Theodore J. Letavic

Influence of drift region on the 1/f noise in LDMOS

The effect of drift region on the flicker noise in LDMOS devices in the linear and saturation regions is analyzed using measured data and device simulations. In the linear region, noise in the drift region arises from gate-drain overlap region and is significant for longer channel length devices. For shorter channel length devices, the sub-surface current flow in the gate-drain overlap region reduces the contribution of noise from the drift region. In the saturation region, noise is dependent on quasi-saturation condition, and reaches its lowest value only when the channel is saturated.

Planar dual gate oxide LDMOS structures in 180nm power management technology

This paper presents a 20V-rated planar dual gate oxide NLDMOS power device structure fabricated in a 180nm power management technology. The performance of the planar dual gate device structure is compared to a conventional STI-based device and it is shown that the planar dual gate structure has superior BVds-Rsp, gm, HCI reliability, and forward safe operating area figures-of-merit. The planar dual gate structure exhibits BVds=32V/14 mΩ.mm2 specific on-resistance (and BVds=20V/7.5mΩ.mm2 for a drift length scaled version), hot carrier reliability in excess of 10 years analog lifetime in all bias regimes, and a linear forward IV characteristic. The planar dual gate architecture is scalable in rated voltage from 7V to 24V, and is an ideal component for the integration of USB switch, battery charging, backlighting, and PA envelope tracking mobile applications.

Lateral tapered active field-plate LDMOS device for 20V application in thin-film SOI

We present a new device design for 20V application in thin body SOI technology. High breakdown voltage is achieved by forming RX-bound field plates which deplete the drift region of an LDMOS structure using only lateral electric field coupling. A baseline 180nm CMOS SOI process is utilized and RX field plate shapes are designed to result in an essentially uniform longitudinal drift region electric field satisfying the RESURF principal. We studied device scaling and the effect of varying the width and length of the angular RX field plates and their relation to impact ionization rate in both floating body and body-contacted n-channel LDMOS deices. 3D TCAD simulations were used to investigate the effect design parameters on electric field and impact ionization. Unitary 20V rated-LDMOS devices are experimentally demonstrated, verifying a LDMOS option to stacked CMOS for high voltage applications in SOI technology.

Novel high voltage LDMOS using a variable fermi-potential field plate for best switching FOM and reliability tradeoff

In this paper, we discuss the fundamental design tradeoff among specific on-resistance (Ron, sp), gate charge (Cgg), quasi-saturation, and reliability characteristics for an integrated high voltage LDMOS. A novel patterned gate design is proposed and implemented in a 120V-rated NLDMOS. Optimal design characteristics are demonstrated with 30% improvement in switching FOM (Ron, sp*Qgg) and a robust Id, lin shift passing 15 years lifetime specification. The new design technique is proven to significantly improve the high voltage LDMOS design tradeoff.