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Deformed wafers and their characteristics.
Type of bow and warp Surface appearance Lattice curvature Comments
flat flat ideal
curved flat
curved curved
flat curved
curved flat slips

Heat treatment

As-produced Czochralski grown crystals often have a level of oxygen impurity that may exceed the concentration of dopant in the semiconductor material (i.e., Si or GaAs). This oxygen impurity has a deleterious effect on the semiconductor properties, especially upon subsequent thermal processing, e.g., thermal oxide growth or epitaxial film growth by metal organic chemical vapor deposition (MOCVD). For example, when silicon crystals are heated to about 450 °C the oxygen undergoes a transformation that causes it to behave as an electron donor, much like an n-type dopant. These oxygen donors, or "thermal donors", mask the true resistivity of the semiconductor because they either add additional carrier electrons to a n-type crystal or compensate for the positive holes in a p-type crystal. Fortunately, these thermal donors can be "annihilated" by heat treating the materials briefly in the range of 500 - 800 °C and then cooling quickly through the 450 °C region before donors can reform. In principle thermal donor annihilation can be performed on wafers at any time during their fabrication; however, it is usually best to perform the heat treatment immediately after wafering since sub-standard wafers may be rejected before additional processing steps are undertaken and thus limiting additional cost. Donor annihilation is a bulk effect, and therefore the thermal treatment can be performed in air, since any surface oxide that may form will be removed in subsequent lapping and polishing steps.

Lapping or grinding

The as-cut wafers vary sufficiently in thickness to require an additional operation, the slicing operation does not consistently produce the required flatness and parallelism required for many wafer specifications, see [link] . Since conventional polishing does not correct variations in flatness or thickness, a mechanical two-sided lapping operation is performed. Lapping is capable of achieving very precise thickness uniformity, flatness and parallelism. Lapping also prepares the surface for polishing by removing the sub-surface sawing damage, replacing it with a more uniform and smaller lapping damage.

The process used for lapping semiconductor wafers evolved from the optical lens manufacturing industry using principles developed over several hundred years. However, as the lens has a curved surface and the wafers are flat, the equipment for lapping wafers is mechanically simpler than lens processing machines. The simplest double-side lapping machine consists of two very flat counter-rotating plates, carriers to hold and move the wafers between the plates, and a device to feed abrasive slurry steadily between the plates. The abrasive is typically a 9 μm Al 2 O 3 grit. Commercial abrasives are suspended in water or glycerin with proprietary additives to assist in suspension and dispersion of the particles, to improve the flow properties of the slurry, and to prevent corrosion of the lapping machine. Hydraulics or an air cylinder applies lapping pressure with low starting pressure for 2 to 5 minutes, which is then increased through most of the process. The completion of lapping may be determined by elapsed time or by an external thickness sensing device. The finished process gives a wafer with a surface uniform to within 2 μm. Approximately 20 μm per side is removed during the lapping process.

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
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
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar 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, Chemistry of electronic materials. OpenStax CNX. Aug 09, 2011 Download for free at http://cnx.org/content/col10719/1.9
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