Electron beam direct writing technology and application in the research of high frequency SAW devices

Communication technologies develop very fast in recent years, especially mobile communication technology. One of the key parts of communication system is the SAW device, which development directions are high frequency, low insert loss and miniaturization. As the frequency is higher, requirement of optical lithography technology increases and the conventional contact lithography technology is inefficient. Three kind of lithography is ideal: UV projection lithography, Electron beam direct writing technology and X-ray lithography. In order to reduce fabrication cost and development cycle, a variably shaped electron beam lithography system (JBX-6A□, JOEL, 1980) was adopted. This system was mainly used for optical lithography reticle fabrication, and it had a low resolution of 1µm. In order to develop the potential capability of the electron beam direct writing system, specially designed substrate exposure clamp, electron beam proximity effect correction graphic design technology and different shaped beam size combination exposure technology were adopted, and the parameter of resist coating, pre-bake, exposure dose, hard bake, etching temperature and time were optimized. As a result, this system got a resolution of 0.5µm. In this paper, research and batch fabrication task of SAW filter (900MHz, 1272MHz, 1575.42MHz and 2300MHz, etc) and SAW resonator (1320MHz and 1440MHz, etc) were successfully completed.