This document discusses key concepts in integrated circuits like wafers, dies, faults, errors, and failures. It explains that a wafer is a thin slice of semiconductor material used to fabricate chips and comes in different sizes. A die is a small block of semiconductor that contains a functional circuit. The document also describes methods to avoid faults like careful design and manufacturing and to build fault tolerance using redundancy.

1. Jabez Winston C
15MU01
1st year M.E Embedded and Real-Time Systems
PSG College of Technology

2. Wafer
 A wafer is a thin slice of semiconductor material, such
as a crystalline silicon, used in electronics for
the fabrication of integrated circuits.
2-inch (51 mm), 4-inch (100 mm), 6-inch (150 mm), and 8-inch (200 mm) wafers

3. Die
 A die in the context of integrated circuits is a small
block of semiconducting material, on which a given
functional circuit is fabricated
Die
Intel Xeon processor E7440 die
containing 1.9 billion transistors.
Die is 22×23 mm (503 mm2)

4. Inside IC packaging
Die

5.  VLSI circuits like microprocessor contains billions of
transistors with feature size in order of nanometers.
 So chances of failure are very high.
 Even if the digital system is designed and
manufactured without faults , the system can develop
faults at later stages.

6. Faults, Errors and Failures
• Fault: A physical defect within a circuit or a system
– May or may not cause a system failure
• Error: Manifestation of a fault that results in incorrect
circuit (system) outputs or states
– Caused by faults
• Failure: Deviation of a circuit or system from its
specified behavior
– Fails to do what it should do
– Caused by an error
• Fault ---> Error ---> Failure

7. Some Real Defects in Chips
• Processing Faults
• Material Defects
• Time-Dependent Failures
• Packaging Failures

8. Fault avoidance
 Fault avoidance (a process oriented concept) seeks to
prevent faults from being introduced into the system
 By carefully designing and manufacturing systems ,
fault can be avoided

9. Fault tolerance
 Fault tolerance (a product oriented concept) accepts
faults in a limited capacity and masks their
manifestation
 A fault-tolerant design enables a system to continue
its intended operation, possibly at a reduced level,
rather than failing completely, when some part of the
system fails.

10. Methods to avoid faults and building fault
tolerant systems
Redundancy
It can implemented in the following ways
 Providing multiple identical instances of the same
system or subsystem, directing tasks or requests to all of
them in parallel.
 Providing multiple identical instances of the same
system and switching to one of the remaining instances
in case of a failure .
 Providing multiple different implementations of the
same specification