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Germanium-antimony-telluride or, particularly, Ge2Sb2Te5 (GST) thin films were deposited by hot-wire (HW) chemical vapor deposition (CVD). Tetraallylgermanium (TAGe), triisopropylantimony (TIPSb), and diisopropyltelluride (DIPTe) were used as precursors for germanium, antimony, and tellurium, respectively. The influence of deposition parameters such as a temperature, pressure, and hydrogen content was investigated. It was found that higher temperature, higher pressure, and lower hydrogen flow yielded higher growth rates of the films. An admixture of hydrogen reduced the Te concentration in the GST thin films and enhanced the content of Ge and Sb. The chemical composition could also be shifted by other deposition parameters but these dependences were not as well determined as in the hydrogen case. Generally, higher germanium concentration was related to smaller amount of tellurium. The films deposited at higher pressure showed significantly higher roughness. Additionally, the switching from low resistivity to high resistivity state was tested.

Thin films of germanium selenide (GexSe100−x with 0<x<57) were deposited on different substrates by hot wire metalorganic chemical vapor deposition using tetraallylgermanium and di-tert-butylselenide. The growth kinetics of the deposition process as well as the properties of the films were investigated. The growth rate was found to decrease with increasing temperature and decreasing pressure. The conformal step coverage was demonstrated. Germanium selenide films covered and subsequently diffused by silver were used as programmable metallization cells for a verification of the electrical switching properties.

Germanium-antimony-telluride or, particularly, Ge 2 Sb 2 Te 5 ͑GST͒ thin films were deposited by hot wire ͑HW͒ chemical vapor deposition ͑CVD͒. Tetraallylgermanium, triisopropylantimony, and diisopropyltelluride were used as precursors for germanium, antimony, and tellurium, respectively. The influence of deposition parameters, such as temperature, pressure, and hydrogen content, was investigated. It was found that higher temperature, higher pressure, and lower hydrogen flow yielded higher growth rates of the films. An admixture of hydrogen reduced the Te concentration in the GST thin films and enhanced the content of Ge and Sb. The chemical composition could also be altered by other deposition parameters but these dependencies were not as well pronounced as in the hydrogen case. Generally, a higher Ge concentration was related to a smaller amount of Te. The films deposited at a higher pressure showed a significantly higher roughness. In addition, the switching from a low to high resistivity state was tested.Phase-change memories ͑PCM͒ are one of the most promising candidates for the next generation of nonvolatile memories. 1 GeSb-Te alloys or, particularly, the Ge 2 Sb 2 Te 5 compound are very attractive and commonly used materials for PCM applications, 2,3 where the reversible transition between crystalline and amorphous phases is utilized. 2-4 The crystalline and amorphous phases correspond to the low resistivity state and the high resistivity state, respectively. The switching between these two states is obtained by Joule heating or, in particular, by a short and large current pulse for the conversion of GST from a low to high resistivity ͑reset operation͒ and by a longer and relatively small current pulse for the transition from a high resistivity to a low one ͑set operation͒. 3 Critical challenges for fabrication of PCM devices are the continued downscaling and reduction of the reset/set currents. 3,4 One way to solve these problems is the transition to a three-dimensional structure, where the chalcogenide material is filled into a contact hole. 5 However, conventional physical vapor deposition techniques are not suitable for the required filling process due to poor step coverage. Therefore, it is necessary to use deposition methods such as chemical vapor deposition ͑CVD͒ or atomic layer deposition ͑ALD͒ that offer a better conformity and composition control. 5,6 Recently, CVD and ALD have been used for producing the ternary Ge-Sb-Te films. 5-9 However, film quality problems, such as film uniformity, roughness, etc., are always an issue for the films deposited by conventional CVD. 7,9 On the other hand, Abrutis et al. 6 and Choi et al. 10 showed that a precursor activation within the CVD process yields a lower surface roughness and a better lateral growth. In addition, activation by a hot wire ͑HW͒ enables the use of a wider range of precursors because of its catalytic character of precursor decomposition. 6 This was also observed in our previous work, 11,12 where detailed comparison between conventional an...

Ge-Sb-Te (GST) thin films were deposited by chemical vapor deposition (CVD) and hot-wire 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.