Kyosuke Miyagi

Floating island and thick bottom oxide trench gate MOSFET (FITMOS) - a 60V ultra low on-resistance novel MOSFET with superior internal body diode

A MOSFET structure named FITMOS has been successfully developed and exhibits record-low loss in the 60 volt breakdown voltage range. The device has a body diode with superior reverse recovery characteristics and exhibits an extremely small value for RonQgd. The distinctive feature of this device is the use of floating islands formed by self-alignment and trench gates with a thick oxide layer on the bottom. This structure can also be used for the terminal portion of the device, so the increase in the number of fabrication process steps is less than 5%. Moreover, the rate of non-defective-gates in 3-by-4-mm rectangular devices on an 8-inch wafer is at least 98%.

Advanced Floating Island and Thick Bottom Oxide Trench Gate MOSFET (FITMOS) with reduced RonA during AC operation by passive hole gate and improved BVdss RonA trade-off by elliptical floating island

A MOSFET structure called a FITMOS (floating island and thick bottom oxide trench gate MOSFET) has been successfully developed that exhibits record-low loss in the 60 V breakdown voltage (BVdss) range. The device has a body diode with superior reverse recovery characteristics and exhibits an extremely small value for RonQgd. The distinctive features of this device are the use of floating P islands formed by self-alignment and trench gates with a thick oxide layer at the bottom. The following improvements achieved progress in the characteristic of FITMOS. At the time of AC operation, the charges in the floating P islands which are a feature of the floating type device become greater, increasing the on-resistance (Ron) due to the JFET effect. This issue was solved by forming passive hole gates in the end walls of the trenches. The Ron under AC operation is equivalent to the Ron under DC operation. The trade-off of BVdss and Ron has been improved by making the form of the floating island into an elliptical form. A BVdss of 83 V and specific on-resistance (RonA) of 36 mOmegamm2 were obtained.

Current-sensing power MOSFETs with excellent temperature characteristics

For MOSFETs with a current-sensing function (current-sensing power MOSFETs), temperature-based changes in the current sense ratio have been a significant problem. This research clarified the mechanisms involved in these temperature-based sense ratio changes and identified the effects of the following on sense ratio temperature dependence: (1) Drift layer impurity concentration and layer thickness, and (2) The position of the sense MOSFET part in the chip. Furthermore, by adopting a FITMOS [1][2][3] structure, it was shown that temperature-based changes in the sense ratio could be reduced from 11.2% to 3.4%.

Floating Islands and Thick Bottom Oxide Trench Gate MOSFET (FITMOS) with Passive Hole Gate -60V Ultra Low On-Resistance Novel MOSFET-

A MOSFET structure called a FITMOS has been successfully developed that exhibits record-low loss in the 60V breakdown voltage range (Kasakian and Perrault, 2001). The device has a body diode with superior reverse recovery characteristics and exhibits an extremely small value for RonQgd. The distinctive features of this device are the use of floating P islands formed by self-alignment and trench gates with a thick oxide layer at the bottom. However, during AC operation, the charges in the floating P islands become greater, increasing the on-resistance due to the JFET effect. This issue was solved by forming passive hole gates in the end walls of the trenches. The on-resistance under AC operation is equivalent to the on-resistance under DC operation

Floating Island and Thick Bottom Oxide Trench Gate MOSFET (FITMOS) Ultra-Low On-Resistance Power MOSFET for Automotive Applications

This paper proposes a new structure for the power MOSFET called FITMOStrade, which is capable of realizing an ultra-low on-resistance that exceeds the unipolar limit in the automotive breakdown voltage range (50 to 100 V). In the past, FITMOS was developed for use as a 60 V breakdown voltage element. However, the demand for high-output devices for vehicle system applications has been growing in recent years, and a high breakdown voltage element is needed to meet this demand. The authors therefore utilized an efficient design of experiment, the D-optimal design, in an attempt to simultaneously optimize the complexly linked multiple characteristics and factors of FITMOS. As a result, the authors verified conditions for obtaining characteristics for excellent breakdown voltage (BVds = 74.0 V), on-resistance (RonmiddotA = 36.4 mOmegamm2 @ Vg = 15 V, excluding substrate resistance), and threshold voltage (Vth = 3.0 V).