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

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 [1]. 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.