1063-7397/05/3403- © 2005 MAIK “Nauka /Interperiodica”
Russian Microelectronics, Vol. 34, No. 3, 2005, pp. 131–139. Translated from Mikroelektronika, Vol. 34, No. 3, 2005, pp. 163–171.
Original Russian Text Copyright © 2005 by Anishchenko, Kagadei, Nefedtsev, Oskomov, Proskurovski, Romanenko.
When a photoresist is removed with a solvent, a
residual thin ﬁlm about 1 nm thick is left due to the pho-
toresist–substrate adhesion (1–10 eV) being far stron-
ger than the photoresist cohesion (
0.1 eV) . The
ﬁlm is commonly removed with oxygen plasmas.
Unfortunately, this method will not work well with
dielectrics such as carbon-modiﬁed silicon diox-
ide [2–4], which are being considered for interlevel
insulation in sub-90-nm integrated circuits . The rea-
son is that an oxygen plasma will react with atomic car-
bon clusters in the dielectric ﬁlm to reduce the carbon
content, thus increasing the dielectric constant [2, 6, 7].
This stimulates a search for plasmas of some other
composition, especially hydrogen-containing ones, that
would be suitable to use with low-
plasmas [2, 7]. However, it
should be pointed out that high-energy charged parti-
cles present in plasmas will adversely affect the semi-
In this study, a stream of low-energy uncharged
hydrogen atoms is experimentally evaluated as a means
of residual-photoresist removal. A comparison is made
with the conventional, oxygen-plasma technique. It is
shown that the new approach is indeed suitable for
GaAs and Si wafers.
The experiment was conducted on semi-insulating
GaAs(100) wafers with an n-GaAs epilayer 0.25
and on p-Si(100) wafers with a resistivity of 20
The n-GaAs epilayer had a carrier density of
The GaAs surfaces were precleaned ﬁrst with a
monoethanolamin solution and then with an aqueous
solution of ammonia in a ratio of
= 1 : 5.
The silicon surfaces were precleaned in an aqueous
solution of hydrogen peroxide and ammonia in a ratio
= 1 : 1 : 4. The wafers were
spincoated with photoresist ﬁlms 0.5–0.6
using an acrylate or a diazonaphthoquinone (DNQ)
photoresist. After a thermal treatment, the acrylate pho-
toresist was exposed to light in the wavelength range
225–260 nm (DRKs-500 mercury lamp); then it was
removed with dimethylformamid. The DNQ photore-
sist was exposed at 350–450 nm (DRSh-250 mercury
lamp) and removed with dimethylformamid or a 0.6%
aqueous solution of KOH.
Residual-Photoresist Removal from Si and GaAs Surfaces
by Atomic-Hydrogen Flow Treatment
E. V. Anishchenko*, V. A. Kagadei*, E. V. Nefedtsev**, K. V. Oskomov**,
D. I. Proskurovski**, and S. V. Romanenko**
*OAO Nauchno-issledovatel’skii institut poluprovodnikovykh priborov, Tomsk, Russia
**High Current Electronics Institute, Siberian Division, Russian Academy of Science, Tomsk, Russia
Received July 12, 2004
—It is shown by experiment that a directed atomic-hydrogen stream offers a means of residual-pho-
toresist removal from Si and GaAs surfaces. The dependence of postprocess surface roughness on process time
and temperature is investigated. It is demonstrated by AFM measurement that the atomic-hydrogen treatment
can reduce GaAs surface roughness. It is concluded that the technique is as effective as the conventional oxy-
Carbon-contaminant contents at the Au/Si interface after precleaning and resist removal
Carbon-contaminant content, rel. units
Precleaning 47 86 20 –
Resist removal 368 510 51 260
Notes: (1) The resist is of the DNQ type. (2) Precleaning uses a NH
O mixture. (3) Resist removal uses an aqueous solution of KOH.