Novel Polymeric Protective Coatings for Hydrofluoric Acid Vapor Etching during MEMS Release Etch

2010 ◽  
Vol 2010 (DPC) ◽  
pp. 000942-000970 ◽  
Author(s):  
Tingji Tang ◽  
Curt Planje ◽  
Ramachandran K. Trichur ◽  
Xing-Fu Zhong ◽  
Shelly Fowler ◽  
...  
Keyword(s):  
Surface Tension ◽  
Hydrofluoric Acid ◽  
Silicon Oxide ◽  
Protective Coatings ◽  
Sacrificial Layer ◽  
Pressure Sensors ◽  
Micro Electro Mechanical System ◽  
Device Fabrication ◽  
Mems Devices ◽  
Acid Vapor

Micro-electro-mechanical system (MEMS) is rapidly becoming a critical part of advanced fabrication technology such as cellular phones, micromirrors, radio frequency (RF) devices, microprobes, and pressure sensors. Release etching of a sacrificial layer of silicon oxide plays an important role in creating the moving parts during these MEMS device fabrication. Traditionally, wet fluorinated etchants have been applied in order to achieve release etching, by which liquid surface tension can cause the MEMS microstructures to stick together (“stiction”) upon removing from aqueous bath or during the drying of released wet-etched structure. It has been demonstrated that using a hydrofluoric acid (HF) vapor release etch can efficiently circumvent stiction phenomena owing to the fact that it substantially eliminates the surface tension that causes the stiction. Conventionally, inorganic based films such as silicon nitride, alumina, SiC, polysilicon, amorphous silicon, and aluminum etc were used as vapor HF etch-resistant mask materials, which require very high temperature and vacuum deposition techniques often lengthy, complicated and costly. Herein, a novel spin-on and polymeric blanket HF-resistant coating material is presented to provide protection of both silicon oxide and aluminum against HF attack during vapor HF etching. Our newly developed polymeric coatings can be processed at lower temperature (<250 °C) and thinner films (less than 10μm) for extended vapor HF etching period (longer than 1 hour). Hence, our vapor HF resistant materials will enable the MEMS industry to significantly lower the cost of manufacturing MEMS devices and will significantly simplify the manufacturing process as well.

A design tool fully adapted to the development of the thin film packaging process used for MEMS devices

2013 ◽  
Vol 2013 (DPC) ◽  
pp. 000937-000986
Author(s):  
Souchon Frederic ◽  
Gervais Anne-Charlotte ◽  
Thouy Laurent ◽  
Saint-Patrice Damien ◽  
Pornin Jean louis
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Residual Stresses ◽  
Silicon Oxide ◽  
Sacrificial Layer ◽  
Design Tool ◽  
Mems Devices ◽  
Fem Model ◽  
Study Case ◽  
Thin Film Encapsulation

MEMS Wafer Level Packaging is required for mass production of MEMS devices: wafer to wafer bonding is usually the current solution, however thin film encapsulation becomes a promising alternative method [1]. Nevertheless, major challenges should be overcome to develop thin film encapsulation, namely the development of a thin cap strong enough to withstand high mold pressures. Consequently, design tools are required to develop successfully thin film encapsulation [2–4]. For that, finite element models (FEM) are commonly used, and this article proposes a generic methodology based on an efficient convergence loop to fit FEM results with experimental data. Our convergence loop guarantees reliable predictive FEM results because our results are double checked with experimental characterizations: we use not only the cap geometry evolution during the process flow, but also the mechanical properties of the cap and especially its stiffness. A study case which shows how to manage the cap deflection during the cap release operation is used to illustrate the relevance of our methodology. To recall [5], the thin film encapsulation requires closed cavities formed above the MEMS devices with surface micromachining techniques: the cavity is formed with a sacrificial layer recovered by a cap. The cap is then perforated by holes to remove the sacrificial layer. Finally, a film is deposited on the cap to seal the cap holes. In practice, the release of the sacrificial layer is one of the most critical operations because the cap can damage the MEMS device due to a buckling effect. Indeed, the residual stresses within the capping layer (compressive residual stresses are usually mandatory) and the geometry of the sacrificial layer have to be tuned in order to control the final shape of the cap. The study case is focused on a test structure with a silicon oxide quadratic plate of 800 μm side length and 3 μm thickness. In practice, the cap geometry has been characterized with a mechanical profilometer; and, a force/displacement curve obtained by nano-indentation technique has been used to extract accurately the mechanical properties of the cap. Then, these experimental data have been used to build our FEM model. The correlation between experimental data and FEM results allows verifying our model because we show that the simulated profile and the simulated stiffness fit successfully with experimental data. The best result has been obtained with a 60MPa compressive residual stress; and, this value is in agreement with experimental measurements. We have used our FEM model to detail the effect of several parameters like the silicon oxide thickness, the residual stresses, the height of the cap edge rolls, or the added value of reinforcement solutions as corrugated membrane or metallic layer. Finally, we conclude that our model is an efficient design tool to optimize the thin film encapsulation. For example, it becomes possible to monitor the buckling effect of the cap by the cavity geometry or the cap material residual stresses.

scholarly journals Cavity-BOX SOI: Advanced Silicon Substrate with Pre-Patterned BOX for Monolithic MEMS Fabrication

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 414
Author(s):  
Marta Maria Kluba ◽  
Jian Li ◽  
Katja Parkkinen ◽  
Marcus Louwerse ◽  
Jaap Snijder ◽  
...  
Keyword(s):  
Complex Geometry ◽  
Pressure Sensors ◽  
Silicon On Insulator ◽  
Test Case ◽  
Mems Devices ◽  
Device Layer ◽  
Mems Fabrication ◽  
Silicon Islands ◽  
Design Freedom ◽  
Deep Brain

Several Silicon on Insulator (SOI) wafer manufacturers are now offering products with customer-defined cavities etched in the handle wafer, which significantly simplifies the fabrication of MEMS devices such as pressure sensors. This paper presents a novel cavity buried oxide (BOX) SOI substrate (cavity-BOX) that contains a patterned BOX layer. The patterned BOX can form a buried microchannels network, or serve as a stop layer and a buried hard-etch mask, to accurately pattern the device layer while etching it from the backside of the wafer using the cleanroom microfabrication compatible tools and methods. The use of the cavity-BOX as a buried hard-etch mask is demonstrated by applying it for the fabrication of a deep brain stimulation (DBS) demonstrator. The demonstrator consists of a large flexible area and precisely defined 80 µm-thick silicon islands wrapped into a 1.4 mm diameter cylinder. With cavity-BOX, the process of thinning and separating the silicon islands was largely simplified and became more robust. This test case illustrates how cavity-BOX wafers can advance the fabrication of various MEMS devices, especially those with complex geometry and added functionality, by enabling more design freedom and easing the optimization of the fabrication process.

scholarly journals Synthesis of Printable Polyvinyl Alcohol for Aerosol Jet and Inkjet Printing Technology

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 220
Author(s):  
Mahmuda Akter Monne ◽  
Chandan Qumar Howlader ◽  
Bhagyashree Mishra ◽  
Maggie Yihong Chen
Keyword(s):  
Polyvinyl Alcohol ◽  
Inkjet Printing ◽  
Micro Electro Mechanical System ◽  
Device Fabrication ◽  
Silicon Substrates ◽  
Excellent Candidate ◽  
Jet Printing ◽  
Inkjet Printing Technology ◽  
Transistor Fabrication ◽  
Aerosol Jet Printing

Polyvinyl Alcohol (PVA) is a promising polymer due to its high solubility with water, availability in low molecular weight, having short polymer chain, and cost-effectiveness in processing. Printed technology is gaining popularity to utilize processible solution materials at low/room temperature. This work demonstrates the synthesis of PVA solution for 2.5% w/w, 4.5% w/w, 6.5% w/w, 8.5% w/w and 10.5% w/w aqueous solution was formulated. Then the properties of the ink, such as viscosity, contact angle, surface tension, and printability by inkjet and aerosol jet printing, were investigated. The wettability of the ink was investigated on flexible (Kapton) and non-flexible (Silicon) substrates. Both were identified as suitable substrates for all concentrations of PVA. Additionally, we have shown aerosol jet printing (AJP) and inkjet printing (IJP) can produce multi-layer PVA structures. Finally, we have demonstrated the use of PVA as sacrificial material for micro-electro-mechanical-system (MEMS) device fabrication. The dielectric constant of printed PVA is 168 at 100 kHz, which shows an excellent candidate material for printed or traditional transistor fabrication.

Design and Simulation of Pressure Sensor for Ocean Depth Measurements

2013 ◽  
Vol 313-314 ◽  
pp. 666-670 ◽  
Author(s):  
K.J. Suja ◽  
Bhanu Pratap Chaudhary ◽  
Rama Komaragiri
Keyword(s):  
Pressure Sensor ◽  
Integrated Circuit ◽  
Output Voltage ◽  
Pressure Sensors ◽  
Micro Electro Mechanical System ◽  
Constant Thickness ◽  
Piezoresistive Pressure Sensor ◽  
Wide Pressure Range ◽  
Processing Techniques ◽  
Wide Pressure

MEMS (Micro Electro Mechanical System) are usually defined as highly miniaturized devices combining both electrical and mechanical components that are fabricated using integrated circuit batch processing techniques. Pressure sensors are usually manufactured using square or circular diaphragms of constant thickness in the order of few microns. In this work, a comparison between circular diaphragm and square diaphragm indicates that square diaphragm has better perspectives. A new method for designing diaphragm of the Piezoresistive pressure sensor for linearity over a wide pressure range (approximately double) is designed, simulated and compared with existing single diaphragm design with respect to diaphragm deflection and sensor output voltage.

Design analysis and fabrication of side-drive electrostatic micromotor by UV-SLIGA

2021 ◽  
pp. 251659842110452
Author(s):  
Rahul Shukla ◽  
Gowtham Beera ◽  
Ankit Dubey ◽  
Varun P. Sharma ◽  
P. Ram Sankar ◽  
...  
Keyword(s):  
Sacrificial Layer ◽  
Micro Electro Mechanical System ◽  
Maximum Torque ◽  
Element Analysis ◽  
Deposited Metal ◽  
Rotor Pole ◽  
Electroformed Nickel ◽  
Microfabrication Technique ◽  
Wet Chemical ◽  
Metal Layers

In the present work, a micro-electro-mechanical system (MEMS)-based electrostatic micromotor is designed and fabricated. Finite element analysis is done and various parameters affecting the torque are studied. Maximum torque is achieved at 120° phase angle. The effect of change in voltage, micromotor height and frequency is analysed and discussed. UV-SLIGA, a microfabrication technique, is used for the fabrication of electrostatic micromotor of height 30µm and higher. UV lithography is conducted by both positive AZ P4620 and negative (SU-8 10 and SU-8 2150) photoresists. Copper (Cu) is used as a sacrificial layer to release the rotor (the movable part) of the electrostatic micromotor. Electroformed nickel (Ni) is used for making stator, rotor and axle, whereas chromium (Cr) is used as a seed layer. The micromotor is fabricated with a stator-rotor pole having configuration ratio of 3:2. The gap between the rotor and axle is 20 µm. Wet chemical etching is used to etch the deposited metal layers (Cr, Ni and Cu). Challenges such as the adhesion between the photoresist mould and substrate, cracks, seepage and misalignment are faced during the microfabrication. These challenges are overcome by optimizing the various parameters. The fabrication of electrostatic micromotor is done successfully and the results are discussed in the article.

Present and Future Applications of MEMS for Automotive Industry

2014 ◽  
Vol 2014 (DPC) ◽  
pp. 001851-001892
Author(s):  
Thibault Buisson
Keyword(s):  
High Pressures ◽  
Failure Mechanisms ◽  
Extreme Environments ◽  
Pressure Sensors ◽  
Harsh Environments ◽  
Fe Model ◽  
Potential Candidate ◽  
Mems Devices ◽  
Technology Modeling ◽  
Sintered Ag

MEMS are found in many applications, ranging from large volume consumer applications such as mobile phones to specific high end devices for defense or space. MEMS market will continue to see steady, sustainable double digit growth for the next six years, with 20% compound average annual growth in units and 13% growth in revenues, to become a $21 billion market by 2017. Automotive applications represent today around 20% of the MEMS market in revenue and are expected to see a 5.4 % growth in the next five years, which means that the penetration of MEMS devices in this market will remain limited. Today, MEMS family in cars is mainly represented by pressure sensors for Tire Pressure Monitoring and Manifold Air Pressure sensing, and accelerometers in ABS and stabilization systems. These applications are reaching maturity, which mean that their growth gets directly related to the car sales. To find new growth opportunities, system integrators have been trying to develop new MEMS based systems to enhance safety, comfort and reduce pollution and energy consumption. The presentation will show emerging applications and the challenges they face from a technical and a market point of view. Diverse electronic packages operate under exceptionally harsh environments, which require extended lifetimes, presenting a significant challenge for the microelectronics community. Operating temperatures above 200 °C together with high pressures, vibrations and potentially corrosive environments implies that some technical issues regarding the development of electronic systems that will operate at such high temperature remain. Technology based on sintering has been recently emerging for power modules, capable of withstanding up to 300 °C. Sintered Ag is one potential candidate for die attachment for extreme environments. The application of sintered Ag has proven already to significantly increase the lifetime of interconnects when compared to solder joints. Both characterization of the failure mechanisms as well as prediction of product life in such environments is critical to the long term reliability of these devices. The present work aims to develop an understanding of how and why attach materials for Si dies degrade/fail under harsh environments by investigating sintered Ag material. New failure mechanisms will become dominant in the sintered Ag technology. Modeling helps understanding how a particular system behaves if conditions are altered. Thus, a 2D axis symmetric die attach model, commonly used to represent microelectronic package assemblies, was generated using Ansys Workbench. The FE-model provided a good understanding of the effect of single parameter variation of different leadframe materials (K64, K14, and FeNi42), chip height, sintered Ag and metallization thicknesses. The FE-model provided a rapid assessment of delamination, cracking and other defects and their location within the package. The effect of the sintered Ag thickness on the plastic strain was only slight. Furthermore, on the chip side, the local thermal mismatch between the Si die and the sintered Ag was the most important loading factor. Also, thicker chips generated higher stresses. Further analysis of simulation and experiment of sintered Ag interconnects will give more insight on dominating failure mechanisms, and help reduce failure risks.

Microbridge Nanoindentation Testing of Plasma-Enhanced Chemical Vapor Deposited Silicon Oxide Films

2004 ◽  
Vol 841 ◽  
Author(s):  
Zhiqiang Cao ◽  
Tong-Yi Zhang ◽  
Xin Zhang
Keyword(s):  
Residual Stresses ◽  
Thermal Annealing ◽  
Microelectromechanical Systems ◽  
Silicon Oxide ◽  
Chemical Vapor ◽  
Device Fabrication ◽  
Residual Deflection ◽  
Compressive Stresses ◽  
Stress Changes ◽  
Chemical Vapor Deposited

ABSTRACTPlasma-enhanced chemical vapor deposited (PECVD) silane-based oxides (SiOx) have been widely used in both microelectronics and MEMS (MicroElectroMechanical Systems) to form electrical and/or mechanical components. In this paper, a novel nanoindentation-based microbridge testing method is developed to measure both the residual stresses and Young's modulus of PECVD SiOx films. Our theoretical model employed a closed formula of deflection vs. load, considering both substrate deformation and the residual stresses in the thin films. In particular, the non-negligible residual deflection caused by excessive compressive stresses was taken into account. Freestanding microbridges made of PECVD SiOx films were fabricated using bulk micromachining techniques. To simulate the thermal processing in device fabrication, these microbridges were subjected to rapid thermal annealing (RTA) up to 800°C. A microstructure-based mechanism was applied to explain the experimental results of the residual stress changes in PECVD SiOx films after thermal annealing.

scholarly journals A Highly Sensitive and Flexible Capacitive Pressure Sensor Based on a Porous Three-Dimensional PDMS/Microsphere Composite

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1412 ◽  
Author(s):  
Young Jung ◽  
Wookjin Lee ◽  
Kyungkuk Jung ◽  
Byunggeon Park ◽  
Jinhyoung Park ◽  
...  
Keyword(s):  
Pressure Sensor ◽  
Sacrificial Layer ◽  
Three Dimensional ◽  
Pressure Sensors ◽  
Capacitive Pressure Sensor ◽  
Mechanical Stimuli ◽  
Highly Sensitive ◽  
Flexible Pressure Sensors ◽  
Fast Rise ◽  
Better Than

In recent times, polymer-based flexible pressure sensors have been attracting a lot of attention because of their various applications. A highly sensitive and flexible sensor is suggested, capable of being attached to the human body, based on a three-dimensional dielectric elastomeric structure of polydimethylsiloxane (PDMS) and microsphere composite. This sensor has maximal porosity due to macropores created by sacrificial layer grains and micropores generated by microspheres pre-mixed with PDMS, allowing it to operate at a wider pressure range (~150 kPa) while maintaining a sensitivity (of 0.124 kPa−1 in a range of 0~15 kPa) better than in previous studies. The maximized pores can cause deformation in the structure, allowing for the detection of small changes in pressure. In addition to exhibiting a fast rise time (~167 ms) and fall time (~117 ms), as well as excellent reproducibility, the fabricated pressure sensor exhibits reliability in its response to repeated mechanical stimuli (2.5 kPa, 1000 cycles). As an application, we develop a wearable device for monitoring repeated tiny motions, such as the pulse on the human neck and swallowing at the Adam’s apple. This sensory device is also used to detect movements in the index finger and to monitor an insole system in real-time.

Self-Aligned Contacting Processes for the 80 nm p-MTJ Device Fabrication by Wet Approach

2018 ◽  
Vol 282 ◽  
pp. 152-157 ◽  
Author(s):  
Hu Shan Cui ◽  
Kai Hua Cao ◽  
You Guang Zhang ◽  
Hua Gang Xiong ◽  
Jia Qi Wei ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Magnesium Oxide ◽  
Building Block ◽  
Silicon Oxide ◽  
Process Integration ◽  
Electrical Contact ◽  
Device Fabrication ◽  
Integration Scheme ◽  
Ferromagnetic Metals ◽  
Wet Etch

In this work, a novel process integration scheme for p-MTJ devices’ passivation and contacting was proposed. The method can efficiently protect the ferromagnetic metals and the magnesium oxide which are the key building block of p-MTJs, and effectively make electrical contact with the interconnect metals for p-MTJs. The scheme consists of passivation of p-MTJs with dual dielectrics - silicon nitride and silicon oxide, followed by planarization and selective wet etch. The proposed integration scheme was successfully demonstrated with 80 nm size p-MTJ devices.

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