The Research Of Novel Nanotube Tunneling Field-Effect Transistor With Electron-Hole Bilayer And Its Reliability

With rapid development of semiconductor manufacturing technology,metal-oxide-semiconductor field-effect transistor（MOSFET）continues to scale in accordance with Moore’s Law.Currently,critical dimension of MOSFET is gradually approaching the physical limit,and the development of device technology has entered the More Moore era characterized by reduced power consumption.Devices based on new principles and materials provide solutions for breaking through the power consumption bottleneck problem,becoming a current research hotspot in semiconductor device technology.Benefiting from band to band tunneling mechanism,tunneling field-effect transistor（TFET）offers extremely low OFF-state leakage current(I_OFF)and steep subthreshold swing（SS）,becoming a promising alternative in low-voltage and low-power fields.However,the inherent conduction mechanism limits ON-state current(I_ON),non-ideal abrupt source-channel junction and interface quality also make TFET difficult to achieve ideal performance.Besides,as the aerospace industry develops,the reliability of low-power device is becoming increasingly important.The structural design of 3-D silicon-based TFETs,reliability issues induced by interface trap and radiation environments still need to be investigated in detail.To address the above issues,a novel TFET structure is introduced and then the performance is optimized by TCAD,and the reliability of the proposed device in terms of interface trap charge and radiation effects has been systematically studied.The main research contents and results are as follows:Firstly,a novel nanotube TFET with electron-hole bilayer（EHBNT-TFET）structure is proposed.By asymmetric structure and proper work-function of inner-gate and outer-gate,EHBNT-TFET achieves line tunneling in the channel,increasing tunneling area and tunneling strength.Compared to the conventional nanotube TFET,With I_OFF decreasing nearly one order of magnitude,EHBNT-TFET exhibits an increased I_ON about 57.2 times and a sub-60 m V/dec SS for seven orders of magnitude of drain current,and the minimum SS is 2.1 m V/dec.The dependence of performance of EHBNT-TFET on source and drain doping concentration,geometric parameters,metal work-function and bias are explored further.The results illustrate that reasonable structural parameters can mitigate the effect of source and drain doping concentration on device performance and achieve steep switching characteristics.Secondly,based on the common trap charges at gate oxide and semiconductor interface in process fabrication,the performance variation of EHBNT-TFET under the effect of different energy distribution of interface traps is investigated,and the corresponding degradation mechanism is proposed.Acting as generation and recombination center,interface trap charges lead to I_OFF degradation.Occupied by carriers,interface traps are charged so that threshold voltage and ON-state current varies.It is found that the performance degradation is mainly caused by interface traps at the outer gate oxide/channel interface and with the energy level about 0.15 e V above the midgap.The effects of changing charge neutrality level（CNL）position at the interface on electrical performance and random fluctuation characteristics are investigated,and it is proposed that optimizing CNL can improve the reliability induced by interface traps.The results show that a reasonable CNL can suppress performance degradation of EHBNT-TFET significantly and provide more stable fluctuation characteristic.Thirdly,a simulation method in device level for ionization damage effect is proposed.The impact of ionization damage effect on DC characteristics and 1/f noise of EHBNT-TFET,and the dependence of ionization damage effect on geometric parameters are investigated.The results show that ionization damage effect mainly results in degraded I_OFF and increased 1/f noise amplitude.The performance degradation mainly originates from the irradiation-induced interface trap charges,which is positively correlated with radiation dose.Steep source and drain doping gradient,large underlap between inner-gate and drain and underlap between outer-gate and source,increased outer-gate work-function,reduced overlap between inner-gate and outer-gate,decreased inner-gate diameter and work-function are beneficial to mitigate ionization damage effect of EHBNT-TFET.Fourthly,single event transient（SET）effect in EHBNT-TFET and the physical mechanism are investigated.The effects of linear energy transfer,characteristic radius,strike angle,electrode bias and strike location on SET response are evaluated in detail.The results reveal that the parasitic bipolar gain effect can be neglected in EHBNT-TFET,and the peak drain current is much higher than I_ON,which is proportional to linear energy transfer.SET response strongly depends on the distribution of heavy ion charge in silicon,electric field at the strike location,and the collection distance from strike location to drain.The characteristic radius,strike angle and electrode bias have significant effects on SET response,and the sensitivities of both strike angle and location of heavy ion depend strongly on characteristic radius.Coupling with ionization damage effect,the immunity of EHBNT-TFET to SET effect is improved.The work mainly involves the structural design and performance optimization of the proposed TFET,the degradation mechanism of interface trap charges and reliability optimization strategy,the influence mechanism of ionization damage effect,and the response mechanism of SET effect,giving new insights for the structural optimization of TFETs,and providing theoretical basis for the reliability appling in radiation environments in the future.