Measurements of current density distribution in shaped e-beam writers

• Four methods for current density mapping in shaped e-beam writers are compared.
• Spatial resolution and signal-to-noise ratio of each method are evaluated.
• These methods can be performed using native equipment of typical shaped EB writer.

In this paper, we present four measurement methods for the two-dimensional mapping of the current density distribution in variable-shaped e-beam writers. All the methods use only the native equipment of the e-beam writer which provides the advantage of relatively easy implementation. The first and second measurement methods are based on the knife-edge technique in which the e-beam is scanned in two directions across a Faraday cup opening and across shaping shutters of the forming system, respectively. In the third method, a phosphor screen is irradiated by a magnified e-beam spot and the current density distribution is represented by the luminescence image on the screen. The fourth method uses electron sensitive resist which is exposed by the e-beam. The developed resist is observed under a microscope and the current density distribution is judged from the resist profile. All the methods are demonstrated in an example, compared, and their spatial resolution and accuracy evaluated.

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