Effects of post oxidation of SiO2/Si interfaces in ultrahigh vacuum below 450 °C

Zahra Jahanshah Rad*, Juha Pekka Lehtiö, Kexun Chen, Iris Mack, Ville Vähänissi, Mikko Miettinen, Marko Punkkinen, Risto Punkkinen, Petri Suomalainen, Hannu Pekka Hedman, Mikhail Kuzmin, Jekaterina Kozlova, Mihkel Rähn, university tart, Hele Savin, Pekka Laukkanen*, Kalevi Kokko

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)
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Growing SiO2 layer by wet-chemical oxidation of Si surfaces before growth of
another insulating film(s) is a used method to passivate Si interfaces in
applications (e.g., solar cell, photodiode) at low temperatures (LT) below 450
oC. We report on potential of LT ultrahigh-vacuum (UHV) treatments combined
with the wet-chemical oxidation, by investigating effects of LT-UHV oxidation
after the wet-chemical growth of SiO2 and before growing Al2O3 film on top of
SiO2/Si. This method modifies the SiO2/Si and is found to (i) decrease defect-
level density, (ii) increase negative fixed charge density, and (iii) increase carrier
lifetime for Al2O3/SiO2/p-Si, as compared to state-of-the-art SiO2/p-Si reference interfaces without LT-UHV. X-ray photoelectron spectroscopy shows that the LT-UHV treatment decreases amount of Si+3 oxidized atoms in chemically grown SiO2 and also amount of carbon contamination. In order to pave the way for further tests of LT-UHV in silicon technology, we present a design of simple UHV instrument. The above-described benefits are reproduced for 4-inch silicon wafers by means of the instrument, which is further utilized to make LT-UHV treatments for complementary SiO2/Si interfaces of the native oxide at silicon diode sidewalls to decrease the reverse bias leakage current of the diodes.
Original languageEnglish
Article number111134
Number of pages8
Publication statusPublished - Aug 2022
MoE publication typeA1 Journal article-refereed


  • silicon passivation
  • wet-chemical oxidation
  • defect level
  • surface science


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