1. Field of the Invention
The present invention relates to an immersion exposure technique used in manufacturing a semiconductor device and, for example, to an immersion multiple-exposure method and immersion exposure system for separately performing multiple exposure of micropatterns and non-micropatterns.
2. Description of the Related Art
In a recently proposed technique, in forming a highly integrated semiconductor circuit device, patterns to be exposed are divided into micropatterns and non-micropatterns and double-exposed to a photoresist film under illumination conditions optimum for the respective patterns (e.g., Jpn. Pat. Appln. KOKAI Publication No. 2000-349010). Immersion exposure will be described as an example. First, an ArF organic anti-reflection material is applied to the element formation surface (major surface) of a wafer by spin coating and baked at 215° C. for 1 minute, thereby forming an 80-nm-thick anti-reflection film. Then, an ArF positive resist is applied to the anti-reflection film by spin coating and baked at 90° C. for 1 minute, thereby forming a 400-nm-thick photoresist film. Next, an immersion exposure protective film is applied to the photoresist film by spin coating and baked at 90° C. for 1 minute.
An ArF excimer laser immersion exposure apparatus exposes the wafer having the stacked structure of the anti-reflection film, photoresist film, and immersion protective film using a halftone mask having a transmittance of 6% under conditions of NA=0.78 and ⅔ annular illumination. The wafer is exposed again using a halftone mask having a transmittance of 6% under conditions of NA=0.92 and σ0.97. The wafer is baked at 100° C. for 1 minute and developed in a 2.38-wt % aqueous solution of tetramethylammonium hydroxide (TMAH), thereby forming a resist pattern.
When the resist pattern formed by the above-described double-exposure was inspected by an optical defect inspection apparatus (2360 available from KIA), a number of defects were found, and the defect density was about 0.7 pieces/cm2. These defects are presumably produced upon double-exposure in immersion exposure because dust particles produced in the first exposure step stick to the immersion protective film and shield the irradiation light in the second exposure step.
USPTO Backgrounds
USPTO Backgrounds