Wafer alignment with laser light curtains

To prevent waste a fork laser can be used to determine the orientation of the wafer after which as much as possible chips can be cut out or split out of a wafer.

Alignment of wafer with fork laser

The production of wafers is a very extensive and complex process. A wafer is a thin round slice of semiconductor material, such as silicon. Electronic and mechanical components are produced on these wafers. This is done through placing dopants. In this case, impurities, atoms of a different material, are applied to change the material properties of the original silicon. There are several dopant techniques that can be used. This ultimately creates the wafers, which vary in size from 25.4 mm to 300 mm. Wafers under 200 mm often have flats (the flat side of the wafer). The (modern) wafers (larger than 200 mm) have notches, with the advantage that less material is used than with flats. The orientation and dopant types of a wafer can then be determined using these flats or notches.

Less waste in wafer production

Waste during the wafers process leads to high costs and slows down the productivity. It is therefore crucial to determine the orientation of the wafer in order to be able to cut or split as many chips as possible from a wafer afterwards.

The L-LAS-TB-AL series sensors from Sensor Instruments are extremely suitable for wafer alignment. By scanning the side and turning the wafer one or more rounds, the positioning can be determined. This is because the notches or flats present are detected, so that it becomes clear what the orientation and the dopant type of the wafer is. An additional advantage is that some damages are detected at the same time.

The L-LAS-TB-F-6-100/100-AL is a fork laser curtain with a horizontal or vertical measuring spot of 6.4 mm by 1 mm. This inspects the wafers for flats and indentations before further processing. The pitch of the fork laser is 100 x 100 mm, with a 2 µm accuracy. In addition, laser curtain is equipped with 2 digital inputs, 2 digital outputs, 1 analog output and an RS232 interface.

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