S-O4-2

Study of plasma-surface reactionsbya multi beam system
イオン・ラジカルビームによるプラズマ表面反応のシミュレーション実験
Kazuhiro Karahashi, Satoshi Hamaguchi
唐橋一浩，浜口智志
DCenter for Atomic and Molecular Technologies, Graduate School of Engineering,OsakaUniversity,
2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
大阪大学大学院工学研究科原子分子イオン制御理工学センター，〒565-0871 大阪府吹田市山田丘2-1
A multi-beam system has been developed for the investigation ofinteractions of reactive ionicand radicalspecies with material surfaces in plasma etching for microelectronicsmanufacturing processes. The
systemcan independently irradiate the sample surface witha mass-selected single-species ion beam andreactive molecular beams, by which etching reactions in plasma environments can be simulated on thesample surface in ultrahigh vacuum (UHV)conditions. Angular and time-resolved measurements ofscattered/desorbed species aremadewith a rotatable quadrupole mass spectrometer (QMS). In-situ
measurements of surface chemical states aremade by X-ray photoelectron spectroscopy (XPS) and Fouriertransform infrared spectroscopy (FTIR).

Dry etching with reactive plasmas has been
widely used in the fabrication of materials.For thedevelopment of integrated semiconductor devices, amore precise control of the etching process isrequired for further progress.It is known thatreactive ion species and reactive neutral species,
which are produced in plasma, play important rolesin etching reactions. However, the mechanisms forsuch etching reactions have not yet been
quantitatively understood because the individual
reactive species cannot be controlled independently
in the conventional etching apparatus.For a better
understanding of etching reactions, it is necessary
to clarify the roles of individual reactive ionsand
neutral species.A beam experimental method is ahighly useful tool for the investigation ofinteractions of individual species with surfaces.
Some features of beam experiments are summarizedin Table 1.Pioneering work by Coburn et al. using
beam experimental methods clearly showed thatsilicon etching reactions on fluorinated surfaces areenhanced by energetic inert ion bombardment[1].Such previous studies provided usefulqualitative understanding of silicon etching thatuses only halogen gas.In practical applications,however, various etching reactions with different
materials used in the manufacturing ofsemiconductor devices must be quantitatively
understood for amore precise control of the etchingprocesses and also the development of processsimulations. Therefore it is important to perform asystematic study onindividual surface chemical
reactions associated with reactive species containedin processing plasmas.

Table 1beam experiments

We have developed a multi-beam (i.e., ion andradical beam)system for the investigation of theinteractions of reactive ions with various material
surfaces (Fig.1) [2] [3] [4] [5]. A photograph of thesystem is give in Fig. 1.

Fig.1.View of the multi-beam system

11than those provided by the injected beams isdesigned to react with the sample surface. The mass
selecting magnet selects only ionic species of a
specified mass from the initial beam, which leaves
only the ion beam of a single species in the rest of
the beam line.
Figure 2 also schematically depicts how the ion
and neutral beams can be injected into a substrate(sample) simultaneously in the reaction chamber.
Charge neural beams of atoms, molecules, and/or
radical species are provided by two molecularbeams. An incident ion energy is measured with theQMS coupled with an energy analyzer, and angularand time-resolved measurements of desorbing
molecules are performed with a rotatable
QMS.In-situ measurements of the chemical statesof molecules in the surface layer of the substrate are
performed by XPS and FTIR.
In the presentation, details of some experimental
results that have been obtained in the multi-beam
will be also presented.

101269847314132

511mFig. 2. A plane view of the multi-beam system.

A plane view of the beam injection system isgiven in Fig. 2. It consists of (1) an ion beam source,(2) a sector-type 90° mass selecting magnet, (3) anion beam line with ion optics, (4) a reaction
chamber, (5) a supersonic molecular beam sourcewith a heatable nozzle, (6) an effusive molecularbeam source with a radio-frequency (RF) plasma
source, (7) a rotatable quadrupole mass
spectrometer (QMS) for the measurement ofscattered/desorbed species from the sample (8) aQMS with an energy analyzer for the beamcharacterization, (9) an X-ray source for X-ray
photoelectron spectroscopy (XPS) [located above
the molecular beam source (6)], (10) an electronenergy analyzer for XPS, (11) Fourier transform
infrared (FTIR) spectrometer, (12) IR optics, (13) aMCT detector for IR, and (12) a load lock chamber.
(The number in the parentheses corresponds to thenumber of each label in Fig. 1.)
A sample (substrate), into which all the beams
are to be injected, is placed in the UHV reaction
chamber, where no atomic/molecular species otherReferences[1] J. W. Coburn, H. F. Winters, and T. J. Chuang: J.
Appl. Phys 48(1997) 3532.
[2]K. Karahashiet al.: J. Vac. Sci. Technol. A22(2004) 1166.
[3] K. Ishikawa and K. Karahashiet al.: J. Vac. Sci.
Technol. A 21(2003) L1..
[4]K. Yanai and K. Karahashi et al.: J. Appl. Phys
97(2005) 53302[5]T.Ito and K. Karahashi et al.: J. Appl. Phys
97(2005) 53302