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Abstract

A new procedure for the production of smooth and defect-free surfaces in the anisotropic etching of silicon in alkaline solutions is described. It has been found that etching in an ultrasonic bath results in the facilitated detachment of hydrogen bubbles at the surface which is suggested to be one of the causes for surface roughening. In the presence of mild ultrasound radiation a significant improvement in surface finish of the orientation has been observed. The inclusion in the bath of oxygen and/or isopropanol results in root mean square roughness values smaller than 20 nm. The effectiveness of bath additives has been related to changes of the contact angle between the liquid/gas/etching interface. Quantitative determination of roughness and surface imaging have been obtained by atomic force microscopy; dissolution rates were studied by profilometry. Etching under ultrasound conditions and the use of additives does not change the etch kinetics, indicating that additional convection only changes hydrogen bubble detachment.

On the Adhesion between Fine Particles and Nanocontacts: An Atomic Force Microscope Study

“…Anisotropic etching with KOH has become a standard and important processing step in the fabrication of bulk micro-machined semiconductor devices [181]. The quality of vertical roughness produced by the etching of Si in aqueous KOH has been studied by varying several experimental parameters such a molarities of KOH, time of etching, temperature, and stirring [181]. All our etching experiments were carried out in 0.25 M KOH that was heated to 70°C.…”

Surface termination and hydrogen bubble adhesion on Si(100) surfaces during anisotropic dissolution in aqueous KOH

“…The overall reaction is [13,14] Si þ 2H 2 Etching defects and surface roughness can result if the hydrogen bubbles produced remain long enough on the surface to mask it from the etching solution [15][16][17][18][19]. The purpose of this work was to investigate the physicochemical aspects of bubble adhesion from measurements of bubble size, lifetime and IR spectroscopy of Si(1 0 0) surfaces in contact with aqueous KOH.…”

Measuring adhesion forces between hydrophilic surfaces with atomic force microscopy using flat tips

“…This method results in a slightly rough surfaces without physical damage to the materials bulk structure [25]. Before etching, the Si wafer was cleaned in an ultrasonic bath of methanol for 15 min Subsequently, the Si wafer was placed in a piranha solution with a 3:1 volume ratio mixture of substrates [26][27][28][29][30][31][32]. For our adhesion measurements, we deliberately select areas which do not contain any large pyramidal hillocks, since this would lead to scatter in the adhesion force data.…”