Study Of Solution Processed High-k Dielectrics And Their Electronic Device Applications

With the continuous development of large-scale and very large-scale integrated circuits,the feature size of field effect transistor（FET）devices has been shrinking,and the conventional gate dielectric SiO₂ film has reached the physical limit due to its lower dielectric constant.Therefore,high dielectric constant（high-k）materials have attracted more and more attention.There are many methods for preparing high-k gate dielectric films,such as physical vapor deposition（PVD）,chemical vapor deposition（CVD）,and atomic layer deposition（ALD）,which are costly,time-consuming,and relying on high vacuum environment.The solution method is another non-vacuum preparation method with the advantages of low cost,simple and flexible operation and easier composition control of the films by adjusting precursor solutions which is important technical process to prepare dielectric films.This paper is dedicated to research solution processed high-k dielectrics and their electronic device applications.Since Ge has higher carrier mobility than Si,at the same time the transition metal chalcogenide（TMDs）2H phase MoTe₂ is a kind of graphene-like two-dimensional material.Compared with graphene,it has excellent electrical,optical properties and intrinsic band gap characteristics,which is an ideal non-silicon semiconductor channel material for electrical devices in integrated circuits.In this paper,Ge（Ge substrate and Ge nanowire）and 2H-MoTe₂ film were selected as research objects,focusing on the following three aspects.:（1）YO_x thin film was determined as the suitable high-k dielectric for Ge MOS devices due to the promising interface characteristics and structural performance from various solution-processed high-k dielectrics(ZrO_x,HfO_x,TiO_x,AlO_x,YO_x and LaO_x).After that,the preparation process of the solution-processed method was further optimized.The best electrical performance of the devices was sucessfully achieved under precursor solution concentration of 0.2M,annealing temperature of 500°C,and O₂ as annealing atmosphere.（2）The intrinsic Ge nanowires were prepared by the CVD method using the gas-liquid-solid mechanism（VLS）as the semiconductor channels,and the YOx as the dielectric by adopting the previous optimization process,intrinsic Ge nanowire transistors were prepared on flexible polyimide（PI）substrate.The device shows a typical hole mobility about 17 cm² V^-11 s^-1,a small threshold voltage V_T^-0.36V,and a drain-source current on/off ratio²×10³,no obvious performance degradation can be observed before and after bending the Ge nanowire transistor to an angle of 30°.（3）Large-area,high-quality 2H-MoTe₂ thin film was prepared by CVD method,HfAlOx as dielectric by solution method to prepare FET devices and conduct performance studies.It is found that when the dielectric film is annealed at 500°C,the transistor device has the highest carrier mobility of¹.52 cm² V^-11 s^-11 and high drain-source current ratio⁵×10⁴.