| 摘要 |
<p>Multi-beam lithography apparatus is used for writing patterns on a substrate (14) such as a wafer for ICs. The patterns may have details of various dimensions. In order to enhance the production rate, it is attractive to write fine details with a small spot 16 and large details with a large spot. It is known to vary the spot size by varying the emissive surface of the electron source. In accordance with the invention the spot size is varied by varying the size (22) of the beam limiting aperture (20), thus enabling optimization of the beam current in dependence on the spot size. A preferred embodiment is provided with an additional (condenser) lens (24) such that the object distance remains constant when the magnification of the lens system (18, 24) is varied.</p> |
