S10-3
Challenges and Prospects of Advanced Plasma Process Technology 2
先端プラズマプロセス技術の課題と展望２Toshihisa Nozawa
野沢俊久
Tokyo Electron LTD, TEL Sendai Technology Center Sendai
1 Techno Hills, Taiwa-cho, Kurokawa-gun, Miyagi 981-3629, Japan
東京エレクトロン株式会社 TELテクノロジーセンター仙台〒981-3629宮城県黒川郡大和町テクノヒルズ1番The plasma process has evolved as a key technology for semiconductor manufacturing. Extensive researchand development efforts on the plasma process technology especially on the etching process have been
done, and great progress have been achieved in practice. Low temperature plasma process for beyond 10nm nodes such as advanced thin film deposition technology using plasma CVD and ALD are facing more
stringent requirements. The challenges and prospects of these techniques are described herein.

1. BackgroundThe
state-of-the-art
miniaturization
ofsemiconductor devices has come to beyond 10nm
nodes. As technology trend evolves, theintroduction of 3D gate, new materials such as ⅢⅤ[1], and practical use of the STT-MRAM [2] has
become necessary and highly demanded.
Traditionally, lithography technology has leaded
miniaturization of semiconductor processing;
however, in the era of sub-10nm, commercializationof EUV lithography system has been seriously
delayed due to lack of productivity. Alternately, thedouble patterning technique by incorporatingplasma etching into current lithography technology
has been applied for process and device
miniaturization [3]. Herein, the challenges andprospects of plasma process technology for beyond
10nm nodes are briefly described.
2. Plasma etching
Plasma etching of conventional films (e.g. Si,SiO2, SiN) have been well studied and understood,
and is being applied to mass production. The
etching equipment technology such as more rigidcontroloveruniformity,stability,andreproducibility are critical for beyond 10nm nodes
device processing in the future. As new materials
are being introduced into devices, plasma etchinghas been facing more challenges to etch thoseunconventional materials, for example, the material
used in MRAM is difficult to be etched and toobtain vertical profile. The breakthrough in etching
technology is unquestionably needed for thesechallenges.
In addition, materials degradation often occurs
during plasma etching process due to plasma

induceddamage(sputtering,VUV,etc.)
Damage-less or even damage-free etching will bedefinitely required for beyond 10nm nodes process,especially for new materials such as Ⅲ-Ⅴmaterials.
Countermeasures for plasma induced damage haveto be developed.
3. Plasma CVD
As Ⅲ-Ⅴ materials and transition metals are
preferred to be processed at less than 400℃, lowtemperature film deposition using plasma
technology with resulting film properties
comparable to that of thermal CVD film isrequired.
4. Plasma ALD
3D device structure has been utilized and films indevices are getting thinner. ALD technology has
been inevitably applied in device processing toachieve extremely thin and conformal deposition.
ALD processing is also preferred to be carried out
at low temperature, which promoted plasma assist
ALD process for high quality conformal film
deposition at low temperature.
5. Prospects for plasma process
Plasma process is a method of using ions andradicals to add and/or remove materials. Higher
density of radicals and ions contributes to obtainhigher quality film property in the low temperatureprocess. It is necessary to use high frequency andhigh power for achieving high density plasmaprocess. Currently, frequency of 400kHz ~2.45GHz [4] is used in the semiconductor process.
Research on high frequency microwave and VHF
plasma has not been sufficient. Further exploration

in this area is expected.
In recent years, in order to reduce the plasma
induced damage, neutral beam [5] and pulsed
plasma [6] have been developed for etching andCVD process [7]. A neutral beam system isphysically isolated from the plasma chamber by theutilization of apertures. Therefore, processing isdone under less irradiation by ions, electrons andUV photons, which avoids or lessens the plasma
induced damage.
Since there is no re-dissociation of reaction
products by plasma, new process phenomena thatwill be different from the conventional plasma
process would be expected in a neutral beamprocess.
6. Summary
To manufacture devices with further higher speed
and higher integration, the development of plasma
etching technology for new materials and plasma
ALD and CVD technology for high quality films isrequired.
References[1] S. Takagi et al: VLSI Technology (2010)147[2] K. Ando et al: J. Appl. Phys. 115, 172607(2014)[3] G. E. Bailey et al. :SPIE 6521, (2007)[4] V. Donnelly: J. Vac. Sci. Technol. A31 (2013)[5] D. Nakayama: J. Phys. D: Appl. Phys. 46(2013)[6] T. Mukai et al: Jpn. J. Appl. Phys. 45(2006)[7] Y. Kikuchi et al: J. Phys. D: Appl. Phys.(2013)

Fig3. DRAM capacitor

Fig.4. ALD method

Fig.5. Conformal SiN film by plasma ALD

Fig.1. 3D gate structure

Fig.2. 3D NAND structure

Fig.6. Schematic diagram of neutral beam system