Use of a high-flow diaphragm valve in the exhaust line of atomic layer deposition reactors

Abstract

In many atomic layer deposition (ALD) reactors, a stop valve is placed between the reaction chamber and the vacuum pump to allow for long precursor exposure times. This valve can lead to a reduction in conductance to the pump, lowering pumping efficiency and increasing the required purging time. In this study, a prototype high-flow (flow coefficient Cv = 1.7) diaphragm valve designed for ALD compatibility was inserted into the exhaust line of an ALD reactor and compared to a standard ALD diaphragm valve (Cv = 0.62). The results show that the chamber base pressure was reduced by 66% with the high-flow valve, which has implications for precursor delivery and mass transport. Furthermore, ZnO films were deposited via ALD, and the variation in thickness across a 100 mm diameter Si wafer was shown to be lower for the high-flow valve, especially with short purging times. These results suggest that the use of a high-flow ALD valve in the exhaust line can be beneficial when attempting to reduce the purging time and improve uniformity in research-scale reactors, and it could eventually be utilized in larger production-scale reactors.