Liquid Phase Deposition Oxide Research Articles

A Silicon Texturing Technique Based on Etching Through a Liquid-Phase Deposited Oxide Mask

This work presents an electrochemical etching technique for silicon (Si) surface texturing that simultaneously occurs during the liquid-phase deposition (LPD) of silicon dioxide (SiO 2 ) on the surface. The method relies on an isotropic electropolish etching through self-defined micropores evolved in the LPD oxide mask, leading to a uniform texture, without requiring any patterning. Hydrofluorosilicic acid/ethanol electrolyte has been used in the etching process. Orientation-independent texturing was successfully realized on spherical Si single crystals for potential application in photovoltaics. The characteristics of Si surface texture and LPD SiO 2 layer were investigated by energy-dispersive spectroscopy, scanning electron microscopy, atomic force microscopy, and Fourier transform IR.

Nitride-based metal–insulator–semiconductor capacitors with liquid-phase deposition oxide and (NH4)2Sx pretreatment prepared on sapphire substrates

Nitride-based metal–insulator–semiconductor (MIS) capacitors with liquid-phase deposition (LPD) oxide and (NH4)2Sx pretreatment were successfully prepared on sapphire substrates. It was found that we can significantly reduce the leakage current densities of the fabricated Al/LPD-SiO2/AlGaN MIS capacitors by using (NH4)2Sx treatment. Compared to the MIS capacitors without (NH4)2Sx treatment, the leakage current densities were remarkably reduced by two orders of magnitude in (NH4)2Sx-treated MIS capacitors. Capacitance–voltage measurement showed that the MIS capacitor without (NH4)2Sx treatment was rather leaky. In contrast, the flat-band voltage shift, fixed oxide charge density and interface trap density of the fabricated MIS capacitor with (NH4)2Sx treatment were much improved to be 2.01 V, 7.22 × 1011 cm−2 and 7.19 × 1011 cm−2 eV−1, respectively. A related mechanism of (NH4)2Sx treatment was discussed by an x-ray photoelectron spectrometer

High 366/254-nm Rejection Contrast GaN MIS Photodetectors Using Nano Spin-Oxide

In this paper, GaN-based metal-insulator-semiconductor (MIS) photodetectors (PDs) with liquid-phase deposition oxide (LPD oxide) or nanospin oxide were fabricated and compared. Compared to the MIS-PDs with LPD oxide, the nanospin-oxide device can dramatically reduce the optical response of 254 nm by two orders while still retaining the same 366-nm optical response as LPD oxide. The 366/254-nm rejection contrast is raised from 5.13 to 413 for the MIS-PDs with LPD and spin oxides, respectively. Thus, one can simply insert a thin (10 nm) nanospin-oxide layer between the metal and GaN to significantly reduce the response of 254 nm. Possible mechanism is discussed here.

Solution-Deposited Amorphous Titanium Dioxide on Silicone Rubber: A Conformal, Crack-Free Antibacterial Coating

Controlled formation of thin oxide films on polymers provides an increasingly important tool for modifying the polymer interface without changing its bulk properties. The successful application of a titania thin film by liquid phase deposition (LPD) from water under near-ambient conditions onto polydimethylsiloxane (PDMS) substrates has been achieved. This offers a convenient, non-line-of-sight-limited method for imparting titania-like properties to the surface of the PDMS elastomer. Conditions have been found for priming the surface of the PDMS to provide for good adhesion of the oxide layer and a suitable combination of film deposition and film drying conditions are described that provide a conformal crack-free titania coating on the PDMS. This is the first report of LPD oxide formation on an elastomer. The application of such titania coatings to controlling bacterial adhesion and growth on the polymer surface is also described. The adhesion of both Gram-negative and Gram-positive bacteria to the modified surfaces is reduced. This reduction is further enhanced by UV irradiation of the TiO2 overlayer prior to introduction of the bacteria.

Growth and Electrical Characteristics of Liquid-Phase Deposited SiO[sub 2] on Ge

The liquid-phase deposition (LPD) of SiO 2 at 50°C on Ge substrates is investigated. Silicic acid (SiO 2 .xH 2 O) is used to saturate hydrofluorosilicic acid at 30°C and this shortens the time required for solution preparation to 3 h. The growth rate of LPD oxide on Ge is much slower than that of LPD oxide on Si at the beginning of the deposition process, while surface roughness of LPD oxide on Ge is larger than that of LPD oxide on Si. A metal-oxide-semiconductor tunneling diode on Ge is fabricated using the LPD oxide. The tunneling current of the Ge diodes at inversion bias increases as LPD oxide thickness increases, indicating that the trap density in the LPD oxide increases with increasing oxide thickness, and the current transport is dominated by the trap assistant tunneling.

Device Quality SiO2 Films by Liquid Phase Deposition (LPD) AT 48°C

AbstractWe describe the preparation, properties and the comparison of SiO2 films deposited by liquid phase deposition from supersaturated solutions with both silica powder and silicic acid. From each solution the resulting [Si (OH)4]-rich supersaturated solution, when suitably diluted with De-Ionised (DI) water deposits SiO2 onto silicon. Our work was motivated by the search for the optimum condition for device quality oxide growth within a low (<300°C) thermal budget, for large area device fabrication, on inexpensive substrates such as glass and plastic. The net growth of the LPD of the oxide layer is result of competition between deposition and etching; the balance and hence the rate of growth being controlled simply and reproducibly by the addition of de-ionised (DI) water. We have produced device grade SiO2 from the solution at 48°C onto both n and p type Si substrates. Control of the oxide properties is achieved in the amount of DI water added to the super-saturated solution. Oxide layers of optimum quality being obtained by the titration of 60ml DI water to 100ml of supersaturated solution. FTIR, ellipsometery, and C-V/I-V measurements were used to characterise the films deposited from solutions of silica powder and silicic acid. The resistivity of the optimum layers from a saturated solution of silica powder was found to be of the order of ≈1011 Ωcm with breakdown field strengths of the order of 3-5 x 106 V/cm. The resistivity of the optimum layers prepared using silicic acid were much higher (1015 Ω-cm), with breakdown field strengths of the order of (9±1) x 106 V/cm. The results approach those for thermally grown silicon dioxide, suggesting that LPD oxide have the potential of device quality insulator on large area substrate.

Characterization and Reliability of Lightly-Doped-Drain Polysilicon Thin-Film Transistors with Oxide Sidewall Spacer Formed by One-Step Selective Liquid Phase Deposition

We have proposed and successfully demonstrated a novel process for fabricating a lightly doped drain (LDD) polysilicon thin-film transistor (poly-Si TFT). The oxide sidewall spacer in the new process is formed by a simple one-step selective liquid phase deposition (LPD) at 23°C. In contrast with conventional methods, this new process does not require an additional photolithographic step for defining the non-self-aligned offset gate, or the deposition of an oxide layer and subsequent etch-back to form the self-aligned sidewall spacer. Devices fabricated by the new process have a lower leakage current and a better ON/OFF current ratio, compared with non-LDD control devices. The new device also shows excellent current saturation characteristics at high bias and better has hot-carrier endurance. Since the apparatus used for LPD oxide deposition is simple and inexpensive, the new process appears to be promising for future high-performance poly-Si TFT fabrication.

CO2 Laser Annealing on Fluorinated Silicon Oxide Films

CO2 laser annealing of fluorinated silicon oxide films grown by liquid-phase deposition (LPD) is proposed to improve the properties of the as-deposited films. It is found that the fluorinated silicon oxide films after laser annealing become much denser and that the effective surface charge density (QSS/q) is reduced significantly. However, the properties of the fluorinated silicon oxide films after laser annealing depended on the power density of the laser beam. It is also found that the effect of laser annealing is most prominent when the power density of the laser beam is controlled at 12 KW/cm2. Based on the experimental results, it may be expected that the structure of a fluorinated LPD-SiO2 film following CO2 laser annealing is similar to those of the thermally grown layers. Thus, CO2 laser annealing is the best candidate for improving the properties of LPD oxide films.

A novel lightly doped drain polysilicon thin-film transistor with oxide sidewall spacer formed by one-step selective liquid phase deposition

We have proposed and successfully demonstrated a novel process for fabricating lightly doped drain (LDD) polycrystalline silicon thin-film transistors (TFT's). The oxide sidewall spacer in the new process is formed by a simple one-step selective liquid phase deposition (LPD) oxide performed at 23/spl deg/C. Devices fabricated with the new process exhibit a lower leakage current and a better ON/OFF current ratio than non-LDD control devices. Since the apparatus used for LPD oxide deposition is simple and inexpensive, the new process appears to be quite promising for future high-performance poly-Si TFT fabrication.

Efficiency improvement in low temperature metal-oxide-semiconductor solar cells by thin metal film deposition on photon receiving area

The recent discovery of the trap assisted tunneling property of low temperature liquid phase deposition (LPD) oxide is beneficial for metal-oxide-semiconductor (MOS) solar cells. Although the thickness of LPD oxide is up to 7 nm, the trap-assisted tunneling currents are still large enough for solar cell’s application. In this work, we fabricate and study the MOS solar cells with oxide prepared by LPD. The I–V curve for LPD oxide grown on bare Si is much different from that on native oxide. The larger tunneling current for LPD oxide grown on bare Si may be due to the boundaries between oxide seeds’ domains. For solar cells application, it’s better to use LPD oxide grown on bare Si. The conduction mechanism of LPD MOS solar cells is also discussed. For solar cells without additional thin transparent Al film, the minority carriers were collected from the accumulation region outside the main electrodes. For solar cells with additional thin transparent Al film, the thin Al electrode can directly collect the minority carriers from the weak inversion region underneath the thin Al film. For a cell exposed under 20 mW/cm2, short circuit current density JSC up to 13.2 mA/cm2, open circuit voltage VOC up to 433 mV, fill factor FF up to 66 and exposure area effective conversion efficiency η* up to 18.9% are obtained for this structure.

17.3% efficiency metal-oxide-semiconductor (MOS) solar cells with liquid-phase-deposited silicon dioxide

Simple and high efficiency silicon metal-oxide semiconductor (MOS) solar cells, with silicon dioxide prepared by a room-temperature liquid phase deposition (LPD) method, are proposed. The thickness of LPD oxide is about 5 nm. After adding a 2/spl sim/5 nm semi-transparent thin Al film between the 200 nm patterned Al cathode, all the solar cells' performance parameters are improved. For a cell exposed under 15 mW/cm/sup 2/, short-circuit current density J/sub SC/ up to 10.7 mA/cm/sup 2/, open-circuit voltage V/sub OC/ up to 412 mV, fill factor FF up to 59, and record effective conversion efficiency /spl eta/ up to 17.3% are obtained for this structure. Photo-conductivity properties of LPD oxide are found and the mechanism is discussed.

Stress in Liquid‐Phase Deposited Oxide Films

To develop a low‐stress dielectric thin film, a novel liquid‐phase deposition (LPD) technique utilizing silica‐saturated hydrofluosilicic solution with only added is proposed. Due to fluorine incorporation, the stress in as‐deposited LPD oxide can be as low as 83.3 MPa (tensile). Addition of greatly affects the stresses in as‐deposited LPD oxide: the less added, the lower the stress will be. The stress variations accompanying thermal cycling have also been clarified. Films deposited with a larger quantity of added exhibited larger stress variations (hysteresis). After ex situ annealing at around 600°C, the total stress decreased to near 0 MPa.

Controlling Fluorine Concentration and Thermal Annealing Effect on Liquid‐Phase Deposited SiO2 − x F x Films

Silicon oxide with fluorine naturally incorporated can be prepared by the liquid‐phase deposition (LPD) method at 15°C. The fluorine is uniformly distributed in the bulk of the LPD oxide. The fluorine incorporation as well as the qualitative properties can be accurately controlled by varying the amount of added. A high temperature process has considerable effect on the low temperature fluorinated oxide. FTIR and XPS spectra show that Si—F and bonds can restructure with densification at higher thermal annealing temperature, and that restructuring is a function of temperature. Film densification with increasing temperature is also discussed in terms of Si—O—Si bond angle and Si‐Si bond length.

Preparation of fluorinated gate oxides by liquid phase deposition following rapid thermal oxidation

The fluorinated gate oxides grown by the method of liquid phase deposition (LPD) following rapid thermal oxidation (RTO) were studied in this work. Samples with and without aluminum are both investigated in the LPD process. It was found that the amount of F atoms decreases as the LPD oxide was treated subsequently by RTO treatment. For a given time of RTO, the longer the LPD time, the larger the amount of F contained in the gate oxides. But for a given time of LPD, the longer the RTO time, the smaller the amount of F contained in the gate oxides. It was found that the radiation induced oxide charge number density shift ΔNot and the midgap interface trap density shift ΔDitm, and the oxide breakdown field Eox exhibit turnaround dependencies on the LPD growth time. In other words, they are dependent on the amount of F atoms incorporated into the gate oxide. Interestingly, it was found that for the gate oxides grown by the LPD process containing Al have better quality than the LPD without containing Al from the viewpoint of radiation hardness and electric breakdown field.

Fabrication of MOSFETs using low-temperature liquid-phase deposited oxide

Low-temperature, high quality liquid-phase deposition (LPD) oxide was developed. The MOSFETs with such a new LPD oxide as gate insulators were investigated. The electrical characteristics, including threshold voltage of 2.1 Volts, peak effective mobility ( μ FE) of 580 cm 2/V·s, and subthreshold swing of 134 mV/decade, show the devices exhibit comparable performance to other low-temperature processed MOSFETs. This demonstrates that LPD oxide can be an suitable candidate for future gate insulators in low-temperature processed MOSFETs.

Bond-structure changes of liquid phase deposited oxide (SiO2−xFx) on N2 annealing

Fluorine can be naturally incorporated into the silicon oxide (SiO2−xFx) prepared by the liquid phase deposition (LPD) method at 35 °C. Fourier transform infrared and x-ray photoelectron spectroscopy spectra show that an annealing treatment can change its bond-structure. Changes in properties accompanying the restructuring are also observed. The annealing also densifies the LPD oxide and reduces its thickness because Si–F intensity decreases and the Si–O–Si intensity increases as annealing temperature increases.

Characteristics of self-induced lightly-doped-drain polycrystalline silicon thin film transistors with liquid-phase deposition SiO/sub 2/ as gate-insulator and passivation-layer

As the passivation layer on the top of undoped offset region for offset-gate structured poly-Si TFTs is exposed to hydrogen plasma, a lightly-doped-like drain region could be equivalently self-induced. The hydrogenated polycrystalline silicon thin-film transistor of this structure, named self-induced lightly-doped-drain (SI-LDD) poly-Si TFTs, was first developed with liquid-phase deposition oxide as both the gate insulator and the passivation layer. This paper describes the optimum hydrogenation condition, and the electrical characteristics for the novel SI-LDD poly-Si TFTs. The effects of DC electrical stress on SI-LDD poly-Si TFTs are also described. Finally a model is proposed to explain the degradation phenomena observed in our SI-LDD devices.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The Physicochemical Properties and Growth Mechanism of Oxide ( SiO2 − x F x ) by Liquid Phase Deposition with H 2 O Addition Only

Silicon oxide formation was studied by a novel liquid phase deposition (LPD) method with addition only at 35°C. The deposition rate could be controlled by varying the quantity of added. The LPD‐oxide was lightly oxygen‐deficient. FTIR spectra and AES depth profiles indicate that a small amount of fluorine was incorporated into the oxide. The composition of LPD‐oxide can be represented as . The physicochemical properties of LPD oxide were investigated, as was the behavior of fluorine in the oxide and the chemical reaction. A model for the LPD mechanism is proposed that satisfactorily explains all of the experimental phenomena observed.