Picoliter droplets for spinless photoresist deposition

In this article, we present an acoustically actuated two-dimensional (2D) micromachined ejector array for a zero waste and spinless droplet-by-droplet photoresist deposition method. The theory of operation, the experimental results obtained with acoustic focused 2D micromachined microdroplet ejector array is demonstrated. The ejector operation at 34.7MHz and generation of 21μm diam photoresist solvent droplets in drop-on-demand and continuous modes of operation are demonstrated. Photoresist droplets are ejected onto a wafer surface by this acoustic ejector array. Photoresist droplets are ejected on drop on demand and interact with each other by surface tension forces to generate photoresist coverage on the wafer surface during photoresist deposition by droplet generation. By overlapping ejected photoresist droplets, formation of a uniform thickness, line coverage is achieved. Multiple photoresist lines are printed simultaneously by a 3×3 ejector array. By overlapping photoresist lines, coverage of a 4in. silicon wafer with photoresist is achieved.