LDMOS-SCR ESD器件漂移区长度对器件性能的影响

The Impact of Drift Implant on ESD Protection Performance of LDMOS-SCR ESD Device

采用软件仿真一系列的横向扩散金属氧化物半导体(Laterally diffused metal oxide semiconductor,LDMOS)可控硅(Silicon controlled rectifier,SCR)静电放电(Electrostatic discharge,ESD)保护器件,获取工作状态的I-V曲线。结果表明,随着漂移区间距缩小,单位面积的失效电流增大,器件的ESD保护水平提高,但器件的维持电压减小,器件的鲁棒性降低。仿真提取关键点的少数载流子浓度、电流密度、电压强度等电学特性,根据采样结果和理论分析,内部载流子输运能力增强,但导通电阻无明显变化是该现象的内在原因。采用0.5μm 5V/18V CDMOS(Complementary and double-diffusion MOS,互补型MOS和双扩散型MOS集成)工艺流片并测试器件,测试结果证实了仿真结论。为了提高器件的失效电流且不降低维持电压,利用忆阻器无源变阻的特性,提出了一种新型的LDMOS-SCR ESD保护器件(M-ESD器件),理论分析表明,该器件内部忆阻器与寄生晶体管组成的系统能够有效地协同工作,在不增大芯片面积和不降低维持电压的情况下,使器件的失效电流增加,提高器件保护水平。

The simulations of LDMOS-SCR ESD devices with various lengths of the drift region have been achieved.I-V curves showed that,with the decreasing of the length of drift region,the protection level of the device upgraded as the failure current per area grew,but the robustness of the device declined due to the decreasing of its holding voltage.Furthermore,minority carrier concentration,current density and electrical field on the key points have been sampled and analyzed during the simulations.It was clearly demonstrated that the reduction of internal carrier transport mobility and the constant of the turn-on resistance resulted in this phenomenon.To verify the simulation results,agroup of LDMOS-SCR ESD devices were fabricated,investigated and characterized by a transmission line pulse(TLP)test system,respectively.The experimental data were consistent with the simulation results.In order to increase the failure current per area without reducing the holding voltage,a new structure of LDMOS-SCR ESD device called M-ESD device was proposed based on the memristor′s purely dissipative character.The memristor can usefully co-operate with other components of M-ESD device to dissipate the energy of ESD surges.Without the enlarging of performance area and the dropping of the holding voltage,the failure current per area of the device increased sharply,and the discharge capacity of the device boosted.