Atomic force microscopy as a process characterization tool for GaAs-based integrated circuit fabrication

摘要

While developing the fabrication process for GaAs-based integrated circuits, numerous situations have been encountered where an in-line and post-process characterization tool which operates in a non-destructive manner was required. We will report several examples which demonstrate that the atomic force microscope (AFM) fills this characterization void in our laboratory. The AFM is extremely useful where the unintentional removal of small amounts of GaAs can be detrimental in the fabrication of devices with very thin active layers, e.g., FET channels within 30 nm of the GaAs surface. We have also characterized the use of AFM as a non-destructive tool to determine complete etching of 1.25 (mu)m Si(sub 3)N(sub 4) via holes for a two-level interconnect process. The AFM has been useful in optimizing the ion implant activation anneal conditions of Al(sub 0.75)Ga(sub 0.25)Sb epitaxial layers by comparing the morphology through RMS roughness measurements. Finally we have observed differences in wet etch results based on prior process history, such as 1-5 nm differences in etch depth and morphological differences of ion implanted vs. non-implanted areas. The results and implications from these various AFM processing studies will be presented in this paper.