Nitridation of vanadium in molecular nitrogen: a comparison of rapid thermal processing (RTP) and conventional furnace annealing

Abstract

The nitridation processes of thin V films in molecular nitrogen at atmospheric pressure in a RTP-system, a conventional tube furnace and a high temperature in situ X-ray diffraction (XRD) reaction chamber with a Pt heating stage were compared. The main differences of these three techniques result from their strongly differing heating rates (RTP 50 K/s, in situ chamber 3 K/s, furnace 0.4 K/s) in combination with effects of traces of oxygen in the N 2 process gas: In the furnace, oxide formation on top of the V film takes place at moderate temperatures during the long heating up period. This oxide layer acts as diffusion barrier for nitrogen and prevents nitride formation at higher temperatures. In RTP, due to the fast ramp up to the process temperature no substantial V oxide layer is formed and nitridation of the entire V film proceeds rapidly. In the in situ XRD chamber, strong VN peaks show up above 800°C and only a few weak peaks indicate the presence of some oxide too. According to special RTP experiments, UV radiation emitted from the tungsten halogen lamps in the RTP system does not play a crucial role for the activation and dissociation of the molecular nitrogen in RTP.