Influence of Solution Volume on the Dissolution Rate of Silicon Dioxide in Hydrofluoric Acid

Abstract

Experimental data and modeling of the dissolution of various Si/SiO2 thermal coatings in different volumes of hydrofluoric acid (HF) are reported. The rates of SiO2 -film dissolution, measured by means of various electrochemical techniques, and alteration in HF activity depend on the thickness of the film coating. Despite the small volumes (0.6-1.2 mL) of the HF solution, an effect of SiO2 -coating thickness on the dissolution rate was detected. To explain alterations detected in HF activity after SiO2 dissolution, spectroscopic analyses (NMR and FTIR) of the chemical composition of the solutions were conducted. This is associated with a modification in the chemical composition of the HF solution, which results in either the formation of an oxidized species in solution or the precipitation of dissolution products. HF2 (-) accumulation in the HF solution, owing to SiO2 dissolution was identified as the source of the chemical alteration.

Reduction of dielectric constant by nanovoids formed through chemical treatment on silica crosslinked polyimide and its effect on properties

“…The H+ ion of the HF attacks the SiOSi bond, where it acts as a Lewis acid. The ion attacks the oxygen atom while the fluorine atom acts as a Lewis base and reacts with the Si atom . Through this reaction, the HF solution breaks the bond of SiO and redistributes the bonding of the atoms and forms SiF 4 .…”

Silicon Oxide Dissolution in Fluorohydrogenates Ionic Liquid

“…This contradicts the results previously obtained in aqueous HF solution, where an increase in the OCP of Si was measured after a full SiO 2 dissolution. 63,64 This OCP increase in HF solution was attributed to a passivation of Si surface due to H termination. The difference in OCP transients measured subsequent to a complete SiO 2 dissolution and Si exposure to EMIm(HF) 2.3 F RTIL and to HF can be attributed to different natures of Si passivity in these two solutions, i.e.…”

“…Similar behavior of Si/SiO 2 wafers during OCP exposure was obtained in HF solution. 63,64 OCP transients of Si/SiO 2 samples obtained from all SiO 2 films (with different thicknesses) are shown in Figure 2b. As can be seen, the initial potential values and exposure time up to the sharp potential drop are significantly reduced with decrease of SiO 2 thickness.…”

Visualization of Charge Carrier Trapping in Silicon at the Atomic Surface Level Using Four-Dimensional Electron Imaging

“…[35][36][37][38][39][40][41][42] Hydrofluoric acid (HF)-based solutions are the etchants most widely used for cleaning Si prior to any processing step. [43][44][45][46] The HF solution removes Si oxides from the surface and terminates dangling bonds with hydrogen atoms to act as a passivation layer. 35,36,43,44 Despite the usefulness of the HF-based cleaning, several angstroms of native oxide regrow on the etched clean surface within minutes.…”

“…A native oxide layer is grown on Si surfaces at room temperature whenever they are exposed to an environment of oxygen and moisture, even for a very short period . The thickness of this native oxide on the Si surface has been determined to be 1–2 nm or even in the angstrom range (few monolayers). − Despite its thin thickness, this native oxide layer, like other surface contaminants, affects the band structure and the electronic properties of the host materials as mentioned in several reports. ,,, Therefore, much attention has been given to characterizing and controlling this native oxide including the effects of different etchants. − Hydrofluoric acid (HF)-based solutions are the etchants most widely used for cleaning Si prior to any processing step. − The HF solution removes Si oxides from the surface and terminates dangling bonds with hydrogen atoms to act as a passivation layer. ,,, Despite the usefulness of the HF-based cleaning, several angstroms of native oxide regrow on the etched clean surface within minutes. − , This reoxidation process becomes slower with time until reaching a saturation thickness. , The atmosphere of the environment, especially the degree of moisture, affects the regrowth rate of this native oxide layer on the etched clean surfaces . Few reports have studied the surface recombination in HF-etched Si wafers using the optical pump–probe technique and lock-in carrierography .…”