Study On Radiation Characteristics And Strengthening Techniques Of Strained Si MOS Device

With the rapid development of microelectronic integrated circuit technology,semiconductor technology with complementary metal oxide as the core has entered the nanometer scale.According to the principle of equal scale reduction,the thickness of MOS gate oxide will also decrease,which will cause the gate leakage current to increase.As a result,the static power consumption of the whole circuit will increase sharply,and the degradation or even failure of electrical performance,which will become the bottleneck for the continuous development of integrated circuits.Therefore,the higher requirements are required for the exploration of new materials,new processes and new devices.Because strained Si technology is compatible with existing silicon technology,and it has high carrier mobility and tunable band-gap,which is one of the MOS important ways to improve strained integration technology at present.The strained integrated devices and circuit technology are widely used in space and military fields.The application of strained integrated devices and circuits will be more and more under the irradiation.Therefore,the research of radiation characteristics and reinforcement technology will become more and more important for strained integrated devices.The purpose of this paper is to improve the radiation resistance of MOS devices operating in space,the spacecraft and the electronic systems working in the nuclear radiation environment.The research work on the anti radiation mechanism and characteristics of the strained Si nano channel MOS device is carried out.At frist,this paper analyzes the enhancement mechanism of strained Si technology and the radiation effect mechanism of MOS devices,and designs uniaxial strained Si Nano MOS device which satisfies the experimental requirements.Secondly,the carrier microscopic transport process of uniaxial strained Si n-channel metal-oxide-semiconductor field-effect transistor has been analyzed under?-ray radiation.The variation of electrical characteristics of the uniaxial strained Si nanometer NMOS has also been investigated under the total dose radiation.A two-dimensional analytical model of threshold voltage(V_th)and carrier mobility model have been developed due to the total dose irradiation taken into consideration.The variation of electrical properties of uniaxial strained Si Nano NMOS devices with total dose irradiation is revealed.A two-dimensional threshold voltage,mobility,trans-conductance and current-voltage characteristic model of small size uniaxial strained Si NMOS is established under the gamma ray irradiation.Meanwhile,based on the quantum mechanism,the hot carrier and gate tunneling current models were established.The total dose radiation experiment of strained Si MOS device was carried out.The experimental data coincide with the theoretical model results,which verify the correctness and feasibility of the established model.Finally,the single effect transient effect of the strained Si MOS device is simulated and analyzed by TCAD,and a new structure of anti-irradiation reinforcement is proposed,which provides the practical and theoretical basis for the radiation reliability and circuit application of strained Si integrated devices in the future.The main progress and achievements of this research work can be summed up in the following four parts:1.The energy band structure of strained Si materials is studied with the law of stress evolution,and the stress is introduced into the channel by the method of process induced stress.The correlation between stress and process is studied by the simulation software.The optimization structure of uniaxial strained Si MOS is proposed.And the optimized process plan is put forward.Based on this scheme,the device sample is prepared to meet the requirements of the experiment.Compared with the relaxation Si nano NMOS,the device driver performance of strained Si nano NMOS increased by an average of 224.6%.Compared with the relaxation Si nano PMOS,the device driver performance increased by192.2%compared with the relaxation Si nano PMOS,which has laid an important"material basis"for the follow-up study of radiation.2.Study on threshold voltage of strained Si nano MOS under total dose irradiation.Based on the damage mechanism of total dose irradiation on MOS devices,a two-dimensional threshold voltage model for uniaxial strained Si NMOS devices is established under the total dose irradiation.The relationship between the threshold voltage and the total dose,the geometric structure of the device and the physical parameters of the material is investigated.It is found that the threshold voltage drift tends to be saturated with the increase of the total radiation dose,but the threshold voltage does not change with the change of the device structure parameters,and on this basis,the transconductance and return are explored.The relationship between the carrier mobility and the irradiation total dose is discussed.In addition,the experimental platform of total dose radiation was built to test the electrical characteristics of the strained Si nano MOS devices before and after irradiation.The results showed that the difference between the calculated results of the threshold voltage model and the measured results was about 2%,and the correctness of the model was verified.The analytical model is accurate and can provide technical reference and theoretical basis for the threshold voltage evaluation of small-scale strained MOS devices under total dose irradiation conditions3.Study on gate current of strain Si nano MOS under total dose irradiation.Based on quantum mechanics,this analytical model for taking into account the degradation of tunneling current under?-ray radiation is built.The evolution of the total dose and the gate current is revealed.It is found that the gate current and the hot carrier gate current increase with the increase of the total radiation dose.The geometric structure parameters of the devices and the change trend of the material physical parameters and the gate current are analyzed and studied.The error of the model calculation results of the strained Si nanoscale MOS hot carrier gate current and the tunnel gate current is about 1.1%and 1.3%respectively,which verify the correctness of the model.The model can provide important theoretical reference for the reliability of small size strained devices and integrated circuits under irradiation.4.The damage mechanism of single event transient effect is revealed for uniaxial strained Si Nano NMOS,and the funnel model was verified by the simulation software.Based on the damage mechanism and the U groove structure on the potential distribution of the additional leakage pole,the collection ability of the additional leakage pole to the charge is enhanced.Therefore,a new uniaxial strained Si nano MOS device structure?U groove structure?is proposed.The results show that the new reinforcement device is resistant to the single event compared with the traditional structure.The irradiation ability was enhanced by 35.22%.The new hardened device provides a useful theoretical reference for the single event effect reliability and circuit application of strained Si integrated devices in the future.