Submicron fabrication techniques using electro-chemical effects and application to unidirectional SAW transducers

Submicron fabrication techniques are very important for higher frequency-range SAW devices. The frequency ranges of mobile communication systems are now in the 1 GHz region and extending to 2~4 GHz. Moreover SAW devices require the frequency range around 10 GHz. Also, unidirectional SAW transducers are very important for high efficiency SAW devices, for example, low loss SAW filters and high efficiency convolvers, etc. In this paper, new selective etching methods of electrodes using the electrochemical effect is proposed. These methods enable to obtain bimetal electrodes of different thickness or different materials using a single photolithography method. The new unidirectional structure, λ/6 type FEUDT, with low loss characteristics made by these methods based on the mask aligner process at 2 GHz is proposed. In addition, the unidirectional IDT of double-electrode structure is obtained conveniently in the GHz range by these methods. Experimental results of filters show low loss characteristics (less than 3 dB) in the GHz range