page_title: Differential interference contrast microscopy
section_title: Applications
hierarchical_section_title: Differential interference contrast microscopy / Applications
caption_attribution_description: English: The subject of this image is a silicon integrated circuit wafer in the region between two circuit die. The oxide should have been fully etched in the horizontal area at the center of the image, but in fact was not - because of a defect in processing. The irregular remaining oxide is highlighted by the Nomarski Differential Interference Contrast microscopy (DIC).
context_page_description: Differential interference contrast microscopy, also known as Nomarski interference contrast or Nomarski microscopy, is an optical microscopy technique used to enhance the contrast in unstained, transparent samples. DIC works on the principle of interferometry to gain information about the optical path length of the sample, to see otherwise invisible features. A relatively complex optical system produces an image with the object appearing black to white on a grey background. This image is similar to that obtained by phase contrast microscopy but without the bright diffraction halo. The technique was developed by Polish physicist Georges Nomarski in 1952.
  DIC works by separating a polarized light source into two orthogonally polarized mutually coherent parts which are spatially displaced at the sample plane, and recombined before observation. The interference of the two parts at recombination is sensitive to their optical path difference.
context_section_description: DIC is used for imaging live and unstained biological samples, such as a smear from a tissue culture or individual water borne single-celled organisms. Its resolution and clarity in conditions such as this are unrivaled among standard optical microscopy techniques.
  One non-biological area where DIC is used is in the analysis of planar silicon semiconductor processing. The thin (typically 100–1000 nm) films in silicon processing are often mostly transparent to visible light (e.g., silicon dioxide, silicon nitride and polycrystalline silicon), and defects in them or contamination lying on top of them become more visible. This also enables the determination of whether a feature is a pit in the substrate material or a blob of foreign material on top. Etched crystalline features gain a particularly striking appearance under DIC.
  Image quality, when used under suitable conditions, is outstanding in resolution and almost entirely free of artifacts unlike phase contrast. However analysis of DIC images must always take into account the orientation of the Wollaston prisms and the apparent lighting direction, as features parallel to this will not be visible. This is, however, easily overcome by simply rotating the sample and observing changes in the image.
caption: Partially etched silicon dioxide in Nomarski DIC
exif: {"Image Orientation": "Horizontal (normal)", "Image XResolution": "600", "Image YResolution": "600", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS4 Macintosh", "Image DateTime": "2009:09:27 17:38:10", "Image ExifOffset": "164", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "302", "Thumbnail JPEGInterchangeFormatLength": "0", "EXIF ColorSpace": "Uncalibrated", "EXIF ExifImageWidth": "2113", "EXIF ExifImageLength": "1550"}