Current-limiting amplifier for high speed measurement of resistive switching data
T. Hennen, E. Wichmann, A. Elias, J. Lille, O. Mosendz, R. Waser, D. J. Wouters, D. Bedau
CCurrent-limiting amplifier for high speed measurement of resistiveswitching data
T. Hennen, a) E. Wichmann, A. Elias, J. Lille, O. Mosendz, R. Waser, D. J. Wouters, and D. Bedau b) IWE II, RWTH Aachen University, 52074 Aachen, Germany Western Digital San Jose Research Center, 5601 Great Oaks Pkwy, San Jose, CA 95119 (Dated: 12 February 2021)
Resistive switching devices, important for emerging memory and neuromorphic applications, facesignificant challenges related to control of delicate filamentary states in the oxide material. As adevice switches, its rapid conductivity change is involved in a positive feedback process that wouldlead to runaway destruction of the cell without current, voltage, or energy limitation. Typically, cellsare directly patterned on MOS transistors to limit the current, but this approach is very restrictiveas the necessary integration limits the materials available as well as the fabrication cycle time. Inthis article we propose an external circuit to cycle resistive memory cells, capturing the full transfercurves while driving the cells in such a way to suppress runaway transitions. Using this circuit, wedemonstrate the acquisition of 10 I , V loops per second without the use of on-wafer current limitingtransistors. This setup brings voltage sweeping measurements to a relevant timescale for applications,and enables many new experimental possibilities for device evaluation in a statistical context. I. INTRODUCTION
Today, much effort is focused on employing emerging ma-terials and physical mechanisms for the purpose of data stor-age and computation . Several schemes make use of Resis-tive Switching (RS), which refers to a large class of relatedphenomena wherein the resistance of a two-terminal devicecan be controlled via electrical stimuli . These effects can beused, as in Resistive Random Access Memory (RRAM), tostore bits as non-volatile resistance states. Resistive switchescan be fabricated using wide variety of CMOS-compatiblematerials, and are highly attractive due to their simple devicestructure, high speed, scalability, and potential for 3D integra-tion as required by next generation memory and computingarchitectures.A central challenge for RRAM is the intrinsically stochas-tic nature of the RS process, which leads to large variability inthe programmed resistance states and switching parameters .Achieving an acceptable level of control over the switchingprocess will require an in-depth understanding of the statisti-cal processes at play, as well as an optimization of active ma-terial together with the control circuitry. For this purpose, itis necessary to drive memory cells through a statistically sig-nificant number switching cycles, and to rapidly test differentmaterials and modes of operation on a wafer probing system.RRAM is commonly benchmarked by direct application ofsquare voltage pulse sequences, but one of the shortcomingsof this approach is that only the resulting resistance statesare typically recorded, while the dynamics of the conduc-tance changes in the material are very often left unmeasured.Quasistatic I , V loops are an alternative measurement whereswitching is induced by an applied voltage that is continu-ously ramped at low speed ( ∼ I , V loops are relatively rich in information,and important parameters such as the resistance non-linearity, a) Electronic mail: [email protected] b) Electronic mail: [email protected] voltage/current switching thresholds, and details of the tran-sition behavior can be extracted. However, the low speed ofthe measurement puts excessive electrical stress on the deviceand makes experiments involving more than a few hundredswitching cycles impractical. + L J K 5 H V L V W D Q F H 6 W D W H + 5 6 / R Z 5 H V L V W D Q F H 6 W D W H / 5 6 6 ( 7 5 ( 6 ( 7 $ S S O L H G 9 R O W D J H ' H Y L F H & X U U H Q W &