Oxidation in RTP and ozone units
Last week I attempted to use the ozone cleaner and RTP to grow an oxide on bare 4″ wafers. I used the spectroscopic ellipsometer to measure the film thickness. I found that ~4 min. in the RTP @ 1150 C with 3 LPM of O2 grew nearly 50 nm of silicon dioxide. Using Tom’s standard recipe for the ozone cleaner (3 min. O2 fill, 3 min. UV lamp and sample stage heating, 3 min. ozone soak), I did not see much of a difference in film thickness between the control and ozone-treated wafer. I should note that the ellipsometer is less reliable when films are below 10 nm (which all native oxides are).
Here are the plots from the ellipsometer and RTP scan:
Control wafer (50:1 HF strip & left in atm 2 days)
Ozone treated
RTP (center measurement)
RTP (1″ from center near back of chamber)
RTP oxide growth temp. profile
There’s a bit of non-uniformity in thickness for the RTP grown oxide. We may be able to reduce this by tweaking the gas flow (3 LPM too high). It may also be worth making a measurement on the RIT SpectraMap which would provide a thickness uniformity map over the entire wafer surface…
Ozone treated
RTP (center measurement)
RTP (1″ from center near back of chamber)
RTP oxide growth temp. profile
There’s a bit of non-uniformity in thickness for the RTP grown oxide. We may be able to reduce this by tweaking the gas flow (3 LPM too high). It may also be worth making a measurement on the RIT SpectraMap which would provide a thickness uniformity map over the entire wafer surface…