PECVD Deposited Germanium Selenide Films for Memory Devices        


Dr. Rene' Rodriguez

Department of Chemistry

Idaho State University

Renewed interest in the use of germanium chalcogenide semiconductors for phase memory materials and for resistive-RAM memory has been driven by the unique properties of these materials including their proclivity to resist radiation damage.  In phase memory, the large difference in conductivity between the amorphous and crystalline forms of germanium selenide provides the off/on basis of the memory. In resistive-RAM the mechanism of action is the formation or retraction of silver nano-bridges through the germanium selenide amorphous glass depending on the polarity of an applied field.

Plasma enhanced chemical vapor deposition (PECVD) of germanium chalcogenide thin films from germanium tetrachloride, hydrogen sulfide and alkyl chalcogenides was studied to determine the viability of these reagents for thin film deposition. Alkylselenide precursors were used successfully for the deposition of germanium selenides.

The effects of relative mass flow rates, substrate temperature, and plasma power density on the deposition rate, the composition, and the morphology of the germanium selenide thin films were determined.   Based on these results, germanium selenide thin films were deposited by PECVD in several stoichiometries, as a thin layers in phase memory and resistive-RAM devices consisting of a W/GexSey / SnSe phase memory stack or a W/GexSey/SnSe/Ag R-RAM stack. The results from the thin film studies and their use in memory devices will be presented.