Department of Electrical Engineering

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IIT Jodhpur

This paper presents a novel process scheme for singulating Micro Electro Mechanical Systems (MEMS) or CMOS devices that may be released or unreleased, which have fragile components and/ or that have within or without in-plane structures. The process comprises spin coating of a polymer based protection material on the back and front of the device wafer, after attaching it to holder wafer. Such protected wafers are then singulated into individual chips using standard dicing saw. The process details, its advantages and results are elaborated. © 2005 IEEE.

World University root node

Proceedings of 7th Electronics Packaging Technology Conference, EPTC 2005

Process technique for singulating fragile devices

Two novel lateral metal-contact radio-frequency microelectromechanical system (RF MEMS) switches are reported. These switches are implemented with quasi-finite ground coplanar waveguide (FGCPW) configuration and actuated by applying electrostatic force on a high-aspect-ratio cantilever beam. It is demonstrated that the insertion loss of the switch is less than 0.2 dB up to 15 GHz and the isolation is higher than 20 dB up to 25 GHz. An RF model of the switches is used to analyse the effects of the switch design parameters and RF performance. The optimization of the switch mechanical design is discussed where the threshold voltage can be lower than 25 V. The lateral switches are fabricated by deep reactive ion etching (DRIE) process on a silicon-on-insulator (SOI) wafer with shadow mask technology.

Journal of Micromechanics and Microengineering

Low-loss lateral micromachined switches for high frequency applications

Lanthanide-incorporated metal nitride (lanthanide-MNx) is investigated as a novel n-type metal gate electrode with tunable work function and good thermal stability for the first time. By incorporating lanthanide elements, such as terbium (Tb), erbium (Er), or ytterbium (Yb), into metal nitride gates, such as TaN and HfN, the work function of MNx can be continuously tuned down to 4.2-4.3 eV even after 1000°C RTA by varying the lanthanide concentrations. In addition, the lanthanide-MNx gates exhibit good thermal stability up to 1000°C on both SiO2 and high-k HfAlO. Possible mechanism for the stability of these metal gates is also discussed and the results show that the enhancement of the nitrogen content in lanthanide-MNx films could be responsible.

Digest of Technical Papers - Symposium on VLSI Technology

Lanthanide-incorporated metal nitrides with tunable work function and good thermal stability for NMOS devices

A method to design an output feedback compensator for a higher order discrete time system with distinct complex eigenvalues via its reduced order model is presented. Its application is shown for vibration control of a smart cantilever beam. As the states are not needed for feedback, the method is simple and can be easily implemented. © 2005 Taylor & Francis Group, LLC.

IETE Journal of Research

Design of output feedback compensator for discrete time system via reduced order model

This paper presents a multirate output feedback based sliding mode control, algorithm which eliminates the chattering. The proposed algorithm uses the output samples for the switching function evaluation and sliding mode control computation. The control is based on the reaching law approach and drives the system trajectory to sliding manifold in finite time. The control law obtained has two parts, nonlinear and linear. The nonlinear part brings the trajectory in the vicinity of the sliding manifold and linear control guarantees that the sliding manifold is reached in one step and thereafter the motion of the system confines to the manifold. The proposed algorithm does not require knowledge of the complete state vector. As in many practical situations, all the states are not available for measurement: the proposed algorithm gives better choice for obtaining similar result. The algorithm is applied to a dc motor system with position measurement only.

Systems Science

Discrete time sliding mode control using multirate output feedback with chattering elimination

In this paper the design of sensorless induction motor speed controller without observer using concept of multirate output feedback discrete time sliding mode control technique is proposed. The nonlinear model of the motor model is linearised at its operating point and the fast output sampling discrete time sliding mode control using output samples is applied to non-linear plant of the motor at its operating (equilibrium) point. This method does not require the complete states of the system for feedback and is easily implementable. © 2005 IEEE.

Proceedings of the IEEE International Conference on Industrial Technology

Multirate output feedback sliding mode controller for sensorless induction motor

In the last few years, the research on discrete-time sliding mode control has received a considerable attention. Unlike its continuous-time counterpart, discrete-time sliding mode control is not robust in general. In this paper, an algorithm is presented for robust discrete-time sliding mode control using the concept of multirate output feedback. © 2005 IEEE.

Robust quasi-sliding mode control of discrete-time systems using multirate output feedback

Power system stabilisers (PSSs) are added to excitation systems to enhance the damping during low-frequency oscillations. The design of decentralised robust PSS for four machines with ten buses using periodic output feedback is proposed. The nonlinear model of a multimachine power system is linearised at different operating points and 16 linear state-space models are obtained. For each of these models an output injection gain is obtained using LQR technique. A decentralised robust periodic output feedback gain which realises these output injection gains is obtained using the linear matrix inequality approach. This method does not require states of the system for feedback and is easily implemented. The robust decentralised periodic output control is applied to the nonlinear model of a multimachine system at different operating (equilibrium) points and gives encouraging results for the design of power system stabilisers.

IEE Proceedings: Control Theory and Applications

Power system stabiliser for multimachine power system using robust decentralised periodic output feedback

Ultrathin SiGe films on insulator, with high Ge fraction, are fabricated through Ge condensation. A two-step oxidation process is pursued where temperatures chosen are lower than that corresponding to the solidous curve of the Si-Ge phase diagram. In this way, the smallest achievable thickness could be decreased further compared to a single step oxidation process. We achieved a uniform Ge fraction of 0.6 at a SiGe thickness of 6 nm, indicating a ten-fold increase in Ge fraction as compared to starting epitaxial SiGe layer. The surface roughness was below 1 nm and XRD analysis indicates that the films are compressive. © 2005 The Electrochemical Society. All rights reserved.

Electrochemical and Solid-State Letters

A two-step oxidation mediated condensation process for ultrathin high Ge content SiGe epitaxial films on insulator

This paper features the modelling and design of a type of multirate output feedback based controller (Fast Output Sampling Feedback-FOS) to control the flexural vibrations of a smart flexible Timoshenko cantilever beam for a Single Input Single Output (SISO) case by retaining the first 2 dominant vibratory modes. Piezoelectric patches are bonded as sensor / actuator to the master structure at different finite element locations along the length of the beam. The beam structure is modelled in state space form using the concept of piezoelectric theory, the Timoshenko beam theory and the Finite Element Method (FEM) technique and by dividing the beam into 4 finite elements and placing the piezoelectric sensor / actuator at one discrete location as a collocated pair at a time, i.e., as surface mounted sensor / actuator, say, at FE position 1 or 2 or 3 or 4, thus giving rise to 4 SISO models of the same plant. FOS feedback controllers are designed for the above 4 models of the same plant. The piezo sensor / actuator pair is moved from the free end to the fixed end of the beam. The effect of placing the collocated sensor / actuator pair at various finite element locations along the length of the beam is observed and the conclusions are drawn for the best performance and for the smallest magnitude of the control input required to control the vibrations of the flexible beam. © 2013, UK Simulation Society. All rights reserved.