Method and apparatus which enable high resolution particle beam profile measurement

The PSF for a metrology array for high resolution particle beam profile measurement has been improved by improving five major elements of the metrology array. While improvement in each of the five elements provides and improved PSF, a combination of all five of the elements provides an unexpected synergistic effect. The individual elements include the use of a plurality of slots as apertures; use of a high-Z material in forming the array; employing sidewalls on the slotted opening apertures where the sidewall forms an angle with a horizontal surface at the base of the array which is at least 75°; employing a knife edge where the upper corner radius ranges from about 1 nm to about 5 nm; and providing a surface finish at the upper corner of each knife edge which is less than 5 nm RMS.