Design Fabrication and Testing a Four Quadrant Silicon

Design, Fabrication, and Testing a Four- Quadrant Silicon Photosensor Student: Tho T. Snow Advisor: Prof. Mustafa G. Guvench Electrical Engineering Department - University of Southern Maine A four-quadrant Si photosensor is designed to fabricate on a 4 -in n-type wafer manufactured by Fairchild Semiconductor Top view of 3 masks designed for a four-quadrant Si photosensor Structural cross sectional view of a quadrant of Si photosensor device Mask # 1 Mask #2 Mask #3 Top view of p++ active layer Metal contact to active layer Metallization pattern three masks aligned on top of each other The goal of this project is to design and fabricate a Si photosensor consisting of four identical photodiodes placing in a square pattern on a Si chip. The photosensor will be used to sense the 2 dimension position of the chip with respect to the spot defined by Red 632. 8 nm He- Ne laser beam. slope = 90 Picture on the left hand side is the control unit of the furnace, and the on the right is a hot furnace tube in which the wafer is placed for oxide growth and dopant diffusion. The photo above is the vacuum chamber used in the metal deposition on the surface of the Si wafer. The metal layer on the wafer shown in the picture above was processed using this vacuum chamber This is the Curve Tracer used in the IV curve plotting and testing of the photodiode. The oxide thickness and the doping concentration of the Si layer underneath the oxide can be determined using capacitance versus bias voltage measurements as shown. And the deposited metal thickness can be determined using the four point resistance probe test