A Comprehensive Study of Effect of Composition on Resistive Switching of Hf x Al 1-x O y based RRAM devices by Combinato
- PDF / 2,768,608 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 103 Downloads / 136 Views
A Comprehensive Study of Effect of Composition on Resistive Switching of HfxAl1-xOy based RRAM devices by Combinatorial Sputtering Pankaj Kumbhare1, Paritosh Meihar2, Senthilkumar Rajarathinam3, Shikhar Chouhan1, Suhit Pai1, Neeraj Panwar1, U. Ganguly1 1 Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India 2 Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India 3 Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India ABSTRACT We use the combinatorial sputter technique to simultaneously sputter HfO2 and Al2O3 targets to obtain a film of HfxAl1-xOy of specific compositions. The effect of oxide thickness, oxide composition (i.e. Hf:Al ratio) and oxygen gettering layer thickness on DC sweep based resistive switching performance of RRAM is investigated. The oxide thickness primarily affects forming voltage and causes the memory window to increase for the thinnest oxide (6 nm, other thicknesses – 12 nm, 18 nm). The composition of oxide has a non-linear effect on the memory window (high to low resistance ratio) and variability of resistance states whereas the variability of set voltage improves significantly for ternary oxide compared to individual binary oxides. Finally, electrode interlayer for oxygen-gettering is also critical where a thin Ti layer of 1.5nm maintains the memory window but reduces variability in HRS, LRS, reduces Vset and Vreset and improves the variability in Vset. INTRODUCTION The resistive switching behavior in transition metal oxides HfO2 have been widely investigated for Resistive Random Access Memory (RRAM) applications [1]. Improvements in memory window and intrinsic stochastic variability in these devices is a challenge [2]. This has motivated the further exploration of various techniques like composition modification by adding elements like Al. For example, HfxAl1-xOy by ALD [3], thermal oxidation [4] etc. have shown improvement in variability, reliability of HfO2 based RRAM. However, different characteristics (e.g. forming voltage) have been reported for similar chemistry but different deposition techniques which indicates film deposition technique dependence of device characteristics. Combinatorial sputtering is a facile and manufacturable method of deposition of ternary oxides. In this work, we propose the use of combinatorial sputtering for high-throughput materials screening for RRAM applications and use the ternary system of HfxAl1-xOy as a model system. EXPERIMENTAL a) Materials Deposition: The 2” HfO2 and Al2O3 targets were placed at opposite sides of a nonrotating 4” Si wafer in confocal RF sputter geometry and sputtered simultaneously in an AJA ATC-2200 Confocal Sputter System to generate films with graded composition. The resultant film was characterized to obtain the composition gradient (i.e. Hf:Al ratio) by X-ray
65
66
67
68
69
CONCLUSIONS In this paper, we have demonst
Data Loading...
