Sram design to facilitate single fin cut in double sidewall image transfer process

Abstract

A double sidewall image transfer process for forming FinFET structures having a fin pitch of less than 40 nm generates paired fins with a spacing determined by the width of a sidewall spacer that forms a second mandrel. Here, the fin pairs are created at two different spacings without requiring the minimum space for the standard sidewall structure. An enlarged space between paired fins is created by placing two first mandrel shapes close enough so as to overlap or merge two sidewall spacer shapes so as to form a wider second mandrel upon further processing. The fin pair created from the wider second mandrel is spaced at about 2 times the fin pair created from the narrower second mandrel. For some circuits, such as an SRAM bitcell, the wider second mandrel can be utilized to form an inactive fin not utilized in the circuit structure, which can be removed. In some embodiments, all dummy inactive fins are eliminated for a simpler process.