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The ArF immersion lithography is a probable technique for the application below 65 nm hp generation. The first immersion lithography scanner, the engineering evaluation tool (EET) being connected inline with a coat/developer (C/D) ACT12 (Tokyo Electron Ltd.), was completed in the end of 2004 and showed that a bit of residual water might make a watermark on the wafer. Tokyo Electron Ltd. and Nikon Corp. have challenged to resolve this problem from a point of view of improvements on the system components for production tools. Nikon improves on local water filling nozzle, wafer table and wafer loader. The nozzle and the wafer table in the exposure tool are optimized to diminish the residual water, while the wafer stage is driven at high speed for high throughput of the production tool. However a bit of water, the amount of which also depends on a topcoat material, may remain. The wafer loader should carry the wafer to the C/D before drying up it. Before post exposure bake (PEB), C/D rinses and dries the wafer immediately to prevent it from the generation of watermark by remaining water. The wafer handling condition including rinse of which is optimized using the ACT12 connected to the EET and have applied to the new C/D LITHIUSi+ connected to S609B, the first Nikon's immersion scanner for mass production.In this report, we present the latest immersion technology, including the wafer contamination control, which is developed through the collaboration between Tokyo Electron Ltd. and Nikon Corp.

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Immersion lithography with ArF light and Ultra Pure Water (UPW) is the most promising technology for semiconductor manufacturing with 65 nm hp design and below. Since Nikon completed the first full-field immersion scanner, the Engineering Evaluation Tool (EET, NA=0.85) at the end of 2004, Toshiba and Nikon have investigated overlay accuracy with the EET which uses the local fill nozzle. EET successfully demonstrated immersion tools are comparable in single machine overlay accuracy to dry tools, and immersion-dry matching has the same level overlay matching accuracy as dry-dry matching. EET also made it clear that overlay accuracy is independent of scanning speed, and both solvent-soluble topcoats, as well as developer-soluble topcoats can be used without degradation of overlay accuracy. We investigated the impact of the thermal environment on overlay accuracy also, assuming that a key technology of overlay with immersion tools must achieve thermal stabilities similar to dry tools. It was found that the temperature of supply water and loading wafer are stable enough to keep the overlay accuracy good. As for evaporation heat, water droplets on the backside of the wafer lead to overlay degradation. We have decided to equip the wafer holder of S609B, the first immersion production model, with an advanced watertight structure.

Ohmic contacts to n-GaN are evaluated by low frequency noise measurements. Ohmic contacts were formed by electron beam evaporation of Ti/Al and their rapid thermal alloying. The electron cyclotron resonance Ar plasma etched surface has a poor Ohmic contact with a typical contact resistance of 8.1´10 -3 W×cm 2 , while the as received surface had a better Ohmic contact with a lower contact resistance of 7.5´10 -6 W×cm 2 . The Ohmic characteristics are monitored by the 1/f noise measurements. Low resistance contacts give the typical 1/f noise characteristics, the amplitude of which increases with the square of the sample current I 2 , while high resistance contacts give the linear noise power dependence on the sample current I. We are able to evaluate, therefore, the quality of the electrodes most sensitive by the 1/f noise measurements. Assuming the relevant electron concentration between the electrodes, the Hooge parameter is estimated as a H = 5.3´10 -6 at room temperature.