Study On The Mechanical Behavior Of Silica Nanoparticles On The Surface Of Monocrystalline Silicon

The improvement of chip performance has led to a more complex manufacturing process of integrated circuit（IC）,which requires higher surface quality of silicon wafers.This requires better cleaning technology for silicon wafer.SiO₂ nanoparticles adsorbed on the wafer surface can cause defects or even damage to integrated circuit.The cleaning technology of the silicon wafer is relatively mature.However,relevant studies mainly focus on the effect of surfactants on nanoparticle removing efficiency at the macroscopic scale.The friction behaviors and desorption mechanism of nanoparticle at the microscopic level need to be systematically studied.Therefore,it is urgent to study the influencing factors and mechanism of the friction behavior of SiO₂ nanoparticles which absorbed on the single crystal silicon surface at the microscopic scale,so as to provide a theoretical reference for the cleaning technology of the silicon wafer and improve the removing efficiency of the nanoparticles.In this paper,the factors and mechanism of the friction force between SiO₂ nanoparticles and pristine silicon surface at the microscopic scale are mainly studied.The main research contents of this paper are as follows:（1）The mechanical model of SiO₂nanoparticles manipulated by AFM was improved.By analyzing the force of the nanoparticles,the theoretical sliding and rolling friction force of the nanoparticles were calculated using the DH model.When the probe is in contact with the substrate,the deflection angle of the probe increases with the normal load,resulting in the increase of the vertical component of the downward pressure on the nanoparticles,which increases the theoretical sliding friction.Because the downward pressure of the probe on the nanoparticles is much less than the adhesion,the increase of the total downward pressure on the nanoparticles is slight,so the increase trend of the theoretical sliding friction is very weak.The increase of nanoparticles size will increase the theoretical friction,but when the nanoparticles size reaches a certain value,the increasing trend gradually slows down.When the adhesion work of the nanoparticles decreases,the theoretical friction force also decreases.The larger the nanoparticles size,the greater the influence of the adhesion work on the theoretical friction force will be.（2）The influence mechanism of the probe speed and load on the friction of SiO₂nanoparticles was explored.The sliding speed of the probe has ignorable effect on the nanoparticle friction in the range of 100 nm/s to 500 nm/s.The increase of the probe normal load will gradually increase the nanoparticles sliding friction.Since the increase in the downforce on the nanoparticles is not large,the friction force of the nanoparticles increases slightly.The motion state of the nanoparticles evolves with the increase of the normal load.When the normal load is relatively small,the motion of the nanoparticles mainly behaving sliding.When the normal load gradually increases to above a threshold value,the rolling of the nanoparticles occurs and the rolling of the nanoparticles becomes dominant with the father increase of load.（3）The effect of nonionic surfactant on the friction force of SiO₂nanoparticles was revealed.The friction force of nanoparticles modified by isopropanol（IPA）and fatty alcohol polyoxyethylene ether（AEO7）was significantly reduced,and the friction force of the nanoparticles after AEO7 modification was the smallest under the same conditions.The nonionic surfactant molecules form hydrogen bonds with the hydroxyl groups on the surfaces of the nanoparticles and pristine silicon,and then adsorb on their surface.This increases the spatial distance between the nanoparticles and the pristine silicon surface,overcoming the van der Waals force and reducing the adhesion force between them,finally resulting in lower friction force.The removing effect of AEO7 on nanoparticles is better than that of IPA at the macroscopic scale,which is consistent with the effect of IPA and AEO7 on nanoparticles friction.