Heavily boron-doped silicon membranes with enhanced mechanical properties for x-ray mask substrate

Heavily boron-doped silicon membranes which show substantial improvement in mechanical properties have been fabricated for x-ray mask substrate by eliminating the misfit dislocation from the membrane. The measured surface roughness, fracture strength, and residual tensile stress of the membrane are 20 Å peak to peak, 1.39×1010 and 2.7×109 dyn/cm2, while those of the conventional heavily boron-doped silicon membrane with high density of misfit dislocations are 500 Å peak to peak, 8.27×109 and 9.3×108 dyn/cm2, respectively. The differences between the two membranes are due to misfit dislocation. Young’s modulus has been extracted as 1.45×1012 dyn/cm2 for both membranes. Also, the lattice constant of strain-free membrane, the in-plane lattice constant of the conventional membrane, and the density of extra-half plane contained in the conventional membrane have been extracted as 5.424 Å, 5.426 Å, and 2.3×104/cm, respectively.