DUAL FOCUS SOLUTON FOR SEM METROLOGY TOOLS

There is provided a charged particle apparatus comprising: a particle beam generator, optics, a first and a second positioning device, both configured for positioning the substrate relative to the particle beam generator along its optical axis, and a controller configured for switching between a first operational mode and a second operational mode. The apparatus is configured, when operating in the first operational mode, for irradiating the substrate by the particle beam at a first landing energy of the particle beam and, when operating in the second operational mode, for irradiating the substrate at a second, different landing energy. When operating in the first operational mode, the second positioning device is configured to position the substrate relative to the particle beam generator at a first focus position of the particle beam and in the second operational mode, to position the substrate at a second, different focus position.