Determination of the Etching Kinetics for the Hydrofluoric Acid/Silicon Dioxide System

Abstract

Etching kinetics for several silicon dioxide films in various hydrofluoric acid solutions have been studied. The low temperature silicon dioxide films were deposited at 450°C and 300 mTorr in SiH4 , O2 , and PH3 and annealed at 950°C for 1 h. The thermal oxides were grown at 1100°C in H2O and O2 . Four hydrofluoric acid solutions were used: dilutions of 49 weight percent HF with deionized water, buffered hydrofluoric acid, surfactant‐buffered hydrofluoric acid, and hydrofluoric acid/hydrochloric acid mixtures. Expressions for etch rate as a function of hydrofluoric acid concentration are presented. Notably, the etching of the low temperature oxides was of the order 1.6–2.0 in HF solutions and of the order 0.5–1.0 in buffered HF solutions. The etching of the thermal oxide was of the order 1.37–1.5 in HF and of the order 0.75–1.07 in buffered HF solutions. The results for the HF solutions provide evidence of a two‐part etching mechanism: first, the acidity causes the formation of the silanol bonds on the silicon dioxide surface and, then, the fluorine species react with the silicon to form SiF4false(normalgfalse) which is soluble in water and forms H2SiF6false(normalaqfalse) . Significant enhancement (as much as 600%) in the etch rate was observed when hydrochloric acid was added to the HF solutions.

Identification of a silicatein(-related) protease in the giant spicules of the deep-sea hexactinellidMonorhaphis chuni

“…Following the experimental (Aizenberg et al, 2005) and Mayer (Mayer, 2005), the organic phases in the rigid bio-silica material provide the spicules with exceptional optical properties and high viscoelasticity. Etching experiments with HF, to partially convert bio-silica to gaseous silicon tetrafluoride (Monk et al, 1993), showed that the lamellae composing the bio-silica shell are not homogeneous; granules/spheres of approximately 100·nm in size are exposed (Müller et al, 2007c). A comparable finding has previously been documented using electron microscopy in demosponges (Pisera, 2003).…”

Defect identification using the core-electron contribution in Doppler-broadening spectroscopy of positron-annihilation radiation

“…Measurements were preceded by methanol cleaning and a 3-min 0.5% HF-acid bath for surface oxide removal, followed by a 1-min H 2 O rinse. [16][17][18] The same etching procedure was used for the study of hydrogen terminated bonds at the surface of silicon. Asreceived, float-zone silicon single crystals ͑resistivity greater than 2000 ⍀ cm͒ were used to examine the surface of Si covered with native oxide.…”

“…Therefore, it is often necessary to remove the oxide film, which is usually done by chemical etching in aqueous hydrofluoric acid, followed by rinsing in water. [16][17][18] It has been established that during this process dangling bonds of silicon get terminated with hydrogen and hydroxide. 24 The corresponding ratio curves for HF-etched Si͑111͒ and Si͑100͒ are shown in Fig.…”

A Theoretical and Experimental Analysis of Macrodecoration of Defects in Monocrystalline Silicon

“…The presence of diffusion effects in dissolution of thermal oxide by HF solutions of various compositions were acknowledged by Monk and Soane ͑1993͒. 35 In current literature, there is an abundance of information on both copper precipitation and decorating etching. However, current understanding of microdefect decoration by etching is based on the difference between the etching rates of the microdefects and of perfect silicon.…”