Method of making position sensing photosensor device

Abstract

A photosensor device (41) having tapered photodiodes (53, 55) that are interdigitated and which is compatible with typical ASIC, CMOS and BiCMOS processes. A left side photodiode array of tapered regions (53) of a first conductivity type is disposed into an epitaxil layer of a second conductivity type. This array of photodiodes is coupled together and further coupled to a first output terminal (43). A right side photodiode array of tapered regions (55) of said first conductivity type is disposed into the epitaxial layer of the second conductivity type, spaced apart from the left side photodiode by a minimum distance. A second output terminal is coupled to the array of right side photodiodes (51). An incident light spot (39) is focused onto the sensor. The amount of current generated at the first and second output terminals (43, 51) will be proportional to the area of the left photodiode array and the area of the right photodiode array which is receiving light. By comparing the current generated at the first and second output terminals, the position of the incident light spot can be accurately measured as a percentage of the total width of the sensor. The photosensor (41) may be used in many applications but is particularly well suited to autofocusing systems. Several embodiments are described which vary the size and number of photodiodes used. An integrated circuit (123) which incorporates the photosensor with the circuitry needed to output a digital position measurement is described.