Weak Illuminators

Illumination can take the form of on-axis or off-axis light. On-axis is used for phase-shifting techniques that use two-beam imaging. Off-axis takes the conventional, on-axis three beam imaging and discards one set of the higher diffraction order light,thus producing a two-beam imaging system. The light can be shaped into different field intensity shapes to provide the best illumination for the feature being imaged.

Illuminators can be strong, where no light is present between illuminator poles, or weak, where there is light between the poles. Weak, off-axis illumination provides contrasts that are slightly less than strong illumination, but can accommodate more types of features and pitches.

PAL provides design and manufacturing services for weak illuminators that can be used in exposure tools allowing insertion of a filter aperture.

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