Alignment Signal from a Mark Deformed by Molecular Beam Epitaxial Overgrowth for Focused Ion Beam Implantation

The geometry of an alignment mark is deformed by molecular beam epitaxial (MBE) overgrowth on it. The secondary electron intensity profile was calculated by using Monte Carlo simulation when a focused ion beam (FIB) scanned across the deformed mark. The calculated result agreed with the measured one and we confirmed that this calculation method can be used even for complicated marks. The peak positions are very distinct after MBE growth and the measured alignment error after growth of a 1 µm layer was less than 0.3 µm. A 4 µm thick multi-layered/doped structure was fabricated by an iterative process in which MBE growth was followed by FIB implantation 4 times with an alignment error of less than 0.5 µm.