What are TTV, Bow, and Warp of silicon wafer?

The parameters of silicon wafer surface, Bow, Warp, and TTV, are crucial factors that must be considered in chip manufacturing. These three parameters collectively reflect the flatness and thickness uniformity of the silicon wafer, directly impacting many key steps in the chip manufacturing process.

What is TTV (Total Thickness Variation)?

TTV (Total Thickness Variation) is the difference between the maximum and minimum thickness of a silicon wafer. This parameter serves as a significant indicator of thickness uniformity across the wafer. In semiconductor processes, the thickness of the silicon wafer must be highly uniform across its entire surface. Typically, measurements are taken at five positions on the wafer, and the maximum difference is calculated. Ultimately, this value serves as a basis for determining the quality of the silicon wafer. In practical applications, for example, the TTV of a 4-inch silicon wafer is generally less than 2 micrometers, while for a 6-inch silicon wafer, it's typically less than 3 micrometers.