A Study of Resist Outgassing as a Function of Photoadditives Chemical Structure

Resist outgassing during exposure is a problem which is of importance both in UV lithography (248 nm or 193 nm) and vacuum lithographies (e.g., e-beam). It has been demonstrated by MIT Lincoln Laboratory with deep-UV and 193 nm lithographies that photo-products may outgas and condense on the exposure tool lens degrading its transmission. Specifically, for 193 nm lens materials, it was found by them that haloaromatic compounds were the most harmful, followed by aromatic and akyl outgassed photoproducts. Similarly, outgassing during e-beam lithography may interfere with the establishment of the high vacuums needed for exposure as well as degrade tool performance. Consequently, we have studied a variety of different chemical designs aimed at reducing outgassing of resists during exposure especially when it comes to deleterious moieties such as iodobenzene.