implantation introduction

ImplantationIntroduction, Principle,

SRIM & TRIM simulation, Thermal Spike Model and Observations from SRIM

K. Kamalakkannan,Research Scholar, Ion Beam Research LabDepartment of Nuclear Physics University of Madras, Chennai

Ion Beam Research Lab, Department of Nuclear Physics

Introduction All the electronic equipment needs Semiconducting materials (p-n type). Doping of impurities (carriers) can be processed by two ways- Diffusion and

Implantation. Diffusion is limiting process due to saturation limit and so, we can’t make high

concentrated carriers. To overcome the diffusion issues of dopants & activation of dopants in material- ion

implantation or ion irradiation is the best. In general using particle accelerators to shoot energetic ions on a material is the basic

process of implantation and irradiation. Ion implantation is a variety of ion irradiation, as is swift heavy ions irradiation from

particle accelerators with very high energies induces ion tracks.


Ion Implantation- Introduction Ion implantation- a materials engineering process by which ions of a material are

accelerated in an electrical field and impacted into a solid. This process is used to change the physics, chemical and/or electrical properties of

the solid- cause many chemical and physical changes in the target by transferring their energy and momentum to the electrons and atomic nuclei of the target material- causes a structural change, in that the crystal structure of the target.

Major components are,1. Ion source2. Accelerator3. Target chamber


Ion Implanter

Implantation

Structuring

Thin FilmDeposition

Ex: Simulation of B ions in SiC 300 keV


Important parameters and Typical values

E

q

I

A

j

Ion Energy (eV)

Ion Charge Number

Ion Current (A)

A Angle of IncidenceE,q,I(cm2)

(cm-2s-1)

Irradiated Area

Ion Flux

(cm-2)Ion Fluence

Remark: “Dose” is often used rather than “Fluence”(although “Dose” should be a volume energy density)

j t

j I

qeA

(10 to 500 keV)

(10 μA to ~30 mA)(60 to 70)

Ion source: Any element including gas in whole periodic table can be chooseTarget: Any target matrix can be choose.


Ion- Solid interactions

Multiple collision With electrons

E= Energy of ions m1, Z1 and m2, Z2= Mass No., At. No. of Incident ions and Target material Rp= Range of ions

When energetic ions passes through matter, it looses its energy in two ways,

1. Electronic energy loss due to inelastic collision with electrons(Se) [Electronic stopping]

2. Nuclear energy loss due to elastic collision with atoms of the solid(Sn) [Nuclear stopping]

Electronic stopping- Dominant at higher energies (tens of MeV & more)- Swift Heavy ion irradiation (SHI)

Nuclear stopping- Dominant at low energies (tens of keV to MeV)


Implantation Simulations- SRIM and TRIM

SRIM- The Stopping and Range of Ions in Matter - Group of programs which calculate the stopping and range of ions (up to 2 GeV/amu) into matter using a quantum mechanical treatment of ion-atom collisions.

TRIM- The Transport of Ions in Matter - Most comprehensive program, accept complex targets made of compound

materials with up to eight layers, each of different materials. It calculate all kinetic phenomena associated with the ion's energy loss: target damage, sputtering, ionization, and phonon production.

Based on a Monte-Carlo calculation which follows the ion into the target, making detailed calculations of the energy transferred to every target atom collision. (multi-layer complex targets)

Developed by J. F. Ziegler and J. P. Biersack


SRIM calculations: Energy Loss- Stopping powers Stopping powers Sn= dE/dx (Differential energy loss per unit length) Low energy ions <2MeV – elastic collision – nuclear energy loss High energy ions > 2MeV – Inelastic collision – electronic energy loss - SHI. Electronic stopping- (Electronic energy loss) Interaction of heavily charged ions

with electrons of the target material through Coulomb forces, produce track of ionization and highly kinetic electrons along the path of the primary ion - latent track (Se>Sth) – Sth depends on the material.

This Electronic stopping forms huge defects (defect clusters, dislocation loop disordered lattice, amorphous etc.)

Nuclear Energy loss- Due to elastic collision at lower energies dominant nuclear stopping. This Causes damage and dislocation of nuclei from their lattice sites due to elastic collisions.

Always produce lattice defects(Interstitial atoms, anionic or cationic vacancies)


Electronic and Nuclear stopping power- Ex: Aluminum

SRIM prediction of electronic and nuclear stopping power of Al ion in different ion energies.

Nuclear stopping power is mostly happened for low energy implantation. The lower value of nuclear stopping power is causes the less defects because the higher nuclear stopping power leads atomic displacements.


Thermal Spike Model The energy-loss mechanism of the projectile-ion leads to electronic and atomic collision-cascades This model replaces the complex process of the atomic collision-cascades by an abrupt temperature

rise in an infinitesimal cylindrical volume around the ion trajectory at the time-of-passage t = 0.

Basic steps of thermal-spike model.

(a) Undisturbed solid at temperature T0. (b) At the time-of-passage the tem perature within a

small cylinder rises rapidly to a much higher temperature T »T0.

(c) After the passage of the ion, defects are thermally created while the thermal energy gradually dif fuses away radially from the ion trajectory.

(d) Remaining are "frozen" defects.


Observations from SRIM and TRIM

Ion Range (Rp)= Range of ionEx: Boron 100 keV in SiC (Rp= 2010 Å)

XY Ions SimulationEx: Boron 100 keV in SiC

Damage events

Ex: Boron 100 keV in SiC


Observations from SRIM and TRIM

Recoil EnergyEx: Al 300 keV in SiC

Energy Loss due to ionizationEx: Al 300 keV in SiC

Also,3D views of ion damages, Range of ions, Recoil energy, Phonon and Lateral range distribution XY ions simulations- Lateral, Longitudinal view and Vacancies can be calculated

Thank You

implantation introduction

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