38137384 Semi Conductor Devices

8/8/2019 38137384 Semi Conductor Devices

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Semiconductor DevicesLecture 1

Dr. Mostafa El-Khamy

8-Oct-09 1ELCT 503, Semiconductors -- Dr. Mostafa El-Khamy


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Course Introduction

Instructor Dr. Mosta a El-Kha

Teaching Assistants utor a : asm ne ga Labs: Yasmine Sanad



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Course Information

References Solid State Electronic Devices Ben G.

Streetman and Sanjay Banerjee

, ,S. M. Sze

. .Korzec, GUC



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Course Syllabus

I. Semiconductor TechnologyI. Growth o Se iconductor

II.Excess Carriers in SemiconductorsIII. P-N Junctions

.

V. Field Effect Transistors Junction FET

VI. Metal Oxide Semiconductor FET(MOSFET)

.8-Oct-09 4ELCT 503, Semiconductors -- Dr. Mostafa El-Khamy


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Course Components

lecture: 2 h, Thursday, 5:00 7:00 p.m. H1

lab: 1 h web page: http://eee.guc.edu.eg/



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Assessment System (tentative)

me o s r u on

assignment 10%

quizzes 15% 2 x 7.5%

a per ormance xmidterm exam 20%

design project 15%

inal exam 45%



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First Transistor

1947

Picture shows a point-contact

plate of n-type germanium and

two line-contacts of gold

supporte on a p ast c we ge.Source:

. ,

The path to the conception of the

junction transistor,

IEEE Tr. on Electron Devices

ED-23, 597 (1976).



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first monolithic integrated circuit

1961

Picture shows a flip-flopcircuit containing 6

devices, produced in

.

Source:

R. N. Ne ce, Semiconductor

device-and-lead structure,

U.S.Patent 2,981,877



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first microprocessor

1971

Picture shows a

four-bit microprocessor .

10 m technology

mm mm

2300 MOS-FETs

z c oc requency

Source:



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Pentium IV processor

Picture shows a ULSI-

Intel Pentium 4.

technology

17.5 mm 19 mm

42 000 000 components

1.6 GHz clock freu nc

Source:

Intel Corporation



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Moores Law



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Si Semiconductor Devices

rocess ow or manu ac ur ngSemiconductor Devices fromSilicon Starting materials, silicon

dioxide for a silicon wafer arehigh-purity polycrystallinesemiconductor from which single

. The single-crystal ingots are

shaped to define the diametero t e mater a an sawe ntowafers.

polished to provide smooth,specular surfaces on which

.



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Crystal Growth

Density of Si: 5 1022 atoms/cm3

semiconductor material a oms mus e o very g pur y: ec ron cGrade Silicon (EGS)

Impurities are reduce to part per billion High Purity Si which is polycrystalline must be

converted to a single crystal

: SiO2 Poly-Chrystalline EG Si Single Chrystal



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EGS

2 e a urg ca ra e SiO2 react with C in the form of coke in an arc furnace at 1800oC

SiO2 + 2C Si + 2CO

Not pure enough for electronic application, not single crystal

Metallurgical Grade Si Electronic Grade Si Reactin with dr HCL to form trichlorosilane

Si + 3HCL SiHCL3 + H2 o 3

chlorides of other impurities, such as FeCL3

Fractional Distillation can be used to separate trichlorosilane Highly pure EGS is obtained by reaction with H2

3 + 2 = +



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Single Crystal Growth

zoc ra s e o Seed crystal needed for growth Seed Crystal is lowered into the

molten material and is raised slowlyw ro a on a ow ng e crys ato grow onto the seed

Meltin oint of Si is 1412 de C

Crystal is rotated slowly to averageout any temperature variations

solidification

Similar method is used for Si, Gean a Si Cylinder is polished and sliced

into individual wafers about 775 um

Silicon crystal grown by the

Czochralski method. This large single-crystal ingot provides 300 mm (12-in.)diameter wafers when sliced using a

thick8-Oct-09 16ELCT 503, Semiconductors -- Dr. Mostafa El-Khamy

saw. The ingot is about 1.5 m long

(excluding the tapered regions), andweighs about 275 kg.


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,notch on one side, being loaded into a wire saw to produce Si wafers; (b) a technicianholding a cassette of 300 mm wafers. (Photographs courtesy of MEMC Electronics Intl.)


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Crystal Growth

Concentration Coefficient: kd = Cs / CL Ratio of Concentration of im urit in rowin cr stal

(Solid) to concentration of impurity in the melt

(Liquid) function of the material, the impurity, temperature

of the solid liquid interface, and growth rate

that of the crystal, crystal becomes doped

.

For uniform doping of the ingot, kd is varied by varying

the pull rate8-Oct-09 18ELCT 503, Semiconductors -- Dr. Mostafa El-Khamy


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Crystal Growth

Example: Si crystal grown by Czochralskimethod desired do in im urit is 1016

phosphorus atoms cm-3 , For P in Si, kd=0.35

CL = CS / kd;

n a concen ra on o n e me = . = .

atoms/cm3



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Device Fabrication



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Device Fabrication

Steps.

2. Selected removal of oxide layer :otomas ng -> oto t ograp y anetchin

3. Introducing dopant atoms in localized

Implanting

4. Interconnection and assembly (metallizationand acka in



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Question

Why did Si replace Ge at the beginning of ICEra? There is no convenient way for controlled doping

form localized P or N regions

. , . ,

ni is proportional to T^3 e^-Eg/KT

ni|Si < ni|Ge, for same temp, Ge will still be

intrinsic compared to Si Si is easier than Ge in forming a stable oxide

SiO2

Si devices can thus be much smaller8-Oct-09 22ELCT 503, Semiconductors -- Dr. Mostafa El-Khamy


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Metals, Insulators and

em con uctors


I l M l d


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Insulators, Metals and

em con uc ors For electrons to experience acceleration inapp ie e ectric ie t ey must e a e to move

into new energy states: i.e. empty states muste ava a e

Insulators (Carbon Diamond): At T=0K the valence band can be com letel filled

with electrons and the conduction band is empty

No charge transport in the valence band, since there are noemp y s a es No charge transport in the conduction band since there are

no electrons


I l M l d


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Insulators, Metals and

em con uc ors Metals: an s over ap or are on y par a y e ,

electrons and empty energy states are intermixed within the

bands, so electrons can move freely under influence of electric

Metals have high electrical conductivity

Semiconductors At 0K have the same structure as insulators: filled

energy band gap

However, the energy band gap E_g in Semiconductors ismuc sma er an n nsu a ors Electrons can be excited from the valence to the conduction band

by thermal or optical excitation e num er o e ectrons or con uct on ncrease y t erma or

optical excitation8-Oct-09 25ELCT 503, Semiconductors -- Dr. Mostafa El-Khamy


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Intrinsic Semiconductor

Electron-Hole Pairs in a semiconductor An Electron in the valence band receive enou h

thermal energy to be excited across the bandgap

to the conduction band to or an electron-holepair

to as a hole



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Intrinsic Semiconductor

n: concentration of electrons in theconduction band

p: concentration of holes in the valence band

ni: ntr ns c carr er concentrat on

= =n

Electronhole

covalentbonding model


crystal.

38137384 Semi Conductor Devices

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