Method of manufacturing a LIGA mold by backside exposure

A mold manufacturing method includes the steps of: disposing a mask layer on a front side and a backside of a first substrate, wherein the first substrate is transparent to a predetermined light source and the mask layer has a top portion and a bottom portion, which are respectively disposed on the front side and the backside and arranged alternately; forming a photoresist layer on the front side of the first substrate; providing the predetermined light source to illuminate the backside of the first substrate so as to expose the photoresist layer to form an exposed portion and an unexposed portion; and removing the unexposed portion to form a patterned structure having trenches and micro-holes arranged alternately; forming a metal layer on the patterned structure of the photoresist layer and the first substrate; and removing the photoresist layer and the first substrate; to remain the metal layer.