When I use Si wafers, I use a three-step process; first, rinse with 99% HNO3 (for removing organics) and then wash with di-water; second, rinse with 70% HNO3 (for removing metal traces) and then di-water again; finally, rinse with 1% HF (for removing native oxide).
Can I use the same first 2 steps, in case of oxide wafers? (my feeling is, why not?)
Thanks!
PS: By oxide wafer, I mean roughly 300 nm of thermal-SiO2 on Si wafer
I don't catch the mean of oxide wafer. What kind of oxide? If your mean silicon dioxide, I think the first 2 steps are available and the third step also can be used to achieve fresh surface.
But the RCA clean process is the common method to clean Si wafer. I think you can use it as backup solution.
FYI:http://en.wikibooks.org/wiki/Microtechnology/Etching_Processes#RCA
I tried both chemical piranha and UV ozone. my best results was with UV ozone as you activate the surface and get the wafer directly
We too rely on UV ozone as it is far safer than acid cleans like the RCA or piranha. However, it doesn't remove any heavy metal contaminants (can only be done by etching some of the oxide). Our normal clean is: ultrasonic clean in chloroform, isopropyl alcohol, and DI water, followed by UV-ozone and then a DI water rinse. Only do the final rinse if you have UV-ozone scrubbed water. 18 MOhm water without the UV-scrubbing will deposit trace hydrocarbon. 10 min for each step (except the rinse) is typical.
It all depends on your preferences. Wet chemical etch (HF bath) is usually used. In some cases dry etch works better. You may find the attached link useful.
http://isnc.cnsi.ucla.edu/pdf/Kirt%20Williams%20Etch%20Table%20I.pdf
dear Sourish,
the key question before selecting a cleaning process, is what surface properties are you looking for?
1) Smooth or rough?
2) Unreactive (fully terminated SiO2 surfaces) OR highly reactive (SiOx - oxygen-poor surface, which can be achieved by the correct final HF).
3) High or low surface energy.
I attach here
a) Fig. 8 from Mat. Sci. Eng. B87, p. 311 (2001), both in color and high resolution black& white of a schematic comparison showing the effect of specific cleaning steps on the surface roughness, composition & termination. Note the chemistry is different than what you use, RCA-inspired (See Figure 1 listing the steps for 4 cleaning process step)
b) the review paper this comes from, Mat. Sci. Eng. B87, p. 311 (2001)
c) one of our more recent conference poster showing surface preparation for thermal oxides, not just native oxides but including thicker thermal oxides, with resulting properties.
d) the same results explained in more detail in our corresponding patent for thermal oxide surface cleaning.
I hope this helps.
Article The formation of ordered, ultrathin SiO2/Si(100) interfaces ...
Data AAAS 2012-BennettKennett.pdf”
Patent Methods for Wafer Bonding and for Nucleating Bonding Nanopha...
Your approach seems on target. and, Yes, first 2 steps, in case of oxidized silicon wafers.
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