KrF Excimer Laser Micromachining of Silicon for Micro-Cantilever Applications (original) (raw)
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Fabrication of MEMS cantilever using laser micromachine
IOP Conference Series: Materials Science and Engineering
This paper presents the fabrication of MEMS cantilever using laser micromachine. This technique of micromachining is able to overcome the problem limitations of conventional lithography. It also facilitates three-dimensional (3D) microfabrication rather than two dimensional (2D) microfabrication of conventional lithography. Prior to fabrication process, wet etching process using KOH solution are carried out on silicon wafer. Etching process is necessary to thin the silicon wafer for the laser micromachine purpose. The etch performance on silicon wafer was investigated by varying the concentration of potassium hydroxide (KOH) solution with respect to time. It can be seen that with higher KOH concentration and higher KOH solution temperature, the etch rate is higher and it will thin the silicon wafer faster. Even though it is beneficial when the time taken for the etching process is faster, this also resulted in a rougher wafer surface. The optimized etch rate is approximately 1µm/min which yield in low surface roughness. The optimized parameters of laser micromachining were implemented to produce MEMS cantilever. Silicon wafer is used because most of the MEMS devices are silicon-based substrate. Three types of microcantilever were fabricated using laser micromachine namely rectangular cantilever, T-shaped cantilever and triangular microcantilever. Scanning electron microscope (SEM) and high power microscope (HPM) were used to obtain the surface morphology on the ablated area of the microcantilevers.
Characterization of MEMS structure on silicon wafer using KrF excimer laser micromachining
2014 IEEE International Conference on Semiconductor Electronics (ICSE2014), 2014
This paper presents preliminary parametric studies of KrF laser micromachining ablation effects on Silicon. Four parameters are studied, namely laser energy, pulse rate, number of laser pulses, and Rectangular Variable Aperture (RVA) in X and Y direction. At present, the study is focused on the production of microchannels using laser micromachine, in which its dimension is examined and measured. We found that the number of laser pulse is non-linearly proportional with the ablated channel width, with the etching rate of approximately 1 to 5 um for 50 laser pulses. This is similar with the measured depth of the microchannel. The changes in the measured channel width are most significant when the laser energy is increased. Some debris and recast can also be observed around the edge of the microchannel particularly during the variation of the laser pulse frequency. When varying the RVA, it is observed that the surfaces of the ablated microchannels are not smooth with a lot of debris accumulated at the channel edge and a few discolorations. Finally, a microcantilever structure is fabricated with the aim of demonstrating the capability of the laser micromachine.
Minimizing the Development Steps of Piezoresistive Microcantilever Using MEMS Micromachining
The conventional photolithography of crystalline silicon techniques is limited to two-dimensional and structure scaling. It is also requiring a lot of time and chemical involves for the whole process. These problems can be overcome by using laser micromachining, which a technique capable of producing three-dimensional (3D) structure and simultaneously avoiding the needs for photomasks. This paper reported the use of RapidX-250 excimer laser micromachine with 248 nm KrF to create in-time mask design and assisting ifabrication of piezoresistive microcantilever structures.Laser micromachining parameters is investigated in order to fabricate the microcantilever, which can be used in multiple applications including acceleration, vibration, bio/chemical detections and also in energy harvesting. Preliminary result shows that the fabricated sensor able to define the differences force and acceleration given regarding the unique electrical characteristic on fabricated piezoresistor.
SN Applied Sciences, 2020
This paper presents the process development and characterization towards microstructural realization using laser micromachining for MEMS. Laser micromachining technique is environmental friendly, fast patterning and able to avoid multi steps in conventional lithography based microfabrication techniques. This research focuses on understanding the dimensional properties of materials of the laser beam on the silicon wafers where microstructures were fabricated. Four main parameters like rectangular variable aperture (RVA-XY) size, number of pulse, stage/table feed rate and laser energy play important role in laser ablation process. The pattern of the microchannel or line with 1 cm length was drawn by AutoCAD software or any CAD software. The pattern in the CAD software is then transferred onto the silicon wafer by using laser micromachining. Finally, high power microscope (HPM) and Stylus Profiler will be used as measurement tools for observing and analysing the width and depth of the microchannel structures fabricated by laser micromachining. When using bigger size of RVA, it will lead to bigger microchannel width. There are a little effects or almost comparable in term of microchannel depth if varying all parameters' value. Surface roughness test also needs to be considered before choosing the best setting for the laser ablation.
Novel Fabrication Method for Surface Micromachined Thin Single-Crystal Silicon Cantilever Beams
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Micropatterning of Silicon Surface by Direct Laser Interference Lithography
Acta Physica Polonica Series a
Direct laser interference lithography is a new and low cost technique which can generate the line- or dot-like periodic patterns over large areas. In the present work, we report on direct fabrication of micrometer structures on Si surface. In the experiments the pulsed high power Nd:YAG laser operating at 1064 nm wavelength was used. Two-beam configuration with an angle of incidence of 40° was employed and different laser fluences up to 2.11 J/cm2 were tested. Areas about 1 cm in diameter have been processed with a single pulse of 10 ns. The laser treated samples were analyzed by atomic force microscopy to investigate the surface topography and to measure the size and depth of the achieved structures. We observed periodic line-like arrays with grating period of the order of 1 μm.
Fabrication of High-Aspect-Ratio Microstructures Using Excimer Lasers
An excimer laser micromachining system is developed to study the process in fabricating high-aspect-ratio microstructures. Specifically, the study experimentally examines process efficiency and the impact of changing major laser operating parameters on the resulting microstructural shapes and morphology. The materials considered in the study include glass, silicon, and aluminum. The ablation or micromachining rate has been observed to be strongly dependent on the operating parameters, such as the pulse fluence, number, and repetition rate. The results specifically indicate that ablation at low fluence and high repetition rate tends to form a V-shaped cavity, while a U-shaped cavity can be obtained at high fluence and low repetition rate. Additionally, the present study also indicates that a three-dimensional V-shaped cavity with large vertex angle can be formed by varying the focus depth of excimer laser. Materials of low thermal conductivity and low melting temperature are indeed more applicable to laser ablation.
A quality study on the excimer laser micromachining of electro-thermal-compliant micro devices
Journal of Micromechanics and Microengineering, 2001
The objective of this research is to improve the quality of the KrF excimer laser micromachining of metal and silicon in fabricating electro-thermal-compliant (ETC) micro devices. The ETC devices combine the actuator and the mechanism into one monolithic compliant continuum and enable a range of mechanical manipulation tasks at micron scale. An efficient method for optimizing the process parameters in laser micromachining, using the orthogonal array-based experimental design method, is presented in this paper. The feed rate of the XY stage, the laser pulse frequency, the discharge voltage and the number of passes were used as the control parameters. The roughness of the machined edge was used as the primary indicator of cutting performance. The roughness of the edges was computed automatically from the optical image of the machined samples. The heat-affected zone, kerf width and rate of cutting depth (depth per one pass) were used as additional quality indicators. The orthogonal array method enabled the optimization of the control parameters by reducing the required number of experiments compared to the traditional full factorial experiment. Furthermore, machining in a liquid environment improved the quality and eliminated more debris and recast compared to machining in the air.
Journal of Micro/Nanolithography, MEMS, and MOEMS, 2013
Conventional photolithography normally utilizes a photomask for patterning light onto a chemical resist film. Therefore, the accuracy of microfabrication is highly dependent on the accuracy of the photomasks. Fabrication of hard masks involves the use of expensive laser pattern generators and other sophisticated machines using very highprecision stages and the necessary control instrumentation; therefore, an inexpensive strategy is highly necessary for laboratory-level fabrication. As this technology is primarily based on raster scanning of a laser beam, the mask making as such becomes a low-throughput process. A strategy of high-throughput manufacturing of hard masks with laser micromachining using a one-step exposure process of a chromated glass slide through a micromachined aluminum shadow mask is proposed. The features that are finally embedded in the mask are highly demagnified and well focused. Optimization of the laser machining process is carried out by considering all processing parameters. The features are characterized using an optical microscope, a scanning electron microscope, and a self-developed image analysis code. Geometrical methods are used to estimate the average edge roughness and feature size. We have also validated the usage of these masks by performing microfabrication on films made of photoresist.
Journal of the Serbian Chemical Society, 2007
The undercutting process of thermal SiO2 microcantilevers with different orientations on (100) Si wafer was studied. The silicon substrate was removed by anisotropic chemical etching with a 25 wt. % aqueous solution of TMAH or a 30 wt. % aqueous KOH solution at 80 ?C. It was found that [110] oriented cantilevers were undercutting frontally along the length and [100] oriented cantilevers experience undercutting along the width of the cantilever, which is a less time consuming process. The studies showed that the [100] orientation of SiO2 microbridges enables theirs fabrication on a (100) oriented Si substrate.