• What materials make up the substrate and films on the wafer?

  Check to see if the substrate and films which make up your wafer are on the materials list, which will indicate which equipment sets are compatible. If they do not appear on the materials list, please contact SpecMat for more information on how to proceed. For information on how to bring in a new chemical or material into SNF, click <here>.
  
  Photoresist is probably the most notorious contaminant, as it is generally used from beginning to end in any process flow, and most of the resist processing tools (ie, aligners and coaters) are unrestricted in terms of the incoming and outgoing equipment groups (see below); however, its effects, particularly in furnaces, can be incredibly damaging. Please ensure your process flow restricts use of photoresist to compatible equipment and that photoresist is sufficiently removed before using any resist-restricted equipment.

• What potential contamination risks are posed at each step in the process flow?

Whether or not a wafer actually contains a specific contaminating material, such as gold, there is great risk of carrying over trace amounts of contaminant, when the wafer is processed in equipment which is normally exposed to other wafers containing this contaminant. Thus, equipment at SNF is grouped by level of contamination risk. For every process tool, equipment groups are designated for which wafers can be fed to, and accepted from, processing in that piece of equipment. Process flow sequence must be designed so that wafers are processed in equipment with equal or increasing contamination risk. Thus, wafers can be processed first in a tool in the "clean" group, and then in one from the "semi-clean" group, but generally not in the reverse order. Remember, that even if the process flow is consistent with the order of equipment groups, materials compatibility, particularly with respect to photoresist, must also be ensured for each piece of equipment. If you have processing requirements the guidelines provided here, please discuss your project with the SpecMat committee. For wafers receiving any processing outside of SNF, click <here>.

More detailed information about the Materials Policies at SNF can be found at these links:

• Chemicals and Materials Control Policy
• Common Chemicals and Materials used at SNF
• Contamination Control using Equipment Groups
• Stanford University Library of MSDS Sheets
• SNF Index of MSDS Sheets
• About New Materials or Chemicals
• Procedures for New Materials or Chemicals
• Labelling of Personal Chemicals Containers
• Chemical Hazard Classes
• Chemical Storage Group Classification
• Special Materials Committee (SpecMat)
• An Introduction to Contamination Issues
• Stanford Chemical Safety Database
• Safety Policies