Structural investigations of shadow masks by means of x-ray reciprocal space mapping

This paper presents high-resolution x-ray diffraction measurements of shadow masks. Shadow masks are used for in situ growing of one- and zero-dimensional semiconductor heterostructures. The masks are produced by selective etching of AlxGa1-xAs-GaAs heterostructures. The lateral dimension of these structures is in the range 10-300 µm; the thickness of the constituting layer varies between 1 and 10 µm. Structures with linear and crossgrid patterns have been measured. The reciprocal space maps of the initial structures show a distortion of the whole sample by the strain of the AlxGa1-xAs layer. After processing, this strain is reduced by an elastic relaxation of the parallel lattice constant. The three-dimensional masks lead to complicated intensity distributions in reciprocal space. The different contributions to the reciprocal space maps are identified by measuring symmetrical and asymmetrical reflections of specially designed structures. This knowledge is useful for the interpretation of the reciprocal space maps of other three dimensional samples, such as semiconductor devices.