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ARTIFICIAL RETINA USING THIN-FILM TRANSISTORS

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lovely angel

on 25 December 2013

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Transcript of ARTIFICIAL RETINA USING THIN-FILM TRANSISTORS

ARTIFICIAL RETINA USING THIN-FILM TRANSISTORS
DRIVEN BY WIRELESS POWER SUPPLY

Cause of Blindness

Damage to:


• Clear structures in the eye, that
allow the light to pass through.


• The nerves within the eye.


• The Optic nerve


• Brain
Fabrication of Thin-Film Transistor


New Masking Technique



• An SiO2 buffer layer is deposited on the glass substrate


• Then, pad poly-Si patterns are formed for source and drain regions



• A 25 nm channel poly-Si layer is deposited by low pressure chemical vapor
deposition (LPCVD) at 600 oC.



• Then a 150 nm SiO2 gate insulator is deposited by electron cyclotron
resonance chemical vapor deposition (ECR-CVD) at 100 oC in a vacuum.

15

Fabrication of Thin-Film Transistor






• Then, a Cr film is deposited at 180 oC.

• First, only p-channel gate electrodes are formed.

• The next step is to form source and drain regions of p-channel TFTs

by the new I/D technique.

• Boron ions are implanted through the gate insulator with a dose of

of 80 keV.

• N-channel gate electrodes are also formed and phosphorus ions are

implanted with a dose of 110 keV by the new I/D technique

• Impurities are activated by a XeCl excimer laser.

16

1

SEMINAR ON



ARTIFICIAL RETINA USING THIN-FILM TRANSISTORS
DRIVEN BY WIRELESS POWER SUPPLY

13

SelfAligned structure and non (S/A) TFT
characteristics


• Parasitic capacitance between the
gate electrode and source and
drain regions of a S/A TFT is
estimated to be only about 2 -5 %
that of a non-S/ATFT



• High speed operation can be
expected.

10

Fabrication of Thin-Film Transistor



Optical microscopic image of the 100 ppi
organic thin-film transistor

14

SelfAligned structure and non (S/A) TFT
characteristics

THANK YOU

28

12

electrode.

• Then implanted into the substrate.
• Impurities can be implanted over
the entire 300 mm square substrate.
• Maximum accelerating voltage of
over 110 KeV which is sufficient
for implanting impurities through
the 150nm SiO2 gate insulator.

extraction
acceleration

an
an

by
and

accelerated
electrode

Fabrication of Thin-Film Transistor





• Ions from discharged gas are

Artificial Thin-Film Transistor Retina






• Implantable microelectronic retinal prostheses



• Externally worn digital camera which samples the wearers visual
environment.



• The first application of an implantable stimulator for vision restoration was
developed by Dr S. Brindley and Lewin in 1968.

6

9

Retinal Implantation







• The epiretinal implant have high image resolutions.

• Stimulus signal can be directly conducted to neuron cells .

• Here living retinas are not seriously damaged.

• The input to the Epiretinal Implant is more easily controlled

Retinal Implantation




Subretinal implant
•Subretinal implants sit on the outer
surface of the retina.


•Directly stimulates the retinal cells


•Replace damaged rods and cones by
Silicon plate carrying 1000’s of light-
sensitive micro photodiodes each
with a stimulation electrode.


•Light from image activates the micro
photodiodes, the electrodes inject
currents into the neural cells.

8

Retinal Implantation



Epiretinal implant
•They sit in the inner surface of the retina.


•They bypass a large portion of the retina.


•Provides visual perception to individuals


•The implants receive input from a
camera


•Electrodes from the implants electrically
stimulate the ganglion cells and axons at
the start of the optic nerve.

7

5

Artificial Thin-Film Transistor Retina



• Recovers the sight sense for sight-handicapped people.



• Electronic Photo devices and circuits substitutes deteriorated
photoreceptor cells.



• Implanted inside the eyes.



• Implanting classified into two types: Epiretinal implant and
Subretinal implant .



• Thin-Film Transistors, fabricated on transparent and flexible
substrates.

3

The Retina

2

Cause of Blindness



Damage to:


• Clear structures in the eye, that
allow the light to pass through.


• The nerves within the eye.


• The Optic nerve


• Brain

BLINDNESS

11

and CMOS configurations.



ION Doping Techniques
• 5% PH3. or 5% B2H6 diluted by hydrogen is used for the doping gas .
• RF plasma is formed in the chamber by RF power with a frequency of
13.56 MHz

Low temperature poly-Si TFTs have been developed.
For integrated drivers, CMOS configurations are used.
High speed operation due to parasitic capacitance in Self-Aligned TFT’s
ion implantation is one of the key factors in fabricating such as TFTs






Fabrication of Thin-Film Transistor

degenerate.
• Loss or damage of central vision.
• Common among aged people.
• Peripheral retina spared.

region

macula

in

• Cones

Macular Degeneration



• Genetically related.

• Gradually progress towards center
of eye.
• Spares the foveal region.
• Tunnel vision results.

• Degeneration of the retina

Diseases of Eye


Retinitis Pigmentosa



• Hereditary genetic disease.

4
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