Long-term stability and electrical properties of fluorine doped polysilicon IC-resistors

The electrical properties and the long-term stability of the resistivity ha ve been studied for boron-doped polysilicon films additionally implanted wi th fluorine. Fluorine was found to block the access of hydrogen to the dang ling bonds. A theoretical model for the drift in resistivity under electric al and thermal stress showed the number of participating hydrogen atoms to be around 2 x 10(10)cm(-2) and the number of grain-boundary traps around 4 x 10(12) cm(-2). The hydrogen atoms were found to be loosely bound to the g rain-boundary silicon atoms with activation energies in the range 0.4-0.7 e V. Hall measurements showed an increased mobility and confirmed the blockin g of grain-boundary traps by fluorine. The active carrier concentration was reduced due to compensation by donors formed by boron-fluorine complexes. The f-factor, i.e. the tunneling behavior, was found to be the same as for films doped with boron only. Limitation of the relevant process- and anneal ing- temperatures to 750 degreesC ensured that most of the implantation dam age was removed and that enough fluorine remained in the film. The activati on energy for removal of fluorine implantation damage was found to be 1.4 /- 0.1 eV (C) 2001 Published by Elsevier Science Ltd.