Production control of shallow trench isolation (STI) at the 130-nm node using spectroscopic ellipsometry-based profile metrology

Abstract

Shallow Trench Isolation (STI), is a critical process module in the manufacture of advanced CMOS devices. To achieve proper control of the STI process, multiple parameters such as film thickness, etched trench depth, and critical dimension (CD) must be measured with a high degree of precision and accuracy. Historically, these varied parameters were required to be measured independently using different metrology techniques/tools. Film thickness required measurement via reflectometry or ellipsometry, etched trench depth required measurement via profilometer or Atomic Force Microscope (AFM), and CD required measurement via low voltage Scanning Electron Microscope (CD-SEM). This paper will demonstrate the use of Spectroscopic Ellipsometry, via KLA-Tencor’s SpectraCD tool, to simultaneously provide all critical parameters of interest for the STI process, with a single in-line measurement. This metrology technique has been developed and evaluated for process control and product disposition at STI etch, on 130nm generation logic devices manufactured in two Texas Instruments’ fabrication facilities -- the DMOS 5 200mm facility and the DMOS 6 300mm facility. A brief description of the SpectraCD measurement theory and STI profile measurement solution for both dense and isolated structures will be given. Details will be provided on the use of real time regression to accelerate metrology model development. This will be followed by data generated from actual STI production material. Precision-to-tolerance (P/T) ratios well below 0.1 will be demonstrated for all parameters of interest on the STI etch measurements. Measurement matching across multiple SpectraCD tools, well within 130nm node process tolerances, will be demonstrated. Correlation of these measurements to other baseline metrology techniques (profilometer, Spectroscopic Ellipsometer or SE, CD-SEM) will also be presented. Finally, a discussion of the Return-on-Investment (ROI) that may be realized from combining three separate measurements into a single measurement will be provided.