Mask aligner
Mask Aligner (dt. About Maskenpositionierer , mask aligner ) are devices or devices for exact positioning of masks for photolithography in the micro-chip production can be used.
In contrast to steppers , mask aligners use a photo mask that contains the template for the entire wafer. This is therefore only exposed once. In the case of steppers, the template on the mask is projected several times next to each other ("steps") onto the wafer.
Usage
Microchips (z. B. CPUs , GPUs , MEMS u. A.) Consist of a plurality of superimposed layers (engl .: layer ). These layers together form the electronic circuits and provide the entire function of the chip.
During production, the levels must be positioned one after the other and one above the other in order to ensure the electrical connections between the levels and to guarantee the functionality of the chip. The first level that is exposed on the wafer contains a set of alignment marks. They have to be very precise and are used to further align the following levels. The positioning markings are clearly marked for the purpose of identifying which brand belongs to which level. This is also important in knowing which mark to align the plane to be exposed to.
The positioning of the substrate to be exposed is supported by so-called laser interferometry . Positioning better than 50 nm is achieved, which is essential for the reliable exposure of large-area wafers.