Neutral Beam Technology Research Articles

(Invited) Challenges for Etch Technology and the Integration of New Channel Materials Beyond 7 nm

Even with the copious advances in logic device fabrication, integration of new channel materials would represent a significant advance in CMOS technology. [1] Successful integration of new channel materials (III-V’s, Ge and SiGe) pose significant challenges for etch technology. Dry (plasma) etch technology can be used to pattern channel materials after they are deposited using an epitaxial process [2]; alternatively channels maybe inserted into bounded (for example an oxide) recesses (for example silicon) fabricated using etch technologies already developed for FinFET and SAQP applications. Less appealing is the use of wet processes that have troublesome crystallographic orientation dependencies. Dry etch technology for most new channel material candidates is not new. [3] Still, with dry etch technology there is the ever-present worry of damage. [4-6] High precision etch technology commonly referred to as atomic later etching (ALE) is an emerging viable option for new channel material integration. [7-10] Some approaches employ non-mainstream techniques such as neutral beam technology [8] or complex precursors. [10] Recent developments reinforce that conventional plasma etch technologies developed using concurrent engineering methods can meet the requirements for 7 and 5 nm logic fabrication. [7,11] This presentation will show how advanced plasma etch technologies provide a path for logic manufacture beyond 7 nm with a realistic picture of the trade-offs that must be handled for the introduction of III-Vs, Ge or SiGe. All in all, etch technologies if successfully implemented for new channel material integration relies of leveraging surface chemistry mechanisms. The presentation will be rounded out with a discussion of how first-principles methods (e.g., DFT methods) can be used to gain insight into important plasma –surface interaction mechanisms. S. Takagi et al., Japanese Journal of Applied Physics 54, 06FA01 (2015) Chen et al,. Nanoscale Research Letters, 7, 431 (2012) Plasma Etching of III–V Nitrides,” by R. Shul, in Processing of Wide Band Gap Semiconductors: Growth, Processing and Applications, 250 (2000), ed., S.J. Pearton F.D. Auret et al., Physica B, 407, 1497 (2012) Kasumandari et al., Appl. Phys. Lett., 103, 033511 (2013) “Dry Etching of Semiconductors at the Nano-and Micro-Scale” by S.J. Pearton in Vistas in Nanofabrication, (2012) A. Ranjan et al., J. Vac. Sci. Technol. A 34, 031304 (2016) S.D. Park et al., Appl. Phys. Lett. 91, 013110 (2007); C. T. Carver et al., ECS J. Sol. St. Sci. Tech., 4 N5005-N5009 (2015) S. M. George, Chem. Rev., 110, 111 (2010) S.D. Sherpa et al., J. Vac. Sci. Technol. A 35, 01A102 (2017)

(Invited) Neutral Beam Technology – Defect-free Nanofabrication for Novel Nano-materials and Nano-devices

In the fabrication of semiconductor devices, reactive plasmas arewidely used in key processes suchasmicrofabrication, surface modificationand film deposition, and there are now demands for processingprecision at the atomic layer level, and for deposition accuracy thatallows the control of structures at the molecular level. However, inultra-miniature nanoscale devices that will become the mainstream inthe future, the use of plasma processes can cause serious problemssuch as abnormal etching and breakdown of insulation films by theaccumulation of ions or electrons emitted from the plasma , also the formation of surface defects (dangling bond) of overa few tens nm in depth by exposure to ultraviolet (UV) emissions fromthe plasma. In particular, since nano-scale devices have a larger surfacearea compared with the bulk material, plasma processes can havea large influence on the electrical and optical properties of devices dueto process-induced defects caused by ultraviolet exposure,since future nano-devices will require size control of three-dimensionalstructures at the atomic layer level, it will be absolutely essential tocontrol surface chemical reactions with high precision and selectivity at the atomic layer level. To achieve charge-free and UV photon irradiation damage-free processes, we have developed a new neutral beam generation system based on my discovery that neutral beams can be efficiently generated from the acceleration of negative ions produced in pulsed plasmas. Using the neutral beam processing, we successfully demonstrated sub-50nm damage-free gate electrode etching, damage-free Si channel etching for 45 nm fin-FETs, ultra-thin gate dielectric film formation for 32 nm fin-FETs, damage-free low dielectric film deposition for 22 nm FETs, and low-damage surface modification of carbon materials (including nanotubes, graphenes and organic moleculers) for future nanodevices. More recently we have investigated processing technologies based on the combination of biotechnology with neutral-beam-based nano-processes, i.e., bio-nano processes, for future nanoelectronics devices and successfully achieved the fabrication of sub-10-nm-diameter and high density Si, Ge, GaAs, InGaAs and Graphene nanodisk (nanodot) array structures. The quantum effects of these nano-scaled structures were shown to manifest themselves at room temperature due to the damage-free surfaces made possible by the neutral beam processes. Now, by using these nanodisk structures, we are actively developing “Novel Quantum Effect Devices”, such as quantum dot solar cell for high energy conversion efficiency of more than 45 % and quantum dot laser. This paper introduces the neutron beam generation technique developed by S. Samukawa [1], and discusses its application to nanoprocessing and nanodevices that have recently been vigorously pursued. We conclude our developed neutral beam process is indispensable to progress atomic layer pure surface reactions for atomic layer process such as etching (ALE) and deposition (ALD).We are actively developing ultra-low-damage nanofabrication techniques using neutral beam technology that tap into the essential nature of nano-materials and nano-structures, and developing innovative nanodevices. S. Samukawa, ECS Journal of Solid State Science and Technology, 4 (6) N5089 (2015).

Optimization of Steady-State Beam-Driven Tokamak Reactors

Recent developments in neutral beam technology prompt us to reconsider the prospects for steady-state tokamak reactors. A mathematical reactor model is developed that includes the physics of beam-driven currents and reactor power balance, as well as reactor and beam system costs. This model is used to find the plasma temperatures that minimize the reactor cost per unit of net electrical output. The optimum plasma temperatures are nearly independent of ..beta.. and are roughly twice as high as the optimum temperatures for ignited reactors. If beams of neutral deuterium atoms with near-optimum energies of 1 to 2 MeV are used to drive the current in a reactor the size of the International Tokamak Reactor, then the optimum temperatures are typically T /SUB e/ approx. = 12 to 15 keV and T /SUB i/ approx. = 17 to 21 keV for a wide range of model parameters. Net electrical output rises rapidly with increasing deuterium beam energy for E /SUB b/ less than or equal to 400 keV, but rises only slowly above E /SUB b/ about 1 MeV. We estimate that beam-driven steady-state reactors could be economically competitive with pulsed-ignition reactors if cyclic-loading problems limit the toroidal magnetic field strength ofmore » pulsed reactors to less than or equal to 85% of that allowed in steady-state reactors.« less

Neutral Beams for Fusion Research: Development and Application

Ion beam technology has advanced immensely during the past 15 years in connection with the application of neutral beam injection heating for fusion research. Ion sources have been scaled up along with necessary modifications, yielding currently a few megawatts of extraction power (e. g., 40 keV-60 A, 0.3-sec pulse). The entire neutral beam injection system has become a multidisciplinary technology including plasma physics, accelerator and beam physics, pumping technology, heat transfer, electrical engineering, and so on. Since the neutral beam injection heating of fusion plasmas has been proved the most viable means of increasing the plasma temperature to ignition, the future demand and requirements are rising with the size of fusion plasma devices. A brief review of the state of the art of neutral beam technology is presented and the direction of the future neutral beam field is discussed.

Fusion: Neutral Beam Technology

Fusion: Neutral Beam Technology

Concept for a High-Power-Density Mirror Fusion Reactor

A concept for a mirror-type fusion reactor based on recent advances in neutral-beam technology is shown to have improved plasma stability, a much higher power density, and a somewhat higher factor of energy gain $Q$, as compared with previous concepts using the magnetic-mirror principle.