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Although lapping would appear to be simple in concept, the successful implementation of a production lapping operation requires the development of a technique and experience to achieve acceptable quality with good yields. Small adjustments to the rotation rates of the plates and carriers will cause the plates to wear concave, convex or flat.

As lapping is a messy process, various efforts have been made to avoid it or to substitute an alternative process. The most likely approach at present is grinding, in which the wafer is held on a vacuum chuck and a series of progressively finer diamond wheels is moved over the wafer while it is rotated on a turn table. Grinding gives a clearer surface than lapping, however, only one side may be ground at a time and the resulting flatness is not as good as that obtained by lapping.

Edge contouring

The rounding of the edge of the wafer to a specific contour is a fairly recent development in the technology of wafer preparation. It was known by the early seventies that a significant number of device yield problems could be traced to the physical condition of the wafer edge. An acute edge affects the strength of the wafer due to: stress concentration, and a lowering of its resistance to thermal stress, as well as being the source of particle chip, breakage, and lattice damage. In addition, the particles originating from the chipped edges can, if present on the wafer surface, add to the defect density (D 0 ) of the IC process reducing fabrication yield. Further problems associated with a square edge include the build-up of photoresist at the wafer edge. The solution to these process problems is to provide a contoured edge with a defined radius (r).

Chemical etching of wafers results in a degree of edge rounding, but it is difficult to control. Thus, mechanical edge contouring has been developed and the result has been a dramatic improvement in yields in downstream wafer processing. Losses due to wafer breakage are also reduced. The edge contouring process is usually performed in cassette-fed high speed equipment, in which each wafer is rotated rapidly against a shaped cutting tool ( [link] ).

Schematic illustration of edge contouring.

Etching

The mechanical processes described above to shape the wafer leave the surface and edges damaged and contaminated. The depth of the work damage depends on the specific process, however, 10 μm is typical. Such damage is readily removed by chemical etching. Etching is used at multiple points during the fabrication of a semiconductor device. The discussion below is limited to etches suitable for wafer fabrication, i.e., non-selective etching of the entire wafer surface.

Wet chemical etching

The wet chemical etching of any material can be considered to involve three steps: (a) transportation of the reactants to the surface, (b) reaction at the surface, and (c) movement of the reaction products into the etchant solution ( [link] ). Each of these may be the rate limiting step and thus control the etch rate and uniformity. This effect is summarized in [link] .

Questions & Answers

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.
Damian
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
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
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
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
How can I make nanorobot?
Lily
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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