Papers by Keyword: PECVD

Abstract: Under different growth conditions, silicon nitride (SiNx) thin films were deposited successfully on Si(100) substrates and glass substrates by plasma enhanced chemical vapor deposition (PECVD). The thickness, refractive index and growth rate of the thin films were tested by ellipsometer. The surface morphologies of the thin films were investigated using atomic force microscope (AFM). The average transmittance in the visible region was over 90%.

Abstract: Aluminum oxide (AlO_x) is currently under intensive investigation for use in surface passivation schemes in solar cells. AlO_x films contain negative charges and therefore generate an accumulation layer on p-type silicon surfaces, which is very favorable for the rear side of p-type silicon solar cells as well as the p⁺-emitter at the front side of n-type silicon solar cells. However, it has been reported that quality of an interfacial silicon sub-oxide layer (SiO_x), which is usually observed during deposition of AlO_x on Silicon, strongly impacts the silicon/AlO_x interface passivation properties [1]. The present work demonstrates that a convenient way to control the interface is to form thin wet chemical oxides of high quality prior to the deposition of AlO_x/a-SiN_x:H stacks by the plasma enhanced chemical vapor deposition (PECVD).

Abstract: The semiconductor industry considers wet cleans to be critical surface preparation steps. The Si/SiO₂ interface, for example, is very critical to achieve high gate oxide integrity and avoid leakage or stacking faults. Similarly, the solar industry has seen the value of wet processes to achieve best cell performance. In this study, we highlight the effect of pre-cleans, texturization and final cleans on cell parameters. We also studied the importance of coupling these wet cleaning and texturization steps with the PECVD steps to achieve the film quality required for highest solar cell efficiency.

Abstract: Hydrogenated amorphous silicon germanium thin films (a-SiGe:H) were prepared via plasma enhanced chemical vapor deposition (PECVD). By adjusting the flow rate of GeH4, a-SiGe:H thin films with narrow bandgap (Eg) were fabricated with high Ge incorporation. It was found that although narrow Eg was obtained, high Ge incorporation resulted in a great reduction of the thin film photosensitivity. This degradation was attributed to the increase of polysilane-(SiH2)n, which indicated a loose and disordered microstructure, in the films by systematically investigating the optical, optoelectronic and microstructure properties of the prepared a-SiGe:H thin films via transmission, photo/dark conductivity, Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR) measurements. Such investigation provided a helpful guide for further preparing narrow Eg a-SiGe:H materials with good optoelectronic properties.

Abstract: Under different growth conditions, silicon Oxide (SiOx) thin films were deposited successfully on Si (100) substrates and glass substrates by plasma enhanced chemical vapor deposition (PECVD). The thickness, refractive index and growth rate of the thin films were tested by ellipsometer. The effects of deposition temperature on the structure and properties of SiOx films were studied using X ray diffraction (XRD), X ray photoelectron spectroscopy (XPS) and UV-Visible spectroscopy. The results show that the SiOx films were amorphous at different deposition temperature. The peaks of Si2p and O1s shifted to higher binding energy with temperature increasing. The SiOx films had high transmissivity at the range of 400-900nm. By analyzing the observation and data, the influence of deposition parameters on the electrical properties and interface characteristics of SiOx thin film prepared by PECVD is systematically discussed. At last, SiOx thin film with excellent electrical properties and good interface characteristic is prepared under the relatively optimum parameters.

Abstract: GeMn magnetic quantum dots (QDs) material were grown with a GeH4/Ar mixed gas under a constant flowing at 400°C by means of plasma enhanced chemical vapor deposition (PECVD) process, then doped with Mn doped using magnetic sputtering technique and annealed at 600 C. The QDs with a Ge0.88Mn0.12 structure derived from the energy spectrum show a wide opening hysteresis loops with a large remnant magnetizations Mr are 0.1410-4 and 0.2510-4 emu/g for the as grown and the annealed samples. Moreover, the magnetic QDs show high quality voltage-current (I-V) and voltage-capacitance (C-V) properties. The magnetic GeMn QDs can be used to fabrication electromagnetic devices.

Abstract: The SiC_xN_yH_z Films Were Prepared by PECVD Method Using Organosilicon Volatile Compound Hexamethyldisilazane as a Precursor. Some Important Physical and Chemical Properties Were Studied by the Complex of Modern Physical Methods. It Was Shown that at Low Deposition Temperatures the Films Contain the Chemical Bonds of Organic Nature and Have Low Values of Young’s Modulus, Refractive Index and Density. They Possess High Elasticity which Indicates to their Polymeric-Like Structure. At Higher Deposition Temperatures the Films Are Inorganic Composite Materials Consisting of Amorphous Part and Nanocrystals of Graphite and Silicon Nitride. Decrease in Optical Band Gap and Coefficient of Thermal Expansion Is Observed with Deposition Temperature Increase.

Abstract: We report new results on a tunneling junction for tandem solar cells using a nano-structured amorphous silicon p⁺ layer (na-Si p⁺) as the recombination layer inserted between the n layer and the p layer. Devices were characterized by their dark current-voltage behavior (I-V), activation energy (E_a) and quantum efficiency (QE). The result shows that the tunnel junction with a na-Si p⁺ insertion layer has higher recombination rates with higher density of defect states of about 2.7×10¹⁹cm^-3 , lower resistance with activation energy of 22meV. The tunnel junction with a na-Si p⁺ insertion layer could be easily integrated into the tandem solar cell deposition process.

Abstract: Pulsed laser was demonstrated to be effective for the crystallization of amorphous hydrogenated silicon (a-Si:H) films deposited on Si wafer. The amorphous films were deposited on (111) Si wafers by plasma enhanced chemical vapor deposition (PECVD). The crystallization treatment was carried out by a low frequency Nd:YAG laser. The crystallinity modifications induced by the laser treatment were evidenced by X-ray diffraction and atomic force microscope (AFM). The influence of laser frequency on the crystallization degree was analyzed in detail. The better crystallinity was obtained at the laser frequency of 10Hz.

Abstract: It has been reported that the etch rate of exposed aluminum lines and pads on MEMS chips can be significantly reduced by dissolving an appropriate amount of silicon (or silicic acid, water glass) and ammonium persulfate (AP) in TMAH solution. However the etch rates of the PECVD silicon nitride films，which is usually underlying aluminum lines and pad, were rarely reported in previous literatures. In this paper, silicon nitride films of high compressive stress, low compressive stress, micro-stress, low tensile stress and high tensile stress are prepared by adjusting the flow ratio of SiH4 to NH3 and plasma power. Then the films are etched in four kinds of previously reported doped TMAH solutions. The experimental results show that silicon nitride films depositing at low flow ratio of SiH4 to NH3 and lager RF power were etched more slowly in doped TMAH solution than that of depositing at high flow ratio of SiH4 to NH3 and low RF power.