GScan: Graphic Design System (GDS) files contain pattern layout designs. This tool analyzes GDS files and outputs information that may be useful for modeling purposes. GDS files are commonly used in the semiconductor manufacturing industry. Processes such as chemical coper deposition, chemical mechanical polishing, and lithography nanoimprint are pattern dependent; this tool could be used to extract pattern density information from the source in GDS format and that information can then be used in modeling software. 

The output from this GDS Scanner tool can be used as input in our tool for simulating the deep reactive ion etching process (forthcoming). 

Currently the program can extract information about:

1. Densities: (area of features per unit area)
2. Perimeters: (perimeter length of features within unit area)
3. Feature Types: (A count of circles squares etc and their areas)

Version History:

• 1.0 GScan Launched

Getting Started: 

1. Launch The GScan tool
2. At the top of the tool, click on the “Upload File” button to import your GDS files.
3. Below the file uploader use the file selection dropdown menu to select the GDS file you want to analyze.
   • a preview will be generated as soon as a file is selected. 
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4. Input settings for GDS File analysis:
   • *** While inputing these settings you can check the GDS file preview window below to see how the program will be partitioning the GDS file during analysis. Settings can be automatically set by clicking on the “Reset defaults” button. 
   • *** If input does not match the default setting, please click on any white area to generate a preview.
   1. Basic Settings:
      • Window Resolution: int
        • Sets the (PxP) pixel resolution of the (NxN) window. Higher resolutions will encourage better density, perimeter, and feature type measurements given a proper window size.
      • Output Data File Name: string
        • The name of the file the GDS analysis data will be saved to. The output file will be saved in the python pickle format and named “FILENAME.pkl”
   2. Advanced Settings:
      • Min x Die Range, Max x Die Range: float, float
        • Minimum and maximum x coordinates of the GDS file that GScan will analyze.
      • Min y Die Range, Max y Die Range: float, float
        • Minimum and maximum y coordinates of the GDS file that GScan will analyze.
      • Window Size: float
        • Sets the length and width of the (NxN) sliding window used when analyzing the GDS files. You may reduce the window size to get a finer scan of the GDS file, however making your window size smaller than the size of small features can prevent the program from accurately determine what feature types lie within the window.
      • Distance Value Multiplier: float
        • By default all distance values are in micrometers. If your GDS file has a different scaling for unit length then set the Distance Value Multiplier accordingly (example: if the scaling of your GDS file is 2 micrometers per unit length you should set the multiplier to 2.)
      • Aspect Ratio for Rectangle Detection: float
        • Used to distinguish squares from rectangles. Value represents (shortest side length / longest side length). If a 4 sided object detected exceeds this aspect ratio, it is classified as a rectangle. Otherwise it is classified as a square.
      • Perimeter Percentage Difference used for Contour Approximation: float
        • When contours are extracted to determine feature types, they are usually composed of many edges. In order to get an approximation of contours detected within the scanning window, we must simplify the contours and reduce the number of contour edges. This perimeter percentage difference should be read as follows: '0.02' translates to "reduce the number of contours used to build the perimeter while keeping the perimeter length within '0.02' percent of the original perimeter length" This helps to smooth over small defects in feature shapes without confusing the feature classifier which is based primarily on the number of edges of the shapes.
      • Maximum Scale of Acceptable Features: float
        • Sets an upper limit on contour / feature sizes. If contour width, height, or area is over the maxScale percent of the window size then the contour is thrown out on the premise that it is just outlining the window and not any actual feature.
   3. Debug Settings:
      • *** Debug settings allow the user to see how features are picked out of the GDS file and gives an idea of how to adjust the feature detection settings to better analyze specific GDS files. When debug mode is active you can only scan over a single window since the mode prints out graphs of contours relating to all windows being scanned over.
      • Debug On: bool
        • Set to true to turn on debug mode
      • Detect Etch Features: bool
        • Only works when debug mode is on. Chooses whether the contours displayed during debug mode are aimed at outlining etched or non-etched features.
   4. Reset defaults:
      • Clicking on the "Reset defaults" button will generate the preview in the same place as the one generated in step one. All settings will be automatically selected.
5. Click on the “Process GDS File” button to analyze your GDS file. This may take from 1 to 30 minutes depending on the number of windows, window resolution, and number of cores used to process the file.
6. After the analysis is complete, use the file selection dropdown menu (below the file processing button) to select the pkl file you want to visualize.
7. You can now visualize the results of the GDS analysis. Use the “Graph Data” drop down menu to select what data you wish to see. Options include:
   • Feature Densities: 
     • The area encompassed by features divided by the area of the scanning window
   • Feature Perimeters: 
     • Total perimeter length of features within the scanning window area
   • Feature Types: 
     • Identifies the most numerous feature type within the scanning window area. Feature types include:
       • Circle / Square Holes: Circular and Square etched areas
       • Circle / Square Pillars: Circular / Square like empty areas
       • Vertical / Horizontal Trenches: Vertically / horizontally long etched areas
       • Vertical / Horizontal Walls: Vertically / horizontally long empty areas
       • No Features: No features detected within the area. If an area is completely etched it will also be classified as an area with no distinct features. 
8. If you wish to download your GDS data, first make sure you have selected your .pkl file from the dropdown. Next select the filetype you want to export to from the “Export Filetype” dropdown menu. Finally click on the “Download Feature Data” Button.

Jupyter Notebook

Researchers should cite this work as follows:

• Jeffrey Spitz, Jie Qiu, Brian Salazar, Hayden Taylor (2019), "GDS Analyzer," https://nanohub.org/resources/gscan. (DOI: 10.21981/XKWS-W136).

  BibTex | EndNote

1. Jupyter notebooks
2. nanoelectronics
3. nanoMFG Node
4. semiconductor manufacturing