Abstract
In order to achieve a high breakdown voltage (BV) for the SOI (Silicon-On-Insulator) power device in high voltage ICs, a novel high voltage n-channel lateral double-diffused MOS (LDMOS) with a lateral variable interface doping profile (LVID) placed at the interface between the SOI layer and the buried-oxide (BOX) layer (LVID SOI) is researched. Its breakdown mechanism is investigated theoretically, and its structure parameters are optimized and analyzed by 2D simulation software MEDICI. In the high voltage blocking state, the high concentration ionized donors in the depleted LVID make the surface electric field of SOI layer (ES) more uniform and enhance the electric field of BOX layer (EI), which can prevent the lateral premature breakdown and result in a higher BV. Compared with the conventional uniformly doped (UD) SOI LDMOS,EIof the optimized LVID SOI LDMOS is enhanced by 79% from 119 V/μm to 213 V/μm, and BV is increased by 33.4% from 169 V to 227 V. Simulations indicate that the method of LVID profile can significantly improve breakdown voltage for the SOI LDMOS.
Highlights
SOI technology has been widely used in high voltage ICs due to its advantages such as superior isolation, high speed, and low loss [1]
A feasible way to increase the breakdown voltage (BV) is to enhance the dielectric layer field (ENDIF), and several new structures have been proposed by ENDIF, in which introducing interface charges is effective and attractive [2]
The simulated results indicate that the method of lateral variable interface doping profile (LVID) profile can significantly improve BV compared with uniformly doped (UD) profile
Summary
SOI technology has been widely used in high voltage ICs due to its advantages such as superior isolation, high speed, and low loss [1]. The variable doping profile is a method of introducing interface charges which was firstly proposed to avoid high voltage breakdown for planar junctions in 1985 [3]. The approach of designing and implementing the linear doping profile on thin SOI for lateral high voltage devices was presented in 1995 [4]. A submicron thin film SOI LDMOS with the variable doping profile and numerical modeling of linear doping profiles were proposed in 1996 and 1999, respectively [5, 6]. After 2000, several new SOI devices structures with linear doping profile were proposed [7,8,9,10,11]. The doping profile of drift region is a combination of linear variable doping and uniform doping in vertical dimension, which is different from the above-mentioned structures. The simulated results indicate that the method of LVID profile can significantly improve BV compared with UD profile
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