Wally Czubatyj

Invited paper: Thin-film Ovonic threshold switch: Its operation and application in modern integrated circuits

The high current switching characteristics of the thin-film Ovonic Threshold Switch (OTS) offer unique advantages in modern applications. This paper covers the current theoretical understanding of the OTS switching process and highlights relevant material and device data. The paper discusses various modern applications of the OTS and OTS integration as a two terminal memory select element applicable for both PCM and RRAM. Also, a novel 3 terminal OTS device is discussed as well as other OTS application as they apply to switching and logic circuits.

MOCVD

Phase-change memory devices fabricated using MOCVD-deposited 30% Ge, 20% Sb, and 50% Te atomic composition, GST325 alloy, are fully characterized. In 100-nm-size test devices, a more than 2x reduction of reset current and set resistance were demonstrated compared with equivalent devices using PVD-deposited GST225. The devices show set speeds of 175-260 ns and a ten-year data-retention temperature of 102°C, comparable with devices made using a PVD GST225 alloy. Cycle endurance of up to 7 × 109 was also demonstrated.

\hbox{Ge}_{3}\hbox{Sb}_{2}\hbox{Te}_{5}

We have demonstrated conformal deposition of amorphous GeSbTe films in high aspect ratio structures by MOCVD. SEM analysis showed the as-deposited GeSbTe films had smooth morphologies and were well controlled for void free amorphous conformal deposition. GeSbTe films adhere well to SiO 2 , TiN, and TiAlN. The morphology and adhesion are stable in 420°C post process. By annealing at 365°C, amorphous GeSbTe films converted into crystalline GeSbTe with polycrystalline grain sizes of 5nm. Film resistivity in the crystalline phase ranged from 0.001 to 0.1 Ω-cm, suitable for device applications. Phase change devices fabricated with confined via structures filled with MOCVD GeSbTe showed cycle endurances up to 1×10 10 with a dynamic set/rest resistance of two orders of magnitude.