why wafer is round
The reason wafers are round is largely attributable to their manufacturing process and physical properties.
Wafers are cut from cylindrical silicon rods (ingots). Silicon rods are usually made by spinning and growing molten, high-purity polysilicon on seed crystals, a process that determines the rod’s natural shape as a cylinder.
why wafer is round
In semiconductor manufacturing, the circular design of the wafers originates from the growth process of single crystal silicon. This method involves melting high-purity polysilicon and then rotating and lifting it through a seed crystal to form a cylindrical single-crystal ingot.
Round wafers are also structurally stronger than square ones, providing better resistance to the effects of edge stresses and reducing breakage during the manufacturing process.
Round wafers can be more evenly coated with photoresist during rotation, which is critical for subsequent lithography steps to ensure uniform photoresist coverage, thereby improving chip manufacturing yields.
As wafers need to undergo multiple photolithography, etching, chemical milling and other process steps, round wafers can more evenly disperse the forces generated during these processes, reducing the risk of breakage due to uneven stress.
