Metallization is a general term that refers to the application of a metal coating to another metallic or non-metallic surface. Depending on the desired result, the coating can consist of metals such as zinc, gold, aluminum or silver.

1. HIGH SPEED
SEMICONDUCTOR
DEVICES
TOPIC
METALLIZATION
SUBMITTED BY
G.BALAJI

2. METALLIZATION:
O Metallization is the process by which the components of the ICS
are interconnected by aluminum conductor or metallization is the
process that connects individual devices together by means of
microscopic wires to form circuits.
O This process produces a thin film of metal layer that will serve as
the required conductor pattern for the interconnection of the
various components on the chips.
O With the help of metallization thousand of devices can be
interconnected using fine line metal patterns.
O The metal films can be formed by various methods like chemical
vapor deposition (CVD) and Physical Vapor Deposition(PVD).

3. REQUIREMENTS OF METALLIZATION:
O Low resistivity.
O Easy to form.
O Easy to etch for pattern generation.
O Should be oxidizable.
O Mechanically stable.
O Smooth surface.
O Should be stable towards high temperature dry or wet
oxidation etc.
O Should not contaminate wafers.
O Good life time.
O Low contact resistance to devices.
O Reliable long term operation.

4. SCHEMATIC REPRESERTTALIOZT:
ADVENTAGE:
O Good Adherence.
O Easy to Deposit.
O Good Mechanical Bonds.
O Good Resistance.
DISADVENTAGE:
O During packaging operation, if temperature goes
beyond 500 degree , Aluminum can get fused and can
penetrate the oxide to cause short circuit.
O Aluminum reacts with gold to form a metallic
compound called purple plague.
Metal
Metal
Drain

5. METALLIZATION APPLICATION IN VLSI:
O Used to form gates for MOSFET.
O Used to make contacts.
O Used to connect thousands of MOSFET internally.
O Provides connection to the outside world.
METHODS OF METALLIZATION:
O Physical vapour Deposition (PVD).
O Evaporation (EVA).
O Sputtering (SPUT).
O Chemical Vapour Deposition (CVD).

6. PROBLEMS IN METALLIZATION:
1. Deopsition: Impurities in the film, adhesion, stress and thickness
non uniformity are the various problems, related to deposition.
Impurities in the film can be minimized by using pure evaporation
and sputtering sources, high vaccum and clean surfaces. Cracks in
the deposition are because of poor adhesion or surface unevenness.
Controlling these effects will eliminate cracks.
2. Processing: Different stages of IC processing utilize metallization.
Gate metal is deposited in early stages and the contact metal towards
the end. Thus the gate metal in subjected to considerable processing
while the contact metal experiences very little processing steps.
3. Metallurgical and chemical Interactions: Metallization can be
completely destroyed by reactions induced by thermally activated
process with the substrates or layer the top.
4. Electro migration: The corresponding current density becomes
lager. High current densities can cause devices failure due to
Electromigration.

7. VACUUM EVAPORATION:
In this process the material to be evaporated is heated in a evacuated
chamber so that it attains a gaseous state. Vapour of thin material
transverse the space from the source to the substrate on which they
eventually land. The pressure is maintained well below 10 torr.

8. DFFERENT PARTS OF THE APPARATUS:
O Roughing Pump: It is used to evacuate the chamber.
O High Vacuum Pump: Maintains high vacuum by reducing pressure
with the help of nitrogen cooled trap.
O Sputter Gas: Is used to clean the surface of the wafers.
The evaporation technique is of following two types:
 GLOBAL: Energy is supplied to the entire mass of the source
present. The major problem with this scheme is that the boat
containing the source material also gets evaporated and thus
contaminates the deposited film.
 LOCAL: It employs laser beam and electron beam evaporation. In
this systems a beam of focused electron is allowed to be incident on
the sources contained in the crucible. The Beam causes the source
material to metal and vaporize locally at the point of incidence of the
beam.

9. DIAGRAM OF LOCAL
EVAPORATION TECHNIQUE:

10. SPUTTER DEPOSITION:
PRICIPLE:
Sputtreing is driven by momentum exchange between the
ions and atoms in the material due to collisions. The process can be
thought of as atomic billiards, with the ion striking a large cluster of
close-packed atoms.
PROCESS:

11. APPARATUS:
The required breakdown voltage is given by the Pascal’s law
P=Chamber Pressure L=Electrode Spacing b= is a Constant

12. ADVANTAGES:
 The ability to deposit a wide variety of metals and insulators
 The capability of cleaning the substrate prior to film deposition.
DISADVANTAGES:
 This process damages the surface of the substrate.

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