Formation mechanism of stains during Si etching reaction in HF–oxidizing agent–H2O solutions

Abstract

The mechanism of stain formation in the chemical etching reaction of silicon has been investigated in HF–oxidizing agent–H2O solutions. The chemical formula of the stain formed during the silicon etching reaction is K2SiF6. The concentration of holes on silicon surface increases with the increase of redox potential and the concentration of oxidizing agent used in manufacturing the etching solution. The increase in the hole concentration accelerates not only the etch rate but also the formation rate of K2SiF6. The etched silicon surfaces are covered with a K2SiF6 layer when redox potential and concentration of oxidizing agent are great at low HF concentrations. This happens because the formation rate of K2SiF6 is much greater than its dissolution rate by HF. Sufficiently high HF concentration in the etching solution is apparently essential to increase the etch rate without the formation of K2SiF6.

Influences of Doping and Crystal Orientation on Surface Roughening upon Alcohol Grafting onto Silicon Hydride

“…Typically, relevant hole densities can be generated only by applying an electrical bias, by photon absorption on the surface [32] or via hole injection from an oxidant [33]-but none of these effects were present in the current experimental conditions. Thus, the ethynylbenzyl alcohol reacted first to the surface via insertion to form a Si-O-C linkage but then it does not possess enough impetus to break the Si-Si backbond due to the electron compensation arising from the sea of electron-rich phosphorous dopant ( Figure 5).…”

Porous Silicon Formation by Stain Etching

“…For example, Hoshino and Adachi produced photoluminescent films with 5-7 wt% K 2 Cr 2 O 7 in 50 % HF solution; however, they also observed the deposition of K 2 SiF 6 as did Mogoda et al (2011). Usually, HF + CrO 3 solutions lead to uniform etching or only roughening of the Si surface (Nahidi and Kolasinski 2006;Kooij et al 1999;Kelly et al 1994;van den Meerakker and van Vegchel 1989a, b;Nahm et al 1997;Gabouze et al 2003). There are several reports of the appearance of thin (Fathauer et al 1992;Beale et al 1986) or patchy porous layers (Kelly et al 1994) as well.…”

Metal-assisted etching of p-silicon—Pore formation and characterization

“…Microscopically local anode (Si) and cathode (metal) sites are formed on the etched surface with local cell currents flowing between the sites during etching. For HF-oxidizing agent-H 2 O etching system, the etching is a two-step process in which the silicon surface is first oxidized by holes injected into the surface when an oxidizing agent is reduced on the cathode [24]. The oxidized surface, anodic sites, successively reacts with HF to form a water-soluble complex.…”

“…The oxidized surface, anodic sites, successively reacts with HF to form a water-soluble complex. When ion is generated and reacts with H + to form positive holes, h + , on the silicon surface according to [24]:…”

“…As a result, K 2 SiF 6 nucleate heterogeneously near the mouths of the pores. The crystallites thus formed grow continuously in three dimensions [19] and the surface acquires passivity due to the formation of K 2 SiF 6 deposit [24]. The formation of K 2 SiF 6 is taking place when the concentration of K 2 Cr 2 O 7 exceeds 0.05 mL L −1 .…”