Abstract: A method for high precision position measurement of two-dimensional structures such as structures on semiconductor wafers or masks, utilizing a reference mask having a two-dimensional grid, the relative position of the structures relative to the grid being identified by opto-electronic scanning using an image sensor and subsequent image processing. The absolute position of the structures to be measured can then be identified from the position of the grid elements. A reference mask is preferably employed whose grid elements carry a binary coding which can be read and decoded by the image processing means. The coding thereby indicates the position of the grid elements in the grid.

Abstract: In the optical imaging of two subjects located in different object planes, at least one objective should be capable of being displaced for focusing relative to the object planes, being displaceable absolutely in a shift-free manner and with a very high positioning reproducibility. To this end, a positioning drive, particularly a piezo positioning drive, effects movement at a housing section which is displaceable relative to the object planes and at least carries the objective, whereby the displaceable housing section must be connected to the remaining, stationarily situated housing via resilient connections which are formed by elastically deformable weak points of the housing. Apparatus fashioned in such a manner are employed particularly for automatic mask adjustment in the transfer of structures in the sub micrometer range on the semiconductor wafers by way of x-ray lithography.