Buffered-oxide etch

BET BMBF BOE Brunauer, Emmett, Teller (surface area) German Ministry of Education and Science Buffered oxide etching... 

BOE represents buffered oxide etch with various ratios of 40% NH4F/49% HF. 

The breakdown strength of PECVD oxide films polished from 180 nm to 130 nm one film was subsequently thinned to SO nm by etching in buffered oxide etch. (From Ref. (36).)... 

H. Proksche, G. Nagorsen, and D. Ross, The influence ofNH4p on the etch rates of undoped Si02 in buffered oxide etch, J. Electrochem. Soc. 139, 521, 1992. 

Molecular acids Fluorides, chlorides, bromides, sulfates, phosphates, nitrogen/oxygen compounds Etch chambers, diffusion furnaces, CVD processes, buffered oxide etch, wet benches using HCl, HF Forms haze crystals on reticles, wafers, and exposure tool optical elements, causes corrosion of A1 and Cu metal lines... 

By deep reactive ion etching (DRIE) of a silicon substrate channel that is 500 mm wide and 250 mm deep, serpentine-shaped long channels are fabricated with large surface areas (see Fig. 6.43). A layer of CVD oxide (1.5-2 mm thick) is first deposited and densi-fled on the Si wafer. A mask with the patterns for the flow channel and inlet/outlet ports is used to pattern a layer of photoresist. The patterns are transferred into the oxide layer using a buffered oxide etch (ammonium fluoride and hydrogen fluoride in water). The photoresist is then removed using a sulfuric acid and hydrogen peroxide mixture, and then a new layer is coated. A second mask... 

Figure 10.14 Microfabrication sequence for the silicon component of the palladium membrane reactor developed by Franz et al. [644.] BOE stands for Buffered Oxide Etching.

Strong acids and oxidizers are often mixed together and sometimes heated to accelerate the chemical reactions. Fume generation can cause a hazardous atmosphere to occur and boiling can spread highly corrosive droplets. Sometimes buffering is used to control the process reaction speed, as in buffered oxide etch (BOE), a solution of hydrofluoric acid and ammonium fluoride. 

Note PGMEA propylene glycol 1-mono-methyl-ether-2-acetate NMP n-methyl pyrrolidone EL ethyl lactate TMAH tetramethyl ammonium hydroxide BOE buffered oxide etch TEOS tetraethyl orthosilicate TDMAT tetrakis(dimethylamido) titanium IPA isopropyl alcohol or 2-propanol. 

Figures Illustration of (A) etched aluminumalloy (Guo etal., 2006), (B) laser-etched silicon wafer with using SF6 3.2kJ/m2 and (C) using OkJ/m (Baldacchini et al., 2006), (D) silicon wafer/photoresist layer overetched by SFg plasma before sonication, (E) after cleaning of residual photoresist and (F) micropillar structured silicon after buffered oxide etching. Images reprinted with permission from (A, D, and E) Elsevier, Copyright 2006,2005, and (B, C, and E) American Society, Copyright2006,2007. Adapted with permission of The Royal Society of Chemistry.

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