3D microscopic model of electron amplification in microchannel amplifiers for maskless lithography

A novel approach for high-throughput maskless lithography is being developed by Arradiance Inc. The patented core technology is based on the combination of field emitters and microchannel electron amplifiers (MCAs) to produce a large array of individually controlled, high brightness electron beams. Brightness, stability, beam to beam uniformity, energy spread, achievable current, and many other parameters must be optimized simultaneously over a large field. Many of these parameters are determined by the characteristics of the amplification process in the MCA array that amplifies, stabilizes and shapes each electron beam. This paper describes a new three dimensional Monte Carlo model of the electron amplification process in a single microchannel. For a given input current and known MCA parameters, we calculate the (generally nonlinear) potential distribution along the channel utilizing a macroscopic saturation model. The static (3D with axial symmetry) electric field is calculated in and around the microchannel from the predicted potential distribution. That field is used to calculate individual electron trajectories along the pore length until their subsequent collision with the pore walls or arrival at the pore exit. The amplification process caused by secondary electron emission from those collisions is modelled for each electron. Evaluation of a large number of input electrons allows the MCA output to be predicted. The model is very useful for optimization of the MCA structure and operational