CVD of Amorphous GeTe Thin Films
- PDF / 2,562,946 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 93 Downloads / 278 Views
1071-F09-10
CVD of Amorphous GeTe Thin Films Philip S Chen, William J Hunks, Matthias Stender, Tianniu Chen, Gregory T Stauf, Chongying Xu, and Jeffrey F Roeder ATMI, Danbury, CT, 06810 ABSTRACT Fourteen germanium (Ge) and two tellurium (Te) precursors were used to deposit Ge and Te thin films by a thermal MOCVD process using various co-reactant gases on TiN/Si and SiO2/Si substrates. Selected results are presented in this paper. Smooth amorphous GeTe films with Te content as high as 48 at% were deposited. Annealing of the amorphous GeTe films at 400 °C under N2 yielded smooth crystalline films that displayed a phase-change induced electrical resistivity reduction of over 300 times.
INTRODUCTION Chalcogenide Ge2Sb2Te5 (GST225) based phase-change memories (PCM) are one of the most promising candidates for next-generation non-volatile memories, with the potential to improve the performance over Flash memories as well as scale beyond the limits of current Flash technology. Most reports of GST films utilize sputtering for deposition in PCM devices. Although functional devices can be produced by this method, it is mostly suitable for planar devices or structures with relaxed geometric features. For the case of planar structures, high reset currents represent a significant challenge. For continued scaling of nano-electric device architectures, and for improved performance and lower costs, deposition into more challenging non-planar structure is needed. Reduction of reset current from 500 µA levels typical of planar devices to below 260 µA using a confined cell structure has been demonstrated by limiting the switched volume of the GST material to the contact plug.[1,2] This also greatly reduces the heat dissipation to the surrounding materials. Therefore, it is necessary to deposit the GST films using a process that offers good conformality such as ALD or CVD for higher aspect ratio structures in high density memory devices. In this paper, we report CVD of GeTe films from several classes of metalorganic precursors.
EXPERIMENT A load locked single wafer deposition chamber equipped with a liquid delivery system and a vaporizer was used for the deposition process. Ge precursors, developed and purified at ATMI, were dissolved in solvent and delivered through a liquid mass flow controller into the vaporizer, where they were mixed with helium carrier gas and introduced through a temperature controlled showerhead above the wafer. A room temperature bubbler was used to provide the alkyl-telluride precursors for the GeTe deposition. Deposition experiments were carried out at chamber pressures between 0.9 and 8 Torr and wafer temperatures between 200 and 440 °C.
Both thermally oxidized Si and 50 nm TiN coated Si wafers were used for Ge and GeTe thin film depositions. The film composition was characterized with XRF, EDS and RBS analyses, while the microstructure was observed by scanning electron microscopy (SEM). The film thickness was measured by XRF using a sputtered Ge2Sb2Te5 standard and verified with cross-sectional SEM, an
Data Loading...
