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Presented By :M.Vikas Vardhan ReddyM.Tech in Computational Engg.ID:[email protected]
Annealing of damages created by Ion-implantations & Masking during Implantation +
characterization of doped layers
04/10/2023
Annealing and its use…
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
Process of repairing implant damage (i.e., “healing” the surface) is called annealing .Also puts dopant atoms in substitutional sites where they will be electrically active
2 objectives of annealing:
1) healing, recrystallization (500 - 600 oC)
2) renew electrical activity (600 - 900 oC)parameters that get most affected are conductivity, the
mobility and the life time.Region of maximum damage?
04/10/2023
Annealing Classes
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
Divided into two classes(based on type of material) they are 1. Pre-amorphised2. No pre-amorphised
Pre-amorphised
T<=400 degrees centigrade3. Partial recovery(clusters disappear)
4. 20% to 30% activation
5. Recovery life time is extreme low
T<=600 degrees centigrade
1. Recrystallization takes place
2. 50% to 90% activation3. Recovery life time is lowT>=950 degrees
centigrade1. Fast recovery
04/10/2023
No Pre-amorphisation
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
Low dose , light ion implantation, we can fully recover of all the parameters ,conductivity, mobility, as well as life time by 800 to 950 degree centigrade.
Heavy ion implantation, low dose we can fully recover of all the parameters by 1000 degree centigrade.
It is difficult to get full activation for high dose heavy ion implantation.
if the life time recovery is not very important than pre amorphisation is better than not pre amorphisation material.(at 600c we get 90% activation)
04/10/2023
Practical cases…
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
Phosphorous in siliconBoron in siliconArsenic in silicon
Phosphorous in silicon Phosphorus is a relatively heavy ion, so it loses its
energy primarily by the nuclear stopping mechanismProjected range proportional to incident energylot of energy to put phosphorus deep into the siliconRp=1.1 μm/M ev.
04/10/2023
Annealing of phosphorus and arsenic
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
As the temperature increases the carrier activation increases till eventually at a point it sort of acquires full activation or let us say, 90% of activation.
arsenic in silicon, arsenic also
behaves in a manner very similar
to that of phosphorus. Rp=0.58 μm/M ev.
04/10/2023
Annealing of boron
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
boron is a light ionRp=3.1 μm/M ev.for boron, for the incident energy range in 10 to 100
kilo electron voltAnnealing behavior of Boron.
Masking during Implantation + characterization of doped layers
04/10/2023
Masking in ion implantation
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
Ion implantation is a room temperature process and therefore you have a larger choice of mask material. You do not have to use silicon dioxide always, like in case of diffusion.
Ion implantation can use photoresist as the maskSilicon and mask layer generate energic ions when ion
beam is incident on semiconductor and these energy ions will have Gaussian principle.
04/10/2023
Gaussian profile
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
d is the masking layer thickness.
If d is large less impurity is put
inside silicon
If d is less large amount of impurity
is put inside silicon
04/10/2023
Masking layer efficiency
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
04/10/2023
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
04/10/2023
Amount of impurity not protected by mask
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
Practical case
04/10/2023
Evaluation of doped layer
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
Junction depthDoping profile
Junction depth Junction depth is measured by lapping and strainingCylindrical groove techniqueInterference fringe method
04/10/2023
Junction depth by lapping and straining
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
Angled lapping
Cross sectional diagram of the junction
04/10/2023
Cylindrical groove method
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
04/10/2023
Interference fringe method
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
Third method to find the junction depthLapped sampleProvide optical flat and subject to monochromatic
radiation usually sodium vapour lamp.Dull fringes appear in p region and we can count it.Now junction depth=no.of dull fringes * wavelength
of monochromatic light.
04/10/2023
Doping distribution
Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of
doped layers
doping distribution, the impurity distribution. Now we can measure the total impurity distribution by doing spectroscopy analysis like SIMS, Secondary Ion Mass Spectroscopy, which will tell us exactly how much impurity is put inside the material.
But, it will not tell us whether this impurity is electronically active or not, whether it is sitting in the substitutional site or it is just sitting anywhere inside the semiconductor
Thank you
