Formation of iridium nanocrystals with highly thermal stability for the applications of nonvolatile memory device with excellent trapping ability

Abstract

This paper presents the formation of iridium nanocrystals (Ir-NCs) embedded in SiO2 matrix and it can be used for potential applications of nonvolatile memory devices. The NC formation is investigated by varying Ir film thickness; and the thermal agglomeration is also studied by applying various annealing temperatures and process time. The results of systematic characterization including capacitance-voltage, transmission electron microscopy, and x-ray photoelectron spectroscopy show that the high work-function (5.27 eV) metallic-NCs have a highly thermal stability (up to 900 °C) and the resulted Al/SiO2/Ir-NCs/SiO2/Si/Al stack can have a good retention ability and significant hysteresis window of 17.4 V.

Improved performance of non-volatile memory with Au-Al2O3 core-shell nanocrystals embedded in HfO2 matrix

“…In the past decade, tremendous efforts have been invested into research of nanocrystal (NC) memories from materials and structures. Semiconductor nanocrystals such as Si, 1 Ge, 2 metal nanocrystals such as Al, 3,4 Ag, 5 Ni, 6 W, 7-9 Pt, 10 Au, [11][12][13][14] Ru, 15 Co, 16,17 ,Ir, 18 and oxide nanocrystals such as IrO x , 19 RuO (Ref. 20) have been reported.…”

Nonvolatile floating gate memory containing AgInSbTe–SiO2nanocomposite layer and capping the HfO2/SiO2composite blocking oxide layer

“…This is ascribed to the high-barrier feature of the HfO 2 /SiO 2 oxide layer which effectively inhibits the injection of charge trapped in AIST NCs to the gate electrode so as to yield a stable V FB shift property during the cycle operation. In comparison with previous studies utilizing at least 20 nm thick blocking oxide layers [12][13][14][15][16][17][18][19], the HfO 2 /SiO 2 composite oxide layer with thickness less than 15 nm is able to suppress the charge injection in the NFGM and implies the good retention property. This is ascribed to the insertion of a PECVD SiO 2 layer with relatively large E g (=9 eV) which renders a sufficiently high barrier to alleviate the charge tunneling.…”

“…Previous studies demonstrated that the nanocomposite layers containing uniformly dispersed AIST NCs can be prepared via the target-attachment sputtering process [26,27] or the composite target sputtering method [42]. In comparison with other NC-based NFGM systems utilizing complicated methods for the charge trapping layer fabrication [10][11][12][13][14][15][16][17][18][19], it would be a great advantage for chalcogenide nanocomposites applied to NFGM since the high-density charge trapping layer can be easily prepared via a one-step, conventional sputtering process.…”

“…Recently, NFGM devices utilizing either semiconductor or metallic nanocrystals (NCs) as the discrete charge storage traps have attracted considerable attention due to their advantages of low lateral leakage current, low power consumption, high operative efficiency and better endurance [4][5][6]. Tiwari et al first implanted the Si NCs in NFGM [7] and, afterwards, various NFGMs containing semiconductor NCs such as germanium (Ge) [8] and SiGe [9] or transition metal NCs such as silver (Ag) [1], ruthenium (Ru) [10], tungsten (W) [11], cobalt (Co) [12], platinum (Pt) [13], gold (Au) [14], nickel (Ni) [15], molybdenum (Mo) [16], chromium (Cr) [17] and iridium (Ir) [18] were reported. Among these, the transition metal NCs provided better memory performance and retention characteristics due to their high thermal stability and suitable physical properties [10][11][12][13][14][15][16][17][18].…”

Charge storage characteristics of Au nanocrystal memory improved by the oxygen vacancy-reduced HfO2 blocking layer

“…Numerous attempts have been made to develop non-volatile memory devices using metal NCs, such as Ni [5], Au [6], Ir [7], and Pt [8], because metal NCs have a higher density of states around the Fermi level, a wider range of available work functions, and smaller energy perturbation compared with their semiconductor counterparts [9]. Further improvement in memory performance can be achieved through the integration of metal NCs with high- κ dielectric materials, such as HfO 2 [10] and Al 2 O 3 [11].…”