Effect of Liner Oxide Densification on Stress-Induced Leakage Current Characteristics in Shallow Trench Isolation Processing

Controlling mechanical stress in the shallow trench isolation (STI) process is an increasing concern because it can affect circuit performance and yield. This paper presents the effect of liner oxide densification on the stress-induced junction leakage current in the STI process, compared to high density plasma (HDP) oxide densification before STI planarization. The simulation was performed for the trench isolation structure. It indicated that high temperature densification of the trench-filled HDP oxide has a high probability of generating STI dislocations due to its inherently large mechanical stress and volume. The crystal defects and the mechanical stresses were significantly reduced by the introduction of liner oxide densification during STI processing; as a result, in the stress-induced junction, leakage characteristics were improved. The characteristics of standby current and column bit failure with regard to device yields have also been discussed.