As we progress through the lower technology nodes of IC (integrated circuit) design, semiconductor designs get more complex. By scaling the technology node, many parameters, such as the width of metal wires and transistor size, tend to be downscaled. In terms of routing resources, 7nm designs are denser than the preceding nodes. As a result, RC (Resistive-capacitive) delays are significantly worse at 7nm technology nodes. When it comes to timing in 7nm, Crosstalk in VLSI plays a crucial role.
What is Crosstalk in Physical Design?
Crosstalk is a phenomenon in which switching of the signal in the one net can interfere with the neighboring net due to cross-coupling capacitance known as cross-talk. The switching net is commonly referred to as “aggressor” and the affected net is referred to as the “victim.” Understanding and mitigating crosstalk is essential in VLSI design, which is a key topic covered in a VLSI design course.
If one net is switching and the other is at a constant value, the switching net may cause voltage spikes in the other static net. This is called as crosstalk noise
When both the nets are switching it leads to additional delay on the net called crosstalk delay. Crosstalk delay can be positive or negative based on the switching directions of the nets. Crosstalk may lead to setup or hold violation.
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When we operate in lower technology nodes like 7nm and below, we find a tremendous influence of crosstalk delay and crosstalk noise. In the tape-out mode, this results in serious timing and noise/glitch violations. If this crosstalk is on a clock signal, it will be even more vital to correct timing breaches promptly as modification of routing for the clock might lead to further timing violations later. As a result, all conceivable timing violation values owing to crosstalk must be determined early in the design process. We don’t have to wait for the signoff tool to report such important timing errors. Instead, we may use the timing statistics as a starting point and a goal to correct such errors early in the chip design process.
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