A single bend energy filter for controlling deflection of a charged particle beam is provided. It includes a first array of electrodes and a second array of electrodes to define a beam channel for the charged particle beam to pass through; an unmatched steering electrode among the first array of electrodes for tuning the bend angle of the charged particle beam; and a plurality of electrical biases applied to the first array of electrodes, the second array of electrodes and the unmatched steering electrode, wherein portion or all of the electrodes have different shapes. A method for controlling deflection of a charged particle beam is also provided. Depending on use of an unmatched steering electrode, the bend angle of the charged particle beam may be fine-tuned, so as to effectively control the deflection of the charged particle beam to achieve a centered beam at the wafer plane.