Morphological, Electrical, and Chemical Changes in Cyclically Contacting Polycrystalline Silicon Surfaces Coated with Perfluoroalkylsilane Self-Assembled Monolayer

Abstract

The evolution of morphology, electrical properties, and chemical composition has been studied in cyclically contacting polycrystalline silicon (polysilicon) surfaces coated with perfluoroalkylsilane self-assembled monolayer (SAM). The microinstrument used is a MEMS cantilever that is repeatedly actuated out-of-plane to impact a landing pad and is then moved in-plane to enable nondestructive in situ inspection of the impacted area. Analyses show that a device with a monolayer coating exhibits signs of surface degradation after a much higher number of cycles than its uncoated counterpart. A sharp increase in contact resistance between the cantilever and landing pad is observed at *10 billion cycles for a coated device, versus *25 million cycles for an uncoated device. Likewise, the onset of grain fracture in the landing pad occurs at *25 billion cycles for the SAM-coated device, versus *3 billion cycles for its uncoated counterpart. The effectiveness of the monolayer coating diminishes after more than 100 billion contact cycles as the SAM layer is removed, and the polysilicon substrate becomes susceptible to adhesive wear.

Reducing the adhesion and friction forces of Si by coating ultra-thin Al2O3 films

“…One approach is to deposit self-assembled monolayers (SAMs) on the surface of MEMS devices. [5][6][7][8][9] The SAMs coatings can reduce the adhesion force of the Si material efficiently by reducing its surface energy and increasing its hydrophobicity. However, the SAMs coatings do not have enough wear resistance, which limits their practical application.…”

Heat treatment effect on the resistivity of polycrystalline silicon films

“…2,3 The circuit complexity and the increasing degree of component integration require continuous improvement and mastering of the properties of this type of material. [4][5][6][7][8][9][10][11][12] In many of its applications, this material is subjected to different heat treatments in order to reduce the defects and allow the implanted ions to take positions where they are electrically active. This has led us in the framework of this study to investigate the heat treatment effect on the resistivity of polycrystalline silicon films.…”