Chalcogenide alloys, in particular Ge2Sb2Te5 (GST), have been used to realize phase-change memories (PCMs) [1,2]. They are the best candidates to evolve NOR-type floating-gate (FG) memories beyond the 45-nm technology node [3-5]. In this work, we have fabricated and characterized GST line test-structure memories, i.e. GST thin films structured into lines that at both sides end in pads of increased area [6]. Test-structures were fabricated by Electron Beam Lithography (EBL) and Inductively Cou-pled Plasma. Patterned lines were §400nm long, §20nm thick and §30nmwide. An overlayer of hy-drogen silsesquioxane (HSQ) has been also patterned for passivation. The samples have been annealed at 220°C to reduce access resistance to 10 kOhm. The structures have been successful switched be-tween SET and RESET states with more than two decade resistivity contrast, with SET pulses as short as 500ns and RESET pulses 300ns long and a melt current of §120?A. Nanosession: Phase change memories 173 Ge2Sb2Te5 LINE TEST-STRUCTURES FOR PHASE-CHANGE NON VOLATILE MEMORIESG. D'Arrigo1, A.M. Mio1, A. Cattaneo2, C. Spinella1, A.L. Lacaita2 and E. Rimini11IMM-CNR, VIII Strada 5, I-95121 Catania, Italy 2Dipartimento di Elettronica e Informazione, Politecnico di Milano, piazza L. da Vinci 32, I-20133 Milano, Italy Chalcogenide alloys, in particular Ge2Sb2Te5 (GST), have been used to realize phase-change memories (PCMs) [1,2]. They are the best candidates to evolve NOR-type floating-gate (FG) memories beyond the 45-nm technology node [3-5]. In this work, we have fabricated and characterized GST line test-structure memories, i.e. GST thin films structured into lines that at both sides end in pads of increased area [6]. Test-structures were fabricated by Electron Beam Lithography (EBL) and Inductively Cou-pled Plasma. Patterned lines were §400nm long, §20nm thick and §30nmwide. An overlayer of hy-drogen silsesquioxane (HSQ) has been also patterned for passivation. The samples have been annealed at 220°C to reduce access resistance to 10 kOhm. The structures have been successful switched be-tween SET and RESET states with more than two decade resistivity contrast, with SET pulses as short as 500ns and RESET pulses 300ns long and a melt current of §120?A. Figure 1: SEM micrograph of a single GST line after the plasma etching of GST . The e-beam lithog-raphy was done using the HSQ resist with 55 nm in thickness and several test was done to reduce the proximity effect in the exposition. The structure was switched between SET and RESET states using pulses of 500ns and 300 ns long. A recovery mechanism, permitting the restore of a set stuck failure with a slow I-V ramp, has been also investigated. For a cell in the initial set min state, a current hysteresis of about 50 ?A has been measured during I-V sweep up and sweep down (voltage ramp 0÷2.7V, pulse duration §300ns), probably due to stoichiometry variation during phase switching. The direct access to the active region of the cell allows to correlate programming characteristics and their electrical-induced variations with structural, morphological and chemical measurements. The structure is a good "work bench" able to indicate how the system changes in function of the cycling. The absence of metal plug in direct contact with the GST line allows a better evaluation of the electri-cal current induced mass transport. We have measured by EDX the changes in chemical composition along pulsed lines (50-200 cycles) and we have found an accumulation of Te in the correspondence of the anode [7]. We present also an alternative approach to study the physics behavior of single cell, in a inverted mushroom configuration, with a plug contacts below the 20 nm in diameter and we show the preliminary results.
Nanosession: Phase Change Memories
G D'Arrigo;
2012
Abstract
Chalcogenide alloys, in particular Ge2Sb2Te5 (GST), have been used to realize phase-change memories (PCMs) [1,2]. They are the best candidates to evolve NOR-type floating-gate (FG) memories beyond the 45-nm technology node [3-5]. In this work, we have fabricated and characterized GST line test-structure memories, i.e. GST thin films structured into lines that at both sides end in pads of increased area [6]. Test-structures were fabricated by Electron Beam Lithography (EBL) and Inductively Cou-pled Plasma. Patterned lines were §400nm long, §20nm thick and §30nmwide. An overlayer of hy-drogen silsesquioxane (HSQ) has been also patterned for passivation. The samples have been annealed at 220°C to reduce access resistance to 10 kOhm. The structures have been successful switched be-tween SET and RESET states with more than two decade resistivity contrast, with SET pulses as short as 500ns and RESET pulses 300ns long and a melt current of §120?A. Nanosession: Phase change memories 173 Ge2Sb2Te5 LINE TEST-STRUCTURES FOR PHASE-CHANGE NON VOLATILE MEMORIESG. D'Arrigo1, A.M. Mio1, A. Cattaneo2, C. Spinella1, A.L. Lacaita2 and E. Rimini11IMM-CNR, VIII Strada 5, I-95121 Catania, Italy 2Dipartimento di Elettronica e Informazione, Politecnico di Milano, piazza L. da Vinci 32, I-20133 Milano, Italy Chalcogenide alloys, in particular Ge2Sb2Te5 (GST), have been used to realize phase-change memories (PCMs) [1,2]. They are the best candidates to evolve NOR-type floating-gate (FG) memories beyond the 45-nm technology node [3-5]. In this work, we have fabricated and characterized GST line test-structure memories, i.e. GST thin films structured into lines that at both sides end in pads of increased area [6]. Test-structures were fabricated by Electron Beam Lithography (EBL) and Inductively Cou-pled Plasma. Patterned lines were §400nm long, §20nm thick and §30nmwide. An overlayer of hy-drogen silsesquioxane (HSQ) has been also patterned for passivation. The samples have been annealed at 220°C to reduce access resistance to 10 kOhm. The structures have been successful switched be-tween SET and RESET states with more than two decade resistivity contrast, with SET pulses as short as 500ns and RESET pulses 300ns long and a melt current of §120?A. Figure 1: SEM micrograph of a single GST line after the plasma etching of GST . The e-beam lithog-raphy was done using the HSQ resist with 55 nm in thickness and several test was done to reduce the proximity effect in the exposition. The structure was switched between SET and RESET states using pulses of 500ns and 300 ns long. A recovery mechanism, permitting the restore of a set stuck failure with a slow I-V ramp, has been also investigated. For a cell in the initial set min state, a current hysteresis of about 50 ?A has been measured during I-V sweep up and sweep down (voltage ramp 0÷2.7V, pulse duration §300ns), probably due to stoichiometry variation during phase switching. The direct access to the active region of the cell allows to correlate programming characteristics and their electrical-induced variations with structural, morphological and chemical measurements. The structure is a good "work bench" able to indicate how the system changes in function of the cycling. The absence of metal plug in direct contact with the GST line allows a better evaluation of the electri-cal current induced mass transport. We have measured by EDX the changes in chemical composition along pulsed lines (50-200 cycles) and we have found an accumulation of Te in the correspondence of the anode [7]. We present also an alternative approach to study the physics behavior of single cell, in a inverted mushroom configuration, with a plug contacts below the 20 nm in diameter and we show the preliminary results.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
