隧穿场效应晶体管工艺及新结构的仿真研究

发布时间：2018-11-15 13:04

【摘要】：随着MOSFET器件的特征尺寸进入纳米尺度,短沟道效应对传统MOSFET器件的性能造成了严重影响,通过尺寸缩小来获得性能提升的方法变得越来越困难。近年来,一种基于量子隧穿机理的场效应器件隧穿场效应晶体管(tunneling field-effect transistor,TFET)被提出。理论上,TFET不仅可以有效抑制短沟道效应,还能突破传统MOSFET亚阈值摆幅(Subthreshold Swing)不能低于60 mV/dec的限制,从而大幅度降低器件的开关功耗。因此TFET被认为是最具前景的超低功耗器件之一。TFET的亚阈值电流对隧穿结附近的缺陷非常敏感,因此离子注入等工艺过程产生的缺陷会对TFET器件的亚阈值摆幅特性产生严重影响。为了减小缺陷对TFET亚阈值特性的影响,本文主要从工艺过程优化和器件结构设计两个方面展开研究。首先,利用TCAD工具分析了工艺参数对TFET器件特性的影响。研究表明,随着源区掺杂剂量的不断增大,中心浓度增加,隧穿电流增大;与横向扩散长度相比,纵向掺杂深度的增加对隧穿电流影响不大。此外,随着温度升高,饱和电流稳定提升。表明在恒定退火时间下,退火温度的提高有助于掺杂元素的激活。其次,分析了不同退火技术对硼离子间隙缺陷集群的修复能力,利用浓度曲线与薄膜电阻率反映缺陷集群的变化。结果表明,采用新型退火方法,薄膜电阻率明显下降,硼离子间隙缺陷集群(BIC)得到明显的修复。最后,研究了栅沟道覆盖和Pocket掺杂对TFET性能的影响。结果表明,侧墙覆盖漏区会使开态电流减小,关断电流增加,并不会对其栅极泄漏电流起到影响;侧墙覆盖源区,器件开态电流增大,关断电流变化不大。此外,本文对传统的TFET结构进行了优化,设计了具有栅源覆盖和源区pocket器件结构的TCAD工艺实现方法;结果表明,随着栅极覆盖长度的增加,栅控能力增强,栅覆盖导致源区覆盖面积内的能带大幅弯曲,隧穿由点隧穿变为面积更大的线隧穿,亚阈值摆幅特性明显改善。添加源pocket结构后,整个晶体管的隧穿电流增加,亚阈值摆幅有所降低。
[Abstract]:With the characteristic size of MOSFET devices entering nanometer scale, the short channel effect has a serious impact on the performance of traditional MOSFET devices, so it is becoming more and more difficult to improve the performance of traditional MOSFET devices by reducing the size of MOSFET devices. In recent years, a field effect transistor (tunneling field-effect transistor,TFET) based on quantum tunneling mechanism has been proposed. Theoretically, TFET can not only effectively suppress the short channel effect, but also break through the limit of traditional MOSFET sub-threshold swing (Subthreshold Swing) which can not be lower than 60 mV/dec, thus greatly reducing the switching power consumption of the device. Therefore, TFET is considered to be one of the most promising ultra-low power devices. The subthreshold current of TFET is very sensitive to the defects near tunneling junctions. Therefore, the defects in the process of ion implantation will seriously affect the subthreshold swing characteristics of TFET devices. In order to reduce the influence of defects on the subthreshold characteristics of TFET, this paper mainly focuses on two aspects: process optimization and device structure design. Firstly, the influence of process parameters on the characteristics of TFET devices is analyzed by TCAD tool. The results show that the tunneling current increases with the increasing of the doping concentration in the source region and the longitudinal doping depth has little effect on the tunneling current compared with the transverse diffusion length. In addition, the saturation current increases steadily with the increase of temperature. It is shown that the increase of annealing temperature is helpful to the activation of doped elements at constant annealing time. Secondly, the repair ability of different annealing technology to the defect cluster of boron ion gap is analyzed, and the change of the defect cluster is reflected by the concentration curve and the film resistivity. The results show that with the new annealing method, the resistivity of the film decreases obviously, and the (BIC) of boron ion gap defect cluster is obviously repaired. Finally, the effects of gate channel coverage and Pocket doping on the performance of TFET are studied. The results show that the on-state current decreases and the turn-off current increases, which does not affect the gate leakage current, while the on-state current increases and the turn-off current does not change much. In addition, the traditional TFET structure is optimized, and the realization method of TCAD process with gate source coverage and source pocket device structure is designed. The results show that with the increase of the gate coverage length, the gate control ability increases, and the energy band in the source area is significantly curved, the tunneling is changed from point tunneling to line tunneling with larger area, and the sub-threshold swing amplitude is improved obviously. When the source pocket structure is added, the tunneling current of the transistor increases and the sub-threshold swing decreases.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN386

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