Valves are an essential part of pumping systems, which are used in a wide variety of applications including medical, automotive, gas sampling, and gas analysis. The objective of this investigation is to design and fabricate microvalve arrays. The valve consists of a polysilicon flap suspended over a through hole in the silicon. It is intended to allow airflow in one direction and inhibit airflow in the reverse direction. The design requires only three mask levels, two on the front of the wafer and one on the backside. The front side masks are level: 1 Anchor and level 2: Flap. The backside mask is Holes. Backside alignment was achieved by placing shims between the Anchor and Holes masks, aligning the two masks to each other, and clamping them together. A double-sided polished wafer was resist coated on both sides and slipped between the two masks. Both sides were exposed using a flood exposure from a broadband mask aligner. The backside holes were masked by thermal oxide and etched using a 40% weight heated KOH solution. The wafers were diced and the valves were released.
"Fabrication of Polysilicon Micro Valve Array,"
Journal of the Microelectronic Engineering Conference: Vol. 14
, Article 17.
Available at: http://scholarworks.rit.edu/ritamec/vol14/iss1/17