Buffered Oxide Etch 5:1 (Avantor 5192-03, CMOS 9LB)
This substance is a mixture of several different chemicals to produce an etchant. Typically, it is made out of hydrofluoric acid and ammonium fluoride with water acting as a buffer. It creates a thin film of silicon dioxide or silicon nitride.
The primary use for buffered oxide etch is in the electronics industry, as the films it produces work well in microprocessors and semiconductors. The reason to use this solution rather than standard hydrofluoric acid is because the buffering agent (ammonium fluoride) slows the etching process so that you get better results. This chemical can also be used to etch certain glasses, along with quartz and SIO2 films.
Because it contains hydrofluoric acid, this substance is highly toxic to humans, and it is highly corrosive to the skin. You must wear safety goggles, gloves, and a breathing mask at all times when preparing and applying buffered oxide etch. If swallowed or inhaled, it can be fatal.