AbstractThe geometry of Berg-Barrett skew reflections (the normal to the specimen surface and the incident and reflected beam vectors are not coplanar) is analyzed with particular reference to (111) silicon. Angular relationships required for obtaining the 78 most intense such reflections are presented on stereographic projections. Skew reflections are utilized to adapt the Berg-Barrett technique of extinction-contrast micrography to the examination of the (111) wafers generally used in integrated circuit technology. Skew reflections are shown to be more suitable for Berg-Barrett micrography than the zero-layer reflections described by Newkirk; in particular, their versatility in providing a means of varying the angle of incidence of the X-ray beam for a specific reflecting plane is demonstrated. A relatively simple experimental arrangement is described for recording skew reflection images. It permits a high resolution X-ray sensitive plate to be placed parallel to the specimen, and their separation to be increased to as much as 5 mm without excessive loss of resolution ; this avoids both image distortion and surface scattering. Furthermore, the specimen area recorded in a single micrograph is 1-3 cm2, which is large enough to eliminate the need for scanning. Exposure times are very short, in the order of 10 min. Micrographs of boron-diffused silicon are presented showing device components delineated by solute strain, strain fields induced in epitaxial silicon films by underlying buried-layer diffusions, and diffusion-induced Lomer-Cottrell dislocations. These micrographs demonstrate the resolution and contrast obtainable over large specimen areas. The capability of the Berg-Barrett technique is discussed in the examination of the near-surface regions directly involved in device fabrication and operation.
On the Stability of 3C-SiC Single Crystals at High Temperatures