Wafer Notch Detection
Maintain accurate alignment of semiconductor wafers with tight space constraints
Knowing the position and orientation of a semiconductor wafer is critical during the wafer fabrication process. This is done by monitoring a notch on the wafer to understand the wafer’s orientation through each step. With wafers costing anywhere between $5,000 to more than $100,000, any misalignment during the fabrication process can result in serious and irreparable defects, requiring the wafer to be scrapped.
Traditional methods for finding the notch use a thru-beam array laser optic sensor that requires a bulky transmitter and receiver positioned above and below the wafer. This takes up valuable mechanical space and adds time while the wafer rotates until the notch is found. With the introduction of transparent wafers (SiC) and other unique wafer coatings, the thru-beam sensor has a difficult time accurately finding the notch adding to an increased chance of misalignment during that specific process.
Cognex In-Sight vision systems accurately identify the wafer’s notch and XY position with an accuracy down to 0.025 pixels. Cognex’s PatMax algorithm accurately detects the wafer’s notch in any orientation and outputs the position and dimensional data back to the assembly robot or PLC. Plus, the vision system ultra-compact body design satisfies extremely tight footprint constraints, which eliminates the need for a laser optic sensor to be positioned above and below the wafer.
Cognex also has a patented low-profile optics system for viewing the entire wafer in cases where manufacturers cannot mount a lens at a longer working distance.