Multilayer thin-film encapsulation plays an important role in Si-based organic micro-displays. In this letter, we demonstrate an efficient and low-process-temperature approach to fabricate high-performance barrier films by inserting in situ plasma oxidized Al layers between SiOx encapsulation layers. Calcium degradation tests show that the water vapor transmission rate of the SiOx/AlOx multilayer barrier film is 2.23 × 10−5 g m−2 day−1 under the conditions of 25 °C and 70% relative humidity after in situ plasma oxidation treatment for 20 min, which is a reduction of two orders of magnitude compared with single-layer SiOx barrier films.