The present invention relates to an electronic beam drawing apparatus, and in particular to, an electron beam drawing apparatus capable of effecting a drawing with a high precision even when there appears a phenomenon in which an organic substance of a drawing objective specimen fixes onto the apparatus.
An electron beam drawing method develops a higher resolution as compared with the conventional optical transcribing method and is hence broadly employed in a pattern generate operation for a precision of a submicron region. The electron beam drawing method is efficient not only in the fine work but also in a highly accurate position alignment. The reason for the high precision of the position alignment resides in that a mark disposed on the side of a substrate is detected by a highly focused electron beam, namely, the detection is accomplished with a high accuracy and in that even when a drawing objective specimen is deformed in an intermediate process, the drawing can be conducted by correcting the deformation.
In the conventional electron beam drawing apparatus, as shown in FIG. 2, an electron beam 2 emitted from a filament 1' of an electron gun 1 is focused and is then shaped through several electron lenses 3, that is, the shape of the electron beam 2 is controlled so as to be deflected by a deflection lens 4 of which an amount of deflection of the beam 2 is controlled by means of an apparatus not shown, so that the beam 2 is irradiated onto a predetermined position of a drawing objective specimen 6 arranged on a movable stage 5. In this operation, a reflected electron 7 is captured by a reflection electron detector 8 and is then processed as positional information by a signal processor 9. As the reflection electron detector 8 in this process, there has been employed a combination including a semiconductor diode, a scintillator, and a photoelectric multiplier. An example of the apparatus of this type has been described in pages 88-91 of the Journal of Vacuum Science and Technology, B Vol. 5, No. 1, Jan/Feb 1987, or in pages 932-935 of the Journal of Vacuum Science and Technology, 19 (4), Nov/Dec 1981.
Since an electron beam is irradiated onto an electron beam resist as an organic film in the electron beam drawing apparatus, there appears a phenomenon in which a product as a result of a reaction effected through the electron beam irradiation is vaporized or an organic substance of the resist is vaporized by the heat produced at the irradiation. A portion of these organic substances or the like is exhausted by means of a vacuum pump and another portion thereof fixes onto parts of the drawing apparatus. In particular, as can be seen from FIG. 2, the reflection electron detector 8 is arranged at a position quite near to the drawing objective specimen 6; in consequence, the amount of the organic substances fixed onto the parts is increased. When the organic substances as an insulating material fix onto a surface of the reflection electron detector 8, there occurs a phenomenon in which due to the reflected electrons 7, electric charges are accumulated on the insulator such as the organic materials fixed on the surface of the detector 8. Because of the accumulated electric charge, the electron beam 2 undergoes a deflection in an electric field produced by the accumulated electric charge; in consequence, there arises a problem that the electron beam 2 does not correctly effect the drawing through predetermined positions determined by the deflection lens 4, which leads to an error in the drawing position.