【作者】 钱聪；

【导师】 张峰； 张正选；

【作者基本信息】 中国科学院研究生院（上海微系统与信息技术研究所） ， 微电子学与固体电子学， 2007， 博士

【摘要】 SOI材料以及SOI器件及有良好的抗单粒子效应和瞬间辐射的能力，但绝缘埋层的存在使得其抗总剂量能力受到限制。在埋层中注入硅离子被认为是一种有效的材料加固方法，这与注入产生的纳米晶硅电子陷阱有关。本文主要研究了离子注入形成的纳米硅在SIMOX材料抗辐照加固中的应用，主要包括两部分内容，一是在SIMOX材料中注入了一定剂量和能量的硅离子并退火，并用MOS器件（包括各种不同的栅结构）和pseudo-MOS两种方法研究了其总剂量辐照效应，并用MEDICI模拟了辐照偏置依赖关系。二是注入硅离子的热氧化物的物理研究，主要研究了纳米硅晶的形成、注入后氧化物的结构、缺陷与注入、退火参数的关系。研究了在经过硅离子注入加固SIMOX晶片上流片得到的、具有环栅、H型栅、条形栅等不同栅结构的部分耗尽NMOSFET／SIMOX器件，在三种不同偏置下的总剂量辐照效应。实验发现，加固器件的背栅阈值电压漂移和漏电流都比未加固的对比样品大为减小，特别是环栅和H型栅，加固效应非常明显。用亚阈电荷分离技术得到了辐照过程中氧化物固定电荷和界面态的变化量及其对阈值电压漂移的贡献，表明加固器件主要是通过减小辐照过程中氧化物净正电荷积累来抑制阈值电压负漂的。还利用Pseudo-MOS的方法研究了SIMOX材料的总剂量辐射效应，这种方法简便易行，证实了硅离子注入能降低辐照引起的阈值电压漂移以及氧化物电荷和界面态增加，提高材料的抗总剂量辐照能力。MEDICI模拟结果证实了背沟道阈值电压漂移与辐照的偏置状态有关。PG偏置是背栅的最劣偏置。研究了热氧化物中注入硅离子后的光致发光谱（PL）、X射线光电子能谱（XPS）、傅立叶红外谱（FTIR）和电子自旋共振谱（ESE）。PL谱研究验证了硅纳米团簇的存在，并证实了这一结构的形成是由于化学变化而非物理损伤引起，且纳米晶的尺寸随着注入剂量的增大而增大。硅纳米团簇能俘获电子，补偿辐照引起的氧化物中的正电荷积累，从而减小SOI器件的背栅阈值电压漂移。XPS研究得到了与硅的不同氧化态对应的化学结构随硅离子注入剂量、退火温度和退火时间的变化。研究表明增大注入剂量将提高纳米硅晶的含量。1000℃和1h的退火情况纳米硅晶的含量最大。FTIR谱研究表明增大注入剂量将导致SiO₂结构的减少，伸展频率的红移可以解释为注入Si原子取代O原子导致了O-Si-O键角的窄化以及Si-Si键的形成。ESR研究确定了不同注入能量和剂量样品的g因子和悬挂键密度，证实了经过退火的纳米Si-SiO₂体系的主要缺陷是P_b中心，即位于Si-SiO₂界面处的Si悬键。更多还原

【Abstract】 Si implantation have been proved to be an effective method to harden the buriedoxide of SOl materials, which limits the application of SOI devices in total-doseenvironment. Si implantation will produce Si nanocystals which can be electron trapsduring the irradiation. My research is focused on the application of Si nanocrystals inthe irradiation hardening of SIMOX materials, which can be devided into two mainparts. One is the total-dose irradiation effect of MOSFET and pseudo-MOS structureon Si-implanted SIMOX, with MEDICI simulation to verify the bias dependence. Theother part is the physical research of Si-implanted thermal oxide to understand theformation of Si nanocrystals and implantation-induced defects, and their relation withimplantation and annealing conditions.Ⅰ-Ⅴcharacteristics of partially-depleted NMOSFETs with various gate structuresfabricated on SIMOX which is hardened by silicon ions implantation were studiedunder total-dose irradiation of three bias conditions. It has been found experimentallythat back gate threshold shift and leakage current was greatly reduced during irradiationfor hardened transistors, comparing to NMOSFETs fabricated on unimplanted wafers,especially for the enclosed gate and H gate structure. Subthreshold charge separationtechnique is employed to estimate the buildup of oxide charge and interface trapsduring irradiation, showing that the reduced⊿V_th for NMOSFET/SIMOX （implanted）is mainly due to the much less buildup of oxide charge than NMOSFET/SIMOX（unimplanted）. The total-dose irradiation effect of SIMOX pseudo-MOS structuresare also investigated. This easy and convenient method testified that Si-implantationcan significantly decrease the irradiation-induced⊿V_th and the buildup of oxide charge and interface traps. MEDICI simulation confirmed that⊿V_th is relevant to the bias stateand PG is the wprst bias condition.We also studied the photoluminescence （PL）, X-ray Photoelectro-Spectroscopy（XPS）, Fourier Transform Infra-Red （FTIR） and Electron Spin Resonance（ESR） of Sinanocrystals embedded in thermal oxide implanted with Si. PL analysis proved theexistence of Si nanocrystals and demonstrated the effect of Si implantation dose, energyand the annealing time on the growth of Si nanocrystals and its emission intensity. Thesize of Si nanocrystals and the PL intensity increase with the Si implantation dose. Thenanocrystals can trap electrons to compensate the positive charge buildup in the buriedoxide during irradiation, thus reduce the threshold voltage negative shift. The XPSresults clearly show the evolution of various chemical structures and the formation of Sinanocrystals in the oxide of our samples. It is found that the concentration of Sinanocrystals increases with Si implantation dose. The 1h annealing at 1000℃willproduce the most Si nanocrystals among all the annealing conditions. FTIRmeasurement showed that the absorption intensity decreases with the Si implantationdose, indicating that increasing the Si implantation dose leads to the reduction of theSiO₂ structure. It is also found that the redshift of stretching frequency of the Si-O bond,which could be interpreted as the narrowing of the O-Si-O bond angle as a result of thereplacement of O atoms by the implanted Si atoms and the formation of Si-Si bonds.ESR research determined the g factors and the density of suspending bonds of samplesimplanted with different energy or dose. It proved that existence of P_b center, i. e., Sisuspending bonds located in the Si-SiO₂ interface.更多还原