Silica conversion of polysilazanes by low-temperature plasma jet generated from Ar and water-vapor mixed gas

Perhydropolysilazane (PHPS), which contains no organic catalyst, chemically reacts with H2O in the atmosphere by heating it at 450 °C for more than 1 h to turn it into a SiO2 film. If silica conversion can be achieved at temperatures below 100 °C, which plastics can withstand, it may be applicable to a wide range of applications, such as flexible electronics. Here, we report a technique for forming SiO2 films with leakage current characteristics very close to those of thermally oxidized (THOX) films that works at a very low temperature of 52 °C with high speed. Using a 9-kV, 30-kHz power supply, a low-temperature plasma jet containing a gas mixture of Ar and water vapor irradiated an 8 nm thick PHPS thin film, inducing silica conversion at a maximum substrate temperature of 52 °C. The current density-electric field strength (J-E) characteristics of metal oxide semiconductor capacitors fabricated with this SiO2 film showed characteristics very close to those of THOX films. In addition, the mechanism of silica conversion of PHPS through low-temperature plasma jet irradiation using this gas mixture was clarified in real-time FT-IR measurements.