Papers by Keyword: Poly-Silicon

Abstract: In this work, we demonstrated a method to fabricate and characterize poly-silicon nanowires for biosensing application using conventional photolithography and etching process. Nanowires Mask must be first designed using AutoCAD, before patterning onto chrome mask. Chrome mask was used for better photo masking and to transfer structure onto poly-silicon layer. The poly-silicon nanowires process flow were developed which includes all the fabrication process such as growth, deposition, lithography and etching process. In order to prove the effectiveness of the fabricated devices as a biologically sensor (Biosensor), the poly-silicon nanowires is modified chemically to allow the integration with biological element. The drain (I_d) was found to increase after the DNA immobilization and hybridization. These results demonstrate that the in-house fabricated poly-silison nanobiosensor is capable as a platform for label-free biosensing. The morphological characterizations were carried out using a Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM). Besides that, the electrical measurement of the poly-silicon biosensor were carried out using a KEITHLEY 6487 picoampmeter/voltage source.

Abstract: The current status of nanofabrication briefly reviewed, then molecular dynamics model of poly-silicon is founded on micro-nanoscale with molecular dynamics method, in which several typical defects are distributed reasonably. Molecular dynamics simulation of nanocutting process is conducted according to the simulation model. Keeping the other conditions remain unchanged, simulating calculation is made by reasonably changing cutting parameters such as cutting velocity and cutting depth, through which the changes of the morphology structure of workpiece surface,cutting force and system potential energy are observed. The simulation results are compared and studied, then the influence laws of each parameter on morphology structure of workpiece surface, cutting force and system potential energy are analyzed. Based on this, the mechanism of poly-silicon nanomachining is discussed .

Abstract: Temperature gradient and solidification rate are two key parameters during polysilicon directional solidification, which are varied to improve the polysilicon production process. Dendritic growth, distribution of impurities, Minority carrier lifetime and resistivity mapping are also discussed in this paper. A better quality of polysilicon ingot is presented by optimized casting process.

Abstract: Aluminum–induced crystallization of sputtered a-Si under two-step annealing procedure on glass substrate is studied. A 200 nm thick a-Si film was deposited by magnetron sputtering on glass and a Al film of 150 nm was sputtered on top. The samples were annealed under two-step annealing procedure. Nucleation and growth of grains were followed by optical microscopy (OM), X-ray diffraction (XRD), Raman spectroscopy, and energy dispersive spectroscopy (EDS). Continuous (111) oriented poly-Si films were obtained with a Raman Peak at 520.8cm^-1. The different annealing periods is discussed.

Abstract: We report in this work some process optimization effort in performing poly silicon removal for replacement gate process integration. Successful wet poly silicon removal after dummy gate patterning is not only conditioned by suitable process conditions during wet removal but is also impacted by process steps prior to gate removal A thorough evaluation of the impact on poly removal from dopants or contaminants introduced in the poly silicon by previous processing is done, resulting in an optimized integration flow with successful poly removal. This work also shows that use of diluted TMAH chemistry instead of diluted ammonia in performing poly silicon removal provides better ability in removing poly silicon especially in narrow gate structures.

Abstract: Nonvolatile memory (NVM) devices with nitride-nitride-oxynitride (NNO) stack structure using Si-rich silicon nitride (SiN_x) as charge trapping layer on glass substrate were fabricated. Amorphous silicon clusters existing in the Si-rich SiN_x layer enhance the charge storage capacity of the devices. Low temperature poly-silicon (LTPS) technology, plasma-assisted oxidation/nitridation method to form a uniform ultra-thin tunneling layer, and an optimal Si-rich SiN_x charge trapping layer were used to fabricate NNO NVM devices with different tunneling thickness 2.3, 2.6 and 2.9 nm. The increase memory window, lower voltage operation but little scarifying in retention characteristics of nitride trap NVM devices had been accomplished by reducing the tunnel oxide thickness. The fabricated NVM devices with 2.9 nm tunneling thickness shows excellent electrical properties, such as a low threshold voltage, a high ON/OFF current ratio, a low operating voltage of less than ±9 V and a large memory window of 2.7 V, which remained greater than 72% over a period of 10 years.

Abstract: The complex chemical reactions in the Si-Cl-H system with relation to modified Siemens process have been studied in this paper based on the thermodynamic data of related substance. The influence of the temperature, pressure and initial feed ratio (n_Si / n_SiHCl3) on the silicon yield have been studied. Furthermore, the diagram of Kinetic constant k as a function of temperature for the rate controlled reaction has also been fitted in the SiHCl3 hydrogen system. Finally 1425K, 1.5atm and the initial feed ratio of 15 is the best conditions. Under these conditions, the silicon yield is 34.815%.

Abstract: Wire electrical discharge machining (WEDM) of polycrystalline silicon (polysilicon) involves high-temperature melting that easily produces cracks on the silicon surface. This paper studies improvements of cracks and craters on surface of polysilicon after wire electrical discharge machining (WEDM) by magnetic force-assisted electrolytic machining (MFA-EM). The effects of different MFA-EM parameters on material removal and surface roughness are explored to understand the machining characteristics of MFA-EM and how magnetic field assistance contributes to high-efficiency and high-quality machining. Experimental results show that compared with standard EM, MFA-EM can achieve better machining efficiency and surface quality because MFA-EM can effectively enhance electrolyte circulation and replenishment, which contributes to better machining stability.

Abstract: This work deals with the investigation of the complex phenomenon of boron (B) transient enhanced diffusion (TED) in strongly implanted silicon (Si) layers. It concerns the instantaneous influences of the strong B concentrations, the Si layers crystallization, the clustering and the B trapping/segregation during thermal post-implantation annealing. We have used Si thin layers obtained from disilane (Si₂H₆) by low pressure chemical vapor deposition (LPCVD) and then B implanted with a dose of 4×1015 atoms/cm2 at an energy of 15 keV. To avoid long redistributions, thermal annealing was carried out at relatively low-temperatures (700, 750 and 800 °C) for various short-times ranging between 1 and 30 minutes. To investigate the experimental secondary ion mass spectroscopy (SIMS) doping profiles, a redistribution model well adapted to the particular structure of Si-LPCVD layers and to the effects of strong-concentrations has been established. The good adjustment of the simulated profiles with the experimental SIMS profiles allowed a fundamental understanding about the instantaneous physical phenomena giving and disturbing the TED process in strongly doped Si-LPCVD layers. It was found that boron TED is strongly affected by the simultaneous complex kinetics of clustering, crystallization, trapping and segregation during annealing. The fast formation of small Si–B clusters enhances the B diffusivity whereas the evolution of the clusters and segregation reduce this enhancement.

Abstract: A monolithic MEMS accelerometer process was established. This process successfully combines our standard BiCMOS technology and MEMS surface micromachining technique. The acceleration sensing element is a kind of comb-finger structure which is built by polysilicon surface micromachining technique. The polysilicon structure is designed to form two capacitors for acceleration sensing. The external acceleration will cause the value of two capacitors to vary in different direction. That means one reduces if the other increases. It was integrated with the signal conditioning circuit. In a single die, the active devices including vertical NPN, lateral PNP, PMOS and passive devices such as capacitors, resistors were fabricated which was followed by the steps to form the acceleration sensing structure. The experiment indicates that the fabricated circuit has the function of sensing capacitive variation and with a scale factor of 100mV/g.