<< Chapter < Page Chapter >> Page >
Section 3.4 describes the physics and application of Schottky Diode and Section 3.5. describes the procedure for realizing ohmic contact.

3.4.schottky diode.

Metal Aluminum is the commonly used interconnection path in Integrated Circuit Technology because it provides a good conducting path and it makes ohmic contacts on the contact pads of the solid state devices being integrated. Bulk ‘Al’ has a resistivity of 2.7×10 -6 Ω-cm but in thin film form its resistivity is higher by a factor of 20 hence it high current densities as high as ~ 10 5 A/cm 2 which is required for high speed switching networks it leads to serious reliability problems of a phenomena known as electromigration which is a major cause of the breakdown of VLSI and ULSI integrated circuits.

At nodes (length of the channel) below 90nm, the pitch (the lateral width of the interconnect) of interconnection is 45nm or less. At this level of integration, to build complex and dense circuits the multilevel metallization is routinely employed. As much as 10 multi layers are used. The metal thickness ranges from a fraction of μm to several μm. The thinner interconnects route signals while thicker layers serve as power bus. Electrical connection between two adjacent levels of interconnects are made through a VIA. To reduce the contact resistance at a contact pad a Silicide such as NiSi 2 is added. In electromigration (also known as the electron wind effect) metal ions are forced to move downstream due to the high electron current densities, along the the grain structure. This results into voids and hillocks in the film at curves and forks.The thinning due to voids leads to excessive heating and break in the conducting path.

Electromigration is prevented by controlling the grain structure along the microcrystallites that form the metal lines. Larger grains have less surface area and therefore resist electromigration. Some alloying metals, such as copper, accumulate in the grain boundaries, locking the atoms thetre into place and thus preventing electromigration. Copper also prevents hillocking of Al films and thus prevents non-unifporm thermal effects. It is thus increasingly common to add Cu to Al in small quantities to form interconnects. Since 1998 IBM has introduced Cu interconnects leading to a much higher performing ICs with no problem of electromigration even at interconnect pitch lower than 90nm. Copper has replaced Aluminum as the interconnect material in nodes below 90nm. Cu has excellent electromigration reliability and 40% lower resistance than Al. It may be deposited by electroplating or by CVD. Copper patterns are etched by damascene process. This wil be given in supplementary sheets.

But ‘Al’ is itself P-Type material as is evident from Figure 3.26 and Table 3.4.1. Hence its deposition on P-Type Semi-conductor will give an ohmic contact but its deposition on N-Type Semiconductor gives rise to rectifying contact and such an interface is a PN Junction diode which in reality is Metal-Semiconductor Diode with very fast switching properties. This Metal Semiconductor was studied by Schottky in great details and hence it is called Schottky Diode.

Questions & Answers

what is mutation
Janga Reply
what is a cell
Sifune Reply
how is urine form
Sifune
what is antagonism?
mahase Reply
classification of plants, gymnosperm features.
Linsy Reply
what is the features of gymnosperm
Linsy
how many types of solid did we have
Samuel Reply
what is an ionic bond
Samuel
What is Atoms
Daprince Reply
what is fallopian tube
Merolyn
what is bladder
Merolyn
what's bulbourethral gland
Eduek Reply
urine is formed in the nephron of the renal medulla in the kidney. It starts from filtration, then selective reabsorption and finally secretion
onuoha Reply
State the evolution relation and relevance between endoplasmic reticulum and cytoskeleton as it relates to cell.
Jeremiah
what is heart
Konadu Reply
how is urine formed in human
Konadu
how is urine formed in human
Rahma
what is the diference between a cavity and a canal
Pelagie Reply
what is the causative agent of malaria
Diamond
malaria is caused by an insect called mosquito.
Naomi
Malaria is cause by female anopheles mosquito
Isaac
Malaria is caused by plasmodium Female anopheles mosquitoe is d carrier
Olalekan
a canal is more needed in a root but a cavity is a bad effect
Commander
what are pathogens
Don Reply
In biology, a pathogen (Greek: πάθος pathos "suffering", "passion" and -γενής -genēs "producer of") in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s.[1][2
Zainab
A virus
Commander
Definition of respiration
Muhsin Reply
respiration is the process in which we breath in oxygen and breath out carbon dioxide
Achor
how are lungs work
Commander
where does digestion begins
Achiri Reply
in the mouth
EZEKIEL
what are the functions of follicle stimulating harmones?
Rashima Reply
stimulates the follicle to release the mature ovum into the oviduct
Davonte
what are the functions of Endocrine and pituitary gland
Chinaza
endocrine secrete hormone and regulate body process
Achor
while pituitary gland is an example of endocrine system and it's found in the Brain
Achor
what's biology?
Egbodo Reply
Biology is the study of living organisms, divided into many specialized field that cover their morphology, physiology,anatomy, behaviour,origin and distribution.
Lisah
biology is the study of life.
Alfreda
Biology is the study of how living organisms live and survive in a specific environment
Sifune
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 Download on the App Store Now




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?

Ask