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Where

τ E = RC delay time constant at EB junction;

τ C = RC delay time constant at CB junction;

τ B = Transit time delay through Base Width;

τ CSCL = Transit time delay through reverse biased CB junction;

v S = scatter limited velocity of electrons while falling down the potential hill at CB junction;

To achieve this objective , we must simultaneously reduce the two transit times, cross-sectional area of capacitances and series resistances. Introduction of C in SiGe base has helped reduce R sh of Base even after thinning as required in vertical scaling.

Reduction in time delay requires that quiescent I C is increased which means that Kirk Effect must be pushed to high Current Density. This is achieved by increasing Collector Dopant Concentration for which we do Selectively Implanted Collector(SIC).

SIC allows higher values of I C , decreases R C and reduces W CSCL . But increase in SIC, means more lateral and vertical diffusion in subsequent heat cycles which leads to higher C CB . So vertical and lateral scaling should be carefully controlled to maximize f T and f max .

Table IX.2. Milestones of Development of SiGe-strained Si FETs.

Device Year of first introduction
FET concept 1926
Si(MOSFET) 1960
Si(CMOS) 1963
First oxidation study of SiGe 1971
SiGe-nMODFET 1986
SiGe-pMODFET 1986
SiGe Photodetector 1986
SiGe SBD 1988
SiGe hole RTD 1988
SiGe BiCFET 1989
SiGe gate CMOS tech 1990
SiGe Wave Guide 1990
SiGe pMOSFET 1991
SiGe electron RTD 1991
SiGe LED 1991
SiGe Solar Cell 1992
SiGe photo transistor 1993
SiGe pMOSFET on SOI 1993
Strained Si pMOSFET 1993
Strained Si nMOSFET 1994
SiGe:C pMOSFET 1996
SiGe pFET on SOS 1997
Submicron SiMOSFET 1998
Vertical SiGe pFET 1998
Strained SiCMOS 2002

SiGe Technology has become the driving force behind the explosion in low cost, light weight, personal communication devices like digital wireless handsets and other entertainment and information technologies such as Digital Set-Top Boxes, Digital Broadcast Satellites, Automobile Collision Avoidance and Personal Digital Assistants. SiGe extends the life of wireless phone batteries and allows more durable communication devices. Products combining the capabilities of Cellular Phone, Global Positioning and Internet access in one package are designed using SiGe.

These multi-function, low cost mobile client devices capable of communication over voice and data networks represent a key element of the future of computing.

SiGe HBT in CMOS for high end PC failed but SiGe HBT succeeded in RF Communication Circuits because of low power consumption.

SiGe Technology is finding extensive applications in:

Wired Communication;

Wireless Communication Circuits;

In Disk Storage;

High speed BW instrumentation;

Discrete SiGe HBT in Amplifiers and Wireless Devices;

IC SiGe HBT in GSM handsets, in CDMA hand sets, in Base stations, in Wireless LAN chipsets and in high speed 10-40Gb/s Synchronous Optical Networks(SONETS) receivers.

Ge grading in Base helps higher transit frequency f T and increase in short circuit current gain β F . By suitable trading of β F with r x ( base spreading resistance), BW can further be improved. By increased Base Doping, r x reduces. This reduction adversely effects β F but gives considerable improvement in transit frequency and in Noise Figure of the device. For same I C (collector current) , SiGe HBT has a higher short circuit current gain, lower RF noise and lower flicker noise or 1/f noise as compared to an identical Si BJT. In SiGe , higher raw speed and lower power consumption can be traded depending upon the application.

Table IX.3 Comparison of CMOS with conventional Si-BJT and SiGe HBT ( after Harame)

Parameters CMOS Si BJT SiGe HBT
f T high high Higher
f max high high Higher
Linearity Best Good Better
V BE (or V Th ) tracking Poor Good Good
1/f noise Poor Good Good
Broad Band Noise Poor Good Good
Early Voltage Poor OK Good
g m Poor Good Good

Real strength of SiGe lies in Analog, RF and Digital Applications in existing CMOS Fabrication Foundaries. This makes possible implementation of new Architecture such as direct conversions and software defined radio.

SiGe BiCMOS Technology.

This technology demands that Low Temperature Epitaxy(LTE) SiGe process be combined with high temperature CMOS processing.

CMOS performance must be retained ( same as the parent CMOS process) after the addition of LTE SiGe in order to use existing digital ASIC Libraries and Design Methodologies.

Similarly CMOS processing must not significantly alter the doping profile ( and hence performance) of SiGe HBT.

In this integration the two primary issues are thermal budget and trade off between process modularity and process sharing.

IBM first generation (5HP) 0.5µm SiGe BiCMOS used a “base equal gate” scheme. A common layer stack is used for both HBT base and FET poly-Si Gates.

Problem arises when CMOS advances to 0.24µm Technology(6HP). At this point CMOS thermal cycle increased significantly because of the need for Source/Drain dopant activation for NMOS and gate side wall oxidation. So “ base after gate” strategy is adopted. HBT is built after the formation of gate, gate spacer, LDD implants and NMOS anneals. This simplified BiCMOS integration of SiGe HBT with newer generation of CMOS.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Solid state physics and devices-the harbinger of third wave of civilization. OpenStax CNX. Sep 15, 2014 Download for free at http://legacy.cnx.org/content/col11170/1.89
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