Characterization of 10 μm thick porous silicon dioxide obtained by complex oxidation process for RF application

This paper proposes a 10 mum thick oxide layer structure, which can be used as a substrate for RF circuits. The structure has been fabricated by anodic reaction and complex oxidation, which is a combined process of low temperature thermal oxidation (500 degreesC, for 1 hr at H2O/O-2) and a rapid thermal oxidation (RTO) process (1050 degreesC, for 1 min). The electrical characteristics of oxidized porous silicon layer (OPSL) were almost the same as those of standard thermal silicon dioxide. The leakage current through the OPSL of 10 pm was about 100-500 pA in the range of 0 V to 50 V. The average value of breakdown field was about 3.9MV/cm. From the X-ray photo-electron spectroscopy (XPS) analysis, surface and internal oxide films of OPSL, prepared by complex process, were confirmed to be completely oxidized. Also the role of RTO was important for the densification of the porous silicon layer (PSL), oxidized at a lower temperature. For the RF test of Si substrate, with thick silicon dioxide layer, we have fabricated high performance passive devices such as coplanar waveguide (CPW) oil OPSL substrate. The insertion loss of CPW on OPSL prepared by complex oxidation process was -0.39 dB at 4 GHz and similar to that of CPW oil OPSL prepared at a temperature of 1050 degreesC (1 hr at H2O/O-2). Also the return loss of CPW oil OPSL prepared by complex oxidation process was -23dB at 10GHz which is similar to that of CPW on OPSL prepared by high temperature oxidation.