Sep 10, 2015

Microfabrication of surface acoustic wave device using UV LED photolithography technique

Microfabrication of typical surface acoustic wave (SAW) devices using low cost ultra-violet light emitting diodes (UV LED) lithography technique is demonstrated. UV lithography is one of the prime fabrication steps while manufacturing SAW devices. Recently, UV LED based lithography has created attention for their low cost setup, low power consumption, and submicron manufacturing features. Interdigital transducers (IDTs) and reflectors of a SAW device generally consist of a long chain of electrodes separated by gaps. Minor fabrication anomalies in these kinds of features can lead to failure in fabrication and thus, the lithography technique should ensure high quality of fabrication. In this work, we have employed a commercially available UV LED torch as a UV source and transferred SAW device features (in an optical chrome mask) such as IDT comb patterns onto photoresist coated piezoelectric substrates through contact lithography technique. Typical SAW devices operating in 130 and 148 MHz were considered for the fabrication. The minimum electrode width dimension fabricated in the present work was 7 μm. The optimized fabrication method adopted to realize the features are presented in the experimental section of this technical note. The optical microscope images and the frequency response of the fabricated devices confirm the successful fabrication using the proposed technique. The fabricated SAW devices features had an accuracy of ±0.5 μm. Although the contact lithography technique using UV LED torch is simple and cost-effective to use, the non-uniform irradiance from the torch has caused irregular pattern transfer in the fabrication trials. However these issues were overcome by optimizing the sample placement under the UV source and UV exposure conditions.

Keywords

  • UV LED Lithography
  • SAW devices
  • Microfabrication
  • Optical lithography
  • MEMS
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