New alignment marks for improved measurement maturity

Abstract:
With shrinking dimensions in the semiconductor industry the lithographic demands are exceeding the parameters of the standard optical lithography. Electron beam direct write (EBDW) presents a good solution to overcome these limits and to successfully use this technology in R&D as well as in prototyping and some niche applications. For the industrial application of EBDW an alignment strategy adapted to the industrial standards is required to be compatible with optical lithography. In this context the crucial factor is the overlay performance, i.e. the maturity of the alignment strategy under different process conditions. New alignment marks improve the alignment repeatability and increase the window of the signal-to-noise ratio towards smaller or noisier signals. Particularly the latter has proved to be a major contribution to a higher maturity of the alignment. A comparison between the double cross and the new Barker mark type is presented in this paper. Furthermore, the mark reading repeatability and the final overlay results achieved are discussed.