Reduction of fixed-pattern noise of BASIS due to low kinetic energy reactive ion and native-oxide-free processing

Reduction of fixed-pattern noise in the base-stored image sensor (BASIS) is achieved with newly developed processes based on ultraclean technology. One is low kinetic-energy reactive ion etching to keep the Si/SiO₂ interface free from plasma damage. The dark current decreases down to 0.4 nA/cm². The other of these processes is native-oxide-free processing to suppress the growth of native oxide on the Si surface. The uniformity of the current gain in a bipolar transistor has been improved with the introduction of these processing methods. These methods improve the Al to n⁺ region contact, exhibiting low and uniform contact resistance without any thermal annealing treatment