Cell projection column for high speed electron-beam lithography system

Abstract

The cell projection column for the high throughput electron-beam lithography system (HL-800D) has been developed. This column forms a conventional variable shaped beam and five kinds of cell pattern beams with a maximum 5 μm dimension. A new in-lens three stage deflection system consisting of a magnetic and two electrostatic deflectors provides low distortion and high speed 5 mm square deflection at 50 kV. Beam shaping optics have a two stage deflector for rectangular beam sizing and cell beam selection. The settling times coincide with three stage deflection system to prevent extra overhead time. The beam shaping system has an inspection function for the cell aperture by switching the crossover focusing. Complicated deflection calibration systems are necessary to correct precisely in advance to exposure. To reduce the correction time, a simplified method which separates time dependent terms from whole correction terms, has been developed. This method decreases the total correction time and procedures, because time dependent terms generally consist of first order terms such as gain and rotation. The correction time is typically reduced to less than 1/10, if the correction term is limited to the first order term. The measured data are statistically averaged and improve the accuracy of the beam correction. Other features of the cell projection column are as follows: (1) long life LaB6 emitter, (2) automatic cell mask handling system, and (3) dry evacuation system. These items provide easy handling and high reliability of the electron beam column.