HV NMOS transistor for IC/MEMS integration on SOI

This paper describes the procedure of creating HV NMOS transistor for IC/MEMS integration on thick SOI wafers. The result of this kind of integration is essential for many next-generation applications. High bias voltages are needed with MEMS devices to create more complex entities on a single chip. SOI wafers are ideal for this kind of integration as MEMS devices can be fabricated using buried oxide layer. Thick SOI also provides a substrate that can be used for CMOS processes with little or no modifications. Two different SOI were used as well as bulk wafers to verify the results. The SOI layer was either uniformly doped or it had a buried p+ layer. The SOI had an 8µm thick device layer with 1µm thick buried oxide. Critical layout parameters are identified and test structures have been designed to study the layout effects. Properties of the HV NMOS transistor for these different substrates and for different layouts are compared. HV NMOS transistor has been successfully fabricated for IC/MEMS integration on SOI.