Scatter Tutorial

Optical Scattering: Measurement and Analysis
(Taught as an “in house” industrial course)

Optical scatter, originally used almost exclusively to characterize the stray light generated by optically smooth surfaces, is now being used as a sensitive, economical way to monitor the surface texture requirements in a variety of applications.  The course, as advertised here, is taught on your site and emphasizes your practical applications. It is also available once or twice each year at SPIE conventions. Look under TSW News to find the SPIE schedule.

The course starts by defining how scattered light is quantified (BRDF, TIS, DSC, etc.). Then roughness quantification terms are defined (rms, PSD, spatial frequencies, etc.). Scatter and roughness are then related to each other for the case of clean, optically smooth surfaces. Because there are other sources of scatter (particles, films and bulk defects) it is often important to determine the scatter source. The course explains measurements that can be taken (by changing wavelength, polarization and incident angle) to help make this determination. The low signal (hard to measure) optical applications were solved first because the math was easy.  Rougher surface scatter relationships are more complicated, but the signals are much larger – making instrumentation easier. There are two key points for these non-optical surfaces: (1) If the texture changes – the scatter changes and (2) these changes (and related product function) cannot be adequately monitored by a single variable – such as RMS Roughness, Haze or Gloss. This often makes scatterometry an economical source of in-process metrology. Scatter measurement issues (noise floor, calibration, etc) and instrumentation are reviewed. The course finishes with applications related to the company’s issues.

It is useful to have sample data relevant to the scatter issues of concern.  A PDF copy of the course notes is supplied prior to the meeting so that attendees can have a set of notes. 

LEARNING OUTCOMES:  This course will enable you to:

  • quantify and analyze scatter in terms of BRDF, TIS, Haze and DSC units
  • explain the instrumentation for obtaining scatter data and evaluate system calibration
  • evaluate the roughness comparison issues between scatterometers and profilometers
  • convert scatter to roughness statistics when possible and understand when it is not possible
  • evaluate the use of scatter metrology for specific
  • write useful application specific scatter specifications

INTENDED AUDIENCE:  The material is directed toward engineers, scientists, and managers who need to understand and apply the basic concepts of scatter metrology to laboratory research and industrial process control. Some knowledge of calculus Fourier composition is helpful, but the course does not require that the student follow mathematical derivations. 

COURSE LENGTH:  The course work takes about half a day depending on questions. This is followed by a half day of consulting and discussion on your scatter issues.

INSTRUCTOR:  Dr. John C. Stover is President of The Scatter Works, Inc., a Tucson firm concentrating on scatter based metrology, consulting, and measurement as they apply to diverse industries. He has researched light scatter related problems for over 40 years and led teams of engineers who developed state-of-the-art scatterometers, verified theoretical relationship between surface roughness and scatter and characterized surface defects to improve wafer metrology. He has been involved with international standards organizations for over 30 years and has over 100 scatter related publications including the book Optical Scattering, which is available from SPIE Press. 

PRICE:  A flat fee (including travel) of $5,000 is charged west of the Mississippi River and $5,500 east of the river.