Patent ID: 8781213

Claim:
An alignment system for aligning a wafer when lithographically fabricating on the wafer a light-emitting diode (LED) having a wavelength λ LED , comprising: the wafer, with the wafer having at least one wafer alignment mark; a rough surface formed on or above the wafer alignment mark and on a layer having a refractive index n, the rough surface having a root-mean-square (RMS) surface roughness σ S that is within one of the following ranges: i) from about 2λ LED to about 8λ LED ; ii) from about (0.5)λ LED /n to λ LED /n; or iii) from about λ LED /n to λ LED ; a light source that illuminates the at least one wafer alignment mark with alignment light having a wavelength λ A that is in the range from about 2σ S to about 8σ S ; a lens configured to form an image of the at least one wafer alignment mark at the alignment light wavelength λ A ; an image sensor configured to detect the image and form therefrom a digital alignment mark image; and an image processing unit electrically connected to the image sensor and configured to receive and compare the digital alignment mark image to an alignment reference to establish a wafer alignment with respect to the alignment reference.