Sharper N/N + profiles over arsenic buried layers using low pressure epitaxy

Abstract

A thin epitaxial layer over a high concentration arsenic buried layer aids design of higher speed I2L, bipolar, VMOS, and linear devices. A new low pressure (40 torr) epitaxial process has been developed in cylindrical production reactors. N- epitaxial layers (1014-1015) have been fabricated over N+ arsenic buried layers (1019-1021). Profiles ofithe N/N+ transition widths off 2 micron thick epitaxial layers have been analyzed with spreading resistance techniques. Device characteristics are shown to indicate that the process produces device quality epitaxy. Low pressure conditions lower the arsenic autodoping from the buried layers, both vertically and laterally between buried layer wells. The low pressure epitaxial process is a new tool to grow higher resistivity layers with sharper N/N+ transition widths.