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.