The efficacy of currently available repair techniques has been assessed for a wide variety of defect types encountered on advanced lithographic masks. Focused ion beam (FIB) with gas-assisted etching and deposition, electron beam induced chemical processing (EBIC), and atomic force microscope based nano-machining (RAVE) were among the different methodologies evaluated. Various types of optical phase-shifting masks for the 45nm lithographic node, as well as nano-imprint lithography (NIL) templates, were used as test vehicles. Defect imaging resolution, spatial process confinement, repair edge placement, end-pointing control, sample damage (undesired changes in topographic or optical properties), and future extendibility served as the primary metrics for gauging repair performance. The primary aim of this study was to provide a single "snapshot" in time of the current development status of each tool for the context of 45nm node mask repair specifications and by no means were there any expectations for a final solution to already be commercially available. However, the results obtained from these tests should provide useful feedback and information to help improve the learning cycle for the development of 45nm lithographic node mask repair systems.
Although various approaches can be used to quantify linewidth roughness (LWR), it is essential to determine it with
sufficient confidence. Statistical fluctuations inherent to the measurement process are making correlation between
performance and LWR challenging. To reduce uncertainty, line width variations and LWR need to be monitored online
in full automation by CDSEM. In this paper, we use this methodology to investigate the effect of LWR on
electrical performance for various device applications. Our results quantify the impact of LWR by using matching
The ability to measure profiles of high-aspect structures is important for the development of new integrated circuit fabrication processes. Delays in the development learning cycle frequently occur due to turn-around time associated with the logistics of off-line laboratory sectioning and analysis. Sample preparation techniques associated with existing cross-sectional imaging methodologies also necessitate destruction of the whole sample. Focused ion beam (FIB) sectioning has recently been used in conjunction with SEM imaging for profile acquisition inside the fabrication facility. However, full acceptance of FIB inside the cleanroom processing area has been slowed by concerns over the threat of Gallium contamination arising from the ion beam. There also exists uncertainty in the fidelity of FIB-based profile acquisition, due to the various artifacts associated with the ion beam mill sectioning process. In this article, the application of and difficulties associated with electron beam induced processing (etch and deposition) for obtaining feature profile shape information on masks and wafers will be described. Purely chemical reactions with much higher material selectivity and less damage have been employed to obtain microstructure profile information using various scanned electron beam tools. The superiority of electron beam induced deposition (compared to FIB) for passivation and replication of the surface topography prior to etching has also been demonstrated. In addition to electron and ion beam based sectioning, a novel atomic force microscope based nano-machining process has been developed for three-dimensional tomographic imaging of high-aspect features on masks and wafers. Images and profiles of feature regions not accessible with FIB/SEM or CDAFM methodologies will be presented. The challenges encountered for practical implementation of this new, non-beam-based, approach to sectioning will also be discussed. Advantages of this approach are: immunity to maximum aspect ratio limitations, superior lateral spatial sampling in X and Y, and no reliance on high-aspect probes for imaging. Therefore, tip-shape issues associated with currently incumbent CDAFM methodologies can be avoided altogether.
CD-SEM is currently poised as the primary method of choice for CD metrology because of its nanometer scale spatial
resolution, superior precision, and relatively high throughput. However, issues still continue to emerge that can threaten
the measurement performance for the various sample types encountered. The impact of issues arising from electron
beam induced modification of the sample materials on critical dimensional metrology and lithographic process control
will be assessed and approaches to mitigate these effects will be proposed. The two primary issues of interest related to
scanned electron beam based measurements of patterned lithographic materials in this article are shrinkage of the ArF
193nm resist and undesired deposition of contaminants occurring during CDSEM measurements.