Reports the microfabricated nickel clamps for packaging of optical fibers in photonics devices. When the fiber is inserted into the silicon V groove, the microfricated clamps fix it in the V groove. Compared with the traditional silicon V grooves, this approach only involves one additional sputtering, photolithography, and electroplating process. Two single-mode optical fibers were fixed into the silicon V groove by the nickel clamp; the measured insertion loss is lower than 0.1 dB.
A novel, electromagnetically driven variable fiber optic attenuator based on micro-electromechanical system (MEMS) technology is described. The attenuation level is adjusted by changing the microshutter position in the optical path. A new technique, termed "nonsilicon surface micromachining," is used to fabricate the shutter, in which a copper layer was used as the sacrificial layer, and the electroplated FeNi as the structure layer. This scheme provides another way to fabricate the optical microstructure. The optical characteristics of the attenuator are theoretically analyzed, and the result is verified by experiments. The MEMS attenuator has fiber-to-fiber insertion loss less than 3 dB at 1550-nm wavelength, dynamic range greater than 40 dB, 0.2-dB repeatability, and return loss better than 40 dB.
A novel micro-mechanical structure has been put forwarded. It is designed for high precision passive alignment and packaging of optical fibres in optoelectronics devices. The electroplated nickel micro clamp has been fabricated above the silicon V grooves. The clamps, work together with the V groove, fix the optical fibers with high precision for optical alignment when the fibers are inserted into the grooves. The fabrication of the micro clamp involves only one more photolithography and electroplating process. two single mode optical fibers have been fixed into the silicon V-groove by the nickel clamp; the measured insertion loss is lower than 0.1dB. The proposed nickel micro clamp is proved to be a low cost, high performance approach that could be widely applied in passive alignment and packaging of fiber in opto-electronics devices.
A novel micromachined electromagnetic actuated variable optical attenuator is described. The attenuation level is adjusted by changing the lateral distance between two V-groove-aligned single-mode fibers. Based on the waveguide transmission theory, the relationship between the attenuation and the offset is analyzed. The fabrication of the device only enrolls common and well-known semiconductor technologies. The packaged volume of the device is 20×10×5 mm3. According to the experiment results, the insertion loss is less than 1 dB, the polarization dependent loss is less than 0.1 dB, dynamic range is larger than 50 dB, and the driving voltage is less than 5 V. It is proven to be a low-cost, high-performance passive device for future all-optical networks.
An eight-channel variable optical attenuator (VOA) array fabricated by MEMS technology is presented. Based on micro electromagnetic actuation, the attenuation level is adjusted by changing the radial offset between the input/output optical fiber. The relationship between the attenuation and the offset was analyzed based on wave-guide transmission theory. The structure parameter was determined through mechanics and magnetic circuit analysis. The device was fabricated and packaged by micromachining technology. The packaged volume of the device is 80×40×12mm3. According to the experiment results, the insertion loss is less than 1dB, the polarization dependent loss is less than 0.1dB, dynamic range is above 35dB and the driving voltage is less than 5V. It is proved to be a low cost, high performance passive device for future all-optical-networks.
In the microoptics field, precise alignment is very important to reduce the coupling losses in optical links. In this paper, a novel device of passive and fixed alignment of optical fiber is proposed. The rectangular V-groove formed by one sidewall of SU-8 resist and the substrate is used to position the optical fiber, and the leaf spring with flexure hinge clamps it. The spring is fabricated by the sacrificial layer technique. The clamping force provided by the spring acts on the upper semi-circle of the optical fiber's cross section, so that the device need not use the additional cover on the optical fiber to perform the vertical location and the final fixing. It has simple structure and process, and is convenient to assemble and integrate with other microparts. The coupling of two optical fibers using the devices in our experiment has less than 1.5dB insert loss.
The hydrogen actuating microactuator works in the caustic electrolyte, the chemical stability of the materials is very important for the lifetime of this kind of microactuators,. As compared with mischmetal (Mm) based LaNi5 series alloy films reported before, palladium layers is more suitable for this purpose, In this paper, a prototype of electrochemical microactuator with Pd/Ni bilayer based on the hydrogen induced actuation is presented, the performance and microfabrication process of this microactuator are described in detail.
The reactive ion etching (RIE) of commercial PMMA sheet has been examined in pure 02 and CHF3/02 plasma. The aim of this study was to optimize the etching PMMA process parameter. Addition of CHF3 , which have a surface passivation effect, to Oxygen plasmas should be obtained vertical edges at an acceptable etch rate. A RIE parallel plate reactor was used and electroplated nickel film was used as mask. We discuss the influence of pure 02 and O2/CHF3 etching gas on etching profile, the influence of the etching parameters such as gas pressure and CHF3/O2 ratio on vertical etching rate, lateral etching rate and etching profile was also investigated.
A PMMA-based reactive ion etching (RIE) process for the fabrication of high aspect ration microstructures is described in this paper. Although the resolution of this process is lower than that of the LIGA process, this process provides a simpler way to get higher height and high aspect ration microstructures. In the process, Ni material is selected as mask and patterned using photochemical etching. The self-bias, which is determined by different etching parameters such as etching power and gas pressure etc., is very important. By optimizing the etching parameters, vertical PMMA profile and 5:1 aspect ratio structures can be obtained. The micro-mask effect and high power etching damage are also demonstrated and discussed in this paper.
Many kinds of bulk hydrogen absorbing alloys undergo dramatic volume expansion when they absorb hydrogen. The maximum volume change varies with substances in the range of several to over twenty percents. Based on these phenomena, a new type of electrochemical microactuator has been designed. Bilayers of hydrogen absorbing alloy and nickel can generate a large bending and deliver high force, and it can work at very low voltage. As the first prototype, MmNi5 alloy film was chosen as the actuating medium, and it is deposited by sputtering method. The principle of this new microacturator and the microfabricating process of this bimorph are presented.
SU-8 is a negative, epoxy type, near-UV photoresist. The resist has been specifically developed for ultrathick, high-aspect-ratio MEMS-type applications. The adhesion of the SU-8 resist with the metallic substrate is very poor, but it is necessary to overcome this shortcoming for providing low-cost LIGA-type process in MEMS applications. In this paper, several metallic films are used as the substrates. The Ti film with oxidation treatment is found to have the strongest adhesion to the resist. SU-8 resist has been proven to be very sensitive to process variations, so the experimental optimizing technique is used in the process. Using processing parameters as control factors, experiments are performed and results are evaluated. As the results being analyzed, a proposed fabrication process is derived from optimizing the control factors. The output structure has straight sidewall profile, fine line and space resolution. The aspect ratio is greater than 20.
RIE is a promising way to fabricate high aspect ratio micro-structures and the PMMA is a widely used thick resist. In this paper, we developed a reactive ion etching of PMMA process in O2 plasma to fabricate micro-structures. High etch rate(0.5 micrometers /min) and smooth surface were achieved. In order to get high selectivity, We use Ni film as mask, which was patterned by photochemical etching. The etch results showed that vertical etch profile(base angle>88 degree(s)), high aspect ratio (5:1) and through-out etching of PMMA(100micrometers in thickness) could be obtained if select optimum etching conditions. We also found that the self-bias is one of the critical parameters during the process. If etching power was too high, the surface would be deformed due to the high energetic particles bombardment
The comparison of Nickel electrodeposition in LIGA process with traditional electroplating by electrochemical methods was reported. The mass transport limitation during microelectroforming in LIGA was studied by linear potential sweep technique, the limiting current is easier to reach for plating into LIGA molds. The A.C. impedance measurement also supports the above viewpoint, beside this, it seems that the mechanism of electrode reaction also differ from that of conventional nickel plating. A semi-automatic electroforming equipment for LIGA process has been developed, various nickel microstructures with high aspect ratios have been fabricated in this equipment. a series of micro nickel gears have been fabricated, an advanced micro gear-box with 2mm diameter has been assembled, it works very well.
TiNi/Si diaphragm is a useful selection for reciprocating motion microactuator, since it needn't complex bias structure and special thermal-mechanical training. The TiNi/Si actuating diaphragm with patterned TiNi resistance strip can improve the dynamic response effectively. The several kinds of pattern of TiNi thin films with various shapes and sizes were designed and processed, and the influences of patterning and Si thickness on the characteristics of phase transformation were analyzed by measuring electrical resistance-temperature curves. Moreover, the stress distributions and maximum deflections of TiNi/Si diaphragms with different Si thickness were simulated by FEA. The results show that the phase transformation behaviors of the TiNi thin films with different Si thickness and various patterns are different. Based on these results, optimized actuating diaphragm with patterned TiNi/Si structure was developed. The thermal actuating results are agreed with simulating results of FEA.
A novel electrochemical actuation based on the hydrogen aborbing-desorping of metal is presented. The hydrogen aborbing-desorping of metal was accompanying with the volume swelling and shrinking, which could be used to convert electrical energy into mechanical energy. This type of actuation not only has usual advantages of electrochemical actuation such as long travel distance and acoustical quiet, but also there was no the concerns of gas leakage of those electrochemical actuation driven by the gas pressure built up by electrolysis of an aqueous electrolyte solution. In this work, a mischmetal (Mm)-Ni based alloy film, MmNi5, was prepared by sputtering method. The MmNi5 film was studied by x-ray diffraction method (XRD) and electrochemical method. It was found that the metal film had undergone phase transformation during its hydrogen absorbing and desorbing cycle, which was first time to be observed for the metal hydride film prepared by sputtering method. The further results of surface micromaching and scanning electron microscope (SEM) indicated that the hydrogen-induced actuation was applicable in MEMS.
SU-8 is a negative, epoxy type, near-UV photoresist. The resist has been specifically developed for ultrathick, high-aspect-ratio MEMS-type applications. It has been proven to be very sensitive to process variations. In this paper, the orthogonal method is used in the process. While three processing parameters are used as control factors, experiments are performed and results are evaluated. As the results being analyzed, a proposed fabrication process is derived from optimizing the control factors. The output structure has straight sidewall profile, fine line and space resolution, and strong adhesion to substrate. The aspect ratio can be greater than 20 in the 200-um-thick resist. Furthermore, several metallic films are used as the substrates. The titanium film with oxidation treatment is found to have the stronger adhesion to the resist. The result will open possibilities for low-cost LIGA-type process for MEMS applications.
The microstructures that have relatively large height, high aspect ratio are very important for improving micro-devices' characteristics. In this paper reactive ion etching (RIE) of PMMA to create high aspect ratio micro-structures was described. We use Ni film as mask, which was patterned by usual photochemical etching, then use O2RIE technology to etch PMMA thick film (100 micrometers ). During the etching process, O2 pressure, etching power are very important for the etching results. There are grass-like residues remained on the etched surface until the PMMA was over etched, this phenomena is caused by the micro-mask effect. With over etched, the grass-like residues can be eliminated. The etched surface is very smooth and the side wall is vertical. The etching depth can get up to higher than 100 (mu) M and the aspect ratio is 5.
Reactive Ion Etching is an effective method for etching of diamond films, in this paper, the influences of maskant, system pressure and the composition of reactive gas on the etch rate and etched surface of diamond were studied. A gas mixture of O2 and Ar was used as the reactive agent, the concentration of Ar in this mixture is in the range of 0 to 100% (V/V), and the etching result reveals that argon is not necessary. The system pressure plays the dominant effect on the etched surface and etched contours of diamond structures. The highest etch rate appears in the range of 60 - 100 Torr, very low and very high pressure both result in etch rate decreasing. The maskant plays an important role in etching process, it can be sputtered and re-deposited on the etched surface of diamond and act as a micro mask, results in rougher etched surface in some conditions. The optimum processing parameters were achieved, and combined this patterning process with conventional photolithography and sacrificial wet etching process, we have formed a new type of surface micromachining technique for fabrication of diamond MEMS structures. Typical MEMS structures such as cantilever beams, diamond micro hinge and diamond tips array have been fabricated successfully.
The patterning of diamond thin films by RIE etching must use hard mask. Ni and NiTi thin films are better candidate to be used as diamond mask based on mask selective ratio and patterning process. NiTi thin film mask has higher etching selective ratio than that of Ni thin film, Ni thin film plating through mask is applicable to small microstructure fabrication because of moderate etching selective ratio, accurate in dimension control and easy to make multilayer microstructure. The diamond thin film microstructure using NiTi and Ni thin film masks fabricated by RIE etching have straight line and sharp sidewall.
CVD diamond films is one of the most interesting materials under consideration for microelectromechanical system (MEMS), especially for optical MEMS, but diamond is difficult to be fabricated due to its hardness and chemical inertness, for this purpose, we have developed a patterning process based on O2RIE etching of CVD diamond films and formed a new type of surface micromachining process for microfabricating of diamond MOEMS microparts, combining with sacrificial releasing and electroplating through mask techniques, this surface micromachining process is able to fabricate fine lines and complicated microstructures, and a diamond micro hinge for free-space micro-optical bench has been fabricated by this process successfully.
A novel micropump actuated by NiTi/Si diaphragm has been developed. In order to optimize the actuating performance of the micropump, the dynamic actuating properties were studied in different actuating conditions such as different actuating currents, frequencies and duty cycles. The experimental result show that there is a maximum displacement when increasing the actuating current and frequency. The influence of duty cycle on maximum displacement when increasing the actuating current and frequency. The influence of duty cycle on maximum displacement with water flow and without water flow is different. The higher the displacement of the diaphragm is, the larger the flow rate is for a given frequency. The displacement of the pump diaphragm depends not only on the flow rate, but also on the moving frequency. The change of the resistance of NiTi strip indicates that the A - M phase transformation is completed partly during dynamic actuating processes. The maximum flow rate of 360 (mu) l/min was obtained in about 50Hz with 1:1 duty cycle in our experiment.
CVD diamond film is an attractive potential material for microelectronics and MEMS application, but patterning of diamond is one of the main difficulties hindering diamond electronics. In this paper, we studied the RIE process for precise patterning of diamond films. Ni/Cr, Cu/Cu or NiTi films were used as maskants, oxygen as reactive gas. The etching results showed that the NiTi film has high etching selectivity when used as mask for diamond etching and its is very convenient to be patterned by the special developed chemical etchant. Using O2 as main etching gas, the RIE can etch the diamond film effectively. The process parameters such as RF power, vacuum pressure have marked influence on the etching rate and the patterning of diamond film has been defined. Combined with sacrifice layer process and electroplating through mask technique, diamond micro hinge has been fabricated on silicon wafer.
The patterning of nickel-titanium SMA thin films was one of critical micromachining issues during developing SMA film devices, now, an excellent etchant for etching of Ni-Ti SMA thin films was developed, therefore, this problem can be solved by photochemical etching easily. The etchant is based on the dilute hydrofluoric acid with several kinds of additives. The etching process is operated at room temperature with the etching rate of (1-5)micrometers /Min. The etched surface is very smooth and the edge of patterned SMA line is exactly the same as that of patterned photoresist. The etch factor is above 1.5 and might be enlarged furthermore. The etchant is stable and the repeatability is also good. This patterning method is compatible with IC processes, so it is easy to design and fabricate any magic pattern for MEMS applications.
A novel micropump actuated by thin film shape memory alloy has been designed, fabricated and tested. It is one of the membrane reciprocating micropumps which is driven by shape recoverable force of NiTi thin film and biasing force of Si membrane. The micropump is composed of a deformable chamber and two Si flap check valves. The structure of pump is simple. The pump was manufactured by Si surface and bulk micromachining technologies, Au-Si eutectic and epoxy bonding. The outer dimension of the micropump is 6*6*1.5 mm/mm/mm. The NiTi/Si composite actuator has an area of 3*3mm/mm with a thickness of 20micrometers Testing result show that the pump has extremely good performance, such as high pumping yield, low power consumption high working frequency. All these advantages are attributed to the patterning of NiTi thin film used as self-heating element and optimizing design of NiTi/Si actuated structure.
Microactuator is one of the important parts in MEMS, various types of microactuators have been developed, which utilize different driving principles such as electrostatic force, piezoelectric effect, shape memory alloys and electromagnetic force. In this paper, the fabrication process of stator winding of (phi) 1mm electromagnetic micromotor is discussed. With high-aspect-ratio photolithography process and mask-plating process, the high- aspect-ratio coils can be fabricated, which greatly reduce the resistance and heat of stator winding. With thick sputtered Al2O3 films as isolation layers between coils, heat resistance of stator winding is improved. A stator winding has been fabricated, which is composed of 6 layer coils, 42 turns and 9 pairs, its diameter is 1mm and minimum line space is 1 micrometers , the maximum operation current of the coils is 180mA and resistor is 12-20 (Omega) . The output torque of the electromagnetic micromotor is 1.5 (mu) Nm. the rotational speed of the motor can be adjusted from several hundred to over ten thousand turns per minute and the rotational direction is reversible.
DEM technique developed by present authors is a new 3D micro fabrication technique for non-silicon materials such as metals, plastics and ceramics. In comparison with LIGA technique, it does not need expensive synchrotron radiation source and x-ray masks. DEM technique has both advantages of bulk silicon micro fabrication technique and LIGA technique. In the present research, we obtained metallic mold insert with structure depth of 180 micrometers and aspect ratio more than 20. A successful development of DEm technique opens a new way for 3D micro fabrication of non-silicon materials.
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