Defect reduction with special routing for immersion lithography

Abstract

Abstract. This letter reports record-breaking low defect counts for immersion lithography, the mechanism for formation of particle-printing defects, and for two new exposure routings to achieve the low defect counts. Both new routings make the slot-scan directions parallel to the field-stepping directions, whereas in the normal routing the two directions are perpendicular to each other. From experimental data, the average defect count for one of the special routings is 4.8 per wafer, while it is 19.7 per wafer for normal routing.

Advances in Patterning Materials for 193 nm Immersion Lithography

“…Therefore, the critical velocity of the resist surface strongly influences both the maximum acceptable wafer scan rate (i.e., wafer throughput) and defectivity (i.e., yield). Much additional work has focused on how to prevent fluid loss by improvements to showerhead design , and stage speed, acceleration, and routing during exposure …”

“…In reality, the velocity at which fluid containment fails is not solely determined by the immersion surface but is also heavily impacted by a number of factors including showerhead design , and stage speed, acceleration, and routing during exposure . However, these simplified dynamic measurements of wetting and dewetting behavior and the accompanying empirical models have generally proved useful in immersion materials design and screening.…”

Optical lithography—present and future challenges

“…These particles are outside of the exposure field but can be printed later, if they remain undisturbed when the wafer moves them under the exposure field in the subsequent step-and-scan sequence. Special step-and-scan sequences, call routing [7], as shown in Fig. 13, can reduce the number of printed particles.…”