• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.163-170
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• 2006

By removing sacrificial layer through ashing process, movable MEMS structure on substrate can be fabricated in surface micromachining. However, MEMS structure includes, during the ashing process, the warping or buckling effects due to stress gradient along the vertical direction of thin film. In this study, we presented method for counteracting the unwanted deflection of MEMS structure and designed using character of deposit process to overcome limited design conditions. Unit cell patterns were designed with character of deposit shape, and their final shapes were adopted using Finite Element Method. Finally, RF MEMS switch was fabricated by surface micro machining as test vehicles. We checked out that alleviation effect for deformation of switch improved by 35%.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.2
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• pp.49-56
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• 2007

MEMS-based storage is being developed as a new storage media. Due to its attractive features such as high-bandwidth, low-power consumption, high-density, and low cost, MEMS storage is anticipated to be used for a wide range of applications from storage for small handhold devices to high capacity mass storage servers. However, MEMS storage has vastly different physical characteristics compared to a traditional disk. First, MEMS storage has thousands of heads that can be activated simultaneously. Second, the media of MEMS storage is a square structure which is different from the platter structure of disks. This paper presents a new request scheduling algorithm for MEMS storage that makes use of the aforementioned characteristics. This new algorithm considers the parallelism of MEMS storage as well as the seek time of requests on the two dimensional square structure. We then extend this algorithm to consider the aging factor so that starvation resistance is improved. Simulation studies show that the proposed algorithms improve the performance of MEMS storage by up to 39.2% in terms of the average response time and 62.4% in terms of starvation resistance compared to the widely acknowledged SPTF (Shortest Positioning Time First) algorithm.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.3
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• pp.82-90
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• 2006

Recently the electrostatic 2-axis MEMS stages have been fabricated for the purpose of an application to PSD (Probe-based Storage Device). However, all of the components(platform, comb electrodes, springs, anchors, etc.) in those stages are placed in-plane so that they have low areal efficienceis, which is undesirable as data storage devices. In this paper, we present a novel structure of an electrostatic 2-axis MEMS stage that is characterized by having large area platform. for obtaining large area efficiency, the actuator part consisting of mainly comb electrodes and springs is placed right below the platform. The structure and operational principle of the MEMS stage are described, followed by a design procedure, structural and modal analyses using FEM(Finite Element Method). The areal efficiency of the MEMS stage was designed to be about 25%, which is very large compared with the conventional ones having a few percentage.

• Journal of Sensor Science and Technology
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• v.30 no.3
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• pp.170-174
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• 2021

As the rising attention to the medical and healthcare issue, Bio-MEMS (Micro electro mechanical systems) platform such as bio sensor, cell culture system, and microfluidics device has been studied extensively. Bio-MEMS platform mostly has high resolution structure made by biocompatible material such as polydimethylsiloxane (PDMS). In addition, three dimension structure has been applied to the bio-MEMS. Lithography can be used to fabricate complex structure by multiple process, however, non-rectangular cross section can be implemented by introducing optical apparatus to lithography technic. X-ray lithography can be used even for sub-micron scale. Here in, we demonstrated lines with round shape cross section using the tilted gold absorber which was deposited on the oblique structure as the X-ray mask. This structure was used as a mold for PDMS. Molded PDMS was applied to the cell culture platform. Moreover, molded PDMS was bonded to flat PDMS to utilize to the sub-micro channel. This work has potential to the large area bio-MEMS.

• Journal of electromagnetic engineering and science
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• v.6 no.2
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• pp.135-145
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• 2006

This paper presents the theory, design, fabrication and characterization of the novel low actuation voltage capacitive shunt RF-MEMS switch using a corrugated membrane with HRS MEMS packaging. Analytical analyses and experimental results have been carried out to derive algebraic expressions for the mechanical actuation mechanics of corrugated membrane for a low residual stress. It is shown that the residual stress of both types of corrugated and flat membranes can be modeled with the help of a mechanics theory. The residual stress in corrugated membranes is calculated using a geometrical model and is confirmed by finite element method(FEM) analysis and experimental results. The corrugated electrostatic actuated bridge is suspended over a concave structure of CPW, with sputtered nickel(Ni) as the structural material for the bridge and gold for CPW line, fabricated on high-resistivity silicon(HRS) substrate. The corrugated switch on concave structure requires lower actuation voltage than the flat switch on planar structure in various thickness bridges. The residual stress is very low by corrugating both ends of the bridge on concave structure. The residual stress of the bridge material and structure is critical to lower the actuation voltage. The Self-alignment HRS MEMS package of the RF-MEMS switch with a $15{\Omega}{\cdot}cm$ lightly-doped Si chip carrier also shows no parasitic leakage resonances and is verified as an effective packaging solution for the low cost and high performance coplanar MMICs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.10
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• pp.1440-1447
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• 2015

This paper describes a study for anti high-shock design of MEMS vibrating ring gyroscope. Structure models was made by MEMS technology processing. MEMS Vibrating Ring Gyroscope mechanical structure were not only anti-high shock simulated with the LS Dyna Ver 971 software but also with mathematical analysis and the finite element method in order to confirm the shock reliability. Shock test result of a MEMS vibrating gyroscope being developed to have gun-hardened survivability while maintaining tactical grade navigation performance for application to various guided projectiles.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.1010-1013
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• 1998

In micromechanical system (MEMS) such as microactuators. thin film has been widely used as structural material. MEMS materials have difference with bulk in terms of mechanical properties. So, we design the advanced test structure for micromechanical properties of MEMS. The designed structure includes the newly developed pre-crack and it is driven by electrostatic force. To measure the fracture toughness, the pre-crack formation in the test structure is developed with conventional etching process. The advanced test structure is fabricated by application of semiconductor technology. After this, we propose analytical methodology to evaluate the fracture toughness and fatigue properties through a prediction of crack behavior from the variations of stiffness and frequency. Additionally, life time of a mirror plane used in DVD(Digital Video Disk) is measured as a function of capacitance and applied voltage under the accelerated conditions. Ultimately, we propose the method to evaluate the micromechanical reliabilities of the MEMS materials using the advanced test structure.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.165-172
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• 2005

In MEMS (Micro-Electro-Mechanical System), packaging induced stress or stress induced structure deformation becomes increasing concerns since it directly affects the performance of the device. In the decoupled vibratory MEMS gyroscope, the main factor that determines the yield rate is the frequency difference between the sensing and driving modes. The gyroscope, packaged using the anodic bonding at the wafer level and EMC (epoxy molding compound) molding, has a deformation of MEMS structure caused by thermal expansion mismatch. This effect results in large distribution in the frequency difference, and thereby a lower yield rate. To improve the yield rate we propose a packaged SiOG (Silicon On Glass) process technology. It uses a silicon wafer and two glass wafers to minimize the wafer warpage. Thus the warpage of the wafer is greatly reduced and the frequency difference is more uniformly distributed. In addition. in order to increase robustness of the structure against deformation caused by EMC molding, a 'crab-leg' type spring is replaced with a semi-folded spring. The results show that the frequency shift is greatly reduced after applying the semi-folded spring. Therefore we can achieve a more robust vibratory MEMS gyroscope with a higher yield rate.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.8
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• pp.1461-1465
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• 2007

A micromachined sensor part for an infrared focal plane array has been designed and fabricated. Amorphous silicon was adapted as a sensing material, and silicon nitride was used as a membrane material. To get a good efficiency of infrared absorption, the sensor was made as a ${\lambda}/4$ cavity structure. All the processes were done in $0.5\;{\mu}m$ iMEMS fab. in the Electronics and Telecommunication Research Institute (ETRI). The processed MEMS sensor structure had a small membrane deflection less than $0.3\;{\mu}m$. This excellent deflection property can be attributed to the rigorous balancing of the stresses of individual layers. The efficiency of infrared absorption was more than 75% in the wavelength range $8\;-\;14\;{\mu}m$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.840-845
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• 2005

This paper presents a robust optimal design method for a periodic structure type of MEMS resonator that is vulnerable to mode localization. The robust configuration of such a MEMS resonator to fabrication error is implemented by changing the regularity of periodic structure. For the mathematical convenience, the MEMS resonator is first modeled as a multi pendulum system. The index representing the measure of mode variation is then introduced using the perturbation method and the concept of modal assurance criterion. Finally, the optimal intentional mistuning, minimizing the expectation of the irregularity measure for each substructure, is determined for the normal distributed fabrication error and its robustness in the design of MEMS resonator to the fabrication error is demonstrated with numerical examples.