25 August 1987 Linewidth Uniformity: A Critical Evaluation Of Spray Geometry And Process Interactions In Ultrasonic Nozzles
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Spatial linewidth replication is a dominant yield limiting factor for most current photolithography processes, typically consuming,/ 50% of the total linewidth variation allowance. Therefore, the reduction of across wafer variation is critical to successful process development. In this study, the primary factors affecting spatial linewidth replication were investigated. These factors include agitation uniformity, wafer rotation rate, develop temperature control, and photo-optimization. Key results are: 1. Nitrogen assisted ultrasonic spray nozzles produced a spatial linewidth standard deviation of .03 μm, compared to .05 μm for a fan spray nozzle. 2. Developer consumption for ultrasonic spray nozzles is approximately 60% less than for standard fan spray nozzles. 3. Head positioning of ultrasonic nozzles is less critical relative to fan spray nozzles for standard organic and inorganic developers. Head positioning for both ultrasonic and fan spray is critical when using high contrast MIF developers. 4. Rotation speeds of 600 - 1000 rpm were found to be optimal for both ultrasonic and fan spray. 5. Developer temperature controls parallel CD variation trends and can be minimized by use of developer temperature controllers and/or exhaust controllers. 6. Photo-optimization typically produced a 3-fold or greater improvement in linewidth uniformity across the wafer. The effect upon linewidth uniformity is demonstrated in a systematic study of the predominant variables.
© (1987) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
David DeBruin, M.Richard Hannifan, Marie Ha, Kenneth Sautter, "Linewidth Uniformity: A Critical Evaluation Of Spray Geometry And Process Interactions In Ultrasonic Nozzles", Proc. SPIE 0771, Advances in Resist Technology and Processing IV, (25 August 1987); doi: 10.1117/12.940338; https://doi.org/10.1117/12.940338

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