Maximising the process window in sub-half-micron optical lithography

✍ Scribed by G. Arthur; B. Martin; C. Wallace

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 258 KB
• Volume: 53
• Category: Article
• ISSN: 0167-9317
• DOI: 10.1016/s0167-9317(00)00283-5

✦ Synopsis

The effect of resist thickness on depth-of-focus (DOF) is examined. It is seen that for maximum DOF the maximum in-coupling point of the swing curve must be selected whether the substrate is highly reflective bare silicon or one utilising a bottom anti-reflective coating (BARC). In addition, it is shown that the maximum DOF on the BARC-coated substrate exceeds that on any point of the swing curve for the bare silicon substrate. The simulation parameters used have been highly refined to give excellent correlation with experiment over a wide range of conditions. Initial practical results are also presented which tend to confirm these simulated results.

I. INTRODUCTION.

Advanced IC manufacture continues to impose heavy demands upon optical lithography in both resist performance and lens design, and it will soon be necessary to obtain routinely dimensions below 180 nm at an imaging wavelength of 248nm. However, one of the consequences of defining dimensions below the wavelength of the incident radiation in production is that process control becomes of prime importance. Process control has many aspects but the work presented here concentrates on methods for maximising the depthof-focus (DOF) available in the imaging film through the use of bottom anti-reflective coatings and choice of resist thickness.