This document discusses metallization in semiconductor device fabrication. Metallization involves depositing a thin metal layer to make interconnections between components on a chip and connections to the outside world. Common applications of metallization include gates, contacts, and interconnects. Aluminum is widely used for metallization due to its conductivity and ability to bond to silicon, though it has drawbacks like a low melting point. Metallization controls circuit speed and voltage by affecting resistance and interconnect lines.

1. Metallization in
Semiconductor Device
Fabrication
Arpan Deyasi
Dept of ECE, RCCIIT, Kolkata, India
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2. Metallization Process in which
[i] a thin layer of metal is formed which is used to
make interconnections between the components on
the chip
[ii] interconnections between the components and
the outside world
Metallization
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Arpan Deyasi, RCCIIT

3. Schematic set-up for metallization
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Arpan Deyasi, RCCIIT

4. Metallization applications are divided into following
groups:
 Gate ---- connects a base (in bipolar transistors) or
gate (in MOSFETs) to the neighboring two regions
 Contact ---- directly in contact with semiconductor
 Interconnects ---- connects number of bipolar
devices or MOSFETs
Classification of Metallization
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Arpan Deyasi, RCCIIT

5. Criteria for Metallization
The metal layer should be of low resistivity
The formation of layer should be easy
The layer should be easy for pattern generation to etched off
The layer should be stable in oxidizing ambient
The layer should have surface smoothness; mechanically
stable with low stress and good adherence
The layer should not react with final metal
The metal should not contaminate devices, wafers
The device characteristics should be good enough
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Arpan Deyasi, RCCIIT

6. Preferred Material for Metallization
 good conductor
 can form mechanical bonds with silicon
 can form low resistance Ohmic contacts with
heavily doped n-type and p-type silicon
In most of the IC’s, Al is the widely used metal for
metallization because
Has Al any disadvantage?
o low melting point
o undesirable electromigration behavior
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Arpan Deyasi, RCCIIT

7. Application of Metallization
 Gate and interconnection metallization controls
the speed of the circuit by controlling the
resistance of the interconnection lines. For high
speed operation, such resistance should be as
small as possible.
 The gate and interconnection metallization also
controls flat band voltage VFB
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Arpan Deyasi, RCCIIT

8. Application of Metallization
 The contact metallization gives electrically and
mechanically stable Ohmic contact having contact
resistance negligibly small compared to the
device
 The top level metal is thick as it carries current
which provides connection to the outside world
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Arpan Deyasi, RCCIIT