The Simulation Investigation On Multi-domain Effects In Ferroelectric-based Electrostatically Doped Transistors

Ferroelectric electrostatic doping technology（Fe-ED）is one of the most promising doping technology for nanoscale devices in more than moore era,which equips with not only the reconfigurability,but also the non-volatility,contributing to the in-memory computation and the increased function density.Additionally,it also exhibits other advantages,like low thermal budget,impurity-free,and the accurate control of doping concentration,type and spatial distribution.Currently,the concept of Fe-ED is usually realized with Hf O₂-based ferroelectrics,because of its excellent CMOS compatibility.However,this leads to the inevitable multi-domain effects,owing to its poly-crystalline status.In this dissertation,the impact of the multi-domain effects on the electrical performance of Fe-ED transistors is carefully investigated,including both the random distribution of ferroelectric（FE）/dielectric（DE）and fluctuation of ferroelectric properties.Due to the DE cannot produce doped impurity,ferroelectric electrostatic doped impurity concentration of the remaining after the FE phase excitation voltage polarization（P_r）decided to size,so after ferroelectricity fluctuations will lead to an excitation voltage of P_r has obvious changes,making doped impurity distribution exist obvious inhomogeneity,leading to volatility in the device electrical characteristics.Therefore,it is necessary to evaluate the effect of multi-domain effect and explore ways to reduce its effect before ferroelectric doping technology is applied in practice.1.The effect of depolarization field on ferroelectric electrostatic doping concentrationThe Fe-ED in semiconductor can be divided into two parts,the polarization driven by external pulse and the depolarization to stabilize the system,which both can be modulated by ferroelectric properties.In order to clear this point,we comprehensively investigated the impact of ferroelectric properties on the concentration of free carriers induced by Fe-ED based on the theory of depolarization.It is demonstrated that:1)With a fixed pulse amplitude and coercive field,an increase in P_r always produces the enhancement in P_FE and N_FE,owing to the boosted ferroelectricity.Thus,a gradually increased open current(I_on)is obtained,accompanied by a more obvious DIBL effects;2)For the contant pulse amplitude and P_r,the P_FE and the N_FE demonstrate the non-monotonic trend over E_C,which is attributed to the balance between depolarization field and the electric field required for the dipole to flip.The I_on and DIBL effects increased first and then decreased;3)For constant pulse amplitude,P_rand E_c,increasingε_FE leads to a decrease in partial voltage of ferroelectric capacitance,resulting in a negative correlation between P_FE and doping concentration N_FE,and a decrease in I_on and a decrease in DIBL effects.2.The influence of hafnium-based ferroelectric multi-domain effectThe hafnium-based ferroelectric multidomain effect and the fluctuation of FE-ED were studied,which helps to analyze the fluctuation of electrical characteristics of Fe-ED devices and estimate the reliability of Fe-ED.The simulation shows that the increased FE/DE ratio can produce a non-monotonic variation in fluctuation of electrical characteristics of Fe-ED device.The peak value of fluctuation locates at the FE/DE ratio of 50%,which is due to the most complicated distribution of FE/DE.At the same time,the increase of the dielectric phase ratio will lead to a rapid decrease in the on-state current of the device,but when the dielectric phase ratio is as high as 90%,the transistor can still be turned on and work due to the lateral diffusion of dopant impurities.The fluctuation of the electrical characteristics of the transistor continues to increase with the increase of P_r,,because the current of the transistor and the variation range of P_r continue to increase with the increase of P_r.The fluctuation of the electrical characteristics of the transistor first increases and then decreases with the increase of E_c,because the current variation range of the transistor first increases and then decreases with the increase of E_c.In addition,based on the nanoscale control radius of ferroelectric doping,the smaller grain size can effectively suppress the performance fluctuation caused by the multi-domain effect.When the grain size is reduced to 2.5 nm×6nm×5 nm,the on-state current fluctuation is only 7%,which is much smaller than the fluctuation of the random fluctuation performance of the process.In summary,based on the Preisach ferroelectric description model,Nanosheet device model and Monte Carlo statistical method,this paper deeply studies the multi-domain effect of ferroelectric doped transistors,clarifies the performance optimization design principles of ferroelectric electrostatic doping technology,and proposes Grain engineering optimization method for its multi-domain effect.The related research further clarifies the application prospect of ferroelectric doping technology in nanometer-sized devices,and promotes the development of high-reliability ferroelectric doping technology.