Reliability of transmission lines fabricated by screen printing for on-wafer measurements at millimeter-wave

The paper proposes new fabrication process for a planar circuits used at microwave and millimeter-wave frequencies. Screen printing technology is demonstrated to fabricate coplanar waveguides (CPW) lines as an impedance standard line for on-wafer device measurements at millimeter-wave frequency up to 110 GHz. The paper discusses the assessment of a screen printing technology in the characteristic of CPW lines fabricated on an alumina substrate usually adopted on an impedance standard substrate (ISS). CPW lines was printed by silver conductive ink and subsequent baking process by hot plate in the nitrogen gas flowing. Feature sizes with approximately 1.0 μm tolerance for signal lines were realized successfully. The surface roughness of conductor was less than 0.5 μm. Printed transmission lines provides insertion losses of 0.17 dB/mm at 60 GHz and 0.30 dB/mm at 110 GHz and it was better than plated CPW line being commercially available, i.e. 0.18 dB/mm at 60 GHz and 0.40 dB/mm at 110 GHz. Furthermore, return loss is almost the same as commercially available ISS, this means the transmission line patterns are almost high precision as same as commercial ISS fabricated by plating and etching. For contact reproducibility as important performance in the measurement process, printed conductors achieved more excellent reproducibility (N=10) than plated conductors, i.e. less than 0.02 dB for magnitude and less than 0.1 degrees for phase in short circuits.