Effect of surface treatments on the electrical properties of fluorinated silicon oxides

In this study, different surface treatments of HF-based etching solutions a re investigated for the predeposition of liquid-phase deposited fluorinated silicon oxides (LPD-SiOF). The effects of each etching solution on the int erface trap density and breakdown field are examined with Al/LPD-SiOF/Si st ructure. From the experimental results, there appears significant growth de lay time for different surface treatments during the initial oxide depositi on, which is defined as the surface modification time to reach an OH-rich s urface promoting the growth of LPD-SiOF film. However, the subsequent depos ition rate remains unchanged for all etching processes, indicating a surfac e-independent deposition process. It is found that a two-step treatment in dilute HF/H2O with 1:200 v/v ratio reveals an average breakdown field of 9. 7 MV/cm and an extremely low average interface trap density (similar to 10( 10) eV(-1) cm(-2)), which are comparable to that of thermal oxides. Moreove r, the rapid thermal annealing process is suggested to clearly improve the oxide quality for this two-step etching process, where early breakdown is e liminated (18% raising for E-BD) and interface properties are substantially improved (33% reduction for D-H). The improvements for device performances are believed to be due to the oxide-free Si surface passivated with hydrog en and reduced surface microroughness (Ra = 0.1 nm). It is evident from our experiments that this new two-step surface treatment is an effective metho d for interface improvement with oxide deposited by LPD or chemical vapor d eposition. (C) 2000 The Electrochemical Society. S0013-4651(99)10-061-2. Al l rights reserved.