Study Of A New Method And Related Effects For Wafer Level Uniaxial Strain SOI

With the reduction of process size,the Si?silicon?material defects gradually exposed,as the main factor restricting the performance of integrated circuits.The sSOI?strained silicon?material combines the advantages of strained Si technology and SOI technology.It has the advantages of low cost,high speed,low power consumption and high integration density.It is an important tool to extend Moore's law.Traditional sSOI reation method use SiGe?germanium silicon?as a virtual substrate,which can only introduce biaxial tensile strain.This method has the disadvantages of obvious dislocation density,complicated process,poor heat dissipation and diffusion of Ge?germanium?.Compared with the biaxial strain SOI,the uniaxial strain SOI has higher mobility,high mobility in the high electric field,and low cost.However,there is no mature and effective preparation method.In this thesis the single-axis stress model of MOS?Metal-Oxide-Semiconductor?device was established.Based on this model,the stress distribution simulation of different gate length and gate height is carried out.The simulation results show that:1)The stress in the channel of the MOS device is introduced by the gate part,the side wall part and the SiN region of the source and drain regions.The influence of the SiN above the source and drain regions on the channel is the main part;2)The SiN film?3?the"step"type structure of the MOS device is the necessary condition for the introduction of the stress;4)the stress in the channel of the MOS device is proportional to the gate height,and the trend of increasing the thickness of the MOS device tends to a fixed value,Inversely proportional to the gate length.Based on the structural characteristics and stress characteristics of SiN and the properties of SOI materials,PECVD?plasma chemical vapor deposition?was used to deposit high stress SiN thin films.The results of stress characterization show that the stress of SiN film is about1.1GPa,and the compressive stress of SiN film is about-1.6GPa.Based on the thermodynamic properties of SOI materials and the stress characteristics and size effects of SiN?silicon nitride?thin films,a new method for wafer-level uniaxial strain SOI based on high stress SiN thin films is proposed,which has advantages of simple process,high strain and Si process compatibility and so on.Based on the thermodynamic properties of SOI and SiN materials and the principle of elasto-plastic mechanics,the strain mechanism of stress generation,stress introduction and stress keeping of the new method is analyzed.The principle is that the SiO₂ and the substrate interface are relaxed by ion implantation and the top layer Si is amorphized;the top layer Si and SiO₂ are stretched or compressed with a high stress SiN thin film;the SiN film is etched into a sub-And the biaxial stress is converted into uniaxial stress by the size effect.The deformation of the SiO₂ buried layer is carried out by annealing and the top layer Si is recrystallized to maintain the stress of the top layer Si.Based on the new mechanism of strain mechanism and process principle,SOI sample?He1?were fabricated by wafer-level uniaxial strain SOI preparation.The SOI sample were characterized by polarized Raman,and the results showed that they had a uniaxial strain effect.The Raman peak shift is about-2.5 cm^-1 and the uniaxial strain is about 0.65%using a 325 nm laser.