Development of the large field extreme ultraviolet lithography camera

We have developed a three-aspherical mirror system which is capable of replicating in a large exposure area (30 mm×28 mm). This system consists of the synchronized scanning mechanism of a mask and a wafer, the alignment optics between a mask and a wafer, the focus detector of a wafer position, and the load-lock chamber for exchanging wafers. The aspherical mirrors have a figure error of 0.58 nm and a surface roughness of 0.3 nm. To obtain a high efficiency mirror, a couple of mirrors were coated with a graded d spacing Mo/Si multilayer. The peak reflectivity is 65% at the wavelength of 13.5 nm. The wavelength matching of each mirror spans 0.45 nm. The mirrors were aligned with a Fizeau-type phase shift interferometer, and a final wave front error of less than 3 nm was achieved. Exposure experiments carried out at NewSUBARU synchrotron facility and a diffraction limited resolution of 56 nm was obtained in an exposure-field size of 10 mm×2 mm in static exposure. Furthermore, fine patterns in an area of 10 mm×5.2 mm were obtained using the mask and wafer synchronized scanning stages. These results revealed that this system can be applied to fabricate large scale integrated devices.