Wynn-Dyson imaging system with reduced thermal distortion
AssigneeUltratech, Inc.
InventorAndrew M. Hawryluk
Life of this patent
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Abstract
A Wynn-Dyson imaging system with reduced thermal distortion is disclosed, wherein the reticle and wafer prisms are made of glass material having a coefficient of thermal expansion of no greater than about 100 ppb/° C. The system also includes a first IR-blocking window disposed between the reticle and the reticle prism, and a second matching window disposed between the wafer and the wafer prism to maintain imaging symmetry. The IR-blocking window substantially blocks convective and radiative heat from reaching the reticle prism, thereby reducing the amount of thermally induced image distortion in the reticle image formed on the wafer.
Claims19
A Wynn-Dyson imaging system that operates with ultraviolet (UV) light, comprising along an optical axis:
- a mirror having a concave surface;
- an aperture stop located at the mirror that determines a numerical aperture of the system;
- a lens assembly with positive refracting power and having a front end and a back end, with the lens assembly being arranged adjacent the mirror and spaced apart therefrom with the front end facing the mirror;
- first and second prisms operably disposed on opposite sides of the optical axis and adjacent the back end of the lens assembly, the first and second prisms having respective first and second planar surfaces, wherein the first and second planar surfaces are arranged adjacent object and image planes, respectively;
- and
- at least one of:
- a) the first and second prisms each being made of a glass material having a coefficient of thermal expansion of no greater than about 100 ppb/° C.;
- and
- b) a first window operably disposed between the planar surface of the first prism and the object plane and that substantially transmits the UV light and that substantially blocks infrared (IR) radiation in a wavelength range from 2 microns to 20 microns, and a second window that is operably disposed between the planar surface of the second prism and the image plane and that substantially transmits the UV light, wherein the first and second windows are configured to maintain imaging symmetry.
The Wynn-Dyson imaging system of claim, wherein the reticle and wafer prisms are made of ULE® glass.
A method of reducing image distortion in a Wynn-Dyson imaging system used to image a reticle onto a wafer using ultraviolet (UV) light, comprising:
- disposing a first window between the reticle and an adjacent reticle prism, wherein the first window is configured to substantially block infrared (IR) light having a wavelength between 2 microns and 20 microns and to substantially transmit the UV light;
- disposing a second window between the wafer and an adjacent wafer prism, wherein the second window substantially transmits UV light;
- irradiating the reticle with the UV light to form an image of the reticle on the wafer using the Wynn-Dyson imaging system, with the UV light heating the reticle to at least 50° C., thereby causing the reticle to emit convective heat and radiative heat;
- blocking with the first window a substantial portion of the convective heat and the radiative heat so that the image of the reticle on the wafer has reduced image distortion as compared with not using the first window and the second window.
A method of reducing image distortion in a Wynn-Dyson imaging system having a primary mirror and an optical assembly and used to image a reticle onto a wafer using ultraviolet (UV) light, comprising:
- providing the optical assembly with reticle and wafer prisms made from an ultra-low expansion (ULE®) glass material;
- and
- irradiating the reticle with the UV light to form an image of the reticle on the wafer using the Wynn-Dyson imaging system, with the UV light heating the reticle to at least 50° C., thereby causing the reticle to emit convective heat and radiative heat;
- and
- wherein the image of the reticle on the wafer has a maximum image distortion of no greater than 0.5 microns.
Dependencies are inferred from the claim text.