Simulation And Experiment Study On Adhesion Of Micro/Nano Roughness Surface

With development of micro-mechanical electronic technology, micro-electromechanical system(MEMS) has gradually become an important research area and the MEMS devices and components have been widely used in our daily life. The objects under micro/nano-scale are different from that under the macro-scale, mainly affected by the surface forces. And the adhesion force is a major failure form in using and manufacturing of MEMS devices. There are many factors affected the surface adhesion, and surface roughness is an important factor among them. In present paper, we studied surface roughness on adhesion. The main work is as follows(1) We compared and analyzed the typical adhesion theories, and introduced an adhesion model that considering surface roughness similar to the Rumpf model and Robinovich model. Besides, the simulation results of Robinovich model were given by using Matlab. We can see from the results that the adhesion force will firstly decrease with increase of the surface roughness, then increase. The change point will delay while increase R and0 H. And the adhesion force decrease faster if 2λ is smaller and R is larger.(2) We introduced the working principle of atom force micro scope, while it measures the surface geometry and force-displacement curve. The parameters of surface roughness were given. We also explained how to calibrate the statistical parameters of the surface roughness. The calibration method of the normal spring constant of the probe was also given. Finally, we introduced the ancillary equipment that used in the experiment.(3) In order to study the influence of surface roughness on adhesion, different concentrations of KOH solution were used to corrode the silicon wafer with different time. We obtained eight samples with different roughness. Then, a worn sharp probe and a plateau probe were respectively used to measure the adhesion force under the ambient condition and in a glove box. The results of experiments were compared to the simulation results of Robinovich model. The results showed that at small roughness, the variation of the adhesion force well fits Robinovich model. Otherwise the adhesion force was slightly larger than the simulation results of Robinovich model due to the capillary force and the electrostatic force. If the roughness was relative large, the adhesion force will not increase like Robinovich model showed.(4) For the purpose of study of influence of AFM parameters on equal roughness surface adhesion, silicon gratings with different period were used to simulate the equal roughness surface. The results showed the influence of the loading force on adhesion was not significant. The adhesion force of silicon grating with large period increased with increase of dwell time, but the variation of the silicon grating was little for small period. The influence of the piezo speed on adhesion was inconsistent, different silicon gratings showed different trends. Thus, there was no definitive conclusion.