MICRO NANOTRIBOLOGICAL STUDIES OF POLYSILICON AND SIC FILMS FOR MEMS APPLICATIONS/

Microelectromechanical (MEMS) devices are currently made from single-c rystal silicon, various polysilicon films and other ceramic materials. Silicon carbide (SiC) film has recently been pursued as a material fo r use in MEMS devices owing to its excellent mechanical properties and high-temperature capabilities. Since surface properties, friction and wear are important issues in such small-scale devices, it is essentia l that the materials used in MEMS have good micro/nanotribological pro perties. Using atomic force/friction force microscopy (AFM/FFM), surfa ce roughness, microscale friction and microscale scratch/wear resistan ce of 3C-SiC (cubic SiC) Alms, as well as undoped single-crystal Si(10 0) and doped and undoped polysilicon films for comparison were measure d. Nanohardness and modulus of elasticity were measured using a Nanoin denter. Surface roughness values showed that the as-deposited films of SiC and undoped polysilicon were rougher than the doped polysilicon f ilm and Sit 100). Polishing of the as-deposited samples resulted in co mparable values of roughness between SiC and undoped and doped polysil icon films, while Si(100) still remained the smoothest and the doped p olysilicon him, the roughest. It was found that the polished SiC and d oped polysilicon films showed the lowest friction followed by undoped polysilicon film, while Si(100) showed high friction. Microscale scrat ch/wear studies clearly showed that SiC film was much more scratch/wea r resistant than the other materials, which showed comparable resistan ce levels. SiC also showed higher hardness and modulus of elasticity c ompared to the other materials. These results show that 3C-SiC film po ssesses desirable micro/nanotribological characteristics that make it an ideal material for use in MEMS devices. (C) 1998 Elsevier Science S .A.,All rights reserved.