Top VLSI Interview Questions

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Advantages and disadvantages of MOSFET
Advantages and Disadvantages of MOSFET Scaling
Back End of the Line (BEOL) CMOS Fabrication Process Steps
Crosstalk delay in VLSI
DEF file in VLSI Design
Difference between the TTL chips and CMOS chips?
Different Types of IC Packaging
Front End of the Line (FEOL) CMOS Fabrication Process Steps
How can you avoid crosstalk?
How does FinFET reduce leakage?
How multiple vias are used to reduce crosstalk?
How the spacing reduces the crosstalk?
List of Sanity Checks in Physical Design
Metal Semiconductor Contact
Modes of Operation of MOSFET
MOS capacitance-voltage characteristics
MOSFET
MOSFET Scaling
Temperature Inversion on Lower Nodes
Two-Terminal MOS Structure
What are the steps involved in semiconductor device fabrication?
What checks are done in Electrical rule check (ERC)
What is better than FinFET?
What is Bulk Connection in CMOS?
What is Double Patterning in VLSI
What is Enhancement mode?
What is Field Oxide?
What is Metastability
What is Schematic & Layout Design
What is Standard Cell Library
What is the Depletion mode?
What is the Epitaxial layer
What is the feedback in VLSI?
What is the odd cycle error in VLSI
Where is FinFET technology used?
Why do we go for FinFET?
Why do we use p substrate in CMOS?
Why NMOS pass strong 0 and weak 1
Why PMOS pass strong 1 and weak 0
Working of ESD Clamp Circuit in VLSI

VLSI Interview Questions

VLSI has two main Domains, Front End and Back End design. In front-end design, RTL and Verilog design are present, while in the back end, layout and physical design are considered. Let’s see some common Interview Questions in VLSI design.

Why do VLSI circuits use MOSFETs instead of BJTs?

BJT and MOSFETs can be produced in very small packages due to their small silicon footprint on IC chips and ease of manufacturing. Additionally, circuits that just use MOSFETs, such as those that use diodes, resistors, etc., can still use digital and memory ICs.

What is Verilog?

The HDL (Hardware Description Language) used to describe electronic circuits and systems is called Verilog. Circuit parts are constructed inside a Module in Verilog. Both behavioral and structural statements are present. Circuitry elements like logic gates, counters, and microprocessors are represented by structural statements. Programming constructs like loops, if-then statements, and stimulus vectors are represented by behavioral statements.

What are two types of procedural blocks in Verilog?

In Verilog, there are two varieties of procedural blocks:

Initial: At time zero, initial blocks only execute once.
Always: As implied by its name, this block loop will run repeatedly and always.

What is the set-up time and hold time?

Set time is the minimum time interval for which the input signal must be stable before the sampling event of the clock for the input signal, while Hold time is the minimum time interval for which the input signal must be stable following the sampling event of the clock for the input signal.

How Verilog is different from a normal programming language?

The following are some ways that Verilog can differ from traditional programming languages

• The concept of simulation time
• Network connections and primitive gates are fundamental circuit principles.

What Happens if Setup and Hold Times Are Violated?

The Flip-Flop output is not guaranteed to be steady if your design has setup or hold time violations. It is unknown if the value is 0, one, or someplace in between. We refer to this as metastability. An FPGA should not have metastability since it could lead to odd behavior. You may learn more about metastability here. The mechanics underlying it are fascinating.

The Different Types Of Skews Used In Vlsi

Local skew: This is the differential between the flip-flops used for launching and landing. 

Global skew: Describes the difference between the component that arrives at the flip flow first and the component that arrives last, both with the same clock domain. The clock is provided in this case, and delays are not measured.

Useful skew: A flip-flop path’s delay in being captured is defined by the useful skew, which aids in creating the conditions necessary for the timing path’s launch and capture. For the purposes of design, the hold requirement in this instance must be satisfied.

Difference Between Synchronous And Asynchronous Reset

Synchronous reset is the logic that will synthesize to smaller flip-flops. Synchronous reset doesn’t allow the synthesis tool to be used easily and it distinguishes the reset signal from other data signals, while Asynchronous Reset will allow the same.

What is Propagation Delay

The length of time it takes for a signal to get from its source to its destination is known as the propagation delay. A fundamental idea underlying the operation of digital circuits is propagation delay.

Propagation Delay is a topic that interviewers frequently inquire about, so it is also a very beneficial one to comprehend. It is now obvious that not all signals spread instantly. Voltage changes propagate down a cable in a relatively little period of time.

List different gates where Boolean logic is used

• AND Gate
• OR Gate
• NOT Gate
• NAND Gate
• NOR Gate
• XOR Gate
• XNOR Gate

What are the various factors that can affect the threshold voltage?

• Doping of the Substrate
• Doping at the Gate
• Length of the Channel
• Oxide thickness
• Body Bias

What is MTBF in VLSI?

Mean Time To Failure (MTTF) is the duration before a part or instrument needs to be replaced after it fails. Mean Time Between Failures (MTBF) is the amount of time it takes to repair a component or piece of equipment after it has broken.

VLSI Interview Questions