Accurate self-calibration of advanced metrology and measurement systems

Abstract

In recent years there has been a rapid development of display technologies, with ever higher pixel density and ever smaller feature sizes being achieved. For example, modern smartphone displays now have densities of more than 800 pixels per inch (ppi) and have pattern elements down to 1.5 m (and they are likely to become even denser in the future).1, 2 These display improvements, however, have also given rise to dramatically higher photomask technology requirements. Indeed, in high-volume production for state-of-the-art displays, many mobile screens are exposed simultaneously from a meter-sized photomask.2 The associated requirements for the overlay precision (i.e., accuracy of lateral dimensions) are quite formidable. To verify the geometry of photomasks used for the production of smartphone screens, we have previously developed a metrology tool—known as the Prexision Mask Metrology System (Prexision-MMS)—which can be used for mask sizes up to that of Generation 8 (G8), i.e., 120