TECHNICAL PRODUCT INFORMATION Buffered Oxide Etchant • FUJIFILM Buffered Oxide Etchants are silicon oxide etchants formulated from high purity 49% Hydrofluoric Acid and high purity 40% Ammonium Fluoride. • Formulations are available in standard NH4F:HF ratios or made to customer specification. • Stringent control of both hydrofluoric acid and ammonium fluoride content ensures lot to lot reproducibility of etch rate characteristics. • A Certificate of Analysis is provided with every lot and includes assay, trace metal analysis, and particle count analysis at 02µ and 0.5µ. • Formulations are also available with OHS™ to improve surface wetting and promote etch uniformity. • Buffered HF's are also used as pre-diffusion and premetallization surface preparations. Buffered hydrofluoric • Etch rates may also vary in SiO2 films due to changes in film densities that result from the presence of dopants. These variations are impacted by dopant type and concentration. • Phosphorous doped films are less dense and tend to etch faster. An increase in phosphorous concentration will increase etch rates. • Boron doped oxide (borosilicate glass) is more dense and tends to etch slower. • Elevated temperatures also increases SiO2 sidewall sloping. • Etching should be done in polypropylene, polyethylene, Teflon® or other fluorocarbon containers. • To minimize fluctuations in etch rate, etch bath temperature should be controlled to ±0.5°C. • Substrates can be etched for a predetermined time or to visual dewet. A 10 to 20 second overetch ensures isolation of features. FUJIFILMFUJIFILM ELECTRONIC MATERIALS ELECTRONIC MATERIALS