Accurate pattern registration for integrated circuit tomography

As part of an effort to develop high resolution microtomography for enginee red structures, a two-level copper integrated circuit interconnect was imag ed using 1.83 keV x rays at 14 angles employing a full-field Fresnel zone p late microscope. A major requirement for high resolution microtomography is the accurate registration of the reference axes in each of the many views needed for a reconstruction. A reconstruction with 100 nm resolution would require registration accuracy of 30 nm or better. This work demonstrates th at even images that have strong interference fringes can be used to obtain accurate fiducials through the use of Radon transforms. We show that we are able to locate the coordinates of the rectilinear circuit patterns to 28 n m. The procedure is validated by agreement between an x-ray parallax measur ement of 1.41 +/-0.17 mum and a measurement of 1.58 +/-0.08 mum from a scan ning electron microscope image of a cross section. (C) 2001 American Instit ute of Physics.