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IMPLANTATION TECHNOLOGYByOnyekanne Maria Chinyerem (40389)Onwudiwe Killian ( 40505 )Ebunu Abraham ( 40501 )Department Of Material Science And Engineering Course: Energy StorageLecturer: Professor Esidor NtsoenzokJanuary 2017African University Of Science and Technology Abuja

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OUTLINEIon implantation overviewDescription of an Implanter and Working principleInnovations in implanter technologyPIII comparison with standard implantersApplications of implanters in semiconductor and non semi conductor materialsInnovative application proposalsSummary and Conclusion Appreciation

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Background and IntroductionION IMPLANTATION: what is it ? !!!!!process by which energetic impurity atoms can be introduced into single crystal substrate in order to change its electronic propertiesIn this process the ions are accelerated to high energies and allowed to impact the silicon surfaces. Because of inherent energy they penetrate into the lattice and are placed inside the silicon lattice. low-temperature technique for the introduction of impurities (dopants) into semiconductors and offers more flexibility than diffusion.

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Background and IntroductionThe idea was proposed by Shockley in 1954, but used for mass production only after late 1970s. Before ion implantation, doping is achieved by diffusion into the bulk silicon from gaseous source above surface, or pre-deposited chemical source on wafer surface.This approach lacks the flexibility and control required by CMOS processing, and ion implantation quickly gained popularity for the introduction of dopant atoms.Modern ion implanters were originally developed from particle accelerator technology. Their energy range spans 100eV to several MeV (a few nms to several microns in depth range). The implantation is always followed by a thermal activation (600-1100oC).

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IMPLANTERS

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DISCRIPTIONSTypical ion implantation parameters:Ion: P, As, Sb, B, In, ODose: 1011 - 1018 cm-2Ion energy: 1 - 400 keV Uniformity and reproducibility: 1%Temperature: room temperatureIon flux: 1012-1014 cm-2s-1The implanter basisIon sourceMass analyzer/spectrometerIon acceleratorNeutral beam trapBeam scannersWaferFaraday cup.

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WORKING PRINCIPLESIon source: Desired ion of the dopant species are generated from ionization of eitherGas/sputtered solidArsine (AsH3), Arsenic Penta fluoride (AsF5), phosphine (PH3), di borane (B2H6), boron tri fluoride (BF3). Ionization is achieved by displacing one or two electrons to give positive ions, since most mass spectrometer works with positive ions. This process is carried out at a voltage of ab0ut 25Kv-40Kv

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Mass analyzer/spectrometer26/01/20178

Ion accelerator: The ions that makes it through the mass spectrometer are been accelerated with a certain voltage (0-175Kv) to ensure the beam of ions travel with a particular kinetic energy. Since the ions will be travelling through a vacuum, acceleration is done to increase the kinetic energy of the ions so that they can make through the vacuum. It is necessary the ions travel through a vacuum to avoid interaction with oxygen, so as not to cause any reaction.Neutral beam trap

The neutral beam trap is composed of an electrostatic charge bars that allow neutral charges to pass freely, while the positively charged are deflected on to the wafer.26/01/20179

Awafer, also called a slice or substrate, is a thin slice of semiconductor material, such as a crystallinesilicon, used in electronics for the fabrication of integrated circuits and in photovoltaics for conventional,wafer-based solar cells.Wafers are formed of highly pure (99.9999999% purity),nearly defect-free singlecrystalline material.One process for forming crystalline wafers is known as czochralski growthinvented by the Polish chemist Jan czochralski.A boule of pure mono crystalline material is hence formed, sliced and polished to form wafers.

Wafer:Beam scanning:The focused ion beam is scanned over the wafer in a highly controlled manner in order to achieve uniform doping.26/01/201710

26/01/201711Faraday cup.For each positive ion that enters the faraday cup, an electron is drawn from ground through the current meter to neutralize the positive charge of the ion. The magnetic field stops outside the secondary electrons from entering and secondary electrons produced inside from exitingThe faraday cup is arranged in a process chamber and beam line, corresponding to an ion beam shooting position

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Advantages of ion implantationExtremely accurate dose controlTailor made and well controlled doping profile large range-of doses-1011 to 1016/cm2 Low Temperature process Wide choice of masking materials (Oxide, PR, Metal) Clean environment (Mass separation, vacuum) Non-Equilibrium process (conc. Excess of S.S. limit)Disadvantages of ion implantationHighly sophisticated and costly. Damage to semiconductor. Dopant redistribution during AnnealingPhotoresist heating and hard to strip

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Innovations Advanced ion implantation technology: takes full advantage of doping and defect engineering approaches such as device leakage, contact resistance, device and process variability and of precision materials modification opportunities. It is necessary that advanced implant tools for sub 20nm node incorporate a variety of novel features and capabilities

Safe delivery source (SDS) technology : this is used for the low pressure storage and dispersing of arsine and phosphine to ion implanters

Ion implantation with scanning probe alignment: A scanning probe instrument which integratesion beamswith the imaging and alignment function of apiezo resistivescanning probe in high vacuum. The beampasses through several apertures and is accurately set by a hole in the cantilever of the scanning probe.

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15Improved single ion implantation with scanning probe alignment :Improved technique for deterministic placement of singledopantatoms by singleion implantationwith scanning probe alignment. Ions are generated in amicrowavedrivenion source,mass analyzed in a Wien filter, and impinge on spin readout devices after alignment of theion beamto regions of interest with a noncontact scanning force microscopeSource: Michael Llg et al, 2012: improved single ion implantation with scanning probe alignment, journal of vacuum science and technology B

Innovation contd.

16Single wafer mechanical scan ion implanter: This makes use of spot beam technology with ionized molecules which maximizes the throughput potential and produces uniform implants with fast setup time and with superior angle control

PIII, What is it?Plasma immersion ion implantation (PIII) is a material modification technique for treating the near-surface regions of materials by implanting energetic ions from a plasma which surrounds the sample.A number of different terms are used, such asplasma source ion implantation (PSII), plasma ion implantation (PII),plasma immersion implantation (PII), plasma-based ion implantation (PBII), plasma implantation (PI or p-technique),plasma doping (also PLAD) and Ionclad. 26/01/201717

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WORKING PRINCIPLEShttp://www.sdsenc.in/sable/1386/exploitation-bentonite/

(source: W. Ensinger 1998)26/01/201718The vacuum chamber can be of two types diode and triode type depending upon whether the power supply is applied to the substrate as in the former case or to the perforated grid as in the latter.Plasma source/generator: electron cyclotron, helicon plasma source, capacitively coupled plasma source, inductively plasma source, DC glow discharge and metal vapour arc ( for metallic species

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The plasma envelopes the sample. The sample is negatively biased. Ions from the plasma are accelerated and implanted into the sample.

26/01/201719Accelerated ion is extracted from plasma using high voltage pulsed DC or pure DC supply and targeting them to the substrate or electrode (cathode for electropositive plasma and anode for electronegative plasma) with semiconductor wafer placed over it so as to implant it with suitable dopants.By means of a pumping system and a gas feed system, an atmosphere of a working gas at a suitable pressure is created, then a plasma is generated Sample holder: The sample to be treated is placed on a sample holder in a vacuum chamber. The sample holder is connected to a high voltage power supply and is electrically insulated from the chamber wall.

Conventional Ion Implantation (CII) Verses Plasma Immersion Ion Implantation (PIII)

Ion Source

Target Beam ScannerIon BeamAnalyzing Magnet

PumpingIon Beam Implantation using an Accelerator

Plasma Immersed Ion Implantation (PBII, PIII)

Plasma Source

Pumping

High Voltage Pulser

+-Target

Difficult to implant to a large area or a complicated shaped targetFor a large area or a complicated shape target.Simple system structure is another good point.But,Not easy to process the target with a narrow hole, trench, etc., or inside of a pipe.Non single ion implantation is another demerit

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21PropertiesStandard implanterPlasma immersion ion implanterHazardousNot easily operated , is sophisticated and not easy to maintainSystem is relatively easy to operate and maintain.

EconomicalThe CII technique is a sophisticated line of sight process where a sample can be doped at room temperatureCapital investment and running cost are substantially lessTime ConsumingProcess time is dependent of sample size and its surface areaProcess time is independent of sample size and its surface area.FlexibleAny shape, size and weight of sample cannot be processedAny shape, size and weight of sample can be processed.

Versatile: Multiple processes cannot be carried out like implantation, deposition, etching, etc., Multiple processes can be carried out like implantation, deposition, etching, etc., and not just semiconductor or metals, even insulating samples can be treated.

High Throughput: Number of samples cannot be processed at the same timeNumber of samples can be processed at the same time

Temperature.Room temperature processLow- temperature process.

22PropertiesStandard implanterPlasma immersion ion implanterUniformity: The sample surface cannot be implanted ensuring uniform dose rate with good conformity.The sample surface can be implanted ensuring uniform dose rate with good conformity.

ImplantationImplantation of multiple species with multiple charges is not possible in the same system Implantation of multiple species with multiple charges is possible in the same system

DRAWBACKSAs no mass separation is possible, there are always chances of implantation of undesired impurities present in the plasma into the target, in addition to the desired dopants.Secondary electrons limit the efficiency and generate x-rays. Accurate in situ dose monitoring is tough. Implant energy distribution is inhomogeneous.

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Applications of ion implantationDopingNitrogen or other ions can be implanted into a tool steel target (drill bits, for example). prosthetic devices such as artificial joints, it is desired to have surfaces very resistant to both chemical corrosion and wear due to friction.ion beam mixing, i.e. mixing up atoms of different elements at an interface.High speed mosfet.Metal parts on heart valves are ion implanted by carbon to make them biocompatibleRadioisotopes are implanted in prosthesis for localized radiotherapy

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Application of PIIIMicro electronics (plasma doping/PLAD)Biomaterials (surgical implants, bio and blood compatible materials)Plastics (grafting, surface adhesion) metallurgy (hard coatings and tribology)Thin metallic coatings on polymeric surfaces example in electronic circuits, sensors, electromagnetic shielding and flexible reflecting surfaces26/01/201725

Innovative applicationsOne source multi element surface treatment of materials : where hardening and surface finishing of a particular material can be carried out using different ions of different elements with a single machine, by ionizing at a particular time, the atoms of the required element. This reduces the need for several equipment in several applications.

Dose controlled coating of materials: where the particular dose for a given surface area can be accurately determined to influence the desired characteristics and properties onto the substrate

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Summary and ConclusionPlasma Immersion Ion Implantation is a potential alternative that circumvents the limitations of conventional ion implantation, such as the requirements of low ion beam current, complicated target handling, non-uniform implantation profile and ion beam scanning complexity for implantation of three-dimensional targets. On account of the maturity and its simplicity, it is believed that the PIII process technology will find many more applications in the surface modification and semiconductor industry. Reliable and non-expensive equipment is still one of the key issues.

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References[1] S.B. Felch et al., Ion implantation for semiconductor devices: the largest use of industrial accelerators, Proceeding of PAC2013, Pasadena, CA USA, ISBN 978-3-95450-138-0. http://accelconf.web.cern.ch/accelconf/pac2013/papers/weyb2.pdf 23/01/17 http://www.epj-onferences.org/articles/epjconf/pdf/2016/10/epjconf_MINOS2015_01002.pdf 23/01/17http://accelconf.web.cern.ch/accelconf/pac2013/talks/weyb2_talk.pdf 23/01/17 http://www-inst.eecs.berkeley.edu/~ee143/fa10/lectures/Lec_08.pdf 23/01/17

Professor N. Esidor, [2017], Lecture Note: Material for Energy and Storage, AUST.Andre Anders , Lawrence Berckeley Laboratory; Handbook of Plasma Immersion ion implantation and Deposition

28https://en.wikipedia.org/wiki/Plasma-immersion_ion_implantation 26/01/2017https://en.wikipedia.org/wiki/Ion_implantation 26/01/2017 Dushyant Gupta. Plasma Immersion Ion Implantation (PIII) Process Physics ANDTechnology

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