A soft-x-ray projection lithography system is developed by the use of multilayer mirrors. To determine the feasibility of a high throughput and a large exposure area, we developed a reduction system that consists of two-aspherical-mirror optics. The figure errors of aspherical mirrors are evaluated by a laser interferometer. The rms aspherical figure errors of concave and convex mirrors are 8.8 and 2.0 nm, respectively, which are not enough to yield a resolution of 0.1 µm. The reduction optics is constructed by adjusting the mirror position to compensate for aberrations, and some trial replications are performed. An exposure area of larger than 10 mm × 0.6 mm with a fine pattern of less than a quarter micrometer is achieved.

A two-mirror telecentric optic has been designed for soft x-ray reduction lithography with high throughput using synchrotron radiation. A resolution of 0.1 μm is achieved at a wavelength of 130 Å with a 15-mm ring field. In the design, aberrations, including distortion, are reduced using aspherical concave and convex mirrors with an ellipsoid surface at a numerical aperture of 0.07. Telecentric imaging is obtained by illuminating a reflection mask using focusing toroidal mirrors. The designed optics achieves a modulation transfer function (MTF) value of over 40% at a spatial frequency of 5000 lines/mm capable of resolving 0.1-μm lines and spaces. The depth of focus is ±1 μm. The distortion is <0.01 μm in the image field. The imaging field is a 12.5-mm radius ring field which enables a 15×15-mm field exposure by the ring-field scanning method. The reduction ratio is 1/5.

Homoepitaxial film growth maintaining primary surface structures of Si substrates was investigated by using the reactive ion beam deposition method proposed recently. This method uses ionized species of reactive SiH4 gas controlled in the low-energy region of less than 500 eV. At 100–150 eV, homoepitaxial film growth on Si(111) and Si(100) maintaining their primary 7×7 and two-domain 2×1 surface structures, respectively, can be achieved at the low temperatures of 650 and 600 °C, respectively. In addition, oxygen impurities on substrate surfaces, due to imperfect substrate cleaning and recontamination caused by residual gases in a growth chamber before film growth, were successfully reduced at 600 °C by irradiating the 100-eV controlled ionized species onto them.

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A new low-temperature film formation technique is proposed. It uses ionized species produced by an electron cyclotron resonance-type microwave ion source with reactive gases and controlled in the low ion energy region, less than about 500 eV. Good quality homoepitaxial films on Si(111) are obtained at 600 °C and 100–500 eV ion energy by using SiH4 as a material gas. By increasing the ion energy to 250-300 eV, homoepitaxial growth at 400 °C can be achieved. Polycrystalline Si films on the same type of substrates can also be obtained at 200 °C.