What is the notch on wafers?

The wafer notch is a V-shaped or U-shaped groove on the edge of a semiconductor wafer. Far from being a defect incurred during the manufacturing process, it is the critical structural marker that was intentionally designed, whose core function lies in enabling precise positioning and orientation identification of the wafer. Wafer flat was used as the orientation marking in the early stages of wafer technology development. However, as wafer sizes gradually increased, the flat-edge design occupied more effective area, thus being gradually replaced by the more compact notch.

What is the function of the wafer notch? 

Chip manufacturing is a nanometer-scale process, in which any directional deviation can lead to circuit failure. Serving as an orientation marking, the wafer notch enables lithography and etching machines quickly identify the crystal orientation of the wafer, ensuring accurate alignment of each process step. Each chip is positioned on the wafer according to a notch, similar to the prime meridian. This ingenious design allows circuit patterns to be lithographed and laid out with the notch as the reference datum. In addition, robotic arms rely on the wafer notch to distinguish the wafer’s front/back side and orientation in highly automated production line, which significantly prevents wafer damage or process errors caused by misoperation. Should the notch become contaminated or damaged, the entire wafer may be rejected as non-conforming.

The wafer notch also plays a crucial role in improving chip manufacturing yield. Since wafer edges are prone to defects such as slip lines and cracks during manufacturing, precise positioning via notches allows equipment to accurately avoid these defective areas, thus reducing waste. Modern production lines also adopt technologies such as air suspension rotation for edge-finding operations. Serving as a marker for non-contact detection, the wafer notch not only avoids contamination caused by mechanical contact but also improves identification efficiency and accuracy.

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