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How a microcontroller is made?

every day whether enough people are

aware of it they experience process is

controlled by integrated circuits

Infineon Technologies develops logic and

memory components around the globe

experts in research and development

centers are working on new semiconductor

and system solutions production takes

place in leading-edge manufacturing

facilities worldwide up to 1 billion

transistor functions fit on a silicon

chip only one square centimeter in size

the watchword for the future smaller

faster more efficient

this is the raw material chips are made

of sand it is made up of silicon dioxide

silicon is the second most common

element on the Earth's crust and only

exists in bonded form complicated

chemical and physical processes are

needed to convert silicon into a

crystalline form and make sure the

crystals will meet all the requirements

necessary for chip production the final

product is a mono crystalline silicon

rod of highest purity

this means the rod has only one impurity

atom for every 10 million silicon atoms

silicon is a semiconductor it's atomic

structure looks like this each silicon

atom has four outer electrons there are

no free charge carriers the pure silicon

mono crystal is a non conductive at room

temperature to make it conductive small

quantities of specific impurity atoms

such as phosphorus are built in

phosphorus has five outer electrons

the fifth phosphorous electron built

into each molecule of the silicon

crystal lattice can move freely because

of this structure the silicon

phosphorous crystal is negatively

charged or n conductive boron atoms on

the other hand have only three outer

electrons when they are built into the

silicon lattice one silicon electron is

missing

this creates electron holes they move

through the crystal like positively

charged electricity particles the

material is positively charged or p

conductive the transistors in modern

memory chips are constructed from P and

n conductive layers such as these

transistors are the smallest control

units in the microchips in the heart of

an N Mo's transistor for example we find

P and n conductive layers of silicon

crystals

an additional layer consists of silicon

oxide and acts as an insulator a layer

of electrically conductive polysilicon

is applied on top of it every transistor

has three connections the middle one is

attached to the gate the electrically

conductive poly silicon if we apply an

electrical charge only to the two outer

connections electricity is unable to

flow the transistor is blocked things

are different when an additional charge

is attached to the middle connection the

electrons from the P layer now wandered

toward the middle connection and

accumulate at the border area between

the silicon crystal and the insulation

gate oxide a channel through which the

electrons can flow is form between the

islands of n conductive material the

electrical circuit is closed the

transistor can be switched back and

forth between current off and current

flow that is to say between zero and

water this binary system is the basis of

electronic data processing

one highly complicated component for

example is this dynamic one gigabit

memory chip on an area of only 1.3

centimeters it can store the contents of

64,000 standard sized sheets of paper if

it were constructed of conventional

components it would cover the area of a

small town layout and designer at the

beginning of chip manufacture the large

number of components calls for an

elaborate design process to define the

circuitry functions of the chip next the

technical and physical characteristics

of the chip are simulated and it's

functions tested up to 1 billion

transistors per chip are connected with

the aid of wiring tools the design tool

forms the connection to a

three-dimensional architecture of

sandwiched layers this construction plan

is transferred to masks

these are reprographic stencils for the

subsequent manufacturing process the

cover precision of the masks is

monitored by a measuring machine which

can detect deviations in the range of a

hundred thousandth of a millimeter

the finished masks of the geometric

image of the circuits that are exposed

one after another in several production

processes

the flawless production of

microscopically small structures calls

for a virtually dust free environment in

which the temperature and humidity are

stable the cleanroom meets these

requirements here in 10 liters of air

there is a maximum of only one dust

particle larger than 1/2 micrometer not

even the purest mountain air can compete

with that

the ventilation filtration and supply

area in the cleanroom is extremely

elaborate here 5.2 million cubic meters

of air are circulated every hour

hundreds of air volume regulators

maintain a constant airflow the silicon

wafers are transported from the 300

millimeter fabrication in hermetically

sealed containers clean rooms inside the

cleanroom so to speak this helps reduce

costly filtration technology the high

technological standard closed material

circuits and energy reclamation keep

environmental stresses to a minimum

supply systems with special containers

and filters maintain the extremely high

purity of the chemicals

the basic material for the chips is a

one millimeter thick silicon wafer this

is a tiny cutout of a wafer edge one

quarter of a micrometer first the

conductive or non conductive layers are

produced by oxidation of the surface at

approximately 1,000 degrees Celsius in a

high-temperature furnace a drop of

photoresist is uniformly distributed by

centrifugal force on the oxide layer

produced thus creating a light-sensitive

layer special exposure machines

so-called wafer steppers transfer the

masks by exposure to the silicon wafer

the accuracy of adjustment to the

features already produced must remain

within a tolerance of 1/100 of a

micrometer

next the photo resist coated wafer is

exposed through a mask the exposed

section can be developed while the

unexposed feature remains

the oxide layer is etched off this

etching process is carried out either by

wet etching or plasma etching in plasma

etching special gases combined with the

layer to be removed this makes it

possible to remove the microscopically

thin layers inside the windows created

by exposure development and etching

after dissolving the remaining

photoresist and then cleansing another

oxidation takes place this time a very

thin layer is affected electrically

conductive poly silicon is deposited on

this insulation layer then once again

photoresist masks and exposure occur and

the exposed photoresist is again

dissolved then the poly silicon and the

thin oxide layer itched off they both

remain intact only in the middle under

the resist layer in the next step and

ion implanter shoots impurity atoms into

the silicon this changes the

conductivity of the exposed silicon by

fractions of a micrometer

structure widths distances and cover

precision are constantly checked after

the residual photoresist has been

removed another oxide layer is applied

once again the cycle of photoresist

exposure removal and dissolution takes

place contact holes are etched in to

open up access to the conductive layers

because the contacts and

interconnections must now be deposited

for this purpose metal compounds are

sputtered onto the wafer in sputtering

machines

once again photoresist and mask

depending on the component over 200

meters of interconnections are created

the unexposed strips show the path of

the aluminum conductor tracks that

remain behind after the etching process

and provide the contact to the

underlying layers more and more often

aluminum interconnections are being

replaced by copper ones because the

outstanding electrical conductivity of

copper guarantees an extremely high data

transfer rate the insulation layer above

the interconnections must be given a

smooth surface which is why the CMP the

chemical mechanical process is used

excess material and the micrometer range

is polished off in this production line

the individual work processes are

repeated four to five hundred times

until the integrated circuit of a

component is completely assembled almost

five hundred one gigabit chips have been

produced on a 300 millimeter silicon

wafer

none of these chips is any larger than a

single key on a computer keyboard molded

into a plastic housing the microchip is

used for several thousand applications

over the past few years the chip

connections have changed considerably on

the first plastic microchip housings

hold still had to be drilled in the

printed circuit boards the later

housings can be directly soldered to the

surface

to save space in the circuit boards the

connections in the latest construction

forms are located on the underside of

the components this way over a thousand

connection contacts can be realized the

third dimension is already being used

for highly complex logic components

sandwich chips are supplied as complete

units all the production phases of chips

are controlled by researchers and

developers using scanning electron

microscopes the comparison with a human

hair shows us the dimensions of today's

micro electronics the checking and flow

analysis equipment is just as precise

for test purposes of focused ion ray

drills precise holes in the connection

allowing intervention into the completed

circuitry the supplementary

interconnection being inserted into the

circuit here is only one micron wide

chip development has become the

pacemaker of our economy micro

electronics is the key industry of our

modern information society

thanks to microchips our lives have

become more mobile worldwide networking

makes everyday professional life easier

the technological accomplishments of

modern telecommunications depend

primarily on progress in the

semiconductor industry

microchips provide convenience and

simplify the storage of images and data

microchips recognize people and

correlations microchips make vehicles

more efficient and even safer Infineon

Technologies is at the forefront of the

industry and sets standards for the

latest cutting-edge technologies never

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