# US 5,703,374 A · Telecentric NUV-DUV irradiator for out-of-contact exposure of large substrates > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,703,374 A - Document ID: US5703374A - Status: Granted - Kind: A - Application number: 08/694,107 - Filed: 1996-08-08 - Granted: 1997-12-30 - Earliest claimed: 1996-08-08 - Assignees: Actinic Systems, Inc. - Inventors: Fausto Caprari - Web page: https://patentgrep.com/patent/US5703374A ## CPC - G03F 7/70058: {Mask illumination systems} - F21V 13/04: the elements being reflectors and refractors {(for vehicle rear lights F21S43/40)} - G03F 7/70791: {Large workpieces, e.g. glass substrates for flat panel displays or solar panels} - 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) - F21V: FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR ## Abstract A condenser lens system is provided for forming an effective circular source of NUV-DUV radiation which is the telecentric stop of the system and is characterized by a short focal length and higher marginal irradiance to compensate for marginal cosine losses. The system utilizes a long arc medium/low pressure mercury lamp which is surrounded by a large paraboloidal reflector and is mounted below the focal point of the reflector to generate a converging radiation beam directed to the condenser lens system. The system then projects the effective circular source of NUV-DUV radiation to a lens system comprising two plano convex lenses to convert the effective circular source into a collimated beam for out-of-contact printing of large substrates. The highly collimated and spatially coherent beam can be used to irradiate a telecentric objective for projection exposure on wafer steppers or flood exposure systems. ## Claims ### Claim 1 An optical system having a reflector for reradiating ultraviolet energy emitted by a mercury lamp as a radiation beam to a condenser lens assembly which directs the radiation beam through an entrance pupil lens and a collimation lens onto an intended plane distal from said mercury lamp, said system comprising: said mercury lamp operating under a predetermined pressure and being an elongated arc having a length to width ratio greater than 2; said reflector being a paraboloidal reflector responsive to said ultraviolet energy emitted by said mercury lamp to provide a converging radiation beam; and said condenser lens assembly responsive to said converging radiation beam to provide an effective circular source which operates as a telecentric stop of said optical system. ### Claim 2 (depends on 1) The optical system according to claim 1, where said predetermined pressure is between 0.5 to 5.0 atmospheres. ### Claim 3 (depends on 1) The optical system according to claim 1, wherein said ultraviolet radiation emitted by said mercury lamp is in the spectral region between 185-440 nanometers. ### Claim 4 (depends on 1) The optical system according to claim 1, further including a dual filter assembly positioned between said effective circular source and said entrance pupil lens, said dual filter assembly operative to reduce chromatic aberration. ### Claim 5 (depends on 1) The optical system according to claim 1, wherein said paraboloidal reflector has an inner surface providing a mirror reflectivity to said ultraviolet radiation emitted by said mercury lamp. ### Claim 6 (depends on 5) The optical system according to claim 5, wherein said inner surface is coated to provide said mirror reflectivity in the wavelength range from 185 nanometers to 440 nanometers. ### Claim 7 (depends on 1) The optical system according to claim 1, wherein said paraboloidal reflector surrounds said mercury lamp and said elongated arc of said mercury lamp is positioned below a focal point of said paraboloidal reflector. ### Claim 8 (depends on 1) The optical system according to claim 1, wherein said converging radiation beam provided is characterized by marginal irradiance greater than irradiance at the center of said converging radiation beam. ### Claim 9 (depends on 1) The optical system according to claim 1, wherein said condenser lens assembly includes first and second plano convex lenses, said first convex plano lens having its vertex facing the vertex of said second plano convex lens. ### Claim 10 (depends on 9) The optical system according to claim 9, wherein said first plano convex lens and said second plano convex lens cooperate to receive said converging radiation beam to create said effective circular source for providing predetermined marginal irradiance and compensate for cosine losses. ### Claim 11 (depends on 1) The optical system according to claim 1, wherein said entrance pupil lens is responsive to said effective circular source to provide an enlarged version of said effective circular source. ### Claim 12 (depends on 11) The optical system according to claim 11, wherein said collimation lens is responsive to said enlarged version of said effective circular source so as to direct a collimated beam from said collimation lens onto said intended plane. ### Claim 13 An ultraviolet radiation source apparatus comprising: a mercury arc lamp operating under a predetermined pressure for producing ultraviolet radiation and being an elongated arc having a predetermined length to width ratio; a paraboloidal reflector cooperating with said mercury arc lamp to provide a converging ray bundle of said ultraviolet radiation; a condenser lens assembly responsive to said converging ray bundle to provide an effective circular source; and means responsive to said effective circular source to direct a modified form of said effective circular source to a given target area at a given plane. ### Claim 14 (depends on 13) The apparatus according to claim 13, wherein said ultraviolet radiation is in the spectral region between 185 to 440 nanometers. ### Claim 15 (depends on 13) The apparatus according to claim 13, wherein said predetermined pressure is between 0.5 to 5.0 atmospheres. ### Claim 16 (depends on 13) The apparatus according to claim 13, wherein said predetermined length to width ratio is greater than two. ### Claim 17 (depends on 13) The apparatus according to claim 13, wherein said elongated arc of said mercury lamp is symmetrically surrounded by an inner surface of said paraboloidal reflector and positioned below the focal point of said paraboloidal reflector. ### Claim 18 (depends on 13) The apparatus according to claim 13, wherein said condenser lens assembly operates to focus said converging ray bundle into said effective circular source of predetermined diameter and higher marginal irradiance to compensate for marginal cosine losses. ### Claim 19 (depends on 18) The apparatus according to claim 18, wherein said condenser lens assembly includes first and second plano convex lenses with their vertices facing each other. ### Claim 20 (depends on 13) The apparatus according to claim 13, wherein said means responsive to said effective circular source includes an entrance pupil lens positioned with respect to said condenser lens assembly to receive said effective circular source and to provide an enlarged version of said effective circular source at an output of said entrance pupil lens and a collimation lens positioned with respect to said entrance pupil lens to receive said enlarged version to provide a collimated beam therefrom that is directed to an out-of-contact mask and wafer at said given plane to expose said wafer according to a mask pattern with said collimated beam. ### Claim 21 (depends on 13) The apparatus according to claim 13, further including a dual filter assembly positioned between said condenser lens assembly and said means responsive to said effective circular source, said dual filter assembly operative to reduce chromatic aberration in said ultraviolet radiation from said effective circular source. ### Claim 22 An optical system for providing an ultraviolet radiation pattern for photolithography, comprising: a mercury lamp operating under a predetermined pressure for producing ultraviolet radiation and being an elongated arc of a given length to width ratio; a paraboloidal reflector symmetrically surrounding said mercury lamp below its focal point to efficiently collect the ultraviolet radiation from said mercury elongated arc lamp for generating a converging ray bundle with higher marginal irradiance than its center; a short focal length condenser lens assembly positioned with respect to said paraboloidal reflector to retrieve said converging ray bundle to provide at an output a predetermined diameter circular pattern indicative of an effective circular source; and an entrance pupil lens and a collimation lens positioned with respect to said condenser lens assembly to provide at an output a collimated beam of high uniformity and stability for projecting said collimated beam to a mask and wafer out-of-contact to each other and radiate such mask and wafer with said collimated beam. ### Claim 23 (depends on 22) The system according to claim 22, wherein said given length to width ratio is greater than 2. ### Claim 24 (depends on 22) The system according to claim 22, wherein said mercury lamp emits said ultraviolet radiation in the range between 185 to 440 nanometers. ### Claim 25 (depends on 22) The system according to claim 22, wherein said mercury lamp is pressurized between 0.5 to 5 atmospheres. ### Claim 26 (depends on 22) The system according to claim 22, wherein said paraboloidal reflector and said short focal length condenser lens assembly cooperate to generate said effective circular source characterized by high marginal irradiance to improve the uniformity at mask and wafer planes. ### Claim 27 (depends on 22) The system according to claim 22, wherein said short focal length condenser lens assembly comprises two short focal length plano convex lenses mounted with their vertices facing each other to increase collection efficiency and reduce spherical aberration. ### Claim 28 (depends on 22) The system according to claim 22, wherein said entrance pupil lens and said collimation lens are plano convex lenses oriented with their convex surfaces toward the longer conjugate to reduce spherical aberration. ### Claim 29 (depends on 22) The system according to claim 22, wherein the ratio of a effective circular source diameter to the diameter of said entrance pupil lens results in a spatial coherency factor not greater than 0.13. ### Claim 30 (depends on 22) The system according to claim 22, further including a dual filter assembly positioned between the condenser lens assembly and said entrance pupil lens, said dual filter assembly operative to reduce chromatic aberration.