Layout Versus Schematic
When you’re verifying the correctness and integrity of an integrated circuit (IC) design, LVS (Layout Versus Schematic) plays a critical role. In this process, we compare the layout of the IC with its corresponding schematic to ensure they match accurately. To perform LVS successfully, you’ll need several key inputs. Here are the inputs for LVS:
Inputs of LVS
Layout Data: The layout data consists of the physical representation of the IC design, including the geometries, metal layers, vias, and other layout elements. It is typically provided in a standardized format, such as GDSII (Graphic Data System II) or OASIS (Open Artwork System Interchange Standard).
Schematic Data: The schematic data contains the circuit’s logical representation, including the interconnections, devices, and their electrical characteristics. It is usually created using Electronic Design Automation (EDA) tools and is represented in formats like SPICE (Simulation Program with Integrated Circuit Emphasis).
Netlist: The netlist represents the connectivity information of the circuit, specifying how the devices and components are interconnected. It serves as a reference for the expected electrical behavior of the IC. The netlist can be derived from the schematic or generated during the synthesis or extraction process.
Technology File: The technology file contains information about the process technology used in the IC design. It provides details about the available layers, their characteristics, design rules, spacing requirements, and other technology-specific constraints. The technology file is important for accurate LVS analysis, as it ensures that the layout conforms to the process technology specifications.
Parasitic Extraction Results: Parasitic extraction is a step that calculates the electrical characteristics and parasitic effects of the layout, such as resistance, capacitance, and interconnect delays. The results of the parasitic extraction, including the parasitic netlist, are utilized during LVS to compare the extracted netlist with the original schematic netlist.
Design Rule Check (DRC) Results: Before conducting LVS, the layout should undergo DRC to ensure compliance with the specified design rules. The DRC results, which identify violations or errors in the layout, serve as an input for LVS. These results highlight areas that may need adjustment or correction to align with the design rules.
By utilizing these inputs, LVS enables designers to verify that the physical layout accurately reflects the intended circuit connectivity and functionality. It ensures that the layout adheres to design rules, matches the schematic representation, and minimizes the risk of functional or manufacturing issues in the final IC product.
