Patent ID: 6255035
Filing Date: 2001-07-03
Classification: G03F,H01L

Abstract:
A process for forming a photoresist image on a substrate which comprises:a) depositing a first positive working photoresist composition onto a substrate to thereby form a first photoresist layer;b) depositing a second positive working photoresist composition onto the first photoresist layer to thereby form a second photoresist layer; the first photoresist composition having a different solubility than the second photoresist composition;c) overall exposing the first photoresist layer to sufficient electron beam radiation to render the first photoresist layer more soluble than prior to exposure, wherein the radiation is concentrated at a predetermined point in the thickness of the first photoresist layer;d) overall exposing the second photoresist layer to sufficient electron beam radiation to render the second photoresist layer more soluble than prior to exposure, wherein the radiation is concentrated a predetermined point in the thickness of the second photoresist layer;e) conducting either step (i), (ii) or (iii):(i) sequentially imagewise exposing the second photoresist layer to radiation, developing the second photoresist layer; imagewise exposing the first photoresist layer to radiation; and then developing the first photoresist layer;(ii) simultaneously exposing both the second and the first photoresist layers to radiation; developing the second photoresist layer; and then developing the first photoresist layer;(iii) sequentially imagewise exposing the second photoresist layer to radiation; imagewise exposing the first photoresist layer to radiation; and then developing the second and first photoresist layers either simultaneously or sequentially;thereby form cavities in the second photoresist layer, such that the diameters of the cavities at an upper surface of the second photoresist layer are less than the diameters of the cavities at a lower surface of the second photoresist layer thus defining cavities having outwardly sloping negative sidewalls and to thereby form cavities in the first photoresist layer, such that the diameters of the cavities at an upper surface of the first photoresist layer are greater than the diameters of the cavities at a lower surface of the first photoresist layer thus defining cavities having inwardly sloping positive sidewalls.