Browse Prior Art Database

Holographic Mask Illuminator for Coupling an Excimer Laser to a Projection Lithography System

IP.com Disclosure Number: IPCOM000043506D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Kirk, JP: AUTHOR

Abstract

In a projection lithography system (such as the Perkin-Elmer 500), one efficient way of obtaining very fine resolution patterns on a wafer is by substituting a pulsed excimer laser light source in place of the mercury arc lamp. However, it is difficult to couple an excimer laser to the system due to inherent variation in the laser beam intensity and optical path length differences between different portions of the beam. Disclosed herein is a holographic condenser and a method of fabricating the hologram to solve this problem. Fig. 1 shows the holographic condenser which comprises a concave reflection hologram (grating) 1, a relay lens 2 and a mask 3 which are illuminated by an excimer laser beam 4.

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Holographic Mask Illuminator for Coupling an Excimer Laser to a Projection Lithography System

In a projection lithography system (such as the Perkin-Elmer 500), one efficient way of obtaining very fine resolution patterns on a wafer is by substituting a pulsed excimer laser light source in place of the mercury arc lamp. However, it is difficult to couple an excimer laser to the system due to inherent variation in the laser beam intensity and optical path length differences between different portions of the beam. Disclosed herein is a holographic condenser and a method of fabricating the hologram to solve this problem. Fig. 1 shows the holographic condenser which comprises a concave reflection hologram (grating) 1, a relay lens 2 and a mask 3 which are illuminated by an excimer laser beam 4. The hologram 1 and relay lens 2 are symmetrical with the optical axis 5 so that each point on the mask has the same angular orientation to the hologram, thereby ensuring uniform illumination by the hologram 1 of the entire curved image arc of the projection system. Since the entire hologram 1 contributes to the illumination of each point in the mask plane, variations in laser beam intensity will not result in a variation in mask illumination. The center of curvature 6 of the hologram 1 is designed to be coplanar with the mask 3 to minimize the range of spatial frequencies and provide telecentric illumination of the mask 3. The hologram 1 is fabricated by using the optical arra...