Ans. According to fig. 5.17(B), we observe that the emitter of the npn-transistor has to an NMOS transistor source returned to VSS. The well resistor takes place between the p+ source nominally to VDD and the n+ well contact. The substrate resistor takes place [...]
Ans. Latch up Triggering – The parasitic npn-pnp circuit has to be triggered and the holding state has to be maintained for latch up to take place. Latch up can be triggered by transient currents or voltages which can take place internally to a [...]
Ans. If every silver lining has cloud, then the cloud that has plagued CMOS is a parasitic circuit effect known as “latch up”. This effect results in the shorting of the VDD and VSS lines, usually resulting in chip self-destruction or at least system [...]
Ans. (i) MOSIS Scalable CMOS Design Rules – Academic designs often use the -based scalable CMOS design rules from MOSIA because they are simple and freely available, and they allow designs to easily migrate from one process to another. These advantages come at the [...]
Ans. The scribe line is a specifically designed structure that surrounds the completed chip and is the point at which the chip is cut with a diamond saw. The construction of the scribe line varies from manufacturer to manufacturer, it is designed to prevent [...]
Ans. Some common circuit element are discussed below – (i) Resistor – In unaugmented processes, resistor can be built from any layer, with the final resistance depending on the resistivity of the layer. Building large resistances in a small area requires layers with high resistivity, [...]
Ans. The most important additions for CMOS logic processes are additional signal-and power-routing layers which are known as interconnect. This eases the routing of logic signals between modules and improves the power and clock distribution to modules. Improved routability is obtained through additional layers [...]
Ans. Twin-tup fabrication process is a logical extension of the p-well and n-well approaches. In this process, we with a substrate of high resistivity p-type material and then create both n-well regions. It is possible to preserve the performance of n-transistors without compromising the [...]
Ans. In complimentary MOS (CMOS) technology, both PMOS and NMOS devices are used. Since the PMOS and NMOS devices require substrate material of opposite type of doping, at least two different CMOS technologies occur. The cross-section of an n-well CMOS technology is shown in [...]
Ans. The p-well process is widely used, therefore the fabrication of p-well process is very vital for CMOS devices. The fabrication steps of p-well process has been developed keeping in view of fig. 5.5. Here, the basic processing steps are similar to NMOS. Step-1 – [...]
Ans. The n-well CMOS fabrication has been to being with a lightly do pen p-type substrate (wafer), create the n-type well for the p-channel transistor in the native p-substrate. Although the processing steps are somewhat complex and depend on the fabrication line, fig. 5.3 [...]
Ans. The CMOS (complementary metal oxide semiconductor) technology is recognized as the leading VLSI system technology. CMOS provides an inherently low power static circuit technology which is capable to provide a lower power-delay product than comparable design-rule bipolar, NMOS, or GaAs technologies. The four main [...]
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