Abstract
A simplified one-diode one-resistor (1D1R) resistive switching memory cell that uses only four layers of TaN/ZrTiO x /Ni/n+-Si was proposed to suppress sneak current where TaN/ZrTiO x /Ni can be regarded as a resistive-switching random access memory (RRAM) device while Ni/n+-Si acts as an Schottky diode. This is the first RRAM cell structure that employs metal/semiconductor Schottky diode for current rectifying. The 1D1R cell exhibits bipolar switching behavior with SET/RESET voltage close to 1 V without requiring a forming process. More importantly, the cell shows tight resistance distribution for different states, significantly rectifying characteristics with forward/reverse current ratio higher than 103 and a resistance ratio larger than 103 between two states. Furthermore, the cell also displays desirable reliability performance in terms of long data retention time of up to 104 s and robust endurance of 105 cycles. Based on the promising characteristics, the four-layer 1D1R structure holds the great potential for next-generation nonvolatile memory technology.
Highlights
As conventional flash memory is approaching its scaling limits, resistive-switching random access memory (RRAM), one of the most promising emerging nonvolatile memories, holds the potential to replace it for future memory-hungry applications because of superior speed, higher density, and complementary metal-oxide-semiconductor (CMOS) compatibility [1,2,3,4]
For self-rectifying RRAM devices, dielectric and electrode should be carefully selected to concurrently meet the requirement of large F/R ratio for diode and high RHRS/RLRS ratio for RRAM where RHRS and RLRS respectively denote the resistance at highresistance state (HRS) and low-resistance state (LRS)
Most device structures with self-rectifying behavior such as Cu/a-Si/WO3/Pt [15], Pt/Al/PCMO/Pt [16], and Pt/ ZrOx/HfOx/TiN/HfOx/ZrOx/Pt [17] still possess unsatisfactory RHRS/RLRS ratio and F/R ratio. It usually requires at least four layers to implement self-rectifying characteristics for aforementioned RRAM devices and the structure compromises the advantage of simple process of selfrectifying devices
Summary
As conventional flash memory is approaching its scaling limits, resistive-switching random access memory (RRAM), one of the most promising emerging nonvolatile memories, holds the potential to replace it for future memory-hungry applications because of superior speed, higher density, and complementary metal-oxide-semiconductor (CMOS) compatibility [1,2,3,4]. Most device structures with self-rectifying behavior such as Cu/a-Si/WO3/Pt [15], Pt/Al/PCMO/Pt [16], and Pt/ ZrOx/HfOx/TiN/HfOx/ZrOx/Pt [17] still possess unsatisfactory RHRS/RLRS ratio (approximately 10) and F/R ratio (approximately 100) It usually requires at least four layers to implement self-rectifying characteristics for aforementioned RRAM devices and the structure compromises the advantage of simple process of selfrectifying devices. The reason to adopt ZrTiOx is that it has been shown to have desirable RRAM characteristics [19] Compared to those published in the literature, the intriguing points of this work lie in four aspects: (1) This is the first structure that uses metal/semiconductor Schottky diodes to rectify current characteristics and the whole structure requires only four layers which are much simpler than other 1D1R structures and even comparable to selfrectifying devices. Compared to those published in the literature, the intriguing points of this work lie in four aspects: (1) This is the first structure that uses metal/semiconductor Schottky diodes to rectify current characteristics and the whole structure requires only four layers which are much simpler than other 1D1R structures and even comparable to selfrectifying devices. (2) This 1D1R cell displays desirable electrical characteristics in terms of forming-free property, RHRS/RLRS ratio higher than 103, F/R ratio larger than 103, operation voltage close to 1 V, negligible resistance change up to s retention time at 125°C, and robust endurance of cycles. (3) Unlike some 1D1R structures that use special materials as diode, all the layers used in this work are fab-friendly and can be fully integrated with existing ULSI process
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