Analytical models of lateral power devices with arbitrary vertical doping profiles in the drift region

Abstract

By solving the 2D Poisson's equation, analytical models are proposed to calculate the surface potential and electric field distributions of lateral power devices with arbitrary vertical doping profiles. The vertical and the lateral breakdown voltages are formulized to quantify the breakdown characteristic in completely-depleted and partially-depleted cases. A new reduced surface field (RESURF) criterion which can be used in various drift doping profiles is further derived for obtaining the optimal trade-off between the breakdown voltage and the on-resistance. Based on these models and the numerical simulation, the electric field modulation mechanism and the breakdown characteristics of lateral power devices are investigated in detail for the uniform, linear, Gaussian, and some discrete doping profiles along the vertical direction in the drift region. Then, the mentioned vertical doping profiles of these devices with the same geometric parameters are optimized, and the results show that the optimal breakdown voltages and the effective drift doping concentrations of these devices are identical, which are equal to those of the uniform-doped device, respectively. The analytical results of these proposed models are in good agreement with the numerical results and the previous experimental results, confirming the validity of the models presented here.

An Analytical Breakdown Model for the SOI LDMOS With Arbitrary Drift Doping Profile by Using Effective Substrate Voltage Method

“…The doping profile influences the breakdown characteristics of the lateral power devices. However, the model in [6] and [17] can only depict the influence of variation of vertical or lateral doping profile, separately. To give a clear breakdown mechanism of SOI LDMOS with arbitrary drift doping profiles, in this part, the method of effective substrate voltage is proposed to simplify the equations and avoid the complex derivation in [6].…”

“…4) Vertical Breakdown: The vertical breakdown assumes to occur at point (L d , t s ). Based on the boundary condition E(L d , t s ) = E c , the vertical BV can be obtained as [6]:…”

“…Thus, the impact of variation in the vertical doping profile on the electric field of power devices can not be discussed using these models. In terms of the device with variation of vertical doping profile, [6] gives a method to model this device based on the assumption that doping profile of each small layer is uniform. However, such a method still incapable of considering the variation of lateral and vertical doping profiles simultaneously as a result of the derivation complexity of which method.…”

An analytical model for the vertical electric field distribution and optimization of high voltage REBULF LDMOS

“…The widths of the substrate depletion layer t S1 and t S2 can be calculated by taking the first-order approximation. [18][19][20] S G D In order to discuss the influences of the n-buried layer on the vertical electric field and the vertical breakdown voltage, the vertical electric field distribution is derived by substituting the two-order Taylor expanded formula into Eq. ( 8) [21] (where…”