Spectroscopic Investigations of Borosilicate Glass and its Application as a Dopant Source for Shallow Junctions

Abstract

Borosilicate glass was investigated as a dopant source for proximity rapid thermal diffusion. A borosilicate gel was spun onto a silicon wafer and the layer was rapid thermally processed to convert it to a borosilicate glass. Fourier transform infrared spectroscopy, spectroscopic ellipsometry, and sheet resistance measurements were used to understand and subsequently optimise the conversion of the gel to a borosilicate glass. The optimum conversion step, which avoided any boron loss from the borosilicate glass layer, was a curing step of 900°C for 45 s. Secondary ion mass spectrometry was used to measure the boron dopant profile of a silicon wafer that was doped with the borosilicate glass layer. The wafer had a surface dopant concentration of 4.7 × 1019 cm–3 and a junction depth of 65.5 nm. Junction diodes, which were fabricated using the glass layer as a dopant source, displayed excellent characteristics, with very low leakage currents and a near ideal forward slope