HF etching is a form of wet etching that uses hydrofluoric acid to etch out surfaces rather than using a dry plasma process. HF etching is capable of etching materials such as amorphous silicon dioxide; quartz and glass at very high etch rates. Since HF etching is a wet process, meaning that it uses chemicals, it creates an isotropic etch. This

Oct 31, 2002 Oxide STANDARD OPERATING PROCEDURE Buffered Oxide etchants have a long history in the IC industry as etchants for SiO2 films as well as for pre-diffusion and pre-metalization surface cleans. The ICL uses a 7:1 BOE as its wet oxide etch and diluted HF (unbuffered) for the surface cleans. Buffered HF has several advantages over unbuffered HF as an etchant, namely improved Characteristics of SiO Etching with a C F /Ar/CHF /O Gas 2 etch rate and the etch selectivity over ACL were increased. For a 300 W/500 W power ratio of 60-MHz HF power/ 2-MHz low-freqeuncy (LF) and a gas mixture of Ar (140 sccm) /C 4F 8 (30 sccm) /CHF 3 (25 sccm) /O 2 (5 sccm) while maintaining 20 mTorr, an anisotropic etch profile with an SiO 2 etch rate of 3350 ˚A/min and an etch selectivity of

by W. Van Gelder and V.E. Hauser - Wafer Wet Etching

Fujifilm has advanced capabilities for the precise blending of Buffered Etchants with tight assay specification ranges, available in multiple NH4F:HF ratios Utilized to etch SiO2 films Utilized as pre-diffusion and pre-metallization surface preparations Formulated from high purity 49% Hydrofluoric Acid and high purity 40% Ammonium Fluoride Both thermally grown and deposited SiO2 can be etched in buffered hydrofluoric acid. However, etching of deposited films proceeds a lot faster than that of the thermal oxide. Densification of the deposited films, by heat treatment at 1000-1200oC for about 15 minutes, results in a fall in the etch rate to approximately the same as that for the –HF – Buffered HF (BHF)-10:1 HF/NH3F “BOE” • Silicon Nitride – Phosphoric acid – Selectivity [Si3N4/SiO2] = 40/1 • Polysilicon – KOH, EDP, and TMAH Wet Etching of Quartz • Anisotropic etching by HF – with 10.9mol/l, Rate ~ 9.6 µm/hr • Ammonium fluoride (NH4F) • Saturated ammonium bifluoride (NH4HF2)

• A 20:1 BHF (Buffered HF) or BOE (Buffered Oxide Etch)A 20:1 BHF (Buffered HF) or BOE (Buffered Oxide Etch) etches thermal oxide at ~ 300Å /min but the etch rate for silicon nitride is only ~10Å/min! • PtilthtfSiPractical etch rates for Si 3 N 4 are achi d i h h ihieved using phosphoric acid (H …

askavantor force com - Buffered Oxide Etch (BOE) Data Below is a table with the freezing point and etch rates for buffered oxide etch mixtures. Table 1269. Buffered Oxide Etch Data