X-ray diffraction has been used to measure the intensity profile of the two-dimensional rods of scattering from a single interface buried inside a bulk material. In both Si(l 1 l)/a-Si and Si(l 1 l)/SiC>2 examples there are features in the perpendicular-momentum-transfer dependence which are not expected from an ideal sharp interface. The diffraction profiles are explained by models with partially ordered layers extending into the amorphous region. In the Si(l 1 l)/a-Si case there is clear evidence of stacking faults which are attributed to residual 7x7 reconstruction.

We demonstrate high resolution reduction imaging in the soft x-ray spectral region using multilayer-coated reflective optics. In particular, a Schwarzschild objective was used at 20:1 reduction with 14 nm radiation to image line and space features from a transmission mask onto a resist-coated silicon wafer with a resolution better than 0.1 μm. The mirrors of the objective were coated with Mo/Si multilayers to provide nearly 40% reflectance at near-normal incidence for the 14 nm radiation. Our results demonstrate that multilayer coatings are capable of enhancing the reflectance of optical components at soft x-ray wavelengths without significantly degrading their imaging performance.

We have measured the stress in Mo/Si multilayer films deposited by magnetron sputtering, using the wafer-curvature technique, and find a strong dependence on background pressure. We find that for multilayers containing 40 bilayers of-4.3 nm Si layers and-2.6 mn MO layers, the stress increases from approximately-280 MPa (compressive) to-450 MPa as the background pressure in the deposition chamber (i.e., measured just prior to deposition) decreases from 1.0X lo-' to 6.0X lo-' Torr. For multilayers of the same period but with thicker MO layers, the dependence on backg&und pressure is even stronger. X-ray (h=0.154 mn) diffraction measurements reveal only.: a slight increase in interfacial roughness for films deposited at high background pressure, but no evidence was found for any differences in the microstructure of the polycrystalline MO layers that bomprise these structures. The peak soft x-ray (X=13 nm) reflectance, which is sensitive to interfacial roughness at longer spatial wavelengths, also shows no correlation with background pressure or stress. Atomic concentrations of incorporated oxygen and carbon, measured with Auger electron spectroscopy, were found to be less than-0.5 at. % for all samples. However, the average hydrogen concentration, as determined from forward-recoil-scattering measurements made using a 2.6 MeV He beam, was found to increase linearly with background pressure. We discuss possible mechanisms for the observed dependence of film stress on background pressure, including gas incorporation and the affect of residual gas atoms on adatom mobility.

The structural and optical properties of Mo/Si and Ru/Si x-ray multilayers prepared by sputter deposition in argon have been examined using high-resolution transmission electron microscopy, optical profilometry, and x-ray and soft x-ray reflectance. We find that for Ru/Si, similar to previous results for Mo/Si, lower argon pressure during deposition results in smoother layers and higher reflectance. For low-pressure deposited multilayers, interfacial roughness is negligible compared to interfacial diffuseness; the presence of amorphous interlayer regions in both of these systems is the major cause of reduced reflectance.

We have examined the correlations between direct surface-finish metrology techniques and normalincidence, soft x-ray reflectance measurements of highly polished x-ray multilayer mirrors. We find that, to maintain high reflectance, the rms surface roughness of these mirrors must be less than ~ 1 Å over the range of spatial frequencies extending approximately from 1 to 100 µm(-1)1 (i.e., spatial wavelengths from 1 µm to 10 nm). This range of spatial frequencies is accessible directly only through scanning-probe metrology. Because the surface-finish Fourier spectrum of such highly polished mirrors is described approximately by an inverse power law (unlike a conventional surface), bandwidth-limited rms roughness values measured with instruments that are sensitive to only lower spatial frequencies (i.e., optical or stylus profileres) are generally uncorrelated with the soft x-ray reflectance and can lead to erroneous conclusions regarding the expected performance of substrates for x-ray mirrors.