Experimental Investigation of Silicon Surface Migration in Low Pressure Nonreducing Gas Environments

Abstract

Silicon migration in four nonreducing gas ambients of helium, neon, argon, and nitrogen at a low pressure ͑10 −3 Torr͒ and in an ultrahigh vacuum ͑10 −9 Torr͒ is studied by monitoring the effect on microfabricated trench structures after a 5 min anneal at 1000°C in each environment. The measurements of the trench corner curvature are used to extract the relative migration rates for each ambient. The migration rate has no ambient gas dependence for the noble gases at 10 −3 Torr and has pressure dependence in the 10 −3 -10 −9 Torr range.

Self-formed cylindrical microcapillaries through surface migration of silicon and their application to single-cell analysis

“…Surface migration of silicon atoms takes place at elevated temperatures 900-1300 • C, albeit below the melting point of silicon 1414 • C. It is typically observed in hydrogen ambient over a wide pressure range 10-760 Torr [45], but also reportedly occurs in an ultrahigh vacuum (UHV) environment [46,47]. Interestingly, however, neither hydrogen nor UHV ambient is absolutely necessary as pointed out by a recent study where migration was encountered in a low-pressure (1 mTorr) non-reducing gas (He, Ne, Ar, N 2 ) ambient [48].…”

“…This could raise a concern over a possible leakage at the interface when a cover plate is mounted on the partition to enclose the remaining microchannels and reservoirs. We believe that this issue can be addressed by performing the anneal step in a low-pressure ambient which is known to induce a smoother surface profile [48].…”

Silicon Migration of Through-Holes in Single- And Poly-Crystalline Silicon Membranes

“…Silicon migration is a mass transportation effect that occurs even below the melting point of silicon. This effect is welldocumented for single-crystalline silicon (sc-Si) by various groups at high temperatures and low-pressure deoxidizing ambient such as hydrogen (H 2 ) and at ultra high vacuum (UHV) [1,2]. The atomiclevel smoothening of silicon transforms small features to minimize the surface energy [1,3,4].…”

A Self-Scanned Active-Matrix Tactile Sensor Realized Using Silicon-Migration Technology

“…This is followed by a thermally induced coalescence of the pores in the buried porous silicon with a higher porosity into a cavity, before the subsequent sealing of the cavity and the formation of a diaphragm using silicon epitaxy. Similar to the process described in [9], the silicon-migration technology (SiMiT) [10], [11] is also a pre-CMOS scheme for constructing a cavity with a cover-diaphragm without the need of a sacrificial layer etch. Instead of creating porosity using an anodic etch that requires an elaborate substrate preparation procedure and suffers from potential metal contamination, SiMiT starts with the patterning of an array of "wells" or "trenches" using a deep reactive-ion etcher (DRIE).…”