A large angle electrostatic deflection, variable shaped, electron beam exposure system

Abstract

In electron beam direct writing, a capability of ‘‘one chip within one deflection field’’ can reduce time wasted in stage moving, and eliminate field stitching errors in a chip. These advantages lead to high throughput and high overlay accuracy for successful VLSI fabrications. A large angle electrostatic deflection, variable shaped, electron beam exposure system (EB57) has been developed to achieve this capability. The key EB57 technologies are a large angle electrostatic deflection and high speed deflection control. Newly developed multiple electrostatic deflectors were designed using an in‐lens, dual channel deflection method. In this method, two types of field and subfield deflectors are equipped inside a projection lens. Deflectors free of third and fifth θ components can provide a large angle of deflection with a 10 mm2 field. 18‐bit digital‐to‐analog converters, and ±800 V amplifiers effect this large field deflection. The high breakdown voltage for the amplifiers is attained by connecting vertical power MOSFETs in series. The settling time of the amplifiers is less than 10 μs at 1/64 full scale. Amplifiers for subfield scanning and beam shaping have a 250 ns settling time at full scale. To correct chip distortions, deflection distortions, and stage positioning errors, a new data correction method that takes rounding off errors into consideration has been applied to a high speed arithmetic unit. This EB57 system can write from 7 to 10 4‐in. wafers per hour with 0.5 μm lithography.