Scanning probe microscopy of deposits employed to image the current density distribution of electron beams

Abstract

The current density distribution in the final spot of an electron beam lithography system can be judged from beam diameter measurements performed by means of a knife edge method or recording beam crossover images with conventional lithographic media. Electron beam induced deposition allows to record traces of the current density distribution of the primary beam only, with very small contributions of secondary electrons and x rays. The readout of the focus and stigmation status is obtained by measuring the three-dimensional appearance of the deposit with a scanning probe microscope. To be able to find the few deposits after transferring the sample to the scanning probe microscope, a ‘‘spotter’’ chip was developed, which supports optical coarse positioning and can be easily scanned by probe microscopes. By scanning a sharp tip structure, deposited by electron beam near the center of the chip, the shape of the probing tip is imaged. This information can be used to unfold the image from the probe tip contributions. Results of beam intensity profiles obtained with this new method using a scanning force microscope are presented.