or the addition of Ge with In is a convenient way to increase the crystallization temperature of the Ge–Sb–Te system [2–5]. It has been known that a wide range of phase change compounds can be formed from the combination of InTe or In 2 Te 3 with InSb, all of which feature semiconducting behaviour, the zinc blende structure and a high crystallization temperature (>220 °C) [3,5,6]. Besides, the In–Sb–Te (IST) system exhibits several phase transitions at different temperatures (for example, in In 3 Sb 1 Te 2 , related to the formation of the binaries InSb and InTe) [7]. The presence of multiple crystalline phases (featuring different resis- tivity levels) has recently been exploited to accomplish multi-level storage within a single memory cell [8]. The thermal design of the PCM device is mandatory, as its oper- ation (program/erase) is triggered by the Joule heating of the active area of the chalcogenide. Furthermore, the propagation of excess heat from one cell to the neighbouring ones, also known as thermal cross-talk, is an undesired phenomenon that has been recognized as a major challenge to the implementation of this technology [9]. Addressing this issue requires the knowledge of the thermal conductivity (k) of the chalcogenide material and of the thermal boundary resistance (TBR) with its surrounding dielectric layers. These quantities are of interest also because they both affect the threshold voltage [10] and the programming energy [11] of the PCM cell. Notably, data available on the thermal properties of In- based tellurides are limited to bulk alloys belonging to the In 2 Te 3 – InSb section [12]. For these reasons, in this work we studied the thermal properties of two InSb-rich compounds of the In–Sb–Te ternary system, obtained by metalorganic chemical vapour deposi- tion. A 3 x experimental setup allowed us to determine the k of thin films of IST and the TBR between IST and various dielectric capping layers. Finally, the effect of deposition, thermal treatment and film roughness was correlated and discussed according to the results found. 0167-9317/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.mee.2013.10.021 ⇑ Corresponding author. Tel./fax: +39 039 603 5938. E-mail address: roberto.fallica@mdm.imm.cnr.it (R. Fallica). Microelectronic Engineering 120 (2014) 3–8 Contents lists available at ScienceDirect Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee