Introduction and Background
The work presented in this paper is part of an ongoing project which uses electrical test structures for the characterisation of advanced photomasks. Previous publications have demonstrated that on-mask test structures are capable of fast and repeatable sheet resistance and critical dimension (CD) measurements on binary and alternating aperture phase shifting masks (Alt-PSMs) [1], [2], [3], [4]. More recently, industry standard optical metrology patterns have been adapted into electrical equivalents on binary masks. These have been used to investigate iso-dense proximity effects [5], to characterise the GHOST proximity correction technique [6] and to compare different metrology methods [7]. The fabricated masks also contained test structures to investigate the dimensional mismatch between closely spaced chrome features [8]. A plate which contained a large number of these structures was subsequently fabricated and this provided an unprecedented volume of data on dimensional mismatch [9] in a photomask manufacturing process.