Description of I.C
How to read I.C
The integrated circuit (IC) chip has found its way into
everything from toasters to communications satellites.
This small electronic device, a miniature package of
transistors, has revolutionized product design and
increased capability while shrinking size and cost in
ICs can be made very compact, having up to
several billion transistors and other electronic
components in an area the size of a fingernail. The
width of each conducting line in a circuit (the line
width) can be made smaller and smaller as the
technology advances; in 2008 it dropped below 100
nanometres and in 2013 it is expected to be in the
tens of nanometres.
1.Read the serial number from the top side of the
IC. The top side of the IC is facing up when the chip
is standing on its pins. You may require a
magnifying glass while reading the IC serial
is produced from
silicon by “pulling” an
◦ polysilicon is melted
◦ “seed crystal” of
silicon is dipped into
◦ silicon grows around
structure of seed as
seed is slowly
Produces an ingot of pure silicon
◦ 400 mm - 1000 mm long (15” - 39”)
◦ 150 mm - 200 mm in diameter (6” - 8”)
Growth is a slow process
◦ 10 - 20 hours
Silicon is often doped as it’s grown
Wafers and Chips
◦ Integrated circuit (IC) chips are manufactured on
◦ Transistors are placed on the wafers through a
chemical etching process
◦ Each wafer is cut into chips (dies)
which are then packaged individually
Chip Manufacturing Process
COPYRIGHT 1998 MORGAN KAUFMANN PUBLISHERS, INC. ALL RIGHTS RESERVED
◦ Small number of transistors (< 100)
◦ Simple and fixed functions
◦ Logic designer must decide how to interconnect
multiple chips for desired function
◦ Agreed upon / standard functionality
◦ Popular in the 1980s – too large in physical size for
much industry use now (good for teaching though!)
Integrated circuit showing
memory blocks, logic and
input/output pads around
Silicon chip High lead solder die attach
Tin/lead plated copper
3C : Computer--- /Communication / Consumables
Personal Computer--- Desktop Computer (DT) /
ADSL / Cable Modem /
IEEE802.11X / Bluetooth / VoIP
Game / DVD / Digital Camera
3C merge--- Digital Home
Dynamic Random Access Memory chips (DRAMs) -
serve as the primary memory for computers
Microprocessors (MPUs) - act as the brains of computers.
Application Specific Integrated Circuits (ASICs) - are
custom semiconductors designed for very specific functions
Digital Signal Processors (DSPs) - process signals, such
as image and sound signals or radar pulses.
Programmable memory chips (EPROMs, EEPROMs,
and Flash) - are used to perform functions that require
programming on the chip.
A logic circuit diagram is drawn to determine the
electronic circuit required for the requested function.
Once the logic circuit diagram is complete,
simulations are performed multiple times to test the
The photomask is a copy of the circuit pattern,
drawn on a glass plate coated with a metallic film.
The glass plate lets light pass, but the metallic film
Due to increasingly high integration and
miniaturization of the pattern, the size of the
photomask is usually magnified four to ten times the
A high-purity, single-crystal silicon called
"99.999999999% (eleven-nine)" is grown from a
seed to an ingot.
The wafers are generally available in diameters of
150 mm, 200 mm, or 300 mm, and are mirror-
polished and rinsed before shipment from the
The wafer is placed in a high-temperature furnace to
make the silicon react with oxygen or water vapor, and
to develop oxide films on the wafer surface (thermal
To develop nitride films and polysilicon films, the
chemical vapor deposition (CVD) method is used, in
which a gaseous reactant is introduced to the silicon
substrate, and chemical reaction produce the
deposited layer material.
The metallic layers used in the wiring of the circuit are
also formed by CVD, spattering (PVD: physical vapor
A resin called "photoresist" is coated over
the entire wafer. (~1μm thick coating.)
Photoresist is a special resin similar in
behavior to photography films that changes
properties when exposed to light.
Placed over the photoresist-coated wafer, which
is then irradiated to have the circuit diagram
transcribed onto it.
An irradiation device called the "stepper" is used
to irradiate the wafer through the mask with
ultraviolet (UV) light.
The photoresist chemically reacts and dissolves in
the developing solution, only on the parts that were
not masked during exposure (positive method).
Development is performed with an alkaline
After the development, photoresist is left on the
wafer surface in the shape of the mask pattern.
"Etching" refers to the physical or chemical etching
of oxide films and metallic films using the resist
pattern as a mask.
Etching with liquid chemicals is called "wet etching"
and etching with gas is called "dry etching".
The photo resist remaining on the wafer surface is
no longer necessary after etching is complete.
Ashing by oxygen plasma or the likes is performed to
remove the residual photo resist.
After the oxide film and nitride film are developed,
a resist pattern is formed on the regions that will
become the device insulation layer.
Ion implantation is performed on the wafer,
forming a p-type diffusion layer.
Next, the oxide film and nitride film on the
diffusion layer are etched.
Using the nitride film pattern as the mask, the oxide
film that will become the device insulation layer is
A transistor is a semiconductor device with a switching
function and three terminals: source, drain, and gate.
An insulation layer called "gate oxide" is first formed on
the wafer surface.
A polysilicon film is deposited onto the gate oxide, and
a polysilicon gate for controlling the flow of electrons
between the source region and the drain region is
formed by lithography and etching.
After the polysilicon gate is formed, an n-type diffusion
layer consisting of both the source and the drain
regions is formed by implantation of impurities
Interconnecting the devices, such as transistors,
formed on the silicon wafer completes the circuit.
the wafer is first covered with a thick and flat
interlayer insulation film (oxide film). Next, contact
holes are drilled by lithograph and etching, through
the interlayer insulation film, above the devices to
Nine-layer Copper Interconnect Architecture
Each IC on the completed wafer is electronically
tested by the tester.
After this inspection, the front-end processing is
In back end processing, a wafer completed
in front end processing is cut into individual
IC chips and encapsulated into packages.
After the IC chips are cut apart,
they are sealed into packages.
The IC chips must first be
attached to a platform called the
The mounted IC chips are connected to the
The IC chips and the lead frame islands are
encapsulated with molding resin for
The packaged IC chips are tested and selected.
The final step of IC chip manufacturing is the
printing onto the package surface and the
finishing of leads. After this step, the IC chips
Ingot is finely shaped using abrasive belts
◦ flat spot added for alignment during processing
Sawed into wafers about 600 microns thick
◦ only a few microns are actually used for IC devices
◦ then etched, polished, and cleaned
◦ stacked in carriers.
Silicon dioxide is created by interaction between
silicon and oxygen or water vapor
◦ Si + O2 = SiO2 or Si + 2H2O = SiO2 + 2H2
◦ protects surface from contaminants
◦ forms insulating layer between conductors
◦ form barrier to dopants during diffusion or ion
◦ grows above and into silicon surface
◦ silicon without a single crystal structure
◦ created when silicon is epitaxially grown on SiO2
◦ also a conductor, but with much more resistance than
metal or diffused layers
◦ commonly used (heavily doped) for gate connections in
most MOS processes
Patterning creates a regular pattern on the surface
of the chip, which is used to create features of the
◦ involves alternative lithography and etching steps
◦ each of several layers involves a separate pattern
◦ patterns are contained on masks
eg, chrome on glass
◦ surface of the wafer is covered with photoresist
organic material sensistive to uv light or X-rays
spin and bake
positive resist becomes more soluable when exposed
resist will be removed where mask is clear
negative resist becomes less soluable when exposed
resist will be removed where mask is opaque
◦ mask placed very close
to wafer, flooded with
◦ solvents remove
Etching removes material
from wafer surface where
resist has been removed
◦ isotropic etching works
at same rate in all
directions of material
◦ anisotropic etching works faster in one direction than the
◦ wet etching uses liquid solvents to remove materials
eg, HF for SiO2
◦ dry etching uses gas to remove materials
can monitor reactants during process, determine
automatically when etching is finished
Finally, remaining photoresist is removed
◦ organic solvents or chromic acid
◦ pure oxygen, to oxidize organic resist materials
Metalization is used to create contacts with the
silicon and to make interconnections on the chip
Desired properties are
◦ low resistivity
◦ good adhesion to silicon and insulators
◦ good coverage of steps in chip surface
◦ immunity to corrosion
◦ ductility (so temperature cycles don’t cause failures)
Aluminum is common choice but
◦ Al causes spikes into Si, giving leaky junctions
◦ high currents carry Al atoms with them, creating shorts
◦ low melting point prohibits high heat processing later
Latest step is to use copper
◦ IBM has been shipping chips with copper for a year
smaller, 50% less power consumption
◦ other fabs to follow soon
Silicon processing steps are performed on whole wafers
◦ 150mm to 200mm in diameter
Each wafer contains
many individual chips
◦ 5mm to 15 mm square
Chips are scribed with a
diamond saw or
or a laser, and fractured
along the scribe lines
Each chip is cemented into a package.
Wire leads from pins on the package to bonding pads on the
chip are installed.
A cover is cemented over the cavity and marked.
Step I: The Beginning-Choosing a substrate
Before actual wafer fabrication, we must choose the starting wafers. The
major choices are the type (N or P), resistivity, and orientation.
In most IC circuits, the substrate has a resistivity in the range of 25-
50Ωcm, which corresponds to a doping level on the order of 1015
The other major parameter we need to specify in the starting substrate is
the crystal orientation. Virtually all modern silicon integrated circuits are
manufactured today from wafer with a (100) surface orientation. The
principal reason for this is that the properties of Si/Sio2 interface are
significantly better when a (100) crystal is used.
Lecture # 2
In order to electrically isolate
individual device a fairly thick
layer of SiO2 in between each
of the active devices (chapter
6) is needed to grow. The
region between the thick SiO2
layers, where devices will be
built, are called the “active”
region of the substrate.
Lecture # 2
For resister, usually a
conducting layer has
been deposited. The
resister value is
R=ρL / W.t
Lecture # 2
In order to transfer resister
information from the design to
the wafer, a process known as
photolithography is used.
For this process a material
known as photoresist is first
spread on the wafer. It is
usually baked at about 100o
order to drive off
solvants from the layer
(photolithographic process will
be covered in chapter 5
Lecture # 2
In order to interconnect the
different resistors on the
chip, another insulating layer
must be deposited.
To make the electrical
contact to the resistor, holes
must be opened in the
insulating layer using the
Finally, the fabrication
process can be completed,
depositing a highly conductive
metal layer by using a third
Lecture # 2
How many layers consist of this
The resister IC technology
discussed above uses
Three etch steps
Four thin film deposition
steps (the lower insulator
film, the resistor film, the
upper insulator, and the
Lecture # 2