Overview:
Equipment in SNF is classified in one (or more) of three contamination group levels, described below. When defining the process flow, the choice of processing tools which are acceptable will depend on the previous tool used. In general, wafers can be processed in only equipment within the same contamination group or in groups representing higher contamination risk (ie, the progression of "Clean" -> "Semi-Clean" -> "Gold-Contaminated" is acceptable, but the reverse is not). Certain equipment (ie,some lithography or approved analytical equipment, general-purpose wet benches, and a few other exceptions) appear in more than one group or all groups, either because of low risk of cross-contamination, or because intervening cleaning procedures reduce contamination risk, or because special precautions may be taken to prevent contamination. Equipment groupings are a very general planning tool -- as you refine your process flow, make sure to check it against the Materials requirements for each individual piece of equipment. There are a few exceptions in which non-standard equipment sequence may be acceptable -- these are explained in the "Materials" page each piece of equipment. If you have non-standard process flow requirements (or any other questions about Materials policy), please discuss your project with a member of the SpecMat committee, who should be able to help you design a process flow to accomodate your needs.

Clean:
Equipment with the lowest tolerance for contamination fall into this group. Other than for photolithography and some approved analytical tools, wafers containing any metals or metal films are strictly prohibited from being processed in this equipment. Wafers that at any point have received processing on any equipment outside of this group cannot be processed on anything listed in this group. Wafers previously undergoing lithography are acceptable for processing (following appropriate photoresist restrictions or resist stripping procedures). Processing in any of the general-purpose wet benches must be done with appropriately dedicated labware to prevent cross-contamination. There are no restrictions as to where the wafers may go (given the appropriate Materials considerations) following processing in this equipment group.

Semi-Clean:
Wafers containing standard metals (Aluminum, Tungsten, Titanium) are acceptable for processing in the equipment listed here. Except for lithography or some approved analytical tools, wafers processed in semi-clean equipment are generally considered to be contaminated with standard metals. Wafers previously undergoing lithography are acceptable for processing (following appropriate photoresist restrictions or resist stripping procedures). Processing in any of the general-purpose wet benches must be done with appropriately dedicated labware to prevent cross-contamination. Wafers processed in equipment from this group can be subsequently processed only in equipment from this or in the Gold-Contaminated equipment group.

Gold-Contaminated:
Wafers containing non-standard metals, including gold, may be processed in this equipment. Except for lithography or some approved analytical tools, wafers processed in this equipment are considered gold-contaminated. There are no restrictions as to which equipment groups previous processing has taken place; however, subsequent processing may take place only in tools in this equipment group.

Litho/Analytical Tools:
Because of their general necessity throughout a process flow, all lithography and some analytical tools as listed here (and also some wet benches, see below) appear in all three equipment groups. Standard resist stripping and equipment-specific, pre-clean procedures designed into the particularly sensitive process modules minimize any potential contamination risk from shared lithography (and other select) tools. Some analytical tools presenting low risk of cross-contamination are listed here; other tools which are particularly sensitive to contamination issues or run high risk of transferring contaminants, are not listed here. Consult the materials guidelines for each of these tools, before processing. As always, when in doubt about contamination risks in any step in your process flow, don't hesitate to contact the SpecMat Committee.

General Purpose Wet Benches:
Certain wet benches have few restrictions on materials, but appear in all equipment groups. The use of designated and/or personal glassware/labware insures that cross-contamination risks are minimized. Consult the Materials use guidelines for each wet bench.