Grain size control of diamond membrane for X-ray mask by use of fluidized bed pretreatment

Using a fluidized bed for pretreatment of the substrate and changing the nucleation density, we have controlled the grain size of 76-mm-diameter diamond membranes for X-ray lithography, formed by microwave plasma chemical vapor deposition (CVD). The nucleation density ranged from 8.4 x 10(5) mm(-2) to 3.4 x 10(8) mm(-2) for pretreatment time ranging from 20 min to 600 min. After pretreatment, we fabricated continuous films. The mean grain size of film fabricated after 600 min of pretreatment was 1/1.4 that of film fabricated after 20 min of pretreatment. The results of evaluation by X-ray diffraction (XRD) and Raman spectroscopy of the films after the two pretreatment times showed the same crystallinity of (111)-textured polycrystalline diamond with low impurity concentrations. A subsequent study of visible light (lambda = 633 nm) transmittance for free-standing membranes indicated that scattering of incident light; was minimized due to the reduced grain size.