Abstract: There is disclosed herein a bipolar transistor structure having a self aligned extended silicide base contact. The contact extends to the position of a base contact window located outside the perimeter of the isolation island on a contact pad formed over the field oxide. This allows the size of the isolation island to be kept smaller and allows a smaller extrinsic base region to be formed. The base contact is formed of titanium and titanium silicide where the titanium/silicide boundary is self aligned with the edge of the device isolation island. The silicide is formed by reacting the titanium which completely covers the exposed epitaxial silicon inside the isolation island. An anisotropically etched oxide sidewall spacer insulates the silicide from the sidewall of the silicide-covered, polysilicon emitter contact.

Abstract: There is disclosed herein a bipolar transistor structure having a self aligned extended silicide base contact. The contact extends to the position of a base contact window located outside the perimeter of the isolation island on a contact pad formed over the field oxide. This allows the size of the isolation island to be kept smaller and allows a smaller extrinsic base regions to be formed. The base contact is formed of titanium and titanium silicide where the titanium/silicide boundary is self aligned with the edge of the device isolation island. The silicide is formed by reacting the titanium which completely covers the exposed epitaxial silicon inside the isolation island. An anisotropically etched oxide sidewall spacer insulates the silicide from the sidewall of the silicide-covered, polysilicon emitter contact.

Abstract: A silicon substrate having a silicon dioxide bird's head is provided. A thermal oxide layer is grown on the exposed silicon surface. A layer, e.g., 4000 A.degree., of phosphogermanosilicate glass is deposited on the thermal oxide and on the silicon dioxide bird's head. The structure is heated to 950.degree. C., causing a reflow of the glass which results in a planar surface. The thermal oxide and the phosphogermanosilicate glass are then wet etched at the same rate with a solution of hydrofluoric acid, ammonium fluoride, and deionized water. The wet etch is terminated when the exposed silicon surface is reached, resulting in a smooth surface as defined by the planar reflow surface. Other embodiments are disclosed.