Anomalous junction leakage current induced by STI dislocations and its impact on dynamic random access memory devices

As the density of dynamic random access memory (DRAM) increases up to giga- bit regime, one of the important problems is the control of the process-ind uced defects and damage. Although the shallow trench isolation (STI) is wid ely used for deep submicron devices, it has a great possibility of generati ng STI dislocations due to its inherently large mechanical stress and damag e. When STI dislocations are located within the depletion region of pn junc tion, anomalous junction leakage current could flow. This junction leakage current degrades the memory cell data retention time and the standby curren t of DRAM, We resolved the problems from STI dislocations as follows; the c rystal defects and the mechanical stress were reduced by optimizing the imp lantation condition and the densification temperature of trench filled high -density plasma (HDP) oxide, respectively. In addition, the residual mechan ical stress before source/drain implantation was relieved through rapid the rmal nitridation (RTN), By using these methods, STI dislocations were succe ssfully clamped outside the depletion region of pn junction.