电导增强型高压功率器件研究

发布时间：2018-08-24 18:19

【摘要】：实现高耐压(BV)和低比导通电阻(Ron,sp)是功率器件设计的关键目标和研究方向,但是,功率MOS的耐压和比导通电阻之间存在着相互制约的2.5on,spRμBV关系,即“硅极限”。为了突破“硅极限”,同时克服常规场板技术的不足,本文提出了两类积累型的低阻横向功率MOS新结构。正向导通状态,该结构在漂移区形成多数载流子的积累层,形成从源端到漏端的连续的超低电阻电流通道;关断耐压状态,延伸栅场板调节漂移区的电场分布,从而提高耐压。利用上述工作机理,器件的比导通电阻由漂移区中积累层电荷决定,不取决于漂移区的掺杂浓度,故无需考虑比导通电阻和耐压的折衷关系,这就有效缓解了2.5on,spRμBV的“硅极限”问题。基于上述工作机理,文中提出了以下两类横向功率MOS新结构:(1)提出了一种积累型超低比导通电阻的U形栅LDMOS。仿真表明:新结构在耐压达到662 V时,比导通电阻仅为12.4 m?·cm2,相比于同样尺寸下的常规结构,新结构的BV提高了88.6%且Ron,sp显著下降了96.4%,且因电流主要由积累层输运,比导通电阻不取决于漂移区的掺杂浓度,所以在器件优化设计时,器件耐压达到最大时其优值(FOM)也最高,打破了Ron,sp与耐压BV之间的制约关系。结合U形栅和积累层的特点,文中又讨论了一种应用于较低电压领域的变形结构。最后针对新结构的器件进行工艺流程设计。(2)提出了一种具有延伸栅的薄层SOI LDMOS。该结构一方面采用衬底刻蚀技术,突破SOI器件纵向耐压的限制,且无需采用常规薄层SOI器件的漂移区线性掺杂技术;另一方面,采用延伸栅场板结构在漂移区形成多子积累层,同时利用延伸栅场板辅助耗尽漂移区而提高漂移区掺杂浓度,二者显著降低器件比导通电阻。仿真表明,该器件耐压达到695.6 V,比导通电阻仅为28.9 m?·cm2。最后,仿真优化表明,新结构耐压随着漂移区长度的增加几乎线性增大,且其掺杂浓度不变,因此,新结构将拓宽SOI技术在高压领域的应用范围。
[Abstract]:The realization of high voltage (BV) and low specific on-resistance (Ron,sp) is the key goal and research direction of power device design. However, there is a mutually restricted relationship between the voltage resistance and specific on-resistance of power MOS, that is, "silicon limit". In order to break through the "silicon limit" and overcome the shortcomings of conventional field plate technology, two kinds of accumulative low resistance transverse power MOS structures are proposed in this paper. In the positive through state, the structure forms an accumulation layer of most carriers in the drift region, which forms a continuous ultra-low resistance current channel from the source end to the drain end, turns off the voltage-resistant state, and extends the gate field plate to adjust the electric field distribution in the drift region, thus improving the voltage resistance. Based on the above working mechanism, the specific on-resistance of the device is determined by the accumulated layer charge in the drift region and does not depend on the doping concentration in the drift region, so it is unnecessary to consider the tradeoff between the specific on-resistance and the voltage resistance. This effectively alleviates the "silicon limit" problem of 2.5 OSPR 渭 BV. Based on the above working mechanism, two new types of transverse power MOS structures are proposed: (1) an accumulative U-gate LDMOS. with ultra-low specific on-resistance is proposed. The simulation results show that when the voltage is 662 V, the specific on-resistance of the new structure is only 12.4 m? cm2, compared with the conventional structure of the same size, the BV of the new structure is increased by 88.6%, and the Ron,sp of the new structure is significantly decreased by 96.4V, and the current is mainly transported by the accumulation layer. The specific on-resistance does not depend on the doping concentration in the drift region, so the optimal value of (FOM) is the highest when the device voltage reaches the maximum in the optimal design of the device, which breaks the restriction relationship between Ron,sp and BV. Combined with the characteristics of U-gate and accumulation layer, a deformed structure applied to low voltage field is also discussed in this paper. Finally, the process flow of the device with new structure is designed. (2) A thin layer SOI LDMOS. with extended gate is proposed. On the one hand, the substrate etching technique is used to break through the limitation of longitudinal voltage resistance of SOI devices, and the linear doping technique of drift region of conventional thin layer SOI devices is not used; on the other hand, the extended gate field plate structure is used to form a polyonic accumulation layer in the drift region. At the same time, the extended gate field plate is used to assist the depletion drift region to increase the drift region doping concentration, both of which can significantly reduce the specific on-resistance of the device. Simulation results show that the device can withstand voltage up to 695.6 V and its specific on-resistance is only 28.9 m? cm2.. Finally, the simulation results show that the voltage resistance of the new structure increases linearly with the increase of drift region length, and the doping concentration is constant. Therefore, the new structure will broaden the application range of SOI technology in high voltage field.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN386

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