We have micromachined a lateral symmetrically bistable buckled beam for snap-in holding structures by oxidizing released beams micromachined on thick silicon-on-insulator wafers. The wafers were prepared by bonding and chemical mechanical polishing, and the structures were fabricated by deep silicon reactive ion etching using the black silicon method, subsequently released and thermally oxidized. The bistability was monitored in situ in a scanning electron microscope using a micromanipulator. Guidelines for designing beams of an expected performance are given and arguments for considering beams that are not `fairly slender' have been found.

No abstract

A design tool for fast and precise determination of the crystallographic orientation in (001) and (011) silicon wafers using anisotropic wet etching is introduced. The design takes advantage of the symmetric under-etching behaviour around, but not at (!), the -directions. The pattern needs to be etched only for a short time, and after a very quick optical inspection it can be used for aligning subsequent masks, using the same masking layer, more or less automatically. Two effects were investigated in a number of common anisotropic etchants: KOH, KOH with isopropyl alcohol (KOH/IPA), ethylenediamine based solutions (EDP), and tetramethyl ammonium hydroxide (TMAH). The precision of the method was found in most cases to be better than .

The hydrophilicity level of commonly used surface treatments prior to silicon fusion bonding has been measured and related to a resulting bond strength. The necessity of hydrophilic silicon surfaces to yield a strong bond has been questioned, even counter-proved. The strongest bonds measured were for hydrophobic, HF-treated wafers annealed at 800~

Wet chemical etching in EDP, pure KOH and KOH with isopropyl alcohol (KOH/IPA) are known to etch different crystal planes with different etch rates. It is shown in this work that etching in EDP or KOH/IPA reverses the etch-rate ratios of (100) and (110) planes, as compared to etching in pure KOH. This can be used to reveal other relatively slow etching planes, other than (111), to be used in new structures. V-grooves, retro-reflector ridges and mesa structures were fabricated bounded by (110) planes with 45 degrees angles to the (100) surface. Also, by using a corner-compensated mask aligned in the (100) direction and etched in pure aqueous KOH, free-standing cubic studs bounded by (100) planes were fabricated.