Silicate glasses have been commonly used in the field of semiconductor device fabrication as an insulator between active layers of the semiconductor device. These materials have relatively low melting temperatures, and can be flowed by heating in order to "planarize" the semiconductor layers. There will typically be contact holes or vias etched into the glass layers using wet etching or dry etching, and the silicate glasses can then be reflowed by heating in order to make smoother tops to the contact holes or vias, which makes the metal connections into the contact holes or vias more durable. The silicate glasses are typically formed of phosphosilicate glass (PSG) or borophosphate silicate glass (BPSG), and the boron and/or phosphorus impurity levels used can be adjusted to affect the silicate glass's melting point. Nasas Glenn Research Center clean room. ... Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium and gallium arsenide. ... Wet etching is the removal of material by immersing the wafer in a liquid bath of chemical etchant. ... Dry etching is the removal of material, typically a masked pattern of semiconductor material, by exposing the material to a bombardment of ions that dislodge portions of the material from the exposed surface. ... Phosphosilicate glass, commonly referred to by the acronym PSG, is a silicate glass commonly used in semiconductor device fabrication for intermetal layers, i. ... Phosphosilicate glass, commonly referred to by the acronym PSG, is a silicate glass commonly used in semiconductor device fabrication for intermetal layers, i. ... Borophosphosilicate glass, commonly known as BPSG, is a type of silicate glass that includes impurities of both boron and phosphorus. ...