<< Chapter < Page Chapter >> Page >


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

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
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
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play

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
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Solid state physics and devices-the harbinger of third wave of civilization' conversation and receive update notifications?