No abstract

A buried injector is proposed as a source of electrons for substrate hot electron injection. To enhance the compatibility with VLSI processing, the buried injector is formed by the local overlap of the n-well and p-well of a retrograde twin-well CMOS process. The injector is activated by means of punchthrough. This mechanism allows the realization of a selective injector without increasing the latchup susceptibility. The p-well profile controls the punchthrough voltage. The high injection probability and efficient electron supply mechanism lead to oxide current densities up to 1.0 A. Em-'. Programming times of 10 ps have been measured on nonoptimized cells. The realization of a structure for 5-V-only digital and analog applications is viable. A model of the structure for implementation in a circuit simulator, such as SPICE, is presented.

Abstruct-High-energy ion implantation is used for forming the collector in vertical bipolar transistors in a BiCMOS process. Secondary defects, remaining after annealing the implant damage, give rise to an increased leakage current and to collector-emitter shorts. These shorts reduce the transistor yield. The use of multiple step implants or the introduction of a C gettering layer are demonstrated to avoid dislocation formation. Experimental results show that these schemes subsequently lower the leakage current and dramatically increase device yield. The presence of C can cause increased collector/substrate leakage, indicating that the C profile needs to be optimized with respect to the doping profiles.