On the fabrication of thin-film artificial metal grid resonator antenna arrays using deep x-ray Lithography

摘要

In this paper, a unique microfabrication approach for designing high permittivity, high gain and wideband thin-film artificial metal grid dielectric resonator antenna (GDRA) arrays for mm-wave applications is presented. Fabrication of the GDRAs with a strip template frame is based on deep-x-ray lithography (DXRL) using a 500 mu m thick polymethylmethacrylate (PMMA) layer as the photoresist. The simple low-cost fabricated DXRL mask for exposure consisted of gold absorbers patterned by direct-write ultraviolet (UV) laser lithography on a carbon substrate. To avoid the trapping of gas bubbles in the dense, high aspect ratio (HAR) deep grid structures, a novel development approach was introduced utilizing in-vacuum, room temperature dip development to facilitate the collapse of forming gas bubbles. The developed voids were subsequently electroplated to a nickel thickness of 300 mu m to obtain high permittivity artificial dielectrics. The paper describes the entire fabrication sequence. Also, the x-ray mask and DXRL structures are examined for dimensional accuracy and structural quality. This strip template frame approach has superior performance in terms of impedance bandwidth, gain and radiation efficiency as compared to the previously published solid template frame approach. For the purpose of the demonstration, a four-element GDRA array sample was fabricated and tested. A wide measured impedance bandwidth of 5 GHz from 58 GHz to 63 GHz and measured broadside radiation pattern with a peak gain of 10.9 dBi was achieved.