Extraction of the electric field in field plate assisted RESURF devices

It has previously been reported that the lateral electric field (Ex) in the drain extension of thin SOI HV (700V) field plate assisted RESURF devices can be extracted from their ID-VD characteristics in the subthreshold regime. In this work the prerequisites for valid field extraction and the (voltage) range of validity are established for linearly graded drain extension based RESURF devices through a combination of analytical calculations and TCAD device modeling. It is shown that the most important condition for field extraction is that an increment dVDS should not affect the lateral field at the already depleted zone. This unique condition is found to be met in the drain extension at distances larger than a specific length (5.3λ) governed by the drain extension silicon and oxide thicknesses. For realistic device parameters the method is shown to hold for devices with a BVDS of ~ 150V and higher.