Quantification of image quality

Pong Wing Tat, Alfred Wong

Research output: Contribution to journalConference articlepeer-review

8 Scopus citations


Traditionally, the common window method is used to quantify image quality in optical lithography. The common window method can take dose variation, focus error, mask critical dimension error and aberrations into account. However, the demerit of the common window method is its computation time. In this paper, a new metric called Normalized Process Latitude (NPL) is proposed. The NPL considers dose variation, focus error, mask critical dimension error and aberrations to output its final quantification value. Its processing time for quantifying one feature is usually within 10 seconds on a PC with 1GHz CPU and 256MB DRAM. We perform several comparisons between the total window value and the NPL. It is found that the NPL draws similar conclusion as the total window. We can conclude that NPL is a sensible figure of merit for image quantification.

Original languageEnglish (US)
Pages (from-to)169-178
Number of pages10
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume4691 I
StatePublished - 2002
Externally publishedYes
EventOptical Microlithography XV - Santa Clara, CA, United States
Duration: Mar 5 2002Mar 8 2002

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


  • Aberrations
  • Chromium-on-glass (COG)
  • Combination
  • ED window
  • Extraction
  • Mask error factor
  • Normalization
  • Normalized image log slope
  • Normalized process latitude
  • Sigrnoid function


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