Material restrictions

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The LNF uses a wide variety of processes and materials, some of which can cause contamination to others' processes. In order to reduce the possibility of contamination, the lab places material restrictions on each tool. There are four main levels of material restrictions in the LNF, described in detail below. They are CMOS Clean, Semi-Clean, Metals, and General. The materials listed in each section are an example of what may be allowed in a tool with that level. A complete list may be found on individual tool pages.

CMOS clean

CMOS clean tools are considered the lowest level of possible contamination and thus have the greatest level of restriction. In order for one's sample to run in a CMOS Clean tool, it must have only have CMOS clean materials and only ever be processed in CMOS clean tools. Some of these tools also require an additional clean, such as a Pre Furnace Clean. Please see individual tool pages for details.

Here is an example list of materials allowed in CMOS Clean tools. Wafer used in CMOS Clean tools must be Prime Grade


Semi-clean is the next level of material restrictions. This level includes all materials in the CMOS Clean group as well as some low-mobility metals and films made in Semi-Clean tools. CMOS Clean and Semi-Clean wafers may be processed in these tools. In order to go back to a CMOS Clean tool, additional cleans may be necessary. For more information, see individual tool pages.

Here is an example list of materials allowed in Semi-Clean tools.


Metals is the lowest level of segregation in the lab. Most materials are allowed in these tools. Any sample processed in a Metals tool is not allowed back into a Semi-Clean or CMOS Clean tool without express permission from LNF staff, by creating a helpdesk ticket. Additional cleans will be required.

Here is an example list of materials allowed in Metals tools.


General class tools allow most Metals class materials, however these systems have a low potential for cross-contamination and therefore the segregation class of a Semi-Clean or CMOS clean wafer is not altered by it. Most metrology and lithography equipment falls in this category.

Here is an example list of materials allowed in General tools.