Applications of atomic force microscopy/scanning capacitance microscopy in imaging implant structures of semiconductor devices

Abstract

Atomic force microscopy [G. Binnig et al., Phys. Rev. Lett. 56, 930 (1986)] and scanning capacitance microscopy [C. C. Williams et al., Appl. Phys. Lett. 55, 203 (1989)] (AFM/SCM) have been widely used to investigate the two-dimensional carrier profile of semiconductor devices. In this work, AFM/SCM was applied to both process control and failure analysis. Several different cases were studied. First, a commercially available integrated circuit device was cross sectioned and polished for the AFM/SCM investigation using standard scanning electron microscopy sample preparation techniques. Implant structures near the gate were clearly resolved. Second, a GaAs device with Zn thermally diffused through the opening of a Si3N4 mask was studied. The lateral diffusion length of Zn was determined. Third, two semiconductor devices, one good and one that had failed, were prepared by cross sectioning, followed by polishing. Implant profiles of similar structures on both devices were imaged. The thickness of the N-well structure was found to be thinner in the failed device by about 0.4 μm. These cases demonstrate applications of AFM/SCM in process control and device failure analysis.