Method of detecting and adjusting exposure conditions of charged particle exposure system

DETAILED DESCRIPTION An object of the present invention is to provide a method of accurately detecting exposure conditions such as a reduction ratio and rotational angle of a pattern that is transferred from a mask to a wafer in a charged particle exposure system, as well as a method of adjusting and establishing optimum exposure conditions of the charged particle exposure system according to the detected reduction ratio and rotational angle.
In order to accomplish the objects, a charged particle exposure system at least comprises an electron gun, an irradiation optical system, an incident mask deflector, a stencil mask, a reduction optical system, and a stage.
The stencil mask has a group of normal patterns and at least two mark patterns.
According to the present invention, a method of detecting and adjusting exposure conditions of the charged particle exposure system comprises the steps of: operating the incident mask deflector to apply charged electron beams emitted by the electron gun to each of the mark patterns of the stencil mask; projecting the electron beams passed through the mark patterns onto the surface of a sample on the stage through the reduction optical system; computing positional relations of images of the mark patterns projected on the surface of the sample; comparing the positional relations computed in the preceding step with positional relations of the mark patterns on the stencil mask, and computing a reduction ratio of the images on the surface of the sample or a rotational angle of the images; and calibrating operating conditions of reduction optical system according to the reduction ratio or rotational angle computed in the preceding step, thereby realizing a required reduction ratio or rotational angle.
According to the present invention of FIG.
1(A), an aperture pattern selecting deflector 55 comprises incident mask deflectors 56a and 56b located on the electron gun side of a stencil mask 6.
The stencil mask 6 has two mark patterns whose positional relations are known