Defectivity issues in topcoat-free photoresists

One method being used to reduce the overall lithography process complexity and cost is to utilize a topcoat-less photoresist. Development of these materials utilizes an additive to prevent water penetration and thus forms the same surface property characteristics created by advanced topcoats. The main challenge for topcoat-less resists is increasing the hydrophobicity without causing too much inhibition at the resist surface - which can lead to bridging or residue defects. The key to such a design is in the balance between leaching control versus dissolution characteristics of the resist without disregarding lithography performance and increasing defectivity. The addition of materials into existing ArF photoresists systems have been shown to modulate the contact angle in water-based immersion lithography. The authors have focused this work on the reduction of defects to achieve defectivity levels that are equal or better than existing systems.