JuHwan Park1,Myeong Jun Jung1,Gun Hwan Kim2,Min Kyu Yang3,Dustin Kendig4,Mohammad Shakouri4,Byung Joon Choi1
Seoul National University of Science and Technology1,Korea Research Institute of Chemical Technology2,Sahmyook University3,Microsanj4
JuHwan Park1,Myeong Jun Jung1,Gun Hwan Kim2,Min Kyu Yang3,Dustin Kendig4,Mohammad Shakouri4,Byung Joon Choi1
Seoul National University of Science and Technology1,Korea Research Institute of Chemical Technology2,Sahmyook University3,Microsanj4
Chalcogenide-based ovonic threshold switch (OTS) devices that exhibit volatile resistive switching depending on the external electrical field are being studied as the selector to solve the sneak path current issue. During repetitive switching, joule heating can occur, and such thermal effect may induce degradation of the devices. Also, the operation of the OTS device is not clearly understood, especially at elevated temperatures. To understand the relationship between volatile electronic switching and thermal effects, thermoreflectance (TR) imaging microscopy analysis was conducted.<br/>In this study, we used TR imaging microscopy to observe the thermal image and real temperature during electrical operation using a Microsanj SanjSCOPE™ Transient Thermal Imaging System . A LED light source is injected onto the devices while an electrical bias is applied. After the CMOS camera captures the reflected light, the temperature is evaluated by comparing the change in reflectivity. For this analysis, GeTe<sub>x</sub> and Se- doped GeTe (SGT) based OTS devices which show superior threshold switching characteristics were fabricated on a Pt bottom electrode. A TiN metal layer was deposited on a chalcogenide thin film to see the thermal boundary resistance between the metal and chalcogenide-based material. A Au metal layer was deposited on the TiN metal layer as a photothermal transducer layer due to its stability and high thermoreflectance coefficient value. As a result of in situ TR imaging analysis, the temperature during operation and localized volatile resistive switching characteristics were observed, which has not been well characterized before. In addition, time-domain thermoreflectance (TDTR) analysis was also conducted by using Transometer™ (TMX Scientific Inc., US). When a heating pulse is applied to the thin film, thermal decay of thermoreflectance over time is observed while applying the probing pulse continuously. From this analysis, the thermal conductivity and thermal boundary resistance of the film stack can be calculated. Thermal conductivities of GeTe<sub>x</sub> films deposited under various conditions were compared to analyze their thermal effects. With multiphysics simulation, we try to understand the elevated temperature and furthermore, its effect on the OTS devices.