A micro-fuel processor with trench-refilled thick silicon dioxide for thermal isolation fabricated by water-immersion contact photolithography

This paper presents a micro-fuel processor to produce hydrogen for micro-fuel cells. The micro-fuel processor has an original design for a heat source and a reforming chamber to improve thermal efficiency. To improve the mechanical strength as well as to maintain the effectiveness of thermal isolation, the reaction area is suspended by trench-refilled thick SiO ₂. When the reaction area was heated at 200°C, the outer silicon frame was at 100°C, confirming the effectiveness of thermal isolation. To fabricate the trench-refilled thick SiO₂ using a contact aligner, water-immersion contact photolithography was used and successfully demonstrated to produce fine patterns with line/space of 2 νm/1 νm (a pitch of 3 νm). The highest temperature could be controlled by tuning the equivalent ratio of H₂-air mixture fed into the catalytic micro-combustor. The conversion rate of methanol to hydrogen by steam reforming was lower than 1% due to uneven temperature distribution and channeling effect.