1. Immersion optical lithography: theory, status and trend --- ELEC5070 Termpaper Topic PAN YUEYUE Nov/26/2014

2. Content Why do we need immersion lithography? From contact lithography to projection lithography Immersion lithography theoretical analysis Manufacture issues –Lens-photon-photoresist induced chemical reaction –Bubble problems –Scanning station Forecast the future development

3. Why do we need the immersion lithography? Get start from the resolution and depth of focus Device integration Enrichment in resolution and DOF New method in microelectronics fabrication Moore’s Law  Integrated and smaller scale

4. From contact lithography to projection lithography Contact, proximate, and projection lithography Ref: http://www.lithoguru.com/scientist/lithobasics.html

5. Immersion lithography theoretical analysis The resolution and depth of focus (DOF) in the immersion lithography. Radiation source (wavelength)

6. Manufacture issues Lens-photon-photoresist induced interaction Materials utilized –optical part: calcium fluoride (CaF 2 ) –Liquid: water for wavelength in 193 and PFPE for wavelength in 157nm –Photoresist: organic Substrate water radiation lens Photon induced reactions lens radiation Substrate water corruption

7. Manufacture issues Bubble problems Where is the bubble ? Photon induced reaction Gas bubbles dissolved in the water

8. Manufacture issues Scanning Station in bulk fabrication WBC: uniform contact between the wafer and the fluid –Large volume of water –shear-stress on the lens in the step and scan system LBC: This method overcomes the drawbacks of WBC –there is no resistance between fluid and len, the shear stress can be minimized by circulating the water in the direction of the scanning –discontinuity between the wafer and the chuck lead to liquid leakage or bubbles Water based configuration Lens based Configuration

9. Forecast the future development Back to these to formula Improve the refractive index  to a bottleneck –The total internal reflection (depends on the three indexes) –Optical denser medium  optical rare medium Improve the radiation source  improve the wavelength