Physical and Electrical Characterization of Deep Trench Isolation in Bulk Silicon and SOI Substrates

In this paper the authors present case studies for physical and electrical characterization of Deep Trench Isolation (DTI) in bulk silicon and SOI substrates. For bulk silicon, experimental results demonstrate how the effectiveness of the isolation is determined by the gain of NPN parasitic device that is formed between neighboring pockets. For SOI, the effectiveness of isolation is determined by encapsulation of dielectrics by the trench connection to the Buried Oxide (BOX). In both cases consistent DTI etch rate is an important factor for good process control. DTI etch rate dependency with pattern density is characterized and used to adjust DTI etch time in order to reduce variability. DTI depth can be monitored in-line using n&k metrology system and by electrical measurements of simplified test structures that are constructed with shallow trench.