# US 4,842,677 A · Excimer laser patterning of a novel resist using masked and maskless process steps > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,842,677 A - Document ID: US4842677A - Status: Granted - Kind: A - Application number: 07/224,416 - Filed: 1988-07-26 - Granted: 1989-06-27 - Earliest claimed: 1988-02-05 - Assignees: General Electric Company - Inventors: Robert J. Wojnarowski; Charles W. Eichelberger - Web page: https://patentgrep.com/patent/US4842677A ## CPC - B44C 1/22: Removing surface-material, e.g. by engraving, by etching {(for multi-layer articles B44C3/005)} - G03F 7/095: having more than one photosensitive layer (G03F7/075 takes precedence) - G03F 7/2006: {using coherent light; using polarised light} - H05K 3/0082: {characterised by the exposure method of radiation-sensitive masks} - H10W 70/614: {the multiple chips being integrally enclosed} - H05K 3/0032: {of organic insulating material} - H05K 3/064: {Photoresists} - H05K 2203/0505: Double exposure of the same photosensitive layer - H05K 2203/0577: Double layer of resist having the same pattern - H05K 2203/107: Using laser light - B44C: PRODUCING DECORATIVE EFFECTS (processes for applying liquids or other fluent materials to surfaces, in general B05D; shaping of plastics or substances in a plastic state B29C; printing processes to produce transfer pictures B41M3/12; thermographic duplication or marking methods B41M5/00); MOSAICS; TARSIA WORK (imitation of mosaic or tarsia work patterns B44F11/04); PAPERHANGING {(labels G09F; multi-step processes for making paper labels or tags B31D1/02)} - G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G) - H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 ## Abstract A dual layer resist configuration is employed for photopatterning high resolution conductive patterns on underlying polymeric or ceramic substrates, particularly substrates exhibiting surface roughness and non-planar design features such as channels, bosses and ridges. More particularly, a thin underlayer of ablatable photoabsorptive polymer is disposed on a metal coated substrate, after which a thicker layer of substantially transparent material is disposed over the polymer. A beam of laser energy, such as that produced by an ultraviolet excimer layer, is directed through the upper layer and is absorbed by the lower layer which is ablated and simultaneously removes the thick layer above it. This results in the ability to etch high resolution features on polymeric and other substrates, particularly copper coated polyetherimide circuit boards. The resist system is also applicable to VLSI wafers even though such wafers usually do not exhibit surface roughness on the scale generally considered herein. It is also equally applicable in various high density interconnect systems used for the direct connection of chip devices. A mask for patterning and a method for making it are also seen to be desirable because of the high laser energy densities generally desired for thorough ablation. An alternate method is also disclosed which employs two laser exposure steps with the first step being a masked operation on only an ablatable layer and with the second step being an unmasked operation on a dual layer material. ## Claims ### Claim 1 A method for photopatterning conductive patterns, said method comprising the steps of: disposing a thin layer of ablatable photoabsorptive polymer on a substrate having a conductive layer thereon, so that said polymer material is in contact with said conductive layer; directing a beam of laser energy on said ablatable polymer, through a mask so as to ablate said polymer layer, whereby said conductive layer is partially exposed; disposing a thick layer of substantially transparent material over said partially ablated polymer layer and said exposed conductive layer, said photoabsorptivity and said transparency being determined with respect to the same frequency range; directing a beam of laser energy through said thick layer so as to ablate said polymer layer and so as to simultaneously remove said thick layer above said ablated polymer layer, whereby select portions of said conductive layer are exposed. ### Claim 2 (depends on 1) The method of claim 1 in which said thin layer is selected from the group consisting of polysulfones. ### Claim 3 (depends on 1) The method of claim 1 in which said thick layer is selected from the group consisting of polymethylmethacrylate, polyethylmethacrylate and polycarbonates. ### Claim 4 (depends on 1) The method of claim 1 in which said laser energy is produced by an excimer laser. ### Claim 5 (depends on 1) The method of claim 1 in which said laser energy is in the ultraviolet frequency region. ### Claim 6 (depends on 1) The method of claim 1 in which said thin layer is between about 0.1 microns and about 10 microns in thickness. ### Claim 7 (depends on 1) The method of claim 1 in which said thick layer is between approximately 1 and approximately 100 microns in thickness. ### Claim 8 (depends on 1) The method of claim 1 further including the step of etching said finally exposed conductive layer. ### Claim 9 (depends on 8) The method of claim 8 further including the step of removing any remaining material of said thick and thin layers. ### Claim 10 (depends on 1) The method of claim 1 further including the step of depositing additional conductive layer material on the exposed portion of said conductive layer. ### Claim 11 (depends on 1) The method of claim 1 further including the step of removing said thick and thin layers. ### Claim 12 (depends on 1) The method of claim 1 in which said second laser beam exposure is performed using a higher powered laser than said first exposure. ### Claim 13 (depends on 1) The method of claim 1 in which said second laser exposure is performed without a mask. ### Claim 14 (depends on 1) The method of claim 1 in which said conductive layer comprises copper. ### Claim 15 (depends on 1) The method of claim 1 in which said mask is not in contact with said substrate. ### Claim 16 (depends on 1) The method of claim 1 in which said substrate exhibits a non-planar surface. ### Claim 17 (depends on 1) The method of claim 1 in which said substrate contains feed-through apertures. ### Claim 18 (depends on 1) The method of claim 1 further including removing said ablated material by vacuum means as it is produced. ### Claim 19 (depends on 1) The method of claim 1 further including removing said ablated material by blowing it away from the ablation side.