Electrical and Reliability Characteristics of MOS Devices With Ultrathin $\hbox{SiO}_{2}$ Grown in Nitric Acid Solutions
TL;DR: In this article, the electrical and reliability properties of ultrathin silicon dioxide, grown by immersing silicon in nitric acid solution have been studied, and it is observed that the temperature, oxidation time, and concentration of the nitric acids solution play important roles in determining the thickness as well as the quality of the oxide.
Abstract: In this paper, electrical and reliability properties of ultrathin silicon dioxide, grown by immersing silicon in nitric acid solution have been studied. It is observed that the temperature, oxidation time, and concentration of the nitric acid solution play important roles in determining the thickness as well as the quality of the oxide. Prolonged exposure to nitric acid degrades the quality of the oxide. However, it was found necessary to reduce the oxidation temperature and the concentration of nitric acid to grow oxide of thickness 2 nm. In these conditions, the leakage current and fixed oxide charge in the chemical oxide were found to be too high. However, when this chemical oxidation was followed by anodic oxidation using ac bias, the electrical and reliability characteristics of metal-oxide-semiconductor (MOS) devices showed tremendous improvement. A MOSFETs with gate oxide grown by this technique have demonstrated low subthreshold slope, high transconductance and channel mobility. It is thus proposed that chemical oxidation followed by ac anodization can be a viable alternative low-temperature technique to grow thin oxides for MOS application.
Citations
More filters
TL;DR: In this paper, a dielectric stack with Al2O3/HfO2/SiO2 (18 nm/16 nm/25 nm) trilayer structure prepared by low temperature in situ natural oxidation during dc sputtering is investigated.
Abstract: In this work, a dielectric stack with Al2O3/HfO2/SiO2 (18 nm/16 nm/25 nm) trilayer structure prepared by low temperature in situ natural oxidation during dc sputtering is investigated We study the electrical characteristics, including the dielectric leakage of 10−8 A/cm2 at Vg=−2 V, the current transport mechanism and trap distributions through the trilayer dielectric stack The Fowler–Nordheim barrier height of the prepared Al2O3 (ϕFN,Al2O3) was extracted as 306±015 eV The current variation ratios [ΔJg/Jg(0)] during constant voltage stressing were found to decrease with raising gate stress voltages for the trilayer stack in comparison with that [ΔJg/Jg(0)] increase with raising gate stress voltages for the two-layer HfO2/SiO2 stack Shallow traps located in HfO2 were supposed to be major trapping centers within the trilayer stack The proposed method of in situ oxidation during dc sputtering is of merit and low in process temperature The trilayer dielectric stacks are an alternative option for no
22 citations
19 Dec 2012
TL;DR: Semiconductor-based ultraviolet photodiodes have been continuously developed that can be widely used in various commercial, civilian areas, and military applications, such as optical communications, missile launching detection, flame detection, UV radiation calibra- tion and monitoring, chemical and biological analysis, optical communications and astro- nomical studies, etc as mentioned in this paper.
Abstract: Semiconductor-based ultraviolet (UV) photodiodes have been continuously developed that can be widely used in various commercial, civilian areas, and military applications, such as optical communications, missile launching detection, flame detection, UV radiation calibra‐ tion and monitoring, chemical and biological analysis, optical communications, and astro‐ nomical studies, etc. [1-2]. All these applications require very sensitive devices with high responsivity, fast response time, and good signal-to-noise ratio is common desirable charac‐ teristics. Currently, light detection in the UV spectral range still uses Si-based optical photo‐ diodes. Due to the Si-based photodiodes are sensitive to visible and infrared radiation, the responsivity in the UV region is still low [3-5]. To avoid these disadvantages, wide-bandgap materials (such as diamond, SiC, III-nitrides and wide-bandgap II–VI materials) are under intensive studies to improve the responsivity and stability of UV photodiodes, because of their intrinsic visible-blindness [6].
10 citations
Cites methods from "Electrical and Reliability Characte..."
...Several fabrication methods have been employed for the formed of ultrathin SiO2 films, such as rapid thermal oxidation (RTO) [36], oxidation with excited molecules and ions [37,38], plasma oxidation [39,40], photo-oxidation [34,41], ozone oxidation [43], metal-promot‐ ed oxidation [44], anodic oxidation [45,46] and nitric acid (HNO3) vapor oxidation [47,48] etc....
[...]
TL;DR: In this article, a tilted-substrate sputtering technique, which provides various film thicknesses in one processing step, was proposed and useful for the characterization of charge distribution in low-temperature dielectric stacks with anodic oxide interfacial layer (ANO-IL).
Abstract: Hafnium oxide dielectric stacks with anodic oxide interfacial layer (ANO-IL) were investigated under low-temperature consideration. A tilted-substrate sputtering technique, which provides various film thicknesses in one processing step, was proposed and useful for the characterization of charge distribution. It was found that charges existed in the HfO2/ANO-IL were smaller than that in HfO2/rapid-thermal-oxidation IL. The prepared samples exhibit good electrical characteristics, including small electrical hysteresis (< 10 mV), low leakage current, high effective dielectric breakdown field of 12.7 MV/cm, and maximum operating voltages of -2.74 V at 25degC and -2.32 V at 125degC for EOT = 2.3 nm stacks under a ten-year lifetime evaluation. The results suggest that the quality of IL in the dielectric stack is a critical reliability issue and that ANO is provided as a candidate for IL consideration of low-temperature dielectric stacks.
9 citations
Cites methods from "Electrical and Reliability Characte..."
...Room-temperature oxidation methods such as anodization or chemical oxidation provided other promising choices for the preparation of low-temperature IL [11], [12]....
[...]
TL;DR: In this article, the oxide layer on the surface of a p-type silicon substrate was grown under various growth times and temperatures while under nitric acid treatment, and an efficiency improvement of absolute 2% was obtained using their laboratory fabrication process.
Abstract: In this study, we investigate the effect of nitric acid oxidation on p-type silicon solar cells. The oxide layer on the surface of a p-type silicon substrate was grown under various growth times and temperatures while under nitric acid treatment. After 30 min of growth at 23 °C, an efficiency improvement of absolute 2% was obtained using our laboratory fabrication process.
9 citations
Dissertation•
01 Jan 2010
8 citations
Cites background from "Electrical and Reliability Characte..."
...It is however possible to chemically grow thin films of SiO2 by exposing the clean silicon to nitric acid (HNO3) [152-153]....
[...]
...Studies on SiO2 films grown via the nitric acid solution method have previously shown that interface trapped charge density is comparable to thermally grown oxide and is likely to be in the range of approximately 10 11 cm -2 , which is an order of magnitude lower than the levels of trapped charge that are necessary here [152]....
[...]
References
More filters
TL;DR: In this article, a 3.5-nm-thick SiO2 layer with a higher atomic density of 2.22×1022∕cm2 was formed by immersion of Si in 40 wt% nitric acid (HNO3) followed by immersion in an azeotropic mixture (i.e., 68 wt % HNO3).
Abstract: 3.5-nm-thick SiO2 layers can be formed at 120 °C by immersion of Si in 40 wt % nitric acid (HNO3) followed by immersion in an azeotropic mixture (i.e., 68 wt % HNO3). The former immersion produces a 1.1-nm SiO2 layer with a low atomic density of 2.19×1022∕cm2, where the layer acts as a catalyst for the decomposition of HNO3. The latter immersion results in a 3.5-nm SiO2 layer with a higher atomic density of 2.22×1022∕cm2. When the postmetalization annealing treatment at 250 °C in hydrogen is performed on the ⟨Al∕3.5-nmSiO2∕Si(100)⟩ metal-oxide semiconductor diodes, interface states are passivated and a low leakage current density (e.g., 8×10−4A∕cm2 at the forward gate bias of 1.5 V) is achieved.
49 citations
"Electrical and Reliability Characte..." refers methods in this paper
...5-nm-thick SiO2 layers with low leakage currents has been obtained by a twostep HNO3 oxidation followed by postmetallization annealing [12]–[14]....
[...]
TL;DR: In this paper, the leakage current density of the as-grown SiO2 layers of 1.3 nm thickness was investigated and it was concluded that the high atomic density results from the desorption of water and OH species, and oxidation of the suboxide species, both resulting in the formation of SiO 2.
Abstract: Spectroscopic and electrical properties of ultrathin silicon dioxide (SiO2) layers formed with nitric acid have been investigated. The leakage current density of the as-grown SiO2 layers of 1.3 nm thickness is high. The leakage current density is greatly decreased by post-oxidation annealing (POA) treatment at 900 � C in nitrogen, and consequently it becomes lower than those for thermally grown SiO2 layers with the same thickness. X-ray photoelectron spectroscopy measurements show that high density suboxide species are present before POA and they are markedly decreased by POA. Fourier transformed infrared absorption measurements show that water and silanol group are present in the SiO2 layers before POA but they are removed almost completely by POA above 800 � C. The atomic density of the as-grown chemical SiO2 layers is 4% lower than that of bulk SiO2 layers, while it becomes 12% higher after POA. It is concluded that the high atomic density results from the desorption of water and OH species, and oxidation of the suboxide species, both resulting in the formation of SiO2. The valence band discontinuity energy at the Si/SiO2 interface increases from 4.1 to 4.6 eV by POA at 900 � C. The high atomic density enlarges the SiO2 band-gap energy, resulting in the increase in the band discontinuity energy. The decrease in the leakage current density by POA is attributed to (i) a reduction in the tunneling probability of charge carriers through SiO2 by the enlargement of the band discontinuity energy, (ii) elimi- nation of trap states in SiO2, and (iii) elimination of interface states. � 2003 Elsevier B.V. All rights reserved.
43 citations
"Electrical and Reliability Characte..." refers background or methods in this paper
...From the spectroscopic studies it has been reported that the concentrations of suboxide species Si and Si are greatly reduced or almost eliminated by postoxidation annealing (POA) and this is attributed to the formation of SiO2 from OH, Si , and Si species [14]....
[...]
...5-nm-thick SiO2 layers with low leakage currents has been obtained by a twostep HNO3 oxidation followed by postmetallization annealing [12]–[14]....
[...]
...9 eV due to the charging effect observed for thicker oxides [14]....
[...]
TL;DR: In this article, anodic oxidation at room temperature with pure deionized water as electrolyte and then followed by high-temperature rapid thermal densification was used to prepare high breakdown endurance thin-gate oxides with thicknesses of about 50 /spl Aring.
Abstract: Anodic oxidation at room temperature with pure deionized water as electrolyte and then followed by high-temperature rapid thermal densification was used to prepare high breakdown endurance thin-gate oxides with thicknesses of about 50 /spl Aring/. It was observed that the oxides prepared by anodic oxidation followed by rapid thermal densification (AOD) show better electrical characteristics than those grown by rapid thermal oxidation (RTO) only. The AOD oxides have a very low midgap interface trap density, Ditm, of smaller than 1/spl times/10/sup 10/ eV/sup -1/ cm/sup -2/ and negative effective oxide trapped charge. From the smaller leakage currents observed during staircase ramp voltage time-zero dielectric breakdown (TZDB) and constant field time-dependent dielectric breakdown (TDDB) testings, it is supposed that the uniform interfacial property and the pretrapped negative charges in AOD oxides are responsible for the improved characteristics.
26 citations
"Electrical and Reliability Characte..." refers background or methods in this paper
...These new techniques include anodic oxidation [3]–[5], laser induced...
[...]
...910442 dielectric layers for MOS device applications [3]–[16]....
[...]
TL;DR: In this paper, a novel and simple method to determine deep ultrathin oxide thickness by measuring the MOS capacitance under the flat-band condition is reported, and the results determined by this method show good agreement with those using capacitance-voltage (C-V) simulation, ellipsometer, and high-resolution transmission electromicroscopy (HRTM) analysis for thin oxides (2/spl sim/3 nm).
Abstract: In this letter, a novel and simple method to determine deep ultrathin oxide thickness by measuring the MOS capacitance under the flat-band condition is reported. The mechanism of this method has been profoundly studied. The results determined by this method show good agreement with those using capacitance-voltage (C-V) simulation, ellipsometer, and high-resolution transmission electromicroscopy (HRTM) analysis for thin oxides (2/spl sim/3 nm). The thickness of pure oxide extracted by this method in this experiment can be down to 1.4 nm despite the obvious C-V distortion.
25 citations
"Electrical and Reliability Characte..." refers methods in this paper
...The gate oxide thickness (tox) has been measured using L2W16S544 Stokes ellipsometer from Gaertner Scientific Corporation and also calculated from the value of accumulation capacitance using a technique recently suggested for ultrathin oxides [20]....
[...]
TL;DR: In this article, the effect of both the laser beam energy density and the substrate temperature on the oxide growth was discussed, and it was established that there exists an interval of laser beam EE density in which the oxidation occurs without surface melting.
Abstract: SiO2 thin films have been obtained by 1064 nm Nd : YAG laser oxidation of p-Si in the presence of O2. The thickness uniformity, dielectric and electrical properties of the layers have been studied. The effect of both the laser beam energy density and the substrate temperature on the oxide growth is also discussed. It was established that there exists an interval of laser beam energy density in which the oxidation occurs without surface melting. The oxidation process is controlled by the laser beam energy density rather than by the substrate temperature (673–748 K) and the higher laser power results in a thicker oxide. X-ray photoelectron spectroscopy (XPS) was used to provide information on the oxide composition. XPS results revealed that the as-grown oxide is a mixed layer of SiO2 and Si2O, which are distributed nonuniformly through the depth. MOS capacitors fabricated on the grown oxide exhibited typical capacitance–voltage, conductance–voltage characteristics. However, the density of interface states and oxide charge density were found to be higher than the typical values of thermally grown oxides. The quality of the oxide layers can be further improved by optimization of the process parameters and/or by post-processing of the grown films. It is concluded that the SiO2 films formed by the technique of Nd : YAG laser-enhanced oxidation at low temperature are potentially useful for device applications.
23 citations
Additional excerpts
...oxidation [6]–[8], and chemical oxidation [9]–[16]....
[...]