Chemical Mechanical Planarization - CMP
Chemical Mechanical Planarization
Chemical Mechanical Planarization aka: CMP is a critical process step in the building of IC devices on the wafer. The CMP process tool is used several times throughout to form the ultra flat surface needed to build the individual layers. Material removal is controlled with extreme precision through a combination of chemical reactions and mechanical abrasion technologies. To simplify, the process does not do it justice as the tolerances from end to end on a 300mm wafer can be 2 angstroms, that’s 2 one hundred millionths of a centimeter or 10⁻¹ᴼ meter!
The CMP process selectively removes material by applying force to the backside of the wafer while suspended upside down against a rotating highly specialized pad that is saturated with a chemical slurry designed to remove the specific target chemical. A typical 300mm wafer can fit about 600 A13 Bionic 7nm chips; thus, precise polish is needed to ensure that each chip on the wafer has the same layer depth. Any over polish could damage the underlying critical feature of the chip. Chemical Mechanical Planarization is critical to maintaining the structure of the IC devise layer after layer and is a critical technological gating process in dealing with the constant miniaturization of the transistor gate size.
Engineering Thermoplastics play a pivotal role in the CMP process. Essentially, CMP is a one application dominant segment for plastic materials. Plastics are used to secure the wafer and carefully control the level and quality of wafer wear. The materials used for the CMP process are manufactured under the strictest quality demands for cleanliness, consistency, low stress, and dimensional stability. CMP for plastics is dominated by CPM retainer rings. These rings are made from highly engineered extruded tubes, with the wafer size dictating the ID size to secure the wafer. Materials are selected based on the chemistry of the slurry used to polish the wafer.
Common material families used for CMP rings are: