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Improved Imaging of Cross Sections using Deposition Precursor

IP.com Disclosure Number: IPCOM000229928D
Publication Date: 2013-Aug-07

Publishing Venue

The IP.com Prior Art Database

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Improved Imaging of Cross Sections using Deposition Precursor

    Technical Field of the Invention
[1000]
The present invention relates to improved imaging of layered materials exposed using a focused ion beam, and is particularly applicable to imaging of cross sections of multi- layered structures.

    Background of the Invention
[1001]
Modern integrated circuits are typically made of multiple layers of materials, such as metals, semiconductors, and insulators, fabricated on semiconductor substrates. To characterize the fabrication process or investigate process problems in semiconductor manufacturing, process engineers often use a focused ion beam to cut a cross section of the integrated circuit and then use a scanning electron microscope to view the edges of the layer in the cross section. For example, process engineers may cut cross sections to observe integrated circuit features, such as poly-silicon gates, amorphous silicon, and various dielectrics and barrier materials and to measure the layer thickness and uniformity.
[1002] A scanning electron microscope forms an image by collecting secondary electrons that are emitted from a surface as the beam is scanned across it, with the brightness at each point of the image being proportion to the number of secondary electrons (or another electron signal) collected from the corresponding point on the surface. The number of secondary electrons emitted at each point depends on the type of material and on the topography. Because many different types of materials emit different numbers of secondary electrons per incident electron, it is easy to observe a boundary, for example, between a metal layer and an oxide layer. Some similar materials, such as oxides and nitrides, emit about the same number of secondary electrons

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for each primary electron, and so the boundary between those materials is often not apparent in the electron beam image.
[1003] One method of making the interface visible is to selectively etch the area of the interface. If one material etches more quickly than the other material, there will be a change in topography at the interface, which will be visible in the image. Processing a work piece to make a feature more visible is referred to as "decoration." One decoration process is referred to as the delineation etchprocess, which comprises chemically assisted focused ion beam etching using a fluorinated hydrocarbon vapor of 2,2,2-trifluoroacetamide. When making an interface visible, it is desirable to change the structure as little as possible so that the process engineer obtains an accurate picture of the work piece. Very low etch rates are therefore desirable to allow the process engineer precise control over the decoration process.
[1004] As feature sizes in integrated circuits decrease, the inherent damage to the sample caused by ion sputtering introduces measurement error that may not be tolerable. When the decoration is performed using an electron beam i...