Application of SiO_2 aerogel film for interlayer dielectric on GaAs with a barrier of Si_3N_4

摘要

Si_3N_4 film was adopted as a barrier layer for SiO_2 aerogel/GaAs system. Si_3N_4/GaAs formed an almost chemically sharp interface and nearly maintained their chemical inertness during in-situ heating until 400℃ under ultra high vacuum condition. One micrometer thick SiO_2 aerogel film was prepared on the Si_3N_4/GaAs system using supercritical drying procedure at 250℃ and under 1160 psi. The thickness of Si_3N_4 barrier layer was varied as 400, 600 and 900 A. The dielectric constant of all SiO_2 aerogel/Si_3N_4/GaAs system was measured as approximately 1.9 and almost no difference was observed from the changes in the thickness of Si_3N_4 barrier layer. The leakage current densities were measured as low as under 2X10~(-7) A/cm~2 and these values are two orders smaller than that of SiO_2 aerogel/GaAs system prepared without the introduction of Si_3N_4 barrier layer. All the aerogel/Si_3N_4/GaAs systems show ohmic conduction at low applying field and space charge limited conduction at high applying field. Furthermore, a reduced leakage current behavior was observed with increased Si_3N_4 layer thickness and could be explained from the electric-field depression effect due to accumulated charges in the films.