GaAs atomic-layer epitaxy in a rotating disc reactor

摘要

Abstract: Current difficulties of Atomic Layer Epitaxy (ALE) include relatively low growth rates and narrow process windows. Gas phase reaction, complex behavior of valve switching and purging times are suggested as the major causes. We have used a movable X- shaped mechanical barrier to divide the growth chamber into four zones. Alternate zones either supply source gas or mask the wafer from exposure to source gases. If the barrier is positioned 0.5 - 2 mm from the wafer carrier, it can efficiently shear off the boundary layer and thereby reduce gas phase reactions. The substrate, continuously rotating beneath the barrier, is alternately exposed to group III and group V sources. The result is that process times are significantly reduced. Initial results have shown a saturated growth rate of up to 0.35 $mu@m/hour at 525$DGR@C and a relatively wide process window. Thickness uniformity of $POM 1% over 85% of a 2 inch wafer has been obtained. !7