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Improving Reliability of
Semiconductor Devices
Major Semiconductor Manufacturer
Semiconductors permeate all the devices we use today, and we take for granted
that they will function reliably. However, in modern semiconductor processes,
the random telegraph noise (RTN) phenomenon has become a critical parameter
affecting device reliability.
What is RTN?
A random telegraph signal is a stochastic process that flips between 1 and +1 with
the number of zero crossings in any period (0,t) described by a Poisson process.
CASE STUDY
Figure 1. A random telegraph signal
+1
0
–1
Company:
• Major semiconductor
manufacturer
Key issues:
• Ensuring process
reliability
• Measuring large amounts
of RTN data
Solutions:
• Keysight B1500A
Semiconductor Device
Parameter Analyzer
• Software to automate RTN
testing
Results:
• Automated RTN testing
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Random telegraph noise in a MOSFET appears as random variations in the drain
current under constant applied gate-to-source (V
GS
) and drain-to-source (V
DS
) voltage
bias. Electron trapping/detrapping is the presumed cause of RTN. It is innate to
semiconductor MOSFET devices, and it has always been present in MOS processes.
Until recently, RTN was mainly a concern of CMOS image sensor manufacturers, as
it would generate erroneous white spots in what should be dark areas. However, as
operating voltages have decreased and lithographies have continued to shrink, RTN
has begun to impact the stability of SRAM cells. Since virtually all integrated circuits
use SRAM for their cache memory, this is critically important to the semiconductor
industry. Virtually all the major industry players now must evaluate their processes for
susceptibility to RTN.
A major semiconductor manufacturer needed a reliable means to evaluate the impact of
RTN on its processes, and Keysight was able to provide a solution.
Figure 2. Random telegraph noise in a MOSFET