With the development of photoelectr

With the development of photoelectric sensing technology and photoelectric imaging equipment, automatic alignment equipment related to them has emerged and been widely applied. In the 1970s or so, there have been corresponding automation equipment used in their own production lines or formed products used in the commercial market A semiconductor manufacturer, for example, application of a point based on laser sensor, through the occurrence of the diameter of the fine of the laser beam to scan the entire surface of the circular wafer, due to the different characteristics of the chip processing technology or material is different, caused the different reflectivity, reflected by laser scanning laser light intensity are then received by photosensitive sensor judgment, the products of this company is in the entire history of the circular wafer to look for the highest reflectivity of streets (street refers to the wafer cut has not been a barrier between the chip), finally can judge out each chip in the circular wafer on the accurate location information This way because of the need for large area scanning, so speed is relatively slow, and then used for locating datum of streets, also not bare chip with the characteristics of basement behind in the 70 s, optical fiber sensor is used for automatic alignment, this method requires first processing special baseline characteristics, but also because of the scanning speed is slow, so also need to be processed out special reference mark