A novel digital x-ray topography system

X-ray topography (XRT) is recognized as being a powerful too] for directly imaging defects in single crystals, semiconductor wafers and epitaxially grown layers. The timely identification of defects can lead to increased yields and significant cost savings in wafer processing. The primary limitation to its general usage within the semiconductor community has been the difficulty in system use and difficulty in integration into an in-line analytical tool. We have developed a novel, high-speed digital XRT method that can be implemented on a standard high-resolution x-ray diffraction (HRXRD) system equipped with a wafer translation stage and a microfocus tube (or a small aperture in front of a standard point source). It is also appropriate for an in-line fab tool with robot loading and automated operation. In this paper, we discuss the theory and present examples from work undertaken on a variety of materials, including: silicon, compound semiconductors and ionic crystals. Reflection and transmission methods are illustrated. Data were collected on a HRXRD system with a microfocus source and a CCD detector, and an innovative software integration and processing algorithm. Algorithms for full automation of the alignment, exposure and data collection processes have been worked out. It is estimated that the dedicated XRT tool now in prototype form will be capable of scanning a full 300 mm wafer in reflection in under two hours at 50 mum resolution and can achieve <15 mum resolution.