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Next, a machine called a stepper ( [link] ) is calibrated to project an extremely fine and focused image through a special type ofreticle film in a manner similar to that of a simple slide projector. The light that is transmitted through the reticle isprojected onto the photoresist layer, which reacts to the light and begins to harden. All of the parts of the wafer exposed to thislight harden into a tough crust while the parts in shadow remain soft. This particular step is known by the name ofphotoelectrochemical etching because it achieves an etching effect, resulting in a chip.

An artist’s illustration of a stepper (image from Solid State Electronics).

Hundreds of copies of the chip are etched onto the wafer until the entire surface has been exposed. Once this process is complete, the entirewafer is submerged into an etching bath, which washes away any parts of the photoresist that remain unexposed along with theinsulating chemicals underneath. The hardened areas of the photoresist, however, remain and protect the layers of materialunderneath them. This process of depositing chemicals, coating with a photoresist, exposure to light over a film mask, and etching andwashing away is repeated more than a dozen times. The result is an elaborate, three-dimensional construction of interlocking siliconwires.

This product is then coated with another insulating layer and is plated with a thin layer of metal, usuallyeither aluminum or copper. Yet another photoresist is laid down on top of this metal plating, and after the wafer is exposed in astepper, the process repeats with another layer of metal. After this step has been repeated several more times, a final wash stepis performed, and a finished semiconductor product rolls off the assembly line, at last.

What is a clean room?

A typical semiconductor fabrication facility, or “fab” in industry jargon, looks like a normal two- or three-story officebuilding from the outside, and most of the interior space is devoted to one or more “clean rooms,” in which the semiconductorsare actually made. A clean room is designed with a fanatical attention to detail aimed towards keeping the room immaculate anddust-free ( [link] ).

An industry clean room at AP Tech (photo from Napa Gateway).

Most if not all surfaces inside these clean rooms are composed of stainless steel, and these surfaces aresloped whenever possible or perforated by grating to avoid giving dust a place to settle. The air is filtered through both theceiling and the floor to remove particles that are down to 1/100 the width of a human hair. Lighting is characteristically brightand slightly yellowish to prevent mildew from forming behind equipment or in recessed corners, and even the workers in a cleanroom must be absolutely spotless.

Workers in these rooms must be covered from head to toe in “bunny suits” that completely seal the body in abulky suit, helmet, battery pack, gloves, and boots. Once sealed in these suits, the workers often look more like space explorers in ascience fiction movie than computer chip employees, but in order to even enter the stainless steel locker room to suit up to beginwith, they must first pass through a series of air lock doors, stand under a number of “air showers” that actually blow dust offof clothing, and walk across a sticky floor matting that removes grime from the bottom of shoes.

Questions & Answers

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
Idrissa Reply
im all ears I need to learn
right! what he said ⤴⤴⤴
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
im not good at math so would this help me
Rachael Reply
I'm not good at math so would you help me
what is the problem that i will help you to self with?
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele 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, Pdf generation problem modules. OpenStax CNX. Sep 23, 2008 Download for free at http://cnx.org/content/col10514/1.4
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