<title>New electron-beam mask writing system for 0.25-um lithography</title>

摘要

A new electron beam (EB) mask writing system based on both the Hitachi HL-700MIII and HL-800D systems is developed. The target of the system is a 0.25 micrometers design rule in semiconductor mass-production. To improve critical dimensions (CD) to better than 0.03 micrometers , an acceleration voltage of 50 kV is used with a variable shaped beam method. Further, EB proximity correction using a pattern area density map which is the same as that of HL-800D has been adopted for the improvement of pattern width linearities. This correction system, which consists of hardware only, covers the entire mask area. In the mechanical system, continuously moving stage with constant velocity and three-axis active vibration- isolation are used to improve positioning accuracy to better than 0.04 micrometers . In addition, a new mask handling system in which a robot carries the mask realizes automatic transportation without human assistance. Some experiments to evaluate the new system have been performed. In particular, the characteristics of masks written with an EB accelerated to 50 kV have been investigated. The results of CD pattern uniformity for a 1 micrometers line pattern over the entire mask area are better that 0.025 micrometers . In addition, pattern linearity using EB proximity correction is within +/- 0.03 micrometers . A stitching accuracy of 0.037 micrometers is obtained.