Kanakasabapathi Subramanian

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.

Experimental Study of a Novel Silicon Carbide MEMS Ignition Device

This paper presents a robust, low power MEMS igniter built using low pressure chemical vapor deposited (LPCVD) polycrystalline Silicon Carbide films. The MEMS igniter design is based on a 5 mum thick, low stress membrane composed of doped and undoped SiC layers making up the resistive heaters and passivation layer respectively. Experimental tests using an optical pyrometer to measure temperature indicate that this igniter can achieve temperatures beyond 1400degC, with less than 10 W power input, and a time response of less than 0.1 sec. Reliability tests were performed to characterize the igniter behavior as a function of time and determine the lifetime of the devices. Lifetime of the igniter at temperatures greater than 1300degC was limited due to the growth of unstable crystobalite oxide layers resulting in membrane fracture. Reliability significantly improved when operation of the igniter was limited to temperatures below 1 100degC.

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.

Thermal simulation for IC devices with large number of heat sources

Due to increasing component density in electronic devices, transient thermal simulations are required to be able to deal with a large number of small size heat sources in a large modeling domain. This paper presents a four-step modeling methodology, which can be applied to this type of thermal problems. The method is composed of multi-scale models and focuses on temporal and spatial temperatures of small size heat sources in a relatively large domain. In large-sale model, small size components are replaced with large volumes, and their material properties are also changed to conserve the thermal resistances and capacitances of the small components. Results from the large-scale model are used as boundary conditions for small-scale model. Mesh reduction and less computation time are the major benefits of the method as compared to directly modeling whole devices. The method is explained and discussed step by step. An example based on a simplified electronic board configuration is provided to demonstrate the methodology.

Six Sigma Methodology for Sensor Package Evaluation

Six sigma methods were used to evaluate the effect of package design on the performance of an oil-isolated resonant pressure sensor. The sensor was rated at 35 mbar range and -55°C to +125°C operating temperature. The accuracy requirement on the sensor was 0.01% full scale and flowed down to an equivalent requirement of < 0.01 mbar of package induced error in the sensor. Beyond this error, package effects would destroy measurement accuracy in addition to underutilizing sensor capability. Six sigma studies and experiments on an optimized package design suggested that repeatability effects cannot be measured to statistical significance by any known external method such as optical interferometry, thus suggesting that a MEMS sensor is possibly the best and only method of evaluating low residual strain.Copyright