Photomask covered with light-transmissive and electrically-conductive polymer material
View Patent ↗A photomask by which no electrostatic damage or damage of a mask pattern due to electrification is produced. The photomask has a substrate; mask patterns formed on the substrate, which are made of a light blocking material and are covered with a light-transmissive and electrically conductive polymer material. Even the mask patterns which are isolated from each other on the substrate are electrically conductive with each other. Typically, the mask patterns are covered with an electrically conductive film made of the light-transmissive and electrically conductive polymer material. The electrically conductive film may have a thickness by which when foreign particles land on the electrically conductive film, an optical image of the foreign particles is defocused on a sample to be exposed in the exposure process, so that shapes of the foreign particles are not transferred. In this case, a pellicle, which is conventionally provided on the substrate, is unnecessary.
1. A photomask for a photolithography exposure process, comprising:
a substrate;
mask patterns formed on the substrate, said mask patterns being comprised of a light blocking material; and
a light-transmissive and electrically conductive polymer material covering the mask patterns and portions of the substrate between the mask patterns in a manner such that the mask patterns are electrically conductive with each other and with portions of the substrate between the mask patterns;
wherein the light-transmissive and electrically-conductive polymer is one of a transparent resin to which an electrically conductive material is added and a polymer having conjugated double bonds.
2. The photomask as claimed in claim 1 , wherein the mask patterns are covered with an electrically conductive film made of the light-transmissive and electrically conductive polymer material.
3. The photomask as claimed in claim 2 , wherein the electrically conductive film has a thickness by which, when foreign particles land on the electrically conductive film, an optical image of the foreign particles is defocused on a sample which is exposed during an exposure process, so that shapes of the foreign particles are not transferred to the sample.
4. The photomask as claimed in claim 1 , wheiein the mask patterns are isolated from each other on the substrate.
5. The photomask as claimed in claim 2 , wherein the electrically conductive film covers almost an entirety of a light irradiation area on the substrate in the exposure process, where the mask patterns are formed in the area.
6. The photomask as claimed in claim 2 , further comprising:
a pellicle, provided on a face of the photomask on which the electrically conductive film is formed, the pellicle having a portion which is positioned above the electrically conductive film and which has a sufficient transmittance for exposure light, by which when foreign particles land on the pellicle, an optical image of the foreign particles is defocused on a sample to be exposed in the exposure process, so that shapes of the foreign particles are not transferred to the sample.
7. The photomask as claimed in claim 1 , wherein the substrate is one of a quartz substrate and a glass substrate.
8. The photomask as claimed in claim 1 , wherein the transparent resin is one of polypropylene, polystyrene and ABS resin.
9. The photomask as claimed in claim 1 , wherein the electrically conductive material is one of metal powder, metal fibers, metal-coated fibers, carbon-coated fibers and metal flakes.