Surface adhesion reduction in silicon microstructures using femtosecond laser pulses

Abstract

A reduction of the adhesion between polysilicon surface-micromachined structures and its silicon substrate using ultrashort pulse laser irradiation has been demonstrated. Polysilicon cantilevers, which adhered to the silicon substrate after final rinse and dry, were freed after irradiation by a 800 nm wavelength laser with pulse duration of 150 fs (full width at half-maximum) and fluences up to 40 mJ/cm2. Increasing the pulse widths to 2.7 ps resulted in significantly fewer freed cantilevers indicating that the process depends heavily on the presence of high-temperature carriers in the silicon. Adhesion reduction has been observed from exposure to a single pulse which results in minimal lattice temperature increase.

Formation mechanism of self-organized nano-ripples on quartz surface using femtosecond laser pulses

“…Since the advent of the first functional femtosecond laser, it has been proven to be a promising and reliable tool for micro/nano-machining of materials for diverse applications [1][2][3][4][5][6][7][8][9][10]. The evolution of femtosecond laser induced periodic surface structures (LIPSS) have been reported on a variety of materials including glasses [10][11][12][13], indium tin oxide (ITO) [14], indium phosphide (InP) [15], and metals [16][17][18][19][20][21][22][23][24].…”

Mechanics of the dynamic release process for stiction failed microcantilever beams using structural vibrations

“…9 Shortly after fabrication (and before being put into operational use), laser pulse heating has been used to repair stiction failed micro-cantilevers. [10][11][12] This process directs a laser pulse at the failed component. The rapid expansion of the heated component produces thermal strains and causes S = unstuck length S = stuck P(x)Cos(Ωt) = Applied Load "Crack Tip" Figure 1 δ Figure 1: A schematic of a micro-cantilever stuck to a substrate.…”

Controlled sacrificial sidewall surface micromachining for the release of high length-to-thickness aspect ratio bridges

“…10 Should adhesion of the structural layer to the substrate actually occur, freeing the stuck structure can be attempted using such techniques as rapid thermal annealing or ultrashort laser pulses. 11,12 With the exception of photoresist infiltration, all these sacrificial release techniques require a combination of extra lithographic processing, specialized equipment, and the integration of new chemistries. In this article, a surface micromachining technique will be demonstrated in which the sacrificial layer itself will serve as a support to prevent the microstructure from contacting the substrate, even as it is being etched.…”