Papers by Keyword: PECVD

Abstract: Amorphous carbon nitride (a-CN_x) is a well-known material that can be used in various applications such as coating for hard disk, wear resistant, humidity sensor and others. In this research, a-CN_x thin films have been deposited by using radio frequency-plasma enhanced chemical vapor deposition (RF-PECVD) with the mixing of pure methane (CH₄) and nitrogen (N₂). The gas ratio of CH₄/N₂, electrode distance, pressure and temperature of deposition is kept constant while deposition time is allowed to vary from 30 to 150 minutes. Raman spectroscopy and field emission scanning electron microscopy (FESEM) have been used to study the bonding and morphology of these films respectively. An increase in deposition time resulted with thedecrease in sp² content in the a-CN_x thin films. Theincrease in the I_d/I_g intensity ratio with the increase in deposition time can be explained by the reducing size of graphitic cluster. Long deposition time retarded the growth rate of a-CN_x thin films due to etching effects. Longer exposure to the etching effect resultingin the creation of small graphitic cluster with the formation of spongy-like porous features.

Abstract: In this paper, the effect of nickel (Ni) catalyst on the growth of carbon nanotubes (CNTs) was studied where the CNTs were vertically grown by plasma enhanced chemical vapor deposition (PECVD) method. The growth conditions were fixed at a temperature of 700°C with a pressure of 1000mTorr for 40 minutes with various thicknesses of sputtered Ni catalyst. Experimental results show that high density of CNTs was observed especially towards thicker catalyst layers where larger and taller nanotubes were formed. The growth rate increases by ~0.7 times with increasing catalyst thickness from 4nm to 10nm. The nucleation of the catalyst with various thicknesses was also studied as the absorption of the carbon feedstock is dependent on the initial size of the catalyst island. From the Raman results, we found that only slight variation in the intensity ratio of G-band over D-band as increasing catalyst thicknesses. The minor difference in G/D ratio indicates that the catalyst thickness does not significantly influence the quality of CNTs grown.

Abstract: The purpose of this work is to study the mechanical characteristics of the silicon nitride(SiN_x) thin films prepared by PECVD technique, some researches as follows were carried out. First, the SiNx thin films were deposited on the two different substrates. Then, the atomic force microscope (AFM) was adopted to test the surface quality of the SiN_x films, and the scanning electron microscope (SEM) was used to test the section morphology of the SiN_x thin films. Finally, the rotating beam structures was applied to measure the residual stress in the SiNx films. The SiN_x thin films with low stress can be fabricated through PECVD, in which the surface roughness values(Ra) are 1.261 nm and 2.383nm, and the residual stress is 43.5 kPa. Therefore, the SiN_x thin films deposited by PECVD are suitable for the preparation of device dielectric films in MEMS.

Abstract: According to integrated circuit (IC) devices, this study proposed a integrated automatic design platform including geometric modeling, finite element simulation analysis, experimental design etc. The platform is a software system, the development of which is driven by product design of IC device chambers. As a module of the platform, the electromagnetic fields simulation part is based on secondary development of Ansys HFSS and the Python language to transfer data, build model and analyze automatically. The validity of the electromagnetic simulation module is verified by an example of PECVD SC300 chamber.

Abstract: The mechanism of high stress in silicon nitride thin film is studied systematically in this paper. The effects of the various process parameters on the stress in silicon nitride thin film deposited by PECVD are analyzed and discussed. The silicon nitride thin film with high compressive and tensile stress has been deposited on the optimized process parameters and the compressive and tensile stress are up to-1.38GPa and 866MPa, respectively. Finally, the method of further improving the stress in silicon nitride thin film is presented.

Abstract: This paper presents an experimental investigation of microstructure and piezoresistive properties of phosphorus-doped hydrogenated nanocrystalline silicon (nc-Si:H) thin films. The phosphorus-doped nc-Si:H thin films (5% doping ratio of PH₃ to SiH₄) were deposited by plasma enhanced chemical vapor deposition (PECVD) technique. The microstructure and surface morphology of the deposited thin films was characterized and analyzed with Raman spectroscopy and atomic force microscopy (AFM), respectively. The piezoresistive properties of the deposited thin films were investigated with a designed four-point bending-based evaluation system. In addition, the influence of temperature on the piezoresistive properties of these thin films was evaluated with the temperature coefficient of resistance (TCR) measurements from room temperature up to 80°C. The experimental results show that phosphorus-doped nc-Si:H thin films prepared by PECVD technique are a two-phase material that constitutes of nanocrystalline silicon and amorphous silicon, and they present a granular structure composed of homogeneously scattered nanoclusters formed by nanocrystalline silicon grains (6nm). Moreover, phosphorus-doped nc-Si:H thin films exhibit negative GF at room temperature and show good thermal stability from room temperature up to 80°C, and the value of GF and TCR is about-31 and-509ppm/°C, respectively. These features could make phosphorus-doped nc-Si:H thin films act as a promising material for piezoresistive-based MEMS sensor.

Abstract: In the traditional PECVD method for growing carbon nanotubes (CNTs), the electric field is an important parameter. Its role is to orient CNT growth and dissociate the H-C bond from hydrocarbon gases. Therefore, high energy ions, molecules, and radicals as plasma elements can affect the verticality of CNTs. In this paper, a new configuration for an electric field for the growth of field-oriented and long CNTs on a glass substrate at temperatures below 400°C is reported. Simulation and experimental data show that CNTs are grown at a considerably lower voltage than traditional methods. Using this method, growing vertical CNT on such low-cost substrate glass is more possible for CNT-based devices and bio-applications where price is important.

Abstract: Diamond-like carbon (DLC) films and nitrogen doped DLC (NDLC) were deposited on glass slide and H13 steel by plasma-enhanced chemical vapor deposition using a commercial RF 13.56 MHz (RF-PECVD). The films have been prepared from CH₄ for DLC and CH₄+N₂ mixtures for NDLC. The deposition process was at 300°C under argon atmosphere for 120 min. Bonding energy and diamond like carbon characteristic of DLC and NDLC films have been characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. Thermalgravimetric Analyzer (TGA) was used to evaluate the thermal stability of the films which were scrapped off from a glass slide substrate. The mechanical properties was characterized, such as hardness by nanoindentation technique, scratch test by Rockwell diamond tip in progressive mode and friction coefficient have been measured in ambient air using a ball-on-disk tribometer.

Abstract: Microcrystalline silicon thin films prepared by plasma enhanced chemical vapor deposition (PECVD). Effects of deposition power on the microstructure properties of the thin films were investigated by Raman spectrometry, Fourier transform infrared absorption spectroscopy (FTIR) and atomic force microscopy (AFM). With increasing deposition power from 100 W to 900 W, the growth rate increased from 0.75Å/s to 2.96Å/s. The Raman spectrometry measurements showed that the peak of all films is nearby at 514 nm. The FTIR spectroscopic analysis exhibit that with power increasing the intensities of both the (Si-H) _n stretching mode component at 2100cm^-1 and wagging mode component at 620cm^-1 increase. The surface morphology of the films using the AFM showed the surface roughness and voids of the films increase with deposition power increasing.

Abstract: We are investigating the effect of different wet chemical surface preconditioning sequences for silicon wafers prior to the deposition of aluminum oxide based passivation layers coated by plasma enhanced chemical vapor deposition. We are focusing on the development of a simple and industrially feasible preconditioning process to achieve a high level of interface passivation after the firing process applied to industrial solar cells. Our process optimization is monitored by characterizing the passivation quality before and after a firing process. We are also investigating the effectiveness of the removal of residual surface iron concentrations by the wet chemical process.