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.
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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....
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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]....
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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]....
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...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]....
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References
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TL;DR: In this paper, the authors proposed a method to identify the weak spots in thermally grown gate oxide and repair them by selective anodization by controlling the applied voltage, ensuring that current flows only through weak spots.
Abstract: The presence of weak spots and pinholes in ultrathin gate oxides significantly increases the leakage current, thereby degrading the device performance This paper proposes a method, which identifies the weak spots in thermally grown gate oxide and repairs them by selective anodization By controlling the applied voltage, it is ensured that current flows only through the weak spots in the oxide during anodization Anodic oxide therefore grows over these weak spots, improving the reliability of the oxide without increasing the gate oxide thickness Significant improvement in electrical characteristics was observed in the gate oxides treated by anodic oxidation
18 citations
"Electrical and Reliability Characte..." refers background in this paper
...that anodization is a very effective postoxidation process for improving the quality of ultrathin thermal oxide [4]....
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TL;DR: X-ray photoelectron spectra (XPS) of thin SiO2 layers grown by pulsed Nd:YAG laser at a substrate temperature of 748 K are presented in this paper.
Abstract: X-ray photoelectron spectra (XPS) of thin SiO2 layers grown by pulsed Nd:YAG laser at a substrate temperature of 748 K are presented The peak decomposition technique combined with depth profiling is employed to identify the composition and chemical states of the film structure It is established that the oxide is non-stoichiometric, and contains all oxidation states of Si in different amounts throughout the film The interface Si/laser-grown oxide is not abrupt, and the coexistence of Si2O3 and Si2O suboxides in a relatively wide interfacial region is found It is concluded that post-oxidation annealing is necessary in order to improve the microstructure of both oxide and near interface region
18 citations
Additional excerpts
...oxidation [6]–[8], and chemical oxidation [9]–[16]....
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01 Jan 2005
TL;DR: SiO2/Si structure can be formed at low temperatures by use of nitric acid (HNO3) oxidation of Si (NAOS) method as discussed by the authors, where Si wafers are immersed in ∼ 40 wt% HNO3 solutions at 108◦C, ∼ 1 nm SiO2 layers are formed.
Abstract: SiO2/Si structure can be formed at low temperatures by use of nitric acid (HNO3) oxidation of Si (NAOS) method. When Si wafers are immersed in ∼ 40 wt% HNO3 solutions at 108◦C, ∼ 1 nm SiO2 layers are formed. The subsequent immersion in 68 wt% HNO3 (i.e., azeotropic mixture of HNO3 with water) at 121◦C increases the SiO2 thickness. The 3.5 nm-thick SiO2 layers produced by this two-step NAOS method possess a considerably low leakage current density (e.g., 1× 10 A/cmi at the forward gate bias, VG, of 1.5 V), in spite of the low temperature oxidation, and further decreased (e.g., 8×10 A/cm at VG = 1.5 V) by post-metallization annealing at 250◦C in hydrogen atmosphere. In order to increase the SiO2 thickness, a bias voltage is applied during the NAOS method. When 10 V is applied to Si with respect to a Pt counter electrode both immersed in 1 M HNO3 solutions at 25◦C, SiO2 layers with 8 nm thickness can be formed for 1 h.
14 citations
TL;DR: In this paper, the leakage current density flowing through the SiO2 layer formed at 350°C followed the Poole-Frenkel mechanism, indicating the presence of trap states in the siO2 band gap, and the trap energy is estimated to be 0.57eV below the Si O2 conduction band.
Abstract: Si can be oxidized at temperatures between 350 and 500°C by use of nitric acid (HNO3) vapor, resulting in 5–10nm SiO2∕Si structure. The oxidation kinetics follows a parabolic law, indicating that diffusion of oxidizing species (i.e., oxygen atoms generated by decomposition of HNO3 molecules) through SiO2 is the rate-determining step. The leakage current density flowing through the SiO2 layer formed at 350°C follows the Poole-Frenkel mechanism, indicating the presence of trap states in the SiO2 band gap, and the trap energy is estimated to be 0.57eV below the SiO2 conduction band. On the other hand, the leakage current density for the SiO2 layer formed at 500°C follows the Fowler-Nordheim mechanism, showing the absence of trap states.
14 citations
TL;DR: In this paper, the authors correlated the electrical characteristics of ultrathin gate oxide with the presence of pinholes by C-AFM studies and showed that the improvement in the gate leakage current in thermally grown oxide is indeed due to the filling of pinhole by selective anodic oxidation.
Abstract: In this work, we have correlated the electrical characteristics of ultrathin oxide with the presence of pinholes by C-AFM studies. Ultrathin gate oxide has been grown thermally as well as by chemical treatment with HNO 3 , followed by selective anodic oxidation. The results of C-AFM studies confirm that the improvement in the gate leakage current in thermally grown oxide is indeed due to the filling of pinholes by selective anodic oxidation, while the absence of pinholes in the chemically grown oxide explains why there is no improvement in the gate leakage current after selective anodisation.
10 citations
"Electrical and Reliability Characte..." refers background or methods in this paper
...the surfaces of both thermal and chemical oxides using Atomic Force Microscopy [15]....
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...oxides grown by thermal oxidation at a temperature range of 700 ◦C–800 ◦C [15]....
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...This was verified by comparing the surfaces of both thermal and chemical oxides using Atomic Force Microscopy [15]....
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