AN INTEGRATED ANALOG SENSOR FOR AUTOMATIC ALIGNMENT

Automatic alignment is a computationally intensive task that slows som e manufacturing processes that require it. In order to improve alignme nt speed, we have designed a sensor that combines the imaging operatio n with the computation of the alignment error, The sensor provides x a nd y translation error signals when an image of the alignment mark is focused upon it. Photodiodes detect the image, and integrated amplifie rs convert the photocurrents into an alignment error signal that is in dependent of illumination level, Alignment is accomplished in two step s, Coarse alignment is performed by operating as a four quadrant senso r, and fine positioning is achieved using edge detection, Measurements have demonstrated a minimum repeatability of 53 ppm and a maximum ban dwidth of 7.5 kHz.