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How to draw a wafer map from an STDF file

The quickest way is to open the file in tsmap, a free, open-source wafer map viewer. It reads STDF directly, so there is nothing to convert, and it runs in your browser with the file read on your own machine and never uploaded. The same steps work for ATDF (the text form of STDF), and tsmap also opens CSV, JSON and Parquet files, which take one extra step to say which column is which.

In four steps

  1. Open tsmap in your browser. There is nothing to install. A desktop version is also available for Linux, macOS and Windows.
  2. Drag your .stdf file onto the window, or choose Open files. A .stdf.gz, .stdf.bz2 or .zip of STDF files opens the same way.
  3. If the file holds many tests, tsmap shows a test selector. Choose the tests you want to keep, or accept the defaults.
  4. Read the map. Each die is one square, coloured by its hard bin. A lot with several wafers opens as a gallery of maps.

No STDF file to hand? Try a sample lot with an edge-ring defect. The sample files are synthetic and contain no real device data.

What you get

  • A bin map for each wafer, coloured by hard bin or soft bin, with the yield for each wafer and for the lot.
  • A parametric map coloured by any test's value, with the test limits marked.
  • Findings: edge rings, clusters and other patterns the analysis notices, listed so you can check them on the map.
  • Insights charts, data tables and reports, and a PNG download from the map toolbar.

The Learn tsmap lessons walk through all of this on a sample lot, and the glossary explains the test-data terms.

What a wafer map from STDF is made of

A wafer map needs one position and one result per die. In an STDF file those come from the part result records (PRR): the die's X and Y coordinates, its hard bin and its soft bin. The wafer information records (WIR and WRR) group the dies into wafers, and the master information record (MIR) carries the lot. Parametric values come from the parametric test records (PTR), which tsmap reads alongside the bins.

Before you trust the picture

  • Which bins count as a pass. The default is bin 1, but your test program may pass in another bin, or several. The yield figure follows the pass bins you set.
  • Retests. When a die is probed more than once, one result stands for it. The last is used by default, and you can choose the first, best or worst.
  • Dies with no position. Some STDF files carry no die coordinates. tsmap keeps those dies as dies without a position, rather than dropping them or guessing a position, and the user guide explains how they are shown.
  • Supported records. tsmap reads STDF version 4. Multiple-result parametric records (MPR) are not read yet, so tests stored that way do not appear, and the log reports how many such records the file had.

Other ways to do it

  • A script. Parse the PRR records with a Python STDF library and plot X and Y coloured by bin. stdf2map is a Python command-line tool that draws bin wafer maps from STDF files. stdf-reader is a Python tool that converts STDF to CSV and includes a wafer map view. Choose these when the map has to come out of a scripted pipeline.
  • Inside your own application. Use the wafermap JavaScript library, which tsmap itself is built on. See wafer maps in JavaScript.
  • Other formats. For a CSV, JSON or Parquet file, tsmap asks you to map the columns (X, Y, bin, test values) before it reads the data, and detects common column names automatically. See Loading your data in the user guide.

Questions

GitHub Discussions is open to anyone using either project, and a sample file helps if something does not open as you expect.