text: In semiconductor technology, it is conventional to fix wafers for various processing steps i.e. to fasten them on corresponding holding instruments. One method often used for holding wafers is to suction the wafers by means of a vacuum and release them from the fixture by applying atmospheric pressure after processing. Methods are furthermore known in which wafers are held on holding instruments by using wax. Other methods employ special adhesive films which lose their adhesive properties, and therefore make it possible to release the wafers, when a particular temperature is exceeded. Methods are also known in which wafers are fixed on adhesive films in order to be diced in a subsequent sawing process. In this case, the sawed subsections remain adhering on the adhesive film. It is furthermore known to employ an adhesive gel film in order to hold wafer subsections on a holding instrument for further processing.
  Devices for fixing two wafers relative to one another are furthermore known in which so-called spacers, a type of wedge, are inserted between two wafers arranged mutually parallel and are mechanically fixed on the edges of the wafers, as disclosed for example in the Applicant's DE 103 44 113 A1. The known devices have significant disadvantages. The gap between the wafers is extremely narrow, so that it is difficult to form a vacuum between the two wafers in a subsequent processing step, particularly when using large wafers with a diameter of about 300 mm. A further disadvantage is that misalignment of the two wafers can occur when the spacers are removed. In addition, the edge regions of the wafers may be damaged by the use of spacers which clamp the edges.