A Method to Improve Fabrication Accuracy of Three-Dimensional Microstructures in Focused Ion Beam Bitmap Milling

In focused ion beam (FIB) sputtering etching process, bitmap file is often used to store the dwell time and location information of ion beam. This paper presents a method for determining the grayscale value of the bitmap accurately. In this method, the variation of sputter yield and the curve form of the microstructures are taken into consideration. The proposed general formula can effectively compensate the error in the desired microstructures. This method is further applied to the production of modified bitmaps. Experimental results show that the shape accuracy of microstructures can be improved obviously.