Abstract
A method of forming 3D high aspect ratio micro structures with different heights includes the steps of: disposing a mask, which has through holes with different size, on a substrate and exposing the substrate through the through holes; forming a negative photoresist layer on the mask and the substrate; providing a light source to illuminate the negative photoresist layer through the substrate and the through holes of the mask so as to form a plurality of exposed portions and an unexposed portion; and removing the unexposed portion and leaving the exposed portions to form a plurality of pillars each having a bottom portion contacting the substrate and a top portion opposite to the bottom portion. A top area of the top portion is somewhat smaller than a bottom area of the bottom portion, and the tapered pillars are allowed to have at least two different heights.