Packaging for a drug delivery microelectromechanical system

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.Includes bibliographical references (p. 52-55).Local drug delivery is a fast expanding field, and has been a center of attention for researchers in medicine in the last decade. Its advantages over systemic drug delivery are clear in cancer therapy, with localized tumors. A silicon microelectromechanical drug delivery device was fabricated for the purpose of delivering chemotherapeutic agents such-as carmustine, a potent brain cancer drug, directly to the site of the tumor. Limitations in the delivery capacity of the device led to the design of a new package. This package is made from thermally bonded Pyrex® 7740 frames that are anodically bonded to the drug delivery chip. It increases the capacity of the chip, is smaller than the previous package and possesses true hermeticity, because of the bonding processes involved. This work describes the fabrication steps of the new package and a problem with the thermal bonding of Pyrex® frames preventing the achievement of a package true to the original design. A temporary solution was devised and the completed package was tested with regards to its intended goals. It managed to increase the load capacity of the chip by a, factor of 10, with potential for more, while decreasing the overall size of the package. Short-term hermeticity was achieved for this package by using a UV-cured epoxy to bond some pieces, which was not in the original design. Future work will focus on finding a permanent solution to the aforementioned problem, and directions for it were suggested.by Hong Linh Ho Duc.S.M

Low-Cost, Water Pressure Sensing and Leakage Detection Using Micromachined Membranes

This work presents the only known SOI membrane approach, using Microelectromechanical systems (MEMS) fabrication techniques, to address viable water leakage sensing requirements at low cost. In this research, membrane thickness and diameter are used in concert to target specific stiffness values that will result in targeted operational pressure ranges of approximately 0-120 psi. A MEMS membrane device constructed using silicon-on-insulator (SOI) wafers, has been tested and packaged for the water environment. MEMS membrane arrays will be used to determine operational pressure range by bursting.Two applications of these SOI membranes in aqueous environment are investigated in this research. The first one is water pressure sensing. We demonstrate that robustness of these membranes depends on their thickness and surface area. Their mechanical strength and robustness against applied pressure are determined using Finite Element Analysis (FEA). The mechanical response of a membrane pressure sensor is determined by physical factors such as surface area, thickness and material properties. The second application of this device is water leak detection. In devices such as pressure sensors, microvalves and micropumps, membranes can be subjected to immense pressure that causes them to fail or burst. However, this event can be used to indicate the precise pressure level that malfunction occurred. These membrane arrays can be used to determine pressure values by bursting. We discuss the background information related to the proposed device: MEMS fabrication processes (especially related to proposed device), common MEMS materials, general micromachining process steps, packaging and wire bonding techniques, and common micromachined pressure sensors. Besides, FEA on SOLIDWORKS simulation module is utilized to understand membrane sensitivity and robustness. In addition, we focus on theories supporting the simulated results. We also discuss the device fabrication process, which consists of the tested device’s fabrication process, Deep Reactive Ion Etching (DRIE) for membrane formation, two different realizable fabrication technique (depending on sensing material) of sensing element, metal contact pads, and connectors deposition. In addition, a brief description and operation procedures of the device fabrication tools are provided as well. We also include detailed electrical and mechanical testing procedures and the collected data

Radiation detectors and sources enhanced with micro/nanotechnology

The ongoing threat of nuclear terrorism presents major challenges to maintaining national security. Currently, only a small percentage of the cargo containers that enter America are searched for fissionable bomb making materials. This work reports on a multi-channel radiation detection platform enabled with nanoparticles that is capable of detecting and discriminating all types of radiation emitted from fissionable bomb making materials. Typical Geiger counters are limited to detecting only beta and gamma radiation. The micro-Geiger counter reported here detects all species of radiation including beta particles, gamma/X-rays, alpha particles, and neutrons. The multi-species detecting micro-Geiger counter contains a hermetically sealed and electrically biased fill gas. Impinging radiation interacts with tailored nanoparticles to release secondary charged particles that ionize the fill gas. The ionized particles collect on respectively biased electrodes resulting in a characteristic electrical pulse. Pulse height spectroscopy and radiation energy binning techniques can then be used to analyze the pulses to determine the specific radiation isotope. The ideal voltage range of operation for energy discrimination was found to be in the proportional region at 1000VDC. In this region, specific pulse heights for different radiation species resulted. The amplification region strength which determines the device sensitivity to radiation energy can be tuned with the electrode separation distance. Considerable improvements in count rates were achieved by using the charge conversion nanoparticles with the highest cross sections for particular radiation species. The addition of tungsten nanoparticles to the microGeiger counter enabled the device to be four times more efficient at detecting low level beta particles with a dose rate of 3.2uR/hr (micro-Roentgen per hour) and just under three times more efficient than an off the shelf Geiger counter. The addition of lead nanoparticles enabled the gamma/X-ray microGeiger counter channel to be 28 times more efficient at detecting low level gamma rays with a dose rate of 10uR/hr when compared to a device without nanoparticles. The addition of 10B nanoparticles enabled the neutron microGeiger counter channel to be 17 times more efficient at detecting neutrons. The device achieved a neutron count rate of 9,866 counts per minute when compared to a BF3 tube which resulted in a count rate of 9,000 counts per minute. By using a novel micro-injection ceramic molding and low temperature (950°C) silver paste metallizing process, the batch fabrication of essentially disposable micro-devices can be achieved. This novel fabrication technique was then applied to a MEMS neutron gun and water spectroscopy device that also utilizes the high voltage/temperature insulating packaging

Diode laser processing of PMMA and LCP materials for microsystem packaging

The thesis describes the development of laser-assisted bonding methods for assembly of microfluidic devices and MEMS packaging. A laser microwelding technique for assembly of transparent polymer substrates for fabrication of microfluidic devices was studied. The transparent PMMA substrates were bonded together using a high power diode laser system with a broad top-hat beam profile and an intermediate titanium thin film consisting of 0.7 mm diameter spots. A tensile strength of 6 MPa was achieved for this novel method which is comparable to that of the previous work in laser welding of polymers. It has been demonstrated that the method is capable of leak free encapsulation of a microfluidic channel. Furthermore, a novel laser-based method using an LCP film for packaging of MEMS, sensors and other microelectronic devices has been investigated. The results show that it is possible to use a laser based method with an LCP polymer for high quality substrate bonding applications. Glass-glass based cavities allow optical transmission and have potential applications for optical sensors and other photonic devices. For glass-glass bonding, it was shown that thin film titanium material can be used as an effective optical absorber in the laser based LCP bonding technique. Laser bonding of glass and silicon using an LCP film has also been achieved but in this case the silicon substrate acted as the absorber to capture the laser power. Laser bonding of a silicon cap to a molded LCP package has also been demonstrated successfully. The results of temperature monitoring using embedded sensors show that the temperature at the base of the LCP package (~130C) is substantially lower than the bonding temperature (> 280C). The results of shear and leak test show good reliability and hermeticity of the laser bonded microcavities. Both two-dimensional and three-dimensional models of heat transfer are developed and studied using the COMSOL Multiphysics software tool to understand the localised laser heating effects. The results are in good agreement with those of the practical work

Low Power Autonomous Microsystem for Oil Well Logging Applications

Downhole environmental monitoring can provide significant benefits to the petroleum industry. The rapid development of semiconductor technology enables autonomous sensing microsystems to operate at extreme environments. By injecting these microsystems into the boreholes and retrieving them after deployment, the geophysical conditions in the area of interest can be obtained. Challenges include high temperature, high pressure, miniaturized system size and packaging. This dissertation describes three generations of the environmental logging microsystem (ELM) for downhole geophysical logging applications. The first generation of the microsystem, ELM1.0, is designed for temperature logging in downhole environments. Each system consists of a power management circuit, a microcontroller with an integrated temperature sensor, and optical indicators. The system electronics are integrated on a flexible printed circuit board and packaged in a steel shell. The ELM1.0 has a packaged size of 8.9×8.9×6.85 mm3. It was tested at up to 125°C, 50 MPa in high salinity condition. The second generation (ELM2.0 & ELM2.1) is upgraded from ELM1.0 by adding a micromachined capacitive pressure sensor for pressure sensing up to 50 MPa. The ELM2.0 & ELM2.1 systems are packaged in steel shells filled with transparent polymer for pressure transfer. The packaged systems have a dimension of 9.5×9.5×6.5 mm3. The third generation (ELM3.0) is upgraded from ELM2.0 with a power switch and a low-cost polyimide pressure sensor for coarse pressure measurement up to 50 MPa. Both ELM2.0 and ELM3.0 systems were successfully tested at up to 125°C, 50 MPa in corrosive environments using laboratory instruments, and in a brine well at a depth up to 1235 m. A progressive polynomial calibration method was used for interpretation of the pressure sensor data from these tests. In addition, a high power micromachined RF switch for radio transceiver applications was designed, fabricated and tested. The RF switch can potentially be used to establish antenna networks for RF communication in the ELM. The switch consists of a bridge structure for electrostatic actuation and capacitive contact. The switch was fabricated with a 7-mask process. The fabricated device showed limited RF performance because of challenges related to the control of residual stress in suspended elements.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138647/1/sui_1.pd

Laser-based packaging of micro-devices

In this PhD thesis the development of laser-based processes for packaging applications in microsystems technologies is investigated. Packaging is one of the major challenges in the fabrication of micro-electro-mechanical systems (MEMS) and other micro-devices. A range of bonding processes have become established in industry, however, in many or even most cases heating of the entire package to the bonding temperature is required to effect efficient and reliable bonding. The high process temperatures of up to 1100°C involved severely limit the application areas of these techniques for packaging of temperature sensitive materials. As an alternative production method, two localised heating processes using a laser were developed where also the heat is restricted to the joining area only by active cooling. Silicon to glass joining with a Benzocyclobutene adhesive layer was demonstrated which is a typical MEMS application. In this laser-based process the temperature in the centre of the device was kept at least 120°C lower than in the bonding area. For chip-level packaging shear forces as high as 290 N were achieved which is comparable and some cases even higher than results obtained using conventional bonding techniques. Furthermore, a considerable reduction of the bonding time from typically 20 minutes down to 8 s was achieved. A further development of this process to wafer-level packaging was demonstrated. For a simplified pattern of 5 samples the same quality of the seal could be achieved as for chip-level packaging. Packaging of a more densely packed pattern of 9 was also investigated. Successful sealing of all nine samples on the same wafer was demonstrated proving the feasibility of wafer-level packaging using this localised heating bonding process. The development of full hermetic glass frit packaging processes of Leadless Chip Carrier (LCC) devices in both air and vacuum is presented. In these laser-based processes the temperature in the centre of the device was kept at least 230°C below the temperature in the joining region (375°C to 440°C). Testing according to MIL-STD-883G showed that hermetic seals were achieved in high yield processes (>90%) and the packages did withstand shear forces in excess of 1 kN. Residual gas analysis has shown that a moderate vacuum of around 5 mbar was achieved inside the vacuum packaged LCC devices. A localised heating glass frit packaging process was developed without any negative effect of the thermal management on the quality of the seal

Development and testing of a micromachined probe card.

This thesis is concerned with the design, fabrication and testing of micro scale probes. The probes were designed to act as temporary electrical connections to allow wafer level testing of integrated circuits. The work initially focused on the creation of free standing nickel cantilevers, angled up from the substrate with probe tips at the free end. These were fabricated using a novel method, combining pseudo grey scale lithography and thick photoresist sacrificial layers. Detailed analysis of the fabrication method, in particular the resist processing and lithography was undertaken and the limitations of the method explored.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Modelling and Design Optimisations of CMOS MEMS Single Membrane Thermopile Detector Arrays

Thermal imaging devices based on Complementary Metal-Oxide-Semiconductor (CMOS) and Micro-Electro-Mechanical System (MEMS) technology are widely used across consumer and industrial applications. The combination of CMOS and MEMS technologies allows for the production of devices with high performance, good reliability and consistent reproducibility. Additionally, these technologies allow devices to be manufactured at low cost and a high volume. There are several types of thermal sensing technologies, however, this thesis mainly focuses on 8×8 thermopile based Focal Plane Arrays (FPAs). The core principles governing the function of thermopiles are based on the Seebeck effect. In this thesis, the structure and fabrication process of thermopile FPAs are described and discussed. The thesis describes the functionality of the array chip and introduces a new experimental technique, called the bi-directional electrical biasing method, which was applied to obtain the device’s responsivity and crosstalk measurements. Compared to traditional measurement approaches using laser sources, this novel method significantly reduces the complexity of the experimental setup, as no external laser source is required. The crosstalk of the 8×8 array is ~2.69% and the responsivity is ~73.1 V/W. A detecting system using a larger array chip was designed, created and successfully applied in a series of experiments that involved gesture recognition and people counting. In order to enhance the performance of the current array device, a 3D simulation model based on the Finite Element Method (FEM) was built using the COMSOL Multiphysics simulation tool. The numerical model was validated by comparing the model’s simulated values for responsivity, crosstalk and temperature distribution with experimental results. The difference between the simulations and experimental results was 90 V/W in the model with tungsten tracks. A 32×32 array design demonstrates the smallest pixel size that can be achieved based on this thermopile array design. The 32×32 array design increased responsivity to ~77.18 V/W and crosstalk remained 6% when the pixel size was reduced further in a 64×64 array design, at this level of crosstalk, image quality is likely to be significantly affected. Future work may focus on the implementation of carbon nanotubes or novel 3D thermopile designs. Carbon nanotubes, when deposited over the array chip, could enhance the absorption of IR radiation. While new thermopiles employing a 3D design could dramatically reduce array size and potentially achieve a fill factor of 100%

Modular integration and on-chip sensing approaches for tunable fluid control polymer microdevices

228 p.Doktore tesi honetan mikroemariak kontrolatzeko elementuak diseinatu eta garatuko dira, mikrobalbula eta mikrosentsore bat zehazki. Ondoren, gailu horiek batera integratuko dira likido emari kontrolatzaile bat sortzeko asmotan. Helburu nagusia gailuen fabrikazio arkitektura modular bat frogatzea da, non Lab-on-a-Chip prototipoak garatzeko beharrezko fase guztiak harmonizatuz, Cyclic-Olefin-Polymer termoplastikozko mikrogailu merkeak pausu gutxi batzuetan garatuko diren, hauen kalitate industriala bermatuz. Ildo horretan, mikrogailuak prototipotik produkturako trantsizio azkar, erraz, errentagarri eta arriskurik gabeen bidez lortu daitezkeenetz frogatuko da