Effects of image contrast and resist types upon line edge roughness (LER)

The effect of aerial image contrast upon line edge roughness (LER) of four different commercial resists-UV210, SEPR-463, Apex-E, and UVII-HS-is examined via scanning electron microscopy (SEM) and atomic force microscopy (AFM). Image contrast is varied by exposing both a detailed foreground pattern and a large open area background pattern on the same wafer location. Contrast varies from 0.37 to 1.0. In the case of UV210, LER measured via AFM is 2.55 nm at 1.0 contrast, 2.16 nm at 0.54 contrast, and 3.6 nm at 0.37. Results from other resists follow this trend, wherein no consistent correlation between LER and aerial image contrast can be drawn. SEM measurements also demonstrate no significant correlation between LER and image contrast in any resist type.

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