Disagreeable Foreign Matter

FM is the industry time for Foreign Matter. Essentially, it is stuff like dust on the surface of the wafer that usually prevents the circuit from operating as it should. Industry wide, it is despised as it decreases wafer yields and decreases profitability. The whole purpose of the semiconductor fab of being a clean room is to reduce sources of dust, vapors, and other particulate from contaminating the product. Once the human and environmental sources are mitigated, the primary sources are maintenance related. Either there are atmosphere leaks in the equipment or the byproducts of the process have accumulated so much that they are out gassing or depositing on the wafer. There are several strategies to minimize FM, but ultimately changes of the consumables are necessary after enough time. Sometimes the distribution of the FM across a batch will clue the maintenance team on what may be the source of the FM. Particulate on the top of the batch would indicate perhaps the top of the tube dropping byproduct onto the wafers while FM on the bottom of the batch would indicate a full trap or out gassing from the buildup in the exhaust. Whatever the cause of the FM, some product can by salvaged by a clean, which is akin to a rinse or polish. Though, Florine is generally not recommended.