Abstract
In this study, a wide range of a-SiNx:H films with an excess of silicon (20 to 50%) were prepared with an electron-cyclotron resonance plasma-enhanced chemical vapor deposition system under the flows of NH3 and SiH4. The silicon-rich a-SiNx:H films (SRSN) were sandwiched between a bottom thermal SiO2 and a top Si3N4 layer, and subsequently annealed within the temperature range of 500-1100°C in N2 to study the effect of annealing temperature on light-emitting and charge storage properties. A strong visible photoluminescence (PL) at room temperature has been observed for the as-deposited SRSN films as well as for films annealed up to 1100°C. The possible origins of the PL are briefly discussed. The authors have succeeded in the formation of amorphous Si quantum dots with an average size of about 3 to 3.6 nm by varying excess amount of Si and annealing temperature. Electrical properties have been investigated on Al/Si3N4/SRSN/SiO2/Si structures by capacitance-voltage and conductance-voltage analysis techniques. A significant memory window of 4.45 V was obtained at a low operating voltage of ± 8 V for the sample containing 25% excess silicon and annealed at 1000°C, indicating its utility in low-power memory devices.
Highlights
Silicon nitride-based dielectrics are drawing considerable attention because of their utility in a wide variety of electronic and optoelectronic applications due to their compatibility with the existing mainstream CMOS technology and tunable emission in visible range, which can be applied for developing non-volatile memories and Sibased light-emitting diodes [1,2,3,4,5,6]
SiN/SiO2 stack structures have wide applications in non-volatile charge memories (NVMs). Their use started since early 1970s as metal-nitrideoxide-silicon (MNOS) structures [15], and their various derivatives, such as metal-oxide-nitride-oxidesilicon (MONOS), silicon-nitride-oxide-silicon (SNOS), silicon-oxide-nitride-oxide-silicon (SONOS), metalnitride-nitride-silicon (MNNOS) structures have remained as the state-of-art techniques for NVMs [16]
Composition of MW-CVD silicon-rich a-SiNx:H films (SRSN) films Figure 1 depicts the variation of atomic content of silicon, nitrogen, and hydrogen, as estimated from Rutherford backscattering (RBS) and elastic recoil detection analysis (ERDA) measurements on 50 nm of SRSN layers deposited on Si-substrates with different gas flow ratios
Summary
Silicon nitride-based dielectrics are drawing considerable attention because of their utility in a wide variety of electronic and optoelectronic applications due to their compatibility with the existing mainstream CMOS technology and tunable emission in visible range, which can be applied for developing non-volatile memories and Sibased light-emitting diodes [1,2,3,4,5,6]. SiN/SiO2 stack structures have wide applications in non-volatile charge memories (NVMs). Their use started since early 1970s as metal-nitrideoxide-silicon (MNOS) structures [15], and their various derivatives, such as metal-oxide-nitride-oxidesilicon (MONOS), silicon-nitride-oxide-silicon (SNOS), silicon-oxide-nitride-oxide-silicon (SONOS), metalnitride-nitride-silicon (MNNOS) structures have remained as the state-of-art techniques for NVMs [16]. The fabrication of uniform, reproducible, and tunable Si nanostructures by simple and flexible technique, compatible with existing CMOS technology, is extremely important In this regard, one of the best methods used for the evolution of Si-ncs in silicon nitride/oxide-based dielectrics is the high-temperature annealing of these films containing excess amount of Si. One of the major issues is the inevitable interface states at the crystalline silicon/dielectric interface. Capacitance-voltage (C-V) and conductance-voltage (G-V) measurements were carried out using HP4192A impedance analyzer through a LABVIEW interface
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