2~10 GHz surface acoustic wave unidirectional inter-digital transducers and low-loss filters using anodic oxidation technology

The frequency ranges of mobile communication systems are now in 2 GHz and in extending to 3~4 GHz. More over SAW devices require the frequency range of around 10 GHz-range. Nano-meter technology below 0.2 μm and new IDT techniques with wider electrode width than conventional ones and new unidirectional transducers with the electrode width around λ/4 are required. We proposed narrow gap IDT using anodic oxidation. Double the operating frequency is obtained using the same line width photo-mask patterns as with conventional transducers. By anodic oxidation of edges of the portions of the Al film under photo-resist, controllable gaps between electrodes with good insulation can be obtained. In this paper, these techniques are applied to realize a surface acoustic wave narrow gap interdigital transducer (NGIDT) and new electrode thickness difference type of narrow gap unidirectional transducers (ETD-NG-UDT) at 10 GHz-range using direct writing electron beam lithography techniques. Experimental result shows 10 dB insertion loss around the 12 GHz-range SAW NG-IDT with an electrode width under 0.15 μm. New ETD-NG-IDT with narrow gap electrode using the photo-resist shadow under the oblique angle evaporation techniques are applied at 2~1O GHz-range low-loss filters. The results show below 3.0 dB at 2 GHz and 10 dB insertion loss at 10 GHz-range