Manufacture of masks and electronic parts
View Patent ↗A precursor that may be imaged by heat is made up of a substrate, for example a copper board, and a composite layer structure composed of two layers. Preferably, the first layer is composed of an aqueous developable polymer mixture containing a photothermal conversion material, which is contiguous to the substrate. The second layer of the composite is composed of one or more non-aqueous soluble polymers, which are soluble or dispersible in a solvent which does not dissolve the first layer. The precursor is exposed with an infrared laser or a thermal print head, and upon aqueous development, the exposed regions are removed, revealing regions of the substrate surface able to be etched or otherwise treated. The second layer may also contain a photothermal conversion material. Alternatively, the composite layer may be free of photothermal conversion material when thermal imaging is carried out using a thermal print head. The precursor may be used, for example, as a mask precursor or electronic part precursor.
1. A method of making a mask or an electronic part, the method comprising the steps of:
I) providing a precursor which comprises:
a substrate having a conductive surface of copper or a copper-rich alloy; and
a thermally sensitive composite layer structure having an inner surface contiguous to the substrate and an outer surface, the composite layer structure comprising:
(a) a first layer having an inner surface, the first layer comprising a first polymeric material and a photothermal conversion material, wherein the first polymeric material is soluble or dispersible in an aqueous solution and the photothermal conversion material comprises an infrared absorbing compound; and
(b) a second layer having an outer surface, the second layer comprising a second polymeric material, wherein the second layer is insoluble in the aqueous solution
II) imagewise exposing the composite layer structure to thermal energy to provide exposed portions and complimentary unexposed portions in the composite layer structure, wherein the exposed portions of the composite layer structure are selectively removable by the aqueous solution; and
(III) applying the aqueous solution to the outer surface to remove the exposed portions of the composite layer structure to produce an imaged article having uncovered areas of the substrate and complimentary remaining regions of the composite layer structure.
2. The method of claim 1 wherein exposed portions of the first layer of the composite layer structure have an increased rate of solubility or dispersibility in the aqueous solution.
3. The method of claim 1 wherein exposed portions of the second layer of the composite layer structure have enhanced permeability to the aqueous solution.
4. The method of claim 1 wherein the aqueous solution has a pH of about 6 or greater.
5. The method of claim 1 wherein the aqueous solution has a pH between about 8 and about 13.5.
6. The method of claim 1 wherein imagewise exposing is carried out with an infrared emitting laser.
7. The method of claim 1 wherein imagewise exposing is carried out with a thermal printing head.
8. The method of claim 1 wherein the method additionally comprises: (IV) etching the article in an etchant to remove the conductive surface of those regions from which the composite layer structure was removed.
9. The method of claim 1 wherein the substrate comprises a semiconductor surface and the method additionally comprises: (IV) doping revealed regions of the semiconductor surface.