Substrate, method of exposing a substrate, machine readable medium
A double exposure method for enhancing the image resolution in a lithographic system, is presented herein. The invention comprises decomposing a desired pattern to be printed on the substrate into at least two constituent sub-patterns that are capable of being optically resolved by the lithographic system, coating the substrate with a first positive tone resist layer and a thin second positive tone resist layer on top of a target layer which is to be patterned with the desired dense line pattern. The second resist material is absorbing exposure radiation during a first patterning exposure and after development during a second patterning exposure to prevent exposure above energy-to-clear of at least a portion of the first resist material underneath exposed portions of the second resist material layer.
1. A method of exposing a lithographic substrate to radiation, said substrate having a first layer of a first positive tone developable material at least partially overlying the substrate and a second layer of a second positive tone developable material with a preselected absorbance for the radiation and at least partially overlying the first layer, comprising:
patterning the second layer with features of the second positive tone developable material in accordance with a first pattern of the radiation by:
exposing the second layer to the first pattern of the radiation, and developing the second positive tone developable material; and
exposing the first layer and said features to a second pattern of the radiation whereby one or more areas of exposure of the second pattern include one or more of said features, and whereby between one or more pairs of adjacent features there is an area of exposure of the second pattern extending inward from the adjacent features and terminating at an unexposed area of the second pattern, and whereby during the respective exposures of the second and first layers said absorbance prevents exposure to above energy-to-clear exposure dose of at least a portion of the first positive tone developable material underneath exposed portions of the second positive tone developable material.
2. A method according to claim 1 wherein the first positive tone developable material is a positive tone resist material.
3. A method according to claim 1 wherein the first positive tone developable material is a first positive tone resist material and the second positive tone developable material is a second positive tone resist material.
4. A method according to claim 2 wherein the radiation is ArF excimer laser radiation and the resist material is a resist material for use with ArF excimer laser radiation.
5. A method according to claim 3 wherein the radiation is ArF excimer laser radiation and the first resist material is a resist material for use with ArF excimer laser radiation and whereby the second resist material is a resist material for use with i-line mercury arc radiation or a resist material for use with KrF excimer laser radiation.
6. A method according to claim 3 wherein the radiation is KrF excimer laser radiation and the first resist material is a resist material for use with KrF excimer laser radiation and the second resist material is a resist material for use with i-line mercury arc radiation.
7. A method according to claims 1 further comprising patterning the first layer by developing the first positive tone developable material.
8. A method according to claims 1 wherein the substrate comprises a target layer facing the first layer of developable material, and constructed and arranged to be lithographically patterned with a desired pattern comprising a first sub pattern and a second sub pattern, whereby the first and second pattern of the radiation correspond to an image of respectively the first and second sub pattern.
9. A method according to claim 8 whereby the image of the second sub pattern is arranged in juxtaposed registry with respect to the image of the first sub pattern on the substrate.
10. A method according to claim 8 whereby the first and second sub patterns are respectively a first and second pattern of lines and spaces.
11. A method according to claim 10 whereby lines of the second pattern of lines and spaces are arranged in interlaced position on the substrate with respect to the lines of the first pattern of lines and spaces.