Kuna Venkat Satya Rama Kishore

Scalable vertical diaphragm pressure sensors: device and process Design, Design for packaging

We present a design, process How, and packaging scheme for a novel three-dimensional capacitive microelectromechanical systems pressure sensor [1], [10]. These sensors present a paradigm shift in pressure sensor technology. They contain an array of vertical diaphragms perpendicular to the wafer plane where each pair of diaphragms requires orders of magnitude lower footprint than traditional in-plane sensors. The sensor can be arrayed or scaled up for increased sensitivity and can be absolute, gauge or differential. Fabrication requires 2-4 masks, depending on process How and has been greatly simplified, without reduction in performance, for high yield and low cost. Multiple geometries have been modeled with sensitivities reaching several fF/kPa and temperature coefficient of sensitivity better than conventional devices. Pressure and electrical ports are individually interchangeable between front and back sides. This allows for a simple design that has only Si facing the sensing environment and the electrical connections on the backside, thus enabling simple packaging for both pressure and electrical ports.

Stability and 2-D Simulation Studies of Avalanche Breakdown in 4H-SiC DMOSFETs With JTE

In this paper, the stability of n-channel 4H-silicon carbide (SiC) DMOSFETs with junction termination extension (JTE) was assessed by measuring the breakdown voltage (BV) of these devices before and after bias stress at a high temperature. The BV slumped after the DMOSFET was bias stressed at 1200 V for 2 h at 175degC, and the slumped BV dynamically recovered to the prestress value during the poststress period. Computer simulation suggests that the BV slump and its recovery are dominated by the positive charge trapping/detrapping phenomena at the SiC/fleld oxide interface in the JTE structure, rather than the trapping/detrapping at the SiC/gate oxide interface in the cell structure. A positive interface charge of approximately one-third of the sheet dopant concentration of the JTE region, lowers BV by 150 V, which is the typical measured BV slump of the DMOSFETs of this paper.

3-dimensional scalable pressure sensors: device and process design

We present the design, process flow and packaging scheme for a novel 3D capacitive MEMS pressure sensor. These sensors present a paradigm shift in pressure sensor technology. They contain an array of vertical diaphragms perpendicular to the wafer plane where each pair of diaphragms requires orders of magnitude lower footprint than traditional in-plane sensors. The sensor can be arrayed or scaled up for increased sensitivity and can be absolute, gauge or differential. Fabrication requires 2-4 masks depending on process flow and has been greatly simplified, without reduction in performance, for high yield and low cost. Multiple geometries have been modeled with sensitivities reaching several fF/kPa and temperature characteristics better than conventional devices. Pressure and electrical ports are individually interchangeable between front and back sides. This allows for a simple design that has only Si facing the sensing environment and the electrical connections on the backside.

Finite Element Analysis of Capacitive Micromachined Ultrasonic Transducer (CMUT) for NDE Applications

This paper presents a comparison of three Finite Element approaches for modeling the behavior of a Capacitive Micromachined Ultrasonic Transducer (CMUT). CMUTs have become very popular over the last decade because of the comparable bandwidth, sensitivity and dynamic range with its piezoelectric counterparts. The ease of fabrication is an added advantage. Modeling of CMUTs is a coupled physics problem, which involves solving Electrostatics and Structural interactions simultaneous. Finite Element models of the CMUT are constructed using the commercial code ANSYS (9.0). Three different approaches of solving the coupled field problem are discussed and the results are compared for resonance frequency, collapse voltage, capacitance and electromechanical coupling coefficient. The approaches discussed involve sequentially coupled‐field analysis, direct coupled‐field analysis and reduced order modeling. Detailed results have been presented for the effect of variation in geometrical factors as predicted by the thre...