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In order for the gas sensor devices to enjoy the miniaturization trend that has consumed much of the electronic device industry, major research in the field is undertaken. The bulky sensor devices of previous generations can not easily be incorporated into a CMOS processing sequence, because of their bulky nature and potential higher cost of production. More recently, materials such as zinc oxide and tin dioxide have shown powerful gas sensing capabilities. Among many potential deposition methods, spray pyrolysis has become a popular approach because of its ease of use and cost effectiveness. A model for spray pyrolysis deposition is developed and implemented within the level set framework. The implementation allows for a smooth integration of multiple processing steps for the manufacture of smart gas sensor devices. From the observations, it was noted that spray pyrolysis deposition, when performed with a gas pressure nozzle, results in good step coverage, analogous to a CVD process. This is mainly due to the atomizing nozzle being placed at a reasonable distance away from the wafer surface and reducing the droplets volume and mass in order to ensure they fully evaporate prior to contact with the substrate surface. A topography simulator for this deposition methodology is presented. [ABSTRACT FROM PUBLISHER]

Highlights: [•] A simulator for spray pyrolysis deposition is created in the Level Set framework. [•] Droplet atomization, transport, and silicon interaction is analyzed and modeled. [•] Stokes force, gravity, electrical force, and thermophoretic forces calculated. [•] Electric (physical transport) and air pressure (CVD) nozzles simulated differently. [•] 3D simulation examples for electric and air pressure spray deposition performed. [ABSTRACT FROM AUTHOR]

The ability to deposit a thin tin oxide film on CMOS chip dies has enabled the manufacture of modern smart gas sensor devices. Spray pyrolysis deposition is used to grow the required thin films, as it is an affordable deposition technique which can be integrated into a standard CMOS processing sequence. A model for spray pyrolysis deposition is developed and implemented within the Level Set framework using Monte Carlo techniques. Two models for the topography modification due to spray pyrolysis deposition are presented, with an electric nozzle and a pressure atomizing nozzle. The resulting film growth is described as a layer by layer deposition of the individual droplets which reach the wafer surface and deposit as ?at round disks or as a CVD-like process, depending on whether the droplets form a vapor near the interface or they deposit a film only after surface collision. Some additional geometries are simulated in order to analyze how the spray pyrolysis technique coats trench structures, essential for increasing the surface area of the gas sensing layer. [ABSTRACT FROM AUTHOR]