Determining the Performance Limits of LDMOS With Three Common Types of Field Oxides

We use a novel algorithm to efficiently search for the physical limits of three different field oxide (FOX) structures for laterally diffused metal-oxide-semiconductor (LDMOS) transistors. The design problem of LDMOS transistors targets the breakdown voltage (BV) in the range of 30–50 V and compares the performance. The power density figure-of-merit (FOM =
$\text {BV}^{{2}}/{R}_{\text {sp(on)}}$
) is the criterion for performance evaluation. LOCal Oxidation of Silicon (LOCOS) and step gate (SG) transistors are optimized within the same design space, enabling a direct comparison of their limits and showing superior performance compared to the shallow trench isolation (STI) transistor. The discussion about which design parameters limit the device’s performance is also included. The comparison result yields a valuable reference for process development.