Research And Application Of Nanoporous Silicon Dioxide In Microwave Power Transistors

Nanoporous silicon oxide films have been considered as one of the best insulated dielectric applied in ultra large-scale integrated (ULSI) circuits and microwave power devices due to its low dielectric constant and good process compatibility.In this paper, Sol-Gel method was used to prepare nanoporous SiO₂ films on silicon wafers by spin coating, aging, supercritical drying and hydrophobic modification. The compositions, microstructures and properties of the films were analyzed by FTIR, SEM, AFM, and spectroscopic ellipsometry etc.The compatibility of nanoporous SiO₂ films with semiconductor manufacturing processes was investigated. It's shown that the adhesion of nanoporous SiO₂ thin films was improved by post-treatment with vacuum annealing or Ar plasma, and the degradation of the film properties had not been observed. The films were not compatible with conventional photography processes. A cap layer or hard mask was required to protect nanoporous SiO₂ films from interactions with photoresists and developers. By the use of PECVD SiO₂ or Si₃N₄ as a cap layer, RIE etching of the nanoporous silicon oxdie films was successfully carried out.Replacing conventional PECVD SiO₂ by nanoporous silicon oxide films in the manufacture of silicon microwave power transistors, DC parameters of the device by nanoporous SiO₂ films were the same as that devices by normal SiO₂. In the of application in microwave power devices, the delightful experimental progresses of nanopours silicon oxide films were obtained. The chips were manufactured successfully, and provided a better foundation for the further research.