Switching performance of low-voltage N-channel trench MOSFETs

Guidelines for optimising the switching behaviour of low-voltage (LV) n-channel trench MOSFETs are presented, with emphasis on the geometry and the doping profile. In our optimisation we focussed on three parameters: the specific on-resistance (R_ds,on), the gate-drain charge density (Q_gd) and the off-state breakdown voltage. We obtained by simulations for the 30 V control switch an R_ds,on of less than 10 mΩ.mm² and an R_ds,on·Q_gd of less than 15 mΩ.nC (applied voltage V_dd=12 V). The result is a stripe cell structure with a trench width of 0.15 μm, a cell pitch of 1.0 μm. For the 25 V synchronous rectifier we obtained in the same feature size figures-of-merit of 5 mΩ.mm² and 17 mΩ.nC.