They also produced a similar, non coated, wafer called Caramel Wafer. Larger diameter wafers allow for more die per wafer. Nanotubes can grow vertically on the collector substrate, such as a silicon wafer. The patent deals with fabrication of integrated circuits on a semiconductor wafer. A finished semiconductor wafer is cut into dies. The wafer serves as the substrate for microelectronic devices built in and upon the wafer. After exfoliation the flakes are deposited on a silicon wafer. The wafer need not be entirely silicon. The phosphorus acts as a dopant used to create n-type layers on a silicon wafer. Thinning also makes the silicon wafer more fragile. This process produces epitaxial graphene with dimensions dependent upon the size of the wafer. Thin-film silicon is an alternative to conventional "wafer" (or "bulk") crystalline silicon. Exposure systems typically produce an image on the wafer using a photomask. The main fabrication facility consists of a wafer fabrication plant. A proximity printer puts a small gap between the photomask and wafer.