Transporter for optical spectrum analyzer in alignment system

Abstract

A Fabry-Perot resonator, also called a Fabry-Perot cavity, is a spectroscopic device of extremely high resolving power and is a very useful tool for alignment of mask and wafer for the multiple exposures necessary to make a semiconductor integrated circuit. When a Fabry-Perot cavity is used for alignment in a multi-exposure imaging procedure, the cavity itself must be very accurately aligned for each exposure. For proper alignment system operation, it is necessary that one of the mirrors of the resonant cavity be fixed with respect to the mask, and the other mirror be fixed with respect to the wafer. This invention provides a mechanical system and method to maintain the alignment of a Fabry-Perot cavity for each exposure. This invention describes a technique in which the Fabry-Perot cavity is transported from one exposure area to the next without need for realignment. After an exposure is completed, the mechanical link between one of the mirrors and the mask is designed to be decoupled while the mask and wafer are relatively displaced for the next exposure. As a result, during the displacement, the relative distance between the optical mirrors of the Fabry-Perot cavity is maintained, as well as the relative orientation. After the displacement is completed, the mechanical link is then re-established so that the alignment system performs in an identical manner for each exposure site.