The role of AFM in semiconductor technology development: the 65 nm technology node and beyond

Abstract

The International Technology Roadmap for Semiconductors (ITRS) predicts that atomic force microscopy (AFM) will become an in-line metrology tool starting at the 65 nm technology node. Others argue that AFM is not suitable beyond the 65 nm node due to probe size limitations. This presentation examines the current state of AFM in semiconductor technology development and manufacturing. The following AFM applications are reviewed: post chemical mechanical polishing (post-CMP) and post reactive ion etching (post-RIE) topography measurements, critical dimension (CD) scanning electron microscopy (SEM) and optical scatterometry (OCD) calibration and long-term accuracy monitoring, across integrated circuit (IC) CD bias measurements (OCD lines vs. real circuit), optical proximity correction (OPC) modeling verification, non-destructive 3D metrology (resist, gate, sidewall offsets, holes and trenches). This current state is contrasted with upcoming requirements, benefits and limitations of metrology tools. The topics include the following: an application specific analysis of AFM limitations, the merits and limitations of transmission electron microscopy (TEM) as reference technique for AFM, CD SEM and OCD, the impact of sample-to-sample bias variation on total measurement uncertainty of TEM, CD SEM, OCD and AFM, the unique role of AFM in establishing across CD metrology correlation and accuracy, and need for a new type of intelligent in-line CD metrology tools, which would combine the merits of OCD, CD SEM and AFM.