Multiple path lens for electron beam writing device - has two perforated magnetic plates spaced and combined with focusing system

摘要

The multiple path lens for focusing a number of parallel beams of radiation for an electron beam writing device for forming a number of identical patterns on a semiconductor wafer in the production of integrated circuit clips, consists of two parallel perforated magnetic plates (1,2). The holes through the plates are in line and the plates can be permanent magnets. They can be of ferromagnetic material and form part of a large magnetic lens (10) with a winding (11) enclosed by an iron casing (12). The magnetisation can be varied by altering the current flow through the winding. In another design, one plate is stopped, having holes of different lengths through it, the spacing between some of the holes in the upper plate and those in the lower plate varying to give a variable magnetic force for correct forcusing. The writing device may use a hybrid lens with the radiation source near its front face, below a condenser lens and a deflection system.