Physical Verification
Physical verification is a critical stage in integrated circuit design, ensuring the accuracy and functionality of the layout by verifying its electrical and logical aspects. This verification is essential to identify and rectify any issues before the manufacturing process begins. While some minor problems can be tolerated if they don’t significantly affect chip yield, others require changes to the layout. Such changes must be minimal and carefully executed to avoid introducing new problems. As a result, experienced design engineers manually perform layout adjustments during this phase. Several methods are employed for physical verification:
Design Rule Checking (DRC): DRC assesses whether the layout adheres to the constraints imposed by the manufacturing technology. It ensures that design elements are properly spaced, sized, and interconnected, while also verifying layer density for processes like chemical-mechanical polishing (CMP).
Layout vs. Schematic (LVS) Checking: LVS verification confirms the functionality of the design. It involves comparing the netlist generated from the layout with the original netlist produced during logic synthesis or circuit design to ensure consistency.
Parasitic Extraction: This method derives the electrical characteristics of layout elements based on their geometric representations. These characteristics, combined with the netlist, are used to validate the electrical behavior of the circuit.
Antenna Rule Checking: Antenna effects, caused by charge accumulation on metal wires, can potentially harm transistor gates during plasma-etch manufacturing steps. Antenna rule checking aims to prevent such issues by evaluating the potential for excess charge accumulation.
Electrical Rule Checking (ERC): ERC confirms the accuracy of power and ground connections, as well as the appropriateness of signal transition times (slew), capacitive loads, and fanouts.
Collectively, these methods ensure the reliability and functionality of the integrated circuit layout, paving the way for successful manufacturing and operation of the final chip.
What is the purpose of physical verification in chip design and layout?
The purpose of physical verification is to thoroughly validate the completed layout to ensure the correct electrical and logical functionality of the chip. It aims to identify and address any issues that could impact chip yield or performance.
What is the purpose of parasitic extraction in physical verification?
Parasitic extraction determines the electrical parameters of layout elements based on their geometric representations. These parameters are then used along with the netlist to verify the electrical characteristics of the circuit.