A Solid State Electron Detector for the EB60 Electron Beam Lithography System

Abstract

This paper discusses the development of a new solid state electron detector (SSD), which is a key component for a high-precision, high-throughput EB direct exposure system, the EB60. The SSD is a low-noise, fast-response detector for a weak input electron beam signal having a nanoampere current and energy of approximately ten kilo electron volts. The SSD has a new metallization structure on the active area for eliminating the effect of incident photons coming from an optical wafer height sensor. For the smallest input signal (15 keV electrons) operation, an SSD with a wide active area of 25 mm² has a current gain of 2300, a rise time of less than 350 ns and a leakage current of 80 pA; this is negligible to the output signal of a microampere. A long-term stability of a 3% current gain decrease after electron beam bombardment for 1000 hours, and a leakage current of 100 pA after bombardment for 5000 hours have been obtained. A highly accurate, high-speed registration mark detection of 0.02 µm and 50 ms per mark has been achieved through the SSD.