Etching Effect On The Formation Of Silicon Nanowire Transistor Patterned By AFM Lithography.

Anisotropic etching of silicon has been widely used in fabrication of MEMS devices for many years. In this work, TMAH and KOH with IPA are used to etch silicon nanowire transistor patterns

A Review of Different Etching Methodologies and Impact of various etchants in Wet Etching in Micro Fabrication

Abstract--The concept of miniaturization was introduced because of advancement in science and technology during 1980s. These miniaturized structures and designs are of high significance for making up with the macroscopic technology, for the sake of interfacing with microscopic world. The fabrication of micro structures and designs which are the advanced applications of micro fabrication are used for the process of micromachining structures in three dimensions as it is essential for interfacing with the nanotechnology. Micromachining which means performing cutting or grinding operations or selective removal of wafer to produce various structures has much important applications like accelerometers which are used to trigger air bags in cars. The lithography and etching processes are used to shape the bulk materials into microstructures in micro fabrication mechanism. Different ion bombardment techniques and chemical reactive mechanisms are used for a type of etching which is carried out in vacuum chamber, whereas chemical solutions are used for another type of etching mechanism whose procedures are finished in a bath. This survey illustrates different etching methodologies and the impact of various etchants in wet etching

Silicon nanowire : fabrication, characterisation and application

PhD ThesisThis thesis focuses on the fabrication considerations and the characterisation of silicon nanowires and their integration into chemical sensors. One aim is to optimize a top-down fabrication process for silicon nanowires, in particular the methods that use optical lithography, wet etching and thermal oxidation. The main concerns here are to achieve a reproducible and high yield fabrication process and to obtain a controllable structure. Extensive work was carried out to study the parameters that affect the repeatability of the process. The properties of silicon nitride films, the oxidation method and the characteristics of the anisotropic etchant were found to be key parameters affecting the reproducibility of the process. Several silicon nitride films were deposited under various conditions and their optical properties were tested before and after thermal oxidation. It was found that the oxynitride thickness depends on the refractive index of the nitride film: the lower the refractive index, the thinner the oxynitride. Then an etching process was developed to selectively etch the oxidised silicon nitride over silicon dioxide. The etching process included two steps: firstly ion milling to remove the oxynitride film and secondly using boiling phosphoric acid to strip the silicon nitride film. Nitride-rich silicon nitride films exhibited higher etching selectivity over silicon dioxide compared with silicon-rich silicon nitride. Based on the etch selectivity, oxynitride thickness, and silicon dioxide thickness the maximum thickness of silicon nitride film that can be used to act as a mask during the fabrication of silicon nanowires was determined. The impact of oxidation method on the reliability of the process was studied, and SOI and bulk silicon samples were oxidised at the same temperature and time using lamp-based RTP radiation and also a furnace with resistive heating. The results showed that the SOI sample is colder than the bare silicon sample when both were heated using the lamp-based RTP. This effect was considered during the fabrication of silicon nanowires to obtain a reliable process. Comprehensive experimental measurements were carried out to compare the characteristics of Tetra-Methyl Ammonium Hydroxide (TMAH) and Potassium Hydroxide (KOH) etching to optimise the fabrication process. The use of TMAH was found to lead to a more reliable process. ii Another aim of the project was to characterise the fabricated devices, and for this the contact properties and the electrical properties of the silicon nanowires needed to be evaluated. Extensive electrical measurements were carried out to study the thermal stability and ohmic contact formation for the silicon nanowire. Three metallization schemes were studied: Al/Ti, Al/W/Ti and Al/Ti/AlOx. All these exhibited ohmic contact to the nanowires. However, Al/Ti/Si and Al/W/Ti/Si were found to be unstable after 425 °C RTP annealing. Al/Ti/AlOx/Si withstood this level of temperature but the contact resistance was about ten times higher than that of Al/W/Ti. The electrical resistivity of the silicon nanowires was then studied; it was found that the measured electrical resistivity decreases with the nanowire thickness. Several models were then developed to explain the apparent increase in resistivity. It was suggested it can be largely attributed to the reduction of the conductive area of the nanowire due to interface traps. Finally, a silicon nanowire sensor was designed and fabricated, and this sensor was used to detect the changes in pH. The preliminary results showed that the sensor detected the change of pH in the buffer solution. However, reliability and yield were low, which was assumed to be due to the large parasitic current between the source/drain and the buffer solution.For a scholarship to pursue my postgraduate studies, I am grateful to Damascus University in Syria

Microcapteurs de hautes fréquences pour des mesures en aéroacoustique

L aéroacoustique est une filière de l'acoustique qui étudie la génération de bruit par un mouvement fluidique turbulent ou par les forces aérodynamiques qui interagissent avec les surfaces. Ce secteur en pleine croissance a attiré des intérêts récents en raison de l évolution de la transportation aérienne, terrestre et spatiale. Les microphones avec une bande passante de plusieurs centaines de kHz et une plage dynamique couvrant de 40Pa à 4 kPa sont nécessaires pour les mesures aéroacoustiques. Dans cette thèse, deux microphones MEMS de type piézorésistif à base de silicium polycristallin (poly-Si) latéralement cristallisé par l induction métallique (MILC) sont conçus et fabriqués en utilisant respectivement les techniques de microfabrication de surface et de volume. Ces microphones sont calibrés à l'aide d'une source d onde de choc (N-wave) générée par une étincelle électrique. Pour l'échantillon fabriqué par le micro-usinage de surface, la sensibilité statique mesurée est 0.4 V/V/Pa, la sensibilité dynamique est 0.033 V/V/Pa et la plage fréquentielle couvre à partir de 100 kHz avec une fréquence du premier mode de résonance à 400kHz. Pour l'échantillon fabriqué par le micro-usinage de volume, la sensibilité statique mesurée est 0.28 V/V/Pa, la sensibilité dynamique est 0.33 V/V/Pa et la plage fréquentielle couvre à partir de 6 kHz avec une fréquence du premier mode de résonance à 715kHz.Aero-acoustics, a branch of acoustics which studies noise generation via either turbulent fluid motion or aerodynamic forces interacting with surfaces, is a growing area and has received fresh emphasis due to advances in air, ground and space transportation. Microphones with a bandwidth of several hundreds of kHz and a dynamic range covering 40Pa to 4kPa are needed for aero-acoustic measurements. In this thesis, two metal-induced-lateral-crystallized (MILC) polycrystalline silicon (poly-Si) based piezoresistive type MEMS microphones are designed and fabricated using surface micromachining and bulk micromachining techniques, respectively. These microphones are calibrated using an electrical spark generated shockwave (N-wave) source. For the surface micromachined sample, the measured static sensitivity is 0.4 V/V/Pa, dynamic sensitivity is 0.033 V/V/Pa and the frequency range starts from 100kHz with a first mode resonant frequency of 400kHz. For the bulk micromachined sample, the measured static sensitivity is 0.28 V/V/Pa, dynamic sensitivity is 0.33 V/V/Pa and the frequency range starts from 6kHz with a first mode resonant frequency of 715kHz.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Fabrication of Nano-Injection Needles for Neural Pathway Study in Mice

The potential of micro-needles to provide an interconnection between the microscopic and the macroscopic worlds makes it one of the most revolutionary fields in health care, allowing for precise transdermal drug delivery of highly targeted small doses of the active compound. Current micro electro mechanical systems (MEMS) technologies, originally designed for the micro-electronics industry, have been utilized in the fabrication of different micro-needle designs and their integration with various micro-fabricated micro-fluidics devices. The target of this thesis is to achieve a micro-needle injection system to deliver several strains of pico-liter volumes of a fluid combination of transgenic virus and luminescent compound, to be injected into the visual cortex of mice in order to study the structure and function of the neural networks of the brain. Micro-needles having a body dimension of 10 mm x 10 mm and a shaft 1 mm wide and 3 mm long have been constructed from silicon wafers, using technologies originally developed for integrated circuit (IC) fabrication. Silicon wafers have also been used in the fabrication of the needle channels having a width of 4 μm and a total depth of 60 μm with a 20 μm deep channel at the base of the 40 μm trench. Both wet and dry bulk micromachining techniques have been used to create the needle bodies and channels. The optimum fabrication method has been found to be the deep reactive ion etching (DRIE) and SiO2 deposition using the plasma enhanced chemical vapor deposition (PECVD) has been used to seal the channels

Bimetallic Thermal Resists for Photomask, Micromachining and Microfabrication

Photoresists and photomasks are two of the most critical materials in microfabrication and micromachining industries. As the shift towards shorter wavelength exposure continues, conventional organic photoresists and chromelquartz photomasks start to encounter problems. This thesis investigates and presents an alternative to organic photoresists and chromium photomasks which overcomes their intrinsic problems. A bimetallic thin film, such as BilIn and SnIIn, creates an inorganic thermal resist with many interesting properties. Both experiments and simulations demonstrate that this class of thermal resists can be converted by laser exposure with wavelengths from 213 nm to 830 nm, showing wavelength invariance. Simulations of the projected wavelength response show that BiIIn thermal resist works down to the 1 nm X-ray range. Exposed bimetallic thermal resists can be developed in two different acid solutions with excellent selectivity. A standard etch (RCA2) can strip the unexposed bimetallic film when photoresist rework is needed. Exposed bimetallic films are resistant to Si anisotropic wet etching and fluorine, O2 and chlorine plasma etching. The Bi/In thermal resist is the first reported resist that works for both wet chemical anisotropic Si etching and dry plasma etching. All these features make the bimetallic film a complete thermal resist. Another very important property of bimetallic thin films is the largest change in the optical absorption ever reported in the literature (3.0 OD before exposure and 0.22 OD after exposure, 365 nm), with the exposed areas becoming nearly transparent. The transmission of the exposed films depends on the laser writing power. Thus, BilIn resist and its class can be utilized as a direct-write photomask material for both binary and grayscale photomasks. Binary photomasks and grayscale photomasks were successfully created. 2D and 3D structures were successfully generated in Shipley organic photoresists using a mercury lamp mask aligner with exposure conditions identical to those for conventional chrome masks. Material analyses show that the transformation after laser exposure of bimetallic thermal resists is an oxidation process. Laser-converted BilIn and S n h oxides have a structure similar to that of indium tin oxide films

Micromachining of Single Cell Array for Oxygen Consumption Rate Analysis

The Oxygen Consumption Rate of biological cells is an important parameter of cellular metabolism. In order to study the behaviour of cell populations, it becomes necessary to capture and store them in one location for analysis. Individual cell analysis within a cell group can provide useful information about the average response of the cell group, as well as identify outliers. Such analysis can be used to identify different groups of cells based on their oxygen levels. However, characterizing the individual cell response within a cell group is challenging since cell dimensions are on the order of a few micrometers. Conventional techniques, such as microtiter plates and flow cytometry, are unable to offer both the high temporal and the high spatial resolution that is required to characterize individual cells. Modern micromachining and microfabrication techniques, on the other hand, allow for the creation of devices that have dimensions that are on the order of a few micrometers. Through a series of thin film deposition, photolithography and thin film etching techniques, it is possible to create single cell trapping structures whose dimensions are only slightly larger than that of individual cells. The aim of this thesis is to create a process flow in order to fabricate such structures on a single crystalline silicon substrate using available micromachining techniques

Micromachining of Single Cell Array for Oxygen Consumption Rate Analysis

The Oxygen Consumption Rate of biological cells is an important parameter of cellular metabolism. In order to study the behaviour of cell populations, it becomes necessary to capture and store them in one location for analysis. Individual cell analysis within a cell group can provide useful information about the average response of the cell group, as well as identify outliers. Such analysis can be used to identify different groups of cells based on their oxygen levels. However, characterizing the individual cell response within a cell group is challenging since cell dimensions are on the order of a few micrometers. Conventional techniques, such as microtiter plates and flow cytometry, are unable to offer both the high temporal and the high spatial resolution that is required to characterize individual cells. Modern micromachining and microfabrication techniques, on the other hand, allow for the creation of devices that have dimensions that are on the order of a few micrometers. Through a series of thin film deposition, photolithography and thin film etching techniques, it is possible to create single cell trapping structures whose dimensions are only slightly larger than that of individual cells. The aim of this thesis is to create a process flow in order to fabricate such structures on a single crystalline silicon substrate using available micromachining techniques

Macroporous Silicon: Technology and Applications

Macroporous silicon (MPS) is a versatile material that since its origin in the early 1990s has seen intense research and has found applications in many fields. MPS is a key technology in photonic crystals research, and optic and photonic applications are its main applications. However, this chapter is devoted to several of the non‐photonic uses of MPS. In particular, new electronic and MEMS devices and applications will be described. Furthermore, in this chapter, the technology of MPS fabrication will be presented