Effect of H2O evolving from TEOS based SiO2 film on the EEPROM cell characteristic

Abstract

In this paper, we investigate the effect of water (H2O) molecules evolving from silicon dioxide (SiO2) film deposited by low pressure chemical vapor deposition (LPCVD) at 670 degrees C on the transistor characteristic of an electrically erasable programmable read only memory (EEPROM) cell. Fourier Transform Infra red (FT-IR) analysis reveals that H2O is captured during film deposition and diffused to silicon surface during high thermal processing. The diffused HO molecules lower threshold voltage (V-t) of cell transistor and, thus, leakage current of the cell transistor is increased. In erased cell, V-t lowering is 0.25 V in which it increases leakage current of cell transistor from 1 to 100 pA. This results in the lowering of high voltage margin of a 512 Kb EEPROM from 2.8 to 2.6 V at 85 degrees C.