Amorphous Ge2Sb2Te5 mechanical modification properties induced by Ge ions implantation

The chalcogenide material are extensively studied, optically and electrically, for the promising characteristic of scaling possibility, beyond silicon technology, as a viable alternative material for non-volatile memories application and it actually define a particular class namely Phase Change Memory. The working principle of these new devices resides in the substantial change of the electrical resistance between the amorphous and the crystalline phases induced by short electric pulses. The two phases are characterized respectively by a high (SET) and a low (RESET) conductive state. The transformation between the crystalline and the amorphous phase is induced by a high current pulse able to melt the cell active volume; its subsequent fast quenching (1 to 10 ns) determines the crystal-to-amorphous transformation. The reverse transition requires instead a slower cooling down from the melt (hundreds of ns) [1-2]. The iterative transformation between the crystalline and the amorphous phase produce not only an iterative transformation on film Sheet Resistance and Reflectivity but also produce an iterative transformation in the mechanical characteristics, i.e. Young Modulus and Hardness. Moreover the physical iterative transformation between crystalline and amorphous phase transformation introduces a swelling and deswelling effect. This is one of the key failure mechanism that is limiting the reliability of the final integration of the PCM system. In this work we consider the mechanical characteristics of as sputtered amorphous Ge2Sb2Te5, and the mechanical modification introduced by ion implantation technique. In particular, the characterization of the mechanical parameters’ modifications is an important aspect for predicting the thermo-mechanical reliability behavior of the whole system. The modification were monitored by two different approach, Nano-indentation [3] and by using resonates amorphous-GST/SiliconNitride nanocantilevers [4,5]. Both techniques were able to observe a Young modulus increasing after implantation indicating the formation of different order reconfiguration obtained by ion-implantation technique.